Water Treatment Handbook UNITOR

8/6/2019 Water Treatment Handbook UNITOR

1/46

Water

Treatment

Handbook

C H E M I C A L S

U N I T O R A S A

Mail: P.O.Box 300 Skyen, N-0212 Oslo, Norw ayOffice: Drammensvn. 211, N-0277 Oslo, Norway

Tel: +47 22 13 14 15. Fax: +47 22 13 45 00Tlx: 76004 UNTOR N

ID.

NO.

08173

REV.

NO.

00

LOBO

09.9

7

5K

COUNTRYOFORIIGIN:NORWAY


2/46

Marine Chemicals

Water TreatmentHandbookA PRACTICAL APPLICATION MANUAL

1st Edition

Unitor ASA, P.O. Box 300 Skyen, N-0212 Oslo, NorwayOffice: Drammensveien 211, N-0277 Oslo, Norway

Tel: +47 22 13 14 15. Fax: +47 22 13 45 00

Tlx: 76004 UNTOR N

ID . NO. 08 173 REV. NO. 00 LOBO 09.97 5K COUNTRY OF ORIGIN: NORWAY


3/46


4/46

1 Water Treatment Philosophyand Overview

1.1 TYPES OF WATER

General

Water could generally be described as the most important of all chemical

substances. Its chemical designation is H2O; the water molecule is composed

of 2 Hydrogen atoms and 1 Oxygen atom.

Natural water

Raw w ater is the description of the water to w hich we have daily access.

We can obtain our water from:

1. The ocean

2. Surface sources (e.g. from lakes)

3. Underground sourc es

The water will vary in composition.

The natural water c ycle may be as below:

While it is evaporating from the surface of a lake or the oc ean into the atmo-

sphere, we can designate the water vapour H2O. In the atmosphere, c louds

will form, and during suitable humidity and temperature, the clouds will

deposit w ater (rain). While the rain is falling towards the earth, it absorbs

gases which are in the air, e.g. CO2 (Carbon Dioxide), SO2 (Sulphur Dioxide)

and O2 (Oxygen).

When the water hits the earth, it absorbs additional Carbon Dioxide (from

biological degradation). The rainwater which is now slightly acid wi ll dissolvevarious minerals from the soil.

INTRODUCTIONThis Product Applications Handbook has been designed to provide specific

information on the variety of chemical and related products and systemsavailable from Unitor.

This handbook will give all the information required to maintain these vari-

ous products, including the application of individual chemical products to

properly maintain Low Pressure, Medium Pressure and High Pressure Boilers,

Diesel Engine Cooling Systems and Evaporators.

Single Function Treatment Products:

1. Hardness Control

2. Alkalinity Control

3. Oxygen Control (Hydrazine)4. Catalysed Sodium Sulphite (Powdered & Liquid)

5. Condensate Control

6. Boiler Coagulant

Low Pressure Boilers, Wate r Treatments:

1. Combitreat (powdered)

2. Liquitreat

3. Condensate Control

Cooling Water Treatments:

1. Dieselguard NB (powder)

2. Rocor NB Liquid

Sea W ater Cooling Treatment:

1. Bioguard

Evaporator Treatment:

1. Vaptreat

IV WATERTREATMENT HANDBOOK 5WATERTREATMENT HANDBOOK


5/46


6/46


7/46


8/46


9/46

3.1.1 Pitting Corrosion

Pitting is the most serious form of waterside corrosion and is theresult of the formation of irregular pits in the metal surface as shown in

the figure below. Evidence of pitting is usually found in the boiler shell

around the water level and is most likely caused by poor storage proce-

dures when the boiler is shut down for lengthy periods, and by inade-

quate Oxygen scavenging.

Pitting corrosion.

3.1.2 Stress Corrosion

Stress corrosion cracking is the process caused by the combined

action of heavy stress and a corrosive environment. The stages of fail-

ure of the metal due to stress corrosion are shown below. Corrosion is

initiated by breakdown of the surface film follow ed by the formation of a

corrosion pit whic h becomes the site for stress corrosion cracking,

eventually leading to mechanical failure due to overloading of the

mechanical strength of the metal. This form of attack is often found

around the ogee ring in vertical auxiliary boilers, when undue stressing

is set up by poor steam-raising procedures.

