Through the physical and chemical analysis of felt pollutants and stuffing, it is found that the pollutants mainly include the following four categories: (1) alkali soluble substances, such as alkali lignin, starch, resin, rosin; (2) The fine fibers in the pulp are often spotted with oil and asphalt to fill the mesh, and the paste mesh is hidden in the inner layer of the blanket, blocking the mesh, or bridging around the mesh, resulting in poor dehydration; (3) Inorganic substances, mainly various fillers, additives and additives. Such as talc powder, alum, calcium carbonate, porcelain clay, titanium dioxide, etc; (4) Oil spots, soluble resin spots, asphalt spots, tar, latex, ink, hot melt glue, etc.
For the above four types of pollutants, mechanical washing can be selected according to the actual situation in production practice.
Felt squeeze roller
It is very similar to ordinary pressed roll in structure. Its upper part is rolled with brass roll surface or artificial stone wheel surface, and its lower rod is wrapped with rubber with hardness of 75~85. The pressure of mixing line is (14.7~19.6) kn/m. Two spray pipes are installed in front of the water squeezing stick. Both sides of the felt are washed and wetted with a large amount of water, and then squeezed and dehydrated by the squeeze roll. In order to improve the washing effect, sometimes (.45~50) ℃ warm water is used as spray washing water. When the speed of the paper machine is less than (200~300) m/min, the felt squeeze roll has a good washing effect. Generally, the transmission system is not set separately for the felt squeeze roll unit. In order to reduce the wear of felts, some paper machines are equipped with separate drives connected with the main drive system.
Tubular felt washer
On high-speed paper machines that produce newsprint and writing paper, the first pressure and the second pressure are usually equipped with tubular felt washers, which are similar to water suction tanks, but have greater structural strength. The suction pipe is a bronze pipe with a diameter of (100~125) mm. The suction joint is 15mm wide and the vacuum degree is 29.33kpa. This kind of tubular felt washer is usually installed in pairs. The washing water is sprayed with two spray pipes above the scrubber. The tubular vacuum felt scrubber has higher wear and operation cost than squeezing water, but it has better washing effect.
Felt purging roller
The porous roller with a diameter of (400~600) mm is surrounded by a bronze roller shell, which is divided into several groups inside, and air is fed into the rod under the pressure of (9.8~19.6) kPa. When the speed of the paper machine is (150~200) m/min, the air consumption is (10~15) m/min per meter width. The purging roller is installed in the felt and wrapped by the felt at an angle of 180 °. The felt is washed by the water spray pipe before entering the blowing roll, and is dried by the air on the blowing stick. The front of the felt in contact with the paper is dirty, and the dirt is blown from the front of the felt. The blowing and mixing is driven and rotated by the felt. It is rarely used in general paper machines, and is usually installed on paperboard machines with large felt weight.
Water absorption rolling felt washer
The structure of the water absorbing roller felt washer is similar to that of the vacuum couch, but the diameter is small and there is no separate transmission. The felt passes through the water spray pipe and then passes through the water suction wheel. In order to prevent the felt from sliding along the rolled surface, the felt is in contact with the stick surface within the range of 90 °, and the vacuum chamber is made wider. The advantage of the water absorption rolling felt washer is that it absorbs water evenly from the felt along the full width of the paper machine, and has less wear on the felt. In order to wash effectively, this kind of felt washing device is generally used on the vacuum paper guiding felt of high-speed paper machine.
Vacuum mobile felt washer
This kind of washer is composed of 1-3 vacuum washing tanks. The box is about 100mm wide and is installed on a slide. A metal gear box driven by the lower pressing rod rotates the screw, and the vacuum washing box moves back and forth on the slide. The washing box is divided into three chambers: one chamber is connected with clean water; The other room is directly sprayed into the felt with steam or 50 ℃ warm water; The third chamber is connected with a vacuum pipeline to absorb the water and dirt passing through the felt, while keeping the felt soft all the time. There is no need to stop washing during the whole service life of the felt. However, the structure of this kind of washer is complex, and it is mostly used on medium speed and high-speed paper machines.
High pressure nozzle washing device
In recent years, high-pressure nozzle has been used to spray wash needled flocking felts, and the effect is good. Because the water spray pressure is very high, the nozzle cannot be fixed in one position, otherwise it is easy to cut the felt. Generally, a nozzle is installed every 300mm in width, and the whole spray pipe is moved laterally. High pressure spray washing makes the water pass through the felt, and at the same time, it uses the suction tank to suck back. High pressure nozzle washing can be used continuously or intermittently, depending on the new and old felts and the degree of dirt. Spray washing for 30min per shift. After high-pressure water spraying, there must be low-pressure water spraying to tidy the surface of the felt and eliminate high-pressure water streaks. Using high-pressure water spray washing, the water consumption is low, and the service life of the felt can be extended (30~50)%.
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