An Overview of Types of Steam Boilers and Its Applications
Steam boilers play an integral part in most of the process and manufacturing industries in today’s world. Steam boilers are ideal for process operations as steam has a higher energy holding capacity and is safe and convenient to use. Depending on various factors such as industrial requirements, applications, fuel availability, steam pressure, volume, etc., steam boilers can be simple or complex. The two primary types of steam boilers used are Fire Tube Boilers and Water Tube Boilers. Over the last years, boiler manufacturers have expanded the options in the two basic types, offering extensive options to the customers. Let us dive deep into the details of both types of boilers.
Fire Tube Boilers:
As the name suggests, fire tube boilers function with the fire (combustion gases) inside the tubes. Fire-tube boilers have been prominent for over the century. Fire tube boilers are preferred by industries requiring high-pressure steam.
Functioning of Fire Tube Boilers:
The burner ignites in tubes immersed in water, which is included in the main vessel of the boiler. With several fire tubes, the heat from the gases passes to the water and heats it to the boiling point. The generated steam is captured in a space above the water and exits from the steam outlet for operational purposes. Since both the steam and water share the same vessel, the steam pressure is restricted. It is important to note that exceeding the vessel pressure beyond its capacity would lead to a hazardous consequence.
Fire-tube boilers can be classified based on the location of their furnace. They are termed external furnaces and internal furnaces.
External furnaces are further divided, into 3 types:
Horizontal-return tubular fire tube boiler
Short firebox fire tube boiler
Compact fire tube boiler
On the other hand, internal furnaces are divided, into 2 types:
Horizontal tubular fire tube boiler
Vertical tubular fire tube boiler
Advantages of Fire Tube Boilers:
Simple design and low maintenance
Easy to operate for efficient performance
Feedwater treatment is not necessary
Economical as compared to Water Tube Boilers
Ideal for Small Industries
Disadvantages of Fire Tube Boilers:
Maximum working pressure up to 20 bar
Overall efficiency up to 75%
Difficult to handle load fluctuations
Possibility of Drum Failures and Explosions if Neglected
Steam generation and steam quality is low as compared to Water Tube Boilers
Water Tube Boilers:
As the name implies, water tube boilers function with the water inside the tubes. The gases from the furnace enter a large containment area, in which it bounces off the rear wall, passing the heat to the water tubes uniformly and efficiently. Water tube boilers reduce fuel costs and are significantly safe to use as the possibility of steam explosion due to failure is less because of less water.
Functioning of Water Tube Boilers:
The water tube boiler consists of multiple water tubes in a chamber. These tubes are sealed and can tolerate pressure individually without impacting the adjacent tube. The heat is passed to the water through the metallic tubes. The water heated rises to the top of the boiler in the steam drum. The steam is produced at a high rate in water tube boilers.
Contrary to fire tube boilers, the heat source surrounds the water in water tube boilers. It results in reduced stress on the boiler. Water-tube boilers are widely used for generating steam at high pressure and volume.
Components of Water Tube Boilers:
Water-tube boilers generally include the following:
Boiler Shell: external cylindrical unit of the pressure vessel
Burner: source of ignition to heat the water
Mud Drum: located at the bottom of the water container that accumulates the impurities from the water. It also facilitates blowdown operations.
Strainer: filter to strain out the solid elements
Sight Glass: monitoring the water levels
Advantages of Water Tube Boilers:
Requires less floor area
Direction of water circulation is well defined
Easily handles load fluctuations
Rate of steam generation and steam quality are high
Overall efficiency up to 90% with an economizer
Ideal for large industries and power plants
Disadvantages of Water Tube Boilers:
Complex in design and high maintenance cost
Requires trained operator for efficient operation
Uneconomical for small industries
Feedwater treatment is essential to prevent overheating and bursting
Efficiency in Steam Boilers:
Boiler manufacturers generally rate the boiler efficiency higher than its actual efficiency. However, by complying with few factors, industries can derive maximum efficiency from steam boilers. Some of the factors that impact boiler efficiency include:
Regular Maintenance of steam boilers enhances the boiler efficiency. In fact, lack of maintenance can reduce the boiler efficiency up to 10%
Boiler accessories like economizers can add up the efficiency level of the steam boiler
Proper boiler size and the frequent on-off cycle can significantly impact the steam boiler efficiency
Rakhoh Boilers manufactures an extensive range of steam boilers for more than 20 process industry sectors in India and overseas. We are reputed to provide high-quality steam boilers such as Membrane Boilers, Bi-Drum Boilers, Husk Fired Boilers, Oil fired Boilers, Waste Heat Recovery Boilers, Thermic Fluid Heaters, etc. Apart from boilers, we provide the best boiler accessories and boiler services that boost the efficiency and performance of the steam boiler system.
Learn more about our products and services at www.rakhoh.com
What is a Steam Boiler ? Types, Parts and Maintenance
You might be shocked to hear that different parts of our everyday life are connected to steam boilers! The food we eat, the clothes we wear, and even the water we use are all affected by steam boilers. Different industries depend on the existence of a boiler in their set up and they can even be helpful for residential uses as well! But what are steam boilers and how do they work? Linquip is here to answer all your questions in this article. Read on to learn more about steam boilers and their use in our daily lives.
What is a Steam Boiler?
Steam Boiler (also known as Boiler) is a heat exchanging system that creates steam for outside use. This vessel contains a set of tubes and two other parts, one for combustion and another to contain water. These are the main component but the system is far more complicated than that and contains many other components that together help achieve the desired outcome.
What are steam boilers used for?
