Remote-Access Online Zeta Potential Monitoring Enhances Wet-End Papermaking

Papermaking is a complex and dynamic process with many possibilities of adjustments and influences in a complex production plant. By high level automation and production monitoring it is possible to increase the efficiency of the process. Starting the papermaking in the wet end area, the monitoring of the charge environment (particle charge and zeta potential) is extremely important.

Unclear charge conditions can lead to losses in product quality, disturbances in the production process and higher consumption of additives. A permanent control is especially important if different chemical additives are used, which are supposed to ensure a well-functioning production process and certain quality requirements of the base paper and finished product. Having information about the charge conditions available helps to optimize the dosage of additives throughout the complete wet-end process and allows the mill technicians and engineers to get a good overview of the status.

Test devices, which provide this necessary information, are for example the CAS touch! Charge Analyzing System and the FPA touch! Fiber Potential Analyzer. These devices are used in the lab and their application is an old hat for papermakers. Beside the used proven methods, both devices offer features for an effective, user-friendly and intuitive handling. Especially chemical suppliers appreciate their small size and light weight for convenient transportation. They are ready for immediate use after unpacking, as no additional components need to be assembled.

However, as the automation and digitalization play an increasing role in the paper industry, as in most other industries too, automatic measurements, which provide reliable and accurate real-time data of the process, get more and more important to meet sustainable, ecological and resource-efficient requirements. Such online measurements have several advantages at the same time: it is not necessary to get samples from the machine and measure them, the results are available in real-time, which allows an immediate intervention in the process, if the process is not running well or quality issues occur. These real-time data cannot only be transferred to the process control system; they can also be transferred to any data cloud anywhere in the world, which enables networked handling of issues by experts, who do not necessarily have to be onsite.

One of such an online device is the emtec FPO Fiber Potential Analyzer Online. The device measures the zeta potential of the fibers automatically and directly at the paper machine. It is performing sampling, measuring, and cleaning, has a very low maintenance effort, and can be installed at various points in the paper machine (two connection points possible), alternately taking samples before and after dosing points of additives, for example. The FPO can perform a maximum of six measurements per hour, though four measurements per hour are standard, depending on process adjustments. The measuring principle of the online device is identical with the measuring principle of the laboratory instrument. Both determine the zeta potential of fibers in suspensions in the wet end area of tissue, paper and board machines, using the equation from Helmholtz and Smoluchowski.

The measurement data includes the surface charge of fibers (fiber zeta potential), streaming potential, conductivity, pH value, and temperature, and is constantly transferred to the process control system, where changes of the fiber charge (e.g. by chemistry) get visible immediately. This makes the device a very helpful tool for the quality control, and supports easily process optimization and quality improvement.

To optimize the use of chemicals in the process, whereas the quality stays at the same level, the FPO Fiber Potential Analyzer Online helps to determine the optimal quantity of chemical additives, such as anionic trash catcher resp. fixing agents, sizing agents, wet and dry strength agents, optical brighteners, softeners and dyes. In addition, the knowledge of the zeta potential supports in different applications: it is decisive for the maximal possible retention of fines, fillers, dyes and resins, for the optimal internal sizing, for the neutralization of negative effects of anionic trash, including pulp mill carryover, for closure of the back water system, recycling of coated production, sludge dewatering as well as for the maximal efficiency of further single process steps.

A good example, which illustrates very well the benefit of using the device, is a paper mill, which produces different paper products on an alternating basis and both types of final paper products have to meet very different standards. Changing the production from one product to another, for example from toilet paper to kitchen towel, requires at least changes to the mix of chemicals added to the process. The change of chemicals or the adjustment of the amount of certain chemicals, which are added to the pulp, leads to changes in the charge environment and especially influences the surface charge of the fibers, the zeta potential. A lack of information about the surface charge of the fibers often leads to issues either with the runnability of the process or the quality of the final product.

The emtec FPO measures the zeta potential online and provides real-time data, which help to reach the required quality of the respective type of paper product, because the surface charge of the fibers indicates very reliably whether the requested quality is likely to be reached. This does not mean that tests in the lab are not necessary anymore. However, with the information provided by the device and the experience of the mill personnel, the optimization of the process works out much faster, which can help to save resources, time and energy.

The FPO, just as other online tools, which provide real-time data, helps the industry to further digitalize and automate the papermaking process. The device does exactly, what a test device, ready for the Industry 4.0, needs to do. It measures fully automatic, with a very low maintenance effort, reliable and accurate, process relevant data. It transfers these data automatically to the mill’s control system or a data cloud. The instant availability of the test data at any place in the world allows networked discussions with people from different parts in the world and fast solutions for possible issues, even by automated changes to the process, if certain specifications get out of the optimal range.

In the meanwhile, it is required to rethink the industries´ role and position in society, including environmental, social and societal considerations to make them more future-proof. To gain this, the Industry 4.0 concept needs to be complemented and extended to Industry 5.0, that focuses on the industries´ service to humanity within planetary boundaries leading to a more sustainable, resilient, and competitive production on a long-term basis. The concept of Industry 5.0 supports the economic performance of industries while respecting the needs and interests of employees and ensuring environmental sustainability.

The use of the emtec FPO maximizes the benefits for both the company and the worker: it strengthens the resilience, means it forces the flexibility and arms them better against disruptions. It makes the work place saver, enables a real-time risk monitoring and management as well as remote work by automatic data transfer. The working environment gets more inclusive by automatic constant measurements, the worker gets more empowered by saving working time, but having all necessary data to reduce waste and the environmental impact by saving resource and energy consumption. For such energy-intensive industries as the paper industry it is of paramount importance to consider the link between energy consumption and economic growth.