Problems and Measures for Production of Common Boxboards from Waste Container Boards

The use of scrap box board to produce ordinary cardboard and brown cardboard, the waste paper processing process is as follows: old box cardboard - hydraulic pulper - cylindrical de-sanding device - CX sieve - single disc mill - intensifier - pulp pool - Paperboard.

In the production, circular screen board machines often appear pasting, paper breakage and other phenomena, which have brought serious impact on the normal operation of production. To this end, we have carefully analyzed the above issues, found the problem, and took certain measures and achieved good results.

1. Problems and Causes 1.1 Paste Web: After the old cardboard was dispelled by the hydraulic pulper, the ink printed on the surface of the cardboard was partly free in the pulp and the other part was still stuck on the fiber. The disperse ink dissociated in the pulp can be washed away when it is dewatered by a rotary screen concentrator. However, part of it still enters the net mill of the paper machine. As the production progresses, it accumulates on the surface of the net, and the ink also adheres to some fine fibers. With dust, the mesh of the circular net becomes smaller until a pasting phenomenon occurs. Paste the net from the copy of the paperboard can be clearly seen there are many longitudinal thin strips of dry impressions, the spacing of each dry impression is equal to the spacing between the spine, seriously affecting the appearance of cardboard quality. The temporary treatment method is to wash the net with steam. After the net washing process, although the pasting phenomenon has temporarily improved, as the adhesion of the ink on the online operation of the paper machine has increased, the above-mentioned pasting phenomenon has occurred soon, which has adversely affected the normal operation of production.

1.2 Paper breakage: Due to the absence of strict sand removal, the dust contained in the pulp blanket, resulting in poor dewatering of the press section, the moisture of the wet paperboard entering the drying section was higher, not only reducing the strength of wet paperboard, but also increasing The steam consumption of the drying section. In addition, the high content of ink and sediment in the pulp also reduces the binding force between wet cardboard fibers. As a result, sticky cylinders often occur, and even paper breaks occur.

1.3 Black paper: printing ink dispersed in wet paperboard. After drying in the dryer, the ink accumulates with the decrease of moisture, and it disperses on the surface of the paperboard with the escape of moisture, on the surface of the paperboard. Many small ink dots are formed. After being calendered by the calender, these small ink dots form a black mark on the cardboard surface, affecting the appearance quality of the cardboard.

2, the measures taken <br> <br> happen paste network, breaks, is the root cause of black paper pulp and ink sediment due to higher dust content. Firstly, when we waste the old cardboard, we add positive sodium carbonate to the hydrapulper and steam, and control the temperature of the pulp in the hydraulic pulper at about 80°C to fully saponify and disperse the ink in the pulp. When the rotary screen concentrator is dehydrated, it is removed together; secondly, the internal force of the storage tank after the cylindrical descaler. The amount of people's traffic volume, which is used as a deinking adsorbent, also absorbs the sediment in the pulp and acts as a clean water. In addition, a 606-type conical sand remover is added after the CX screen for further desanding and arranging. The slag rate is controlled below 5%. After the above measures are taken, the pasting phenomenon of the wire mesh paper machine net cage is basically eliminated, the dewatering of the press section of the paper machine is strengthened, the service life of the blanket is prolonged, the sticking cylinder and the paper breakage phenomenon rarely occur in the drying section, and the dry impression on the paper surface. And black ink also disappeared.