| Sludge is usually produced in the sewage treatment process,generally in the form of flocculent,with high water content,which brings great pressure to the sludge disposal industry in China.In order to solve this problem,this study explores a scientific,efficient and pollution-free sludge disposal method with the principle of "reduction and harmlessness",which is of great significance to environmental protection.The study first showed the drying performance of the sludge,and analyzed and treated the condensate produced during the sludge drying process;Secondly,the incineration characteristics of the sludge were studied by thermogravimetric analysis and elemental analysis.The key parameters of the mud drying or combustion process provide reference for the subsequent practical application;finally,the design work of the sludge rotary drying furnace and the incinerator is completed based on the experimental data as an important reference.The conclusions of this paper are as follows:Under isothermal conditions and in the same drying time,the rate of water content declines with the decrease of initial water content.Also,the evaporation rate of water shows a decreasing trend;the sludge's drying performance with high organic matter will deteriorate;the relevant parameters such as initial moisture,sludge type and thickness are maintained.In the case of uniformity,the higher the drying temperature,the less time consuming and the higher the drying rate;when the drying temperature is determined at 160? and pH=8.14,the NH3-N and COD values of the condensed water are 580 mg/L and 1144 mg/L,respectively.These condensates need to be treated by matching sewage treatment systems to meet the standards before they can be sent to municipal sewage treatment plants.The thermogravimetric experiments indicate that sludge moisture content has little effect on the burnout temperature and combustion temperature of sludge;the ignition temperatures of sludge are between 208 and 216?,which indicates the sludge shows ideal combustion performance.The ignition temperature of sludge is not high and the studied sludge has ideal combustion performance.The calorific value of sludge samples was measured by calorimeter.The results showed that the low calorific value of sludge samples was higher than the ones stipulated in GBT 24602-2009 standard for sludge disposal in municipal wastewater treatment plants without adding any combustion aids.Therefore,the method of sludge incineration in this project is feasible.Effectively measuring the heavy metal elements in the leachate of dry sludge and incinerated bottom ash by atomic fluorescence spectrometry and atomic absorption spectrometry.The results show that the leachate of dry sludge and high-temperature incineration bottom ash are all in domestic garbage.Within the standards of landfill pollution control standards(GB 16889-2008),there is no problem of heavy metal contaminants when the sample is dried or incinerated.Based on the above test conclusions of sludge drying and incineration,a project is designed to treat 300 tons of sludge per day.At the same time,the treatment units of sludge receiving storage system,sludge drying system,sludge incineration system,waste heat utilization system and flue gas treatment system,etc.have been optimized.Finally,the process route of sludge receiving storage?sludge drying?pre-funace feeding?sludge incinerator?waste heat boiler?cyclone?bag gust collector?wet deacidification tower has been determined.Combined with engineering cases,the design and operation parameters of sludge drying-incineration system are introduced,and the disposal paths of waste gas,waste residue and waste water produced by the system are described respectively.Finally,the economy of the project is preliminarily analyzed. |
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