UNDERSTANDING BOILER

Understanding Boiler
Boilers are pressure vessels with shapes and sizes designed to produce steam or steam. Steam with a certain pressure is then used to flow heat to a process.

WORK PRINCIPLE
The working principle of a boiler (Saturated steam) can be seen in the picture below.

Feed water after going through the pretreatment process in the softener or air condensate pumped to the economizer.
At the economizer there is an initial warm-up that uses the exhaust heat in the chimney. Initial heating is intended to improve the efficiency of the boiler.
lass=”yoast-text-mark” />>Then the feed water goes into the kettle but the chemichal is given according to the prescribed dose.
>After that the feed water which is heated in the steam boiler turns the phase into steam and is ready to be distributed.
After the steam turns the phase back into water (water condensate), it can be pumped back into the kettle again. Make up water is only used to replace water loss due to the blowdown process.

BOILER SYSTEM

Feed water system
Feed water is the water supplied to the boiler to be converted into steam. While the feed water system is an automatic water supply system for boilers according to steam requirements. There are two sources of feed water, namely:
o Condensate: steam that has changed phase into water (condensing)
o Make up water: raw water that has been processed

To improve the efficiency of boiler feed water before being supplied to a heated boiler, first use waste heat from the chimney.

Steam System
The steam system is the process of controlling steam production in a boiler, such as: capacity, pressure, etc. Furthermore, steam is distributed to users through the pipeline.

Fuel System
Fuel system is all equipment or equipment used to provide boiler fuel. The equipment used depends on the type of fuel used by the boiler.

BOILER CLASSIFICATION

Various forms of boilers have developed following technological advancements and evaluations of previous boiler products which are affected by boiler exhaust gases that affect the environment and what kind of steams products will be produced. The following classifications of boilers have been developed:

a. Based on pipe type:
Fire Tube:
The type of fire pipe boiler has the characteristics: producing low steam capacity and pressure.
>How it works: the ignition process occurs in the pipe, then the heat generated is delivered directly into the boiler which contains water. The size and construction of the boiler affect the capacity and pressure produced by the boiler.

Water Tube:
The type of water pipe boiler has the characteristics: producing high capacity and steam pressure.
>How it works: the ignition process takes place outside the pipe, then the heat generated heats the pipe containing water and beforehand the water is conditioned first through an economizer, then the steam produced first is collected in a steam-drum. Until the pressure and temperature are appropriate, through the secondary superheater stage and the new superheater the steam is released into the main distribution pipe. In a water pipe, flowing water must be conditioned on minerals or other substances which dissolve in the water. This is a major factor that must be considered for this type.

b. Based on the fuel used:

Solid Fuel
The type of solid fuel boiler has the characteristics: the price of combustion raw materials is relatively cheaper compared to boilers that use liquid fuel and electricity. The value of efficiency of this type is better when compared to electric type boilers.
>How it works: heating that occurs due to combustion between mixing solid fuels (coal, baggase, rejected products, municipal waste, wood) with oxygen and heat sources.

Fuel Oil<br />The type of liquid fuel boiler has the characteristics: the price of the most expensive combustion raw materials compared to all types. The value of this type of efficiency is better compared to solid fuel and electricity boilers.
s=”yoast-text-mark” />>How it works: heating that occurs due to combustion between mixing liquid fuels (diesel, IDO, residue, kerosene) with oxygen and heat sources.

<strong>Gaseous Fuel
The type of gas fuel boiler has the characteristics: the price of the cheapest combustion raw material compared to all types of boilers. The value of efficiency of this type is better when compared to all types of boilers based on fuel.
>How it works: combustion that occurs as a result of mixing gas fuel (LNG) with oxygen and heat sources.

 Electric
The type of electric boiler has the characteristics: the price of heating raw materials is relatively cheaper compared to boilers that use liquid fuel. The value of efficiency of this type is lowest when compared to all types of boilers based on their fuel.
>How it works: heating that occurs due to a power source that supplies a heat source.
c. Based on boiler use:
# Power Boiler
The type of power boiler has characteristics: its main use as a producer of steam as a power plant, and the remainder of steam is used to run industrial processes.<br class=”yoast-text-mark” />>How it works: the steam produced by this boiler uses a boiler water tube type, the resulting steam has a large pressure and capacity, so it is able to rotate the steam turbine and produce electricity from the generator.

Industrial Boiler

The industrial boiler type has characteristics: its main use is to produce steam or hot water to run industrial processes and as an additional heater.<br />How it works: the steam produced by this boiler can use a type of water tube or fire tube boiler, the results of the steam produced have a large capacity and moderate pressure.

