Measurement and Testing
These are in particular: • Temperature compensation between 5°C and 45°C • Air pressure compensation between 600hPa and 1200hPa • Carrier gas dependency between cx
(CO2 ) and cx (CH4 ) • High long-term stability with a reference measurement
By using a gold-plated analysis cell, changes in the refl ection properties can also be effectively prevented so that the long-term stability can be signifi cantly improved. The
INFRA.sens® sensor is shown in Fig. 2.
gas
force and the container now tilts back to the starting position. The process is repeated in a certain time interval ∆t, depending on the volume fl ow. The number n of tilting movements is recorded and multiplied by the volume ∆V ejected per tilting process. This conversion then gives the total volume Vtotal
or the volume fl ow by converting to the time ∆t:
43 = n-∆V
Furthermore, the fermentation vessels can be easily removed from the top of the heating oven for brief visual inspections, even during fermentation. Three different stirring blades are available to achieve optimum adaptation to the viscosity of the fermentation substrate.
With the maximum of 18 fermentation vessels, 3 blank samples, 3 cellulose samples and 4 different fermentation substrates can be tested simultaneously as triplets.
[1]
A typical measuring range is 1 to 1000 mL/h, with calibration taking place at 500 mL/h. An accuracy of +/-3% is specifi ed for the MilliGascounter. The accuracy can be further improved by using special evaluation software that automatically corrects the dynamic (volume fl ow-dependent) error. The algorithm converts the measured values at the current volume fl ow into the true volume based on the calibration curve. The remaining residual error is then less than +/-1% over the entire measuring range.
The software supplied enables:
• Recording and standardization of volume and volume fl ow of up to 18 MilliGascounters in real time
• Data storage in the PC and on an SD card in the interface module for data recovery in the event of a power failure
• Control of the stirrers (speed, interval mode) • Setting the temperature of the heating oven (thermostat)
• The rack made of aluminum profi les and stainless-steel shelves offers space for up to 18 MilliGascounters and up to 18 optional CO2
absorption bottles.
Fig. 2:
INFRA.sens®
gas measurement module for the simultaneous
analysis of methane (CH4) and carbon dioxide (CO2 plated sample cell (AK30mm)
) in an internally gold-
The measured temperature and pressure values required for compensation are recorded directly in the analysis cell using a microsensor. This provides the exact physical data of the gas to be measured and improves the quality of the electronic compensation.
Data communication takes place via an RS232 interface. A USB interface, a CAN interface and a Modbus protocol are also available. The module is supplied via a 24DC connection, and the electrical power consumption is P<2Watt.
Fig. 6: Production rate P(t) as a function of fermentation time for different substrates (Scherer et al. 2021)
The production rate P(t) of methane then results from the gas analysis (c concentration) and the volume fl ow:
The total amount of CH4 Fig. 4: MilliGascounter for detecting low gas fl ows according to Scherer Biogas batch fermentation system
The great advantage of the RITTER biogas batch fermentation system is that the fermentation vessels are tempered on all sides in the heating oven. In contrast to the temperature control of the fermentation vessels in a water bath, this prevents uncontrolled cooling of the upper part of the bottle due to ambient air and air currents.
Summary
The described biogas batch fermentation system is ideally suited for use under laboratory and pilot plant conditions. By using fast- indicating gas sensors (
INFRA.sens®
the current gas concentration values (CH4
) with a low dead volume, and CO2
) can be
recorded reliably and without a signifi cant delay. In conjunction with the described fl ow measurement, the exact production rate P(t) is obtained as a function of time t during the entire test run.
The described gas measurement system can also be extended to other components present in the biogas, such as hydrogen sulfi de (H2
water vapor (H2
Fig. 3: Array of 9
INFRA.sens® CO2 and CH4
internal tubing (Viton® gas measurement modules for measuring the
gas concentrations in the respective fermentation vessels with )
Flow measurement
The MilliGascounter was specially developed to measure very small gas volumes (Scherer 1990). The gas fl ows into a chamber fi lled with sealing liquid. A tilting container is arranged in this chamber, in which the gas volume ∆V (≈3mL) collects in the upper part. The displacement of the sealing liquid creates a buoyancy force, causing the container to tilt to the other side. The previously accumulated gas volume is released and can escape via the outlet. This tilting process directs the gas supply into the other chamber so that it now fi lls with the gas. In this position, too, the displacement of the sealing liquid creates a buoyancy
S), oxygen (O2 O), etc.
Literature
Wiegleb, G.: Gas Measurement Technology in Theory and Practice, Springer Verlag Wiesbaden 2023 (https://doi. org/10.1007/978-3-658-37232-3)
Scherer, P.: Gas measuring device. German Patent DE 4006508 C2 2.3.1990
Thrän, D, Pfeiffer, D.: New approaches to process optimization in biogas plants, Volume 19, Part 3, Biomass energy use Federal Ministry for Economic Affairs and Energy (2015)
Fig. 5: View of the entire biogas batch system on a mobile laboratory trolley
Author Contact Details Prof. Dr. Gerhard Wiegleb • Wi.Tec-Sensorik GmbH • Address: Schepersweg 41-61, D-46485 Wesel, Germany • Email:
ge.wiegleb@witec-sensorik.de • Web:
www.witec-sensorik.de
Scherer, P. A., Arthur, R., Antonczyk, S.: Accelerated Biomethane Potential assay for straw with artifi cially fl occulated sludge and defi ned synthetic manure. Bioresource Technology Reports 15 (2021) 100787
Author Contact Details Dr.-Ing. Joachim Ritter • Dr.-Ing. RITTER Apparatebau GmbH & Co. KG • Address: Coloniastrasse 19-23, D-44892 Bochum, Germany • Email:
dr.ritter@ritter.de • Web:
www.ritter.de
), ammonia (NH3 ),
(volume VCH4
) produced per batch is obtained by integration over the time t:
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