Let’s discuss the advantages and disadvantages of the shell gasification process and the Texaco gasification process

Shell gasification is a relatively outdated method; it requires high labor intensity and a large number of workers Texaco gasification is currently quite advanced and can be remotely automated.

The SHELL furnace has a high content of useful gases and a high carbon conversion rate, but it requires large investment and its operation is currently not very stable; it has good adaptability to different types of coal. The GE furnace has a low content of useful gases and a relatively low carbon conversion rate, but it requires less investment and its operation is currently very stable; it has poor adaptability to different types of coal.

Introduction to the Process Principle and Flow of Texaco Gasification 1.1: The water-coal slurry pressurized gasification process belongs to the fluidized bed gasification type; water-coal slurry is used as the feed, with pure oxygen serving as the gasifying agent. The gasification pressure can be selected between 2.0 and 8.5 MPa, while the gasification temperature is around 1300–1500°C. The wet gas mainly contains CO, H2, CO2, H2O, N2, H2S, CH4, etc. The main reactions that occur in the gasifier are: (1) the thermal pyrolysis of coal and the combustion gasification of volatiles; (2) the reaction between fixed carbon and the gasifying agents (oxygen, steam) ； (4) Reaction between the generated gas, the vaporizing agent, and fixed carbon. Process flow: The raw coal is wet-ground to produce a coal slurry with a concentration of around 63% (wt). This slurry is pumped to the top of the gasifier using a high-pressure coal slurry pump, where it enters the Texaco nozzle together with pure oxygen (98%). Inside the gasifier, the coal slurry is atomized by the nozzle, and it undergoes a partial oxidation reaction with the oxygen to produce water gas (syngas). The gasification furnace of this device has a pressure of 3.0 MPa and a temperature of around 1300°C. After exiting the gasifier, the syngas passes through a venturi tube and a scrubber tower for humidification and dust removal before being sent to subsequent processes for the production of synthetic ammonia or methanol. The ash is collected in an ash lock and discharged from the system regularly. The black water has its heat recovered through flashing, and then is subjected to sedimentation treatment before being returned to the system for use. 1.2 The device has the following features: (1) Wide range of applicable raw materials. Various types of bituminous coal, semi-bituminous coal, and subbituminous coal can be used for gas production, and there are no strict requirements regarding the moisture, ash content, volatile matter content, or ash fusion point of the coal. This allows manufacturers to source coal from local sources, thereby **reducing costs**. (2) High content of active gas components. The effective components (CO+H2) account for 80%-82%, while in the Lurgi gasification process, the effective gas components (CO+H2) are only 50%-70% (see Table 1). Slag discharge is pollution-free, and wastewater pollution is minimal and easy to treat. Due to high-temperature gasification, the gas contains very low levels of methane (CH4≤0.1%), has no tar, and the waste residue can be utilized comprehensively. (3) Wide vaporization pressure range. Industrial plants are available for pressures ranging from 2.5 to 6.5 MPa, with 4.0 MPa being the most common; a higher gasification pressure can save energy required for compressing syngas. (4) The carbon conversion rate is high. The conversion rate of carbon is as high as 98%. (5) Heat utilization in the gasifier. Gasifiers come in three types of processes: quenching, waste pot, and a combination of quenching and waste pot. The gasification process can be selected based on the product. Syngas is produced by the quenching process, with a gas-to-steam ratio of 1.4; it is particularly suitable as a feed gas for the production of synthetic ammonia and methanol (see Table 2), and can also be used for hydrogen production and carbonyl synthesis gas, offering a wide range of applications. The waste heat recovery process is suitable for combined power generation projects using gas turbine cycles, with the high-pressure steam generated as a by-product being used in steam turbine generators to achieve multiple forms of energy supply. (6) The gasification furnace has a simple structure and high production capacity. There are no transmission devices inside the gasifier, giving it a relatively simple structure. A gasifier with a diameter of Φ3200mm and a gasification pressure of 4 MPa can produce more than 760 tons of synthetic ammonia per day from the syngas generated. Disadvantages: High requirements are placed on the quality of coal – it needs to be highly reactive and have a low ash melting point. Since the raw material used in this process is water-coal slurry (containing about 60% carbon), strict requirements are imposed regarding its fluidity, ability to form a slurry, ash melting point, grindability, and ash content; trial firing is necessary to approve such coal. Changing the type of coal also requires approval through trial firing. At the same time, water-coal slurry contains 35% moisture, resulting in higher specific oxygen consumption and higher specific coal consumption. At the same time, the service life of the gasifier nozzles is short, the refractory materials are prone to erosion and damage, the ash treatment system is large-scale, and the treatment of wet ash is difficult, resulting in a significant environmental impact on the plant site. 2. SHELL gasification: Currently, Shell’s gasification units, ranging from pilot plants to large-scale industrial facilities, all use the waste boiler process. The process is as follows: The raw coal is crushed and transported by conveyance systems to the coal grinder, where it is ground into coal powder (90% of which has a particle size of 100 μm on a mass basis), and then dried. The coal powder passes through normal-pressure coal powder bins, pressurized coal powder bins, and feed bins, before being delivered to the nozzles of the gasification furnace using high-pressure nitrogen. The oxygen from is pressurized and preheated by an oxygen compressor, then mixed with medium-pressure superheated steam before being introduced into the nozzle. Under pressurized conditions in the gasification furnace, pulverized coal, oxygen, and steam undergo carbon oxidation and various conversion reactions. The hot gas at around 1500°C at the top of the gasification furnace is cooled by cold gas after dust removal to about 900°C before entering the waste heat boiler. The gas, after having its heat recovered from the waste boiler, enters a dry dust removal and wet dust cleaning system; the gas resulting from this treatment has a dust content of less than 1 mg/m3 and is then sent to subsequent processing stages. Technical features of the device: (1) Dry coal powder feeding, high gasification temperature, and wide range of applicable coal types – bituminous coal, subbituminous coal, lignite, and petroleum coke can all be gasified; it tolerates a wider range of coal ash fusion points compared to other gasification processes. It is also used for coal types with high ash content, high moisture content, and high sulfur content. (2) The vaporization temperature is around 1400–1600°C; the carbon conversion rate exceeds 99%. The product gas is relatively clean, free of heavy hydrocarbons, with an extremely low methane content. The proportion of useful gases (CO + H2) in the gas reaches over 90%. (3) Low oxygen consumption; compared to water-coal slurry gasification, the oxygen consumption is about 20% lower. (4) The single furnace has a high production capacity; the currently operational furnaces operate at a gasification pressure of 3.0 MPa, with the ability to process 2,000 tons of coal per day. However, there are no operational devices available in the country at present. (5) The vaporization furnace features a water-cooled wall structure without refractory brick lining, requiring less maintenance, having a longer operating cycle, and no need for a backup furnace. (6) It has a high thermal efficiency: approximately 83% of the heat energy in the coal is converted into syngas, while about 15% of the heat energy is recovered as high-pressure or medium-pressure steam, resulting in an overall thermal efficiency of around 98%. Disadvantages: The process is complex and lengthy, with high investment costs.

