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Process heat applications of HTR-PM600 in Chinese petrochemical industry: Preliminary study of adaptability and economy
Annals of Nuclear Energy 110 (2017) 73–78
Contents lists available at ScienceDirect
Annals of Nuclear Energy journal homepage: www.elsevier.com/locate/anucene
Process heat applications of HTR-PM600 in Chinese petrochemical industry: Preliminary study of adaptability and economy Chao Fang ⇑, Qi Min, Yanran Yang, Yuliang Sun Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China Collaborative Innovation Center of Advanced Nuclear Energy Technology, Beijing 100084, China The Key Laboratory of Advanced Reactor Engineering and Safety, Ministry of Education, Beijing 100084, China
a r t i c l e
i n f o
Article history: Received 23 January 2017 Received in revised form 14 April 2017 Accepted 13 June 2017
Keywords: HTR-PM600 Process heat applications Petrochemical industry
a b s t r a c t High Temperature Gas Cooled Reactor (HTGR) could work as heat source for petrochemical industry. In this article, the preliminary feasibility of a 600 MW modular HTGR (HTR-PM600) working as heat source for a typical hypothetical Chinese petrochemical factory is discussed and it is found that the joint of HTRPM600 and petrochemical industry is achievable. In detail, the heat and water balance analysis of the petrochemical factory is given. Furthermore, the direct cost of heat supplied by HTR-PM600 is calculated and corresponding economy is estimated. The results show that though there are several challenges, the application of process heat of HTGR to petrochemical industry is practical in sense of both technology and economy. Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction High Temperature Gas Cooled Reactor (HTGR) with the feature of inherent safety is considered as a kind of promising Gen IV nuclear power system. In addition to generating electricity efficiently, the HTGR is also an potential choice for producing hydrogen, industrial heat application and cogeneration cycle, which could reduce the fossil fuel consumption and greenhouse gas emission during the technical process. Specially, HTGR is the only candidate that can supply high temperature process heat for industrial application, which will make it stand out in the process heat supply market compared with other nuclear reactors (Idaho National Laboratory, 2010). Because of its excellent characteristics, HTGR is thought to be used in the petrochemical industry (Idaho National Laboratory, 2011). In China, the petrochemical factory consists of refinery plants and chemical plants. Most refinery plants use an upstream device that consists of several sets of crude oil distillation and a downstream device consists of more than ten sets of secondary processing facilities. Most chemical plants use the upstream device consists of several sets of ethylene units, aromatic complex units, ammonia synthesis units, and chlor-alkali units, etc. and the downstream part usually consists of more than
⇑ Corresponding author at: Energy Science Building A302, Tsinghua University, Haidian District, Beijing 100084, China. E-mail address: [email protected] (C. Fang). http://dx.doi.org/10.1016/j.anucene.2017.06.024 0306-4549/Ó 2017 Elsevier Ltd. All rights reserved.
ten sets of chemical process units. All the units need heated steam and the parameters of steam are distinguishing in different units. In different countries, the design and corresponding arrangement of petrochemical factory is different so as a preliminary feasibility study, we only focus on Chinese petrochemical factory. In this article, the adaptabilities of 600 MW modular HTGR (HTRPM600) as heat source to a hypothetical Chinese petrochemical factory are studied and the corresponding technical economic analysis is given, which is an exploration of the application of HTGR process heat to the petrochemical industry.
2. Scheme of HTGR process heat supply in petrochemical factory Fig. 1 shows a representative flow chat of a hypothetical Chinese petrochemical factory with 10,000,000 t/year of petroleum refining and 1,000,000 t/year of ethylene producing. The left part shows the petroleum refin plant consisting of 10 main facilities and the right part shows ethylene producing plant (chemical plant) consisting of 12 main facilities. The corresponding technical parameters and quantity demanding of the steam are also shown and the precision of data is suitable for calculating the balance of heat and water. It is found that there are four different steam pipe networks: ultra-high pressure steam (12.0 MPaG, 490 °C), high pressure steam (4.0 MPaG, 420 °C), medium pressure steam (1.0– 1.2 MPaG, 260–290 °C) and low pressure steam (0.35–0.4 MPaG, 190 °C).
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C. Fang et al. / Annals of Nuclear Energy 110 (2017) 73–78
Fig. 1. Chart of a Hypothetical Chinese Petrochemical Factory with 10,000,000 t/year of Petroleum refining and 1,000,000 t/year of Ethylene Producing (Unit: t/h).
According to the calculation of steam quantity, the refinery plant needs a self-owned thermal power station providing 4.0 MPaG high pressure steam with 158.6 t/h, and 1.0–1.2 MPaG medium pressure steam with 22.4 t/h. The chemical plant needs a self-owned thermal power station providing 4.0 MPaG high pressure steam with 405.6 t/h. So the total amounts of steam needed by the whole factory are 4.0 MPaG steam with 564.2 t/h and 1.0– 1.2 MPaG steam with 22.4 t/h. Ultra-high pressure steam pipe network of self-owned thermal power station (12.0 MPaG) are connected to ethylene unit of chemical plant and when ethylene unit is on operation or under low load operation, main steam for driving turbine from cracking gas compressor is supplied by selfowned power station instead of cracking fumace because the steam supplied by cracking fumace is insufficient. Under normal condition, there would be no flow (NNF) in the steam pipe connected to ethylene unit but the steam pipe should keep warm. Based on the above-mentioned conditions and parameter matching performance, Modular HTGR could be used as the steam supply system of petrochemical factory instead of its own thermal power station. Here, the HTR-PM600 (6 250 MW modular HTGR) with a 600 MW corresponding steam turbine is selected and the basic flow chart of the scheme is illustrated in the Fig. 2. The design of the primary loop and the parameters of the steam generator of HTR-PM600 remain the same as the HTR-PM (Zhang et al., 2006) and the design of the secondary loop will be further improved according to the specific parameters of petrochemical factory. The main parameters of HTR-PM600 are shown in Table 1.
