Steam Boiler: Water Treatment System

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Chlorination System in Power Plant

The chlorination system in power plant or dosing liquid chemicals is installed to treat the water (scale inhibition and bio-fouling protection) to use in main cooling water system.

Chlorination system shall be supplied to provide continuous and intermittent shock chlorine dosing to the seawater intake to fulfill the need of the chlorine for the whole Power Plantpurposes.

The chlorination system shall have sufficient capacity to allow intermittent shock dosing of hypochlorite selection into the intake CW pump which can then be directed into either or the circulating water systems by appropriate sectional isolation of the CW discharge header.

It is the intent of this specification that a proven and reliable system shall be provided. The chemicals and dosage rate shall be established to control of corrosion, bio fouling and scale formation efficiently and also maintaining residual chlorine in the cooling water discharge from the main condensers considering the Environmental Regulation, plant performance and life, water quality variations, economies of chemical, etc.

The chlorination system shall consist of the following dosing systems:

Sodium Hypochlorite dosing system with dosing pumps
Valves and piping
Chlorination dosing package, this package has dosing pumps. A test kit for dosing pump is provided for measuring the bacterial content. For the common drives like the filing pump & the chemical drain pump a receptacle is provided for each of the pumps.

The chlorination system shall be arranged and designed to provide complete flexibility of operation in terms of solution strength dosing quantity and treatment timings. The solution shall be injected into the sumps by injection pump from the chemical dosing tank, however.

The chlorination system should be equipped with all of the system in a complete set including piping, valves, pumps, control and instrumentation, equipment and accessories as required for normal operation. The system shall be including to the following component but not limited to:

NaOCl dosing pumps
Bromine dosing pumps
Scale Inhibitor dosing pumps
NaOCI dosing tank
Bromine dosing tank
Scale Inhibition dosing tank
Chemical drain pumps
Residual Chlorine Analyzer skid comprising of Y-type Strainer, Self Priming Pump, and Residual Chlorine Analyzer
Chemical agitator equipment (including automatic stirrer) and accessories
Safety equipment including as follow but not limited to:

Eye Wash Station and Safety Shower
Warning Horn
Breathing apparatus (with mask and Glove)

All components of chlorination system shall be made with suitable materials and has good corrosion / chemical resistant for long time operation.

Feedwater Treatment, Boiler Water Conditioning and Steam Purity

Feedwater treatment, boiler water conditioning and steam purity is important to be known. It is very important to monitor and control boiler water chemistry to prevent failures due to corrosion. The single largest cause of pressure part failures is waterside corrosion.

The successful operation of steam generating equipment depends upon a firm control of feed water and boiler water to assure free from scale formation and corrosion due to water and steam in the boiler.

Scale formation in boilers is prevented by providing good make-up water to the feedwater system and by avoiding condensate contamination. For higher pressure of boiler, the make-up must be of condensate quality such as provided by evaporation or by demineralization.

Corrosion of metal surfaces in contact with water and steam constitutes the major maintenance expense to the power industry. The condensate and feed water must be free of dissolved corrosive gases and the pH of the water must be properly adjusted to prevent the attack of metal surfaces.

The oxygen content in the feed water must be reduced to low levels by effective deaeration in the condenser and in deaerating heaters. Care must be taken to prevent the introduction of air into heater drips which may be added to the condensate. Make-up water from storage tanks should not be added directly to the feed water system without deaeration. Minimum forced boiler outage time has been realized where the oxygen content has been reduced and held below 0.01 ppm. It is important to maintain a chemical reducing environment in the boiler water and chemicals such as hydrazine have been used effectively to achieve this.

Low pH feed water readily dissolves iron and copper in the pre-boiler equipment. These corrosion products when introduced into the boiler will contribute to the corrosion of boiler steam generating surfaces. Oxides of iron and copper may permit the diffusion of boiler water to the heated surfaces of the unit and cause locally high concentrations of boiler water salines that result in the attack of the tube metal.

