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Water treatment Chemicals & its Philosophy

BY
COLONEL.DR
BAHAA BADR
CHEMICAL CONSULTANT

Water is our most important resource, when it is used in heating & cooling systems.

There are number of problems that can arise independently the sources of supply ie. Lakes, Rivers, Well or Municipality.

It is difficult to envision the range of problems that the life sustaining substance can cause.

Hardness Salts primarily calcium and magnesium carbonates have reverse solubility this means that these salts are at equilibrium at any given temperature but as water is heated, this equilibrium is upset and in order to re-establish equilibrium at the elevated temperature the amount of hardness salts that water can keep in solution must decrease.

The result of all this is precipitation of the excess hardness which manifests itself as a scale deposit on heat transfer surfaces.

This deposit acts as an insulator and inhibits the efficient transfer of heat.

The result is fuel inefficiencies with boiler tube rupture due to overheating and increase maintains cost.

Microbiological organisms can infect ion exchange resins, rendering them useless.

Treatment programs whether applied to Steam Generators, Open Recalculating Cooling Systems, Hot Water or Chilled Water Systems are designed to maximize the useful life of welted component at an acceptable cost while minimized negative environmental impact on the receiving streams.

Normally treatment is through mechanical means i.e. Filtration, clarification, Ion Exchange, Degasification and Decoration.

The effluent from these pre-treatment streams is then chemically treated to render benign those impurities that have escaped the pre treatment phase this is accomplished through the judicious application of chemical formulation The appropriate product in right amount at the proper feed point (optimizing chemical feed).

Where replacement of existing treatment program would result in cost saving and for improved protection then such a change is proposed and the recommended program is evaluated for both performance and cost effectiveness.

Our approach provides a true service program rather then a sale effort that so disguised as a service program.

It is one of our primary goals to design a water treatment program that is fully compatible with plant operations.

A well designed water treatment program complements plant operations rather than call for changes in procedures to accommodate the treatment program.

No water treatment programs will live up to its potential in the absence of proper control.

Why Should Purify Water

Water is nature's most wonderful, most abundant and most useful compound.

Presence of impurities in the water, limiting its application and requires treatment before water can be used.

The substance contained in natural or raw water can be listed broadly as follows:-

1) Suspended Impurities are dispersion of solid particles that are large enough to be removed by filtration or settling.

The particles which are lighter than water float on the surface.

Suspended impurities include:

(a) Clay silt --- causes turbidity
(b) Bacteria --- some cause disease.
(c) Algae, Protozoa ---- cause order, colour and turbidity.

2) Dissolved inorganic impurities. Some impurities are dissolved in water when it moves over the rocks, soil, etc., These include :

Calcium and Magnesium Bicarbonate--causes alkalinity and hardness.
Carbonate-- ---- Do -----
Sulphate--cause hardness
Chloride ---- ------- Do -----
Sodium Bicarbonate--causes alkalinity and softening.
Carbonate-- ------- Do -----
Fluride--cause molted enamel of teeth
Chloride--cause taste
Metals and Oxide Mangages--produces blak or brown colour
Iron Oxide--cause taste, hardness, corrosiveness and red colour.
Lead--causes arsenic poisoning
Gases Hydrogen sulphide--causes foul rolten egg smell, acidity and
corrosion of metals

3) Organic Impurities include :
Suspended Vegetable---imparts colour taste and acidity.
Animal (dead) ---- produces harmful disease germs.

Dissolved Vegetable ---- produces bacterias
Animal ---- causes pollution of water and produces disease germs.

1) pH
2) Conductivity
3) Total Dissolved Solids
4) Alkalinity
5) Total Hardness
6) Chlorides
7) Iron
Silica
9) Sulphite

pH:-
pH is a measure of the concentration of hydrogen ion. It is defined as follows:

pH = -log(H+)

where (H+) is the activity of the hydrogen ion (activity in most cases is equivalent to concentration

A neutral solution is defined to have a pH of 7 and as the solution becomes more acidic (an excess of H+ ion) the pH drops below 7.
As the solution becomes more basic (an excess of OH- ion) the pH increases.
The pH scale varies between pH = 1 where the H+ concentration is 1 Molar (very acidic) to pH = 14 where the OH- concentration is 1 Molar (very basic).

