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Using internals in kilogram-laboratory fixed bed pyrolysis of coal has been newly reported to greatly upgrade the pyrolysis performance in terms of the yield and quality of the produced tar and pyrolysis gas. This work is devoted to further verifying such a finding through pyrolysis tests in enlarged fixed bed reactors with and without internals at obviously increased coal treatment capacities of about 100 kg of coal per test. The reactors were electrically heated, and the tests were via batchwise operation, while Yilan sub-bituminous coal was used. Comparing the results from reactors without and with the particularly designed internals demonstrated that the use of internals increased the heating to the coal bed by about 20%, while the tar yield was 87.0% of the Gray-King (G-K) tar yield, which was obviously higher than 46.9% of the G-K tar yield from the reactor without internals. In the tar from the internal-enhanced reactor, the content of light tar (boiling point below 360 °C) was about 71 wt %. Raising the furnace temperature from 900 to 1100 °C increased the tar yield from 80.5% to 90.3% of the Gray-King tar yield for the reactor with internals. Parametric studies were performed for coal particle size, heating furnace temperature, and coal moisture content.

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.

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The fixed-bed reactor with internals has been proposed to enhance the pyrolysis performance for coal. In this study, the pyrolysis behavior of different coal moisture contents and the reaction mechanism were investigated in an indirectly heated fixed-bed reactor with internals. The results showed that, at a furnace temperature of 900 °C, the increased coal moisture content went from 0.41 to 11.68 wt % and significantly modified the temperature fields, thereby prolonging the pyrolysis time to reach 500 °C and then enhancing the condensation and trapping of the coal at the bed center. Therefore, the tar yield and light tar content were raised from 9.21 and 63.7 wt % to 10.74 and 64.5 wt %, respectively. However, when the coal moisture content exceeded 16.77 wt %, the tar yield and light tar content decreased to 8.55 and 62.0 wt %, respectively. In addition, the higher heating value (HHV) of char with internals was dramatically higher than that without internals, and the char HHV in the reactor with internals rose primarily and then decreased with the increase in the coal moisture; meanwhile, its fixed carbon content of char showed an increase, followed by a decline. In contrast, the pyrolysis products varied slightly in the reactor without internals.