Corncob Char Research Articles

A new quantitative method via on-line mass spectrometer: Application in biomass char/NO reaction

A novel quantitative analysis method via on-line mass spectrometer (OMS) was developed to calculate the mass flows of the reactants and products for the reaction between NO and biomass char in micro-fluidized bed. The experimental results showed that the quantitative method could accurately calculate the mass flow rate of each gas even though there were ion currents overlapping at mass-to-charge ratio (m/z) = 12,16, and 28 when CO, CO2 and N2 were simultaneously present in OMS. Furthermore, the method facilitated the quantitative analysis of gaseous reactants and products, thereby enabling the assessment of mass conversions of carbon (C) and nitrogen (N) in the NO reduction reaction. It was observed that CO was the predominant carbon-containing product in the reaction involving biomass char and NO at 900 °C, with over 96 % of nitrogen in NO participating in the reduction reaction being converted to N2. This study also revealed that increasing the fluidization number, NO concentration, and temperature in the micro-fluidized bed could significantly accelerate the conversion processes of C and N in the reduction of NO by biomass char. The peak mass flow rates of CO, CO2, and N2 were found to increase correspondingly with higher NO concentrations and temperature levels. The NO reduction process over sawdust char was compared to that of corncob char, showing a higher maximum NO reduction efficiency. The reaction order with respect to NO concentration was determined to be 0.82 for corncob char and 0.68 for sawdust char. Additionally, the apparent activation energies were determined to be 92.35 kJ/mol for corncob char and 125.60 kJ/mol for sawdust char, respectively.

Synergistic co-combustion of carbon-rich fraction from coal gasification fine slag and corncob char: Performance, mechanism, kinetics, and thermodynamics

Coal gasification fine slag (FS) is a coal-based solid waste with high carbon content, and landfill-based disposal causes water-soil-gas composite pollution. Co-combustion is a common method of solid waste thermal disposal, and corn cob is used as an auxiliary fuel for co-combustion because of its energy density and ease of handling and processing. In this paper, the thermal degradation characteristics, interaction mechanism, kinetics, and thermodynamics of co-combustion RC (carbon-rich fraction obtained by flotation) and CC (corncob char) were studied. The results showed that physicochemical properties suggested that RC and CC will complement and promote each other in the combustion process. The addition of CC reduced the RC ignition temperature and improved the overall combustion performance. The interaction effect was mainly due to metal catalysis, the effect of the porous carbon structure, the thermal effect, and the hindering effect of ash. The activation energy was reduced due to the blending of RC-CC, and the activation energy was lowest (132.19 kJ/mol) when the RC adding ratio was 60%. The co-combustion process was controlled by the F3 model (chemical third-order reaction kinetics), and it was a typical gas-solid phase reaction with a progressive process from the outsides toward the insides. Thermodynamic analysis showed that the co-firing process was an extremely complex multi-stage reaction. The results of this study provide a theoretical reference for the synergistic resource utilization of coal gasification fine slag and waste biomass.

Sorbents for phosphorus recovery and reuse prepared from corn cob char and rice husk ash: A life cycle and cost assessment

This study compared the environmental impacts and cost of providing phosphorus fertilizer using the commercial fertilizer monoammonium phosphate (MAP) and three novel sorbents that had been exposed to phosphorus rich model animal wastewaters. The novel sorbents were corn cob chars amended with either Mg(OH)2 or bittern, and calcium silicate hydrate (CSH) synthesized from Ca(OH)2 and rice husk ash. Both Mg-chars had lower environmental impacts than MAP at all pH values, with major contributions from pyrolysis, farming, and Mg(OH)2 production. CSH had higher environmental impacts and cost than any other material due to its comparatively low solubility, meaning more of it was required to release a given mass of phosphorus. Mg-char (bittern) had the lowest environmental impacts and cost since it was derived from a natural Mg source (model seawater bittern) rather than a commercial chemical source. Mg-chars for phosphorus recovery and reuse could help achieve a more sustainable phosphorus cycle.

