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Energy Efficiency E-modules - Guidance
Steam and High Temperature Hot Water Boilers
Application of Steam and Pressurised Hot Water Boilers in the Public Sector | 2
Contents
1 Introduction 4
2 Learning Objectives and Outcomes 4
2.1 Learning Objectives 4
2.2 Learning Outcomes 4
3 Overview and Principles of Steam and Pressurised Hot Water 5
3.1 Theory of Water at Pressure 5
3.2 Why Use Steam? 5
3.3 Key Components - The Steam Boiler 5
3.4 Key Components - The Burner 6
3.5 Steam Traps 6
3.6 Key Components - The Hot Well 7
4 Opportunities for Energy Saving in the Public Sector 8
4.1 Opportunities for Energy Saving - The Boilerhouse 8
4.2 Opportunities for Energy Saving - Steam Distribution 8
5 Energy Saving Opportunities - Boiler Replacement and System Upgrades 9
5.1 Maximise Combustion Efficiency 9
5.2 Flue Gas Economisers 9
5.3 Flash Steam Recovery 9
5.4 Boiler Blowdown Heat Recovery 10
6 Energy Saving Opportunities - Monitoring Boiler Performance 11
7 Energy Saving Opportunities - Steam Distribution 12
7.1 Insulation 12
7.2 Plate Heat Exchangers - Heating 12
7.3 Plate Heat Exchangers – Domestic Hot Water (DHW) 12
8 Energy Saving Opportunities - Maintenance 13
8.1 Maximising Combustion Efficiency 13
8.2 Keep Boiler Surfaces Clean 13
8.3 Water Treatment and TDS Control 13
8.4 Steam Trap Monitoring 14
9 Building Business Case 15
9.1 Before considering a Major Steam System Improvement Project 15
9.2 Information Gathering 15
9.3 Business Case - Case Study 15
Steam and High Temperature Hot Water Boilers | 3
10 Useful Links and References 17
Steam and High Temperature Hot Water Boilers | 4
1 Introduction
This guidance follows the format of the associated e-module, “Steam and High Temperature
Hot Water Boilers”, to provide further details on the subjects covered in the module.
Please note that module users working in a healthcare environment should always refer to
the relevant Scottish Health Technical Memorandum (SHTM) prior to considering installation
of the measures suggested in the module. The advice given in the SHTM may conflict with
the advice given in this module, as it has been developed for the wider public sector. The
relevant SHTM can be found on the Health Facilities Scotland website.
2 Learning Objectives and Outcomes
2.1 Learning Objectives
The learning objectives from this module are:
Understand the principles of steam and pressurised hot water; and
Assess and prioritise the opportunities for energy saving in the public sector
2.2 Learning Outcomes
The learning outcomes from this module are:
Explain the principles of steam and pressurised hot water supply systems;
Identify where the opportunities for energy reduction exist in Scottish public sector sites
and buildings;
Understand the key components of an energy efficient boiler house;
Describe the main energy recovery technologies, including their typical efficiency range
and the advantages and disadvantages of each technology;
Undertake a simple monitoring exercise of a boiler house to understand operating
efficiency; and
Understand the key aspects in relation to steam and pressurised hot water projects
when building a business case.
Steam and High Temperature Hot Water Boilers | 5
3 Overview and Principles of Steam and Pressurised Hot Water
3.1 Theory of Water at Pressure
Normally when water when it is heated above 100 degrees Celsius it boils and create steam.
This is only true however, when the water is at atmospheric pressure. If the water is being
heated in a sealed vessel, then the pressure in vessel will begin to rise as the contents
expands. This increase in pressure makes it more difficult for the water molecules to
separate to form steam, thus effectively raising the boiling point of the water.
This is a simplified example of how a steam or high temperature hot water system operates.
In a steam boiler the pressure is regulated to produce steam with the desired temperature
and pressure. For example, a steam boiler controlled to produce steam at 7 bar will have a
temperature of approximately 170°C.
3.2 Why Use Steam?
There are two main reasons why steam has been used for heating in the public sector.
The first application is when temperatures of over 90°C are required. This is more common
in manufacturing than in the public sector, though there are some healthcare applications
where steam is required for high temperature applications, such as for sterilisation.
The second application for steam is to transport heat over large distances. Steam is
advantageous in this situation as the higher temperatures mean smaller pipes can be used
to transport equivalent quantities of heat. The requirement for pumping power is therefore
substantially reduced.
