Screw Press Sludge Dewatering Machine AS-NH 404/SC Series Technical Manual

The schematic diagram above shows the main body of the screw press, which consists of fixed rings and moving rings overlapping each other, The front section is for concentration and filtration, while the resection is for extruding the sludge. A screw shaft runs through it, driving the moving rings in the ringpieces to rotate, thus achieving gradual dehydration. The gap along the screw shaft progressively decreases, thereby continuously increasing the pressure within, ultimately ensuring thorough dehydration. This process aims to reduce the moisture content of the sludge. The rotation and pressing of the ring pieces also serve to clean the rings during operation.

3.1 Equipment Data

6.1 Sludge Pump Selection

The sludge pump continuously transfers sludge from the sludge pool to the dewatering machine without the need for a high-pressure pump. The sludge transfer rate per unit time is calculated based on the maximum processing capacity of the dewatering machine for dry sludge and the actual concentration of the sludge.

Suppose the model is EA-404 with a maximum dry sludge processing capacity of 800 [kg-DS/h] and a sludge concentration of 10,000 [mg/L] (the sludge concentration determines the selection of the sludge pump and should be accurately measured).

Sludge transfer pump capacity = 800 [kg-DS/h] × 1000 [g/kg] ÷ (10,000 [mg/L] ÷ 1000 [mg/g]) = 80 m³/h.

A submersible sewage pump with a capacity of ≤80 cubic meters per hour (with adjustable function) can be chosen. It is advisable to set the height of the sludge dewatering machine higher than the sludge pool to minimize the excess sludge flowing back to the sludge pool due to excessive pump flow. It is recommended to install a valve on the sludge transfer pipe to allow excess sludge to quickly return to the sludge pool.

6.2 Dosing Pump (Metering Pump) Selection

The dosing pump is used to transport the polymer flocculant solution to the flocculation mixing tank of the dewatering machine. The additional amount of polymer flocculant can be calculated based on the dry sludge processing capacity of the dewatering machine, flocculant addition rate, and dilution ratio. The flocculant addition rate is related to the properties of the sludge and the type of flocculant; the ideal floc diameter is 5mm. The dilution ratio can also be adjusted according to actual conditions.

Suppose the model is EA-404 with a capacity of 900 [kg-DS/h], a powder polymer coagulant addition rate of [0.6%], and a dilution ratio of 1000 times. Polymer flocculant pump capacity = 900 [kg-DS/h] × 0.6% × 1000 × 1000 [g/kg] ÷ 60 [min/h] = [50 liters/minute]. It is recommended to choose a 50L/min metering pump

6.3 Dosing System

1. Automatic Dosing Machine (1 set)

Features: Automatically add water and chemicals as long as a sufficient amount of dry flocculant is prepared. The dosing amount is relatively stable, although the equipment is expensive

2. Manual Dosing Barrel (1 set)

Features: Mainly consists of a mixer and a dosing barrel, but it is not easy to operate the equipment unattended for long periods. It can also lead to unstable concentration configurations, causing waste.

The above calculation data is for reference only and should not be used as actual operational data; actual site data should be calculated based on the site conditions.