印染污泥-稻壳混烧底灰中沸石产物对重金属的钝化机制研究

The incineration technology has been widely used in the disposal of dyeing sludge, and a large amount of bottom ash would be produced during incineration process. Heavy metals enriched in the bottom ash are easy to release into environment through solid-liquid reaction, so it has significant environmental risk. The previous work of the applicant showed that the addition of rice husk as an auxiliary material can passivate the bottom ash effectively, and the release of heavy metal from bottom ash is significant negative correlation wtih the formation of zeolite minerals, but the specific mechanism is still unknown. The project aims to regulate the leaching characteristics of heavy metals in bottom ash through optimizing the co-combustion condition of dyeing sludge and rice husk. The response relationship between heavy metal leaching and zeolite product would be determined, based on the correlation analysis between the leaching characteristic of heavy metals and the geochemical characteristics of the carrier. The formation mechanism of zeolite should be illustrated by coupling the in-situ and ex-situ testing technology, the effect mechanism of zeolite product on the of heavy metals in bottom ash will be revealed. The quantitative passivation mechanism model of heavy metals in bottom ash will be constructed, combining the experimental simulation of the reaction process between zeolite and heavy metals with geochemical model. The proposal is expected to provide scientific basis for the in-situ passivation of heavy metals in bottom ash produced from dyeing sludge incineration, which have fundamental practical significance.

焚烧技术已广泛应用于印染污泥的处置，焚烧过程中会产生大量底灰。底灰中所富含的重金属易通过固-液反应向环境释放，存在极大的环境风险。申请人前期工作表明在污泥焚烧过程中引入稻壳辅料能有效钝化底灰，并且底灰中重金属释放与混烧过程中沸石矿物的生成呈显著的负相关，然而具体的原位钝化作用机制尚不明晰。本项目通过印染污泥-稻壳混烧制度的优化，调控混烧底灰中重金属的浸出行为；基于重金属浸出特性与底灰载体的地球化学特性的相关分析，明确重金属浸出行为与沸石产物的响应关系；耦合原异位测试技术，阐明沸石的形成机制，揭示底灰中沸石产物对重金属的作用机制；联合沸石与重金属反应过程的实验模拟及地球化学模型，构建底灰中重金属的定量钝化机理模型。该研究为印染污泥焚烧底灰中重金属的原位钝化提供科学依据，具有十分重要的现实意义。

焚烧具有最大限度减量化，破坏全部有机污染物，回收处理过程中能量等优点，因此焚烧被视为印染污泥处理的最佳可行技术之一。然而焚烧过程的固相副产物，焚烧底灰捕集了印染污泥中绝大部分的重金属，其具有极高的二次污染风险。因此，如何降低印染污泥焚烧底灰中重金属的浸出已成为保障印染污泥安全焚烧的关键环节。本项目拟通过构建印染污泥-稻壳协同焚烧体系，实现焚烧底灰中重金属的原位钝化，并解析其详尽的原位钝化机制。研究结果表明稻壳的引入能有效提升印染污泥的燃烧效率，并同步抑制过程中污染气体的释放，尤其含硫气体。混烧过程可概括为四阶段（D3→F3→D1→F3）动力学模型。尽管稻壳的引入一定程度促进了印染污泥焚烧过程中重金属向气相的转移，但底灰依然是印染污泥中重金属的主要载体。需要指出的是，通过印染污泥-稻壳协同焚烧系统的优化，可实现焚烧底灰中重金属浸出浓度与浸出率的降低，并于原位促进重金属向残渣态的转化。混烧底灰中重金属的原位钝化与其矿相（Gismondine和CaSO4）生产密切相关。其中Gismondine为主控因子，其对重金属浸出行为的调节作用是通过沉淀/溶解，吸附和晶格固化的共同作用来实现的。该研究为印染污泥的无害化处理提供了更为绿色、低碳的路径，具有十分重要的现实意义。