The pick-up of metals from pre-boiler surfaces can be minimized by the addition of volatile alkaline chemicals that raise the pH of the feed water. Ammonia or various amines, added Lo maintain a pH range of 8.5 - 9.0 have produced the best results.

The philosophy of control of boiler water pH varies widely. The caustic-based treatment, the coordinated phosphate treatment and the volatile treatment have all been successfully applied however the latter two methods of control are preferred in higher pressure boilers.

For this boiler, the coordinated phosphate treatment is adopted with using sodium-phosphate (Na3PO4) and hydrazine (N2H4).

Recommended Water Quality

The recommended limitation value of feed water and boiler water is as follows:

		Feed Water	Boiler Water
pH at 25 degC		8.5 – 9.0	9.3 – 9.8
Hardness (CaCO3)	ppm	0.0	-
Micro-Mhos/cm at 25 degC		-	< 200
Dissolved solids	ppm	-	< 100
Oxygen	ppm	< 0.007	-
Silica	ppm	-	< 1.5
Al	ppm	< 0.03	-
Fe	ppm	< 0.03	-
Cu	ppm	< 0.01	-
Hydrazine (N2H4)	ppm	> 0.02	-
Phosphate (PO4)	ppm	-	2 - 6

Boiler Blowdown

Boiler blowdown will be a really essential aspect of almost any water treatment application. Boiler blowdown has function to control content level of impurities in boiler water. Determination amount of boiler blowdown is crucial: very much will leads to high cost of chemical water treatment and energy loss; very little will leads to too much content level of impurities. There are not specific rules to regulate amount of boiler blowdown due to variation in quality of water may differ from one location to other location. It may range from 1% until 25% according to the flow of feedwater.

Blowdown could be performed intermittently or continuously. Boiler blowdown can be performed either from the bottom of steam drum, header, or mud drum, or it could be performed from the base of steam boiler. The following are several principles to assist determine an efficient boiler blowdown application:

For boiler with fire tube type, blowdown may be done either intermittently or continuously. It could be blown down through the base of boiler. Timeframe, rate of recurrence, and type be determined by operating conditions, design boiler, and the kind of water treatment system.
For steam boiler which has drum type, the content level of water must be regulated through blowdown via steam drum. Continuous boiler blowdown is definitely recommended.
Likewise in steam boiler with drum type, blowdown through bottom header or mud drum will perform removal of suspended solids in steam boiler. Attempting to manage the content level of impurities through blowdown from this place could result in a serious interruption of water circulation and leading to deterioration to steam boiler. If bottom blowdown is performed, it must be in quick timeframe or intermittent. This condition is established by operating conditions, design boiler, and also the deposition rate of suspended solids.

Removal of Suspended Solids

Feedwater of boiler without treatment usually consists of suspended solids such as bacteria, silt and mud. When the suspended solid is left in the feedwater, this substance can certainly lead to difficulties, like deposits or foaming in steam boiler.

Removal of suspended solids can be performed by filtration or clarification process. One popular system requires the two processes; the water is initially distributed via a clarifier that eliminates almost the entire suspended solid, then the rest is eliminated by filter.

To carry out the clarification process, a flocculent assist is put together with raw water in both water feed series and in the “quick mixture area” of the clarifier. Main clarification takes place in “quick mixture area”, in which compact solids are made. The solids raise larger in the “slow mixture area” and also settle in “settle area”. The producing sludge is eliminated through base of device though clarified water is moved through the top part by stuffed towards a launder (a unit which features significantly such as a pool skimmer). A rake at base of clarifier goes gradually via settled sludge to maintain water from solidifying.

Other removal of suspended solids such as filtration could be performed some various methods. the majority of popular filters are granular filters medium, created from garnet, anthracite, and sand. Different kinds of filters, such as strainers, sock filters, and cartridge filters are employed in several installations. Filter bed level, filter medium option, and some other design variables are established by the standard of boiler water specifications.

