The IChemE Energy Award – recognizes the best project or process to demonstrate innovation in renewable energy, alternative energy sources, efficient energy use or the development of energy production methods that reduce energy and water intensity.
GWE’s entry involved a world first with Chok Chai Starch in Thailand, where a GWE RAPTOR® system is used to convert wet pulp waste product from the processing of cassava roots into biogas (methane) green energy, at their tapioca starch plant in Uthai Thani.
Vega Baja, Puerto Rico
London, Ontario, Canada
RAPTOR® stands for RAPid Transformation of Organic Residues. It is a robust liquid state anaerobic digestion process that converts almost any organic residue (waste) or energy crop (substrate) into biogas, “green” electricity, renewable natural gas (RNG), or heat.
The process consists of enhanced pretreatment followed by multi-step biological fermentation, and typically includes digestate treatment, biogas conditioning, and utilization.
A RAPTOR® plant is a total solution, from the logistics for the organic waste intake and handling and ending with the production “green” forms of energy.
The detailed design of GWE’s RAPTOR® systems is always adapted to the specific needs imposed by the three major application sectors:
Suitable substrates can be in the form of liquid slurries or wet solid residues. The process at a RAPTOR® plant always begins with a reception facility, including liquid storage tanks and solid organic waste storage boxes, tanks, bunkers or silos. Solid organic feed is more or less continuously extracted from the reception and storage boxes and transported into the preprocessing facilities.
Depending on the types of substrates to be processed, several different approaches are taken regarding pre-processing and pulping of the wastes. Simple, uncontaminated materials can be prepared in a quick mixer device, consisting of a hopper with a rugged double shaft disk shredder, liquid inlet pipe, and a slurry extraction pump. Large amounts of contaminated waste can be processed in a GWE reception pit and decontamination system, to remove metals, plastics and cardboard, which are not suitable for digestion. Liquid (liquid wastes, clean water, or recycled final effluent) is added in a suitable amount to convert the organic solids into liquid slurry of manageable consistency.
Proper blending of the substrates is key to successful operation of a RAPTOR® plant when treating wastes from various sources. The decontaminated and pulped, blended material is then sent to a holding tank or tanks for storage prior to digestion.
For the highest possible conversion efficiency of waste material into biogas within the digestion stage, the organic feedstocks require pretreatment. GWE’s RAPTOR® plant can include one or more of the pretreatment steps that are chosen based on the composition of your raw organic wastes. Possible pretreatment technologies include:
The suitably pre-treated and blended organic waste slurry is then transferred at a controlled rate into GWE ANAMIX™ digesters. As solids digestion occurs twice as fast at high temperature than at low temperature, thermophilic digestion (50–55°C) is usually preferred. The exception to that are applications with organic wastes high in nitrogen, which can require an intermediate temperature or mesophilic digestion at 35-40°C.
Our standard ANAMIX™ digesters, use energy efficient and low-maintenance mechanical mixing systems in the form of a large top entry mixer and are available in sizes up to 3.2 MG (12,000 m3). Depending on the application, optional equipment might be required to ensure optimal performance. Possible extras include a foam breaker fan, a scum control system or a (sloped) bottom grit trap.
Customized reactor configurations can also be utilized depending on the customer’s needs and local situation.
The RAPTOR® tanks are always fully insulated and heated externally, by recycling the digester contents through a unique heat exchanger.
Depending on the type and characteristics of the organic waste applied as feedstock, biogas production rates of up to 6.3 Nm3/day of biogas for every cubic meter of digester volume can be obtained in RAPTOR® plants.
The ANAMIX™ reactor digestate is usually treated in a centrifuge or sludge press for separation of the nondigestible solids (wet sludge cake), which is ideal as fertilizer in agriculture. Sludge cake drying and pelletizing systems are also available on request, if further processing is needed.
The remaining liquid digestate constitutes a small wastewater stream, and is often managed by recycling to add to the fresh solid waste in the pretreatment stages, recycled to a TAR pretreatment unit, disposed of in a conventional aerobic wastewater treatment plant prior to sewer discharge, or treated in a complete, dedicated zero-discharge wastewater treatment plant that includes RO-concentration and evaporation. For agricultural RAPTOR® plants, the digestate is usually stored and spread on fields in the appropriate season as liquid fertilizer.
RAPTOR® efficiently converts the Organic Fraction of Municipal Solid Waste (OFMSW) and/or Source Separated Organics (SSO) into valuable electricity and heat, or renewable natural gas (RNG).
Diversion of organic waste from local communities and businesses from the landfill helps to prolong the life of such disposal sites, reducing the need for new ones. As it is a closed process, it is also provides a greater reduction in greenhouse gas generation than a landfill or composting operation, neither of which have control of methane and carbon dioxide emissions.
Biogas generated in the RAPTOR® process is desulphurized and partially dried, using GWE’s SULFURIX™ scrubbers and GASODRIX™ dryer systems, and typically used in a Combined Heat and Power (CHP) unit for green power generation, or further treated to remove carbon dioxide and upgraded to create renewable natural gas (RNG).
Government aid under the form of grants, soft loans or regulated minimum prices for power from renewable sources sold to the public grid, are often available from local, regional, and federal sources, to make power generation or RNG production an economically attractive application for the biogas. GWE can often assist with identification of, and development of applications for such incentives.
Industries and applications: Food waste (source-separated organics); agro-industry residues (beet pulp, tapioca pulp, sugar beet waste, onion processing wastes, vegetable/potato waste); industrial residues (brewery waste, food processing wastes, paper mill sludge); energy crops (corn silage, various grasses, Algae).