In the pulp and paper industry, pH measurement plays an important role in process control to maintain high quality standards. Reliability and process safety are paramount when operating in a pulp and paper environment.
Arjo Wiggins is a world leading manufacturer of technical and creative papers and offers a vast product range to a wide customer base. With a group turnover of approximately 1,7 billion Euros and employing 7000 people worldwide, it is the only group to provide a global offering in paper security solutions.
Problem
The site was having difficulty in obtaining an in-line pH reading in its Voith pulper vessel. As the paper bales are loaded into the vessel and broken down with water/chemical additions they are liable to damage the pH electrode. Paul Vinecombe, project engineer, explains, "I wanted a system that would be reliable and robust enough to stand up to the application. Not to forget, customer and technical support is also very important."
Mettler Toledo solution
After discussing the issue with Mettler Toledo, the InTrac 777 pneumatic housing with InPro 4250 sensor and pH 2100e transmitter proved to be the best system for the company's requirements. This system was needed in order to update the existing equipment. Mettler Toledo products had already been successfully installed in other areas of the plant.
The new equipment is being used in three parts of the plant's processes: First, in the pulper - at the start of the process the pneumatic housing is linked to the conveyor that loads the bales into a pulping vessel. When the conveyor starts the housing is retracted. Once the bale has broken up the electrode is inserted into the process providing an in-line reading without breaking the housing or electrode. This is an important step as the pH of the pulp is critical to provide the right material for the next steps of the manufacturing process.
Second, in the size press - a neutralisation process - pH is used to control the process to provide the correct mix of agent to coat the paper.
Third, the new equipment is used in paper machine (wet end) - another neutralisation application where the system controls the dosing of acid or base to provide the correct pH value. Certain products are very pH-critical and the systems are vital in achieving optimum processes.
The pH-electrode
The InPro 4250 combined pH electrode has a temperature sensor designed for demanding chemical applications. The Xerolyt Plus solid polymer reference electrolyte is in direct contact with the measuring solution, thereby eliminating junction clogging. This new electrolyte is resistant to solvents, strong acids and alkali - meeting the tough requirements specified by the application and meeting the maintenance expectations of Arjo Wiggins. The pH 2100e state-of-the-art transmitter is suitable for both simple or demanding applications. Available as a 4-wire or 2-wire version, this enhanced pH transmitter line offers superior performance, advanced sensor and transmitter diagnostics and leading edge functionality. Plus it provides reliable and accurate results and is ideal for regulating and controlling processes.
In addition the new retractable housing InTrac 777 has a flushing chamber where the electrode can be cleaned and calibrated if necessary - without interrupting the process. This enhanced housing incorporates a Trilock safety system, which increases process safety and reliability even in harsh environments.
Since the installation, the site has seen dramatic improvements. The retractable housing has improved the cleaning/calibration of the sensor and reduces sensor breakage. Process efficiency and measurement accuracy has improved.
In addition to this new system, the site also uses Mettler Toledo products for controlling the pH of the back water in its paper machines. The pH sensor/transmitter is used to control the acid/alkali addition to keep the pH within range and ensure the product meets the required specification. Here the InPro 4250pH electrode is again used in conjunction with a 2800X pH transmitter for dosing control.
For more information contact Chris de Jager, Microsep, 011 386 8300, chris.dejager@microsep.co.za, www.microsep.co.za
| Tel: | +27 87 092 7300 |
| Email: | info@microsep.co.za |
| www: | www.microsep.co.za |
| Articles: | More information and articles about Microsep |
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