3. Preliminary calculation of heat and water balance 3.1. Working condition regardless of the ultra-high pressure steam heat supply Under normal condition, regardless of the case that chemical plant uses ultra-high pressure steam pipe network to supply steam, the ultra-high pressure steam of 12.0 MPa, 490 °C will not be provided. Thus, the system of HTR-PM600 with steam turbine
need to provide two levels of extraction steam. The first level extracting steam cylinder (high pressure cylinder) provides high pressure steam of 4 MPaG, 420 °C with a full load extraction flow of 564.2 t/h (158.6 t/h of which goes to refinery plant and 405.6 t/h of which goes to chemical plant). The second level of extraction steam cylinder (medium pressure cylinder) provides medium pressure steam of 1.0–1.2 MPa, 260–290 °C with the load rating of 22.4t/h. HTR-PM600 will use 600 MW steam extraction and condensing turbine to provide heat, which is same with HTR-PM (double extraction turbine). Because the high pressure steam pipe network of refinery plant is required to provide quite large volume of steam, the turbine should be switched to a high pressure cylinder to extracting steam and the steam will go to the next level medium cylinder for working after being extracted (Treese et al., 2006). Limited by the temperature of the primary loop inlet of steam generator, the feed water temperature of secondary loop stays the same as the original design (205 °C). In this way, the feed water re-heating system of this project is same as the one of HTR-PM, which adopts one high pressure heater (1#), one oxygen deaerator (2#), and four low pressure heater (3#6#). The total chart is shown in Fig. 3 In order to analyze the heat and water balance of the scheme, the following assumptions were made: (1) The shaft seal, valve stem leakage and other auxiliary steam losses are not considered. (2) Enthalpy rising of each level of heat exchangers is constant. (3) Relative efficiency of high pressure cylinder is 0.8, relative efficiency of medium and low pressure cylinder is 0.87. (4) Electric load is determined by heat load. (5) Two stages of steam extraction are adjustable. (6) Pressure losses of extractive steam pipe is 2%. (7) The upper end temperature difference of high level pressure heater is 0 °C, the upper end temperature difference of low level pressure heater is 2.8 °C, lower end temperature difference between high level and low level pressure heater is 5.6 °C (the same with the project of HTR-PM).
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Fig. 2. Charts of the Hypothetical Chinese Petrochemical Factory Matched with HTR-PM600 (Unit: t/h).
Table 1 Main Thermal Parameters of HTR-PM600. Items
Parameters
Units
Values
Parameters of Reactor
Total Thermal Power Working Pressure of Helium in the Primary Loop Temperature at Core Inlet Temperature at Core Outlet Mass flow of Helium
MW MPa °C °C kg/s
6 250 7.0 250 750 96
Parameters of Steam Generator (SG)
Temperature at the Inlet of Secondary side of SG Pressure at the Inlet of Secondary side of SG Flow of Each SG Temperature at the Outlet of Secondary Side of SG Pressure at the Outlet of Secondary Side of SG
°C MPa kg/s °C MPa
205.2 15.2 96.13 571 13.2
Parameter of Steam Turbine
Rated Flow of Main Steam Rated Electrical Power Inlet Steam Pressure Inlet Steam Temperature Exhausting Steam Pressure of Low Pressure Cylinder Capacity of Bypass System of SG Flow of Supply Water when Staring-Up
t/h MW MPa °C kPa / /
2076 653 13.24 566 4.9 50% 30%
The electric power output of HTR-PM600 is about 507 MW, which manifests a reduction of 146 MW due to supplying heat. The heat supplying of steam turbine are list in Table 2, the main steam flow is 2076 t/h from the HTGR, the operation parameters of high pressure heat steam and medium pressure heat steam in Table 2 are chosen according to the heat load of each level. The enthalpy-entropy diagram chart is shown in Fig. 4, in which the work process of steam turbine and isobars of each step are drawn with different colors. The curve for p = 13.24 Mpa and p = 4.8 Mpa are for high-pressure cylinder and medium-pressure cylinder respectively, and the extraction pressure, temperature and flow rate are also listed in Table 2. In Fig. 4 the isobars from p = 1.76 Mpa to p = 0.027 Mpa are the six levels of steam extraction, the operation parameters of each level are list in Table 3, and the parameters of feed water re-heating system are shown in Table 4.
3.2. Working condition of ultra-high pressure steam heat supply Under certain circumstances, the HTR-PM600 has to provide ultra-high pressure steam (12 MPa, 490 °C) with 601.7 t/h. When this happens, the bypass pipe of the main steam pipe will provide appropriate ultra-high pressure steam directly by reducing the heat and pressure. Simultaneously, the steam turbine will switch to load shedding working condition; flow will be 1474.3 t/h, which is 71% of the load rating. In this case, it will not be able to provide high pressure steam of 4 MPa, 420 °C for the factory. Thus, the turbine has to provide high pressure steam of low parameter temporarily; meanwhile the heat load of refinery has to work under a reduced parameter condition. Since providing ultra-high pressure steam is an unexpected situation only for a moment, there is no need to optimize the design of the turbine for this case. If this condition lasted for a longer period, then a loop of new steam source
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Fig. 3. Flow Chart of Heat System of Hypothetical Petrochemical Factory Matched with HTR-PM600.
Table 2 Results of Heat Supplying of Steam Turbine. No.
Parameter
Unit
Value
1 2 3 4 5
Main Steam Flow Main Steam Pressure Main Steam Temperature High Pressure Heat Steam Pressure Extraction Steam Temperature of High Pressure Heat Steam High Pressure Heat Steam Flow Medium Pressure Heat Steam Pressure Medium Pressure Heat Steam Temperature Medium Pressure Heat Steam Flow Enter Flow of Medium Pressure Cylinder Steam Enter Flow of Low Pressure Cylinder Steam Low Pressure Cylinder Exhaust Pressure Exhaust Pressure Power Generation
t/h MPa °C MPa °C
2076 13.24 566 4.8 420.6
t/h MPa °C t/h t/h t/h t/h kPa MW
564.2 1.22 254 22.4 1511.8 1348.6 1055.4 4.9 507.2
6 7 8 9 10 11 12 13 14
would be added into the system, which can be adjusted according to the specific situation. Fig. 4. Enthalpy-Entropy Diagram of Steam Extraction of Steam Turbine.