Oxygen Scavenger

Nearly all of oxygen in feedwater of steam boiler is eliminated through deaerator nevertheless some amounts of oxygen is continue to current that may, eventually lead to corrosion in steam boiler. To avoid that, oxygen scavenger is included to boiler water, ideally in deaerator storage space tank thus the scavenger can get optimum time period to start up by using residual oxygen. Within specific conditions, for example when feedwater of boiler is employed for attemperation to decrease steam temperature, different places are more suitable.

The best generally applied oxygen scavenger can be sodium sulfite. It is low-cost, more efficient and quickly reacts by using the trace quantities of oxygen. It might be simply calculated in boiler water.

Generally oxygen scavenger is good solution to eliminate oxygen. There are situations in higher pressure boilers (commonly preceding 900 psig), in which several of sulfite might decompose and get into steam, leading to problems in condensing steam turbines and condensate systems. In this instance, replacement (generally organic-dependent) oxygen scavengers could be utilized.

Innovative oxygen scavengers had been presented nowadays. The determination to utilize oxygen scavengers or depend on sodium sulfite must solely be designed by these experienced to generate water treatment of boiler conclusions. In all conditions the modern product must be properly included and its performance considered relating with working procedures.

Silica Removal from Boiler Water

Silica can not be removed by exchange of cation - hydrogen or exchange of sodium zeolite. Silica removal can be performed partially in the process of lime - soda, either in cold or hot. Silica is highly undesirable impurity because it can cause formation of scale which attached very strong.

Silica removal from boiler water can be done by using dolomite lime or active magnesia in the softener. If using coagulation and previous deposition, some silica will can be removed by coagulate ferry. This substance is very suitable if concentration of silica is in additive water.

This method can not remove all soluble silica, but may reduce its concentration until sufficiently low so that blowdown disposal in steam boiler can be used to prevent scale formation inside boiler when it's done properly. The most commonly treatment that is used to produce water that contains very little silica is demineralization.

Silica in Boiler Water

Silica is not soluble either in water or in acid and silica is usually in the form of colloids. Silica is found in almost all rocks and susceptible to weathering. The main natural source of silica is mineral quartz. Anthropogenic source of silica is relatively very small.

The presence of silica in water does not make problem for human kind because it is not toxic to living things. However, for water which is designated for industrial use, the presence of silica can cause problem on piping system and other equipment because it can form deposit of silica.

The deposit of silica in boiler water which occurs is as follow:

Analcite (Sodium alumina silicate - Na₂O.Al₂O₃.4SiO₂.2H₂O) is formed as result of the aluminum content in boiler water through feedwater. Aluminum which is usually delivered is aluminum that is used in pre-treatment in which less supervision occurs in its implementation. Little aluminum content in feedwater can cause high deposit of silica in boiler water. Therefore feedwater treatment must be controlled to eliminate aluminum and silica.

Acmite (Sodium Ferrous Silica - Na₂Fe₂O₃ 4SiO₂) and crust Fe - Si can be formed from corrosion result. Acmite can be found easily in connection of boiler parts where it easy to occur corrosion.

What is Alkalinity?

Alkalinity is defined as water capacity to neutralize acid, or the quantity of anions in water which can neutralize hydrogen cations. Composer alkalinity water are bicarbonate anion (HCO₃^-), carbonate (CO₃^2-) and hydroxide (OH^-). Borate (H₂BO₃^-), silicate (HSiO₃^-), phosphate (HPO₄^2- and H₂PO₄^-), sulfide (HS^-), and ammonia (NH₃) also contribute to alkalinity. However, the main formers of alkalinity are bicarbonate, carbonate, and hydroxide. Among the three ions, the bicarbonate present in most natural water.

Alkalinity is the water defenses against acidification. In natural water, alkalinity mostly due to the presence of bicarbonate and the remaining is caused by carbonate and hydroxide.

