Digestate drying

DRYCAKE and TEMA Process enter into strategic alliance to elevate digestate drying in USA  and Canada

 DRYCAKE is an engineered products and services company Focused on Process Equipment and Design for Waste Reuse Recovery for municipal and industrial wastewater. While TEMA Process B.V. is a specialised design and manufacturing company for Fluid Bed Drying Systems for  drying of  biomass, food/feed, chemical and mineral industry. TEMA Equipment & Plants can be successfully used for several products in the Biomass Industry, examples are: Digestate, sludge, biomass etc. This strategic alliance will manage the digestate output from the biogas plant. The TEMA Process Fluidized Bed dryer are used for energy-efficient drying of the digestate using waste heat of biogas plants.

Biogas production: The biogas is converted by a CHP ( Cogeneration or combined heat and power) engines into electrical and thermal energy.(Nutrient Recovery and Reuse Technology, NRR). Homogenised feedstock is hydrolysed in a separate unit and fed to a thermophilic digester. Digestate (9% dry matter, DM) is sent to a centrifuge for solid/liquid separation where the solid fraction that contains 90-95% of the initially separated total phosphorus (P) is dried on a Tema process fluid bed dryer while the liquid fraction is sent to floatation and reverse osmosis (RO) unit. Drying of solid fraction is accomplished by recycling waste heat from CHP engines.

 The digestate is dried to reduce weight, reducing storage and transport costs. The end product which is the dried material can be converted either into fuel, organic fertilizer or can be further refined.  

 The drying process

Back-mix:

The back mix system is used for materials that cannot fluidise due to the high moisture content of the material. The digestate/sludge is mixed with dried product. This back mix flow enables better fluidisation and drying.

 Fluidized bed Dryer/cooler:

A continuous fluid-bed system is a machine in which a continuous flow of “wet” powder, granular or flakes material is conveyed over a perforated bed.  The fluid bed dryer dries the material at relative low temperatures and can use the waste heat available (f.e. from cogeneration) to ensure optimum use of heat energy.

Hot drying air is blown through the holes of a perforated plate.  The wet solids are lifted from the bottom and causes the  solids to behave as a fluid. The air velocity is adjusted to keep the moving layer of material fluidized.

Conveying of the product is achieved by means of a low-frequency, high amplitude shaker mechanism. The “Shaking” motion plug flow of the Tema fluid bed, allows first-in, first-out drying of products and well-mixed fluidization, which covers the entire  spectrum and is able to accurately control the spread of residence time. The high speed of the process and controlled temperature ensure the optimum efficiency of the process.

 Advantages of continuous fluid-bed dryer system technology

·        Low energy consumption compared to other type of dryers

·        Accurate control of the residence time, product is dried uniformly

·        Gentle on sensitive materials (no friction)

·        Low operating costs

·        Cooling section integrated in dryer

·        Handling of sticky products (from centrifuges or filters)

·        Small  footprint

·        Process flexibility

·        Reliable system, less downtime