Introduction to the partial water quenching process package for Shell gasification

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This post was last edited by lflsedin on 2015-8-9 09:00. Introduction to the water quenching process package in Shell’s gasification technology. Shell’s gasification technology is mature and reliable, but it requires a high level of investment. To deliver more value to our customers, we have been actively seeking ways to reduce costs without compromising our advantages of wide coal variety compatibility, high efficiency, reliability, and environmental friendliness. By the beginning of this year, we had successfully developed some water-quenched gasification process packages, enabling us to provide customers with basic engineering design services. This process retains the existing design of the gasifier (feed at the bottom, multiple nozzles, upward flow of syngas, and separation of ash and slag by gravity), and it still uses the clean syngas from subsequent stages as a quenching gas to cool the hot syngas exiting from the upper part of the gasifier from 1600ºC to 900ºC; thereafter, it enters a water quenching chamber where atomized water is sprayed to further reduce the temperature to 500ºC. Since the quenched syngas is only at 500ºC, a primary cyclone separator can be used to remove most of the dry ash. Thereafter, the remaining fly ash in the syngas is removed using a two-stage Venturi scrubber, and it then enters the wet scrubber tower. The temperature of the syngas exiting the wet scrubber is 220–230ºC, with a water vapor content of 60%, which fully meets the requirements of sulfur-tolerant shift reactors for water vapor. The feature of this process is that it eliminates the syngas cooler, and a conventional cyclone separator is used in place of the ceramic filter. Although the amount of ash water increases slightly (due to the lower dust removal efficiency of the cyclone separator compared to the ceramic filter), the overall investment in the gasification unit can still be reduced by about 20%. At the same time, since most of the fly ash is removed by dry methods, the amount of ash water to be treated is lower compared to a complete water quenching process, which reduces the risk of scaling and blockages in the ash water system and maintains the advantage of the dry powder gasification process in terms of its compatibility with medium/high-ash coal types. Furthermore, compared to the original process, this process requires the fewest modifications. Key components such as the gasifier and syngas quenching have been fully validated. Cyclone separators have been in use at the Buggenum power plant in the Netherlands for many years, and they have also been applied in China’s Yuntianhua and Datang Dolun projects. Overall, this process reduces investment costs without posing any risks to customers. Of course, since the syngas cooler is omitted, the thermal efficiency of the entire system will decrease. As an example, for a gasification unit with a capacity of 2000 tons per day that uses Shenfu coal, the original process allows for the production of 2500 tons per day of high-quality steam (at 400ºC and 5.2 Mpa). After accounting for the steam required for sulfur-tolerant conversion processes (taking methanol production as an example), there is still more than 2000 tons per day of steam available to be fed into the medium-pressure pipeline network to drive turbines. With partial water quenching now in use, the aforementioned steam production is no longer present; accordingly, the sulfur-resistant conversion unit downstream does not require additional steam, and a certain amount of low-quality medium/low-pressure saturated steam is generated. This post was last edited by Tianya Langji on 2009-1-18 at 17:52.]