Industrial tasks and boilers have always had a fairly close relationship, and the differing technical nature of each and every sector of industry means that boilers in general cover a broad range of specifications.
Consider the differences in the needs for heat production between the petrochemical and steel-cutting industries and even with just these two examples, the varied needs that need to be met by industrial boilers, are met through a few very different types of them.
Here we will explore these differences. Since boilers represent a solution that often needs to be bespoke to those facilities that use them, it makes sense that there are various types and designs.
We will do this by exploring six different types of boilers in terms of how they work, what their key features are, and how they can benefit certain types of facilities.
So, let’s get started:
Water Tube Boilers
Due to their ability to produce staggering pressures of up to 1500psi (103 bar), water boilers are commonly used for the production of thermal power in plants and facilities.
This, in turn, gives water tube boilers an extensive mass flow rate of between 4500kg/h and 120 000kg/h. Essentially allowing for more steam to be transferred each hour.
Here’s how they work:
Like many other types of combustion products, much of the functionality of water tube heaters relies on a central tube. In this case, water flows inside of the tube (as opposed to fire tube boilers which have water flowing on the outside of the tube).
This water is heated thanks to the concentrations of combustion gas that are flowing on the outside of the tube. When this gas is ignited, it heats the tube, producing superheated steam that can climb to temperatures of up to 550°C.
The combined high flow rate, temperature production and pressure of water tube boilers makes them one of the most efficient. Because of this, they are remarkably fuel efficient, resulting in lower costs of consumption.
They are also ideal for facilities that are challenged by available building space. This in in thanks to their flexibility when it comes to design.
Because of the extremely high pressures, as well as temperatures produced by water tube boilers, they have a noticeable improvement on the plants that make use of them.
There are one or two disadvantages to be aware of when using water tube boilers. They have fairly high maintenance costs, for one, but that is the result of their flexible and often complex design.
They are also not well suited to smaller industrial plants, since they are most effective when processing extremely high volumes of steam.
Fire Tube Boilers
While water tube boilers have water flowing through a tube while being heated from combustible gasses on the outside; the opposite is true for fire tube boilers.
Fire tube boilers contain a combustible gas within their tubes, while the water meant for heating flows along the tube’s outside. This allows the water on the outside of the tube to be evaporated, reaching temperatures of up to 170 °C, to create steam.
The temperature difference between the water tube boiler and the fire tube boiler is not the only major variance between them. The fire tube boiler also produces significantly less pressure than its water tube counter part at just about 100psi (6.8 bar).
Because of this, they are better suited to smaller scale plants than they are to large industrial ones. This might explain why they aren’t as commonly used today as they were in the past.
Even though they provide significantly less heat and pressure than fire tube boilers, there are still a number of benefits to water tube ones. The benefits are generally a matter of practicality when compared to the former.
Where maintenance is concerned, the fire tube boiler requires much less of it, which amounts to more consistent performance at less of a long-term cost; at least as far as upkeep is concerned.
Fire tube boilers are also uncomplicated to operate efficiently; unlike water tube boilers which do require some level of specialised skill.
The next benefit concerns the treatment of feed-water, which in other solutions is considered a necessary task to minimise health hazards.
They also offer a fair level of efficiency considering their running costs, with a flow rate of up to around 12000 kg per hour. This makes them ideal for use in smaller industrial facilities.
There are one or two disadvantages concerning the operation of fire tube boilers.
The first is that they are not particularly efficient when compared to other types, and this is due to poor thermal exchange not using thermal radiation.
They also have a greatly limited capacity for steam production, temperatures and pressure when compared to other boilers, which can be off-putting for larger facilities.
Still, they are quite a bit more affordable, both in their investment and running costs, so for others they might be perfect.
Packaged boilers take on a bit of a different design to the ones we have mentioned above, particularly with regards to the design of their flow tube. Whereas fire and water tube boilers sport an open design, the tube in packaged boilers is encapsulated, which creates a restricted space for combustion.
This restricted combustion also gives packaged boilers a much higher evaporation rate than other types of boilers, while simultaneously raising their thermal efficiency when compared to others.
These types of boilers require a supply of electricity for power supply, fuel for combustion, as well a feed of the water that is to be evaporated.
There are a number of unique benefits associated with packaged boilers when compared to the other types on this list.
The first major benefit is the exceptional efficiency that they offer compared to other types of boilers, especially when you consider their fuel consumption rate.