The main job of a steam boiler is to produce steam. Steam boilers are essentials whenever you want to create heat or steam. These boilers can be small or large depending on the task they are designed for. Whether it is for commercial use or industrial use, boilers are there as an important part of the process.
A steam boiler can be used to generate electricity, process foods, chemical manufacturing, create pulp and paper, and they are even an essential part of the fashion industry to help in dyeing process. These are just some of the great tasks of steam boilers not to mention that even making a small candy might need steam boilers! So, they play a huge role in our everyday life.
Types of steam boilers
Steam boilers have different types but there are two basic ones and others are somewhat an extension of these two: Firetube and Watertube.
Firetube boiler
In this steam boiler type, the combustion gases flow inside tubes and transfer heat to the water. They can be categorized into the number of passes, meaning the number of times that gas flows around the vessel to transfer heat to water. Two zones have been designed for turnaround: Dryback and Waterback. First one is refractory-lined and in the second design, the turnaround zone is water-cooled which eliminates the refractory lining.
Watertube boiler
In this type of steam boiler, the tubes contain flowing water and the exhaust gases are in the shell side passing around the tube surface to affect the temperature of the water inside the tubes. Watertube boilers are used in places that go through high steam pressures since they can withstand higher internal pressure than chamber shells in the firetube type. The steam pressure for these types can be as high as 3,000 psi or sometimes even higher.
Watertube boilers are also capable of generating saturated or superheated steam for different uses specially for processes that include dry, high energy, and high-pressure steam such as steam turbine power generation.
Steam boiler parts and components
Different boilers might have different designs, but three main parts remain the same throughout various designs: The combustion chamber, the heat exchanger, and the burner. Now, we will briefly explain each one.
1. The combustion chamber
This chamber, usually made from cast iron, is responsible for burning the fuel inside. The heat this chamber generates will be transferred to the heat exchanger part of the system. plus, the temperatures inside the combustion chamber can be increased up to several hundred degrees in a short period of time.
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2. The heat exchanger
A series of flue passages filter the water around the combustion chamber in a hydronic boiler system. Next, the boiling water gone under pressure will be pumped through pipes into heaters or radiators and the heat energy produced in the boiler will be separated from the water.
3. The burner
When the system is required to produce heat, the thermostat will send electronic signals to the burner to activate the reaction. The burner is the part that initiates the combustion reaction inside the boiler. An outside source with the help of a filter mechanism pumps fuel to the boiler. The source is often an adjacent fuel tank. The fuel then turns into a fine spray with the help of burner’s nozzle and will be ignited which results in reaction in the combustion chamber.
How do steam boilers work?
Steam boilers mainly work the same way. They create a combustion reaction between fuel and air to ignite a flame into different tubes. The heat produced from this reaction will be transferred from the tubes into the water and the water evaporates into steam. The produced steam will then be used for a specific heating application. Next, the steam is condensed back into the water as condensate and can be collected and returned to the boiler.
Which steam boiler is better?
It is difficult to say which steam boiler is better. Although firetube boilers sell more in the market, watertube boilers are more capable for different uses. As it was mentioned earlier, tolerating high pressure is among the most important traits of watertube boilers. So, it depends on the customer use to pick the better choice.
Steam boilers maintenance
Steam boilers need low maintenance that includes cleaning the system to keep the efficiency of the set up as high as possible. Removing residue and debris from the chamber and replacing gaskets and different equipment, as well as efficiency check, are all on the list of steam boiler maintenance and it requires an expert to keep an eye on the system.
Is steam boiler the same as a steam generator?
Many people assume these two are the same, but it is a little tricky. Steam generators compared to steam boilers, contain less steel in their design and they use a single tube coil instead of boiler tubes and a feedwater pump continuously pumps feedwater through the coil. Steam generators convert water into steam but in a single pass through the water coil transferring the hot gas into the desired output.
Steam generators, on the other hand, are smaller than steam boilers since they don’t use any pressure vessel. But the main difference is that steam generators have low turn-down rates and are less capable of providing steam. with that being said, let’s review some of the advantages of steam boilers.
Advantages of a steam boiler
If you need to know what the perfect system that can fulfil each and every requested demand is, you should consider the output and the capabilities of the system. Even though steam generators are quick, their capacity is low. So, one of the advantages of a steam boiler can be the fact that they can live up to your expectations through various demands. They are durable and robust enough to get you through many years. All you need to do is to have an expert for its annual maintenance.
Steam boiler planning Industrial Heat
Combustion takes place in pass 1, the flame tube. Roughly half the heat is transferred here, primarily by means of thermal radiation to the flame tube walls. The combustion is complete at the end of the flame tube and the flue gases are diverted in the internal water-cooled reversing chamber into pass 2.
Roughly 35% of the thermal output is then transferred in the pipe panel of pass 2. The flue gases then enter the reversing chamber at the front on the outside at a temperature of ~400°C where they are redirected to pass 3.
After pass 3, the temperature of the gases is still normally 200 – 280°C, depending on the temperature of the medium in the water chamber of the boiler.
This heat potential can then be further utilised in an integrated economiser so that a temperature of 90 – 140°C is reached at the flue outlet.
This allows single flame-tube boilers to reach a steam output of up to 28,000kg/h.
Double flame-tube boilers can be used to achieve higher outputs. These boilers feature two flame tubes with separate second and third smoke-tube pass arranged in parallel in the water space. This allows boilers with steam outputs of up to 55,000kg/h to be built. The unrestricted single flame-tube operation also increases the reliability and control range of the boiler.
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