Editorial Pollutant Formation and Control during Fuel Thermochemical Conversion

State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University, 710049 Xi’an, Shaanxi, China Shandong Engineering Laboratory for High-efficiency Energy Conservation and Energy Storage Technology & Equipment, School of Energy and Power Engineering, Shandong University, 250061 Jinan, Shandong, China SINTEF Energy Research, Sem Saelands vei 11, 7034 Trondheim, Norway University of Pannonia, Faculty of Engineering, Institute of Chemical Engineering and Process Engineering, MOL Department of Hydrocarbon & Coal Processing, Egyetem u. 10, H-8200 Veszprém, Hungary

e pollution emissions from the utilization of fuels have become a troublesome global problem due to its severe hazard to both human health and the environment. e pollutants emissions, such as SO 2 , nitric oxides (NO x ), CO 2 , heavy metals, and particulate matters (PM), have limited the utilization of environmental-friendly fuels and require to be reduced [1][2][3][4]. ese pollutants come from the combustion, gasification, and pyrolysis process of coal, biomass, wastederived fuels, and other solid fuels [1,5]. Regulations and legislations are being updated for limiting emissions from thermal conversion of fuels and negative effects to human health and environment.
ere are ongoing research activities and technology development aiming at understanding, controlling, and preventing formation and emission of these pollutants. us, the aim of this special issue was to publish research papers addressing recent advances on the fuel thermochemistry and the following pollution issues.
After the evaluation of manuscripts submitted to the special issue, we have accepted ten for publication in the special issue. Liu and coworkers investigated the influence of inner and secondary air ratios (ISA/OSA) on the coal combustion characteristic and flame shape. In particular, the study was carried out in a swirl burner with a prechamber in a 14 MW pilot scale pulverized-coal combustion system. ey found that the flame shape size exhibited an inflection point with increasing ISA/OSA and the ratio of 1 : 2 was the optimized case under experiment conditions. Xu and coworkers studied the denitrification of decomposing furnace for NO x reduction. ey modeled the 2500 t/d new dry-process cement kiln decomposing furnace and verified the simulation methods by the field test. ey concluded that the NO concentration, NH 3 escape, and denitrification efficiency could be limited to 187.60 mg/m 3 , 32.40 mg/m 3 , and 74.75%, respectively.
Huang and coworkers built a reactor network analysis model with a detailed mechanism to describe and calculate the process in the sulfur recovery unit. en, they used the verified model to find the optimum condition parameters for a real device in the Puguang gas field. e results were able to correlate to the best sulfur recovery to reduce pollution emissions and improve economic performance.
Yu and coworkers simulated the CO 2 emissions of China's power industry with different carbon tax levels based on the TIMES model. ey quantitatively studied the power consumption demand, primary energy consumption structure, CO 2 emission characteristics, emission reduction potential, and cost of different carbon tax levels. e authors predicted the peak value of CO 2 emissions during 2030-2040; the medium carbon tax level was recommended for the most elastic impact on the national economy and the smallest GDP loss.
Wang and coworkers concerned the mechanism of chlorine corrosion to heating surface in the boiler for corrosion prevention and the safety of boiler operation. ey studied the reaction kinetics of chlorine corrosion by the weight gain method and simulated the temperature, atmosphere, and fouling in the boiler. e authors reported a fast corrosion rate in the early stage of ash deposits but a slower rate after the formation of the protective layer on heat transfer tube surfaces. Low temperature and concentration of HCl in the gas phase were suggested. Another work by the authors is the investigation on the corrosion mechanism related to ash deposition on the boiler heating surface. ey concluded that the addition of biomass aggravated the corrosion of metal tubes, and T91 was the ideal material for the biomass-fired boiler against metal corrosion.
Lin and coworkers investigated the effect of B 2 O 3 additives on the crystal behavior of high Ti-bearing blast furnace slag. e authors concluded that the B 2 O 3 additives can restrain the appearance of the perovskite phase, decrease the apparent viscosity, and promote the metallurgical properties of Ti-bearing blast furnace slag. eir findings provided a feasible and convenient method to prevent the slagging problem for Ti-bearing blast furnaces.
Mohamed and coworkers aim to synthesize Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II), and Cd (II) complexes with the new diazo ligand (H 2 L) and to examine their physical properties involving spectral behaviors and the electrical conductance values. ey determined the efficiency of the synthesized complexes against pathogenic bacteria and obtained the contact angle, molecular structure, and molecular docking. e results showed that the Cd (II) complex can be considered as a super hydrophobic material and has significant biological activities with different sensitivity levels.
e binding between H2L and its Cd (II) complex with receptors of crystal structure of S. aureus (PDB ID: 3Q8U), crystal structure of protein phosphatase (PPZ1) of Candida albicans (PDB ID: 5JPE), receptors of breast cancer mutant oxidoreductase (PDB ID: 3HB5), and crystal structure of Escherichia coli (PDB ID: 3T88) was predicted and given in details.
Finally, this special issue includes two comprehensive reviews. Wang and coworkers reviewed the urea pyrolysis in three parts: urea pyrolysis pathway, catalytic hydrolysis of HNCO, and catalytic pyrolysis of aqueous urea solution.
ey proposed that the current research focused on the analysis of urea pyrolysis products and exploration of catalysts used to improve ammonia yields, but the mechanism study and development of a kinetic model with high accuracy need further exploration. Hameed and coworkers presented the state-of-the-art review on utilizing biomass and sewage sludge in combination with coal for improvement in energy conversion processes. ey concluded the blending impact on tar release, alkali and ash, char characteristics, and thermal co-conversion behaviors. is study will provide recent development and future prospects for cothermal conversion of these blends.
In conclusion, the current special issue offers updated information to the readers on the recent advancements regarding Pollutant Formation and Control during Fuel ermochemical Conversion and gives a deeper insight into their formation mechanisms and control strategy. It is clearly evidenced that the thermochemical conversion of fossil fuel is a current topic and needs further investigation towards their clean and efficient utilization.

Conflicts of Interest
e editors declare that they have no conflicts of interest regarding the publication of this special issue.