A review on wood powders in 3D printing: processes, properties and potential applications

Three-dimensional (3D) printing is a technology that, for a multitude of raw materials, can be used in the production of complex structures. Many of the materials that currently dominate 3D printing (e.g. titanium, steel, plastics, and concrete) have issues with high costs and environmental sustainability. Wood powder is a widely available and renewable lignocellulosic material that, when used as a fibre component, can reduce the cost of 3D printed products. Wood powder in combination with synthetic or natural binders has potential for producing a wide variety of products and for prototyping. The use of natural binders along with wood powder can then enable more sustainable 3D printed products. However, 3D printing is an emerging technology in many applications and more research is needed. This review aims to provide insight into wood powder as a component in 3D printing, properties of resulting products, and the potential for future applications

Patient reactions to cancelled or postponed heart operations.

Objectives The aim was to survey the rate and cause of cancellations of planned cardiac operations at a Swedish clinic during 1999, and to study how the patients were affected. Design Questionnaires were distributed to 74 patients who had their operations cancelled. Their mood after discharge was measured with The Hospital Anxiety and Depression scale. Ninety-three patients, who were operated on without postponement, served as controls. Results Sixty-one percent of the patients in the cancellation group reacted negatively, especially if the reason for cancellation was organizational (P = 0.03). The women in the cancellation group had a significantly higher degree of depression than men (P = 0.01) and both women (P = 0.02) and men (P = 0.003) in the control group. Most of the patients, however, were satisfied with the nursing staff's reception and information. Conclusions The patients reacted negatively to the cancellation, especially if it had organizational reasons. Women subjected to cancellation had a significantly higher degree of depression than other patients. To be avoided, organizational and medical problems must be identified in time. One way to do this is to introduce a preadmission nurse clinic

Does Mechanical Screening of Contaminated Forest Fuels Improve Ash Chemistry for Thermal Conversion?

The effect of mechanical screening of severely contaminated forest fuel chips was investigated, focusing on main ashforming elements and slagging tendency and other properties with relevance for thermal conversion. In this study, screening operations were performed according to practice on an industrial scale by combining a star screen and a supplementary windshifter in six different settings and combinations. Mechanical screening reduced the amount of ash and fine particles in the accept fraction. However, the mass losses for the different screening operations were substantial (20−50 wt %). Fuel analyses of the non-screened and the screened fuels showed that the most significant screening effect was a reduction of Si and Al, indicating an effective removal of sand and soil contaminations. However, the tested fuel’s main ash-forming element’s relative concentration did not indicate any improved combustion characteristics and ash-melting behavior. Samples of the accept fractions and non-screened material were combusted in a single-pellet thermogravimetric reactor, and the resulting ashes’ morphology and elemental composition were analyzed by scanning electron microscopy−energy dispersive X-ray spectrometry and the crystalline phases by powder X-ray diffraction. Results from both these analyses confirmed that screening operations had no, or minor, effects on the fuels’ ash chemistry and slagging tendencies, i.e., the fuels’ proneness to ash melting was not improved. However, the reduction of ash and fine particles can reduce slagging and other operational problems in smaller and more sensitive combustion units

Development and application of a novel cake strength tester

Caking can cause many problems in industries during processing or storage of particulate materials. Caking magnitude depends on several factors, for instance temperature, consolidation stress and storage time. In this research paper, a novel force displacement and easy-to-use caking tester for measuring quantitatively cake strength as a result of elevated temperature, consolidation stress and storage time is introduced. The developed tester outweighed the conventional uniaxial unconfined failure caking tester due to the defined location of the failure plane to maximise repeatability, the necessity for a lower quantity of powder, maximised exposed surface and lower wall friction as well as production costs. The experimental design has been conducted by changing the temperature, consolidation stress and storage duration. The results showed that the tester could distinguish cake strength between different experimental conditions. A statistical model has been successfully developed to study the effect of each variable on the cake strength

Application of design of experiments (DoE) for optimised production of micro- and mesoporous Norway spruce bark activated carbons

