Regarding the furnaces for powder coal gasification

Water-coal slurry gasifier: Advantages: The water-coal slurry gasification process developed by Texaco in the United States (which became part of Chevron at the beginning of 2002 and was acquired by GE in May 2004) involves grinding coal with water to produce a water-coal slurry with a concentration of 60–65%. Pure oxygen is used as the gasifying agent, and the gasification reaction takes place under high temperature and pressure – with a gasification pressure ranging from 3.0 to 8.5 MPa and a gasification temperature of 1400°C. Liquid slag is produced as a by-product; the composition of the gas consists of about 80% CO and H2, with no organic substances such as tar or phenols present, thus causing no environmental pollution. The carbon conversion rate is 96–99%, the gasification efficiency is high, the furnace structure is simple, energy consumption is low, operational efficiency is high, and the process can handle a wide range of coal types. Currently, Texaco’s largest commercial facility is the Tampa Power Plant, which falls under the DOE’s CCT-3 program. It was approved for development in 1989, came online in July 1996, and verification operation was announced in December of the same year. The unit is a single furnace with a daily coal processing capacity of 2,000–2,400 tons; the gasification pressure is 2.8 MPa, the oxygen purity is 95%, the slurry concentration is 68%, the cold gas efficiency is around 7:6%, and the net power output is 250 MW. Disadvantage: The Texaco gasifier consists of a nozzle, a gasification chamber, and a quenching chamber (or waste heat boiler). The nozzle is three-channel: process oxygen flows through channels 1 and 3, while the water-coal slurry flows through channel 2, located between the two oxygen jets. Water-coal slurry gasification nozzles often suffer from nozzle wear, primarily due to the erosive action of the water-coal slurry on metal materials at high linear velocities (around 30 m/s). Nozzles, gasifiers, quenching rings, etc., are the key technologies for Texaco water-coal slurry gasification. High maintenance costs. Advantages of aerospace furnaces: 1. High-temperature gasification, high efficiency and energy savings, high carbon conversion rate (≥99%), high cold gas efficiency (≥82%), and high content of useful gases (≥90%). 2. Wide range of coal types that can be used; fuels can be diversified, and coal sources can be sourced locally. 3. The control system has a high degree of automation, along with a comprehensive security interlock system. 4. It boasts excellent environmental performance, with low levels of pollutants emitted. 5. It possesses independent intellectual property rights, features a mature and reliable manufacturing process, with all major equipment being domestically produced. Disadvantages: 1. The coal needs to be ground to a particle size of less than 100 mesh, and its moisture content must be reduced to 2%; both of these processes require significant amounts of energy. 2. The space furnace has been in operation in China for a relatively short time, and mature operational experience has not yet been developed. The advantages of the Ende furnace are as follows: (1) The Ende furnace is a powder coal gasification furnace, which features a high coal gasification rate and high production efficiency. (2) The Endre furnace combines a gasification furnace, a thermal decomposition furnace, and a water-gas furnace; it can use different gasifying agents (air, oxygen-enriched air with steam, pure oxygen with steam) to produce reducing gases of various compositions, thereby increasing the gas yield from coal. (3) Ender furnaces can use lignite, long-flame coal, and/or weakly coked coal; these fuels are widely available and inexpensive. (4) In the coal-to-gas production process using Ende furnaces, cooling water is recycled and does not flow outside; as a result, there is little wastewater and pollutants such as tar generated, and the coal slag can be used to make coal slag bricks or as a component in sintering processes. (5) Ender furnaces have a high gas production rate per unit volume; one Ender furnace with a capacity of 40,000 m3/h can replace 16 conventional gas generators with a diameter of 3 m, thus reducing construction costs. Furnace models with capacities of 10,000 cubic meters, 20,000 cubic meters, or 40,000 cubic meters can also be constructed as needed. (6) The Endre furnace is easy to start and stop – it can be shut down in just a few minutes ； The hot standby furnace can be started up in one hour to supply qualified gas ； (7) The effective gas composition of an Endre furnace is higher than that of a conventional generating furnace, reaching 68–75%. This is achieved when the moisture content of the coal is around 20% and its calorific value is about 4500 calories; if the moisture content of the coal is reduced to below 15%, the effective gas composition can reach 80%. (8) Coal with a total moisture content of 30% can also be used; there is mature operational experience, few devices need to be maintained, and maintenance costs are low. The disadvantages are as follows: 1. There is a lot of waste material, and the circulating water tends to scale ； 2. The manufacturer of the by-product has no solution ； 3. Drying lignite is difficult, and transporting the dried coal poses challenges as well, with associated safety issues. 4. Coal with good activity (lignite, bituminous coal) should be used. Existing treatment methods include: 1. Increasing the number of cyclone separators to reduce the amount of material carried away, and using bag filters as an additional safeguard; this can address the issue of material loss, which is a key problem with Ende furnaces ； The problem with circulating water can be easily resolved by reducing the amount of carryover substances. Since these substances are removed, the temperature of the circulating water drops, which significantly reduces the likelihood of scaling. Adding chemicals then makes it possible to completely solve the issue ； 2. The treatment of the by-product, namely fly ash, used to be a major issue, but it can now be resolved; fly ash can be directly utilized in fly ash boilers ； Fly ash can also be used to make bricks. 3. The drying of lignite can be accomplished using the equipment provided by Shenggong Drying Equipment Co., Ltd., which ensures a 20–30% reduction in water content ； The dried coal can be transported using gas transport systems provided by Jinan Yulong Pneumatic Conveying Equipment Company, without any safety issues. :)

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