Low Temperature Sludge Dryer

low temperature sludge dryer product 01
low temperature sludge dryer product 01

A low-temperature sludge drying system uses heat-pump dehumidification and circulating warm air to remove moisture from dewatered sludge. The enclosed air circuit recovers heat and can reduce heat loss and odour release. Actual energy consumption and any need for ventilation or odour treatment depend on the sludge, equipment configuration and operating conditions. Condensate must be collected and its quality assessed before reuse, return to treatment or discharge; further treatment may be required.

The closed air circuit combines dehumidification with heat-pump heat recovery to reuse part of the process heat. Heat losses and electricity consumption remain, so performance should be evaluated using the selected model’s energy data under the intended feed moisture, output moisture, loading and ambient conditions.

How the low temperature sludge dryer works?

Low temperature sludge dryer uses refrigeration system to cool down and dehumidify the wet air from the drying room, while recovering the latent heat of moisture condensation to heat the drying air again, which is a combination of dehumidification (dehumidification drying) and heat pump (energy recovery), and is the recycling of energy in the drying process. The working stages of low temperature sludge drying system are mainly divided into four as follows.

  1. Preheating stage: sludge dryer just started to be dried material problem is very low, in the material and hot air contact, sludge dryer hot air first of all the temperature of the material and moisture temperature, so that it reaches the temperature of moisture vaporization. This stage is characterized by the material has zero agile increase to a certain value, the time is very short.
  2. Constant velocity stage: As the heat continues to transfer, so that the sludge dryer moisture and material surface issues continue to rise, but the surface of the moisture due to the stem of vapor pressure to the air vaporization diffusion, will make the material surface issues reduced. After the evaporation of the surface moisture, the internal moisture of the sludge dryer material will continue to flow like the surface, so that the surface remains moist, and the rate of drying will not change. This stage is characterized by the moisture has material vaporization, sludge dryer material inner layer of moisture to its surface diffusion speed is very agile, the material surface always remains moist, drying speed is unchanged and has “big value”.
  3. Reduction stage: Because the speed of water outflow inside the sludge dryer material is lower than the speed of gasification on the surface, then the surface of the material will be partly in dry form, so the amount of water gasified is reduced. The characteristics of this stage are the same as the second stage, the water is surfaceized by the material, while the wet surface is gradually reduced, and the speed of drying is in uniform landing.
  4. The material reaches the equilibrium water content or critical water content stage: As the speed of drying decreases, the central temperature of the sludge dryer material surface dry will keep rising, heat transfer to the interior, so that the evaporation surface moves to the interior, the water becomes steam and then diffuse flow to the surface. Firstly, the water content in the sludge dryer material is getting less and less, and the resistance encountered by the water flow is getting bigger and bigger, and the drying speed is landing quickly, secondly, the water contained in the sludge dryer material is balanced with the temperature of the air: that is, the water content of the material has reached the balanced water content under certain conditions, at which time the drying speed is zero, and the drying process is completely finished.

Features

  • Strong drying capacity
  • Enclosed air circulation helps reduce odour release
  • Heat-pump recovery reuses process heat
  • Lower operating costs
  • Low-temperature operation limits thermal exposure; dust controls depend on the sludge and installation

Applications

  • Municipal sludge
  • Industrial sludge
  • Printing and dyeing
  • The paper
  • electroplating
  • chemical
  • leather
  • The pharmaceutical

FAQ

There are many kinds of low temperature drying methods, such as adsorption drying, vacuum drying, cooling drying, heating drying, vacuum spray drying, etc. In general, the main feature is a method of drying objects at a lower temperature.

Low-temperature heat-pump drying can recover heat and reduce thermal exposure of the sludge. Whether it is the better option depends on sludge properties, required final moisture, energy prices, available waste heat and the project’s installation and operating costs. An enclosed process can reduce odour release, but the need for ventilation, odour control and condensate treatment must be assessed for the actual application.

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