SaskPower s Boundary Dam power plant: Integrated Carbon Capture and Storage project Boundary Dam, Saskatchewan, Canada

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1 SaskPower s Boundary Dam power plant: Integrated Carbon Capture and Storage project Boundary Dam, Saskatchewan, Canada Report on the industrial visit ( ) Dr Lionel Dubois Research Coordinator CO2 Capture and Conversion Scientific Coordinator of the ECRA Academic Chair Ir Sinda Laribi Research Engineer PhD Student ECRA Academic Chair University of Mons Faculty of Engineering (FPMs) Chemical and Biochemical Engineering Department November 2015 Dr L. Dubois & Ir S. Laribi ECRA Academic Chair Faculty of Engineering UMONS Belgium 1

2 Introduction In the framework of the «3 rd Post Combustion Capture Conference (PCCC-3)» organized at Regina (Saskatchewan, Canada) from 08 to 11 September 2015, Sinda Laribi and Lionel Dubois from the ECRA Academic Chair took part to the industrial visit of the world largest integrated Carbon Capture and Storage (CCS) plant installed at the Boundary Dam power plant of SaskPower company. The purpose of the present document is to summarize the main relevant information in relation with this industrial visit and especially regarding the Carbon Capture part. Presentation of the Boundary Dam CCS Project As illustrated on Fig.1, the Boundary Dam CCS Project includes four parts: 1/ Boundary Dam Carbon Capture Project; 2/ Carbon Capture test facility; 3/ Carbon Storage and Research Centre; 4/ Amine Chemical Laboratory. Figure 1: Illustration of the four parts included into the Boundary Dam CCS Project Fig. 1 gives also a summary of each component of the project. Indeed, in addition to the Boundary Dam Carbon Capture plant which will be further detailed in the present report, the global project includes: a carbon capture test facility (at Shand power plant) where different CO2 capture techniques are tested, the carbon storage and research centre focusing on the demonstration of CO2 storage and the amine chemical laboratory working in direct support to the CO2 capture carried out at Boundary Dam power plant. Dr L. Dubois & Ir S. Laribi ECRA Academic Chair Faculty of Engineering UMONS Belgium 2

3 A global overview of the Boundary Dam Carbon Capture project is given on Fig. 2. Figure 2: Global overview of the integrated Boundary Dam CCS project The SaskPower s Boundary Dam coal-fired power plant has a total production capacity of 800 MW. It is composed of six units installed from 1959 to The project concerns only the Unit No.3 of 150 MW production capacity. The flue gas (precise composition not communicated but the CO2 content was announced in the range 10 to 15%) from this unit is sent to the capture plant (see Fig. 3) where the SO2 and the CO2 are captured with an efficiency of 100% and 90% respectively thanks to a Shell Cansolv technology (more details later in this document). The captured SO2 is transformed in sulfuric acid and valorized as valuable by-product in the chemical industry. The resulting captured CO2 is compressed, transported through pipelines (Cenovus Energy), stored geologically (deep saline aquifer of more than 3 km depth, see Fig.4) and also valorized thanks to Enhanced Oil Recovery (EOR) in the Weyburn local oil field which is recognized as one of the largest geological CO2 storage project in the world. At full capacity, the SaskPower Integrated Carbon Capture and Storage (ICCS) Demonstration Project captures over 10 6 tco2/y, reflecting a 90% CO2 capture rate for the 139 MW (net output) coal-fired unit. Note that there are different local drivers that promote CCUS in the Saskatchewan region such as the new federal regulation for new and refurbished coal fired power plants effective in 2015 which fixes the CO2 emission limit at 420 kg/mwh. Moreover, the coal based generation is an important part of SaskPower s generation portfolio and there are large local coal reserve which allows a price stability. The fact that CO2 can be used for Enhanced Oil Recovery (EOR) in local oil field is also an important factor. Dr L. Dubois & Ir S. Laribi ECRA Academic Chair Faculty of Engineering UMONS Belgium 3

