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Pilot Demonstration-reporting on CO2 Capture from a Cement Plant Using Hollow Fiber Process
Available online at www.sciencedirect.com
ScienceDirect Energy Procedia 114 (2017) 6150 – 6165
13th International Conference on Greenhouse Gas Control Technologies, GHGT-13, 14-18 November 2016, Lausanne, Switzerland
Pilot demonstration -reporting on CO2 capture from a cement plant using hollow fiber process. M-B Hägga*, A. Lindbråthena, X. Hea, S.G. Nodelandb, T. Canterob a
Department of Chemical Engineering, Norwegian University of Science and Technology, N-7491, Trondheim, Norway b Air Products Norway, Vige Havnevei 78, N-4689 Kristiansand, Norway
Abstract One way of contributing to combat the climate change is to capture CO2 from fossil fuel flue gases. Membranes will clearly represent one of the emerging technologies to be used for CO2 capture. In this work, a membrane pilot at the Norcem Cement factory in Norway is reported for CO2 capture from a high CO2 content (17 mol. % wet base) flue gas. The polyvinylamine (PVAm) based hollow fiber fixed-site-carrier (FSC) membrane modules (up to 18m2) was installed at the site. The membrane modules were received as commercial modules from Air Products (US-Norway), and were coated in-situ at NTNU in Norway. The testing results indicated a 70 mol.% CO2 purity can be easily achieved in single stage. The membrane also presented a good stability by exposure to high concentration SO2 and NOX for a long period without significant performance change. Improved design for both process and module will be needed for further scaling up of the membrane CO2 capture process. Based on the test results, a techno-economic feasibility analysis of CO2 capture from was conducted, using process simulation and cost estimation. Keywords: FSC membrane; CO2 capture; pilot demonstration; flue gas; cement factory; hollow fiber; process simulation
©©2017 Authors. Published by Elsevier Ltd. This 2017The The Authors. Published by Elsevier Ltd. is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of GHGT-13.
* Corresponding author. Tel.: +47 73594033; fax: +47 73594080. E-mail address: [email protected]
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of GHGT-13. doi:10.1016/j.egypro.2017.03.1752
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Introduction
The International Energy Outlook 2016 (IEO2016) reference case reported that world energy-related carbon dioxide (CO2) emissions would increase from 32.3 billion metric tons in 2012 to 35.6 billion metric tons in 2020 and 43.2 billion metric tons in 2040 [1]. Control of anthropogenic emissions of CO2 is one of the most challenging environmental issues related to global climate change. The problem is, however, now in worldwide focus, and in conjunction with the 21st Conference of Parties in Paris, December 2015, many countries submitted new intended emission reduction goals under the UNFCC (United Nations Framework Convention on Climate Change). Carbon capture and sequestration (CCS) could be a promising way to mitigate CO2 emission into atmosphere with the key advantage on continuously using fossil fuels without causing significant CO2 emissions. The main application of CO2 capture is likely to be at large CO2 point sources: fossil fuel power plants and industrial plants, particularly the manufactures of iron, steel, cement and chemicals, and natural gas plants [2]. CCS is the only technology which can achieve deep cuts in CO2 emissions across fossil-fired power plants and carbon intensive industries. According to IEA (2013) the industry sector contributes with 25% of the total CO 2 emissions worldwide, and within this sector the cement industry accounts for about 27%. – see Fig. 1 [3] The emissions for cement industry include both the burning of fossil fuels as well as CO2 from the calcination process. To achieve the goal of IEA’s Energy Technology perspective 2012 (ETP), it is obvious that it must be the emissions from cement and iron and steel must be cut dramatically by 2050, and substantial deployment of CCS in industrial applications is necessary. Both the burning of fossil fuels and the raw material limestone (CaCO 3) used in the cement industry usually contains Sulphur and produces SOx and NOx in the combustion process. Most of the plants around the world have installed sulphur removal by scrubbing of the flue gas before emitting. This will take down the temperature of the gas before the gas is directed to a CO2 capture plant. There are different technologies at different maturity levels for carbon capture – the most mature is capture by chemical or physical absorption using amines. This first generation capture technologies have already been tested at large pilot scale facilities and demo plants. Among the 2 nd generation capture technologies are membranes where smaller pilots are being tested – this will be the focus of the current report. Other technologies which potentially can be used for CO2 capture are physical adsorption, cryogenics or chemical looping The technology maturity and advance are different as stated Figueroa et al.[4]. An innovative CO2 capture membrane process fitted for flue gas at a cement factory will be reported here significant cost reduction benefits can potentially be realized once they are commercialized. A main advantage for the membranes is that it is an environmentally friendly technology with no chemicals or other waste products. The technology is already commercialized in the selected gas separation processes such as air separation, natural gas sweetening, biogas upgrading, and hydrogen production during the last two or three decades, and will become steadily more attractive due to its high energy efficiency, relatively low cost and low environmental impact. The challenges related to the membrane process for carbon capture from flue gas, is basically the low pressure (atmospheric) at which it is delivered, and the potentially detrimental effects of SOx and NOx on the membrane material itself. Then for all the capture technologies, the whole value chain has to be considered – capture, transportation and storage – in order to have the technology applied.
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Fig 1. Industrial CO2 emissions in five sectors, projected up to 2050 in the ETP baseline scenario which assumes no new policies other than those currently (2011) in place. By 2050 CO2 emissions from total industry and fuel transformation sectors is predicted to increase by 120% in the ETP Baseline scenario [3]
2 2.1
Membrane technology for CO2 capture Membrane materials
Various membrane materials such as common polymers, microporous organic polymers (MOPs), fixed-site-carrier (FSC) membranes, mixed matrix membranes (MMMs), carbon molecular sieve membranes (CMSMs) as well as inorganic membranes have been reported to be used for CO 2 separation [2]. Membrane materials can be tailored or functionalized to meet the criteria for a specific gas separation process. Different materials possess various separation properties, thermal and chemical stabilities, mechanical strength as well as cost. Thus, choice of membrane material for gas separation is mainly based on its physical and chemical properties and process operating condition. 2.2
Separation principles
Gas molecules transport through a membrane is taken place by a driving force of chemical potential difference (which normally manifests itself as a either trans-membrane pressure- and/or concentration difference). Different transport mechanisms such as solution-diffusion (S-D), facilitated transport, Maxwell model and molecular sieving are dominating in different types of membranes: common polymeric membranes, fixed-site-carrier membranes, mixed matrix membranes and carbon membranes. Solution-diffusion mechanism can be well used to describe gas transport through a common polymeric membrane where Fick’s first law is employed as shown in Fig. 1. Gas flux J i for component i through membrane is described as
Ji
Di
dci dxi
(1)
Here Di is the diffusion coefficient for component i and dci dxi is the driving force. For an ideal system, gas solubility is independent on concentration and can be described by Henry’s law ( c component i, Ji (m3(STP)/(m2.h)), can be modified by,
Ji
Pi 'pi l
Pi pH xi,F pL yi,P l
S u p ). Thus, the flux of
(2)
Where Pi is permeability (m3(STP)m/(m2.h.bar), Barrer) of component i [5], l is membrane thickness (m), Δp is driving force, p is total gas pressure (subscripts H and L represent high pressure and low pressure sides, respectively) (bar). xi,F and yi,P are mole fraction of component i on feed and permeate sides, respectively.
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When gas transport through a facilitated transport membrane, the flux of reactive component A (such as CO2) will be the sum of both solution-diffusion and carrier-mediated diffusion (i.e., facilitated transport, FT), which can be expressed as follows [6, 7],
JA
D DA c A,0 c A,l AC c AC ,0 c AC ,l l l
(3)
Where DA and DAC are diffusion coefficient of Fickian diffusion and carrier mediated (complex) diffusion, respectively, and l is membranes thickness of a selective layer. For the polyvinyl amine (PVAm) based fixed-sitecarrier (FSC) membranes developed by Memfo group at NTNU, the carrier is chemically bonded to the polymer matrix. A schematic diagram for the CO 2 separation from through a FSC membrane is shown in Fig. 2, where CO 2 passes through a membrane based on facilitated transport and solution-diffusion mechanisms, while the non-reactive gas molecules such as N2 and O2 can only transport via solution-diffusion mechanism. Thus, this type of membrane shows both high CO2 permeance and selectivity of CO2 over other gas molecules.
