Clean Coal Technologies in Japan

2A4. Pressurized Internal Circulating Fluidized-bed Combustion Technology (PICFBC)
Research and development: Japan Coal Energy Center; Ebara Corporation
Project type: Coal Production and Utilization Technology Promotion Grant
Period: 1992-1998

Technology Overview

1. Overview
PICFBC’s basic technology is the technology of the internal
circulating fluidized-bed combustion boiler (ICFBC) described inthe preceding section. The PICFBC mounts ICFBC in apressurized vessel.

2. Features
The pressurized internal circulating fluidized-bed boiler (PICFBC)
applies the circulation flow technology of the previously-described
ICFBC. Accordingly, the load is controllable without varying theheight of the fluidized-bed. In addition, cooling of the combustion
gas is avoided because the intra-bed heat transfer tubes are notexposed on the bed during the load controlling action, which
minimizes the generation of CO2 and eases the maintaining
temperature at the inlet of the gas turbine. Since the wear
problems of the heat transfer tube in the bed are decreased,

silica sand can be used as the fluidizing material, and the amountof limestone can be minimized to a level necessary for the intrafurnace desulfurization, thus suppressing the generation of ash.
Furthermore, the main combustion chamber has no intra-bed
heat transfer tube so that the problem of interference of the intrabed heat transfer tube against the movement of the particles
does not occur, which prevents the generation of agglomeration,
the solidification of a melted medium.

3. Technology overview

Fig. 1
Schematic drawing of PICFBC

and the circulation flow is created between the main combustion
chamber and the heat recovery chamber.
Figure 2, (p. 27), shows a basic system flowchart of a pilot plant
test in Sodegaura plant. The coal feed unit has two lines: the lockhopper system, which feeds lump coal, and the CWP (Coal WaterPaste) system, which feeds coal as slurry mixed with water. The
flue gas dust is removed by a ceramic high-temperature bag filter.
The lock hopper system technology is applied to develop thepressurized two-stage gasification technology.

Figure 1 shows a schematic drawing
of a PICFBC. The cylindrical pressure
vessel contains a cylindrical ICFBC.
Similar to ICFBC, silica sand is usedas the fluidizing material. Thefluidized-bed is divided into the main
combustion chamber and the heatrecovery chamber by the tilted
partition. The swirling flow is createdin the main combustion chamber,

4. Study sites and application fields
The PICFBC pilot plant test was carried out at a site next to theIdemitsu Kosan Co., Ltd.’s Coal Research Laboratory (Nakasode,Sodegaura City, Chiba). Potential applications include the steam
turbine generator, using the generated steam, and the gas
turbine generator, using the combustion flue gas. IGCC at coalfired thermal power plants, therefore, are potential candidates forthe technology. Photo 1 shows a PICFB hot model installation of4 MWth. Photo 2 shows an overview of a pressurized two-stage
gasification plant (30 t/d of waste plastics throughput). The
pressurized two-stage gasification technology can be utilized tosynthesize ammonia from coal, as well as to produce hydrogenfor fuel cell power generation. The pressurized two-stage

gasification technology has been in operation as a commercialplant (195 t/d of waste plastics throughput) at Showa Denko
K.K.’s Kawasaki plant since 2003.

Photo 1PICFBC facility

Photo 2Pressurized, two-stage gasification plant

5. Period of development
The ICFBC pilot plant test was carried out from 1992 to 1997,
jointly conducted with the Center for Coal Utilization, Japan (nowknown as JCOAL), as a Coal Utilization Technology Promotion
Grant Project of the Ministry of Economy, Trade and Industry(formerly the Ministry of International Trade and Industry). The

test operation began in December 1996. The pressurized, twostage gasification technology was developed jointly with Ube
Industries, Ltd. Demonstrative operation of the plant (30 t/d ofwaste plastics throughput) began in January 2000, andcommercial operation commenced in January 2001.

6. Progress and study subjects
As a coal-fired PICFBC, the study progressed to the pilot plant
test at Sodegaura. The technology, however, was developed to apressurized two-stage gasification technology in which a thermalload and a lock hopper system in the pressurized fluidized-bed

have been applied. The issues of the pressurized system include
the improvement of the reliability of the lock hopper system in thefuel charge line as well as measures to prevent low temperature
corrosion.
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