创建于06.17

The Selection and Application of Slurry Pumps

I. Introduction

In many fields of modern industrial production, such as mining, metallurgy, power generation, construction, and sewage treatment, it is often necessary to transport liquid mixtures containing solid particles, namely slurry. As a key equipment specially used for such transportation tasks, the performance of the slurry pump and the appropriateness of its selection are directly related to the stability, efficiency, and cost of the production process. The correct selection and rational application of slurry pumps can not only ensure the smooth progress of the production process and improve production efficiency but also effectively reduce equipment wear and maintenance costs and extend the service life of the equipment. Therefore, in - depth understanding of the selection principles and application points of slurry pumps is of vital significance for practitioners in related industries.

II. Working Principle of Slurry Pump

The slurry pump is essentially a special type of centrifugal pump, and its working principle is based on the basic working mechanism of the centrifugal pump, with optimized design for the characteristics of slurry transportation. The slurry pump is mainly composed of components such as the impeller, pump casing, shaft seal device, and motor. Among them, the impeller is the core component of the pump, usually with a special shape and structure, and the blades are thick and wide with a broad flow channel to adapt to the transportation requirements of high - concentration and large - particle slurry. The pump casing plays the role of collecting and guiding the liquid flow and converting the kinetic energy of the liquid into pressure energy. The shaft seal device is used to prevent the leakage of the liquid in the pump and ensure the normal operation of the pump. The motor provides power for the operation of the pump.

When the slurry pump is started, the motor drives the pump shaft, making the impeller rotate at high speed in the pump casing. The rotation of the impeller generates a strong centrifugal force, so that the slurry in the pump cavity is subjected to an outward force. In the central area of the impeller, due to the liquid being thrown to the outer edge of the impeller, the pressure decreases, forming a negative pressure area. At this time, under the pressure difference between the external atmospheric pressure and the negative pressure in the pump cavity, the slurry is sucked into the pump from the pump inlet. With the continuous rotation of the impeller, the slurry sucked into the pump is continuously thrown to the edge of the impeller under the action of centrifugal force and obtains higher speed and kinetic energy. When the slurry leaves the impeller and enters the pump casing, the flow channel in the pump casing gradually expands, and the flow rate of the slurry decreases. According to the law of conservation of energy, its kinetic energy is gradually converted into pressure energy, so that the slurry can be discharged from the pump outlet at a higher pressure and transported to the specified position through the pipeline. In this process, because the slurry contains solid particles, these particles will have a strong scouring and wear effect on the flow - through components of the pump, such as the impeller and pump casing. Therefore, when designing and manufacturing the slurry pump, it is necessary to select materials with high wear resistance to manufacture these flow - through components to ensure that the pump can operate stably for a long time under harsh working conditions.

III. Key Points for Slurry Pump Selection

(一) Analysis of Transport Medium Characteristics

1. Particle Properties

The hardness, shape, density, and other properties of solid particles in the slurry have a significant impact on the wear degree of the slurry pump. Particles with higher hardness, such as quartz sand, will cause more serious wear to the flow - through components of the pump during transportation; and particles with irregular shapes and sharp edges will have a stronger wear effect than circular particles. In addition, when the particle density is large, the overall specific gravity of the slurry increases, which will increase the transportation load of the pump.

2. Particle Size and Classification

Particles of different sizes have different wear positions and degrees on the flow - through components of the pump. Larger - sized particles mainly wear the impeller inlet, the head of the blades, and the inlet area of the pump casing; while smaller - sized particles are more likely to form uniform wear in the internal flow channel of the pump. At the same time, it is also important to understand the particle size distribution (i.e., classification), because this will affect the selection of the pump type and the determination of operating parameters. For example, for slurry containing a large number of large particles, it is necessary to select a pump type with a broad flow channel for the flow - through components and capable of passing large particles; while for slurry with a wide range of particle sizes, it may be necessary to consider using an impeller with a special design to adapt to the transportation of particles of different sizes.

3. PH Value

The acidity - alkalinity (PH value) of the slurry is one of the key factors determining the selection of pump body materials. When the slurry is acidic, it has strong corrosiveness to metal materials, especially when the acidity is strong and contains solid particles, the synergistic effect of corrosion and wear will accelerate the damage of the pump. At this time, it is necessary to select materials with good acid resistance, such as stainless steel, high - chromium cast iron, etc., or use special anti - corrosion coatings. On the contrary, when the slurry is alkaline, although the corrosiveness to general metal materials is relatively weak, certain alkaline media may have a corrosive effect on specific materials, and it is also necessary to select appropriate materials according to the specific situation.

