Incineration And Pyrolysis

Incineration

Akash TikheM.Sc. Environmental Science

Bharati Vidyapeeth, Pune

IncinerationMSW is burnt in a properly designed furnace under

suitable temperature and operating conditions. This process is called as incineration.

It is one of the most effective method of reducing the volume and weight of municipal solid waste.

The process consists of controlled burning of waste at high temp (1200- 1500°C).

It sterilizes and stabilizes the waste with reduction in the volume.

Incineration It is a process in which carbon, hydrogen and other

elements in the waste mix with oxygen in the combustion zone and generates heat. This reaction is called as oxidation.

For complete oxidation the waste must be mixed with appropriate volume of air. Approx. 5000kg of air is required for each tone of solid waste burned. It differs with moisture content, heating values of waste and type of combustion .

Proper temp must be maintained for suitable length of time.

Incineration Process

Incineration Process

IncinerationThe process can reduce MSW by about 90% in volume

and 75% in weight.

Temperature ensures good combustion and complete elimination of odour.

The combustion process is based on 3T’s1.Time2.Temperature3.Turbulence (gas velocity)

Objectives of Incineration

1. Volume Reduction- To combust SW to reduce their volume to 1/10th without producing offensive gases and ash.

Volume reduction depends upon the MSW composition. General volume reduction is by 90% and weight by 75%.

2. Stabilization of waste– output from incinerator is more inert than input due to oxidation of organic components of waste stream.

Objectives of Incineration

3. Recovery of energy from waste – Energy recovered from burning of waste is used to generate steam for on site electricity generation or export to local heating schemes.Combined heat and power plants increase the efficiency of energy recovery by producing electricity as well as utilizing residual heat.It reduces demand on fossil fuels.

4. Sterilization of waste– Important for incineration of clinical/biomedical waste. It ensures pathogen destruction prior to final disposal.

Advantages of incineration

The volume and weight of the waste are reduced to a fraction of its original size.

Waste reduction is immediate, does not require long term residence.

Waste can be incinerated on site without carted to a distant area.

Air discharge can be effectively controlled for minimal impact on the atmospheric environment.

Advantages of incinerationThe ash residue is usually non putrescible or sterile.

Technology exists to completely destroy even most hazardous material in a complete effective manner.

Requires relatively small disposal area compare to land burial. Particularly popular in countries such as Japan where land is a scarce resource.

By using heat recovery techniques the cost of operation can often be reduced or offset through the use or sale of energy. (resource recovery/ waste to energy facility)

Advantages of incineration

Denmark and Sweden have been leaders in using the energy generated from incineration for more than a century, in localized combined heat and power facilities supporting district heating schemes.

A number of other European countries rely heavily on incineration for handling municipal waste, in particular the Netherlands, Germany and France.

Disadvantages of incineration The capital cost is high.

Skilled operators are required.

All materials are not incinerable (construction and demolition waste).

Supplemental fuel is required to initiate and at times to maintain the incineration process.

The most publicized concerns from environmentalists about the incineration of municipal solid wastes (MSW) involve the fear that it produces significant amounts of dioxin and furan emissions.

Disadvantages of incineration The solid residue remaining in the furnace after incineration is

called as bottom ash which ultimately go for land disposal. The bottom ash may contain metals like lead and cadmium, can be treated prior to disposal.

Dioxins occur as in the incineration of chlorine-containing substances such as PVC (polyvinyl chloride)

Health effects such as Developmental of abnormalities in the enamel of children's teeth. Central and peripheral nervous system Thyroid disorders Damage to the immune systems Endometriosis Diabetes

Disadvantages of incineration

Fly ash is the incinerator ash carried along in the combustion airstream. So air pollution control devices are installed to remove fly ash and potentially harmful gaseous contaminants.

Thus, Installation of air pollution control equipment make the process expensive.

These equipments are located after the furnace and before the stack.

Important Factors For Incineration

1. waste moisture content– The greater the moisture content , more fuel is required to destroy the waste.

2. Heating Value–With no significant heating value incineration would not be a practical disposal method.

Important Factors For Incineration

3. Inorganic salts– waste rich in inorganic, alkaline salts are troublesome to dispose of in a conventional incineration system.

A significant fraction of the salt get collected on furnace surface, creating a slag or cake which severely reduces the ability of an incinerator to function properly.

4. High sulfur or halogen content– The presence of chlorides or sulfides in waste will normally result in the acid forming compounds in the off gas.

