Fabrication of solar stills for desalination and study the effect of photo catalyst on desalination

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Chapter 1

1.1 Introduction

The Solar energy is green, renewable and powerful available within our lives and can be considered for many applications. One of these applications is the evaporation of sea water.

The single slope of solar distillation still is one of many methods that can be used for evaporating the sea water and converts it to fresh water.

The solar still desalination process can give very good results and the efficiency is very high for producing fresh water and one of the examples is the desalination of the sea water.

1.2 Definition of desalination

Is to convert salt water into pure water for suitable use. This is done through many ways by desalination.

1.3Methods of water desalination

- water desalination through distillation

- by using the methods of desalination membranes

- water desalination in a crystal or freeze.

1.4 Desalination through distillation

The basic idea of a distillation process is to raise the temperature of salt water to the boiling point and composition of water vapor that is then condensed into water and then treated to be water fit for drinking or irrigation.

1.5 Methods of distillation: of which we mention some important ways:

1 - Normal distillation:

Is boiling salted water in a water tank without pressure. Water vapor and climb to the top of the tank and out through the conductive path to the condenser, which intensify the water vapor that turns to water droplets are collected in a tank of distilled water. This method is used in desalination plants with small production capacity.

2 - Multi-stage distillation flashlight:

Depending on the fact that decides the degree of boiling liquids is directly proportional to the pressure awareness of the smaller pressure on the degree of boiling liquid. In this method, with sea water heated to room after a row of low pressure

turned water into water vapor is condensed on the surfaces of cool and collected and treated in quantities suitable for drinking.

3 - Lock Stitch Multi-distillation stages (multi-effect):

The distillate multiple effects benefit from the vapors rising from the evaporator to the first step in the second evaporator. Accordingly, the condensation heat is used to boil water in the sea in the second evaporator, and thus the second evaporator works with the fumes coming from the evaporator first, and become a vapor in the evaporator as the second task of steam heating in the evaporator first. Similarly, the evaporator works with third of the evaporator and the second, and so is called each evaporator in the string effect.

4 - Distillation using solar energy:

This method relies on the utilization of solar energy to heat the sea water so that the degree of evaporation and then is condensed on the surfaces of cool and collected in tubes.

5-Steam distillation in a ROM.:

While using a multi-effect distillation units and the sudden evaporation of an external source of steam heating as the primary source of heat, the compression of steam distillation - which is usually abbreviated to compression distillation - used as a source of thermal vapor on the pressure after the steam. In this way, you can get the high economic power. However, it is necessary to obtain the mechanical energy using a compressor (or any form of power learned to other devices such as compressor extruder Bukhari steam-ejector compressor). Despite these different operation of the distillation process for the ideal it should be noted that the sources of how much heat is the case in other distillation processes, which were discussed in the present chapter.

Heated sea water initially in the tubular heat exchanger, using both water and salt water and fresh water expelled outside of the unit and then boiled sea water inside the tubes distilled. And vapor pressure, and then refer to distilled with frequent outside the pipe, which provides the heat necessary for the process of boiling. And to withdraw non-gas condensation from the vapor space and condensation pump-mediated withdrawal or repellent Steam whichever suits.

The compressor is the heart of the distillation unit. If you do not press fumes, it can not condensation on the pipes carrying water to the sea because the boiling temperature of the intensification of pure steam at a pressure of less than a certain temperature of boiling salt water at this pressure. For example, if the vapor pressure of an atmospheric pressure, the water vapor condenses at a temperature of 100 m, but the sea water concentration of multiple boils at about 101 AD. In order for the vapor condensation at a temperature of 101 m, it is required at least for these vapors to press the pressure of 1.03 atmospheres.

1.6 Desalination membranes method

Reverse Osmosis:

The reverse osmosis process in comparison with modern processes of distillation and dialysis were provided commercially in the seventies. The process of reverse osmosis as a separation of water from brine-ROM through the membrane. All that is needed to heat or change in shape.

In practice is pumped into the feed water in a closed vessel where it is compressed on the membrane, and when some of the water passes through the membrane increases the water content of the remaining salt. At the same time, the part of the feed water is disposed of without passing through the membrane. Without this phase, the steady increase in the salinity of feed water will cause many problems, such as increased salinity, sediments, and increase the osmotic pressure across membranes. Range from the amount of water disposed in this way between 20 to 70% of nutrition depending on the amount of salt in them.

