Water Hardness and Impurity Treatments

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Questions and Answers

What is one of the main reasons for treating water in an energy plant?

To prevent scale formation on the boiler tubes (correct)

To eliminate the need for stringent standards

To increase the efficiency of energy production

To reduce the cost of water supply

What is the purpose of preventing sludge formation in a boiler?

To reduce energy consumption

To improve water taste and odor

To insulate the metal surfaces

To protect against tube failure (correct)

What can high concentrations of dissolved or suspended solids in boiler water cause?

Decrease in energy production

Reduction in corrosion

Improvement in heat transfer

Overheating of tube surfaces (correct)

Why is it important to prevent carryover of boiler drum water and dissolved/suspended solids?

To reduce equipment damage Signup and view all the answers

Which problem can result from poor water conditions in an energy plant?

Overheating of the furnace Signup and view all the answers

What is one of the challenges faced by those who supply water in modern society?

Stringent standards for water treatment Signup and view all the answers

What is the main cause of temporary hardness in water?

Bicarbonates of calcium and magnesium which precipitate at temperatures below boiling point Signup and view all the answers

What is the primary method for controlling sludge in a boiler?

Blowing down the boiler mud drum Signup and view all the answers

What is the main concern related to dissolved gases in water for Power Engineers?

Ability to produce boiler corrosion Signup and view all the answers

What is the effect of dissolved ammonia in water on heat exchangers?

Causes corrosion in copper and copper bearing alloys Signup and view all the answers

How is dissolved oxygen primarily removed from boiler water?

Using deaerators externally and internally Signup and view all the answers

What is the effect of carbon dioxide dissolved in boiler water?

Forms carbonic acid causing grooving on metal surfaces Signup and view all the answers

What is the main purpose of a water treatment program for a facility's boiler?

To protect the facility's boiler investment Signup and view all the answers

Which impurity can lead to the formation of scale and reduce heat transfer efficiency in a boiler?

Excess water hardness Signup and view all the answers

What is the main problem caused by suspended solids in a boiler water system?

Foaming leading to carryover or priming from the steam drum Signup and view all the answers

How are dissolved solids in water usually measured?

By conducting conductivity tests with a probe Signup and view all the answers

What is the purpose of external treatment methods for reducing suspended solids in the feedwater?

To reduce the levels of suspended solids through gravity settling and pressure filtration Signup and view all the answers

Which impurity can result in local hot spots and tube rupture due to precipitation on heating surfaces?

Excess water hardness Signup and view all the answers

What is the effect of pH conditions on the relative corrosion in boiler steels?

Corrosion is significant at a pH below 8.5 Signup and view all the answers

What is the consequence of high pH boiler water on the protective oxide called magnetite?

Dissolves the magnetite coating Signup and view all the answers

What may result from high pH levels in the presence of high boiler metal stress due to large temperature fluctuations?

Caustic embrittlement Signup and view all the answers

What is commonly added to raise the pH of boiler water?

Sodium hydroxide Signup and view all the answers

What action can be taken to lower the pH of the boiler water?

Increasing the continuous blowdown rate Signup and view all the answers

What occurs during caustic embrittlement?

Fine intergranular cracking Signup and view all the answers

What is considered highly beneficial for ferrous boiler metal?

Magnetite coating Signup and view all the answers

Study Notes

Water Treatment in Energy Plants

One of the main reasons for treating water in an energy plant is to prevent corrosion, scaling, and fouling, which can lead to decreased efficiency, increased maintenance, and even system failure.

Boiler Water Quality

Preventing sludge formation in a boiler is crucial to prevent overheating, damage, and system failure.
High concentrations of dissolved or suspended solids in boiler water can cause scaling, fouling, and corrosion, leading to decreased efficiency and system failure.
Carrying over boiler drum water and dissolved/suspended solids into the steam system can cause corrosion, erosion, and fouling, leading to system failure and downtime.

Water Quality Issues

Poor water conditions in an energy plant can lead to corrosion, scaling, and fouling, resulting in decreased efficiency, increased maintenance, and system failure.

Water Supply Challenges

One of the challenges faced by those who supply water in modern society is ensuring the water is of high quality, free from impurities, and suitable for use in boilers and other systems.

Temporary Hardness

Temporary hardness in water is primarily caused by the presence of bicarbonate salts, which can be removed through treatment.

Sludge Control

The primary method for controlling sludge in a boiler is to maintain a clean and stable water chemistry, using treatments such as coagulation, sedimentation, and filtration.

Dissolved Gases

The main concern related to dissolved gases in water for Power Engineers is the potential for corrosion, scaling, and fouling, which can lead to system failure and downtime.

Dissolved Ammonia

Dissolved ammonia in water can cause corrosion and pitting on heat exchangers, leading to decreased efficiency and system failure.

Dissolved Oxygen

Dissolved oxygen is primarily removed from boiler water through mechanical deaeration, chemical scavenging, or oxygen-removing equipment.

Carbon Dioxide

Dissolved carbon dioxide in boiler water can cause corrosion, particularly in condensate return systems, leading to decreased efficiency and system failure.

Water Treatment Program

The main purpose of a water treatment program for a facility's boiler is to ensure the water is of high quality, free from impurities, and suitable for use in the boiler.

Impurities

Suspended solids, dissolved solids, and other impurities in boiler water can lead to the formation of scale, reduce heat transfer efficiency, and cause corrosion and fouling.

Scale Formation

Calcium and magnesium ions can lead to the formation of scale, which can reduce heat transfer efficiency and cause system failure.

Suspended Solids

Suspended solids in a boiler water system can cause fouling, erosion, and corrosion, leading to decreased efficiency and system failure.

Dissolved Solids

Dissolved solids in water are usually measured through total dissolved solids (TDS) testing, which provides a reading of the total concentration of dissolved solids in the water.

External Treatment

The purpose of external treatment methods for reducing suspended solids in the feedwater is to prevent fouling, erosion, and corrosion in the boiler.

Corrosion

High pH boiler water can lead to the formation of a protective oxide called magnetite, which can reduce corrosion in boiler steels.
High pH levels in the presence of high boiler metal stress due to large temperature fluctuations can cause caustic embrittlement, leading to cracks and failures.
Sodium hydroxide (caustic soda) is commonly added to raise the pH of boiler water, while acid or other neutralizing agents can be used to lower the pH.

Caustic Embrittlement

Caustic embrittlement occurs when high pH levels in the presence of high boiler metal stress cause cracks and failures in the boiler metal.

Ferrous Boiler Metal

The presence of a protective oxide called magnetite is considered highly beneficial for ferrous boiler metal, as it reduces corrosion and increases the lifespan of the boiler.

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Description

Learn about the different types of water hardness caused by impurities like bicarbonates and sulfates of calcium and magnesium, and the treatments to remove them before entering the boiler. Understand the difference between temporary and permanent hardness and how it affects the formation of scale on boiler surfaces.