Gasification as a Decarbonization Solution for the Circular Economy
The perception that gasification of waste is primarily waste destruction with minor electricity production is outdated. Gasification presents a greater opportunity to remove waste feedstock from our society while playing a major role in the circular green economy. Municipal solid waste, reject plastics and paper, forest biomass waste and many other wastes contain molecules waiting for release in a process to repurpose the molecules into a valuable syngas such as hydrogen, aviation fuel and bio-gasoline to name a few.
The OMNI Conversion Technologies Gasification & Plasma Refining System (GPRSTM) is one such mature gasification process on the market today.
To test the OMNI200™ technology OMNI CT designed and built a complete facility to process 135 tonnes per day or raw, unsorted NSW. The OmniSyngas™ was sent to Jenbacher IC engines to make electricity.
The OMNI200™ GPRS™ unit is a complete integrated system. It receives and converts at a rate of 200 tonnes per day (67,000 tonnes per year) a wide variety of energetic wastes to a clean syngas tailored to the final application.
Plasma gasification provides a number of key benefits:
- Proprietary feeder air lock
Feed preparation is minimal for a wide variety of waste: only shredding to 10cms (4”) required. The OMNI200™ GPRS™ feeder air lock consists of two horizontal positive displacement piston pumps, each capable of delivering the full rated throughput. This provides a plug of compressed feedstock that permits feedstock to enter the converter without air entering the system.
- Horizontal moving grate gasifier
The converter consists of a vessel with a series of horizontal moving grates. The grate sections provide forward movement and agitation of the feedstock. Oxygen and steam heated by recovered heat from the refining process are introduced in measured amounts at each grate rising through pile, to cause efficient drying and pyrolysis.
- Vertical Fixed Bed Updraft Gasifier
Char enters from the converter at the top together with particulate recovered from the gas cleaning system. Oxygen-rich moist heated gas coming from the lower section gasifies the fixed carbon and heavy metals. Gas rich in CO, H2 and some CH4 rises from the gasifier, leaving behind the inorganic portion. This fraction is heated by the reaction to the melting point and drips through a water cooled grate into the Solids Residue Melter below.
- Solids Material Recovery Vessel (SRM)
The SRM is maintained at a temperature sufficient to superheat the molten solids with burners fueled by OmniSyngas™. Additional oxygen and steam are introduced using injection nozzles above the superheated melt. The oxygen-rich atmosphere in the SRM ensures decarbonization of the melt. The melt is tapped continuously and quenched with water to make a nonleachable slag product which has a number of beneficial uses.
- Syngas Plasma Refining Chamber
All gasification in the OMNI CT process takes place without plasma. Plasma is only used for refining. In the refining chamber, a small amount of oxygen is mixed with the syngas to raise its temperature, while it simultaneously subjected to the plumes of (2) plasma torches. The torches provide only about 4% of the total heat for the process, but ensure plasma catalysis. Plasma catalysis uses active species of free radicals and electrons to crack bonds of long chain molecules into simpler ones. The overall fuel/oxygen ratio is controlled to produce the desired temperatures. Plasma catalysis is extremely efficient at breaking down tars and hazardous compounds, removing 99.95% of tars at about 3000C less than would be required without the plasma.
- Gas Cooling and Conditioning to end use
The syngas is cooled and moisture is removed through a proprietary integrated process. Particulate, HCL, sulfur and heavy metals including mercury, are removed. The end output is a consistent energy rich, tar free OMNISyngas™. All particulate is recycled back into the process, for 100% diversion from landfill into either useful syngas or nonleachable aggregate.
Omni CT has commercialized a truly omnivorous waste conversion system to produce a valuable Syngas.
By employing a grate based gasifier rather than a fluidized bed gasifier waste preparation is minimal and robust. The process is omnivorous with regards to waste supply.
OmniSyngas™ is a refined gas tailored to a wide range of applications.
OmniSyngas™ is a precursor to the production of hydrogen and bio-fuels. Municipal solid waste has more than 50% biogenic content. This will produce green fuels and offset methane from waste sent to landfills. Since methane has 25x the GHG effect of CO2, these fuels can be produced with a negative carbon footprint. Further reduction is possible by separating the CO2 in the syngas and sequestering it.
Below is an example of hydrogen production using MSW in a single Omni200™ GPRS™ with CO2 capture for industrial use.
Comparison to Electrolysis
90% of the energy consumed by GPRS™ to create H₂ comes from the waste feedstock. Whereas all the energy used in electrolysis comes from electricity.
In the OMNI CT system, most of the energy in the hydrogen comes from waste, unlike electrolysis, where it must come from the grid, since water contributes no energy. As a result, the OMNI CT system uses less than 20% of the electricity required for electrolysis to produce a kg of hydrogen.
Gasification can be an integral part of the circular economy, converting waste streams to valuable fuel in a more efficient process than current technologies today. Robust efficient gasification of waste will play a growing solution to meet decarbonization targets.