Stress corrosion

15WATERTREATMENT HANDBOOK

3 Problems of Boiler Water

Feedwater produced by distillation for use in a boiler is not pure, even w ith a

good distillation method. Worse still is ordinary water taken from ashore to beused as feedwater. The water will contain some of the elements (impurities)

mentioned in Chapter 5.

Problems will then arise when the water is used in the boiler. The types

of problem will depend on the type of impurities and in which quantities they

are present.

The most common problems are:

CORROSION

SCALING CARRYOVER

3.1 CORROSION

The corrosion processes can affect boilers in the following ways:

General wastage is the overall reduction of metal thickness and is common

in heating surface areas, such as boiler tube w alls. This thinning of boiler

tubes is often found in boilers having open feed systems (mostly auxiliary

boilers) without any protective treatment. An example of wastage is given inthe figure below.

14 3 / PROBLEMS OF BOILER WATER

General wastage of a boiler tube.


10/46


11/46

3.3 CARRYOVER

Carryover is any contaminant that leaves the boiler with the steam.

Carryover can be:

Solid Liquid Vapour

Effects of carryover:

Deposits in non-return valve Deposits in superheaters

Deposits in control valves Deposits on turbine

Carryover in superheaters can promote failure due to overheating.

Turbines are prone to damage by carryover, as solid particles in steam can

erode turbine parts. When large slugs of water c arry over wi th steam, the

thermal and mechanical shock can cause severe damage.

Causes of carryover:

Mechanical:

Priming Sudden load changes Boiler design

Soot blowing High water level

Chemical:

Foaming due to:

High Chlorides High TDS High alkalinity

Suspended solids Oil Silica

The most common form of encrustation in a steam system stems from

carryover. The boiler manufacturers stipulate a maximum allowed salinity of

the boiler water (as a rule at 0.4Be = 4000 mg salts dissolved per l itre). If this

value is exceeded, there is a risk of normal bubble size being prevented;

larger bubbles will be produced and the turbulence in the water surface w ill

increase and cause foaming.The foam may be carried over w ith the steam,

particularly when the generation of steam is at maximum, which c auses boiler

water (containing Sodium Hydroxide and salt) to pass out into the steam

pipes.

The content of Silicic Acid is important for boilers wi th high pressures.

Silicic Acid in its volatile form may be carried away with the steam and be

deposited on turbine blades, for instance, on whic h it w ill form a very hard,

porcelaine-like scale.

However, not only the chemical composition may cause carryover. Circum-

stances such as periodic overloads, periods of a too high a water level (or more

correctly: too small a steam volume) are two of the most common causes.

Finally, impurities from the condensate, such as oil from the preheaterscoils if they are leaking are very common causes of priming.

19WATERTREATMENT HANDBOOK18 3 / PROBLEMS OF BOILER WATER

Ill ustration ofTypical Conditions With

a Clean Boiler Tube

Change in Conditions Whena Layer of Scale of just 3 mm

Thickness Exists

The scale causes the fuel consumption to increase by approx.18 percent.

Stress w ill arise in the steel as a result of the insulating effect of the scale.

Excess Fuel Consumption in % ,depending on Thickness of ScaleCurve of middle values. The differences in the test results c an be

explained by differences in the composition of scale (poroushard).


12/46

Typical pac kaged boiler. Packaged boilers inc lude a pressure vessel, burner, all the controls, airfans, and insulation. The boiler is tested at the manufacturers plant and shipped to t he customer,ready for use, when the fuel lines and piping and electrical connections have been installed.

Typical Scotc h Marine f iretube boiler (courtesy of Orr & Sembower, Inc.).


4 Types of Boiler

What is a boiler?

A boiler is a steel pressure vessel in which water under pressure is c on-verted into steam by the application of combustion. In other words, it is

simply a heat exchanger which uses radiant heat and hot flue gases, liberated

from burning fuel, to generate steam and hot water for heating and

processing loads.

There are two types: Fire tube boilers and water tube boilers.

