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High-pressure liquid ammonia pump units help reduce dependence on imports. Author/Source: China Chemical Industry News. Date: May 25, 2016. Clicks: 60. Developing standardized and serialized products through a systematic approach. In early May, the project related to the development of large-scale industrial nitrogen fertilizer production technologies – namely, the centrifugal high-pressure liquid ammonia pump unit project – passed the product evaluation. The successful application of this equipment broke the foreign monopoly and laid the equipment foundation for China’s first domestically produced large-scale fertilizer project. The development of this device has enabled our country to break free from its reliance on imported high-pressure liquid ammonia pumps. It is understood that the high-pressure liquid ammonia pump can raise the pressure of the liquid ammonia coming from the ammonia synthesis plant, and it mixes with ammonium methylate to enter the urea synthesis tower. Liquid ammonia has a low density and high vapor pressure, making it highly volatile ； Moreover, liquid ammonia is highly toxic, and the ammonia gas produced by its vaporization is explosive. Therefore, high performance and reliability are required of high-pressure liquid ammonia pumps, which are key equipment in urea production. High-pressure liquid ammonia pumps can be of three types: reciprocating piston pumps, high-speed partial-flow pumps, and medium-speed multi-stage centrifugal pumps. Reciprocating pumps are efficient and were generally used in early small-scale fertilizer production ； High-speed partial-flow pump units have low pump reliability, high maintenance costs, and significant maintenance difficulties; there are virtually no application cases of such units either domestically or internationally ； Medium-speed multi-stage centrifugal pumps feature high reliability, low operating and maintenance costs, and ease of inspection and repair. However, only a few companies such as EBARA and FLOWSERVE are capable of manufacturing this type of pump. At present, there is a lack of research in China on medium-speed multi-stage centrifugal high-pressure liquid ammonia pumps, and no patent achievements have been developed yet. In recent years, a few companies have ventured into the research and development of liquid ammonia pumps, but there are no reports of successful development and application of high-pressure liquid ammonia pumps. There is essentially no work in China on the design, manufacturing, research, and application of high-pressure liquid ammonia pumps. Almost all the high-pressure liquid ammonia pumps used in fertilizer production facilities in our country are imported from abroad; they come at high market prices, entail a strong reliance on foreign technology, and leave the products subject to external control. Currently, the market for liquid ammonia pumps in China’s large-scale fertilizer industry is almost monopolized by the Japanese company Ebara. The breakthrough this time relates to the centrifugal high-pressure liquid ammonia pump units, which are part of a project aimed at developing comprehensive technologies for the industrial production of large-scale nitrogen fertilizers. The development of this technology package is part of a major scientific and technological project funded by China National Petroleum Corporation. It was initiated in June 2010 at Ningxia Petrochemical Company through collaboration among entities such as Ningxia Petrochemical Company, Hangzhou Daliu Industrial Co., Ltd., and China Global Engineering Corporation. After the project was launched, faced with the situation in China where high-pressure liquid ammonia pumps in large fertilizer plants all relied on imported equipment – equipment and spare parts being expensive, having long lead times, requiring strong technical dependence, and subjecting the industry to external control – the technical staff at Ningxia Petrochemical conducted thorough and detailed research. After the pump itself was manufactured, the production factory conducted tests using clean water as the medium. One of the developers, Ningxia Petrochemical Company, relied on actual engineering applications and carried out practical testing using real liquid ammonia at the installation site. Through actual engineering applications, performance indicators such as monitoring capabilities, vibration and noise levels, and operational stability are evaluated, and performance comparison tests are conducted with similar foreign products on the same operating platform. After the installation and testing were completed in June 2012, the research and development equipment was put into industrial operation at the urea plant of the Second Fertilizer Factory. It has been in operation for over 18 months now; industrial performance tests and on-site inspections have been carried out, and it is fully capable of replacing imported reciprocating high-pressure liquid ammonia pumps. It meets the plant’s need for backup centrifugal high-pressure liquid ammonia pumps, ensuring the stable, continuous, and efficient operation of the urea plant. It is reported that this centrifugal high-pressure liquid ammonia pump unit is a medium-speed multi-stage centrifugal pump. It consists of a pump, a drive motor, a speed increase gearbox, a frame, a monitoring and control system, a seal water station, an oil station, etc. The pump is designed as a double-housing multi-stage centrifugal pump; its inner housing features a horizontally split core package structure. With a flow rate of 107 m3/h and a head of 3500 m, it can meet the requirements for transporting high-pressure liquid ammonia in urea production plants with an annual capacity of 800,000 tons. Based on operational monitoring, the design and manufacturing of this pump meet the requirements of the contract as well as the standards specified in API610, Version 10. The pump shaft vibration is 50 μm at the front end and 17 μm at the rear end; the vibration of the bearing housing is less than 1 mm/s, and the rotor operates smoothly ； The noise level of the pump at a distance of 1 m from the pump unit shall not exceed 85 dBA ； It features a continuously rising and stable head-flow curve, ensuring a smooth upward trend without peaks, a wide efficient range, and low hydraulic pulsation. Experts from the project team stated that the overall technical specifications of the unit are at the international leading level, and its pump efficiency is superior to that of similar foreign products; this lays a foundation for the localization of key equipment in the 45/80 domestic large-scale fertilizer production project. This project has obtained 1 invention patent and 4 utility model patents. At the same time, by building on this foundation, the researchers developed their own HTDB products that are at the international leading level (i.e., high-pressure liquid ammonia pump systems such as ultra-high pressure boiler feed pumps and pumps used in nuclear power plants). These products were eventually standardized and serialized, and they are now widely used in various industrial processes across the country, enabling the localization of high-pressure liquid ammonia pumps and bringing significant economic and social benefits.