Fermenters in agricultural biogas plants are often covered with single or double-wall membrane systems. The latter are permanently supported with air to prevent biogas losses and emissions of biogas into the atmosphere. Over the course of years, the membrane foils are subjected to material changes. This can lead to increased emissions or in the worst-case lead to rupturing of the membrane.

TRAS 120 (Safety Requirements for Biogas Plants) states: “The tightness of membrane systems must be monitored. For this purpose, they shall be operated with an additional outer covering of the gas membrane, which allows continuous monitoring of the gap. Membrane systems that do not meet this requirement shall be replaced by a monitorable double walled system at latest by the end of their service life or after irreparable damage to the membrane”. Furthermore, the paper defines a maximum permissible membrane permeation.

Therefore, long-term monitoring is considerably important. The service life can be extended by permanently monitoring the membrane roofs. This not only reduces investment costs, but also waste products and the costs for the disposal of plastic membranes.

The new GA-s hybrid air monitoring system is based on the long standing proven modular concept of the hybrid series. Solely the gas modules are adapted to the requirements of air analysis.

The specific challenge here is the small measuring range of only a few ppm for methane compared to biogas. The standard measuring systems available on the market today for biogas in the Vol.-% range are not suitable, because they cannot measure the small concentrations with sufficient accuracy. Binder´s optical measuring cell was especially developed for this application and tested under real conditions. It can also measure methane concentrations of 50 ppm very accurately. In addition, a differential measurement of outlet air versus inlet air is carried out because often there are already low methane concentrations in the air in the vicinity of the fermenter (see weekly screenshot). This enables an exact representation of the actual permeation without distortion by external influences – a patent application has already been filed for the process.

Fermenters in agricultural biogas plants are often covered with single or double-wall membrane systems. The latter are permanently maintained with air to prevent biogas losses and emissions of biogas into the atmosphere. Over the course of years, the membrane foils are subjected to changes. This can lead to increased emissions or in the worst-case lead to rupturing of the membrane.

TRAS 120 (Safety Requirements for Biogas Plants) states: “The tightness of membrane systems must be monitored. For this purpose, they shall be operated with an additional outer covering of the gas membrane, which allows continuous monitoring of the gap. Membrane systems that do not meet this requirement shall be replaced by a monitorable double walled system at latest by the end of their service life or after irreparable damage to the membrane”. Furthermore, the paper defines a maximum permissible membrane permeation.

Therefore long-term monitoring is considerably important. The service life can be extended by permanently monitoring the membrane roofs. This not only reduces investment costs, but also waste products and the costs for the disposal of plastic membranes.

The new GA-s hybrid air monitoring system is based on the long standing proven modular concept of the hybrid series. Solely the gas modules are adapted to the requirements of air analysis.

The specific challenge here is the small measuring range of only a few ppm for methane compared to biogas. The standard measuring systems available on the market today for biogas in the vol.% range are not suitable because they cannot resolve the small concentrations with sufficient accuracy. The optical measuring cell specially developed for this application and tested under real conditions can also measure methane concentrations of 50 ppm very accurately. In addition, a differential measurement of inlet air versus outlet air is carried out because often there are already low methane concentrations in the air in the vicinity of the fermenter (see weekly screenshot). This enables an exact representation of the actual permeation without distortion by external influences – a patent application has already been filed for the process.

The analyzer station can also be used for exhaust air applications by using a H₂S measuring cell with a customized measuring range.

The field transmitters of the COMBIMASS® series are suitable for flow rate measurement of compressed air and technical gases at medium temperatures up to 220°C. The flow transmitters apply thermal dispersion technology in order to measure directly in dry gases the standard volumetric or gas mass flow, regardless of the operating pressure and temperature of the medium (DIN 1343).

These special flow meters of the COMBIMASS® series perform fully digital signal processing. Important features of the transmitter electronics for the purposes of practical operation are the temperature compensation and the opportunity to select different measuring modes (choice between constant current or constant temperature principle).

The electronics of the COMBIMASS® AL100 is located in a compact aluminium enclosure. the enclosure of SS100 is of stainless steel. As an option for this type of enclosure a 8 digits LED display for indication of actual flow rate or totalized flow is available.

The flow transmitter gets configurated individually according to the installation situation (pipe run), gas composition and measuring range. Each flow meter will get calibrated prior to shipment at our CAMASS® calibration Lab, simulating real pipe run and operation conditions. All flow meter have an integrated calibration reserve, which can be activated later on if required.

