Mobile incinerator

The role of incineration of waste and equipment used for it has changed radically in the recent years. While they were formerly notorious as pollutant spewing technical monsters in the eyes of citizens' groups, nowadays, thermal waste treatment facilities are considered to be the essential pillars of sustainable, forward-looking recycling and raw material sectors.

One benefit of thermal waste treatment facilities is to avoid the yield of methane gas that is a by-product of decay that damages the climate strongly. Another is the production of energy during incineration which helps protection of the environment. Valuable resources will also be conserved by means of separation and exploitation of the recyclables in the waste before incineration.

Trigger of development

Since 2005, in the European Union, waste can be disposed of, only if it was subject to a treatment before, so that the substances contained in it will become inert, thus to a large extent no more harmful reactions with the environment will occur in the landfill body. The incineration process takes a key role in the waste management by fulfilling this requirement of the Waste Storage Regulation and the Landfill Regulation.

Main purpose

The main purpose of incineration is to reduce the waste volume and destruction of potentially dangerous substances.

The incineration of waste is classified as an act of exploitation in the Waste Framework Directive adopted in May 2008. The waste that can be used for energy production is subject to the free trade policy and may be moved in the EU trans-boundary. The waste that is to be eliminated entirely, for example hazardous and toxic waste, must be disposed in the vicinity of their origin.

Since the volume of waste is growing continuously, landfilling does not seem to be a long-term solution for waste disposal.

To eliminate this volume, currently, only two approaches remain:

The first approach is waste incineration and the second one, which is probably the best solution, is waste avoidance in addition to re-utilization by means of recycling. That means, the reintroduction of valuable materials into the production cycle. This is possible only if economically feasible and environmentally acceptable methods are available.

Forecast of future developments

The interest of new design of incinerators and incineration process focus on further improvements in energy efficiency and the further savings of CO2. Engineers are working on several aspects of it, from the optimization of the fuel consumption of the plants, to increasing the efficiency of the equipment. Similarly, they work for better techniques for utilization of rest materials and utilization of slag and flying ash. Today more than 80 percent of slag and flying ash are already being used, mainly in earth filling or in road construction.

Role of mobile incineration in the cycle of waste management

Mobile incinerators provide a useful addition to the available standards in waste management.

The elimination of hazardous and toxic waste on site is one of the major uses of mobile incinerators.

A mobile incinerator unit is the most suitable product for countries that are starting to tackle waste management, because in such cases, there are no previous statistics about the amount of waste and its composition. Therefore all initial data is based on assumptions only. Until more accurate data can be collected, mobile incinerator units help make the transition, with their mobility and flexibility.

Description of mobile incinerators

A mobile incinerator is an incineration system mounted on a semi-trailer. Modern incinerators enable complete and sterile incineration of waste. They can be operated virtually anywhere.

A modern mobile incinerator unit (MIU) is capable of incinerating waste at a temperature of up to 1,200 °C (2,192 °F). This means, it is designed to incinerate all kinds of waste as well as infected hazardous waste. This satisfies the requirement that, waste of hospitals and health facilities must be burnt at a minimum temperature of 1,100 °C (2,012 °F) acc. to the rules of environmental protection. It can also be used to dispose of household waste, as a measure of environment protection.

Applications of mobile incineration units

Arguments for mobile incineration

An important argument for the mobile incineration is, due to its mobility, it can go to the place of origin of the waste.

This behavior makes it unique, and allows it to be used for waste disposal of several cities and/or hospitals at the same time.

Fighting against epidemics is a serious issue for authorities responsible for the health of their citizens in every country.

In case of an epidemic it is required to dispose the infected hazardous waste of the diseased, hospitals and health facilities as soon as possible.

Latest burner and control technology, together with a flue gas cleaning system is the basis of a modern mobile incinerator unit that meets the highest environmental standards. (See section Emissions)

Process description of a mobile incinerator unit (state of the art)

Fuel

Natural gas, diesel or biodiesel (so called green fuel) is usable as fuel for the mobile incinerators.

