Mixture Of Char Research Articles

Discernment of synergism in co-pyrolysis of starch, lignin, and cellulose: Properties and reactivity of char production

Starch, lignin, and cellulose are selected as representatives of solid waste, and the effects of these three main components and their interactions on the characteristics of the corresponding pyrolysis char are researched. The findings indicate that the interaction between starch (0.0216 min−1) and lignin (0.0203 min−1) could result in a lower oxidation reaction rate (0.0172 min−1) of the pyrolysis of their char mixture, which is associated with a slight collapse of the fibrous sheet structure. According to the comparison of the crystalline phases identified by X-ray diffractometry research, the interaction between lignin and cellulose improves the degree of carbon ordering, leading to the presence of C-faces (100) in the lignin + cellulose char sample. Raman analysis explains that the interaction between starch and lignin results in increased size and thickness of graphitic domains, and a similar trend is observed in the starch and cellulose char samples. Conversely, the band area ratio ID4/IG values of the mixed char samples are comparable to those of the two corresponding single-component char samples, indicating that no interaction occurs in the sp2–sp3 mixed structures. The results indicate that the carbon conversion increases with increasing temperature. Otherwise, the interaction between lignin and cellulose improves the degree of carbon ordering. The results of this study are anticipated to contribute to a better understanding of the mechanisms involved in the interactions of waste components on char production by pyrolysis of solid wastes.

KNO3-Loaded Coffee Husk Ash as a Heterogeneous Alkali Catalyst for Waste Frying Oil Valorization into Biodiesel.

In this study, a heterogeneous basic catalyst was synthesized from a catalyst composite material (CCM) of coffee husk ash and char mixture (A/C) impregnated with KNO3 and employed to transesterify crude waste frying oil (WFO). The effect of CCM calcination temperature (CCMCT) (500-700 °C) on the catalyst physicochemical properties was investigated. A differential scanning calorimeter was used to examine potential phase changes during the calcination of A/C and CCM. The catalysts from each CCMCT were characterized by X-ray diffraction (XRD), Brunauer-Emmet-Teller surface area analyzer, scanning electron microscopy (SEM), SEM with energy-dispersive X-ray diffractometer, colorimeter, and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrometer. The methoxy functional group FTIR peak integral value and the dynamic viscosity of the biodiesel synthesized by each catalyst were used to determine the qualitative WFO conversion. Furthermore, the quantitative WFO conversion was determined using nuclear magnetic resonance (1H NMR) analysis. Crystallinity, elemental composition, basicity, and morphology of catalysts were highly dependent on the CCMCT. Without transesterification condition optimization (reaction temperature of 45 ± 2.5 °C, catalyst loading of 3 wt %, methanol to oil molar ratio of 12:1, and reaction time of 1 h), a higher catalytic performance (72.04% WFO conversion) was reached using a catalyst from the CCMCT of 600 °C. When using a coffee husk ash catalyst without KNO3 impregnation (C-00-600), the WFO conversion was only 52.92%. When comparing the C-25-600 and C-00-600 catalysts, it was observed that KNO3 impregnation had a substantial impact on the catalyst crystallinity, basicity, and morphology.

Reconsidering the use of ferrous hydroxide for remediation of chlorinated ethylene contaminated groundwater: Ultra-fast trichloroethene dechlorination by ferrous hydroxide and bone char mixture

The prevailing view is that dehalogenation of chlorinated ethene by Fe(OH)2 or adsorbed Fe2+ alone is extremely slow or impossible. In this study, a novel composite was prepared by facile mixing of Fe2+, NaOH, and bone char (BC) at room temperature, providing an unprecedented trichloroethene (TCE) dechlorination rate. In the fastest dehalogenation test, 20 μM TCE was removed within 30 min in the presence of 30 mM Fe2+, 4.5 mM NaOH, and 2.0 g/L BC (pH ∼ 5.5), following the pseudo-first-order kinetics with a rate constant of 7.81 h−1. The kinetics feature switched from zero-order to first-order kinetics at increasing BC dosage, indicating that TCE was adsorbed and reduced on BC surface. The major dehalogenation products were non-chlorinated acetylene, while chlorinated products were not detected. Even though the TCE dehalogenation ceased after six reuse cycling tests, a complete recovery of dehalogenation was achieved by the following base injection under excess Fe2+ condition. Moreover, this system could completely remove 20 μM TCE within 6 h in real groundwater at varying pH (5–10). Life cycle assessment (LCA) demonstrated that Fe(OH)2 and BC mixture shows better environmental sustainability in comparison with regular iron based material. In addition, the easy, flexible, and tunable synthesis of Fe(OH)2/BC mixture favors its injection and distribution in the contaminated zone. This study provides evidence to reconsider ferrous hydroxide as an inexpensive and efficient reductant for the remediation of soil and groundwater contaminated with chlorinated ethenes (CEs).