3.3 Key Components - The Steam Boiler
There are several key components of a steam system that must be considered. At the heart
of the system is the steam boiler.
The most common type of steam boiler in use is the 3 pass, wet back shell boiler and so this
will form the basis for this e-module. There are numerous other less common types
including:
Lancashire Boilers - with twin internal flues/combustion chambers.
Two pass-dry back - where the burner and flue exit are on the same side of the boiler.
Reverse flame boilers - where combustion gases ‘bounce’ back of the furnace back wall
before passing though tubes around the side of the combustion chamber.
Details of these alternative designs can be found in some of the further reading outlined at
the end of this guidance document.
In the 3 pass, wet back shell boiler the fuel is burnt in the combustion chamber and the
combustion gasses pass along the combustion chamber, transferring heat to the ‘wet’ side
of the boiler through the ‘wet back’. This is a space behind the combustion chamber where
water flows. This increases heat transfer area and decreases the standing losses of the
boiler. Typically up to 65% of heat transfer occurs in this first pass.
Steam and High Temperature Hot Water Boilers | 6
The combustion gasses then turn at the back of the boiler and pass through a number of
tubes, which are surrounded by water. This forms the second pass. The process is then
repeated one final time giving the third pass before exiting the boiler through the flue. .
On the wet side of the boiler, the bulk of the space is filled with water, with a small space at
the top of the boiler where steam forms.
3.4 Key Components - The Burner
The burner is the part of the system that does the bulk of the work in a steam or high
temperature system. When the burner starts up, the first stage is the purge cycle, when
cold air is blown through the combustion chamber to purge it of any residual gases from the
previous cycle. The burner then burns burning oil or gas in the combustion chamber to
maintain steam pressure in the system.
How fluctuations in the demand for steam are matched depends on the type of burner.
Some old systems may have a single stage on/off, burner which simply switches on and off
as required. This is the least efficient type. More common are two stage burners, which
have high and low fire settings allowing a degree of modulation to meet demand. Most
modern boilers have fully modulating control. These are the most efficient type as they
allow the burner to ramp up and down to meet the varying demand. In an ideal scenario
this allows the burner to fire constantly without switching off at all, which reduces losses
from purge cycles and improves efficiency.
Another important aspect of the burner is the provision of combustion air. This is achieved
using a fan. Changes in air demand with varying firing rate are met either by using
mechanical dampers or by varying the speed of the fan. This and other aspects such as
digital combustion control are explored in more detail later.
A good way to ensure that the burner is efficient is to specify that it must meet the
requirements set out in the UK Government Enhanced Capital Allowance Scheme Energy
Technology List for burners.
3.5 Steam Traps
Once steam leaves the boiler it is distributed to the various users via the steam distribution
network. Usually, once the steam has delivered heat to the user via the heat exchanger or
coil, it condenses back into its liquid form. This is known as condensate.
This condensate is at high temperature and should be recovered and returned to the hot
well (see below). A key challenge in steam systems is how to remove the condensate
without also releasing some of the energy in the system. When hot condensate experiences
a pressure drop ‘flash steam’ can form and can be potentially lost from the system taking
thermal energy with it. This can be a particular issue when condensate first passes into the
condensate recovery side of the system.
In order to prevent this, steam traps are used. These devices allow condensate to pass
whilst ‘trapping’ steam (including flash steam) and keeping it within the steam side of the
system. Steam traps are typically installed on condensate lines immediately after the
heating coil and on long runs of steam pipe to remove any condensate which may have built
up. From these, condensate is piped away, usually to a condensate vessel before returning
to the hot well.
Steam and High Temperature Hot Water Boilers | 7
Steam Traps can be either:
Thermostatic - operated by changes in fluid temperature, allowing fluid to pass when it
senses the lower temperature of condensate;
Mechanical - operated by changes in fluid density, allowing denser condensate to pass
whilst restricting the flow of steam; or
Thermodynamic - operated by changes in fluid dynamics, relying on the formation of
flash steam from the condensate.
3.6 Key Components - The Hot Well
Condensate, on its return to the boiler house, is collected in a tank known as a hot well.
This vessel is normally located at a high level within the boiler house. Cold water is also
added to the system to replace water lost through steam or condensate loss from any
steam used in the distribution system. In systems where there is high steam use, and thus
a high demand for cold water to top up the system, there may also be a steam supply to
the hot well direct from the boiler. This is known as steam sparge, where steam can be
injected into the hot well to raise its temperature.