1.7 Uses of solar energy

The solar energy is being used since the human beings existed on this earth and we still use this energy in our day to day activities, for example, we use the Sun heat to dry our clothing, plants make food by the use of the Sun rays and accordingly Animals eat these plants and when animals die and after millions of years these animals forms other sources of energy such as coal, oil and natural gas.

Chapter 2

2.1 Literature Review

In one of the studies conducted by Mr.Muafage Suliman regarding the effect of water depth on the performance evaluation of solar still, the study took about six months and he repeated the exercise with different quantity of depth in the still basin and the all the experiments showed that the still productivity is strongly dependent on the climatic condition and the design as well as the operational conditions. As a result, with decreased water depth the productivity of water increases significantly and the parameters performance of the water productivity was closely related to the incident solar radiation intensity. Mr. Muafages study highlights the concept of using greenhouse solar stills was found to be very attractive method for obtaining the fresh water even for small scale demands due to the several economic and technical advantages due to the inexpensive technology that includes the material cost and manufacturing. In addition, the experiment also concluded that the efficient utilization of the solar energy could minimize the need of expensive conventional sources of energy. Mr.Muafage Suliman Study Other study is about the solar desalination with humidification-dehumidification cycle. Most of the desalination process consumed much and large quantity of the the energy such as gas or oil. Solar desalination has emerged as renewable energy technology for provide fresh water. Combining the principle of humidification-dehumidification with the solar desalination result in increasing the overall efficiency of the desalination plant. Study by Mr.Said Al-Hallaj

Laboratory experiments showed that by using Photocatalyst for treating dairy effluent with various parameters such as catalyst concentration, initial concentration, angle of tilt of solar flat plate reactor and flow rate can efficiently treat dairy effluent. With the use of photocatalyst the degradation of dairy effluent can be done successfully, and the experiment highlighted that with lower flow rates the degradation would be faster. Reference: Janhavi Inamdar and S.K. Singh

There is a strong need to improve the single solar still performance and increase the production rate of distilled water, by using different types of absorbing material this can be achieved. The use of absorbing material such as coated and uncoated sponge and black rock was a plus in improving the performance of single solar still. The only negative point was on the metallic wiry sponges that corrosion started to appear in certain parts of the sponge. Reference: Salah Abdallah, Mazen M. Abu-Khader, Omar Badran.

The Photocatalysis process is a great environmental application with high potential in the near future if used in the processes to water purification and treatment. It can be utilized for the decomposition of organic and inorganic compounds and removal of trace metals as well as destruction of viruses and bacteria. The advantage is it does not leave toxic and the disadvantage is it is slow compared with traditional methods. Reference: Radwan A. Al-Rasheed.

By implementing the greenhouse effect of solar energy, the solar desalination would be a successful renewable energy source of producing fresh water from seawater or brackish. To enhance the overall efficiency of conventional basin type solar still, different semiconducting oxides like CuO, PbO2 and MnO2 have been utilized as photocatalysts and the result come with metal oxides and in particular, PbO2 is most effective among the three oxides used also all the three oxides are effective in lowering TDS of raw water to almost equal extent and the total alkalinity is also reduced with all the three metal oxides and PbO2 is most effective among all. Reference: Suresh G. Patel, Shilpi Bhatnagar, Jitendra Vardia, Suresh C. Ameta

The photocatalytic organic content reduction of a selected synthetic municipal wastewater by the use of heterogeneous and homogeneous photocatalytic methods under solar irradiation has been studied at a pilot-plant scale at the Plataforma Solar de Almeria. In the case of heterogeneous photocatalysis the effect of catalysts and oxidants concentration on the decomposition degree of the wastewater was examined. the reduction of the organic content of a synthetic municipal wastewater has be successfully carried out by applying a heterogeneous and a homogeneous solar photocatalytic method. Referance: M. Kositzia, I Poluo.

Other sudy is about the utilization of new technique to improve the efficiency of horizontal solar desalination still done by Mr.Nabil Hussain. Hence the study cover the energy required to use in the process of desalination seawater directly proportional to the amount of salt extracted from the water. The study cover the quantity of fresh water use in the house for drinking and cooking and also for cleaning and garden as well as other purposes. The study suggested improving the efficiency of the basin type solar desalination still. The force condensing system sucks the water vapor from the evaporator zone, condenses it in a separate unit, and does not allow it to condense on the glass roof inner surface. Also the condensing method is not relying on natural convection mechanism, more vapour reches the condenser with more of fresh water .Study done by Mr.Nabil Hussain

Chapter 3

3.1 Importance of the project:

The project is important from several aspects including, for example: -

- In economic terms.

- An environmental perspective.

