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Carbon capture from industrial processes
Carbon capture from industrial processes
5
Although fossil-fueled power-generation plant accounts for the majority of large stationary sources emitting .0.1 Mt-CO2/year, similar quantities are also emitted from single sources in a number of other industries and are therefore targets for the application of carbon capture technologies. Industrial activity (excluding consumption of electrical power) accounts for around one-fifth of global CO2 emission, the most important of these emitters—cement production, iron and steel production, oil refining, and natural gas processing—are dealt with in this chapter.
5.1
Cement production
Worldwide cement production results in the emission of B2 Gt-CO2 (2015—at a global average CO2 intensity of 0.8 t-CO2/t-cement), some 5% of total anthropogenic CO2 emissions. These emissions are split roughly equally between CO2 emitted from the calcination process (B52%) and emissions from the combustion of fuel to fire cement kilns (B48%). Portland cement is a mixture of predominantly di- and tricalcium silicates (2CaO SiO2, 3CaO SiO2), with smaller amounts of other compounds such as calcium sulfate (CaSO4), magnesium, aluminum and iron oxides, and tricalcium aluminate (3CaO Al2O3). The cement production process is shown schematically in Figure 5.1. After pre-heating, the milled raw feed is calcined at B860 C and then a controlled mixture of materials is sintered in a kiln, typically a horizontal rotary kiln, at a temperature of B1450 C. Calcium carbonate (CaCO3) is the primary raw material and may be in the form of crushed limestone, shells, or chalk. A variety of secondary raw materials are used as the source of silica and other minerals, including sand, shale, clay, blast furnace slag, and coal ash. The latter may be introduced directly by firing the cement kiln with pulverized coal or by importing fly or bottom ash from a coal-fired power plant. The main reaction taking place in the process is the conversion or calcining of calcium carbonate to calcium oxide, a highly endothermic reaction requiring 3.56.0 GJ/t-cement produced, depending on plant efficiency. Calcination and the other main chemical reactions proceed as follows: CaCO3 1 heat ! CaO 1 CO2
(5.1)
2CaO 1 SiO2 ! 2CaO SiO2 ðBelliteÞ
(5.2)
Carbon Capture and Storage. DOI: http://dx.doi.org/10.1016/B978-0-12-812041-5.00005-2 © 2017 Elsevier Inc. All rights reserved.
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Limestone Milling Fly ash, blast furnace slag, etc.
Filtering (bag house)
Raw meal pre-heat
Raw meal silo
Rotary clinker kiln
Precalciner
Fuel Air
Clinker
Cooling
Milling
Bagging
Figure 5.1 Cement production process.
3CaO 1 Al2 O3 ! 3CaO Al2 O3
(5.3)
4CaO 1 Al2 O3 1 Fe2 O3 ! 4CaO Al2 O3 Fe2 O3
(5.4)
CaO 1 2CaO SiO2 ! 3CaO SiO2 ðAliteÞ
(5.5)
The CO2 released in the initial calcining reaction in Reaction (5.1), known as the process CO2, combined with the CO2 from combustion of the kiln fuel (coal, oil, or natural gas) yields a flue gas with a [CO2] in the range of 14%33%.
5.1.1 Post-combustion capture from cement plants Capture of CO2 from the combined flue gas can be achieved using the technologies applicable to post-combustion capture from power-generation plants, including chemical and physical solvents (Section 6.2); sorbents, particularly hightemperature sorbents (Section 7.1); and membranes (Section 8.7). Compared to “conventional” post-combustion applications, the higher [CO2] enables these technologies to achieve higher separation efficiencies in cement plant applications. Calcium looping (CaL—see Section 6.3) is widely seen as an obvious postcombustion technology for cement plants, in view of the synergy in handling and processing of the common raw materials, as well as the potential for close process integration and for purge CaO to be used in cement production. CaL was one of the four technologies that has been investigated in a 4-year project, commencing in 2014 at the Norcem operated cement plant at Brevik, Norway. The preliminary results and planned next steps in this project are summarized in Table 5.1. The advanced amine pilot was particularly successful and demonstrated the feasibility of capturing 400 kt-CO2/year, almost 50% of the Brevik plant’s total
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Table 5.1 Preliminary results and next steps in Norcem pilot tests Technology Description and preliminary results
Next steps
Amine 16-month pilot test of proprietary solvent absorption (S26) using Aker Solutions mobile testing unit; robust operation with . 90% capture rate, energy consumption lower than seen in other applications; degradation, consumption, and emissions of amines and degraded products also low; assessed TRL 9 (proven in operational environment) Solid 3-month trial of bench-scale fluidized bed sorbent reactor; assessed TRL 5 (technology valid in relevant environment) Membranes 6-month bench-scale trial using polyvinylamide (PVAm) membranes; promising membrane durability yielding 60%70% CO2 recovery; assessed TRL 5 Calcium 1-year study and lab-scale pilot; more looping rapid sorbent degradation than expected; assessed TRL 3 (experimental proof of concept)
Conceptual study commenced in 2015 for large-scale capture plant
Further testing planned with largescale pilot, aiming to achieve higher sorbent loading Immature Phase II concept led to project termination; new consortium being established to progress Phase II Developing larger scale pilot
emissions, using waste heat alone for solvent regeneration. This was considered to be the only technology likely to be mature enough for commercial deployment in the 2020 timeframe.