3.3. Calculation of water balance Fig. 2 shows that HTR-PM600 provides steam for petrochemical factory through the corresponding turbine. For the flow of steam provided is 586.6 t/h (under the heat load rating condition), it has to receive the water returning from the steam system of petrochemical factory. The feed water that returning to the HTR-PM600 is basically from the oxygen extractor of petrochemical factory and the water of steam condenser. The steam from other thermal users will not return to the system. The water balance calculation of whole factory is shown in Table 5. It is accessible to obtain the additional water supply for factory is 4.6 t/h, which is basically equivalent to the volume of boiler blow-off. Though the water is nearly balanced in the factory, but here the water qualities of different parts are not considered. In that case, it is obvious that the turbine of HTR-PM600 need addi-
tional purified water supply. However, this scenario has to be made in detail for a certain petrochemical factory.
4. Economic analysis There are many factors effecting on the economy of this substitution project and as a preliminary study, here the direct cost method (Lepadatu, 2013) is considered to study difference of steam supplied by self-owned power station and HTR-PM600. What should be emphasized here is the electricity price of HTRPM600 is considered as the same with HTR-PM commercial price in China (capital, cost of financing, revenue, fuel, operations, governmental allowance and etc. are all considered) and the prices of coal and steam supplied by the self-owned thermal power sta-
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C. Fang et al. / Annals of Nuclear Energy 110 (2017) 73–78 Table 3 Extraction Parameters of Feed Water Re-heating System.
Table 5 Water Balance Calculation of Whole Factory.
No.
Parameter
Unit
Value
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
First Level Steam Extraction Pressure First Level Steam Extraction Temperature First Level Steam Extraction Flow Second Level Steam Extraction Pressure Second Level Steam Extraction Temperature Second Level Steam Extraction Flow Third Level Steam Extraction Pressure Third Level Steam Extraction Temperature Third Level Steam Extraction Flow Fourth Level Steam Extraction Pressure Fourth Level Steam Extraction Temperature Fourth Level Steam Extraction Flow Fifth Level Steam Extraction Pressure Fifth Level Steam Extraction Temperature Fifth Level Steam Extraction Flow Sixth Level Steam Extraction Pressure Sixth Level Steam Extraction Temperature Sixth Level Steam Extraction Flow
MPa °C t/h MPa °C t/h MPa °C t/h MPa °C t/h MPa °C t/h MPa °C t/h
1.76 295 57.3 1.22 254 83.5 0.639 188 80.15 0.272 130.3 75.63 0.097 98.81 71.7 0.028 67.12 65.66
Table 4 Parameters of Feed Water Re-heating system. No.
Parameter.
Unit
Value
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
1# High pressure heater inlet temperature 1# High pressure heater inlet temperature 1# high pressure heater temperature rise 1# High pressure heater inlet enthalpy 1# High pressure heater outlet enthalpy 1# high pressure heater enthalpy rise 2# Deaerator inlet temperature 2# Deaerator outlet temperature 2# Deaerator temperature rise 2# Deaerator inlet enthalpy 2# Deaerator outlet enthalpy 2# Deaerator enthalpy rise 3#Low pressure heater inlet temperature 3#Low pressure heater outlet temperature 3#Low pressure heater temperature rise 3#Low pressure heater inlet enthalpy 3#Low pressure heater outlet enthalpy 3#Low pressure heater enthalpy rise 4#Low pressure heater inlet temperature 4#Low pressure heater outlet temperature 4#Low pressure heater temperature rise 4#Low pressure heater inlet enthalpy 4#Low pressure heater outlet enthalpy 4#Low pressure heater enthalpy rise 5#Low pressure heater inlet temperature 5#Low pressure heater outlet temperature 5#Low pressure heater temperature rise 5#Low pressure heater inlet enthalpy 5#Low pressure heater outlet enthalpy 5#Low pressure heater enthalpy rise 6#Low pressure heater inlet temperature 6#Low pressure heater outlet temperature 6#Low pressure heater temperature rise 6#Low pressure heater inlet enthalpy 6#Low pressure heater outlet enthalpy 6#Low pressure heater enthalpy rise
°C °C °C kJ/kg kJ/kg kJ/kg °C °C °C kJ/kg kJ/kg kJ/kg °C °C °C kJ/kg kJ/kg kJ/kg °C °C °C kJ/kg kJ/kg kJ/kg °C °C °C kJ/kg kJ/kg kJ/kg °C °C °C kJ/kg kJ/kg kJ/kg
191.5 205.1 13.67 821.7 881.9 60.19 157.7 188 30.26 665.9 798.3 132.4 126.8 157.7 30.91 533.5 665.9 132.4 95.45 126.8 31.34 401.1 533.5 132.4 63.86 95.45 31.59 268.7 401.1 132.4 33.47 63.86 30.39 141.8 268.7 126.9
tion are all from engineering practice, which make the results significant to the Chinese owner of petrochemical industry as reference. 4.1. Cost of steam supplied by self-owned power station For the convenience of calculations, high pressure steam (4 Mpa, 420 °C) assumes to be supplied by coal boiler (selfowned power station). Hence, 120.66 kg standard coal needs to be used for 1t steam created from normal temperature water. It
Item
Parameter
Value (t/h)
Steam Entering Steam System
Steam Applied by HTRPM600 Steam Applied by Cracking Furnace Steam Produced by Process Heat 1 Steam Produced by Process Heat 2 Steam Produced by Process Heat 3 Total
2076
Steam from Other Thermal Users that not Return to the System.
Other Other Other Other Other Other Other Total
13.3 115.3 262.7 232.9 188.5 80 162.1 1054.8
The Feed Water that Returning to HTRPM600
Deaerator 1 Deaerator2 Feed Water Return from Condensing Cycle Total
Users Users Users Users Users Users Users
1 2 3 4 5 6 7
Additional Water Supply for Factory
615 327.7 16.6 47.5 3082.8
144 399.2 1489.4 2032.6 4.6
Table 6 High Pressure Steam Cost Supplied by Self-Owned Power Station. No.
