Comparison between Decanter Centrifuge and Belt Filter Press

1 The theoretical comparison of belt machine and centrifuge

Since the belt machine used to be the mainstream of sludge dewatering in the sewage treatment plant, the advantages of the centrifuge are shown in the treatment effect and compared with the belt machine. The centrifuge has the following advantages for the belt machine:

A decanter centrifuge uses the principle of centrifugal sedimentation to separate solids and liquids. Because there is a strainer in the system, it will not cause plugging, and the machine will use a filter belt to separate solids and liquids. To prevent the plugging of the filter belt, high-pressure water is needed to continuously flush it;

2 Centrifuge is suitable for the concentration and dewatering of various types of sludge, and it also applies to all types of sludge with the machine, but the remaining activated sludge requires a large amount of dosage and is difficult to dewater;

3 When the concentration of feed is changed in the dehydration process of the centrifuge, the rotation and torque of the rotating drum and screw will be automatically tracked and adjusted. Therefore, no special operation is required, and the belt filter will change the feed concentration when the feeding process changes. The speed, belt tension, dosage, and flushing water pressure all need to be adjusted and the operating requirements are high;

4 In the centrifuge, fine sludge can also be separated from water, so the dosage of flocculant is less, and the dosage of general mixed sludge when dewatering is: 1.2kg/t [dry sludge], sludge recovery The rate is above 95%, and the water content of the cake after dewatering is about 65% to 75%. The filter belt cannot be too dense due to the filter belt. To prevent the fine sludge from leaking, more flocculants are required. In order to make the sludge form a large floc, the dosage of the general mixed sludge when dewatering is more than 3kg/L [dry mud], the sludge recovery rate is about 90%, and the water content of the mud cake after dehydration is about 80%;

5 The dewatering power of the sludge per cubic meter of sludge is 1.2kw/m3, and the noise during operation is 76-80db. The continuous operation is 24 hours a day and the machine is shut down for shutdown. No washing water is required during the operation, and the sludge is dewatered per cubic meter of sludge. The power consumption is 0.8kw/m3, the noise during operation is 70-75db, and the filter cloth needs to be slackened and maintained. Generally, only two shift operations are arranged every day, and the filter cloth is constantly washed with high-pressure water during the operation.

6 Centrifuge has a small footprint, simple installation and commissioning, supporting equipment is only dosing and in and out of the material conveyor, the whole machine fully sealed operation, the workshop environment is good; while the belt machine covers an area of ​​large, supporting equipment in addition to dosing and in and out of material delivery Outside the machine, it is necessary to flush the pump, air compressor, sludge conditioner, etc. The whole machine is poorly sealed, and the high pressure cleaning mist and odor pollute the environment. If the management is not good, it will cause overflow of mud;

7 The consumable parts of the centrifuge are bearings and seals. The maintenance cycle of the discharge spiral is generally more than 3a. In addition to bearings and seals, the filter belts need to be replaced, which is expensive;

2 Analysis of the actual use of the belt machine and centrifuge:

8 Calculation of operating expenses. Centrifuge manufacturers use the following algorithm when comparing the dewatering costs of centrifugal dewatering and belt filter presses:

example:

With a machine dosage of 4kg/(t[dry mud]), the single processing power consumption is 0.8kW/m3 slurry, the flushing water: sludge slurry is 1:1; the centrifuge dosage is 3kg/(t[dry mud] ]) Calculated, stand-alone processing power consumption to 1.2kw/m3 slurry, flushing water to 0, electricity costs 0.5 yuan / kw, water charges 0.5 yuan / m3, drug costs 80 yuan / kg.

Take an 8×104t/d sewage treatment plant as an example, the dry sludge volume is 10t/d, the solid content in the inflow mud is 3% (concentrated sludge), the mud volume is 333m3/d, and the dewatered sludge contains solids. Rate> 20%. Calculated:

Belt filter press: the drug fee is 3200 yuan/d; the electricity fee is 133. 2 yuan/d; the water fee is 166.6 yuan/d. The daily operating cost of the machine is ∑=3200+1332+166.6=3499.8 yuan/d.

Decanter centrifuges: drug costs 2400 yuan / d; electricity costs 199.8 yuan / d; water fee is 0 yuan / d; the centrifuge's daily operating cost is 259 = 2599.8 yuan / d.

The operating fee difference: 900 yuan / d, 1a 360d, â–³ = 900 yuan / d 360d = 324000 yuan. That is, the 1a operating fee is 32.24 million yuan more than the centrifuge.

Therefore, based on the above analysis, the centrifuge manufacturer concludes that the principle of sludge dewatering is more appropriate than that of the belt machine; the centrifuge has lower flocculation requirements than sludge because of high separation efficiency. Low drug consumption, low operating costs and good dehydration yield.