Techno-Economic Analysis of a 550 MW e Atmospheric Iron-Based Coal-Direct Chemical Looping Process

Transcription

1 Technical Paper BR-1911 Techno-Economic Analysis of a 550 MW e Atmospheric Iron-Based Coal-Direct Chemical Looping Process Authors: L.G. Velazques-Vargas, D.J. DeVault, T.J. Flynn, and T. Siengchum Babcock & Wilcox Power Generation Group, Inc. Barberton, Ohio, U.S.A. L. Zeng, A. Tong, S. Bayham, and L.-S. Fan The Ohio State University Columbus, Ohio, U.S.A. Presented to: 3rd International Conference on Chemical Looping Date: September 9-11, 2014 Location: Göteborg, Sweden

2 Techno-economic Analysis of a 550 MW e Atmospheric Iron-Based Coal-Direct Chemical Looping Process BR-1911 Luis G. VELAZQUEZ-VARGAS 1# *, Douglas J. DEVAULT 1, Tom J. FLYNN 1, Tritti SIENGCHUM 1, Liang ZENG 2, Andrew TONG 2, Samuel BAYHAM 2, L.-S. FAN 2. 1 Babcock & Wilcox Power Generation Group, Inc., 20 South Van Buren Avenue, Barberton, OH 44203, USA 2 The Ohio State University, William G. Lowrie Chemical and Biomolecular Department, 140 W Nineteenth Ave, Columbus, OH 43210, USA *Corresponding Author, address, # Presenting Author Abstract Babcock & Wilcox Power Generation Group, Inc. (B&W PGG), in collaboration with The Ohio State University (OSU), has performed a technoeconomic analysis of a commercial 550 MW e iron-based Coal-Direct Chemical Looping (CDCL) power plant. The CDCL process consists of a unique moving bed reactor, namely the reducer, where coal is fully converted using iron oxidebased oxygen carrier particles. In the reducer, the oxygen carrier is reduced from Fe 2 O 3 to a mixture of FeO and Fe. The conversion of coal generates a stream of carbon dioxide (CO 2 ) that can be sequestered. The reduced oxygen carrier particles leaving the reducer are then oxidized back to Fe 2 O 3 using air in the combustor reactor. The oxygen carrier oxidation reaction liberates heat that is used to produce steam for the supercritical Rankine cycle. The CDCL process has shown the potential for lower capital and operating costs as compared to first generation carbon capture technologies such as amine-based solvent systems. Based on the results of the techno-economic evaluation, B&W PGG projects that the CDCL process will achieve 96.5% CO 2 capture with a 28.8% increase in the cost of electricity when compared to a supercritical pulverized coal (PC)-fired power plant with no CO 2 capture. In this study, the advancement in the design of the CDCL process along with the latest experimental data on the 25 kw th pilot plant is presented. The results from the techno-economic study on a commercial CDCL plant are also discussed. 1

3 1 Background Information Coal is an important primary energy source and is used to produce 40% of the electricity worldwide [1]. The use of coal, however, releases large quantities of carbon dioxide (CO 2 ) to the environment. According to the International Energy Agency, more than 70% of the carbon dioxide emissions that arise from power generation can be attributed to coal [1]. Given the environmental concerns on climate change, there is a growing interest in reducing CO 2 emissions from coal-fired power plants. To help reduce the environmental impact of coal in the future, power plants may be required to adopt carbon capture and sequestration (CCS) technologies. There are several available CO 2 capture technologies such as monoethanolamine (MEA) absorption that can be retrofitted onto coal-fired power plants. However, these technologies are currently very capital and energy intensive and increase the cost of electricity by more than 60%. This increase in cost of electricity makes the CCS technologies unattractive to be widely adopted by utilities. As an alternative to MEA absorption, there are oxy-combustion technologies being developed worldwide for the production of energy with integrated CO 2 capture. These technologies are projected to be more economical and more efficient. Among them, the Coal-Direct Chemical Looping process is emerging as a promising technology capable of high efficiency with low cost for carbon capture. Figure 1 shows a schematic diagram of the CDCL process. The CDCL process uses an Fe 2 O 3 - based oxygen carrier particle to fully convert coal in a moving-bed reducer reactor. Here, coal is fully oxidized forming predominantly CO 2 and H 2 O while the Fe 2 O 3 is reduced to a mixture of FeO and Fe. After cleanup and compression, the CO 2 can be sequestered or used for enhanced oil recovery. The reduced particles (FeO and Fe) from the reducer are then transported to the combustor reactor where they are re-oxidized with air. The oxidation of the Fe and FeO mixture generates heat that is used to produce steam for power generation. Once the particles are fully regenerated, they are pneumatically recycled to the reducer reactor where another reduction-oxidation (redox) cycle begins. 2