Some levels of alkalinity content are required in boiler water, so the complete removal of alkalinity in the boiler is rare to be performed except in demineralization treatment. Some of alkalinity is also required to provide optimum pH in feedwater to prevent corrosion in piping and equipment.

Alkalinity form is in HCO₃^-, CO₃^2-, or OH^-. If water city is made in softening, alkalinity is usually formed in bicarbonate (HCO₃^-) form; if lime adhesive is reduced, its content usually excess carbonate (CO₃^2-), but water may also contain some hydroxides (OH^-). When the bicarbonate and carbonate having heat in the boiler, bicarbonate and carbonate rupture to release CO₂ as in the following equation:

2NaHCO₃ → Na₂CO₃ + H₂O + CO₂ ↑

Natrium carbonate is then split again into:

Na₂CO₃ + H₂O → 2NaOH + CO₂ ↑

Carbon dioxide gas does not dissolve when the steam becomes solid, producing corrosive carbonic acid:

CO₂ + H₂O ↔ H₂CO₃ ↔ H⁺ + HCO₃^-

The amount of CO₂ produced is proportional to alkalinity. Because of an alkalinity that delivers twice as much CO₂ formed from HCO₃^- by CO₃^2- due to interference of bicarbonate is the sum of reactions above. Carbonic acid is usually neutralized with chemical treatment at each steam directly or indirectly through boiler to produce pH around 8.5 to 9.0. Reduction of alkalinity in the boiler feed water is necessary to minimize the formation of CO₂ and reduce costs of chemical treatment.

Hardness Testing

Hardness is usually expressed as CaCO₃. Several methods of hardness testing can be used to analyze hardness. Some of methods of hardness testing that are commonly used as follow:

Hardness testing with Total Method

This method is used to calculate hardness based on concentration of divalent ions in water such as Ca²⁺, Mg²⁺, and SR²⁺. Calculation of hardness based on concentration of divalent ions can be calculated by using following equation:

Hardness as CaCO₃ (mg/l) = M²⁺ (mg/l) x (50 / equivalent weight M²⁺)

Where M²⁺ = divalent ion metal

Example: From the analysis of water is known that water contain ions (mg / l)and only divalent cations Ca²⁺, Mg²⁺, and SR²⁺ that are calculated as the cause of hardness, so total hardness based on concentration and equivalent weight of each divalent ion of hardness as following table:

Figure 1: Table of Hardness Testing with Total Method

Hardness testing with EDTA (Ethylenediamine Tetra Eacetic Acid) Titration Method

Complexometri titration reaction includes the formation of complex ions or formation of neutral molecules that dissociate in solution. Thus fundamental requirement of complex formation is high level of solubility. End point titration is determined by metal indicator or by potentiometer and spectrophotometer.

This method uses solution of EDTA (ethylenediamine tetra eacetic acid) as the standard solution. Metal indicator is used to determine the end point of titration. The indicator is usually used is Eriochrome Black T (EBT).

Eriochrome Black T as indicator will form complex compound entirely with EDTA which is added, in other words, the addition of excess EDTA solution is indicated by changes in solution color from red to blue. This reaction is running complete at pH 8-10. Buffer solution is added to maintain pH solution. Ca²⁺ and Mg²⁺ will form complex compounds in red wine color with EBT.

M²⁺ + EBT →(M EBT)_{complex compounds in red wine color}

Changes will more clearly when the pH gets higher, but high pH can cause hardness ions loss from solution, due to precipitation of Mg(OH)₂ and CaCO₃. At pH> 9, CaCO₃ already begin to form.

