Selection of pumps in evaporation crystallization system

The important role of the pump in the evaporation system:

Material Transfer: Pumps are an indispensable power source in evaporation crystallization systems, responsible for transporting raw liquids, intermediates, condensate, or finished concentrates from one vessel to another, or pushing liquids through heaters, heat exchangers, and other equipment.

Circulation and agitation: In some crystallization processes, pumps (e.g., forced circulation pumps in forced circulation evaporators) are also used to maintain the circulating flow of the solution, helping to evenly distribute heat, prevent local overheating, and promote uniform crystal growth.

Control flow and pressure: By adjusting the speed or opening, the pump can precisely control the flow into the evaporator and the pressure inside the system, which is essential to maintain a stable evaporation rate and crystallization conditions.

Carefully selecting the right pump for evaporation and crystallization is critical to improving overall system performance and economic efficiency. Considerations for the selection of pumps for evaporation crystallization systems:

Flow and head: According to the specific needs of the evaporation and crystallization system, accurately calculate the flow rate and head of the required pump to avoid the pump running in inefficient areas, affecting energy consumption and efficiency.

Corrosion resistance and material: The evaporation and crystallization process often involves corrosive media such as acid, alkali and salt, and the material of the pump needs to be able to resist the erosion of these media, so the material selection of the pump is very important, and the materials often selected include various stainless steel, titanium, alloy steel or non-metallic materials such as PVDF, PTFE coating, etc.

Temperature and pressure tolerance: The evaporation crystallization process can be accompanied by high temperatures and pressures, and it is important to ensure that the design temperature and pressure level of the pump are higher than the actual operating conditions to ensure safe and reliable operation.

Wear resistance: There may be solid particles in the crystallization process, and the wear resistance of the overflow parts of the pump is high, so it is necessary to consider whether the structural design of the pump can reduce wear when selecting, such as using open impellers or wear-resistant bushings.

Self-priming capacity and cavitation resistance: Some processes may require the pump to have good self-priming capacity, especially in the working conditions where there are frequent start-ups and stops or cavitation is easy to occur, a pump with sufficient self-priming height should be selected.

Sealing form: Considering the characteristics of the medium and environmental protection requirements, choose the appropriate sealing method, such as single-acting mechanical seal, double-acting mechanical seal or magnetic drive pump, to prevent leakage.

Maintenance and cleaning: The maintenance cycle and cleaning requirements of the evaporation and crystallization equipment should also be considered in the selection of pumps, and the pump type that is easy to disassemble, maintain and clean should be preferred.

Energy efficiency: Choosing a high-efficiency pump type, such as a pump that meets or exceeds the relevant energy efficiency standards, can effectively reduce operating costs and meet the industrial trend of energy conservation and emission reduction.

Specific selection instructions for evaporation crystallization system pumps:

1. Selection of forced circulation pump in multi-effect or MVR evaporator:

Flow and head: low head, large flow, choose chemical axial flow pump or mixed-flow pump.

Corrosion resistance and material: Chloride-containing salts can be titanium or duplex stainless steel, and other salts can be made of stainless steel and other corrosion-resistant materials.

Sealing form: It involves solid-liquid two-phase slurry transportation, and mainly uses double-end water-cooled mechanical seals

Drive and transmission mode: generally use the motor as the power source, the coupling connection, belt (including full suspension or semi-suspension)

2. Selection of mother liquor pump, feed pump, and dope pump in multi-effect or MVR evaporator:

Head and flow: medium flow, medium head, depending on the specificsDepending on the actual situation of the project, chemical centrifugal pumps (including chemical flow pumps orchemical channel pumps, etc.).

Impeller form: open or semi-open impeller is used for solid-liquid two-phase slurry transportation, and closed impeller can be used for simple liquid phase conveying to obtain higher work efficiency

Sealing form: Double-end water-cooled mechanical seals are often used for solid-liquid two-phase slurry transportation, and single-end mechanical seals can be used for normal temperature water-like liquid media.

Drive and transmission mode: generally connected by coupling.

3. Selection of condensate pump in multi-effect or MVR evaporator:

Head and flow: medium flow, medium head, depending on the specificsDepending on the actual situation of the project, chemical centrifugal pumps are generally selected

Impeller form: Closed impeller

can be used for simple liquid phase conveying

Sealing form: high-temperature resistant single-acting mechanical seal can be used

Drive and transmission mode: generally use coupling connection or direct motor transmission

Self-priming capacity and cavitation resistance: Pumps with large anti-cavitation allowance or pneumatic diaphragm pumps with large suction lift are used.

4. Vacuum pump selection in multi-effect or MVR evaporator:

When a high vacuum degree is required, a dry screw vacuum pump or a jet vacuum pump can be used;

When the vacuum pumping volume is large, the roots vacuum pump or the roots vacuum pump can be used in combination with other vacuum pumps.

The water ring vacuum pump is suitable for occasions containing a large amount of steam, but it needs to be equipped with a water seal to replenish water. In order to reduce water consumption, it can be changed to a liquid ring vacuum pump and equipped with an indirect cooling and cooling device. In the case of multi-effect or MVR evaporator without special circumstances, generally uses a water ring vacuum pump as a vacuum source, and is equipped with a water cooling and reuse system, and uses circulating water to cool down the water seal and replenish the water, and uses closed-loop use.