Some views on the development and design of water

Some views on the development and design of water ring vacuum pump

as we all know, water ring vacuum pump and water ring compressor have the characteristics of simple structure and convenient use and maintenance, so they have been widely used in all walks of life. Especially with the characteristics of isothermal compression, it is very easy to pump and compress flammable and explosive gases

here are some superficial views on its development and design development

1 large scale due to the development of coal, chemical, pharmaceutical, paper and other industries, the requirements for water ring vacuum pumps are increasingly developing towards large scale. Before 2000, there were only enterprises in China that could produce water ring vacuum pumps with an air extraction of more than 100m3/min, and the annual output of the country was only a few, mainly including ten ultrasonic vibration drilling, ultrasonic vibration grinding and ultrasonic vibration milling. After only three years, by 2003, there were more than 10 manufacturers that could produce large pumps with a capacity of more than 100m3/min in the country (among which there were 7-8 in Zibo area alone). According to incomplete statistics, the output of large pumps in the country reached more than hundreds. These products are mainly used in: (1) the coal mine industry has strengthened the safety requirements for coal mines, so the water ring vacuum pump, In particular, large-scale water ring vacuum pumps have become a necessary safety requirement for the coal mining industry. For example, last year, a Mining Bureau in Shaanxi ordered a number of super large water ring vacuum pumps with a gas extraction capacity of 400m3/min, which are used to extract gas. Some large coal mines use 7-8 large pumps with a gas extraction capacity of more than 100m3/min. With the further strengthening of national safety work, large and extra large water ring vacuum pumps will be more and more widely used in coal mine systems. In addition, due to the rapid increase of coal production, the vacuum filter used in coal washing and coal preparation also developed to large-scale. In the 1980s, most of them were equipped with SZ-4 water ring vacuum pump with an extraction volume of 27m3/min, which was also large at that time. In recent years, coal mine filters have been equipped with large water ring vacuum pumps with an extraction capacity of 80-150m3/min, some of which reach more than 200m3/min, and the gas volume continues to increase. (2) Chemical industry a) chlor alkali industry in recent years, China has launched many large-scale infrastructure and technological transformation projects. The real children of these projects need a lot of PVC materials, especially the prosperity of real estate, which has further promoted the development of the PVC industry. According to the statistics of chlor alkali industry, China produced 4.1 million tons of PVC last year and imported 200 tons. According to the prediction of the industry, the national demand will reach 8million tons in 2005 and 15million tons in 2010. It is precisely because of the rapid increase in demand that enterprises in China's chlor alkali industry have been transformed and expanded, and many new enterprises have been added in recent one or two years. The development of chlor alkali enterprises must be supported by water Shaanxi air pump and water ring compressor J. in the past, the largest water ring vacuum pump and water ring compressor used to pump and press acetylene and hydrogen, advanced functional ceramic materials, were only 30m3/min. now, enterprises with an annual output of 100000 tons of caustic soda and 100000 tons of PVC need more than 70m3/min of water ring vacuum pump and water ring compressor. What needs special introduction here is that the development of this industry has promoted and accelerated the development and production of high i-force water ring compressors. For a long time, when the suction pressure of water ring compressor in China is 1 atmospheric pressure or slightly lower than the upper atmospheric pressure, the discharge pressure is o.1mpa, that is, the compression ratio is 2. Some enterprises have produced water ring compressors with discharge pressure up to 25mpag, and only 1-2 specifications. In order to adapt to the production of PVC, 91 the former major equipment office of the State Council put forward the research and development of vinyl chloride recovery water ring compressor in the key technical equipment research project of the "Eighth Five Year Plan" - the research and development of equipment with an annual output of 4 tons of low polymerization degree PVC plant. This water ring compressor for recovering vinyl chloride monomer requires that the discharge pressure should reach o 6mpag, and the exhaust volume should reach 700m3/min. After several years of efforts, our company passed the technical appraisal organized by the former Ministry of machinery of the people's Republic of China in December 1996, and the customer technology has met the requirements of tackling key problems. On the basis of this product, our company has developed a series of products, with the exhaust volume from 90m3/min to 2000m h。 As this equipment is one of the key equipment in the PVC industry, this kind of water ring compressor has been popularized and applied under the situation of PVC projects in China in recent years, completely replacing imports. b) Chemical fertilizer industry the chemical fertilizer industry, especially the production of phosphate fertilizer, is also the key industry supported in China's economic macro-control. Due to the above-level and large-scale technical transformation of new projects and old enterprises, large and extra large water ring vacuum pumps have also been applied here. For example, a phosphate fertilizer enterprise in Yunnan has added three extra large water ring pumps with an extraction capacity of 300m3/min in one transformation. In addition, many phosphate fertilizer enterprises still need to have a large air extraction capacity when the pressure is 80-100hpa absolute pressure, so the two-stage water ring vacuum pump and the two-stage water ring vacuum pump with atmospheric ejector have unique advantages when used under this working condition. Many fertilizer enterprises have eliminated the reciprocating vacuum pump with high vibration noise and high vacuum degree, and replaced it with the two-stage water ring vacuum pump, which has received good results, It can be said that two-stage water ring vacuum pump will be more and more widely used in this industry. c) At the end of last century and the beginning of this century, China's national debt accounted for a large proportion of the paper industry. Paper mills all over the country rushed to transform to a higher level and scale, which greatly promoted the development and production of large-scale water ring vacuum pumps. A paper mill in Northeast China once rebuilt 6 super large water ring vacuum pumps (the largest water ring vacuum pump produced in China at present) with a total power of 400KW. It can be said that in recent years, 50% of the large-scale water ring vacuum pumps with pumping capacity of more than 100m3/min are used in the paper industry, and this development trend is increasing. d) Vacuum concentration, dehydration, drying and distillation are the main processes of pharmaceutical enterprises in the pharmaceutical industry, and the technological transformation of pharmaceutical enterprises is also on the level and scale, which is more obvious in some large pharmaceutical enterprises. In the past, most small pumps with a capacity of less than 10m3/min were used, but now, in the project bidding of these enterprises, medium and large pumps with a capacity of more than 20m3/min have accounted for the majority. In addition, many factories in the pharmaceutical industry used to use more two-stage water ring vacuum pumps with an extraction volume of 6-12m3/min, but now they are equipped with two-stage water ring vacuum pumps with an extraction volume of m3/min, and some reach 60m3/min. for example, a joint venture pharmaceutical factory in Sichuan bought 10 pumps with an extraction volume of 60m3/min in a tender last year. In addition to the above industries, the vacuum systems of food and beer enterprises in the light industry, as well as metallurgy, power generation, petrochemical, building materials and other industries are developing towards large-scale aspects. For example, an aluminum plant in Shandong has used many water ring vacuum pumps with an extraction capacity of 85m3/min for a long time, while the extraction capacity of water ring vacuum pumps required by the equipment bidding of last year's technological transformation project should reach 140m3/min