4. Liquid Phase Composition

In addition to solid particles, the liquid phase composition in the slurry cannot be ignored. The liquid phase may contain various chemical substances, such as acid, alkali, salt solutions, and organic solvents. The properties and concentrations of these chemical substances will affect the corrosiveness, viscosity, and other characteristics of the slurry. For example, a liquid phase containing a high concentration of salt may aggravate the corrosion of metal materials; and certain organic solvents may have a swelling or erosion effect on non - metallic materials such as rubber, leading to the failure of components such as seals. Therefore, when selecting a pump, it is necessary to fully understand the liquid phase composition so as to select the corresponding pump body materials and sealing forms.

5. Specific Gravity and Concentration of Slurry

The specific gravity of the slurry refers to the mass of the slurry per unit volume, which reflects the density of the slurry. A slurry with a larger specific gravity requires the pump to provide greater head and power during transportation to overcome gravity and flow resistance. The concentration of the slurry is usually expressed by volume concentration (Cv) or weight concentration (Cw). Generally speaking, with the increase of concentration, the viscosity of the slurry increases, the fluidity becomes poor, and it will have adverse effects on the transportation capacity and wear degree of the pump. For the transportation of high - concentration slurry, it is necessary to select a pump type that can adapt to high - viscosity media, has a large flow capacity and strong wear resistance, and at the same time, reasonably determine the operating parameters of the pump to ensure the stable operation of the pump.

(二) Consideration of Operating Environment and Working Conditions

1. Temperature

The temperature of the transported medium affects the slurry pump in two main aspects. On the one hand, high temperature will reduce the viscosity of the liquid and increase its volatility, which may lead to the aggravation of the cavitation phenomenon of the pump. Cavitation refers to the phenomenon that when the local pressure of the liquid in the pump is lower than its saturated vapor pressure, bubbles are formed in the liquid, and these bubbles burst in the high - pressure area, generating a strong impact force, causing damage to the flow - through components of the pump. Therefore, when transporting high - temperature media, it is necessary to select a pump type with good cavitation resistance and take corresponding measures, such as reducing the installation height of the pump and increasing the inlet pressure, to avoid the occurrence of cavitation. On the other hand, high temperature will also affect the sealing materials and lubrication system of the pump. Some sealing materials may lose elasticity, age, or even fail at high temperatures, resulting in leakage; and high temperature will reduce the viscosity of the lubricating oil, affect its lubrication performance, and increase the wear of components such as bearings. Therefore, for high - temperature working conditions, it is necessary to select high - temperature - resistant sealing materials and appropriate lubrication methods, and monitor and control the operating temperature of the pump.

2. Flow Rate

Flow rate is one of the important parameters for slurry pump selection, which represents the volume of slurry that the pump can transport per unit time, usually in cubic meters per hour (m³/h). When determining the flow rate, it is necessary to accurately calculate according to the needs of the actual production process. For example, in a mineral processing plant, the flow rate of the slurry pump needs to be determined according to the ore processing capacity, the concentration of the slurry, and the requirements of the process flow. At the same time, it is also necessary to consider the fluctuation situation in the production process and appropriately reserve a certain flow margin to ensure that the pump can still meet the production needs when the working conditions change. If the flow rate is too small, it will not be able to meet the production transportation requirements and affect the production efficiency; if the flow rate is too large, it will cause energy waste, increase the operation cost, and may cause the pump to run in a non - efficient area, shortening the service life of the pump.

3. Head

Head refers to the vertical height that the pump can lift the liquid, in meters (m). In the selection of slurry pumps, accurately calculating the head is of great importance. The calculation of the head needs to consider many factors, including the actual vertical lifting height, the length of the pipeline, the pipe diameter, the number of bends, the resistance of pipe fittings such as gate valves and reducers, as well as the frictional resistance loss and local resistance loss of the slurry during flow in the pipeline. The actual vertical lifting height refers to the vertical distance from the suction port of the pump to the transportation end, which is the main component of the head. The longer the length of the pipeline, the smaller the pipe diameter, and the more bends and pipe fittings, the greater the pipeline resistance, and the higher the required head. The frictional resistance loss is the energy loss caused by the friction between the slurry and the inner wall of the pipeline, and its size is related to factors such as the flow rate of the slurry, viscosity, and pipeline roughness. The local resistance loss is the energy loss caused by the change of the liquid flow state in the local areas such as the bends, valves, and reducers of the pipeline. When calculating the head, it is necessary to comprehensively consider these factors and appropriately increase a certain head margin according to the actual situation to compensate for the performance degradation of the pump caused by wear and other reasons during operation. Generally speaking, the head margin can be taken as about 10% of the rated head according to the actual working conditions. If the head is insufficient, the pump will not be able to transport the slurry to the specified height, resulting in the failure to complete the transportation task; if the head is too large, the operating efficiency of the pump will be reduced, and the energy consumption will increase.

