The single screw press is a mechanical extrusion dewatering device. It adopts spindle with variable diameter and variable pitch. The material passes through the spiral blade with variable pitch and the spiral main shaft with variable diameter to gradually compress the volume of the material system. The medium with fluidity is discharged through the screen to achieve solid-liquid separation to improve the dryness of the material.
As for the application of single screw press, it is mainly used for the extraction and concentration of black liquor from alkali, acid cooking of wood pulp, bamboo pulp, and straw pulp. It is also used for the concentration of waste paper pulp and waste liquid extraction. It uses a spatial volume change produced by a variable diameter and variable pitch spiral to squeeze the fibers for black liquor extraction and pulp concentration. It has the advantages of high black liquor extraction rate, less fiber loss, and wide adaptability of pulp.
As a common paper pulp making machine, it is related to the pulp quality and whole paper pulp solution. How to select a single screw press? The first thing you should do is learn machinery fully.
Advantages of single screw press
The single screw press has the advantages of large compression ratio, simple operation, low energy consumption, high pulp concentration, stable pulping concentration and reliable operation of the equipment.
- The unique design of the structure, mainly using variable diameter variable pitch spiral, so that the material is compressed in the slowly decreasing space, so that the pulp layer is exceptionally dehydrated;
- With its slow speed, there are large or hard objects (such as iron) in the equipment. When the debris is automatically squeezed into the space of the spiral blade, the wear of the debris is avoided;
- The coned disc with a large compression ratio highly concentrates the pulp to achieve the purpose of liquid extraction.
- The material enters from the feed port at the upper end of the filter drum, and under the action of the spiral main shaft rotating and having a certain compression ratio, the water is continuously dehydrated and sent to the discharge port for discharge, and the water extruded from the pulp pass through the filter drum and enters the water tray, finally flows out of the white water outlet.
- A pneumatic cone is arranged at the spiral discharge to control the pressure of the pulp to adjust the concentration of the pulp;
- To ensure the consistency of the dehydration inside and outside the pulp layer, the sleeve of the main shaft has a hole for auxiliary dehydration.
Application of single screw press
The single screw press is mainly used for the low-concentration or medium-concentration pulp of the second-stage mill to the concentration required by the second-stage high-concentration mill or the pulp washing after the screening and bleaching. The variable diameter variable pitch spiral gradually reduces the volume of the pulp from the inlet to the outlet and is gradually dehydrated by different compressive forces, and the pulp “plug” is formed at the outlet by the pneumatic back-pressure device to increase the pulp concentration. The filtrate which is squeezed out of the machine through a filter drum outside the screw shaft and the filtrate can be diluted according to the applied position or discharged after recycling the fiber with a rotary fiber recovery machine.
Notes for single screw press
The single screw press has an ideal operation effect on pulp concentration, and the process configuration and the operation are both simple. If it can be successfully applied to the black liquor extraction of chemical pulp, it will increase the black liquor extraction rate and facilitate the process configuration with the cold blow. However, there are several problems in the use that need to be paid attention.
- The fiber loss rate is relatively large. Due to the low feed concentration, the fiber loss rate is relatively high. A reasonable fiber recovery device should be arranged according to the different positions of the equipment. It is recommended to use two-stage filtration and recovery in the black liquor extraction section. There are various types of way to recycle, such as two drum fiber recycling machine, the different meshes are in series for recycling, and the drum or pressure black liquor filter filtration recovery.
- It is sensitive to the suitability of pulp drainability. Because the rotation speed of the equipment is relatively high, the pulp concentration is relatively blocked, which is sensitive to the change of pulp drainability, especially for the wheat straw pulp with poor drainability. Therefore, the length of the three regions of the spiral shaft, the compression ratio and the frequency conversion speed range must be rationally designed according to the nature of the pulp, which achieves economical and reliable operation.
