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Comparison Table of TEXACO Coal Water Slurry and SHELL Powder Gasification Processes Comparison Table of TEXACO Coal Water Slurry and SHELL Powder Gasification Processes Serial Number Item SHELL Process TEXACO Process 1 Gasification Process Fluidized bed Fluidized bed Liquid slag discharge Liquid slag discharge 2 Suitable coal types Lignite, bituminous coal, petroleum coke Various bituminous coals, petroleum coke 3 Gasification pressure/MPa 2.0~4.0 Typically 4.0~6.5 4 Gasification temperature/°C 1400~1600 1300~1400 5 Gasifying agent Oxygen Oxygen 6 Feed method Dry coal powder 60% coal water slurry 7 Maximum coal feed rate per furnace/t•day-1 2000 2000 8 Oxygen volume flow/m3/km3 (CO+H2) 330~360 380~430 9 Volume fraction of carbon conversion/% ≥99 95~98 10 Volume fraction of cold gas efficiency/% 80~85 70~76 11 Volume fraction of CO+H2 in coal gas/% ~90 ~80 1. TEXACO Coal Water Slurry Pressurized Gasification Process (TGP) The TGP process uses coal water slurry as the feed; a slurry with a concentration of 60–65% is prepared and then pressurized for gasification in a fluidized bed. The coal water slurry reacts with oxygen under high temperature and pressure to produce syngas, with liquid slag being discharged as a byproduct. A vaporization pressure of 2.7–6.5 MPa and a vaporization temperature of 1300–1400°C are used, achieving 80% CO+H2. The maximum daily coal feeding rate per Texaco gasifier in the world is 2000 t/d. The Texaco gasification process has a minimal impact on environmental pollution. Based on the requirements for processing different products in the post-gasification stages, pressurized water-coal slurry gasification features three process flows: the quenching flow, the waste boiler flow, and the combined waste boiler and quenching flow. In ammonia synthesis production, the quenching process is commonly used; the raw gas coming out of the gasifier is directly quenched with water. The raw gas after quenching contains a high amount of water vapor, and it can be sent directly to the shift system without the need for additional steam, resulting in lower investment costs due to the absence of waste heat boilers. When the product gas is used in combined heat and power generation systems with gas turbine cycles, the waste heat recovery process is commonly employed, with the resulting high-pressure steam being used in steam turbine generators. To use the product gas as hydroxyl syngas for methanol production, only partial conversion of the raw gas is required, typically employing a combined waste heat boiler and quenching process. Also known as the semi-waste boiler process, in this approach, the raw gas coming out of the gasifier is cooled to around 700°C using a radiant waste boiler, and then quenched with water to the desired temperature, so that the steam generated by the sensible heat of the raw gas can meet the requirements of certain conversion processes in subsequent stages. 2. Shell Dry Coal Gasification Process (SCGP): The Shell dry coal gasification process consists of the following main units: ① coal grinding and drying, ② coal pressurization and feeding, ③ gasification and synthesis gas cooling, ④ slag removal, ⑤ ash removal, ⑥ washing, ⑦ wastewater stripping and clarification, etc. The SHELL gasifier is a vertical cylindrical gasifier. A membrane-type water wall composed of boiling water-cooled tubes is installed around the furnace chamber, and its inner wall is lined with a heat-resistant coating. During gasification, the molten ash forms a liquid film on the coating of the inner wall of the water wall, flowing down along the wall for separation. An anti-corrosion method based on the use of slag to protect against further damage is employed, which effectively solves the problems of severe damage to high-temperature refractory materials and frequent maintenance needs. An annular space is provided between the water wall and the cylindrical shell, which facilitates the placement of the inlet water collection pipes and outlet steam collection pipes, as well as simplifies the inspection and maintenance of the water wall ； The annular space is filled with pressurized syngas at a temperature of 250–300°C. It has the following advantages: - The gasifier interior is equipped with a membrane-type water wall, allowing it to withstand high gasification temperatures. There are fewer restrictions on the ash fusion point of the raw coal. -The carbon conversion rate is high, with a value of ≥99%. -Due to the dry powder feed, the concentration of active gases (CO+H2) in the crude syngas is above 90%, with a low CO2 content. -It features high gasification efficiency, low consumption of raw coal and oxygen, and high utilization rate of raw materials. -It features a large capacity per furnace, a long operation cycle, and no need for a backup furnace. -With multiple sets of counter-flow burners, the output volume of syngas can be adjusted by turning off one or more sets of burners, providing great operational flexibility. -Syngas is relatively clean; the gas produced by high-temperature gasification does not contain harmful substances such as tar and phenols, which facilitates its purification. -Environmental advantages: During normal operation, there is virtually no waste gas emission ； Since the vast majority of process water can be recycled, less wastewater is discharged. The slag produced at high temperatures has stable properties, causes little environmental impact, and can also be used as a building material. -The process technology is advanced and reliable; a gasification unit capable of processing 2,000 tons of coal per day per furnace has been successfully built in Demkolec, the Netherlands, for use in combined cycle power generation. Both the Shell and Texaco gasification processes are reliable and viable options for gasification. The Shell process has the following characteristics: ① It can handle coals with higher ash fusion points ； ②High gasification efficiency, high effective gas content, and low consumption of coal and oxygen ； ③The single-series production capacity is high, with no need for a backup furnace ； ④The production has good continuity. The disadvantages of the Shell process are: ① It lacks industrial application experience in syngas production; in other words, there is no operational experience from systems used in methanol or ammonia synthesis that can be utilized as a reference ； ②The coal fed into the furnace is transported by pneumatic conveying, which limits further increases in gasification pressure; the pressure is kept between 2 and 4 MPa. ③The investment is much higher than that for coal water slurry gasification, approximately twice that of Texaco’s coal water slurry gasification process.