 Commercial Boilers
The commercial boiler type has the characteristics: its main use is as a producer of steam or hot water as a heater and in addition to carrying out the commercial operation process.
How it works: the steam produced by this boiler can use a type of water tube or fire tube boiler, the results of the steam produced have a large capacity and low pressure.

Residential Boiler
The type of residential boiler has the following characteristics: its main use is producing steam or low pressure hot water used for housing.
How it works: the steam produced by this boiler uses a type of fire tube boiler, the results of the steam produced have low pressure and capacity

Heat Recovery Boilers
The type of heat recovery boiler has the characteristics: its main use is producing steam from unused hot steam. These results are used to run industrial processes.
How it works: the steam produced by this boiler uses a type of water tube boiler or fire tube boiler, the results of the steam produced have a large pressure and capacity.

d. Based on boiler construction:
 Package Boiler
The type of boiler package has characteristics: boiler assembly is carried out in the manufacturer, direct delivery in the form of a boiler.

Site Erected Boiler
Site erected boiler type has characteristics: boiler assembly is carried out in the place where the boiler will be located, shipping is carried out per component.

Boiler Types Based on Their Application

Boilers can be classified according to their application, operating capacity, pressure, construction, fuel, and heat-transfer arrangement. The correct boiler type must be selected according to the required steam capacity, operating pressure, steam quality, process load, installation area, transportation access, fuel availability, and applicable safety regulations.

Industrial Boiler

An industrial boiler produces steam or hot water for manufacturing and industrial processes. Typical applications include:

• Food and beverage processing
• Textile production
• Chemical processing
• Palm-oil processing
• Plywood and wood production
• Paper manufacturing
• Pharmaceutical production
• Rubber and plastic processing
• Industrial drying
• Tank and reactor heating

Industrial boilers may use fire-tube, water-tube, once-through, electric, biomass, or heat-recovery construction.

A fire-tube boiler is commonly selected for moderate steam capacity and pressure. A water-tube boiler is generally preferred when the application requires higher capacity, higher pressure, faster response, or superheated steam.

Industrial boiler capacity can range from several hundred kilograms of steam per hour to hundreds of tonnes per hour, depending on the process.

Commercial Boiler

A commercial boiler supplies hot water or steam for commercial buildings and service facilities, including:

<ul>

• Hotels
• Hospitals
• Shopping centres
• Office buildings

<li>Commercial laundries

• Restaurants
• Educational facilities
• Apartment buildings
• Sports facilities
• Public buildings

Commercial boilers generally operate at lower capacities than large industrial boilers. They are primarily used for:

• Domestic hot water
• Space heating
• Laundry
• Kitchen operation
• Sterilisation
• Swimming-pool heating
• Building services

The boiler may use a fire-tube, water-tube, condensing, electric, or modular configuration. Steam pressure and capacity depend on the actual application and cannot be classified as low pressure in every case.

Residential Boiler

A residential boiler normally produces hot water for:

• Space heating
• Radiator systems
• Underfloor heating
• Domestic hot-water systems

Most residential boilers are compact hot-water units rather than industrial steam boilers. Common designs include:

• Wall-mounted boiler
• Condensing boiler
• Combi boiler
• Electric boiler
• Small gas-fired boiler

A residential boiler is not always a fire-tube boiler. Modern units may use compact coil, sectional, finned-tube, or condensing heat-exchanger construction.

Residential equipment generally has a much lower heat output than commercial or industrial boilers.

Heat-Recovery Boiler

A heat-recovery boiler produces steam or hot water by recovering energy from a hot exhaust-gas stream that would otherwise be discharged.

Potential heat sources include:

• Gas-turbine exhaust
• Engine exhaust
• Furnace exhaust
• Kiln exhaust
• Incinerator exhaust
• Process-reactor exhaust
• High-temperature dryer exhaust
• Industrial flue gas

The correct term is waste exhaust heat, not “unused hot steam.” The exhaust gas transfers heat to water inside the boiler, producing hot water, saturated steam, or superheated steam.

A Heat Recovery Steam Generator, or HRSG, captures energy from a gas-turbine exhaust and uses it to generate steam. This operating principle is also explained by the U.S. Department of Energy.

Depending on its design, a heat-recovery boiler may use:

• Water-tube construction
• Fire-tube construction</li>
• Smoke-tube construction
• Economiser coil
• Once-through steam generator
• Multi-pressure HRSG

Some systems use supplementary firing when the available exhaust energy is insufficient to meet the required steam demand.

Comparison of Boiler Types by Application

<td>Heat-recovery boilerSteam or hot waterPower and process plantsProject-specific

The terms industrial, commercial, and residential describe the boiler’s application. They do not automatically determine whether the boiler must use a fire-tube or water-tube design.</p>

Boiler Types Based on Construction and Assembly

Package Boiler

A package boiler is primarily assembled and tested at the manufacturer’s workshop before being delivered to the installation site.

