Studies on high degree continuous expression of a multi-stage screw press.

1)采用螺杆式模头，由等螺距等深型螺杆和无孔圆筒组成的螺杆式模头，实现了褐煤的高度连续脱水。当使用模具时，高度压缩的蛋糕完全从压机上排出，尽管模具阻力很大。螺杆的脱水性取决于螺杆的深度、轴向长度和螺杆与模具螺旋角的差异。2)采用两种螺杆不同旋转的两级脱水系统，进一步提高了螺杆的表现力。两个螺旋角不同的蠕虫以两种不同的速度旋转。由于蠕虫的纵向速度不同，在两个蠕虫的边界点附近产生了高压分布。随着旋转比的增大，脱水率显著增加。3)根据滤饼局部水压变化的原理，得到滤饼厚度与滤液体积的关系，为滤饼平均孔隙率和平均过滤阻力的确定提供依据。根据变压条件下获得的过滤数据，近似确定了局部孔隙率和局部比过滤阻力。

Continuous solid-liquid separation for dewatering slurry to a high degree was studied in use of a screw press with two separate driving systems.1) The high degree continuous expression of Brown coal was achieved by use of a screw type die, comprised of a constant pitch-constant depth type screw and an unperforated barrel. When the die was used,the highly compressed cake was throughly discharged from the press, though the die-resistance was great. Dehydration was dependent on the thread depth, the axial length, and the difference in helical angles between worm and die.2) Further improvements of screw expression were achieved by using a two-stage deliquoring systems with different rotations of two worms. Two worms of different helical angles rotated at two different speeds. The high pressure distribution was produced in the vicinity of the boundary point of two worms due to the difference in the longitudinal velocity of worms. The deliquoring increased markedly while the rotation ratio increased. The expression performance was evaluated based on the theory of batchweise operation.3) The relation between cake thickness and filtrate volume, which serves as a basis of the determination of average void ratio and average filtration resistance, was obtained on the principle of the change in local hydraulic pressure of filter cake. On the basis of the filtration data obtained under variable pressure conditions, local porosity and local specific filtration resistance were determined approximately.