Dual utilization device and method for exhaust steam waste heat produced during superheat steam drying of sludge

Abstract

The invention relates to a dual utilization device and method for exhaust steam waste heat produced during superheat steam drying of sludge The device comprises a shaftless screw feeder, air valves, a heater, a double-shaft stirring dryer, a sludge particle forming machine, a net belt dryer, a tail gas washing tower, cyclone separators (A and B), fans (A and B) and a heat exchanger, wherein the shaftless screw feeder, the double-shaft stirring dryer, the sludge particle forming machine and the net belt dryer are sequentially connected, and a material channel is formed; the heater, the double-shaft stirring dryer, the cycle separator A, the fan A and the air valve B are sequentially connected to form an internal circulation air channel; the shaftless screw feeder, the cyclone separator B, the heat exchanger and the tail gas washing tower are sequentially connected to form an external air channel; the heat exchanger, the fans and the net belt dryer are combined for drying. The device and the method have the advantages that dual utilization of exhaust steam waste heat is realized, the device and the method are efficient and energy-saving, and condensation can be effectively prevented; zero-pollution discharge of waste water and waste gas is realized; formed sludge can be used for preparing fertilizers, and reutilization of the sludge 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 CN1686876A 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 used for heating. The sludge is dried, 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 CN102260033A and CN102276131A 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. 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, which in turn affects sludge reuse

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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