Method for utilizing fume afterheat of cement plant to heat-dry sludge and prepare cement by firing sludge

Abstract

The invention discloses a method for utilizing fume afterheat of a cement plant to heat-dry sludge and prepares cement by firing sludge. The method comprises the following steps of: respectively sending the fume afterheat discharged by a cement rotary kiln to a first sludge drying and granulating device and a second sludge drying and granulating device, for purpose of two-stage sludge drying; 2) stacking urban sludge in a sludge storage warehouse and carrying out pretreatment prior to the drying; 3) using a component-type feeder to send the pretreated sludge into the first sludge drying and granulating device, for purpose of first-stage sludge drying; 4) using a conveyor to send the sludge after the first-stage sludge drying into the second sludge drying and granulating device, for purpose of second-stage sludge drying; and 5) mixing the sludge subject to two-stage sludge drying with clay and lime material to form raw material, and obtaining the cement by grinding, calcining, cooling and powdering the raw material. In the method, waster materials are used for treating waster materials, so that the urban sludge is harmlessly treated and recycled, and remarkable social and environmental effects can be generated.

Description

technical field [0001] The invention relates to a method for drying sludge by utilizing waste heat of flue gas in a cement plant and firing the sludge into cement. Background technique [0002] According to the "Eleventh Five-Year Plan" of the national environmental protection and the "Eleventh Five-Year Plan" for the construction of urban sewage treatment and recycling facilities nationwide, all cities in my country must build sewage treatment facilities by 2010, and the urban sewage treatment rate should not be lower than 70%. It is estimated that the national urban sewage treatment capacity will exceed 100 million tons per day, and at the same time, it can be expected that the accompanying sludge (with a moisture content of about 80%) will be as high as 30 million tons per year, plus the dredging sludge of polluted rivers and lakes and urban sewer sludge etc., the amount of municipal sludge produced every year is not only very large, but also increases at a growth rate of 1...

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Problems solved by technology

[0004] At present, my country mainly adopts temporary landfill disposal method for urban sewage treatment plant sludge and river and lake dredging sludge, which not only costs a lot of money and occupies a lot of land resources, but also causes serious secondary pollution to the ecological environment, especially The sewage in the sludge seeps down, and the damage to groundwater resources is even more unpredictable. In fact, there is no space and place suitable for stacking this kind of sludge around the city. Pollution hazards that effectively negate the environmental benefits of sewage treatment and river dredging

Faced with the fact that the environmental problems caused by sludge are becoming increasingly acute and the hazards of sludge are increasing, people try to use sludge as fertilizer for agriculture or greening. However, various heavy metals contained in sludge limit the impact of soil on sludge. The adaptability of utilization, studies have shown that removing 1mg / L of heavy metals from wastewater will accumulate 10,000mg / L of heavy metals in sludge, which will accumulate in the soil and enter the food chain through the absorption of crops, eventually endangering Human health, even if some sludge comes from urban domestic sewage, although the heavy metal content is low, the pathogens and persistent organic pollutants contained in the sludge, as well as various chemicals added in the sewage treatment process, will bring pollution to the environment. potential hazard

[0005] Referring to the practice of sludge incineration abroad, some places try to achieve the purpose of sludge incineration through incineration. However, the investment in sludge incineration equipment is high, the energy consumption is large, and the operation cost is expensive. The cost of sludge incineration is 400 yuan. In addition, the incineration of sludge will bring pollution to the atmospheric environment and the residue after incineration still needs to be disposed of. According to my country's national conditions, sludge incineration is economically unaffordable and technically not yet feasible. Complete

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