B (N2, O2) CO2
Support
Selective layer l
Feed
B
HCO3-
H2O NH2
B CO2
CO2 NH3+
Permeate
CO2
H2O NH2
PVAm Fig. 2 Gas transport through a PVAm based FSC membrane
Feed pressure is crucial to get high flux by enhancing the contribution from both S-D and FT. However, after carrier saturation, further increasing feed CO2 partial pressure will not enhance the FT. Even though CO 2 flux will continue to increase due to S-D contribution, the trade-off between energy consumption and reduced membrane area (flux increase) should be identified to determine the optimal operating condition. Thus, a moderate feed pressure (e.g., 2.53bar) was recommended as the optimal operation condition of FSC membranes [8]. It is also expected that diffusion coefficient based on both S-D and FT mechanism will be enhanced by increase of temperature. Therefore, membrane system may get better performance if operating at relatively higher temperature (e.g., ca. 50 °C). The temperature dependency on the selectivity is harder to predict due to the dependency of both solubility and diffusion coefficients, and hence should be further tested. 2.3
Membranes for post-combustion CO2 capture
Choosing a suitable membrane material is mainly dependent on feed gas compositions, process conditions and specific separation requirement. If high purity of products is required, higher membrane selectivity will be preferred. If large quantities of gas need to be treated, higher CO2 permeance will be preferred. For CO2 capture from flue gas, both high selectivity and high CO2 permeance are needed in order to achieve an economical viable process. Not many types of membranes have this potential – among these few are the facilitated transport membranes. It is worth noting that membrane separation performance is not only dependent on material itself, but also process design and operating condition. Some literature has already reported process design and feasibility analysis on membrane
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system for CO2 capture from flue gas, examples are: [8-13]. Merkel et al. reported a three-stage membrane system with air sweep to achieve high CO2 recovery and purity while being economically competitive with existing commercial carbon capture technology [13]. However, the designed process needs to retrofit existing power plants by integration of high CO2 content air into boiler, which increases process operation complexity. Thus, technoeconomic feasibility for such complex process should be further investigated. A two stage membrane system with integration of compression heat showed a nice potential for CO 2 capture with a 48.7 $ per tonne CO2 captured from a refinery with 18,260 kmol/h flue gas in our previous work [9]. It was found that both process and cost model were different in the literature. Thus, optimization of membrane system design and defining a suitable cost model are essential to document techno-economic feasibility of membrane system for CO2 capture in a more realistic way. Membrane process is energy-saving, space-saving, easy to scale-up, and could be a potential technology for CO2 separation. However, there are still some challenges related to the limited application of a membrane system for post combustion CO2 capture as reported in the literature [14, 15]. Thus, development on high performance and optimization of process design are crucial to bring membranes into future commercial application. The patented PVAm FSC membranes has been tested at EDP’s power plant in Sines (Portugal) on the working of membranes in a real flue gas in 2011 (NanoGloWa project, EU 6 th framework programme), and the membranes showed a stable performance during the testing period [16]. However, the employed plate-and-frame module presented a low efficiency, and was found to be difficult in upscaling. Thus, the focus in this work is to report the latest progress on pilot hollow fiber membrane system for CO2 capture from flue gases in cement factory. 3
Pilot facility at Norcem, Brevik, Norway
The Norcem Cement at Brevik is one of two factories that the company Norcem has in Norway. The Norcem Company is part of the Heidelberg Cement group. The plant at Brevik has been in operation since 1916, and has an annual average production of 1.2 million tons of cement. The cement production releases greenhouse gas emissions both directly and indirectly: the heating of limestone (calcination) releases CO2 directly, which accounts for more than 50% of all CO2 emission in cement production; the burning of fossil fuels to heat the kiln indirectly results in CO 2 emissions. The plant is emitting approximately 800 000 tons of CO2 yearly. (total flue gas flow emitted is averaged to 333 600 Nm3/h) The plant is, when in normal operation (feedstock: coal and mixtures of waste), using SO2 scrubbing as a semi-dry system (lime slurry) for removal of the high loads of SO 2. When switching the raw material (different types of limestone), the scrubber may be out of operation for a shorter period, which results in the peaks of SO 2 in the flue gas. The NOx is reduced by SNCR (Selective Non Catalytic Reduction) by addition of ammonia after the burner. Since Norcem are basing their production on different raw materials, the SOx and NOx loads varies. The plant is continuously monitoring dust, SO2, NOx, TOC and HCl – other type of emissions on a monthly basis.
3.1
Environmental policy at the Factory
The cement industry represents 5 to 7% of global anthropogenic CO2 emissions and is therefore pursuing solutions to reduce these. Strong pressure has been put by European cement producers to explore post-combustion carbon capture technologies for their kilns. Application of carbon capture and storage (CCS) from cement kilns would have great potential to reduce CO2 emission from this industry, but will naturally also influence the cement production costs. Thus, the European cement industry (through Heidelberg Cement) is taking big interest in low-cost CCS technologies. Employment of CCS is considered as one of the most important techniques to achieve the Norcem Zero CO 2 Emission Vision 2030 – a test site for carbon capture technologies is placed in Brevik, Norway, and funding of this project is mainly provided by the CLIMIT program in Norwegian Research Council. The project in Brevik was launched 2013 to test process feasibility with four different technologies (amine absorption, membranes, solid adsorbent, and chemical looping). This is the first pilot-scale membrane system that has been tested in cement factory to document the working of the PVAm based FSC membranes (developed by Memfo group at NTNU) for CO 2 capture from a 17 mol.% (wet base) CO2 flue gas. Even though many issues related to process and module designs cannot achieve a
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stable and high performance membrane system, the FSC membranes (one stage) showed a CO 2 purity up to 72% for short period when all process parameters were well controlled [17]. The membrane concept has been further developed with a pilot hollow fiber membrane system (ca. 20 m2) from spring 2016 (MemCCC project), now also with the possibility of a two stage system. This paper is focusing on the obtained data form these hollow fiber pilot tests. 3.2
Pilot membrane system at Norcem
The pilot membrane system has been designed as a close cooperation of the partners in the current consortium (NTNU, Norcem and Air Products Norway). The modules (see fig. 3B) were commercial hollow fiber modules delivered from Air Products in the US, which were coated with the FSC-membrane at NTNU, Norway. There can be several reasons for performing a pilot test for a new technology, or the application of technology in a novel field. In this project the maturing of the unit operations to be implemented in a future large scale membrane CO 2 capture, a quantity called “Technology readiness level” or TRL according to the EU-definition [18]. Currently the membrane system is evaluated to be at TRL level 5 (“Technology validated in relevant environment (industrially relevant environment in the case of key enabling technologies)”). The intention is that the experience gained from piloting will cause the TRL level to increase to level 6 (“Technology demonstrated in relevant environment (industrially relevant environment in the case of key enabling technologies)”) Fig. 3 shows a 3D simulation snapshot of the layout of the containerized pilot membrane system at Norcem, Brevik. Fig. 4 gives a simplified flow sheet for the pilot.
A)
B) Fig 3 A) 3D simulation of the arrangement inside the Pilot plant in MemCCC. B) Picture of a hollow fiber FSCmembrane module, containing ca 4m 2 membrane surface area
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Fig. 4 Simplified flow diagram of the MemCCC pilot
The design of the pilot is focusing on the handling of condensed water, preventing the compressor from being flooded in case of problems or unintentional stops, but still keeping the water molecules accessible to the CO2-carrier inside the membrane material (see fig. 2). 4
Pilot testing results
During the pilot tests at Norcem, Brevik several campaigns are already completed and others are pending. The first campaign was to measure the process selectivity for one single hollow fibre module. A representative sample set of these measurements are given in Table 1 Table1 One single module, (Ca 4m2 membrane area) Feed Temp [°C] 39 Pressure [Bara] 3.3 * Mol per cent CO2 19.4 Mol per cent O2* 10.3 Flow Nm3/h 31.0
Retentate 33 2.8 18.7 10.4 28.5
Permeate 31 0.196 83.0 9.34 1.2*
*measured at 1 bara Another completed campaign was run to primarily test durability of the material, and to secondly investigate the scalability of the modules, and the influence of different physical module layouts. During this campaign the NOx and SO2 loads for the pilot varied greatly depending on which raw material the Norcem Brevik factory was using and particularly during the switch between the different raw materials see figure 5. The scrubber at the plant would, during these periods, be out of operation, although the humidifier in front of the membranes may have reduced the SO 2-NOx loads slightly.
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Fig 5 SO2 and NOx load in the (Note the logarithmic scale on the concentration axis) as a function of the runtime.
