IECM Technical Documentation: CO2 Purification Unit (CPU) Models

Transcription

1 IECM Technical Documentation: CO2 Purification Unit (CPU) Models November 2017

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3 IECM Technical Documentation: CO 2 Purification Unit (CPU) Models Prepared by: Hari C. Mantripragada Edward S. Rubin The Integrated Environmental Control Model Team Department of Engineering and Public Policy Carnegie Mellon University Pittsburgh, PA November 2017

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5 Table of Contents CO2 Purification Unit 1 Objective of this Report... 1 CPU Performance Models... 1 Flue gas Compressor and Drying model... 3 Partial Condensation Model... 4 Distillation Model... 8 CO 2 Compressor Model CPU Efficiency Factor Order of Calculations CPU Cost Model User-Specified Configuration IECM Screens Case Studies References Integrated Environmental Control Model - Technical Documentation Table of Contents v

6 List of Figures Figure 1. CO2 purity requirements for different applications [NETL QGESS, 2014]... 2 Figure 2. Schematic of a typical CPU process... 3 Figure 3. Variation of CO2 purity and recovery with pressure and flash temperature Figure 4. Variation of CO2 recovery with pressure and flash temperature Figure 5. CO2 recovery and purity for condensation and distillation Figure 6. Regression equations for capital cost of CPI Figure 7. "Set Parameters" config screen for the CPU unit Figure 8."Set Parameters" purification screen for the CPU unit, 99.99% purity case Figure 9. "Set Parameters" purification screen for the CPU unit, high purity case Figure 10. "Set Parameters" purification screen for the CPU uni, low purity case Figure 11. Sensitivity analysis results Figure 12. Sensitivity analysis for the CPU case studies Integrated Environmental Control Model - Technical Documentation vi

7 List of Tables Table 1. Regression coefficients for the partial condensation model... 5 Table 2. Regression equations for the combined condensation and distillation model... 9 Table 3. Case studies to calculate CPU efficiency factor Table 4. Relevant flow rates and capital costs of CPU from the 2010 DOE Oxycombustion Report Table 5. Case study input assumptions and results Integrated Environmental Control Model - Technical Documentation vii

8 Acknowledgements This work was supported by the National Energy Technology Laboratory. The authors also acknowledge Karen Kietzke and Dr. Haibo Zhai for their help in incorporating the performance and cost models into IECM. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors alone and do not reflect the views of any agency. Integrated Environmental Control Model - Technical Documentation Acknowledgements viii

9 CO 2 Purification Unit Objective of this Report This documentation reports the performance and cost models of a CO2 purification unit (CPU) used for oxy-combustion and some post-combustion CO2 capture technologies at coal-fired power plants. CPU is needed to increase the purity of CO2 product stream to meet appropriate pipeline standards. Some of these standards are prescribed in the NETL QGESS document on CO2 purity requirements, as shown in the figure 1 (NETL, 2013). Based on the specifications, CO2, H2O, O2, Ar and N2 are considered to be important components for design. Only these components are considered in developing the CPU performance and cost models. Since SOx and NOx are removed almost completely by the CO2 capture units, in conjunction with SO2 polishing unit, these components are not explicitly considered in the models. CPU Performance Models The process design of CPU depends on the design constraints of CO2 product that goes into the pipeline. There are four major components of a CPU, as listed below (NETL, 2010; Besong et al, 2013): 1. Flue gas compression and drying: The CO2-rich flue gas which needs to be purified is first compressed to a pressure of about 30 bar. Most of the water vapor in the flue gas condenses because of this compression. Water vapor is further removed by an additional drying unit. If no further purification is needed, this dry CO2-rich flue gas can be further compressed for pipeline transport. Depending on the inlet flue gas, the CO2 product purity from this step could be between 80-90%, with all the other impurities (mainly Ar, N2 and O2) remaining in the CO2 product. 2. Partial condensation: Most pipelines require further improvement in CO2 purity. The compressed and dry gas from the above-mentioned step is cooled using external refrigeration to a temperature close to the critical point of CO2 (-59 o C). The cooled gas is then sent through a flash unit where majority of the CO2 is separated from other gases. The CO2 product now reaches a purity of around 95%, with the other gases (Ar, N2 and O2) contributing to the remaining 5%. The purity and recovery of CO2 can be adjusted varying the operating conditions such as the flash temperature and the number of flash Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 1