Alkalinity:-

Alkalinity in water is due to presence of bicarbonates, carbonates and hydroxyed ions.
In raw water alkalinity is mainly due to bicarbonates; however, sometime carbonates may also be present.
Out of three ions only two ions can exist in any systems. That is OH, CO3, or HCO3 can either exist alone or in combination with one more ions.

P Alkalinity :-Alkalinity to phenolphthalein represents alkalinity due to OH ions plus ½ CO3 (pH 8.3)

Total Alkalinity :- Alkalinity to methyl orange represents alkalinity due to OH ion plus CO3 ion plus HCO3 ions (pH 4.3)

Relation between HO, CO3, HCO3 and total Alkalinity
I / Hydroxide is Carbonates is Bicarbonate is Total Alkalinity is
P = Nil Nil Nil M M
2P < M Nil 2P M – 2P M
2P = M Nil 2P Nil M
2P > M 2P – M 2(M – P) Nil M
P > M M Nil Nil M

Total Hardness

Total Hardness of water represents the sum of the concentration of all metallic cations, other than the cations of the alkali metals and is expressed as equivalent CaCO3 concentration in ppm.
In most waters, nearly all hardness is due to Ca and Mg ions; but in some waters measurable concentration of Fe, Al, Mn, Zn and others may be present.

Calcium

In vast majority of raw water calcium is the main source of hardness.
In boiler and cooling water systems calcium salts are the main cause of scale.

Although calcium is primarily known for its scale forming tendencies, it also acts as cathodic corrosion inhibitor.
All factors being equal, water containing calcium salt will not be as corrosive as soft water.

Magnesium

Magnesium usually forms hydroxides or silicates in boiler water, which are desirable types of sludge.
If boiler water alkalinity is low, undesirable magnesium phosphate often forms which
is sticky and scale forming.
In cooling water system, magnesium only precipitates when pH is over 10.0.

Relation between Total Hardness( TH ) And Total Alkalinity (M)
If Non Alkaline Hardness is Alkaline Hardness is Total Sodium Alkalinity is
TH > M TH - M M Nil
TH = M Nil TH Nil
TH < M Nil TH M – TH
Chloride

All chloride salts are highly soluble in water, so scale is not a problem when chloride salts are concerned, but they are very corrosive in oxidizing environmental.
Chloride is prominent in crevice corrosion and pitting all.

Sulphate

Most raw water contains sulphate. Presence of sulphate aggravates corrosion and be objectionable in concentrating water high in calcium, as in evaporative systems.

Iron

Iron is normally found in soluble ferrous Iron.
On contact with air oxidizing agents, iron is converted to ferric iron and iron insoluble hydroxides or oxides.
It will support to growth of iron bacteria and sulphate reducing bacteria.

Silica
Silica is present in almost all minerals and is found in fresh water.
Silica is objectionable at high concentration in cooling tower makeup, because at this uncertainty about its solubility limit.
It is objectionable in boiler feed water makeup is not only because it may from a scale in the boiler itself, but also because it volatility's at high temperature and pressure and redeposit on turbine blades.

Conductivities

The specific conductivity of water is a measure of its ability to conduct an electrical current. It is important as a direct measure of total amount of dissolved minerals and gases in the water.

Total Dissolved Solids (TDS)

The term total dissolved solid refers to the matter that remains as residue upon evaporation of filtered water.

Cooling water treatment chemicals

BY
COLONEL.DR
BAHAA BADR
CHEMICAL CONSULTANT

A. CORROSION
Corrosion is an electrochemical reaction converting the metal into its oxide.

Corrosion requires an anode, cathode & an electrolyte.

The metal acts as an anode & cathode while water acts as an electrolyte.