Co-combustion of carbon-rich fraction from coal gasification fine slag and biochar: Gas emission, ash sintering, heavy metals evolutions and environmental risk evaluation

Mixed combustion of carbon-rich fraction (RC) from coal gasification fine slag and corncob char (CC) is an effective way of energy recycling. In this paper, the co-firing performance and kinetics of RC and CC were studied, and gas emission pattern, ash sintering trend and the migration and transformation behavior of heavy metals during combustion were explored. The results showed that the combustion performance was enhanced and the reaction activation energy was reduced during the blends burning. The synergistic effect between co-combustion reactions decreased emissions of gaseous pollutants. With the increasing RC compounding ratio and combustion temperature, the ash sintering tendency weakened. Cr and Ni were mostly enriched in the bottom ash, whereas Cu, Zn, As, Cd, and Pb tended to migrate to fly ash and flue gas. Cu, Zn, As, and Pb were in the form of stable fractions. Temperatures accelerated the chemical forms of Cr, Ni, Cu, Zn, and Cd being transformed into stable fractions. The environmental evaluation index suggested that the potential environmental risks of Cr, Zn, Cd, and As were relatively high. The results of this study provide guidance for the synergistic combustion disposal of double solid waste.

Determination of intrinsic kinetic of corncob char gasification with CO2 and steam using multipore diffusion model

The intrinsic heterogeneous reactivity of biochar in CO2 and steam gasification plays an important role in thermochemical reactor design, adjusting operating conditions, and predicting the quality of biomass gasification products, especially when the combined valorization of syngas and biochar with important textural properties is required. In the present work, the intrinsic heterogeneous kinetics of CO2 and steam gasification of corn biochar is estimated by fitting a multimodal pore size distribution (PSD) with random capillary model evolution with respect to the experimental results by thermogravimetric analysis (TGA). As novelty the independence of the initial biochar textural properties was considered, using two samples with different initial pore size distributions (PSDs): A1 sample with an initial surface area of 54.09 m2/g and A2 sample with 22.14 m2/g. The experimental intraparticle gradient effect is considered by using samples with a particle size of 149 µm conventionally larger than those reported to guarantee chemical kinetic control at 60 µm. The apparent kinetics obtained by TGA revealed a difference of 70 kJ/mol for CO2 gasification and 30 kJ/mol for steam gasification in contrast to initial PSD change. The average activation energies and pre-exponential factor obtained by parametric fitting of the model with respect to the evolution of the conversion for CO2 gasification were E = 210.2 kJ/mol and A0 = 1.13*106 g/m2s, while steam revealed E = 136.64 kJ/mol and 7.1*102 g/m2s. Furthermore, the model reduced the activation energy differences with respect to different PSDs by 5 kJ/mol for CO2 and 18 kJ/mol for steam biochar gasification.

Corn Cob Char as Catalyst Support for Developing Carbon Nanotubes from Waste Polypropylene Plastics: Comparison of Activation Techniques.

The future and continuity of nanomaterials are heavily dependent on their availability and affordability. This could be achieved when cheap materials are actively employed as starting materials for nanomaterials synthesis. In this study, waste corn cob char was used as support during the preparation of the NiMo catalyst, and the effect of different char-activating techniques on the microstructure, yield and quality of carbon nanotubes (CNTs) obtained from waste polypropylene (PP) plastics using the chemical vapor deposition (CVD) technique was investigated. Properties of the catalysts and obtained nanomaterials were evaluated by XRD, SEM, N2 physisorption experiment, FTIR, Raman spectroscopy and TEM. Results showed improved surface properties of the NiMo catalyst supported on chemically (NiMo/ACX) and physically activated char (NiMo/ACT) compared to the NiMo catalyst supported on non-activated char (NiMo/AC0). High-quality CNTs were deposited over NiMo/ACT compared to NiMo/ACX and NiMo/AC0. It was also observed that different activation methods resulted in the formation of CNTs of different microstructures and yield. Optimum yield (470.0 mg CNTs/g catalyst) was obtained with NiMo/AC0, while NiMo/ACT gave the least product yield (70.0 mg CNTs/g catalyst) of the as-produced nanomaterials. Based on the results of the analysis, it was concluded that utilizing a cheap pyrogenic product of waste corn cob as a catalyst support in a bimetallic NiMo catalyst could offer a promising approach to mass producing CNTs and as a low-cost alternative in CNTs production from waste plastics.

