Influence of pressure on pyrolysis of black liquor: 2. Char yields and component release

This is the second in a series of papers concerning the behavior of black liquor during pyrolysis at elevated pressures. Two industrial black liquors were pyrolyzed under pressurized conditions in two laboratory-scale devices, a pressurized single-particle reactor and a pressurized grid heater. Temperatures ranging between 650 and 1100 degrees C and pressures in the range 1-20 bar were studied. Char yields were calculated and based on analysis of some of the chars the fate of carbon, sodium, potassium and sulfur was determined as a function of pyrolysis pressure. At temperatures below 800 degrees C little variation in char yield was observed at different pressures. At higher temperatures char yield increased with pressure due to slower decomposition of sodium carbonate. For the same reason, sodium release decreased with pressure. Sulfur release, however, increased with pressure primarily because there was less opportunity for its capture in the less-swollen chars.     

Influence of pressure on pyrolysis of black liquor: 1. Swelling

This is the first of two papers concerning the behavior of black liquor during pyrolysis under pressurized conditions. Two industrial kraft liquors were pyrolyzed in a laboratory-scale pressurized single particle reactor and a pressurized grid heater at temperatures ranging from 650 to 1100 degrees C and at pressures between 1 and 20 bar. The dimensions of the chars produced were measured and the specific swollen volume was calculated. Swelling decreased roughly logarithmically over the pressure range 1-20 r. An expression is developed to predict the specific swollen volume at elevated pressure when the volume at 1 bar is known. The bulk density of the char increased with pressure, indicating that liquors will be entrained less easily at higher pressures.     

Sunflower shells utilization for energetic purposes in an integrated approach of energy crops: laboratory study pyrolysis and kinetics

Sunflower is a traditional crop which can be used for the production of bioenergy and liquid biofuels. A study of the pyrolytic behaviour of sunflower residues at temperatures from 300 to 600 degrees C has been carried out. The experiments were performed in a captive sample reactor under atmospheric pressure and helium as sweeping gas. The yields of the derived pyrolysis products were determined in relation to temperature, with constant sweeping gas flow of 50 cm3 min(-1) and heating rate of 40 degrees Cs(-1). The maximum gas yield of around 53 wt.% was obtained at 500 degrees C, whereas maximum oil yield of about 21 wt.% was obtained at 400 degrees C. A simple first order kinetic model has been applied for the devolatilization of biomass. Kinetic constants have been estimated: E=78.15 kJ mol(-1); k(0)=1.03 x 10(3)s(-1).     

Jute stick pyrolysis for bio-oil production in fluidized bed reactor

Pyrolysis of jute stick for bio-oil production has been investigated in a continuous feeding fluidized bed reactor at different temperatures ranging from 300 degrees C to 600 degrees C. At 500 degrees C, the yields of bio-oil, char and non-condensable gas were 66.70 wt%, 22.60 wt% and 10.70 wt%, respectively based on jute stick. The carbon based non-condensable gas was the mixture of carbon monoxide, carbon dioxide, methane, ethane, ethene, propane and propene. The density and viscosity of bio-oil were found to be 1.11 g/mL and 2.34 cP, respectively. The lower heating value (LHV) of bio-oil was found to be 18.2 5 MJ/kg. Since bio-oil contains some organic acids such as formic acid, acetic acid, etc., the pH and acid value of the bio-oil were found to be around 4 and 135 mg KOH/g, respectively. The water, lignin, solid and ash contents of bio-oil were determined and found to be around 15 wt%, 4.90 wt%, 0.02 wt% and 0.10 wt%, respectively.     

Fast pyrolysis of soybean cake: product yields and compositions

This study was an investigation of the role of important parameters influencing pyrolysis yields from soybean cake. Experiments were carried out at temperatures ranging from 400 to 700 degrees C, for various nitrogen flow rates, heating rates and particle sizes. The maximum liquid yield was 42.83% at a pyrolysis temperature of 550 degrees C with a sweeping gas rate of 200 cm3 min(-1) and heating rate of 700 degrees C min(-1) for a soybean cake sample having 0.425 < D(p) < 0.85 mm particle size. The various characteristics of liquid product were identified. Thus, the aliphatic sub-fraction of the bio-oil was analysed by GC-MS and further structural analyses of bio-oil and aromatic and polar sub-fractions were conducted using FT-IR and 1H-NMR. The H/C ratios and the structural analysis of the fractions obtained from the biocrudes showed that the fractions were quite similar to currently utilised transport fuels.     

