Volume flow or mass flow measurements in synthesis gas (e.g. from wood gasifiers) are not trivial due to fluctuating gas compositions. Synthesis gas is a multi-component gas mixture, which essentially consists of a non-combustible portion of nitrogen/carbon dioxide and a combustible portion of hydrogen/carbon monoxide and small portions of hydrocarbons. Depending on the material to be gasified and fluctuations in material quality, the gas composition of the resulting gas also varies more or less. Each thermal mass flow meter of the COMBIMASS series is calibrated to one gas composition. If the actual gas composition deviates from the calibration conditions, greater measurement value falsifications may be expected. Especially, fluctuating hydrogen contents in the gas flow shift the measurement signal significantly.

An acceptable accuracy of the gas flow measurement can be achieved if the thermal sensor is combined with a heat conductivity sensor. With the help of the second sensor in the flow-calmed area, the hydrogen concentration in the gas can be determined. Resulting signal is read into the electronics of the thermal sensor via a 4-20 mA signal. The sensor then corrects its measured value accordingly. The COMBIMASS® syngas measuring system is thus a device combination in an in-line design with flanges on both ends.

Prior to delivery, each system is calibrated in our CAMASS® calibration laboratory, taking into consideration the actual operating conditions with regard to gas composition and installation situation (internal pipe diameter, flow direction, …) Officially pre-tested measuring sections, standard orifices and precision inclined tube manometers are used as references. In addition, calibrated pressure and temperature transmitters enable the exact determination of the operating conditions and volume flows on site. These measuring devices are regularly checked by external laboratories as part of ISO quality assurance. State-of-the-art computer and simulation programs based on decades of experience are used to calculate the calibration data and determine the correction factors for temperature compensation.

A COMBIMASS® multipoint system allows precise measurements of flow rate of pressurized air and technical gases even with short inlet and outlet pipe sections, nominal diameters larger than DN 500 or rectangular ducts. In such situations flow profile distortions may occur, which normally lead to errors in flow metering of gases. All flow meter of COMBIMASS® series (basic, eco, eco-bio+) can be used in combination with the COMBIMASS® multi electronics in a field housing. The flow meter are powered by the field housing. Analog output signals or current loop signals can be read into the electronics for further processing and signal compensation.

By installing multiple measuring points over the cross-section of the pipe or duct and averaging the flow signals, COMBIMASS® multi enables accurate and reproducible results even in such difficult applications. The COMBIMASS® multi was designed to build up a high performance multipoint system for thermal flow rate measurement of gases. There can be a number of flow transmitters connected to the PLC-based COMBIMASS® multi electronics.

For applications, which are critical from a safety point of view or in such cases where faulted re-sults may cause considerable costs due to uneconomical process control, COMBIMASS® multi enables redundant monitoring of gas flow rates. Permanent functionality checks of the connected sensors as well as continuous plausibility checking of the flow signals guarantee outstanding relia-bility of the system. In case of any inconsistency or if one of the connected sensors fails an alarm will be immediately released. In such case of malfunction, COMBIMASS® multi automatically con-siders only those signals of the working flow sensors for signal processing, thus largely avoiding erroneous measuring results.

For indication of the measured flow rates or selected compensation parameters as well as for programming of the multipoint system the PLC is placed in the field housing for indoor or outdoor installation, powered with 24 VDC or 230 VAC. The 4.3”-touch-TFT graphic display (7” size can be supplied as an option) can be placed on a holder inside the cabinet or in the door of the cabinet with a protection cover (if mounted outdoors). The field housing can be made from stainless steel or plastics, for wall mounting or mounted on a rack.
All kinds of data transmission are available: analog signals, Ethernet Modbus TCP, Modbus RTU, Profibus, Profinet or Ethernet IP. COMBIMASS® multi allows indication and checking of the actual reading of any of the connected flow transmitters in the field. For monitoring of flow rate or temperature limits up to three switch points can be field set using additional relay outputs. Via those relay outputs either an alarm may be released.

COMBIMASS® multi features processing of external control signals in order to run complex appli-cations. In order to enable monitoring of those external control signals an analog input as well as a relay input are available.

The typical configuration of a measuring system includes a COMBIMASS® series thermal flow meter whose signal is constantly corrected based on the current gas composition and a gas quality measurement in front of the CHP. The analyser station is suitable for the cyclic analysis of methane, CO, CO2 and H2 in the synthesis gas. The CO and H2 contents have a significant influence on the calorific value and are therefore especially accurate to measure. This requires e.g. for hydrogen the use of a COMBIMASS® thermal conductivity sensor developed especially for this case.

