The world's largest sludge incineration project - Dongguan sludge treatment project
1. Basic Information
Dongguan sludge centralized treatment and disposal project, covering an area of about 132.95 acres, with a construction scale of 2,700 tons/day of sludge treatment capacity (60% moisture content), adopts the process of "bubbling fluidized bed incineration + waste heat recovery and utilization + flue gas treatment", supporting wastewater treatment, deodorization, waste heat power generation, photovoltaic power generation and other projects. With a total investment of 2.188 billion yuan, the project started construction in March this year and is expected to be completed and put into operation in 2026. Project scale: The short-term sludge treatment scale is 2000t/d (calculated by 60% moisture content), and the land with long-term sludge treatment scale of 700t/d (calculated by 60% moisture content) is reserved.
2. Sludge situation
The sludge comes from the sludge from more than 50 municipal sewage plants in Dongguan City, and the sludge is treated by the sewage plant with a moisture content of about 60% and transported to the sludge incineration plant for incineration. In recent years, the weighted average of sludge moisture content of more than 50 sewage plants involved in the sludge has varied from season to season. After 2021, the weighted average value of sludge moisture content of sewage plants will be stable between 50~55%, and the weighted low calorific value of dry basis will also have an overall improvement trend.
3. Why incineration
An important factor restricting sludge land use is the pollution of heavy metals and persistent organic compounds. Therefore, sludge should ensure that its heavy metal and persistent organic matter content does not exceed the standard when used for land use, and the dosage should also be controlled during the application process to avoid the accumulation of heavy metals and persistent organic matter. Incineration is the most thorough sludge disposal method. Sludge incineration destroys all organic matter, kills pathogens, and minimizes sludge volume. The incinerated ash can be used for phosphorus recovery, which is conducive to resource recycling. The steam generated during sludge incineration can be used to generate electricity and be used as a resource when it is affordable. At the same time, by strengthening the flue gas purification measures, the emission standards can be achieved, and the slag produced after incineration can be used as building materials. In general, sludge incineration is a reliable disposal route for large cities with large sludge production and concentration.
4. Incineration process
The fluidized bed incinerator is the most suitable furnace type for sludge incineration, in which the bubbling fluidized bed has the following advantages compared with the circulating fluidized bed:
The fluidization velocity of the bubbling bed is low, so that the flue gas wears less on the heat transfer surface and requires less energy consumption; The bubbling bed does not need to be equipped with separators, return devices and corresponding other facilities, and the structure is simple, the investment is low, and the maintenance is convenient.
For sludge, bubbling fluidized bed is a more suitable sludge incineration equipment. According to statistics, the vast majority of foreign sludge incineration projects are incinerated by bubbling fluidized bed incinerators. There have been a number of examples of projects using this type of incinerator to incinerate sludge in China. The bubbling fluidized bed incinerator used in this project was based on SUEZ's Thermylis 2R incineration technology.