2 completeness. It should be said that before 2000, almost all domestic manufacturers of water ring vacuum pumps mainly sold single pumps, and few users ordered complete sets of equipment. In the past two years, the proportion of complete sets of equipment in the equipment bidding of technological transformation projects in the chemical and pharmaceutical industries has become larger and larger. Generally, separators, coolers (heat exchangers), replenishment pumps, valves, instruments, pipe fittings and control devices are required to form a closed cycle, And it is required to be connected with the OCS system of the enterprise to control the liquid level, pressure, force, etc. The requirements for this kind of electromechanical integrated equipment are becoming more and more common in many industries

3 a large amount of air extraction is required under high vacuum. Vacuum distillation, concentration, dehydration, drying in many chemical and pharmaceutical industries and the extraction of tail gas in power plants require a large amount of air extraction between the suction pressure of 3-8kpa. The pumping capacity of a single-stage water ring vacuum pump in this range is quite weak, while the two-stage water ring vacuum pump and the two-stage water ring vacuum pump with a primary air ejector are characterized by a large amount of air suction in this range, Before 2000, the demand for two-stage pumps was mostly below 15m3/min, but now it reaches m3/min. In addition, it should also be pointed out that when the single-stage water ring vacuum pump is equipped with a primary air ejector, if the design is reasonable, there is still a large pumping capacity when the suction pressure is 4-5kpa, which greatly expands the application range of the single-stage water ring vacuum pump. For example, a certain Aircraft Research Institute in China uses several such pumps. To sum up, it can be seen that water ring vacuum pumps and water ring compressors, as basic crude and low vacuum acquisition equipment, have been widely used in various industries. It can also be said that the rapid development of various industries in the national economy has promoted the development and production of water ring vacuum pumps and water ring compressors. Therefore, in order to make it better adapt to the development of various industries, the following superficial views are put forward on the research and development of this pump. (1) With feasible design and high-performance seals, the working reliability of the water ring vacuum pump and water ring compressor during the mean trouble free operation period (MTBF) of the whole machine is improved, that is, the mean trouble free operation period is higher than other rough and low vacuum acquisition equipment, and the mean trouble free operation period can reach more than 10000 hours. However, with the strengthening of technical progress in various industries and the improvement of the reliability requirements of the whole vacuum system, the reliability requirements are correspondingly higher. Especially under the working conditions with strict safety requirements such as chemical industry and coal mine gas extraction, the pump should operate continuously for a long time, and the international advanced level can reach more than tens of thousands of hours. Therefore, in order to truly improve the reliability of the whole machine, the development of water ring vacuum pump and water ring compressor, the limitations of manufacturing conditions and the quality status of seals (especially mechanical seals) need to be further strengthened in the above aspects. (2) Adopting the optimization design method, we should strive to improve the efficiency of pumps and reduce energy consumption. Water ring vacuum pumps and water ring compressors are products with high energy consumption and low efficiency, which is a recognized fact. Small pumps are generally% and large pumps are 40% or slightly higher. Such low efficiency is extremely incompatible with the national requirements for mechanical and electrical products and the current situation of energy shortage in China. Therefore, the optimization design method should be adopted as soon as possible to establish mathematical models for the geometric parameters of the impeller and the starting position and area of the suction and exhaust holes, which are the most critical factors affecting the efficiency of the pump, carry out the optimization design, select the best combination scheme of the parameters, and use the relevant theories and calculation formulas of vapor-liquid two-phase flow to design, so as to minimize the eddy current loss of the water ring and achieve the purpose of improving efficiency. Therefore, it is an important work for the design, development and production enterprises of water ring vacuum pump to successfully design and develop high-efficiency and energy-saving water ring vacuum pump and compressor as soon as possible to eliminate the backward products with high energy consumption and low efficiency. (3) Increase the gas volume at the working point with atmospheric ejector. In foreign countries, whether single-stage water ring vacuum pump or two-stage water ring vacuum pump is equipped with air ejector to improve the air extraction under low suction pressure, there are still many cases. From the technical data of foreign technologically advanced enterprises, it can be seen that when the single-stage water ring vacuum pump is equipped with a primary air ejector, the suction pressure is 5kpa, and the pumping rate can reach 65-70% of the pumping rate (the common condition point of the single-stage water ring vacuum pump commonly used by users) when the pump is not equipped with air injection, and the two-stage water ring vacuum pump is equipped with a primary air