Pumps used in petrochemical plants can be divided into the following categories according to their use: 1. Feed pumps Petrochemical plants not only feed raw materials to the distillation column, but also sometimes booster and send them to the reactor. Pump, and sometimes after the first pump after the furnace. If it is the first furnace after the pump, the pump is required to send a very high temperature, may be as high as 380. C or even higher. For example, thermal cracking raw material pump is an example, because the petrochemical plant production is continuous , Some devices require one or two years does not overhaul, so the requirements of such pumps is highly reliable.American APl610 provides for the continuous operation of the refinery pump 25,000 h not overhaul.This kind of pump flow generally have a little Balance, in order to adapt to changes in the amount of raw materials.But at this time also requires the head fluctuations should be as small as possible.In most cases, the net negative suction head is required to be negative, namely the infusion pump, the level of raw material tank level Should be higher than the suction port of the pump, especially high temperature feed pump. 2. Circulating pump As the petrochemical process reaction, absorption, separation and other operations need to be carried out at the same time, after the absorption liquid regeneration device to be returned to the reduction, a variety of reaction system catalyst cycle, the extraction process of solvent recycling, heavy oil direct Desulfurization process hot oil cycle, caustic washing and alkali regeneration tower cycle between the cooling process of coolant recirculation and so require the use of circulating pump, the pump pressure drop during the cycle is generally small fluctuations, while the flow is a little certain fluctuations. After the pump is selected, it can run under the rated working condition. The key is to select the suitable pump material for the medium. 3. Return pump This pump is used to control the heat balance of the distillation tower pump, such as the top of the reflux, a side of the return flow, often with the reboiler together to make the tower or a certain section of the heat, so that the entire tower up and down Heat balance. In another example, degassing in a distillation column or desorption column requires a return flow before the unit is fully decommissioned. The requirement for this type of pump is that the characteristic curve must be flat, especially with no hump performance curve. 4. Bottom pump or reboiler pump At the bottom of the tower, in order to maintain the heat, the pump is usually used to circulate the liquid between the bottom of the tower and the heat source. Most of the liquid is large flow and is in high temperature and saturation. The main problems are: (1) Under high temperature pump seal, bearings, body heat should be good; (2) to ensure normal suction under high temperature, cavitation does not occur in the pump required pump required net positive suction pressure head as small as possible Suction pipe to minimize losses, and leave enough margin. 5. The majority of finished pumps are liquid under normal temperature and pressure conditions, sometimes the overhead or side drawn liquid directly to the product tank. The main problem is to maintain product purity, for this reason sometimes shield pump. Dosing pumps are mostly used to inject chemical solvents, anti-corrosion drugs, etc., require a more accurate delivery.Generally used reciprocating metering pump or gear pump or screw pump.At the same time with the injection amount adjustment device. 7. Asphaltic paraffin wax pump due to viscosity, wax, although transported at high temperatures, still use more reciprocating steam pump, or positive displacement pump.This is also to prevent the event of viscous high wax, can have an automatic protection . 8. Slurry pumps, such as the delivery of catalyst slurry pumps, contain both solid particles at high temperatures and are a special type of impurity pump with poor working conditions. 9. Light Hydrocarbon Pumps Since light hydrocarbons are volatile, they work at high pressure and low temperature and cause frost once they leak. One of the keys to this type of pump is the sealing problem. In addition, such pumps prevent cavitation is extremely important, rather sacrificing a little The efficiency also must guarantee the safe operation.This kind of pump many uses the multistage centrifugal type of the cylinder bag, the appearance like the submersible pump inhabitant buries in the ground many more to prevent the cavitation erosion. For petrochemical pumps, a higher or highest level of pump is required, as all of the feed liquid is nearly flammable and most of the temperature and pressure conditions are harsh. The United States has determined based on experience gained from the use and manufacturing sectors A centrifugal pump for the oil industry, oil refinery manufacturing specifications, published by the American Petroleum Institute APl610. The user can use this specification as the basic basis, combined with its own characteristics of the proposed specifications of the specification of the centrifugal pump has been described in detail , Chemical equipment other than oil refining if you need to use an important pump or harsh conditions, but also the appropriate selection according to this specification made of a variety of pumps.