Parameter
Unit
Value
1 2 3 4 5 6 7 8 9
High Pressure Steam Enthalpy Normal Temperature Water Supply Enthalpy Calorific Value Of Standard Coal Boiler Efficiency Standard Coal Consumption/T Steam High Quality Steam Coal Prices (5500 Calories/T) Price of Standard Coal Coal Cost Accounting Cost Per Ton Steam
kJ/kg kJ/kg kJ
3261.5 84.0 29,260 90% 120.66 84.6 107.7 70% 18.46
kg $/t $/t $/t
Table 7 Cost of Medium Pressure Steam Supplied by Self-Owned Power Station. No.
Parameter
Unit
Value
1 2 3 4 5 6
High Pressure Steam Enthalpy Medium Pressure Steam Enthalpy Internal Efficiency for Steam Turbine Power Generation of Steam On-Grid Price of Electricity Cost of Steam
kJ/kg kJ/kg
3261.5 2958.16 80% 67.41 0.069 13.9
kWh/t $/kWh $/t
is known that the coal accounts for 70% of the total cost and the rest 30% includes the cost of desalting water, auxiliary equipment, and other electricity costs in the cost of self-owned power station. According to the price of standard coal is 107.7 $/t (average price in the past five years in China), the cost of high pressure steam is about $18.46/t. The exhaustive calculation results are listed in Table 6. Since medium pressure steam is supplied by steam turbine of self-owned power station, the cost of medium pressure steam is the expense of high pressure steam subtracting the steam for electricity that generated before the medium pressure steam extracts. Medium pressure steam generates at the rate of 67.4 kWh/t before extraction, thus, the cost of medium pressure steam would be approximate $13.9/t (the electricity on-grid of thermal power is
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C. Fang et al. / Annals of Nuclear Energy 110 (2017) 73–78
self-owned power station, are all based on current data in China, which makes this study significant to future Chinese project.
Table 8 Cost of Heat Steam Supplied by HTR-PM600. No.
Parameter
Unit
Value
1 2
MW MW
653.1 507.2
3
Rated Capacity of HTR-PM600 Generating Capacity Under Rated Heat Supply of HTR-PM600 Average Price of Electricity
0.077
4
Reduction of Electricity Supply
5 6
Total Cost of Steam Average Cost of Steam
$/ kWh kWh/ h $/h $/t
4.3. Sensitivity analysis
No.
Parameter
Unit
Value
The cost of steam provided by thermal self-owned power station is frequently influenced by the market prices of coal. In addition, the on-grid price of electricity of HTR-PM600 is varying in the future. When doing sensitivity analysis, we assume that the price for high quality raw coal (5500 kcal) using in power station ranges from $53.8/t to $130.8/t and the on-grid price for electricity generated by HTGR ranges from $0.054/kwh to $0.1/kwh (Sullivan et al., 2003). The calculation result is shown in Fig. 5. It shows that the lower the on-grid price for electricity generated by HTGR and the higher the price for coal would be, meanwhile, the cost of heat supplied by HTGR is lower as well.
1 2
Total Cost of HTGR Heat Supply Cost of Self-Owned Thermal Power Station Providing High Pressure Steam Cost of Self-Owned Thermal Power Station Providing Medium Pressure Steam Saved Cost of HTGR Per Hour Saved Cost of HTGR Whole Year
$/h $/h
10,104 10,473
5. Conclusion and remark
$/h
311
$/h $/h
681 5,964,615
145,942 10,104 16.6
Table 9 Cost Comparison of HTR-PM600 and Self-Owned Thermal Power Station.
3 4 5
In summary, there is feasibility in using HTGR to provide process heat for petrochemical industry. In addition. Although the steam turbine of HTR-PM600 needs a redesign, the mature technology of turbine in thermal power station could be readily adopted. Furthermore, the economy of this scheme is also acceptable. The benefit to the environment is also impressive because it is known that an self-owned powered station of a typical petrochemical factory consumes 70t of standard coal per hour and 620,000t of standard coal per year. By using HTR-PM600 instead of self-owned power station, carbon and pollutant emissions will be greatly reduced, which would make great contribution to the environmental protection. In the future, some detail work will be carried especially on heat and water balance and technical economic analysis with the method of levelized unit electricity cost (LUEC). However, all this work should be based on a certain real site. Acknowledgment
Fig. 5. Relationship between the Saved Costs of Steam with the Price of Coal and the Electricity Price of HTGR.
This work was supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. ZX06901). References
considered as $0.069/kWh, which is overvalued for conservative estimation). The results are listed in Table 7. 4.2. Cost of steam supplied by HTR-PM600 The cost of HTR-PM600 heat supply is determined by the reduction of electricity supply due to heat supply (Department of Energy, 2007). The average price of electricity is 0.077$/kWh so the cost of HTR-PM600 heat steam supply is 10,108$/h and the cost of high medium pressure steam is 16.6$/t. Under the same power, the cost of HTR-PM600 providing heat could save $681/h compared with the self-owned thermal power station, therefore it could add up to $5,964,615 for a whole year (Parkash, 2003; Perry et al., 2008). The detail results are shown in Tables 8 and 9. What should be emphasized is in this article, the price of electricity supplied by HTGR, the price of coal and steam supplied by
Department of Energy, Cost and Performance Baseline for Fossil Energy Plants, DOE/ NETL-2007/1281, 2007. Idaho National Laboratory, High Temperature Gas-Cooled Reactor Projected Markets and Preliminary Economics, INL/EXT-10-19037, 2010. Idaho National Laboratory, HTGR-Integrated Coal and Gas to Liquids Production Analysis, INL/TEV-672, Rev. 2, 2011. Lepadatu, V.G., 2013. Variable costs method (direct-costing) and its application area. Metal. Int. 18 (1), 85–89. Parkash, S., 2003. Refining Processes Handbook. Elsevier, Amsterdam, pp. 35–39. Perry, R.H., Chilton, C.H., Green, D.W., 2008. Perry’s Chemical Engineers’ Handbook. McGraw Hill, New York, New York, pp. 24–28. Sullivan, W.G., Wicks, E.M., Luxhoj, J.T., 2003. Engineering Economy. Prentice Hall, Upper Saddle River, New Jersey, pp. 143–146. Treese, S.A., Pujado, P.R., Jones, D.S.J., 2006. Handbook of Petroleum Processing. Springer, Dordrecht, pp. 112–116. Zhang, Z.Y., Wu, Z.X., Sun, Y.L., et al., 2006. Design aspects of the Chinese modular high-temperature gas-cooled reactor HTR-PM. Nucl. Eng. Des. 236, 485–490.