5.1.2 Oxygen enrichment and oxyfuel processes The addition of oxygen to the air drafting the burners—the so-called oxygen enrichment—has been practiced in cement kilns since the early 1960s and results in increased clinker production and reduced fuel consumption. Fuel consumption is reduced in part because nitrogen in the air does not need to be heated up to combustion temperature. Oxygen enrichment increases flame temperatures (to B3500 C), which has an impact on kiln refractory design and materials, and also increases [CO2] in the kiln flue gas stream, which, as noted previously, further aids post-combustion capture. Oxyfueling can also be applied as a cement plant capture technology, either in partial or full oxyfuel configurations. In a partial oxyfuel configuration only the calcining step takes place under oxygen and 60%75% of the process CO2 can be captured, while for full oxyfueling, with both the calciner and kiln operating under oxy-combustion conditions, a capture rate greater than 90% is possible. Apart from the provision
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Table 5.2 Research and development issues for oxyfuel cement production R&D
Description
[CO2] impact on reaction kinetics Burner design
Assessing the impact of high [CO2] on calcination and clinker quality Development of oxygen-drafted burners for clinker kilns, paralleling work on burners for oxyfuel steam boilers Durability of kiln refractory lining Optimal cooling systems for full oxyfuel configurations Process modeling, addressing the impact of oxyfuel on flue gas enthalpy and recirculation, heat transfer phenomena, energy demand optimization, and material flows
Kiln lining Clinker cooling Plant and process simulation
of an ASU, plant modifications are required to the calciner and pre-heaters in the case of a partial configuration and to the kiln burners, flue gas recycle (to control kiln temperature) and clinker coolers in the full oxyfuel configuration. In both cases attention would also be required to seals to prevent air ingress diluting the 85%90% CO2 off-gas stream, which could be directly compressed for transportation and storage after dehydration and possibly FGD. Research into oxyfuel technology for cement production has been ongoing since 2007, when the European Cement Research Academy started a long-term carbon CCS project. Phases I to III of this project (20072011) included technical studies and lab-scale research on both post-combustion and oxyfuel options and subsequent phases will focus on the oxyfuel route. Research topics being addressed by this and other ongoing projects are summarized in Table 5.2. Pilot-scale trials of a partial oxyfuel configuration conducted in 20112012 at the FLSmidth plant in Dania, Denmark, have also confirmed the feasibility of retrofitting for partial oxyfuel operation, as well as the stability of calciner operation and the product quality. Projected commercial-scale capture costs (h50/t-CO2) were shown to be competitive with an amine-based reference case. Further developments toward full commercial deployment can be expected from the ECRA project, which is planning toward a 2018 construction start date for a 5001000 t-clinker/day pilot plant, and also from the EU-funded CEMCAP project, which started in 2015 and will develop pilot- and demonstration-scale tests for full oxyfueling.
5.1.3 Cement production from carbon capture processes Alongside carbon capture from conventional cement production, a number of venture capital companies are developing proprietary post-combustion capture processes that aim to produce cement or cement additives by the precipitation of calcium and magnesium carbonates from seawater reacted with power plant flue gas CO2. This process is described in Chapter 22.
Carbon capture from industrial processes
5.2
107
Steel production
Integrated coal-fueled steel mills accounted for B65% of the 1.5 Gt of global steel produced in 2016, consuming B19 GJ/t-steel produced and emitting a global average of B1.8 t-CO2/t-steel produced. In the first stage of the steelmaking process, highgrade coal (anthracite) is used to fuel a blast furnace in which iron is extracted by reduction from the ore hematite (Fe2O3), using carbon monoxide as the reducing agent. The key reactions taking place in the furnace are as follows. Coal is combusted with oxygen to produce carbon dioxide and heat, while limestone, introduced as a fluxing agent to remove impurities from the iron, is calcined to produce CaO plus CO2 via the same reaction as in cement production (Reaction (5.1)). The CO2 product from these two reactions then reacts with more carbon, producing carbon monoxide: CO2 1 C ! 2CO
(5.6)
Carbon monoxide reduces the hematite ore to produce molten iron (pig iron), which is collected at the base of the furnace: Fe2 O3 1 3CO ! 2Fe 1 3CO2
(5.7)
The calcined limestone combines with impurities to form slag, primarily calcium silicate, which floats on top of the molten iron and can be removed: CaO 1 SiO2 ! CaSiO3
(5.8)
In the second stage of the steelmaking process, known as basic oxygen steelmaking (BOS), the carbon content of pig iron is reduced from a typical 4%5% to 0.1%1% in an oxygen-fired furnace. The excess carbon is oxidized to carbon monoxide, which can be recycled as a fuel gas or used as the reducing agent. At the same time other impurities, such as phosphorus and sulfur, are oxidized to form acidic oxides, neutralized by the addition of lime, and recovered as a slag that has a variety of recycling uses (see, for example, cement production in the previous section, and mineral carbonation in Section 10.3.1). Alloying elements such as chromium, manganese, nickel, and vanadium are also added at this stage to achieve the required steel composition and properties. Blast furnace gases contain close to 30% CO2, after full combustion of the CO fraction, while the overall flue gas stream from an integrated steel mill is B15% CO2. The same CO2 capture options introduced above for power-generation plant can therefore also be applied to a steel mill: G
G
Post-combustion CO2 capture from the overall flue gas stream; amine absorption (Chapter 6), membrane separation (Chapter 8), and hydrate-based capture (Chapter 9) have been studied among others. Firing the blast furnace with oxygen rather than air, yielding a furnace off-gas that is a pure CO and CO2 mixture.
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G
Carbon Capture and Storage
Capturing CO2 in a pre-combustion step and using hydrogen instead of carbon monoxide as the reducing agent in Reaction (5.7); that is:
Fe2 O3 1 3H2 ! 2Fe 1 3H2 O
(5.9)
The oxygen-fired blast furnace option is interesting in that it can reduce CO2 emissions from an integrated steel mill by 40%, even without CCS, due to the reduced coke consumption in the blast furnace. One pre-combustion option that has been developed in the EU-funded CACHET and CAESAR projects is the application of sorption-enhanced water-gas shift reaction to convert blast furnace gas to hydrogen, with CO2 captured in a potassium carbonate hydrotalcite-based sorbent from which it is recovered by a pressure swing. The technology is being further developed under the EU STEPWISE project (see Section 7.2). As an alternative to iron production in a blast furnace, direct-reduced iron (DRI) is produced by reducing iron ore using a mixture of hydrogen and carbon monoxide (Reaction (5.7) and (5.9)) at temperatures of 8001000 C. The first commercial CCS project at a steel plant began operating in November 2016 at the Emirates Steel DRI plant in Mussafah, Abu Dhabi. The plant produces syngas (H2 1 CO) for the direct reduction reactions by steam reforming locally abundant natural gas, and the DRI plant off-gas, containing 98% CO2, in dehydrated, compressed to scCO2 and transported 43 km for EOR at the ADNC operated BAB and Rumaitha oil fields. The project will capture 800 kt-CO2/year when fully operational. Recycling of scrap steel, using electric-powered arc or induction furnaces, accounts for B35% of overall shipped steel volume worldwide, with production of c. 550 Mt-steel reported from this type of process in 2016. Recycled steel is significantly more energy-efficient than new steel production, requiring only B25% of the energy input per unit of steel shipped. A mini-mill typically consumes 4.06.5 GJ/tsteel produced, reducing CO2 emissions by B80% to B0.3 t-CO2/t-steel. Since energy input is in the form of electrical power, the reduction of related CO2 emissions reverts to the discussion of CCS in the power-generation sector.
