The CCP Gasifier
Recently, a consortium of Japanese utilities led by Toyo Electric and The Central Research Institute of Electric Power Industry (CRIEPI) formed the Clean Coal Power R&D Company (CCP), which announced the construction of a commercial-scale
250 MW (1700 t/d) IGCC demonstration plant at Nakoso, Japan. Start-up is planned for 2007 (Kaneko, Ishibashi, and Wada 2002). The CCP gasifier features a dry feed with two-stage operation, but it uses air as the oxidant. The technology was initially developed by CRIEPI and Mitsubishi Heavy Industries (MHI) and tested in a 200 t/d pilot plant, also at Nakoso.
While pressurized dry-feed entrained-flow gasifiers can be considered to be proven technology (e. g., SCGP, Noell), and the same can be said of two-stage feeding (E - Gas), this is the first attempt to combine these two attractive features in a single gasifier.
Operating the first, “combustor,” stage in a combustion mode promotes very high temperatures and simplifies separation of the liquid slag from the gas. The oxidant, although stated as being air, is in fact enriched slightly with surplus oxygen from the nitrogen plant, which supplies inert gas for feed transport.
At the second, “reductor,” stage only coal is introduced, without any further oxidant. In the endothermic reaction with the gas from the first stage the coal is devolatilized and tars are cracked sufficiently that no problems occur in the downstream convective cooler. Most of the char is also gasified. Remaining char is separated from the gas in a cyclone and candle filter for recycle to the first stage. The
Figure 5-22. The CCP Gasifier (Source: Kaneko, Ishibashi, and Wada 2002) temperature drop over the reductor stage is 700°C with a reactor outlet temperature of around 1000°C.
Carbon conversion rates of 99.8% and more have been achieved regularly with a variety of coals.