Phosphate Uptake by Precipitation in Model Animal Wastewaters: Adjusting Ionic Strength and Ionic Composition to Maximize Phosphorus Removal

While phosphorus is a limited resource that is essential for agriculture, its release to the environment adversely impacts water quality. At the same time, animal wastewaters contain significant quantities of phosphorus and nitrogen that can be recovered for beneficial use. Phosphorus uptake experiments were performed with magnesium-treated corn-cob char and with magnesium silicate prepared using silicate from rice straw at pH 8 and 9. The concentration of dissolved phosphorus as a function of total added ammonium chloride (NH4Cl) was determined, and chemical equilibrium modeling was used to investigate the concentration trends of dissolved and mineral species. According to chemical equilibrium modeling, carbonate alkalinity exerted a significant magnesium demand, with approximately half of all added magnesium forming magnesite (MgCO3(s)). As total added NH4Cl increased, excess Cl− complexed with dissolved Mg2+ in competition with orthophosphate, freeing orthophosphate to precipitate, mainly as the mineral struvite (NH4MgPO4·6H2O(s)). As the concentration of added NH4Cl increased by a factor of ten, measured concentrations of dissolved phosphorus decreased by a factor of ten, meaning that ionic composition has the potential to significantly impact the amount of phosphorus that can be recovered from wastewaters for beneficial use.

Autocatalytic co-upgrading of biochar and pyrolysis gas to syngas

A new strategy is exploited toward dramatically increased carbon utilization efficiency of biomass fast pyrolysis by implementing co-upgrading of by-products (biochar and pyrolysis gas) of fast pyrolysis. Simultaneous autocatalytic conversion of biochar and pyrolysis gas is demonstrated using a fixed-bed reactor and an isothermal thermogravimetric analyzer. The reaction of corncob char with simulated pyrolysis gas reveals the feasibility of producing valuable CO and H2 under suitable reaction temperature (>800 °C). The reactivity of biochar and simulated pyrolysis gas increases with increasing potassium content. The raw corncob biochar exhibits high reactivity owing to its high indigenous potassium content. Furthermore, kinetic analysis demonstrates that the modified random pore model (MRPM) satisfactorily describes the reaction behavior of corncob biochar and CO2. The activation energy calculation verifies that the co-upgrading of raw corncob biochar and pyrolysis gas for the production of syngas is feasible at suitable temperature without further treatment.

A study on the new type of radicals in corncob derived biochars

Biochars prepared from pyrolysis of biomass have been studied for a broad range of applications. It was reported that biochars contained radicals measurable by electron spin resonance (ESR) but the radicals have not been quantitatively related with the pyrolysis conditions nor with the chars’ structure. This work shows, through O2 adsorption or titration, that the chars derived from corncob pyrolysis in the temperature range of 300–750 °C contain 3 types of radicals, instead of the 2 types already reported in the literature, such as the one that reversibly adsorbs O2 and the one that does not adsorb O2. The newly found radicals in fresh corncob chars locate mainly at the methylene moieties linked to aromatic rings, and irreversibly disappear by exposure to O2, which leads to the formation of C–O and CO bonds. It is also found that the evolution of corncob char structure shows a two stage behavior, the first stage takes place in the pyrolysis temperatures of 300–600 °C while the second stage takes place in the pyrolysis temperatures of 600–750 °C. This two stage behavior can be characterized by the structural parameters determined commonly by 13C nuclear magnetic resonance, Raman spectroscopy, in-situ diffused reflectance Fourier Transform infrared spectroscopy, elemental composition, O2 adsorption, as well as ESR.

