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Application of jet vacuum pump in chemical industry at this stage
Abstract: At present, vacuum technology is more and more widely used in such industries as vacuum evaporation, crystallization, distillation, sublimation, drying, vacuum concentration, dehydration, chemical reaction absorption and vacuum conveying materials in petroleum, chemical and pharmaceutical industries, Various processes using vacuum technology can save energy, speed up the reaction, improve product quality, increase economic efficiency also gradually formed a consensus, but the vacuum technology is a science edge, China's vacuum industry is the liberation of the former Soviet Union after digestion and absorption , The United States, Japan, Germany developed on the basis of products, although in recent years the number of vacuum equipment manufacturers in China have mushroomed, but many manufacturers for their production of vacuum pumps in different processes how to use selection and Not clear (not to mention the design of new products based on user-supplied process parameters), which gives the user a lot of inconvenience selection, this article will be based on my company more than 30 years of production, development and supporting experience, described in Several typical chemical industry chemical process how to choose the jet vacuum pump. Key words: water jet vacuum pump, new type high efficiency steam jet vacuum pump, soda jet vacuum pump, soda ejector vacuum pump, chemical process and application. First, several concepts on the vacuum pump How to apply a good vacuum pump in the processing of chemical production, you need to make clear the following concepts: 1, "vacuum" concept: "vacuum" is less than one atmosphere in a given space The gaseous state of pressure, that is, the density of gas molecules in the space, is lower than the density of gas molecules in the area at atmospheric pressure. The state of space without gas is called absolute vacuum. 2, vacuum pump: is used to produce, improve and maintain the vacuum device. 3, the amount of pumping: the vacuum pump in the work under pressure pumping unit of time the flow of gas. Unit: kg / h or m3 / h; 4, the ultimate pressure (vacuum): vacuum pump in the case of zero absolute pressure can be achieved. Unit: Pa, KPa, MPa or mmhg (the ultimate pressure minus the local atmospheric pressure is the ultimate vacuum); 5, the working pressure (vacuum): jet pump rated suction absolute pressure. Unit: Pa, KPa, MPa or mmhg (working pressure minus the local atmospheric pressure for the work of vacuum); 6, working steam pressure: steam jet vacuum pump working steam pressure. Unit: MPa or kgf / cm2; 7, working steam consumption: steam jet vacuum pump unit steam consumption. Unit: kg / h; 8, cooling water temperature: water jet pump circulating water temperature or steam jet vacuum pump condenser circulating water temperature. Unit: OC; 9, the amount of cooling water circulation: per unit time through the water jet or steam jet pump condenser circulating water flow. Unit: kg / h; Second, the chemical industry common several vacuum pumps and their advantages and disadvantages 1, the chemical industry often use several kinds of vacuum pumps - chemical industry common vacuum pump can be simply divided into variable volume vacuum pump and jet vacuum pump Variable volume vacuum pump is the use of cycle changes in the volume of the pump to complete the intake and exhaust devices, reciprocating vacuum pump, rotary vane vacuum pump, slide valve vacuum pump, water ring vacuum pump, Roots vacuum pump is a variable volume vacuum pump. Jet vacuum pump is the use of Venturi effect of high-speed jet pressure drop generated by the gas delivered to the exit of a momentum transfer pump, water jet vacuum pump, steam jet vacuum pump, steam jet spray pump in series, soda spray jet pump belong to the same combination of vacuum pumps. 2, variable volume vacuum pump working principle and advantages and disadvantages (1) reciprocating vacuum pump, rotary vane vacuum pump, slide valve vacuum pump, Roots vacuum pump piston reciprocating motion or rotation of the gas inhalation, compression and discharge. Their advantage is that the new pump has a relatively high degree of vacuum, but the piston is a running part, so piston wear can not be avoided, as the number of maintenance increases the working vacuum will continue to decline until it can not meet the production requirements. Such pumps work noise, fuel consumption, high failure rate is also a fatal shortcoming, generally need to open a spare one, which virtually increases the equipment investment and operating costs. In addition, if such a pump is used to suck a condensable gas such as steam to emulsify the lubricating oil, it can only be applied to suction of non-condensable (air-based) gas or to suction of a granular medium It also limits its scope of application. (2) water ring vacuum pump is installed in the pump housing with a multi-vane eccentric rotor rotation, the water thrown into the pump housing to form a concentric water ring with the pump housing, water ring and the rotor blades to form a volume cycle so that the Gas is drawn in, compressed and drained. It has the advantage of low vacuum pumping capacity, you can directly suction steam condensable gas. Its disadvantage is the low degree of vacuum; can not be aspirated with the granular media; rotor rotation is not easy to do anti-corrosion treatment, it can not be aspirated with corrosive media. 3, jet vacuum pump working principle and advantages and disadvantages jet vacuum pump is the use of Venturi effect of pressure drop generated by the high-speed jet gas exports to the export of a momentum transfer pump. It is divided into water jet vacuum pump, steam jet vacuum pump, steam injection pump in series, steam jet spray combination. Jet vacuum pump with its wide range of vacuum, you can directly suction steam and other condensable gas and granular media, simple structure, easy operation, no maintenance of small operating parts, energy saving and other advantages of more and more widely The application of chemical operations in the various processes, the following describes the working principle of various jet vacuum pump. (1) Water jet vacuum pump working principle and structure diagram Water jet vacuum pump equipment composition see its structure diagram, its working principle is: circulating water in the water tank after circulating pump to produce some work pressure, flow rate, with a certain pressure , The