Comprehensive utilization of the pyrolysis products from sewage sludge

Abstract

Bio-oils were produced from pyrolysis of sewage sludge in a horizontal tubular furnace under the anoxic or anaerobic conditions, by varying operating parameters and moisture content (MC) of the feedstock. Physicochemical properties of the obtained bio-oil (such as density, acid value, kinematical viscosity, high heating value and flash point) were analysed and compared with Chinese fuel standards. T_end, RT and β were found critical to control the yield and physico-chemical properties of bio-oil products. The relative importance of various parameters such as T_end, RT, β and MC was determined and the optimum values for the lowest kinematic viscosity and acid value and the highest yield of the bio-oil were achieved using the orthogonal matrix method. The parameters 550°C, 45 min, 5°C min⁻¹ and MC of 10% were found effective in producing the bio-oils with most of the desirable physico-chemical properties and yield. Benefit analysis was conducted to further optimize the operating parameters, considering pyrolysis treatment, comprehensive utilization of the pyrolysis products and final disposal of sewage sludge; the results showed the best economy of the pyrolysis parameters 450°C, 75 min, 3°C min⁻¹ and MC of 10%. The char obtained under this condition may serve as a microporous liquid adsorbent, while the bio-oil may serve as a low grade fuel oil after upgrading it with conventional fuel oil and deacidification. Pyrolysis products may become economically competitive in addition to being environment friendly.

Keywords:

• sewage sludge
• comprehensive utilization
• pyrolysis products
• benefit analysis
• upgrading

Disclosure statement

No potential conflict of interest was reported by the authors.

Funding

This work was supported by Ministry of Construction of China, [2013ZX07315-001].