Boiler and Auxiliaries Identification

OBJECTIVES

1. To identify all major external components associated with gas fired boilers.
2. To describe the function of all major components.

THE FIVE MAJOR EXTERNAL COMPONENTS OF A GAS FIRED BOILER

1. FEED-WATER SYSTEM

• Water supply and backflow preventer: The water supply comes direct from the city, and then finally into the boiler. A backflow preventer is a device used to prevent backflow. It does this through an air gap used to provide a barrier to the backflow.
• Water softener system: Water softeners are for pre-treatment equipment for boiler feed water, cooling towers, entire water supply and various types of process water.
• Feed-water tank: The feed water is put in to the steam drum from a feed pump. In the steam drum the feed water is then turned into steam from the heat. After the steam is used it is then dumped to the main condenser. From the condenser it is then pumped to the feed tank.
• Feed-water tank drain valves: It provides a connection for water to enter the water tank, a connection for the tank drain, a connection for a tank pressure relief valve, a connection for an air inlet valve or a water pressure gauge, and a connection for water to leave the tank to enter the building’s water piping system.
• Feed-water tank sight glass: A sight glass is a transparent tube through which the operator of a tank or boiler can observe the level of liquid contained within.
• Feed-water tank temperature indication: The feed-water tank temperature indication enables the plant operator to monitor/control feed-water heater levels and decrease their plant’s heat rate.
• Feed-water tank temperature control valve and sensor: This helps to control scaling, corrosion, and eventually hot spots and tube failures.
• Chemical pumps and sampling system: The chemical pumps feed systems treat feed-water and condition blowdown sludge against corrosion and scaling
• Boiler 1 & 2 feed-water pump: The pump 1 & 2 are used to pump feed-water into a steam boiler. The water that is supplied or returning condensate produced as a result of the condensation of the steam produced by the boilers.

2. BOILER SYSTEMS

A boiler system is simply a process used to heat up water by the means of a gas or oil-fired burner which then converts the water into steam. The steam travels through various pipes to the convectors and then generates heat used to warm the room. After a while the steam cools by condensing into water, and returns to the boiler to be heated again.

3. BOILER AIR / FUEL SYSTEMS

The boiler fuel system comprise of various units that is used create steam by applying heat energy to water. The fuel source releases its energy in the form of combustion taking place inside the boiler furnace for the boiler to convert water to steam.

• Main fuel line: Supplies the fuel gas from outside the plant to the boiler
• Fuel metering and regulation system: Regulates the quantity of fuel gas that is been supplied into the boiler.
• Main fuel shutoff valves: As fuel enters through the main fuel line, the valves allow for easy shut-off of fuel flow to the boiler.
• Main burner pressure regulators: If natural gas and air are inside the boiler when the burner is lit, the boiler can explode. Therefore, boiler steam pressure and water level are monitored and controlled by means of burner pressure regulator.
• Low and high pressure switches: For sensing fluid pressure. The pressure-sensing element are arranged to respond to the difference of two pressures.
• Blower motors: Power the fans that distribute heat throughout the boiler.
• Air Dampers: Controls the flow of air through the boiler.
• Igniters: Converts the fuel that is being fed into the boiler through the main fuel line into heat by lighting a connected burner.
• Flame scanners: Monitor the boiler fires and detect the presence or absence of flame in a boiler.

4. STEAM SYSTEM, EXHAUST STEAM AND CONDENSATE:

STEAM SYSTEM

As the boiler heats up the water that generates steam, the steam travels at a very high pressure through various valves, a low pressure turbine, and is then exhausted into the condenser. The valves are used to maintain a set pressure in other to protect most of the steam components which is used to rotate the turbine. The stop valve is used to stop the steam as it flows into the turbine in case of any problem that could damage the turbine.

The check valve is used to control the amount of steam which flows into the turbine thereby controls the speed of the turbine when it is connected to the grid used to generate electricity by the help of an attached generator.

CONDENSATE

The final place for the steam that is produced in the boiler is the condenser. In the condenser, the steam turns back into water by means of a heat exchanger which condenses the steam into liquid by cooling.

EXHAUST STEAM:

The exhaust steam is used to release the steam that no longer has enough heat energy after it has being used.

5. BLOW-DOWN SYSTEM

During the process of the steam generated, if any impurity carry over with the steam it would cause overheating in the superheater tubes. The blowdown system is used to prevent deposit of impurities into other surface like the turbine blades.

DISCUSSIONS

What did you learn about the equipment or technique?

In this lab experiment, I have learnt about the five major external components of a gas fired boiler. How each stages is essential for generating steam. It is important to thoroughly understand the need for boiler to generate steam can also be catastrophic when no proper care is put in place.

What problems were encountered?

The few problems that could be encountered are as follow:

• If there is no safety valves installed on top of the boiler to protect the steam system components from over pressure,
• As fuel enters through the main fuel line, the valves that allow for easy shut-off of fuel flow to the boiler is broken causing fuel leakage that could cause fire outbreak.

How this equipment or technique could be applied to chemical production?

In chemical production, the equipment or technique could be applied to chemical production for the following reasons:

• As water heats up and converts to steam, the steam is used to power or rotate the blades of the turbines for generating electric which provides the voltage and current used to power other electrical equipment for the chemical production.
• The steam could be used for processing chemical products by means of sterilization.
• The steam could be used to power heating and air conditioning units in the chemical production plant.

CONCLUSION

The Process flow and P & ID diagram gave me the opportunities to have a broader understanding a boiler system and how each components work to generate steam.

REFERENCES

Boiler: power generation. Retrieved from: Wikipedia

https://en.wikipedia.org/wiki/Boile (power_generation)

Main steam supply and Feedwater system. Retrieved from: Candu

https://canteach.candu.org/Content%20Library/19930205.pdf