Techno-Economic Study of CO 2 Capture from a Cement Plant

Transcription

1 Górazdze Cement SA (HeidelbergCement) Techno-Economic Study of CO 2 Capture from a Cement Plant Dursun Can Ozcan, Hyungwoong Ahn, Stefano Brandani s.brandani@ed.ac.uk University of Edinburgh, Institute for Materials and Processes

2 Outline 1. Background 2. Detailed Base Cement Plant Simulation 3. Integration of Selected CO 2 Capture Technologies with the Base Cement Plant: Ca-looping Process Ca-Cu Looping Process Indirect Calcination Amine Process Membrane Process 4. The Economic Evaluation of the CO 2 Capture Processes 5. Conclusions Ozcan D.C., Ahn H. and Brandani S. Process Integration of a Ca-Looping Carbon Capture Process in a Cement Plant. International Journal of Greenhouse Gas Control, 2013, 19, DOI: /j.ijggc

3 1. Background Global CO 2 emissions hit a new record of 34.5 Gt in Gt by ,2 CO 2 concentration has reached 400 ppm in 2013, representing an increase of 24% from Fossil fuels will remain as dominant energy provider for combustion systems unless clearer alternative energy systems are developed. 4 The UK aims for at least 80% reduction in its CO 2 emissions relative to 1990 levels by Olivier et al., PBL 2013 Report. 2 IEA, World Energy Outlook Dlugokencky and Tans, NOAA/ESRL, IEA, World Energy Outlook Climate Change Act,

4 Carbon Capture and Storage (CCS) A promising and an emerging way of reducing CO 2 emissions from the main contributors: fossil-fuelled power stations and industrial processes Up to 19% reductions in CO 2 emissions by 2050 can be achieved 1 CO 2 capture accounts for 65-85% of the overall cost associated with CCS 2 It is important to develop efficient and cost-effective carbon capture technologies 1 IEA, Energy Technology Perspectives, Rao and Rubin, Environ. Sci. Technol., 4467,

5 Motivation and Objectives The demand of cement has reached 3.78 billion tons in The cement industry is the second largest anthropogenic greenhouse source. 2 It is important to extend CO 2 capture to cover cement industry to reach the CO 2 capture target stated in the Climate Change Act. 3 In this study, the primary aims are: o Evaluate the techno-economic performance of the Ca-looping process for CO 2 capture from cement plants o Investigate an advanced configuration of the Ca-looping process where the energy intensive ASU is replaced with a CLC o Assess various alternative carbon capture technologies including oxycombustion, amine process, indirect calcination and membrane processes 1 CW Group, Global Cement Volume Forecast Report, IEA, Carbon Emission Reductions up to 2050, Climate change act,

6 2. CO 2 Emissions from Cement Industry Schematic diagram of a cement plant 60% of the total emission accounts for calcination of limestone in raw meal A more efficient thermal management has potentially reduced CO 2 emissions 1 Carbon capture technology is essential to reduce CO 2 emission up to 90% 1 Hasanbeigi et al., Renewable and Sustainable Energy Reviews, 6220,

7 Chemical Reactions Reaction ΔH (kj) For 1kg of CaCO 3 (Calcite) CaO + CO 2 (g) CaCO 3 AS 4 H (pyrophyllite) α-al 2 O 3 + 4SiO 2 (quartz) + H 2 O(g) +224 AS 4 H AS 2 H 2 (kaolinite) α-al 2 O 3 + 2SiO 2 (quartz) + 2H 2 O(g) +538 AS 2 H 2 2FeO OH (goethite) α-fe 2 O 3 + H 2 O(g) +254 FeO OH 2CaO + SiO 2 (quartz) ß-C 2 S -734 C 2 S 3CaO + SiO 2 (quartz) C 3 S -495 C 3 S 3CaO + α-al 2 O 3 C 3 A -27 C 3 A 6CaO + 2 α-al 2 O 3 + α-fe 2 O 3 C 6 A 2 F -157 C 6 A 2 F 4CaO + α-al 2 O 3 + α-fe 2 O 3 C 4 AF -105 C 4 AF o The enthalpy of formation of 1kg of a Portland cement clinker is around kj/kg 1,2 1 Cement Chemistry, H F W Taylor, 2 nd ed Mojumdar et. al. Ceramics Silikaty, 110,

8 Phase Change in Cement Plant Preheaters out Pre-Calciner Kiln Pre-heaters 30% sulphur reacts with oxygen Partial CaCO 3 calcination Partial clay minerals decomposition Pre-calciner CaCO 3 calcination (>90%) and clay mineral decomposition completed. Partial conversion of CaO to C 2 S. Kiln C 2 S to C 3 S conversion. C 3 A and C 4 AF formed. Aluminate and Ferrite melting. Cement Chemistry, H F W Taylor, 2 nd ed

