**4.2 Experimental Setup**

A 50 kg/hr prototype downdraft gasification plant is also belonging to WIRC and located in Saha Pathana Industrial Park in Kabin Buri, Prachinburi province, Thailand. This plant consists mainly of 5 parts, as in the following: fuel preparation system, downdraft gasifier, heat exchanger, gas cleaning unit and internal combustion engine-generator, as shown in Figure 15.

Fig. 15. A 50 kg/hr prototype downdraft gasification plant

The downdraft gasifier can be divided into fuel hopper, reaction zone and ash discharging zone and has a capacity to load fuel about 50 kg/hr for 7 hours operation continuously. Shell and tube heat exchanger is applied in order to preheat the air which is served as gasification agent. Gas cleaning system consists of cyclone, venturi scrubber, and dust removal unit. The internal combustion engine-generator for power generation is a 4-strokes diesel engine with 4- cylinders and can produce 50 kW electricity, 380/400 V and 50/60 Hz, as illustrated in Figure 16.

Fig. 16. Internal combustion engine-generator for power generation

#### **4.3 Experiment procedure**

144 Renewable Energy – Trends and Applications

A 50 kg/hr prototype downdraft gasification plant is also belonging to WIRC and located in Saha Pathana Industrial Park in Kabin Buri, Prachinburi province, Thailand. This plant consists mainly of 5 parts, as in the following: fuel preparation system, downdraft gasifier, heat exchanger, gas cleaning unit and internal combustion engine-generator, as shown in Figure 15.

Blower

Tar box

The downdraft gasifier can be divided into fuel hopper, reaction zone and ash discharging zone and has a capacity to load fuel about 50 kg/hr for 7 hours operation continuously. Shell and tube heat exchanger is applied in order to preheat the air which is served as gasification agent. Gas cleaning system consists of cyclone, venturi scrubber, and dust removal unit. The internal combustion engine-generator for power generation is a 4-strokes diesel engine with 4- cylinders and can produce 50 kW electricity, 380/400 V and 50/60 Hz,

Dust eliminator

Gas storage tank

Dust cyclone separator

Moisture separator

Engine

Paper filter

**4.2 Experimental Setup** 

Downdraft gasifier Pelletizing machine

as illustrated in Figure 16.

Heat exchanger

Fig. 15. A 50 kg/hr prototype downdraft gasification plant

Fig. 16. Internal combustion engine-generator for power generation

Cyclone

Venturi scrubber

Venturi scrubber

The experiment prodecure is as same as described in Section 3.3 of this chapter but only pelletized PEFB was used as feedstock. The air flow rate for the experiments in a prototype downdraft gasifier was varied from 90 to 120 Nm3/hr with an interval of 10 Nm3/hr. Distinguish from Section 3.3 was that the producer gas obtained from a prototype downdraft gasifier at the most suitable condition was further used as fuel in the internal combustion engine-generator. The electrical load, in this case: electrical heater, varied from 18 to 36 kW with the step of 6 kW. The consumption of both diesel and producer gas was recorded and the rate of diesel replaced by producer gas in percent can be calculated by Equation 10. Finally, the overall efficiency for power production from pelletizing PEFB is calculated by Equation 11.

$$\mathbf{R} = \frac{\left(\dot{\mathbf{m}}\_{\mathrm{d},\mathrm{o}} - \dot{\mathbf{m}}\_{\mathrm{d},\mathrm{d}}\right)}{\dot{\mathbf{m}}\_{\mathrm{d},\mathrm{o}}} \tag{10}$$

$$
\mathbf{n}\_{\rm IT} = \mathbf{n}\_{\rm E} \cdot \mathbf{n}\_{\rm G} \tag{11}
$$

Where R is the rate of diesel replaced by producer gas, md,o is the mass flow rate of diesel consumption in case of using diesel as single fuel and md,d is the mass flow rate of diesel consumption in case of using dual fuel. η<sup>T</sup> , η<sup>E</sup> and η<sup>G</sup> represent the overall efficiency, engine efficiency and cold gas efficiency, respectively.

#### **4.4 Results and discussions**

#### **4.4.1 Producer gas composition and its lower heating value**

The composition and heating value of producer gas obtained from air gasification of pelletized PEFB in a protoype downdraft gasifier are shown in Figure 17.

From Figure 17, the concentration of H2, CO and CH4 increases with increasing air flow rate until the air flow rate of approximately 100-105 Nm3/hr and decreases with higher air flow rate. At the air flow rate of 100 Nm3/hr, the highest concentration of CO and CH4 can be obtained, consequently, the maximum heating value of 6.99 MJ/Nm3 also occurs.

Fig. 17. Producer gas composition with different air flow rates for pelletized PEFB in prototype gasifier