FOLLOWING FACTORS AFFECT THE RATE OF CORROSION

a) Metallurgy of the system
b) PH of circulating water
c) Dissolved gases
d) Dissolved and suspended solids
e) Water velocity
f) Temperature
g) Microbial growth

IMPORTANT TYPES OF CORROSION WHICH ARE FREQUENTLY FOUND IN COOLING WATER SYSTEMS

a) General type of corrosion
b) Localized corrosion
c) Corrosion due of velocity
d) Corrosion due to mechanical stress

HOW DO THE CORROSION INHIBITORS WORKS IN COOLING WATER TREATMENT

The Corrosion Inhibitors present in Water Treatment Chemicals form the passivation film on the metal surface.

Thus this surface is impervious to ions transfer or oxygen attacks and this barrier is arresting the corrosion.

As the film is very thin, it in no way affects the heat transfer.

B. SCALING
Scaling is defined as the hard and adherent deposits formed due to precipitation of sparingly soluble salts in water

The most commonly occurring scalants in cooling water systems are carbonates, sulphates, phosphates and silicates of calcium and magnesium

Scale Deposition

The scale deposits give rise to the following problems in cooling water systems

a) Reduced heat transfer decreasing the heat transfer efficiency.
b) Increased pressure drop on water side.
c) Under Deposit Corrosion.

Following are the factors which affect the scaling in cooling water system

a) Temperature
b) pH
c) Solubility

HOW DOES THE ANTISCALANT WORK?

For scaling to form, the crystal of scaling salt has to grow sufficiently in size.

When the crystal is growing the ANTISCALANT is absorbed on the crystal, blocking the growth site.

Thus the crystal cannot grow in size.

Even it the crystal grows, it is imperfect and the structure is very fluffy.

The small or fluffy crystals cannot form hard deposits hence Scaling does not occur.

In presence of ANTISCALANT, the metal surface remains free from Scaling.

The ANTISCALANTS inhibit scale formation by increasing the solubility of scalants in water and help to remain higher levels of scalants in dissolved form.

FOULING

Fouling is the deposition of suspended particles.

The particulate matter generally accumulates at low velocity areas in the cooling water system.

If cooling water is on the shell side of the heat exchanger then because of low velocity the fouling material settles on the shell side

Fouling Deposition

THE POTENTIAL FOULANTS IN COOLING WATER SYSTEMS ARE AS

FOLLOWS

a) Dust and silt.
b) Corrosion Products.
c) Sand
d) Natural organics
e) Microbial matter

THE FOLLOWING FACTORS AFFECT THE FOULING OF THE SYSTEM

a) Water characteristics
b) Temperature
c) Water velocity
d) Microbial growth

HOW DOES THE ANTIFOULANT WORK?

For fouling to take place, small suspended particles have to come together to form Agglomerate.

Most of the suspended matter is in the colloidal state and have a small electric charge on them.

ANTIFOULANT is polymeric in nature and when it is absorbed on suspended particles, it will increase the negative charge on the particle.

As like charges repel, the suspended particles are thus kept apart, preventing their agglomeration.

The particles thus stay dispersed in the water and are prevented from depositing and fouling the system.

Cooling water treatment programs

BY
COLONEL.DR
BAHAA BADR
CHEMICAL CONSULTANT

C. MICROBIAL GROWTH

Cooling water gives the excellent conditions for growth of various microorganisms.

The temperature and pH of circulating water are ideal conditions for the growth of algae and various bacteria's.

Also the organic matter, inorganic salts, sunlight etc. provides abundance of nutrients for the growth of these microorganisms. Following are the problems faced because of various microorganisms:

a) Algae

Air, water & sunlight are the three basic requirements for algae growth.
Excessive growth of algae on the deck of cooling tower can choke the distributor nozzles and reduce the water flow through cooling tower thus reducing its efficiency.

Excessive growth on the louvers, fill material increases the load on structure and may cause the failure of structure.

Algae mass can also get carry into the heat exchangers and plug the exchanger tubes.

b) Bacteria

There are various species of bacteria found in cooling water system.