Contents lists available at ScienceDirect
Annals of Nuclear Energy journal homepage: www.elsevier.com/locate/anucene
Process heat applications of HTR-PM600 in Chinese petrochemical industry: Preliminary study of adaptability and economy Chao Fang ⇑, Qi Min, Yanran Yang, Yuliang Sun Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China Collaborative Innovation Center of Advanced Nuclear Energy Technology, Beijing 100084, China The Key Laboratory of Advanced Reactor Engineering and Safety, Ministry of Education, Beijing 100084, China
a r t i c l e
i n f o
Article history: Received 23 January 2017 Received in revised form 14 April 2017 Accepted 13 June 2017
Keywords: HTR-PM600 Process heat applications Petrochemical industry
a b s t r a c t High Temperature Gas Cooled Reactor (HTGR) could work as heat source for petrochemical industry. In this article, the preliminary feasibility of a 600 MW modular HTGR (HTR-PM600) working as heat source for a typical hypothetical Chinese petrochemical factory is discussed and it is found that the joint of HTRPM600 and petrochemical industry is achievable. In detail, the heat and water balance analysis of the petrochemical factory is given. Furthermore, the direct cost of heat supplied by HTR-PM600 is calculated and corresponding economy is estimated. The results show that though there are several challenges, the application of process heat of HTGR to petrochemical industry is practical in sense of both technology and economy. Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction High Temperature Gas Cooled Reactor (HTGR) with the feature of inherent safety is considered as a kind of promising Gen IV nuclear power system. In addition to generating electricity efficiently, the HTGR is also an potential choice for producing hydrogen, industrial heat application and cogeneration cycle, which could reduce the fossil fuel consumption and greenhouse gas emission during the technical process. Specially, HTGR is the only candidate that can supply high temperature process heat for industrial application, which will make it stand out in the process heat supply market compared with other nuclear reactors (Idaho National Laboratory, 2010). Because of its excellent characteristics, HTGR is thought to be used in the petrochemical industry (Idaho National Laboratory, 2011). In China, the petrochemical factory consists of refinery plants and chemical plants. Most refinery plants use an upstream device that consists of several sets of crude oil distillation and a downstream device consists of more than ten sets of secondary processing facilities. Most chemical plants use the upstream device consists of several sets of ethylene units, aromatic complex units, ammonia synthesis units, and chlor-alkali units, etc. and the downstream part usually consists of more than
⇑ Corresponding author at: Energy Science Building A302, Tsinghua University, Haidian District, Beijing 100084, China. E-mail address: [email protected] (C. Fang). http://dx.doi.org/10.1016/j.anucene.2017.06.024 0306-4549/Ó 2017 Elsevier Ltd. All rights reserved.
ten sets of chemical process units. All the units need heated steam and the parameters of steam are distinguishing in different units. In different countries, the design and corresponding arrangement of petrochemical factory is different so as a preliminary feasibility study, we only focus on Chinese petrochemical factory. In this article, the adaptabilities of 600 MW modular HTGR (HTRPM600) as heat source to a hypothetical Chinese petrochemical factory are studied and the corresponding technical economic analysis is given, which is an exploration of the application of HTGR process heat to the petrochemical industry.
2. Scheme of HTGR process heat supply in petrochemical factory Fig. 1 shows a representative flow chat of a hypothetical Chinese petrochemical factory with 10,000,000 t/year of petroleum refining and 1,000,000 t/year of ethylene producing. The left part shows the petroleum refin plant consisting of 10 main facilities and the right part shows ethylene producing plant (chemical plant) consisting of 12 main facilities. The corresponding technical parameters and quantity demanding of the steam are also shown and the precision of data is suitable for calculating the balance of heat and water. It is found that there are four different steam pipe networks: ultra-high pressure steam (12.0 MPaG, 490 °C), high pressure steam (4.0 MPaG, 420 °C), medium pressure steam (1.0– 1.2 MPaG, 260–290 °C) and low pressure steam (0.35–0.4 MPaG, 190 °C).
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C. Fang et al. / Annals of Nuclear Energy 110 (2017) 73–78
Fig. 1. Chart of a Hypothetical Chinese Petrochemical Factory with 10,000,000 t/year of Petroleum refining and 1,000,000 t/year of Ethylene Producing (Unit: t/h).
According to the calculation of steam quantity, the refinery plant needs a self-owned thermal power station providing 4.0 MPaG high pressure steam with 158.6 t/h, and 1.0–1.2 MPaG medium pressure steam with 22.4 t/h. The chemical plant needs a self-owned thermal power station providing 4.0 MPaG high pressure steam with 405.6 t/h. So the total amounts of steam needed by the whole factory are 4.0 MPaG steam with 564.2 t/h and 1.0– 1.2 MPaG steam with 22.4 t/h. Ultra-high pressure steam pipe network of self-owned thermal power station (12.0 MPaG) are connected to ethylene unit of chemical plant and when ethylene unit is on operation or under low load operation, main steam for driving turbine from cracking gas compressor is supplied by selfowned power station instead of cracking fumace because the steam supplied by cracking fumace is insufficient. Under normal condition, there would be no flow (NNF) in the steam pipe connected to ethylene unit but the steam pipe should keep warm. Based on the above-mentioned conditions and parameter matching performance, Modular HTGR could be used as the steam supply system of petrochemical factory instead of its own thermal power station. Here, the HTR-PM600 (6 250 MW modular HTGR) with a 600 MW corresponding steam turbine is selected and the basic flow chart of the scheme is illustrated in the Fig. 2. The design of the primary loop and the parameters of the steam generator of HTR-PM600 remain the same as the HTR-PM (Zhang et al., 2006) and the design of the secondary loop will be further improved according to the specific parameters of petrochemical factory. The main parameters of HTR-PM600 are shown in Table 1.
