The Effect of Atmospheric Pressure on the Measurement of Deaeration Vacuum of Viscose

Still remaining in the viscose, the viscose fiber is strongly reduced.

In addition, the metal elements such as manganese, cobalt, and iron in the pulp ash promote the aging of alkali fibers, affecting the aging time, and the calcium salts have a serious negative effect on the filtration performance, thus affecting the quality of the fibers and also directly Affects the stability of process parameters. The improvement of pulp quality will inevitably reduce its inherent inorganic and organic impurities.

Raising the purity of pulp can be achieved by strengthening mechanical and chemical impurity removal methods. Specific methods: 1 Strictly control the quality of good lint and various raw materials; 2 Ensure the quality of water; 3 Improve the alkali rate for cooking and improve the washing materials. Quality; 4 strengthen pickling, especially pre-acid treatment.

3. Pay attention to the quality of beating and improve the performance of alkali absorption Beating is another key process to control the alkali absorption performance of pulp. In order to achieve the best reaction performance of different pulps, in addition to various factors of chemical refining in the pulping process, the alkali absorption value and swelling index that reflect the alkali absorption performance of the pulp are used to filter the performance and spinnability of the viscose. There are also non-negligible effects. Only those pulps with good alkali absorption ability can undergo vigorous expansion under the action of the alkaline solution. The fibers become coarse, the internal surface area increases, and the number of active hydroxyl groups increases, making it easier for cellulose to interact with various chemicals. The obtained alkali fiber is more uniform and can also have higher reaction performance in the acidification. If the alkali absorption performance is not good, although chemical reactions can also occur, it is difficult, and the alkali fibers are not uniform, and the viscose filtration performance and spinnability of the resulting viscose are relatively poor.

The beating process can fully destroy the primary wall that is not completely destroyed during the cooking process. This mechanical action only increases the surface activity of the fibers without chemical reactions. Different lint, should use different beating methods. For the cooking method with poor cooking effect, hard-feeling material and type I and n types of velvet, it is better to use lower beating concentration, to keep abreast with the knife, to shorten the beating time, and to slow down the rate of increase in the degree of mitigation; And the method of beating the ideal material for cooking is to appropriately increase the beating concentration so that the beating is carried out in a slow and abundant time, and the degree of dehydration is appropriately increased to avoid excessive fiber cut-off.

In order to improve the alkali absorption performance of the pulp, the influence of the papermaking process cannot be ignored. Increasing the dewatering effect of the paper making machine can cause the cellulose to form a natural interweaving state during molding, and more small fibers can be easily removed from the fiber layer, which is beneficial to improvement. Pulp alkali absorption properties. To reduce the surface temperature of the dryer as much as possible, increase the pressure of the positive and main pressure, and increase the alkali absorption and swelling ability of the pulp.

To improve the quality of pulp, in addition to the above, the process parameters of each process should be comprehensively balanced in production.

Influence of Atmospheric Pressure on Viscosity Measurement of Viscose Deaeration Cui Dawei (Dandong Chemical Fiber Co., Ltd., Liaoning 118002) Deaeration is a link in the process of making glue in viscose fiber production with the aim of minimizing spun-bonding. The content of air bubbles in the glue, thereby reducing the production of wool in the viscose fiber. The quality of the defoaming quality is directly related to spinning spinnability, cheese strikeability, and thus product quality level.

In actual production, viscose uses either static deaeration or continuous deaeration. In addition to deaeration time, the degree of vacuum when vacuum is used is also an important measure of defoaming quality. The measurement method usually uses a vacuum gauge or U-type manometer direct measurement. When the vacuum degree indicated in the table is lower than the reading required by the process, the method of vacuum leak detection is generally adopted to solve the problem. This method sometimes works and sometimes it does not work. The degree of vacuum measured now is based on the relative value of the external atmospheric pressure constant or when the change is not significant. A non-true vacuum degree is negative pressure. The atmospheric pressure around us is changing at any time. For this purpose, I did a comparison measurement of atmospheric pressure (using an empty box-type barometer and a U-shaped mercury manometer). Take the example of Dandong District at 7:00 am everyday, indoor and outdoor. The highest pressure value. At the time (January 8, 1997) reached 104hpa, equivalent to 781mmHg column, the lowest value (June 9th) only 998hpa, equivalent to 748mmHg column, a difference of 33mmHg column; and the pressure value of the day is not the same, such as September 1997, September 17th: The early seven o'clock pressure is l13hpa, 1 o'clock noon is 1004hPa, the late seven o'clock is lOOlhpa, sooner or later the difference is 12hpa, namely 9mmHg column. The following shows the atmospheric pressure and U-type vacuum gauge display graphs (Figure 1) from August 15 to September 29, 1997.

It can be seen from Figure 1 that the two curves have very close variation, and the difference between the two is plotted in Figure 2, which is basically a constant straight line, and this value is the true vacuum-negative pressure. The representative is what we need to control in our actual production. The smaller the negative pressure, the closer the vacuum is to the atmospheric pressure, the better the defoaming effect. Therefore, we believe that the measurement of vacuum in actual production should introduce atmospheric pressure as a reference, and use the difference as a basis for measuring the effectiveness of defoaming.

After more than one year of practical application, when the difference deviates from the straight line, we find out the problems of the X equipment or the phenomenon of pipeline leakage. It is not surprising that we see “strange” when reading the vacuum gauge beyond 760 mmHg.

In the viscose defoaming process, in addition to adjusting the defoaming time based on the true value of the vacuum degree, the following points must also be taken into account in order to improve the quality of defoaming: Pay attention to ensure the tightness of the vacuum system, including piping, valves, and equipment And so on, only the seal is good enough to realize the true performance of vacuum equipment.

The use of more efficient vacuum equipment, the current domestic vacuum equipment, such as effective vacuum pump can increase the vacuum degree above the lOmraHg column. Its disadvantages are large energy consumption and high cost.

When the water ring vacuum pump and the water jet pump are used, the temperature of the medium water should also be as low as possible, because when the vacuum pump reaches a certain equilibrium, the direct factor affecting the vacuum (or negative pressure) is its saturation. Steam pressure, and its value is directly related to water temperature.

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