The washing pretreatment and torrefaction pretreatment of corn stalk were performed in this study. The effects of both separate and combined pretreatments on the pyrolysis were studied using TG-FTIR and a fixed bed reactor. Washing pretreatment had little impact on the physicochemical properties of corn stalk, contributing mainly to the removal of some ash and metallic species. Torrefaction pretreatment, on the contrary, decreased the oxygen content but increased the ash content. TG-FTIR analysis showed that TG/DTG curves of corn stalk (CS), washed corn stalk (W-CS), torrefied corn stalk (T-CS), and torrefied-washed corn stalk (TW-CS), in turn, showed a right shift trend, and the initial decomposition temperatures increased obviously. Among the samples, W-CS had the lowest values of 27.58 and 29.76 wt % for the final residue mass in the TG curve and the biochar yield, respectively, and the highest bio-oil yield of 48.32 wt %, indicating that the removal of metallic species facilitated the pyrolysis of corn stalk and reduced the secondary cracking of pyrolysis volatiles. Moreover, torrefaction pretreatment greatly promoted the generation of combustible gases and phenols of bio-oil, whereas it remarkably reduced the acids of bio-oil. The combination of water washing and torrefaction preserved the advantages of each method on its own, illustrating this combination was a promising pretreatment for improving pyrolysis products.

Wood dust produced in medium-density fiberboard (MDF) processing is a major occupational hazard in wood industry and may damage processing equipment. In many wood processing factories, dust collecting systems need to be optimized for the distributional and morphological characteristics of dust in the workshop so that economical and efficient dust control can be achieved. In this study, weighting, image analysis and scanning electron microscopy (SEM) were applied to explore the effects of different cutting speeds on the distribution and morphology of dust generated in MDF milling. The results showed that most dust particles were less than 100 μm and that the aspect ratios (AR) were between 0.6 and 0.7. There was significant difference in particle number size distribution (PNSD) between the dust at different sampling positions. Less amount of dust was located close to cutting center, and fine dust was more likely to appear far away from cutting center. Cutting speed was associated with PNSD, but had little effect on AR. The findings provide spatial distribution characteristics of MDF dust during milling, which can be helpful for optimizing cutting parameters and locating dust collecting hoods to minimize dust exposure.

The massive amounts of dust formed during bamboo CNC milling presents serious risks to human health and equipment. The present study aimed to determine the particle size distribution (PSD) and shape characteristics of bamboo milling dust derived from different average chip thicknesses. Spindle speed and feed rate were varied in combination, in setting up two experimental groups having the same average chip thicknesses. Sieving and flatbed scanning image analyses were collectively utilized for the morphological analysis of bamboo dust. The results showed that less than 5% of the particles were below 100 μm in terms of mass, but represented more than 83% in number. Average chip thickness was positively correlated with a mass proportion of bamboo dust with large size, which was preferably generated when reducing spindle speed instead of increasing feed rate. Spindle speed and feed rate individually affected the particle size and particle size distribution instead of average chip thickness. The aspect ratio, roundness and convexity of bamboo milling dust were augmented with a reduction in particle size, indicating that bamboo milling dust with smaller size had more a regular shape, a smoother profile and fewer corners. These findings provide a theoretical basis for better understanding bamboo milling dust and its related control in the bamboo processing industry.