FAQs

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Water
It is a tasteless, odourless colourless liquid in its pure state. It is the only inorganic material existing in three forms a. ICE b. WATER c. STEAM (Vapour) These three things occurs within the earth's natural temperature range. Water can be converted into steam at a convenient temperature. Because of this nature, the water is ideal for process and for generating power. General : Generally speaking 100% pure water is not existing. All natural water contains impurities like dissolved solids, dissolved gases and suspended matters. Water is a universal solvent. It dissolves the rocks and soil it touches. It dissolves gases from atmosphere. It picks up suspended matters from earth. Above all, it gets contaminated by industrial wastes life dyes, oil and process materials. To be more precise the types of impurities the water contains on what it contacts and amount of impurities depends on time it contacts (retention time).
Type of Water : Fresh water supply can be classified into two major catergories by the source of water viz-a-viz

Source of Water
Surface Water
Ground Water

River
Shallow

Stream
Deep-well

Reservoir
Bore-well

Generally speaking, ground water like borewell or well water will be a continous flow of water and contains more dissolved solids like irons, silica and other minerals. Whereas in surface water like river water and others the total dissolved solids will be less which results in total hardness. However continous addition of industrial wastes like dyes, processed chemicals Et.al in river water contaminate the same. In bore well continous consumption of water makes the situation still worse. Sea Water : The sea water is the another source of water, but it contains about 36gms of minerals (almost solids) in the litre. The minerals contents in fresh water is far les than that of sea water. some experiments is being carried out to convert the sea water into ordinary water (for industrial use) , however, the treatment cost per litre is so high that it cannot be used for any industrial purposes.
River Water : Usually the river water will be containing less hardness than that of ground water. for instance, the bore well water total hardness will be around 700 to 800 Mg/l, whereas the same can be around 300Mg/l in river water, However, the river water will contain more suspended solids which will affect the costly equipment if the water is used directly.

Minerals : The water picks up minerals from rocks consists chiefly of:
Sl. No. Chemical Name Common Name
1. Calcium Carbonate CaCo3 Lime-stone
2. Magnesium Carbonate MgCo3 Dolomite
3. Calcium Sulphate CaSo4 Gypsum
4. Magnesium Sulphate MgSo4 Epsum Salt
5. Silica Sio2 Sand
6. Sodium Chloride Nacl Common Salt
7. Hydrated Sodium Sulphate (Na2SO4 . 2H20) Glauber Salt