4 Water Enhancer Gas Recycle Fan CO 2 Compressor FGD H 2 O CO 2 Sequestration CO 2 +H 2 O Spent Air Bag House ID Fan FGD Stack Fe 2 O 3 Fly Ash and Carrier Particle Fines Coal Coal Prep. Reducer Electricity Carrier Particle Makeup (Fe 2 O 3 ) Air ID Fan FeO/Fe Combustor Steam Water HP IP Steam Cycle Pump LP Cooling Tower Figure 1 Coal-Direct Chemical Looping Process for Power Generation. 2 Current Status of the CDCL Technology In the last decade, The Ohio State University (OSU) has developed an iron-based oxygen carrier particle that undergoes multiple reduction and oxidation cycles without significant decrease in activity. OSU s oxygen carrier particles are over ten times more reactive than iron ores and recyclable for more than 100 reduction-oxidation cycles. OSU has further improved particle support materials that enhance reaction rates and provides increased structural strength. OSU s oxygen carrier particles have low raw material cost, high oxygen carrying capacity, high melting point, high sulfur and ash resistance, low attrition rates and low environmental risks. The unique design of the reducer reactor uses a gas-solid counter-current contacting pattern that allows for complete coal utilization while achieving a high-purity CO 2 in the reducer reactor [2]. The combination of the iron-based oxygen carrier particles and the moving-bed technology allows for smaller reactor volumes which translate into lower capital costs. The moving bed design also allows the use of relatively large particle sizes compared to the char and attrited fines. The size difference between oxygen carrier and coal ash, which is roughly one order of magnitude different, facilitates the ash separation step. Furthermore, the reducer reactor design uses non-mechanical valves which increases system reliability and reduces particle attrition. 3

5 OSU has designed, constructed and operated an integrated 25 kw th -scale CDCL unit. The unit has been successfully demonstrated for over 680 hours of cumulative operation with various types of fuels, including metallurgical coke, and sub-bituminous, bituminous, and lignite coal. OSU s CDCL pilot unit achieved 200 hours of continuous, integrated operation; the longest reported continuous demonstration worldwide of a chemical looping pilot process for solid fuel conversion. Results obtained from the 25 kw th unit are shown in Figure 2. Figure 2a shows the carbon conversion profile as a function of time. As shown, the carbon utilization ranged between 80 and 100%, with an average during the 200 hours of 96.5%. Figure 2b shows the gas concentration profile at the outlet of the reducer. The CO 2 purity is close to 99%. Impurities were found to be traces of carbon monoxide and methane. The gas concentration profile at the outlet of the combustor is shown in Figure 2c. A depleted oxygen concentration was found, indicating oxygen consumption by the particle regeneration. Traces of carbon monoxide, carbon dioxide and methane were also found, indicating low carbon carryover to the combustor from the reducer. a) b) c) Figure 2 Sample data from the 200-hr run in the 25 kw th CDCL unit: a) Carbon conversion profile, b) Reducer outlet gas concentration profile, c) Combustor outlet gas concentration profile [4]. 4