5.3
Oil refining
Worldwide, CO2 emissions from oil refineries account for B3% of global anthropogenic emissions and amounted to B0.9 Gt-CO2 emitted to the atmosphere in 2015. As noted in Table 2.3, the 2008 IPCC analysis of large point sources identified 638 refineries emitting an average of 1.25 Mt-CO2/year. The crude oil feed to an oil refinery is a mixture of many hydrocarbon components from methane, the lightest with a molecular weight of 16, out to long-chain molecules with molecular weights in the hundreds. The refining process, shown schematically in Figure 5.2, starts by separating out up to 10 “fractions” of this
Carbon capture from industrial processes
109
Refinery gas
Atmospheric distillation
LPG Isomerization
Hydro desulfurization
Vacuum distillation
H2
Residues
Alkylation Hydro cracking
Diesel oil
Oligomerization
Hydro conversion H2
Refinery gas
Premium gasoline
Reforming Crude oil
Catalytic cracking
Partial oxidation Steam reforming
Coke, refinery fuel
Figure 5.2 Oil refining schematic process flow scheme.
mixture by a distillation process under atmospheric pressure. Crude oil is heated to 500700 C and fed to the base of a distillation tower. As the vapor rises and cools, first the heavier and then progressively lighter components condense and are recovered as liquid fractions, with gases recovered from the top of the tower. The heavy residues recovered at the base of this initial distillation still contain significant lighter components, which are recovered in a further distillation under vacuum. The second stage in the process, known as conversion, is the breaking down of larger molecules in the heavy fractions to meet the demand for lighter and highervalue products. This “cracking” process requires the presence of either catalysts (catalytic or cat-cracking), commonly zeolite, aluminum hydrosilicate, and bauxite; steam (steam cracking); or hydrogen (hydrocracking); and temperatures ranging from 400 C (catalytic) up to 850 C (steam). Further distillation is used to separate the products resulting from the cracking process. Other important steps in the conversion process are: G
G
Catalytic reforming: a platinum or platinumrhenium catalyst is used to promote the conversion of distillates in the 100- to 150-molecular weight range (light naphtha) into heavier aromatics for use in gasoline blending and petrochemicals. Hydrogen is a byproduct of this reaction and is commonly used for hydrocracking. Alkylation: a catalyst such as hydrofluoric acid or sulfuric acid is used to convert lowmolecular-weight compounds, such as propylene (C3H6) and butylene (C4H8), into highoctane hydrocarbons used in gasoline blending. Sulfuric acid used in alkylation may be a byproduct from desulfurization (see below).
In upgrading, the final step in the refining process, undesirable compounds are removed and product characteristics are adjusted to comply with delivery
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specifications. Hydrodesulfurization (HDS), or hydrotreating, is an important upgrading step required to meet stringent environmental standards, for example, in producing low-sulfur diesel to reduce SO2 emissions. HDS is achieved by contacting the unfinished products with hydrogen at 370 C and a pressure of 6.0 MPa in the presence of a catalyst such as nickel molybdate (NiMoO4). Sulfur atoms in the hydrocarbons bond with hydrogen to produce hydrogen sulfide (H2S) and are then recovered as elemental sulfur or sulfuric acid. An oil refinery is fueled by burning top-gas from the distillation process, supplemented as needed by additional fuel oil. Some 50% of consumed energy is used to generate process heat while the remaining 50% is used for power generation, hydrogen production for hydrotreatment and hydrocracking, and plant utilities. Refinery energy consumption and attendant CO2 emissions are highly variable and depend strongly on the complexity of the refining processes employed, particularly the “deep conversion” capability required to process heavier crude oils. Typical selfconsumption ranges from 6%8% by weight of the crude oil processed for conventional conversion processes to 11%13% by weight for deep conversion, which has a significantly higher hydrogen requirement. The trend toward greater demand for lighter refined products will result in upward pressure on self-consumption in the future, making energy efficiency, process integration, and carbon capture important if growth in emissions from this sector is to be avoided. Options for capturing CO2 in the refining processes include the integration of power generation and hydrogen production in an IGCC plant, which achieves precombustion capture of CO2. Emissions from process heating can be captured either by oxyfueling or by post-combustion capture from the heater flue gases, or by also integrating process heat production into an IGCCCHP plant.
5.4
Natural gas processing
Natural gas, produced either from gas fields or as associated gas with oil production, contains varying amounts of non-hydrocarbon gases, of which CO2, N2, and H2S are the most common examples. Many large natural gas fields have CO2 concentrations of up to 20%, while some fields with . 50% CO2 are also produced. Indonesia’s Natuna field is an extreme example for commercial natural gas production and contains 71% CO2. The volume of CO2 currently produced with natural gas has been estimated at 50 Mt-CO2/year and is therefore modest compared to global emissions. However, the removal of acid gases such as CO2 and H2S from natural gas—a process known as gas sweetening—is important because the technologies developed in this area have broader application for CO2 capture in areas such as power generation. Natural gas consumption is also projected to grow more rapidly than other fossil fuels, in part due to its lower carbon intensity as a power-plant fuel. Exploitation of more difficult gas reserves, often with higher CO2 content, will also require capture and storage if increasing emissions from this sector are to be avoided.
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CO2 removal from natural gas is now a mature technology that has been applied on an industrial scale since the 1980s. The end-use specification, whether for pipeline transport into a supply grid or for liquefaction and onward transport as liquefied natural gas (LNG), requires the CO2 concentration to be reduced to 23 mol%. Various technologies have been applied, including physical and chemical solvents, membranes, and cryogenic separation, with the preferred technology in any specific application depending on the feedstock and required output compositions. Statoil’s Sleipner field development in Norway is the longest running example of CCS from natural gas, in this case associated gas from oil production; since start-up in 1996, about 1 Mt-CO2 has been captured each year by amine absorption and injected into the underlying Utsira aquifer. The details of specific technologies and applications in natural gas processing are covered in Chapters 69, while further references to the Sleipner project will be found throughout Part III.