In this work, Norway spruce (Picea abies (Karst) L.) bark was employed as a precursor to prepare activated carbon using zinc chloride (ZnCl2) as a chemical activator. The purpose of this study was to determine optimal activated carbon (AC) preparation variables by the response surface methodology using a Box-Behnken design (BBD) to obtain AC with high specific surface area (S-BET), mesopore surface area (S-MESO), and micropore surface area (S-MICR). Variables and levels used in the design were pyrolysis temperature (700, 800, and 900 degrees C), holding time (1, 2, and 3 h), and bark/ZnCl2 impregnation ratio (1, 1.5, and 2). The optimal conditions for achieving the highest S-BET were as follows: a pyrolysis temperature of 700 degrees C, a holding time of 1 h, and a spruce bark/ZnCl2 ratio of 1.5, which yielded an S-BET value of 1374 m(2) g(-1). For maximised mesopore area, the optimal condition was at a pyrolysis temperature of 700 degrees C, a holding time of 2 h, and a bark/ZnCl2 ratio of 2, which yielded a S-MESO area of 1311 m(2) g(-1), where mesopores (S-MESO%) comprised 97.4% of total S-BET. Correspondingly, for micropore formation, the highest micropore area was found at a pyrolysis temperature of 800 degrees C, a holding time of 3 h, and a bark/ZnCl2 ratio of 2, corresponding to 1117 m(2) g(-1), with 94.3% of the total S-BET consisting of micropores (S-MICRO%). The bark/ZnCl2 ratio and pyrolysis temperature had the strongest impact on the S-BET, while the interaction between temperature and bark/ZnCl2 ratio was the most significant factor for S-MESO. For the S-MICRO, holding time was the most important factor. In general, the spruce bark AC showed predominantly mesoporous structures. All activated carbons had high carbon and low ash contents. Chemical characterisation indicated that the ACs presented disordered carbon structures with oxygen functional groups on the ACs' surfaces. Well-developed porosity and a large surface area combined with favourable chemical composition render the activated carbons from Norway spruce bark with interesting physicochemical properties. The ACs were successfully tested to adsorb sodium diclofenac from aqueous solutions showing to be attractive products to use as adsorbents to tackle polluted waters

Using macromolecular composition to predict optimal process settings in ring-die biomass pellet production

This study was performed to investigate if the process settings that give high pellet durability can be modelled from the biomass’ macromolecular composition. Process and chemical analysis data was obtained from a previous pilot-scale study of six biomass assortments that by Principal Component Analysis (PCA) was confirmed as representative for their biomass types: hardwood, softwood bark, short rotation coppice (SRC), and straw and energy crops. Orthogonal Partial Least Squares Projections to Latent Structures (OPLS) models were created with the content of macromolecules as factors and the die compression ratio and the feedstock moisture content at which the highest pellet durability was obtained as responses. The models for die compression ratio (R2X = 0.90 and Q2 = 0.58) and feedstock moisture content (R2X = 0.87 and Q2 = 0.60), rendered a prediction error for obtained mechanical durability of approximately ±1%-unit, each. Important factors for modelling of the die compression ratio were: soluble lignin (negative), acetyl groups (negative), acetone extractives (positive), and arabinan (positive). For modelling of the feedstock moisture content, Klason lignin (negative), xylan (positive), water-soluble extractives (negative), and mannan (negative), were the most influential. Results obtained in this study indicate that it is possible to predict optimal process conditions in pelletizing based on the macromolecular composition of the raw material. In practice, this would mean a higher raw material flexibility in the pellet factories through drastically reduced risk when introducing new raw materials

Facile Synthesis of Sustainable Activated Biochars with Different Pore Structures as Efficient Additive-Carbon-Free Anodes for Lithium- and Sodium-Ion Batteries