I really don’t know if those on the second floor understand this: the shell gasification technology isn’t yet fully mature. It requires large investments, uses dry powder gasification, and can handle a variety of coal types. Although it is claimed to be suitable for all coal types, there is always a better option. Its technological level is superior to that of Texaco gasification. Texaco gasification is more mature, but in terms of technology it should be considered obsolete; it uses wet gasification, is limited by the type of coal that can be used, and requires less investment. Yankuang took almost 10 years from introducing this technology to developing its own innovations

 Shell gasification technology: This is an advanced gasification technique developed by the Dutch company Shell. It uses pure oxygen and steam for gasification, with dry powder as the feed material. The gasification temperature ranges from 1400 to 1700°C, achieving a carbon conversion rate of 99% and a yield of effective gases (CO+H2) of over 90%. Liquid slag is produced, and a special water-cooled wall gasifier is used, ensuring a long service life. By using the waste boiler process, high-pressure steam can be produced as a by-product. Dry powder gasification results in a lower oxygen consumption (~15%). But nitrogen sealing is required, and the vaporization pressure must not be too high ； Gasification furnace (with waste boiler), complex and large in structure ； Both equipment costs and patent fees are relatively high. Due to the use of nitrogen for sealing and purging in Shell gasification, the inert component content in the syngas produced is approximately 5%; as a result, more off-gas is required for methanol synthesis. If the recovery of hydrogen from off-gases is not taken into account, 1.47 tons of raw coal are consumed per ton of methanol produced ； If hydrogen recovery from off-gases is considered, the amount of raw coal required per ton of methanol can be reduced to 1.27 tons. Assuming the same methanol synthesis off-gas, Shell gasification produces 21 kg more methanol per ton of coal than Texaco gasification ； However, due to the approximately 5% content of inert components in the methanol synthesis gas produced by Shell gasification, the amount of methane synthesis off-gas generated is three times that of Texaco gasification methanol synthesis off-gas. If hydrogen recovery from the off-gases is not taken into account, the coal consumption per ton of methanol is actually more than 8% higher than that in the Texaco gasification process ； Therefore, if Shell gasification is used to produce the raw gas for methanol synthesis, a hydrogen recovery device for the vent gas must be installed in the methanol synthesis circuit, which requires additional investment. If hydrogen recovery from the off-gases is also taken into account, the coal consumption per ton of methanol produced by the two gasification processes differs little, as shown in the table above. The gasification pressure of Shell can reach up to 4.0 MPa; if a synthesis pressure of 6.0 MPa is used for methanol synthesis, the synthesized fresh gas needs to be compressed. Based on preliminary calculations, if the gasification pressure is 4.0 MPa and 600,000 tons of methanol are to be produced, the shaft power required for compressing the fresh gas is 6,360 kW. Therefore, to produce methanol synthesis gas using Shell gasification, an additional compressor for purifying the synthesis gas is required; if this compressor is driven by a steam turbine, its cost is around 20 million yuan ； At the same time, the low pressure of the transformed gas entering the low-temperature methanol washing purification unit also leads to increased investment in the purification system. Furthermore, the high level of inert gases in the synthetic cycle gas increases the power consumption of the cycle compressor in the synthesis loop by about 600 kW ； As a result, on the one hand, it increases the cost of manufacturing synthetic compressors, and on the other hand, it raises operating and production costs. At present, only a few large-scale facilities using coal as raw material are operational for combined-cycle power generation; there is limited experience in industrialization, the technology relies on imports, and domestic technical support is scarce. Four Shell gasification units are under construction in the country, and several other projects have also signed contracts for their introduction ； However, based on the actual construction situation, the supply cycle for gasifiers is at least 18 months, and the low degree of localization of key equipment results in high investment costs and long construction periods for Shell’s gasification plants, thereby increasing the investment risks.  