Furnace

Charging of a unit

The furnace of a modern mobile incinerator plant consists of a main combustion chamber (primary chamber) and a post combustion chamber (secondary chamber). Charging is carried out mostly from the front of the main combustion chamber through a feed opening system, which is closed by a gate valve. A check valve behind the feed opening prevents direct contact with the combustion chamber. Feeding is automatically controlled by a furnace control system. An automated burner serves for the heating of the combustion chamber subject to the calorific value of the waste charged. The feed opening is released as soon as the necessary flue gas temperature is reached. Two types of design are normally in use; a) an incinerator without grate and b) a rotary-kiln (pyrolysis). In the post combustion chamber the gas is heated to minimum of 850 °C (1,560 °F) in order to ensure an environmentally friendly emission based on the European Union Directive (85/337/EEC) on Environmental Impact Assessments (known as the EIA Directive). The normal combustion temperature is minimum 850 °C (1,560 °F) and up to 1,200 °C (2,190 °F), depending on the process settings. At the end of the thermal process, ash extraction is done through an ash door.

Flue gas cleaning system

Not all available devices in the market have a flue gas treatment plant. But there are devices available with a dry flue gas cleaning system according to the rigorous European standards. Such a flue gas system mainly consists of a dry sorption system for SO2, HCI, HF, dust reduction, heavy metals, dioxins, etc. To protect the whole system, an automatic emergency water injection facility at the combustion chamber serves for the cooling of flue gas in case, too much waste or waste with too high calorific value is charged. Mobile incinerator units with such a system are environmental friendly.

Fuel and water tank

A fuel and a water tank are mostly installed on or under the semi-trailer.

Fan and stack

Mostly a fan transports the flue gas to the stack.

Electrical, instrumentation and control equipment and its standards

The electrical, instrumentation and control equipment of such a modern incinerator unit includes a main switch, an emergency switch as well as all necessary safety catches, contactors, relays and clamps, key switches for the start up and so on. All measuring, controlling and adjusting functions are realized in a modern mobile incineration plant. There are some safety limits which are processed by the hardware of such a plant. For start-up and operation of the mobile units, most have their own electrical generator on board for power supply. The whole equipment has to comply with European (e.g. DIN 41494, DIN 41488) and/or international (e.g. IEC Publication 297) standards.

Emissions of a modern mobile incinerator with a flue gas cleaning system

Under normal operation conditions, mobile incinerators are consistently able to keep emissions well below respective limits, for example in accordance to the German TA-Luft regulation. Often, emissions are well below the limits. This applies especially to the polychlorinated dibenzodioxins and furans (dioxins and furans). In spite of sophisticated technology, it may happen that higher emission values are reached due to inhomogeneous fuel (waste composition), especially in the phases of start up, shut down and malfunction of a plant.

Legally permitted emission levels

The legally permitted emission levels usually are far above the actual emissions of pollutants if the emissions over a period of one year is considered.

It should be emphasized however that these isolated instances of exceeding the limits has no effect on public health since even these higher values are usually still within the limits permitted for other technical or chemical plants.

The impact of waste composition on emissions

Domestic waste has a calorific value of approx. from 5,000 kJ/kg (12,000 BTU/lb) to approx 12,500 kJ/kg (29,000 BTU/lb). Industrial waste shows much higher fluctuation. This inhomogeneity pose a problem during the thermal treatment of waste. The exact composition of waste that is subject to fluctuation can not usually be estimated initially but it shows its potential energy as well as its pollutants during combustion. sorting the waste, recycling and composting has significant influence on the composition of waste which in turn affects its heating value. The large possible variation in calorific value and composition of the waste require a highly complex automatic control during the thermal treatment that must take into account both the reliability of the process and the requirements of environmental protection. Since the requirements of environmental protection and the reliability are contradictory to each other, there must be compromising solutions that are mutually acceptable for both sides. The parameters of O2 and CO concentration and fire room temperature are the main basic variables to be controlled when designing the process.

Summaries of EU legislation

EUROPA > Summaries of EU legislation > Environment > Waste management

General framework

Hazardous waste

Waste from consumer goods

See also

External links