10 stages. A typical design includes a 2-stage flash, which has been modeled in this study (Pipitone and Boland). 3. Distillation: Though a high enough CO2 purity is achieved, amount of O2 in the CO2 product cannot be adequately controlled with partial condensation. A further distillation step is required to increase the CO2 purity to more than 99% and reduce the O2 content to less than 100ppm. 4. CO2 final product compressor: The CO2 product from any of the above three steps is compressed to pipeline pressure. Figure 1. CO2 purity requirements for different applications [NETL QGESS, 2014] Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 2

11 Figure 2. Schematic of a typical CPU process (NETL, 2010) These four steps have been modeled using Aspen Plus and the performance results are used to develop reduced order models for different equipment. The details of these models are described below. Flue gas Compressor and Drying model The first step in CPU is compression of flue gas (clean of impurities such as SOx and NOx) to about 30 bar. In the process, most of the water vapor is condensed. The remaining water vapor is removed in a separate drying unit. A 6-stage intercooled compressor was modeled using Aspen Plus (v9). Inlet water vapor concentration and outlet pressure were varied to study their effect on the amount of water vapor condensed in the compressor, the required compression energy and cooling duty for intercooling between stages. Reduced order models are then developed for these variables. The isentropic efficiency of the compressor is assumed to be 100% so that the IECM user defined efficiency can be used for calculation of the energy requirements. The temperature of interstage cooling was fixed at 38 o C. Pressure was varied from bar. Inlet flue gas temperature was varied from o C. The following regression equations were obtained: EffH2O,condensed = *Pcompr *yH2O,fg *(Pcompr1) *(yH2O,fg) (Pcompr1)*( yh2o,fg) (R 2 = 98.48%) (1) Q_cool_MJ/k = *Pcompr *Tfg *yH2O,fg *(Tfg) *(yH2O,fg) 2 (R2=95.27) (2) EffQcool = *Effcompr *Tfg *(Effcompr) *(Tfg) *Effcompr*Tfg (R 2 = 99.19%) (3) Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 3

12 Qcool,act (MJ/kmol inlet FG) = Qcool,ideal*EffQcool (4) Wcompr,ideal (kwh/kmol inlet FG) = *Pcompr *Tfg *yH2O,fg (R2=99.66) (5) Wcompr,act = Wcompr,ideal/Effcompr (6) Mole flow rate of condensed water is given as: MH2O,condensed = EffH2O,condensed*MH2O,in (7) All of the remaining water vapor in the dry gas is assumed to be dried in the dryer unit which utilizes activated alumina adsorbents. The adsorbents are regenerated using waste N2 streams. The captured water vapor is assumed to go out with the waste N2 stream and is not accounted for in the CPU model. Mfg,dry = Mfg,in MH2O,in (8) This gas goes into the partial condensation unit. Partial Condensation Model The compressed flue gas is sent to a partial condensation system. The dried flue gas is first cooled in a heat exchanger to -27 o C and then sent to a flash chamber where most of the CO2 condenses, along with some other gases. The non-condensed gases which consist of the remaining CO2 and other gases is sent to another heat exchanger where they are cooled to a much lower temperature (between -59 and -40 o C) and flashed again in a second flash chamber. More CO2 is recovered from the gases. The condensed CO2-rich liquids from both the flash chambers are mixed and either compressed to pipeline pressure or sent for further purification. The partial condensation process was also modeled using Aspen Plus. To develop reduced order models, the following parameters were varied: inlet flue gas composition, inlet pressure, and the 2 nd flash stage temperature. Reduced order models were developed for the purity and recovery of different gas components and for the cooling load required for the process. Inlet flue gas composition is expressed in terms of the ratio of molar flow rates (and hence mole fractions) of different gas components to the CO2 mole flow. IECM oxy-combustion module was used to estimate the ranges of gas compositions by varying the coal type and excess air ratio. The ranges for different components in the inlet flue gas are: O2/CO2: N2/CO2: Ar/CO2: Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 4