- The scientific point

3.2 Objective of the project

The project objectives cover the following points:

To fabricate an equipment for desalination by using solar energy

To observe the variations of different parameters like pH, conductivity, TDS, Total alkanity, Chlorideetc with and without photo catalyst

To conduct experiments at different volume of water and analyse the effect .

To understand the evaporation process using solar energy and with photocatalyst and analyzing the data that come out of the experiments through the samples of evaporated water

Comparing all result of the sample in different atmospheric temperature.

Chapter 4

4.1 The model design

I selected strong material that will not be affected when the experiment is going on and also will not be affected by the sun chine. The wood is my selection for this purpose to avoid the problem for the model (Box).

The model consists of the following items:

- Water proof wood 12 mm

- Glass 4mm

- Aluminum sheet

- SS vessel

- Digital measuring device

4.2 Fabrication cost:

The fabrication of the project model cost me about R.O 145.000

Photo before start the process.

Above photo during the evaporation process

4.3 Working Principle:

Solar radiation falling through the glass cover and heat is received by the water. Then sea water starts evaporating and this vapor is moved to the upward direction and condenses to small drop of fresh water. After that the water is moving down along the inclined glass cover and collected in a measuring jar.

Following characteristics were measured: -

- PH

- Conductivity

- Alkalinity

- total Hardness

- Chloride

- Iron

- Phosphate


Following photo show the water temperature and outside temperature along with humidity

Chapter 5

5.1 Result and analysis:-

Comparison of characteristics with and without the photocatalyst for a quantity of 1 liter of sea water.

Characteristics Without catalyst With catalyst

PH 3.54 5.88

Conductivity 410 62.2

Alkalinity 0 6

Total Hardness 12.8 11.6

Chloride 82 16

Iron 0.02 0.04

Phosphate 0.1 0.11

TDS 197.8 29.3

Comparison of characteristics with and without the photocatalyst

for a quantity of 3 liter of sea water.

Characteristics Without catalyst With catalyst

PH 4.14 6.08

Conductivity 350 30.7

Alkalinity 0 7.6

Total Hardness 20 11

Chloride 78 3

Iron 0.01 0.01

Phosphate 0.09 0.01

TDS 170 14.2

Comparison of characteristics with and without the photocatalyst

for a quantity of 5 liter of sea water.

Characteristics Without catalyst With catalyst

PH 3.72 6.28

Conductivity 305 23.3

Alkalinity 0 7.6

Total Hardness 18 19.1

Chloride 66 2.5

Iron 0.02 0.02

Phosphate 0.1 0.1

TDS 145.3 10.6

5.2 Mass Flow Rate

Mass flow rate with and without catalyst for a volume of 1 liter

Date 28-Jun-10 4-Jul-10

Atmospheric Temperature 34 C 35 C

Water Temperature 31 C 31 C

Sr No Time in hrs Without Catalyst With Catalyst

1 9 0.01 0.02

2 10 0.02 0.02

3 11 0.04 0.05

4 12 0.08 0.07

5 13 0.3 0.3

6 14 0.8 0.9

7 15 1.01 1.1

8 16 0.7 0.7

9 17 0.5 0.6

Total Qty collected in liter 0.346 0.376

Mass flow rate with and without catalyst for a volume of 3 liter

Date 30-Jun-10 6-Jul-10

Atmospheric Temperature 36 C 46 C

Water Temperature 31 C 33 C

Sr No Time in hrs Without Catalyst With Catalyst

1 9 0.001 0.002

2 10 0.002 0.002

3 11 0.02 0.02

4 12 0.05 0.05

5 13 0.08 0.8

6 14 0.09 0.9

7 15 1 1.1

8 16 0.6 0.06

9 17 0.4 0.04

Total Qty collected in liter 0.224 0.297

5.3 Mass flow rate graph

Graph 1

Mass flow rate Vs Time for a volume of 1 liter

Graph 2

Mass flow rate Vs Time for a volume of 3 liter

Chapter 6

6.1 Conclusion:-

By using the solar energy single slope still design, experiments were conducted at different volume of saline water with and without using the photocatalyst. It was found more fresh water was produced by using photocatalyst. Also the quality of desalinated water was improved by using the photocatalyst.

Also observed that the more desalinated water was produced when the volume of water is less and even the atmospheric temperature is low still there is a possibility for the evaporation process.

Photocatalyst is one of the methods that can be used for water treatment. Hence we can use it to extract and decomposition the bacteria in the organic as well as inorganic compounds.

The other advantage of the solar energy system is it is cheaper method and environmental friendly.