Processes 2021 , 9 , 1117
8of 11
where, i represents the number of data groups, N represents the number of data groups, Δ H 1 represents the evaporation heat obtained by the new method, Δ H 2 represents the evapora- tion heat obtained by the old method.
Figure4. Comparison of results between the new and old methods in the laboratory.
The laboratory verification results show that the new method can achieve the credibil- ity of the old method. However, the new method can greatly simplify the test process of the water evaporation heat in paper drying process. 3.2. Industrial Verification The verification object is a pre-drying process of high-strength corrugated paper with an annual output of 80,000 tons. The paper machine has 48 dryer cylinders, a speed of 500 m/min, a width of 4 m, and can produce high-strength corrugated paper with basis weight of 100 g/m 2 . Figure 5 shows the schematic diagram of paper drying process. The material flow in and out of the pre-dryer section is clearly marked. In the actual production process, the paper drying is completed in the dryer-section, that is, a group of horizontally arranged heating dryer cylinders. The paper is pasted on the surface of the dryer cylinders to evapo- rate and dry. The production is continuous and the paper is moving forward dynamically, generally, the speed of the paper machine is 1000~2000 m/min. In this case, it is difficult to obtain the data of the moisture content of paper with time. Therefore, the drying curve of the production process is usually recorded as the change of the moisture content of the paper with different drying positions(u~N). The moisture content of the paper can be measured by hand-held portable sensor, and the drying position is usually indicated by the cylinder number of different positions. Figure 6 shows measurement and analysis of drying curve in industrial production. The basis weight of paper web was measured by a portable sensor (NDC 8110-F/104 from NDC infrared Engineering Co., Ltd., Los Angeles, CA, USA). This kind of small single-sided sensor can be extended into the narrow gap between the dryer cylinders, and it can be used to measure quantitatively on-line on the surface of the wet web without affecting the normal production. The drying curve data represented by paper moisture ( u ) and cylinder number ( N ) are recorded online as shown in Figure 6. The experimental model, Gaussian model and Fourier model were used to fit the test data. The fitting curves
Made with FlippingBook Online newsletter maker