Boiler and Classification
May 16, 2021
Steam Boiler is a device to produce water vapor, which will be used for heating or propulsion. Boiling fuels range from the popular coal and fuel oil, to electricity, gas, biomass, nuclear and others. The boiler was the most important part of the invention of the steam engine which was the trigger for the birth of the industrial revolution.
A steam boiler must meet the following requirements:
1. Within a certain time must be able to produce steam with a certain weight and pressure greater than 1 atmosphere.
2. The steam produced should be as low as possible
3. If an advanced heating device is used, then in irregular use of steam, the steam temperature should not change much and must be easily adjusted
4. At the time of motion where the use of steam varies, the steam pressure must not change much
5. The steam should be able to be formed with the lowest possible amount of fuel
6. The fuel-shifting arrangement must be such that the fuel can be burned without the need for excessive cost and effort.
Material
The vessel in a steam boiler is usually made of steel (steel / alloy steel), or initially of wrought iron. Stainless steel is actually not recommended (by the ASME Boiler Code) for use in the wet parts of modern steam boilers, but is often used in super heaters that will not be exposed to boiler fluids. Copper or brass are often used because they are easier to use. manufacturing for small steam boilers. Historically, copper is often used for firebox (especially for steam locomotives, because of its malleability and high heat conductance; however, today, the high cost of copper is an uneconomical and cheaper option to use substitutes (such as steel). )
For most Victorian boilers, only open the highest quality wrought iron, which is assembled using a rivet. The high quality of the sheet and its suitability for high reliability are used in critical applications, such as high pressure steam boilers. In the 20th century, design practically moved towards the use of steel, which is stronger and cheaper, with welded construction, which is faster and with less labor.
Cast iron is used for heating vessels for water heating. Although a heater is usually called a "boiler", because its purpose is to make hot water, not steam, because it operates at low pressure and avoids actual boiling. The brittleness of cast iron makes it unsuitable for high pressure steam boilers
Applicable regulation in Indonesia
Certification for Steam Boiler and Steam Boiler operators refers to the following regulations:
1. ASME sect. I, II, and V
2.The Steam Act of 1930
3. Steam Regulations 1930
4. Law No. 1 year 1970
The inspection is carried out by a Dinas Tenaga Kerja Dan Transmigrasi, through a body appointed by the Ministry of Manpower. Operators must attend boiler training through a 3rd party appointed by the Ministry of Manpower to conduct training and issue certificates.
Boiler Working Principle
A boiler or steam boiler is a machine device that functions to convert water into steam. The process of changing water to steam occurs by heating the water in the pipes by utilizing the heat from the combustion of fuel. Combustion is carried out continuously in the combustion chamber by flowing fuel and air from outside.
The steam produced by the boiler is superheated steam with high pressure and temperature. The amount of steam produced depends on the heat transfer surface area, flow rate and heat of combustion applied. Boilers whose construction consists of pipes filled with water are called water tube boilers.
Water Tube Boiler water tube boiler
In generating units, boilers are also commonly referred to as steam generators, considering that the meaning of the word boiler is only boilers, while in reality, high-pressure superheated steam is produced from the boiler.
In terms of the fuel used, the PLTU can be divided into:
1. Coal Fired Power Plant
2. PLTU Minyak
3. Gas power plant
4. Nuclear power plant or nuclear power plant
Types of coal-fired power plants can still be distinguished based on the combustion process, namely PLTU with pulverized coal combustion (PC Boiler) and PLTU by burning bulk coal (Circulating Fluidized Bed).
The difference between PLTU Coal and PLTU oil or gas is in the equipment and systems for handling and burning fuel as well as handling the ash waste. Coal steam power plants have more and more complex auxiliary equipment than oil or gas power plants. PLTU gas is the PLTU with the simplest tools to help.
Layout of Pulverized Coal (PC) Coal Boiler Layout of Pulverized Coal (PC) Coal Boiler Layout of the Circulating Fluidized Boiler (CFB) Layout of Circulating Fluidized Boiler (CFB) Judging from the pressure of the boiler combustion chamber, PLTU can be divided into:
1. PLTU with Pressurized Boiler
2. PLTU with Balanced Draft Boiler
3. PLTU with Vacuum Boiler
The furnace pressure control system is usually called the draft or static pressure in the combustion chamber where the fuel combustion process takes place. PLTU with a pressurized boiler (positive combustion chamber pressure) is used for burning fuel oil or gas. Positive combustion chamber pressure is caused by air blowing from the forced compressed fan (FDF). The exhaust gases exit the combustion chamber to the atmosphere due to the pressure difference.