The analyser station is completely modular. All pumps, valves and gas modules are individually mounted on DIN rail for easy maintenance. The gas modules can be recalibrated in the station. This serves the long-term stability of the measured values. As an alternative to manual calibration an autocalibration function is also available with permanent connection of one or more test gas cylinders.

The operator can adjust the acceptable deviation of the measurement results from the calibration state for a specific project. If the desired accuracy during recalibration cannot be achieved any more due to actual wear, the gas modules should be checked at the manufacturer. Using traffic light system, service cycles can be automatically adapted to the frequency of use or the accuracy requirements. The current status of the gas modules is signaled by traffic light colors: green – ready for operation and accurate; yellow – maintenance / recalibration is coming soon; red – maintenance now. Due to the traffic light system, service cycles can be automatically adapted to the frequency of use or the accuracy requirements.

The data can be stored internally or transmitted via various standard interfaces. Optional modules for remote dial-in can be used for function testing, maintenance diagnostics and/or data transmission. An optional life bit indicates the operating ability of the station. An (optional) independent power supply executes the operation of the station even after failure of the regular power supply and certainly ensures an alarm message.

The interior of the station and the syngas are monitored for pressure and temperature. Optionally, the measured data can be checked for plausibility and therby increasing the manipulation safety. A key-operated switch or password-protected software prevents improper modification of configuration parameter.

Gas analysis in general requires a high level of technical effort to maintain long-term accuracy and reliability, which is ultimately also reflected in the purchase price and maintenance costs. If several gas analysis instruments are used, not only the cost of ownership and maintenance costs, but also the uncertainty of measurement sum up, so that it is hard to recognise a trend at an early stage.

If an analyser station is sent in for maintenance to the manufacturer, the operator must waive for values during this time. Due to the modular design, all spare and wearing parts can be replaced by the operator himself or by a service company.

The operator can also use a second set of gas modules while the used ones are under revision / refurbishment if the availability requirements are very high. Alternatively, loan modules are available.

Special features of the analyzer station COMBIMASS® GA-s hybrid syngas

• Analyser station expandable up to to several gas measuring points in one or more cabinets
• 7 “graphic display with history and diagram function
• Further hardware such as gas cooler, UPS, redundant pumps etc. available
• Manual Calibration/ Auto Calibration of Gas cells and Modules
• Gas Feedback to process line possible
• Analog signals of further gas quantities, temperature or humidity measurements can be recorded and evaluated
• Powerful data transmission via Ethernet Modbus TCP, Modbus RTU via RS485 or analog outputs 4-20 mA, Profinet, Profibus DP or Ethernet IP optionally available
• Remote access for data transmission/ Maintenance diagnosis via GSM/ GPRS/ or Ethernet, optionally with life bit transmission
• Data storage on site is possible on USB stick / SD card
• Plausibility test of gas parameters
• Possible to define customized concentration limits, which shall transmit single alarms or a common alarm, digital signals via potential-free relays or alarms in the bus
• Gas cooler for gas temperatures above +40°C
• Special cabinets for outdoor installation, for stand mounting, optionally available in stainless steel, with an extendable UPS

The design of the analyzer station GA-s hybrid premium is completely modular. All pumps and valves are mounted on small top-hat rail-plates for easy service and replacement. The gas cells and its required electronics are mounted in modules for top-hat rail assembly inside the cabinet.

So it becomes possible to measure several gas streams with different gas concentration in time cycles or continuously. Furthermore the flexibility of configuration details regarding gas ways and sampling sequencies increases too. Several parallel gas circles can be built up and so also more than one gas stream can get analyzed continuously. Beside typical NDIR-technologies also electrochemical as well as heat conductivity sensors can be used.

Using a special electronic, even electrochemical oxygen cells can be used for continuously analysis if required, these cells can regenerate themselves. If the application has a safety function in the back, identically gas circles can be built up and operated in parallel.
Gas pump and valves can analyze the biogas of several gas streams in time cycles (valve type NC) or continuously (valve type NO). Data can be stored internally and/ or transferred to the main PLC via various standard interfaces. There are some further options for an external access available, for monitoring of operation/ alarms, maintenance monitoring and data transmission. A life-bit can be sent out to a central server to monitor operating ability (option only). An uninterruptible power supply unit (UPS) can be used to keep the station in operation for a while when power supply is interrupted to send out an alarm message (option only).
The inner cabinet as well as the gas streams are monitored for pressure and temperature. Measuring data can be checked for plausibility for systems with improved requirements on manipulation safety (option only).

