Application of Liquid‑Ring Vacuum Pumps in Starch Production

In the starch industry (corn, cassava and potato starch), 2BV / SK series liquid‑ring vacuum pumps are widely used for drum vacuum filters and multi‑effect evaporation & concentration processes. Advantages: resistant to water vapor, tolerant to small amounts of entrained liquid droplets, isothermal compression, well‑suited for food‑grade wet‑process production lines.

1. Main Application Points in Starch Production Lines

1.1 Drum Vacuum Filter (Primary Application)

It is for dewatering wet starch slurry and represents the largest load for liquid‑ring vacuum pumps in starch plants.

Function: The vacuum pump generates negative pressure of ‑0.04 ~ ‑0.09 MPa. Starch slurry adheres to filter cloth and forms filter cakes. Free moisture is extracted by vacuum, reducing filter‑cake moisture content to approximately 38‑42% in preparation for subsequent flash drying.

Process flow: Drum → Distribution valve → Gas‑water separator (critical component) → Liquid‑ring vacuum pump.

Key note: A gas‑water separator must be installed on the suction side. Filtrate and fine starch particles are separated inside the separator; liquid is discharged via centrifugal pump while only gas enters the vacuum pump. If fine starch powder is drawn directly into the pump chamber, it will rapidly form scale and abrade the impeller.

1.2 Multi‑Effect Evaporation & Concentration for Starch Syrup / Starch Milk

It extracts non‑condensable gas from multi‑effect evaporators to maintain vacuum inside evaporators, lowering material boiling point to avoid starch gelatinization and deterioration and realize low‑temperature concentration. It handles large volumes of water vapor. Liquid‑ring vacuum pumps feature good adaptability to vapor‑laden gas and are standard vacuum equipment for starch evaporation sections.

1.3 Auxiliary Applications

Vacuum priming for equipment and storage tanks

Vacuum filtration and dewatering of protein slurry and gluten liquid

2. Selection Guidelines for Starch Process Conditions (for foreign‑trade quotation reference)

Pumping capacity: Based on drum filter area, approx. 15‑25 m³/min per square meter of filter area. Water‑vapor volume shall be added for multi‑effect evaporation service.

Operating vacuum: Stable operating vacuum for filters: ‑0.06 ~ ‑0.08 MPa. Avoid long‑term operation under ultimate vacuum, otherwise cavitation will damage the pump.

Material selection:

Ordinary corn starch: Cast iron pump casing and cast iron impeller.

Cassava / potato starch with slightly acidic media: Upgrade impeller and pump casing to 304 stainless steel for corrosion resistance.

Shaft seal: Mechanical seal is preferred for food‑grade service (standard for 2BV models).

Mandatory auxiliary components:

Suction‑side gas‑water separator (prevents fine starch ingress; indispensable for starch processes)

Circulating service‑water supply system

Cavitation‑protection pipeline

Vacuum‑regulating bypass valve to stabilize system negative pressure

Common customer misconception: Purchasing only the vacuum pump without gas‑water separator. Short‑time operation will cause impeller scaling & clogging and rapid vacuum deterioration.

3. Typical Failures & Operation Precautions for Starch Industry

3.1 Scaling and clogging by fine starch powder (most frequent failure)

Symptoms: Vacuum drop, insufficient flow, pump passages blocked by starch scale, increased motor current.

Root cause: Gas‑water separator malfunction; fine starch particles sucked into pump and gelatinize & deposit upon contact with circulating water.

Countermeasures:

Periodically clean the gas‑water separator.

Fit filter screen inside the separator.

Rinse pump interior with warm water on a regular basis.

3.2 Excessive service‑water temperature

Vacuum performance of liquid‑ring pumps is highly sensitive to service‑water temperature. When water temperature exceeds 40 °C, saturated vapor pressure rises and vacuum declines significantly.

Control inlet service‑water temperature ≤15‑25 °C. For circulating cooling system, keep return water temperature below 40 °C.

3.3 Prohibited operations

Dry‑running start‑up is forbidden.

Do not run continuously under ultimate vacuum; keep cavitation‑protection pipe activated.

After shutdown, drain residual water from pump casing and separator to prevent starch mildew accumulation and pump freeze‑cracking in winter.