5.5
Pulp and paper production
The global paper and pulp industry accounts for around 2% of total direct CO2 emissions from industrial sources—around 0.5 Gt-CO2/year. Worldwide, the most commonly used papermaking process is the Kraft process, in which chemicals are used to free cellulose fibers in the raw material from the lignin binding agent. The main steps in the Kraft process, using wood as the raw material, are shown schematically in Figure 5.3 (optional steps shown in lighter shading). After debarking and chipping the raw material, extraction of the cellulose fibers to be used in papermaking is achieved in the Kraft process by the addition of sodium sulfide (chemical pulping). Other processes use
Pulp making
Wood preparation
Chemical pulping
Chemical recovery
Bleaching
Pulp drying
Lime kiln
Market pulp
Paper making
Forming
Stock preparation
Re-pulping
Pressing
Pre-drying
Surface treatment
Finishing
Final drying
Paper/board product
Figure 5.3 Schematic flow diagram of the Kraft pulping and papermaking process. Source: After Kong, Hasanbeigi, and Price, 2014.
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mechanical and thermo-mechanical methods to separate the fibers but these are more energy intensive. The digested pulp is then separated into three components; “black liquor”—containing dissolved combustible components such as lignin and hemicellulose—is evaporated and combusted as fuel, and the pulping chemicals are recovered from the residual “green liquor” by the addition of lime (CaO) in a causticizer. The resulting lime mud (CaCO 3) is regenerated in a lime kiln—identical to the calcination step in cement production (see Reaction (5.1)). The most energy-intensive steps in the papermaking process are drying of the final paper product (25%30% of total energy requirement), evaporation of black liquor during chemical recovery, and lime mud calcination in the lime kiln, the latter also generating high levels of process CO2. Most paper mills include their own power generation island and the main CO2 mitigation option is in applying the capture technologies described in Chapter 4 to these plants. The byproducts of raw material preparation (e.g., wood bark and fines) and the chemical pulping process (e.g., concentrated black liquor) are also used to fuel power generation, either in conventional boilers or in more efficient gasification combined cycle plant. These fuels are also combusted directly in process boilers, for example, in black liquor evaporation which is a major energyconsuming step, and CO2 capture from these boilers—by either post-combustion or oxyfueling—will be important to minimize emissions. Process CO2 from the lime kiln can also be captured using the approaches described above for the cement industry, such as oxyfuel combustion in the kiln. Residues such as boiler ash from various parts of the process can also be used as a raw material for the production of PCC. This is an important mineral filler used in paper production and the production process, which also captures CO2, is described in Chapter 22. Because the carbon capture opportunities in the pulp and paper industry follow closely on those in the power and cement industries, industry-specific work has been limited to desk studies and reviews. As well as the financial hurdles, the need for a well-established and geographically dispersed transportation and storage infrastructure is noted as an important enabler, particularly since many mills emit less than 0.5 Mt-CO2/year. It is also worth noting that a large part of the CO2 emitted by the industry—almost 80% in Europe—results from biofuel combustion, and energy efficiency improvements could reduce the fossil fuel use or energy import of many mills to zero. CCS in the pulp and paper industry would therefore be largely BECCS, and wide application would make the industry carbon negative.
Carbon capture from industrial processes
5.6
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References and resources
5.6.1 References Bjerge, L., 2015. Norcem CO2 Capture Project. Presented at the TEKNA CO2 Conference, Trondheim, Norway. 9 January 2015. Carrasco-Maldonadoa, F., Spo¨rl, R., Fleiger, K., Hoenig, V., Maier, J., Scheffknecht, G., 2016. Oxy-fuel combustion technology for cement production—state of the art research and technology development. Int. J. Greenhouse Gas Control. 45, 189199. Decroocq, D., 2003. Energy conservation and CO2 emissions in the processing and use of oil and gas. Revue de l’Institut Franc¸ais du Pe´trole, Oil & Gas Science and Technology. 58, 331342. Gazzani, M., Romano, M.C., Manzolini, G., 2015. CO2 capture in integrated steelworks by commercial-ready technologies and SEWGS process. Int. J. Greenhouse Gas Control. 41, 249267. Gielen, D.J., 2003. CO2 removal in the iron and steel industry. Energy Convers. Manage. 44, 10271037. Hasanbeigi, A., Arens, M., Price, L., 2014. Alternative emerging iron making technologies for energy-efficiency and carbon dioxide emissions reduction: a technical review. Renewable Sustainable Energy Rev. 33, 645658. Hoenig, V., Hoppe, H., Emberger, B., 2007. Carbon Capture Technology—Options and Potentials for the Cement Industry. European Cement Research Academy, Report TR 044/2007. IEAGHG, 1999. The Reduction of Greenhouse Gas Emissions from the Cement Industry. IEA Greenhouse Gas R&D Programme, Cheltenham, UK, Report PH3/7. Knudsen, J.N., Bade, O.M., Askestad, I., Gorset, O., Mejdell, T., 2015. Pilot plant demonstration of CO2 capture from cement plant with advanced amine technology. Energy Procedia. 63, 64646475. Kong, L., Hasanbeigi, A., Price, L., 2014. Emerging Energy-Efficiency and Greenhouse Gas Mitigation Technologies for the Pulp and Paper Industry. Lawrence Berkeley National Laboratory, USA, LBNL Paper LBNL-5956E. Kuramochi, T., Ramı´rez, A., Turkenburg, W., Faaij, A., 2012. Comparative assessment of CO2 capture technologies for carbon-intensive industrial processes. Prog. Energy Combust. Sci. 38, 87112. Mollersten, K., Gao, L., Yan, J.-Y., Obersteiner, M., 2004. Efficient energy systems with CO2 capture and storage from renewable biomass in pulp and paper mills. Renewable Energy. 29, 15831598. Schneider, M., 2015. ECRA’s Oxyfuel Project. Presented at the International CCS Conference, Langesund, Norway. 2021 May 2015. Wilkinson, M.B., et al., 2003. CO2 capture from oil refinery process heaters through oxyfuel combustion. In: Gale, J., Kaya, Y. (Eds.), Proceedings of the Sixth International Conference on Greenhouse Gas Control Technologies. Elsevier, Oxford, UK.
5.6.2 Resources CEMCAP (EU Horizon 2020 funded project to reduce emissions from cement production): www.sintef.no/projectweb/cemcap. Concrete Sustainability Hub (MIT research group dedicated to improving the sustainability of concrete production and use): cshub.mit.edu.
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ECRA (ongoing steel industry CCS project): www.ecra-online.de. Norcem (developing capture technology for the cement industry): www.norcem.no/en/ carbon_capture. Technische Universita¨t Hamburg-Harburg (oxyfuel cement production RD&D): www.tuharburg.de/alt/iet/research.html. World Steel Association (global steel industry approach to CO2 emissions reduction): www. worldsteel.org/publications/position-papers/Steel-s-contribution-to-a-low-carbon-future. html. EU STEPWISE project: www.stepwise.eu.
