In the dehydration process of potato starch production, filter presses, as key equipment, directly affect the moisture content of starch products, production efficiency, and subsequent processing quality. The selection of feed pumps for filter presses is a core factor determining the efficient operation of this process. Currently, the commonly used pumps in the industry are mainly piston slurry pumps and slag slurry pumps, which exhibit significant differences in working principles, performance parameters, and applicable scenarios. Based on the process characteristics of potato starch production, this article systematically compares the technical features of the two types of pumps, providing professional references for the rational matching of pumps with filter presses.
In potato starch production, the material processed by filter presses is refined starch milk, whose main components include starch particles (with a particle size of approximately 15-50μm), moisture, and a small amount of residual potato residue fibers (usually less than 0.5mm in length), with a concentration generally ranging from 18-25°Bé. This material property and the filtration process impose three core requirements on the delivery pump:
High-pressure stability: Filter presses need to press starch milk into the filter chamber at a working pressure of 0.8-2.0MPa to achieve solid-liquid separation through filter cloth. The stability of pressure directly determines the uniformity of the filter cake—when the pressure fluctuation exceeds ±0.1MPa, the moisture content deviation of the filter cake will exceed 3%, seriously affecting the energy consumption of the subsequent drying process.
Low-pulsation flow characteristics: Starch milk has a certain viscosity. If the flow pulsation is too large, it will cause local overload on the surface of the filter cloth, leading to the blockage of filter pores by fine components and a sharp increase in filtration resistance. Statistical data shows that when the flow pulsation coefficient exceeds 5%, the filtration cycle will be extended by more than 20%.
Anti-adhesion and wear-resistant performance: Starch tends to form viscous colloids when the temperature is below 55℃. If there are dead corners in the pump cavity or the flow rate is too low, sedimentation and agglomeration are likely to occur. At the same time, although a small amount of potato residue fibers have low hardness, long-term delivery will still cause wear to the flow-passing components inside the pump.
Piston slurry pumps belong to positive displacement pumps, which realize material delivery through the reciprocating movement of pistons in the cylinder. Their structural characteristics make them naturally suitable for the working needs of filter presses.
In terms of pressure performance, the rated working pressure of piston slurry pumps can reach 1.0-3.0MPa, with high pressure adjustment accuracy. Through frequency conversion speed regulation or flow control valves, pressure stability control at the 0.1MPa level can be achieved, fully meeting the full-process pressure requirements of filter presses from feeding, pressing to pressure holding. Actual application data from a starch factory shows that when using piston slurry pumps, the pressure fluctuation of the filter press can be controlled within ±0.05MPa, and the standard deviation of filter cake moisture content is reduced to 1.2%.
In terms of flow characteristics, piston slurry pumps can effectively offset the flow pulsation caused by the reciprocating movement of a single cylinder through multi-cylinder combination (commonly 3-cylinder or 5-cylinder). Combined with an outlet pressure stabilizing device, the pulsation coefficient can be controlled below 3%. This stable flow output ensures that starch milk is evenly distributed on the surface of the filter cloth, controlling the filter cake thickness deviation within 2mm and significantly reducing the probability of filter cloth blockage.
In terms of material adaptability to starch milk, piston slurry pumps adopt a straight-through flow channel design without complex rotating components such as impellers, avoiding the shearing and breaking of starch particles inside the pump. At the same time, the seal between the cylinder and the piston uses food-grade wear-resistant rubber, which can not only withstand slight wear from potato residue fibers but also prevent the adhesion of starch colloids. Tests by an equipment manufacturer show that after 8 hours of continuous operation of the piston slurry pump, the amount of internal sediment is only 1/5 of that of traditional pumps.
As a type of centrifugal pump, slag slurry pumps mainly deliver materials through the centrifugal force generated by the high-speed rotation of the impeller. They are originally designed to handle high-concentration, large-particle slag-like materials and have obvious performance limitations in the potato starch filtration process.
In terms of pressure, the rated working pressure of conventional slag slurry pumps is mostly in the range of 0.2-0.8MPa. Even with multi-stage series connection, it is difficult to ensure pressure stability. When the filter chamber of the filter press is filled with materials, the system resistance rises sharply, and the outlet pressure of the slag slurry pump will fluctuate violently, often exceeding the safe working range of the filter press. A case study shows that the probability of filter plate rupture due to sudden pressure rise in the filtration system using slag slurry pumps is 7 times that of the piston pump system.
In terms of flow characteristics, the flow rate and pressure of slag slurry pumps show a significant inverse relationship. When the pressure of the filter press chamber rises from 0.5MPa to 1.5MPa, the flow rate will decrease by 40%-60%. This non-linear change leads to uneven feeding in the filter chamber, and the thickness of the filter cake near the feed port is more than 30% thicker than that at the far end. At the same time, the turbulence generated by the rotation of the impeller intensifies the collision and breaking of starch particles, increasing the viscosity of starch milk by 15%-20% and further increasing the difficulty of filtration.
In terms of material adaptability, the gap between the impeller and the pump casing of the slag slurry pump is easily entangled by potato residue fibers, and flow attenuation may occur after 4 hours of operation. Moreover, the shearing force generated by the high-speed rotation of the impeller will damage the integrity of starch particles, reducing the gelatinization temperature of starch by 2-3℃ and affecting the processing performance of the final product.
Comprehensively considering technical characteristics and practical application effects, the pump selection for filter presses in potato starch production should follow the principle of "piston slurry pumps as the main choice, slag slurry pumps for special cases only".
For large-scale production enterprises (with a daily potato processing capacity of more than 100 tons), 3-cylinder or 5-cylinder piston slurry pumps are preferred. Although their initial investment is 30%-50% higher than that of slag slurry pumps, they have significant advantages in operating costs: the filtration cycle is shortened by 15%-20%, the filter cloth replacement cycle is extended to twice the original, and the annual comprehensive energy consumption is reduced by approximately 8%. Taking a production line with a daily processing capacity of 200 tons as an example, the use of piston slurry pumps can save about 120,000 yuan in costs annually.
For small-scale workshop-style production (with a daily potato processing capacity of less than 30 tons), if low-pressure plate-and-frame filter presses (working pressure ≤0.6MPa) are used, small slag slurry pumps can be selected as a transitional solution. However, it is necessary to install supporting pressure buffer tanks and regular cleaning devices, and the machine should be shut down every 2 hours to check the impeller entanglement to avoid production interruption.
It is worth noting that with the popularization of food-grade stainless steel piston pumps, their maintenance costs have been significantly reduced. The latest self-lubricating sealing technology has extended the replacement cycle of piston seals to more than 800 hours, completely solving the problem of frequent maintenance of traditional piston pumps.
In the filtration process of potato starch production, piston slurry pumps have become the optimal choice for most production scenarios due to their technical advantages of high-pressure stability, stable flow rate, and strong adaptability. Slag slurry pumps can only be used as an alternative solution under specific low-pressure and small-capacity conditions, but they require bearing higher operational risks and maintenance costs.
