3 Basic Concept For Design

a. System Flow

Process flow sheet of the lOOOkW pilot plant is shown in Fig. 1.

b. System configuration

The lOOOkW pilot plant's major components are stack, reformer, cathode blower, heat recovery system, electric equipment, control, and utility facilities. Two kinds of fuel cell stacks are used and 4 stacks of250 kW class in total are connected with two 500kW class inverter. Each 500kW unit has a cathode blower and it can be operated independently. All other equipments are one for this pilot plant. Specification of each components are as follows.

(a) Fuel Cell Stack

Two 250kW cross-flow type stack and two 250kW parallel-flow type stack are used for this pilot plant. By the investigation of the influence of operating temperature on voltage decay rate, the operating temperature of the stacks was modified to be lower than the initial design value.

(b) Reformer

We apply a catalytic burner to the reformer, because the heat value of anode outlet gas is low. Steam / carbon ratio (S/C) for reforming is planned to be 3.5 with allowance to avoid carbon formation and deposition inside the cell. ( c) Cathode Blower

We apply magnetic bearing to the cathode blower for high efficiency under 640 °C.

(d)Heat Recovery System

The heat recovery system is consist of the turbine compressor and the heat recovery steam generator (HRSG).

The turbine compressor has an auxiliary combustor to secure power, that is necessary for the plant start-up and to maintain amount of steam produced by the HRSG.

(e) Electric Equipment

The PWM control type inverter is used to obtain high efficiency and to reduce harmonic distortion. A large capacity IGBT is applied for the inverter device. (0 Control

The plant is controlled by two operators in the central control room.

Fig. 1 1 OOOkW pilot plant System Configuration



Fuel cell stack A

250kW x 2, Cross flow type. Cell area 1.20m2

Fuel cell stack B

250kW x 2, Parallel flow type. Cell area 1.02m2


2-stage catalytic combustion, 18 tubes

Cathode blower

Radial type. Magnetic bearing

Turbine compressor

T: Axial x 2-stage, C: Radial x 2-stage

Heat recovery steam generator

Smoke tube boiler

Anode blower

Radial type


500kWx 2, PWM control

Table 2. Specifications of major components

Table 2. Specifications of major components

(g) Utility facilities and others

The control air supply line has a back-up line of nitrogen in order to keep operation reliability and safety.

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