Method for preparing high-strength lightweight aggregate from municipal sludge

Abstract

The invention provides a method for preparing high-strength lightweight aggregate by using municipal sludge. The method comprises the following steps: firstly, mixing and stirring the sludge to generate slurry; conducting pyrohydrolysis to enable the properties of the slurry to be fundamentally changed in a high-temperature hydrolysis reaction and the dehydration performance of the slurry to be greatly improved; dehydrating the slurry through a high-pressure plate-and-frame filter press; subjecting a ceramsite blank to granulation and balling through a ceramic preparation process, carrying out high-temperature roasting and conducting ceramsite screening so as to obtain the high-strength lightweight aggregate; and conducting resource treatment and recycling on the whole ceramic preparation process through tail water treatment, flue gas purification and deodorization processes and the assistance of a waste heat boiler, thereby achieving low-energy and environment-friendly process effects. According to the method for preparing the high-strength lightweight aggregate, defects in the prior art are overcome, and the method is high in sludge mixing amount, low in admixture requirement, compact in ceramsite structure, high in ceramsite strength, wide in application range, high in economic benefit, friendly to environmentally and low in energy consumption.

Description

technical field [0001] The invention relates to the technical field of municipal environmental engineering, in particular to a method for dehydrating and roasting municipal sludge into high-strength lightweight aggregate after undergoing a high-temperature hydrolysis reaction. Background technique [0002] Sludge is a by-product of sewage treatment, which contains toxic and harmful substances and needs to be stabilized, reduced and harmless. With the increasing awareness of the environmental risks and hazards of sludge in various places in recent years, the trend of "paying equal attention to mud and water" is gradually taking shape. Sludge disposal is the trend of the water pollution prevention and control industry. [0003] Sludge treatment technology is mainly based on sludge recycling, and the direction of sludge recycling can be roughly divided into: fertilizer, material, and fuel. Through combing and comparison, it can be found that the utilization of sludge fertilize...

AI Technical Summary

Problems solved by technology

[0004] At present, in the prior art, the process of using sludge to prepare high-strength lightweight aggregate mainly has the following three shortcomings: 1. Most of the sewage treatment plants use polyacrylamide (PAM) to dehydrate the sludge to about 80% , PAM is a polymer flocculant, but also a water-retaining agent, polyacrylamide is white powder or small particles, the density is 1.302g / cm 3 (23°C), the glass transition temperature is 153°C, and the softening temperature is 210°C

2. At present, there are still high levels of organic matter and heavy metals in the sludge after drying in most processes. The organic matter can easily lead to loose ceramsite structure and poor compression resistance during the firing process, resulting in narrow use area and low economic benefits. At the same time, heavy metals will also cause secondary pollution to the environment after the ceramsite is put into use

3. At present, two-stage rotary kilns are mostly used in the firing process of pottery. The ceramsite produced by this method has low density and high energy consumption. The flue gas emission is easy to exceed the standard.

At the same time, the flue gas and ceramsite waste heat in the process are directly discharged and wasted, and the heat energy is not fully utilized, resulting in a large energy consumption in the entire process.

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