4.1 FIRE TUBE BOILER

Hot flue gases flow inside tubes that are submerged in water within a shell. Pressures up to about 10 bar

Produce up to 14 tonnes of steam/hr

Can meet wide and sudden load fluctuations becauseof large w ater volumes

Usually rated in HP

4.2 WATER TUBE BOILER

Water flows through tubes that are surrounded by hot combustion gasesin a shell.

Usually rated in tons of steam/hr

Used for H.P. steam

High capacity

BOILERS HAVE SIX BASIC PARTS

1) Burner2) Combustion space

3) Convection section

4) Stack

5) Air fans

6) Controls and accessories

20 4 / TYPES OF BOILER


13/46

4.5 HIGH TEM PERATURE WATER (HTW) HEATING SYSTEM S

In recent years, interest has been revived in high temperature hot water

heating systems for institutional, industrial and commercial plants. By

increasing the temperature and pressure of the hot w ater and increasing the

size of the generators, some advantages are gained over the low pressuresteam heating systems previously used. In other cases, special forced

circulation boilers have been designed, which consist of many rows of tubes

without a steam drum. In another type, heat is supplied by steam from

a standard type of boiler which heats the water in a direc t contact heater.

This is referred to as a cascade system.


4.3 FIRETUBE BOILERS

Wet back designs

Have a water wall at the back of the boiler in the area where c ombustion

gases reverse direction to enter tubes.

Dry back designs

Refractory is used at the back, instead of a w ater wall. Internal maintenance

is simplified, but refractory replacement is expensive and overheating,

gauging and cracking of tube ends at the entrance to return gas passages

often cause problems.

4.4 CLAYTON STEAM GENERATOR

The coil type generator is a vertical coil with fuel combustion taking place

inside the coil. High quality feedwater and a closely monitored chemical treat-

ment programme are mandatory. The most common problem is Oxygen

pitting on the inside portion of the coil near the fire. The two most commonname brands are Vapor-Clarkson and Clayton.

22 4/ TYPES OF BOILER

Medium-sized watertube boilers may be classified according to three basic tube arrangements.

WATERSYSTEM AND STEAMSYSTEM


14/46

WATERTREATMENT HANDBOOK

5.1 TYPICAL BOILER SETUP ON A MOTOR SHIP

5.1.1 The Boiler System

This does not just consist of a boiler. As indicated by the figure above, it

is a complete plant. Most motor ship boilers operate at low pressure,

that is, not more than 20 bar pressure. This makes it suitable for the

single treatment: the combined boiler w ater treatment.

The steam plant consists of the following:

Storage tank

This tank wil l hold the make-up water to be supplied to the various

systems as they lose water through leaks and through evaporation.

Normally, this water is made by a low pressure evaporator (this will

be described later on). The water produced in this way is normally of

good quality if the evaporator is set up correctly. When it is introduced

to the boiler, it will require the minimum amount of treatment. However,

at some stage the vessel will very likely take water from ashore, and

the quality can vary considerably. This water w ould probably require

more treatment to correctly c ondition it for use.

Hot w ell, observation tank or cascade tank

This has a very important function for the dosing of chemical treat-

ments. This is where all the water c ollects on returning from the various

areas where steam has been used. It is also where water enters the

system from the storage tank(s) to make up the quantity required in the

system. If the steam has been used for heating fuel, the returns fromthat tank may contain oil, or if cargo heating has been used, some of

25

4.6 FIRETUBE BOILERS

Advantages:

Lower initial cost

Few controls

Simple operation

Disadvantages:

Drums exposed to heat, increasing the risk of explosion

Large water volume, resulting in poor circulation

Limited steam pressure and evaporation

WATERTUBE BOILERS

Advantages:

Rapid heat transmission

Fast reaction to steam demand

High efficiency

Safer than firetube boilers

Disadvantages:

More control than firetube boilers

Higher initial cost

More complicated to operate

24 4 / TYPES OF BOILER

5 Boiler Systems


15/46


16/46


17/46


18/46


19/46


20/46


21/46


22/46


23/46


24/46


25/46


26/46


27/46


28/46

11.7.3 Recommended Sampling Points

Point (A) Condensate pH, Ammonia, Chlorides.Point (B) Feed Water Dissolved Oxygen, pH, TDS, Chlorides.

Note: Testing can be done at the disc harge from the feed pump. However, if highdissolved Oxygen residuals are found, water in the storage area of the de-aeratorshould be checked to ensure no air i s leaking into the feed pump.