The exposure of the membranes to these very high loads of especially SO 2 as shown in figure 5, gave valuable information on durability of the material under harsh flue gas conditions. A main objective of this test campaign was to test out the durability of the membrane material. The tests were performed using a low driving force. The module design is still being developed, hence these modules do not have an optimal membrane process performance (i.e., gas permeance and selectivity). This means that the absolute value for the permeate purity in fig. 6 and the permeate flow in fig. 7 are not fully optimized. The important value here is to investigate the stability of the measured values over time. At runtime 21000 min the temperature was increased by 5°C, this explains the small dip in the registered measurements.
Fig 6 Constant feed flow measurements for a 3 module in parallel configuration.
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Fig 7 Permeate flow during the run of 3 modules in parallel.
The peaks and zero readings in fig 7 are erroneous signal due to water interference in the flow orifice. Table 2 is giving a typical parameter set for the warmer temperature section of the campaign (after 21000 minutes of runtime) Table 2. Three modules in parallel (Ca 18m2 membrane area) Feed Temp [°C] 43 Pressure [Bara] 1.63 Mol per cent CO2 15.7 Mol per cent O2 12 3 Flow Nm /h 37.3
Retentate 37 1.45 13.7 12 40.2
Permeate 36.3 0.196 60.0 11 1.05
The orifice for the permeate flow used to obtain the permeate flow in fig. 7 is a bit oversized (0 to 10 m3(STP)/h), Hence, the resolution in the measuring range is a bit low to the range in fig. 7. This orifice has later been replaced with one with a more proper size. This means that the relative change in permeate flow (the slope of a linear fit to the data of fig. 7) is lower than the measuring uncertainty for the orifice. Hence, the reported time frame is too short to detect any significant performance change. Another test campaign was run with a two staged retentate series cascade with one stage consisting of two modules in parallel (see fig. 8). The order of the stages has been looked into and is seemingly not important for the overall performance, although there is a pressure drop difference in the membrane stage 2 versus the membrane stage 1.
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Fig 8 Two staged membrane cascade applied at Norcem, Brevik.
5 5.1
Process description and simulation basis Process description and simulation basis
In order to document the process and economic feasibility of membrane systems the averaged obtained performance at the current pilot test unit for the polyvinylamine (PVAm) FSC membranes (developed by the Memfo group at NTNU) was used in process simulation. The following assumptions were made: x No pressure drop was employed in the permeate side (flue gas feeding from shell side) x The efficiency of compressor is assumed to be 75 %. x A counter-current configuration is used in the membrane transport model x No compression of the captured CO2 is included. x Compressor is used as vacuum pump The measured data from table 1 was used as a basis to perform a trial and error approach to manually obtain the process selectivity that can will describe the measured permeate composition on wet basis. Due to the harsh corrosive condition at the cement plant it is difficult to obtain stable, reliable humidity measurements. Hence, experience data from previous knowledge was applied. As seen in table 1 and 2 the O2 content of the flue gas is relatively high (10 to 12 mole %), this is a challenge both for the NOx generation by the burner and for the membrane flue gas separation because the CO 2/O2 selectivity is much lower than the CO2/ N2 selectivity (See table 3). Hence, a more reasonable 4% O2 was chosen for the simulations of a full Norcem, Brevik sized plant. The simulation basis, as obtained using the current pilot system is given in table 3
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Table 3 Simulation basis Category Feed (Before compression)
Feed Feed at membrane inlet Retentate Permeate Membrane performance (Process evaluated) Simulation targets
Parameter Temperature Pressure Flow Composition*
Value 25 1.01 333 600
Unit °C Bar(a) Nm3/h %
Temperature Pressure Pressure Pressure Selectivity (Based on table 1, and model fit) Capture ratio Captured CO2 purity
39 3.3 2.8 0.2 CO2/N2=87; O2/N2=14 H2O/N2=167
°C Bar(a) Bar(a) Bar(a) -
80 95
% %
CO2: 19.4; O2: 4.0; N2: 74.8; H2O: 1.8
*
: the impurities of SO2, NOx and fly ashes are not included here.
5.2
Cost model
Capital cost estimation is based on major equipment cost in a process (e.g., compressor, vacuum pump and membrane unit), which can provide an accuracy in a range of -25% to 40%, typically for the preliminary feasibility analysis of different processes. Table 4 shows the cost models and parameters for CO2 capture from flue gas. Table 4 Cost models and parameters for CO2 capture with membranes Category Parameter Capital Expenditure (CAPEX) Membrane skid cost (CM)
Value 50 US$/m2
Compressor, vacuum pump cost (CBM, i) Total module cost (CTM) Grassroots cost (CGR)
Eq. 4 Eq. 6 Eq. 7
Electricity cost (EC) OPEX
0.04 $/kWh EC
Annual Operating Expenditure (OPEX)
Annual capital related cost (CRC) CO2 capture cost
0.2 × CGR +0.3 × CM (CRC+OPEX) / annual captured CO2, $/ton CO2 captured
Other assumptions
Membrane lifetime Equipment lifetime Project lifetime Operating time
5 years 25 years 25 years 8000 hrs/year
The cost estimation tool (CAPCOST 2012 [19]) is employed for the calculation of capital cost of major equipment . The bare module costing (CBM) technique accounts to purchase cost (C0P) of equipment in base condition (carbon steel material and near ambient pressure), and a multiplying bare module factor (FBM)is used to cover the specific equipment type, specific materials of construction and operating pressure. Bare module cost (CBM) of each piece of equipment is sum of direct and indirect costs,
CBM
C p0 FBM
(4) Data for the purchased cost of the equipment, at ambient operating pressure and using carbon steel construction, Cop, were fitted to the following equation [19]: ݈݃ଵ ܥ ൌ ܭଵ ܭଶ ݈݃ଵ ሺܣሻ ܭଷ ሾ݈݃ଵ ሺܣሻሿଶ (5)
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where A is the capacity or size parameter for compressor and vacuum pump (kW). The coefficient of K1, K2, and K3 for different compressors are given in the CAPCOST 2012 [19], and the applicable compressor power ranges from 450kW to 3000kW. (The feed flue gas compressor was modelled as stainless steel, the others as carbon steel) Total module cost (CTM) refers to the cost making a small and moderate expansion to the existing facility, which includes contingency and contractor fee (15% and 3% of the bare module cost, respectively) in addition to direct and indirect costs [19], which is calculated as follows: n
CTM
1.18¦ CBM ,i
i 1 (6) The grassroots cost (CGR) refers to the completely new facility construction, which considers auxiliary facilities cost (site development, auxiliary buildings, off-sites, etc) in addition to the total module cost, and can be evaluated from n
CGR
0 CTM 0.5¦ C BM ,i i 1
(7) where n is total number of individual unit, is the bare module cost in the base condition. A chemical engineering plant cost index (CEPCI) of 556.8 (September 2015) is adopted for all inflation adjustments. Apart from major equipment, membrane skid cost is estimated to be 50 US$/m2 membrane surface area by considering the cheaper materials used for large-scale FSC membrane production. The membrane lifetime is assumed to 5 years, and need to replace the membrane modules. Annual capital related cost (CRC) is estimated to be 20 % of grassroots cost, which covers depreciation, interest, and equipment maintenance (also membrane replacement cost). For operating expenditure (OPEX), only electricity cost is considered to simplify cost estimation (price based on [20]). It is worth noting that cooling unit operation has negligible influences on cost and is thus not included (Cooling towers are normally built in industrial plants (such as power plants), and cooling water used in membrane process is very small). The specific CO2 capture cost ($/tonne CO2) is then estimated by, ܥெ
ܱܥଶ ܿܽ ݐݏܿ݁ݎݑݐൌ 5.3
ோାைா ௨௧௨ௗைమ
(8)
Process simulation
Process simulation was conducted based on the PFD given in Fig. 8, two different processes: A) without recycling, and B) with 2nd stage retentate recycling was simulation. It is worth noting that vacuum pump is not standard equipment in HYSYS, and its power consumption was estimated by a compressor.
A)
B) Fig. 9 Simulated processes A) No recycle B) 2nd stage retentate recycle
The simulation results are shown in Table 5. The specific energy consumption of 1.2 GJe/ton CO2 captured is also considered to be low compared to a MEA absorption system (1.42 MJe/kg CO2 [20]).