The above minerals are contributing to the major part of the total dissolved solids (TDS) over and above, small quantites of iron, manganese, chlorides and other minerals, wastes from industries like dyes, processed chemical contaminates the ground water.
Purity of Feed water : The feed water purity is a matter of both amount of impurities and nature of impurities. for instance the impurities like hardness, iron and silica are more concern than sodium salts. The purity requirement for any feed water depends on how much steam is produced. Hence the boiler design and the feed water parameters plays a vital role in selecting the treatment. The low pressure boilers can tolerate slightly higher feed water hardness. However, Proper internal treatement by chemical should be supplemented.
Treatment of feed water: Before feeding the water into Boiler following aspects are to be taken into consideration:
1. Removal of suspended matters
2. Removal of Dissolved solids for prevention of scales
3. Conditioning to prevent precipitation
4. Elimination of certain gasses to prevent corrosion
5. Prevention of foaming and carry over
6. Prevention of caustic embrittlement
7. Removal of oil and grease
The boiler feed water impurities can be eliminated by the mixture of both external and internal treatment. The treatments are classified as follows:
1. External Internal
2. Precipitation Chemical
3. Exchange
4. Distillation
5. Reverse Osmosis
External Treatment
Precipition Method: It is a functional way of treating water externally. Even though it is not being used now a days. Let us briefly discuss about this method.
Exchange Method: This is the method of softening water by zeolite. The name is generally applied to the process whereby sodium is substituted by another metal by exchange material not necessarily of zeolite class. In the process, calcium and salt are retained by the resin and equivalent amount of sodium salt passed out with water leaving the resin. Once the exchange capacity is exhausted regeneration is carried out with strong salt solution.
Cation Exchange: It is exchanged for one cation for another exchange of calcium magnesium, sodium, for hydrogen by means of exchange material (Hydrogen resin). the exhausted exchange material is regenerated by passing the solution of mineral acid through the resin (usually HCL).
Anion Exchange: In the anion exchange process, the sulphate chloride, nitrate ions Et.al. are exchanged by hydrogen ions. The exchange is carried out by passing the water through the bed of synthetic resin.
Strong Base Anion Exchange: Strong base resin are totally ionised through the complete pH range. Removed silica and carbonic acid in sodium slit form the cation resin is converted to sodium- bydroxide in the resin. The process is given below:
NaCl + ROH -----> NaOH + ROI
Distallation Method: Raw water is distilled in evaporator to procude distillate. It is almost completely free from dissolved solids. This method is not being used for low and medium pressure boilers. There are other methods like Deaeration, reverse osmosis and activated carbon filters. Deaeration: It is used to remove the dissolved oxygen and carbondioxide.In this method the steam deaerator breaks up water into spray and then pass the steam across and throw it to force out distilled gases like oxygen and carbondioxide. The oxygen content can be reduced to 0.5 Mg/L. Again this process not required for low and medium pressure boilers.
Reverse Osmosis: It is the latest and sophisticated method of treating the watter. In this process a synthetic semi-permeable membrance is used to remove the minerals to the maximum extent. Water is treated in this process the outlet will be of very good quality and total dissolved solids (TDS) of around 100-110 Mg/L. This method is so costly that is not being used for boilers and the another major problem in this is, disposal of effluent water which comes out of this process.
Activated Carbon Filter: This filter is being used ro remove chlorine, colour and odour. when the raw water directly fed into any costly equipments like softener, D.M. Plant and R.O. Plant suspended matters in the water which enters along with the water into the system may affect the costly material like resin and R.O. Membrane. To avoid this problem A.C. Filter with pressure Sand Filter (PSF) is being used before the water fed into the system.
Internal Treatment
Internal treatment of water is the method in which chemical is being used to treat the feed water inside the boiler and is essential where or not the water is pre-treated by external treatment, regardless of the quantity of feed water. In some cases, external treatment of water is not necessary and the water can be treated by internal method alone. Internal treatment can constitute slow treatment when the boiler operates at low pressure. Large amount of condensate return and the raw water is of good quality, then the internal treatment alone will be sufficient. However, medium and high pressure boilers requires external treatment of make-up water along with the internal treatment as even a small amount of oxides can cause very high fuel consumption or may reduce the life of the equipment.
Internal Treatment Programme: Purpose of internal treatment programme can be classified as follows: React with incoming feed water hardness to prevent it from precipitation on the boiler metal as a scale.
Conditioning of any matter such as hardness, sludge in the boiler and make it non-sticky to the boiler metal.
Provide anti-foam protection to the reasonable concentration of cycle and to avoid carry-over.
Schavenge the oxygen from feed water and to provide enough alkalinity to prevent boiler from corrosion.
In addition to these, the programme is designed in such a way that it also protects the steam condensate system from corrosion.
Chemical used in Internal Treatment: Today all th eboilers use varieties of internal treatment chemicals. Phosphate has been the main chemical until the polymers came into being. But for the low and medium pressure boilers still we continue to use phosphate for maintaining scale from metal surfaces.In internal treatment where polymer condition the calcium and magnesium in the feed water. Polymer forms soluble complexes with the hardness, where as phosphate precipate the hardness. Sludge conditioners are also used to aod in conditioning the precipated hardness, while selecting these process care should be taken so that they are both effective and stable at the operating pressures. Certain synthetic and organic material are used as anti-foam agent. In some cases to schavenge the oxygen in the feed water separate chemicals are used as Hydrazine, DEWBORN-102-A Et.al. Condenste system protection can be accomplished by using filming amines such as DEWBORN 181.
Internal Treatment Chemicals Reaction with Hardness: Calcium bicarbonate entering with the feed-water is broken down at normal boiler temperature to form calcium carbonate since CaCo3 is realtively insoluble, it precipitates. Sodium carbonate partially breakes down at high temperature to Sodium hydroxide and CO2 . When chemical such as DEWBORN 102A which is basically a phosphates based chemical is used in internal treatment, they react with calcium bicarbonate to form calcium phosphates and sodium carbonate. In the presence of sufficient caustic alkilinity magnesium bicarbonate will poreciptate as magnesium hydroxide and will react with silica to form magnesium silicate. The above minerals precipitated from the soltion form sludge, which is being conditioned by sludge conditioner, which is incorporated in DEWBORN 102, prevent its sticking from the boiler metal. And then the conditioned sludge is being removed by proper Blow-Down. The sludge conditioner also did aid in conditioning any suspended solids contamination that may enter the boiler through the feedwater such as iron oxides.
Internal Treatment for Scale Prevention

