3. Challenges
Global generation of Solid Waste will double by 2025.
Solid waste generated by 300 million people living in urban
India is 30 million tonnes per year.
1,00,000 MT SW generation every day in India.
Opportunities
SW is the only alternative waste to energy generation. SW
supplies 10% of global power.
The high heating value of SW indicates the need of waste to
energy plants.
Plasma gasification is the unique opportunity to mitigate the
above challenges.
4. • Oldest method, waste disposed in landfills.
• Waste digested anaerobically and produce
biogas used as source of heating.
Land filling
•Mass burn technology in presence of oxygen
•Waste burn in incinerators and converted into
ash and harmful greenhouse gases.
Incineration
•Thermal treatment in the absence of oxygen at
low temperature.
•Syngas, pyrolysis liquid and coke obtained as
products.
Pyrolysis
•Partial oxidation of waste at high temperature.
•Products are low quality syngas, slag and
metals.
Gasification
• Waste is converted into syngas and
vitrified slag at very high temperature.
• No emission of greenhouse gases.
Plasma
Gasification
6. Origin of Plasma
• Plasma is a fourth state of matter.
• Discovered by British physicist Sir William
Crookes in 1879.
• Heating a gas at very high temperature lead to ionization
of atoms and turns it into plasma.
• Natural plasma can be seen in lightning, sun stars, comet
etc.
• Firstly used by metal industry in 1800 in metallurgical,
mechanical operations and in 1900 chemical industry made
acetylene from natural gas.
• Plasma technology used by NASA in 1960 and become
popular.
7. •Plasma consists high electrical conductivity, more
independently acting species, high velocity particles and
particles interact at long range through electric or magnetic
forces.
•Man made plasma produced by plasma torches using
electricity as a heating source and air as ionized gas.
•The plasma torches create the flow of plasma by using a
650V DC or AC and generate the temperature of about
2000-20,000°C.
8.
9. Municipal
solid waste
Low level
radioactive
waste
Biomedical
waste
Waste coal
Steel scrap
Asbestos and
asbestos
containing
material
Incinerator
ash
10. Plasma Gasifier
Gasifier is the central component of the
plasma gasification process.
The gasifier equipped with its components
plasma torches, air or oxygen as ionized gas
and feedstock.
The plasma arc converts organic waste into
synthetic gas and inorganic material into
vitrified slag.
The gasifier is maintained under negative
pressure about -5mm due to minor air in
leakage.
The inside of vessel lined with refractory and
sealed with stainless steel.
The chemical reactions take place are
C + H2O CO + H2
C + CO2 2CO
11. • The major products are synthesis gas and
vitrified slag.
• Syngas has a high temperature cooled down
through heat recovery units.
• Syngas as a fuel for electricity generation.
• Rock like vitrified slag as construction
aggregates.
• Other products are hydrochloric acid, hydrogen
sulfide obtained from syngas cleaning.
12. Plasma gasification holds a potential to add to the supply of
renewable energy resource in these times of uncertain
energy supplies.
Any material can be processed in plasma arc system. To
achieve a favorable energy balance the volume of inorganic
should be minimized.
There is no emission of harmful greenhouse gases.
Concentrations of dioxins are very low as compared to
incineration due to high temperature.
Plasma gasification technology has a high operating cost and
capital cost due to high electrical power requirement
13. • 2009 BP statistical review of world BP plc.
57th edition 45p.
• Lisa Zyga (2012) plasma gasification
transforms garbage into clean energy, science
blogger. Inventorspot.com, via: popular
science
• Helsen, L.,2000 low temperature pyrolysis of
CCA treated wood waste. PhD. Thesis,
Heverlee, KU Leven.
• Manual of solid waste 2008
Notes de l'éditeur
Per capita waste generation in major cities ranges
from 0.20 Kg to 0.6 Kg. Generally the collection efficiency ranges between 70 to
90% in major metro cities whereas in several smaller cities the collection
efficiency is below 50%.
