Energy Procedia Energy Procedia 00 (2010) 000–000 www.elsevier.com/locate/XXX
GHGT-10
New Energy Efficient Processes and Improvements for Flue Gas CO2 Capture Masahiko Tatsumi1, Yasuyuki Yagi1*, Kouji Kadono1, Kazuhiko Kaibara1 Masaki Iijima2, Tsuyoshi Ohishi2, Hiroshi Tanaka2, Takuya Hirata3, Ronald Mitchell2 １
2
Power Engineering R&D Center, Kansai Electric Power Co., 1-7 Hikaridai, Seikacho, Sourakugun, Kyoto 619-0237, Japan Mitsubishi Heavy Industries, Ltd., Environmental & Chemical Plant Division, Plant and Transportation Systems Engineering & Construction Center, 3-3-1 Minatomirai, Nishi-ku, Yokohama 220-8401, Japan 3 Hiroshima R&D Center, Mitsubishi Heavy Industries, Ltd., 4-6-22 Kannon-Shinmachi, Nishi-ku, Hiroshima-shi, Hiroshima 733-8553, Japan
Abstract The Kansai Electric Power Co., Inc. (KEPCO) has developed energy efficient chemical absorbents and economical processes which aim to reduce the cost of CO2 capture, in collaboration with Mitsubishi Heavy Industries, Ltd. (MHI). Together the companies have been developing and critically testing high efficiency, economical absorbents according to the latest absorbent development procedures and process simulation for CO2 capture processes. This work has been ongoing since 1991, using several Japan based R&D facilities and a pilot plant, used to verify improvements, located at Nanko Power Station in Osaka, Japan. Following significant testing of a range of absorbents in the mid 1990s, KS-1TM, KS-2 and KS-3 were developed. Based on subsequent rigorous evaluation of the three solvents, KS-1TM was selected for commercialization because of its overall technical and economical merits. During long-term pilot plant testing, the improved absorbents demonstrated superior performance in relation to the regeneration energy requirements leading to the following results: 2.94MJlkg-CO2 in combination with KS-1TM " and the Kansai Mitsubishi Carbon Dioxide Recovery (KM-CDR ProcessTM) commercial process. In addition, practical, commercially applicable improved absorbent properties such as low corrosiveness and low solvent consumption were also confirmed. KEPCO and MHI continue development work in this area and the current status is summarized as follows: The highly successful R&D phase has led to the commercial deployment of CO2 capture technology and seven (7) commercial CO2 capture plants are currently under operation, with a maximum CO2 capture capacity of 450 metric tons per day (tpd). These commercial plants are deployed in the chemical and fertilizer industry, where the operational performance is assisting in the improved development of R&D concepts. Two (2) further commercial plants are under construction, with commissioning expected in Q3 2010. For further cost reductions in relation to CO2 capture, recent work has focused on developing new energy efficient chemical absorbents and processes. Following modifications to the Nanko CO2 capture pilot plant a new "Energy Saving Process" , was developed, which leads to a greater than 10% steam consumption reduction over the MHI conventional process using KS-1TM absorbent. Additionally the same reduced steam consumption was recorded for tests using the KS-1TM absorbent. A thermal energy requirement of less than 2.5 MJ/kg-CO2 in combination with KS-1TM and the "New Energy Efficient Process" has been confirmed under the optimum operation condition of the CO2 capture process. In addition to select new absorbents which feature the best profile and fit to the actual operating condition, KEPCO and MHI have intensively evaluated vapor-liquid equilibrium (VLE) and reaction kinetics for a range of newly developed absorbents and their performance is presented in this paper. The above data was obtained using the Nanko CO2 capture pilot plant which operates under a natural gas fired boiler condition and we expect that the thermal energy requirement of coal fired boiler flue gas (with greater CO2 concentration condition) will be further reduced. Corresponding author. Tel.: +81-50-7104-9072, Fax: +81-50-7104-8938 E-mail address:
[email protected]
Corresponding author. Tel.: +81-50-7104-9072, Fax: +81-50-7104-8938 E-mail address:
[email protected]
KEPCO and MHI are continuing pilot tests for the "Energy Saving Process", leading to the application of this new process in commercial CO2 capture plant design. This paper introduces and presents the current status of the KEPCO & MHI CO2 capture technology and concepts for future energy reduction improvements. The paper will also include test results in relation to newly developed absorbents, and the "New Energy Efficient Process", which have enhanced the performance and reduced the associated energy penalty of the CO2 capture process. KEPCO and MHI are continuing the development of efficient absorbents and optimized processes, thus helping to facilitate the future wide scale deployment of CO2 capture technology as an effective counter measure against global warming. Keywords; KEPCO, MHI, global warming, CO2 capture, solvent, technological improvements, energy saving
1.0 Introduction and Background In response to issues concerning global warming and the contribution of industrial CO2 into the earth’s atmosphere, Kansai Electric Power Company (KEPCO) and Mitsubishi Heavy Industries, Ltd. (MHI) have been working together since 1990 to develop an advanced CO2 capture chemical absorption process which can be applied to the power generation sector as an effective and economic means to reduce industrial CO2 emissions. 2.0 CO2 recovery pilot plant at the Nanko Power Station The pilot plant was installed at KEPCO’s Kanko Power Station, located in Osaka, in 1991. The Nanko Power Station is fired by liquefied natural gas (LNG) and the CO2 content in the flue gas is about 10% and is almost atmospheric pressure. Figure 1 shows the view of the CO2 capture pilot plant, and the corresponding specifications and process flow schematic are shown in Table 1 and Figure 2 respectively.
Figure 1. Nanko CO2 capture Pilot Plant Table 1. Specification of Nanko Pilot Plant Description Flue Gas Flow Rate CO2 Recovery Volume CO2 Recovery Rate Recovered CO2 Purity
Unit 600 Nm3 / h (1/3000 of 600MW flue gas) 2 tpd 90 % (design basis) 99.9 %
To stack Wash water cooler
CO2 recovery Cooler
Water washing
CO2 separation
Cooler
Flue gas cooler
Ｐａｃｋｉｎｇ
Absorber
Regenerator CO2 Heating steam
Flue gas
Flue gas blower
Recirculation pump CO2 rich absorbent
Reboiler
Cooler
Figure 2. Process flow of Nanko CO2 capture pilot plant
Corresponding author. Tel.: +81-50-7104-9072, Fax: +81-50-7104-8938 E-mail address:
[email protected]
3.0 Development of new absorbents including the commercially applied KS-1TM solvent The initial R&D test campaigns were undertaken using monoethanolamine (MEA) as an absorbent. However results indicated that MEA is highly corrosive, and requires significant energy for absorbing and recovering CO2 at around 900 kcal/kg- CO2, which leads to a large low pressure steam requirement. To reduce the overall regeneration energy requirement, which is the most important issue for chemical absorption, we conducted a number of extensive tests using various kinds of amines in the early 1990s. This led to the development of three new kinds of advanced absorbents (KS-1TM, KS-2 and KS-3). Figure 3 shows the rate of CO2 absorption in relation to steam supply for the 3 KEPCO and MHI developed solvents versus MEA. This data shows that the steam requirement for the KEPCO and MHI developed absorbents was reduced by more than 30kg/h compared with MEA. The energy required for regeneration of the KEPCO and MHI developed absorbents was about 700 kcal/kg- CO2 (about 2.9MJ/kg CO2). This data was based on long-term continuous operation and represents a 20 to 25 percent energy saving compared with MEA. Based on subsequent rigorous evaluation of the 3 KEPCO and MHI developed solvents, KS-1TM was selected for commercialization because of its overall technical and economical merits.
