Plasma Pyrolysis
Pyrolysis System| Features | Plasma Torch | Process Details | Emission Details | Pyrolysis Technology| Energy Recovery

Safe Remediation of Medical, Chemical and Hazardous Waste

Pyrolysis is the thermal disintegration of carbonaceous material into fragments of compounds in an oxygen-starved environment. Plasma pyrolysis (also called plasma gasification) exploits the thermochemical properties of plasma. The particle kinetic energy in the form of heat is used for decomposing chemicals. In addition, the presence of charged and excited species renders the plasma environment highly reactive which can catalyses homogeneous and heterogeneous chemical reactions.

When the process is optimised, the most likely compounds to form from carbonaceous matter are methane, carbon monoxide, hydrogen, carbon dioxide and water molecules. The high temperature and high enthalpy inhibits the formation of hydrocarbons. Plasma process has option of selecting the gas medium, which helps in changing the by-products. High temperature reduces the required residence time for pyrolysis.

Plasma Pyrolysis technology has been developed by FCIPT in collaboration with TIFAC.
Pyrolysis System

Technical Description of the FCIPT System
  • The system consists of feeder, primary and secondary chambers, scrubber and induced draft fan mounted on a common movable platform of size 5’x 8’.
  • The double port feeding mechanism is easy to operate, leak proof and is charged with inert gas to prevent air venting into the hot zone. Fish mouth door has been provided with a cover of heat resistant material, which do not allow heat to enter the hopper.
  • A plasma torch is mounted on the circular end wall. The torch is aligned in such a way that waste material falls into the hot zone of the plasma arc. The torch cathode and anode are cooled by forced water flow. In addition, auxiliary cooling of anode with air has been incorporated in the plasma torch.

The pyrolysis product gas enters the secondary chamber through a burner, which is mounted vertically enabling easy flow of the product gas into the combustion chamber ensuring extended flame length. The treated secondary off gas is scrubbed in a shower and ejected into the atmosphere
Plasma Pyrolysis System
Features

Technical, operational and Commercial Data
  • Waste feed mechanism with inert gas lock to prevent puffing
  • Arrangement for the removal of solid residues.
  • Positioning of plasma torch for efficient heat transfer.
  • Shielding of plasma torch after shutdown.
  • Controlled injection of sub-stoichiometric air during pyrolysis.
  • Metal shell in the primary chamber for proper heat distribution.
  • Low impedance for pyrolysis product gas flow.

Operational advantages:
  • compactness.
  • can be fully automated.
  • can be located inside the hospital building.
  • heat recovery for hospital utilities.
  • no segregation required.
  • above 95% volume reduction
Plasma Torch

High Temperature Plasma Generation
  • The non transferred plasma torch is based on arc ignition between a thermionic tungsten cathode and a co-axial copper anode, both water-cooled Anode and cathode are immersed in an axial magnetic field.
  • Nitrogen is the plasma gas. Air or steam can be injected into the plasma to increase the enthalpy and to produce sub-stoichiometric incineration.
  • The torch is powered by a thyristor-controlled rectifier, which has controls to match the torch impedance.
  • Spectroscopy diagnostics reveal that the temperature near the cathode is around 20,000ºK and is around 1,500ºK close to the material under treatment.

The magnetised non-transferred plasma torches developed at FCIPT have been adapted for pyrolysis technology. These torches are characterised by extended hot flame. Air plasma torches are also being developed to mitigate the logistic problems associated with nitrogen usage.
Plasma Torch
Process Details

Gasification and Combustion
  • The waste introduced into the extended hot zone of the primary chamber is pyrolysed. The pyrolysis product gas contains CO and Hydrogen along with hydrocarbons and is combustible.
  • This is ignited in a burner inside the secondary chamber.
  • 2 ft. flame ensures 2sec residence time flame temperature is more than 1200° C CPCB requirement of 1050+-50° C gas temperature in the secondary chamber achieved without extra fuel
  • The exhaust gas is scrubbed and released into the atmosphere is almost colorless.
Emission details

Gases  Before treatmentAfter treatment
CO>20,00040-85
NO x 4503-35
SO2501-20
HCl83-3952-15
Hydrocarbons> 20,00020-95
Pyrolysis Technology

Technology extension to chemical and toxic wastes

Technology up gradation includes IGBT based torch power systems and development of air plasma torches. A bootstrap system, which uses the combustion heat to reduce the electrical energy for pyrolysis, has been tested.

Pyrolysis technology is being adapted for safe disposal of plastic carry bags in ecologically sensitive locations around the country. These include Andamans and Nicobar Islands, Sikkim, Himachal Pradesh and Goa under a DST sponsored project.

The FCIPT Medical Waste Remediation Technology has been transferred to Bhagwati Pyrotech Private Ltd., a division of Bhagwati Spherocast Ltd., Ahmedabad. They are installing six commercial units for the propagation of the technology in major hospitals around the country. This project is being financed by the Department of Science and technology.
Energy Recovery

Improving the economic viability of waste destruction

  • Pyrolysis converts waste into CO, methane and Hydrogen. Product gases will be processed in an atmospheric pressure non-equilibrium plasma reformer to improve the energy recovery potential of the product gas.
  • Energy recovery options explored include heat and chemical energy recovery. The feasibility of using the product gas for direct fueling of IC engines is being explored.

GasesContribution
N245.03%
H222.63%
CO26.65%
CH41.50%
CO24.20%
Hydrocarbons0.45%

With successful development of these technologies, waste destruction using plasma systems will acquire economic viability in addition to meeting statutory requirements. The FCIPT technology also finds a niche in small and medium size waste destruction market.
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