13 Regression models were developed for the desired parameters. Table 1 shows the coefficients for linear regression of mole fractions of CO2, Ar and O2. Mole fraction of N2 is calculated as (1 mole fractions) of other components. The table also shows the coefficients for quadratic regression of cooling duty and recovery of CO2 from the partial condensation unit. yn2,out = 1 yco2,out yn2,out yo2,out. Table 1. Regression coefficients for the partial condensation model Coefficient y O2,out y Ar,out y CO2,out rec CO2 Constant P compr (bar) T flash ( o C) (Ar/CO 2) (N 2/CO 2) (O 2/CO 2) (P compr) E (T flash) (Ar/CO 2) (N 2/CO 2) (O 2/CO 2) (P compr)*(t flash) (P compr)*(ar/co 2) (P compr)*(n 2/CO 2) (P compr)*(o 2/CO 2) (T flash)*(ar/co 2) (T flash)*(n 2/CO 2) (T flash)*(o 2/CO 2) (Ar/CO 2)*(N 2/CO 2) (Ar/CO 2)*(O 2/CO 2) (N 2/CO 2)*(O 2/CO 2) R Q cool (MJ/kmol CO2 prod) From the regression equation, it was found that purity varies more with pressure than with temperature. At each pressure, the range of variation of purity with temperature is An average temperature of -50 o C is fixed for the purity equation. By doing this, purity is now a function of flue gas composition and pressure only. The adjusted coefficients are given in the table. The user fixes purity and recovery. From these two values, pressure and temperature are calculated. Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 5

14 Figure 3. Variation of CO2 purity and recovery with pressure and flash temperature. Range of CO2 purity: For a given temperature, purity increases with lower pressures. So the minimum purity occurs at 35 bar and maximum purity occurs at 25 bar. These values are used to calculate the range of CO2 purity. yco2_min = yco2 at 35 bar (9) yco2_max = yco2 at 25 bar. (10) For a specified purity, the operating pressure is calculated by solving the quadratic equation of CO2 purity. Quadratic term of the equation is calculated as follows: a_p=a_yco2(7); Linear term of the equation is calculated as follows: b_p=a_yco2(2) + a_yco2(13)*(ar/co2) + a_yco2(14)*(n2/co2) + a_yco2(15)*(o2/co2); Constant term of the equation is calculated as follows: c_p=a_yco2(1) + a_yco2(3)*0 + a_yco2(4)*(ar/co2) + a_yco2(5)*(n2/co2) + a_yco2(6)*(o2/co2) + a_yco2(9)*(ar/co2)^2 + a_yco2(10)*(n2/co2)^2 + a_yco2(11)*(o2/co2)^2 + (Ar/CO2)*(a_yCO2(19)*(N2/CO2) + a_yco2(20)*(o2/co2)) + a_yco2(21)*(n2/co2)*(o2/co2) yco2 Finally, pressure is calculated as follows: p = (- b_p sqrt(b_p^2-4*a_p*c_p))/(2*a_p) (11) Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 6

15 Figure 4. Variation of CO2 recovery with pressure and flash temperature. Range of CO2 recovery: At a given pressure, recovery increases with lower temperature. So the minimum recovery occurs at -40 o C and maximum recovery occurs at -55 o C. These values are used to calculate the range of CO2 recovery, for the pressure calculated above. recco2_min = recco2 at -40 o C. (12) recco2_max = recco2 at -55 o C. (13) For a specified pressure (calculated from CO2 purity) and recovery, the operating temperature is calculated by solving the quadratic equation of CO2 recovery. Quadratic term of the equation is calculated as follows: a_t_flash = a_recco2(8); Linear term of the equation is calculated as follows: b_t_flash = a_recco2(3) + a_recco2(12)*p + a_recco2(16)*(ar/co2) + a_recco2(17)*(n2/co2) + a_recco2(18)*(o2/co2); Constant term of the equation is calculated as follows: c_t_flash = a_recco2(1) + a_recco2(2)*p + a_recco2(4)*(ar/co2) + a_recco2(5)*(n2/co2) + a_recco2(6)*(o2/co2) + a_recco2(7)*p^2 + a_recco2(9)*(ar/co2)^2 + a_recco2(10)*(n2/co2)^2 + a_recco2(11)*(o2/co2)^2 + p*(a_recco2(13)*(ar/co2) + a_recco2(14)*(n2/co2) + a_recco2(15)*(o2/co2)) + (Ar/CO2)*(a_recCO2(19)*(N2/CO2) + a_recco2(20)*(o2/co2)) + a_recco2(21)*(n2/co2)*(o2/co2) recco2. Finally, temperature is calculated as follows: T_flash = (-b_t_flash sqrt(b_t_flash^2-4*a_t_flash*c_t_flash))/(2*a_t_flash) (14) Flow rates of components in the CO2 product are given as: MCO2,product = recco2*mco2,in MN2,product = yn2,out*mco2,product/yco2,out MO2,product = yo2,out*mco2,product/yco2,out MAr,product = yar,out*mco2,product/yco2,out Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 7

