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RAPTOR® an Award-winning Waste-to-energy Solution

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.

RAPTOR® Unleashing the Power of Organic Waste

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.

RAPTOR® A Complete Waste-to-energy Solution

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:

  • Industrial;
  • Agricultural;
  • Municipal.

How does RAPTOR® benefit your business?

  • Can make your existing business more sustainable and less fossil-fuel dependent;
  • It is a complete solution, including the waste reception facilities, digestate processing, biogas conditioning, and utilization, rather than just an anaerobic digestion system;
  • Designs are optimized for your application and specific organic waste streams;
  • The organic feedstocks can be modified due to the RAPTOR®‘s flexible and adaptable process application;
  • Effectively transforms your waste into profitable products;
  • GWE control software allows for remote monitoring of the facility for smooth operation and uninterrupted processing;
  • Solid digestate can be sold as an agricultural fertilizer or compost, for additional return on investment.

Intake logistic and preprocessing of wastes

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 the liquid slurry of manageable consistency.

Proper blending of the substrates is key to the successful operation of a RAPTOR® plant when treating wastes from various sources. The decontaminated and pulped, a blended material is then sent to a holding tank or tanks for storage prior to digestion.

Pretreatment for rapid 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:

  • Enzymatic pretreatment
    When specific (hemi-) cellulosic substrates are present in the waste feedstocks, the proper pretreatment is a high-temperature enzyme reactor. This high-temperature enzymatic treatment solubilizes organic matter prior to fermentation and enhances fermentation speed overall.
  • Chemical pretreatment
    In some cases, this mild caustic treatment is applied at elevated temperatures. Its purpose is to partially hydrolyze hard-to-digest polysaccharides and proteins and to increase biogas yields within the anaerobic reactor.
  • Thermal pretreatment
    Heating of the waste slurry for hygienization is sometimes required for some types of waste, for example when they originate from the animal food processing industry. Thermal pretreatment allows protein denaturation and cell autolysis. It is used in combination with enzymatic, chemical or mechanical pretreatment.
  • Biological pretreatment
    The most commonly applied pretreatment process is the GWE Thermophilic Acidification Reactor (TAR). The TAR enhances the digestibility of many organic substrates via partial solubilization of solids, low pH-induced protein denaturation, and polysaccharide hydrolysis, and is utilized in applications containing primarily pre- and post-consumer food waste, manures, and food production/processing residuals.
  • Mechanical pretreatment
    Mechanical pretreatment is included in most RAPTOR® systems, either in the form of pulping via a hammermill or GWE’s POWERPULPER system, which is a powerful chopper pump-equipped pulping unit that turns coarse slurry into a uniform mash. Mechanical treatment, including pulping and size reduction, is designed to increase the surface area of the waste open to digestion, remove shells, skins, and other coatings on the waste, and begin the breakdown of the structure of the waste, in order to speed up the digestion of the material.

Rapid anaerobic digestion

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 temperatures than at low temperatures, 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.

How can RAPTOR® benefit communities?

The RAPTOR® process for OFMSW and source-separated organics (SSO)

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 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.

  • The overall sustainability of the region is improved after a renewable energy source like RAPTOR® is developed;
  • RAPTOR® anaerobic digestion contributes to significant greenhouse gases (GHG) reduction and fossil fuel savings;
  • It is a complete organic waste-to-energy plant, including management of all end products and residuals, allowing for easy implementation in complete partnership with GWE;
  • GWE control software allows for remote monitoring of the facility for smooth operation and uninterrupted electricity delivery, rain or shine, day or night. Other renewable energy methods like wind or solar are impacted by time of day, weather, and other factors that have no impact on RAPTOR®;
  • System digestate can be used as an agricultural fertilizer or compost, providing additional value from the waste.

Biogas Utilization–Green Power and Vehicle Fuel from the RAPTOR® Process

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 the 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).

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