The running speed of the filter belt controls the dewatering time of the sludge in each working area, which has influence on the solid content of the mud cake, the thickness of the mud cake and the difficulty degree of the mud cake. The lower the speed, the higher the solid content of the mud cake, the thicker the mud cake, the easier it is to remove from the filter belt. On the contrary, the higher the belt speed is, the lower the solid content of the mud cake is, the thinner the mud cake is, the more difficult it will be to peel off. Therefore, the quality of mud cake, the lower the speed of the better, but the speed of the direct impact on the dewatering machine processing capacity, the lower the speed, the smaller the processing capacity. For a certain kind of sludge, there is an optimal range of speed control, in this range, the dewatering machine can not only ensure a certain processing capacity, but also get high quality mud cake, solid recovery rate is also higher. For the sludge mixed with primary sludge and activated sludge, the speed should be controlled at 2 ~ 5m/min. When the amount of mud is high, take the high belt speed, and take the low belt speed. Activated sludge in general should not be carried out with a separate type of filter press dewatering, otherwise the speed should be controlled below 1.0m/min, processing capacity is very low, very uneconomical.
No matter how much into the mud, with speed generally not more than 5m/min. Because the belt speed is too high, it will greatly shorten the gravity dehydration time, so that the sludge in the mold area can not meet the requirements of extrusion, into the low pressure zone or high pressure zone, the sludge will be squeezed out of the filter belt, resulting in the run of the material.
Control of filter belt tension
It is obvious that the tension of the filter band will affect the solid content of the cake, because the pressure and shear force applied to the sludge layer is directly determined by the tension of the filter belt. The greater the tension, the higher the solid content of the cake. For mixed sewage sludge, the general tension control in 0.3 ~ 0.7MPa, often in 0.5MPa. When the tension is too large, the sludge will be squeezed out of the filter belt in the low pressure area or high pressure zone, resulting in running, or into the filter belt caused by blockage.
In most cases, the tension of the upper and lower filter bands is equal. However, if the tension of the upper and the lower filter strips is adjusted appropriately, the tension of the lower filter belt is slightly lower than that of the upper filter belt, and sometimes the cake formation rate is obviously improved.