Physical and chemical characteristics of products from the torrefaction of yellow poplar (Liriodendron tulipifera)

Milling Characteristics of Coal and Torrefied Biomass Blends in a Roller Mill

CO₂ emissions from coal power generation could be reduced by maximizing the amount of torrefied biomass that can be used in pulverized-coal-fired power plants. In this study, to evaluate the milling performance of coal and torrefied wood pellets (TPs), various blend ratios were tested using a bench-scale roller mill. Neutral sugar analysis was performed to evaluate the biomass-derived part of the milled products. Under the test conditions, mill power consumption and differential pressure increased with the TP content. As the TP content increased, the particle size of the milled products also increased. Furthermore, the biomass-derived neutral sugar content and the xylose/glucose (X/G) ratio were higher in the larger particles of the milled product and in the samples collected inside the roller mill than those in the input feedstock. The biomass-derived part with the highest X/G ratio accumulated inside the roller mill, which is probably why the mill power and differential pressure increased with the TP content. The TP, with poor grindability, was discharged from the mill with a larger particle size than that of coal. Although torrefaction treatment pyrolyzed the biomass, the degree of torrefaction can vary within the pellets depending on the torrefaction conditions. To ensure stable operation of the roller mill and an effective reduction in the size of the coal-TP blend, the selection and use of uniformly and sufficiently torrefied wood pellets are important.

Investigation of Biochar Production from Copyrolysis of Rice Husk and Plastic

Biomass renewable energy has become a major target of the Thailand Alternative Energy Development Plan (AEDP) since the country's economy is largely based on agricultural production. Rice husk (RH) is one of the most common agricultural residues in Thailand. This research aims to investigate yields and properties of biochar produced from copyrolysis of RH and plastic (high-density polyethylene (HDPE)) at different ratios, temperatures, and holding times. For both individual and copyrolysis, the temperature variation generated more pronounced effects than the holding time variation on both biochar yields and properties. For individual pyrolysis of RH, the maximum biochar yield of ∼54 wt % was obtained at 400 °C. A shift in temperature from 400 to 600 °C resulted in RH biochars with higher fixed carbon (FC) and carbon (C) contents by ∼1.11-1.28 and 1.06-1.22 times, respectively, while undetectable changes in higher heating values (HHVs) were noticed. For copyrolysis, obvious negative synergistic effects were observed due to the radical interaction between the rich H content of HDPE and RH biochars, which resulted in lower biochar yields as compared to the theoretical estimation based on individual pyrolysis values. However, the addition of HDPE positively impacted the FC and C contents, especially when 10 and 20 wt % HDPE were added to the feedstock. Besides, higher HDPE blending ratios resulted in biochars with improved HHVs, and >1.5 times improvement in HHV was reported in the biochar with 50 wt % HDPE addition in comparison with RH biochar obtained under the same conditions. In summary, biochars generated in this study have the potential to be utilized as a solid fuel or soil amendment.

Effect of Biomass Carbonization on the Grinding of Coal/Biomass Mixtures

To increase the co-firing ratio of biomass in existing pulverized coal-fired power plants, biomass should be pulverized to obtain a particle size suitable for combustion. However, evaluation of the particle size distribution of each coal and biomass mixture via traditional fuel analysis is difficult. Because coal does not contain neutral sugars, the particle size distribution of biomass in the mixture can be estimated based on its neutral sugar content. The current study was conducted to evaluate the effect of biomass carbonization on the grinding process via neutral sugar analysis. Mixtures of coal and carbonized pine chips with three different degrees of carbonization were prepared and ground using a Hardgrove grindability index mill. In the pulverized mixtures of low carbonized biomass and coal, the biomass content at all particle size ranges was nearly the same as that of the input feedstock. As the degree of biomass carbonization increased, the biomass content in the mixture of large particle sizes was decreased, whereas it was increased in the mixture of small particle sizes. The current study indicated that particle size distribution of coal and biomass in the pulverized mixture depends on the degree of carbonization of biomass.

The RDF/SRF torrefaction: An effect of temperature on characterization of the product - Carbonized Refuse Derived Fuel

The influence of Refuse Derived Fuel (RDF)/Solid Recovery Fuel (SRF) torrefaction temperature on product characteristic was investigated. RDF/SRF thermal treatment experiment was conducted with 1-h residence time, under given temperatures: 200, 220, 240, 260, 280 and 300°C. Sawdust was used as reference material. The following parameters of torrefaction char from sawdust and Carbonized Refuse Derived Fuel (CRDF) from RDF/SRF were measured: moisture, calorific value, ash content, volatile compounds and sulfur content. Sawdust biochar was confirmed as a good quality solid fuel, due to significant fuel property increase. The study also indicated that RDF torrefaction reduced moisture significantly from 22.9% to 1.4% and therefore increased lower heating value (LHV) from 19.6 to 25.3MJ/kg. Results suggest that RDF torrefaction may be a good method for increasing attractiveness of RDF as an energy source, and it could help unify RDF properties on the market.

