Integrierte Vermeidung und Verminderung der Umweltverschmutzung

3.2.51 Cleaning and disinfection (U.1)
3.2.51.1 Water
Chapter 3
Large quantites of water are required for cleaning and disinfection. In many installations, this is
the main consumer of water, with the amount depending on the type and size of equipment to be
cleaned and the materials processed. Cleaning and disinfection produces waste water. This
typically contains soluble organic material, FOG, SS, nitrate, nitrite, ammonia and phosphate
from product remnants and removed deposited soil. It also contains residues of cleaning agents,
e.g. acid or alkali solutions. In principle, the cleaning and disinfection agents that are used are
discharged via the waste water, either in their original state or as reaction products.
3.2.51.2 Solid output
Product residues may be recovered during cleaning.
3.2.51.3 Energy
Cleaning is commonly carried out at elevated temperatures, which, therefore, requires the use of
energy to heat water and produce steam.
3.2.52 Energy generation and consumption (U.2)
3.2.52.1 Water
Boiler treatment chemicals, silica and other soluble minerals are concentrated within boilers.
They are removed by blowing down the boiler at a rate of 1 % to more than 10 % of the steam
production rate. The blowdown water is discharged and treated either in an on-site or off-site
WWTP. Blowdown needs to take place to maintain the efficient, and ultimately safe, operation
of the boiler.
3.2.52.2 Air emissions
The main products resulting from the combustion process are CO2 and water vapour.
CO2 emissions from coal firing are almost twice as those from natural gas. The contaminants
generated and emitted depend on the fuel type, combustion process and combustion plant
design. These are SO2, CO, NOx and dust.
Emissions of SO2 are a result of the sulphur content of the fuel. Gas has only trace amounts of
sulphur. Gasoil has up to 0.1 % by weight of sulphur. Coal has between 0.5 % and 2.5 % by
weight of sulphur. Fuel oil may have up to 3.5 % by weight of sulphur.
Emissions of NOx depend, not only on the fuel, but also on the inherent design of the
combustion unit and the flame temperature. Gas, generally, does not contain any significant
amounts of nitrogen compounds but will produce NOx from the oxidation of the nitrogen in the
combustion air. Therefore, NOx from gas combustion is the lowest of any fossil fuel. NOx
emissions may be reduced by steam injection into the burning chamber of the gas turbine or by
using low NOx burners.
When the product is heated by direct contact with combustion gases, VOCs and odours are
released with the process air. The heat released at a chimney depends on the fuel type and plant
design. The consumption of purchased electricity does not cause emissions at FDM installations
as the emissions take place at the power station. Information about emissions at large
combustion plants, i.e. those with a rated thermal input exceeding 50 MW, is available in the
“Large combustion plants BREF” [220, EC, 2003].
RHC/EIPPCB/FDM_BREF_FINAL January 2006 145