CO2 Absorption (%)
100 MEA
90 80 70
KS-1TM KS-2
60
KS-3
50 50
100
150
200
Steam Supply (kg/h)
Figure 3. Comparison of the efficiency of MEA and absorbents developed by KEPCO and MHI 4.0 Commercial CO2 capture plants Along with technical development and improvements highlighted above, nine (9) commercial CO2 recovery plants, using KS-1TM solvent, have been delivered worldwide, with the first plant deployed in Malaysia in 1999 (Figure 4). In the majority of the commercial CO2 recovery plants, CO2 is recovered from a natural gas fired reformer flue gas and used as a feedstock which reacts with ammonia to produce urea which is used as a fertilizer. 33 88
77
2006 India (Aonla) 450 t/d
44
2006 India (Phulpur) 450 t/d
2010 Pakistan 340 t/d
22
2010 Bahrain 450 t/d
99
KEY
2005 Japan 330 t/d
2010 Vietnam 240 t/d
Plants under operation
Plants under construction
66
2009 Abu Dhabi 400 t/d
55
2009 India 450 t/d
11
1999 Malaysia 200 t/d
Figure 4. Map of MHI commercial CO2 recovery plant locations 4.1 Example of a commercially operating CO2 capture plant As an example, two (2) commercial 450 tpd CO2 recovery plants were supplied to the Indian Farmer’s Fertilizer Co-operative Ltd. (IFFCO), which currently represent the largest operating post combustion CO2 capture plants in
Corresponding author. Tel.: +81-50-7104-9072, Fax: +81-50-7104-8938 E-mail address:
[email protected]
the world (Fig. 5). An outline of each plant is provided in Table 2 and these plants have been operating, with high performance, since commissioning in December 2006.
CO (CDR)Plant Plant–– CO22 Recovery Recovery (CDR) IFFCO PhulpurUnit Unit(India) (India) IFFCO Phulpur
CO 2 Recovery CO Recovery(CDR) (CDR)Plant Plant–– 2 IFFCO AonlaUnit (India) IFFCO AonlaUnit (India)
Figure 5. Commercial 450 tpd CO2 recovery plants for IFFCO (Aonla site and Phulpur units) India Table 2. Commercial CO2 capture plant performance for IFFCO’s Aonla and Phulpur units Measurement Item Aonla CO2 Recovery (CDR) Phulpur CO2 Recovery (CDR) Plant Plant Flue gas flow rate (Nm3/hr) 132,000 129,000 Flue gas CO2 concentration (%) 8.1 8.2 Flue gas NOx concentration 254 257 (vol-ppm) Flue gas SO2 concentration 6 6 (vol-ppm) CO2 recovery rate (%) 90 90 CO2 product purity (%) >99.9 >99.9 5.0 Process Improvements 5.1 Improved Process For further reduction of steam consumption in the CO2 capture process, we have developed a unique patented concept that utilizes lean solvent and steam condensate heat for regeneration inside the stripper. Figure 6 shows the outline of the Improved Process flow, as reported in GHGT-8. This process has now been applied commercially to one of MHI’s newly deployed CO2 capture plants; the 400 tpd FERTIL plant in Abu Dhabi (Fig. 7). Treated Gas
C.W.
CO2
Absorber
Flue Gas Quencher C.W.
C.W.
Heat Recovery & Solvent Regeneration
Flue Gas
C.W.
Figure 6. Process flow of the Improved Process
Steam Condensate
Stripper
Corresponding author. Tel.: +81-50-7104-9072, Fax: +81-50-7104-8938 E-mail address:
[email protected]
Figure 7. Commercial CO2 recovery plant in Abu Dhabi utilizing the Improved Process. 5.2 Energy Saving Process The process improvements, identified below, were tested and the high performance of the Energy Saving Process was confirmed through modification of the Nanko CO2 capture pilot plant. - Increased CO2 loading of rich amine by reduced absorber temperature - Reduced absorbent heat loss by decreasing absorbent recirculation rate - Reduced CO2 reflux cooler heat loss by lowering the temperature at the top of the regenerator 5.3 Nanko pilot test results using KS-1TM In order to evaluate the effectiveness of the improvements described above, several tests were conducted at the Nanko CO2 capture pilot using KS-1TM solvent. As a result, a CO2 recovery and regeneration energy requirement of 603kcal/kg CO2 (= 2.53MJ/kg CO2) was achieved by demonstrating the Energy Saving Process. This represents an overall energy reduction of about 10 percent when compared with the Improved Process described in section 5.1. The test results of recent process improvements at the Nanko CO2 capture pilot plant are shown in Table 3. 