Investigation of the transport characteristics of Pb(II) in sand-bone char columns.

Pb(II) leakage from batteries, dyes, construction materials, and gasoline threaten human health and environmental safety, and suitable adsorption materials are vitally important for Pb(II) removal. Bone char is an outstanding adsorbent material for water treatment, and the effectiveness in Pb(II) removing need to be verified. In this paper, the transport characteristics of Pb(II) in columns filled with a sand and bone char mixture were studied at the laboratory scale, and the influences of the initial concentration, column height, inlet flow rate, and competing ion Cu(II) on Pb(II) adsorption and transport were analyzed. The Thomas and Dose-Response models were used to predict the test results, and the mechanisms of Pb(II) adsorption on bone char were investigated. The results showed that the adsorption capacity of the bone char increased with increasing column height and decreased with increasing initial Pb(II) concentration, flow rate, and Cu(II) concentration. The maximum adsorption capacity reached 38.466 mg/g and the saturation rate was 95.8% at an initial Pb(II) concentration of 200 mg/L, inlet flow rate of 4 mL/min, and column height of 30 cm. In the competitive binary system, the higher the Cu(II) concentration was, the greater the decreases in the breakthrough and termination times, and the faster the decrease in the Pb(II) adsorption capacity of the bone char. The predicted results of the Dose-Response model agreed well with the experimental results and were significantly better than those of the Thomas model. The main mechanisms of Pb(II) adsorption on bone char include a surface complexation reaction and the decomposition-replacement-precipitation of calcium hydroxyapatite (CaHA). Based on selectivity, sensitivity, and cost analyses, it can be concluded that bone char is a potential adsorbent for Pb(II)-containing wastewater treatment.

Bioremediation of Crude Oil Contaminated Soil Using Pig Droppings and Bone Char

Oil extraction operations as well as equipment failure and infrastructure vandalism have caused serious environmental pollution with crude oil spills world-wide. The remediation of the polluted sites is an environmental problem beckoning for solution. In this study, the possibility of pig droppings and pig bone char mixture (biostimulant) to stimulate and optimize crude oil biodegradation in soil was investigated. Exactly 500g of loamy soil was spiked with 3% (w/w) of crude oil. The spiked soil was amended with varying percentage mixtures of the biostimulant and labelled A – E. The spiked soil without biostimulant served as the Control. Each experiment was setup in six (6) replicates, carried out for six weeks, and destructively sampled and analysed on a weekly basis. The removal efficiencies of the biostimulated and unbiostimulated soils were observed to range from 66.70 to 86.70% and 3.69%, respectively. The biodegradation first-order rate constants ranged from 0.1978 to 0.3391wk-1 and 0.0050wk-1 for the biostimulated and unbiostimulated soils, respectively. Optimum removal of total petroleum hydrocarbon (TPH) was observed for biostimulated soil C comprising 50% bone char and 50% pig droppings. Results from biostimulated soils A, B, D and E indicated that pig droppings is a more effective biostimulant than pig bone char. A first-order kinetic model adequately predicted the removal of TPH with the optimum biostimulant. It is concluded that using agro-organic waste materials such as pig droppings and pig bone char in a ratio of 1:1 can offer a simple, effective, inexpensive and environmentally friendly solution to the problem of soil contamination with crude oil.

