That is, to produce 3000 nm3/hour of generator gas with a lower heating value of 1500 kcal/nm3, it is necessary to gasify about 2075 kg/hour of brown coal with known composition.
This calculation procedure is suitable for any organic solid fuel or a mixture of solid fuels. In the case of a mixture of solid fuels, the lower heating value of the mixture is determined as the total of the lower heating values calculated for each of the components of the mixture.
- As stated above, it is possible to gasify solid fuels of any type, including brown coal and black coal, provided that the fuel does not conglomerate at high temperatures of 1100 ÷1300 °C.
The gas-generating unit GUK-1-5-M-2, shown in Figure 1, provides the feasibility of the gasification process, according to which it is possible to produce, from any solid fuel, the specified volume of generator gas (for example, 3000 nm3/hour) with the specified lower heating value (for example, 1500 kcal/kg) and with the same chemical composition, that is, 28 ÷ 32 percent CO, 20 ÷ 24 percent H2, and 46 ÷ 48 percent N2.
It is shown in Figure 1 that the gas-generating unit contains two independent inlets for fuel, that is, the inlet for charging fuel (1) and the inlet for standby (additional) fuel (54). This design allows fuels of different types, with different properties, and at the specified ratio between the fuel rates to be fed into the gas-generating unit. The process of mixing the charging fuel with additives or another fuel is accomplished in the fuel section of the gas-generating unit due to the rotation of the shaft of the metering device with a sprocket-based drive (55).
Gas generators No. 1 and No. 2 operate in parallel-series arrangement, according to which the final generator gas (39) is produced by the gas generator No. 2 only. The unrefined generator gas (17), which is produced by the gas generator No. 1, is fed into the mixing section of the gas-generating unit and used for enriching the charging fuel to be fed into the gas generator No. 2.
This technology allows the thickness (depth) of the reducing zone of the gas generator No. 2 to be increased in several times, and, as a result, it is possible to reduce all combustion products, which are formed in the burning area of the gas generator No. 2, as follows:
C + CO2 = 2CO;
C + H2O = CO + H2;
C + 2NO = N2 + CO2.
Low-temperature coke filling the whole gas filtering section of the gas-generating unit is cooled by a special cooling device and converted into an effective absorbing-filtering layer, acting as an additional gas cleaning element. The whole generator gas produced passes through this element. The regeneration of the low-temperature coke goes on at all times in the process of gasification of raw charging fuel.
The low-temperature coke, on absorbing and filtering all impurities in the generator gas, drops down and is used as working fuel for the gas generator No. 1. The impurities are subjected to high-temperature treatment at 1100 ÷ 1300 °C.
This gasification process provides the possibility to dispose, by thermal decomposition, toxic and contaminating substances, herbicides, pesticides, pharmaceutical waste, and other foreign substances. Virtually all chemical substances in solid, liquid, or gaseous state, with the possibility to be disposed by thermal decomposition, cannot entry the external environment due to using this ecologically clean gasification technology on the basis of the proposed gas-generating unit.
Depending on the chemical composition of the charging fuel and the properties of substances to be disposed, it is possible to determine the optimal ratio between the quantity of chemical impurities and the quantity of the charging fuel . If these quantities are presented in weight units, this ratio is in the range from 0.5:10 through 1.5:10.
The chemical substances, decomposed in the high-temperature zone of the gas generator No. 2, enter the low-temperature filtering section, which prevents reverse reactions with the decomposition products, and together with the low-temperature coke enter the high-temperature zone of the gas-generator No. 1. The decomposition products after repeated thermal action convert into neutral chemical compounds formed in the result of reaction with chemical elements present in the fuel ash, or into individual neutral chemical elements. These chemical compounds or elements together with the fuel ash pass through the cooled ash removal section of the gas-generating unit and are fed by the conveying screw (37 in Figure 1) to the ash collector (see Figure 2).
If in the fuel ash there are no chemical elements capable to bind or neutralize the chemical elements of the decomposition products, the decomposition products are added to the charging fuel through the branch pipe for receiving fuel (53). It is possible to bind the chemical elements of the decomposition products, such as chlorine-containing, sulfur-containing, phosphorus-containing, and other substances, using appropriate additives. The decomposition products cannot emerge from the gas-generating unit due to the availability of the internal additional gas cleaning element.
- As is shown in Figure 2, the gas-generating unit is exposed to vacuum generated by the vacuumizing station (see Figure 2). The vacuumizing station contains two special suction ventilators which create vacuum in the ring-shaped gas collector (38 in Figure 1) of the gas generator No. 2, overcoming the hydraulic resistance of the drop catcher, two scrubbers, and cyclone. The generator gas under vacuum flows trough the branch pipe (40 in Figure 1) to the gas collector (see Figure 2).
In the process of gas flow, the generator gas is cleaned from solid impurities and excess moisture, and takes on the properties of ready-to-use final generator gas.
The design content of entrainment water in the purified generator gas does not exceed 0.07 g/nm3.
- The installed power of all electric drives and other electrical equipment elements of the solid-fuel power-generating plant (see Figure 2) is 140.8 kW, and the consumed power is 92.2 kW.
The volume of water required for cooling and washing the gas-generating unit is about 100 m3. Water circulates around a closed path, with trivial evaporation losses which can be replenished.
The consumption of water for cooling the gas-generating unit is virtually not required because in the cooling jackets of the gas-generating unit and heat exchangers (see Figure 2) continuously circulates about 6.5 m3 of this heat transfer medium. Due to the heat transfer medium circulation, additionally 0.6 MW of thermal power can be generated.