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Department for Business, Energy and Industrial Strategy

Heat Recovery from Flash Steam and Boiler Blowdown Condensate

1.1    Scope

Significant amounts of heat can be recovered from boiler blowdown water condensate and from flash steam. This category is relevant for steam condensate collection and boiler blowdown systems, not process heat recovery. Boiler blowdown water can contain significant levels of contaminants that reduce the efficiency of the heat recovery process. 

The Energy Technology List (ETL) encourages the purchase of heat recovery equipment that is specifically designed to recover heat from flash steam and/or water from boiler blowdown.

1.2    Definitions

Boiler blowdown is a necessary process undertaken in steam boilers to control the level of total dissolved solids (TDS) within the boiler. The number of times a boiler is blown down depends on how dirty the boiler feedwater is. The product is discharged into a flash vessel which reduces the pressure of the liquid, and results in flash steam and boiler blowdown water. Heat recovery then may take place, both on the flash steam and boiler blowdown water, by means of heat exchangers.

Flash steam is also the by-product when steam condensate is released from high pressure to low pressure, typically in a vented collection tank. Heat recovery may take place upon this flash steam by means of heat exchangers. Steam condensate is then returned to the boiler feed tank, deaerator or can be used within process. 

1.2.1    Categories 

The ETL Scheme covers three categories of product:

  1. Flash steam recovery vessels or packages with associated control and safety devices
  2. Heat exchanger units or packages with associated control and safety devices
  3. Flash steam vessel with heat exchanger packages with associated control and safety devices

Where packages may include the following components necessary for operation of the equipment: pressure gauges, vacuum breakers, vent heads, valves and steam traps.

To be eligible for inclusion on the ETL, products shall meet the requirements as set out below.

1.3    Requirements 

1.3.1    Eligibility requirements  

To be eligible products, shall:

  • Be specifically designed to recover heat from flash steam and / or water from boiler blowdown, by means of heat exchangers and/or flash steam recovery vessels used within boiler systems. 
  • Conform to the requirements of the The Pressure Equipment (Safety) Regulations 2016 in respect of their design, manufacture and testing procedures.

1.4    Verification for ETL Listing 

There are no testing requirements, however manufacturers shall provide sales and technical brochures to evidence the conformity of their products against the requirements from section 1.3.

1.5    Conformity testing

Products listed on the ETL may be subject to the scheme’s conformity testing programme in order to ensure listed models continue to meet the ETL requirements.

1.6    Review

1.6.1    Indicative review date 

This specification will be reviewed during the 2023/24 ETL review cycle.

1.6.2    Illustrative future direction of the requirements  

If uptake increases, consideration can be given to differentiating models based on the amount of energy saved.