Investigation of coal-biomass interaction during co-pyrolysis by char separation and its effect on coal char structure and gasification reactivity with CO2

The interaction between coal and biomass has been widely investigated. However, the mechanism is always proposed based on physicochemical structure and reactivity of char mixture. In this work, char mixture after co-pyrolysis of anthracite and biomass was separated based on different shape and size, and then structure and reactivity of the coal char were analyzed to reveal mechanism of coal-biomass interaction. Anthracite char samples with different corn straw (CS) blending ratios were prepared by pyrolysis in a fixed bed reactor at 600 and 900°C. The AAEM concentration and microcrystalline structures of coal char were examined by inductively coupled plasma-optical emission spectrometry (ICP-OES) system and X-ray diffraction (XRD). The gasification reactivity of char sample after separation was analyzed by TGA under CO2. The results show that concentration of active K and Mg in coal char samples gradually increased and more disordered carbon structure formed as the CS proportion in the blending increased from 0 to 80%. The coal char in the blending captured more AAEM species by volatile-char interactions instead of escaping with volatile from biomass during co-pyrolysis process. Meanwhile, higher pyrolysis temperature led to volatilization and inactivation of K and Na, and also decrease in graphitization degree. Moreover, both addition of CS and low pyrolysis temperature could promote gasification reactivity of coal char sample. Furthermore, a satisfactory linear correlation (R2=0.9009) between alkali index AI and R0.5 of the char samples was established. This indicated that AAEMs performed the dominate effect to enhance gasification reactivity of coal char during co-gasification of coal and biomass.

Investigation of microwave-assisted pyrolysis of biomass with char in a rectangular waveguide applicator with built-in phase-shifting

Fast biomass pyrolysis is a promising technique for thermochemical conversion of biomass into chemicals and biofuels (bio-oil and syngas). Microwave heating can increase process efficiency. The effect of microwave absorber and microwave power level are studied for their effect on pyrolysis process temperature, product yields, and product composition. A novel microwave system was designed with a continuous sliding short enabling phase shifting to mitigate standing wave effects in the low loss load. Pyrolysis experiments on pine sawdust were carried out at varying microwave input powers (600, 900, 1200, and 1500 W) and with varying amounts of biochar added to the feedstock (0, 10, and 20% by weight) in a 4 × 3 full factorial experimental design. Pine sawdust without the aid of microwave absorber failed to reach pyrolysis temperatures by dielectric heating, only reaching 200 °C even at 1500 W power. Pyrolysis yields were correlated to absorbed power rather than input power as temperature is more strongly correlated to absorbed power. Addition of biochar was found to have a significant effect on the absorbed powers and resulting pyrolysis temperatures, increasing temperatures 4 fold from 0% to 10% char, however, no significant difference was found when char mixture was increased from 10 to 20%. Yields of char decreased with increasing absorbed microwave power, while non-condensable gas increased, indicating increased thermal cracking to non-condensable gases with increasing process temperature. Water-free bio-oil yields were found to increase with absorbed power. The liquid product from microwave pyrolysis of pine sawdust is composed primarily of phenols, with little changes in yield at all absorbed powers. Carbonyl functional groups and furans decreased while polyaromatics increased with increasing absorbed power due to the increased decomposition of lignin. The greatest net energy yields were observed for pyrolysis run at 900 W applied microwave power and 20% char.

Non-isothermal gasification of biomass char and coal char mixture in CO2 condition

ABSTRACT Non-isothermal thermogravimetry method was used in the paper to investigate the gasification properties of biomass char (BC), coal char (CC), and their blended char at different mass ratios of 1:3, 1:1,3:1 under CO2. The results showed that with the increase of heating rate, the gasification curve moved to high-temperature zone and the peak rate of gasification increased, the gasification reactivity improved, and the gasification time reduced from 26.8 min to 6.78 min. Increasing BC share, the gasification rate also increased and the gasification time was shortened as the high specific surface area of BC had a great influence on gasification reactivity. The volumetric model (VM), the shrinking core model (SCM), and the random pore model (RPM) were applied to describe the reaction behavior of the chars and the results showed that all three models could describe the gasification process of char, while among them, RPM model achieved the best-fitting result. By RPM model, the activation energy of BC/CC at mass ratios of 0:4,1:3,1:1,3:1,4:0 was obtained, which were 240.74 kJ/mol, 129.16 kJ/mol, 108.54 kJ/mol,102.53 kJ/mol, and 97.01 kJ/mol, respectively. The decrease in activation energy with the increase of biomass char content could be ascribed to the higher specific surface area of BC and the lower carbon structure uniformity of BC.