53WATERTREATMENT HANDBOOK52 11 / HIGH PRESSURE BOILER WATER CONTROL

12 Boiler Wet Layup

Boilers are likely to suffer more from corrosion during periods when not in use

or laid up. They must be protected. Proper layup procedures are essential.Corrosion will occ ur if :

A. Low pH conditions occur.

B. Oxygen is present in the boiler water.

The procedure starts 23 days before the layup date

1 Test the boiler treatment levels and blow down the boiler at regular inter-

vals to reduce potential sludge. The boiler should not be laid up dirty.

2 Raise the treatment levels for alkalinity to the maximum allowable level for

that boiler pressure.3 The boiler should then be treated with a high level of Oxygen Control after

it has been isolated from the main steam line. Gentle firing of the boiler

should be used to fully circulate the treatment w ith the boiler vented.

150200 ppm Hydrazine is dosed into the boiler. (This works out at

1.25 litres/ tonne of water.)

NB! Full water capacity must be used to calculate this not working capacity.

4 The vent cock on top of the boiler should be opened and the boiler filled

wi th feedwater that is as hot as possible (90 C).

5 The boiler should be given a head of water to ensure that the boiler is kept

full of w ater. This is achieved by connecting a hose of a drum of treated

water to the boiler vent cock to make up for any losses due to leaks.

6 Where super heaters are in place, the manufacturers instructions must

be followed.

7 This principle of wet layup can be used for exhaust gas economisers, etc.

8 Wet layup of boilers is for the short term. A different procedure should

be used for a long term layup .

Returning to ServiceDrain the boiler of excess Hydrazine, refill with water and warm through in the

normal way.


29/46


30/46


31/46


32/46


33/46


34/46


35/46


36/46


37/46

3) Calculate the amount of cleaner required for a solution strength of 2 % i.e.

20 litres per 1000 litres cooling water. Drain of similar amount of cooling

water from engine if necessary. Add Tankleen Plus to the expansion tank

or return tank.

4) Circulate the solution through the system and heat until the water reaches

a temperature of about 60 C.

5) Continue circulation of the solution through the system for a minimum

of 5 hours.

6) Take a sample of cleaning solution from the system after a minimum

of 5 hours.7) When cleaning is completed, drain off the cooling water system, and

thoroughly flush with clean water prior to refilling and adding an anti-

corrosion treatment such as Dieselguard NB or Rocor NB Liquid.

71WATERTREATMENT HANDBOOK70 15 / DIESEL ENGINE COOLING WATER TREATMENT

16 Reporting Analysis Results

One important aspect of a good water treatment management system is to

ensure that analysis results and any action taken are recorded as the events

take place and the reports are properly maintained for future reference.

As mentioned earlier, special log forms are supplied separately for both

boiler water treatment and diesel engine cooling w ater treatment. These

should be completed by the w ater treatment officer responsible. Attention

should be paid not only to recording the results of various water analyses,

but to reporting any changes in circ umstances that may have a direct or an

indirect influence on the r esults, including any major cleaning or repairs to

the system.

In order that Unitor may keep a watc hful eye on water treatment pro-

grammes onboard individual vessels, it is essential that the instructions forour Rapid Response programme are followed and logs sent promptly to our

Rapid Response Centre for review and comment.

Unitor will monitor the progress and performance of the onboard water

treatment programme and liaise with the vessels head office and ship

accordingly.

Examples of how to complete the report logs are given overleaf. Make sure

you use the correct log form in conjunction w ith your treatment programme.

Picture page 72, 73, 74, 75, and 76, shows log examples.