Physical and thermochemical characterization of rice husk char as a potential biomass energy source

The fixed bed pyrolysis of rice husk was studied under conventional conditions with the aim of determining the characteristics of the charcoal formed for its applicability as a solid fuel. Thermoanalytic methods were used to determine the kinetic parameters of its combustion. Palletisation using different binders and techniques to improve the time of sustained combustion of the char pallets were investigated. The optimum temperature for carbonization to obtain a char having moderately high heating value was found as 400 degrees C. For the active char combustion zone, the order of reaction was nearly 1, the activation energy 73.403 kJ/mol and the pre-exponential factor 4.97 x 10(4)min(-1). Addition of starch as a binder and 10% ferrous sulphate heptahydrate or sodium hypophosphite as an additive enhanced the ignitibility of the char pallets.     

Fermentation of kraft black liquor for the production of citric acid by Candida tropicalis

Summary The production of citric acid by batch fermentation with the yeast strain Candida tropicalis ATCC 20240 was chosen as a potential process for the valorization of kraft black liquor. The effect of nitrogen concentration was studied and direct bioconversion of acetate to citrate was achieved when no nitrogen was supplemented to the medium. The use of kraft black liquor's acetate as a potential substrate for citric acid production was investigated. The acid precipitated liquor was highly inhibitory when its concentration was above 25% of the fermentation broth content. The yields of citric acid at low concentrations of kraft black liquor (5% and 15%) were the same as those recorded in synthetic acetate medium. Other organic acids present in the liquor may affect the yields and rates of citric acid production over acetate. Substrate uptake rates and product formation rates were lower, however, in comparison to synthetic media. The utilization of immobilized biomass improved the process parameters on kraft black liquor and enhanced the fermentation capabilities.     

Comparison of non-catalytic and catalytic fast pyrolysis of corncob in a fluidized bed reactor

Fast pyrolysis of corncob with and without catalyst was investigated in a fluidized bed to determine the effects of pyrolysis parameters (temperature, gas flow rate, static bed height and particle size) and a HZSM-5 zeolite catalyst on the product yields and the qualities of the liquid products. The result showed that the optimal conditions for liquid yield (56.8%) were a pyrolysis temperature of 550 degrees C, gas flow rate of 3.4 L/min, static bed height of 10 cm and particle size of 1.0-2.0mm. The presence of the catalyst increased the yields of non-condensable gas, water and coke, while decreased the liquid and char yields. The elemental analysis showed that more than 25% decrease in oxygen content of the collected liquid in the second condenser with HZSM-5 was observed compared with that without catalyst. The H/C, O/C molar ratios and the higher heating value of the oil fraction in the collected liquid with the catalyst were 1.511, 0.149 and 34.6 MJ/kg, respectively. It was indicated that the collected liquid in the second condenser had high qualities and might be used as transport oil.     

Lime pretreatment and enzymatic hydrolysis of corn stover

Corn stover was pretreated with an excess of calcium hydroxide (0.5 g Ca(OH)2/g raw biomass) in non-oxidative and oxidative conditions at 25, 35, 45, and 55 degrees C. The optimal condition is 55 degrees C for 4 weeks with aeration. Glucan (91.3%) and xylan (51.8%) were converted to glucose and xylose respectively, when the treated corn stover was enzymatically hydrolyzed with 15 FPU/g cellulose. Only 0.073 g Ca(OH)2 was consumed per g of raw corn stover. Of the initial lignin, 87.5% was maximally removed. Almost all acetyl groups were removed. After 4 weeks at 55 degrees C with aeration, some cellulose and hemicellulose were solubilized as monomers and oligomers in the pretreatment liquor. When considering the dissolved fragments of glucan and xylan in the pretreatment liquor, the overall yields of glucose and xylose were 93.2% and 79.5% at 15 FPU/g cellulose. The pretreatment liquor has no inhibitory effect on ethanol fermentation.     

