Flue gas condensation is a process, where
flue gas is cooled below its water
dew point and the heat released by the resulting
condensation of water is recovered as low temperature heat.
Cooling of the flue gas can be performed either directly with a
heat exchanger
A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct conta ...
or indirectly via a condensing
scrubber.
The condensation of water releases more than per ton of condensed water, which can be recovered in the cooler for e.g.
district heating
District heating (also known as heat networks or teleheating) is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating a ...
purposes.
Excess condensed water must continuously be removed from the process.
The downstream gas is saturated with water, so even though significant amounts of water may have been removed from the cooled gas, it is likely to leave a visible stack plume of water vapor.
The heat recovery potential of flue gas condensation is highest for fuels with a high moisture content (e.g. biomass and
municipal waste
Municipal solid waste (MSW), commonly known as trash or garbage in the United States and rubbish in Britain, is a waste type consisting of everyday items that are discarded by the public. "Garbage" can also refer specifically to food waste, a ...
), and where heat is useful at the lowest possible temperatures. Thus flue gas condensation is normally implemented at biomass fired boilers and waste
incinerators connected
district heating
District heating (also known as heat networks or teleheating) is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating a ...
grids with relatively low return temperatures (below approximately ).
Efficiency exceeding 100 %
Flue gas condensation may cause the heat recovered to exceed the
Lower Heating Value
The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it.
The ''calorific value'' is the total energy rele ...
of the input fuel, and thus an efficiency greater than 100%. Since historically most combustion processes have not condensed the fuel, usual efficiency calculations assume the combustion products are not condensed. This assumption is implicit when basing calculations on the Lower Heating Value. A more rigorous approach would be to base efficiency calculations on the
Higher Heating Value
The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it.
The ''calorific value'' is the total energy relea ...
, which typically results in efficiencies less than 100%.
Should the flue gases be cooled below , even efficiencies based on the Higher Heating Value may exceed 100%, since typical heating value definitions assume that all heat is released when combustion products are cooled to somewhere between and .
See also
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Scrubber
*
Wet scrubber
The term wet scrubber describes a variety of devices that remove pollutants from a furnace flue gas or from other gas streams. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the ...
*
Heat exchanger
A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct conta ...
*
District heating
District heating (also known as heat networks or teleheating) is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating a ...
*
Energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...
References
External links
On Flue gas Condensation by Götaverken Miljö AB
Scrubbers
Industrial processes
Heat exchangers
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