Carbonization of corncobs for the preparation of barbecue charcoal and combustion characteristics of corncob char

The paper examines the process of carbonization of waste from corncobs at carbonization temperatures within a range of 300–700 °C in a laboratory-scale reactor. These studies are important because of reductions in wood resources for the preparation of barbecue charcoal due to environmental protection laws and legislative processes in many countries aimed at the protection of forest resources. The results presented here include the physical and chemical properties of char as a function of carbonization temperatures as well as the characteristics of the heating rate of a fixed bed of corncobs and within a single corncob particle. The combustion characteristics of the char were determined using thermogravimetric analysis. The results show that the volatile matter yield of the char decreased, whereas the fixed carbon yield and higher heating value (HHV) increased, along with higher carbonization temperatures. TGA analysis shows that the ignition and burnout temperature of the char increased, with a simultaneous decrease in the value of the S index, along with increased carbonization temperatures. The results show that carbonization temperatures of 500 °C and above meet the standards for the production of barbecue charcoal.

A comparative investigation on direct carbon solid oxide fuel cells operated with fuels of biochar derived from wheat straw, corncob, and bagasse

A direct carbon solid oxide fuel cell (DC-SOFC) is an all-solid-state device that can directly convert the chemical energy of carbon into electricity with high efficiency and low pollution. This study assesses the feasibility of using carbon-rich biochar derived from wheat straw, corncob, and bagasse, respectively, as the fuels of DC-SOFCs. The chars are characterized using thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Raman spectroscopy, and tapping apparatus. Different quantities of K, Si, S, Ca, Mg, and Fe are found from the chars. It turns out that the output performances of the DC-SOFCs are closely related to the characteristics of the chars used. The peak power densities of 187 and 204 mW cm−2 at 800 °C are achieved by the cells with wheat straw char and corn cob char, whereas the cell with bagasse char performs the highest output performance of 260 mW cm−2. Cells with 0.5 g chars of wheat straw, corn cob, and bagasse discharge at a constant current density of 140 mA cm−2, and it lasts for 15 h, 24 h and 22 h, respectively. The Boudouard reaction reactivity is assessed by analyzing the emitted gas compositions of DC-SOFCs discharging at a constant current density of 500 mA cm−2 via gas chromatography (GC). It turns out that the higher CO concentration representing the faster Boudouard reaction on the fuel.

Hydrogen-rich syngas produced by catalytic steam gasification of corncob char

Corncob char catalytic steam gasification for hydrogen-rich syngas was investigated using a lab-scale fixed bed gasifier to study the effects of temperature, steam flow rate, catalyst type and loading. The method of char absorbing catalyst was used to load catalyst in this work. Four alkali salts of KOH, K2CO3, NaOH and Na2CO3 were selected to pretreat corncob char. Results showed that hydroxides exhibited higher catalytic behavior. Further investigation on the effect caused by varying KOH concentrations to gasification performance has been done, and the maximum hydrogen yield of 197.8 g/kg char was obtained with 6 wt% concentration of KOH solution. Temperature and steam flow rate both has a positive influence on char conversion. Rising temperature promoted the hydrogen yield, and maximum hydrogen yield was obtained at 900 °C. With the steam flow rate increased from 0.2 g/min to 0.4 g/min, hydrogen yield increased by 84%, but a slight increase was found when steam flow rate further increased to 0.8 g/min.

Conversion of bio-char to CaC2 at low temperatures-morphology and kinetics

The conversion of bio-char to CaC2 is a potential way to achieve the production of high-value-added chemicals from biomass. The unique properties of bio-char, such as its fine particles, high activity, and low ash content, provide a high reaction rate, low reaction temperature, and high CaC2 purity, which increase the feasibility of converting bio-char to CaC2. This work investigates the morphological behaviors of the solid reactants and the products, as well as the reaction kinetics, in terms of changes in activation energy and the particle size of the reactants. The experiments were carried out using a thermal gravimetric analyzer coupled with a mass spectrometer (TG-MS) at temperatures lower than 1700 °C using corncob char and CaO as the starting materials. The TG-MS data and kinetics modeling show that at temperatures of 1400–1700 °C, the reaction of corncob char and CaO with a particle size of 22–114 μm is predominantly under reaction control, but is slightly affected by the size of the reactants. During the course of the reaction, the reacting solids agglomerate via the formation of CaC2 without apparent melting.