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Table 5 Simulation results Process A: W/O recycling
Membrane area, m2 Flue gas compressor, kW Interstage compressor, kW Vacuum pump, kW Captured CO2 flow, kmol/h CO2 recovery, % CO2 purity, % Total membrane area, m2 Footprint (40 feet container numbers) Total power demand, kW Specific energy consumption #, GJe/ tonne CO2 captured Process B: W/ recycling Membrane area, m2 Flue gas compressor, kW Interstage compressor, kW Vacuum pump, kW Captured CO2 flow, kmol/h CO2 recovery, % CO2 purity, % Total membrane area, m2 Total power demand, kW Specific energy consumption #, GJe/ tonne CO2 captured
5.4
1st stage 9.08E+05 1.90E+04 3.99E+03 6.36E+03 1.02E+05 80.45 95.05 9.98E+05 15 3.40E+04 1.20
2nd stage 8.99E+04
7.85E+05 1.90E+04 3.95E+03 6.30E+03 1.02E+05 80.00 95.01 8.68E+05 3.38E+04 1.20
8.30E+04
4.68E+03
1.15E+02 4.45E+03
Cost estimation
Cost estimation is conducted to evaluate economic feasibility of CO 2 capture with a FSC membrane system. Bare module costs of major equipment (coolers and condensers are not included) were estimated on the basis of specific equipment cost and power consumption. A skid cost of 50 US$/m2 is assumed here – this is higher than reported in our previous work of 35 US$/m2 by considering the piping and valve connection between modules. The specific CO2 capture cost was shown in Table 2, which is comparable to our previous reported results (47$/ton CO2 captured [8, 9]). Membrane unit cost was found to be ca.40% of total capital cost as shown in Table 6, which significantly influences the specific CO2 capture cost. The sensitivity analysis of membrane unit cost should be conducted.
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Table 6 Cost estimation results Process W/O recycling
W/ recycling
5.5
Parameter
Cost, $
Membrane skid cost (CM) Equipment cost (CGR) Annual OPEX Annual CRC CO2 captured, ton/h Specific capture cost, $/ton CO2 captured Membrane skid cost (CM) Equipment cost (CGR) Annual OPEX Annual CRC CO2 captured, ton/h Specific capture cost, $/ton CO2 captured
4.99E+07 6.90E+07 1.09E+07 2.88E+07 102.23 48.49 4.34E+07 7.00E+07 1.08E+07 2.70E+07 101.62 46.54
Sensitivity analysis
Gas permeance of membrane module. For the process with recycling, increasing gas permeance (compared to the testing results obtained in the current system) by the improvement of module design and the optimization of process condition, the specific CO 2 capture cost will decrease as shown in Fig. 8. Based on current experience and the potential scaling up, it is considered realistically to improve CO2 permeance by 60% without loss of selectivity, and thus the specific CO2 capture cost can be brought down to ca. 40 $/ton CO2 captured).
Specific CO2 capture cost, $/ton CO2
Specific cost versus module performance improvement 49 47 45 43 41 39 37 0
20
40
60
80
100
Module gas permeance improvement, % Fig. 8 Sensitivity analysis of gas permeance of membrane module on CO2 capture cost
Membrane skid cost Membrane cost can significantly influence the specific CO2 capture cost. Thus, the sensitivity analysis on membrane cost is conducted with the variation of membrane skid cost from 30-100 US$/ m2. The scenario on process with recycling was chosen as a study case, and the results are shown in Fig. 9.
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Specific CO2 capture cost Specific CO2 capture cost, $
65 60 55 50 45 40 35 20
30
40
50
60
70
80
90
100
110
Membrane skid cost, $ Fig. 9 Sensitivity analysis of membrane skid cost on CO2 capture cost
6
Conclusions
It is a major step change to go from relatively small pilot sized modules in lab under strict controlled operating conditions, to run a test facility with larger modules and exposure to real flue gas at the cement plant. The most valuable results obtained after 6 months of running, is that the membranes tested are handling the harsh flue gas conditions extremely well. Likewise, the membrane system is handling stops and start-ups at the plant without problems, and is quickly regaining performance. The tests will continue for in total 9 months. It can further be stated that the module design will need to be optimized to fit the best operating conditions, in order to increase the performance (permeance and selectivity) and reach the same high values as have been thoroughly documented under more easily controlled conditions [9]. The simulations and cost estimations performed in this study are based on current measured values with the installed pilot at the cement plant, and not on an optimized process with optimized, prototype membrane modules. The experience gained is, however, considered to be very valuable, and gives a very good basis to move onto the next TRL level for demonstration of the technology. Acknowledgements The authors want to acknowledge our partners in Air Products AS Norway, and NORCEM, Heidelberg Cement for the input and collaboration in the project, and likewise the CLIMIT program represented by GASSNOVA under the grant # 249036, for the funding of this study through the MemCCC project. . References: [1] International Energy Outlook 2016, http://www.eia.gov/forecasts/ieo/emissions.cfm Cited September 22nd, 2016 [2] X. He, Q. Yu, M.-B. Hägg, CO2 Capture, in: E.M.V. Hoek, V.V. Tarabara (Eds.) Encyclopedia of Membrane Science and Technology, John Wiley & Sons, Inc., 2013.
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[3] Carbon capture and storage in industrial applications 2011, http://www.iea.org/publications/freepublications/publication/technology-roadmap-carbon-capture-and-storage-2013.html Cited September 23rd, 2016 [4] J.D. Figueroa, T. Fout, S. Plasynski, H. McIlvried, R.D. Srivastava, Advances in CO2 capture technology—The U.S. Department of Energy's Carbon Sequestration Program, IJGGC, 2 (2008) 9-20. [5] W.J. Koros, H. Ma, T. Shimidzu, Terminology for membranes and membrane processes (IUPAC Recommendation 1996), J Membr Sci, 120 (1996) 149-159. [6] D.R. Paul, J.P. Jampol'skij, Polymeric gas separation membranes, CRC Press, Boca Raton, Fla., 1994. [7] T.-J. Kim, B. Li, M.-B. Hägg, Novel fixed-site–carrier polyvinylamine membrane for carbon dioxide capture, J Polym Sci Part B: Polym Phys, 42 (2004) 4326-4336. [8] X. He, M.-B. Hägg, Energy Efficient Process for CO2 Capture from Flue gas with Novel Fixed-site-carrier Membranes, Energy Procedia, 63 (2014) 174-185. [9] X. He, C. Fu, M.-B. Hägg, Membrane system design and process feasibility analysis for CO2 capture from flue gas with a fixed-site-carrier membrane, Chem Eng J, 268 (2015) 1-9. [10] X. He, M.-B. Hägg, Hollow fiber carbon membranes: Investigations for CO 2 capture, J Membr Sci, 378 (2011) 1-9. [11] X. He, M.-B. Hägg, Hollow fiber carbon membranes: From material to application, Chem Eng J, 215–216 (2013) 440-448. [12] K. Ramasubramanian, H. Verweij, W.S. Winston Ho, Membrane processes for carbon capture from coal-fired power plant flue gas: A modeling and cost study, J Membr Sci, 421–422 (2012) 299-310. [13] T.C. Merkel, H. Lin, X. Wei, R. Baker, Power plant post-combustion carbon dioxide capture: An opportunity for membranes, J Membr Sci, 359 (2010) 126-139. [14] A. Brunetti, F. Scura, G. Barbieri, E. Drioli, Membrane technologies for CO2 separation, J Membr Sci, 359 (2010) 115-125. [15] E. Favre, Membrane processes and postcombustion carbon dioxide capture: Challenges and prospects, Chem Eng J, 171 (2011) 782-793. [16] M.B. Hägg, M. Sandru, T.J. Kim, W. Capala, M. Huijbers, Report on pilot scale testing and further development of a facilitated transport membrane for CO2 capture from power plants in: Euromembrane 2012, London, UK, 2012. [17] M.-B. Hägg, X. He, V. Sarfaraz, M. Sandru, T.-J. Kim, CO2 Capture using a Membrane Pilot Process at Cement factory, in Brevik Norway- lessons learnt, in: The 8th Trondheim CCS Conference (TCCS8), Trondheim, 2015. [18] TRL Scale, http://www.innovationseeds.eu/Virtual_Library/Knowledge/TLR_Scale.kl Cited October 4th, 2016 [19] R. Turton, R.C. Bailie, W.B. Whiting, J.A. Shaeiwitz, D. Bhattacharyya, Analysis, synthesis, and design of chemical processes, Fourth Edition, Pearson Education, Upper Saddle River, NJ, 2013. [20] X. Zhang, X. He, T. Gundersen, Post-combustion Carbon Capture with a Gas Separation Membrane: Parametric Study, Capture Cost, and Exergy Analysis, Energ Fuel, 27 (2013) 4137-4149.