4. Outlet Pressure Reserve Requirements

In some specific application scenarios, such as the feeding of cyclones, plate - and - frame filter presses, and spiral classifiers, there are special requirements for the outlet pressure of the slurry pump. The cyclone is a device that uses centrifugal force for solid - liquid separation or classification, and its feeding pressure needs to be maintained within a certain range to ensure that the cyclone can work normally and achieve good separation or classification effects. If the feeding pressure is too low, the processing capacity and separation efficiency of the cyclone will be reduced; if the feeding pressure is too high, the internal structure of the cyclone may be damaged. The plate - and - frame filter press is a device used for dewatering the slurry. In the feeding stage, a higher pressure is required to ensure that the slurry can smoothly enter the filter chamber of the filter press and make the filter cake reach a certain moisture content. The spiral classifier is used for classifying the solid particles in the slurry, and its feeding speed and pressure will also affect the classification effect. Therefore, when selecting a pump, it is necessary to accurately determine the outlet pressure of the slurry pump according to these specific process requirements and select a pump type and configuration that can meet the pressure requirements.

5. Site Conditions and Installation Methods

Site conditions have an important impact on the installation method and outlet direction of the slurry pump. When selecting the installation method, factors such as the size of the installation space, the bearing capacity of the ground, and the convenience of operation and maintenance need to be considered. Common installation methods include horizontal installation and vertical installation. Horizontal installation is suitable for occasions with a large installation space and good ground conditions. Its advantages are that the installation and maintenance are relatively convenient, the center of gravity of the pump is low, and the operation stability is good; the disadvantage is that it occupies a large area. Vertical installation is suitable for occasions with limited installation space, such as underground mines, sewage treatment ponds, etc. Its advantages are small floor space and can be directly installed in the liquid, but the maintenance is relatively difficult, and the requirements for the waterproof and heat dissipation of the motor are high. In addition, it is also necessary to determine the outlet direction of the pump according to the layout of the pipeline and the requirements of the process flow. The outlet direction of the pump should be able to be conveniently connected with the pipeline, reduce the use of bends and pipe fittings, reduce the pipeline resistance, and improve the transportation efficiency.

IV. Common Types and Characteristics of Slurry Pumps

(一) Centrifugal Slurry Pumps

Centrifugal slurry pumps are the most widely used type of slurry pumps, and their working principle is based on the role of centrifugal force. As mentioned above, through the high - speed rotation of the impeller, the slurry in the pump cavity obtains speed and kinetic energy under the action of centrifugal force and is discharged from the pump outlet. Centrifugal slurry pumps have the following remarkable characteristics:

1. High Transportation Efficiency

Their unique impeller design and volute structure can make the liquid obtain a high conversion efficiency of kinetic energy and potential energy in the pump, thus realizing efficient slurry transportation. Under the design working conditions, the efficiency of centrifugal slurry pumps can usually reach a relatively high level, which can meet the requirements of large - scale industrial production for slurry transportation volume.

2. Good Wear Resistance

In order to cope with the scouring and wear of solid particles in the slurry, the flow - through components of centrifugal slurry pumps, such as impellers and pump casings, are usually made of high - hardness and high - wear - resistant materials, such as high - chromium cast iron and alloy wear - resistant steel. These materials have excellent wear - resistance and can operate stably for a long time under harsh working conditions, effectively extending the service life of the pump.

3. Wide Application Range

Centrifugal slurry pumps can adapt to the transportation needs of slurries with different concentrations, particle sizes, and viscosities. By reasonably selecting the diameter of the impeller, the number and shape of the blades, and the rotational speed of the pump and other parameters, they can be suitable for various working conditions from low - concentration and fine - particle slurries to high - concentration and large - particle slurries. In addition, centrifugal slurry pumps can also select corresponding corrosion - resistant materials according to the corrosiveness of the transported medium, further expanding their application range.

4. Simple Structure and Convenient Maintenance

The structure of centrifugal slurry pumps is relatively simple, mainly composed of components such as impellers, pump casings, shaft seal devices, and bearings. The structures and installation methods of these components are relatively mature, and they are easy to manufacture and repair. In daily maintenance, only need to regularly check the wear condition of the impeller, the sealing performance of the shaft seal, the lubrication condition of the bearings, etc., and timely replace the worn components to ensure the normal operation of the pump. Moreover, due to the simple structure, the versatility of the components is strong, and it is possible to more conveniently obtain suitable accessories when the components need to be replaced.

