Combustion grate

Waste treatment in modern waste incineration plants

Modern waste incineration plants enable efficient and environmentally friendly residual waste treatment. Thermal utilisation mineralises the waste, significantly reduces the volume of waste and at the same time generates energy in the form of heat and electricity.

Advantages of waste incineration

Reduction in the volume of waste

The volume of residual waste is reduced by approx. 90%.

Landfill savings

The amount of residual waste that has to be sent to landfill is significantly reduced.

Emission reduction

Pollutants and greenhouse gases such as methane are minimised.

Energy recovery

The heat from incineration is used to generate electricity and district heating.

Disposal of hazardous waste

Hazardous components of the residual waste are safely destroyed.

Combustion process

Waste treatment in modern waste incineration plants

In all plants, the residual waste is completely incinerated at high temperatures (850 °C or higher). A drying and gasification process ensures optimum energy utilisation. The incineration temperature is regulated by the calorific value of the waste and the excess air.

Environmentally friendly residual waste incineration

The 17th BImSchV (Federal Immission Control Act) defines strict requirements for the incineration conditions in order to ensure environmentally friendly residual waste incineration. These include, among other things;

Minimum oxygen content
Minimum dwell time of the waste in the incineration chamber
Minimisation of pollutant emissions and flue gases
Disposal of residual waste

The incineration of residual waste produces various residual materials such as bottom ash, boiler ash and fly ash. These must be disposed of in accordance with waste legislation.

Combustion systems in comparison

Grate firing

Good combustion results, high controllability of oxygen supply and dwell time.

Rotary kiln

Suitable for moist and difficult-to-combust waste, but higher emissions.

Fluidised bed process

High combustion intensity, but more complex control and higher dust load.

Fixed bed and smooth surface burners

Poor combustion results, some unburnt material in the ash.

Summary

Combustion systems in comparison

Modern waste incineration plants make an important contribution to sustainable waste management.

By utilising the latest incineration technologies and efficient waste gas cleaning systems, residual waste can be recycled in an environmentally friendly way and energy can be generated at the same time.

The most environmentally friendly results are achieved in grate firing plants.

With this type of incineration, the oxygen supply and dwell time can be controlled very well and therefore the most environmentally friendly process results are generally achieved.

The ZANNI combustion grate

The services in detail

The advantages of ZANNI combustion grate technology lie in the details.

It offers enormous potential for the combustion process!

The grate surface is very large and the supply of combustion air within the combustible materials is optimised. This is because the residence time of the combustible materials can also be easily controlled by skilfully supplying the required oxygen to the waste.

Maximum control of the combustion process.

An extension of the time can be achieved with minimum effort.

Multi-medium incineration grate

Due to its design, the ZANNI combustion grate is suitable for solids and sludge.

Solids can be, for example, municipal waste, industrial waste, clinical and other contaminated waste.

Solid waste can also be mixed with liquids.

Sludges can be oily sludges, sewage sludge and others.

The criteria for the amount of waste sent for incineration 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 swirls into the combustible materials in large quantities and conveys them along the grate.

The swirled combustion air turns the combustible materials around, breaks them up and supports the entire combustion process.

This also achieves a high throughput rate per unit area of the grate.

The system allows the user a flexible selection of load cases.

Depending on the application and, above all, on requirements, either mass throughput or dwell time can be selected.

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

This is a huge step forward in combustion technology.

Characteristics

Multi-medium combustion grate,
suitable for solids and moist sludge (residual moisture max. 25%), such as sewage sludge,
no moving parts,
dynamic and efficient,
high throughput rates,
low investment costs,
low operating costs,
low maintenance costs,
simple replacement.

Residual moisture simply summarised

It is quick and easy to explain why the residual moisture of sludge needs to be reduced:

Increased emissions of pollutants

Incomplete combustion leads to increased emissions of pollutants such as dust, carbon monoxide, sulphur dioxide and hydrogen chloride.

Lower combustion temperature

The combustion temperature drops if the water content of the sludge is too high. This can lead to incomplete combustion and the formation of soot.

Slag formation

The slag produced during the incineration of sewage sludge can lead to problems during storage and disposal if the residual moisture content is high.

Pre-drying to improve the incineration process

To ensure optimum incineration of the sludge, the sludge is usually dried before incineration. In this way, the residual moisture can be reduced to the desired value of 25%.

Further useful information

Residual moisture

The residual moisture of the sewage sludge can vary depending on the process and plant.

Requirements

The exact requirements for the residual moisture are defined by the local regulations and the authorisation notices of the individual plants.

Drying process

There are various methods for drying sewage sludge. Depending on the requirements and local conditions, these can be, for example, drum dryers, belt dryers or fluidised bed dryers.

Retrofitting old systems

Particularly in existing incineration plants, an enormous advantage in terms of operating conditions and environmental protection can be achieved with minimum effort for conversion or retrofitting.

Available as a completely closed stand-alone system with side panels and grate, or as a pure combustion grate adapted to the structural conditions.

The only requirement is that a sufficient air supply is guaranteed and that the system and the stove are accessible for installation.

Interesting aspects of sludge incineration

On this incineration grate, the sewage sludge can be burnt out to the maximum at high temperatures.

The ZANNI grate process enables simple and efficient thermal utilisation of sewage sludge. The grate surface is very large and the supply of combustion air within the combustible materials is optimised.

The arrangement of the combustion shingles is designed to ensure that the sludge is transported safely over the combustion grate. The combustion air cools the grate, absorbs the energy and dries the sludge even faster in the first stages by preheating it. This also protects the grate.

The hot air generated upstream of the filter can be used as preheated combustion and circulating air. In this way, a heat cycle can be created. This supports combustion and reduces costs.

Recycling process

Incineration minimises the amount of sewage sludge.

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

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

Incineration can be decentralised on site in the immediate vicinity of the sewage sludge producer, thus eliminating transport costs and the associated emissions.

This is also an additional contribution to environmental protection.

Maintenance effort

Furnace grates are always classic wear parts.

Time means costs.

The costs show how good an investment was.

Example configuration

Plant capacity:

1000 kg/h sludge up to 2000 kg/h solid waste

Patented ZANNI grate:

Special high-temperature resistant stainless steel

Maintenance effort:

Cooling time: ~ 2 days

Grate replacement: ~ 2 days

Heating up time: ~ 2 days

Advantages of the ZANNI combustion grate

Lower purchase costs:

The combustion grate is significantly cheaper than other grates with comparable performance.

Low maintenance:

The combustion grate has no moving parts and is therefore very easy to maintain.

Durable:

The combustion grate is made of high-quality materials and is therefore very durable.

Cheaper spare parts:

The low-cost combustion grate is the wearing part and can therefore be replaced easily and inexpensively.

Easy to operate:

The control of the combustion grate is simple and self-explanatory.

Reliable:

The control system is reliable and ensures optimum combustion.

Greater flexibility:

The combustion grate can be operated with different fuels.
Lower maintenance costs: The combustion grate is less susceptible to wear and damage.
Longer service life: The combustion grate has a longer service life than conventional grates.

Summarising

The ZANNI combustion grate is a good choice for users who are looking for a maintenance-friendly, durable and flexible solution.

Ease of use, reliability, reduced sensitivity to fuel quality and the option of manual or automatic control of the combustion air are further advantages of the ZANNI combustion grate.

However, it is important that a high quality fuel is used to ensure optimum combustion, longevity of the grate and reduction of emissions.