Compounds in Raw Water Treating Chemicals Sludge Formed

Calcium Bicarbonate DEWBORN - 101 A ( Carbonate & Phosphate )

Calcium Carbonate
- - Tricalcium Phosphate

Calcium Sulphate - Calcium Carbonate
- - Tricalcium Phosphate

Magnesium Sulphate - Magnesium Hydroxide

Internal Treatment with Sulphate: When calcium and magnesium sulphates enter through the boiler feed water into the boiler it becomes insoluble due to boiler temp. When with the phosphate and alkalinity producing hydroxipatite which is less sticky, more readily conditioned product than Calcium Phosphates. Magnecium also gets removed similar to calcium sulphate and both these sludges are getting removed through blow down.
Internal Treatment for Silica: In untreated water silica tend to precipate directly as scale and hot spots on the boiler metal and will combine with calcium to produce a hard calcium silicate scale. This scale is basically a bad conductor to heat, strongly adhere to boiler metal which result in excess of fuel consumption, puncture due to under deposit corrosion. Treatment for silica involves keeping the boiler water alkalinity high enough to hold silica in solution. There is enough magnesium in water to precipitate silica as cludge. Organic matters such as (Strach tend to prevent silica from sticking to the boiler metal. Magnesium silicate gets conditioned by the sludge conditioners which is used in DEWBORN 101 A and DEWBORN - 102 A et.al. gets removed through blowdown easily with this we can minimise the problem due to silica in the boiler.

