Texaco in Huaihua

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Huainan coal was used in the research on Texaco’s pressurized water-coal slurry gasification technology. 1. Current status of Texaco’s pressurized water-coal slurry gasification technology: The Texaco gasification process is the second generation of coal gasification technologies introduced in 1978; it features a wet feed system, in which coal and water are ground into a slurry before being pumped into the gasifier. Compared with the dry feeding system, the wet feeding process is simpler, safer and more reliable, with higher feeding flexibility. Its technical features include a wide range of adaptability to different types of coal, with no strict restrictions on the activity of the coal; however, there are certain requirements regarding the ash fusion point of the coal (which generally needs to be below 1400°C) ； Large production capacity per furnace ； The carbon conversion rate is high, reaching 96%-98%, and the wastewater generated during production contains no pollutants such as tar or phenols ； The gas quality is good, with the effective gas content (CO+H2) reaching around 80%, and a low methane content, making it suitable for use as syngas. To enhance the fluidity of the liquid slag and enable liquid slag discharge, this process operates at high temperatures of around 1400°C. At the end of the last century, manufacturers in regions such as Lunan, Shanghai, the Wei River area, and Huainan in China adopted the Texaco gasification process; they built facilities using this technology and brought them into operation, accumulating considerable experience in production and operation. As a result, they were able to meet the requirements for long-term, high-load operation along with safe and stable performance. However, years of operational experience have also shown that the Texaco water-coal slurry gasification technology has a serious flaw, namely its strict requirements regarding the fusibility of the raw coal ash. To ensure the efficient operation of the Texaco water-coal slurry gasifier, Shaanxi Weihe and Shandong Lunan adjusted the types of raw coal used: Shaanxi Weihe switched from the originally planned Huangling coal to Huating coal, while Shandong Lunan changed from \"**\" coal to a mixture of washed and refined coal. Huaihua Group is a comprehensive enterprise that has been engaged in the production and development of coal chemical products for many years. In recent years, the company’s technical staff have analyzed and studied the quality characteristics of Huainan coal, as well as those of Yima and Huating coals. They proposed the use of coal blending techniques and flux additives to enable partial or full utilization of Huainan coal in Texaco gasifiers; numerous experiments were conducted, yielding certain experience and results. 2. Research Content 2.1 Coal quality indicators of Huainan coal The Huainan coalfield is one of the top ten coalfields in the country, with a prospective coal reserve of 44.4 billion tons, proven reserves of 30 billion tons (at depths above -1200 meters), and existing reserves of 15.3 billion tons. Huainan’s coal reserves account for half of those in East China, amounting to the combined total of Shandong and Jiangsu provinces. In 2003, the Huainan coal mining area produced a total of 35 million tons of coal, while in 2004, 38 million tons were mined throughout that year. The main uses of coal in Huainan are power generation and direct combustion; the proportion of coal used in the chemical industry is extremely small. The methods of utilization are crude and inefficient, resulting in severe environmental pollution and energy waste. The coal from Huainan is mainly composed of gas coal and 1/3 coking coal. It has a medium volatility level, extremely low sulfur and phosphorus content, high calorific value, good cohesion, good grindability, and a high carbon content; hence it is an excellent type of coal for use as fuel as well as a raw material for the chemical industry (Table 1). Due to its high ash fusion point (1500°C) and high ash content (29%), coal faces limitations in applications within the coal chemical industry. High ash content requires a complex slag discharge system in the gasification furnace. To enable liquid slag discharge, the furnace walls must be able to withstand temperatures of around 1700°C. Currently, the Texaco gasification furnaces used by Huaihua can handle temperatures up to 1360°C, and existing refractory materials are not capable of withstanding such high temperatures of 1700°C. Therefore, the existing coal gasification technologies cannot meet the requirements of Huainan coal, and a completely new approach is necessary in terms of the design of the raw materials for the gasifier as well as the slag and ash-water treatment systems. Table 1: Quality parameters of Huainan coal (wt)
Industrial analysis: Total moisture %, Ash %, Volatile matter %, Lower heating value MJ/kg, Total sulfur %, True density g/cm3, Haas grindability 6-8, 22-29, 26-30, 20.5-23.5, 0.2-0.6, 1.46-1.58, 55-75
Elemental analysis: Carbon %, Hydrogen %, Nitrogen %, Oxygen %, Phosphorus %, Chlorine %, Fluorine ppm – 58-64, 3.8-4.2, 0.9-1.2, 6.5-8.0, 0.01-0.05, 0.01-0.03, 150-240
Ash fusion temperature: DTSTHTFT
Composition of coal ash: %SiO2, Fe2O3 – >1500, >1500, >1500, >1500; 53.0-58.0, 2.5-4.5. Al2O3, CaO, MgO, TiO2, SO3, Na2O, K2O – 30.0-34.0, 1.2-3.0, 0.6-1.8, 1.2-1.8, 0.8-1.5, 0.3-0.8, 0.5-1.2