In some applications the gas composition is changing in time, local flow profile changes on gas flow rates or stroke of control valves placed directly downstream of the flow meter. All these operational influences will lead directly to a reading falsification, if not detected and compensated simultaneously in operation.

The correction can be done in an external field housing COMBIMASS® convert or directly in the flow meter series of AL100 / SS100. These meter have additional analog inputs to read in the changing conditions e.g. humidity, gas composition, stroke of control valves etc. Integrated correction function compensates external influences on the reading.
Only corrected flow will be transmitted to the PLC. As an option also the other operation conditions can be transmitted. Integrated relay can be configurated customized and used as a counter.

As an option to the 4-20 mA analog inputs and outputs signals can be transmitted via Modbus RTU. HART is available as an option too, which uses the 4-20 mA wiring for easy adjustment of parameter during start-up or operation, if required.

As an option to the integrated display, the field housing COMBIMASS(R) convert with graphic display can be supplied for wall or stand assembly. Several flow and other process sensors can be connected to one field housing.
Graphic display is configurated and deliverd customized. All measuring values can be displayed. For transmission of the signals all common types of communication are available.

The VACOMASS® jet control valve is an innovative, flow-optimized stainless steel control valve. In terms of control range and product quality, this development represents a milestone in the evolution of air control valves and fittings. It is unique and with worldwide patent applications.

It closes gas-tight and offers a linear operating characteristic over virtuall he entire operating range. The valve has been developed and optimized specifically for high precision air control and distribution with minimal pressure loss, resulting in comparatively low operating costs. It fulfills all requirements defines in the Advisory Leaflet DWA-M 229-1 (September 2017) and the new “Handbook of Energy North Rhine-Westphalia” (January 2018).

Various configurations of the control system are possible depending on local conditions and the existing geometry of the piping system. When using diaphragm control valves or butterfly valves, the pipe cross section is typically reduced at the start of the measurement and control section and expanded again at the end in order to achieve the required control effect. These control elements generally exhibit a limited range of linear operation in the upper and lower stroke range. In control applications, this inevitably leads to unfavourable operation of the valve at low stroke and thus to high pressure losses and reduced control quality.

In most cases, the VACOMASS® jet control valve can be installed directly in the pipe without the need to reduce/expand the diameter. Thanks to the linear operating characteristic over virtually the entire operating range, fluctuating air requirements, dimensioning errors or later changes scarcely have an impact on the performance of the valve.

The air flow meter can be positioned only 0.5*D in front of the control valve.

The accuracy of the instrument depends strongly on the installation situation or the flow profile at the installation site (see leaflet DWA M 264 Edition 2015). If there is not sufficient straight inlet and outlet pipe run or if the flow is disturbed due to pipe fittings, valves etc. at the inlet area, the sensor can also be placed directly in front of the control valve. Depending on the design of the valve and the required accuracy of the measurement, a signal correction based on the current opening position is may be required (simultaneous flow profile correction). This can be done either directly in the sensor head (types AL100/ SS100) or in the separate evaluation electronics VACOMASS® flexcontrol.

The following types of devices are available:

VACOMASS® flow meter SS

The electronics is located in a compact, pressure-resistant stainless steel housing (material 1.4571) with a separate terminal compartment.Optionally an integrated display is available.

VACOMASS® flow meter AL

The electronics is placed in the standard aluminum housing. Optionally an integrated display is available.

VACOMASS® flow meter AL DIN

The electronics ist placed in a compact aluminum housing without display.

VACOMASS® flow meter AL 100

The electronics is placed in a special aluminum housing with an optional display. The instrument has an analogue input for reading in the position feedback of the control valve. Reading is corrected by current stroke to achieve a precise air flow measurement..

VACOMASS® flow meter multi

In big pipelines, it can make sense to place several sensors individually in different insertion depths. A weighted average over different signals from several sensors in the case of irregular flow profile can be calculated in order to be able to measure the air volume correctly. All sensor types (SS, AL or AL DIN) can be used. The evaluation of the measuring signals takes place via the electronics VACOMASS® flexcontrol multi.

