Quantification of Cholesterol Oxidation Products In Egg Yolk Powder Spray-dried with Direct Heating

A direct-heated spray dryer with an evaporative capacity of up to 7 kg H₂O/hr was used to identify processing conditions responsible for formation of cholesterol oxidation products (COPS) in spray-dried egg yolk. Outlet air temperature and nitrogen oxides (NO_x) in the combustion gases were the only conditions that affected COPS levels. At outlet temperature 150°C, total COPS concentrations in the spray-dried product were 75 ppm at 5 ppm NO_x and 213 ppm at 300 ppm NO_x. In products dried at 75°C outlet temperature, total COPS concentrations were 21 ppm at 5 ppm NO_x and 58 ppm at 300 ppm NO_x. In general, individual COPS responded to outlet temperature and NO_x in the same manner as total COPS.     

Emissions of chromium, copper, arsenic, and PCDDs/Fs from open burning of CCA-treated wood

Aged and weathered chromated copper arsenate (CCA) treated wood was burned in an open burn research facility to characterize the air emissions and residual ash. The objectives were to simulate, to the extent possible, the combustion of such waste wood as might occur in an open field or someone's backyard; to characterize the composition and particle size distribution (PSD) of the emitted fly ash; to determine the partitioning of arsenic, chromium, and copper between the fly ash and residual ash; and to examine the speciation of the CCA elements. This work reports preliminary air emission concentrations and estimated emission factors for total particulate matter, arsenic (As), chromium (Cr), copper (Cu), and polychlorinated dibenzodioxins/dibenzofurans (PCDD/F) totals and toxic equivalents (TEQs). The partitioning of As, Cr, and Cu between the emitted fly ash and residual ash is examined and thermochemical predictions from the literature are used to explain the observed behavior. Results indicate a unimodal fly ash PSD between 0.1 and 1.0 microm diameter. In addition to a large carbonaceous component, between 11 and 14% of the As present in the burned CCA treated wood was emitted with the air emissions, with the remainder present in the residual ash. In contrast, less than 1% of both the Cr and Cu present in the wood was emitted with the air emissions. PCDD/F levels were unremarkable, averaging 1.7 ng TEQ/kg of treated wood burned, a value typical for wood combustion. Scanning electron microscopy (SEM) was unable to resolve inorganic particles consisting of Cu, Cr, or As in the wood samples, but X-ray absorption fine structure (XAFS) spectroscopy confirmed that the oxidation states of the CCA elements in the wood were Cu2+, Cr3+, and As5+. SEM examination of the fly ash samples revealed some inorganic microcrystals within the mostly carbonaceous fly ash, while XAFS spectroscopy of the same samples showed that the oxidation states after combustion were mixed Cu+ and Cu2+, Cr3+, and mixed As3+ and As5+. Estimates of the ratios of the mixed oxidation states based on the XAFS spectra were As3+/(total As) = 0.8-0.9 and Cu+/(total Cu) = 0.65-0.7. The Cu and Cr present in the fly ash were determined to coexist predominantly in the two oxide phases CuCrO2 and CuCr2O4. These results indicate that the open burning of CCA-treated wood can lead to significant air emissions of the more toxic trivalent form of As in particle sizes that are most respirable.     

Systematische Untersuchungen der Wirkung aggressiver Gase auf Fichtenholz

In extension of previously described chemical investigations on spruce wood treated with formaldehyde, ammonia, sulfur dioxide and chlorine, sorption experiments were made applying the same gases. The wood samples treated with gases were also tested in bending stress. Wood absorbs ammonia very quickly, but the gas is only slightly bound. The absorption of chlorine takes place only slowly, but chlorine is almost completely bound. In contrast to NH₃ and Cl₂ more SO₂ is absorbed with increasing moisture of wood. While treatments with formaldehyde and NH₃ cause an increase of wood strength, treatment with SO₂ causes a minor, treatment with Cl₂ a deep drop in strength respectively. All results of the chemical and physical investigations are finally compiled in a schedule giving an estimate of the effects of aggressive gases on spruce wood.     

Probleme bei der thermischen Verwertung von Wald-, Rest- und Altholz

One of the most difficult problems is the distinction between treated and untreated wood. The thermal utilization of treated wood in Germany is more restrictively regulated than that for untreated wood. Accordingly, due to insufficient possibilities for use in particle board production, biological treatment, dumping, and the strong restrictively regulated export, it is necessary to burn wood and wood residues. Even in untreated woods chemical elements are present, which are also contained in wood preservatives, e.g. you can find mercury, arsenic, fluorine, chromium, copper, or tin in different quantities in natural wood. In Germany, it is prohibited to burn treated wood in plants without air cleaning equipment. Under economic aspects it would be too expensive to use plants with air cleaning equipment for burning wood. It is therefore necessary in Germany to determine some parameters to characterize the natural condition. This would be additional a basis for the distinction between treated und untreated wood.     