Study on the mechanism of desulfurization and denitrification catalyzed by TiO2 in the combustion with biomass and coal

The effects of Ca/S molar ratio, catalyst type, catalyst dosage, temperature on desulfurization and denitrification efficiency were investigated in the coal-powder combustion with corn cobs as biomass. The thermal characteristics of Shanxi coal and corn cob blends with V-TiO2 were evaluated by thermogravimetric analyzer. The catalytic mechanisms of V-TiO2 on combustion, desulfurization and denitrification were discussed, suggesting that the mechanisms are in good agreement with the experimental data. The results show that the control parameters of the ideal desulfurization and denitrification efficiency should follow that the dosage of V-TiO2 catalyst is 8% with a Ca/S ratio of 2.3 at a treatment temperature 850 °C. Meanwhile, the combustion efficiency could be effectively improved with the mixture of corn cob and V-TiO2. The thermal characteristics of coal char and corn cob char blends with V-TiO2 were evaluated using thermogravimetric analysis and derivative thermogravimetry methods to discuss the heterogeneous NO reduction mechanisms. The results show that the biomass chars were more active than coal chars in reducing NO, and the specific surface area of the chars was increased with V-TiO2, which indicates that V-TiO2 exhibits significant influence on catalytic combustion, desulfurization and denitrification.

Catalytic reforming of tar using corncob char and char-supported potassium catalysts

This work aims to investigate the importance of biomass char and the metal oxides in the ash in tar cracking during the volatile–char interactions. Experiments were carried out in a two-stage fixed reactor, and corncob, one typical agricultural biomass rich in potassium, was chosen as raw material. Results showed that char and char-supported potassium catalysts have good activity for tar elimination due to the good absorbability of char and catalytic property of potassium. In particular, tar conversion efficiency can reach 95.8% by using 1.5 K-char catalyst at 700 °C. The reforming reactions can be significantly enhanced during the volatile–char interactions in the presence of char and char-supported potassium catalysts. As a result, the syngas yield increased significantly with increasing temperature and supported K+, particularly the combustible gases including H2, CO and CH4. Physical and chemical structure of char changed due to reforming reactions related to the carbon, while the content of potassium was almost unchanged.

Experimental and kinetic studies on co-gasification of petroleum coke and biomass char blends

The non-isothermal thermogravimetric method was applied to petroleum coke (PC), corncob char (CC) and their blends with the different mass ratios under CO2 atmosphere. The results show that CC with highly developed pore structure, high content of alkali metals and low degree of order had more reactivity than that of PC. The gasification reactivity of PC could be effectively improved by blending with CC. Meanwhile, there was obviously synergetic effect for the co-gasification of PC and CC. With the increase of mass ratio of CC, the synergetic effect first increased and then decreased. The synergetic effect was most obvious when CC mass ratio was 20%. Three nth-order representative gas-solid models: volume reaction model (VM), random pore model (RPM) and unreaction core model (URCM) were used to interpret the carbon conversion data. The overall fitting result of the RPM was slightly better than that of the VM and URCM. Furthermore, the synergetic effect between PC and CC was observed from the kinetics data calculated by RPM. The activation energy determined for PC and CC gasification was 203.2 kJ/mol and 243.3 kJ/mol, respectively, whereas, the lowest activation energy for their blends was 197.8 kJ/mol when CC ratio was 20%.

Study on CO2 gasification reactivity of biomass char derived from high-temperature rapid pyrolysis

Three biomass chars, corncob char (CC char), palm shell char (PS char) and soybean straw char (SS char), prepared at different pyrolysis temperatures (1073K, 1273K and 1473K) under nitrogen atmosphere, the gasification characteristics of which were studied at different heating rates by means of non-isothermal thermogravimetric method. Effects of biomass type, pyrolysis temperature on chemical component, morphologic structure, carbonaceous structure of char, and further on gasification characteristics were investigated. Results showed that the order of gasification reactivity of these three chars from high to low was SS char, CC char, and PS char. With the increase of pyrolysis temperature, gasification reactivity of char decreased. The gasification properties of char were determined by carbonaceous structure, which meant the gasification reactivity decreased with the increase of the uniformity of carbonaceous structure. Three nth-order representative gas-solid reaction models, random pore model (RPM), volume reaction model (VM), unreacted core model (URCM) were applied to describe the reactive behavior of chars. A marked compensation effect exists in the gasification reaction of different chars. Concluded from kinetics analysis that the RPM performed best, of which, the activation energies lay in the range of 183.1–263.4kJ/mol.

