Sludge co-incineration with waste in grate furnaces
- Robust, simple and very competitive
The Babcock & Wilcox Vølund method for co-incineration of sludge with waste is based on the following, which can easily be adapted to existing conventional waste furnaces:
The sludge is smeared evenly across the surface of the waste layer in the furnace in order for the sludge and waste to be incinerated together in a so-called "sandwich incineration process". The water content of the sludge replaces part of the secondary air, which is normally injected to regulate temperatures, and energy production is thereby maintained. Further, the co-incineration takes place without reducing the normal waste quantity being fed into the furnace.
The high calorific value of the waste often leads to excessive furnace temperatures. “Sludge sandwich operation” stabilises the incineration when firing sludge (68-82% water) in quantities of up to approx. 10% of the waste by weight, and the volume of flue gases is also slightly reduced. The NOx level remains unchanged and the CO level is normally reduced slightly.
Feeding of the sludge is automatically controlled together with the feeding of the waste, but sludge feeding is automatically limited by the furnace temperature, which should not be too low, e.g. not below 1050°C.
Sludge is normally fed by a piston pump which delivers the sludge through a pipe line to a number of injection feed funnels in the waste feed chute on the furnace side. The sludge is thus drawn into the furnace chamber on top of the waste. A prepress feeding the sludge pump makes it possible to mix bigger waste particles or waste powders into the sludge to be fired.
This also makes it possible to co-incinerate particulate matters or powder waste fractions with accurate dosing equipment in a completely closed, hygienic and odour-free patented system.