Numerical study of the segregation of pyrolized char in a bubbling fluidized bed according to distributor configuration

In this study, computational particle fluid dynamics were applied to investigate the segregation characteristics of char particles in a bubbling fluidized bed. We examined the bubble behavior and the consequent segregation of char particles with respect to the nozzle arrangement of the distributor in a bubbling fluidized bed. The segregation characteristics of a mixture of char and sand particles were analyzed in terms of pressure fluctuation, bubble diameter, the number of bubbles, and the mixing index. It was observed that an increasing number of nozzles resulted in a decreased bubble diameter, which led to better segregation between char and sand particles. The mixing index of char and sand particles decreased from 0.75 to 0.42 from nnozzle = 8 to nnozzle = 17, then increased to 0.50 at nnozzle = 20. When the number of nozzles was more than nnozzle = 17, the bubble diameter increased, and the number of bubbles decreased because the bubbles coalesced with surrounding bubbles.

Effects of fresh and aged chars from pyrolysis and hydrothermal carbonization on nutrient sorption in agricultural soils

Abstract. Leaching of nutrients from agricultural soils causes major environmental problems that may be reduced with amendments of chars derived from pyrolysis (pyrochars) or hydrothermal carbonization (hydrochars). Chars are characterized by a high adsorption capacity – i.e. they may retain nutrients such as nitrate and ammonium. However, the physicochemical properties of the chars and hence their sorption capacity likely depend on feedstock and the production process. We investigated the nutrient retention capacity of pyrochars and hydrochars from three different feedstocks (digestates, Miscanthus, woodchips) mixed into different soil substrates (sandy loam and silty loam). Moreover, we investigated the influence of char degradation on its nutrient retention capacity using a 7-month in situ field incubation of pyrochar and hydrochar mixed into soils at three different field sites. Pyrochars showed the highest ability to retain nitrate, ammonium and phosphate, with pyrochar from woodchips being particularly efficient in nitrate adsorption. Ammonium adsorption of pyrochars was controlled by the soil type of the soil–char mixture. We found some ammonium retention on sandy soils, but no pyrochar effect or even ammonium leaching from the loamy soil. The phosphate retention capacity of pyrochars strongly depended on the pyrochar feedstock with large phosphate leaching from digestate-derived pyrochar and some adsorption capacity from woodchip-derived pyrochar. Application of hydrochars to agricultural soils caused small, and often not significant, effects on nutrient retention. In contrast, some hydrochars did increase the leaching of nutrients compared to the non-amended control soil. We found a surprisingly rapid loss of the chars' adsorption capacity after field application of the chars. For all sites and for hydrochar and pyrochar, the adsorption capacity was reduced by 60–80 % to less or no nitrate and ammonium adsorption. Thus, our results cast doubt on the efficiency of char applications to temperate zone soils to minimize nutrient losses via leaching.

Magnetic separation of carbon-encapsulated Fe nanoparticles from thermally-treated wood char

Wood char, a by-product from the fast-pyrolysis process of southern yellow pine wood for bio-oil production, was carbonized with Fe nanoparticles (FeNPs) as a catalyst to prepare carbon-encapsulated Fe nanoparticles. A magnetic separation method was tested to isolate carbon-encapsulated Fe nanoparticles from the carbonized char. X-ray diffraction pattern clearly shows that Fe-containing materials were completely separated from the carbonized wood char mixture using a magnet. The amorphous carbon in the material which adhered to the magnetic bar was significantly decreased in comparison with the non-adhered material. Carbon graphitic layers encapsulated FeNPs were observed in the adhered material through high-resolution transmission electron microscopy. In addition, many long and tangled-multi-layered graphitic carbon structures grew from the surface of carbon-encapsulated Fe nanoparticles.

