液相循环水热法污泥减量及资源化利用

Sludge reduction and resource utilization based on hydrothermal process with processing liquid recycling

摘要:

为攻克目前污泥水热产物价值相对较低、水热液过剩等问题,提出将水热液作为水热介质多次循环利用的工艺方案。通过分析污泥中氮、磷及有机质等重要资源在水热固、液相中的转化及分配规律,探究水热液循环利用在提高污泥水热产物价值、节约水资源方面的可行性和潜在优势。结果表明:水热液循环利用促进液相产物中氮、磷成分积累,在250 ℃水热条件下,3次循环后液相氨氮质量浓度高达17 000 mg/L,液相总磷质量浓度为200 mg/L,分别是一次水热结果的4倍和5倍,显著提升水热液的资源回收效率；水热液循环利用促进水热固相的成炭过程,有助于提高污泥水热炭化产物的利用价值。通过调控水热反应强度、增加水热液循环次数,可实现水热产物价值最大化,同时提升水资源利用效率。研究结果可为水热法实现市政污泥高效减量化、资源化利用提供理论和技术支撑。

Abstract:

To resolve the problems such as the relatively low utilization value of hydrothermal products and excess processing liquid, this study proposed a multiple recycling process scheme with hydrothermal processing liquid as the HTC medium. By analyzing the transformation and distribution of nitrogen (N), phosphorus (P), and organic matters in hydrothermal solid and liquid phases, the feasibility and advantage of the hydrothermal recycling approach for improving the utilization value of sludge by-products and saving water resources were investigated. It was found that under the HTC condition of 250 ℃, N-containing components in hydrothermal liquid increased with recycling. After three cycles, the concentration of NH+₄-N and P in liquid reached 17 000 mg/L and 200 mg/L respectively (being 4 and 5 times the primary hydrothermal processing liquid), significantly improving the efficiency of hydrothermal resource recovery. The conversion of organic components to solid phase promoted carbon formation, with the utilization value of hydrochar products increased. In conclusion, regulating the intensity of hydrothermal reactions and increasing the recycling cycles of processing liquid tend to maximize the utilization value of hydrothermal products and improve the efficiency of water use. The results provide a fresh insight for popularizing the hydrothermal technique to achieve sludge reduction and resource utilization.