Carbonate Hardness and Non-carbonate Hardness

Classification of hardness can be classified based anion that has association with metal ion namely carbonate hardness and non-carbonate hardness. In the carbonate hardness, calcium and magnesium ions associated with CO₃^2-and HCO^3-. In the non-carbonate hardness, calcium and magnesium ions associated with SO₄^2-, Cl^-and NO^3-. Carbonate hardness very sensitive to heat and easy to make sediment at high temperatures such as the following reaction:

Ca(HCO₃)₂ → CaCO₃ _sediment + CO₂ + H₂O

Mg(HCO₃)₂ → Mg(OH)_{2 sediment} + 2CO₂

Therefore, carbonate hardness can be called as temporary hardness. Non-carbonate hardness can be called as permanent hardness because calcium and magnesium that bind with sulfate and chloride, does not make sediment and hardness values does not change despite in high temperature.

Part of the total hardness is equivalent to bicarbonate that participates in the presence of carbonate alkalinity in accordance with carbonate hardness. Since the alkalinity and hardness are determined in CaCO₃, carbonate hardness can be calculated by following formula:

If the total alkalinity < total hardness so carbonate hardness = total alkalinity.

If the total alkalinity ≥ total hardness so carbonate hardness = total hardness.

Non-carbonate hardness = total hardness - carbonate hardness.

If total alkalinity exceeds total hardness so some of anion constituent of alkalinity (bicarbonate and carbonate) associated with single valence cations (monovalent), for example, potassium (K⁺) and natrium (Na⁺) that are not detected in determination of hardness. Conversely, if total hardness exceeds total alkalinity so some of cation constituent of hardness (calcium and magnesium) bind to sulfate (SO₄^2-), chloride (Cl^-), silicate (SiO₃^2-) or nitrate (NO^3-) that are not detected in determination of alkalinity. Therefore the relationship between hardness and alkalinity is not always positive; or greater hardness is not always accompanied with higher alkalinity and vice versa.

Calcium and Magnesium Hardness

Water hardness can be classified based on metal ion namely calcium hardness and magnesium hardness. Most of natural water has calcium and magnesium hardness due to calcium and magnesium ions. Calcium and magnesium hardness often need to be known to determine amount of lime and soda ash which is needed in the process of water softening (lime-soda ash softening). If the calcium hardness value is known so magnesium hardness can be determined through the following equation:

Magnesium hardness = Total Hardness - Calcium hardness

In determining hardness value of total hardness, calcium hardness and magnesium hardness, the presence of iron and manganese are considered as nuisance because it can react with the reagent which is used. Therefore, calcium hardness is assumed greater than the level of calcium ions, and vice versa. The following equation can be used to get the level of calcium ions and magnesium ions of hardness value:

Levels of Ca²⁺ (mg/liter) = 0.4 x calcium hardness

Levels of Mg²⁺ (mg /liter) = 0.243 x magnesium hardness

Classification of Hardness

Classification of hardness can be categorized based on some parameters such as based on metal ions, based on anion that has association with metal ion and based on CaCO3 content.

Classification of hardness based on metal ion can be divided as follow:

Classification of hardness based on anion that has association with metal ion can be divided as follow:

Classification of hardness based on CaCO3 content can be divided as follow:

Soft hardness if contains 0-75 mg/l CaCO3 content.
Semi hardness if contains 75-150 mg/l CaCO3 content.
Hardness if contains 150-300 mg/l CaCO3 content.
Very hardness if contains more than 300 mg/l CaCO3 content.

Definition of Hardness

Definition of hardness is water properties that is caused by the presence of ions or metal cations which has valence two. Cations are the main cause of hardness. The cations are Ca²⁺, Mg²⁺, SR²⁺, Fe²⁺ and Mn²⁺, while anions contained in the water are HCO^3-, SO₄^2-, Cl^-, NO^3-.

Water hardness is generally described as reaction of water to soap to produce foam or ability to cause scale or crust on hot water pipes, boilers, and other metal equipment. Water hardness is very important with respect to the various uses of water, because of the tendency to form crust. Water that has very low hardness, with only little soap will have a lot of foam, but if there is high water hardness, can cause the waste of soap. Water hardness should be optimum, because if too high will cause the crust, and if too low will cause corrosion at high temperatures.