9 Mass and Energy Balances Composition of raw meal feed Clinker composition The simulated clinker compositions are in good agreement with those estimated by the Bogue equation The CO 2 generation intensity is around 0.8 ton CO 2 /ton clinker that is within the range of ton CO 2 /ton cement 1 The required thermal energy for unit clinker production is estimated to be 3.13 MJ th /kg clinker in an agreement with reported values 2 ( MJ th /ton clinker) 1 IEA, Tracking Industrial Energy Efficiency and CO2 emissions, WBCSD, Cement Industry and CO 2 Performance,

10 3. Calcium Looping Process Charitos et al., Powder Technology, 117, La Perada, Spain (1.7 MW pilot plant, Ca-looping agent (CaO) circulates between two reactors: CaO + CO 2 CaCO 3 (ΔH 923 K = 171 kj/mol) * Carbonator: CO 2 from the exothermic carbonation reaction at 600 C C * Calciner: CaCO 3 is regenerated to CaO by endothermic calcination above 870 C Advantages: cheap CaO sorbent; relatively small energy penalty; mature CFB systems, smaller ASU; purge for cement manufacture Challenges: Sintering (loss of reactive surface area), sulphation and attrition 10

11 Carbonator Model Two mathematical models for carbonator have been compared in the study; The simple model (all active fraction of CaO reacts with CO 2 ) The rigorous model 1 : * CFB model operates in the fast fluidization regime * Particle distribution part has been applied from K-L model; lower dense region and upper lean region * The CO 2 concentration at the exit has been estimated from the gaseous material balance by considering the first order kinetic law of carbonation degree The effect of sulfidation was considered by adjusting the k and X r constants corresponding to sulfidation level of Piaseck limestone 2 (valid up to 1% sulfidation) The carbonator model was implemented fully into UniSim via a component object model (COM) interface 1 Romano, M.C. Chem. Eng. Sci. 257, Grasa et al. Ind. Eng. Chem. Res., 1630,

12 Selection of an Optimal Feed Stream 40 Raw mill 1 st Preheater 2 nd Preheater 3 rd Preheater 4 th Preheater Precalciner Kiln CO 2 concentration (mole%) Relatively low (~22 vol%) Higher CO 2 concentration (~35 vol%) 0 Temperature [C] Raw Mill 1 st Preheater 2 nd Preheater 3 rd Preheater 4 th Preheater Pre-Calciner Kiln Cooler Flue gas needs to be heated up to 650 C. Solid Flow Gas Flow Flue gas temperature is around 650 C no preheating is required. The flue gas temperature and CO 2 mole fraction varies over the cement process 12

13 Process Integration 1) The flue gas from 3 rd Preheater is diverted to the carbonator. 2) CO 2 depleted flue gas from the carbonator is routed to the 2 nd Preheater for the raw material preheating. 3) Part of excess air from the cooler is used for additional raw material heating. 4) Purge from the carbon capture calciner is sent to the kiln. 13

14 Results Carbonator Model 6 5 Rigorous model (w/ S) Rigorous model (w/o S) Simple model F R /F CO F 0 /F CO 2 F 0 = flow of make-up CaCO 3 ; F CO2 = flow of CO 2 in the carbonator gas inlet Range of F 0 /F CO2 ratios have been examined Lower limit is set as 0.20 The heat demand in raw mill cannot be met Upper limit is determined as 5.80 No calcite in the raw materials 14

15 Results Efficiencies Incremental energy consumption per CO 2 avoided [GJ th /ton CO 2 avoided] % CO 2 recovery in the carbonator 90% CO 2 avoidance Energy Consumption without Heat Recovery At oxy-calciner Energy Consumption with Heat Recovery At oxy-calciner Carbon Dioxide Avoidance Rate At oxy-calciner CO 2 avoidance rate [%] Incremental energy consumption per CO 2 avoided [GJ th /ton CO 2 avoided] Energy Consumption without Heat Recovery Energy Consumption with Heat Recovery CO₂ recovery in the carbonator CO 2 recovery in the carbonator [%] F 0 /F CO2 F 0 /F CO2 Either 90% CO 2 recovery in the carbonator or 90% overall avoidance rate. The net energy consumption per unit clinker production is in the range of 5.0 to 5.5 GJ th /ton clinker. The incremental energy consumption estimates are similar and give a minimum at 5.1 F 0 /F CO2 with a value of 2.5 GJ th /ton CO 2 avoided. 15

16 Alternative CO 2 Capture Options Indirect calcination: Tackles CO 2 emission resulting from limestone calcination 1 Hybrid configuration: An additional CO 2 capture unit (amine) combined with the indirect calcination process to improve CO 2 avoidance rate Standalone amine process: A retrofit integration including a CHP plant for steam generation Rodriguez et al., I&ECR, 2126,

17 Process Integration Indirect Calcination Limestone and clay minerals are fed into two separate raw mills 10% calcination in the preheater Potential air leakages have been neglected (negative impact on CO 2 purity) 17

