FRIDGE RECYCLING
Purification of all CFC / HCFC / HFC / VOC
General Description
The combined CFC / VOC recovery plant generally consists of a catalytic cracking
abator and a chemical scrubber. The combined solution provides a compact,
favourable and economical solution for onsite purification of all fugitive emissions
from the fridge recycling process; thus reducing waste, disposal and operating
cost.
This proven and developed technology has been successfully in operation for more
than 7 years, where system is used to purify exhaust air containing ODS (OZONE
DEPLETING SUBSTANCES). The mixture of organic and non-organic gases,
formed during the mechanical pulverisation and recovery of blowing agent from the
insulation material in fridge and freezers are completely purified to within UK and
European standards for air emission limits.
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The main extracting fan delivering the exhaust fumes from the mechanical
pulverisation process maintains the airflow through the plant. This allows the
purification plant to continuously operate in a slight negative pressure; thus
avoiding fugitive leaks and emissions to the installation area.
The full abatement plant is supervised and operated from a dedicated control
panel. All switches, instruments, and lamp indicators are situated on the panel as
well as a flow diagram on which the actual running mode is indicated.
The system includes 5 separate stages to control peaks and eliminate various
pollutants:
1)
•
Dust filter
•
Adsorber
•
Catalytic Abator
•
Chemical scrubber
•
Neutralization of waste water
Dust filter
Pulse jet filter and cartridge filters are used to collect any duct particles and prevent
foam from accessing the other parts of the abatement plant.
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2)
Adsorber
Selected media is used to dampen pollutant peaks and remove heavy metals.
3)
Catalytic Abator
Catalytic abator systems normally installed to purify air outlet from production
facilities or processes with organic compounds. The catalyst encourages thermal
oxidation of organic solvents at low temperature.
While VOC organic pollutants normally converts into CO2 and H2O; but for CFC,
HFC and HCFC refrigerant compounds, the selective catalyst used allows
hydrolysis of the pollutants by thermal cracking on the catalyst. This allows the
reaction to convert fluorine and chlorine halogenated compounds to HF and HCl
respectively without poisoning the catalyst.
The exhaust air flows from the shredding, separation and pulverisation steps are
introduced through a heat recovering system where the heat is supplied by the
already cleaned air, before going into the Catalytic chamber. A flameless electric
heater is used for preheating the process air and to achieve the set controlled
temperature for the purification process.
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The LESNI catalytic plant system for decomposing CFC and HCFC from the fridge
recycling process was specifically developed so that a very high degree of safety
and purification is achieved.
Example for Freon 11
CFCl3 + 2 H20 ⇒ CO2 + 3 HCl + HF
Example for Freon 12
CF2Cl2 + 2 H20 ⇒ CO2 + 2 HCl + 2 HF
Example for VOC such as Pentane
2 C5H10 + 15 O2 ⇒ 10 CO2 + 10 H2O
Once the inorganic gases CFC (Freon 11, 12 etc.) and other HCFC have been
hydrolysed and selectively converted in the catalytic abator, according to the
chemical reactions above, the acid fumes generated are treated in the next step of
the LESNI purification process.
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4)
Chemical scrubber
The chemical scrubber downstream of the catalytic abator placed to neutralise the
acid exhaust generated before discharging to atmosphere.
The scrubber will treat the inorganic gases that formed in the previous step such as
HCl and HF. The gases are initially cooled in a quenching tower and then absorbed
and neutralised in the absorption column. The scrubber liquid will be kept alkaline
by adding NaOH and the gases together with the NaOH form soluble harmless salt
products.
When the concentration of salt reach a certain level, the controller will desalt the
scrubber tank and refresh the liquid by adding water and NaOH automatically.
5)
Neutralisation of waste water
The waste water/salt mix generated from previous step is then neutralized in the
final step before permitting discharge of the final salt solution effluent through the
drains or sewers depending on local authorities and demands.
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Note:
1. Because of the complex design parameters used to build up such a system it is
very important that LESNI A/S gets as precise description of the process and
operating conditions.
2. Generally, we design our plant to meet strict legislation and shall target local
authority emission limits specified with high efficiency and reliability.
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