The Working Principle of Vacuum Filtration

Basic Principle: Pressure Difference Drives Filtration

The core principle of vacuum filtration is the creation of a pressure gradient across the filter medium.

  • Atmospheric pressure acts on the liquid above the filter
  • Reduced pressure (vacuum) is applied below the filter
  • This pressure difference forces the liquid to pass quickly through the filter

As a result, the liquid (filtrate) is drawn into the flask, while the solid particles are retained on the filter surface.

Vacuum filter working principle: the laboratory vacuum filtration device uses porous substances (sieve plates or filter membranes, etc.) to block large particulate matter and allow substances smaller than the pores to pass through. The vacuum filter uses a vacuum pump(Standard Diaphragm Vacuum Pump, Anti-Corrosion Vacuum Pump) to provide a pressure difference to force the feed liquid to flow along the surface of the filter membrane at a certain flow rate. Substance molecules larger than the molecular weight cut-off of the membrane do not pass through the filter membrane, and substances or molecules smaller than the molecular weight cut-off of the membrane pass through the membrane to form dialysate.

Because the membrane separation process is purely physical, it has the characteristics of no phase change, energy saving, small size, and detachability. It is widely used in laboratories, including food, medicine, beverage, and drinking water industries, and environmental protection. Determination of suspended solids in the field and sample pretreatment for microanalysis or purification of solvents. Applying vacuum filtration can greatly reduce processing time and increase efficiency compared to gravity flow.

principle-of-vacuum-filtration             work-principle-of-vacuum-filtration-for-particle-application

The vacuum filtration system has two outlets: one is the return fluid (concentrate) outlet, and the other is the dialysate outlet. The key components of a vacuum filtration system are the membrane filter and the vacuum pump. The amount of dialysate flowing out per unit membrane area per unit time is called membrane flux (LMH), which is the filtration rate. Factors affecting membrane flux are temperature, pressure, solid content (TDS), ion concentration, viscosity, etc. For organic matter with different compositions, different membranes are selected according to the molecular weight of the organic matter, and an appropriate membrane process is selected to achieve the best membrane flux and rejection rate, thereby increasing production yield and reducing investment scale and operating costs.

Based on the vacuum filter working principle, we also need to use Hawach 300mL/ 500mL Glass Solvent Filters, Stainless Steel Three-Branches Vacuum Filtrations, and Glass One-Branch Vacuum Filtrations. etc., for you to achieve the vacuum filtration system.

Vacuum Filtration Instruction Drawing

A vacuum filtration machine generally refers to drum vacuum filters. Its main body is a cylindrical filter drum, the filter drum rotates one circle, and the functions of each part in the filtration process are as shown on the right. About two-fifths of the lower half of the filter is immersed in the lye tank. When the filter drum rotates, all the filter surfaces are in contact with the alkali liquid in the lye tank, the filtrate is sucked into the filter drum, and the heavy alkali crystal is attached. on the filter cloth.

The function of rotating the drum in one circle can be divided into the following five processes:

(1) The pumped filtrate starts at the center of the bottom of the lye tank, slightly to the left (about 14°). To the liquid level it stops, and the liquid is sucked into the filter drum, and the heavy alkali crystal is attached to the felt filter cloth (or metal filter cloth). This is the real filtering effect.

(2) The first time it is sucked dry: The liquid (filtrate) in the filter cake is sucked dry from the beginning of the liquid level to about 300 to 400 mm under the alkali solution tank.

(3) Wash: from the first time the suction position to the upper washing tank, it is about 150 mm, which is the washing stage with washing. The washing water in the filtrate is about 0.2-0.25 m3/t soda ash, and the washing water remaining in the heavy alkali is about 0.36-0.4 m3/t soda.

Glass One-Branch Vacuum Filtrations
Glass Three-Branches Vacuum Filtrations
300ml Glass Solvent Filters

(4) The second stage starts from the washing of the water tank until the scraper. The mother liquor and washing water remaining in the heavy alkali continue to be sucked dry, that is, the real sucking dry phase, which accounts for about one-quarter of the area of the filter drum. At the same time as sucking dry, there are three pressure rollers to help squeeze out the moisture in the heavy alkali. To minimize the moisture content, the filter drum speed must not be too fast.

(5) The lower part of the blowing blade (below the horizontal line) sucks the filtrate and then introduces compressed air (a part of which is carried out under the liquid level). The 3- to 4-mm alkali layer remaining on the filter cloth is removed by air to restore the filter cloth’s performance.

During the continuous rotation of the filter drum, the functions of these five stages are repeated to complete the operation of the heavy alkali filtration.

Summary

The working principle of vacuum filtration is based on using a pressure difference to force liquid through a filter medium, enabling rapid separation of solids and liquids. By combining specialized equipment and reduced pressure, it significantly improves filtration speed, efficiency, and product dryness.