Sludge Conditioning in Internal Treatment: The suspended solids carried along with feed water into the boiler affect both the boiler cleanliness and steam purity. The suspended solids for varying tendencies to deposit hot metals. The suldge conditioners play a vital role in preventing these sludges from depositing and form insulating boiler scale. The role of sludge conditioners is to keep boiler water suspended solids from depositing and form scale from the boiler metal. DEWPHOS 102, DEWTREAT 101 chemicals have been incorporated with sludge conditioners to keep the sludges in the conditioning stage so as to remove through blow-down easily.
Usual problems faced in the Boiler Internal Treatment : There are three major types of problem faced in the boiler:
1) Scale or deposits form in improperly treated boiler water reducing the effeciency of the boiler and increasing fuel consumption considerably.
2) CORROSION: It is due to dissolved oxygen and will cause tube failure and unplanned boiler shut-down.
3) CARRY OVER: It is a sludge or colour along with the steam which can contaminate the process so for example, the carry over of colour may spoil the knitted cloth in the vinches. The treatment of boiler feed requires the planned programme that involves proper selection of treatment method of application and control limits. It also requires continuous maintainance of best feedwater quality, chemical control and boiler water concentrations. The feed water blow-down parameters must be consistently monitored.
Foaming: Foaming in boiler caused by small stable bubbles and the steam entering in the boiler water surfaces. The water fall around each bubble is more stable by increase in suspended or dissolved solids in boiler water may also be caused by oil detergent or organic matter.
Caustic Embrittlement: Caustic embrittlement is cracking on boiler steel resulting from stresses metal by concentrate of caustic . As it is, there is no simple test for detecting embrittlement. A special device has to be used for detecting casutic embrittlement, but usually by detecting and maintaining caustic alkalinity and boiler blow down water, caustic embrittlement can be avoided. Basically, caustic embrittlement in boiler designing have reduced the caustic embrittlement problem considerably.
Internal Treatment for Caustic Embrittlement: Practical experience has shown that sludge conditioner such as used in DEWBORN - 101 A or DEWPHOS 102 applied to the boiler water are effective in preenting caustic cracking of boiler steel. This method os called co-ordinated phosphate - ph method in which all of the boiler alkalinity is analytically maintained in the form of phosphate rather than caustic soda.
Advantage of Internal Treatment: The prime advantage in the internal treatment is that it can eliminate the need for expensive external treatment equipment, this give a definite economic advantage. In addition, to this internal treatment reduces the requirement for man-power, as the external treatment equipment requires additional man-power. However, internal treatment with moderate external treatment can eliminate the problem to the maximum extent. A qualified technical personnel specialised in water treatment may be consulted for selecting the appropriate method of treatment according to the system.
Treatment Monitoring: Monitoring of chemical can be classified as follows :
Chemical Feeding: Chemical is being added into the boilers either nu chemical feed pumps or directly into the feed water line. In some cases, chemical is being added into the feed water tank as a sludge dosage.
Controlling of Chemical Dosage: Chemical dosage purely depends upon the amount of feed water and the quality of feed water. while selecting the dosage proper care has to be taken. for example, DEWBORN 101A & DEWPHOS 102 being suggested on the basis of feed-water total hardness whereas DEWBORN 182 catalysed hydrazine hydrate is being dosed on the basis of feed water has to be maintained by way of slightly extra dosage during te initial period, so that any change in the feed water parameters will be taken care bythe reserve of this chemical. Boiler Water Analysis : Routine control test of boiler feed water and blow-down water has to be carried out. So that, any change in the parameters can be adjusted by way of reducing or increasing the chemical dosage.
Parameters to be Tested: Water parameters testing can be varying according to the operating pressure of boilers usually for the low pressure boilers and medium pressure the total hardness, p' alkalinity, M' Alkalinity, Caustic alkalinity(2P-m) pH, phosphate, silica, chlorides, iron, total dissolved solids (TDS) has to be checked, in both the feed water and boiler blow-down water with regualr intervals so as to control the above said parameters as per ISI standards.
Chemical Requirement of Feed Water and Boiler Water for Low Pressure Boilers.
Serial No. Characteristic F.W. B.B.W.
1. Total Hardness as CaCo3 10 NIL
2. pH 8.5 to 9.5 11 to 12
3. Dissolved Oxygen 0.1 -
4. Silica as Sio2 upto 5 -
5. Total Alkalinity as CaCo3 - 700
6. Caustic alkalinity as CaCo3 - 350
7. Sodium sulphate as Na2SO3 - 30 - 50
8. Sulphate / Caustic Alkalinity - Ratio - 2.5 & Above
Units of Water Analysis: The most common unit is parts per million(Ppm) this can be better explained with the following example. 1ppm of salt means one milligram of salt in 1 litre of water for the high pressure boiler, still parts per billion is being used. But all parameters expressed as CaCo3 excepting few like Iron, silica, et.al. The units are expressed in CaCo3 because molecular weigh of calcium carbonate is 100.
In the High Pressure boilers normally Phosphate hideout will be a major problem. This is caused due improper ratio between Phosphate and Sodium. To sort out these problems Amine treatment is suggested. Amine treatment is also called as All Volatile Amine Treatment. By using this result can be achieved best manner. These are called neutralizing, film forming amine which doesn't add up to TDS of boiler water which is a critical parameter for High Pressure boilers.
To select the right treatment for a cooling water system it is necessary to understand the nature of problems that the water can cause. The main problems associated with an open recirculatory cooling water system are

1) Scaling and fouling
2) Corrosion
3) Microbiological growth

Scaling and Fouling Scaling is the precipitation of hard and adherent salts of relativity low soluble water constituents, like calcium and magnesium, on the metal surface. These scales have very poor thermal conductivity and their control is therefore absolutely essential for proper heat transfer efficiency. Some of the common scales are: 1. Calcium carbonate 2. Calcium sulphate 3. Silicate scales 4. Calcium orthophosphate 5. Magnesium salts 6. Iron salts

Calcium Carbonate This is the most commonly encountered scale in cooling water systems and it forms an extremely hard and adherent deposit.
Ca(HCO3)2 -----> CaCO3 + CO2 + H2O

Calcium bicarbonate is present in almost all cooling waters. Increasing temperature and pH decomposes the bicarbonate and CO2. Although calcium bicarbonate is moderately soluble in water, calcium carbonate is not. It precipitates at the hot spots of the heat exchangers and a dense adherent scale is often formed on the heat exchanger surfaces. Suspended matter may get entrapped into the CaCO3. Scale layer forming a deposit larger in volume, but lesser in density.

