Pulp Stock Composition and Consistency Analysis Using a Guided Microwave Spectrometer, 1998 Process Control, Electrical & Info. Conference Proceedings

Guided Microwave Spectrometry (GMS) is a major technology advancement for the on-line composition measurement of liquids, slurries, and granular solids. First developed in the mid 90’s for the food industry, this revolutionary approach combines advanced microwave spectral technology with a proprietary wave guide design to deliver high resolution and repeatability. GMS is a non contacting technology that sees the entire process stream to analyze a representative sample even if the mixture is non-homogenous. Combined, the many characteristics of GMS technology can provide significant advantages to the paper industry in product quality, raw material usage, and energy consumption.

GMS differs from other microwave techniques that measure only dielectric constant via phase shift or propagation time. GMS measures three independent bulk electrical properties plus temperature which can be used to further diagnose the makeup of the pulp. Since several components of pulp stock have different electrical properties, their respective percentages can be determined by measurement of these electrical properties.

In the consistency lab test defined by TAPPI T240-om93 the weight of a dried pad divided by the weight of the original sample determines consistency. This dried material may be comprised of many different things such as , clay, polymers, and coloring additives. The overall effect of changing these things can change the consistency result. There is value to the paper maker in knowing what percentage of the stock is fiber, what is water, and what are other components. This paper will discuss the possibility of generating this information on-line.