5
Although fossil-fueled power-generation plant accounts for the majority of large stationary sources emitting .0.1 Mt-CO2/year, similar quantities are also emitted from single sources in a number of other industries and are therefore targets for the application of carbon capture technologies. Industrial activity (excluding consumption of electrical power) accounts for around one-fifth of global CO2 emission, the most important of these emitters—cement production, iron and steel production, oil refining, and natural gas processing—are dealt with in this chapter.
5.1
Cement production
Worldwide cement production results in the emission of B2 Gt-CO2 (2015—at a global average CO2 intensity of 0.8 t-CO2/t-cement), some 5% of total anthropogenic CO2 emissions. These emissions are split roughly equally between CO2 emitted from the calcination process (B52%) and emissions from the combustion of fuel to fire cement kilns (B48%). Portland cement is a mixture of predominantly di- and tricalcium silicates (2CaO SiO2, 3CaO SiO2), with smaller amounts of other compounds such as calcium sulfate (CaSO4), magnesium, aluminum and iron oxides, and tricalcium aluminate (3CaO Al2O3). The cement production process is shown schematically in Figure 5.1. After pre-heating, the milled raw feed is calcined at B860 C and then a controlled mixture of materials is sintered in a kiln, typically a horizontal rotary kiln, at a temperature of B1450 C. Calcium carbonate (CaCO3) is the primary raw material and may be in the form of crushed limestone, shells, or chalk. A variety of secondary raw materials are used as the source of silica and other minerals, including sand, shale, clay, blast furnace slag, and coal ash. The latter may be introduced directly by firing the cement kiln with pulverized coal or by importing fly or bottom ash from a coal-fired power plant. The main reaction taking place in the process is the conversion or calcining of calcium carbonate to calcium oxide, a highly endothermic reaction requiring 3.56.0 GJ/t-cement produced, depending on plant efficiency. Calcination and the other main chemical reactions proceed as follows: CaCO3 1 heat ! CaO 1 CO2
(5.1)
2CaO 1 SiO2 ! 2CaO SiO2 ðBelliteÞ
(5.2)
Carbon Capture and Storage. DOI: http://dx.doi.org/10.1016/B978-0-12-812041-5.00005-2 © 2017 Elsevier Inc. All rights reserved.
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Limestone Milling Fly ash, blast furnace slag, etc.
Filtering (bag house)
Raw meal pre-heat
Raw meal silo
Rotary clinker kiln
Precalciner
Fuel Air
Clinker
Cooling
Milling
Bagging
Figure 5.1 Cement production process.
3CaO 1 Al2 O3 ! 3CaO Al2 O3
(5.3)
4CaO 1 Al2 O3 1 Fe2 O3 ! 4CaO Al2 O3 Fe2 O3
(5.4)
CaO 1 2CaO SiO2 ! 3CaO SiO2 ðAliteÞ
(5.5)
The CO2 released in the initial calcining reaction in Reaction (5.1), known as the process CO2, combined with the CO2 from combustion of the kiln fuel (coal, oil, or natural gas) yields a flue gas with a [CO2] in the range of 14%33%.
5.1.1 Post-combustion capture from cement plants Capture of CO2 from the combined flue gas can be achieved using the technologies applicable to post-combustion capture from power-generation plants, including chemical and physical solvents (Section 6.2); sorbents, particularly hightemperature sorbents (Section 7.1); and membranes (Section 8.7). Compared to “conventional” post-combustion applications, the higher [CO2] enables these technologies to achieve higher separation efficiencies in cement plant applications. Calcium looping (CaL—see Section 6.3) is widely seen as an obvious postcombustion technology for cement plants, in view of the synergy in handling and processing of the common raw materials, as well as the potential for close process integration and for purge CaO to be used in cement production. CaL was one of the four technologies that has been investigated in a 4-year project, commencing in 2014 at the Norcem operated cement plant at Brevik, Norway. The preliminary results and planned next steps in this project are summarized in Table 5.1. The advanced amine pilot was particularly successful and demonstrated the feasibility of capturing 400 kt-CO2/year, almost 50% of the Brevik plant’s total
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Table 5.1 Preliminary results and next steps in Norcem pilot tests Technology Description and preliminary results
Next steps
Amine 16-month pilot test of proprietary solvent absorption (S26) using Aker Solutions mobile testing unit; robust operation with . 90% capture rate, energy consumption lower than seen in other applications; degradation, consumption, and emissions of amines and degraded products also low; assessed TRL 9 (proven in operational environment) Solid 3-month trial of bench-scale fluidized bed sorbent reactor; assessed TRL 5 (technology valid in relevant environment) Membranes 6-month bench-scale trial using polyvinylamide (PVAm) membranes; promising membrane durability yielding 60%70% CO2 recovery; assessed TRL 5 Calcium 1-year study and lab-scale pilot; more looping rapid sorbent degradation than expected; assessed TRL 3 (experimental proof of concept)
Conceptual study commenced in 2015 for large-scale capture plant
Further testing planned with largescale pilot, aiming to achieve higher sorbent loading Immature Phase II concept led to project termination; new consortium being established to progress Phase II Developing larger scale pilot
emissions, using waste heat alone for solvent regeneration. This was considered to be the only technology likely to be mature enough for commercial deployment in the 2020 timeframe.
