The most popular future paper machine drying at hi

2022-07-29
  • Detail

Future paper machine: drying at high speed (IV)

in fact, the fixed siphon system is fixed at a certain position, and the result is that the condensate and the siphon work together, not mutually exclusive. The low pressure difference of 2 ~ 4psi is enough to evacuate the condensate through the vertical siphon

when the running speed exceeds 900m/min, the fixed siphon uses the centripetal force (the force generated by the rotating edge) to discharge the condensate from the drying cylinder. The required differential pressure is actually reduced; In some cases, the pressure through the contact is as low as 0psi. Paper workers can now control the temperature through pressure rather than emptying. This is particularly beneficial to the wet end dryer to prevent the cylinder from sticking and slowly increase the paper temperature

gardner answer: the main problems of condensate removal are: the method of reducing the residual condensate load and the method of stirring the film (is the spoiler better?), A method of reducing the pressure on a fixed siphon

gl & V answer: with the increase of drying speed, it is particularly important to effectively remove condensate. The condensed water exists as an edge in the drying cylinder, which is an obstacle to heat transfer. In addition to the heat transfer problem, improper emptying will lead to the vibration problem of the paper machine, which will increase at high speeds

jhk answer: the internal dimension of the pipe and the inner diameter of the dryer journal will limit the emptying of the dryer at high speed. The rate of condensation, which is sensitive, will be a factor

johnson answer: the main problem of removing condensate at all speeds is to ensure that it can occur. Since condensate is the greatest resistance to heat transfer, the efficiency of removing condensate is a key determinant of the productivity of the paper machine. At high speeds, problems such as pressure difference, steam flow rate and condensation degree still need attention

poor removal of condensed water will lead to uneven water distribution, 38% wrinkling and shrinkage of the coal from the paper sheet, and have a significant impact on the paper machine's operating performance and total drying capacity. The effective removal of condensate also depends on a properly designed drainage system

if the dryer discharge system cannot operate smoothly, the latest technology of siphon design cannot provide satisfactory results. A well-designed system will be flexible, can adapt to the needs of paper grade changes, can control the maximum steam pressure, use the least steam, and control the maximum steam flow and pressure difference

thermowisconsin A: there are many problems to be discussed here. You can report them in detail. However, the main problem of high-speed condensate removal can be summarized as the paper quality problem, which may damage the equipment, cause efficiency loss, and the condensate is unnecessarily discharged into the factory

valmet answer: there is no problem in draining the dryer of the paper machine when the high pressure testing machine is installed at an uneven speed, and as long as the steam and condensing system can bear the load, the working performance of the fixed siphon should be very good. TAPPI magazine asked: is the current siphon technology competent? Are other technologies required

beloit A: the current siphon technology is competent even at high speeds. In the late 1970s, there was a concern that the industry would reach its limit in draining condensate. At that time, the rotary siphon system had been used in the drying cylinder of the high-speed paper machine. These siphons are in contact with the inner surface of the dryer through a small hole, so as to achieve the condensate thickness required by the heat transfer rate. The pressure difference required to drain the edge condensate by using the reverse siphon system increases with the increase of vehicle speed. At high speeds, the differential pressure needs to exceed 1bar

due to the inherent mechanical instability of the long cantilever support of the fixed siphon system, its sealing to the shell surface cannot reach the required range. In the late 1970s, a spoiler bar was developed for the drying cylinder. The baffle rod is fixed on the inner surface of the drying cylinder to make the condensed water turbulent and maintain a high heat transfer rate through the condensing layer

high turbulence may occur even in thick condensing layer, so large and easy to operate siphon spacing can be used, and fixed siphons can be restored in industry. The fixed siphon uses a collector to lead the condensate out of the drying cylinder, and the pressure difference is very small

although there are a variety of other technologies to choose from, there are no inherent constraints for removing condensate with a fixed siphon at high vehicle speeds

deublin answer: the current fixed siphon technology is not only suitable for use now, but also can be used when the speed of the paper machine is increased so that the previous experimental data can be queried at any time in the future. When the paper machine is transformed to high productivity, bearing, balance and other problems may become constraints. For many years to come, Fixed siphon technology "if there is a good bidder who can be competent for the high-speed paper machine.

gardner answer: fixed siphon is the only feasible way at high speed. Further research is needed on fixed siphon.

gl & V answer: due to the impact of condensate on the pickup plate" It actually helps to evacuate, so theoretically, the high-speed fixed siphon should work better at high speed

another important issue to consider is that the influence of vehicle speed on the differential pressure required to drain the condensate increases. The fixed siphon is adopted. Since the emptying pipe does not rotate, there is no need to overcome the pressure difference of centrifugal force acting on the condensate. (to be continued)

Copyright © 2011 JIN SHI