Rushan Bie

Biomass gasification technology is a crucial pathway for obtaining clean syngas and achieving efficient utilization of carbon resources. However, tar is one of the main factors restricting the industrialization of biomass gasification technology. Among various solutions, catalytic steam reforming is regarded as the most promising solution. Currently, natural minerals and Ni-based catalysts have been demonstrated to be effective and economically viable for tar removal, which are widely used in industrial fluidized beds. Therefore, the basic reaction principles of tar steam reforming were briefly introduced. The development of tar steam reforming catalysts, focusing mainly on natural minerals and Ni-based catalysts, have been studied in this review. The catalytic cracking mechanisms of natural minerals such as dolomite and limestone, as well as the steam reforming mechanism of Ni-based catalysts, have been thoroughly summarized. In addition, the active sites of the catalysts, reaction pathways, and the essence of catalyst deactivation are discussed. Based on this, the catalytic effect of these two catalysts for steam reforming of tar in the fluidized bed was summarized. Further, the engineering challenges (such as mass transfer, wear, and continuous regeneration) and the corresponding process optimization measures were comprehensively reviewed, and future perspectives are discussed.

In the context of the growing share of renewable energy and the impending decommission of a large number of coal-fired units, nuclear energy is the only green energy that can replace coal power for a stable, clean, efficient, and large-scale power supply. This article compares the differences between coal power and nuclear power in terms of thermal system, thermal cycle, turbine parameters, and safety. It discusses the possibility of replacing the boiler of a coal power plant with nuclear power, that is, replacing the boiler of a coal power plant with a nuclear reactor for generation/heating/cogeneration. For coal-fired units with similar capacity that do not use a reheat cycle (at or below high pressure) and nuclear power units (such as a high-temperature gas-cooled reactor), as well as coal-fired units with a reheat cycle (ultra-high pressure and above) and nuclear power units (such as pressurized water reactors), there are great differences in steam parameters. In terms of steam turbines, the size of nuclear power units is relatively larger, requiring additional dehumidification measures. In addition, the safety factors and management methods considered in the site selection, construction, and operation of nuclear power plants are more stringent and complex, and comprehensive analysis and evaluation are needed in aspects such as waste treatment and accident emergency response. Except for the relevant provisions of the American Society of Mechanical Engineers code for pressure vessels, nuclear power units are not compatible with coal-fired units in terms of safety standards. Therefore, considering comprehensively, it is believed that the scheme of nuclear power replacing coal-fired units for power generation/heating/cogeneration program is not feasible at present.

The development of wind power has brought about increasing challenges in decommissioning, among which DWTBs (decommissioned wind turbine blades) are the most difficult component to deal with. To enable the cost-effective, energy-efficient, and environmentally friendly large-scale utilization of DWTBs, an experimental study on thermogravimetric and pyrolysis characteristics of DWTBs was carried out. A new process involving recycling glass fiber with pyrolysis gas re-combustion and flue gas recirculation as the pyrolysis medium was innovatively proposed, and the simulation calculation was carried out. Thermogravimetric experiments indicated that glass fiber reinforced composite (GFRC) was the main heat-generating part in the heat utilization process of blades, and the blade material could basically complete pyrolysis at 600 °C. As the heating rate increased, the formation temperature, peak concentration, and proportion of combustible gas in the pyrolysis gas also increased. The highest peak concentration of CO gas was observed, with CO₂ and C₃H₆ reaching their peaks at 700 °C. The solid product obtained from pyrolysis at 600 °C could be oxidized at 550 °C for 40 min to obtain clean glass fiber. And the pyrolysis temperature increased with the increase in the proportion of recirculation flue gas. When the proportion of recirculation flue gas was 66%, the pyrolysis temperature could reach 600 °C, meeting the necessary pyrolysis temperature for wind turbine blade materials. The above research provided fundamental data support for further exploration on high-value-added recycling of DWTBs.

The rapid expansion of the scale of wind power has led to a wave of efforts to decommission wind turbine blades. The pyrolysis of decommissioned wind turbine blades (DWTBs) is a promising technological solution. Microwave pyrolysis offers the benefits of fast heating rates and uniform heat transfer, making it a widely used method in various heating applications. However, there are few studies on the microwave pyrolysis of DWTBs, and pyrolysis characteristics under different boundary conditions remain unclear. In this paper, we investigate the pyrolysis characteristics of DWTBs by utilizing silicon carbide (SiC) particles as a microwave absorbent. The results demonstrated that, when the microwave heating power increased from 400 W to 600 W, the heating rate and pyrolysis final temperature of the material increased, resulting in a reduction in pyrolysis residual solid yield from 88.30% to 84.40%. At 600 W, pyrolysis gas components included C₂H₄, CH₄, and CO, while the tar components included phenol and toluene. The highest degree of pyrolysis was achieved under the condition of an SiC particle size of 0.85 mm, with better heating performance, and the calorific value of the pyrolysis gas generated was 36.95 MJ/Nm³. The DWTBs did not undergo pyrolysis when SiC was not added. However, when the mass ratio of SiC to DWTBs was 4, the tar yield was 4.7% and the pyrolysis gas yield was 17.0%, resulting in a faster heating rate and the highest degree of pyrolysis. Based on this, an optimal process for the microwave pyrolysis of DWTBs was proposed, providing a reference for its industrial application.

Pyrolysis of reed black liquor was tested in the form of both dried powder in a thermogravimeter connected to a mass spectrometer (TG-MS) and fed droplets (RBLD) in an atmospheric fluidized bed at temperatures of 530-780 degrees C. The effects of temperature were examined to clarify the variations in composition of gaseous products and the microscopic appearance of char. Examination was also performed for the releases of species containing Na, K, and Cl during pyrolysis. The results obtained show that the concentration of combustible components (CH4, H-2, and CO) in pyrolysis gas increased with increasing bed temperature to reach 66.1% at 780 degrees C. There are more Na, K, and Cl releasing into the gaseous product at higher temperatures. The variation in the micromorphology of char from RBLD pyrolysis has been obtained and analyzed.

Four additives including two specimens of kaolin clay, limestone, and a byproduct of a sugar mill (BSM) (mainly CaCO3) were utilized to increase ash fusion temperature (AFT) of corn straw. The results showed that the ash softening temperature (ST) was increased by 250 to 380 °C and agglomeration or slagging could be avoided during combustion with each additive. Meanwhile, the slagging/fouling tendency of all ash samples fell within the “low” range according to alkali index. Lime was shown to have the best effect, which indicated that calcium oxide was the best compound to increase the AFT of corn straw densification (CSDF). Both kaolin specimens made the fusion range very narrow. BSM had the least effect on ST among the four. All the additives diluted the concentration of chlorine by more than 50%. No agglomeration or slagging phenomenon appeared in real boilers burning CSDF with lime blended as additive.