In the pulp & paper industry, various “liquors” are used with wood chips and other raw materials to create paper and other cellulose-based products. This process is commonly known as the Kraft process. In the Kraft process, operators typically distinguish liquors by color: black, green, red, and white. Each of these liquors possesses unique properties, and operators utilize them at different stages. Due to the unique chemical compositions of the liquors, operators utilize conductivity measurements throughout the process to monitor the variability of the liquors and process media
Conductivity levels are used for liquor monitoring throughout the Kraft process so that operators can optimize the usage of chemicals such as NaOH and Na2S. The measurements can aid in reducing chemical consumption and associated costs. Additionally, conductivity measurements can minimize the process’s environmental impact by preventing overuse or waste of chemicals. Operators are also keen to reduce spills or leaks due to the highly alkaline and potentially corrosive media within the process.
The Challenge Found in Liquor Monitoring
In the Kraft process, it is crucial to prevent cross-contamination and the buildup of carry-over chemicals. Due to the unique properties of the liquors and their distinct roles throughout the process, operators must ensure that the chemical composition of these liquors is not compromised. Conductivity measurements allow operators to evaluate liquor quality and concentration throughout the process. However, operators take these measurements under high temperatures in a process prone to aggressive media buildup. This can cause issues with sensor durability, accuracy, and lifespan. Additionally, the Kraft process naturally comprises high ionic and chemical activity. These factors challenge operators looking to keep their conductivity measurements consistent and accurate.
The Solution
The K25 is a 4-electrode, coaxial conductivity sensor designed for heavily polluted and fibrous media. The K25’s integrated PT 1000 temperature element assures proper temperature compensation and accurate concentration measurement. This low-maintenance sensor design enables simultaneous conductivity and temperature measurement, making it a perfect solution for the demands of the Kraft process. The sensor has a large measuring range of 0 … 1,000 mS/cm. Additionally, the K25’s four electrodes allow for less susceptibility to polarization, ensuring consistent, accurate measurements in aggressive processes like liquor monitoring.
The SensoGate WA 131 is a pneumatic retractable holder capable of integrating 225 mm sensors into virtually any process. This holder has an inlet and an outlet to bring cleaning solutions into the chamber. Additionally, the SensoGate utilizes a “cyclone cleaning” process. Rinse media disperses 360° around the sensor for a thorough cleaning. These capabilities address aggressive media that coincide with the Kraft process and increase sensor life and accuracy.
The Stratos Multi provides comprehensive data integration and analysis capabilities. These capabilities empower operators to make informed decisions and fine-tune process parameters for maximum efficiency and product quality. This versatile transmitter can connect with various sensors, including M4 Knick’s K25 four-electrode conductivity sensor. The robust design guarantees reliability and low maintenance requirements, even in harsh operating conditions found in the Kraft process.
The Customer’s ROI
Extended Sensor Life: The K25’s four electrodes are less susceptible to polarization when measuring aggressive media. The Sensogate’s cleaning capabilities also allow for a more consistent and thorough sensor cleaning, mitigating failure due to buildup.
Optimized Chemical Consumption: Accurate conductivity measurements in liquor monitoring allow operators to optimize the doses of chemicals introduced to the process.
Improved Process Quality: Conductivity measurements reflect the progress of lignin removal from the wood chips, which is crucial for producing high-quality pulp. Consistent and precise control of conductivity levels helps achieve the desired pulp properties such as strength, brightness, and uniformity.
Enhanced Safety: Full isolation from the process using the Sensogate boosts operator safety and greatly decreases the potential for exposure to process media.