Dielectric barrier discharge treatments at atmospheric pressure for wood surface modification

In this research, the effect of dielectric barrier discharge on mechanically manufactured (sawn, planed or polished) wood surfaces is investigated. The experiments have shown that the best hydrophilia is obtained with a cold plasma discharge in air under atmospheric pressure. Other gases such as helium, nitrogen, and argon have been tested, too. Changes of the wood surface properties were determined by absorption of water and contact angle measurements. As a result of a 1 to 20 seconds long exposure to plasma, wood surfaces became hydrophilic. The absorption of water in wood can be changed up to 22 times higher after plasma treatment in air for 20 seconds duration. The fracture strength of glued wood has been increased by 68% after this plasma pretreatment. Using plasma treatment in methane or acetylene wood surfaces are changed to hydrophobic properties. After plasma treatment for 1 min. in a Ar:CH₄=80:20 gas mixture under atmospheric pressure, the absorption of water in wood is 32 times lower than without plasma treatment. As mentioned before, plasma treatment can produce hydrophobic and hydrophilic wood surfaces. But a good homogeneity of the gas discharge is necessary for the plasma treatment of wood.     

Emission of PCDD/F, PCB, and HCB from combustion of firewood and pellets in residential stoves and boilers

To assess potential emissions of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and hexachlorobenzene (HCB) from residential combustion of biofuels, experiments were performed in which various types of pellets and firewood were combusted in four types of stoves and boilers, with both full and reduced rates of air supply. Intermittent combustion of wood pellets resulted in emissions of 11 ng-(WHO-TEQ)/kg combusted fuel (dry weight). A modern, environmentally certified boiler yielded somewhat lower emissions of PCCD/F and PCB than a wood stove. Both gave <0.1 ng(WHO-TEQ)/m3n (1.3-6.5 ng(WHO-TEQ)/kg) and considerably lower emissions than an old boiler (7.0-13 ng(WHO-TEQ)/kg). No positive effect on emissions could be observed in full air combustion (simulating the use of a heat storage tank) compared to combustion with reduced air. Two of the wood combustion experiments included paper and plastic waste fuels. Chlorine-containing plastic waste gave rise to high emissions: ca. 310 ng(WHO-TEQ)/ kg over the whole combustion cycle. The homologue profiles of PCDD/Fs show characteristic differences between ashes and flue gas from combustions with different levels of air supply. These differences do not, however, seem to have any correlation to the relative amount of toxic congeners.     

Emissions during combustion of particleboard and glued veneer

The combustion of particleboard and glued veneer was studied in order to evaluate if there are any negative effects on the environment from incineration of waste with adhesive. The particleboard was made with urea formaldehyde (UF) resin and the veneers were glued with different types of adhesives, UF, polyvinyl acetate, emulsion polymer isocyanate (EPI), melamine urea formaldehyde (MUF) and phenol resorcinol formaldehyde. The combustion tests were carried out in a fluidised sand bed reactor with a good oxygen supply at temperatures between 500°C and 1000°C for particleboard and at 750°C and 850°C for glued veneer. The emissions were compared with the emissions from combustion of pure wood and pellets made from wood. The results show that the emissions from both particleboard and glued veneer are similar to the emissions from pure wood. The only main difference is that the nitrogen oxide (NO_x) is increased when particleboard and nitrogen-containing adhesives, like UF, EPI and MUF, are combusted. The nitrogen from the adhesive is only to a minor extent converted to NO_x, e.g. only 4% of the nitrogen in particleboard gives NO_x.     

Beitrag zur Prüfung der Brandeigenschaften,insbesondere der Schwerentflammbarkeit,von Platten aus Holz und Holzwerkstoffen