18 Process Integration Hybrid and Amine Solvent: 30 wt% MEA Steam source: CHP Plant SCR and FGD units for NO x and SO x emissions CO 2 avoidance rate is set to 90% by adjusting capture efficiency in the absorber 18

19 Process Integration Membrane Process A vacuum pressure of 0.22 bar and feed pressure of 1.1 bar to give a pressure ratio of 5, which was reported as economically affordable 1 Commercial membrane, Polaris TM with a CO 2 permeance of 1000 GPU and CO 2 /N 2, CO 2 /O 2 and CO 2 /H 2 O selectivities of 50, 10 and 0.2, respectively 2 Two feed gas locations: Option 1, preheater exit gas stream (32 mol%); Option 2, end-of-pipe gas stream (22 mol%) Four dual stage configurations: different combinations using counter-current and cross flow modules 1 Merkel et al., Journal of Membrane Science, 126, Merkel et al., Journal of Membrane Science, 441,

20 Results - Comparison CO 2 capture technology Indirect calcination Hybrid process Amine process Membrane process Type of integration Only hot solid circulation Flue gases from the kiln and combustor Flue gases from the CHP and cement plants Retrofit or 1 st preheater CO 2 capture efficiencies (%) CO 2 capture rate CO 2 avoidance rate (%) Net power generation (MW e ) Energy Consumption (GJ th /ton CO 2 avoided)

21 4. Economic Analysis The final conclusion of the comparison of various different system integrations should take economic feasibility into consideration Levelised cost of cement production (LCOC) has been estimated for the base cement plant and the capture cases The cost of CO 2 avoided can be calculated from the increase in LCOC Levelised cost of cement production ratio of the net present value of total capital, variable and operating costs of a cement plant to the net present value of cement production over its operating life TCR t total capital requirement M t O&M cost V t variable cost, C t cement production rate Cc carbon capture process t and r are the operating year and discount rate IEA, CO 2 Capture in the Cement Industry, July 2008/3,

22 Economic Analysis The main financial assumptions were taken from IEA 1 and IEA GHG R&D programme Technical & Financial Assessment Criteria 2 The reference cost data were updated using the six-tenths rule and the M&S index The fuel and raw material costs were taken from IEA 1, DOE 3, etc. As a base approach, the same electricity cost was utilized as revenue for surplus power generation 4 The additional benefits from ETS is included 5 (industries emitting CO 2 pay a 14 /ton CO 2 ) The following equation proposed by Abad et al 6 was employed to estimate the cost of CuO/Al 2 O 3 sorbent. C m was given as 1 $/kg OC 1 IEA, CO 2 Capture in the Cement Industry, July 2008/3, IEA GHG, Technical & Financial Assessment Criteria DOE Greenhouse Gas Emissions Control by Oxygen-firing in CFB, Rodriguez et al., ES&T, 2460, IEA GHG, Biomass CCS Study, Abad et al., Chem. Eng. Sci., 533,

23 Results Cost Estimates 200 ETS Variable 160 O&M Important sensitivities: Revenue of power generation Reuse of CLC sorbent Grid emission factor Emission regulations LCOC [ /ton cement] Cost of CO 2 avoided [ /ton CO 2 avoided] Base Cement Plant Ca-looping (0.6) Ca-Cu Indirect looping (0.02) Calcination Amine Process Hybrid Process All results are for 90% CO 2 avoidance The values in the parentheses refer to F 0 /F CO2 ratio TCR Membrane Process 0 Ca-looping (0.6) Ca-Cu looping (0.02) Indirect Calcination Amine Process Hybrid Process Membrane Process 23

24 5. Conclusions Different ways of capturing CO 2 from cement plants by integrating it with Calooping, Ca-Cu looping, indirect calcination, amine and membrane processes have been investigated The base cement plant is in good agreement with those reported in the literature The gas stream leaving the 3 rd preheater was selected to be a feed suitable for the carbonator since o it does not have to be preheated o it has a higher CO 2 partial pressure and lower total volumetric flow rate o a simpler design of steam cycle for heat recovery is possible The fuel consumption of 2.5 to 3.0 GJ/ton CO 2 avoided which depends on the F 0 /F CO2 ratio with a heat recovery system is estimated for the Ca-looping process, while the cost is in the range of /ton CO 2 avoided 24

25 Conclusions The energy consumption reduces to 1.7 GJ th /ton CO 2 avoided in the Ca-Cu looping process because of the absence of an ASU, but the cost of sorbent is the major concern for this system. It was presented that the indirect calcination process can provide partial CO 2 reduction (56%) when it is properly integrated to a cement plant The hybrid process provides improvements in energy consumption and cost compared to the standalone amine process Membrane process is competitive with the Ca-looping process in terms of energy consumption and cost For more details on all the projects from our group please see 25

26 Acknowledgements Carbon Capture Group Members Financial Support: Turkish Ministry of Education Honeywell for providing UniSim R400 software Part of this work was awarded the first prize at the 2013 UniSim Design Challenge Student Competition for Europe, Middle East and Africa 26