6 Recently, B&W PGG was awarded a grant from the U.S. Department of Energy (DOE) to evaluate the commercial viability of the CDCL process. The project has two phases. In Phase I of the project, B&W PGG performed a techno-economic analysis of a 550 MW e iron-based CDCL commercial system. The results from this economic evaluation are summarized in the next section. For Phase II, B&W PGG will demonstrate the operation of the system at a 100 kw th scale. The facility will be located in B&W PGG s research center in Barberton, Ohio, USA. This demonstration will answer some of the technology gaps identified during Phase I of the project. 3 CDCL Plant Performance Simulation Table 1 shows the process simulation results for a 550 MW e supercritical CDCL plant and compares these results for plants using conventional technology. The CDCL power plant can achieve 96.5% CO 2 capture and compression to 153 bar (2,219 psi), while achieving an energy penalty (i.e., percent reduction in net efficiency) of 8.8% relative to a base supercritical PC power plant without CO 2 capture. This represents a substantial improvement compared to the 27.6% energy penalty associated with the use of a post-combustion MEA scrubbing system for CO 2 capture and compression from a supercritical PC plant. The increased net efficiency in the CDCL plant compared to the MEA plant arises largely because the CDCL plant does not require steam extraction for solvent regeneration. The solvent regeneration energy requirement significantly lowers the gross efficiency of the MEA plant and accounts for about two-thirds of its energy penalty. In contrast, the energy penalties in the CDCL plan arise from the fans and compressors required to overcome the pressure drop associated with transporting the carrier particles through the process. Table 1 Net Power Calculation for the Base Plant, MEA Plant, and CDCL Plant Base Plant (DOE Case 11) MEA Plant (DOE Case 12) CDCL Plant Coal Feed Rate (lb/h) 409, , ,549 Heat Input (MW t) 1,400 1,935 1,537 Steam Cycle Gross Power (kw) 580, , ,000 Total Auxiliaries (kw) -30, , ,653 Net Power (kw) 549, , ,347 Gross Efficiency (HHV, %) Net Efficiency (HHV, %) Energy Penalty (% Relative to the Base Plant) 27.6% 8.8% 4 CDCL Plant Economic Analysis B&W PGG performed an economic analysis of the CDCL process following DOE/NETL s Quality Guidelines. The Total Plant Cost (TPC) includes the advanced technology (CDCL equipment) and conventional balance of plant equipment. Capital costs for the CDCL process equipment were developed from B&W PGG cost estimating methodology commonly used for commercial proposals, 5

7 and supplemented with vendor cost data/quotes for most major equipment. The cost of balance of plant equipment was taken from the supercritical baseline (Case 11) from the NETL Report, Cost and Performance Baseline for Fossil Energy Plants Volume 1: Bituminous Coal and Natural Gas to Electricity (341/082312) and adjusted based for increase in capacity. A standard power rule of 0.6 was used to adjust the bare erected cost of equipment for the increase in capacity. The appropriate contingencies, variable costs and fixed costs were then added to the adjusted number. The capital cost estimate for the 550 MW e supercritical CDCL power plant is summarized in Table 2. Account Number Table 2 CDCL Power Plant Capital Costs Title Capital Cost ($x1000) 1 Coal & Sorbent Handling $ 49,476 2 Coal & Sorbent Prep and Feed $ 23,453 3 Feedwater & Misc. BOP Systems $ 102,728 4 CDCL Equipment $ 536,262 5 Flue Gas Cleanup $ 166,324 5B CO 2 Removal & Compression $ 87,535 6 Combustion Turbine/Accessories $ - 7 HR, Ducting & Stack $ 48,258 8 Steam Turbine Generator $ 156,140 9 Cooling Water System $ 47, Ash/Spent Sorbent Handling System $ 15, Accessory Electric Plant $ 66, Instrumentation & Controls $ 27, Improvements to Site $ 17, Buildings & Structures $ 71,487 Total Plant Cost (TPC) $ 1,416,222 Fixed operation and maintenance (O&M) costs are based on estimated staffing levels per the NETL Report, Cost and Performance Baseline for Fossil Energy Plants Volume 1: Bituminous Coal and Natural Gas to Electricity (341/082312). Adjustments were made for the additional staff required for the compression and purification unit (CPU). The plant operations personnel composite wage rate used to determine fixed O&M costs is 39.70$/hr. Variable O&M consumable costs are listed in Table 3. Table 3 Variable O&M Consumable Costs Consumable Cost Illinois No. 6 Coal, $/10 6 Btu HHV $2.94 Metal Oxide, $/ton $ Natural Gas (Startup Fuel), $/10 6 Btu HHV $6.13 Raw Water, $/1000 gal $1.67 Water Treatment Chemicals, $/lb $0.27 Ammonia, $/ton $330 Limestone, $/ton $33.48 Fly Ash/FGD Solids Disposal, $/ton $

