Products of incineration

sifting

fine material include ash, metal fragments, glass, unburnt organic substances etc..

residue

all solid material that are left after incineration

remove continuously or in batches

clinker and fly ash

10% is the fused ashes, etc.. is use as component of cement, concrete or road making.

the fly ash comes from the gas scrubbing unit

the quantity of fly ash usually 12 – 15 kg/tonne of refuse

also used in cement making, concrete, brick and road making

suspended particulates

flue gas

vented air emitted from a chimney after combustion in burner. It can include nitrogen oxides, carbon dioxides, water vapor, sulfur dioxides, particles and many chemical pollutants

(FSL)

the equipments used to remove are:

the fabric filter – almost 100% efficiency

electronic precipitations -96 – 100% efficiency

wet scrubbers – 94 – 97%

cyclones – 60 – 65%

settling chamber – 10 – 30%

wetted baffle spray – 10 – 53%

waste gas

removed via the stack

the high and diameter depends amount of climatic and lanscaping of the area

heavy metal

found in the stack gas, bottom ash, filter dust or in salt and sludges from dust cleaning

the heavy metal are:

Cd, Cl, Cr, Cu, F, Pb, Hg, Ni, S and Zn.

Fraction %

Stack gas %

Bottom ash %

Filter dust %

Salt and sludges from gas cleaning %

Cadmium 0.04 11 85 3.6

Chlorine 0.12 9 15 76

Chromium 0.01 94 5.8 0.27

Copper 0.01 95 4.9 0.53

Fluorine 1.5 69 3.0 26

Lead 0.01 75 24 0.9

Mercury 2.1 7 5.1 86

Nickel 0.04 87 13 0.61

Sulphur 0.47 50 10 40

Zinc 0.05 49 51 0.7

Acid Gas

SO2, HCL and HF can be remove by three methods

wet method Dry method semi dry method

Wet method

Pollutions are removed by large quantities of slaked lime or aqueous sodium hydroxide in Ventury scrubbing system

The limestone mixed by two ways:

with the waste before incineration

introduce separately into the furnace

Semi dry method

used a spray of lime (CaO) mixed with water into the flue gas flow

Organic pollutant – high level of toxicity

Persistence in the environment

The emission of dioxin can be control with further treated of flue gas by;

adsorption onto activated carbon filters

catalyst uses:

mix metal oxide catalyst

destroy the dioxin by reaction with O2

NOx controlled by in fluidised bed incinerator by controlling the amount of air inlet to the cobustion process

Where NOx production cannot be prevented, it is remove by the injection of urea or ammonia into the flue gas.

Advantages of incineration

incineration is sanitary, odourless and dustless

residue only 20% of the original weight and can be used for making cement and other materials for construction industry

require very little space and very few personnel

can be located centrally even within the town and reducing transportation costs.

energy production and other by-product could generated revenue

ash and other residue are pathogen-free

pre sorting and recycle could be incorporated and this reduces the volume to be incinerated

Disadvantages of incineration

high capital cost and high operating cost

take time to plan, design construction

require skill personnel

disposal of ash require landfill

may cause air pollution and long term environmental effect

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