5.1.2 Oxygen enrichment and oxyfuel processes The addition of oxygen to the air drafting the burners—the so-called oxygen enrichment—has been practiced in cement kilns since the early 1960s and results in increased clinker production and reduced fuel consumption. Fuel consumption is reduced in part because nitrogen in the air does not need to be heated up to combustion temperature. Oxygen enrichment increases flame temperatures (to B3500 C), which has an impact on kiln refractory design and materials, and also increases [CO2] in the kiln flue gas stream, which, as noted previously, further aids post-combustion capture. Oxyfueling can also be applied as a cement plant capture technology, either in partial or full oxyfuel configurations. In a partial oxyfuel configuration only the calcining step takes place under oxygen and 60%75% of the process CO2 can be captured, while for full oxyfueling, with both the calciner and kiln operating under oxy-combustion conditions, a capture rate greater than 90% is possible. Apart from the provision
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Table 5.2 Research and development issues for oxyfuel cement production R&D
Description
[CO2] impact on reaction kinetics Burner design
Assessing the impact of high [CO2] on calcination and clinker quality Development of oxygen-drafted burners for clinker kilns, paralleling work on burners for oxyfuel steam boilers Durability of kiln refractory lining Optimal cooling systems for full oxyfuel configurations Process modeling, addressing the impact of oxyfuel on flue gas enthalpy and recirculation, heat transfer phenomena, energy demand optimization, and material flows
Kiln lining Clinker cooling Plant and process simulation
of an ASU, plant modifications are required to the calciner and pre-heaters in the case of a partial configuration and to the kiln burners, flue gas recycle (to control kiln temperature) and clinker coolers in the full oxyfuel configuration. In both cases attention would also be required to seals to prevent air ingress diluting the 85%90% CO2 off-gas stream, which could be directly compressed for transportation and storage after dehydration and possibly FGD. Research into oxyfuel technology for cement production has been ongoing since 2007, when the European Cement Research Academy started a long-term carbon CCS project. Phases I to III of this project (20072011) included technical studies and lab-scale research on both post-combustion and oxyfuel options and subsequent phases will focus on the oxyfuel route. Research topics being addressed by this and other ongoing projects are summarized in Table 5.2. Pilot-scale trials of a partial oxyfuel configuration conducted in 20112012 at the FLSmidth plant in Dania, Denmark, have also confirmed the feasibility of retrofitting for partial oxyfuel operation, as well as the stability of calciner operation and the product quality. Projected commercial-scale capture costs (h50/t-CO2) were shown to be competitive with an amine-based reference case. Further developments toward full commercial deployment can be expected from the ECRA project, which is planning toward a 2018 construction start date for a 5001000 t-clinker/day pilot plant, and also from the EU-funded CEMCAP project, which started in 2015 and will develop pilot- and demonstration-scale tests for full oxyfueling.
5.1.3 Cement production from carbon capture processes Alongside carbon capture from conventional cement production, a number of venture capital companies are developing proprietary post-combustion capture processes that aim to produce cement or cement additives by the precipitation of calcium and magnesium carbonates from seawater reacted with power plant flue gas CO2. This process is described in Chapter 22.
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Steel production
Integrated coal-fueled steel mills accounted for B65% of the 1.5 Gt of global steel produced in 2016, consuming B19 GJ/t-steel produced and emitting a global average of B1.8 t-CO2/t-steel produced. In the first stage of the steelmaking process, highgrade coal (anthracite) is used to fuel a blast furnace in which iron is extracted by reduction from the ore hematite (Fe2O3), using carbon monoxide as the reducing agent. The key reactions taking place in the furnace are as follows. Coal is combusted with oxygen to produce carbon dioxide and heat, while limestone, introduced as a fluxing agent to remove impurities from the iron, is calcined to produce CaO plus CO2 via the same reaction as in cement production (Reaction (5.1)). The CO2 product from these two reactions then reacts with more carbon, producing carbon monoxide: CO2 1 C ! 2CO
(5.6)
Carbon monoxide reduces the hematite ore to produce molten iron (pig iron), which is collected at the base of the furnace: Fe2 O3 1 3CO ! 2Fe 1 3CO2
(5.7)
The calcined limestone combines with impurities to form slag, primarily calcium silicate, which floats on top of the molten iron and can be removed: CaO 1 SiO2 ! CaSiO3
(5.8)
In the second stage of the steelmaking process, known as basic oxygen steelmaking (BOS), the carbon content of pig iron is reduced from a typical 4%5% to 0.1%1% in an oxygen-fired furnace. The excess carbon is oxidized to carbon monoxide, which can be recycled as a fuel gas or used as the reducing agent. At the same time other impurities, such as phosphorus and sulfur, are oxidized to form acidic oxides, neutralized by the addition of lime, and recovered as a slag that has a variety of recycling uses (see, for example, cement production in the previous section, and mineral carbonation in Section 10.3.1). Alloying elements such as chromium, manganese, nickel, and vanadium are also added at this stage to achieve the required steel composition and properties. Blast furnace gases contain close to 30% CO2, after full combustion of the CO fraction, while the overall flue gas stream from an integrated steel mill is B15% CO2. The same CO2 capture options introduced above for power-generation plant can therefore also be applied to a steel mill: G
G
Post-combustion CO2 capture from the overall flue gas stream; amine absorption (Chapter 6), membrane separation (Chapter 8), and hydrate-based capture (Chapter 9) have been studied among others. Firing the blast furnace with oxygen rather than air, yielding a furnace off-gas that is a pure CO and CO2 mixture.
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Capturing CO2 in a pre-combustion step and using hydrogen instead of carbon monoxide as the reducing agent in Reaction (5.7); that is:
Fe2 O3 1 3H2 ! 2Fe 1 3H2 O
(5.9)
The oxygen-fired blast furnace option is interesting in that it can reduce CO2 emissions from an integrated steel mill by 40%, even without CCS, due to the reduced coke consumption in the blast furnace. One pre-combustion option that has been developed in the EU-funded CACHET and CAESAR projects is the application of sorption-enhanced water-gas shift reaction to convert blast furnace gas to hydrogen, with CO2 captured in a potassium carbonate hydrotalcite-based sorbent from which it is recovered by a pressure swing. The technology is being further developed under the EU STEPWISE project (see Section 7.2). As an alternative to iron production in a blast furnace, direct-reduced iron (DRI) is produced by reducing iron ore using a mixture of hydrogen and carbon monoxide (Reaction (5.7) and (5.9)) at temperatures of 8001000 C. The first commercial CCS project at a steel plant began operating in November 2016 at the Emirates Steel DRI plant in Mussafah, Abu Dhabi. The plant produces syngas (H2 1 CO) for the direct reduction reactions by steam reforming locally abundant natural gas, and the DRI plant off-gas, containing 98% CO2, in dehydrated, compressed to scCO2 and transported 43 km for EOR at the ADNC operated BAB and Rumaitha oil fields. The project will capture 800 kt-CO2/year when fully operational. Recycling of scrap steel, using electric-powered arc or induction furnaces, accounts for B35% of overall shipped steel volume worldwide, with production of c. 550 Mt-steel reported from this type of process in 2016. Recycled steel is significantly more energy-efficient than new steel production, requiring only B25% of the energy input per unit of steel shipped. A mini-mill typically consumes 4.06.5 GJ/tsteel produced, reducing CO2 emissions by B80% to B0.3 t-CO2/t-steel. Since energy input is in the form of electrical power, the reduction of related CO2 emissions reverts to the discussion of CCS in the power-generation sector.