3. Preliminary calculation of heat and water balance 3.1. Working condition regardless of the ultra-high pressure steam heat supply Under normal condition, regardless of the case that chemical plant uses ultra-high pressure steam pipe network to supply steam, the ultra-high pressure steam of 12.0 MPa, 490 °C will not be provided. Thus, the system of HTR-PM600 with steam turbine
need to provide two levels of extraction steam. The first level extracting steam cylinder (high pressure cylinder) provides high pressure steam of 4 MPaG, 420 °C with a full load extraction flow of 564.2 t/h (158.6 t/h of which goes to refinery plant and 405.6 t/h of which goes to chemical plant). The second level of extraction steam cylinder (medium pressure cylinder) provides medium pressure steam of 1.0–1.2 MPa, 260–290 °C with the load rating of 22.4t/h. HTR-PM600 will use 600 MW steam extraction and condensing turbine to provide heat, which is same with HTR-PM (double extraction turbine). Because the high pressure steam pipe network of refinery plant is required to provide quite large volume of steam, the turbine should be switched to a high pressure cylinder to extracting steam and the steam will go to the next level medium cylinder for working after being extracted (Treese et al., 2006). Limited by the temperature of the primary loop inlet of steam generator, the feed water temperature of secondary loop stays the same as the original design (205 °C). In this way, the feed water re-heating system of this project is same as the one of HTR-PM, which adopts one high pressure heater (1#), one oxygen deaerator (2#), and four low pressure heater (3#6#). The total chart is shown in Fig. 3 In order to analyze the heat and water balance of the scheme, the following assumptions were made: (1) The shaft seal, valve stem leakage and other auxiliary steam losses are not considered. (2) Enthalpy rising of each level of heat exchangers is constant. (3) Relative efficiency of high pressure cylinder is 0.8, relative efficiency of medium and low pressure cylinder is 0.87. (4) Electric load is determined by heat load. (5) Two stages of steam extraction are adjustable. (6) Pressure losses of extractive steam pipe is 2%. (7) The upper end temperature difference of high level pressure heater is 0 °C, the upper end temperature difference of low level pressure heater is 2.8 °C, lower end temperature difference between high level and low level pressure heater is 5.6 °C (the same with the project of HTR-PM).
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Fig. 2. Charts of the Hypothetical Chinese Petrochemical Factory Matched with HTR-PM600 (Unit: t/h).
Table 1 Main Thermal Parameters of HTR-PM600. Items
Parameters
Units
Values
Parameters of Reactor
Total Thermal Power Working Pressure of Helium in the Primary Loop Temperature at Core Inlet Temperature at Core Outlet Mass flow of Helium
MW MPa °C °C kg/s
6 250 7.0 250 750 96
Parameters of Steam Generator (SG)
Temperature at the Inlet of Secondary side of SG Pressure at the Inlet of Secondary side of SG Flow of Each SG Temperature at the Outlet of Secondary Side of SG Pressure at the Outlet of Secondary Side of SG
°C MPa kg/s °C MPa
205.2 15.2 96.13 571 13.2
Parameter of Steam Turbine
Rated Flow of Main Steam Rated Electrical Power Inlet Steam Pressure Inlet Steam Temperature Exhausting Steam Pressure of Low Pressure Cylinder Capacity of Bypass System of SG Flow of Supply Water when Staring-Up
t/h MW MPa °C kPa / /
2076 653 13.24 566 4.9 50% 30%
The electric power output of HTR-PM600 is about 507 MW, which manifests a reduction of 146 MW due to supplying heat. The heat supplying of steam turbine are list in Table 2, the main steam flow is 2076 t/h from the HTGR, the operation parameters of high pressure heat steam and medium pressure heat steam in Table 2 are chosen according to the heat load of each level. The enthalpy-entropy diagram chart is shown in Fig. 4, in which the work process of steam turbine and isobars of each step are drawn with different colors. The curve for p = 13.24 Mpa and p = 4.8 Mpa are for high-pressure cylinder and medium-pressure cylinder respectively, and the extraction pressure, temperature and flow rate are also listed in Table 2. In Fig. 4 the isobars from p = 1.76 Mpa to p = 0.027 Mpa are the six levels of steam extraction, the operation parameters of each level are list in Table 3, and the parameters of feed water re-heating system are shown in Table 4.
3.2. Working condition of ultra-high pressure steam heat supply Under certain circumstances, the HTR-PM600 has to provide ultra-high pressure steam (12 MPa, 490 °C) with 601.7 t/h. When this happens, the bypass pipe of the main steam pipe will provide appropriate ultra-high pressure steam directly by reducing the heat and pressure. Simultaneously, the steam turbine will switch to load shedding working condition; flow will be 1474.3 t/h, which is 71% of the load rating. In this case, it will not be able to provide high pressure steam of 4 MPa, 420 °C for the factory. Thus, the turbine has to provide high pressure steam of low parameter temporarily; meanwhile the heat load of refinery has to work under a reduced parameter condition. Since providing ultra-high pressure steam is an unexpected situation only for a moment, there is no need to optimize the design of the turbine for this case. If this condition lasted for a longer period, then a loop of new steam source
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Fig. 3. Flow Chart of Heat System of Hypothetical Petrochemical Factory Matched with HTR-PM600.
Table 2 Results of Heat Supplying of Steam Turbine. No.
