Skip to main content

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

Many Types of Cake Filters

In previous post, there are three general types of filters, which are cake filters, clarifying filters, and crossflow filters. In this post, I want to share specifically about many types of cake filters.

When slurry enters cake filters, some solid particles enter the pores of the medium and are immobilized, but soon others begin to collect on the septum surface. A visible cake of significant thickness builds up on the surface and must be periodically removed. Cake filters are used almost entirely for liquid-solid separations.

Cake filters may operate with above-atmospheric pressure upstream from the filter medium or with vacuum applied downstream. Either type can be continuous or discontinuous, but most pressure filters are discontinuous.

Figure below shows many types of cake filters. 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

Introduction to Filtration

These days, I feel like learning topics related to solid processing. After I learned about agitation process and its scale-up, I want to learn about filtration process.

So, in this post I want to share you general preview of filtration process. Honestly in my career until now, I already handled one project related to filtration equipment, which is my very first project: pre-feasibility study of carboxymethyl cellulose plant. The filtration equipment used in the project was rotary vacuum filter.

I hope by learning and writing what I read here in this blog will refresh my knowledge and hopefully useful in the future projects. Read More

Step-by-Step Methods on Nongeometric Scale-up for Liquid Agitation

This post would be quite long since agitation scale-up involved trials and evaluation of the parameters. This post is based on Handbook of Chemical Engineering Calculations Fourth Edition by Nicholas P. Chopey.

To understand better about how to scale-up nongeometric liquid agitator, I will use an example. We will make one change at a time to understand its effect.

The example is below:

A process involving water-like liquid must be scaled up from an agitated 18-in diameter, 15-gallon pilot-scale reactor to a 120-in diameter, 7000-gal large scale reactor.

The pilot scale has a 18-in straight side and the large-scale reactor will have a 168-in straight side. Both reactors have ASME dished heads on the top and bottom.

Successful process performance was obtained in the pilot scale with two 6.0-in diameter pitched-blade turbines operating at 350 rpm. It is proposed that the large-scale reactor use hydrofoil impellers instead of pitched-blade turbines, for improved liquid motion.

Each pitched-blade turbine has a turbulent power number of 1.37 and each hydrofoil has a power number of 0.3.

Past scale-up experiences with similar processes, but with geometrically similar tanks, were successful when impeller tip speed was held constant. Read More

Simple Calculation Methods to Estimate Power Required to Rotate Agitator Impeller

This post is a little different from usual. Honestly, I seldom dealing with agitation process. As you may know from my posts, my projects are mostly in oil and gas field. So, agitation process is very rare in oil and gas processing. However, I think I need to learn something beyond what I already learned until now to improve myself.

In this post, I want to share simple calculation methods to estimate power required to rotate agitator impeller. In the future, maybe I will deal with project involving agitation process. Read More

How To Calculate Required Wall Thickness and Schedule of Pipe

In this post I want to share how to calculate minimum required wall thickness and schedule of pipe. Before we jump into calculation steps, let’s review what pipe schedule is.

Pipe schedule expresses thickness of pipe. It is not actual measurement, but as a guide based on wall thickness formula.

Two pipes with the same diameter may have different schedules, which means they have a different wall thickness. So, somebody specifying a pipe for a high-pressure application will select a bigger number which represents a bigger schedule or thicker wall.

I made a simple spreadsheet on how to calculate required wall thickness and schedule of pipe. I found that the calculation is quite mechanical. Maybe some process engineers, even me, do not really used to this calculation. The calculation involves allowable stress, weld quality factor, etc. I do not think all process engineers should understand about how to calculate pipe wall thickness. But it would be better if we do.

Read More

How to Estimate Hydrate Inhibitor to Depress Hydrate Formation

In previous post, I shared what is hydrate formation and primary conditions promoting hydrate formation. Quick review, hydrate in natural gas system is a physical combination of water and other small molecules to produce a solid which has an ice-like appearance. Hydrate should be control because it will cause several problems. The problems include restriction in flowlines, causing physical damage to chokes and instrumentation. One method to control hydrate formation is to inject hydrate inhibitor into production stream.

Read more: Hydrate Prediction using Pressure-Temperature Correlation Read More