## 4 Waste Conversion for Fuel Gas Production
### Influence of External Conditions on the Characteristics of the Pyrolysis and
[63] found that, with the temperature rise, the gas yield increased from 3.46 to 5.97 g/kg, and the liquid yield decreased from 6.04 to 3.57 g/kg; the yield of the solid part varied in a small range from 0.45 to 0.6 g/kg. The increase in the gas yield with an increase in temperature from 600 to 700 \({}^{\circ}\)C is mainly associated with an increase in the concentrations of methane, ethylene, and propylene. A similar effect was also found when using waste lubricating oil as an additive to the coal-water slurry [62]. With an increase in temperature from 800 to 1000 \({}^{\circ}\)C, the gas volume increased up to 2.8 times due to the intensification of coal decomposition reactions. The proportion of the solid residue decreased to 1.5 times [62]. [PERSON] et al. [63] concluded that the pyrolysis conditions should be determined based on the purpose of the pyrolysis products. In the petrochemical industry, which involves the use of petrochemical feedstocks, a temperature range of 650 to 700 \({}^{\circ}\)C and a pressure of 0.1 MPa should be selected. Under these conditions, most of the hydrogen contained in the waste oil is converted to olefins C\({}_{2}\)-C\({}_{4}\) olefins and BTX (benzene, toluene, and xylene). For the related industries producing gas fuel and liquid, a temperature of 700 \({}^{\circ}\)C and a pressure of 0.5-1 MPa are preferred. In this case, a higher proportion of hydrogen is converted to C\({}_{1}\)-C\({}_{3}\) alkanes and BTX (preferred as fuel). In addition to temperature, the oxidizing medium of pyrolysis/gasification has a significant effect on the characteristics of these processes. [PERSON] et al. [64] used water steam as a gasifying agent during gasification waste cooking oil (WCO) in a plasma chemical reactor. The effect of the gasifying agent-to-feedstock ratio on the gasification efficiency of waste cooking oil has been studied. As the Steam/WCO ratio increased from 1.31 to 2.33, the H\({}_{2}\) concentration increased from 40.58 vol% to 47.9 vol%[PERSON] This is due to steam reforming, water-gas shift, and cracking reactions. CO concentrations practically did not change and amounted to 22-23.5 vol%[PERSON] An increase in the Steam/WCO ratio from 1.31 to 2.33 resulted in a slight decrease in the methane content from 9.44 vol% to 7.83 vol%. This will be explained by reverse methanation and hydrogenation reactions, whereby methane and water forms hydrogen, carbon monoxide, or carbon [PERSON]. The CO\({}_{2}\) concentration increased from 5.83 vol% to 7.74 vol%. The lower calorific value of the generator gas with varying the Steam/WCO ratio changed from 12.5 MJ/Nm\({}^{3}\) to 13.2 MJ/Nm\({}^{3}\), which indicates the generation of good quality gas in a water-steam medium[PERSON]  
Gasification of coal-oil emulsion is lab-scale gasifier at temperatures between 800 and 925 \({}^{\circ}\)C was studied by [PERSON] et al. [99]. Oxygen-steam and oxygen-CO\({}_{2}\) mixtures were chosen as the gasifying atmosphere. It has been established that, during the gasification of coal-oil emulsion of a water steam medium, lower heating values of the produced gas were two times higher (18-20 MJ/m\({}^{3}\)) than the calorific value of the gas (18-20 MJ/m\({}^{3}\)) obtained during gasification in oxygen-CO\({}_{2}\) mixtures, due to high content of diluting CO\({}_{2}\). The amount of CO\({}_{2}\) in the composition of the gas decreased by 43% in the water steam medium. The concentrations of H\({}_{2}\), CH\({}_{4}\), and CO increased by 20%, 30%, and 15%, respectively [99]. Gasification of coal-oil slurry, bio-oil, and coal-water-slurry in entrained-flow gasifier was studied by [PERSON] et al. [100]. The N\({}_{2}\)-water steam mixture was chosen as the gasifying medium.