The jet pump is a device that uses the negative pressure formed by the high-energy fluid to pass through the nozzle to generate a high speed to absorb the fluid. The high velocity of the nozzle outlet creates a negative pressure because the fluid ejected at the high velocity can entrain the surrounding fluid and flow toward the diffuser. In the diffuser, the velocity gradually slows down, and the velocity energy becomes pressure energy. When this pressure is greater than the external atmospheric pressure, the fluid in the diffuser will flow out. Its characteristics are simple and reliable, continuous work, no rotating parts, and long life; but its nozzles are easily blocked by debris, and the efficiency is low, with a maximum value of 30% (when the volume injection coefficient u=V2/V1 is 1 In the case of , when u is greater than 1 or less than 1, the efficiency is reduced. V1, V2 are the volumes of the working liquid and the liquid to be transported).
Jet pump is widely used in conveying and compressing mixed gas and steam, liquid and solid equipment. Gas or liquid is often used as power medium. The use of jet pumps to generate vacuum is another very important application. The main principle of the jet pump is that the liquid or gas ejected by the power nozzle at a high speed drives and accelerates the surrounding liquid, gas or solid. This movement results in the mixing of the driving and entrained substances. The velocity of the jet decreases at the diffusion and the pressure increases. Unlike conventional pumps, jet pumps operate without moving parts. Jet pumps are available in a wide variety of materials such as cast iron, steel, stainless steel, Hastelloy, titanium, enamel, glass, plastic and graphite, and in various sizes. The suction volume is from 1 to 2,000,000m3/h, and when the suction pressure reaches 10-2mbar, the size can be from a few centimeters to more than 30 meters. Because of the diversity of jet pumps, they have been widely used in various fields, such as chemical reactors, exhaust systems, water treatment equipment, mixing tanks, storage tanks, wastewater treatment equipment, heating systems, heating gas supply systems, power plants, Water supply for swimming pools, salmon plants, etc.
And the formation of vacuum in different industrial fields. The formation of vacuum with jet pumps using water vapor as the motive medium is an important field of application. The high-speed jet it delivers is several times the speed of sound, so the jet pump can also handle large volumes of material in a vacuum with ease. Because a single-stage jet pump can only overcome an extremely limited compression ratio, when the suction pressure is low, several jet pumps must be installed in series. The suction pressure of the multi-stage water vapor jet vacuum pump can reach as low as 0.01mbar. In order to condense most of the motive water vapor and minimize the suction of the next stage, a condenser is usually placed between the two jet pumps. Depending on the application, direct contact condensers or surface condensers are used. In the jet pump, water vapor is mainly used as the power medium. In most industries, water vapor is produced in large quantities as the basic energy and is therefore very readily available. During the condensation of power steam, more or less waste water is produced.
Although the volume is small, and even taking into account the cost of wastewater discharge, the water vapor jet pump is still the most economical vacuum pump, but there is always a certain negative impact on the vacuum jet pump. As an option, product steam is therefore increasingly used in the operation of jet pumps. For example, solvent vapor, chlorobenzene, toluene, butanediol, ethylene, ethylene glycol, furan. In this case, the motive steam is condensed and re-evaporated to be used as motive medium. Due to the low evaporation temperature of organic steam, in most cases this mode of operation is more energy efficient than operation with water steam. Another important operating range of jet pumps using product steam as a motive medium is that water is not allowed to be mixed into the process material. For optimum efficiency, jet pumps using product steam as the motive medium still need to be studied in detail. In terms of structure and function, this jet pump is not much different from the vacuum jet pump that uses water vapor as the power medium, and has the same advantages: simple structure; safe and reliable operation, no maintenance; long service life, wear-resistant damage; appropriate material selection can be corrosion-resistant; all materials can be manufactured.
In addition, because the condensate is recycled, there is no emission pollution. Jet vacuum pumps are used in various industrial fields, and the following are several important application fields. In the chemical industry, gea jet pump company has developed a combination pump, which has been widely used. The distinctive features of this pump are its compact size and dual design construction. The two parallel pumps can be operated independently of each other alternately or simultaneously, making it possible to carry out maintenance without stopping the machine. In the chemical industry, if stainless steel cannot meet the corrosion resistance requirements, ceramic/graphite vacuum jet pumps can be used to remove corrosive gases and water vapor. The jet pump is made of ceramic and the surface condenser is made of graphite. Surface condensers consist of a compact condenser. This structure has the advantages of small size, less space required and simple on-site assembly. In the refinery, the steam vacuum jet pump is combined with the liquid ring pump for the vacuum distillation column system of the refinery.
The combination of these two pumps keeps steam, water and electricity consumption low. Due to the large amount of gas produced (in the range of 104 to 106 m3/h), the steam vacuum jet pumps from gea Jet Pumps are very suitable for this purpose. At the same time, the operation is safe and reliable, and it is not easy to fail. Likewise, a situation involving large volume flows is in the vacuum generation of steelmaking degassing. In order to produce a certain quality of steel, some raw steel processing needs to be carried out under vacuum. This vacuum pump must have two functions. One is to quickly evacuate the operating container to achieve the desired pressure. This means that the initial suction capacity of the vacuum jet pump must be large (several thousand kg/h). The second is to remove a large amount of inert gas (approximately equivalent to 0.6mbar, several hundred kg/h) while maintaining low pressure. In addition, vacuum jet pumps are used for edible oil deodorization, production of polymers for chemical compounds, seawater desalination, oil dehydration, conditioning of food, beverages and tobacco, suction of spinning baths and many other fields of application.