Summary With the help of the “Plattenschlot” method which is intended to be included into the German standard DIN 4102, comparative fire tests on wood and wood-base materials were carried out. The materials were partly unprotected and partly protected by fireretardant preservatives. The temperature of the air of combustion, the temperature of the shaft wall as well as the loss of weight were measured. The results, average values of three equal tests, were represented in diagrams and discussed. The curves resulting from graphic differentiation were very instructive for the speed of temperature changes and for the speed of the loss of weight. For the evaluation of the behaviour of the examined board-materials also the dimensionless combustion measure can be brought up. The total results were additionally represented in 2 tables. For the new edition of DIN 4102 it was lately being considered to acknowledge the property “flame-retardant” only if the maximum temperature of the air of combustion does not exceed 250°C and the loss of weight does not rise beyond 30%. Though two thirds of the materials examined failed, the test procedure is, according to the authors' opinion, not too strict. With respect to safety, the maximum temperature of the air of combustion has to be coupled with the maximum loss of weight. Considering the fact that within the region of 220 to 280°C the pyrolysis of wood begins to become exothermical, it should even be investigated whether this maximum temperature permissible should not be reduced. Tests have shown that with sufficient effectiveness of the fire-retardant preservatives this condition can, without difficulties, be complied with. Also spruce of 20 mm in thickness, which untreated is highly endangered, as well as 12 mm plywood having been painted with intumescent preservatives became acceptably “flame-retardant”. It is important to concert gluing technique and fire protection.

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Mitteilung aus dem Institut für Holzforschung und Holztechnik der Universit?t München     

Stand der Vergasungstechnik für die thermische Nutzung von Biobrennstoffen am Beispiel Holz

The interest of economy and policy as well as research and development is focussed on the “reduction of carbon-dioxid-emissions“ and the “sustainable development“. Therefore the thermal utilization of biological material as fuel has become most important. Among the biological material wood, and especially waste wood, has a particular position. Concerning the thermal utilization of wood/waste wood the gasification is advantageous compared to the combustion, because of the possibility to generate electric current in a gasmotor or a gasturbine. To optimize the utilization of the caloric value under economical and technical aspects decentral concepts and fixed bed gasifiers should be applied. In Middle and East Europe experts determine a considerable requirement for gasification plants of 1 to 5 MW_th. Unfortunately none of the existing gasification concepts can guarantee a safe and efficient, much less a continuous operation. The article describes the principles of different gasification concepts (such as fixed bed or fluidized bed gasifiers), the disadvantages and benefits of the types of fixed bed gasifiers as well as the experiences gained at several pilot plants. The demand for research and development is discussed.     

Study of thermal properties of wood plastic composite reinforced with cellulose micro fibril and nano inorganic fiber filler

Wood plastic composite was prepared by mixing wood fibrils into polypropylene with an internal mixer. Nano wollastonite was dispersed in the composite to compensate for the poor thermal characteristics of the product. Thermal properties of the obtained composite were studied by different techniques including thermo gravimetrical analysis, differential scanning calorimetry, limited oxygen index and oxidative induction time. It was found that introduction of nano wollastonite increased thermal stability as well as crystallinity in the composite due to high specific surface area of nano inorganic fiber filler. Also, flammability resistance and the required oxygen content to burn the composite were enhanced as wollastonite was added to the wood plastic composite. However, wollastonite increased oxidation of the sample because it is composed of metal oxides.     

Nitric oxide reduction in coal combustion: role of char surface complexes in heterogeneous reactions

Nitrogen oxides are one of the major environmental problems arising from fossil fuel combustion. Coal char is relatively rich in nitrogen, and so this is an important source of nitrogen oxides during coal combustion. However, due to its carbonaceous nature, char can also reduce NO through heterogeneous reduction. The objectives of this work were on one hand to compare NO emissions from coal combustion in two different types of equipment and on the other hand to study the influence of char surface chemistry on NO reduction. A series of combustion tests were carried out in two different scale devices: a thermogravimetric analyzer coupled to a mass spectrometer and an FTIR (TG-MS-FTIR) and a fluidized bed reactor with an on line battery of analyzers. The TG-MS-FTIR system was also used to perform a specific study on NO heterogeneous reduction reactions using chars with different surface chemistry. According to the results obtained, it can be said that the TG-MS-FTIR system provides valuable information about NO heterogeneous reduction and it can give good trends of the behavior in other combustion equipments (i.e., fluidized bed combustors). It has been also pointed out that NO-char interaction depends to a large extent on temperature. In the low-temperature range (<800 degrees C), NO heterogeneous reduction seems to be controlled by the evolution of surface complexes. In the high-temperature range (>800 degrees C), a different mechanism is involved in NO heterogeneous reduction, the nature of the carbon matrix being a key factor.     

