Sensors & Transducers


Conductivity sensors reduce washing costs

October 2015 Sensors & Transducers

In pulp and paper processes, great emphasis is placed on reducing the costs of brown stock washing. The main purpose is that the black liquor and pulp must be separated after they exit the digester, so that the pulp can go onto the papermaking process. This separation occurs on brown stock washers, where water is used to wash the black liquor from the pulp. The efficiency of the brown stock washing operation has a big influence on costs, chemical recovery and environmental compliance.

Concentration of chemicals is key

Brown stock, the ‘dirty’ pulp coming out of the digester, is washed in a concurrent system with cleanliness increasing with each wash. The goal is to achieve clean stock using a minimum amount of fresh water and to avoid unnecessary dilution of the white liquor chemicals fed at the digester. These chemicals are concentrated in the recovery boiler, and a high concentration of water makes this process inefficient or even impossible.

The concentration of chemicals in the solution coming out of the last stage washer determines the cleanliness of the stock as well as the dilution factor. At this stage, fresh water is added to the system. The amount added determines the cleanliness of the stock, and the concentration of chemicals in the solution going to the recovery boiler. There is a fine balance between effective washing and conservation of the liquor concentration for downstream processing.

Even though it is called the dilution factor, concentration of the brown stock is fairly high and can be successfully determined by conductivity measurement. At this stage in the process, conductivity is in the range of 50 to 100 mS/cm, depending on the individual plant, process and stock. That corresponds to concentrations in the low one digit percent range. Dilution in that sense is relative to the two digit concentrations present in the digester. Conductivity measurement at the brown stock washers requires a sensor that is immune to clogging from pulp fibres and that can tolerate the white liquor chemicals.

Mettler Toledo’s Ingold InPro 7250 inductive conductivity sensor and M400 transmitter offers a solution for this application. The InPro 7250 is designed for in-line measurements of conductivity/concentration in pulp and paper processes. Using the InPro 7250 probe, no electrodes are directly in contact with the process and therefore not directly affected by contamination. The InPro 7250 is constructed of PEEK, which is highly resistant to the white liquor chemicals. For best performance, the InPro 7250 should be installed where it will be in contact with a representative sample of the washing solution, for example, in the washer itself or in the drain line.

The M400 transmitter offers simple operation, precise and reliable measurements and accepts both analog probes and digital sensors.

For more information contact Darren Prinsloo, Microsep, +27 (0)11 553 2300, darren.prinsloo@microsep.co.za, www.microsep.co.za



Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

The smallest most powerful infrared sensor in the world
Sensors & Transducers
The superior performance and robustness of Telco’s infrared sensors ensures that there are no limits to any mining and industrial applications.

Read more...
Easy parameter setting of vision sensors
ifm - South Africa Sensors & Transducers
Contour verification and object inspection are two of the most important functionalities in industrial imaging. With the new O2D5xx series, ifm now offers a solution that perfectly masters both functionalities

Read more...
New range of vision units
Beckhoff Automation Sensors & Transducers
Beckhoff has added four new vision units to its VUI2000 series. They integrate a camera, illumination and liquid lens technology for simplified installation.

Read more...
Condition monitoring sensor
Sensors & Transducers
The Balluff BCM Gen2 Condition Monitoring Sensor is an advanced IIoT-ready device designed for real-time machine health monitoring.

Read more...
Inductive IO-Link sensors
Turck Banner Southern Africa Sensors & Transducers
Turck Banner is expanding its sensor range, with inductive measuring sensors with IO-Link and an analogue output for flush and non-flush mounting.

Read more...
Value of PDS grows with data and sensing technology
Sensors & Transducers
Rapidly developing technology is constantly being harnessed by proximity detection systems (PDS) to deliver steadily improved functionality to customers. Booyco Electronics sees improved PDS solutions being developed, such as the combination of multiple different sensing technologies into a single fully integrated solution.

Read more...
Pulp fiction or pulp precision?
VEGA Controls SA Sensors & Transducers
The density of fruit concentrate has a direct impact on the flavour, texture and overall quality of the final product. The VEGA Minitrac 31, VEGASOURCE 31, and the KV 31 mounting bracket present a failproof solution that effectively addresses the technical complexities associated with high temperature, viscosity and fouling.

Read more...
Telco sensors in the pulp and paper industry
Gail Norton Instrumentation Sensors & Transducers
The pulp and paper industry poses a major problem for most photoelectric sensors. The high level of contamination in these dusty, dirty and grimy environments makes it impossible for most competing sensors to operate and sense reliably and efficiently.

Read more...
Vibration monitoring with IO-Link
ifm - South Africa Sensors & Transducers
Machine vibrations are important indicators when it comes to assessing the current condition of a machine. fm’s new and smart IO-Link vibration sensor helps to implement a simple and scalable condition monitoring approach using only a single device.

Read more...
Unique industrial asset monitoring solution
WIKA Instruments Sensors & Transducers
WIKA WikaPredict offers a unique industrial asset monitoring solution, combining advanced sensors and artificial intelligence. As a leader in predictive maintenance, it helps clients enhance operational performance and increased efficiency.

Read more...