Ideally, the hot well temperature will be as high as possible without reaching the point
where condensate starts to boil off, thus wasting energy. The higher the condensate
temperature, the less work required in the boiler to raise steam. Another issue is the
oxygen content of boiler water. Oxygen is a significant factor in boiler corrosion and
normally steps are taken to reduce oxygen levels such as adding oxygen scavengers. As
oxygen is less soluble in hot water, raising the temperature of the hot well reduces the
amount of these oxygen scavenging chemicals that are required.
Steam and High Temperature Hot Water Boilers | 8
4 Opportunities for Energy Saving in the Public Sector
4.1 Opportunities for Energy Saving - The Boiler House
To consider where energy savings can be made, the location of losses in the system must
be explored.
The most significant energy loss is the flue gas losses which typically account for around
18% of all boiler losses. This can be reduced by deploying a flue gas economiser. This is an
additional heat exchanger that traps heat from the flue gasses.
To maximise efficiency, boiler feed water must be at as high a temperature as possible. This
is best achieved by maximising condensate return temperature, ideally through recovering
condensate in a fully insulated system. Although steam sparge can be used to boost
temperatures, this should not be used in preference to steps to maximise condensate return
temperatures.
Boiler blowdown accounts for losses of around 3% on average. This can be reduced by
ensuring good water treatment and by implementing boiler blowdown heat recovery, usually
to pre-heat boiler feed water.
Boiler radiative losses account for around 2% of total energy consumed and can be
minimised by ensuring good insulation of the boiler and scheduling of boiler operation where
a site has multiple steam boilers.
Finally, there are heat transfer losses which again account for around 2-3% of the energy
consumed by the boiler. This can be minimised by ensuring the water is well treated and by
frequent cleaning of the boiler.
4.2 Opportunities for Energy Saving - Steam Distribution
There are also opportunities for making savings in the distribution system, although it is
more difficult to quantify the savings available.
The most important area to focus on is to ensure that any steam leaks are repaired as soon
as possible. Steam is an expensive resource and steam leaks are often the cause of a
needless waste of energy, water and boiler chemicals. Particular attention should be given
to valves and flanges where leaks most commonly develop.
Even though condensate is less energy intensive than steam, nevertheless high levels of
heat, water and boiler chemical loss will result if condensate leaks are not quickly repaired.
As noted previously, steam traps are an important part of the steam distribution system and
these should be regularly maintained to ensure they are functioning properly.
Malfunctioning steam traps which are allowing steam to escape from the system along with
condensate can be a significant source of losses within the distribution system.
Finally, poor thermal insulation can lead to unnecessary losses within the system. This
should be addressed at the earliest opportunity, with priority given to high temperature
steam pipework and fittings. As well as the cost savings from insulating pipes, there can
also be an improvement in steam quality as there will be less cooling of the steam as it
travels through the pipe and therefore less build-up of condensate and wet steam.
Steam and High Temperature Hot Water Boilers | 9
5 Energy Saving Opportunities - Boiler Replacement and System Upgrades
5.1 Maximise Combustion Efficiency
As combustion is the process with the highest losses within the system, it is worth
considering how this process may be improved. One of the most effective approaches is to
install a digital combustion control, sometimes referred to as a digital combustion and
management control (DCMC) or a direct digital combustion control (DDCC), on the burner of
a steam boiler.
The amount of fuel used by the burner is highly dependent on the air to fuel ratio. Modern
digital control systems offer precise adjustment and optimisation of air and fuel
characteristics, thus minimising energy consumption.
This approach is most cost effective if specified when installing a new steam boiler, although
it can be retrofitted to boilers with modulating burners, or when installing a new burner. It
can lead to savings of up to 5%.
Where the system can accept this modification, further savings are available from variable
speed control of the fan providing combustion air compared with a single speed fan linked to
mechanical dampers.
5.2 Flue Gas Economisers
A flue gas economiser recovers more heat from the flue gas (which can be at temperatures
of around 200°C) as it exits the boiler. Flue gas economisers can be fitted to the flue
immediately after the boiler. In practice, it is the boiler feed water that is passed through
the flue gas economiser. As a result, they require the boiler to have modulating water level
controls and a variable speed control of the boiler feed pump to ensure a constant flow of
water through the heat exchanger. These units are usually available off the shelf from
steam boiler manufacturers and, where space allows, can be retrofitted to existing boilers.