Steam gasification reactivity of char from rapid pyrolysis of bio-oil/char slurry

A slurry of bio-oil and char originating from wood pyrolysis is a promising gasifier feed-stock because of its high energy density. When such a slurry is injected into a high temperature gasifier it undergoes a rapid pyrolysis yielding a char which then reacts with steam. The char produced by pyrolysis of an 80 wt% bio-oil/20 wt% char mixture at heating rates of 100–10,000 °C/s was subjected to steam gasification in a thermogravimetric analyzer. The original wood char from the bio-oil production was also tested. Gasification was conducted with 10–50 mol% steam at temperatures from 800 to 1200 °C. Reactivity of the slurry chars increased with pyrolysis heating rate, but was lower than that of the original chars. Kinetic parameters were established for a power-law rate model of the steam-char reaction, and compared to values from the literature. At temperatures over 1000 °C, the gasification rates appeared to be affected by diffusional resistance.

Study on the Characteristics of the Oil Shale and Shale Char Mixture Pyrolysis

The pyrolysis experiments of the mixture fuels of Huadian oil shale and its shale char prepared at a retorting temperature of 520 °C were conducted using a Q5000IR thermogravimetric analyzer, and the characteristics of the copyrolysis at different mixing ratios were obtained. The release of organic matter tended to decrease while the decomposition of inorganic constituents tended to increase slightly with increasing shale char fraction. The interaction during the copyrolysis was investigated by comparing the experimental result with the theoretical one and only some little interaction was observed. The reactivity between 250 and 600 °C followed a decreasing trend with the increase of shale char fraction due to the lower volatile content and carbon condensation structures in shale char, and for each sample, the reactivity increased first and then decreased as the temperature increased because of the rearrangement of internal structure of sample particles. According to the kinetic analysis, increasing the shale char fraction in the mixtures would result in a decreasing apparent activation energy at temperatures ranging from 250 to 600 °C since the pyrolysis of shale char in this temperature range did not undergo the process of the decomposition of bitumen which existed in the pyrolysis of oil shale and needed much energy.

Understanding the Effect of the Transition Period during the Air Gasification of Dried Sewage Sludge in a Fluidized Bed Reactor

Air gasification of dried sewage sludge (DSS) in a fluidized bed has been studied as an effective alternative for the management of this material in a usable way. Nevertheless, one of the major issues in this technology is to deal with the tar formed during the process. To minimize the tar production, it is very important to optimize the operating conditions. In a previous work (Manyà et al., Energy Fuels, Vol. 19, 629–636, 2005) some unexpected results, in which tar production increases with the equivalence ratio, have been obtained. As it has been mentioned in that work, tar production could present unexpected trends while the bed composition changes from sand to a mixture of char and sand. Ashes contained in char have catalytic active metals which could promote gasification reactions. As the char content in the bed increases, the catalytic activity in the reactor could increase too, until the steady state is achieved. The aim of this work is to characterize the non-stationary period and its influence on the overall results obtained from gasification tests. Experiments have been carried out in a laboratory-scale BFB reactor at atmospheric pressure and at a reactor temperature of 1123 K with an equivalent ratio of 30%. Results show that at the beginning of the experiments the tar production was higher, until the steady state is reached. The gasification study has been enhanced with an analysis of tar composition by means of GC/MS and GC/FID. An effect of the transition period has been observed in tar composition also. The nitrogen aromatics percent increased with time whereas the polycyclic aromatic hydrocarbon decreased.

Analysis of gasification reaction of coke formed using a miniature tubing-bomb reactor and a pressurized drop tube furnace at high pressure and high temperature

Coal gasification to produce gaseous fuel such as CO and H 2 is well-known as one of the key technologies for utilization of coal. Coal gasification mainly involves two steps: the initial rapid devolatilization of coal to produce char, tar and gases and the subsequent gasification of the char produced. Char gasification, being the slower step, is believed to control the overall conversion process. It is, however, known that solid carbon called coke (soot) is formed from the volatiles produced during the initial devolatilization at high temperature above 1000 ∘ C. Since the gasification reactivity of the coke is expected to be rather low, it is important to examine if the coke is really formed and to estimate the gasification reactivity of the coke if it is formed. In this study it was clarified that the coke is actually formed at high temperature and high pressure from the equilibrium calculation and experiments using a miniature tubing-bomb reactor (mini-TBR) and a pressurized drop tube furnace (PDTF). The ratio of coke to char was roughly 1 to 1 for the solid carbons prepared by the PDTF. The gasification reactivity of the coke was found to be 1 20 – 1 6 of the char when compared at 1200 ∘ C. SEM and TEM observations also clarified that the solid carbon obtained by PDTF was the mixture of char and coke.