4 Figure 3: Illustration of the flue gas going from the coal-fired power plant to the combined SO2-CO2 capture plant 4a. Dr L. Dubois & Ir S. Laribi ECRA Academic Chair Faculty of Engineering UMONS Belgium 4

5 4b. 4c. Figures 4a, b, c: Illustrations of the injection well at SaskPower s Carbon Storage and Research Centre Note that due to a delay during the industrial visit we didn t have the opportunity to visit the Carbon Capture Test facility at Shand power plant (see Fig. 5). The purpose of this Carbon capture test facility is to evaluate different CO2 capture technologies (especially amine based absorption-regeneration process in the present case) by testing it on a real flue gas coming from the Shand coal power plant. Figure 5: Illustration of the Carbon Capture Test Facility at Shand Power plant As illustrated on Fig. 5, this facility is equipped with stairways in order to facilitate the access to take measurements, samples, etc. Dr L. Dubois & Ir S. Laribi ECRA Academic Chair Faculty of Engineering UMONS Belgium 5

6 Summary of the SO 2 -CO 2 capture plant in the Boundary Dam CCS Project The different vendors, partners and technology providers involved in the Boundary Dam project are given in Tab. 1. Table 1. Primary project vendors and partners of the Boundary Dam project The SaskPower Boundary Dam ICCS Project was announced as a major step towards the global deployment of the Shell Cansolv post-combustion CO2 capture technology. The technology uses two types of amines to capture both SO2 and CO2. The Cansolv process line-up for the SaskPower BD3 ICCS Project, presented in Fig. 6, includes a particular design enhancement: the selective heat integration with Shell Cansolv s innovative combined SO2/CO2 capture system helps to reduce energy requirements associated with carbon capture. With this approach, the Capture Plant steam requirement is significantly reduced. The pre-conditioned flue gas coming from the BD 150 MW unit N 3, after passing through an electrostatic precipitator, is firstly injected in the bottom of a first absorber where SO2 is absorbed in an amine based solvent (certainly a tertiary alkanolamine but not officially confirmed as it is confidential). The SO2-rich solution is pumped to a stripper where the solvent is regenerated before being sent back to the SO2-absorber and the SO2 is stripped out of the solvent and sent to a complementary unit in order to be converted into commercial sulfuric acid. To give an idea, roughly a tank and a half per day (± 60 th2so4/day) can be converted for use in fertilizer, filtration systems, chemistry labs, or a wide variety of other industrial purposes. Dr L. Dubois & Ir S. Laribi ECRA Academic Chair Faculty of Engineering UMONS Belgium 6

7 Figure 6: Shell Cansolv combined SO2/CO2 capture process used at Boundary Dam The remaining gas (still containing the major part of the initial CO2 but no more SO2) is sent to the CO2 absorption-regeneration process where it is captured (90% absorption efficiency) thanks to the use of another solvent (primary/secondary alkanolamine alone or activated solution but not officially confirmed as it is confidential) and then released at the top of the CO2-stripper in a gaseous form. The CO2 is then pressurized in an adjacent building to 170 bar (liquid state) and sent via pipeline to a metering station where the feed is split for disposition at an EOR field (66 km from the plant) or a geological injection site (2 km away). Based on the flow sheet presented on Fig. 6, different element can be highlighted: a part of the heat coming from the SO2 gas product is recovered to be used in the CO2- regeneration step ( Heat Recovery 2 on the flow sheet); a part of the heat coming from the regenerated solvent at the outlet of the CO2-stripper is directly reinjected into this stripper ( Heat Recovery 1 on the flow sheet, which seems corresponding to a Lean Vapor Compression (LVC) configuration); two amine purification units are directly included into the flow sheet in order to treat the regenerated solvents (no details on the purification process were given but it seems to be a thermal reclaiming unit). Note that a separate closed-cycle water treatment system and cooling towers were built for the capture facility to ensure that if any amine ever leaked, it would not be released to the environment. Dr L. Dubois & Ir S. Laribi ECRA Academic Chair Faculty of Engineering UMONS Belgium 7

