As we all know, due to the water ring vacuum pump and water ring compressor has the advantages of simple structure, easy to use and maintain, so it has been widely used in all walks of life. Especially with the characteristics of isothermal compression, easily sucked, compressed flammable gases. Here to talk about its development and design and development of a few superficial views.
Due to the development of the coal mine, chemical industry, pharmacy and paper making industries, the demand for water ring vacuum pumps has become more and more large-scale. Before 2000, our country was able to produce only 3-4 enterprises in the water ring vacuum pumps with the pumping volume of more than 100m3 / min. The annual output of the country is only a few dozen or so units. And only three years later, by 2003 the country can produce more than 100m3 / min large pump manufacturers more than 10 (only Zibo area there are 7--8), according to incomplete statistics, the country's large pump Production up to hundreds of units, these products are mainly used in:
(1) Coal mining industry
As the state has stepped up its safety requirements for coal mines, pumping water gas vacuum pumps, especially large-scale water ring vacuum pumps, has become a mandatory safety requirement in the coal mining industry. For example, the number of pumping units ordered by a mining bureau in Shaanxi Province last year was more than 400m3 / min large water ring vacuum pump is used to extract gas, and some large coal mines use more than 100m3 / min up to 7-8 sets of pumps. As the state further strengthens its safety work, large-scale and extra-large water ring vacuum pumps will be more and more widely used in coal mining systems.
In addition, due to the rapid increase of coal production, the vacuum filter used in coal washing and coal preparation also went large-scale development. In the 1980s, most SZ-4 water ring vacuum pumps with a pumping volume of 27 m3 / min It was also larger at that time. In recent years, the coal mine filter are equipped with a large amount of pumping capacity of 80-150m3 / min water ring vacuum pump, and some reached more than 200m3 / min, but also the gas volume continues to increase.
(2) chemical industry
a) Chlor-alkali industry
In recent years, China has launched many large-scale capital construction projects and technological transformation projects. The actual projects of these projects require a large amount of PVC materials, especially real estate, which has further promoted the development of the PVC industry. According to the requirements of the chlor-alkali industry Statistics show that China produced 4.1 million tons of PVC last year and 200 tons of imported materials. According to the forecast of the industry, the national demand in 2005 will reach 8 million tons, and by 2010 it will reach 15 million tons precisely because of the rapid increase in demand, making China's chlor-alkali industry enterprises to expand production expansion and near One or two years a lot of new businesses. The development of chlor-alkali enterprises, water and air pumps and water ring compressor must be supporting j to extract and compress acetylene and hydrogen water ring vacuum pump and water ring compressor in the past but also the largest 30m3 / min, and now with an annual output of 100,000 tons Caustic soda and 100,000 tons of PVC companies need water ring vacuum pump and water ring compressor up to 70m3 / min.
What needs to be specially introduced here is precisely because of the development of this industry, to promote and speed up the development and production of high I-force water ring compressors. For a long time, China's water ring compressor is generally when the suction pressure of 1 atm or slightly lower than the pressure, the exclusion of pressure O. 1MPa, that is, the compression ratio is 2, and some enterprises have produced water ring compressors with the pressure up to 25MPaG, and only 1-2 specifications. In order to adapt to the production of polyvinyl chloride, the former major equipment office of the State Council proposed in the "85" major technological equipment research project - the research and development of an equipment with an annual output of 4 tons of low polymerization degree polyvinyl chloride unit Research topics, this recovery of vinyl chloride monomer water ring compressor requires suction pressure at atmospheric pressure or micro negative pressure, the discharge pressure to reach O.55-0.6MPaG, and the displacement to reach 700m3 / min. After several years of hard work, our company passed the technical appraisal organized by the former Ministry of Machinery Industry in December 1996, and the customer technology has reached the key requirements. On the basis of this product, our company has developed a series of products, displacement from 90m3 / min to 2000m. / H. Since this equipment is one of the key equipment in the PVC industry, under the circumstance of the large PVC project in China in recent years, the water ring compressor has been popularized and applied, completely replacing the import.
b) Fertilizer industry
The fertilizer industry, especially the production of phosphate fertilizer, is also the key industry supported by China's macroeconomic regulation and control. As the technical innovation of the new projects and the old enterprises are above the level and scale, the large and extra-large water ring vacuum pumps are also here Application, such as a phosphate fertilizer company in Yunnan, a transformation of the new pumping capacity of 300m3 / min 3 large water ring pump.
