Inspection Report on Linquan Aerospace Furnace

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Report on the Inspection of Aerospace Gasification Technology
Aerospace gasification technology is a new type of gasification process that has developed in recent years. From January 28 to 30, 2009, we visited the Linquan Fertilizer Factory in Anhui to examine the research and development as well as pilot testing of this aerospace gasification technology. The findings of this inspection are summarized as follows:

I. Operation status of the aerospace furnace and existing problems
1. Operation status of the aerospace furnace unit
In 2006, Linquan Company collaborated with Beijing Aerospace Petrochemical Technology Equipment Engineering Company (Beijing Aerospace Institute No. 11) to implement energy-saving technological upgrades to the synthetic ammonia production process, using China’s own proprietary HT-L (aerospace furnace) pulverized coal pressurized gasification technology. Construction began in October 2006, and all work was completed by October 2008, resulting in the construction of a unit with a diameter of 2.8 meters. The first 35-hour operation test was conducted in November 2008; after nearly two months of analysis and adjustments, the second ignition and feeding of the gasifier took place on January 18, 2009, with methanol product being produced on that day. Since the air separation system did not reach its designed production capacity at startup, the system load remains around 75%; to date, the plant has been operating steadily for 12 days. The main process parameters of the unit are as follows: Gasification pressure: 3.5 MPa; Gas production rate: 45,000 Nm3/h (dry gas); Furnace temperature (wall temperature): 300–350°C (furnace internal temperature is not accurately measured); Coal feeding rate: 35 tons per hour; Carbon content in ash: 1–2%; Ash discharge volume: approximately 120 tons per day (on a wet basis); Carbon content in fine ash: 20%; Ash discharge volume: approximately 40 tons per day (on a wet basis). Gas composition: 60% CO, 32% H2, 9% CO2, CH4 < 1%. Main consumptions: 1.5 tons of raw coal per ton of product, 350 kWh of electricity per ton, and 3 tons of steam per ton. 2. Problems encountered during the unit’s commissioning: From the second batch of feed, it can be seen that the unit operates relatively stably and its performance meets the design requirements to a large extent. However, there are still some issues, mainly including: (1) Excessive system interlocks, along with insufficient skill among operators, which has led to multiple shutdowns of the unit. (2) Issues with the flow meter of the coal feeder caused the furnace temperature to reach 1800°C, resulting in the damage of the insulation pins at the upper part of the furnace. (3) Key equipment such as powder furnace nozzles and special valves has not yet undergone long-term operation, and further testing is required. (4) Due to unstable operation, the carbon content in the slag and furnace ash is relatively high. (5) Fine ash and slag have a high moisture content, making subsequent treatment more difficult. (6) Coal consumption: The designed coal consumption is 1.4 t/t (5000 Kcal/kg); due to unstable operation, the current coal consumption is 1.5–1.6 t/t. 3. Land area occupied and investment: The total height of the gasification and coal preparation units is 75 m, with an area of 60×30 m². The total investment is 700 million yuan, of which 250 million yuan is invested in the gasification unit. II. Characteristics of the Aerospace coal gasification technology: The Aerospace furnace represents a combination of Texaco’s and Shell’s coal gasification technologies. This technology incorporates the advantages of advanced foreign coal gasification techniques, making full use of the strengths of specialized aerospace technologies as well as the research results related to aerospace petrochemical equipment. It involves independent development of key coal gasification equipment such as the HT-L furnace and gasification burners, and makes use of mature chemical processes to create a set of coal gasification technologies with independent intellectual property rights. Its features are as follows: l It uses coal dust as raw material, which takes advantage of the wide distribution and diversity of coal resources in China. l It employs a fluidized bed pressurized gasification system along with a water-cooled wall structure; the gasification pressure is 4 MPa and the gasification temperature is above 1700°C, meeting the technical requirements for efficient utilization of coal. l It adopts technologies such as rapid cooling processes and recycled use of ash and slag, enabling effective treatment of harmful elements such as ash and sulfur in the syngas, as well as comprehensive utilization of the ash and slag – thus meeting environmental cleanliness standards. l All equipment is domestically produced, and the entire process technology possesses independent intellectual property rights; this results in lower construction costs and operational maintenance expenses, facilitating its adoption in fields such as power generation and chemicals. This technology has reached the international advanced level in gasification technology, meeting China’s needs for large-scale and efficient gasification solutions. It can replace foreign gasification technologies, and holds great strategic significance for promoting independent innovation in the core technologies related to the clean and efficient utilization of coal resources in China. III. Understanding of the plant’s operation and suggestions: 1. The space furnace system has too many interlocks; during testing, changes in data can potentially cause the system to shut down. It will need to be figured out through future operations. 2. The trial operation time of the space furnace is very short; currently, the operation cycle is only 12 days, and the maximum load is only 75%. The operation data and consumption figures need to be further verified through subsequent operations to determine whether they meet the design requirements. 3. In accordance with the design requirements of the space furnace, the nozzles inside the furnace need to be inspected every 6 months. That is, the space furnace needs to be shut down every 6 months for maintenance of the nozzles. 4. The operating temperature of the space furnace is 1400–1900°C. To prevent the temperature sensing elements from being damaged, the sensing point is located 1 centimeter within the insulation layer of the water-cooled wall inside the furnace. The actual combustion temperature inside the space furnace is much higher than the operating temperature, and the service life of components such as nozzles, insulation materials for the water-cooled walls, and mounting pins in this furnace still needs to be tested. 5. The steam generated as a by-product in the space furnace is entirely saturated steam; if superheated steam is required, it can only be used after reducing the pressure. It causes certain difficulties in the steam balance of the entire plant. 6. The space furnace has not yet been tested under long-term continuous operation. 7. There are few domestic manufacturers that produce complementary products such as black water valves, self-regulating valves, oxygen valves, and other special types of valves. At present, although the domestic pressurized coal gasification technology using space furnace systems has many advantages when compared with advanced foreign coal gasification technologies such as TEXACO’s water-coal slurry pressurized gasification technology and SHELL’s pressurized coal gasification technology, there is still no record of long-term operation. It is recommended to conduct further and more thorough evaluations of various operational parameters of these space furnace systems, particularly by gathering actual operational data after a period of use. Additionally, it is necessary to observe more closely the stability of the gasification system and special valves over long periods of operation, in order to understand their actual performance in practice. In terms of both technical and economic indicators, aerospace gasification technology has reached international advanced levels, giving it a strong competitive advantage in the market. However, the operating time of its demonstration unit is short, and some issues have not yet become apparent. In the future, we will continue to monitor its development in order to provide scientific evidence for leaders when making decisions regarding gasification technologies.