Part 2 CCT Overview
Coal-fired Power Generation Technologies (Combustion Technologies)

2A5. Coal Partial Combustor Technology (CPC)
Research and development: Japan Coal Energy Center; Kawasaki Heavy Industries, Ltd.;JFE Steel Corp.; Chubu Electric Power Co., Inc.; and J-POWER
Project type: Coal Production and Utilization Technology Promotion Grant
Period: 1978-1986 (9 years)

Technology Overview

1. Background and technology overview
Owing to the abundant reserves and wide distribution ofhigh speed into a swirling melting furnace in a tangential

producing countries, the supply of coal is highly stable, and coaldirection, thus partially combusting (gasification) the coal underis well positioned as an important energy source for the future.

the conditions of a high-temperature, heavy load, and strong

However, compared with other fuels, such as oil and gas, coal

reducing atmosphere. After most of the ash in the coal is melted

contains large amounts of ash and nitrogen, which poses manyand separated for removal, the produced fuel gas is subjected toutilization issues, including equipment problems caused by ash,secondary combustion. CPC is a technology of coal gasificationand significant increases in NOx emissions. Furthermore, global

combustion in a boiler or a gas turbine to utilize coal highly-warming has become an international concern in recent years,efficiently and in an environmentally compatible manner. Theremaking it an urgent requirement to develop technology to reduce

are two variations of CPC technology: one utilizing atmospheric

CO2 emissions, one of the main causes of global warming. Sincepressure to produce atmospheric pressure clean gas with low

coal generates a large volume of CO2 per calorific value, there iscalorific value, and the other under a further pressurized

a need worldwide to develop technology to use coal in a highly-environment to produce highly-efficient power generation inefficient, environmentally compatible way. A Coal Partial

combination with a gas turbine.

Combustor (CPC) is a furnace where coal and air are injected at

2. Atmospheric pressure coal partial combustor technology
Slag-tap boilers aim to reduce the volume and detoxify the ash
Pre-heating burnerdischarged from the boiler and to use difficult-to-combust coal.
They have been constructed and have been operated in a large

Preliminary

number of Western countries. The conventional slag-top boiler

combustor

BaffleSecondarycombustor

has the advantages of high combustion efficiency and therecovery of ash as nontoxic molten slag. However, the method
Combustionair

has the drawback of significant NOx emissions caused by hightemperature combustion.

High-temperature
combustion gas

Responding to this issue, our technology development focused
Pulverized
coalon the development of a coal partial-combustor system aiming tosimultaneously remove the ash from coal and limit NOxemissions. The developed system has the CPC directly mounted
to the side wall of the boiler. The combustible gas generated in
the CPC is directly injected to the boiler furnace, where the gas iscompletely combusted with injected air.
As small to medium coal-fired boilers, CPC can significantly

Molten slag

reduce NOx emissions while maintaining the compactness of theboiler on a scale similar to that of an-oil fired boiler. It can recoverFig. 1 Schematic drawing of an atmospheric pressure coal partial
combustor (CPC) boiler

all the coal ash as molten slag. Figure 1 shows a schematic
drawing of a atmospheric pressure CPC boiler.

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Clean Coal Technologies in Japan

3. Pressurized coal partial combustor technology
On the basis of the results of the atmospheric pressure CPC

Figure 2 below shows a basic flow chart of a pressurized CPC pilot

development, the development of pressurized CPC technology

plant having 25 t/d of coal gasification capacity (operating at 21%

began, with the objective of developing a high-efficiency power

oxygen). The pilot plant ran the coal gas generation test using CPC

generation system by pressurizing CPC and combining it with aunder a pressure of 20 ata, which can be applied to a gas turbine.

gas turbine.

The test proved the effectiveness of the pressurized CPC.

Pressurized pulverized coal feeder

Kerosene tankGas cooler

Ceramic filter

Gas incinerator
Pulverized coalproduction unit

Denitration unit
Flux feeder

Liquid oxygen tankChar hopper

CoolerPrimary air compressor
Slag tankChar feeder

Air compressor

Desulfurization unit

Liquid nitrogen tankFig. 2 Basic flow chart of a pressurized CPC pilot plant

4. Issues and feasibility of practical application
Atmospheric pressure CPC technology has already been brought
into practical application as a low NOx emission technology inswirling melting furnaces of municipal waste gasification melting
furnaces and in very low NOx boilers for heavy oil combustion.
Atmospheric pressure CPC technology is also being used in thedevelopment of a coal-ash-melting, low NOx boiler. A pilot plant
test for the pressurized CPC technology is nearing completion,and the technology is in the research and development stage inthe private sector, with the aim of bringing it to practical use.
These basic technologies have also been integrated with thedevelopment of biomass gasification gas turbine power generation
technology.

Photo 1 Pilot plant30