1. Overview and objective of IGCC demonstration test
Integrated Coal Gasification Combined Cycle (IGCC) is a high-efficiency power generation technology which gasifies coal to be used as the fuel for gas turbines. Japanese power companies promoted the research and development of IGCC technology, applying a Nakoso pilot plant (PP)-type gasifier1,2 as the core technology3. The PP-type gasifier utilizes dry-coal-fed, oxygen-enriched air-blown, pressurized two-stage entrained beds, as shown in Figure 1. This is expected to provide higher efficiency than preceding gasifiers from abroad. On the basis of the feasibility study results, an IGCC demonstration test project was started with the aim of validating IGCC’s reliability, operability, maintainability, and profitability, and to confirm the feasibility of a coal-fired IGCC commercial plant.
Compared with conventional pulverized coal-fired power plants, IGCC has many advantages, such as:
- Improved power generation efficiency: Compared with conventional pulverized coal-fired power plants, IGCC can increase power generation efficiency by approximately 20% for commercial plants.
- Lower environmental burden: Owing to the increase in power generation efficiency, the emissions of SOx, NOx, and dust per generated power unit are lower. In addition, CO2 emissions are reduced to the level of the heavy-oil-fired power generation process.
- Flexibility to use different grades of coal: IGCC can use coal with low ash melting points, which is difficult to use in conventional pulverized coal-fired power plants. As a result, IGCC broadens the variety of coal grades that can be used in coal-fired power plants.
- Increase in fields that can utilize the ash: Since IGCC discharges coal ash in the form of glassy molten slag, the ash is expected to be effectively used as component for civil engineering work.
- Reduction of water consumption: Since the generated gas is desulfurized directly, IGCC does not need a flue gas desulfurization unit, which consumes large amounts of water. Accordingly, IGCC uses significantly less water than conventional pulverized coal-fired power plants.
2. Specifications and objective of IGCC demonstration plant
Figure 2 shows the process flow of the IGCC demonstration plant. Table 1 lists the main specifications and target values. Figure 3 is a conceptional drawing of the IGCC demonstration plant. The scale of the plant (250 MW, 1700 t/d of coal feed) is about one-half of a commercial plant. The gasifier is of the Nakoso PP-type. A wet gas clean up system with MDEA has been adopted. The gas turbine is a 1200°C-class gas turbine, with a corresponding output of 250 MW.
3. Organization for executing the IGCC demonstration test
The IGCC demonstrative test is being conducted by Clean Coal Power R&D Co., Ltd. (CCP R&D Co., Ltd.), which was established by nine power companies and J-POWER. The Ministry of Economy, Trade and Industry is subsidizing 30% of the project costs, and 70% of the costs are being borne by a total of eleven entities: nine power companies, J-POWER and the Central Research Institute of Electric Power Industry (Fig. 4).
4. Timetable and progress
Table 2 shows the schedule of the demonstration project. The demonstration plant has been under construction since March 2006. A three-year test operation of the plant is scheduled to begin in the second half of FY2007.
5. Activities to date
The pilot plant test (200 t/d of coal feed), which is a preliminary stage of the demonstration test, was carried out from 1986 to 1996 at Joban Joint Power Co., Ltd.’s Nakoso power plant in Iwaki City, Fukushima, (Fig. 5). The pilot plant test was conducted jointly by nine power companies, plus J-POWER and the Central Research Institute of Electric Power Industry, as an entrusted project of NEDO. A pilot plant test of 4,770 hours, including 789 hours of continuous operation, proved the practical applicability of the IGCC technology3. Based on the success of the pilot plant test, a demonstration test introduced an optimum system, which was selected following a feasibility study conducted by NEDO. After conducting a variety of surveys, Joban Joint Power Co., Ltd.’s Nakoso power plant was again selected as the site for the demonstration test, which is being conducted at the same site of the pilot plant.
References
1) Shozo Kaneko et al., "250MW AIR BLOWN IGCC DEMONSTRATION PLANT PROJECT,"Proceedings of the ICOPE-03, pp. 163-167, 2003.
2) Christopher Higman, Maarten van der Burgt, "Gasification," pp. 126-128, 2003.
3) Narimitsu Araki and Yoshiharu Hanai: Bulletin of Japan Energy, 75-9, pp. 839-850, 1996.
Source: New Energy and Industrial Technology Development Organization (NEDO), Japan Coal Energy Center (JCOAL)
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