5.3
Oil refining
Worldwide, CO2 emissions from oil refineries account for B3% of global anthropogenic emissions and amounted to B0.9 Gt-CO2 emitted to the atmosphere in 2015. As noted in Table 2.3, the 2008 IPCC analysis of large point sources identified 638 refineries emitting an average of 1.25 Mt-CO2/year. The crude oil feed to an oil refinery is a mixture of many hydrocarbon components from methane, the lightest with a molecular weight of 16, out to long-chain molecules with molecular weights in the hundreds. The refining process, shown schematically in Figure 5.2, starts by separating out up to 10 “fractions” of this
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Refinery gas
Atmospheric distillation
LPG Isomerization
Hydro desulfurization
Vacuum distillation
H2
Residues
Alkylation Hydro cracking
Diesel oil
Oligomerization
Hydro conversion H2
Refinery gas
Premium gasoline
Reforming Crude oil
Catalytic cracking
Partial oxidation Steam reforming
Coke, refinery fuel
Figure 5.2 Oil refining schematic process flow scheme.
mixture by a distillation process under atmospheric pressure. Crude oil is heated to 500700 C and fed to the base of a distillation tower. As the vapor rises and cools, first the heavier and then progressively lighter components condense and are recovered as liquid fractions, with gases recovered from the top of the tower. The heavy residues recovered at the base of this initial distillation still contain significant lighter components, which are recovered in a further distillation under vacuum. The second stage in the process, known as conversion, is the breaking down of larger molecules in the heavy fractions to meet the demand for lighter and highervalue products. This “cracking” process requires the presence of either catalysts (catalytic or cat-cracking), commonly zeolite, aluminum hydrosilicate, and bauxite; steam (steam cracking); or hydrogen (hydrocracking); and temperatures ranging from 400 C (catalytic) up to 850 C (steam). Further distillation is used to separate the products resulting from the cracking process. Other important steps in the conversion process are: G
G
Catalytic reforming: a platinum or platinumrhenium catalyst is used to promote the conversion of distillates in the 100- to 150-molecular weight range (light naphtha) into heavier aromatics for use in gasoline blending and petrochemicals. Hydrogen is a byproduct of this reaction and is commonly used for hydrocracking. Alkylation: a catalyst such as hydrofluoric acid or sulfuric acid is used to convert lowmolecular-weight compounds, such as propylene (C3H6) and butylene (C4H8), into highoctane hydrocarbons used in gasoline blending. Sulfuric acid used in alkylation may be a byproduct from desulfurization (see below).
In upgrading, the final step in the refining process, undesirable compounds are removed and product characteristics are adjusted to comply with delivery
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specifications. Hydrodesulfurization (HDS), or hydrotreating, is an important upgrading step required to meet stringent environmental standards, for example, in producing low-sulfur diesel to reduce SO2 emissions. HDS is achieved by contacting the unfinished products with hydrogen at 370 C and a pressure of 6.0 MPa in the presence of a catalyst such as nickel molybdate (NiMoO4). Sulfur atoms in the hydrocarbons bond with hydrogen to produce hydrogen sulfide (H2S) and are then recovered as elemental sulfur or sulfuric acid. An oil refinery is fueled by burning top-gas from the distillation process, supplemented as needed by additional fuel oil. Some 50% of consumed energy is used to generate process heat while the remaining 50% is used for power generation, hydrogen production for hydrotreatment and hydrocracking, and plant utilities. Refinery energy consumption and attendant CO2 emissions are highly variable and depend strongly on the complexity of the refining processes employed, particularly the “deep conversion” capability required to process heavier crude oils. Typical selfconsumption ranges from 6%8% by weight of the crude oil processed for conventional conversion processes to 11%13% by weight for deep conversion, which has a significantly higher hydrogen requirement. The trend toward greater demand for lighter refined products will result in upward pressure on self-consumption in the future, making energy efficiency, process integration, and carbon capture important if growth in emissions from this sector is to be avoided. Options for capturing CO2 in the refining processes include the integration of power generation and hydrogen production in an IGCC plant, which achieves precombustion capture of CO2. Emissions from process heating can be captured either by oxyfueling or by post-combustion capture from the heater flue gases, or by also integrating process heat production into an IGCCCHP plant.
5.4
Natural gas processing
Natural gas, produced either from gas fields or as associated gas with oil production, contains varying amounts of non-hydrocarbon gases, of which CO2, N2, and H2S are the most common examples. Many large natural gas fields have CO2 concentrations of up to 20%, while some fields with . 50% CO2 are also produced. Indonesia’s Natuna field is an extreme example for commercial natural gas production and contains 71% CO2. The volume of CO2 currently produced with natural gas has been estimated at 50 Mt-CO2/year and is therefore modest compared to global emissions. However, the removal of acid gases such as CO2 and H2S from natural gas—a process known as gas sweetening—is important because the technologies developed in this area have broader application for CO2 capture in areas such as power generation. Natural gas consumption is also projected to grow more rapidly than other fossil fuels, in part due to its lower carbon intensity as a power-plant fuel. Exploitation of more difficult gas reserves, often with higher CO2 content, will also require capture and storage if increasing emissions from this sector are to be avoided.
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CO2 removal from natural gas is now a mature technology that has been applied on an industrial scale since the 1980s. The end-use specification, whether for pipeline transport into a supply grid or for liquefaction and onward transport as liquefied natural gas (LNG), requires the CO2 concentration to be reduced to 23 mol%. Various technologies have been applied, including physical and chemical solvents, membranes, and cryogenic separation, with the preferred technology in any specific application depending on the feedstock and required output compositions. Statoil’s Sleipner field development in Norway is the longest running example of CCS from natural gas, in this case associated gas from oil production; since start-up in 1996, about 1 Mt-CO2 has been captured each year by amine absorption and injected into the underlying Utsira aquifer. The details of specific technologies and applications in natural gas processing are covered in Chapters 69, while further references to the Sleipner project will be found throughout Part III.