6. Development of new absorbents 6.1 Energy calculation simulation for CO2 recovery The required energy to recover and regenerate CO2, using the chemical absorption process, largely depends on three fundamental characteristics; (1) "the heat of reaction of CO2 in chemical absorbent ", (2) "gas-liquid equilibrium of CO2 and absorbent" and (3) "reaction rate constant". Since these characteristics are independent from each other, required energy for CO2 recovery and regeneration, as an overall performance indicator is difficult to predict. However, as reported in GHGT 9, KEPCO and MHI have developed a method to calculate the CO2 recovery energy with the data obtained through laboratory tests such as; (a) "reaction heat of CO2 and absorbent", (b) "effective absorption capacity from vapor-liquid equilibrium data" and (c) " CO2 absorption rate derived from reaction rate constant. This calculation flow is shown in Figure 7. Performance of new absorbents was predicted utilizing this calculation method. ●回収熱量計算式 Energy calculation for CO2 Recovery Laboratory test data ラボ試験データ Gas liquid equilibrium
Reaction rate 反応速度
気液平衡 Relate to specific & 顕熱・蒸発熱に関連 vaporization heat
Recovery rate
吸収率
Heat of reaction
反応熱
Relate to heat of 熱離熱に関連 dissociation
Relate to CO2 CO2回収量に関連 recovery volume
Figure
Energy calculation for CO2 recovery CO2回収エネルギーを計算
7. Calculation flow sheet of CO2 recovery energy
Corresponding author. Tel.: +81-50-7104-9072, Fax: +81-50-7104-8938 E-mail address:
[email protected]
6.2 Nanko CO2 capture pilot plant test results of newly developed absorbents Nanko CO2 capture pilot plant tests were conducted using two newly developed absorbents whose performance was predicted by the method described in 6.1 above. As a result, the best performing of these absorbents achieved a CO2 recovery and regeneration energy requirement of 583kcal/kg CO2 (= 2.44MJ/kg CO2) using the process performance described in section 5.2 above. The characteristics of this new absorbent, regarding corrosiveness and volatility, were confirmed through a series of recent laboratory tests. The results, together with KS-1 TM absorbent, are shown in Table 3. Table 3. Nanko CO2 capture pilot plant test results of KS-1TM and new absorbents Test conditions Test results
KS-1TM
10.2 10.2
System condition Cooling : Yes or No Energy Saving : Yes Cooling : No Cooling : Yes
New absorbent 1 (yet to be officially named) New absorbent 2 (yet to be officially named)
10.3 10.4
Cooling : No Cooling : Yes
85.0 87.3
694 601
10.1
Cooling : No
84.7
657
10.3
Cooling : Yes
77.8
583
Test absorbent
CO2 concentration at plant Inlet (%)
CO2 recovery rate (%)
Required energy for CO2 recovery (kcal/kg CO2)
90.3 82.5
669 603
7. Future plan 7.1 Application to commercial CO2 capture plant Since overall effectiveness of these various CO2 capture process and technology improvements has been proven using the Nanko CO2 capture pilot plant tests, these improvements will be applied to commercial CO2 capture plants, to be designed and delivered by MHI. As an example, a recent CO2 capture plant delivered in the Middle East (Fig. 8) incorporates the Improved Process described in section 5.1 and this is currently the highest performing commercial CO2 capture plant. In addition to commercialization of the process improvements on commercial plants using LNG fired flue gas, data on the performance of these systems will be collected for coal fired flue gas via various coal fired CCS demonstration projects being developed around the world. It is expected that coal fired flue gas with higher concentrations of CO2 will lead to a further reduction in CO2 capture and regeneration energy requirement. Therefore, for coal fired flue gas conditions, the steam consumption will be even less then what has been reported in this paper; 603kcal/kg CO2 (= 2.53MJ/kg CO2). 8. Summary KEPCO, together with MHI, will continue to develop new, higher performance absorbents and processes to further reduce the energy requirement associated with CO2 capture and to ensure this important technology can be deployed, on a global scale, as an effective and economical countermeasure to climate change. If higher performing and economically superior absorbents are developed, utilization of such absorbents will be taken into consideration as alternatives to the current commercial offering of KS-1TM. 9. References (1) Y. Yagi, Development and Improvement of CO2-Capture system. 8th International Conference on Green House Gas Control Technology (2006) (2) Y. Yagi. Etal, Calculation method for predicting thermal energy required for CO2 recovery plant, 9th International Conference on Green House Gas Control Technology (2008) (3) S.Kishimoto et. al., Current Status of MHI’s CO2 Recovery Technology and Optimization of CO2 Recovery Plant with a PC Fired Power Plant. 9th International Conference on Green House Gas Control Technology (2009)
