Abstract
The energy efficiency of the drying section of paper machine is determined by the technology of heat flows arrangements in it. Paper drying is the most energy-consuming stage of paper production. The thermal mode of the drying section is provided by the steam condensate system which is a part of it. Analysis of exergy increments shows that almost all elements of the drying thermal process are characterized by low exergy efficiency. The main ways for increasing the degree of thermodynamic perfection of the processes occurring in the drying section of the paper machine are identified based on the exergy analysis. It is assumed that the deep internal heat recovery of the steam-air mixture for heating the source air will increase the exergy efficiency of the heat recovery plant and reduce heat removal to the environment. The effectiveness of development and implementation of a closed cycle use of steam-air mixture in the drying section was examined. Building a closed cycle provides that the air mainly has a process duty, that is, it is a transport agent for the transfer of moisture and heat along a closed circuit. The calculations show that the exergy efficiency of the processes in the recovery unit of the drying section of the paper machine of the existing production is 28.6% against 66.29% for the proposed method.
Highlights
The energy efficiency of a paper machine (PM) is largely determined by the technology for heat flows arrangement in the drying section
The wire section is designed to remove the main part of moisture and formation of the paper web, the press part is aimed at removing the additional moisture by pressing
It can be concluded that, despite the relatively small amount of moisture removed in the drying section of the PM (0.7%), the energy consumption here is maximum, and the amount of heat input in the form of saturated steam from the CHP is determined by this particular section of PM
Summary
The energy efficiency of a paper machine (PM) is largely determined by the technology for heat flows arrangement in the drying section. From under the hood cap of the PM drying section the air-steam mixture 1 (Fig. 1) with a temperature of 100 °C is fed into the first recovery stage 2 (TU-1). The air-steam mixture gives some part of heat to the process (drying) air 17 supplied from the machine room with a temperature of 28 °C, and heats it up to 42 °C. Outside air in the winter period is heated in the second recovery stage 3 up to temperature of 0 °С, and it is heated to 20 °С in a heater 8 by steam from the thermal power plant. From the heater 8, the heated air is supplied to the machine hall 11, where it assimilates the heat of equipment and reaches temperature of 28 °C, at which it enters the first recovery stage 2. The temperature of the air discharged from the scrubber is 45 °С
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