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13th International Conference on Greenhouse Gas Control Technologies, GHGT-13, 14-18 November 2016, Lausanne, Switzerland
Pilot demonstration -reporting on CO2 capture from a cement plant using hollow fiber process. M-B Hägga*, A. Lindbråthena, X. Hea, S.G. Nodelandb, T. Canterob a
Department of Chemical Engineering, Norwegian University of Science and Technology, N-7491, Trondheim, Norway b Air Products Norway, Vige Havnevei 78, N-4689 Kristiansand, Norway
Abstract One way of contributing to combat the climate change is to capture CO2 from fossil fuel flue gases. Membranes will clearly represent one of the emerging technologies to be used for CO2 capture. In this work, a membrane pilot at the Norcem Cement factory in Norway is reported for CO2 capture from a high CO2 content (17 mol. % wet base) flue gas. The polyvinylamine (PVAm) based hollow fiber fixed-site-carrier (FSC) membrane modules (up to 18m2) was installed at the site. The membrane modules were received as commercial modules from Air Products (US-Norway), and were coated in-situ at NTNU in Norway. The testing results indicated a 70 mol.% CO2 purity can be easily achieved in single stage. The membrane also presented a good stability by exposure to high concentration SO2 and NOX for a long period without significant performance change. Improved design for both process and module will be needed for further scaling up of the membrane CO2 capture process. Based on the test results, a techno-economic feasibility analysis of CO2 capture from was conducted, using process simulation and cost estimation. Keywords: FSC membrane; CO2 capture; pilot demonstration; flue gas; cement factory; hollow fiber; process simulation
©©2017 Authors. Published by Elsevier Ltd. This 2017The The Authors. Published by Elsevier Ltd. is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of GHGT-13.
* Corresponding author. Tel.: +47 73594033; fax: +47 73594080. E-mail address: [email protected]
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of GHGT-13. doi:10.1016/j.egypro.2017.03.1752
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Introduction
The International Energy Outlook 2016 (IEO2016) reference case reported that world energy-related carbon dioxide (CO2) emissions would increase from 32.3 billion metric tons in 2012 to 35.6 billion metric tons in 2020 and 43.2 billion metric tons in 2040 [1]. Control of anthropogenic emissions of CO2 is one of the most challenging environmental issues related to global climate change. The problem is, however, now in worldwide focus, and in conjunction with the 21st Conference of Parties in Paris, December 2015, many countries submitted new intended emission reduction goals under the UNFCC (United Nations Framework Convention on Climate Change). Carbon capture and sequestration (CCS) could be a promising way to mitigate CO2 emission into atmosphere with the key advantage on continuously using fossil fuels without causing significant CO2 emissions. The main application of CO2 capture is likely to be at large CO2 point sources: fossil fuel power plants and industrial plants, particularly the manufactures of iron, steel, cement and chemicals, and natural gas plants [2]. CCS is the only technology which can achieve deep cuts in CO2 emissions across fossil-fired power plants and carbon intensive industries. According to IEA (2013) the industry sector contributes with 25% of the total CO 2 emissions worldwide, and within this sector the cement industry accounts for about 27%. – see Fig. 1 [3] The emissions for cement industry include both the burning of fossil fuels as well as CO2 from the calcination process. To achieve the goal of IEA’s Energy Technology perspective 2012 (ETP), it is obvious that it must be the emissions from cement and iron and steel must be cut dramatically by 2050, and substantial deployment of CCS in industrial applications is necessary. Both the burning of fossil fuels and the raw material limestone (CaCO 3) used in the cement industry usually contains Sulphur and produces SOx and NOx in the combustion process. Most of the plants around the world have installed sulphur removal by scrubbing of the flue gas before emitting. This will take down the temperature of the gas before the gas is directed to a CO2 capture plant. There are different technologies at different maturity levels for carbon capture – the most mature is capture by chemical or physical absorption using amines. This first generation capture technologies have already been tested at large pilot scale facilities and demo plants. Among the 2 nd generation capture technologies are membranes where smaller pilots are being tested – this will be the focus of the current report. Other technologies which potentially can be used for CO2 capture are physical adsorption, cryogenics or chemical looping The technology maturity and advance are different as stated Figueroa et al.[4]. An innovative CO2 capture membrane process fitted for flue gas at a cement factory will be reported here significant cost reduction benefits can potentially be realized once they are commercialized. A main advantage for the membranes is that it is an environmentally friendly technology with no chemicals or other waste products. The technology is already commercialized in the selected gas separation processes such as air separation, natural gas sweetening, biogas upgrading, and hydrogen production during the last two or three decades, and will become steadily more attractive due to its high energy efficiency, relatively low cost and low environmental impact. The challenges related to the membrane process for carbon capture from flue gas, is basically the low pressure (atmospheric) at which it is delivered, and the potentially detrimental effects of SOx and NOx on the membrane material itself. Then for all the capture technologies, the whole value chain has to be considered – capture, transportation and storage – in order to have the technology applied.
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Fig 1. Industrial CO2 emissions in five sectors, projected up to 2050 in the ETP baseline scenario which assumes no new policies other than those currently (2011) in place. By 2050 CO2 emissions from total industry and fuel transformation sectors is predicted to increase by 120% in the ETP Baseline scenario [3]
2 2.1
Membrane technology for CO2 capture Membrane materials
Various membrane materials such as common polymers, microporous organic polymers (MOPs), fixed-site-carrier (FSC) membranes, mixed matrix membranes (MMMs), carbon molecular sieve membranes (CMSMs) as well as inorganic membranes have been reported to be used for CO 2 separation [2]. Membrane materials can be tailored or functionalized to meet the criteria for a specific gas separation process. Different materials possess various separation properties, thermal and chemical stabilities, mechanical strength as well as cost. Thus, choice of membrane material for gas separation is mainly based on its physical and chemical properties and process operating condition. 2.2
Separation principles
Gas molecules transport through a membrane is taken place by a driving force of chemical potential difference (which normally manifests itself as a either trans-membrane pressure- and/or concentration difference). Different transport mechanisms such as solution-diffusion (S-D), facilitated transport, Maxwell model and molecular sieving are dominating in different types of membranes: common polymeric membranes, fixed-site-carrier membranes, mixed matrix membranes and carbon membranes. Solution-diffusion mechanism can be well used to describe gas transport through a common polymeric membrane where Fick’s first law is employed as shown in Fig. 1. Gas flux J i for component i through membrane is described as
Ji
Di
dci dxi
(1)
Here Di is the diffusion coefficient for component i and dci dxi is the driving force. For an ideal system, gas solubility is independent on concentration and can be described by Henry’s law ( c component i, Ji (m3(STP)/(m2.h)), can be modified by,
Ji
Pi 'pi l
Pi pH xi,F pL yi,P l
S u p ). Thus, the flux of
(2)
Where Pi is permeability (m3(STP)m/(m2.h.bar), Barrer) of component i [5], l is membrane thickness (m), Δp is driving force, p is total gas pressure (subscripts H and L represent high pressure and low pressure sides, respectively) (bar). xi,F and yi,P are mole fraction of component i on feed and permeate sides, respectively.
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When gas transport through a facilitated transport membrane, the flux of reactive component A (such as CO2) will be the sum of both solution-diffusion and carrier-mediated diffusion (i.e., facilitated transport, FT), which can be expressed as follows [6, 7],
JA
D DA c A,0 c A,l AC c AC ,0 c AC ,l l l
(3)
Where DA and DAC are diffusion coefficient of Fickian diffusion and carrier mediated (complex) diffusion, respectively, and l is membranes thickness of a selective layer. For the polyvinyl amine (PVAm) based fixed-sitecarrier (FSC) membranes developed by Memfo group at NTNU, the carrier is chemically bonded to the polymer matrix. A schematic diagram for the CO 2 separation from through a FSC membrane is shown in Fig. 2, where CO 2 passes through a membrane based on facilitated transport and solution-diffusion mechanisms, while the non-reactive gas molecules such as N2 and O2 can only transport via solution-diffusion mechanism. Thus, this type of membrane shows both high CO2 permeance and selectivity of CO2 over other gas molecules.
