Hydrogenation in the food industry

07 December 2009

The process of hydrogenation involves the addition of hydrogen (H2) to produce a chemical reaction with organic compounds (hydrocarbons). It is hugely important and widely used in the food industry where, for example H2 molecules are added to unsaturated vegetable oils and fats.

Complete hydrogenation converts unsaturated fatty acids into saturated ones for use in products like margarine. In order for the process to be successful, catalytic hydrogenation has to take place under elevated temperature or pressure.

Bronkhorst, a Netherlands headquartered company that specialises in measurement and control of flow and pressure, has developed a combination of electronic pressure and thermal mass flow controllers that is suited to the hydrogenation process.

The desired process pressure is maintained within the vessel where the reaction takes place. Simultaneously, the required amount of reaction gas is controlled with a constant flow that does not pulsate.

A Bronkhorst ‘E-7000 Series’ control unit, with push button menu, controls the process. External connection to an analogue setpoint source, or a serial interface to PC/PLC using RS232 or a fieldbus, is offered. Due to the use of thermal mass flow meters the gas flow measurement is virtually independent of both pressure and temperature. Furthermore, this eliminates the need for data manipulation and correction factors as direct totalisation of the level of consumption is made, whilst the display also shows the flow rate.

By utilising the E-7000 control unit, a set-point for the pressure is generated for the EL-PRESS electronic pressure transducer with integral PID controller. The EL-FLOW mass flow controller (MFC) receives a similar setpoint for the maximum quantity of reaction gas. This gas is bled into the reactor and the process pressure will start to rise. When the desired pressure is reached, the MFC will control just as much flow as necessary for the reaction, automatically keeping the pressure constant. Finally, as the saturation phase of the reaction is reached, the gas consumption will decrease.

Wout van ‘t Wel, manager of marketing and communication at Bronkhorst, concluded: “Compared to other solutions, the Bronkhorst method eliminates the need for complex automation software and restricts the maximum flow, which for safety reasons may be important in certain processes“.

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