Calcium sulphate has much higher solubility than carbonate and this fact is used as the basis of scale control by acid free. The sulphate ions replace alkalinity enabling operation of the cooling system at higher cycles without exceeding carbonate solubility limits. Silicate Scales Silicate scales deposition must be prevented as they are extremely difficult to remove once formed. Silicate scaling can be prevented by: 1. Limiting the silica in the water to 160 mg/1 max. 2. (Mg mg/l as CaCO3) X (SiO2 mg/l as SiO2) should be kept below 35,000 Calcium orthophosphate Orthophosphate, in the cooling water, is formed by the reversion of polyphosphate, commonly used as an inhibitor. The orthophosphate readily combines with the calcium ions present in the water, forming the highly insoluble and trouble-some calcium orthophosphate sludge. This sludge has very poor thermal conductivity and can seriously affect heat transfer. The sludge also leads to under deposit corrosion and therefore its control and conditioning, if and when formed, is extremely important.

Magnesium salts have less scaling potential because a. They are generally more soluble than the calcium slats with the result that the late are precipitated first. b. Their concentration is usually considerably lower than that of calcium salts.

Factors that effect scaling
1. Temperature: The common scalants found in cooling water, CaCO3 and CaSO4, exhibit inverse solubility i.e. their solubility decreases with increasing temperature. Generally the amount of scale increases with increase in teperature.

2. pH or alkalinity: The solubility of CaCO3 decreases with increasing pH. Alkaline pH usually increases the scaling potential. However, some materials like silicate are more soluble in the alkaline range.

3. Solubility: For water borne deposits to form, the potential scaling material should be carried as a soluble constituent of the cooling water to some degree. Under the conditions, each potential scalant exhibits a definite solubility limit. Once this limit is exceeded, the solution gets supersaturated and precipitated forms leading to scaling. In addition, other dissolved solids also influence scale forming tendencies. In general, higher the level of scale forming dissolved solids, greater the chances of scale formation.
Fouling is the deposition of suspended matter, insoluble in water. They can be water borne or air borne. Some of the common foulants are: - Dirt and silt - Sand - Fly ash - Corrosion products - Natural Organics - Microbial matter - Macrobial matter The particulate matter generally accumulate in the low velocity areas or in areas where there is an abrupt change in the direction of flow or flow velocity.

Factors that affect fouling

1. Water characteristics: Fouling will depend on the suspended impurities carried by the water. Surface waters have greater fouling tendency, as the amount of suspended matter picked up by them is greater.

2. Temperature: Fouling tendency increases with increasing temperature. Heat transfer surfaces which are hotter than the cooling water, accelerate fouling.

3. Velocity: Fouling is greater in areas of low velocity while it is less severe in areas of high velocity. Normal velocity is 1 to 2 metres/second.

4. Microbial growth: Micro-organisms can deposit on any surface. Certain bacteria like iron bacteria utilize corrosion products leading to voluminous deposits. Also, slim secreted by bacteria, acts as binders and entrap material which normally would not have deposited.

5. Macrofouling: Certain macro-organisms like corbicula clam and mussels cause severe fouling problems due to their ability to proliferate on tube sheet faces and within tubing. As small as 0.2 mm in size at the onset corbicula are transported in to the cooling water system from water source as larvae or small juveniles. They have the ability to self-fertilize, grow and reproduce even at temperatures above 65 Degree F. They not only cause condenser tube blockages, but the decomposition of this trapped biogrowth can also lead to corrosion of stainless steel and copper alloy tubing during plant outages. Macroscopic biofouling can cause as much as 3-4% loss of production in a 600 mw power station, (according to a recent survey of the Electric Power Research Institute, U.S.A)

6. Corrosion products: Insoluble corrosion product mixes with other foulants like debris, micro-organisms, etc. and aggrevates fouling. It also serves as a nutrient for iron bacteria, promoting their growth.

