What is the principle of energy saving and steam saving in the drying section of the paper machine?

Whether the steam supply system in the drying section of the paper machine is very reasonable will have a great impact on the quality of the final paper produced in the drying section, the consumption of steam, and the operation management.

1. Principle design

When we are making paper, we must be able to ensure that we can flexibly adjust the temperature of each part to facilitate obtaining a suitable drying temperature curve; when making paper, we must effectively use steam to save energy and facilitate discharge. Non-condensable gas in the system in order to improve heat transfer efficiency.

2. Energy saving and gas saving principle

①In order to meet these requirements, we generally use the method of multi-stage steam venting instead of single-stage steam venting. The reason is that single-stage steam venting is only reserved for some low-speed paper machines. The characteristic of the steam system is that the drying cylinders of the multi-drying cylinder drying section can be divided into several groups, generally 3 to 5 groups. The number of drying cylinders is less than 20, and some are only divided into two groups. The new steam from the boiler is generally Only the first group of drying cylinders is fed, and the second group uses the secondary steam generated by the decompression and reboiling of the condensed water of the first group of drying cylinders, so the temperature of the second group of drying cylinders is lower than that of the first group.

②The third group uses the secondary steam of the second group of drying cylinders, and so on. Generally, the number of times the steam passes through is called "segment", so it is called multi-stage steam, and because the steam flows continuously in the cylinder , so it is also called a steam circulation method with a steam cycle.

③For drying cylinders with multi-stage steam opening, the number of drying cylinders in each stage can be arranged according to the following ratios: three-stage steam opening can be 1:2:4 or 1:3:6, four-stage, 1:2:4: 6. The most is the first stage, which is discharged in turn. The fresh steam from the boiler enters the first stage drying cylinder set in front of the calender, and the condensed water and uncondensed steam discharged from the drying cylinder of this stage enter the first stage. In the first-stage steam-water separator, the reboiled secondary steam and the first-stage uncondensed steam enter the second-stage as the heating steam of the second-stage. For three-stage heating steam.

④The dry cloth cylinder is heated by new steam, and the secondary steam discharged from the condensed water through the steam-water separator can be mixed with the second steam of the first-stage steam-water separator and sent to the second-stage. The new steam pressure of the third-stage steam opening is 0.3~0.8MPa (3~8kg/cm2), and the exhausted gas pressure after the third stage is 0.02~0.8MPa (0.2~0.8kg/cm2). If the temperature of the second stage is not enough, the intake steam of the first stage can be increased amount, thereby increasing the amount of uncondensed vapor in the first stage.

⑤You can also open the valve on the new steam pipeline to directly add new steam. Similarly, when the temperature of the third section is insufficient, you can also directly add new steam. The condensable gas and the steam from the last stage of the reboiler often enter the condenser connected with the vacuum pump, and the condensed water and the condensed water of each stage are returned to the boiler together to recover its heat.

⑤You can also open the valve on the new steam pipeline to directly add new steam. Similarly, when the temperature of the third section is insufficient, you can also directly add new steam. The condensable gas and the steam from the last stage of the reboiler often enter the condenser connected with the vacuum pump, and the condensed water and the condensed water of each stage are returned to the boiler together to recover its heat.

⑥Looking at the aspect of multi-stage steam ventilation, multi-stage steam ventilation can ensure that there is no accumulation and non-condensable gas in each drying cylinder, and this big guarantee is conducive to improving the heat transfer efficiency of the drying cylinder, but the temperature of each section is different, Through debugging, the appropriate drying temperature curve can be determined according to the requirements of the production process.