Principal Research Results

Development of Biomass/Waste Power Generation Systemwith Carbonizing Gasifier and Gas Engine
BackgroundTo create a sustainable recycle-oriented society, it is important to develop the utilization technology for biomass and solid
waste, which are promising energy resources. In general, biomass and solid waste are widely and thinly distributed, so it is not easy togather up them in large amounts. Therefore it is difficult to improve the generating efficiency of the biomass and solid waste power
generation system through adoption of large-scale operations.

Objectives
The aim of our project is to suggest a small-scale and high-efficiency power generation system utilizing biomass and solidwaste. The integration of carbonizing gasification technology and the gas engine technology allows such a power generation system.
The performances of the carbonizing gasifier and the gas engine are evaluated with the demonstration test facilities as a joint researchof CRIEPI and Kansai EP (Kansai Electric Power Co., Inc.), in order to put the developed system to practical use.

Principal Results
1. Features of the system
CRIEPI has developed the carbonizing gasifier using biomass and solid waste as fuel. On the other hand, Kansai EP has
developed the small and high-efficiency gas engine generator with natural gas. The small-scale and high-efficiency power generation
system with biomass and solid waste (as shown in Fig.1) has been devised by integration of both technologies. The installation ofcarbonizer, as a pretreatment of gasifier, makes it possible to use a variety of fuels. The utilization of waste heat from the gas engine,as a heat source of the carbonizer, results in high thermal efficiency of the system.
2. Performance of carbonizing gasifier
A gasification test (as shown in Fig.2) of Japanese cedar as a typical woody biomass was carried out. Table 1 shows theindustrial analysis and ultimate analysis of Japanese cedar. As the result of the test, the calorific value of produced gas was higher than
1,000kcal/m3N by maintaining air ratio of 0.42 or less. The performance of gasifier achieved cold gas efficiency over 67.5% (calorificvalue of produced gas 1,170 kcal/m3N, carbon conversion over 99%) at 0.39 air ratio.
3. Performance of gas engine
The original gas engine generator (rated power 440kW) runs on natural gas, and has adopted a pilot ignition system whichshows high ignition performance. The gas-supplying system of the gas engine was redesigned for the low-calorie gas. In case of theproduced gas, of which calorific value is about one-tenth of that of natural gas, the rated power of the gas engine was 320kW, and thegenerating efficiency of the gas engine reached 34% in LHV basis. Furthermore, the stable operation of the gas engine with a lowcalorie produced gas, of which calorific value is 850kcal/m3N, was carried out by optimization of fuel-feeding condition. It means thathigh-moisture biomass is available as the fuel of this system. Fig.3 shows the operation condition of the gas engine.
4. Performance of the system
In the operation of the carbonizing gasification and gas engine power generation system with biomass and waste, the performance targets of gasifier and gas engine were attained (as shown in Table 2). The combined efficiency of the gasifier and gas engine
power generation system was over 23% on LHV basis. So, the system was found to be small-scale, but to have an extremely-highperformance (as shown in Fig. 4).

Future Developments
Some modifications of the system for higher performance will be made. The heat transfer test of the gas-gas heat exchanger
will be planned. The test data will be useful in the design of the exhaust gas heat exchanger. The feasibility study on the practical plantof this system with food-processing waste will be carried out.
Main Researcher: Maromu Otaka, Ph. D.,
Research Scientist, Fuel Reforming Engineering Sector, Energy Engineering Research Laboratory
Reference
M. Otaka, M. Ashizawa, K. Kidoguchi and M. Tashiro, 2007, “Development of High-Efficiency Small-Scale Biomass Gasification
Process”, Proceedings of 3rd International Bioenergy Conference and Exhibition (BIOENEGY 2007), Finland, pp.499-505.

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7. New Energy

Table 1 Industrial analysis andultimate analysis of woody
biomass (cedar)

exhaust gas
pyrolyticgas
Urban Garbage,
Waste Wood,
Shredder Dust,
etc…

syngasfuel
Carbonizer

cleangas
Cleanup&Gas Cooler

Gasifier

Power
Generating
Unit

industrial
analysischarmoisture 6.0 - 7.3
ash0.2
VM84.5
FC15.3exhaust gas

To feed thecarbonizer withmost of thewastes including
urban garbage,
shredder dust, etc.

To carbonize andpyrolize wastes athigh efficiency by
exhaust heat from thesystem without using
supplemental fuel.

To reform
pyrolytic gas at
temperature over1000 degC byusing carbonizedchar as fuel.

To generate
electric power by
gas engine andto utilize
sensible heat ofexhaust gas
for carbonizer

Cooling thereformed gas, toremove hazard us
constituents out of
the gas and purify
it into fuel gas.

CHNOS

ultimateanalysis

higher heating value

wt%wt%,dbwt%,dbwt%,db50.30
6.210.06
43.21
0.02wt%,dbwt%,dbwt%,dbwt%,dbwt%,db

19.84

MJ/kg

Fig.1 Basic flow of carbonizing gasification gas engine
power system

1200

300

1000

Cold Gas Efficiency %

800
10080

1200

250

1000

1060kcal/Nm3
200

800

150600Power Output
Fuel Flow Ratio
Fuel HHVRate Speed

100
50

60
400.301400

1220kcal/Nm3

0.35

0.40
Air Ratio -

0
17:00

0.45

17:10

17:20

17:30
Time

17:40

400

Rate Speed rpm
Fuel Flow Ratio Nm3/h
HHV kcal/Nm3350

Generating Power kWHHV kcal/Nm3

1400

2000
18:00

17:50

Fig.3 Operation condition of gas engine(decreasing HHV of fuel gas)

Fig.2 Gasification performance of cedar

The calorific value of produced gas decreases from 1220kcal/m3N to 1060kcal/m3N,
the gas engine generator is to be stably-operated. Therefore, the rated power and rated
speed maintain the constant value 320kW and 1200rpm respectively.

A decrease in air ratio increases calorific value of
produced gas, but air ratio under 0.39 increases
unburnt carbon, and decreases cold gas efficiency.

unit
higher heating value kcal/m3Nof produced gastarget

actual1000 1000-1250

cold gas efficiency%

6567.5

carbon conversion

%

9099

flow rate fluctuation%

1510generating efficiency %,LHV
of gas engine

3234%,LHV

20

23

total efficiencyof system

As a result of the demonstration test, the carbonizing gasifier
and gas engine showed good performance exceeding the targets.
Total generating efficiency of the system reached 23% on
the LHV basis.

Gross Thermal Efficiency ％50Table 2 Performance of present system

Circulating FluidizedBed Boiler

40
PresentSystem

30

Bubbling
Fluidized BedBoiler

20
10Stoker Boiler
0100

1,000

10,000100,000

1,000,000

Generation Power kW

Fig.4 Comparison with other biomass-fired power plants
The new biomass/solid waste power generation system co-developed withKansai EP is small-scale, but shows higher efficiency than otherbiomass/solid waste-fired power systems.

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