Parameter
Unit
Value
1 2 3 4 5
Main Steam Flow Main Steam Pressure Main Steam Temperature High Pressure Heat Steam Pressure Extraction Steam Temperature of High Pressure Heat Steam High Pressure Heat Steam Flow Medium Pressure Heat Steam Pressure Medium Pressure Heat Steam Temperature Medium Pressure Heat Steam Flow Enter Flow of Medium Pressure Cylinder Steam Enter Flow of Low Pressure Cylinder Steam Low Pressure Cylinder Exhaust Pressure Exhaust Pressure Power Generation
t/h MPa °C MPa °C
2076 13.24 566 4.8 420.6
t/h MPa °C t/h t/h t/h t/h kPa MW
564.2 1.22 254 22.4 1511.8 1348.6 1055.4 4.9 507.2
6 7 8 9 10 11 12 13 14
would be added into the system, which can be adjusted according to the specific situation. Fig. 4. Enthalpy-Entropy Diagram of Steam Extraction of Steam Turbine.
3.3. Calculation of water balance Fig. 2 shows that HTR-PM600 provides steam for petrochemical factory through the corresponding turbine. For the flow of steam provided is 586.6 t/h (under the heat load rating condition), it has to receive the water returning from the steam system of petrochemical factory. The feed water that returning to the HTR-PM600 is basically from the oxygen extractor of petrochemical factory and the water of steam condenser. The steam from other thermal users will not return to the system. The water balance calculation of whole factory is shown in Table 5. It is accessible to obtain the additional water supply for factory is 4.6 t/h, which is basically equivalent to the volume of boiler blow-off. Though the water is nearly balanced in the factory, but here the water qualities of different parts are not considered. In that case, it is obvious that the turbine of HTR-PM600 need addi-
tional purified water supply. However, this scenario has to be made in detail for a certain petrochemical factory.
4. Economic analysis There are many factors effecting on the economy of this substitution project and as a preliminary study, here the direct cost method (Lepadatu, 2013) is considered to study difference of steam supplied by self-owned power station and HTR-PM600. What should be emphasized here is the electricity price of HTRPM600 is considered as the same with HTR-PM commercial price in China (capital, cost of financing, revenue, fuel, operations, governmental allowance and etc. are all considered) and the prices of coal and steam supplied by the self-owned thermal power sta-
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C. Fang et al. / Annals of Nuclear Energy 110 (2017) 73–78 Table 3 Extraction Parameters of Feed Water Re-heating System.
Table 5 Water Balance Calculation of Whole Factory.
No.
Parameter
Unit
Value
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
First Level Steam Extraction Pressure First Level Steam Extraction Temperature First Level Steam Extraction Flow Second Level Steam Extraction Pressure Second Level Steam Extraction Temperature Second Level Steam Extraction Flow Third Level Steam Extraction Pressure Third Level Steam Extraction Temperature Third Level Steam Extraction Flow Fourth Level Steam Extraction Pressure Fourth Level Steam Extraction Temperature Fourth Level Steam Extraction Flow Fifth Level Steam Extraction Pressure Fifth Level Steam Extraction Temperature Fifth Level Steam Extraction Flow Sixth Level Steam Extraction Pressure Sixth Level Steam Extraction Temperature Sixth Level Steam Extraction Flow
MPa °C t/h MPa °C t/h MPa °C t/h MPa °C t/h MPa °C t/h MPa °C t/h
1.76 295 57.3 1.22 254 83.5 0.639 188 80.15 0.272 130.3 75.63 0.097 98.81 71.7 0.028 67.12 65.66
Table 4 Parameters of Feed Water Re-heating system. No.
Parameter.
Unit
Value
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
1# High pressure heater inlet temperature 1# High pressure heater inlet temperature 1# high pressure heater temperature rise 1# High pressure heater inlet enthalpy 1# High pressure heater outlet enthalpy 1# high pressure heater enthalpy rise 2# Deaerator inlet temperature 2# Deaerator outlet temperature 2# Deaerator temperature rise 2# Deaerator inlet enthalpy 2# Deaerator outlet enthalpy 2# Deaerator enthalpy rise 3#Low pressure heater inlet temperature 3#Low pressure heater outlet temperature 3#Low pressure heater temperature rise 3#Low pressure heater inlet enthalpy 3#Low pressure heater outlet enthalpy 3#Low pressure heater enthalpy rise 4#Low pressure heater inlet temperature 4#Low pressure heater outlet temperature 4#Low pressure heater temperature rise 4#Low pressure heater inlet enthalpy 4#Low pressure heater outlet enthalpy 4#Low pressure heater enthalpy rise 5#Low pressure heater inlet temperature 5#Low pressure heater outlet temperature 5#Low pressure heater temperature rise 5#Low pressure heater inlet enthalpy 5#Low pressure heater outlet enthalpy 5#Low pressure heater enthalpy rise 6#Low pressure heater inlet temperature 6#Low pressure heater outlet temperature 6#Low pressure heater temperature rise 6#Low pressure heater inlet enthalpy 6#Low pressure heater outlet enthalpy 6#Low pressure heater enthalpy rise
°C °C °C kJ/kg kJ/kg kJ/kg °C °C °C kJ/kg kJ/kg kJ/kg °C °C °C kJ/kg kJ/kg kJ/kg °C °C °C kJ/kg kJ/kg kJ/kg °C °C °C kJ/kg kJ/kg kJ/kg °C °C °C kJ/kg kJ/kg kJ/kg
191.5 205.1 13.67 821.7 881.9 60.19 157.7 188 30.26 665.9 798.3 132.4 126.8 157.7 30.91 533.5 665.9 132.4 95.45 126.8 31.34 401.1 533.5 132.4 63.86 95.45 31.59 268.7 401.1 132.4 33.47 63.86 30.39 141.8 268.7 126.9
tion are all from engineering practice, which make the results significant to the Chinese owner of petrochemical industry as reference. 4.1. Cost of steam supplied by self-owned power station For the convenience of calculations, high pressure steam (4 Mpa, 420 °C) assumes to be supplied by coal boiler (selfowned power station). Hence, 120.66 kg standard coal needs to be used for 1t steam created from normal temperature water. It
Item
Parameter
Value (t/h)
Steam Entering Steam System
Steam Applied by HTRPM600 Steam Applied by Cracking Furnace Steam Produced by Process Heat 1 Steam Produced by Process Heat 2 Steam Produced by Process Heat 3 Total
2076
Steam from Other Thermal Users that not Return to the System.
