Prime Minister Narendra Modi may want a “Swachh Bharat” (clean India) by 2019, but sweeping the streets does not address the enormity of India’s real garbage challenge.
s prosperity grows, 62 million tonnes of garbage is generated everyday by the 377 million people living in urban India, now the world’s third-largest garbage generator.
However, it’s not the amount of waste generated that’s as much of an issue as the fact that more than 45 million tonnes, or 3 million trucks worth, of garbage is untreated and disposed of by municipal authorities everyday in an unhygienic manner leading to health issues and environmental degradation.
These 3 million trucks, if laid end to end, would cover half the distance between the earth and the moon. Or to put it another way, that’s the distance you would cover if you made 15 trips between Mumbai and Los Angeles.
For another, we must find renewable and environmental friendly fuel to replace the fossil fuel, as the storage volume in the world is finite. For many years, opposition to the use of municipal solid waste as an energy resource has been nearly universal among activists and regulators because of bad experiences with traditional garbage incineration which are associated with high level of toxic emissions. While with the development of technology, solid waste is potential raw material as renewable energy while reducing greenhouse gas emissions and the need the for landfill space.
Classification of Solid Waste
Solid waste is classified into the three main types by making reference to the sources of waste and the institutional arrangements for waste collection and disposal. These three types of solid waste are municipal solid waste, construction waste and special waste. Municipal solid waste includes domestic waste, commercial waste and industrial waste.
Most of the special waste, such as chemical waste can cause pollution to the environment or become a risk to heath, so that they can no be used as the raw material of fuel.
Important Properties of MSW Pellet or Briquette
Producing energy from trash is known as a “waste-to-energy” option. Several such options have existed for many years and are in extensive use throughout Europe and limited use in the United States. One of the more exciting options that has been proposed within the last decade is to convert waste into solid recovered fuel(SRF), refuse derived fuel(RDF) or process engineered fuel(PEF). The most common forms of this kind of fuel are pellets and briquettes.
Rubbish briquetting and pelletizing is a technology to change idle rubbish into useful and valuable energy. The technology is an agglomeration process that can be categorized as densification technology which makes the bulk density of rubbish to be compact and dense. Physical and chemical behavior of raw material has significant influence of the briquette quality as a fuel.
Pre-treatment before MSW Pelletizing
1. Primary Size Reduction
Twin Shaft Primary Shredder is designed to Shred Municipal Waste to less than 100 mm size. The Shredder comes along with Main Drive Motor, Reduction Gear Box, Integral components, Starter Panel.
2. Separation & Drying
AIR DENSITY SEPARATOR AND DRYER
Air Density Separator (ADS) consists of a rectangular column designed to separate out light fractions from heavy inerts. The material is introduced at the top section and air blast is given at its bottom. The bottom fraction consists of heavy material. Both incoming and outgoing materials are passed through their respective airlock valves. It is a three stage process. High pressure air blast de-agglomerates the incoming materials and very light fraction is sucked up. Furthermore, the air blast from the bottom of the column moves the medium size fraction of the material up in the air. Heavies fall through the airlock and get discharged. Hot air can be injected in the system as per moisture content of material.
Rotary Tromell is used for separating out the fine sand and silt from the municipal waste before it can be sent for further processing. The material tumbles in the rotary screen as it moves ahead across the length of the screen and the fine silt and sand gets removed from through the holes provided in the screen. The rest of the material is discharged onto the Belt Conveyor which carried the material for further processing.
3. Secondary Size Reduction
Twin Shaft Secondary Shredder is designed to Shred Municipal Waste to less than 50 mm size. The Shredder comes along with Main Drive Motor, Reduction Gear Box, Integral components, Starter Panel.
4. Fine Grinding
The Fine Shredder is designed to have size reduction of DF fluff of Municipal Solid Waste after it is passed through the Secondary Shredder. The material from the Fine Shredder is lifted through the pneumatic transfer system consisting of Pipelines, Cyclone, Pneumatic Fan and Air Lock.
Pellet press is designed to produce fuel pellet from 16 – 25 mm diameter by extrusion. Ground and Conditioned material is fed to pellet press by gravity feed. Roller on the die presses the material in die holes and extrudes the material. Length of pellet can be adjusted by knife provided below the die. Pellets so formed are cooled on cooling conveyor and send for storage. Die temperature monitoring for the pellet press has been provided to reduce operational problems.
Obstacles During MSW Pellet Production
Paper or plastics are easy to be contaminated by other materials like food and liquids. Because of contamination and imperfect sorting, between 5 and 25 percent of a materials recovery facility’s incoming recyclables are discarded and sent to landfills. The waste, called “residue” in the waste management business, is a valuable mixture of paper and plastics that is currently lost to the ground.
It is impossible to remove all the hazardous materials such as PVC plastics. In many countries, laws strictly prohibit thermal destruction of PVC due to its harmful emissions, but with so many different forms of PVC in the waste stream it is virtually impossible to eliminate it.