Curing temperature effect on smokeless fuel briquettes prepared with molasses and H 3PO 4☆

Chars from the co-carbonisation of a low-rank coal and olive stones have been used to prepare environmental acceptable smokeless fuel briquettes. The blend was a mixture of char, molasses and H 3PO 4. This acid was added to favour the polymerisation of the binder. The effect of the curing temperature on the physico-chemical features of the briquettes was studied by Fourier Transform Infrared Spectroscopy and Temperature Programmed Decomposition followed by Mass Spectrometry. The presence of H 3PO 4 as well as the curing process at 200 °C of temperature, contribute to the formation of carboxylic acids which lead to the production of briquettes with adequate mechanical properties.

Investigation into alternative sludge conditioning prior to dewatering

The principal objective of this work is to provide a more effective alternative for sludge conditioning prior to mechanical dewatering. The common use of polyelectrolytes often results in the final cake solids concentration not sufficiently high for the sludge to be beneficially reused or safely disposed. The pyrolysed domestic refuse (char) was used to increase the structural strength and permeability of biological sludges in order to increase final cake solids concentration. The laboratory experiments have proven that the mixture of char and a small quantity of polyelectrolyte (0.5 to 1kg per ton of dry solids), used as a conditioner prior to centrifugation and filtration tests, produced cake solids concentration superior to that obtained by using polyelectrolyte on its own. Laboratory dewatering by filtration with admixture of char and polymer, resulted in cake solids concentration of 30 and above 40 per cent.

Investigation into alternative sludge conditioning prior to dewatering

The principal objective of this work is to provide a more effective alternative for sludge conditioning prior to mechanical dewatering. The common use of polyelectrolytes often results in the final cake solids concentration not sufficiently high for the sludge to be beneficially reused or safely disposed. The pyrolysed domestic refuse (char) was used to increase the structural strength and permeability of biological sludges in order to increase final cake solids concentration. The laboratory experiments have proven that the mixture of char and a small quantity of polyelectrolyte (0.5 to I kg per ton of dry solids), used as a conditioner prior to centrifugation and filtration tests, produced cake solids concentration superior to that obtained by using polyelectrolyte on its own. Laboratory dewatering by filtration with admixture of char and polymer, resulted in cake solids concentration of 30 and above 40 per cent.

95/00643 Rapid pyrolysis of Chinese Chaili washed middling coal in a down-flow reactor and combustion of mixture of char and sand in an up-flow reactor

95/00643 Rapid pyrolysis of Chinese Chaili washed middling coal in a down-flow reactor and combustion of mixture of char and sand in an up-flow reactor

ELECTROMAGNETIC ENHANCEMENT OF CHEMICAL REACTIONS (Devolatilization of Char and Coal)

Abstract Char in the microwave energy field may enhance chemical reactions by three different ways as described below: (1) directly react with elements in molecules when contacted, (2) create free radicals when the gas molecules contact char,and (3) provide heat to adjacent solid particles. To understand the interactions between char and microwave energy, we first investigated the microwave energy absorption by char and also by the mixture of char and coal at various apparent bed temperatures and various ratios of coal to char in the mixture. The experimental results clearly demonstrated that pyrolysis products are excellent absorbents of the microwave energy. To enhance the pyrolysis rate of coal with the microwave energy, it was necessary to add char that increased energy absorption rate. Coal/char mixture pyrolysis started immediately when the microwave energy was applied. Also, microwave energy absorption rate increased to 73% of input power. When coal concentration in the coal/char mixture exceeded 5...