A hardware key or a password can be used to secure the configuration settings.
Gas analysis stations require a high technical expenditure, which settles in the long run also in the purchase price and in maintenance costs, to achieve long-term accuracy and reliability. An auto-calibration function with a precise span gas will keep accuracy at best level. If several instruments (portable and stationary) must be bought, the total costs for investment and maintenance become high, but also measuring errors can rise up.

The gas cells and modules can be recalibrated easily. Long-time accuracy of analysis is kept at a high level. Beside manual calibration mode also an auto-calibration mode is available, if a spangas bottle(s) is (are) connected permanently with the analyzer cabinet.
The actual situation of the gas modules is displayed on the screen using traffic light colours: green – okay, yellow – recalibration recommended, service required soon, red – recalibration was not finished successfully, service now. The plant operator can define acceptable deviations of each gas module on his own customized (based on the nature of the project). If this defined accuracy cannot be achieved any more after recalibration, gas module shall be sent to the manufacturer for refurbishment. Due to the use of the traffic light system for maintenance monitoring, service frequencies can be adjusted on frequency of use respectively on the requirements on accuracy. Fixed cycles are not necessary any more.

The standardized low-costs modular analyzer station COMBIMASS® GA-s hybrid eco consists of a ventilated cabinet for indoor installation, such as in CHP-rooms, for analysis of biogas in fixed time cycles. All conncetions on the side wall are prepared to plastic hoses. The cabiner contains a gas pump, 1-3 gas modules and required No. of valves for analysis of GAS 1-2, for purging the gas lines and to connect a test gas.

There are 5 standardized configurations of gas modules available:  1xCH4, 1xH2S, 2xH2S, 1xCH4 & 1xH2S as well as 1xCH4 & 1xH2S & 1xO2.

All signals from gas modules are pressure and temperature compensated. The analyzer station is equipped with max. 3 analog outputs 4-20 mA for data transmission and 1 digital output for common alarm. As an option all data and all single alarms can be transferred via Modbus RTU to the main PLC.

A test gas input allows a check and recalibration of gas modules at site by Binder Service or by another authorized and certified Service Company.

Maintenance of the modular System becomes very simple: Filter and other wearing parts can be replaced by the operator (without limitation of warranty), gas modules should be checked every 12 months at Binder or at authorized local service company. If necessary, cells should be replaced in time to keep availability and accuracy high. Binder can supply spare modules for the duration of service. Replacement of gas modules can be done by the operator within 2 minutes only.

Specification of COMBIMASS® GA-s hybrid eco

• analysis of max. 2 gas streams
• data transmission: max. 3 analog signals  4-20 mA, 1 common alarm, alternative option: data and all single alarms via Modbus RTU
• all connections on side wall of the cabinet are prepared for plastic gas hoses, alternative option: for stainless steel tubes
• gas cooler can be added, if gas temperature at the inlet of the cabinet will be higher than +40°C
• prepared for wall mounting in a plastic cabinet, alternative options: stainless steel cabinet, assembly on a stand

The new series of extremely robust, low maintenance and efficient portable measuring instruments COMBIMASS® GA-m series represents a mile­stone in the development of mobile gas analy­sers. All common require­ments are optimally fulfilled in the analysis of fermentation gas, sewage gas and dump gas from landfills.

Due to it’s easy to service structure, and with modules plug-in, the systems can be extended at and upgraded to the latest version at any time. The powerful internal gas pump also makes measurements in gases with negative pressure possible. The gas cells can be supplied with different measuring ranges.

The data can be stored, measuring sampling point-referred and can be read out to the PC. The internal data logger is very efficient.

Servicing contracts with supply of spare devices ensure availability throughout the whole year.

The COMBIMASS® eco-bio+ flow meter is developed particularly for the agricultural anaerobic digestion market using thermal dispersion technology. This principle determines directly the gas flow rate at standard pressure and standard temperature.  The sensor consists of a heated and a non-heated reference electrode. When the flow is crossing the sensor, the heated one is cooling down an represents thus a measure for the number of molecules (mass flow). However the dampness portion of the biogas is measured too. Therefore the flow rate at standard conditions according to the German standard paper DIN 1343 (0°C, 1,01325 bar, 0% rel. humidity) cannot be measured directly, since the request 0% rel. humidity is not fulfilled.

