Gasification

The gasification process can be roughly divided into: 1. Atmospheric pressure fixed-bed gasification； 2. Pressurized gasification with a fixed coal layer (e.g.: Ruhr gasifier) ； 3. Fluidized-bed gasification ； 4. Dry gas-flow bed coal gasification (e.g.: KT furnace, Shell furnace) ； 5. Wet gas-flow bed pressurized gasification (e.g.: Texaco furnace). The acidic gases produced as a result of gasification mainly include H2S and CO2; desulfurization is used to remove H2S, while decarburization is used to remove CO2. It is likely that the author is referring to the latter. The methods for removing CO2 include: 1. Low-temperature methanol washing ； 2. Polyethylene glycol dimethyl ether method ； 3. Propylene carbonate method ； 4. Improved thermal potassium-alkali method ； 5. Methyl diethanolamine method (used in some small ammonia plants) ； 6. Ammonia water absorption method (carbonization method) ； 7. Monoethanolamine method (MEA method) ； 8. Pressure swing adsorption method. Among them, 1, 2, and 4 can all be used to remove H2S. Abroad, the main decarbonization method is the modified thermal potassium-alkali process among chemical absorption methods ； In physical absorption methods, polyethylene glycol dimethyl ether and low-temperature methanol washing are widely used in China, while the propylene carbonate method is rarely used.

Gasification can also use an Endler furnace.

Project: Pressurized Ruchi, Texaco, Shell Dry Coal Powder. Raw coal processing: Crushing–screening, Coal grinding–pulping, Coal grinding–drying. Ash content requirements for raw coal: Generally no limit, Low, Low. Cost of raw coal processing: Low, High, Relatively high. Transport of raw coal: Easy, Relatively easy, Difficult. Gasification pressure (MPa): 2–3, Low; 2–6.5, High; 2–4, Relatively high. Gasification temperature (°C): 900–1100, Low; 1300–1400, Relatively high; 1400–1600, High. Coal input per furnace per day (t/d): 1000–1300, Low; 2000, Relatively high; 2500, High. Oxygen consumption (m³/1000 m³): 267–350, Low; 380–430, High; 330–360, Relatively high. Carbon conversion rate (%): 88–95, Low; 96–98, Relatively high; ≥99, High. Efficiency of cold gas (%): 65–75, Low; 70–76, Relatively high; 80–85, High. Overall thermal efficiency (%): 80–90, Low; 90–95, Relatively high; ≥98, High. Experience in commercial operation: Abundant, Basically abundant, Limited

Project: Pressurized Lucchini, Texaco, Shell Dry Coal Powder. Environmental treatment and characteristics: Must be treated, Good; Requires treatment, Good; Requires treatment, Good. Dry gas CO+H2 (%) : Low, Higher, High. Dry gas CH4 (%) : High, Low, Very low. Effective CO+H2 yield: Low, Higher, High. Water vapor consumption: High, –, Higher. Electricity consumption: Low, High, High. Coal powder conveying gas: –, –, Required. Equipment investment: Low, High, High. Footprint: Large, Smaller, Smaller

Serial Number Item Non-slag–slag separation gasification technology Other gasification technologies 1 Gasification feedstock Water-coal slurry Water-coal slurry 2 Gasification principle Partial oxidation Partial oxidation 3 Number of oxygen supply stages in the gasifier 2 1 4 Relationship between oxygen supply to the main burner in the gasifier and the chemical equivalents required for reaction Unrestricted Restricted 5 Axial temperature profile in the gasifier Low–high–low High–low 6 Temperature at the end of the main burner in the gasifier Low (200°C lower) High 7 Effective gas composition Slightly higher than that in the Texaco furnace, approximately 0.32% 8 Length-to-diameter ratio of the gasifier With uniform axial temperature, the length-to-diameter ratio can be increased; with an axial temperature that decreases from high to low, the length-to-diameter ratio should not be increased