DESCRIPTION

Technical Description

In a biogas plant, microorganisms biologically degradate the organic starting substances (substrate) under exclusion of light and oxygen. The product of this anaerobic degradation is a gas mixture which primarily consists of methane. This gas mixture is called biogas.

The experimental plant CE 642 serves to demonstrate the generation of biogas in a practical manner. The substrate is a suspension of shredded organic solids. It is hydrolysed and acidified in the first stirred tank reactor. Here, anaerobic microorganisms convert the long-chain organic substances into short-chain organic substances. The biogas forms in the second stirred tank reactor in the last step of the anaerobic degradation. It contains mainly methane and carbon dioxide. This two-stage method enables the ambient conditions to be adjusted and optimised in both reactors separately. The digestate is collected in a separate tank.

Temperature and pH value are controlled in both reactors. The resulting biogas is dried in a column. The column is filled with silica gel. Subsequently, the flow rate, humidity, methane content, carbon dioxide content and temperature of the biogas are measured. The system is controlled by means of a PLC which is operated via a touch screen. The measured values can be transmitted to a PC via USB and analysed with the GUNT software.

The experimental plant enables both a continuous and a discontinuous (batch) operation mode. Anaerobic biomass from a biogas plant is required for the experiments. E.g. potatoes or maize can be used to produce the substrate. An inert gas (e.g. carbon dioxide) is required to flush the experimental plant.

The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.

Learning Objectives / Experiments

- achieving a stable operating state
- influence of the following parameters on the biogas generation
  * temperature
  * substrate
  * volumetric loading
  * pH value
- influence of the operation mode on the biogas yield 
  * single stage or dual stage
  * with and without post-fermentation
  * continuous and discontinuous
- determining the following parameters depending on the operating conditions
  * biogas yield
  * biogas flow rate
  * biogas quality