Questions regarding the production of ammonia and urea from coal gas

Using coal as the raw material, the currently mature methods include gasification of coal slurry to produce gas, sulfur-resistant low-temperature shift reaction, low-temperature methanol washing for desulfurization and decarbonization, deep cryogenic purification using liquid nitrogen, turbine compressors, Brown or Topsoe low-pressure synthesis, and the stripping method is preferred for producing urea. The key technologies for large-scale installations are mainly from abroad. The largest existing plant capacity is around 450,000 tons per year. This post was last edited by wycasia on 2008-2-20 15:13]

Thank you. What is the maximum scale for a single production line in China nowadays? Producing synthetic ammonia

This post was last edited by GSP on 2014-9-18 at 13:45. The raw materials for synthetic ammonia include roughly the following: coal (various gasification processes: coal water slurry (gas flow bed), pulverized coal (gas flow bed), lump coal (fixed bed, fluidized bed – with slightly smaller particle size)). In China, we currently have a 200,000-ton capacity plant for synthetic ammonia production; however, domestic coal gasifiers are still relatively rare.

At present, the largest coal gasification ammonia production plant in China is the Weihe Fertilizer Plant in Weinan, Shaanxi Province, which uses the pressurized coal slurry gasification process to produce 300,000 tons of ammonia and 520,000 tons of urea per year.

The domestically produced gasifiers in Gucheng, Shaanxi, have a daily production capacity of 200 tons. Currently, there are over 20 Shell gasifiers in use in China. Given the conditions of coal availability in China, Shell gasifiers are the preferred choice. For a production capacity of 180,000 tons of synthetic ammonia, atmospheric-pressure batch gasification is used, with each unit producing 13,000 Nm3/h of syngas; the main manufacturing area is located in Shanxi； An atmospheric-pressure continuous gray polymerization fluidized-bed gasifier with a capacity of 20,000 Nm3/h of syngas per unit, used by Tianjin Alkali Plant ； The pressurized continuous Ruqi process has a capacity of 40,000 NM3/H per unit, and it is used by Tianji ； The Texaco water coal slurry process for pressurized continuous gasification has a capacity of around 40,000 NM3/H per unit ； Shell dry coal powder gasification features low oxygen consumption, strong adaptability, and high thermal efficiency; however, it requires large investment and offers great operational flexibility. It is used by Yuntianhua. The Shell furnace for 500,000 tons of synthetic ammonia is about 200–300 million yuan more expensive than that of Texaco; it produces 10% more syngas per ton of coal, the oxygen production equipment is 15–25% smaller, and the power generation efficiency of the waste heat recovery system can be increased by 2–4%. Ningxia Ningmei is collaborating with GSP to develop gasification technology, which is expected to be ready by 2015. These days, when producing synthetic ammonia and urea from coal, methanol is generally produced as a by-product; otherwise, the economic efficiency is relatively low.

Currently, coal-based gas is used to produce synthetic ammonia and urea, and the capacity of the plants under design for a single production line amounts to 870,000 tons of urea per year. Gasification can use Texaco, GSP, BGL, etc., but compared to the latter two, Texaco has higher requirements regarding the type of coal. The purification section uses low-temperature methanol washing (Linde technology can be employed, or domestic technologies such as those from Huahere Research Institute and Huanqiu can be used). For ammonia synthesis, KBL and Danish Topsoe technologies are utilized. For urea production, the StacamiBond carbon dioxide stripping technology is recommended; all the technologies used in this proposed process are mature ones.

Currently, the gasification technologies for producing synthetic ammonia using coal as a raw material include fixed-bed batch gasification, fixed-bed oxygen-enriched gasification, Enfield furnace gasification, and Ruhr process gasification. Modern large-scale synthetic ammonia plants employ GE coal water slurry gasification technology, four-nozzle opposed gasification technology, SHELL gasification technology, as well as domestic multi-feedstock slurry gasification technologies. The most mature technology at present is GE’s coal slurry gasification technology; systems with pressure levels of 4.0 MPa, 6.5 MPa, and 8.7 MPa have been put into operation in China. GE has already signed 33 technology transfer contracts in China. The four-nozzle gasification technology developed in China is also good, although its investment requirement is slightly higher than that of GE’s technology. Shell’s gasification technology has not performed as well as expected at present, and further improvement and refinement are needed. The urea production technology based on the Stamicarbon 2000+ system is considered mature in China! The largest ammonia synthesis plants currently in operation have a capacity of 300,000 tons per year. The ammonia synthesis technology designed by our company enables a capacity of 400,000 tons per year, with an operating flexibility of 110%, which can be considered the highest in China.