Hardness of water varies from place to place. Generally, surface water has more hardness than ground water. Water hardness depends on the natural geological formations and with what water is in contact. The water hardness can be found in England, South Atlantic, North Pacific: Iowa, India, Arizona, Mexico because they are countries that has fairly high water hardness.

Reverse Osmosis System

Reverse Osmosis system is the movement process of water from low concentration solution of to high concentration solution due to osmotic pressure. This movement process through semi permeable membrane, where movement process of water will stop after the concentration of two solutions is same. Reverse Osmosis system requires hydrostatic pressure higher than the difference of osmotic pressure so that water can flow from the higher concentration solution through semi permeable membrane.

Reverse Osmosis systems are generally composed of four processes as follow:

Pretreatment

Feedwater is first processed to fit the conditions of membrane to remove suspended solids, adjusting pH operations and add inhibitor to control scaling caused by constituents such as calcium sulfate.

Giving pressure

Feed water that has been processed, its pressure will be increased by the pump up to the desired operating pressure to conform to membrane and feed water salinity.

Membrane separation

Semi permeable membrane inhibits the course of feed water through it. Water output from membrane produce clean water which is called permeates, and retained on the membrane is called concentrate. However, because there are no membranes that can work 100% perfect, then there is a small part of salt that can still pass through membrane.

Stabilization

Water output membrane (product water) is usually adjusted to pH first before being transferred to distribution system.

Boiler Feed Water Treatment

Water used in boilers is water which the content of mineral had been released and filtered (demin water) because the mineral content in water can damage the parts of boiler. To eliminate the mineral content in water, can use the flocculation and clarification steps. Flocculation is the process of removal of particles suspended in water either large or colloidal compounds are suspended in water. Content levels of these particles are expressed as turbidity. The flocculation steps are:

Filtration process

Filtration is the process of filtering large-sized dirt. The filtered impurities are organic compounds, fine particles, color compounds and microorganisms.

Coagulation

Coagulation is done to remove dirt impurities form compounds that are ionic.

Water generated from the process above is called with demineralized water (demin water). But in demin water still contained dissolved gases such as carbon dioxide and oxygen can cause corrosion of pipes and tubes. To eliminate the solution of these gases is performing deaeration process. Deaeration process is performed in the deaerator process on the two stages, namely:

Mechanically

Deaeration process mechanically is done by stripping process with low steam (LS). This can eliminate the solution of oxygen and carbon dioxide by up to 0.007 ppm.

Chemically

Deaeration processes chemically are carried out by injecting solution of hydrazine (N2H4). The end result of deaeration process is called Boiler Feed Water (BFW) which is then used as feed water to the steam boiler.

Control Phosphate in Steam Boiler

Control phosphate in steam boiler is controlling process of phosphate which is supplied into steam boiler. Phosphate is soluble in water alkalinity in the boiler so that the concentration can be maintained by adding sodium phosphate which having different alkalinity.

Depending on the substances contained in the feed water and desired level of alkalinity in the boiler water and also the selected phosphate, so the control of phosphate can be equipped with add alkali in the form of sodium carbonate or sodium hydroxide.

The main function of phosphate in the application of high pressure is to provide a defense to alkalinity of boiler water. Phosphate solution can be mixed from three basic sources of phosphate are: sodium phosphate, disodium phosphate and trisodium phosphate.

The presence of hydrogen cation in the phosphate compound will affect amount of alkalinity of boiler water and relationship of boiler water pH. During the pressure of steam boiler increases, the number of reduced alkalinity in order to minimize ability to rust.

With the addition of certain chemicals, so the salts of calcium and magnesium as calcium phosphate and magnesium is precipitated as magnesium hydroxide or magnesium silica if there is silica ions.

Steam Carryover in Boiler Water

Steam carryover occurs when minerals from boiler water come out with steam into boiler parts such as superheater, reheater, turbine, and the others. Contaminated steam will make these boiler parts damage because solid particle in the steam will hit superheater tubes or turbine blades so produce momentum energy when hit these particles.