Other Other Other Other Other Other Other Total
13.3 115.3 262.7 232.9 188.5 80 162.1 1054.8
The Feed Water that Returning to HTRPM600
Deaerator 1 Deaerator2 Feed Water Return from Condensing Cycle Total
Users Users Users Users Users Users Users
1 2 3 4 5 6 7
Additional Water Supply for Factory
615 327.7 16.6 47.5 3082.8
144 399.2 1489.4 2032.6 4.6
Table 6 High Pressure Steam Cost Supplied by Self-Owned Power Station. No.
Parameter
Unit
Value
1 2 3 4 5 6 7 8 9
High Pressure Steam Enthalpy Normal Temperature Water Supply Enthalpy Calorific Value Of Standard Coal Boiler Efficiency Standard Coal Consumption/T Steam High Quality Steam Coal Prices (5500 Calories/T) Price of Standard Coal Coal Cost Accounting Cost Per Ton Steam
kJ/kg kJ/kg kJ
3261.5 84.0 29,260 90% 120.66 84.6 107.7 70% 18.46
kg $/t $/t $/t
Table 7 Cost of Medium Pressure Steam Supplied by Self-Owned Power Station. No.
Parameter
Unit
Value
1 2 3 4 5 6
High Pressure Steam Enthalpy Medium Pressure Steam Enthalpy Internal Efficiency for Steam Turbine Power Generation of Steam On-Grid Price of Electricity Cost of Steam
kJ/kg kJ/kg
3261.5 2958.16 80% 67.41 0.069 13.9
kWh/t $/kWh $/t
is known that the coal accounts for 70% of the total cost and the rest 30% includes the cost of desalting water, auxiliary equipment, and other electricity costs in the cost of self-owned power station. According to the price of standard coal is 107.7 $/t (average price in the past five years in China), the cost of high pressure steam is about $18.46/t. The exhaustive calculation results are listed in Table 6. Since medium pressure steam is supplied by steam turbine of self-owned power station, the cost of medium pressure steam is the expense of high pressure steam subtracting the steam for electricity that generated before the medium pressure steam extracts. Medium pressure steam generates at the rate of 67.4 kWh/t before extraction, thus, the cost of medium pressure steam would be approximate $13.9/t (the electricity on-grid of thermal power is
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self-owned power station, are all based on current data in China, which makes this study significant to future Chinese project.
Table 8 Cost of Heat Steam Supplied by HTR-PM600. No.
Parameter
Unit
Value
1 2
MW MW
653.1 507.2
3
Rated Capacity of HTR-PM600 Generating Capacity Under Rated Heat Supply of HTR-PM600 Average Price of Electricity
0.077
4
Reduction of Electricity Supply
5 6
Total Cost of Steam Average Cost of Steam
$/ kWh kWh/ h $/h $/t
4.3. Sensitivity analysis
No.
Parameter
Unit
Value
The cost of steam provided by thermal self-owned power station is frequently influenced by the market prices of coal. In addition, the on-grid price of electricity of HTR-PM600 is varying in the future. When doing sensitivity analysis, we assume that the price for high quality raw coal (5500 kcal) using in power station ranges from $53.8/t to $130.8/t and the on-grid price for electricity generated by HTGR ranges from $0.054/kwh to $0.1/kwh (Sullivan et al., 2003). The calculation result is shown in Fig. 5. It shows that the lower the on-grid price for electricity generated by HTGR and the higher the price for coal would be, meanwhile, the cost of heat supplied by HTGR is lower as well.
1 2
Total Cost of HTGR Heat Supply Cost of Self-Owned Thermal Power Station Providing High Pressure Steam Cost of Self-Owned Thermal Power Station Providing Medium Pressure Steam Saved Cost of HTGR Per Hour Saved Cost of HTGR Whole Year
$/h $/h
10,104 10,473
5. Conclusion and remark
$/h
311
$/h $/h
681 5,964,615
145,942 10,104 16.6
Table 9 Cost Comparison of HTR-PM600 and Self-Owned Thermal Power Station.
3 4 5
In summary, there is feasibility in using HTGR to provide process heat for petrochemical industry. In addition. Although the steam turbine of HTR-PM600 needs a redesign, the mature technology of turbine in thermal power station could be readily adopted. Furthermore, the economy of this scheme is also acceptable. The benefit to the environment is also impressive because it is known that an self-owned powered station of a typical petrochemical factory consumes 70t of standard coal per hour and 620,000t of standard coal per year. By using HTR-PM600 instead of self-owned power station, carbon and pollutant emissions will be greatly reduced, which would make great contribution to the environmental protection. In the future, some detail work will be carried especially on heat and water balance and technical economic analysis with the method of levelized unit electricity cost (LUEC). However, all this work should be based on a certain real site. Acknowledgment
Fig. 5. Relationship between the Saved Costs of Steam with the Price of Coal and the Electricity Price of HTGR.
This work was supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. ZX06901). References
considered as $0.069/kWh, which is overvalued for conservative estimation). The results are listed in Table 7. 4.2. Cost of steam supplied by HTR-PM600 The cost of HTR-PM600 heat supply is determined by the reduction of electricity supply due to heat supply (Department of Energy, 2007). The average price of electricity is 0.077$/kWh so the cost of HTR-PM600 heat steam supply is 10,108$/h and the cost of high medium pressure steam is 16.6$/t. Under the same power, the cost of HTR-PM600 providing heat could save $681/h compared with the self-owned thermal power station, therefore it could add up to $5,964,615 for a whole year (Parkash, 2003; Perry et al., 2008). The detail results are shown in Tables 8 and 9. What should be emphasized is in this article, the price of electricity supplied by HTGR, the price of coal and steam supplied by
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