Design and calibration of a flow-following sensor prototype for operation up to 175°C

In kraft pulping process, plup is produced by cooking wood chips at high temperature with chemical liquors in a kraft pulp digester. The temperature uniformity inside the digester is difficult to determine precisely due to the digester size and complexity. This paper presents the design and calibration of a prototype flow-following sensor that measures and records temperature at regular time intervals inside a kraft pulp digester. To make a large-scale deployment economical, the sensor consists of mainstream automotive-grade electronic components. Experimental results show that the prototype can operate reliably at 175°C for 2 hours continuously and over 50 hours cumulatively. After calibration, the accuracy of the temperature measurement is better than ±0.51°C while the overall time accuracy is better than ±141s for a typical 8 hour long digester run.