Depending on the scope of supply, a package boiler may arrive complete with:

• Boiler pressure vessel
• Burner
• Combustion controls
• Level controls
• Feedwater pump
• Valves
• Safety devices
• Control panel
• Instrumentation
• Insulation and casing
• Boiler fittings and mountings

After delivery, the site team normally connects the boiler to:

• Fuel supply
• Electrical power
• Feedwater line
• Steam outlet
• Blowdown line
• Chimney
• Condensate-return system
• Water-treatment system

A packaged shell boiler is delivered with its primary mountings and requires site utility and piping connections before operation, as described in the Spirax Sarco packaged shell boiler guide.

Advantages of a Package Boiler

• Shorter site-installation period
• Better workshop quality control
• Factory assembly and testing
• Lower amount of field welding
• Compact arrangement
• Easier transportation for small and medium capacities
• Faster commissioning

Limitations of a Package Boiler

<ul>

• Restricted by road-transport dimensions
• Restrict

ed by lifting capacity

• Restricted by site-access dimensions
• Less suitable for extremely large capacities
• Site modifications may be difficult after fabrication
• Foundation and access routes must be prepared before delivery

Site-Erected Boiler

A site-erected boiler is delivered in separate components and assembled at its permanent operating location.

Components may include:

• Steam drum
• Mud drum
• Water-wall panels
• Boiler bank
• Furnace structure
• Superheater
• Economiser
• Air preheater
• Steel supporting structure
• Casing and refractory
• Fans
• Ducting
• Fuel-handling equipment
• Control and safety systems

Site-erected construction is generally selected when:

• Boiler capacity is too large for transportation as one package
• Site access is restricted
• The boiler requires a large furnace
• Biomass or solid fuel is used
• High pressure or superheated steam is required
• The equipment must be integrated into an existing plant
• Transportation weight and dimensions exceed local limits

Advantages of a Site-Erected Boiler

• Suitable for very large boiler capacities
• Allows a customised furnace and heat-transfer surface
• Suitable for biomass and solid fuel
• Can accommodate complex emission-control equipment
• Suitable for high-pressure water-tube construction
• Can be integrated with power-generation systems

Limitations of a Site-Erected Boiler

• Longer construction schedule
• More field welding and inspection
• Greater dependence on site conditions
• Higher installation complexity
• Requires temporary facilities and lifting equipment
• Requires strict quality control during erection
• Commissioning generally takes longer

Package Boiler vs Site-Erected Boiler

1: Industrial Package Boiler for a Food Factory

A food-processing factory requires saturated steam for cooking, cleaning, and production.

Project data:

• Steam demand: 2,500 kg/hour
• Working pressure: 10 barg
• Operating time: 16 hours/day
• Fuel: natural gas
• Steam condition: saturated
• Available installation area: limited
• Production load: relatively stable

Recommended Boiler

A 2.5-ton/hour packaged fire-tube steam boiler can be considered.

The fire-tube package boiler is appropriate because:

• The steam capacity is within a practical package-boiler range.
• The required pressure is moderate.
• Saturated steam is sufficient.
• Workshop fabrication reduces field work.
• The complete boiler can be delivered as one major package.
• Installation and commissioning can be completed relatively quickly.
• A modulating gas burner can follow changes in steam demand.

Main Supporting Equipment

The installation should include:

• • • Modulating gas burner
    • Gas train
    • Feedwater pump
    • Water softener
    • Feedwater tank
    • Chemical dosing

  <

li>Blowdown tank

• Steam header
• Chimney
• Control panel
• Safety valves
• Low-water-level protection
• Pressure control and h

• igh-pre

ssure limiter

Why a Water-Tube Boiler Is Not the First Choice

could technically produce the required steam, but it may create unnecessary complexity for this moderate-capacity, saturated-steam application.

A water-tube boiler would become more attractive if the project required:

• Much higher steam capacity
• High operating pressure
• Superheated steam
• Very rapid load response
• Integration with a steam turbine

2: Commercial Boiler for a Hotel

A hotel requires hot water for guest rooms, kitchen operation, laundry, and swimming-pool heating.

Project data:

• Peak hot-water load: 700 kW
• Supply temperature: 80°C
• Return temperature: 60°C
• Fuel: LPG or natural gas
• Operating pattern: variable
• Available boiler room: compact

Recommended Boiler

The hotel can use:

• One 700 kW hot-water boiler; or
• Two 400 kW boilers operating in cascade.

