Principle and Technological Model of the Process
In (Peters et al., 2013) more than 220 variants of the SOFC operation with recirculation of anode gases and without it have been calculated. It has been concluded that the choice of the scheme has little effect on the process efficiency, thus it is advisable to choose the simplest scheme. In the scheme proposed the anode gases recirculation is not considered. Planar fuel cells with direct flow of fuel and oxidizer are used. Catalysts at the anode and cathode are made of Ni-YSZ and (ZrO2)0.9 (Sc2O3)0.1 is used as an electrolyte.
Figure 1 presents a schematic diagram of conversion of the motor diesel fuel into synthesis gas by the process of air conversion in the catalytic burner in order to ensure the operation of the electrochemical generator. The main units of the installation for the synthesis gas production are a catalytic burner for conversion of the diesel fuel vapor - 1, a blower - 3, a synthesis gas cooler - 4, an electrical customer - 5, an electrochemical generator based on SOFC - 6, a waste-heat boiler-utilizer (WHB) - 7, a diesel fuel filter - 9, a fuel pump - 10, a network heater – 12 and thermal insulation - 13.
Figure 1. Schematic diagram of mini-CHPP on products of air conversion of motor diesel fuel and electrochemical generator:1 - catalytic burner; 2 - air pipe; 3 - compressed-air blower; 4 - synthesis gas cooler; 5 – electrical customer; 6 - electrochemical generator based on SOFC; 7 - waste-heat boiler-utilizer; 8 - motor diesel fuel manifold; 9 - fuel filter; 10 - fuel pump; 11 – flow-sensing element; 12 – network heater; 13 - thermal insulation I- air input; II - motor diesel fuel input; Ш - output of combustion products; IV- electrical power output.
Motor diesel fuel is supplied to WHB for heating to boiling and evaporation and enters the catalytic burner in a vaporized form. There also comes the air heated in WHB. When the air flow rate α = 0.4 diesel conversion occurs with the formation of synthesis gas. Then the synthesis gas is cooled from 1284 °C to 800 °C in the cooler by the air supplied to the cathode channel.
Synthesis gas is supplied to the anode channel. At the ECG anode, a share of the hydrogen is oxidized by the oxygen of the air supplied to the cathode channel. Products from the anode channel and vitiated air from the cathode channel are fed to the waste-heat boiler, where the remaining hydrogen and carbon monoxide are oxidized. The heat of oxidation is used for heating the primary air and evaporation of the diesel fuel. Then the combustion products from WHB enter the network heater to heat the network water for the needs of hot water supply to heat consumers. Combustion products after the network heater are removed through the stove chimney at a temperature of 120 °C.