In addition, a hot-tapping unit with ball valve to be mounted in the existing pipeline can be supplied. There are two versions available:

VACOMASS® OEIN-S

Hot tapping unit with manually operated ball valve with flexible insertion depth

VACOMASS® OEIN-F

Hot tapping unit with manually operated ball valve and fixed insertion depth and fixed sensor orientation

Druckregler werden vor allem dort eingesetzt, wo schwankende Drücke vergleichmäßigt werden sollen. Mithilfe einer Membrane wird der Druck erfasst und mit dem Sollwert verglichen. Über die resultierenden Kräfte wird der Sitz des Ventils kontinuierlich und selbsttätig neu eingestellt.

Typische Ausführungen sind: Druckreduzierregler und Überströmer.

Unsere pneumatischen Präzisionsdruckregler zeichnen sich besonders dadurch aus, dass sie applikationsspezifische Anforderungen hinsichtlich zulässiger hoher Regelgüte bei kompakter Baugröße, Vibrationsfestigkeit, Langlebigkeit und Vordruckunabhängigkeit besonders gut erfüllen.

Alle Produkte entsprechen den üblichen europäischen Normen wie z.B. Druckgeräterichtlinie.

Neben den typischen amerikanischen Prozessanschlüssen wie z.B. NPT sind auch die europäischen standardmäßig lieferbar. Den Anforderungen hinsichtlich Korrosion und Medienbeständigkeit wird mit unterschiedlichen Konstruktionswerkstoffen begegnet.

Die FAIRCHILD Präzisionsdruckregler sind federbelastete, mit einer Steuermembrane versehene, Proportionalregler. Dabei ergibt sich die erforderliche Verstellkraft des Ventils aus der Differenz zwischen Federkraft und der, auf der Unterseite der Membrane wirkenden, durch den Steuerdruck produzierten Gegenkraft. (more…)

The VACOMASS® square diaphragm control valve is a technically optimized sliding gate control valve with gas-tight shut-off and a square control aperture. It is used for precise and low-loss control of airflow and distribution in the aeration tanks of a wastewater treatment plant. The valve has a falling flow axis to achieve sensitive control of normal and tangential flows (e.g. after elbows) and is designed according to DIN EN 60534-2-3.

Within the usual control range the valve has a control curve that is proportional to the open area, and it can be used from 0-100% stroke. It is designed to have a pressure loss of less than 10 mbar at full load and 100% stroke.

The control valve body consists of two halves that are designed to be of wafer or end-of-line type. The inner surface has a groove for a PTFE/ carbon gasket that makes the valve gas-tight and serves as an external guide for the valve´s knife-edge sliding gate. The combination of stainless steel on Teflon/carbon allows precision movement of the plate without vibrations or jamming.

Depending on local pipe run, there are two different types of measuring and control pipe section available:

Compact System:
The VACOMASS® air flow meter can be installed only 500 mm in front of the VACOMASS® square diaphragm control valve. Using simultaneous flow profile correction, flow can be measured very precisely. Even If necessary, piping related influences disturbances of the flow profile can be examined and compensated during calibration in Binder´s CAMASS® Calibration -Lab.

Separated system:
If there is sufficient straight pipe run available (depending on the number and kind type of pipe fittings as well asand the geometry of the pipe run/ pipe reduction, a minimum distance of 10*D upstream to the installation place of the VACOMASS® flow meter), the flow meter will can be installed min.at least 5*D in front of the VACOMASS® square diaphragm control valve. Standard calibration can be applied, flow profile correction is not necessary. The total length of the measurementing and control section becomes is much longer compared to compact system and in most cases of refurbishments not available.

Conventional control systems are typically based on the measurement and direct control of the dissolved oxygen concentration, in larger wastewater treatment plants often superimposed by other process parameters such as the ammonium and/or nitrate concentration. Due to the size of the tank, system inertia, unfavorable dimensioning of blowers and use of butterfly valves as control valves with poor or insufficient control performance (details see DWA M 229-1, September 2017 edition), there will be delays in the control response. These delays can be in the range of 1-5 minutes and thus lead to deviations of the actual concentration compared to the setpoint of up to 1.5 mg / l.

In the negative case, this deviation can lead to an undersupply of  oxygen in the aeration tanks with a negative impact on the sludge properties and effluent quality with respect to ammonium concentration. In the positive case, this leads to over-aeration of the biological stage leading to unnecessary energy consumption. Over-aeration might also cause significant adverse process effects such as carryover of dissolved oxygen into denitrification zones (reduction in denitrification performance, increase in nitrate nitrogen in the effluent) or mineralization of the activated sludge. These adverse effects occur relatively quickly in underloaded sewage treatment plants.