7. Oil: Oil often adheres to the metal surface and has the ability to bind deposits. Oil has very poor thermal conductivity and can seriously affect heat transfer. Oil serves as a nutrient for micro -organisms reflecting in increased microbial growth. Oil also, prevents film forming inhibitors from reaching and passivating the metal surfaces. The percent reduction in overall hest transfer coefficient due to different scalants at varying scale thickness is given in Table 1 to Table 4. the overall efficiency of a power plant depends upon the vacuum is the exhaust steam condenser. Condensers operating at high vacuum permit expansion of the steam to the lowest possible temperature. The overall clean heat transfer coefficients for the condensers in thermal power plants are usually high and are therefore very sensitive to the scale thickness. A deposit thickness of even a fraction of a millimeter would result in drastic reduction in the heat transfer efficiency and in turn in condensers vaccum. The increased heat rejection will ultimately lead to drop in power generation. In the auxiliary system where water is used for bearing cooling, deposit formation would result in excessive heating of the metal leading to its eventual failure. It is always prudent to prevent deposit formation by suitable treatment on condensers/heat exchangers rather than letting it form and then cleaning it mechanically or chemically. Deposit formation will not only result in revenue loss due to lowered generation rate but will also lead to shortened equipment life due to periodic cleaning. Cleaning can result in irreplaceable metal loss besides the fact that it can never return the equipment to its original state of cleanliness. This also means that the period between successive cleanings is progressively reduced. Maintaining deposit free surfaces therefore assumes great importance and suitable conditioning of the circulating water is an absolute necessity. The constant generation rate derived with proper conditioning more than pays for then additional cost of treatment besides keeping the equipment healthy.
In the main condensers of a power generating unit, corrosion is a lesser problem due to the noble metallurgy generally involved. However it does become a problem in the auxiliary system where carbon steel is usually the material of construction. a. Corrosion is an electrochemical phenomenon by which a metal returns to its natural state. Being an electrochemical process, for corrosion to occur, a corrosion cell consisting of an anode, a cathode and an electrolyte must exist. At the anode, metal ions dissolve into the electrolyte (water). As the metal ions go into solution at the anode, electrons are left behind which migrate through the metal to the other points (cathode), where the cathodic reaction takes place i.e. the electron is consumed. Oxygen is always present in the cooling water system and reaction (i) is the most prevalent in completing the cell. The second reaction is in conditions of low pH due to excess acid feed and this is one of the reasons why corrosion is accelerated in acidic pH. Some important factors that affect Corrosion are:

1. pH: The corrosion potential increases as the pH is lowered.

2. Oxygen and other dissolved gases: Some of the other gases besides oxygen mentioned earlier that influence corrosion are CO2, NH3, H2S and Chlorine. The presence of these gases increases the corrosion potential of the circulating of water.

3. Dissolved and suspended solids. Normally higher solids content would mean increased corrosion potential due to the higher conductivity. However it is just the reverse because the hardness salts presents in the water forms a passive film on the metal, which inhibits corrosion. This is the reason why soft water is more corrosive that hard water. Suspended solids influence corrosion by erosive or abrasive action. They can also settle on metal surface producing localized corrosion cells.

4. Microbial growth: Microbial growth promotes the formation of corrosion cells and also the by products of some organisms are corrosive.

5. Velocity: In high velocity and turbulent waters, oxygen is rapidly distributed and passivation layer of corrosion inhibitors are often removed resulting in increased corrosion. High velocity can also lead to erosion of metal surface, protective films and oxides. At the same time low velocity can lead to deposition giving rise to localized corrosion cells.

6. Temperature: As the temperature increases the diffusion of oxygen to the metal surface also increases, promoting corrosion. Above 70 deg.cel. the loss of dissolved oxygen exceeds the amount made available in diffusion, and a decreased in corrosion rate occurs.
Cooling towers are an excellent example of water systems that provide optimum conditions for microbial growth. Temperature and pH are usually within the ideal ranges and generally there is an abundance of nutrients required for their growth such as organic matter, organic salts and sun light. Under these conditions, it is conceivable that bacterial concentration may increase by six million times while during the same time, inorganic salts may concentrate only six times. Micro organism enter a cooling tower through the sources. They may be present in the make up water supply or in the dust and air, which enter the cooling tower. The major problems microbes are: 1. Algae. 2. Fungi. 3. Bacteria.

Algae: Air, water, and sunlight are the three basic requirement for algae growth. The distribution decks and side walls of a cooling tower fulfill all these requirements and there fore represents an excellent growth environment for algae.

Fungi: Fungi lack chlorophyll and are therefore non-photo synthetic, resulting in dependence on nutrients provided by organic matter. In cooling water systems fungi can used wood as a source of nutrients an can destroy the wood.