GE gasification technology: This technology belongs to the fluidized bed gasification category, and it was developed by the former American company GE (Texaco) based on the principles of oil and gas gasification. It involves adding additives, fluxes, and water to coal to grind it into a water-coal slurry, which is then injected under pressure into a gasification furnace where it undergoes combustion and partial oxidation reactions with pure oxygen. The gasification temperature is 1300–1400°C, and the gasifier has no moving parts. For gasifiers used in the production of syngas, a cold quench process is mostly employed. Since this technology uses water-coal slurry as the feed and a large amount of water must be gasified, both the coal consumption and oxygen consumption per unit volume of (CO+H2) are higher compared to Shell gasification. However, its raw water gas contains very little inert gas; therefore, in methanol synthesis, not only is the amount of recycled gas low and compression work saved, but the amount of vent gas is also small, allowing for the omission of a vent gas hydrogen recovery system. Without a hydrogen off-gas recovery system, 1.356 tons of raw coal are consumed per ton of methanol; whereas with such a system in place, the coal consumption per ton of methanol can be reduced to 1.31 tons. GE gasification also has the following advantages: each unit can process a large amount of coal, with a maximum daily processing capacity of 2,000 tons per unit, resulting in high production efficiency ； The gasification pressure is high, so the fresh gas does not require pressurization, and the power consumption for compressing the syngas is reduced; this is especially beneficial when producing methanol, as it enables isobaric synthesis ； It has a high content of useful gases (CO+H2), and the fresh syngas produced contains low levels of inert components, making it particularly suitable as syngas for methanol production, with low emissions of off-gases from methanol synthesis. Coal has a wide range of adaptability. Coal dust can be utilized, resulting in a high raw material utilization rate ； Low levels of waste gases, liquids, and solids; minimal environmental pollution, and the waste residue can be used as a raw material for cement ； GE gasification technology is the most widely used in China; the Lunan Fertilizer Plant, Weihe Fertilizer Plant, the tri-generation systems at the Shanghai Coking Plant, and the Huainan Fertilizer Plant have all been upgraded or expanded using water-coal slurry gasification technology.

SHELL’s powder coal gasification process has a wider range of coal types it can handle compared to slurry coal gasification; its gasification parameters are superior to those of slurry coal gasification, with a higher proportion of useful gas components. It also features higher efficiency in producing cold gas and in carbon conversion, as well as a longer lifespan for its internal components. The high water content in slurry coal gasification leads to higher consumption, lower performance metrics, and stricter requirements regarding the quality of the coal used. However, the construction period for SHELL furnaces is relatively long, and there are currently many issues during commissioning, such as numerous leaks in the coal powder preparation system, unstable dense-phase transportation, and a high pressure difference in the activation gas distributor which makes it prone to damage. Clogged waste slag, easily damaged ceramic ash filter tubes, and a relatively high nitrogen content in the gasification products.

I. Advantages and disadvantages of the Texaco gasifier Main advantages: simple preparation, transportation, metering, and control of water-coal slurry; safety and reliability； The local production rate of equipment is high, resulting in lower investment costs. Main disadvantages: 1. The pulping concentration of lignite is approximately 59% to 61% ； The pulping concentration for bituminous coal is 65% ； Since the water content in gasified coal slurry consumes 8% of the coal used in the furnace, the oxygen consumption is 12% to 20% higher compared to using dry coal powder as a raw material, resulting in lower efficiency. 2. It requires coal with low ash and low ash melting point as raw material, and operation at high temperatures; although the gasification efficiency and gas quality are high, the oxygen consumption is high and the equipment investment is substantial. Suitable for the ammonia synthesis process; no additional steam is required for complete conversion. II. Advantages and disadvantages of Shell’s gasification technology: Advantage: Dry coal powder is used as the feed, resulting in 15% lower oxygen consumption compared to water-coal slurry ； The carbon conversion rate is high, reaching 99%, and the coal consumption is 8% lower than that of water-coal slurry ； It is easy to adjust the load; by shutting off a pair of nozzles, the load is reduced by 50% ； The furnace lining is a water-cooled wall; its lifespan is said to be 20 years, while the lifespan of the nozzles is 1 year. Main drawback: Higher equipment investment compared to coal-water slurry gasification technology ； The structure of gasifiers and waste boilers is too complex, increasing the difficulty of processing. Suitable for the methanol process, namely partial conversion.