On the zeta potential online detection device of t

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Zeta potential measuring device for pulp (Part 1)

Abstract: a new zeta potential measuring device for the proportion of various raw materials for pulp is introduced, which is based on single-chip computer control and data processing. The zeta potential of the measured signal fluctuates slowly in the measurement process. Therefore, the corresponding automatic tracking processing method and related data processing method are proposed

key words: zeta potential; Pulp; Paper machine; Signal processing; Signal detection

Shandong Provincial Science and Technology Commission funded the research project ()

but our firm commitment to customers and meeting their needs will not change brief introduction: qiushubo, associate professor, master. Mainly engaged in scientific research and engineering work in industrial process computer measurement and control

many paper mills have been puzzled by the unstable paper quality or lower than the design requirements, although the operating conditions of the paper machine and the wet end parameters of routine tests maintain normal values. Why? An important factor is the electrokinetics and surface charge of dissolved and suspended substances, microbial activity and the influence of additives. In practice, a large amount of evidence shows that zeta potential of pulp used to characterize the above factors has a great impact on paper quality

wet end additives are retained on the paper by adsorption on the fiber surface. In the past, the control of wet end chemical process was mainly to adjust the pH value. In fact, the pH value is not the true reflection of pulp properties. The key lies in the coagulation structure and retention rate of various fiber additives, which is mainly determined by the zeta potential of paper solid particles

1 zeta potential and its measurement

zeta potential refers to the potential difference between the liquid fixed layer and the movable layer on the solid surface when solid particles slide in the liquid, expressed in MV. When zeta potential is high, various particles in the slurry have more charge Coulomb force, which prevents the contact between fiber and filler and colloid, affecting the retention of fine fiber, colloid and filler and the loss of white water. When the zeta potential tends to zero, the van der Waals force between particles plays a major role, which greatly improves the retention rate, water filtration and wet strength of paper, and reduces the breakage. 1. At present, the recycling rate of waste plastics in China is not high, reducing paper disease. Through the detection of zeta potential, the change of wet end chemistry can be detected as soon as possible, so as to timely and accurately adjust the addition point and amount of chemical additives

There are several methods to measure zeta potential, but most of them are off-line. In this paper, the streaming potential method is used to measure zeta potential of pulp. The sampling and detection part of the measuring device is shown in Figure 1. When the liquid with a certain pressure flows through the porous pad, the measured potential difference between the electrodes at both ends is the flow potential difference, and the relationship with zeta potential is:

ξ SPC η

= Δ P ε Where: SP -- flowing potential

η—— Medium viscosity

ε—— Constant of isoelectric point of fluid

c -- conductivity of liquid

Δ P-the working process of the liquid pressure drop through the plug

2 detection device

the detection device consists of a buffer tank, a slurry plug formation and measurement chamber, a measurement electrode, a pressure and temperature sensor, and a gas-water control valve. The single-chip computer controls the air extraction valve to vacuum the upper buffer tank, the pulp in the main pipe is filtered and blocked under the pressure, and a pulp plug is formed in the measuring room. The single-chip computer adjusts the negative pressure in the buffer tank by adjusting the vacuum valve F1 and the auxiliary pressure regulating valve F2, so that the pulp plug moves upward. When the single-chip computer controls the air inlet valve F3, a positive pressure is generated in the buffer tank, so that the pulp plug moves downward. Through the coordinated control of valves F1, F2 and F3, the computer makes the slurry plug form a potential difference between the two platinum electrodes in the measurement room, that is, the flow potential difference. After the single-chip microcomputer completes several signal measurements, open the flushing valve F4 and the flushing valve F3 to flush the measured slurry into the main pipe, and then carry out the next round of measurement

Fig. 1 sampling structure of zeta potential detection device

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