Pumps for the petrochemical industry are the most widely used transmission equipment in petrochemical production equipment. They transport various liquid media such as crude oil, refined oil, chemical raw materials, and various intermediate products and finished products to other places like the heart transports blood.
Pumps used in the petrochemical industry account for one-third of the total industrial pumps used in the country. Screw pumps are typical pumps used in the petrochemical industry.
The following describes what pumps are used in petrochemical industries according to various uses:
1. Feed pump
The petrochemical plant not only needs to transport the crude oil to the distillation tower but also sometimes boosts the pressure and then sends it to the reactor. Sometimes it is the furnace first and then the pumps, sometimes it is the pump first and then the furnace. If it is the furnace first and then the pump. It requires the pump to deliver a high temperature, which may be as high as 380qc, or even higher. For example, the thermal cracking raw material pump is an example. Since the production of petrochemical plants is continuous, some devices require no major repairs for one or two years, so the requirement for this type of pump is high reliability: the US AH 610 stipulates that the pumps of refineries must run continuously for 25,000 hours Not overhauled. The flow rate of this type of pump generally has a little margin to adapt to changes in the number of raw materials. But at this time, it is also required that the head fluctuation should be as small as possible: in most cases, the net positive suction head is required to be negative, that is, the perfusion pump, the liquid level of the raw material tank should be higher than the suction port of the pump. Especially high-temperature feed pumps. At present, domestic high-temperature oil pumps basically use heat-conducting oil pumps.
2. Circulation pump
Since the reaction, absorption, separation, and other operations in the petrochemical process need to be cycled, and the absorption liquid must be sent back to the device for reduction after regeneration. Catalyst circulation in various reaction systems, solvent circulation in the extraction process, hot oil circulation in the direct desulfurization process of heavy oil, circulation between alkali washing and alkali regeneration towers, and cooling liquid recirculation in the refrigeration process all require the use of circulation pumps. When the pump circulates, the pressure drop generally does not fluctuate greatly, but the flow rate fluctuates slightly. After the pump is selected, most of them can run under rated working conditions. The key is to choose the right pump material for the medium. For example, the liquid to be transported is an acidic liquid. It is recommended to use pump products made of fluoroplastic materials. For example fluoroplastic centrifugal pumps.
3. Reflux pump
This kind of pump is the pump used to control the heat balance of the refinery distillation column, such as the top reflux, and certain sideline reflux, and is often used together with the reboiler. Make the top of the tower or a certain section get heat, and make the whole tower get heat balanced up and down. Another example is degassing in a distillation tower or a desorption tower, which requires reflux before the device is completely shut down. The requirement for this type of pump is that the characteristic curve must be flat, especially the performance curve with a hump should not appear.
4. Bottom pump or reboiler pump
In order to maintain heat at the bottom of the column, a pump is usually used to circulate the liquid between the bottom of the column and the heat source. Most of the liquid has a large flow rate and is in a high temperature and saturated state. The main problem is:
(1) The seals, bearings, and thermal alignment of the pump body should be excellent under high-temperature conditions;
(2) Under high-temperature conditions, normal suction is guaranteed without cavitation. When selecting a pump, the net positive suction head required by the pump is required to be as small as possible. Minimize the loss on the suction line as much as possible, and leave enough margin.
5. Finished pump
Most of the liquids are transported under normal temperature and pressure conditions, and sometimes the liquid extracted from the top of the tower or the sideline is directly sent to the product tank. The main problem is maintaining product purity, for which canned pumps are sometimes used.
6. Metering pump
It is mostly used to inject chemical solvents, anti-corrosion drugs, etc., and requires a relatively high output volume. Generally used: mechanical diaphragm metering pump or gear pump or screw pump: it is also equipped with an injection volume adjustment device.
7. Bitumen paraffin pump
Due to its high viscosity and wax content, reciprocating steam pumps or positive displacement pumps are often used for conveying at high temperatures. This is also to prevent automatic protection in case of high viscosity and high wax.
8. Slurry pump
For example, the pump for conveying catalyst slurry is a special impurity pump with high temperature and solid particles, which is a kind of harsh working condition.
9. Light hydrocarbon pump
In view of the fact that light hydrocarbons are volatile, they mostly work at high pressure and low temperature, and once they leak, they will produce self-frost. One of the key points of this type of pump is the sealing problem. in addition. It is extremely important for this type of pump to prevent cavitation, and it is better to sacrifice a little efficiency to ensure safe operation. This type of pump mostly adopts a multi-stage centrifugal type barrel bag, which looks like a submersible pump and the suction port is mostly buried underground to prevent cavitation.
For pumps used in the petrochemical industry, almost all the conveying fluids are flammable, and most of the greenhouses and pressure conditions are very harsh. According to the experience accumulated by the use and manufacturing departments, the United States has established the manufacturing specifications for centrifugal pumps used in the petroleum industry and refineries and published them by the American Petroleum Institute AH 610. The user can use this specification as the basic basis, and then combine its own characteristics to propose an order specification. This specification has detailed descriptions for centrifugal pumps. If important pumps or harsh conditions are required for chemical equipment other than petroleum refining, various pumps made according to this specification should also be selected appropriately.