Economisers can reduce boiler consumption by up to 5% and are particularly effective
where condensate return temperature is low, as this offers the greatest potential for heat
recovery. In general, economisers are best applied to gas fired boilers, though economisers
for oil boilers are available.
5.3 Flash Steam Recovery
A major source of flash steam generation is in systems where the rate of condensate return
is high and where condensate is at a high temperature. Here, flash steam loss typically
occurs when the hot well temperature rises close to 100°C and water starts to boil off to
atmosphere (as the hot well is not pressurised). It is possible to recover some of the energy
in the steam by using the hot condensate to pre-heat the boiler feed water under
pressurised conditions. This often allows the boiler feed water to rise to temperatures of up
to 110°C.
This type of heat recovery works by first passing the returning hot condensate through a
flash steam separation vessel. This vessel separates the flash steam from the condensate,
sending each to a dedicated heat exchanger. In this way the boiler feed water from the hot
well is pumped through the first heat exchanger where some of the heat from the
condensate is recovered. This raises the boiler feed water temperature and reduces the
Steam and High Temperature Hot Water Boilers | 10
condensate temperature. The condensate then returns to the hot well. The boiler feed water
then passes through the second heat exchanger. Here it is further heated at pressure by the
flash steam, which in turn is then condensed before joining the first condensate line and
returning to the hot well. The boiler feed water is then pumped in to the boiler at high
temperature, thus reducing the fuel required by the boiler to raise steam.
5.4 Boiler Blowdown Heat Recovery
The use of chemicals to dose the boiler feed water leads to the presence of suspended solids
in the boiler. These tend to collect as sludge at the bottom of the boiler, which is removed in
a process known as a blowdown. This can be done manually or using automatic total
dissolved solid (TDS) control.
As noted previously, up to 3% of the energy entering the boiler as fuel can be lost during
boiler blowdown. Automatic TDS control ensures that the boiler only blows down when this
is required and so reduces the energy lost in this process. It is possible to improve the
system efficiency further by implementing boiler blowdown heat recovery.
Blowdown heat recovery works by passing the hot blowdown fluid into a flash steam vessel,
which separates the steam from the condensate/sludge. The recovered steam is then
delivered to the hot well where it is mixed with the returning condensate and any mains
cold water being used to top up the supply (thus making up for any lost steam or
condensate) before being fed in to the hot well.
The condensate is passed through a strainer and then a plate heat exchanger, which is also
used to preheat the cold water top up supply to the hot well. This raises the temperature
and reduces the fuel required of the boiler to raise steam.
This process can recover up to 80% of the energy in the blowdown fluid, whilst also
reducing the requirement for treated make up water by recovering the flash steam.
Steam and High Temperature Hot Water Boilers | 11
6 Energy Saving Opportunities - Monitoring Boiler Performance
Monitoring boiler performance requires data. This can include temperatures, pressures, flow
rates and timing boiler firing. To achieve continuing energy savings, it is recommended that
metering is installed to monitor boiler performance.
As a minimum, it is recommended that the boiler house is fitted with:
A dedicated fuel meter;
A cold water meter on the hot well top up; and
A steam meter on the main steam header.
The data from these meters can then be collected and a high level assessment of boiler
house performance can be undertaken. It is important that the meters are accurate. Some
types of steam meter in particular will require maintenance and recalibration at regular
intervals.
The steam meter reading can be converted to kW or kWh by noting the operating pressure
and using steam tables. The fuel meter reading can be converted to kW or kWh using
conversion factors for the calorific value of the fuel. Dividing the energy in the steam by the
energy in the fuel can provide an indicator, albeit simplistic, of boiler house efficiency
helping identify any deterioration in performance that may require investigation. The cold
water meter is used to track the volume of water being added to the system. Any increase
in the water supply may suggest an issue that is affecting energy performance, for example
excessive boiler blowdown or major steam and condensate leaks.
Other simple checks that can be made to monitor boiler house performance include:
Checking the TDS control settings against those recommended for the boiler type in
order to avoid excessive blowdown;
Checking the oxygen readings on any burner displays and comparing with past
combustion efficiency checks; and
Timing the burner on/off patterns to assess for excessive boiler cycling.
An infrared thermal imaging camera is a good tool to help assess the boiler performance.
