A device and method for double utilization of exhaust steam and waste heat of sludge superheated steam drying

Abstract

The invention relates to a device and method for dual utilization of waste steam and waste heat of superheated steam drying of sludge, including a shaftless screw feeder, an air valve, a heater, a biaxial stirring dryer, a sludge particle forming machine, a mesh belt dryer, Tail gas scrubber, cyclones (A, B), fans (A, B) and heat exchangers. Shaftless screw feeder, double-shaft stirring dryer, sludge granule forming machine, and mesh belt dryer are connected in sequence to form a logistics channel; heater, double-shaft stirring dryer, cyclone separator A, fan A, and air valve B are sequentially connected. The connection forms an internal circulation air flow channel; the shaftless screw feeder, cyclone separator B, heat exchanger, and tail gas scrubber are sequentially connected to form an external air flow channel; the heat exchanger, fan, and mesh belt dryer form a combined drying. The invention has the beneficial effects of realizing dual utilization of waste steam and waste heat, high efficiency and energy saving, and effective prevention of condensation; zero-pollution discharge of waste water and waste gas; sludge is used to make fertilizer after forming, and sludge reuse is realized.

Description

technical field [0001] The invention relates to a sludge drying device and method, in particular to a device and method that uses superheated steam as a drying medium and double utilization of waste heat. Background technique [0002] With the improvement of China's urbanization level, the amount of urban sewage treatment is increasing, and the amount of sludge that needs to be safely treated is increasing day by day. As of the end of March 2014, a total of 3,622 sewage treatment plants have been built in cities and towns in my country, with a sewage treatment capacity of about 153 million m 3 / d, the output of sludge with 80% water content has exceeded 30 million tons; in 2015, the total annual output of sludge (80% water content) in my country will reach 33.59 million tons; it is estimated that by 2018, the sludge with 80% water content will Sludge production will further exceed 40 million tons (Ruan Chenmin. Directional thinking on the development of my country's sludge t...

AI Technical Summary

Problems solved by technology

However, the steam generated by the first-stage paddle dryer is simply used for sludge incineration after treatment but cannot be used for other drying processes and the sludge cannot be reused

[0007] Chinese patent CN 1686876 A discloses a superheated steam drying method for sludge and its drying device. The tail gas produced by sludge drying is used to exchange heat with liquid substances such as water or freon, methanol, etc., and the water after heat exchange is heated. It is used for sludge drying, and the tail gas after heat exchange becomes a saturated soda-water mixture with a temperature of about 100°C. It wastes a lot of energy to treat the high-temperature saturated soda-water mixture and discharge it directly

However, the device does not reuse the tail gas produced in the pre-drying process, nor recover the sensible heat of the condensed water

[0009] Chinese patents CN 102260033 A and CN 102276131 A also disclose a sludge secondary steam compression drying method. During the drying process, sludge and oil are mixed in proportion, and the grade is improved by compressing the secondary steam. There is non-condensable gas and affected by the efficiency of the compressor, the energy loss in the entire compression process is large, resulting in high energy consumption; the oil and sludge are mixed in the drying process, although the two are separated after drying, it is difficult to completely separate the two , thus affecting the reuse of sludge

As the number of stages increases, the drying system becomes more and more complex, and the investment cost of equipment increases. The larger the number of stages, the smaller the temperature difference and the worse the drying effect. The use of pressure superheated steam has higher requirements for system safety.

[0011] Existing methods and devices for utilizing waste heat from sludge superheated steam are difficult to fully recover and utilize waste heat from waste steam. The method of improving the grade of waste steam through steam compression is greatly affected by external factors such as compressor efficiency and purity of waste steam, and the overall thermal efficiency is not high.

In addition, most of the dried sludge is treated by traditional sludge treatment methods, and it is difficult to reuse the sludge

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