Study On Paper Machine System Configuration With Multiple Product Production

<Paper Industry Development Policy> stated that the structure of paper products adjusted to "thinner, better quality, upper grade and more variety". Under the background that the waste paper used to produce newsprint was affected by the international market, and that the newsprint product was oversupplied and that about 260 tons of cultural paper with middle and lower quality will be abandoned, Fujian Nanzhi Co., Ltd. convert the paper machine which was planned to produce color offset newsprint to that would produce both high-grade newsprint paper, electrostatic copy paper and offset printing paper. Through the research for the paper machine system configuration of varieties of cultural paper, it was an important reference for the new production line and the old factories’technology transformation, it was also meaningful for promoting the development of the paper industry in China.This paper concerned about selection and ratio of fibers for newsprint, offset paper and electrostatic copy paper according to the technical requirements of cultural paper. Pulp preparation process, high concentration screening process, pulp approach system and papermaking process were conducted and proved, the paper machine’s automatic control system and its overall program was discussed. Newsprint, static copy paper and offset printing paper which reached the national superior or A grade quality standard were produced by using different production technology. The paper machine system was designed to produce varieties of cultural paper as well as newsprint, electrostatic copy paper, offset printing paper and so on simultaneously. Designed production ability of the paper machine was 791t/24h, designed mechanical speed was 1400m/min, designed production speed of the winding machine was 1300m/min and the machine’s width was 5800mm. The whole production process included pulp preparation, pulp approach system, papermaking and so on. The pulp preparation system included pulping system, high concentration screening and refining; pulp approach system included dilution, screening and cleaning, gas exclusion, addition of additives, and approach system, etc; forming system included forming section, press section, surface sizing and dry section, calendaring, winding and rewinding. The optimum designation of the whole process laid the foundation for producing various kinds of paper.In approach system, calcium carbonate filler, AKD sizing agents and wet chemical agents were added. Wet chemical agents included PAM, bentonite and organic particle retention and drainage system. Addition of AKD could improve water resistance, calcium carbonate filler could improve sheet formation, smoothness, opacity, whiteness, dimensional stability, the printability of paper printing and reduced production cost. Addition of the wet chemical additives could increase the retention of fines and filler, dry strength and wet strength of paper. It also needed dilution, purification, filtration, gas exclusion and impulse exclusion before the prepared pulp entering the headbox. The setting up of the storage for white liquor out of machine made an insurance for running of while liquor circle system. Different kinds of impurities were removed by five-stages cleaning and two-stages screening. Deaeration device could be used to remove the gas in the approach system and improve the formation of the sheets. The headbox affiliated closed air cushion with dilution water was applied. The maximum dilution flow of the headbox was 10% of that in weir plate. Two bundles were used against the pulp’s flocculation, the floating slice was used to control the degree of the turbulence and reduce the pulp’s re-flocculation. Attenuator with overflow weir was installed on the headbox. The pulp would be discharged when it was beyond the pulp overflow weir. The attenuator could reduce the longitudinal quantitative fluctuations which were caused by the pressure pulses due to the short cycle.Roll former which included both long net dehydration and top net dehydration was used. Long net dehydration could be controlled by adjusting angle of scraper, number and vacuum degree. Top net dehydration could be controlled by regulating the suction element. Roll former had strong dehydration and good formation ability. Roll former could adapt to different paper basis weight and speed of the machine with different operational requirements. Two-stage shoe press technology was applied. Average pressure of 4130kpa was exerted in the 254mm-long pressure shoe, wide-pressure zone was equivalent to normal pressure method with pressure of 1050kN/m, press time was 4-6 times longer than traditional press, as a result, higher degree of dry was obtained. SymRun drying was applied in pre-drying section, all steam heated drying cylinder was arranged in a single-row upon the vacuum roll; single net was arranged first and double net followed in the post-drying section. Three-stage ventilation was used in the dryer section. SymRun air box was located above the vacuum roll, negative pressure was achieved between the two dry carpet district to ensure paper absorb onto the dry carpet in entire dryer section and avoid breakage. Surface sizing included both top and bottom sizing, which could combine the low amount internal sizing and surface sizing, the latter of which controlled the ultimate degree of sizing. Synthetic polymer and starch surface sizing agent was used to improve the surface strength and water resistance, because the mixture sizing agent could penetrate into the paper then filling the gap between the sheet. A single pressure zone of soft calendar was used with design speed of 1800m/min, the hot roll maximum line pressure of 200kN/m, the minimum line pressure of 15kN/m, the maximum surface temperature of 150℃. The upper roll was heated by oil. Soft calendaring could greatly improve the paper smoothness and gloss, control the thickness of the paper.The original TMP and DIP production line, coupled with the new production line for producing varieties of cultural paper was used to adjust the production process and produce newsprint, electrostatic copy paper and offset printing paper, etc. The newsprint reached the state superior product quality standard, while the electrostatic copy paper and offset printing paper reached the state A grade product quality standard. Although varieties of configuration and investment were added to meet the requirements of various kinds of paper, equipment was also difficult to achieve ideal performance; at the same time, it needed high requirements on the production scheduling management; this production line could be flexible to exchange product variety to meet the clients’requirements, ensure high machine operating rates, achieve better economic returns, consistent with the principles of engineering economy.