A method for secondary adjustment of the steam box and adjustment of the moisture content of the paper banner

Abstract

The invention discloses a secondary adjusting steam box and a method for adjusting the paper horizontal web water content. The secondary adjusting steam box comprises a steam box body, a master steam pipe and a master air exhaust pipe. A master pipe control valve is arranged at the inlet end of the master steam pipe. A preheating chamber is arranged outside the steam box body. The preheating chamber is arranged on a pipeline between the inlet end of the master steam pipe and the master pipe control valve in a communicating mode through a preheating branch pipe. The steam box body is sequentially provided with an air exhaust area, a steam spray area and a retention area in the advancing direction of paper, wherein the bottom of the air exhaust area is provided with a porous plate or a gap-type plate, the bottom of the steam spray area is provided with a porous plate or a gap-type plate and the bottom of the retention area is opened. Primary adjusting is conducted by using air carried by the paper, so that the problem that the steam heat transfer effect is affected by the air carried by the paper is solved and the secondary adjusting amount is reduced; secondary adjusting is conducted through steam flows of steam chambers of the steam box body, so that the purpose of adjusting the paper horizontal web water content is achieved. Due to the fact that the secondary adjusting amount of the steam flows is small, the flow difference between all the steam chambers is greatly reduced, steam is prevented from flowing among all the steam chambers and the adjusting effect is guaranteed.

Description

technical field [0001] The invention relates to the technical field of pulping and papermaking, in particular to a method for secondary adjustment of a steam box and adjustment of the moisture content of a paper banner. Background technique [0002] The steam box sprays steam along the paper banner, the steam condenses in the paper and releases latent heat, thereby increasing the temperature of the wet paper web, reducing the surface tension and viscosity of water in the wet paper web, and improving the dehydration capacity of the wire section, the press section and the drying cylinder At the same time, it can adjust the uniformity of the moisture content of the paper banner, improve the printing performance of the calendered paper and the coating performance of the coated paper, and the uniformity of the printing performance, so the steam box is widely used Various paper machines, especially special paper machines with high product quality requirements. [0003] The functi...

AI Technical Summary

Problems solved by technology

The disadvantage of this method is that when the flow rate of one steam room is relatively low, the steam of the surrounding steam room with high flow rate will run through and replenish, especially when the steam box is installed in the mesh part and used in conjunction with the vacuum box, the disadvantage of this method It is very obvious that when the steam flow rate of a certain chamber drops below the capacity of vacuum suction, the vacuum box will draw steam from the surrounding steam chamber with a large steam flow rate, even if the steam chamber with a small flow rate is located on both sides, due to the side plate It is thicker than the partition in the middle, and there are even other isolation devices, so the possibility of supplementing air is relatively small, so that the vacuum box makes the steam flow in all places develop in a uniform direction, thus affecting the adjustment effect of the steam box

[0004] US Patent US3945881, in order to solve the above problems, divides the vacuum box into the same number of vacuum chambers as the steam box, and controls them separately, so that when the steam flow rate of a certain chamber decreases, the pumping flow of the corresponding vacuum chamber also decreases. But the disadvantage of this method is to use two sets of control systems, while making the vacuum box more complicated

[0005] U.S. Patents US4249992 and US4331510 proposed another solution. The steam flow rate and pressure in each chamber of the banner are the same, and the moisture content of the paper banner is adjusted by changing the contact area between the steam and the paper in each chamber of the banner, and more steam is provided for parts with high humidity. The action time, and the part with low humidity reduces the contact area between steam and paper. Since the steam flow rate of each chamber is the same, the steam flow rate will not flow between each chamber, but this method requires a complex and unique internal structure

[0006] On the other hand, the content of non-condensable gas in the steam is an important factor affecting the effect of the steam box. The non-condensable gas in the steam will greatly reduce the condensation speed of the steam in the paper and affect the heat transfer effect of the steam. The steam box is installed on the paper The paper will bring in a large amount of air during its operation. If no measures are taken, the air will enter the space formed by the steam box and the paper, thereby reducing the heat transfer efficiency of the steam.

[0007] Traditional equipment has no measures to prevent air from being brought into the steam sprayed by the steam box. Now some equipment sprays a large amount of steam at the paper inlet in front of the steam box in order to prevent the airflow brought in by the paper, but this method is difficult to control the amount of steam injection. If the steam flow rate is too large, it will cause steam overflow, waste steam, and affect the workshop environment; if the flow rate is too small, the purpose of preventing airflow will not be achieved

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