8 More specifically, using the information given during the industrial visit, it was pointed out that the Boundary Dam capture site is composed by the following sections: 1. Purification of flue gas: the flue gas is previously purified thanks to filtration systems in order to eliminate fly ashes, metals, etc. As the regulations don t stipulate the need of De-NOx systems, it is not installed at Boundary Dam even if low-nox burners are used. 2. Pre-scrubber cooler: it cools and quenches gas, and it also removes some remaining dust, chlorides and fluorides. The water is recovered, the ph is adjusted and this water is used as make-up water for the cooling tower. This technique has two advantages: a lot of water make-up is saved and it is also useful for the removal of water soluble flue gas contaminants. 3. SO2 scrubber: as previously described, it removes the Sulphur dioxide to protect the CO2 capture process thanks to the use of an amine chemical solvent which absorbs selectively the SO2 before being later converted to sulfuric acid. 4. Caustic Polish: in the top of the SO2 scrubber, it removes 100% of any remaining SO2 and it reuses residual caustic generated within the CO2 capture system. 5. CO2 absorber: as previously described, this packed column captures the CO2 using an amine-water blend. A water wash section is included in the top of the column in order to absorb any residual amine and nitrosamine from the flue gas and avoiding any residual harmful emission in the atmosphere. 6. SO2 and CO2 strippers: two different stripping columns are used to regenerate each solvent and produce pure CO2 and SO2 flows. 7. Sulfuric acid plant: the SO2 is catalytically converted to market grade H2SO4 (SO2 is oxidized to SO3 and then H2SO4 is formed: SO3 + H2O H2SO4 leading to SO4 - - once dissolved into water) before being trucked (production of around th2so4/day). 8. CO2 compressor: the CO2 is compressed for pipeline transport to 172 bar thanks to the use of a 8 stages with intercooler between each stage except before the last stage. After the first floor stage, two desiccant driers remove moisture from CO2. At the end of the process chain, the CO2 production was evaluated at 3320 tco2/day ( 10 6 tco2/year) with 99.9 % of purity. 9. Heat rejection: inside the SO2-CO2 capture process, coolers are used to control the heat generation due to the exothermicity of the amine absorption reaction. The plant includes an evaporative cooling tower but also a water treatment plant whose waste water is rejected to an ash lagoon. Dr L. Dubois & Ir S. Laribi ECRA Academic Chair Faculty of Engineering UMONS Belgium 8

9 Based on different SaskPower s documents, the following reasons justify the choice of the Shell Cansolv s combined SO2-CO2 capture process: - Most of the capture technologies require ultra-low levels of SO2 in the flue gas prior to CO2 capture due to preferential absorption of SO2 by the amine solvent used in the CO2 capture unit. Using an SO2 capture system ahead of the CO2 capture system facilitates the removal of flue gas contaminants and has several advantages: o competitive pricing on the combined process package; o technical and operational simplicity by integration of a single, combined SO2 and CO2 capture plant with the power plant rather than use of separate capture systems; o the Cansolv combined capture process includes an energy recovery system that enables heat used to regenerate the SO2 solvent to be used in the CO2 capture system, which reduces the parasitic load of the combined capture system on the power plant and make it the most energy-efficient technology choice for Boundary Dam Unit 3. - SaskPower had gained considerable experience in technologies to capture and remove SO2 when designing the Shand Power Station as a requirement of its environmental permit. However, such low SO2 flue gas emission levels were not something that SaskPower had worried about before. One logical and proven process that was considered for achieving low SO2 flue gas emissions was high-performance Limestone Forced Oxidation (LSFO) scrubbing, an industry standard. While LFSO is an expensive process, it is a mature technology and commercially well understood, resulting in near zero risk of deployment. The LFSO process requires large quantities of limestone, which when reacted with SO2 produces calcium sulphate. In favorable markets, the calcium sulphate can be used to produce wallboard. However, Saskatchewan was not a region where wallboard produced from LFSO by-product would be commercially viable due to the distance of a limestone source (1000 km away in western Alberta) and the equally long transportation distance to off-takers (the end-user market). Consequently, LFSO was dismissed as an option for removing sulphur dioxide from the flue gas at Boundary Dam Unit 3. Ultimately, the regenerating amine in the Cansolv SO2 capture process was appealing from a costeffectiveness perspective in comparison to LFSO. The proven performance of the Cansolv SO2 capture process deployed at other coal-fired power stations in China and elsewhere was an important consideration. - The SO2 captured in the solvent absorption process could be recovered and converted into saleable Sulphuric acid that could be used by Saskatchewan-based chemical manufacturers to make Sulphur-based fertilizer. This additional valueadded by-product contributed to the positive business case for the combined Cansolv SO2-CO2 capture system. Considering these different technical, economical and local characteristics, it was quite logical for SaskPower to choose the combined SO2-CO2 capture technology proposed by Shell Cansolv. Dr L. Dubois & Ir S. Laribi ECRA Academic Chair Faculty of Engineering UMONS Belgium 9

