Optimization of the GSP powder gasification technology introduction plan

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Optimization of the Introduction Plan for GSP Powder Gasification Technology Author/Source: Tan Chengmin, Cao Zhaojun (Guizhou Kaiyang Chemical Co., Ltd., Kaiyang 550300) Date: 10-13-2008 The 500,000 t/year ammonia synthesis project of Guizhou Kaiyang Chemical Co., Ltd. was constructed with joint funding from Yankuang Guizhou Energy Chemical Company and Guizhou Kailin Group. It is one of the largest and most technologically advanced ammonia synthesis facilities in China, aimed at providing liquid ammonia as a raw material for the ongoing Kaiyang phosphate-coal chemical industry complex. Ammonia is delivered via pipeline to supply the downstream phosphate-ammonium fertilizer production units on a 24/7 basis. The plant utilizes advanced domestic and international technologies such as low-temperature methanol washing and liquid nitrogen washing, as well as centrifugal syngas compression units driven by fully condensed steam turbines. The coal gasification technology adopts Germany’s GSP pressurized coal gasification process; after thorough investigation into the operational characteristics and development history of this technology abroad, and by combining it with China’s advanced experience in Texaco water-coal slurry gasification, the technical plan for introducing this gasification technology has been optimized. This report presents the details of these optimizations. 1 Properties of raw coal in Guizhou: The dry powder gasification technology is well-suited to the anthracite from Guizhou, which is characterized by high ash content, high ash fusion temperature, and high sulfur content. The analysis of the raw coal is shown in Table 1. http://www.zaoqiwang.com/upload1/0808121609138215.jpg 2 Introduction to GSP gasification technology 2.1 Understanding of GSP gasification technology The process of introducing Texaco’s water-coal slurry and Shell’s coal powder gasification technologies in China has been a long and tortuous one, illustrating the difficulties involved in bringing a key technology from an introduced state to a mature stage. Since its first exchange with German Future Energy Company on May 17, 2005, Guizhou Kaiyang Chemical Co., Ltd. has held numerous discussions with experts from German Future Energy Company and Collin Company. Through these exchanges, it has gained a basic understanding of the current patent status of the GSP gasification technology, its actual technological development history, as well as the greatest advantages and existing problems of this technology. As a new dry coal powder gasification technology, GSP gasification combines many advantages of both Shell gasification and Texaco gasification. Its investment is almost half that of Shell gasification; no furnace is required, and annual maintenance costs are low (mainly due to the absence of the need to replace refractory materials and the burner’s service life exceeding 8,000 hours). It can also be used with coals that have a higher ash fusion temperature. 2.2 Characteristics of GSP gasification technology 2.2.1 Main advantages (1) Completely tar-free products ； (2) Up to 99% carbon conversion rate ； (3) Wide range of feed coal types ； (4) High gasification capacity, smaller equipment size compared to other devices with the same processing capacity, and long service life ； (5) The gasifier has a long service life; the water wall system can last over 10 years, and the furnace body has an even longer lifespan. 2.2.2 Characteristics of special equipment from the technical provider: The service life of the gasification furnace (water wall) is 10 years (under normal operation) ； Burner (feed burner) lifespan: 10 years (burner tip maintenance up to 2 times per year) ； The service life of the dense-phase feeding system is 15 years. 2.2.3 Reliability (expected service life, including maintenance and downtime) Expected service life of the vaporizer vessel: 25 years ； Expected service life of the water wall: 25 years ； The expected service life of the pressure vessel is 25 years. 3 Optimization schemes for the GSP gasification technology. The gasification zone mainly includes: the grinding and drying of coal powder ； Compact transportation and gasification of coal powder ； Preliminary purification of raw coal gas, treatment of black water. 3.1 Grinding, Drying, and Preparation of Coal Powder: Looking at the Shell gasification technology introduced from abroad, the process of grinding, drying, and preparing dry coal powder is almost entirely designed in China. Based on the operations of Hubei Shuanghuan and Sinopec Dongnitrogen, it can be concluded that China’s coal powder production technology is fully reliable. The GSP gasification technology is almost identical to Shell gasification in terms of coal preparation, and the experience gained with Shell gasification can be fully utilized as a reference. Therefore, the coal preparation unit should be separated out in the scope of implementation and designed by domestic firms, which not only addresses the issue of reliability but also reduces costs. 3.2 Dense-phase transportation of coal powder and gasification: The technology for dense-phase transportation of coal powder and gasification in the context of GSP gasification technology is already in use abroad, while in China only similar experimental installations exist. Therefore, it is necessary to introduce this advanced technology in order to reduce risks. 