The present work elucidates facile one-pot synthesis from biomass forestry waste (Norway spruce bark) and its chemical activation yielding high specific surface area (SBET) biochars as efficient lithium-and sodium-ion storage anodes. The chemically activated biochar using ZnCl2 (Biochar-1) produced a highly mesoporous carbon containing 96.1% mesopores in its structure as compared to only 56.1% mesoporosity from KOH-activated biochars (Biochar-2). The latter exhibited a lower degree of graphitization with disordered and defective carbon structures, while the former presented more formation of ordered graphite sheets in its structure as analyzed from Raman spectra. In addition, both biochars presented a high degree of functionalities on their surfaces but Biochar-1 presented a pyridinic-nitrogen group, which helps improve its electrochemical response. When tested electrochemically, Biochar-1 showed an excellent rate capability and the longest capacity retentions of 370 mA h g-1 at 100 mA g-1 (100 cycles), 332.4 mA h g-1 at 500 mA g-1 (1000 cycles), and 319 mA h g-1 at 1000 mA g-1 after 5000 cycles, rendering as an alternative biomass anode for lithium-ion batteries (LIBs). Moreover, as a negative electrode in sodium-ion batteries, Biochar-1 delivered discharge capacities of 147.7 mA h g-1 at 50 mA g-1 (140 cycles) and 126 mA h g-1 at 100 mA g-1 after 440 cycles

Microalgae biomass as a sustainable precursor to produce nitrogen-doped biochar for efficient removal of emerging pollutants from aqueous media

Preparing sustainable and highly efficient biochars as adsorbents remains a challenge for organic pollutant management. Herein, a novel nitrogen-doped carbon material has been synthesized via a facile and sustainable single-step pyrolysis method using a wild mixture of microalgae as novel carbon precursor. Phosphoric acid (H3PO4) was employed as activation agent to generate pores in the carbon material. In addition, the effect of melamine (nitrogen source) was evaluated over the biochar properties by the N-doping process. The results showed that the biochar’s specific surface area (SSA) increased from 324 to 433 m2 g− 1 with the N-doping process. The N-doping process increased the percentage of micropores in the biochar structure. Chemical characterization of the biochars indicated that the N-doping process helped to increase the graphitization process of the biochar and the contents of oxygen and nitrogen groups on the carbon surface. The biochars were successfully tested to adsorb acetaminophen and treat two synthetic effluents, and the N-doped biochar presented the highest efficiency. The kinetics and equilibrium data were well represented by the General-order model and the Liu isotherm model, respectively. The maximum sorption capacities attained were 101.4 and 120.7 mg g− 1 for the non-doped and doped biochars, respectively. The acetaminophen adsorption mechanism suggests that the pore-filling was the dominant mechanism for acetaminophen uptake. The biochars could efficiently remove up to 74% of the contaminants in synthetic effluents

Pelleting torrefied biomass at pilot-scale – Quality and implications for co-firing

The co-firing of solid biofuels in coal plants is an attractive and fast-track means of cutting emissions but its potential is linked to biomass densification. For torrefied materials this topic is under-represented in literature. This pilot-scale (121–203 kg h−1) pelleting study generated detailed knowledge on the densification of torrefied biomass compared to untreated biomass. Four feedstock with high supply availability (beech, poplar, wheat straw and corn cob) were studied in their untreated and torrefied forms. Systematic methods were used to produce 180 batches of 8 mm dia. pellets using press channel length (PCL) and moisture content (MC) ranges of 30–60 mm and 7.3–16.6% (wet basis) respectively. Analysis showed that moderate degrees of torrefaction (250–280 °C, 20–75 min) strongly affected pelleting behaviour. The highest quality black pellets had a mechanical durability and bulk density range of 87.5–98.7% and 662–697 kg m−3 respectively. Pelleting energy using torrefied feedstock varied from −15 to +53 kWh t−1 from untreated with increases in production fines. Optimal pelleting MC and PCL were reduced significantly for torrefied feedstock and pellet quality was characterised by a decrease in mechanical durability and an increase in bulk density. Energy densities of 11.9–13.2 GJ m−3 (as received) were obtained