Novel incineration technology integrated with drying, pyrolysis, gasification, and combustion of MSW and ashes vitrification

The conventional mass burn systems for municipal solid waste (MSW) emit large amount of acidic gases and dioxins as well as heavy metals due to the large excess air ratio. Additionally, the final process residues, bottom ash with potential leachability of heavy metals and fly ash with high level of heavy metals and dioxins, also constitute a major environmental problem. To deal with these issues more effectively, a novel MSW incineration technology was developed in this study. MSW drying, pyrolysis, gasification, incineration, and ash vitrification were achieved as a spectrum of combustion by the same equipment (primary chamber) in one step. In practice, the primary chamber of this technology actually acted as both gasifier for organic matter and vitrifying reactor for ashes, and the combustion process was mainly completed in the secondary chamber. Experiments were carried outto examine its characteristics in an industrial MSW incineration plant, located in Taiyuan, with a capability of 100 tons per day (TPD). Results showed that (1) the pyrolysis, gasification, and vitrification processes in the primary chamber presented good behaviors resulting in effluent gases with high contents of combustibles (e.g., CO and CH4) and bottom ash with a low loss-on-ignition (L.o.l), low leachability of heavy metals, and low toxicity of cyanide and fluoride. The vitrified bottom ash was benign to its environment and required no further processing for its potential applications. (2) Low stack emissions of dioxins (0.076 ng of TEQ m(-3)), heavy metals (ranging from 0.013 to 0.033 mg m(-3)), and other air pollutants were achieved. This new technology could effectively dispose Chinese MSW with a low calorific value and high water content; additionally, it also had a low capital and operating costs compared with the imported systems.     

Differential pressure characteristics of wood impregnated with compressed gases, liquids and supercritical fluids

Pressure difference characteristics at high pressure impregnation of two hardwood and three softwood species with CO₂, ethanol, hexane and supercritical mixtures were analysed in a high pressure autoclave. The investigation shows that typical penetration characteristics of wood depending on species measured in terms of pressure difference between the surrounding and the centre are true for gases, liquids and supercritical fluids. The known fact that pressures higher than 16 bar may cause wood destruction is confirmed once more. In contrast to known investigations we can show that pressures up to 175 bar can be applied to wood samples without wood destruction if the pressure difference between surrounding and centre does not exceed 16 bar. The supercritical phase of ethanol/CO₂-mixture is a potential media for technical application. It allows fast penetration at high pressures increasing at 16 bar/5 min combined with low pressure differences even at high pressure levels of 175 bar without wood destruction.     

Emissions of parent, nitro, and oxygenated polycyclic aromatic hydrocarbons from residential wood combustion in rural china

Residential wood combustion is one of the important sources of air pollution in developing countries. Among the pollutants emitted, parent polycyclic aromatic hydrocarbons (pPAHs) and their derivatives, including nitrated and oxygenated PAHs (nPAHs and oPAHs), are of concern because of their mutagenic and carcinogenic effects. In order to evaluate their impacts on regional air quality and human health, emission inventories, based on realistic emission factors (EFs), are needed. In this study, the EFs of 28 pPAHs (EF(PAH28)), 9 nPAHs (EF(PAHn9)), and 4 oPAHs (EF(PAHo4)) were measured for residential combustion of 27 wood fuels in rural China. The measured EF(PAH28), EF(PAHn9), and EF(PAHo4) for brushwood were 86.7 ± 67.6, 3.22 ± 1.95 × 10(-2), and 5.56 ± 4.32 mg/kg, which were significantly higher than 12.7 ± 7.0, 8.27 ± 5.51 × 10(-3), and 1.19 ± 1.87 mg/kg for fuel wood combustion (p < 0.05). Sixteen U.S. EPA priority pPAHs contributed approximately 95% of the total of the 28 pPAHs measured. EFs of pPAHs, nPAHs, and oPAHs were positively correlated with one another. Measured EFs varied obviously depending on fuel properties and combustion conditions. The EFs of pPAHs, nPAHs, and oPAHs were significantly correlated with modified combustion efficiency and fuel moisture. Nitro-naphthalene and 9-fluorenone were the most abundant nPAHs and oPAHs identified. Both nPAHs and oPAHs showed relatively high tendencies to be present in the particulate phase than pPAHs due to their lower vapor pressures. The gas-particle partitioning of freshly emitted pPAHs, nPAHs, and oPAHs was primarily controlled by organic carbon absorption.     