3.3 Raw gas purification and black water treatment systems 3.3.1 Understanding of domestic and international raw gas purification and black water treatment systems From the history of GSP gasification development, it is difficult to assess the effectiveness of raw gas purification; since the main purpose of GSP gasification abroad is to supply fuel gas, the requirements regarding dust content are not as strict as those for gas used as raw material in chemical production. It is hard to imagine that the design of raw gas purification systems could be much more advanced than those used by Texaco. As is well known, the dust content in the GSP gasification syngas directly affects the service life of the shift catalysts in subsequent processes, thereby impacting the operation of the plant. In addition, the technologies for purifying the raw gas produced in Texaco’s gasification process and for managing the blackwater system have also undergone numerous improvements during their development in China. The impact on the conversion catalysts used in various plants varies as well; in particular, the blackwater system remains a factor that affects the long-term operation of the gasification systems. Plants have made significant efforts and carried out technical upgrades regarding this system. Although stable production was ultimately achieved, the experiences and lessons learned from these efforts are worth considering. The coarse gas purification and black water treatment system for coal slurry gasification at Yankuang Guotai Chemical Co., Ltd. was designed by East China University of Science and Technology. This design completely broke away from the reliance on imported German-Turkish coal slurry gasification technology. After nearly a year of operational testing, it has proven capable of operating over long periods of time. Therefore, when introducing this system, it made sense to separate the coarse gas purification and black water treatment components and have East China University of Science and Technology handle their design – this approach not only ensured reliability but also reduced costs. 3.3.2 Preliminary purification of crude gas via staged purification: Yuncheng Guotai Chemical Co., Ltd. employs a \"staged purification\" approach for the preliminary purification of crude gas, which consists of three units – a mixer, a separator, and a water washing tower – to form a process flow for the preliminary purification of syngas (see Figure 1). This involves first carrying out \"rough separation\" followed by \"fine separation\", and it is an efficient and energy-saving method. A separator is installed after the mixer to remove 80%–90% of the fine ash, resulting in syngas that is cleaner before entering the water washing tower ； The washing water fed into the wash tower is cleaner than the wetting washing water fed into the mixer, which ensures an effective washing effect; it allows the system pressure to be reduced (0.08 MPa–0.10 MPa), results in good separation, and keeps the fine ash content in the syngas low (<1 mg/m3). At the same time, the hierarchical purification method avoids the clogging problem in the initial purification stage of raw gas. At the initial stage of feeding into the Texaco water-coal slurry gasifier, the scale deposits attached to the inner walls of the process gas outlet pipelines fall off due to heating and the action of high-speed airflow, which can easily lead to blockages in the outlet pipelines of the wash tower. Thanks to the presence of the separator, ash and scale are trapped inside it in advance; even if the drainage pipeline of the separator becomes blocked, the carbon scrubber can still carry out the function of discharging ash. http://www.zaoqiwang.com/upload1/0808121609573857.jpg 3.3.3 Treatment Process for Sludge-Containing Black Water: Yuncheng Guotai Chemical Co., Ltd. employs a process in which the steam generated by the evaporation of sludge-containing black water is used for direct heat exchange with gray water, thereby recovering heat while simultaneously facilitating mass and heat transfer; the process flow is shown in Figure 2. Its advantage is: no hidden risks that could affect long-term operation ； Heat recovery is efficient; the temperature difference between the high-temperature gray water and the flash steam is <2°C, resulting in high thermal efficiency. The imported Degussa coal-water slurry gasification technology uses an indirect heat exchange method, which causes severe scaling and blockage of the heat exchange equipment, preventing the system from operating for extended periods of time. http://www.zaoqiwang.com/upload1/0808121610202490.jpg 4 Conclusion In line with the basic requirements of modern coal chemical industry, the project should make use of advanced technologies, optimize the process routes, pay close attention to the combination of environmental protection and economic benefits, and minimize investments where the technology is mature and reliable. For the same project scale, when a Shell gasification process is adopted, the total investment amounts to around 3.1 billion to 3.5 billion yuan. By drawing on some advanced experiences from domestic Texaco gasification projects and using an optimized, relatively simplified GSP implementation process, the investment is reduced to about 2.4 billion yuan, which not only **reduces costs** but also **enhances the competitiveness of the project**.