Torrefaction of invasive alien plants: Influence of heating rate and other conversion parameters on mass yield and higher heating value

With the aim of controlling their proliferation, two invasive alien plants, Lantana camara (LC) and Mimosa pigra (MP), both widespread in Africa, were considered for torrefaction for renewable energy applications. Using thermogravimetric analysis, the influence of heating rate (HR: 2.18-19.82°Cmin(-1)) together with variable temperature and hold time on char yield and HHV (in a bomb calorimeter) were determined. Statistically significant effects of HR on HHV with optima at 10.5°Cmin(-1) for LC and 20°Cmin(-1) for MP were obtained. Increases of HHV up to 0.8MJkg(-1) or energy yield greater than 10%, together with a 3-fold reduction in torrefaction conversion time could be achieved by optimisation of HR. Analysis of the torrefaction volatiles by TG-MS showed that not only hemicelluloses, but also lignin conversion, could influence the optimum HR value.

Bioethanol production from deacetylated yellow poplar pretreated with oxalic acid recovered through electrodialysis

Electrodialysis (ED) was used to develop a multistage oxalic acid recovery and pretreatment system to produce ethanol from deacetylated yellow poplar. Pretreatment of the biomass was performed at 150°C for 42 min using 0.16 M oxalic acid. The efficiency of oxalic acid recovery from the hydrolysate reached up to 92.32% in all the stages. Ethanol production and ethanol yield of ED-treated hydrolysate in each stage showed a uniform pattern ranging from 6.81 g/L to 7.21 g/L and 0.40 g/g to 0.43 g/g, respectively. The results showed that efficiency of ethanol production increased when deacetylated biomass and ED process was used. Ethanol yield from the pretreated biomass using simultaneous saccharification and fermentation (SSF) was in the range of 80.59-83.36% in all the stages. The structural characterization of the pretreated biomass at each stage was investigated and structural changes were not significantly different among the various pretreated biomass.

Structural and chemical modifications of typical South African biomasses during torrefaction

Torrefaction experiments were carried out for three typical South African biomass samples (softwood chips, hardwood chips and sweet sorghum bagasse) to a weight loss of 30 wt.%. During torrefaction, moisture, non-structural carbohydrates and hemicelluloses were reduced, resulting in a structurally modified torrefaction product. There was a reduction in the average crystalline diameter (La) (XRD), an increase in the aromatic fraction and a reduction in aliphatics (substituted and unsubstituted) (CPMAS (13)C NMR). The decrease in the aliphatic components of the lignocellulosic material under the torrefaction conditions also resulted in a slight ordering of the carbon lattice. The degradation of hemicelluloses and non-structural carbohydrates increased the inclusive surface area of sweet sorghum bagasse, while it did not change significantly for the woody biomasses.

Torrefaction of pomaces and nut shells

Apple, grape, olive, and tomato pomaces as well as almond and walnut shells were torrefied at different temperatures and times in a muffle furnace. The fiber content and thermal stability of the raw byproducts were examined and the moisture and ash contents, elemental composition, and gross calorific values of the raw and torrefied samples were characterized. Response surface methodology and a central composite design were used to examine the effects of temperature and time on mass and energy yields of the torrefied byproducts. Raw apple pomace had the highest hemicellulose content, whereas raw grape pomace had the highest lignin content. Raw tomato pomace had the highest gross calorific value because of its high carbon content. Temperature had a larger effect on mass and energy yields than time. Grape pomace generally had the highest mass and energy yields. Also, energy yields of the byproducts could be predicted from mass loss values.

Torrefaction of cedarwood in a pilot scale rotary kiln and the influence of industrial flue gas

Torrefaction of cedarwood was performed in a pilot-scale rotary kiln at various temperatures (200, 230, 260 and 290°C). The torrefaction properties, the influence on the grindability and hydroscopicity of the torrefied biomass were investigated in detail as well as the combustion performance. It turned out that, compared with raw biomass, the grindability and the hydrophobicity of the torrefied biomass were significantly improved, and the increasing torrefaction temperature resulted in a decrease in grinding energy consumption and an increase in the proportion of smaller-sized particles. The use of industrial flue gas had a significant influence on the behavior of cedarwood during torrefaction and the properties of the resultant solid products. To optimize the energy density and energy yield, the temperature of torrefaction using flue gas should be controlled within 260°C. Additionally, the combustion of torrefied samples was mainly the combustion of chars, with similar combustion characteristics to lignite.