Reverse Osmosis Options for Water Supply to a Thermal Power Station

DOI: http://dx.doi.org/10.24018/ejers.2019.4.10.1506 143  Abstract—Water in industry is used for operations such as production processing, washing, dissolving, cooling, transportation. Industries often require large amount of water with vary quality. Water quality depends on the purpose of water use. The steam electric power generation industry is defined as that establishment primarily engaged in the steam generation of electrical energy for distribution and sale. Those establishments produce electricity primary from a process utilizing fossil type fuel (coal, oil, or gas) or nuclear fuel in connection with a thermal cycle employing the steam–water system as the thermodynamic medium [2]. Water with in boiler drum and steam generation tubes and headers must be soft and clean. Reverse Osmosis is an effective and proven technology to produce water that is suitable for many industrial applications that require demineralized or deionized water with neutral pH and without turbidity and aggressive.


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Abstract-Water in industry is used for operations such as production processing, washing, dissolving, cooling, transportation. Industries often require large amount of water with vary quality. Water quality depends on the purpose of water use. The steam electric power generation industry is defined as that establishment primarily engaged in the steam generation of electrical energy for distribution and sale. Those establishments produce electricity primary from a process utilizing fossil type fuel (coal, oil, or gas) or nuclear fuel in connection with a thermal cycle employing the steam-water system as the thermodynamic medium [2]. Water with in boiler drum and steam generation tubes and headers must be soft and clean. Reverse Osmosis is an effective and proven technology to produce water that is suitable for many industrial applications that require demineralized or deionized water with neutral pH and without turbidity and aggressive.

I. INTRODUCTION
Reverse osmosis is a technology that is used to remove a large majority of contaminants from water by pushing the water under pressure through a semipermeable membrane.
In recent years, membrane processes have been used increasing for the production of industrial waters so reverse osmosis (RO) became the best technology after the development of efficient membrane and the use of energy recovery devices.

A. Technical and Economical Relevance of Reverse Osmosis
Al though typically thought to be expensive and relatively experimental; membrane technology is an advancing quickly, becoming less expensive, improving performing, and extending life expectancy.

B. Reverse Osmosis Process
Reverse Osmosis is the flow solvent through semipermeable membrane, from a concentrated solution to dilute solution. This flow results from the driving force created by the difference in pressure between the two solutions.
Osmotic pressure is the pressure that must be added to the concentrated solution side in order to stop the solvent flow through the membrane. Reverse Osmosis is the process of reversing the flow forcing water through a membrane from a concentrated solution to dilute solution to produce filtered water (see Fig. 1 and 2, the osmosis process).

C. Reverse Osmosis Advantages:
Reverse Osmosis (RO) has a number of innate advantages. Because it is all liquid and use hydrostatic pressure as energy source, RO modules plant can be very compact, operation is relatively simple and modules are readily replaced, furthermore the energy input can be quite low because it can approach the free energy of separation [10].
The objective of this paper is to design a reverse osmosis plant to produce pure water to make steam in boilers of thermal power station (Dr. Sharief electric power plant).
For precious advantages of RO, it became better than the ion exchange, because ion exchange consumes large quantities of regeneration chemicals such as brine, acid and caustic materials that can present significant handling and disposal problems, also this paper investigate of the economic cost of installing Ro plant: Thermal power plant in Sudan contribute 40% of total electric power generation. In Sudan there are three big  This station helps to: -Improve the performance of the national grid.
-Meet the increase in energy demand due to the expansion of the industries, agriculture and urban project. -Increase the amount of energy generation provided the national grid.

II. MATERIAL AND METHODS
The membrane system design depends on available feed water and the application. The system design information and the feed water analysis should be collected first.
Sample 1: explain the Blue Nile river analysis in Table II Sample (2) explain clarified water analysis in Table II, the clarified water is the source feed water of RO design of Dr. Sharief Station the case study of this paper A. Methodology  TABLE III shows parameters of clarified water which I will explain in test method (pH, conductivity, turbidity, total dissolve solid (T.D.S) and total suspend solid (T.S.S) and SDI Test methods: see table (1) explain ASTM methods for properties of water.

1) pH
The standard test for pH of water is Direct standardization technique. It is employed in this test method for routine batch samples two buffer solutions are used to standardize the instrument under controlled parameters.
2) The conductivity of water The conductivity of water is applicant to field and routine laboratory measurement of electrical conductivity of water using static sample.

3) The turbidity of water
The turbidity of water is done by the photo electric nephelo meter operation. It is based on instrumental comparison of intensity of light scattered by the contained static water sample under defined conditions to intensity of light scattered by reference standard light.
The higher the intensity of scattered light, the higher turbidity of sample.

4) The hardness
The hardness is calcium and magnesium ions in water. It is sequestered by addition of disodium ethylene di-amine tetra acetate. The end point of the reaction is detected by means of chrome black T, which has a red color in the presence of calcium and magnesium and a blue color when they are sequestered.

5) Dissolved (TDS)
Substance that are completely water soluble A direct relationship between TDS and conductivity there is no exact conversion TDS (mg /L) = 0.67* electrical conductively

6) SDI (silt density Index):
The SDI test procedure in eludes the following -A 500 ml volume feed water is forced through a standard filter under special test conduction -After 15 min the is repeated using the same filter -The filtration time t 1 and t2 are used to determine the SDI Where T is 15 minutes Other test conditions include the following -Applied pressure difference a cross the membrane is 2bar -Filter pore diameter is 0.45mm -When t2 is for time t1, the SDI equal5 -A water sample that totally blocks the membrane filter has a SDI value 6.7 -SD1< 5 max, standard SD1<3 The procedure to design RO/NF membrane system can explain in 10 steps: -Steps 1: Consider feed source, feed Quality product flow and required product quality -Step2: Select the flow configure and number of passes.

III. RESULTS AND DISCUSSIONS
A. Importance definitions and equation 1) Recovery % Percent Recovery is the amount of water that being "recovered 'as good permeate water. (1)

2) Flux
Flux is the rate of permeate flow per membrane area.
3) The type of membrane

B. The staging Ratio (Array-Ratio):
For a system with four vessels in the first stage and two vessels in second stage the stage ratio 2:1 C. Two-stage system defined as: The concentrate (or reject) from the first stage then becomes the feed water to the second stage. The permeate water is collected from the first stage is combined with permeate water is collected from the second stage see Fig. 3.  IV. CONCLUSIONS Industrial plants are use water After treatment and when use it to produce steam they use demin water, the aim of this work was to excess the possibility of effective removal ions responsible for water hardness and formation of scale deposits by ion exchange (Resin) and I was design plant to do the same process but use membranes namely RO. To product 50 ton/ h permeate form one train of clarified water.
In Preliminary calculation for brackish water (Surface water) from (Blue Nile) flux between (10-14) gfd and (400ft 2 filmatic membrane area) Or (25 L/m 2 /h) the number of membranes needed was 54 membranes for each train and which require 9vessel for each train and recovery was 80% and the stages =2 And stage ratio (array) 2:1 this membrane under high pressure pump =400psi (27bar).

V. RECOMMENDATIONS
Surface water always causes problem of fouling and high ratio of silts and organic material so when installing Ro Plant for Dr. Shrief station must put two cartridges filter before Ro also we can use the ion exchange with Ro in combination together to reduce chemical cost. Proper pretreatment and monitoring of Ro system is crucial to preventing costly repairs and unscheduled maintenance with the correct system Elision maintenance program, and experience service support, Ro system should provide many years of high purity water.