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Pyrolysis is a thermal process that turns waste into useful resources. Materials such as biomass, plastics or sludge are heated in the absence of oxygen and broken down into valuable products such as fuels or oils, syngas and biochar. Unlike burning, pyrolysis reduces harmful emissions and offers a sustainable way to recover energy from waste.
Pyrolysis chemically breaks material down in accordance with its chemical structures. The fixed carbon and ash content of the materials will remain as solid whereas the volatile content of the materials will be released as a gas mixture.
The higher the temperature of the pyrolysis, the more chemical breakdown of the material will occur resulting in a more stable biochar and the less condensable portion of the syngas that will be produced giving a richer syngas.
This is the basis of Anergy High Temperature Pyrolysis (HTP) which is to operate at a higher temperature as compared to conventional pyrolysis.
Pyrolysis is one of the thermochemical processes available to process waste and convert it into useful energy. Others include gasification and incineration.
The absence of oxygen in the process allows biochar to be produced.
The oxygen that is present in gasification and incineration will consume and oxidise the fixed/organic carbon content of the material to maintain the high operating temperature.
The biochar produced from the pyrolysis process can be sequestered. The sequestration of biochar slows down the release of greenhouse gases into the environment.
Oxygen for the gasification and incineration generally comes from the environment which contains 78% nitrogen.
The inert nature of nitrogen will dilute the syngas from the gasification and incineration processes such that it has lower calorific value as compared to syngas from pyrolysis process.
Conventional Pyrolysis has its disadvantages that limits its utilisation to reduce waste in the industry.
The temperature that conventional pyrolysis operates (400oC - 650oC), in addition to the absence of oxygen, encourages tar formation.
Tar is made up of complex hydrocarbons that can condense and solidify in pipes, causing blockages to pipes, creating operational issues.
A lot of downtime and maintenance will be required to remove the blockages due to the tar build-up.
Conventional pyrolysis could potentially create 3 different products which are the char, pyrolysis oil and syngas. However, not all 3 products may be of value.
The char may contain volatile content of above 12%. This means that the char product may not be stable and may self-ignite when exposed to the environment.
The pyrolysis oil is unrefined and will require upgrading before it can be useful which elevates the CAPEX and adds further complications to the process.
The syngas that have been stripped off for pyrolysis oil will have much lower energy content.
Anergy High Temperature Pyrolysis (HTP) process is superior as compared to conventional pyrolysis.
On top of having the benefits of the pyrolysis, HTP also eliminates the disadvantages of the conventional pyrolysis.
The general pyrolysis process utilising Anergy’s HTP can be described as follows:
Feed stock is loaded into a feed bin equipped with a sealing rotary valve to maintain an oxygen starved condition and transported via a conventional feed screw into the pyrolysis unit.
In this process, feedstock is slowly heated in a rotating heat tube using indirect heat from gas burners. With no oxygen present within, the material does not burn and instead is thermally broken down into char and unrefined syngas. Char product is cooled and collected.
Unrefined or raw syngas from the pyrolysis process contains impurities in the form of inorganics, dust and tar which are removed in the cleaning process prior to utilising the syngas for the intended application.
Biochar is a porous carbon containing solids produced from thermal processing in a low oxygen environment such as pyrolysis.
Biochar is a name given to char products that come from sustainable sources such as biomass, wood chips, nut shells, etc.
Biochar has diverse applications including:
Soil enhancement
Carbon sequestration
Coke replacement for steel making
Wastewater filter
Syngas is a mixture of hydrogen, carbon monoxide, carbon dioxide and hydrocarbons which are combustible.
Various methods are available to produce electricity such as gas engine generator, steam turbine, organic rankine cycle, etc.
Anergy HTP system uses a gas engine generator due to the high calorific value of the syngas.
The syngas composition of hydrogen, carbon monoxide and carbon dioxide can be reacted to produce fuels in different forms.
Fischer Tropsch (FT) reaction of syngas could yield a mixture of diesel, gasoline and jet fuel. (*disclaimer - depend on the feed specification which affects the syngas composition).
The catalytic hydrogenation process of the syngas could yield methanol as a product.
The catalytic dehydration process of the methanol could yield Dimethyl Ether (DME) as a product. DME is an alternative to propane and diesel. DME can be blended into propane or diesel to decarbonise the oil & gas industry.