They also offer fairly easy installation and are also easy on the space that they take up, making them perfect for facilities with space limitations.
Packaged boilers also offer automatic burn management, which can help you minimise the costs of running them.
Because of their compact design, they are also fairly easy and affordable in terms of their maintenance, which will help your facility save in the long-run.
Of course, packaged boilers do come with a few disadvantages to be aware of if you are to get the best use out of them. Most of these cons can be overlooked in the face of the advantages that they offer, but it is still worth your while to know what they are.
The first thing to consider is the cost of investing in and implementing the use of a packaged boiler. They do come with a hefty initial cost which can be off-putting. But when compared to their long-term savings on running and maintenance costs, this initial price-tag is worth it.
They can also be fairly difficult to clean, particularly when it comes to their tubes since they are encapsulated. This can make maintenance a bit of a chore.
Packaged boilers are also better suited to small-medium plants and facilities than they are too large ones. This is partly due to their compact design but is also because of their limited capacity for steam production and thermal transfer
Fluidised Bed Combustion Boilers
Fluidised bed combustion boilers have a very different design to any of the previously mentioned types on this list.
Where other types make use of a combustible gas either inside or outside of an inner tube, these types generate heat through the production of high-velocity air.
Air moving at high speeds passes through a bed that has been divided and covered with sand. As the air moves through the bed, it creates a lot of turbulence, which in turn causes the sand to become suspended in the air.
As this happens, the sand on the bed becomes super-heated, to the point that it actually melts into a fluid. The risen temperatures of the sand are thusly ideal for instantly igniting coal or other fuels, at temperatures between 850 degrees Celsius and 950 degrees Celsius.
The next unique feature is that the fuel being used for combustion can be either a solid, a liquid or a gas.
These types of boilers are uniquely beneficial, especially to more concentrated industrial zones.
The first major benefit includes their incredibly high combustion efficiency thanks to the rate at which they can ignite the fuel, which allows facilities to save a lot of time on their heating processes, even when done to high capacities.
They are also flexible in terms of the fuel types they use, being able to use solid, liquid or gas-based fuels interchangeable. They also allow for low-grade fuel to be burnt efficiently, while also producing less pollution.
What makes these types of boilers particularly well-suited to industrial tasks is that they offer exceptional resistance to corrosion and erosion, while also requiring fairly easy maintenance.
While the exterior of these types of boilers is highly resistant to erosion, their inner tubes may be damaged by it over time.
Also, should any clogging occur in the inlet of the bed, there is a chance that the system will produce uneven air temperatures.
Due to their high thermal efficiency, they also have to stand for a very long time when they are cooled, with extreme examples taking as long as 48 hours.
They also have a slightly lower combustion temperature when compared to the average boiler, at around 750 °C.
Pulverised Fuel Boilers
The pulverised fuel boiler gets its name from the types of fuel it uses for combustion, which is what sets it apart from any other boiler on this list.
This is because they rely on the supply of powdered fuel for their operations, which is usually coal.
For these boilers, coal is first reduced to a powder using a grinding mill. Once it has been ground down, the coal is then transferred to the boiler’s combustion chamber and is taken there using a current of hot air.
Once in the combustion chamber, the coal is then ignited to produce temperatures as high as 1700 degrees Celsius.
Because of the temperatures they use, and because of the type of fuel they require, pulverised fuel boilers are most commonly used in coal power plants.
There are a number of benefits to using these types of boilers, most of which are associated with efficiency.
For instance, thanks to the fact that the coal being used for fuel is ground down, it offers a greater surface area during combustion. This, in turn, results in improved thermal efficiency for the boiler.
The next big advantage is that they tend to be more efficient with the air that they use. Due to the improved efficiency from ground coal, these boilers have a greatly reduced need for secondary air during combustion.
One of the main disadvantages of using these types of boilers is a result of the ground coal that gives it efficiency.
This is that, during combustion, these types of boilers generally produce an excess pf fly ash, which can be a real chore to remove from the system’s exhaust.
Since the coal being used is rendered to a powder and therefore acts as somewhat of gas, it also presents a possibility of an explosion, and so must be used with absolute care.
Contact Combustion & Heating Systems for Details
As you can see, there are a number of different types of boilers out there, each with its own characteristics that meet certain types of facilities and plants.
If your facility is in the market for high-quality heating systems on the West Rand, be sure to get into contact with our representatives today, or visit the Combustion & Heating website today for further details on our offers and services.