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Address: Lixing Industrial Park, Xueguan road, Zhucheng.
Phone：0536－6557999 （marketing）
0536－6557998 (after-sale)
0536－6557996 （fax）
Mobile：13721950199
Website：http//www.zcqj.com
Network real name：Zhucheng Light Machine
E-mail：zcqjwhf@126.com
Operator：Wang Huanfan |
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| Comparisons of belt filter press machine and centrifugal machine on theory |
1. Because belt machine is the most popular set in water treatment companies, so we take it as the competitor of centrifugal machine. Centrifugal machine has the following advantages:
①Spiral centrifugal machine takes advantage of centrifugal settling theory to separate solid and liquid. Blockage can be avoided because of no filter screen. Otherwise, belt machine uses filter screen, and it needs high pressure washing constantly to prevent blockage;
②Centrifugal machine is proper for thickening and dewatering of all kinds of sludge as same as the belt machine. But belt machine needs large quantity of medicine to treat active sludge, and it is very difficult.
③It’s not necessary to let some one operate because slip of rotor and torque of spire can be adjusted automatically when the sludge consistency changes in the centrifugal machine’s dewatering process. Otherwise, there is a high operating demand for belt machine, because when the sludge consistency changes, belt speed, intension, medicine quantity and water pressure need adjustment.
④Flocculants quantity is very small, because even tiny sludge can be separated from water in the centrifugal machine. The general medicine quantity of fixed sludge dewatering is 1.2kg／t (dry sludge). Recovery rate of sludge is above 95%. Filter mass water ratio after dewatering is about 65％－75％. To treat the tiny sludge, large quantity of flocculants is needed. The general medicine quantity of fixed sludge dewatering is 3kg/L (dry sludge). Recovery rate of sludge is about 90%. Filter mass water ratio after dewatering is about 80％.
⑤Electric power consumption for each cubic meter of centrifugal machine is 1.2kw／m3.Running noise is 76－80db. It has 24h running ability, and don’t need washing when it running. But Electric power consumption for each cubic meter of belt machine is 0.8kw／m3. Running noise is 70－75db. It can’t works for 24hours. The filter fabric needs cleaning, maintenance and washing.
⑥Centrifugal machine use little space, and it is easy to adjust. Coordinated sets are only conveyer of medicine and conveyers for sludge entering and exiting. Plants’ environment is good because of its sealed operating; Otherwise, belt machine needs lots of space, and its coordinated sets also includes washing pump, air compressor, and sludge mixer. It has bad tightness. Environment is bad. Sludge maybe overflow because of bad management.
⑦Wearing parts of centrifugal machine are axle and sealing element. Spire’s repairing period is above 3a; Otherwise, for belt machine, besides axle and sealing element, belt needs replacement and it is expensive.
⑧Running cost count. The following way is used when comparing centrifugal machine and belt machine on running cost:
Assumption:
Belt machine: medicine quantity: 4kg/t (dry sludge), single machine electric power consumption: 0.8kw/m3 sludge, washing water: sludge: 1:1; centrifugal machine: medicine quantity: 3kg/t (dry sludge), single machine electric power consumption: 1.2kw/m3 sludge, washing water: 0, electric power cost: 0.5 yuan/kw, water fee: 0.5yuan/m3, medicine fee: 80yuan/kg.
Take an 8×104t/d sewage treatment company as an example: dry sludge quantity: 10t/d. sludge rate after thickening: 3%. Slurry: 333m3/d. sludge rate after dewatering>20%. The result:
Belt sludge filter press machine: medicine cost: 3200元/d, electric power cost: 133.2元/d；water fee:166.6yuan/d；daily running cost: ∑=3200+1332+166.6＝3499.8元／d。
Spiral centrifugal machine: medicine cost: 2400元/d, electric power cost: 199.8元/d；water fee:0yuan/d；daily running cost:∑=2599.8元／d。
Running cost balance: 900yuan／d，1a takes 360d, △=900yuan／d×360d=324000yuan. Belt machine’s running cost is 324000yuan more than centrifugal machine.