SOME OF THE MOST FREQUENTLY FOUND BACTERIA IN COOLING SYSTEMARE

I Pseudomonas

These are aerobic bacteria, which secrete slime.

This slime acts as a binding material and fouls the System.

II Sulphate Reducing Bacteri

These are anaerobic bacteria which reduces sulphate ions to sulphides.

These bacteria grow under the deposits and yields under deposit corrosion.

There are also other aerobic bacteria like nitrifying bacteria, which reduces the pH of circulating water and iron bacteria and sulphur oxidizing bacteria which hamper the efficiency of the system.

HOW DO THE BIOCIDES WORK?

BIOCIDES are chemicals that interfere with basic life process of a cell.

BIOCIDES act as a poisonous material to the Algae cells.

They will either rupture the cell wall or get into the cell and damage the metabolism inside the cell.

We have extremely strong BIOCIDES, which would kill Algae in few days of time.

Regular dosage of BIOCIDES will not allow Algae to grow, once destroyed. Killing of Algae is the visible sign of the action of BIOCIDES as the dead Algae will turn from Green to Yellowish-brown.

However, if initial growth of Algae is very high, it will be desirable to clean the Algae manually as much as possible.

Otherwise, there is a chance of dead Algae becoming a large mass of foulants in the water and chocking the strainers in the pipelines.

The problems associated with the use of water in cooling systems are serious but carefully prescribed and monitored "Total Cooling Water Treatment" program can curtail their occurrence.

The damage will begin immediately. Equipment designed to last for years can break down in just days due to some form of uncontrolled corrosion scale, microbial growth or fouling.

These problems are control by "Total Cooling water Treatment" program, which will include both chemical and mechanical methods for controlling problems.

For example, depending on the design and location and water Chemistry, water treatment program may include some or all of the following:

1) Corrosion Inhibitor
2) Dispersant
3) Biocide
4) Scale Inhibitor

Through the implementation and proper monitoring of these specialized total water treatments program, the problems associated with water in cooling systems can be controlled.

To make our program success, we incorporate monitoring tools to ensure that Treatment program of the system is become more effective every passing day

Chiller water treatment chemicals

BY
COLONEL.DR
BAHAA BADR
CHEMICAL CONSULTANT

Closed systems usually contain a combination of different metals, which provide a high potential for galvanic corrosion.

The potential for dissolved oxygen attach is generally quite low in closed systems because of small amount of makeup water the main oxygen source.

However, in systems that require substantial makeup because of loss of water from leaks, oxygen is continually supplied and oxygen corrosion presents a serious problem.

Oxygen can, at elevated temperatures or at point of high heat transfer, cause severe pitting corrosion.

Since relatively little makeup is added to most closed recirculating systems, it is practical and desirable to maintain the system in a corrosion -free condition.

This is normally achieved by applying Chemicals Treatment at rather high concentrations.

Because water circulating through a closed system is not exposed to atmosphere, fouling by airborne silt and sand is rare.

However, fouling by microbial masses may occur in closed systems where makeup rate is significant or process leaks encourage bacterial growths.

These are controlled with biological control agents formulated to be compatible with the Chemical Treatments and operating conditions found in closed systems.

Scale should be a minor problem in a closed system since the water is not concentrated by evaporation.

In a tightly closed system, none of the common scale-forming constituents deposit on metal surfaces to interfere with heat transfer or encourage corrosion.

With high make up rates, however, additional scale forms with each new increment of water added so that in time, scale becomes significant.

In addition, there is opportunity for sludge, rust, and suspended solids to drop out at low flow points and bake on heat transfer surfaces to form a hard deposit.

Therefore, scale retardants and dispersants are usually included as part of closed system Chemical Treatment program where makeup rates are high.

Often soft water or condensate is used for make to closed systems depending on the characteristics of the system being protected.

For a successful Chiller Water Treatment, it is requires regular analysis for control of correct Treatment Chemical Residuals.

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