methods to increase energy efficiency of industrial boiler

8/18/2019 Methods to Increase Energy Efficiency of Industrial Boiler

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Methods to increase energy efficiency of industrial boilers

Boilers are an essential part of many industrial facilities – they serve to provide hot water

and steam for various applications, from sterilisation and cleaning to performing mechanicalwork. As an indispensable tool, there are great benefits to be obtained from running these

boilers at optimum efficiency, providing the best performance, safety and energy efficiency

possible.

Boilers are also energy intensive components of industrial facilities. Steam generation

systems in the United States account for 34% of all energy used in production, and in the

United Kingdoms, up to one third of all energy consumption is used to heat water [1]. This

shows that increasing the energy efficiency of boiler systems can bring great improvements

to business operating cost and the environment.

What are boilers?

Most boilers have three parts: a burner that

converts fuel to heat, a heat exchanger that

transfers the heat to steam or hot water, and a

boiler vessel. A chimney stack draws off the

combustion by-products (flue gases), and the

steam and hot water flows through a

distribution system to its end uses. Natural gas

and oil are the most common fuel used in

boilers, though electric boilers are generally

found where combustion boiler pose fire risk

and where it is important to reduce emissions.

Boilers face heat and energy losses through the following means:

Flue gas losses: These heat losses are due to the temperature of the flue gases and

are a function of excess air as well as the flue and combustion air temperature

Feedwater: Low feedwater quality leads to increased blowdown rate, and other

losses along the distribution system due to scale build-up

Radiation losses: This is the radiant heat loss from the boiler casing

Blowdown losses: Heated water is periodically discharged from boilers to control

concentration of suspended solids and prevent sludge formation

Figure 1: Boilers in an industrial application


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Ways to increase boiler energy efficiency

To minimise the heat lost by boilers, and to increase their energy efficiency, the above

sources of heat and energy losses can each be addressed by the following means:

Boiler combustion management: This aims to minimise excess air in combustion asthe more hot oxygen and nitrogen that escapes from the flue, the more energy is lost.

Oxygen concentration of the flue gas is analysed and can then be controlled and

adjusted.

Flue gas temperature is also a good indicator of boiler efficiency. By measuring flue

temperature and comparing its changes against steam load, ambient temperature,

and oxygen content, boiler efficiency can be monitored. Flue gas temperature should

be kept as low as possible to increase energy efficiency

Figure 2: Schematic of the operation of an industrial boiler

Pre-treatment of feedwater: Treatment of feedwater involves the removal of

impurities that can cause sludge build-up in the boiler and scale build-up along the

distribution system. Clarification and filtration of feedwater remove suspended

material, while demineralisation removes dissolved impurities

Boiler casing insulation: To minimise heat loss through radiant heat loss from the

boiler casing, proper insulation techniques and the maintenance of insulation layers

are required. Insulation must be ensured to be free from contamination by water or

other liquids which can affect its ability to retain heat

Blowdown heat recovery: Blowdown water contains significant energy that can be

recovered. Two main methods are used. Flash steam is created when blowdown

occurs and if the blowdown stream is directed to a flash steam vessel, the flash

steam can be recovered for low-pressure steam applications.

Blowdown water from either the blowdown stream or the liquid drain of the flashsteam vessel could also be used to pre-heat feedwater using a heat exchanger.


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The energy efficiency of a boiler can also be increased with

the application of an economiser. This is a heat exchanger

that utilises the waste heat from the flue gas to pre-heat the

boiler feedwater, thus reducing the amount of input heat

required from the boiler to bring the temperature of feedwater

to required level.

The methods highlighted above will help to minimise the energy and heat loss as a result of

inherent restrictions in boiler design. To further increase efficiency of steam, hot water or

process heating systems, it depends, ultimately, on the system design. Facilities owners will

have to ensure boilers are sized according to process requirements, and keep in mind that

using a number of integrated smaller boilers to handle peak demand and possible expansion,

rather than one over-sized boiler. By adopting these methods and strategies, industrialfacilities owners will be able to gain from the improved energy efficiency of boilers and lower

operating costs.

For more information on increasing energy efficiency of industrial boilers, please visit:

http://www1.eere.energy.gov/manufacturing/tech_assistance/pdfs/steamhandbook.pdf

http://www.sustainability.vic.gov.au/resources/documents/Best_Practice_Guide_Heating.pdf

Contr ib uted by H2PC Asia resourc e team of E2 writers. Please contact [email protected]

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[1]. Energy Efficiency Best Practice Guide: Steam, Hot Water and Process Heating Systems

http://www.sustainability.vic.gov.au/resources/documents/Best_Practice_Guide_Heating.pdf

Figure 3: Boiler economiser
http://www1.eere.energy.gov/manufacturing/tech_assistance/pdfs/steamhandbook.pdfhttp://www1.eere.energy.gov/manufacturing/tech_assistance/pdfs/steamhandbook.pdfhttp://www.sustainability.vic.gov.au/resources/documents/Best_Practice_Guide_Heating.pdfhttp://www.sustainability.vic.gov.au/resources/documents/Best_Practice_Guide_Heating.pdfmailto:[email protected]:[email protected]:[email protected]://www.sustainability.vic.gov.au/resources/documents/Best_Practice_Guide_Heating.pdfhttp://www.sustainability.vic.gov.au/resources/documents/Best_Practice_Guide_Heating.pdfhttp://www.sustainability.vic.gov.au/resources/documents/Best_Practice_Guide_Heating.pdfmailto:[email protected]://www.sustainability.vic.gov.au/resources/documents/Best_Practice_Guide_Heating.pdfhttp://www1.eere.energy.gov/manufacturing/tech_assistance/pdfs/steamhandbook.pdf

methods to increase energy efficiency of industrial boiler

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