SU1225820A1 - Method of automatic control for process of dehydration - Google Patents

Description

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The invention relates to wastewater treatment, in particular to the dewatering of sewage sludge by centrifugation.

The drawing shows a diagram of the device that implements the proposed method.

The device contains a centrifuge 1, a mixer tank 2, a return pipe 3 for the dried sludge, a return control valve 4, a reagent supply valve 5, a sediment supply pump 6

ka, pump 7 for supplying dewatered sludge (cake), flow meter 8 of initial sludge, flow meter 9 sludge, flow meter 10 returning dewatered sludge, meter 11 concentration of solids in the sediment, meter 12 composition of centrate, multiplier 13, unit 14 comparison, unit 15 quantity of solids phase and control 16 return dehydrated sludge, block 17 comparison, regulator 18 of the reagent, the flow meter 19 reagent, block 20 of the comparison, the adder 21, block 22 of the comparison, the controller 23 of the pump capacity of the sludge.

The method is carried out as follows.

Pre-set the minimum possible value of the difference in the speeds of rotation of the drum and the screw, providing the optimum degree of dewatering. This value is kept constant during the whole cycle of operation of the centrifuge 1. Then, based on the requirement of the operation of the plant at rated capacity, the initial mode of operation is set. With the return of dehydrated sludge. In the event that the signal at the output of the inhabitant 13 is greater than the specified value, valve 4 is closed and there is no return of the dehydrated sludge. When this signal becomes less than a predetermined value, valve 4 opens and begins returning the dehydrated sludge to the inlet. The dehydrated enters through conduit 3: the return of the dehydrated sludge under the action of pressure generated by pumping cake 7 to the mixer tank 2. where it mixes with the original sludge and with the pump

15 6 served on dehydration. This control loop processes the existing mismatch in the load, keeping it at a nominal level. The second loop serves to control the supply of the reagent by the content of suspended substances in the centrate, which is determined using meter 12 (turbidity meter). Comparison of the measured value with the specified value of the fugate quality is carried out in comparison unit 17; in case of a mismatch, the position of the reagent supply valve 5 is changed by means of the regulator 18. At the same time, the flow meter 19 measures the reagent consumption and compares in block 20 comparison with the allowable value of Qp. When the reagent consumption exceeds the QP, the flow of dewatered sludge is reduced by decreasing the set point of the unit 15 for setting the amount of solid phase.

In order to ensure the required liquid capacity, the flow of sediment to the centrifuge 1 is controlled.

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the power of the setting device 15 installs the sign- 40 of this with the help of flow meters 8 and 10

The amount of solids fed to the centrifuge is set by the allowable consumption of reagent Qp.

In the course of operation, control is carried out using two circuits. In the first control loop of the flow meter 9, the flow rate of the precipitate after the mixer is measured, and with the aid of the meter 11, the concentration of the solid phase in the sediment. At the entrance to the centrifuge. These values are fed to a multiplier 13, in which the amount of solids in the sediment is determined. The signal from the output of the multiplier 13 is compared in the comparison block 14 with a predetermined value and is fed to the regulator 16, which controls the control valve 4 to return, installed in the pipeline 3

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return dehydrated sludge. If the signal at the output of the inhabitant 13 is greater than the specified value, the valve 4 is closed and there is no return of the dehydrated sediment. When this signal becomes less than a predetermined value, valve 4 opens and the return of the dehydrated sludge to the inlet begins. Dehydrated enters the pipeline 3: return dehydrated sludge under the action of the pressure generated by pump 7 pumping cake into the tank mixer 2 ,,. where it mixes with the original sludge and with the pump

15 6 served on dehydration. This control loop processes the existing mismatch in the load, keeping it at a nominal level. The second circuit serves to control the supply of reagent on the content of suspended substances in the centrate, which is determined using a meter 12 (turbidity meter). Comparison of the measured value with the target value of the centrate quality is carried out in comparison unit 17, in case of a mismatch with the help of the regulator 18, the position of the reagent supply valve 5 is changed. At the same time, the flow meter 19 measures the consumption of the reagent and compares in block 20 comparison with the permissible value of Qp. When the reagent consumption exceeds QP, the flow of dewatered sludge is reduced by decreasing the set point of the unit 15 for setting the amount of solid phase.

In order to provide the required liquid capacity, the flow of sediment to the centrifuge 1 is controlled.

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the flow rates of the raw and returned precipitated precipitates are determined by means of the adder 21, the required capacity of the sludge feed pump 6, compared with the sludge flow rate in the comparator unit 22 and the magnitude of the error in the slug supply pump regulator 23 adjusts the output to the required the amount

P r and m er. For a rotary centrifuge with a rotor diameter of 350 mm, in order to ensure the efficiency of sediment retention of dry matter, 96% of the solid phase applied to the centrifuge must be equal to the product of the centrifuge Q capacity of 3.0 m / s by the concentration of solids

the phases at its input C, 3.8%, i.e. 11, A kg / s. This value is set using the setting device 15, while the dose of the reagent (flocculant) should be Other 3.1 kg / t. When the concentration of the solid phase decreases by

1225820

the centrifuge inlet 1.5 times from the output of the device to the inlet of the device begins to deliver a part of the dewatered sludge at a rate of 0, 15, the dose of reagent e becomes equal to 3.2. kg / t. The economy of the reagent is 0.9 kg / ton.

Oagyazh

Claims (2)

1. METHOD FOR AUTOMATIC CONTROL OF THE WASTE WASTE DEWATERING CENTRIFUGATION BY CENTRIFUGATION, including Measurement of sludge flow rate and solid phase concentration at the inlet of the centrifuge, maintaining its constant value and adjusting the reagent flow rate according to the quality of the centrate, characterized in that, in order to reduce dewatering costs due to reagent saving, additionally part of the dehydrated sludge is fed from the centrifuge at the inlet, the amount of solid is determined from the current values of sludge flow rate and solid phase concentration phase in the sludge, depending on which the flow rate of part of the dehydrated sludge is adjusted with correction according to the amount of reagent flow. 2. The method according to claim 1, with the fact that in addition <d measure the flow rate of part of the dehydrated sludge and the flow rate of the initial sludge and maintain the flow rate of sludge at the inlet of the centrifuge equal to the sum of the measured flow rates. SU „1225820