METHODS OF WASTE DISPOSAL

WASTE DISPOSAL PROBLEM

Waste is one of the major challenges modern world is facing today. Every year billions tones of waste are generated and these amounts are rising steadily. Waste disposal can cause negative impacts on health and the environment, including pollutions to air and water.

Waste also represents a loss of natural resources (such as the metals or other recyclable materials it contains, or its potential as an energy source). Proper waste treatment can protect public health and the quality of the environment whilst supporting conservation of natural resources. a>

MECHANICAL BIOLOGICAL TREATMENT

• Mechanical and biological treatment plants pre-treat wastes, generating a number of output streams for further processing

• Only biodegradable wastes can be processed

• Does not solve problem of non-recyclable waste such contaminated plastics, laminated paper

WASTE INCINERATION


General public perception to incinerators due to the potential health impacts of incineration emissions and ashes is negative.

• Require complex and expensive gas cleaning system

• Metal after incineration oxidized and can not be further used

• Ashes require special disposal or further expensive treatment.

WASTE GASIFICATION

• Practical applicability of gasification for mixed waste is limited by several main operating issues related to feed size, moisture, high particle loading, tar formation and ash removal

• Preprocessing costs/energy requirements make gasification being is not really viable for mixed wastes

PLASMA GASIFICATION

• Still in the development stage and does not have commercial references for general wastes

• Suffers several drawbacks such as high energy consumption and life-time of electrodes

• Justified in case of treatment of radioactive wastes

PYROLYSIS


PYROLYSIS TECHNOLOGY

Pyrolysis is the thermal decomposition of waste into gas and solid phases in the absence of the external oxygen/air supply. The process takes place under the temperatures typically around 500-600 C.

Some of the advantages of pyrolysis:

• Relative insensitive to the input materials

• Pyrolysis process does not generate products associated with the burned waste

• Pyrolysis is self-sustainable; i.e. energy is required only for start-up operations

PYROLYSIS WASTE-TO-ENERGY PLANT

Pyrolysis gas undergos the secondary combustion and then steam generation in heat recovery steam generator ( waste-heat boiler), which consequently will be sent to steam turbine to generate electricity. Flue gas is cleaned prior to disposal through stack. Formed pyrolysis char can either be used as a product (biochar) or processed at the pyrolysis plant to generate more energy.

Our waste-to-energy pyrolysis plant is based on this approach. More than 25 years of practical experience in pyrolysis technolgy have led to the modern version of the pyrolysis process. The pyrolysis plant performance is related to the quality of feedstock input namely calorific value and moisture content. Due to the built-in design features, the pyrolysis system under the consideration successfully accommodates sudden fluctuations in the waste quality from its average value, which occur within the pyrolysis facility design range.

Pyrolysis gas could also be cracked and cleaned in order to be used as fuel in a gas engines. Pyrolysis gas conditioning is a complicated issue and additional drawback is that further treatment of the pyrolysis char will be performed at the high temperatures around 1500 C, which makes difficult plant operating and maintenance.

PYROLYSIS LIQUIFACTION PLANT

The gaseous product of pyrolysis can cooled down followed by oil condensin. Liquefaction is applicable on industrial scale for a limited number of feedstock, such as plastics or rubber.

MATERIALS RECYCLING AND PRODUCTION

Pyrolysis is used not only for waste disposal and /or energy generation but also for recycling and new materails production:

• Laminated metals recycling

• Biochar production

• Phosphorus recovery

• Activated carbon regeneration

• Calcination

PYROLYSIS ENVIRONMENTAL DATA

collected at the operating industrial pyrolysis facilities demonstrate the compliance of the pyrolysis facility with the Eu regulations and in particular with regard to the dioxins/furans and heavy metals since they have potential impact to human health.

The pyrolysis plant does not produce waste water effluent from the gas cleaning system. Along with this obvious environmental advantage it also makes the system less expensive.

No special chemicals, which may have impact on the overall environmental performance, are required for the process. Under normal operating conditions only conventional reagents such as sodium bicarbonate and activated carbon are be required.

Another environmental aspect is the reduction of the residuals to be sent for landfill disposal. Just some non-reacted lime and formed calcium compounds collected in the bag filter chamber are sent to landfill disposal. Volume of the solid process residuals to be landfilled is also reduced due to further utilization of char. Solid remains represent a harmless material comprising mainly mixture of silicic acid with oxides of calcium, iron and aluminum as well as with some sulphates and carbonates. Harmless ash can be used in the building industry, e.g as road fillers.

PYROLYSIS ADVANTAGES

The pyrolysis system demonstrates:

• Stable operation for a broad range of waste quality

• Emissions from the system are well below the limit values

• Flexibility in design and operation achieved by a modular design

• Effective initial waste volume reducing

• Efficient recovery of the materials and energy from the process

• Low operational costs; no supplementary external fuel supply for the normal operation, i.e.significant reduction of running costs

The pyrolysis system is designed for treatment of variety of different wastes such as municipal solid waste (MSW), sewage and oil sludge, automotive shredder residuals (ASR or car fluff), e-waste, rubber and tyres, medical waste, plastics, agricultural waste, as well as cleaning of the contaminated soil. Dozens of the commercial pyrolysis facilities for treatment of different feedstocks were designed and built so far.

The pyrolysis facility can operate as stand-alone waste-to-energy plant as well as the part of big power plants. In the last case the pyrolysis process thermally treats the waste and generates fuel, namely pyrolysis gas and pyrolysis char. These fuels are then co-fired in the power plant boiler unit. Pyrolysis process in this configuration disposes waste, simultaneously replacing part of the fossil fuels, consumed by the power plant.

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