Areas of poor insulation or refractory (the heat resistant lining in the boiler) can be quickly
identified, as can any uninsulated valves, fittings, pipework or other ancillary items. This
can be particularly important after annual strip downs to ensure that the insulation and
refractory have not been damaged, and sections removed have been replaced. Taking a
before and after infrared image is a good way to ensure that the boiler has returned to its
pre-maintenance state or better. This method can also be used for other items that require
annual strip downs, such as shell and tube heat exchangers.
Steam and High Temperature Hot Water Boilers | 12
7 Energy Saving Opportunities - Steam Distribution
7.1 Insulation
Insulation is important with steam systems, both for the boiler and the distribution systems.
Heat loss from uninsulated or poorly insulated steam systems can be particularly high due
to the high temperatures involved. For more information on thermal insulation of boilers,
pipework and fittings see Module 6, How to Implement Thermal Insulation to HCVAC
Services.
7.2 Plate Heat Exchangers - Heating
Savings can be made by replacing large shell and tube heat exchangers or calorifiers with
more compact plate heat exchangers.
There are a number of benefits to this approach including reduced standing losses, since
plate heat exchangers are much more compact than shell and tube heat exchangers, so
there is less surface area for heat loss to atmosphere. It also results in improved
controllability as plate heat exchangers can respond much more quickly to fluctuations in
demand, improving overall efficiency and reducing maintenance costs. Unlike calorifiers,
plate heat exchangers do not require a full annual shutdown.
Packaged heat exchangers are available on the market and can be installed on existing
systems relatively easily.
7.3 Plate Heat Exchangers – Domestic Hot Water (DHW)
Plate heat exchangers can also be applied to domestic hot water applications, where similar
benefits apply. In addition, they eliminate the need for large water storage vessels thus
reducing the risk posed by legionella bacteria and further reducing ongoing maintenance
costs.
Steam and High Temperature Hot Water Boilers | 13
8 Energy Saving Opportunities - Maintenance
8.1 Maximising Combustion Efficiency
There are some key maintenance activities which, when carried out properly, can help ensure
steam system efficiency is optimised. One method is monitoring boiler combustion efficiency.
Regular monitoring of combustion efficiency can help ensure that any deterioration in boiler
performance is identified early and that boiler efficiency is maximised. For combustion to be
carried out effectively, the mixture of fuel and air must be correct. Too little air will result in
incomplete combustion, too much will cause increased heat loss up the flue. Both cases will
mean that more fuel is required to deliver heat to the boiler than when air supply is
optimised.
The following conditions should be checked regularly:
Flue gas temperatures;
Flue gas constituents;
Flame shape; and
Fuel and air trim settings.
A combustion efficiency check will produce a printout which gives, among other things, a
reading of the net combustion efficiency. It is worth noting that typically, a 2% reduction in
oxygen levels in the flue gas will provide a fuel saving of 1.2%.
Regular monitoring of combustion conditions can help the user to address any minor issues
to ensure optimum conditions when they arise. This prevents the boiler from operating
inefficiently for long periods.
8.2 Keep Boiler Surfaces Clean
Keeping boiler surfaces clean can help maximise heat transfer efficiency and ensure energy
is not being wasted. Steam boilers are particularly susceptible to the build-up of debris on
the wet side of the boiler as dissolved solids and particles in the water can be deposited on
the boiler surfaces.
Build-up can be reduced by treating the boiler feedwater, however the boiler should be
cleaned at least once a year during the insurance inspection to ensure optimum heat
transfer.
8.3 Water Treatment and TDS Control
Water treatment is required in steam boilers to ensure effective operation. The water supply
for the wet side of the boiler will contain various particles and impurities, which can cause
issues with steam systems if not treated.
These issues include:
Reduced efficiency as surfaces are fouled and boiler blowdown is required more often;
Increased cleaning costs as the process of keeping the boiler clean becomes more
laborious; and
Carryover. This is where TDS particles are carried in the steam into the distribution
system can cause reduced heat transfer at points of use and potentially damaging
Steam and High Temperature Hot Water Boilers | 14
corrosion of plant and pipework. In extreme cases this can lead to catastrophic failure
of plant – clearly something to be avoided.
Good water treatment and control of TDS can help minimise the risk of these issues
occurring and ensure the boiler operates efficiently. For more information on water
treatment and TDS control, see the further reading section at the end of this module.