16 Distillation Model Distillation is used to further purity CO2. The main design parameter for the distillation column is the amount of O2 present in the CO2 product. Depending on the application, O2 purity should be <100 ppm or < 10 ppm. recco2 = *((Ar+N2)/CO2) *(O2/CO2) + 3.8x10-5 *(O2 ppm) *(Tdistill) (R 2 =98.97%) If O2 ppm and Tdistill are specified, recco2 can be calculated from the equation above. On the other hand, if O2 ppm and recco2 are specified, the above equation can be used to calculate Tdistill. To simplify calculations for a combined partial condensation and distillation process, Tdistill is fixed at its minimum value of -59 o C and O2 concentration is fixed at 10ppm. Qcool,distill (MJ/kmol gas in) = *yCO2,in *Tdistill *( yco2,in) 2 (R2=98.97%) The CO2 product from the distillation column is almost 100% CO2 and a very small amount of O2. The presence of N2 and Ar is negligible, compared to the concentration of O2. Hence it is assumed that only CO2 and O2 are present in the CO2 product and the other gases go out through the vent stream. Molar flow rates of gases in CO2 product and vent streams are calculated as follows: MCO2,product = recco2*mco2,in MO2,product = yo2/(1 yo2)*mco2,product MCO2,vent = (1-recCO2)*MCO2,in MO2,vent = MO2,in MO2,product MN2,vent = MN2,vent MAr,vent = MAr,vent For simplifying calculations, a combined partial condensation and distillation model was developed. Inputs to this are the flue gas composition into CPU. Table 2 shows the coefficients for parameters in a combined partial condensation and distillation model. Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 8

17 Table 2. Regression equations for the combined condensation and distillation model Coefficient rec CO2 Q cool (distillation only) (MJ/kmol CO2 prod) Coefficient T_flash ( o C) Constant Constant P compr (bar) P compr (bar) T flash ( o C) (Ar/CO 2) (Ar/CO 2) (N 2/CO 2) (N 2/CO 2) (O 2/CO 2) (O 2/CO 2) rec CO (P compr) (P compr) (T flash) E-05 (Ar/CO 2) (Ar/CO 2) (N 2/CO 2) (N 2/CO 2) (O 2/CO 2) (O 2/CO 2) (rec CO2) (P compr)*(t flash) (P compr)*(ar/co 2) (P compr)*(ar/co 2) (P compr)*(n 2/CO 2) (P compr)*(n 2/CO 2) (P compr)*(o 2/CO 2) (P compr)*(o 2/CO 2) (P compr)*(rec CO2) (T flash)*(ar/co 2) (Ar/CO 2)*(N 2/CO 2) (T flash)*(n 2/CO 2) (Ar/CO 2)*(O 2/CO 2) (T flash)*(o 2/CO 2) (Ar/CO 2)*(rec CO2) (Ar/CO 2)*(N 2/CO 2) (N 2/CO 2)*(O 2/CO 2) (Ar/CO 2)*(O 2/CO 2) (N 2/CO 2)*(rec CO2) 216 (N 2/CO 2)*(O 2/CO 2) (O 2/CO 2)*(rec CO2)* R R T_flash prediction was close to temperatures higher than -55 o C. So the lower end of T_flash is changed from -59 o C to -55 o C. The range of T_flash now is -55 o C to -40 o C. Figure 5. CO2 recovery and purity for condensation and distillation. Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 9