B (N2, O2) CO2
Support
Selective layer l
Feed
B
HCO3-
H2O NH2
B CO2
CO2 NH3+
Permeate
CO2
H2O NH2
PVAm Fig. 2 Gas transport through a PVAm based FSC membrane
Feed pressure is crucial to get high flux by enhancing the contribution from both S-D and FT. However, after carrier saturation, further increasing feed CO2 partial pressure will not enhance the FT. Even though CO 2 flux will continue to increase due to S-D contribution, the trade-off between energy consumption and reduced membrane area (flux increase) should be identified to determine the optimal operating condition. Thus, a moderate feed pressure (e.g., 2.53bar) was recommended as the optimal operation condition of FSC membranes [8]. It is also expected that diffusion coefficient based on both S-D and FT mechanism will be enhanced by increase of temperature. Therefore, membrane system may get better performance if operating at relatively higher temperature (e.g., ca. 50 °C). The temperature dependency on the selectivity is harder to predict due to the dependency of both solubility and diffusion coefficients, and hence should be further tested. 2.3
Membranes for post-combustion CO2 capture
Choosing a suitable membrane material is mainly dependent on feed gas compositions, process conditions and specific separation requirement. If high purity of products is required, higher membrane selectivity will be preferred. If large quantities of gas need to be treated, higher CO2 permeance will be preferred. For CO2 capture from flue gas, both high selectivity and high CO2 permeance are needed in order to achieve an economical viable process. Not many types of membranes have this potential – among these few are the facilitated transport membranes. It is worth noting that membrane separation performance is not only dependent on material itself, but also process design and operating condition. Some literature has already reported process design and feasibility analysis on membrane
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system for CO2 capture from flue gas, examples are: [8-13]. Merkel et al. reported a three-stage membrane system with air sweep to achieve high CO2 recovery and purity while being economically competitive with existing commercial carbon capture technology [13]. However, the designed process needs to retrofit existing power plants by integration of high CO2 content air into boiler, which increases process operation complexity. Thus, technoeconomic feasibility for such complex process should be further investigated. A two stage membrane system with integration of compression heat showed a nice potential for CO 2 capture with a 48.7 $ per tonne CO2 captured from a refinery with 18,260 kmol/h flue gas in our previous work [9]. It was found that both process and cost model were different in the literature. Thus, optimization of membrane system design and defining a suitable cost model are essential to document techno-economic feasibility of membrane system for CO2 capture in a more realistic way. Membrane process is energy-saving, space-saving, easy to scale-up, and could be a potential technology for CO2 separation. However, there are still some challenges related to the limited application of a membrane system for post combustion CO2 capture as reported in the literature [14, 15]. Thus, development on high performance and optimization of process design are crucial to bring membranes into future commercial application. The patented PVAm FSC membranes has been tested at EDP’s power plant in Sines (Portugal) on the working of membranes in a real flue gas in 2011 (NanoGloWa project, EU 6 th framework programme), and the membranes showed a stable performance during the testing period [16]. However, the employed plate-and-frame module presented a low efficiency, and was found to be difficult in upscaling. Thus, the focus in this work is to report the latest progress on pilot hollow fiber membrane system for CO2 capture from flue gases in cement factory. 3
Pilot facility at Norcem, Brevik, Norway
The Norcem Cement at Brevik is one of two factories that the company Norcem has in Norway. The Norcem Company is part of the Heidelberg Cement group. The plant at Brevik has been in operation since 1916, and has an annual average production of 1.2 million tons of cement. The cement production releases greenhouse gas emissions both directly and indirectly: the heating of limestone (calcination) releases CO2 directly, which accounts for more than 50% of all CO2 emission in cement production; the burning of fossil fuels to heat the kiln indirectly results in CO 2 emissions. The plant is emitting approximately 800 000 tons of CO2 yearly. (total flue gas flow emitted is averaged to 333 600 Nm3/h) The plant is, when in normal operation (feedstock: coal and mixtures of waste), using SO2 scrubbing as a semi-dry system (lime slurry) for removal of the high loads of SO 2. When switching the raw material (different types of limestone), the scrubber may be out of operation for a shorter period, which results in the peaks of SO 2 in the flue gas. The NOx is reduced by SNCR (Selective Non Catalytic Reduction) by addition of ammonia after the burner. Since Norcem are basing their production on different raw materials, the SOx and NOx loads varies. The plant is continuously monitoring dust, SO2, NOx, TOC and HCl – other type of emissions on a monthly basis.
3.1
Environmental policy at the Factory
The cement industry represents 5 to 7% of global anthropogenic CO2 emissions and is therefore pursuing solutions to reduce these. Strong pressure has been put by European cement producers to explore post-combustion carbon capture technologies for their kilns. Application of carbon capture and storage (CCS) from cement kilns would have great potential to reduce CO2 emission from this industry, but will naturally also influence the cement production costs. Thus, the European cement industry (through Heidelberg Cement) is taking big interest in low-cost CCS technologies. Employment of CCS is considered as one of the most important techniques to achieve the Norcem Zero CO 2 Emission Vision 2030 – a test site for carbon capture technologies is placed in Brevik, Norway, and funding of this project is mainly provided by the CLIMIT program in Norwegian Research Council. The project in Brevik was launched 2013 to test process feasibility with four different technologies (amine absorption, membranes, solid adsorbent, and chemical looping). This is the first pilot-scale membrane system that has been tested in cement factory to document the working of the PVAm based FSC membranes (developed by Memfo group at NTNU) for CO 2 capture from a 17 mol.% (wet base) CO2 flue gas. Even though many issues related to process and module designs cannot achieve a
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stable and high performance membrane system, the FSC membranes (one stage) showed a CO 2 purity up to 72% for short period when all process parameters were well controlled [17]. The membrane concept has been further developed with a pilot hollow fiber membrane system (ca. 20 m2) from spring 2016 (MemCCC project), now also with the possibility of a two stage system. This paper is focusing on the obtained data form these hollow fiber pilot tests. 3.2
Pilot membrane system at Norcem
The pilot membrane system has been designed as a close cooperation of the partners in the current consortium (NTNU, Norcem and Air Products Norway). The modules (see fig. 3B) were commercial hollow fiber modules delivered from Air Products in the US, which were coated with the FSC-membrane at NTNU, Norway. There can be several reasons for performing a pilot test for a new technology, or the application of technology in a novel field. In this project the maturing of the unit operations to be implemented in a future large scale membrane CO 2 capture, a quantity called “Technology readiness level” or TRL according to the EU-definition [18]. Currently the membrane system is evaluated to be at TRL level 5 (“Technology validated in relevant environment (industrially relevant environment in the case of key enabling technologies)”). The intention is that the experience gained from piloting will cause the TRL level to increase to level 6 (“Technology demonstrated in relevant environment (industrially relevant environment in the case of key enabling technologies)”) Fig. 3 shows a 3D simulation snapshot of the layout of the containerized pilot membrane system at Norcem, Brevik. Fig. 4 gives a simplified flow sheet for the pilot.
A)
B) Fig 3 A) 3D simulation of the arrangement inside the Pilot plant in MemCCC. B) Picture of a hollow fiber FSCmembrane module, containing ca 4m 2 membrane surface area
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Fig. 4 Simplified flow diagram of the MemCCC pilot
The design of the pilot is focusing on the handling of condensed water, preventing the compressor from being flooded in case of problems or unintentional stops, but still keeping the water molecules accessible to the CO2-carrier inside the membrane material (see fig. 2). 4
Pilot testing results
During the pilot tests at Norcem, Brevik several campaigns are already completed and others are pending. The first campaign was to measure the process selectivity for one single hollow fibre module. A representative sample set of these measurements are given in Table 1 Table1 One single module, (Ca 4m2 membrane area) Feed Temp [°C] 39 Pressure [Bara] 3.3 * Mol per cent CO2 19.4 Mol per cent O2* 10.3 Flow Nm3/h 31.0
Retentate 33 2.8 18.7 10.4 28.5
Permeate 31 0.196 83.0 9.34 1.2*
*measured at 1 bara Another completed campaign was run to primarily test durability of the material, and to secondly investigate the scalability of the modules, and the influence of different physical module layouts. During this campaign the NOx and SO2 loads for the pilot varied greatly depending on which raw material the Norcem Brevik factory was using and particularly during the switch between the different raw materials see figure 5. The scrubber at the plant would, during these periods, be out of operation, although the humidifier in front of the membranes may have reduced the SO 2-NOx loads slightly.
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Fig 5 SO2 and NOx load in the (Note the logarithmic scale on the concentration axis) as a function of the runtime.