10 Summary of the relevant figures of the Boundary Dam CCS Project The different data that were given during the visit and also available in different SaskPower documents are summarized in Tab. 2. Table 2. Summary of data available for the Boundary Dam project Unit Boundary Dam 150 MW Unit N 3 Flue gas composition Not communicated (CO2 content in the range 10 to 15 %) CO2 capture capacity 3300 tco2/day CO2 compressed to 170 bar, stored and used for EOR H2SO4 production capacity th2so4/day Budget billion CAN $ (1.005 billion ): 562 million CAN $ for the power plant 905 million CAN $ for the capture plant Note: 240 million CAN $ provided by a federal grant Construction 4.5 millions persons.hours Plant enclosed dimensions Building dimensions: 130 m x 37 m 9 m high at the south end 23 m high at north end Equipment Largest commercially available plate and frame heat exchangers CO2 compressor: - procurement by SaskPower and installation by SNC-Lavalin - 8-stage Integrally geared reciprocating compressor: - performance: 170 bar differential pressure CO2 and SO2 Absorber towers - Ceramic lined concrete, packed towers - Height : CO2 tower: 55 m and SO2 tower: 40 m - Construction: Concrete block wall on the outside, ceramic tiles lined and 316 stainless steel covers - Multiple absorption sections: 430 tons of total packing - Compact overall footprint design and cost reduction considerations CO2 rich Amine Stripper - Stainless Steel tower with internal packing - Dimensions: 7 m diameter x 41 m height - Total weight: 240 tons (shop fabricated and shipped to site in one piece detailed review of roads, bridges and high voltage transmission lines required) - 70 tons of structured packing. Energy information Total heat exchanged & rejected, including heat of CO2 compression: BTU/hr 717 GJ/h 5.2 GJ/tCO2 considering 3300 tco2/day (137.5 tco2/hour considering 24 hours working/day) Regarding the emissions Control, aside from the CO2 and SO2 which are captured in the new facility, other traditional emissions from Unit 3 are managed both according to regulation and capture process needs. NOx, which are not regulated in Saskatchewan, are controlled with overfire and underfire air and low-nox burners, which allows a reduction of around 50% of such emissions. Mercury is not controlled at Boundary Dam, although activated carbon injection is used at the nearby SaskPower Shand and river stations. Note that as for particulate matter from Unit 3, the flue gas is washed at least seven times after the precipitator, so it s virtually at zero after the capture process. Dr L. Dubois & Ir S. Laribi ECRA Academic Chair Faculty of Engineering UMONS Belgium 10

11 Finally, the performances of the Boundary Dam Unit 3 carbon capture are summarized in Tab. 3 with a short and a more detailed tables presenting the global emissions reduction before and after the installation of the CCS unit. Table 3. Summary of the Boundary Dam Unit 3 carbon capture project performance Dr L. Dubois & Ir S. Laribi ECRA Academic Chair Faculty of Engineering UMONS Belgium 11