18 Recovery is higher at lower temperatures and higher pressures. For a given flue gas, recco2_min = recovery at 25 bar and -40 o C (15) recco2_max = recovery at 35 bar and -55 o C (16) Fix p=30 bar. If T_flash is <-55oC, then p=35 bar. If T_flash>-40oC, then p=25 bar. (17) CO2 Compressor Model CO2 compressor was also modeled in Aspen Plus as a function of varying inlet and outlet pressures. Inlet pressure was varied between 25 and 35 bar, and the outlet pressure was varied between 120 and 160 bar. The following regression equations were developed from the results of the Aspen models. Work required for compression (kwh/kmol CO2 product total): WCO2compr,ideal (kwh/kmol CO2 product total) = *Pin(bar) *Pout(bar) (R2=99.57%) WCO2compr,act (kwh/kmol CO2 product total) = WCO2compr,ideal/EffCompr (18) WCO2compr,act (kwh/kmol CO2) = WCO2compr,act (kwh/kmol CO2 product total) / Purity Cooling duty required for compressor inter-cooling is given by the following equations: Qcool,CO2compr (MJ/kmol CO2 prod total) = *Pin(bar) *Pout(bar) *Eff_compr (R2=99.59) (19) To convert it to per kmol of CO2, this has to be divided by CO2 purity. This heat is supplied by cooling water. CPU Efficiency Factor The CPU refrigeration load requirement (partial condensation and distillation) calculated using the models above were validated with the energy requirement values presented in the DOE 2010 Oxy-fuel report. The DOE reports present the total CPU energy requirement, which includes refrigeration and compression. For these case studies, compression work is calculated from the IECM models developed above and subtracted from the total work given in the DOE report. KeyLogic clarified that the refrigeration system used is an auto-thermal system, which means that the refrigeration load is met by internal heat integration without any need for external electrical input. A CPU adjustment factor was calculated to account for modeling differences between the Aspen models and the models used in the DoE report. The coefficients are shown int table 3. Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 10

19 CPUfactor = WDoE/WIECM (20) CPUfactor = for compression only and for partial condensation (21) CPUfactor = for partial condensation + distillation (22) The overall CPU energy requirement is calculated as: WCPU (kwh/kmol CO2)= (WCompr,fg + WCO2Compr)*CPUfactor (23) Units for all the parameters above should be converted to kwh/kmol CO2. Table 3. Case studies to calculate CPU efficiency factor DOE case S12E S12F L12F S13F L13F Partial CPU configuration Partial condensation + Distillation condensation Inlet CO 2 mole fraction Inlet H 2O mole fraction Ar/CO N 2/CO O 2/CO Temperature of flue gas ( o C) Purity Recovery CO 2 product total (kmol/hr) 12,285 12,049 12,707 11,543 11,601 CPU energy total (kw) 62,100 64,740 67,140 62,090 65,780 CPU energy (kwh/kmol CO 2 prod) Calculated values Pressure (bar) T_flash ( o C) Refrigeration load (kwh/kmol CO 2 prod) Compression load (kwh/kmol CO 2 prod) CPU efficiency factor Order of Calculations The following order should be used for the overall system calculation: 1. Choose a configuration: a. Capture with impurities [only FG compression and drying] b. High CO2 purity (95-97%) [Partial condensation] Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 11

20 c. Ultra high CO2 purity (99.99%) [Partial condensation + Distillation] 2. Specify CO2 purity and recovery a. Config (a): Purity = CO2 mole fraction after drying b. Config (b): User specifies purity and recovery. Ranges are calculated using equations 9, 10, 12 and 13. c. Config (c): Purity is fixed at 99.99% (O2 purity = 10ppm). Ranges for recovery are calculated using equations 15 and Determine system operating pressure a. Config (a): Assume 30 bar b. Config (b): Equation 11, using coefficients from Table 1 c. Config (c): Equation 17, using coefficients from Table 2 4. Determine flash temperature a. Config (a): No flash b. Config (b): Equation 14, using coefficients from Table 1 c. Config (c): Equation 17, using coefficients from Table 2 5. Determine compression energy using Equation 6 and Equation Determine cooling duty to be supplied by cooling water using Equation 4 and Equation Determine refrigeration duty a. Config (a): No refrigeration b. Config (b): Qcool using coefficients in Table 1 c. Config (c): Qcool using coefficients from Table 1 + Table 2 8. Calculate CPU efficiency using Equation 21 or Calculate total CPU refrigeration energy required using Equation 23 CPU Cost Model CPU capital cost data was obtained from the 2010 DOE report on oxy-combustion power plants. Table 4 shows the data, along with relevant flow rates. Table 4. Relevant flow rates and capital costs of CPU from the 2010 DOE Oxycombustion Report DOE Oxyfuel Report Case S12D S12E S12F L12F S13F L13F Total CPU inlet flow (kmol/hr) 20,281 18,885 18,977 19,772 18,712 18,598 Total CO 2 prod flow (kmol/hr) 15,952 12,285 12,049 12,707 11,543 11,601 CO2 removal cost (x $1,000, 2007) CO 2 condensing HX $ 3,424 $ 4,292 $ 4,256 $ 3,759 $ 4,169 $ 4,376 CO 2 compression and drying $ 98,224 $ 77,523 $ 77,806 $ 80,579 $ 75,697 $ 78,375 Total $ 101,648 $ 81,815 $ 82,062 $ 84,338 $ 79,866 $ 82,751 The costs for individual components are plotted and exponential regression equations were fit as a function of flow rates. The capital cost of compression and drying unit fits well with CO2 product flow rate while that of the condensing heat exchanger fits well with the total CPU inlet flow rate, as shown in figure 6. Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 12