(二) Axial Flow Slurry Pumps

The working principle of axial flow slurry pumps is different from that of centrifugal slurry pumps. It mainly relies on the axial thrust generated by the blades of the impeller when rotating to transport the liquid. The impeller of the axial flow slurry pump is usually composed of multiple twisted blades, which are installed on the pump shaft. When the impeller rotates, the blades push the liquid to flow axially, and the liquid obtains energy under the action of the blades, thus realizing the transportation of the slurry. Axial flow slurry pumps have the following characteristics:

1. Large Flow and Low Head

The impeller design of axial flow slurry pumps enables them to generate a large axial flow during operation, but the head is relatively low. Therefore, it is suitable for occasions that need to transport large - flow and low - head slurries, such as river dredging, aeration tank mixing and transportation in sewage treatment plants, etc. In these working conditions, axial flow slurry pumps can give full play to their flow advantages and efficiently complete the transportation task.

2. Compact Structure and Small Floor Space

Due to the relatively simple structure of the impeller and pump body of the axial flow slurry pump, the overall structure is relatively compact, so its floor space is small. This has obvious advantages in some occasions with limited installation space, such as the underground pump room of the urban sewage treatment plant, and can effectively save space resources.

3. Strong Adaptability to Liquids

Axial flow slurry pumps have a certain adaptability to the concentration and particle size of solid particles in the slurry. Although the wear degree of their flow - through components is relatively larger than that of centrifugal slurry pumps, in some working conditions where the solid particle concentration is not particularly high and the particle size is relatively small, axial flow slurry pumps can still operate stably. And by reasonably selecting the impeller material and structure design, the adaptability to slurries with different properties can be further improved.

4. Relatively Flat Efficiency Curve

Axial flow slurry pumps have relatively small efficiency changes within a certain flow range, and the efficiency curve is relatively flat. This means that in the actual operation process, when the flow changes to a certain extent, the efficiency of the pump will not drop significantly, and it can maintain a relatively stable operation state. This is of great significance for some working conditions with large flow fluctuations, which can ensure that the pump can operate efficiently under different flow rates.

(三) Mixed Flow Slurry Pumps

Mixed flow slurry pumps integrate the working principles of centrifugal and axial flow slurry pumps, with impeller shape and structure lying between the two. When a mixed flow slurry pump operates, the liquid is subjected to both centrifugal force and axial thrust from the impeller, resulting in a mixed flow pattern as the liquid exits the impeller. These pumps feature the following characteristics:

1. Performance Between Centrifugal and Axial Flow Types

The flow rate and head performance of mixed flow slurry pumps fall between those of centrifugal and axial flow slurry pumps. They can provide higher head than axial flow pumps while achieving larger flow rates than centrifugal pumps. This makes them suitable for applications requiring moderate flow and head—scenarios that do not demand extreme values. For instance, they are widely used in tailings transportation in mines, slurry conveyance in industrial circulating water systems, and similar contexts. In these (working conditions), mixed flow slurry pumps leverage their comprehensive performance advantages to meet production needs effectively.

2. Wide High-Efficiency Range

Mixed flow slurry pumps exhibit a relatively broad high-efficiency zone, meaning they maintain high operational efficiency across a certain range of flow rates and heads. This characteristic enhances their adaptability to fluctuating working conditions. When production processes experience changes in flow or head requirements, mixed flow slurry pumps can still operate within the high-efficiency zone, avoiding significant efficiency drops caused by variations. This leads to energy savings and reduced operational costs.

3. Relatively Simple Structure

The structure of mixed flow slurry pumps is similar to that of centrifugal slurry pumps but is comparatively simpler. They are also composed of main components such as the impeller, pump casing, shaft seal device, and bearings, with mature manufacturing and installation processes that facilitate maintenance and repair. Compared to centrifugal slurry pumps, mixed flow slurry pumps feature optimized impeller blade shapes and flow channel designs, enabling better adaptation to slurry flow characteristics, reducing energy loss, and improving overall pump performance.

4. Extensive Applications

Owing to their comprehensive performance characteristics, mixed flow slurry pumps find wide applications across various industrial sectors. In addition to the aforementioned mining and industrial circulating water systems, they play a crucial role in slurry transportation for construction, power generation, chemical engineering, and other industries. For example, they reliably handle tasks such as mud transportation in construction, ash slurry conveyance in thermal power plants, and raw material/product transportation in chemical production.

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