Linear low-temperature drying

Product Overview:

The low-temperature drying equipment for sludge is a processing technology that utilizes the circulating dry air within the system to provide heat energy for indirectly heating the sludge. It combines heat transfer, mass transfer, and sludge agitation to accelerate the drying efficiency of the sludge. This technology can reduce the moisture content of sludge from 80% to 85% to less than 10% as dry sludge blocks. This technology can reduce the volume of sludge by one-fourth. It only requires electricity consumption and does not need other auxiliary energy sources. The energy consumption is one-third of that of conventional electric heating or direct heating drying equipment. However, if the customer has waste steam or waste hot water above 70°C, the waste heat energy can be utilized for supplementary heating, significantly reducing the energy consumption for sludge drying. The system has no special requirements for the humidity and temperature outside, and the entire system can maintain a high operating efficiency continuously.

During the dehumidification and drying process of this product, there is no emission of any waste gas. At the same time, the latent heat and sensible heat of water vapor are recovered, and the recovered heat is reused to supplement the heat required for sludge drying heating. Therefore, it can significantly reduce the energy consumption for sludge drying.

Process Principle:

The sludge dehumidification and drying machine utilizes a dehumidification heat pump to conduct heat circulation and condensation dehumidification and drying of the sludge:

1. Dehumidification drying recovers the latent heat of water vapor and the sensible heat of the air in the exhaust air. During the dehumidification drying process, there is no waste heat emission. In traditional sludge thermal drying systems, 90% of the heat supplied is converted into the latent heat of water vapor and the sensible heat of the hot air lost through the exhaust air.

2. Dehumidification drying consists of two major parts: the conveyor belt and the heat source equipment section.

3. The heat pump drying unit adopts the reverse Carnot cycle principle. It uses a small amount of electricity to drive the compressor to do work, thereby cooling and reducing the water vapor in the indoor air through the evaporator to condense into water and discharging it outside. Then, it raises the temperature through the condenser, and the warmed air, due to its unsaturation, can continue to absorb the moisture from the materials, ultimately achieving the desired dry state of the materials.

4. The normal operation of the drying room and the heat source equipment is achieved through the independently developed micro-computer automatic control system. It can intelligently control the start and stop times of the unit according to the actual process requirements of the drying room, and control the temperature inside the drying room and other aspects, thereby improving the drying quality while saving time, effort and effort.

Process Flow:

The sludge is transported by a pump to the metering tank. The sludge that has been metered is then sent to the coagulation tank where it undergoes a full flow process and is subsequently mixed with the coagulant through stirring to form stable flocs. These flocs are then sent to the dewatering unit. The flocs undergo gravity concentration in the concentration section while advancing towards the dewatering section. The gap between the moving ring and the fixed ring in the dewatering section gradually narrows, and a back pressure plate is present at the sludge cake discharge outlet, creating a forward resistance to ensure that the sludge is fully dewatered in the dewatering section and is discharged in the form of a sludge cake.

Main features: 

Energy conservation

By adopting the heat pump heat recovery technology, in the closed system drying mode, there is no any waste heat emission. For every ton of 80% wet sludge, it is dried to 20%, with a total electricity consumption of 195 kwh; for every 1 kWh of electricity, 30 kilograms of water can be removed. The dehumidification performance ratio is 1:30 kg.H2O/kw.h; for every ton of 80% wet sludge, it is dried to 60%, with a total electricity consumption of 125 kw.h. 

Safety

The low-temperature drying process at temperatures below 80°C is highly suitable for the operation of sludge drying systems in municipal, dyeing, and papermaking industries. It is safe without any explosion risks and does not require nitrogen flushing. The oxygen content during the sludge drying process is less than 12%; the dust concentration is less than 60 gm³ per cubic meter; the particle temperature is less than 70°C; there is no "gluey phase" stage in the urban sludge drying process (about 60%); the dried material is in a granular form, without dust hazards; the discharge temperature is low (<50°C), no cooling is required, and it can be directly stored. 

Environmental protection

Adopting a low-temperature (40-75°C fully enclosed drying mode, without any odor emission outside, and no need for specialized and complex odor removal devices; using the low-temperature drying process, the amount of H2S and NH3 released is significantly reduced; the condensate water is mixed with the moisture) system (or directly discharged), saves the cost of treating condensate water during the drying process. 

High efficiency

During the drying process, there is no loss of organic matter, and the dry material has a high calorific value, making it suitable for later resource utilization; the capacity reduction is 67%, the weight reduction is 80%, which can save a large amount of transportation costs later; it can be suitable for drying sludge with moisture contents ranging from 83% to 50%.

Stability

The sterilization is carried out by the Pasteur pasteurization method, which involves low-temperature heating. The sterilization temperature can be above 70°C and the duration can reach 90 minutes to 120 minutes. This method can effectively kill more than 96% of the microorganisms. 

Negative pressure operation

When the fan side of the unit is on the drying line side, the interior of the box is in a negative pressure state. This prevents the leakage of gas inside the box.

Free adjustable temperature setting

The drying time and drying temperature can be freely set. The outlet temperature of the unit can be freely adjusted within the range of 65°C to 80°C, ensuring the quality of drying.

Intelligence

Fully automatic operation, saving a significant amount of labor costs; the moisture content of the discharged material can be adjusted arbitrarily (from 10% to 50%). Durable

The equipment is made of corrosion-resistant materials such as stainless steel, and the heat exchangers are treated with electroplating anti-corrosion treatment, ensuring a long service life. 

Innovative technology

Overcomes the technical bottleneck of high-temperature performance in pump drying technology, with superior high-temperature performance, solving the problems of frost formation and poor high-temperature performance in air-source heat pump drying machines during winter;

Breaks through the technical bottlenecks of traditional dehumidifiers and ordinary heat pump dehumidification drying machines;

Solves the technical problem of poor dehumidification performance of traditional dehumidification equipment under high-temperature and low-humidity conditions, even with the compressor running but not dehumidifying;

According to different moisture contents of sludge cakes, different molding technologies can be adopted to reduce the drying time of sludge cakes and provide the comprehensive energy efficiency of the drying system.

Sludge Drying System (Linear Type) Selection Parameters