COMBUSTION GRATE

Waste treatment in modern waste incineration plants makes it possible to mineralise the residual waste, reduce the volume of waste, save on landfill volume, reduce waste emissions (including methane, a dangerous greenhouse gas), remove harmful or hazardous components, provide thermal energy and, if there is sufficient thermal combustion energy, produce electricity.

In all incineration systems, complete combustion of the fuel takes place at temperatures above 1,000°C, preceded by a drying and gasification process.

The incineration temperature achieved is determined by the calorific value of the waste and the excess air from the incineration.

The german 17th BImSchV for example defines the combustion conditions with regard to oxygen content, residence time and combustion temperature for environmentally friendly combustion, i.e. minimisation of emissions on the flue gas side.

A further prerequisite for environmentally friendly residual waste incineration is the disposal of the residual materials produced. 

This results in rust slag, boiler ash and fly ashes.

The ash content of the waste is determined by its composition and is generally between 15 - 35% of the waste throughput.

The burnout of the residues that are led to incineration is influenced by the incineration technology, i.e. grate firing, rotary kiln or fluidised bed process.

The worst combustion results are achieved by systems without combustion grate, such as fix-bed or smooth surface burners.

In this case there is a partly large amount of unburnt material in the ashes.

In all processes, the oxygen content supply to the burnable material and the residence time play an important role. 

The ZANNI combustion grate

The grate area is very big and the supply with combustion air inside the combustible materials is optimal.

Because due to the clever supply of the needed oxygen into the waste it is also easy possible to control the residence time of the combustible materials.

Controlling of the incineration process at a maximum.

An extension of time can be reached with a minimum of effort.

Multi-Medium combustion grate

Due to the design of the ZANNI combustion grate it is suitable for solids and sludges.

Solids could be for example municipally waste, industrial waste, clinical and other  contaminated waste.

The solid wastes could be also mixed with liquids.

Sludges could be oily sludges, sewage sludge and others.

Criteria for the amount of waste fed into the incinerator are the composition of the combustible material and thus its calorific value.

Functionality of the system

The heat resistant steps of the grate are equipped with air impulse slots, as a kind of nozzles. 

The air swirl with a huge amount into the combustible materials and convey them along the grate.

The swirling combustion air turns over the combustible materials, cracks it up and assist the whole combustion process.

Therfore also a high throughput rate is achieved per unit area of grate.

The system allows the user to be flexible in the choice of load cases.

Either mass throughput or residence time can be selected, depending on the application and, above all, on demand. 

Everything can be controlled by the air flow rate and air pulses.

That is a giant step in the combustion technology.

Features

- Multi-medium combustion grate,
- suitable for solids and sludge, such as sewage sludge,
- no moving parts,
- dynamic and efficient,
- high throughput rates,
- low investment costs,
- low operating costs,
- low maintenance costs,
- easy replacement.

Retrofitting of old plants

Especially in existing combustion plants an  enormous advantage in operation  conditions and environmental protection  can be achieved with minimum effort for  conversion or retrofitting.

It can be supplied as a completely closed stand  system with side parts and grate, 

or adapted to  structural conditions as a pure combustion grate. 

The only condition is that a sufficient air supply is ensured and that  the system and the furnace are accessible for assembly.

Interesting aspects of the system for the incineration of sewage sludges

On this combustion grate the sewage sludge can be burned out to a maximum at high temperatures.

The ZANNI-Grate-Process makes it possible to thermally recycle sewage sludge easily and efficiently.

The grate area is very big and the supply with combustion air inside the combustible materials is optimal.

The arrangement of the combustion shingles is designed for a safe discharge of the sludge via the combustion grate.

The combustion air cools the grate, absorbs the energy and dries the sludge even faster on the first stages by preheating.

This also protects the grate. 

The hot air generated before the filter can be used as pre-heated combustion and circulation air.

In this way a heat cycle could be created.

That support the combustion and reduce costs.

Recycling process

The amount of sewage sludge is minimised to a maximum by combustion. 

Phosphorus, as a valuable component of the sewage sludge, can be recovered from the remaining ash in a later recycling process.

This grate technology enables sustainable waste management through independent thermal utilisation of the sewage sludge and the recovery of residual substances from the ashes.

The incineration can be decentralised on site in close proximity to the producer of the sewage sludge, thus eliminating transport costs and associated emissions.

This is also an additional contribution to environmental protection.

COMBUSTION GRATES AND MAINTENANCE EFFORTS 

Maintenance efforts
Cooling down time *: ~ 2 days
Grate Replacement **: ~ 2 days
Heating up time *: ~ 2 days