Tar reduction in pyrolysis vapours from biomass over a hot char bed

The behaviour of pyrolysis vapours over char was investigated in order to maximise tar conversion for the development of a new fixed bed gasifier. Wood samples were decomposed at a typical pyrolysis temperature (500 °C) and the pyrolysis vapours were then passed directly through a tar cracking zone in a tubular reactor. The product yields and properties of the condensable phases and non-condensable gases were studied for different bed lengths of char (0–450 mm), temperatures (500–800 °C), particle sizes (10 and 15 mm) and nitrogen purge rates (1.84–14.70 mm/s). The carbon in the condensable phases showed about 66% reduction by a 300 mm long char section at 800 °C, compared to that for pyrolysis at 500 °C. The amount of heavy condensable phase decreased with increasing temperature from about 18.4 wt% of the biomass input at 500 °C to 8.0 wt% at 800 °C, forming CO, H₂ and other light molecules. The main mode of tar conversion was found to be in the vapour phase when compared to the results without the presence of char. The composition of the heavy condensable phase was simplified into much fewer secondary and tertiary tar components at 800 °C. Additional measures were required to maximise the heterogeneous effect of char for tar reduction.     

The thermal decomposition studies of solid iron bamboo (Dendrocalamus strictus) - potential precursor for eco-materials

Block samples of carbonized solid iron bamboo (Dendrocalamus strictus) - unique genus among bamboos, were prepared by means of slow pyrolysis. They are expected to be promising monolithic supports for various composites. The purpose of this study is to describe the thermal decomposition of rectangular shapes cut from solid stems of Dendrocalamus strictus, raw and pre-charred in a wide range of temperatures: 300, 350, 400, 500 and 600 degrees C. The DTG thermograms of carbonized solid iron bamboo (char), determined at temperatures up to 900 degrees C, exhibited minima even for samples previously pyrolysed at temperatures over 400 degrees C, at which decomposition of plant material have to be completed. For pre-charred samples, the temperature of the DTG peaks increased, while the weight loss registered in the temperature range up to 900 degrees C decreased, with increasing temperature of carbonization. It was found that extension of time of holding at final temperature of carbonization decreased a height of the DTG peaks to full reduction of it after heating along the time of 8h. It was suggested that bamboo tar remaining in vessels after carbonization reacts with the bamboo char creating new compounds that decompose in distinctly higher temperatures.     

Pyrolytic characteristics of biomass acid hydrolysis residue rich in lignin

Pyrolytic characteristics of acid hydrolysis residue (AHR) of corncob and pinewood (CAHR, WAHR) were investigated using a thermo-gravimetric analyzer (TGA) and a self-designed pyrolysis apparatus. Gasification reactivity of CAHR char was then examined using TGA and X-ray diffractometer. Result of TGA showed that thermal degradation curves of AHR descended smoothly along with temperature increasing from 150 °C to 850 °C, while a “sharp mass loss stage” for original biomass feedstock (OBF) was observed. Char yield from AHR (42.64-30.35 wt.%) was found to be much greater than that from OBF (26.4-19.15 wt.%). In addition, gasification reactivity of CAHR char was lower than that of corncob char, and there was big difference in micro-crystallite structure. It was also found that CAHR char reactivity decreased with pyrolysis temperature, but increased with pyrolysis heating rate and gasification temperature at 850-950 °C. Furthermore, CAHR char reactivity performed better under steam atmosphere than under CO₂ atmosphere.     