8.4 Steam Trap Monitoring
Steam traps are an integral part of a steam system and their effective operation is
imperative to the overall efficiency and efficacy of the steam system. One way to ensure
that steam trap failure is identified as soon as it occurs is to implement a steam trap
monitoring system to detect any failures and allow them to be addressed promptly.
This approach is particularly worth considering for large steam systems where keeping on
top of maintenance can be difficult. An automatic monitoring system can help the operator
target maintenance resource at problem areas and ensure energy is not being wasted due
to poor steam trap performance.
Steam and High Temperature Hot Water Boilers | 15
9 Building the Business Case
9.1 Before Considering a Major Steam System Improvement Project
When thinking about replacing boilers, it is important to consider all other low cost
measures which could be implemented to save fuel consumption prior to proceeding. For
example, it may be prudent to ask the following questions of the project:
1. Have the controls been optimised? It is important to make sure that energy is not being
wasted through poor control as this can usually be rectified for relatively low cost.
2. Is insulation up to standard? Insulating hot pipework and valves is a low cost way to
save energy and money and this should be taken account of before considering new
boiler plant.
3. Is the best fuel being used? If the site uses oil, is there a natural gas connection
available? Could gas burners be retrofitted to the existing boilers?
4. Is the building appropriately zoned? Could improved zoning help with better control? If
so, this should be done before replacing boiler plant, or it could be included as part of
the same project.
Once all of the above have been considered, an effective business case can be made.
9.2 Information Gathering
To build an effective business case, one of the most important things is to gather accurate
information. In particular, collect the following data:
The building or boiler total fuel consumption;
The boiler combustion efficiency;
The building peak heating demand;
The age of the existing boilers; and
In addition, it is likely that any boiler replacement will require modification to the
existing pipework and flue. As a result consider any other site specific issues which may
influence the viability of the project, for example:
o Is the boiler house in the basement?
o Could flue or modified pipe routes be complicated?
o Is redundancy required anywhere in the system?
o How will hot water be provided?
9.3 Business Case - Case Study
Consider this example of a successful steam boiler replacement project. The site had been
operating with an ageing temporary boiler plant which had reached the end of its
serviceable life. As a result, a business case was developed for the installation of new steam
raising plant to service the site.
Under this project, two new boilers were installed in an existing boiler house.
This project was progressed as an energy and carbon saving project, with a focus on
making the new installation as energy efficient as possible. Therefore the new installation
included:
Flue gas economisers on both boilers;
Digital combustion control;
Variable speed control of the burner fan;
Steam and High Temperature Hot Water Boilers | 16
Controls interface with the site BMS;
Automatic TDS Control and boiler blowdown;
Oxygen trim control of the boiler house; and
Enhanced thermal insulation of pipework.
After installation the boiler performance was monitored and the following savings were
recorded:
27% reduction in gas consumption, or 6,745,000 kWh per year;
A cost saving of £141,000 per year;
CO2 savings of over 1,200 tonnes per year; and
A reduction in water consumption by 11,000 m3 or £17,000 per year.
Against a capital cost of £630,000 this is a payback of 4.5 years, giving an attractive return
on investment for the site. This example shows the kind of financial and energy savings that
can be made from replacing old, inefficient steam boilers with new systems.
Application of Steam and Pressurised Hot Water Boilers in the Public Sector | 17
10 Useful Links and References
Title Source Link
Steam Tutorials Spirax Sarco www.spiraxsarco.com/resources/steam-engineering-tutorials.asp
Steam & High Temperature hot water
boilers overview (CTV052) The Carbon Trust
www.carbontrust.com/media/13332/ctv052_steam_and_high_temperat
ure_hot_water_boilers.pdf
How to implement blow down heat
recovery (CTL020) The Carbon Trust
www.carbontrust.com/media/147111/j7940_ctl020_how_to_implement_
blowdown_heat_recovery_aw.pdf
How to implement oxygen trim control
(CTL147) The Carbon Trust
www.carbontrust.com/media/147167/j8054_ctl147_how_to_implement_
oxygen_trim_control_aw.pdf
How to implement advanced combustion
control (CTL058) The Carbon Trust
www.carbontrust.com/media/147147/j7971_ctl058_advanced_combusti
on_aw.pdf
Enhanced Capital Allowance Scheme DECC https://etl.decc.gov.uk/etl/site/etl.html
Application of Steam and Pressurised Hot Water Boilers in the Public Sector | 18