5.5
Pulp and paper production
The global paper and pulp industry accounts for around 2% of total direct CO2 emissions from industrial sources—around 0.5 Gt-CO2/year. Worldwide, the most commonly used papermaking process is the Kraft process, in which chemicals are used to free cellulose fibers in the raw material from the lignin binding agent. The main steps in the Kraft process, using wood as the raw material, are shown schematically in Figure 5.3 (optional steps shown in lighter shading). After debarking and chipping the raw material, extraction of the cellulose fibers to be used in papermaking is achieved in the Kraft process by the addition of sodium sulfide (chemical pulping). Other processes use
Pulp making
Wood preparation
Chemical pulping
Chemical recovery
Bleaching
Pulp drying
Lime kiln
Market pulp
Paper making
Forming
Stock preparation
Re-pulping
Pressing
Pre-drying
Surface treatment
Finishing
Final drying
Paper/board product
Figure 5.3 Schematic flow diagram of the Kraft pulping and papermaking process. Source: After Kong, Hasanbeigi, and Price, 2014.
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mechanical and thermo-mechanical methods to separate the fibers but these are more energy intensive. The digested pulp is then separated into three components; “black liquor”—containing dissolved combustible components such as lignin and hemicellulose—is evaporated and combusted as fuel, and the pulping chemicals are recovered from the residual “green liquor” by the addition of lime (CaO) in a causticizer. The resulting lime mud (CaCO 3) is regenerated in a lime kiln—identical to the calcination step in cement production (see Reaction (5.1)). The most energy-intensive steps in the papermaking process are drying of the final paper product (25%30% of total energy requirement), evaporation of black liquor during chemical recovery, and lime mud calcination in the lime kiln, the latter also generating high levels of process CO2. Most paper mills include their own power generation island and the main CO2 mitigation option is in applying the capture technologies described in Chapter 4 to these plants. The byproducts of raw material preparation (e.g., wood bark and fines) and the chemical pulping process (e.g., concentrated black liquor) are also used to fuel power generation, either in conventional boilers or in more efficient gasification combined cycle plant. These fuels are also combusted directly in process boilers, for example, in black liquor evaporation which is a major energyconsuming step, and CO2 capture from these boilers—by either post-combustion or oxyfueling—will be important to minimize emissions. Process CO2 from the lime kiln can also be captured using the approaches described above for the cement industry, such as oxyfuel combustion in the kiln. Residues such as boiler ash from various parts of the process can also be used as a raw material for the production of PCC. This is an important mineral filler used in paper production and the production process, which also captures CO2, is described in Chapter 22. Because the carbon capture opportunities in the pulp and paper industry follow closely on those in the power and cement industries, industry-specific work has been limited to desk studies and reviews. As well as the financial hurdles, the need for a well-established and geographically dispersed transportation and storage infrastructure is noted as an important enabler, particularly since many mills emit less than 0.5 Mt-CO2/year. It is also worth noting that a large part of the CO2 emitted by the industry—almost 80% in Europe—results from biofuel combustion, and energy efficiency improvements could reduce the fossil fuel use or energy import of many mills to zero. CCS in the pulp and paper industry would therefore be largely BECCS, and wide application would make the industry carbon negative.
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5.6
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References and resources
5.6.1 References Bjerge, L., 2015. Norcem CO2 Capture Project. Presented at the TEKNA CO2 Conference, Trondheim, Norway. 9 January 2015. Carrasco-Maldonadoa, F., Spo¨rl, R., Fleiger, K., Hoenig, V., Maier, J., Scheffknecht, G., 2016. Oxy-fuel combustion technology for cement production—state of the art research and technology development. Int. J. Greenhouse Gas Control. 45, 189199. Decroocq, D., 2003. Energy conservation and CO2 emissions in the processing and use of oil and gas. Revue de l’Institut Franc¸ais du Pe´trole, Oil & Gas Science and Technology. 58, 331342. Gazzani, M., Romano, M.C., Manzolini, G., 2015. CO2 capture in integrated steelworks by commercial-ready technologies and SEWGS process. Int. J. Greenhouse Gas Control. 41, 249267. Gielen, D.J., 2003. CO2 removal in the iron and steel industry. Energy Convers. Manage. 44, 10271037. Hasanbeigi, A., Arens, M., Price, L., 2014. Alternative emerging iron making technologies for energy-efficiency and carbon dioxide emissions reduction: a technical review. Renewable Sustainable Energy Rev. 33, 645658. Hoenig, V., Hoppe, H., Emberger, B., 2007. Carbon Capture Technology—Options and Potentials for the Cement Industry. European Cement Research Academy, Report TR 044/2007. IEAGHG, 1999. The Reduction of Greenhouse Gas Emissions from the Cement Industry. IEA Greenhouse Gas R&D Programme, Cheltenham, UK, Report PH3/7. Knudsen, J.N., Bade, O.M., Askestad, I., Gorset, O., Mejdell, T., 2015. Pilot plant demonstration of CO2 capture from cement plant with advanced amine technology. Energy Procedia. 63, 64646475. Kong, L., Hasanbeigi, A., Price, L., 2014. Emerging Energy-Efficiency and Greenhouse Gas Mitigation Technologies for the Pulp and Paper Industry. Lawrence Berkeley National Laboratory, USA, LBNL Paper LBNL-5956E. Kuramochi, T., Ramı´rez, A., Turkenburg, W., Faaij, A., 2012. Comparative assessment of CO2 capture technologies for carbon-intensive industrial processes. Prog. Energy Combust. Sci. 38, 87112. Mollersten, K., Gao, L., Yan, J.-Y., Obersteiner, M., 2004. Efficient energy systems with CO2 capture and storage from renewable biomass in pulp and paper mills. Renewable Energy. 29, 15831598. Schneider, M., 2015. ECRA’s Oxyfuel Project. Presented at the International CCS Conference, Langesund, Norway. 2021 May 2015. Wilkinson, M.B., et al., 2003. CO2 capture from oil refinery process heaters through oxyfuel combustion. In: Gale, J., Kaya, Y. (Eds.), Proceedings of the Sixth International Conference on Greenhouse Gas Control Technologies. Elsevier, Oxford, UK.
5.6.2 Resources CEMCAP (EU Horizon 2020 funded project to reduce emissions from cement production): www.sintef.no/projectweb/cemcap. Concrete Sustainability Hub (MIT research group dedicated to improving the sustainability of concrete production and use): cshub.mit.edu.
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ECRA (ongoing steel industry CCS project): www.ecra-online.de. Norcem (developing capture technology for the cement industry): www.norcem.no/en/ carbon_capture. Technische Universita¨t Hamburg-Harburg (oxyfuel cement production RD&D): www.tuharburg.de/alt/iet/research.html. World Steel Association (global steel industry approach to CO2 emissions reduction): www. worldsteel.org/publications/position-papers/Steel-s-contribution-to-a-low-carbon-future. html. EU STEPWISE project: www.stepwise.eu.