Pyrolysis

PyrolysisPyrolysis is a thermochemical decomposition of

organic material at elevated temperatures in the absence of oxygen.

It involves the simultaneous changes of chemical composition and physical phase, and is irreversible.

Pyrolysis is a type of thermolysis and is most commonly observed in organic materials exposed to high temperature.

PyrolysisPyrolysis of organic substances produces gas and

liquid products and leaves solid residue richer in carbon content, char.

Pyrolysis is used heavily in the chemical industry for example to produce charcoal, activated carbon, methanol and other chemicals.

It is also a tool of chemical analysis, for example in mass spectrometry and in carbon-14 dating.

PyrolysisPyrolysis occurs whenever food is exposed to high

enough temperatures in a dry environment such as roasting, toasting or grilling, baking, frying, grilling and caramelizing.

In normal cooking, the main food components that undergo pyrolysis are carbohydrates (including sugars, starch, and fiber) and proteins.

Pyrolysis of fats requires a much higher temperature and it produces toxic and flammable products.

PyrolysisIn many industrial applications, the process is

done under pressure and at operating temperatures above 430º C.

For agricultural waste typical temperature range is 450º-550º C.

PyrolysisPyrolysis

Management of Biomedical Waste

The goals of biomedical waste treatment are to reduce or eliminate the waste’s hazard, and usually to make the waste unrecognizable.

Biomedical waste if often incinerated. An efficient incinerator will destroy pathogens and sharps.

An autoclave may also be used to treat biomedical waste. An autoclave uses steam and pressure to sterilize the waste or reduce its microbiological load to a level at which it may be safely disposed off.

Management of Biomedical Waste

Biomedical waste is a waste that is either putrescible or potentially infectious. It is generated from hospitals, health clinics, nursing homes, medical labs, research centers, funeral homes and veterinarians.

Biomedical waste may be solid or liquid. Examples are discarded blood, sharps, unwanted microbiological cultures and stocks, discarded body parts, human and animal tissues, used bandages, discarded gloves, etc.

Management of Biomedical Waste

For liquids and small quantities a 1-10 % solution of bleach can be used to disinfect biomedical waste.

Solution of NaOH and other chemical disinfectants may also be used depending upon the waste’s characteristics.

Management of Hazardous Waste

Hazardous waste is waste that poses substantial or potential threats to public health and the environment.

Hazardous wastes are material that are known or tested to exhibit one or more of the following four characteristics:Ignitability (flammable)ReactivityCorrosivityToxicity

Management of Hazardous Waste

Hazardous wastes may be found in different physical states such as gaseous, liquids or solids depending upon the source of generation.

Many types of businesses generates hazardous waste. For example dry cleaners, automobile repair shops, hospitals and photo processing centers, etc.

Some larger companies such as chemical manufactures, electroplating and oil refineries generates some hazardous waste.

Management of Hazardous Waste

Historically, some hazardous wastes were disposed of in regular landfills.

This resulted in unfavorable amounts of hazardous materials seeping into the ground and eventually entered into natural hydrological systems.

Many hazardous waste undergo different treatments in order to stabilize and dispose of them.

These treatment can be recycling, incineration, pyrolysis and secure landfilling.

Recycling of Hazardous wasteMany items that can become HW disposal problems can be

recycled into new products or sometimes reclaimed.

Some reclamation processes are the recovery of acetone from spent solvents and lead from metals.

Lead acid batteries or electronic circuit boards can be recycle.

Zinc can be gathered from smelting furnaces.

Most flammable materials can be recycled into is industrial fuel.

Incineration of Hazardous Waste

Flammable HW can sometimes be burned as energy sources. For example many cement kilns burns HW like used oils or solvents.

Incineration treatment not only reduce the amount of HW but also they generate energy from the gases released in the process.

Incineration of particular waste releases toxic gases produce by the combustion of byproducts or other materials and this can affect the environment.

Pyrolysis of Hazardous WasteSome HW may be eliminated using pyrolysis in an

ultra high temperature electrical arc, in inert condition to avoid combustion.

This treatment method may be preferable to high temperature incineration in some circumstances such as in the destruction of concentrated organic waste types, including PCBs, pesticides and other persistence organic pollutants.

Landfilling of Hazardous Waste

Land disposal of HW contains the waste in a landfill, waste pile, injection well or other land based disposal area.

Thank You