8 The cost of electricity (COE) has been separated into its primary components: capital, fixed operating, fuel, oxygen carrier, and variable operating costs. The study shows that the CDCL process has the potential to meet DOE s target of 90% CO 2 capture with less than a 35% increase in the COE. Table 4 summarizes the economic analysis results for the CDCL plant and compares them with results for the base and MEA plants. The increase in cost of electricity according to this study is about 28.8%. Table 4 Economic Analysis Results for the Base Plant, MEA Plant, and CDCL Plant. Base Plant c (DOE Case 11) MEA Plant c (DOE Case 12) CDCL Plant Total Overnight Cost ($/kw) a 2,453 4,207 3,214 First-Year Capital Cost ($/MWh) a,b First-Year Fixed O&M Cost ($/MWh) First-Year Fuel Cost ($/MWh) First-Year Oxygen-Carrier Cost ($/MWh) First-Year Variable O&M Cost ($/MWh) First-Year Cost of Electricity ($/MWh) % Increase Over Base Plant % 28.8% a Includes bare erected cost, engineering and home office costs, process and project contingencies, and owner s costs. b Computed using a first-year capital charge factor of for the base plant and for the MEA and CDCL plants. c Extracted from DOE/NETL-2012/ Conclusions The results from B&W PGG s techno-economic evaluation of OSU s CDCL process indicate that the 550 MW e commercial scale CDCL power plant can meet and exceed the DOE goal for 90% capture at a less than 35% increase in cost of electricity. B&W PGG projects that the COE for CDCL power generation plant to increase by 28.8% while removing 96.5% of the CO 2. The economics for the CDCL technology compare favorably to first generation integrated gasification combined cyle (IGCC), oxy-coal combustion, and amine-based post-combustion CO 2 capture systems. The CDCL technology looks very promising. The Ohio State University has developed an iron oxidebased oxygen carrier particle suitable for operation in the CDCL process and has also demonstrated the technology at a 25 kw th scale. This unit has been continuously operated for more than 200 hours with a cumulative time of nearly 680 hours. The CDCL system has been demonstrated with various types of fuels including metallurgical coke, and bituminous, sub-bituminous and lignite coals. The CDCL moving bed configuration allows for increased or even near complete coal utilization, high CO 2 purity generation, and high particle conversion. Given the knowledge that OSU has accumulated regarding oxygen carrier particle design and B&W PGG s experience with commercial scale moving and fluid bed reactor designs, the 7

9 project team is confident and prepared to take the next step in developing the CDCL technology. 6 Acknowledgements This material is based upon work supported by the Department of Energy under Award Number DE-FE The advice and encouragement of the US DOE-NETL Project Manager, Mr. Steve Richardson, is gratefully acknowledged. Copyright 2014 Babcock & Wilcox Power Generation Group, Inc. All rights reserved. No part of this work may be published, translated or reproduced in any form or by any means, or incorporated into any information retrieval system, without the written permission of the copyright holder. Permission requests should be addressed to: Marketing Communications, Babcock & Wilcox Power Generation Group, Inc., P.O. Box 351, Barberton, Ohio, U.S.A Disclaimer Although the information presented in this work is believed to be reliable, this work is published with the understanding that Babcock & Wilcox Power Generation Group, Inc. (B&W PGG) and the authors and contributors to this work are supplying general information and are not attempting to render or provide engineering or professional services. Neither B&W PGG nor any of its employees make any warranty, guarantee, or representation, whether expressed or implied, with respect to the accuracy, completeness or usefulness of any information, product, process, method, or apparatus discussed in this work, including warranties of merchantability and fitness for a particular or intended purpose. Neither B&W PGG nor any of its officers, directors, or employees shall be liable for any losses or damages with respect to or resulting from the use of, or the inability to use, any information, product, process, method, or apparatus discussed in this work. 8 References [1] K. Burnard and S. Bhattacharya, Power Generation from Coal, International Energy Agency, France, [2] T. Thomas, L.-S. Fan, P. Gupta, and L.G. Velazquez-Vargas, Combustion Looping Using Composite Oxygen Carriers, U.S. Patent No. 7,767,191. [3] Samuel C. Bayham, Hyung R. Kim, Dawei Wang, Andrew Tong, Liang Zeng, Omar McGiveron, [4] Mandar V. Kathe, Elena Chung, William Wang, Aining Wang, Ankita Majumder, and Liang-Shih Fan (2013), Iron-Based Coal Direct Chemical Looping Combustion Process: 200 h Continuous Operation of a 25-kWth Subpilot Unit, Energy Fuels, 27, pp