Hydrogen production by suspension self-rotation enhanced pyrolysis of sludge particles in cyclone

Abstract

The challenges faced by sludge pyrolysis units, including poor heat transfer efficiency and uneven heating of material groups, significantly hinder the green and low-carbon transformation and sustainable development of sludge treatment. The suspension self-rotation of sludge particles in a cyclone enhances particle heat transfer, thereby improving the pyrolysis process. In this study, we developed a novel method for sludge pyrolysis using Cyclone Suspension Self-Rotation Pyrolysis Reactor (CSSPR). Through numerical simulation and high-speed camera visualization, we analyzed the effects of cyclone cone angle, particle size, and inlet flow rate on particle suspension self-rotation. A systematic investigation was conducted into the mechanisms by which “particle suspension self-rotation” enhances “sludge particle pyrolysis”. Consequently, an effective method for utilizing hydrogen-rich gas produced by sludge suspension self-rotation pyrolysis was developed. The results showed that CSSPR with a 9° cone angle achieved optimal suspension autorotation efficiency. Under optimal conditions—sludge particle moisture content of 31.89% and particle suspension rotation rate of 100%, the hydrogen production per unit of sludge reached up to 265.78 mL/g, which is 1.3 times higher than that produced in a static state. Compared to traditional fixed-bed pyrolysis technology, CSSPR demonstrated superior pyrolysis performance, achieving a 155.78 mL/g higher hydrogen yield per unit of sludge. This study offers a novel approach to developing sludge resource pyrolysis technology, thereby providing an effective pathway for addressing climate change and advancing environmental governance.