Plate and Frame Filtration

Name

: Ng Peng Sang

Student ID

: 003754

Title Subject

: Lab Report : Chemical Engineering Lab.

(H83CEL) Date Supervisor Due date

: 21st December 2009 : Dr. Dominic Foo : 21st December 2009

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CONTENTS Title page

1

Contents

2

Summary

3

Introduction

4

Literature Review

5-10

Experimental

11-13

Results

14-18

Discussions

19-21

Conclusion

22

Nomenclature

22

References

23

Appendix

24-27

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SUMMARY Filtration is a widely used unit operation of Chemical Engineering Process which utilizes the separation of solid and liquid. It uses the theory of solid and liquid separation by flowing liquid with solid suspension through porous mediums or screens which retain the solid suspensions and liquid flows out as filtrate. It is generally used in various industry, such as wastewater treatment industry, food and beverages industry, pharmaceutical industry and chemical industry. Plate and frame filter press is one of the most used filtering machines around due to its simplicity in usage and efficiency it produced. Few considerations has to be decided in order to operate this machine. Firstly, is the selection of filter mediums where a filter medium must have pores smaller than the size of solid suspension in liquid flow or else filtration would not be occurring as the pores would not be able to filter solid suspension. Cake compressibility, on whether it produce compressible cake or incompressible cake, is any factor that needs to be considered to operate this machine. Next, filter aids is important as well as it is applied to solve problems arising from slow filtration rate, unsatisfactory filtrate clarity or rapid medium binding. An experiment has been conducted using a small scale filter press with only the selection of filter paper available. Newspaper sludge is chosen as the feed for this experiment as it can be used to represent pulp and paper industry. It is blended together with water before experiment starts. It is found in this experiment that concentration of mixture affects volumetric flux, as increased concentration of mixture will give a reduction in volumetric flux. In addition, increased in concentration of mixture will give a rise in the pressure of the filter pump. The percentage reduction of solid in mixture and the efficiency is found to be reducing as the concentration of mixture is increased. There are difficulties in this experiment whereby viscosity is unable to be measured and parallax errors are involved when readings are taken. Inadequate equipment in laboratory leads to some discrepancies in the graphs.

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INTRODUCT ION Plate and frame filter press is one of the most used filtering machines in the industry and this filter press also has a good reputation in the industry for being the simplest and most efficient machines available in market. It is widely used in industries, namely food and beverage industry, paper and pulp industry, wastewater treatment, pharmaceutical and chemical industries. Prior to the availability of a small scale plate and frame filter press, an experiment is conducted with intentions to achieve few objectives as follow: 1) To determine the relationship between the concentration of mixture and the volumetric flux.

2) To determine the effect of concentration of mixture on pressure of the filter pump.

3) To determine the percentage reduction of solid in mixture and the efficiency of the plate and frame filter press.

Before the experiment is conducted, feed has to selected and prepare beforehand. A variety of choices of feed are available to conduct the experiment for example

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paper sludge which represents paper and pulp treatment and blended fruits which represents food and beverage industry.

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LITERATUR E Plate and frame filtration. Filtration is a widely used unit operation of Chemical Engineering Processes which separates solids from fluids. According to Coulson & Richardson Volume 2, “Filtratrion is the separation of solids form a suspension in a liquid by means of a porous medium or screen which retains the solids and allows the liquid to pass in termed filtration”. This means that fluids or slurries are forced through the pores of the medium which causes solid particles larger than the pores of the filter medium to be removed. As time passes, particles deposited will slowly build up over time and this would lead to the formation of layer of solids which is called a filter cake. As a thicker filter cake is formed, flow resistance increases and this causes pressure to increase which greatly affects the rate of filtration. It is applicable in various industries such as wastewater treatment, paper and pulp industry and as well as food and beverages industry. In wastewater treatment industries, it is a must to make sewage harmless before it is disposed to prevent pollution. One of the most important reasons to treat wastewater is to control the Bio-chemical oxygen demand (BOD) of the water, which is the oxygen required for biological decomposition of biodegradable organic matter under aerobic conditions. Filtration is one of the process used in order to treat wastewater. It is stated in Basic Environment Engineering by R.C. Gaur that “Filtration is a physical and chemical process for separating suspended and colloidal impurities from water by passage through a porous bed made up of gravel and sand.”

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There are a lot of different types of filter equipments. Filter equipments consists of bed filters, bag filters, filter press, pressure leaf filters, cartridge filters, vacuum filters, band filters, rotary drum filters and rotary disc filters. The experiment that is about to be conducted is based on a plate and frame filter press which is one type of filter press. The other type of filter press is called recessed plate or chamber press.

Figure 1: The plate and frame filter press available in laboratory.

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Figure 2: An example of industrial-scale plate and frame filter press. (Coulson & Richardson Volume 2)

In general, plate and frame filter press functions as solids removal from slurries or fluid. It has a series of plates and frames in alternating arrangements which are covered with fiber cloths or filter papers. In order to remove solids from slurries or fluids, selection of a filter paper or fiber cloths are of high importance. According to Tarleton and Wakeman (2007), they state that, “The term filter medium can be defined as ‘any material that, under the operating conditions of the filter, is permeable to one or more components of a mixture, solution or suspension, and is impermeable to the remaining components’ (Purchas and Sutherland, 2002)”. Tarleton and Wakeman (2007) also claimed that, “Selection of the filter medium must take account into many factors; criteria by which a medium is assessed include the permeability of clean medium, its particle retention capability and the permeability”. So, if selection of filter medium is not critically considered before operation filter presses, there might be occurrence of using filter mediums with too big pores which will eventually end up to a very small cake formed, or no cake formed at all. Main Type

Subdivisions

Smallest particle retained (µm) (approximate)

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Solid fabrications

Metal sheets

Rigid porous media

Cartridges

Plastic sheets

Flat wedge-wire screens

100

Wire-wound tubes

100

Stacks of rings

5

Perforated

100

Woven Wire

5

Ceramics and stoneware

1

Carbon