Preparation and characterization of activated carbon derived from the thermo-chemical conversion of chicken manure

Physico-chemical properties of a bioorganic char were modified by pyrolysis in the presence of NaOH, and with subsequent physical activation of carbonaceous species with CO2 a value-added activated carbon was fabricated. Bioorganic char is produced as a co-product during the production of bio-fuel from the pyrolysis of chicken litter. Untreated char contains approximately 37 wt% of C and approximately 43-45 wt% of inorganic minerals containing K, Ca, Fe, P, Cu, Mg, and Si. Carbonization and chemical activation of the char at 600 degrees C in the presence of NaOH in forming gas (4% H2 balanced with Ar) produced mainly demineralized activated carbon having BET (Brunauer, Emmett, and Teller) surface area of 486 m2/g and average pore size of 2.8 nm. Further physical activation with CO2 at 800 degrees C for 30 min resulted in activated carbon with BET surface area of 788 m2/g and average pore size of 2.2 nm. The mineral content was 10 wt%. X-ray photoelectron spectroscopy (XPS) indicated that the latter activation process reduced the pyrrolic- and/or pyridonic-N, increased pyridinic-N and formed quaternary-N at the expense of pyrrolic- and/or pyridonic-N found in the untreated char.     

Co-production of alpha-amylase and beta-galactosidase by Bacillus subtilis in complex organic substrates

Various nutrients belonging to three categories, carbon, organic nitrogen and complex organic sources, were investigated for the first time in terms of their effect on the co-production of extracellular thermostable alpha-amylase and beta-galactosidase by Bacillus subtilis, a bacterium isolated from fresh sheep's milk. Among the organic nitrogen sources tested, tryptone and corn steep liquor favored their production. Substitution of soluble starch by various starchy substrates, such as corn flour, had a positive effect on both enzyme yields. Furthermore, a two-fold higher production of both enzymes was achieved when corn steep liquor or tryptone was used in combination with the different flours. Among the divalent cations examined, calcium ions appeared to be vital for alpha-amylase production. The crude alpha-amylase and beta-galactosidase produced by this B. subtilis strain exhibited maximal activities at 135 degrees C and 65 degrees C, respectively, and were also found to be significantly stable at elevated temperatures.     

Effect of hot-water extraction on alkaline pulping of bagasse

The effect of hot-water extraction on alkaline pulping was investigated. The properties of black liquor and pulp strength of bagasse were analyzed. The extraction was conducted at 160 °C for 30 min where 13.2% of the mass was dissolved in the extraction liquor. Untreated bagasse and extracted bagasse were digested by soda and soda-AQ processes at 17% and 15.5% (with 0.1% AQ) alkali charge (NaOH). Cooking temperatures were 160 °C and 155 °C respectively. The pulp from extracted bagasse had a lower Kappa number and a higher viscosity compared to the pulp from the untreated bagasse. The black liquor from pulping extracted bagasse had a lower solid content, a lower viscosity and a lower silica content, but a higher heating value than that from pulping of untreated bagasse. Hot-water extraction resulted in a significant decrease in bleaching chemical consumption and the formation of chlorinated organics. Pulp strength properties such as the tensile index and the burst index were found to be lower, but the tear index, bulk, opacity and pulp freeness were found to be higher when hot-water extraction was applied.     

Pyrolytic behavior of waste corn cob

The powder of the agricultural waste corn cob was pyrolyzed in a tube-typed stainless steel reactor of 200 ml volume under N2 atmosphere. The compositions of the gases and liquid obtained at different pyrolytic temperatures below 600 degrees C at the heating rate of 30 K/min were analyzed. With the increment of the pyrolytic temperature, the yields of the solid and the liquid products were decreased, but the yield of gas products was increased. The liquid products were approximately 34-40.96% (wt%), the gas products were 27-40.96% (wt%) and the solid products 23.6-31.6% (wt%). There were less changes for the yields of these products above 600 degrees C. The gas products were analyzed by gas chromatography (GC) as CO2, CO, H2, CH4, C2H4, C3H6, C3H8, etc. When the temperature was 350-400 degrees C, the gases had CO2 and CO 80-95% (v/v). When the temperature increased continuously, yields of H2, CH4, C2H4, C3H6 and C3H8 gradually increased. The liquid products were identified by GC-MS as phenols, 2-furanmethanol, 2-cyclopentanedione, etc. The Fourier transform infra-red spectrophotometer (FT-IR) analysis of the liquid product showed a strong -OH group absorption peak. Differential thermogravimetric analysis (DTG) showed that thermal decomposition process involves two steps. The heating rate affects not only the activation energy of the decomposition reaction, but also the path of the reaction. With the increment of the heating rate, the maximum rate temperature of the decomposition reaction was shifted to a higher temperature, and the order and activation energy of the total decomposition reaction were decreasing.     