Steam carryover or contaminated steam can be caused by some parameters as follow:

- Sudden load changes

- Operation boiler is not controlled well

- Steam separator in steam drum is not working well

- Water treatment is not performed perfectly or there is leakage of impurities in feedwater system

Steam carryover or contaminated steam can be avoided by holding the dissolved solids in boiler water below a certain level through a systematic analysis and control on the provision of chemicals and blow down.

Coagulation and Flocculation in Boiler Water

Coagulation and flocculation is the process to give coagulant and flocculants materials into boiler water by injection. Coagulation is the neutralization process of charges so the particles can be very close to one another. Flocculation is the unification process between particles that had been already much closed to one another so the particles will attract each other and form flock. Chemicals which are injected to reduce turbidity at inlet clarifier as follow:

Alum Sulfate (Al₂(SO₄) . 18 H₂O)

Alum sulfate serves to form clump of suspended particles in water. When alum is contacted with water then hydrolysis will occur which produces aluminum hydroxide and sulfuric acid. The addition of alum depends on water turbidity and flow rate. The following below is the reaction of alum sulfate:

Al₂(SO₄) . 18 H₂O + 6H₂O → 2Al(OH)₃ + 3H₂SO₄ + 18H₂O

Al(OH)₃ in the form of colloidal will settle with other impurities and shipped with water while H₂SO₄ will result acidic water.

Caustic Soda (NaOH)

Caustic soda serves to neutralize the acid caused by reaction in previous process. Concentration of caustic soda is added depends on acidity of solution. pH expected between 6-8. The following below is the reaction of caustic soda:

H₂SO + 2NaOH → Na₂SO₄ + 2H₂O

Chlorine (Cl₂)

The addition of chlorine is intended to kill microorganisms in water, in addition it also prevent the growth of moss on clarifier wall which can interfere the next process.

Coagulant Aid (Polymer)

Coagulant aid serves to accelerate deposition process because the addition of this material will bind particles that had agglomerated before into bigger clumps (flock) so make it easier and faster to settle.

Boiler Water Specification

The sources of water which is used for boiler water are from sea, river, boreholes, rain, and other water sources. The quality of each water source is not same although using same type; it is influenced by environment in each water sources. Water source from river had been contaminated by people’s activity and industrial activity; therefore it needs to be performed water treatment system.

Boiler water specification must meet the requirement to prevent further problem in operation of boiler. The boiler water must be free from mineral and other impurities that are not desired to reduction of efficiency steam boiler.

Boiler water specification must meet certain prerequisites as described in following below:

PH Condensate = 8.0 – 9.0

Sulfite residual = 20 – 50 ppm

Phosphate residual = 20 – 50 ppm

Iron = max 2 ppm

Silica = max 150 ppm

T. Hardness = -

O – Alkalinity = min 2.5 x SiO₂

M – Alkalinity = max 800

P – Alkalinity = -

TDS = max 3500 ppm

Conductivity = max 500 µhos/cm

PH = 10.5 – 11.5

Condensate Recovery in Power Plant

Condensate is essentially distilled water which is originally taken from steam out from turbine generator. Steam will be condensed into condensate form in condenser. Condensate has ideal quality as boiler water, so condensate recovery is performed to be supplied into steam boiler again. But if the condensate is contaminated then condensate should not be used for further processing.

Condensate is the result of heat exchanger process. Steam should be totally converted into condensate (liquid form). If there is steam contain in condensate, steam should be trapped with equipment which is called steam trap. Pressure and temperature of steam from turbine generator after pass condenser will be reduced by flash steam process. Flash steam is a process to discharge steam into atmosphere. The amount of steam which is discharged into atmosphere is approximately 10% - 15%.

Condensates will losses its mass about 13% if flash steam is performed. The quality of condensate should be maintained so can be used again and distributed to deaerator to get further treatment. The following below is example figure that show circuit of steam and condensate.

Figure 1: Circuit of Steam and Condensate