The VACOMASS® system continuously monitors the local air supply and therefore recognizes even the smallest deviations in the set point. The local control immediately intervenes and compensates the influence of external disturbances on the air distribution. VACOMASS® flexcontrol is a PLC-based field housing or a complete control cabinet with hardware and software modules for control of process of nitrogen removal, diffuser maintenance and monitoring of signal quality used for control.  Data communication between SCADA/  main PLC and flexcontrol can be done via various bus systems, a remote dial-in can be activated for parameter monitoring & adjustment, support of the operator and other functions.

Operation is done on the 7 “-touch screen or on the screen in the control room. The operator can change the control parameters at any time on site or via remote dial-in. Each control loop has its own processor with process-specific configurated software which works fully independently. All DIN-rail modules and can be easily changed by the operator in case of failure, all remaining control loops are not affected at all. An optional redundant local PLC will take over operation automatically in case of failure of local PLC.This creates highest operational safety and flexibility. Up to 12 control loops can be implemented in one cabinet. Any number of control cabinets can be connected so that both the smaller plants and large sewage treatment plants can use the same standardized and so cost-effective building blocks.

All common interfaces are available. The freely expandable number of inputs and outputs or data transmission with bus systems open up the possibilities for data acquisition and evaluation for further process monitoring and optimization. Safety updates can be installed remotely.In order to promptly recognise trends in sewage treatment plant, sending of standardised status messages can be activated.

In most cases, the process control system only specifies the setpoint for dissolved oxygen concentration (which can also be calculated in flexcontrol based on the ammonium concentration). In case of deviations from DO-setpoint, the new required stroke of the control valve is calculated and precisely adjusted one step. This reduces operating frequencies compared to the stepwise adjustment of the new stroke and premature wear of the actuator and valve.

The VACOMASS® elliptic diaphragm control valve is a technically optimized sliding gate control valve with gas-tight shut-off and a lenticular/ elliptical control aperture. It is used for precise and low-loss control of air flow and distribution in the aeration tanks of a wastewater treatment plant. The valve has a falling flow axis to achieve sensitive control of normal and tangential flows (e.g. after elbows), and is designed according to DIN EN 60534-2-3.

The control valve body consists of two halves that are designed to be of wafer or end-of-line type. The inner surface has a groove for a PTFE/ carbon gasket that makes the valve gas-tight and serves as an external guide for the valve´s knife-edge sliding gate. The combination of stainless steel on Teflon/carbon allows precision movement of the plate without vibrations or jamming. A wave breaker in the outlet area of the valve body (patent pending) prevents high-pitched noise generation.

Within the usual control range the valve has a stable control curve, and it can be used from 0-100% stroke. It is designed to have a pressure loss of less than 10 mbar at full load and 100% stroke. The design stroke in control mode typically ranges between 30 – 70%, pressure drop will range between 8-15 mbar (technically required for a stable control and distribution of aeration air at stable and optimum boundary conditions – same pressure conditions related to water depth, aerators etc.).

Air flow rate can be increased significantly and easily for cleaning of aerators (air bumping, flexing) and/or pulse aeration in nitrification zones without mixer during non-aerated process phases by increasing the stroke up to 100% without increase of header pressure. This control valve complies with the requirements of the new standard paper of German Water and Wastewater Association M 229-1, published in September 2017 regarding pressure drop and related energy efficiency.

Depending on local pipe situation, there are two different types of measuring and control pipe section possible:

Compact System: The VACOMASS® air flow meter can be installed 500 mm in front of the VACOMASS® elliptic diaphragm control valve. Simultaneous flow profile correction for very precise flow measurement is applied based on actual stroke of the valve. If necessary, piping related disturbances of the flow profile can be examined and compensated during calibration in Binder´s CAMASS® Calibration Lab.

Separated system: If there is sufficient straight pipe run (depending on the type of pipe fittings and the geometry of the pipe run, a minimum distance of 10*D upstream of the VACOMASS® flow meter), the flow meter can be installed at least 5*D in front of the VACOMASS® elliptic diaphragm control valve. Standard calibration can be applied, flow profile correction is not necessary. The total length of the measurement and control section is much longer and in most cases not available.