The exposure of the membranes to these very high loads of especially SO 2 as shown in figure 5, gave valuable information on durability of the material under harsh flue gas conditions. A main objective of this test campaign was to test out the durability of the membrane material. The tests were performed using a low driving force. The module design is still being developed, hence these modules do not have an optimal membrane process performance (i.e., gas permeance and selectivity). This means that the absolute value for the permeate purity in fig. 6 and the permeate flow in fig. 7 are not fully optimized. The important value here is to investigate the stability of the measured values over time. At runtime 21000 min the temperature was increased by 5°C, this explains the small dip in the registered measurements.
Fig 6 Constant feed flow measurements for a 3 module in parallel configuration.
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Fig 7 Permeate flow during the run of 3 modules in parallel.
The peaks and zero readings in fig 7 are erroneous signal due to water interference in the flow orifice. Table 2 is giving a typical parameter set for the warmer temperature section of the campaign (after 21000 minutes of runtime) Table 2. Three modules in parallel (Ca 18m2 membrane area) Feed Temp [°C] 43 Pressure [Bara] 1.63 Mol per cent CO2 15.7 Mol per cent O2 12 3 Flow Nm /h 37.3
Retentate 37 1.45 13.7 12 40.2
Permeate 36.3 0.196 60.0 11 1.05
The orifice for the permeate flow used to obtain the permeate flow in fig. 7 is a bit oversized (0 to 10 m3(STP)/h), Hence, the resolution in the measuring range is a bit low to the range in fig. 7. This orifice has later been replaced with one with a more proper size. This means that the relative change in permeate flow (the slope of a linear fit to the data of fig. 7) is lower than the measuring uncertainty for the orifice. Hence, the reported time frame is too short to detect any significant performance change. Another test campaign was run with a two staged retentate series cascade with one stage consisting of two modules in parallel (see fig. 8). The order of the stages has been looked into and is seemingly not important for the overall performance, although there is a pressure drop difference in the membrane stage 2 versus the membrane stage 1.
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Fig 8 Two staged membrane cascade applied at Norcem, Brevik.
5 5.1
Process description and simulation basis Process description and simulation basis
In order to document the process and economic feasibility of membrane systems the averaged obtained performance at the current pilot test unit for the polyvinylamine (PVAm) FSC membranes (developed by the Memfo group at NTNU) was used in process simulation. The following assumptions were made: x No pressure drop was employed in the permeate side (flue gas feeding from shell side) x The efficiency of compressor is assumed to be 75 %. x A counter-current configuration is used in the membrane transport model x No compression of the captured CO2 is included. x Compressor is used as vacuum pump The measured data from table 1 was used as a basis to perform a trial and error approach to manually obtain the process selectivity that can will describe the measured permeate composition on wet basis. Due to the harsh corrosive condition at the cement plant it is difficult to obtain stable, reliable humidity measurements. Hence, experience data from previous knowledge was applied. As seen in table 1 and 2 the O2 content of the flue gas is relatively high (10 to 12 mole %), this is a challenge both for the NOx generation by the burner and for the membrane flue gas separation because the CO 2/O2 selectivity is much lower than the CO2/ N2 selectivity (See table 3). Hence, a more reasonable 4% O2 was chosen for the simulations of a full Norcem, Brevik sized plant. The simulation basis, as obtained using the current pilot system is given in table 3
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Table 3 Simulation basis Category Feed (Before compression)
Feed Feed at membrane inlet Retentate Permeate Membrane performance (Process evaluated) Simulation targets
Parameter Temperature Pressure Flow Composition*
Value 25 1.01 333 600
Unit °C Bar(a) Nm3/h %
Temperature Pressure Pressure Pressure Selectivity (Based on table 1, and model fit) Capture ratio Captured CO2 purity
39 3.3 2.8 0.2 CO2/N2=87; O2/N2=14 H2O/N2=167
°C Bar(a) Bar(a) Bar(a) -
80 95
% %
CO2: 19.4; O2: 4.0; N2: 74.8; H2O: 1.8
*
: the impurities of SO2, NOx and fly ashes are not included here.
5.2
Cost model
Capital cost estimation is based on major equipment cost in a process (e.g., compressor, vacuum pump and membrane unit), which can provide an accuracy in a range of -25% to 40%, typically for the preliminary feasibility analysis of different processes. Table 4 shows the cost models and parameters for CO2 capture from flue gas. Table 4 Cost models and parameters for CO2 capture with membranes Category Parameter Capital Expenditure (CAPEX) Membrane skid cost (CM)
Value 50 US$/m2
Compressor, vacuum pump cost (CBM, i) Total module cost (CTM) Grassroots cost (CGR)
Eq. 4 Eq. 6 Eq. 7
Electricity cost (EC) OPEX
0.04 $/kWh EC
Annual Operating Expenditure (OPEX)
Annual capital related cost (CRC) CO2 capture cost
0.2 × CGR +0.3 × CM (CRC+OPEX) / annual captured CO2, $/ton CO2 captured
Other assumptions
Membrane lifetime Equipment lifetime Project lifetime Operating time
5 years 25 years 25 years 8000 hrs/year
The cost estimation tool (CAPCOST 2012 [19]) is employed for the calculation of capital cost of major equipment . The bare module costing (CBM) technique accounts to purchase cost (C0P) of equipment in base condition (carbon steel material and near ambient pressure), and a multiplying bare module factor (FBM)is used to cover the specific equipment type, specific materials of construction and operating pressure. Bare module cost (CBM) of each piece of equipment is sum of direct and indirect costs,
CBM
C p0 FBM
(4) Data for the purchased cost of the equipment, at ambient operating pressure and using carbon steel construction, Cop, were fitted to the following equation [19]: ݈݃ଵ ܥ ൌ ܭଵ ܭଶ ݈݃ଵ ሺܣሻ ܭଷ ሾ݈݃ଵ ሺܣሻሿଶ (5)
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where A is the capacity or size parameter for compressor and vacuum pump (kW). The coefficient of K1, K2, and K3 for different compressors are given in the CAPCOST 2012 [19], and the applicable compressor power ranges from 450kW to 3000kW. (The feed flue gas compressor was modelled as stainless steel, the others as carbon steel) Total module cost (CTM) refers to the cost making a small and moderate expansion to the existing facility, which includes contingency and contractor fee (15% and 3% of the bare module cost, respectively) in addition to direct and indirect costs [19], which is calculated as follows: n
CTM
1.18¦ CBM ,i
i 1 (6) The grassroots cost (CGR) refers to the completely new facility construction, which considers auxiliary facilities cost (site development, auxiliary buildings, off-sites, etc) in addition to the total module cost, and can be evaluated from n
CGR
0 CTM 0.5¦ C BM ,i i 1
(7) where n is total number of individual unit, is the bare module cost in the base condition. A chemical engineering plant cost index (CEPCI) of 556.8 (September 2015) is adopted for all inflation adjustments. Apart from major equipment, membrane skid cost is estimated to be 50 US$/m2 membrane surface area by considering the cheaper materials used for large-scale FSC membrane production. The membrane lifetime is assumed to 5 years, and need to replace the membrane modules. Annual capital related cost (CRC) is estimated to be 20 % of grassroots cost, which covers depreciation, interest, and equipment maintenance (also membrane replacement cost). For operating expenditure (OPEX), only electricity cost is considered to simplify cost estimation (price based on [20]). It is worth noting that cooling unit operation has negligible influences on cost and is thus not included (Cooling towers are normally built in industrial plants (such as power plants), and cooling water used in membrane process is very small). The specific CO2 capture cost ($/tonne CO2) is then estimated by, ܥெ
ܱܥଶ ܿܽ ݐݏܿ݁ݎݑݐൌ 5.3
ோାைா ௨௧௨ௗைమ
(8)
Process simulation
Process simulation was conducted based on the PFD given in Fig. 8, two different processes: A) without recycling, and B) with 2nd stage retentate recycling was simulation. It is worth noting that vacuum pump is not standard equipment in HYSYS, and its power consumption was estimated by a compressor.
A)
B) Fig. 9 Simulated processes A) No recycle B) 2nd stage retentate recycle
The simulation results are shown in Table 5. The specific energy consumption of 1.2 GJe/ton CO2 captured is also considered to be low compared to a MEA absorption system (1.42 MJe/kg CO2 [20]).