21 The final cost functions are given as: CCondensingHX ($M, 2007) = 2x10 12 (CPU inlet flow, kmol/hr) CCompr and Drying ($M, 2007) = (Total CO2 product, kmol/hr) Note: CPU inlet flow contains water vapor. Total CO2 product includes CO2 as well as other impurities. CCPU,total = CCondensingHX + CCompr and Drying Figure 6. Regression equations for capital cost of CPI. Other than the internal electricity consumption, there are no other VOM costs for the CPU unit. FOM costs are the same as the standard IECM defaults. User-Specified Configuration In this configuration, users can specify their own purity, recovery, energy penalty and cost. Mass balance equations are given below. Mgas,in (kmol/hr) = flue gas into CPU after direct contact cooler, sulfur polisher and drying. (After removal of H2O and all other components, other than Ar, N2, CO2 and O2). MCO2,out (kmol/hr) = MCO2,in * Recovery Mgas,out = MCO2,out/purity MAr,out = (1/3)*(1 purity)*mgas,out MN2,out = (1/3)*(1 purity)*mgas,out MO2,out = (1/3)*(1 purity)*mgas,out User can specify energy penalty in kwh/tonne CO2 (default value is 120 kwh/tonne) and Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 13

22 CPU capital cost in $M/tonne/hr CO2 (default value is 0.175). Direct cost of CPU = (CPU unit cost, $M/tonne/hr CO2)*(CO2 product, tonne/hr). IECM Screens Figures 7-10 show the input (Set Parameters) and output (Get Results) screens of the CPU model in IECM. The plant configuration is a PC plant with Membrane-based post-combustion CO2 capture unit. Figure 7. "Set Parameters" config screen for the CPU unit. Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 14

23 Figure 8."Set Parameters" purification screen for the CPU unit, 99.99% purity case. Figure 9. "Set Parameters" purification screen for the CPU unit, high purity case.. Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 15

24 Figure 10. "Set Parameters" purification screen for the CPU uni, low purity case. Case Studies Case studies were conducted using the performance and cost models developed before. NETL case S12E was used as the base case for inlet flue gas flow rate and composition. The results are presented in table 5. Sensitivity analysis was conducted by varying the purity and recovery. Results are shown in the following figures. Figure 11. Sensitivity analysis results. Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 16

25 Figure 12. Sensitivity analysis for the CPU case studies. Table 5. Case study input assumptions and results. Configuration Compression Partial Distillation only condensation Inlet CO 2 mole fraction Inlet H 2O mole fraction Inlet flue gas temperature ( o C) Ar/CO N2/CO O2/CO CPU inlet flow (kmol/hr) 18,885 18,885 18,885 Dried gas flow (kmol/hr) 15,625 15,625 15,625 Purity (%) Recovery (%) CO 2 product total (kmol/hr) 15,625 12,787 11,931 Minimum purity (%) Maximum purity (%) Pressure (bar) Minimum recovery (%) Maximum recovery (%) Flash temperature ( o C) Refrigeration duty (kwh/kmol CO2 prod) W_compr_total (kwh/kmol CO2 prod) W_compr_total (kwh/tonne CO2) eff_cpu W_CPU_total (kwh/kmol CO2) Cost_CondensHX ($M, 2007) Cost_Compr and Drying ($M, 2007) Cost_CPU_total ($M, 2007) Cost_CPU_total ($M/tonne/hr CO2, 2007) Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 17

26 References Besong, M.T., Maroto-Valer, M.M., Finn, A.J., (2013). Study of design parameters affecting the performance of CO2 purification units in oxy-fuel combustion. International Journal of Greenhouse Gas Control. 12, National Energy Technology Laboratory (2010). Cost and performance for low-rank pulverized coal oxy-combustion plants, Final Report, DOE/NETL-401/ National Energy Technology Laboratory (2013). Quality guidelines for energy system studies CO2 impurity design parameters, DOE/NETL-341/ Integrated Environmental Control Model - Technical Documentation CO2 Purification Unit 18