Comparison of methanol production using Texaco and Shell gasification technologies

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Comparison of Methanol Production Using Texaco and Shell Gasification Technologies 1 Overview of Texaco and Shell Gasification Technologies 1.1 Texaco Gasification Technology The Texaco water-coal slurry pressurized gasification technology is a coal gasification method developed by the American company Texaco in the early 1980s. In this process, coal particles of a certain size along with small amounts of additives are ground together with water in a mill to form a non-Newtonian fluid that can be pumped; this fluid then undergoes an incomplete combustion reaction with oxygen or oxygen-enriched air under pressure and high temperature to produce high-temperature syngas. The high-temperature syngas either has its heat recovered through indirect heat exchange in radiant boilers and convection boilers (the waste heat recovery process), or it is cooled directly in water (the quenching process). After gas washing to remove dust and further cooling, it becomes the feed gas for subsequent processing stages. In this process, the gas from the waste boiler is further cooled and dust-freeed, after which it is used together with the high-pressure steam generated by the gas turbine to achieve integrated gasification combined cycle power generation (IGCC) ； The gas from the cryogenic process is suitable for producing hydrocarbons and synthetic ammonia. China’s first set (the 5th in the world) of Texaco water-coal slurry pressurized gasification and ammonia synthesis plant was put into operation in April 1993 at the Lunan Fertilizer Plant in Shandong Province. It is currently operating well, with a configuration of two units in service and one as a backup. 1.2 Shell Gasification Technology: The Shell pulverized coal gasification process was developed by Shell’s research institute in Amsterdam, the Netherlands. In 1978, a pilot plant with a capacity to process 6 tons of coal per day was built; more than 30 different types of coal were tested there. In 1976, a gasification plant with a capacity of 150 tons of coal per day was constructed in Hamburg, Germany. In 1987, a plant capable of processing 250 tons of high-sulfur bituminous coal per day was built in Houston, the United States. Later, another plant was built to process 400 tons of high-ash lignite per day (equivalent to a gasification plant that can produce 100kt of synthetic ammonia per year), and 18 different types of coal were tested using this plant. After the construction of the aforementioned demonstration plant, the Dutch power generation authority decided to use Shell’s coal pulverization gasification technology to build a gasification facility in Demkolec, the Netherlands, with a capacity to process 2,000 tons of coal per day. This facility came online at the end of 1993 and has been in operation for over a decade now. The coal gasification unit, which uses Shell’s powder coal gasification technology for the production of syngas, and was designed by Wuhuan Chemical Engineering Company under China National Chemical Engineering Group Corporation, was successfully commissioned for the first time in Shuanghuan, Hubei, recently. The unit is currently operating steadily. 2 Comparison of various indicators for Texaco and Shell gasification technologies. The comparison of the various characteristic indicators for Texaco and Shell gasification technologies is shown in Table 1. Table 1 Comparison of Technical Parameters for Texaco and Shell Gasification Technologies | Parameter | Texaco | Shell |
|------------------|---------------|-------------|--------------|
| Gasification pressure / MPa | 2.8–6.5 | 2.0–4.0 | |
| Gasification temperature / °C | 1300–1400 | 1400–1700 | |
| Maximum capacity per furnace / t/day | 350–2000 | 1000–2800 | |
| Type of gasifier | Hot-wall, single nozzle | Cold-wall, multiple nozzles | |
| Coal feeding method | Water-coal slurry concentration >60% (pumped) | Coal powder transported using nitrogen or carbon dioxide; 80% of the coal powder particles have a size >90% | |
| Carbon conversion rate / % | 96–98 | >99 | |
| Inert gas content in purified gas / % | | | |