PLTU with Balanced Draft Boiler (balanced pressure) is commonly used for burning coal fuel. The combustion chamber pressure is kept slightly below atmospheric pressure, usually around –10 mmH2O. This pressure is generated from the arrangement of two fans, namely the induced draft fan (IDF) and the forced draft fan (FDF). FDF functions to supply combustion air to the combustion chamber (furnace) in the boiler, while IDF functions to suck gas from the combustion chamber and throw it into the atmosphere through the chimney. Meanwhile, the PLTU with a vacuum boiler has not been developed anymore, so that currently no one has implemented a PLTU with a negative pressure boiler.
Boiler Water Cycle
The water cycle is a chain link in the working fluid cycle. The boiler is supplied with water and produces steam to flow into the turbine. Water as a working fluid is filled to the boiler using a fill water pump through the economiser and accommodated in the steam drum.
The economiser is a tool which is the last water heater before it goes into the drum. Inside the economiser, water absorbs exhaust gas heat that comes out of the superheater before being discharged into the atmosphere through the chimney.
The equipment that is passed in the water cycle is the boiler drum, down comer, bottom header and riser. The water cycle in the steam drum is, water from the drum drops through the down comer pipes to the bottom header. From the underwater header, it is distributed to the heating pipes (risers) which are arranged to form the walls of the boiler combustion chamber. In the riser, the water is heated and rises to the drum again due to the temperature difference.
Heat transfer from the fire (flue gas) to water in boiler pipes occurs by radiation, convection and conduction. As a result of heating, besides the temperature rising to boiling, water also circulates naturally, namely from the drum down through the down comer to the lower header and back up to the drum through the riser pipes. The existence of this circulation is very necessary in order to cool down the heating pipes and speed up the heat transfer process. The speed of circulation will affect the production of steam and increase in pressure and temperature.
Apart from natural circulation, it is also known as forced circulation. For this type of circulation a circulation pump is used.. Some of the advantages of the forced circulation system include:
1. Faster start (warm-up) time
2. Has a better response in maintaining water flow to heating pipes at start and full load.
3. Prevents the possibility of stagnation on the evaporation side
4. Water cycle in the boiler Water cycle
Classification of Steam Boilers
There are many kinds of steam boilers, and their development can keep up with today's technological advances. Of the many kinds of kettles need to be grouped into several parts. according to its use, construction and others. Below will be described the groupings in outline:
Division according to the Steam Act
Due to different places of use, according to Article 9 of the Steam Law, Steam Boilers are divided into three, namely:
1. Fixed kettle or land kettle, namely boilers used on land such as factories, power plants and others which have a fixed foundation.
2. Boats, namely boilers used on ships. Here, the boiler safety equipment usually has a slightly different construction from other boilers, given the condition of the ships that are always shaking while sailing.
3. Movable Kettles. namely boilers that are not included in the two groups of boilers mentioned above, such as railway boilers, pile boilers and others.
Division according to the construction
The boiler is made to produce steam by heating the water in it by hot gases from the combustion of fuel. The kettle should work as efficiently as possible; meaning that it must be able to produce as much steam as possible
n minimum fuel consumption.
Therefore, the boiler construction must be such that the heat from the fuel must be absorbed as much as possible by the boiler water to produce steam. To achieve this, the boiler construction is made of an arrangement of pipes that separate the water and the hot gases that heat the water.
Judging from the position of the boiler pipe is divided into:
1. Horizontal example: B&W Section
2. Vertical example: Foster Wheeler
3. Italic example: B&W Integral
Judging from the substances flowing in the pipe, the kettle is divided into three groups, namely:
1. Fire Tube Boiler
In this boiler, hot gases flow in the pipe, while the heated water is outside the pipe. Fire pipe boilers are typically used for steam capacities up to 14,000 kg / hr with a pressure of 18 kg / cm2. Fire pipe boilers can use fuel oil, gas or solid fuel in their operation. For economic reasons, most fire tube boilers are constructed as a "packaged" boiler (factory assembled) for all fuels.
For example: - Kettle Schots
- Cochran kettle
2. Water Tube Boiler
In this boiler, what flows in the pipe is boiler water, while the heating gases are outside the pipe. At the present time, these water pipe boilers are more rapidly developed. In a water pipe boiler, water is fed to the boiler through pipes into the drum. The circulating water is heated by the combustion gases to form steam in the steam region in the drum. This boiler is chosen when the steam demand and steam pressure are very high as in the case of boilers for power generation. Modern boilers are designed with steam capacities between 4,500 - 12,000 tonnes / hour, with very high pressure. Many water pipe boilers are constructed in packages if fuel oil and gas are used. For water pipe boilers running on solid fuel, it is not generally designed in a package manner. The characteristics of water pipe boilers are as follows:
a. Fored, induced and balanced draft help to increase combustion efficiency.
b. Less tolerant of water quality produced from water treatment plants.
c. Allows for a higher level of heat efficiency
For example: - Babcock and Wilcox kettle
- Foster Wheeler's Kettle
- Yarrow kettle
- I S D
- E S D (ESD I, II, III and IV)
3. Fire Pipe and Water Pipe Combined Boiler
In this boiler, there are two types of pipes, namely fire pipes and water pipes. The construction is generally like the Schots Kettle. And it seems that this boiler is made to correct the deficiencies that are contained in the Schots Kettle, such as poor water circulation in the boiler.
