Sludge drying machine uses closed cooling tower

After water purification, wastewater and sewage will produce a large amount of sludge with a water content of about 99%. After dehydration by conventional sludge dehydration equipment, it becomes sludge with a water content of about 80-85%. With the increase in sewage treatment volume, the annual sludge output has also increased rapidly. According to the survey results, nearly 80% of the sludge produced by wastewater treatment stations and sewage treatment plants has not been properly reduced and resourced. How to reduce and resource sludge with huge output and complex components has become an urgent problem to be solved. Further drying of sludge is a very feasible method for sludge reduction. This type of pre-dehydrated sludge can be further dried by conventional drying equipment to achieve the purpose of reducing and facilitating transportation. However, today's sludge drying equipment generally has the problems of high energy consumption and low energy utilization. Further drying of this type of pre-dehydrated sludge without generating secondary waste gas pollution and how to efficiently reduce energy consumption are technical problems in the field of environmental protection.

At present, for the method of further drying sludge with a moisture content of 80-85%, the sludge drying process equipment used more at home and abroad is mainly thermal drying technology, including fluidized bed drying, belt drying, horizontal rotary drying, paddle drying, vertical disc drying, spray drying and other process equipment. Drying technology and equipment need to be selected in combination with the requirements of different sludge treatment and disposal projects while comprehensively considering the technical maturity and investment and operation costs. At the same time, the dust and odor emissions generated during the sludge drying process need to be additionally treated with additional facilities for prevention and control. The sludge drying equipment commonly used in the market currently has high energy consumption and generally needs to be used under the condition of waste heat source heating. If common energy sources (such as natural gas, coal, steam, etc.) are used directly, the processing cost is extremely high and it is difficult to maintain normal operation. However, most sewage treatment plants have no waste heat source and lack heat that can be directly recycled. If conventional thermal drying technology is used, a large amount of funds will be invested in the construction of heat sources and energy consumption, and the cost performance is too low. In addition, the existing sludge drying technology mostly uses single-performance equipment to implement drying treatment. When drying the sludge, there will inevitably be dust and odor emissions. If no additional treatment and prevention facilities are added, it will inevitably cause secondary pollution to the environment.

The heat pump low-temperature sludge drying treatment system uses a heat pump unit as the heat source for drying sludge. No fuel is consumed during the drying process, which can save transportation and storage fuel costs while avoiding fuel pollution to the environment. In addition, due to the high energy efficiency ratio of the heat pump unit, it can reduce energy consumption by more than 30%, saving electricity while having good safety performance. The closed cooling tower is mainly used in the refrigeration cycle in the heat pump low-temperature drying system. The closed cooling tower prevents the condensed water from direct contact with the fungi and algae in the sewage. At the same time, the water evaporation and sewage discharge are less than one-third of the open cooling system, making it the preferred equipment for energy saving and environmental protection. For water cooling in heat pump low-temperature sludge drying system, the general water flow rate is determined by the following rules: Common formulas for determining the circulating water volume of cooling towers based on other known conditions:

1.Cooling water volume = host cooling capacity (KW) × 1.2 × 1.25 × 861/5000 (m3/h)

2.Cooling water volume = host condenser heat load (kcal/h) × 1.2/5000 (m3/h)

3.Cooling water volume = host condenser heat load (m3/h) × 1.2 (m3/h)

4.Cooling water volume = host cooling capacity (refrigeration tons) × 0.8 (m3/h)

5.Cooling water volume = host evaporator heat load (kcal/h) × 1.5 × 1.25/5000 (m3/h)

6.Cooling water volume = host evaporator heat load (m3/h) × 1.2 × 1.25 (m3/h)

7.Cooling water volume = main unit evaporator heat load (refrigeration tons) × 1.2 × 1.25 × 3024/5000 (m3/h) Note: In the above: 1.2 is the selection margin and 1.25 is the condenser load factor.