In addition, there are many technological requirements of phosphate fertilizer companies in the pressure of absolute pressure 80 - lOOhPa, still have a larger pumping capacity, so two water ring vacuum pump and air ejector with two water ring vacuum pump used here Under various operating conditions, it has unique advantages. Many chemical fertilizer companies eliminated the reciprocating vacuum pumps with large vibration and high vacuum and replaced them with two-stage water ring vacuum pumps, and received good results. It can be said that the two levels of water rings Vacuum pump applications in the industry will be more extensive.
c) Paper industry
The end of the last century and the beginning of this century, China's national debt into the paper industry occupies a large proportion of paper mills across the country scrambling to reform on the level, on the scale, which greatly stimulated the development and production of large-scale water ring vacuum pump, a paper mill in Northeast China A transformation of pumping capacity of 400IIl3 / min large water ring vacuum pump (currently the largest production of water ring vacuum pump) 6, with a total power of 400kW. It can be said that in recent years, the pumping capacity of more than 100m3 / min 50% of large water ring vacuum pump is used in the paper industry, and this trend continues unabated.
d) Pharmaceutical industry
Vacuum concentration dehydration, drying, distillation is the main process of pharmaceutical companies, pharmaceutical companies technological transformation is also on the level, on the scale, which in some large pharmaceutical companies even more obvious. In the past, most of them used small pumps of less than 10 m 3 / min, and now large and medium-sized pumps account for the majority of the project bidding in these enterprises with an extraction volume of more than 20 m 3 / min. In addition, many plants in the pharmaceutical industry used to have more two-stage water ring vacuum pumps with a suction volume of 6 - 12 m3 / min, and now both have 20-30 m3 / min two-stage water ring vacuum pumps and some also reach 60 m3 / min For example, a joint venture pharmaceutical factory in Sichuan last ten bid to buy 10 pumps with a pumping capacity of 60m3 / min.
In addition to the above industries, the vacuum systems of light industry, food industry, beer industry and metallurgy, power generation, petrochemical and building materials industries all develop to large scale. For example, a certain aluminum plant in Shandong has long been using multiple water rings with an extraction volume of 85 m3 / min Vacuum pump, and last year's technical transformation project bidding equipment required water ring vacuum pump exhaust volume to reach 140m3 / min.
2 complete set
It should be said that in 2000 before the domestic water ring vacuum pump manufacturers are almost all single-pump sales, very few users set complete sets of equipment, and the past two years, chemical, pharmaceutical industry, technological transformation project equipment bidding complete sets Equipment, the proportion of equipment is increasing, the general requirements with splitters, coolers (heat exchangers), rehydration pumps, valves, meters, fittings and control devices, the formation of closed loop, and requires the OCS system connected with the enterprise, On the level, pressure, power and other online control.
The requirements for such mechatronic plants are becoming more common in many industries.
3 higher vacuum requires a larger amount of exhaust
Many chemical and pharmaceutical industries, vacuum distillation, concentration, dehydration, drying and power plant extraction exhaust require suction pressure of 3 - 8kPa between the larger pumping capacity, a single-stage water ring vacuum pump pumping in this area Gas capacity has been quite weak, and two-stage water ring vacuum pump and a two-stage water ring vacuum ejector features a large intake in this region, the demand for two-stage pumps before 2000, mostly Is 15m3 / min or less, and now up to 40-50m3 / min. In addition, it should also be noted that, when a single-stage water ring vacuum pump with a stage air ejector, if the design is reasonable, the suction pressure is 4 - 5kPa still have a larger pumping capacity, which greatly expanded the single-stage water ring vacuum pump Use, such as China's aircraft Institute on the use of such pumps more than one.