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Table 5 Simulation results Process A: W/O recycling
Membrane area, m2 Flue gas compressor, kW Interstage compressor, kW Vacuum pump, kW Captured CO2 flow, kmol/h CO2 recovery, % CO2 purity, % Total membrane area, m2 Footprint (40 feet container numbers) Total power demand, kW Specific energy consumption #, GJe/ tonne CO2 captured Process B: W/ recycling Membrane area, m2 Flue gas compressor, kW Interstage compressor, kW Vacuum pump, kW Captured CO2 flow, kmol/h CO2 recovery, % CO2 purity, % Total membrane area, m2 Total power demand, kW Specific energy consumption #, GJe/ tonne CO2 captured
5.4
1st stage 9.08E+05 1.90E+04 3.99E+03 6.36E+03 1.02E+05 80.45 95.05 9.98E+05 15 3.40E+04 1.20
2nd stage 8.99E+04
7.85E+05 1.90E+04 3.95E+03 6.30E+03 1.02E+05 80.00 95.01 8.68E+05 3.38E+04 1.20
8.30E+04
4.68E+03
1.15E+02 4.45E+03
Cost estimation
Cost estimation is conducted to evaluate economic feasibility of CO 2 capture with a FSC membrane system. Bare module costs of major equipment (coolers and condensers are not included) were estimated on the basis of specific equipment cost and power consumption. A skid cost of 50 US$/m2 is assumed here – this is higher than reported in our previous work of 35 US$/m2 by considering the piping and valve connection between modules. The specific CO2 capture cost was shown in Table 2, which is comparable to our previous reported results (47$/ton CO2 captured [8, 9]). Membrane unit cost was found to be ca.40% of total capital cost as shown in Table 6, which significantly influences the specific CO2 capture cost. The sensitivity analysis of membrane unit cost should be conducted.
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Table 6 Cost estimation results Process W/O recycling
W/ recycling
5.5
Parameter
Cost, $
Membrane skid cost (CM) Equipment cost (CGR) Annual OPEX Annual CRC CO2 captured, ton/h Specific capture cost, $/ton CO2 captured Membrane skid cost (CM) Equipment cost (CGR) Annual OPEX Annual CRC CO2 captured, ton/h Specific capture cost, $/ton CO2 captured
4.99E+07 6.90E+07 1.09E+07 2.88E+07 102.23 48.49 4.34E+07 7.00E+07 1.08E+07 2.70E+07 101.62 46.54
Sensitivity analysis
Gas permeance of membrane module. For the process with recycling, increasing gas permeance (compared to the testing results obtained in the current system) by the improvement of module design and the optimization of process condition, the specific CO 2 capture cost will decrease as shown in Fig. 8. Based on current experience and the potential scaling up, it is considered realistically to improve CO2 permeance by 60% without loss of selectivity, and thus the specific CO2 capture cost can be brought down to ca. 40 $/ton CO2 captured).
Specific CO2 capture cost, $/ton CO2
Specific cost versus module performance improvement 49 47 45 43 41 39 37 0
20
40
60
80
100
Module gas permeance improvement, % Fig. 8 Sensitivity analysis of gas permeance of membrane module on CO2 capture cost
Membrane skid cost Membrane cost can significantly influence the specific CO2 capture cost. Thus, the sensitivity analysis on membrane cost is conducted with the variation of membrane skid cost from 30-100 US$/ m2. The scenario on process with recycling was chosen as a study case, and the results are shown in Fig. 9.
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Specific CO2 capture cost Specific CO2 capture cost, $
65 60 55 50 45 40 35 20
30
40
50
60
70
80
90
100
110
Membrane skid cost, $ Fig. 9 Sensitivity analysis of membrane skid cost on CO2 capture cost
6
Conclusions
It is a major step change to go from relatively small pilot sized modules in lab under strict controlled operating conditions, to run a test facility with larger modules and exposure to real flue gas at the cement plant. The most valuable results obtained after 6 months of running, is that the membranes tested are handling the harsh flue gas conditions extremely well. Likewise, the membrane system is handling stops and start-ups at the plant without problems, and is quickly regaining performance. The tests will continue for in total 9 months. It can further be stated that the module design will need to be optimized to fit the best operating conditions, in order to increase the performance (permeance and selectivity) and reach the same high values as have been thoroughly documented under more easily controlled conditions [9]. The simulations and cost estimations performed in this study are based on current measured values with the installed pilot at the cement plant, and not on an optimized process with optimized, prototype membrane modules. The experience gained is, however, considered to be very valuable, and gives a very good basis to move onto the next TRL level for demonstration of the technology. Acknowledgements The authors want to acknowledge our partners in Air Products AS Norway, and NORCEM, Heidelberg Cement for the input and collaboration in the project, and likewise the CLIMIT program represented by GASSNOVA under the grant # 249036, for the funding of this study through the MemCCC project. . References: [1] International Energy Outlook 2016, http://www.eia.gov/forecasts/ieo/emissions.cfm Cited September 22nd, 2016 [2] X. He, Q. Yu, M.-B. Hägg, CO2 Capture, in: E.M.V. Hoek, V.V. Tarabara (Eds.) Encyclopedia of Membrane Science and Technology, John Wiley & Sons, Inc., 2013.
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[3] Carbon capture and storage in industrial applications 2011, http://www.iea.org/publications/freepublications/publication/technology-roadmap-carbon-capture-and-storage-2013.html Cited September 23rd, 2016 [4] J.D. Figueroa, T. Fout, S. Plasynski, H. McIlvried, R.D. Srivastava, Advances in CO2 capture technology—The U.S. Department of Energy's Carbon Sequestration Program, IJGGC, 2 (2008) 9-20. [5] W.J. Koros, H. Ma, T. Shimidzu, Terminology for membranes and membrane processes (IUPAC Recommendation 1996), J Membr Sci, 120 (1996) 149-159. [6] D.R. Paul, J.P. Jampol'skij, Polymeric gas separation membranes, CRC Press, Boca Raton, Fla., 1994. [7] T.-J. Kim, B. Li, M.-B. Hägg, Novel fixed-site–carrier polyvinylamine membrane for carbon dioxide capture, J Polym Sci Part B: Polym Phys, 42 (2004) 4326-4336. [8] X. He, M.-B. Hägg, Energy Efficient Process for CO2 Capture from Flue gas with Novel Fixed-site-carrier Membranes, Energy Procedia, 63 (2014) 174-185. [9] X. He, C. Fu, M.-B. Hägg, Membrane system design and process feasibility analysis for CO2 capture from flue gas with a fixed-site-carrier membrane, Chem Eng J, 268 (2015) 1-9. [10] X. He, M.-B. Hägg, Hollow fiber carbon membranes: Investigations for CO 2 capture, J Membr Sci, 378 (2011) 1-9. [11] X. He, M.-B. Hägg, Hollow fiber carbon membranes: From material to application, Chem Eng J, 215–216 (2013) 440-448. [12] K. Ramasubramanian, H. Verweij, W.S. Winston Ho, Membrane processes for carbon capture from coal-fired power plant flue gas: A modeling and cost study, J Membr Sci, 421–422 (2012) 299-310. [13] T.C. Merkel, H. Lin, X. Wei, R. Baker, Power plant post-combustion carbon dioxide capture: An opportunity for membranes, J Membr Sci, 359 (2010) 126-139. [14] A. Brunetti, F. Scura, G. Barbieri, E. Drioli, Membrane technologies for CO2 separation, J Membr Sci, 359 (2010) 115-125. [15] E. Favre, Membrane processes and postcombustion carbon dioxide capture: Challenges and prospects, Chem Eng J, 171 (2011) 782-793. [16] M.B. Hägg, M. Sandru, T.J. Kim, W. Capala, M. Huijbers, Report on pilot scale testing and further development of a facilitated transport membrane for CO2 capture from power plants in: Euromembrane 2012, London, UK, 2012. [17] M.-B. Hägg, X. He, V. Sarfaraz, M. Sandru, T.-J. Kim, CO2 Capture using a Membrane Pilot Process at Cement factory, in Brevik Norway- lessons learnt, in: The 8th Trondheim CCS Conference (TCCS8), Trondheim, 2015. [18] TRL Scale, http://www.innovationseeds.eu/Virtual_Library/Knowledge/TLR_Scale.kl Cited October 4th, 2016 [19] R. Turton, R.C. Bailie, W.B. Whiting, J.A. Shaeiwitz, D. Bhattacharyya, Analysis, synthesis, and design of chemical processes, Fourth Edition, Pearson Education, Upper Saddle River, NJ, 2013. [20] X. Zhang, X. He, T. Gundersen, Post-combustion Carbon Capture with a Gas Separation Membrane: Parametric Study, Capture Cost, and Exergy Analysis, Energ Fuel, 27 (2013) 4137-4149.
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