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Types of Liquid-Solid Separation

Most process industries require the separation of solid and liquid phases, and several techniques are utilized to accomplish this. Figure below shows several types of liquid-solid separation techniques.

Liquid-solid separation methods
Liquid-solid separation methods

Gravity or centrifugal force can be used to separate materials based on their different densities, or in the case of filtration, the particle size and shape. The best method to apply will be specified by the solids concentration, feed rate, size, composition of the solid particles, the objective of separation (clear liquid or solid product), and degree of dryness of the solid required. Read More

Basic Filtration Equation

Let’s learn the basic filtration equation which may be useful in sizing and evaluating many types of filtration unit. Disclaimer, this is also the first time in my working life learning about filtration equation, so if you find any mistakes, please feel free to comment below.

There are two terms in basic filtration equation. The first is, if the filtration occurs at constant pressure. And the second is, if the filtration occurs at constant flow rate. If the filtration occurs at constant pressure, then the flow rate will progressively diminished because the filter bed is steadily growing in thickness. Whereas, if the filtration occurs at constant flow rate, then the pressure must be gradually increased.

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Several Types of Clarifying Filtration

In previous post, I shared several types of filtration methods and more about cake filters. In this post, I want to share to you several types of clarifying filtration.

Read also: Introduction to Filtration

Read also: Many Types of Cake Filters

The main objective of clarifying filters is to remove small amounts of solids or liquid droplets from either liquids or gases. The liquid may be drinking water, wine, beer, oil, etc., and it is usually the liquid which is the valuable product.

In clarifying filters, the particles are trapped inside the filter medium or on its surfaces. Surface forces catch the particles and immobilize them on the surfaces or within the flow channels.

In general, clarifying filtration are categorized into liquid clarification and gas cleaning. Read More

A Simple calculation on How to Determine Time Required to Obtain Certain Volume of Filtrate

In this post, I want to share how to do a simple calculation on determination of time required to obtain certain amount of filtrate in a filtration test. We will still use basic equation as in previous post.

Read previous post: How to Determine Cake Resistance in Filtration Systems

For example, we have this case.

A filter press with a surface of 50 m2

C (weight of solid per volume of liquid) = 135 kg solid/m3 liquid

μ = 0.001 N sec/m2

α (specific resistance of the cake) = 1.1 (1011) m/kg

Rf (resistance of filter cloth) = 6.5 (1010) m-1 Read More

How to Determine Cake Resistance in Filtration Systems

Purpose of this post is to determine cake resistance in filtration systems, as a function of operating pressure of filter. Before we jump into the calculation, let us learn first several basic calculation in filtration system.

As filtration proceeds, a porous cake of solid particles is built up on a porous medium, usually a supported cloth. The flow of liquid is laminar because of the fineness of the pores. Therefore, the following equation represented the phenomena:

Q = \frac{{dV}}{{dt}} = \frac{{A\Delta P}}{{\mu R}}

The resistance is made up of filter cloth Rf and that of cake Rc which may be assumed proportional to the weight of the cake. Read More