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    pH and oxygen measurement in algae based biofuel production process

    Alvi Technologies

    Algae Based Bio-Fuel Production Process

    Algae is used in bio-fuel production employing catalytic or fermentation processes. Another approach is the production of methane through anaerobic fermentation of the algae mass. Energy efficiency of algae due to photosynthesis conversion per growing area is higher than for all other renewable raw materials, and their productivity with regard to starch, oil, and fatty acids is seven times higher.

    Algae can be grown in external laboratories or plants and can take up to three months to grow a specific amount for feeding into a bio-reactor. A typical pilot plant may consist of a piping system permeable to light. In between the pipes, low energy fluorescent tubes emit the precise wavelength of light required by the algae for photosynthesis. The electricity for the lights and CO2 for the algae are provided by the combined heat and power plant. However, the CO2 rich exhaust gases from the power plant cannot be fed directly into the bioreactor tubes, since they are too hot at a temperature of approx. 90°C and contain sulphuric acids, which must be filtered out first.

    The exhaust gases are therefore passed through a container filled with zeolites to filter, cool, and also dry them, following which they are fed into the tubes of the reactor filled with water and algae. In addition to providing CO2, they also have the important function of keeping the water in motion, preventing layers of algae from depositing on the walls of the tubes and making them opaque.

    For every cultivation of the reactor with a new generation of algae – which requires ten days until harvest – the chemical equilibrium in the salt water has to be checked and adjusted first by monitoring the pH and oxygen.

    Memosens monitors oxygen and pH for bioreactors:

    The pH value and oxygen content of the water is very important as the algae require an acidic environment, but the CO2 supply must be reduced in case of over acidification. The recently launched Knick Memosens and MemoRail can be used to continuously measure both oxygen and pH values along with temperature to ensure process optimisation. This becomes very practical to field process technicians, because they can pre-calibrate the digital sensors in the lab and don’t have to perform the calibration in the close confines of the reactor. The sensor values are also transmitted to the control room by Knick MemoRail system. In a control cabinet, MemoRail liquid process analysers by Knick receive the values from the Memosens sensors.

    Solar cell of the future

    The resource and space saving instruments, which are mounted on DIN rails feature a compact 12.5mm wide modular housing and are restricted to the essential functions, since the use of pre-calibrated Memosens sensors and the provisioning and visualisation of the measurement values in the control room eliminates the need for on-site visualisation on the transmitter.

    The measured process values and the temperature are output on two standard signal floating current outputs, which can be connected to all common controllers or analysis devices. The MemoRail units transmit the analogue values to a data logger in the control cabinet, which in turn sends the recorded data to the computers in the control room via TCP/IP.

    The control centre can expand its instrumentation equipment by adding Portavo series portable analysers. These Knick devices are currently the only portable analysers with Memosens technology, which can measure pH values, conductivity, or dissolved oxygen. In the event that faults or an interruption in the transfer of data should occur, Portavo is able to perform quick and simple reading of the sensors and values directly at the measuring point. These handy devices recognise the sensors automatically and store all relevant data at the push of a button. All values can be uploaded from the device to the control room computers via the USB interface.

    Alvi Technologies  supplies toxic and explosive gas monitoring instruments and alarms with respiratory protection.

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