Final development of biosensor for biogas plant
The aim of the project was to test the recently developed VFA online sensor under long-term operation at a large-scale biogas plant (Lintrup). The goal was to identify requirements of the system for installation at the biogas plant, the maintenance needs for continuous operation and how to use the data analysis for control of the biogas process.
The aim of the present project is the final development and testing of a biosensor for the measurement of specific volatile fatty acids (VFA) on a selected biogas plant. VFA measurement is one of the best parameters for monitoring the stability of the biogas process and eventual overload. So far, a number of Danish biogas plants use manual methods for estimation of the content of total VFA (TVFA). This parameter has been shown to potentially indicate the load of the process and eventual imbalances if measured frequently (2-3 times per week). But even daily measurements are not sufficient if sudden changes in the process stability occur. This has in many cases in the past lead to process collapse without previous warning from the manual TVFA measurements. The new technology developed under the EFP project 'On-line VFA measurement in biogas plants' makes it possible to give information about the actual process condition by direct measurement of the specific VFA concentrations. Preliminary testing showed that information basis allows very precise insight into the actual load of the process and can give immediate warning on process disturbances that can lead to decrease in biogas yield and eventual reactor failure if the plant operator do not react immediately. However, so far it has not been possible to evaluate in practical use, to what extend these new process parameters can be used for controlling the biogas process of a full-scale biogas plant. In the present project the sensor will be installed at a selected biogas plant and tested by the plant operators in cooperation with the developers. The measured data will be placed at the biogas plant's disposal and will be evaluated with respect to an optimized process control of the biogas plant. The project will result in a finished evaluation of the product marked, product versions, price fixing and potential for further development
The substrate at Lintrup biogas plant showed to have a quite a different composition than during earlier testing at Snertinge biogas plant, which made further adaptation of the system necessary. This adaptation gave, however, new experience with the system and the current version is now suitable for installation at a variety of biogas plants. It showed that the online sensor needs daily check of operation, but after routine operation has started the operation costs should not exceed 79,000 Dkr per year. Using the VFA online sensor for control of the biogas process the process economy will be improved as soon as process failures can be avoided which else would lead to a stop of substrate feeding for three weeks per year. During the testing the VFA device showed its suitability of instant detection of process disturbances. Normal operation was characterized by a dynamic response of the acetate and iso-valerate concentration along the feeding periods, a propionate concentration below 5 mM that was rather independent of the single feeding and a concentration level of butyrate, iso-butyrate and valerate below detection limits First signs of process disturbances were higher levels of propionate of more than 10 mM that persisted for several days after feeding stop. Furthermore, the concentration levels of butyrate, iso-butyrate and valerate increased above detection limits. The recovery of the process was best indicated by the decrease of the propionate concentration. A severe inhibition of the process was mainly characterized by relatively high levels of butyrate, iso-butyrate, iso-valerate and valerate that persisted over a longer period. The continuous online VFA analysis enables thus the plant operator to get an overview of the regular VFA concentration pattern of the reactor, to detect sudden changes in the biogas process and to optimize the process without running the risk of jeopardizing the reactor performance
Key figures
Category
Participants
| Partner | Subsidy | Auto financing |
|---|---|---|
| Bioscan A/S |
Contact
Søltofts Plads - bygn. 221
DK-2800 Kgs. Lyngby, Denmark
Ahring, Birgitte K. (prof.), 45256183, birgitte.k.ahring@biocentrum.dtu.dk
Øvr. Partnere: Danmarks Tekniske Univ., Institut for Produktudvikling; Bioscan A/S