Bacteria: There are many kinds of bacteria found in cooling water systems. 1. Pseudomonas. 2. Sulphate reducing bacteria. 3. Iron bacteria. 4. Nitrifying Bacteria. Identifying these bacteria in cooling water there are many types of procedures available which include both micro biological testing and inorganic testing for further details contact our technical personnel.
Scale Prevention: a. Over designing of systems. b. Limiting the cycle of concentration. c. Softening the make up water. d. Acid feed to maintain the pH between 6.0 and 6.5. e. Mechanical means like increase water velocity or using sponge balls for on pipe line cleaning. f. Periodical cleaning. g. Treatment with Chemicals. In all these methods there are advantages and disadvantages. Hence let us look at the TREATMENT WITH CHEMICALS. Treatment with chemicals are most practical and cost effective method to control deposition. Scale formation is controlled by the mechanize of threshold inhibition and crystal distortion. Threshold phenomenon is a mechanism by which substochimetric amounts of the chemical prevents or retards the growth of scale forming crystals. These chemicals are absorbed on the surface of the crystals and, interface with the nucleation of the scalant crystals preventing orderly lattice type growth. Crystal formation is retarded and when they are formed they are highly distorted, leading to a soft friable scale, which can be easily dispersed by the movement of water. This property permits operation of the cooling water systems at higher pH, and high cycle of concentration.
Corrosion inhibitors prevents the metal from reverting to its neutral oxide state. Depending on the corrosion reaction it controls, a corrosion inhibitors can be anodic, cathodic or general. Some of the various chemicals used for corrosion prevention: Chromate- Poly phospate, Zinc- poly phosphates, Zinc- organo phosphonate, organo phosphonate-azole.
Chemical that kill micro organisms are termed as biocides. It is difficult to kill the organisms in the cooling water systems. What is best achieved is the maximum killing and control of growth. The efficiency of the biocides are depending upon the nature and amount of pollutant such as hydrocarbons, pH, temperature, and other nutrients such as orthophosphates present in the water. Some of the best biocides are: Chlorine, Methylene bisthiocyanates, Metallic biocides, Aldehydes, Quaternary Ammonium Compound, There are other best biocides are available to control microbial growth in the cooling water systems. Suggesting of biocides should be based on various parameters.
The success of any treatment program is based on the parameters being maintained and to achieve this closed monitoring of water parameters and chemicals dosage should carried out. The evaluation should be done for, 1. Corrosion. 2. Scale & Fouling. 3. Micro biological growth. The method of monitoring these problems may be referred in our site by navigating technical service page.
The use of process chemicals in the manufacture of raw sugar has evolved rapidly over the past thirty years. Innovations in every phase of the manufacturing process have been widely reported with varying degrees of success. Yet while one mill can show improvements resulting in direct economics benefits, there another mill that can show that thy do not work. With this obvious disparity there is often lack of confidence in process chemicals. The result is that they are often inadequately used and improperly applied. Process chemicals do work, but there are multitudes if ever changing operational factors that alter the performance and hence the intended result. Often times factors beyond the control of the mill are the culprit briefly type of soil variety of cane method of harvesting, time between cutting and processing and even the weather dictate the conditions under which the mill must operate within the mill itself, mechanical problems leading to inefficient processing affect the quality of the product from grinding through final molasses exhaustion. If process chemicals are in use but not adjusted to compensate for the abnormal conditions, they are very often blamed for not working. In some mills is common practice to feed chemicals only when there is a recognized problem and to stop feeding when it is behaved that the problem is resolved. And in the extreme then use may be discontinued because it was perceived that they did not work. It is extremely important to recognize that process chemicals should be used continuously without interruption in order achieve additions sucrose recovery. Application rate should be adjusted to correspond to changed in mill conditions as determined by proper analytical method but their usage should never be stopped on the belief that money will be saved in the end. Testing evaluation and data gathering should become routine in the daily operations of the mill. For example in one mill six different points are sampled and a 24-hour composite of each sample point to analyzed for dextran. By trending historical data, the mill can predicate anticipated operational difficulties. This type of sampling and testing procedure should be expanded to serve as early warning of changed throughout the production process so that appropriate actions can be taken. By interpreting test data and identifying changes in the process stream, for whatever reason, process chemicals can be used to the mill advantage.