Wood processing for energy use

Forest biomass has been used as an energy source since ancient times. Since then, several ways of using them have emerged, along with technologies to improve their energy quality. One can cite genetic improvement, thermal transformation through pyrolysis for charcoal and torrefied biomass production, and mechanical transformation through compaction, to produce pellets and briquettes and chipping for the production of chips. However, it is somehow difficult to find articles on these topics that are clearly and objectively presented, making it difficult to read them. The objective of this work was to search data on the ways of processing forest biomass and solutions for the better use of this biomass and its energy use. Therefore, Google Scholar was used as a database from which articles already recognized and others with less impact were obtained. The following search words were used: Eucalyptus, Pinus, wood chips, pellets, briquettes, charcoal, and torrefied wood. To filter the results obtained, the articles that appeared as the most relevant were selected first, then filtered for articles with less than five years from publication, and those at less than two years of publication. Next, the selected articles went through a verification of the data contained in them, and the necessary information was removed from each, which were the species, immediate analysis, extractives, HCV, etc. These data were organized in tables according to the type of processing, prioritizing the values of greatest interest in each analysis, along with the appropriate references. It was observed from the data obtained that the results are compatible among different researchers in their analyses. For samples processed without thermal treatment, the initial characteristics of the wood are maintained, and when going through pyrolysis or torrefaction, these characteristics are changed.

Fuel Properties of Torrefied Biomass from Sapindus Pericarp Extraction Residue under a Wide Range of Pyrolysis Conditions

In this work, a novel biomass, the extraction residue of Sapindus pericarp (SP), was torrefied by using an electronic oven under a wide range of temperature (i.e., 200–320 °C) and residence times (i.e., 0–60 min). From the results of the thermogravimetric analysis (TGA) of SP, a significant weight loss was observed in the temperature range of 200–400 °C, which can be divided into the decompositions of hemicellulose (major)/lignin (minor) (200–320 °C) and cellulose (major)/lignin (minor) (320–400 °C). Based on the fuel properties of the feedstock SP and SP-torrefied products, the optimal torrefaction conditions can be found at around 280 °C for holding 30 min, showing that the calorific value, enhancement factor and energy yield of the torrefied biomass were enhanced to be 28.60 MJ/kg, 1.36 and 82.04 wt%, respectively. Consistently, the values of the calorific value, carbon content and molar carbon/hydrogen (C/H) ratio indicated an increasing trend at higher torrefaction temperatures and/or longer residence times. The findings showed that some SP-torrefied solids can be grouped into the characteristics of a lignite-like biomass by a van Krevelen diagram for all the SP-torrefied products. However, the SP-torrefied fuels would be particularly susceptible to the problems of slagging and fouling because of the relatively high contents of potassium (K) and calcium (Ca) based on the analytical results of the energy dispersive X-ray spectroscopy (EDS).

Pilot-Scale Experimental Study on Impacts of Biomass Cofiring Methods to NOx Emission from Pulverized Coal Boilers—Part 2: NOx Reduction Capability through Reburning versus Cofiring

In this study the NOx reduction capability of reburning three biomasses (i.e., wood pellet, torrefied biomass, and empty fruit bunch) via 12 cases (i.e., four reburning ratios for every biomass) is investigated in a 1 MWth-scale pilot-scale furnace. These reburning cases are compared with 12 cofiring cases presented in the Part 1 paper on a consistent basis. It is found that, for every cost to purchase and prepare biomass, reburning technology provides significantly better NOx abatement performance than cofiring (up to 3.4 times). NOx reduction effectiveness as high as 4.9 could be achieved by reburning, which means the percent of NOx abatement could be 4.9 times higher than the percent of reburning ratio. It is found that the highest NOx reduction per thermal unit of biomass happens at the lowest reburning ratio, and increasing the reburning ratio leads to a reduction in NOx abatement effectiveness in an exponential decay manner. Unlike cofiring technology, reburning was found to have little dependence on the fuel characteristics, such as fuel ratio or fuel-N, when it comes to NOx abatement potential.