flow rate of water into the water ejector collector chamber through the orifice of the plurality of Laval nozzle jet, the formation of high-speed jet ejector mixing chamber to produce a vacuum, the pumping medium under vacuum into the ejector mixing chamber , Fully mixed with high-speed water flow in the mixing chamber and decelerated by the Venturi tube, discharged into the circulating water tank after pressurization, non-condensable gas is precipitated, and the condensable gas overflows from the overflow port of the water tank, so repeated work is performed. Its advantage is low machine type, higher than the water ring vacuum pump vacuum, instead of W-type reciprocating vacuum pump can cancel the front condenser, saving one-time investment in equipment and operating costs. (2) Working principle and structure diagram of water-jet tandem jet vacuum pump In series with one or more steam jet vacuum pumps in series in front of the water jet vacuum jet ejector, the steam-water tandem jet vacuum pump can be seen in the structure. The working principle is: a certain pressure of saturated or superheated steam through the Laval nozzle decompression rate of increase into the steam ejector mixing chamber, the mixing chamber to produce a vacuum, the pumping medium is drawn into the mixing chamber and the working steam mixing, mixing After the fluid through the diffuser, the speed decreases, the pressure rises until it reaches the next stage suction pressure into the next stage after the steam jet pump or water jet pump. It is a low level machine type, the vacuum is relatively high, can replace the water ring - Roots unit, Rotor - Roots direct suction condensable vapor, but it is pumping in a high vacuum non-condensable gas is limited . (3) The working principle and process flow chart of the new high-efficiency steam jet vacuum pump The new high-efficiency steam jet vacuum pump is composed of one or more steam jet pumps and efficient condensers. The saturated or superheated steam under a certain pressure is decompressed through the Laval nozzle After the speed increase, enter the mixing chamber of the steam ejector to make the mixing chamber generate a vacuum. The drawn medium is sucked into the mixing chamber to be mixed with the working steam. The mixed fluid passes through the diffusion tube, the speed drops and the pressure increases until reaching the next Level inlet pressure into the next level after the steam ejector. After the mixed fluid from the steam ejector in front of the condenser enters the high efficiency condenser, the condensable fluid is cooled to discharge the liquid with the non-condensable gases out of the condenser with the cooling water (see the flow chart of the new high efficiency steam jet vacuum pump) . It can be installed at any height. It is suitable for pumping media with relatively small amount of non-condensable gas, most of which can be made into condensable vapor. It can save more than 60% of working steam instead of the traditional multistage steam jet vacuum pump. (4) Working Principle and Process Flow Chart of Fusible-Water Combination Jet Vacuum Pump It is composed of a first-class in-line vacuum pump in series with the first-level condenser behind the first-level condenser of the conventional steam injection pump. The working principle thereof is shown in the technology of the combined jet vacuum pump flow chart. It overcomes the shortcomings of the steam jet vacuum pump and the water jet vacuum pump, and exerts their advantages, which can not only achieve a higher working vacuum but also have a larger pumping capacity than the conventional multistage steam jet vacuum pump to save working steam More than 50%, saving more than 30% of cooling water, without the need to start the pump, evacuation tower time is short. (5) Multi-stage steam jet vacuum pump has the advantages of simple structure, convenient use and stable and reliable operation. The disadvantage is that the steam consumption is high (operation cost is high) and must be installed above 11m. $$ Div $$ Third, the combination of technology to choose a reasonable vacuum pump In the chemical production process, according to the specific work required by the work of the pressure level and the nature of the suction gas to choose a reasonable vacuum pump, generally first determine the specific work required pressure, Vacuum with high vacuum (low working pressure), vacuum evaporation, drying, concentration, crystallization, dehydration, decoloration, chemical reaction absorption and vacuum conveying materials required by vacuum distillation, rectification and sublimation processes, etc. Low vacuum Work pressure high). Working pressure is determined, according to the size of the amount of suction and the nature of the suction gas to choose a reasonable vacuum pump. 1, according to several types of vacuum pump work pressure can be achieved to list the scope of application of various vacuum pumps. 2, suction of different gases to choose a different jet vacuum pump (1) water jet vacuum pump is suitable for working pressure greater than 25mmhg (3.3KPa), sucking a variety of gases, especially in condensable condensable vapor (ie, Condensed gas condensation), with dust, granular media, its advantages are more prominent. When the work pressure is relatively small, non-condensable pumping gas volume is larger, you should choose steam jet pump and steam in series, steam jet spray combination. (2) The working pressure of series water jet vacuum pump can reach 2mmhg (267Pa), but it is smaller than the new type high efficiency steam jet vacuum pump, steam jet water jet vacuum pump and multistage steam jet vacuum pump, which is suitable for batch production of small and medium-sized enterprises. (3) The new high efficiency steam jet vacuum pump working pressure can reach 0.5mmhg (65Pa), suitable for most of the gas to be aspirable condensable gas, non-condensable gas occupies a relatively small proportion of the process. (4) The working pressure of the soda ejector vacuum pump and multistage steam ejector vacuum pump can reach 10Pa, which can suck various gases. The difference between them is that the soda ejector vacuum pump saves the working steam consumption and saves the operation than the multistage steam ejector vacuum pump cost. Fourth, the application of some of the typical process of some manufacturers Application of industrial applications Rugao Double Horse Chemical Co., Ltd. vacuum evaporation water jet vacuum pump instead of three steam jet vacuum pump Rugao Double Horse Chemical Co., Ltd.