Slow Pyrolysis Performance and Energy Balance of Corn Stover in Continuous Pyrolysis-Based Poly-Generation Systems

Abstract

In order to analyze pyrolysis performance and energy balance of corn stover pyrolysis, a poly-generation pyrolysis unit that coproduced biochar, pyrolysis gas, and liquids was used. Corn stover was naturally dried and crushed to lengths of 4–7 mm before pyrolysis at 450, 550, and 650 °C. The physical and chemical properties, yield rate, and influence of technological parameters were analyzed. In addition, a full energy balance analysis was carried out. The results show that the quality of corn stover char was primarily affected by pyrolysis temperature and material residence time, where a residence time of at least 30 min was required for conversion in this unit. The higher heating value (HHV) of pyrolysis gases reached ∼20 MJ/Nm3 at pyrolysis temperatures of 550 and 650 °C, providing a useful gaseous fuel. In terms of energy balance, biochar contributing 47.88% accounted for most of the enthalpy of products, followed by pyrolysis gas (36.17%), wood tar (13.14%), and light oil (1.74%), and the last fraction, wood vinegar, accounted for only ∼1.07% of the total product enthalpy. The theoretical energy efficiency of the poly-generation system was 82.1%. Pyrolysis at temperatures of 550 and 650 °C could provide fuel gases that contained enough energy to support the heating requirements of the system. The researcher offers an important new direction for comprehensive development of straw utilization for energy and materials, not only in China, but worldwide.

RETRACTED: A pilot-scale biomass pyrolytic poly-generation plant performance study and self-sufficiency assessment

“…Continuous pyrolysis conditions include pyrolysis temperature, material residence time, and feeding rate. The heating rate is another important factor that is affected by the above factors, and as such cannot be controlled independently from the other parameters (Cong et al, 2018;. Slow pyrolysis has a wide range of working conditions using moderate temperatures (up to 600 °C) to produce biochar (Basu, 2010;Cong et al, 2017).…”

“…The mass distribution of different fractions produced by slow pyrolysis typically changes depending on residence time, particle size, and pyrolysis temperature. In order to remove any variability associated with the residence time and particle size, the mean residence time was pre-set as 30 min based on preliminary tests and previous studies (Cong et al, 2018) and the particles of comparable size were used, as introduced in Section 2.1.…”

“…The pyrolysis temperature was deemed to be important to achieve a self-sufficient system, and too low pyrolysis temperatures cannot provide pyrolysis gas with sufficient energy to support the heating system (Crombie et al, 2014Cong et al, 2018. Table 2 shows the required energy for each test calculated by reused pyrolysis gas for the heating system, the available energy in pyrolysis gas and oil, as well as the possibility of a self-sufficient system.…”

Prospective contributions of biomass pyrolysis to China’s 2050 carbon reduction and renewable energy goals

“…Overall, from a techno-economic perspective, it is suggested that this kind of BIPP system with biochar returned to soil and biofuels used for direct energy use, power generation, and industrial use should be developed on a relatively large scale with higher pyrolysis temperatures between 550 and 650 °C. There also are studies showing that the variation of pyrolysis parameters could influence the profitability of the process technology 35 , 36 . To date, there has been a large number of published studies discussing properties of biochar and biofuels produced at pyrolysis temperatures of 300–700 °C 37 , 38 .…”

Co-combustion, co-densification, and pollutant emission characteristics of charcoal-based briquettes prepared using bio-tar as a binder

“…Charcoal exhibited a more intense rate of weight loss during the second stage, and this occurred at a distinctly lower temperature than that of the semi-coke. The curve of biotar was the most tortuous, which indicated that the weight loss fluctuated throughout the process owing to its complex components consisting of phenols, amides, and lipids with >20C atoms [31]. The burnout indices and integrated combustion indices of the materials are listed in Table . 2.…”