In old times, the land filling is the least sustainable and most popular method for disposing of trash.
The waste disposed is digested anaerobically also called a biochemical conversion and produce biogas used as a source of heating.
It has drawbacks such as producing harmful gases like CO2 and methane and large surface area is needed for disposal.
Pyrolysis is a thermo chemical degradation of organic material in the absence of oxygen.
The products obtained are pyrolysis gas called syngas, pyrolysis liquid and solid cake richer in carbon content.
Indirect heating is done in different reactors like fluidized bed, rotary kiln, moving bed, fixed bed etc. The temperature maintained at 450-550°C.
Due to its low temperature produces less pollutants.
Pyrolysis process has some drawbacks like solid residue disposed to landfill, a major environmental disposing.
It is a mass burn technology.
It is oxidation of combustible material contained in the waste. Excess O2 is added to attain burning at low temperature. It converts the waste into flue gas, ash and heat.
The flue gases obtained are CO2 and H2O with emission of harmful gases like NOx, SOx, VOC etc.
This process has drawbacks such as high level of green house gases and large amount of ash sent to a landfill for disposal.
Pyrolysis is a thermo chemical degradation of organic material in the absence of oxygen.
The products obtained are pyrolysis gas called syngas, pyrolysis liquid and solid cake richer in carbon content.
Indirect heating is done in different reactors like fluidized bed, rotary kiln, moving bed, fixed bed etc. The temperature maintained at 450-550°C.
Due to its low temperature produces less pollutants.
Pyrolysis process has some drawbacks like solid residue disposed to landfill, a major environmental disposing.
Plasma consists of a collection of free moving electrons and ions. Energy is needed to strip electrons from atoms to make plasma. The energy can be thermal, electrical or light . DC torches are better than AC torches due to less flicker generation, less noise, better control, lower electrode consumption and lower power consumption. The transferred torches or non transferred torches classification depends on whether arc is electrically transferre to work piece or not. The transferred torch operate with low gas flows and high operate voltages. But in non transferred torch needs high operating currents and have lower efficiencies. Thermal-plasmas are atmospheric-pressure plasmas characterized by high enthalpy content
and temperatures around 2000–20,000 degrees. Non-equilibrium plasmas are low-pressure plasmas charac-terized by high electron temperatures and low ion and
neutral temperatures. This paper focuses on thermal-plasma, which is a source of concentrated energy, posi-tive and negative ions, highly active radicals and intense
radiation. Thermal-plasma devices operate from a few
tens of watts to a few MW.
It is important to note that although they are unbound, these particles are not ‘free’. When the charges move they generate electrical currents with magnetic fields, and as a result, they are affected by each other’s fields. This governs their collective behavior with many degrees of freedom.
Products are syngas which has calorific value of about 320Btu/cubic foot and used as an alternative for fuel and vitrified slag used in construction aggregates.
Other products hydrogen sulfide, hydrochloric acid etc. depends on the formation of feedstock and are separated in cleaning system from syngas
Steam is also added to promote syngas reactions. The production of other products other than syngas depends on waste stream. It is sealed with stainless steel. The plasma gasifier is a refractory lined vessel and sealed with stainless steel. The reactors are large and operate at a slightly negative pressure, meaning that the feed system is simplified because the gas does not want to escape. The gas has to be pulled from the reactor by the suction of the compressor. Each reactor can process 20 tons per hour (tph) compared to 3 tph for typical gasifiers. Because of the size and the negative pressure, the feed system can handle bundles of material up to 1 meter in size. This means that whole drums or bags of waste can be fed directly into the reactor making the system ideal for large scale production.
Exit Gas, 1700 C
Coke Bed, 1800 – 4000 C
Torch Plume, > 5000 C
Slag Pool, 1700 – 1800 C
First, it is a convenient way to provide thermal energy in a gasification process.
Second, controlling the amount of heat input to the process by means of the plasma torches allows
controlling the composition of the syngas. Third, the hydrogen to carbon monoxide ratio can be modified
easily to suit the needs of the end use.