In summary, it can be seen that the water ring vacuum pump and water ring compressor as a rough rough vacuum access to equipment has been widely used in various industries, it can be said that the rapid development of various sectors of the national economy to promote the water ring vacuum pump and Water ring compressor development and production. Therefore, in order to make it better adapt to the development of various industries, the following points of superficial view are put forward on the research and development of this pump.
(1) With the feasibility of design and high-performance seals, to improve the machine's mean time between failures (MTBF)
The operational reliability of water ring vacuum pumps and water ring compressors, that is, mean time between failures, should be said to be higher than other rough vacuum acquisition equipment, with an MTBF of up to 10,000 hours. However, with the enhancement of technological progress in various industries and the increase in the reliability requirements of the entire vacuum system, the reliability requirements are also correspondingly higher. Especially in such chemical and coal mine gas under such stringent safety conditions, the pump to long-term continuous operation, the international advanced level up to tens of thousands of hours or more. Therefore, water ring vacuum pump and water ring compressor design work of the development and manufacturing conditions and seals (especially mechanical seals) the quality of the status quo to truly improve the reliability of the machine still need to further the above aspects Work to further strengthen.
(2) Adopting optimized design method to improve pump efficiency and reduce energy consumption
Water ring vacuum pumps and water ring compressors are energy intensive and inefficient products, which is generally accepted as a fact that small pumps are typically 30-35% and large pumps are up to 40% or slightly higher. This low efficiency is in line with national electromechanical Product requirements and the current situation of China's energy shortage is extremely incompatible. Therefore, the optimal design method should be used as soon as possible to establish the mathematical model of the geometric parameters of the impeller and the initial position and area of â€‹â€‹the suction and exhaust holes, which affect the efficiency of the pump, to optimize the design, select the best combination of the parameters and adopt The theory and calculation formula of vapor-liquid two-phase flow are designed to minimize the eddy current loss of the water ring and achieve the purpose of improving efficiency. So as soon as possible design and development of energy efficient water ring vacuum pumps and compressors to eliminate high energy consumption, low efficiency of backward products is placed in water ring vacuum pump design and development, production enterprises in front of an important task.
(3) Increase the amount of gas at the point of operation with the air ejector.
Abroad, whether single-stage water ring vacuum pump or two-stage water ring vacuum pump with air ejector to improve the suction pressure at lower suction pressure situation is still more. From the technical information of advanced foreign enterprises can be seen on the single-stage water ring vacuum pump with a stage of the air ejector, the suction pressure of 5kPa point, the suction rate up to the pump without air injection suction pressure of 400hPa Point pumping speed (common user of the single-stage water ring vacuum pump of the total points) of 65 - 70%, two water ring vacuum pump with a stage of the air ejector, the suction pressure of 1.5kPa point pumping rate can be Up to 70 - 75% of the pumping rate of the suction pressure of 8 kPa (common operating point of two-stage water ring vacuum pump) without the air ejector, thus greatly expanding the application range of the water ring vacuum pump, namely Meet the chemical, pharmaceutical, light industry, equipment, metallurgy, power generation and other industries require suction pressure 1.5 - 5kPa point pumping rate of the process conditions. At present, however, the domestic one is the application of water ring vacuum pump with atmospheric ejector is not widely enough; the second is the pumping speed at 1.5 - 5kPa point smaller, with the advanced technology level of foreign manufacturers have a certain gap. To further promote the application, we should study to improve the design of the air ejector and the optimal ratio of the water ring vacuum pump. Since the air flow in the taper of the nozzle of the air ejector (Laval nozzle) and the diffuser is supersonic The exchange of momentum in the process of mixing the two streams of air and gas to be drawn is complicated and can not be completely relied on the theoretical calculation method. Therefore, it is necessary to carry out many experiments. However, the application of the water ring vacuum pump and its efficiency From the perspective of strengthening the pilot study, and strive to improve its pumping efficiency
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