For example: - Werkspoor kettle
- Howden's kettle - Johnson
Judging from its use, the kettle is divided into:
Stationary boiler (stationary boiler) or fixed boiler. Which includes stationary are boilers that are placed on a fixed foundation, such as boilers for power generation, for industry etc.
Mobile boiler, portable boiler. Included in car boilers are boilers that are installed on a moving foundation (car), such as locomotive boilers, mobile locomotives and long boilers and others that seem to include marine boilers.
Judging from the location of the kitchen (Furnace Position), the kettle is divided into:
Internally fired steam boiler. In this case the kitchen is located (burning occurs) inside the kettle. most fire pipe boilers use this system.
Outernally fired steam boiler. In this case the kitchen is located (burning occurs) inside the kettle. most plumbing boilers use this system
Judging from the number of passages (Boiller Tube), the kettle is divided into:
Single tube steam boiler. In a single tube steam boiler, there is only 1 hallway, fire aisle and water aisle. Cornish boiler is a single fire tube boiler and simple vertical boiler is a single water tube boiler.
Multi tube steam boiler. Multi fire tube boilers, for example, scotch boilers and multi water tube boilers, for example, boilers B and W, etc.
Judging from the Drum Cover Shaft (Shell), the kettle is divided into:
Vertical steam boilers, such as cocharn boilers, clarkson boilers etc.
Horizontal steam boilers, such as cornish boilers, Lancashire, Scotch etc.
Judging from the shape and layout of the pipe, the kettle is divided into:
Boiler with straight, curved and squiggly pipes (stright, bent and sinous tubeler heating surface)
Boiler with a flat and sloping pipe (horizontal, inclined or vertical tubeler heating surface)
Judging from the circulation of water boilers (water circulation), boilers are divided into:
1. Natural circulation steam boiler.
In a natural circulation boiler, the circulation of water in the boiler occurs naturally, namely water that lightly rises, while natural convection flow occurs. Generally, boilers operate on a natural flow basis, such as Lancashire, Babcock & Wilcox boilers
2. Forced circulation steam boiler.
In forced-flow boilers, peksa flow is obtained from a centrifugal pump driven by an electric motor, such as a la-mont boiler, a benson boiler, a loeffer boiler and a velcan boiler.
Judging from the working pressure, the kettle is divided into:
low working pressure: ≤5 atm
medium working pressure: 5-40 atm
high working pressure: 40-80 atm
very high working pressure:> 80 atm
Judging from the capacity, the kettle is divided into:
low capacity: ≤2500 kg / hr
medium capacity: 2500-50000 kg / hr
high capacity:> 50000 kg / hr
Judging from the heat source (heat source), the kettle is divided into:
steam boiler with natural fuels
steam boiler with artificial fuel
steam boiler with electric kitchen
steam boiler with nuclear energy
Auxiliary Boiler
Namely a boiler that produces steam, which is used for auxiliary equipment, such as pumps, heaters and others. The types of boilers that are usually used as auxiliary boilers are, for example:
La Mont Exh Gas Economicer
Cochran Composite Boiler
B & W M - type
Foster Wheeler D - type.
Large motor boats generally have an auxiliary kettle. The benefits of this auxiliary kettle are for heating on the ship, such as space heating, kitchen, fuel. as well as to move auxiliary planes.
In general, this kind of boiler is oiled apart from the oil. usually also combined with the use of heat from the exhaust gas that comes out of the motor
There are several kinds of arrangements or systems, including:
On a ship there is an auxiliary kettle which is lined with oil. and a separate boiler which is specially sealed with the exhaust gas of the main motor. And each of these can occur independently of the formation of steam.
La Mont system.
The La Mont boiler is widely used to utilize a portion of the exhaust gas heat from the main motor for steam formation. This boiler is usually placed on the exhaust gas path of the main motor or in the chimney, thus it is located higher than the main motor (See figure).
The function of this boiler is actually only as a place for circulation of heat up, while the place for forming the steam is in another auxiliary boiler. Thus a circulation pump is needed to divert the water in the auxiliary boiler (for example Cochran) to the La Mont kettle to finally return to the auxiliary boiler again after taking heat. The steam generation produced by the auxiliary boiler is usually with a pressure of about 7 ato and a boiler water temperature of about 170 ° C.
The exhaust gas temperature ranges from 300 - 400 ° C and leaves the La Mont boiler about 220 ° C.
The La Mont kettle is heated by exhaust gases, almost all of which are a number of spiral-shaped pipes. Each spiral pipe ends connected by an intake and exhaust cabinet.