Granular activated carbons from broiler manure: physical, chemical and adsorptive properties

Broiler manure produced at large concentrated facilities poses risks to the quality of water and public health. This study utilizes broiler litter and cake as source materials for granular activated carbon production and optimizes conditions for their production. Pelletized manure samples were pyrolyzed at 700 degrees C for 1 h followed by activation in an inert atmosphere under steam at different water flow rates, for a period ranging from 15 to 75 min. Carbon physical and adsorptive properties were dependent on activation time and quantity of steam used as activant, yields varied from 18% to 28%, surface area varied from 253 to 548 m2/g and copper ion adsorption varied from 0.13 to 1.92 mmol Cu2+/g carbon. Best overall performing carbons were steam activated for 45 min at 3 ml/min. Comparative studies with commercial carbons revealed the broiler cake-based carbon as having the highest copper ion efficiency.     

Compositional and Thermal Evaluation of Lignocellulosic and Poultry Litter Chars via High and Low Temperature Pyrolysis

Inorganic elements in biomass feedstocks can influence thermochemical reactions as well as the resultant char’s elemental, compositional, and thermal characteristics. Chars were produced using slow pyrolysis under low (≤400°C) and high (≥500°C) temperature regimes from sugarcane bagasse, peanut hulls, pecan shell, pine chips, poultry litter, and switchgrass. The chars and raw feedstocks were characterized for their elemental, structural, and thermal properties to ascertain the implications of feedstock selection and pyrolysis temperatures on these properties. Char mass yields from the six feedstocks ranged between 28% and 78% by weight while carbon yields ranged between 44% and 89%. In both instances, lower yields were obtained with increasing pyrolysis temperature. Higher pyrolysis temperatures (≥500°C) resulted in more neutral to alkaline chars possessing greater ash contents and increased aromatic character with narrow O/C and H/C ratios. A significant exponential curve response (r ²?=?0.87, P?<?0.001) was revealed between char mass yields vs. pyrolysis temperature. All raw feedstocks and chars contained mixed amounts of macro-, micro-, and trace element concentrations. The higher heating values (HHV) tended to increase with heightened pyrolysis temperature with some chars producing >30 MJ kg^?1. The chars’ HHV values inversely correlated to their total ash and Cl content. Lignocelluloses chars had better thermal characteristics and lower ash quality concerns implying suitable service in thermal energy production. In contrast, poultry litter char had greater ash contents, medium HHV values, and contained corrosive inorganic elements, which rendered it problematic as a feedstock for thermal energy generation.     

Physicochemical characteristics and toxicity of nickel oxide particles calcined at different temperatures

The physicochemical characteristics and cytotoxicity of two types of commercial nickel oxide particles (black and green nickel oxide) and five types of nickel oxide particles prepared by calcination of the black nickel oxide at 600–1000°C were studied. Thermal analysis with mass spectroscopy showed that the black nickel oxide particles contained approximately 1.4% impurity, which seemed to be basic nickel carbonate. The calcination treatment at 600°C increased the nickel content and decreased the oxygen content, but these remained constant in the particles treated at higher temperatures (700–1000°C) and in the green nickel oxide particles. The water solubility of black nickel oxide particles was markedly greater than that of the other particles, especially in the first 24 h after mixing with water. The solubility of the calcined particles decreased with increasing calcination temperature. The cytotoxicity of these particles was evaluated by the viability of rat alveolar macrophages and by the inhibition of cell proliferation in Chinese hamster ovary cells. The black nickel oxide was the most cytotoxic of the particles examined, and this may be attributable, at least in part, to a rapid dissolution of nickel from the contained impurity. The toxicity of the calcined particles decreased with increasing calcination temperature. These results indicate that water solubility, which depends on calcination temperature, modulates the acute cytotoxicity of nickel oxide particles.