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Biomass Conversion to Renewable Resources:
quasar converts biomass into renewable resources using a proven process called anaerobic digestion. Anaerobic digestion is a natural process where microorganisms break down organic waste materials (biomass) in the absence of oxygen.
High Solids Anaerobic Digestion:
Farmers have been using low solids anaerobic digestion as a means of managing manure for hundreds of years. quasar's process has advanced this proven technology by increasing the percentage of volatile solids that can be processed (high solids). |
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| quasar ecoFARMsystem 550 |
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| The primary driver behind high solids vs. low solids anaerobic digestion is that more energy (biogas) can be extracted from high solids material in a smaller digester capacity. A secondary benefit is that end products, such as liquid fertilizer and compost, are concentrated. |
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quasar's process begins by introducing biomass to the system. Biomass from municipal wastewater treatment facilities, agricultural sources, alcohol and ethanol distillers, and food manufacturing companies can be accepted in either liquid or solid form.
The description below is based on a quasar ecoCITYsystem 2250 design.
Digestible biomass will be loaded into a receiving hopper located in the plant building for odor control. Live bottom hopper augers will direct the waste toward the center of the hopper and discharge material into a progressive cavity pump. Material is pumped through a grinder and then to the Biomass Equalization Tank. The hopper odor control doors will remain closed when trucks are not discharging biomass.
A pump will transfer the thick material through a grinder and into process lines where the fresh biomass will mix with heated recycled biomass and return to the Biomass Equalization Tank.
Trucks bringing liquid biomass can discharge directly to the Biomass Equalization tank. The liquid biomass will be pumped through a strainer mechanism to filter out any unwanted solid material and discharged into the open hopper pump handling the high solids biomass. It will be pumped to the Biomass Equalization Tank with the high solids biomass stream. |
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The Biomass Equalization Tank is a 500,000 gallon insulated, bolted steel tank. The tank has a 60 foot diameter and is approximately 30 feet tall. This tank serves as a hydraulic buffer and can store up to 6 days of conditioned biomass. The tank has 3 side entry prop mixers to prevent stratification of the material, ensuring a consistent mix for feeding. The tank has a gas tight steel roof. A pipe connects the head space in the tank with the Digester Tank and Dual Purpose Tank to maintain equalized gas pressure in the system. This has the added benefit of controlling odor. This will also provide an area for displaced gas due to filling/discharging or temperature expansion. Gas can be displaced to the other tanks and is directly connected to the flexible membrane roof in the dual purpose tank. Safe pressure levels are also maintained by an over/under pressure relief valve mounted to the tank. |
| Biomass Equalization Tank |
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The Digester Tank in a C2250 system has a working volume of 1,250,000 gallons. This insulated, bolted steel tank is approximately 60 feet in diameter and 60 feet tall. A single, slow turning top mounted agitator provides continuous mixing. The conditioned biomass from the Biomass Equalization Tank is dosed into the tank at a turbulence zone created by the agitator to minimize the time required to obtain a complete mix. Biogas produced in the tank can flow freely to the Dual Purpose Tank via a pipeline exiting from the tank roof. The digestate is heated prior to entering the tank and the temperature will be maintained at approximately 100°F.
The 500,000 gallon Dual Purpose Tank is of identical construction to the Biomass Equalization tank, except for the roof. The Dual Purpose Tank has a flexible membrane roof to provide gas storage for the system. This area is always pressurized. A relief valve maintains the proper air chamber pressure. |
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Digester Tank |
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The outer membrane protects the inner membrane from the environment. The inner membrane contains the biogas (gas enters from the Biomass Equalization Tank, Main Digester, and gas produced in the Dual Purpose Tank). The inner membrane inflates and deflates according to the amount of biogas in the system. When gas is not present, the inner membrane is supported by a column and cable system to keep the membrane from contacting the biomass.
After digestion, the biomass will be pasteurized to further reduce pathogens to obtain Class A Biosolids designation per EPA 40 CFR 503. Tank temperature and holding time will be controlled with data recording for evidence of pasteurization. |
| Dual Purpose Tank |
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Energy is recovered from the pasteurized material through a biomass to biomass heat exchanger as it is pumped to a holding tank. The energy recovered from the pasteurized biomass is transferred to the biomass from the Dual Purpose Tank. The biomass is heated to a final temperature of 170°F through a heat exchanger.
The suspended solids in the digested material will be mechanically separated from the water in a dewatering press. The cake biomass after this step will be approximately 25% dry solids. All plant operations will be monitored using a SCADA system.
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