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Content archived on 2022-12-27

OPTIMIZATION OF A HOUSEHOLD WASTE INCINERATION FUME TREATMENT PLANT

Objective

To build an efficient fume treatment process for a household waste incineration plant (District of Reims) combining semi-dry recovery of chlorinated pollutents with continuous measurement of and energy recovery from, the fumes. Annual energy saving is 865 TOE and payback time for further replications is estimated at 8,6 years.
The project concerns the domestic waste incineration plant of the district of REIMS, FRANCE built in 1987/1988.
It was essentially aimed at improving the energy saving while assuring a flue gas cleaning level corresponding to the national regulations.
The temperature of the gas coming out of the boiler is inferior to the one nomrally found in such installations.
The gases are humidified by water spray then neutralized by injection of slaked lime before being purified through sleeve filters where dusts and chlorine compounds are collected.
The most innovative part of the project consisted in a last exchanger on low heat temperature flue gas to recover some final energy before exhaust.
The results obtained on the first part of the project have met to expectations, the boilers have a good thermal return, and the flue gas cleaning process responds to the regulation.
On the other hand, the last part of the project concerning the additional energy recovery on flue gas before exhaust wasnot satisfactory and had to be dropped. This decision was taken because efficient filtration tuning involved too low flue gas temperature to hope for efficient energy recovery. In addition, these conditions implied big difficulties in the running of the installation because the exchangers used to choke up every two days.
This failure has many reasons: A temperature to high in the secondary part of the exchanger minimizing the gap of temperature needed for a good heat exchange mechanism. A seasonal heat demand of the network forbidding any continuous process. A choke up phenomenon on the exchanger probably induced by the low flue gas temperature and their condensation.
The treatment line comprises two parts :
- A pulverization tower where water is vaporised in the fumes with a subsequent cooling down of the fumes from 220 deg.C to 180 deg.C to increase the efficiency of chlorinated compounds recovery. A mixture of fresh Ca(OH)2 powder and recycled solids from the downstream filtration step is fed directly into the fumes duct leading from the pulverisation tower.
The lime is renewed according to the HCl concentration which is continuously monitored in the fumes. Consumption of lime is 13 kg/Ton of household waste treated.
- Then the fumes are filtered to eliminate dust and fine lime particles in a 880 m2 bag filter made of anti-acid glass with a teflon coating. This filter is cleaned by means of low pressure air in counter current. With this efficient fume treatment process, it is possible to recover more sensible heat from the fumes, than with conventional processes. Indeed, the dechlorinated fumes may be cooled down to 130 deg.C rather than 240 deg.C. as is usual, thus allowing for a 0.013 toe energy saving per ton of household waste treated. The energy recovered is transferred to a district heating network via an intermediate liquid heat carrier.

Call for proposal

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Coordinator

ARES ENERGIESYSTEME GMBH
EU contribution
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Address
RAIFFEISENRING 5
68789 St. Leon-Rot
Germany

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