Electricity generation from corn cob char though a direct carbon solid oxide fuel cell

Solid oxide fuel cell (SOFC) is a potential technology for utilizing biomass to generate electricity with high conversion efficiency and low pollution. Investigations on biomass integrated gasification SOFC system show that gasifier is one of the high cost factors which impede the practical application of such systems. Direct carbon solid oxide fuel cell (DC-SOFC) may provide a cost effective option for electricity generation from biomass because it can operate directly using biochar as the fuel so that the gasification process can be avoided. In this paper, the feasibility of using corn cob char as the fuel of a DC-SOFC to generate electricity is investigated. Electrolyte-supported SOFCs, with yttrium stabilized zirconia (YSZ) as the electrolyte, cermet of silver and gadolinium-doped ceria (GDC) as the anode and the cathode, are prepared and tested with fixed bed corn cob char as fuel and static ambient air as oxidant. The maximum power output of a DC-SOFC operated on pure corn cob char is 204 mW cm−2 at 800 °C and it achieves 270 mW cm−2 when Fe of 5% mass fraction, as a catalyst of the Boudouard reaction, is loaded on the corn cob char. The discharging time of the cell with 0.5 g corn cob char operated at a constant current of 0.1 A lasts 17 h, representing a fuel conversion of 38%. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and Raman spectroscopy have been applied to characterize the char-based fuels.

Gasification behaviors and kinetic study on biomass chars in CO2 condition

Non-isothermal thermogravimetry method was used in the paper to investigate the gasification properties of four biomass chars. The chemical composition and microstructures of biomass chars were analyzed by chemical analysis, scanning electron microscope (SEM) and BET method. The results show that the initial gasification temperature (T0.1) and total gasification temperature (T0.9) of peanut shell char (PS-char), corncob char (CC-char) and bamboo char (BB-char) are close, and rice shell char (RS-char) has relatively higher T0.1 and T0.9. Gasification reactivity of biomass char is in the order of BB-char>CC-char>PS-char>RS-char. It has been confirmed by chemical analysis and microscopic structure analysis that there is a good correlation between the biomass char gasification reactivity and the alkali index; that is, the greater the alkali catalytic index, the higher the catalytic effect. The random pore model (RPM), volume model (VM) and unreacted shrinking core model (URCM) were used to fit the experimental data. The results show that the experimental data agree better with the RPM than with other two models. The apparent activation energies of non-isothermal gasification of PS-char, CC-char, BB-char and RS-char calculated by RPM are 238.6kJ/mol, 302.7kJ/mol, 284.9kJ/mol and 242.2kJ/mol.

Isothermal CO2 Gasification Reactivity and Kinetic Models of Biomass Char/Anthracite Char

Gasification of four biomass chars and anthracite char were investigated under a CO2 atmosphere using a thermo-gravimetric analyzer. Reactivity differences of chars were considered in terms of pyrolysis temperature, char types, crystallinity, and inherent minerals. The results show that the gasification reactivity of char decreased with the increase of pyrolysis temperature. Char gasification reactivity followed the order of anthracite coal char (AC-char) ˂ pine sawdust char (PS-char) ˂ peanut hull char (PH-char) ˂ wheat straw char (WS-char) ˂ corncob char (CB-char) under the same pyrolysis temperature. Two repesentative gas-solid models, the random pore model (RPM) and the modified random pore model (MRPM), were applied to describe the reactive behaviour of chars. The results indicate RPM performs well to describe gasification rates of chars but cannot predict the phenomenon that there appears to exist a peak conversion for biomass chars at a high conversion rate, where the MRPM performs better.