A two-boiler cascade arrangement offers several advantages:

• Better part-load efficiency
• One unit can remain available during maintenance
• Capacity follows occupancy
• Lower frequency of burner cycling
• Greater operational reliability

This application does not require an industrial steam boiler unless the hotel laundry, kitchen, or sterilisation system specifically requires steam.

3: Residential Boiler for an Apartment Building

An apartment building requires hot water and space heating with a peak load of 200 kW.

A modular condensing hot-water boiler system is more suitable than a steam boiler because:

• The required water temperature is relatively low.
• Condensing operation can improve seasonal efficiency.
• The system is compact.
• No steam distribution system is required.</li>
• Operation can follow changes in building occupancy.
• Multiple modules provide redundancy.

This example demonstrates that residential classification refers to the application and load—not specifically to a fire-tube construction.

4: Heat-Recovery Boiler on a Gas-Turbine Exhaust

A factory operates a gas turbine to generate electricity. The turbine produces a continuous high-temperature exhaust stream.

Instead of releasing all exhaust energy through the stack, the factory installs a Heat Recovery Steam Generator.

The HRSG can supply steam for:

• Production processes
• Boiler-feedwater heating
• Absorption chilling
• Space heating
• Steam-turbine power generation

Main Design Data Required

• Exhaust-gas flow
• Exhaust inlet temperature
• Permitted outlet temperature
• Exhaust-gas composition
• Particulate loading
• Required steam pressure
• Required steam capacity
• Feedwater temperature
• Allowable gas-side pressure drop
• Operating-hour profile

The available heat can be estimated from:

Q=m˙g×Cp,g×(Tin−Tout)Q = \dot{m}_g \times C_{p,g} \times (T_{in}-T_{out})

Where:

• QQ = recoverable heat
• m˙g\dot{m}_g = exhaust-gas mass flow
• Cp,gC_{p,g} = exhaust-gas specific heat
• TinT_{in} = exhaust inlet temperature
• ToutT_{out} = exhaust outlet temperature

The actual steam output must include heat-transfer efficiency, fouling, pinch-point temperature, approach temperature, and operating-load variation.

Benefits of Heat Recovery

• Reduces wasted exhaust energy
• Reduces supplementary fuel consumption
• Produces useful steam or hot water
• Improves overall plant efficiency
• Can support combined heat and power operation
• May reduce operating cost and emissions per unit of production

The system is economically attractive only when the waste-heat supply and steam demand occur at compatible times.

5: Package vs Site-Erected Boiler for a Palm-Oil Factory

A palm-oil factory requires:

• • Steam capacity: 25 tonnes/hour

• Fuel: palm kernel shell and fibre

• Working pressure: 25 barg
• Continuous operation
• Large combustion chamber
• Emission-control equipment

Package-Boiler Evaluation

fully assembled package boiler would be difficult to transport because of:

• Large furnace dimensions
• High equipment weight
• Road-width limitations
• Bridge-load limitations
• Crane-capacity requirements

Site-Erected Boiler Evaluation

site-erected water-tube boiler is more suitable because:

• Its components can be transported separately.
• The furnace can be designed for biomass combustion.
• A travelling grate or reciprocating grate can be incorporated.
• Large water-wall surfaces can be installed.
• Superheater and economiser sections can be added.
• Dust collector and air-pollution controls can be integrated.
• The boiler can be designed for continuous high-capacity operation.

Recommendation

For this project, a site-erected biomass-fired water-tube boiler is more appropriate than a package fire-tube boiler.

Boiler Selection Summary

Equipment too large for road transportSite-erected boiler

Conclusion

Industrial, commercial, residential, and heat-recovery boilers are classified mainly according to their application and heat source. Package and site-erected boilers are classified according to their method of fabrication, delivery, and installation.

A commercial or industrial boiler can use either fire-tube or water-tube construction. A residential boiler is generally a compact hot-water unit, while a heat-recovery boiler generates steam or hot water from process exhaust energy.

Package boilers are suitable when the complete unit can be assembled, transported, and installed economically. Site-erected boilers are selected when the boiler is too large for delivery as one package or requires a highly customised furnace and pressure-part arrangement.

PT Indira Mitra Boiler provides engineering, supply, fabrication, installation, commissioning, maintenance, and burner services for industrial steam boilers, hot-water boilers, thermal oil heaters, package boilers, and site-erected boiler projects.

PT Indira Mitra Boiler
Office: (021) 352 95874
WhatsApp: +62 813-8866-6204 (Ratman Bejo)
www.indiramitraboiler.co.id
www.burner.co.id
info@indira.co.id
idmratman@gmail.com
Workshop: Tangerang – Indonesia
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