Knick PROTOS pH Measurement systems from Alvi Technologies were selected for use in the Shell Rheinland Refinery (Germany). At the Refinery , fractions of heavy oil are left at the end of the fuel extraction process. Shell then uses these to operate an oil-fired power station to supply the site. In the associated flue-gas desulfurization plant, the waste-water treatment is monitored at three points of measurement with average pH values between 2 and 10.
The deposits occurring in this pH range place enormous stress on the points of measurement, requiring regular maintenance that can be costly. Previously, automation failed due to a lack of appropriate (mechanically and chemically resistant) fittings. Knick's pH measurement systems were used in order to automate calibration, as well as permitting access for maintenance while the plant is still in operation. Three major components work together to formulate the pH measurement systems. These include the Protos 3400 analyzer, the Ceramat WA 150 retractable fitting, and the Unical 9000 automated cleaning and calibration system.
Automated measuring systems, such as the PROTOS make life easier in terms of the extreme challenges placed on the pH measurement points due to the outstanding separation efficiency in flue gas desulfurization plants. An alkaline solution, often lime water, is used to absorb the sulphur dioxide, and is sprayed from above in the absorber tower or scrubber while the flue gas is channelled upwards in a counter flow. The reaction creates a lye from which gypsum can be extracted through precipitation and flocking. This is sometimes used in the construction industry. The remaining excess water is neutralized by adding sulphuric acid to bind it with the excess lime.
The solution to this problem is the implementation of The Ceramat WA 150 sensor lock-gate combined with the Unical 9000 automatic cleaning and calibration system. This system performs the complete automation of this measuring task. With the aid of the Ceramat WA 150 sensor lock-gate, the sensor is automatically cleaned and calibrated on a regular basis. The Ceramat sensor lock-gate has proved to be particularly successful in extremely difficult processes where fittings with O-ring seals fail, comprising of indestructible, rotating ceramic element and a corrosion-resistant, carbon fiber reinforced, fixed PEEK plastic housing.
The Unical 9000 automated cleaning and calibration system was used as an electro-pneumatic controller for insertion and retraction of the sensor and the pumps for the buffer and cleaning solutions. This system was monitored, and fitted with an alarm which can be triggered if necessary. A key advantage of this system is the reduction of maintenance costs, due to the fact that Calibration of the sensor is fully automatic and takes place by means of preset or plant-specific program flows, guaranteeing both increased measuring accuracy and economic use of the media.
The last component used in the pH measuring system is the Protos 3400 analyzer. This analyzer enables the integration of different measuring functions. With the aid of a SmartMedia card, up to five parameter sets can be saved. Protos also facilitates the definition of individually accessible operating levels protected by pass codes, meaning that every user only has access to the device functions relating to their duties.
The Protos 3400 modular process analysis system, Unical 9000 electro-pneumatic controller and the Ceramat WA 150 sensor lock-gate formulate a complete measuring system, which can be used in other applications, such as the chemical, pharmaceutical and foodstuffs industries.
developed a complete solution characterised by maximum availability, optimal process management, minimal maintenance expenditure and low operating costs.