Through the above analysis, centrifugal machine companies make the following conclusion: on theory, centrifugal machine is proper than belt machine on sludge dewatering; centrifugal machine is suggested because it is efficient, needs little medicine, and has low running cost.
2.Analysis of real state of centrifugal machine and belt machine.
I made a research on the above advantages of centrifugal machine, according to my designing experience and customer research. Now let me analyze separately:
Item ①and ⑥ are true. I have my own opinion on the other items.
3.Scope of application
Centrifugal machine is not proper for all sludge. It is not proper for sludge which contains mineral composition like fly ash. Fly ash stays on the inner wall of centrifugal machine, and hard to be removed. As the result, the sludge can not get out. It happened in a company located on the north of our country. Centrifugal machine can’t work, so it is replace by belt machine, and the company suffered huge losses.
4.control of sludge entering
Item ③: Slip of barrate and torque of spire can be adjusted automatically while belt machine need someone to adjust. In fact, intension change has bigger affect on centrifugal machine than belt machine.
5.Item④: it’s a truce that recovery rate of sludge of centrifugal machine is higher than belt machine’s. But that doesn’t mean belt machine is not useful, because it will be retreated.
Medicine quantity is controversial. Belt machine companies will say belt machine also needs little medicine. A 15×104t/d city sewage treatment factory uses a spiral centrifugal machine which the medicine quantity is 1.7－2.0kg. Some materials all show that a shanghai sewage treatment company made a test on belt machine. Medicine quantity is also about 20kg. It is really hard to indicate difference between them because of the different sludge character.
6.Electric power consumption
In fact, centrifugal machine’s electric power consumption is more than belt machine.
Noise of centrifugal machine is harsh, while belt machine is even better, because it’s washing noise; it also can run for 24hours, but it is not as reliable as the centrifugal machine.
7.life span of machines
Item⑦: Axle’s life span of a high quality belt machine is more than 20a. It’s same to the main engine. The filter belt needs replacement. It can work for 2000h continuously. If it works discontinuously, it also needs replacement for every 2－3a. Cost of belt replacement is not too many, because whether the belt machine is imported or not, the belt can be replaced by domestic belt. On the other side, if the spire needs replacement, an imported one is necessary because the technology distance of spiral centrifugal machine is too big. So it’s very difficult and the cost is too high.
8.running cost count
There’re many problems in the count way of running cost of the two kinds of machine. Running cost includes: medicine cost, electric power cost and water fee. At first, water fee should be excluded, because the water it used is free. Second, which machine uses more medicine is controversial. I take a sewage treatment factory as an example to count the real running cost. The result:
Dry sludge quantity: 10t/d，solid sludge rate before thickening:0.8％。hypothetical electric power cost: 0.5yuan／kw，medicine fee: 60yuan／kg.
Running cost balance: （1938 －143）kwh×0.5yuan／kwh＝897.5yuan
According to the manufacturer, and the present PAM price is 60yuan/kg, so belt machine costs more medicine like the following: 10t／d×1kg／t＝10kg/d, and the cost is 10×60=600yuan. If belt machine costs more medicine than centrifugal machine, generally speaking, belt machine also cost less money than centrifugal machine: 897.5－600＝297.5yuan/day, it’s about one hundred thousand Yuan a year. In fact, there’s no doubt on centrifugal machine’s electric power consumption while belt machine’s electric power consumption is controversial. If medicine cost of these two machines is same, centrifugal machine would cost 897.5yuan more than belt machine. The result is that centrifugal machine costs 330000yuan more than belt machine.
So according to running cost, centrifugal machine doesn’t cost less money than belt machine.
9. Investment
Price of imported high grade belt machine is about $200000. Homemade one is cheaper. The above centrifugal machine costs about $300000. There’re some differences because of grade or other reasons. Generally, centrifugal machine is more expensive than belt machine on the same grade. But centrifugal machine needs less space, and some money can be saved, so the total cost of these two kinds of machine is very familiar.
10. Conclusion
We can make the following conclusion: advantages of centrifugal machine: sludge is dry and has sealed working environment. It doesn’t need washing. Advantages of belt machine: save electric power and has less noise. So we should refer to the real condition to decide which one is better.
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