38/46

73WATERTREATMENT HANDBOOK72 16 / REPORTING ANALYSIS RESULTS

Unitor ASAChemical Business UnitP.O. Box 300 SkyenN-0212 OsloNorway

C H E M I C A L S


39/46


Unitor ASAChemical Business UnitP.O. Box 300 SkyenN-0212 OsloNorway

C H E M I C A L S

Unitor ASAChemical Business UnitP.O. Box 300 SkyenN-0212 Oslo

Norway

C H E M I C A L S

17 W T S


40/46


17 Water Tests, Summary

17.1 SPECTRAPAK TEST KITS

309 Test Kit: Nitrite pH

Cl

310 Test Kit: P-Alkalinity

Cl

pH

311 Test Kit: P-Alkalinity

M-Alkalinity

PO4

Cl pH

312 Test Kit: Hydrazine/Sulphite

PC 22 Test Kit: P-Alkalinity

M-Alkalinity

PO4 Cl

pH

Conductivity

Hardness

Ammonia

Hydrazine

Silica

Samples to be tested: Boiler water

Feed water

Condensate return

Make up water

Engine cooling water

17.2 TESTING

Boiler water: P-Alkalinity

M-Alkalinity

Cl

PO4 pH

Hydrazine/Sulphite

Conductivity

Silica

Appearance

UnitorASA

ChemicalBusinessUnit

P.O.Box300

S

kyen

N-0212

Oslo

Norway

C

H

E

M

IC

A

L

S


41/46


42/46

18 Evaporator Treatment


43/46

83WATERTREATMENT HANDBOOK82 18 / EVAPORATOR TREATMENT

18 Evaporator Treatment

THE FRESH WATER EVAPORATOR (OR GENERATOR)

There are two main types:THE VACUUM or FLASH EVAPORATOR

and

THE STEAM HEATED EVAPORATOR

18.1 THE VACUUM EVAPORATOR

Vacuum is maintained in the evaporator, considerably reducing the boiling

point of the water.

The heat source used is the engine jacket water. The jacket water is

circulated through the lower section of the evaporator where the heating

section is. This heating section is a series of vertical tubes surrounded by the

heating water. Sea water is pumped into the vertical tubes from below to be

heated by the jacket water. The water vapour produced rises to the top of the

evaporator w here it comes into c ontact w ith cooling tubes and condenses.

The condensate is then taken off for storage. The system is very efficient

when c orrectly set up, but there are several points to consider:

A. 3 percent of seawater is dissolved minerals.

B. Evaporators of this type have a tendency to allow the seawater to foamand so salt is carried over with the distilled water.

The treatment is to be fed continuously. The evaporator vacuum will pull

the treatment in and it will enter the evaporator with the seawater.

Sufficient treatment should be mixed for 24 hours operation. Treatment is

essential to keep the evaporator operating efficiently for longer periods

of time. It works in the following w ays:

a. Some of the dissolved solids may form scale and the treatment

will help prevent the solids from adhering to the heating surfaces andkeep these scale formers in solution.

b. The sludge will be conditioned to make extraction of the concentrated

sea water (brine) easier.

c. The foaming tendency of the brine will be suppressed by anti-foaming

agents.

Unitor treatment is: Vaptreat.

Average dosage: 0.3 l/10 tonnes of distillate produced.

This is calculated on a standard brine density of 1.038 kg/l.

19 M arine Equipment


44/46

85WATERTREATMENT HANDBOOK84 18 / EVAPORATOR TREATMENT

FRESH WATER GENERATORType AFGU 1-E-10/1-E-15

19 M arine Equipment

19.1 SOM E COM M ON M ARINE EQUIPM ENT

19.1.1 High Pressure Boilers > 30 bar Babcox & Wilcox Combustion Engineering

Foster Wheeler IHI

19.1.2 Low Pressure Boilers < 30 bar

Sunrod Aalborg Coc hran Osaka Kaw asaki M HI

19.1.3 Slow Speed Diesel Enginees < 120 rpm

M itsubishi Sulzer MAN B & W Gtavrken Fiat GMT

19.1.4 M edium Speed Diesel Engines 120900 rpm War tsila Sulzer Pielstic k Enter pr ise MAN B & W

MaK Deutz Ber gen Diesel Daihatsu

19.1.5 High Speed Diesel Engines > 900 rpm

Hitac hi Yanmar EMD Cummins Cater pillar

19.1.6 Evaporators

Alfa-Laval Desalt Atlas (bought by Alfa-Laval) Nirex

M axim Weir

Notes: Notes:


45/46


Notes:

86 20 / NOTES

Notes:

Notes:


46/46

88 20 / NOTES

Notes:

Water Treatment Handbook UNITOR

Documents

Transcript of Water Treatment Handbook UNITOR