The function of dryer for sludge is to drying some pollutant wastes discharged from the factories. If the waste is not dried, then the discharge standards for factory will not be achieved. Therefore, the dryers for sludge is extremely important for enterprises. How does this type of dryer work? What is the drying principle? Let us to know the dryer for sludge for detail.

The principle of dryer for sludge:

The dryer for sludge uses heat pump technology to recycle the heat generated during the sludge drying process, and its energy-saving effect is ideal. In the sludge drying process, in order to drying the sludge, a dehumidification heat pump is used to heat and dehumidify air. It is a type of convective hot air drying method. The drying medium of convective hot air drying is dry and hot air, and the moisture in the material absorbs the heat in the air and then vaporizes, so as to achieve the purpose of drying.

Compared with the hot air drying mode commonly used in the past, the heat pump low-temperature drying mode is very different from the traditional mode in terms of air dehumidification and air circulation. During the low-temperature drying process of the heat pump, both of the air in the heat pump drying room and the air in the drying chamber is in a closed cycle. The originally hot and humid air in the drying room is dehumidified and cooled down under the action of the refrigeration system of the heat pump. When the hot and humid air passes through the hot evaporator, the low-pressure refrigerant will absorb the heat from the air, and then the cold air will be transferred to the condenser through the compressor, and the condensed moisture will be discharged in the form of liquid water. The low-pressure refrigeration steam is provided by the evaporator and sent to the condenser by the compressor. When the dry & cold air enters to the condenser, the high-pressure refrigerant is condensed to release heat, and then the air is heated to become dried air and enters the drying chamber afterwards. The condenser flows out of the high-pressure refrigerant, which will enter the evaporator and step down under the function of expansion valve. The aforesaid process will be continue to circulate until the sludge moisture content reaches the relevant requirements. This process increases the heat recovery cycle, which can recover the heat generated during the heating process as much as possible. Meanwhile, this process use the heat for heating and drying, so that the dehydration efficiency of this process has been significantly improved.

Drying process

The moisture content of the dried sludge is 97-98%

The sludge is send into the sealed chamber. Flocculant will be added into the sludge. The feeding screw pump has been installed. Firstly, it uses the pressure of the feeding pump to squeeze most of the free water. After the feeding process is completed, the water pump is turned on. The high pressure of the water pump is used for squeezing the mud cake in the chamber. Making sure that the filter cake is dense enough to squeeze out the water as much as possible.

After the squeeze process, the vacuum system and heating system can be started. Steam is added between the diaphragm plate and the heating plate, and air is used to heat the sludge in the chamber. At the same time, the vacuum pump is turned on and the chamber is evacuated to form a negative pressure, which reduces the boiling point of water. After the water in the sludge boils and vaporizes, a vacuum pump is used to extract the water &vapor mixture, which will be sent to the condenser where the liquid water is discharged regularly. The exhaust gas needs to be purified and should not be discharged before it meets the required standards.

After the sludge is filtered, squeezed, blown by strong air flow, and thermally dried by the vacuum, the moisture in the sludge has been removed to the greatest extent. The water content in the sludge and the amount of sludge is significantly reduced, which can meet the harmless requirement and reduction treatment of the sludge. The whole dehydration and drying process are very fast, which only last for 4h-4.5h.