The maximum waterdamp portion at saturation point depends only on gas temperature and is represented by a well-known equation. The temperature information of the non-heated reference sensor is used to determine and compensate the humidity in the biogas directly in the electronic board of the flow meter. Thus the dry gas mass flow can be determined at standard conditions finally, if the installation point is chosen well at a place where the gas is waterdamp saturated.

So the use of the COMBIMASS® eco-bio+ for verification of annual gas production (e.g. in CDM-projects) becomes possible. Further manipulation-poor and -safe instruments are available for special applications.

Thermal mass flow meter are suited particularly well for the use in wet biogas compared to other technologies (e.g. Vortex, ultrasonic, mechanical counters), since even at low gas speeds the measurement is very precise.

A further substancial advantage is that all necessary compensation can take place directly in that one measuring instrument. No further sensor, hardware or compensation computer are necessary.

The installation is not more simply at lower costs, the failure of probability is lower than using a combination of three measuring instruments (temperature, pressure and flow rate) and no error summarization will take place.

The field transmitters of the COMBIMASS® eco series are suitable for gas flow measurement and cover a wide range of different applications. The instruments can be employed for process temperatures up to 220°C and are available in explosion proof versions. The flow transmitters apply thermal dispersion technology in order to measure directly in dry gases the standard volumetric or gas mass flow according to DIN 1343, regardless of the operating pressure and temperature of the medium.

All units of the COMBIMASS® series are characterized by high-performance 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® eco is located in a compression-proof dual compartment stainless steel enclosure. Optionally a 8 digits LED display with control panel is available for indication of actual flow rate or totalized flow as well as for field programming of the flow meter.

The sensor which is in contact with the gas is made of a high-grade stainless steel (316 TI). If the gas is especially coroosive, alternative available materials are Hastelloy, Inconel, Titan, Tantal or further materials on request.

For transmission of the flow signal an isolated 4-20 mA analog output as well as a field selectable pulse output are available.
As an option to the 4-20 mA analog output signal 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.
For intrinsically safe operation a dedicated process interface module has been developed for the power supply of the flow transmitter. In such a case, the signal output is done via an I/O module installed downstream of the process interface module.
The circuitry of the process interface module and the I/O module is located in a top DIN-rail housing for easy switch cabinet assembly. Also an optionally available graphic display can be installed there.
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 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.

The field transmitters of the COMBIMASS® series are suitable for flow rate measurement of compressed air and technical gases at medium temperatures up to 130°C. The flow transmitters apply thermal dispersion technology in order to measure in dry gases directly the normal volumetric or gas mass flow, regardless of the operating pressure and temperature of the medium (DIN 1343).

Even these basic flow meters of the COMBIMASS® series already 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® basic is located in a compact aluminium enclosure. 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.

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 easily 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.

One understands the combinations of valves under the Tank blanketing system, which are used especially for langer tanks and tank storage to protect against unacceptable pressure and vacumm situations and also inertiate if necessary. The structural protection against impermissible overpressure or vacuum in these cases usually implemented with weight-loaded valve systems, s.a. Overpressure and Vacuum protection.

These large tanks are designed for almost atmospheric pressure. For the specification of the valves, this means that only a very small pressure range is available for large volume flows, within which these valves work. The requirements of the valves for blanketing are particularly high because the pressure control via the control system is too slow and thus the reaction time of the entire system is too slow.The VALVE CONCEPTS® Vacu-Gard® 1078 and 1049 Secure-Gard® have been specially developed for this purpose. The Vacu-Gard® is a high-precision pilot-operated system, similar to a pressure reducer and requires no auxiliary power. This ensures that the main valve is either completely open or completely closed. The system operates independently of inlet pressure fluctuations and the flow rate with a repeat accuracy of 0.2 mbar and a hysteresis of max. 0.7 mbar. The maximum flow rate can be precisely determined with the Flowplug (defined reduction in cross-section). If the supply pressure fails, the Vacu-Gard® closes securely.

The Secure-Gard® is pilot-operated and achieves full opening even at a pressure rise of 10% above the set value and below the set value, the valve seat closes below set pressure.

The characteristics of both devices allow optimum utilization of the existing pressure range and thus the widest possible spread of the setting values.The consumption of inert gas is reduced, thus also the costs for the procurement of the inert gas and the thereby lower burden on the exhaust gas treatment plant / the environment.

Often, in the large tanks, all nozzles are used up, the space is not optimal, the tank cover would be weakened by further nozzles and a renewed acceptence would be required. This can be done with the VCI 2049 Manifold System, which is mounted on a nozzle on the tank. Blanketing Vacu-Gard® and vent Secure-Gard® are mounted directly to the VCI 2049.