4AE3 U11 C4 Review

What is the primary function of an electric boiler?

To convert water into high or low-pressure steam or hot water (correct)
To generate electricity
To reduce energy costs
To facilitate aluminum smelting

In which type of facilities are electric boilers commonly used?

Power plants
Laundries and kitchens
Aluminum smelters
All of the above (correct)

What is one of the advantages of using electric boilers in traditional power plants?

They can be used to increase efficiency during times of low electrical demand (correct)
They are more expensive to install
They are only used for high-pressure applications
They can increase energy costs

What is one of the uses of low capacity electric boilers?

To keep standby steam generators warm (A) Signup and view all the answers

Why might running electric boilers be more cost-effective than running large fossil fuel boilers?

Running large fossil fuel boilers at low output can cost as much or more than running electric boilers (B) Signup and view all the answers

What is one of the reasons why electric boilers are used in certain facilities?

Because large amounts of electricity are available at low cost (C) Signup and view all the answers

What is an advantage of electric boilers over fuel-fired boilers in terms of space requirements?

They do not require furnace space for combustion (D) Signup and view all the answers

What is the percentage of energy delivered by electricity that is absorbed as heat in the boiler?

99% (D) Signup and view all the answers

What is a safety advantage of electric boilers over fuel-fired boilers?

They pose no threat of furnace explosion (D) Signup and view all the answers

What is the highest voltage at which electrode boilers can be designed to operate?

25 kV (D) Signup and view all the answers

What is a limitation of most electric boiler designs in terms of pressure?

They are limited to about 3100 kPa (B) Signup and view all the answers

What is the purpose of the control sleeve in an electrode boiler?

To control the amount of water that sprays on the boiler electrodes (B) Signup and view all the answers

What is the function of the stand-by heater in an electrode boiler?

To reduce startup time (D) Signup and view all the answers

What is the role of mineral salts in an electrode-style electric boiler?

They make the water an excellent conductor (B) Signup and view all the answers

What is the main difference between electrode boilers and immersion boilers?

The path of the electric current (A) Signup and view all the answers

In a submerged electrode design electric boiler, what happens to the steam production rate when the load increases?

It increases (B) Signup and view all the answers

What is the purpose of the float valve in a submerged electrode design electric boiler?

To control the water supply to the regulating chamber (A) Signup and view all the answers

How is the steam production of an immersion boiler controlled?

By turning on and off the power supply to one or more heating elements (D) Signup and view all the answers

What is the purpose of the low water cut-off in an immersion boiler?

To protect the elements and the shell from overheating (D) Signup and view all the answers

What is the difference between a submerged electrode design and a jet-type electrode design electric boiler?

The water is sprayed onto electrodes in a jet-type electrode design (A) Signup and view all the answers

What is a disadvantage of electric boilers compared to fossil fuels?

Electricity is usually more expensive than fossil fuels (B) Signup and view all the answers

What is a characteristic of the packaged boiler concept?

It includes controls, feed pumps, and condensate tank all within one cabinet (A) Signup and view all the answers

What is the maximum pressure at which immersion boilers can produce steam?

2100 kPa (C) Signup and view all the answers

What is a safety precaution that operators must take when approaching electric boiler electrical connections?

They must observe safe limits to avoid dangerous contact (B) Signup and view all the answers

How is the boiler output controlled in an electrode boiler?

By raising or lowering the control sleeve (A) Signup and view all the answers

What is the function of the proportioning feed water regulator in an electrode boiler?

To maintain a constant water level in the boiler (C) Signup and view all the answers

What is a primary benefit of using electric boilers in traditional power plants?

Reducing the overall energy costs (B) Signup and view all the answers

In what type of facilities are electric boilers often used due to the availability of low-cost electricity?

Aluminum smelters (D) Signup and view all the answers

What is a potential advantage of using electric boilers over large fossil fuel boilers during periods of low process steam demand?

Lower operating costs (C) Signup and view all the answers

What is a common use of low-capacity electric boilers?

Low-pressure heating (D) Signup and view all the answers

How can electric boilers be used to support standby steam generators?

By keeping standby steam generators warm (A) Signup and view all the answers

What is a characteristic of electric boilers that makes them suitable for certain power plant applications?

Flexibility in steam production (B) Signup and view all the answers

What is the primary reason why electric boilers do not produce smoke, dust, or ashes?

They do not use fuel to generate heat (D) Signup and view all the answers

What is the purpose of the electrodes in an electrode-style electric boiler?

To produce steam through the passage of electric current (D) Signup and view all the answers

Why is the steam production rate in a submerged electrode design electric boiler self-regulating?

Because the pressure in the generating chamber changes with the load (A) Signup and view all the answers

What is the primary advantage of electric boilers in terms of environmental impact?

They produce no pollution at the point of use (A) Signup and view all the answers

Why are electric boilers typically more expensive to operate than fuel-fired boilers?

Because electricity is usually more expensive than fossil fuels (A) Signup and view all the answers

What is the primary difference between a submerged electrode design and a jet-type electrode design electric boiler?

The way the water is supplied to the electrodes (B) Signup and view all the answers

Why is it necessary for operators to observe safe limits when approaching electric boiler electrical connections?

To avoid electrical shock (C) Signup and view all the answers

What is the primary function of the control cylinder in an electrode boiler?

To position the control sleeve hydraulically (D) Signup and view all the answers

What is the purpose of the generating chamber in an electrode-style electric boiler?

To produce steam in response to the load (A) Signup and view all the answers

What is the purpose of the nozzle plate in an electrode boiler?

To direct the water to the counter electrode (D) Signup and view all the answers

Why do electric boilers pose no threat of furnace explosion?

Because they do not use fuel to generate heat (A) Signup and view all the answers

How do immersion heater boilers vary their firing rate and steam production?

By turning on and off the power supply to the heating elements (C) Signup and view all the answers

What is the primary advantage of electric boilers in terms of installation and replacement?

They can be installed or replaced quickly and easily (A) Signup and view all the answers

What is the function of the low water cut-off in an immersion boiler?

To protect the elements and shell from overheating (B) Signup and view all the answers

What is the maximum capacity of electrode boilers?

Up to 85 450 kg of steam per hour (B) Signup and view all the answers

What is the role of the electronic boiler pressure and load control system in an electrode boiler?

To maintain the steam pressure at set point (A) Signup and view all the answers

What is the arrangement of the heating elements in an immersion boiler?

Submerged beneath the boiler water level (A) Signup and view all the answers

What is the purpose of the boiler design shown in Figure 3?

To demonstrate the operation of an immersion boiler (C) Signup and view all the answers

What is the effect of increasing the load requirements on an electrode boiler?

The control sleeve is raised to increase steam production (B) Signup and view all the answers

What is the benefit of the packaged boiler concept in electric boilers?

Simplified maintenance and operation (C) Signup and view all the answers