Hybrid Mixers and Slow Speed Agitators: Reduce Costs and Increase Revenue for Biogas Plants

KSB (USA), experienced supplier of pumps and mixers, announced that biogas systems that implement a combination of its hybrid mixers and slow speed agitators can reduce mixer energy requirements by 50 to 75 percent.

KSB's mid-sized Amaprop 1000 hybrid mixers are engineered specifically for biogas production. These versatile tools are an important part of an optimised mixing procedure that can reduce operational energy needs, increasing energy output and revenues for the plant.

Biogas production is a growing segment of the renewable energy industry. Raw materials (aka substrates) such as liquid manure, field silage, and other agricultural waste or by-products are blended and fermented with bacteria to produce a clean, natural gas that can be used to generate electricity. Environmentally friendly fertiliser by-products with an enhanced nutrient load are also produced.

Proper mixing is critical for efficient biogas production. The system should be able to handle large flow volumes, creating consistent flow throughout the entire tank at sufficient turbulence levels to disperse solids. This type of flow — known as shear flow distribution — can be maximised by customising the layout and configuration of mixing equipment based on the types of substrate used and the expected concentration of solids.

KSB Amaprop mixers are optimised for each mixing task to ensure a specific flow volume and deliver enough thrust to move the medium through all sections of the fermenting tank. Use of multiple, properly positioned mixing units, each of which processes the reduced, diluted material created by other units, can help to prevent short circuiting flow paths and support the best possible transformation process.

In biogas plants that depend primarily on traditional high speed mixers (turbulence generators) to moisten and disperse floating solids and to prevent sedimentation, approximately 10 percent of produced energy goes back into running the plant. Sixty percent of that power is typically devoted to running the plant mixers.

In contrast, plants that implement a system combining hybrid mixers and slow speed agitators enjoy a much more efficient and profitable operation. Using KSB hybrid mixers and agitators as individual parts of a well-designed biogas production system creates a complete mixing solution — one that uses the right mixing design for each part of the digesting process.

The interactive performance of these components can reduce mixer energy requirements by 50 to 75 percent. This means more overall energy output and higher revenues.

KSB slow speed agitators accelerate the bulk flow of the substrate throughout the reactor and generate local shear flow to release gas bubbles from fermenting liquid. These slow speed agitators are much more energy-efficient than traditional turbulence generators and can handle large flow volumes while delivering high thrust.

KSB Amaprop 1000 hybrid mixers, which are specifically designed for use in biogas applications, combine all the benefits of an agitator with the turbulence-generation of a traditional mixer. If substrate viscosity increases, hybrid mixers can adjust the conveying action to offset the increase and maintain optimal flow.