Device and method for enhancing heat and mass transfer for superheated steam drying of sludge

Abstract

The invention relates to a device and a method for enhancing heat and mass transfer for superheated steam drying of sludge. The device enhances heat and mass transfer in a superheated steam drying process of the sludge by improving heat and mass transfer conditions between inside and outside of the sludge, is applicable to drying of sludge with high water content, and is characterized in that clockwise and anticlockwise helical blades are staggered on a single shaft by 45-degrees, an axial included angle between each clockwise helical blade and the central shaft is perpendicular to an axial included angle between each anticlockwise helical blade and the central shaft, the pitch of the clockwise helical blades is different from that of the anticlockwise helical blades, and the height of thebottom edge of each clockwise helical blade is equal to the height of the top edge of each anticlockwise helical blade. Gaps between the sludge are increased during sludge movement, sludge and superheated steam two-phase flow is improved, contact efficiency of the sludge with the superheated steam is increased, heat and mass transfer outside the sludge is improved, the sludge with different wet content is mixed, higher temperature difference and higher humidity difference are formed among the sludge, and heat and mass transfer inside the sludge is enhanced. The device has the advantages thatheat and mass transfer inside and outside the sludge in the drying process are enhanced, the drying process is accelerated, the drying quality is improved, and the drying efficiency and the energy using rate are increased.

Description

technical field [0001] The invention belongs to the field of sludge drying, and relates to a sludge drying heat and mass transfer enhancement device and method, in particular to a sludge drying heat and mass transfer enhancement device and method using superheated steam as a drying medium. Background technique [0002] With the increase of urban population, the amount of urban sewage treatment is also greatly increasing, and the output of sludge is also increasing year by year. Sludge contains a variety of harmful substances. If it cannot be treated effectively, it will cause great harm to the environment. destruction. Moreover, the untreated sludge will emit a bad smell, directly affect human health, and has carcinogenic effects. Therefore, the treatment of sludge is facing a severe situation. [0003] Sludge is a substance with high water content. The water content of sludge produced by general sewage treatment plants is above 95%, and the water content is still above 90%...

AI Technical Summary

Problems solved by technology

However, this device only increases the heating area to enhance heat exchange, and improves the utilization rate of heat energy by setting an insulating layer between the inner and outer shells, without changing the movement state of the sludge and the internal mass and heat transfer of the sludge, and the drying rate of the sludge is low.

[0009] Chinese patent CN 205138138 U discloses a spiral propulsion type continuous drying device, which uses dispersing blades and helical blades to make the materials fully contact with the drying medium during the process of breaking up and raising, and the device strengthens the breaking up of sludge To achieve the purpose of enhancing heat exchange, but it does not improve the movement state of the drying medium and the mass and heat transfer of the sludge boundary layer, and the heat of the drying medium is not fully used

[0010] Chinese patent CN 103693838 A discloses a sludge drying device and method. The device is set through a sleeve connected to two cavities, and the sludge and the drying medium are respectively spirally moved in their respective cavities to increase the amount of sludge. The heat exchange efficiency with the drying medium, but this device only prolongs the movement time between the sludge and the drying medium, and does not change the movement effect of the sludge and the heat transfer inside the sludge, and the sludge is prone to uneven heating

[0011] For the drying of sludge with high moisture content, the current drying device does not have enough two-phase flow between sludge and superheated steam, and the sludge is easy to stick together, and the contact with superheated steam is not sufficient, which affects the mass and heat transfer of the boundary layer, and adjacent The temperature difference and concentration difference between the sludge are not high, which affects the mass and heat transfer inside the sludge, resulting in poor heat and mass transfer effect of the drying medium, which not only affects the drying rate, but also affects the drying effect, and the drying degree of the dried sludge uneven

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