As for which vaporization method is better, it cannot be simply generalized. It depends on the type of coal, investment, and comprehensive benefit analysis

Historically, in coal gasification, slurry coal (Texaco), lump coal (Lurgi, BGL), and pulverized coal (SHELL) have been used. In China, pulverized coal (used in space furnace technology) and slurry coal (using Yankuang’s multi-nozzle opposed coal gasification process) are also employed. Coal gasification is highly dependent on the quality of the coal; if the coal has good slurry-forming properties, Texaco can be used, while if it has good caking properties, SHELL can be utilized (although it is relatively expensive). If the quality of the coal isn’t that good, then BGL can be used – it can gasify even what is considered waste material – and it is relatively inexpensive, but a briquetting unit is required. If there’s no money, then go with domestic options. However, it’s likely that the capabilities will only be sufficient for projects of type 3050; for space furnaces, it’s possible to use projects of type 2030

Reply: Typical domestic coal gasification processes and representative companies: 1. Traditional fixed-bed batch gasification, with a maximum ammonia synthesis capacity of around 200,000 tons, namely the so-called 18/30 mode. There are currently approximately 20–30 such units in China, including Jinfeng Coal Chemical and Shandong Shouguang Alliance. 2. Luchi coal gasification, represented by Shanxi Tianji Chemical, produces 300,000 tons of synthetic ammonia per year. 3. GE (formerly TEXACO)’s water-coal slurry gasification technology, represented by Shaanxi Weihe Chemical, has an annual production capacity of 300,000 tons of synthetic ammonia. The second-phase expansion has been completed, adding an additional 200,000 tons per year of methanol production capacity; thus, the total annual capacity for ammonia and methanol amounts to 500,000 tons. 4. SHELL pressurized coal gasification: represented by Guizhou Tianfu, Yuntianhua, Sinopec’s three oil-to-coal conversion projects (in Anqing, Yueyang, and Hubei for fertilizer production), as well as Guangxi Liuhua, with an annual ammonia and alcohol production capacity of around 500,000 tons. 5. Atmospheric pressure oxygen-enriched continuous gasification: due to the soaring price of coke, these plants have been shut down or modified. 6. East China University of Science and Technology employs multi-nozzle opposed water-coal slurry gasification; represented by Hualu Hengsheng, it produces 300,000 tons of synthetic ammonia per year. This post was last edited by zjyang168168 on 2008-4-3 10:41.]

The above posts provide a deeper understanding of ammonia and urea production via coal-based gas synthesis; thank you all for your help

The largest scale of a single set of ammonia synthesis plants in operation at present is 600,000 tons per year, owned by Jin Kai

I will briefly share my views on the gasification choice for the ammonia synthesis project. It is not recommended to choose BGL: first, BGL requires lump coal, meaning high requirements for raw materials; second, BGL contains CH4, at around 10%, and the conversion or removal of this CH4 adds complexity to the process beyond that of the main product; third, wastewater from BGL is difficult to treat due to its high organic content. A fluidized bed can be used, but Shell is not recommended; firstly, its investment is high, and the subsequent gas separation system is complex. It is said that its operation has only just begun to stabilize. Optional foreign gasifiers: GE, GSP, Corning; domestic gasifiers: Aerospace Gasifier, Tsinghua Gasifier, Four-Nozzle Gasifier, Multi-Component Slurry Gasifier. In addition, there are new domestic technologies such as Guotuo’s Kaiyang Gasifier, Ningbo Institute’s Dongfang Gasifier, Wuhuan Institute’s Wuhuan Gasifier, and Ningmei’s Ningmei Gasifier. It is not recommended to choose foreign technologies; firstly, patent fees are high, and secondly, we should support domestic solutions, as domestic gasification technologies also operate stably. Between pulverized coal and water-coal slurry, I prefer water-coal slurry; the processing and transportation of pulverized coal are complex, and high precision is required for the materials used in valves. Based on the coal quality analysis data, water-coal slurry is feasible; Tsinghua furnaces, four-nozzle systems, and multi-component slurries can be used. The pulping quality is not good; powder gasification can be an option, and there are more operating projects for space furnaces.