Pyrolysis is an Emerging Green Technology | RealEngineer.com

April 9, 2010 by RealEngineer.com

Pyrolysis is an emerging technology and its green credentials when the feed is biomass are top notch. Everyone who has lit a wood or coal fire and watched it burn has seen pyrolysis. Pyrolysis is usually the first chemical reaction that occurs in the burning of many solid organic fuels, like wood, cloth, and paper, and also of some kinds of plastic.
In a wood fire, the visible flames are not due to combustion of the wood itself, but rather of the gases released by its pyrolysis; whereas the flame-less burning of embers is the combustion of the solid residue (charcoal) left behind by it.
Although the basic concepts of the process have been validated, the performance data for an emerging technology have not been evaluated according to methods approved by EPA and adhering to EPA quality assurance/quality control standards.
Waste is converted to a fuel by heating the waste which burns just as coal or wood does under the right controlled conditions. Whereas incineration fully converts the input waste into energy and ash, these processes limit the conversion so that combustion does not take place directly.
Waste Plastic under pressure and catalytic cracking produces fuel and can be used as a fuel source. Under certain temperature conditions the plastic macromolecular chains are broken down into small molecular chains (simple hydrocarbon compounds) and those small molecular compounds contain C4 to C20, this compound is a component of petrol, coal oil, and diesel.
Anhydrous pyrolysis can also be used to produce liquid fuel similar to diesel from solid biomass.
Fast pyrolysis occurs in a time of a few seconds or less. Therefore, not only chemical reaction kinetics but also heat and mass transfer processes, as well as phase transition phenomena, play important roles. Fast pyrolysis is a process in which organic materials are rapidly heated to 450 – 600 degrees C in absence of air. Under these conditions, organic vapors, permanent gases and charcoal are produced.
Researchers at Virginia Tech have identified pyrolysis as a potential technology for disposing of poultry litter. The ultimate goal of the project is to develop transportable pyrolysis units to process the waste from poultry growers within one locality, thus reducing transportation cost. Researchers believe that the char, an inert and highly porous material, plays a key role in helping soil retain water and nutrients, and in sustaining microorganisms that maintain soil fertility. Researchers have obtained from wood – initially beech and then coniferous species – oils with almost ideal characteristics. Straw, which has a lower energy yield – 50% as opposed to 70% for wood – is also due to be analysed in the near future.
Bill Gates’ personal investment vehicle, is reportedly backing Sapphire Energy, a start up working towards a commercial-scale facility to produce oil from algae, but we think he would do well to look at gasification and pyrolysis as his energy technology because there are so many possibilities in this technology.
Gasification technology also offers the possibility to create a new domestic supply of gas. It works by converting the hydrocarbons in coal, biomass and waste petroleum products into a gas called “syngas” that can be used in place of natural gas to generate power, or used in manufacturing as fuel or feedstock. Gasification avoids many problems which can occur in biogas digesters, and is also able to process lignin and cellulose, which are hard to ferment.
Steve Evans is enthusiastic about gasification and other renewable energy sources like anaerobic digestion plants. He also runs a great web site about the biogas.