草浆黑液的燃烧性能

燃烧是碱回收的关键工序, 而草浆黑液比木浆黑液难燃烧。事先测定一些与草浆黑液燃烧有关的参数, 可以准确地预测碱回收车间建成后黑液的燃烧性能, 以保证碱回收锅炉的正常运行。     

Untersuchungen über Emissionen bei der thermischen Verwertung von holzschutzmittelhaltigen Holzresten

Since the introduction of strict legal conditions, the disposal of used wood and wood residues treated with wood preservatives became subject of many and diverse discussions. An alternative to disposal and recycling in principle is the thermal utilization, the application of which, however, is ruled by the emission behaviour of the individual fuel components during the combustion process. Due to the fact that up to now only few experimental findings on emissions of organic and inorganic substances during the combustion of wood treated with wood preservatives were known, the combustion behaviour of wood residues and used wood containing wood preservatives, after mixing with untreated wood in a ratio of 1∶4, was investigated in several test series. The presented results for organic solvents, creosote, Cu-HDO and CCB show that the concentrations of the harmful chemicals occuring in the exhaust gas correspond approximately to those registered for untreated wood. Even properties decreasing the emissions were found for Cu-HDO and CCB. The fixed limit values for polychlorinated dibenzodioxins and dibenzofurans also can be observed provided there exist good combustion conditions.     

On-line analysis of gas-phase composition in the combustion chamber and particle emission characteristics during combustion of wood and waste in a small batch reactor

The emission of particulate matter and gaseous compounds during combustion of wood and refuse-derived fuel in a small batch reactor is investigated by laser mass-spectrometric on-line measurement techniques for gas-phase analysis and simultaneous registration of physical aerosol properties (number size distribution). The gas-phase composition is addressed by a laser-based mass spectrometric method, namely, vacuum-UV single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS). Particle-size distributions are measured with a scanning mobility particle sizer. Furthermore, a photoelectric aerosol sensor is applied for detection of particle-bound polycyclic aromatic hydrocarbons. The different phases of wood combustion are distinguishable by both the chemical profiles of gas-phase components (e.g., polycyclic aromatic hydrocarbons, PAH) and the particle-size distribution. Furthermore, short disturbances of the combustion process due to air supply shortages are investigated regarding their effect on particle-size distribution and gas-phase composition, respectively. It is shown that the combustion conditions strongly influence the particle-size distribution as well as on the emission of particle-bound polycyclic aromatic hydrocarbons.     

Entsorgung von mit Holzschutzmitteln behandelten Hölzern

Recycling wood and industrial wood residues often contain various wood preservatives. The waste management for these residues can be recycling, deposition or combustion. Among the three possibilities combustion is the best way of usage. The combustion of wood residues containing organic or inorganic preservatives is influenced by the elementary composition of the preservative and the thermal and oxidative reaction pathes in the flame. Organic preservatives mostly can be thermally destructed by usual combustion conditions. Elevated combustion conditions are necessary for preservatives based on tar oils and chlorinated compounds. Among inorganic compounds, mercury and arsenic based preservatives have a considerable environmental impact. Other elements like copper, sinc, borine or chrome remain in ashes and cinders reducing the emmission problems towards an effective dust removal.     

Development of a continuous membrane nanobubble generation method applicable in liquid food processing

A novel continuous nanobubble generation method was developed using a commercial ceramic membrane as a nanobubble generator. CO₂ and air were infused externally across the ceramic membrane (pore size 50 nm) into the water flowing inside the ceramic membrane tube. Infusion of each gas was done in a single (20 s) and multiple passes (180 s) at 20–21°C. Results showed that gaseous nanobubbles could be generated even in a single pass. Low power ultrasound (200 kHz, 30W) was applied for the rapid assessment of nanobubble stability. Single-pass ultrasound treatment of the samples was carried out at two levels: 2.6 and 5.1 J mL⁻¹. Among the samples in which gases were infused for multiple passes, air nanobubbles were found more stable than CO₂. In contrast, an opposite trend was observed in those samples in which gases were infused in the single-pass only (20 s). This process has the potential to be applied to food processing industries, such as to enhance the products’ sensory attributes, the efficiency of membrane separation, food drying and liquid food transportation systems.     

Research on GA-BP neural network model of surface roughness in air drum sanding process for poplar

Roughness is an important property of wood surface and has a significant influence on the interface bonding strength and surface coating quality. At present, there is little research on theoretical models for poplar fine sanding. In this study, poplar wood was fine-sanded with an air drum. An orthogonal experiment was carried out to study the effects of abrasive grain size, feed rate, belt speed, air drum deformation and air drum pressure on the surface roughness of poplar wood. The simulation models of the longitudinal roughness and the lateral roughness of the sanding surface were established based on BP neural network optimized by genetic algorithm (GA-BP neural network), and verified by the experimental data. The results show that the influence of sanding parameters on longitudinal roughness and lateral roughness is similar. The order of influence is abrasive grain size?>?belt speed?>?feed speed?>?air drum deformation and air drum pressure. The longitudinal roughness and lateral roughness of the surface of the poplar can be well predicted by GA-BP neural network. The average relative error of the predicted longitudinal roughness and lateral roughness are 2.67% and 2.65%, respectively.