Co-pyrolysis of saw dust and oily sludge with waste-heat utilization of steel slag on rotary kiln simulated engineering practice

Abstract

Pyrolysis of oily sludge (OS) possesses actual problems of high viscosity and high energy consumption in industry. This paper introduced saw dust (SD) to achieve physical viscosity reduction of OS, and then completed OS pyrolysis via steel slag (SS) with sufficient waste heat to replace external heat sources. The rotation of rotary kilns reactor with fins inside were utilized for pyrolysis, which exhibited excellent heat transfer effect for SS heating as validated by discrete element analysis (DEM) simulation. Temperature program and fixed temperature pyrolysis were respectively investigated and the latter one obtained higher yield of oil and gas. Especially SD addition increased the yield and quality of calorific value products (pyrolysis oil and gas). SS not only provided heat source but a lot had catalytic effect on pyrolysis, in which the [O] compounds provided by metal oxides could destroy the stability of chemical bond and deepen the cracking reaction. The energy equilibrium was calculated by heat capacity and reaction energy barrier. Finally, the pyrolytic residue was utilized as soil remediation agent by evaluating Ryegrass growth. Trace FeOx promoted photosynthesis and cellular respiration in plants, while excessive FeOx led to difficulty in respiration and decay of roots. Therefore, this new approach provides an alternative direction for collaborative treatment of OS, SD, and SS with co-benefits from three feedstocks to save energy and produce high-quality products of gas and oil.