Tar Vapor Research Articles

The Effect of Carbon Infiltration Through CVI Techniques on The Physical Properties of ZTA

The preference for a ceramic matrix composite, in many applications, is due to its allowance for alterations, with regards to the filler or reinforcement used. Among the well-known ceramic matrix composites, is the carbon nanotube reinforced ceramic matrix composite. This ceramic composite, which possesses excellent properties, is used exclusively for high-end applications. However, other than the fact that this composite is prone to damage, in a high temperature environment during the sintering process, its use also comes at a high cost. Among the solutions to these drawbacks, is the introduction of carbon into the ceramic composite, through the chemical vapour infiltration (CVI) process. Initially, pyrolysis of biomass is applied on the empty fruit bunch (EFB), for the generation of tar vapour. Pyrolytic carbon is then produced through secondary reaction, during contact with the ceramic surface. The findings, derived from previous studies, indicate that the physical properties of ZTA improve with the infiltration of carbon, until optimum holding time is arrived at. The optimum holding time, of 2.5 hours for the CVI process, is due to the lowest surface area (3.605 m2/g) and the highest density (3.787 g/cm3). This can be attributed to the reduction in porosity, as the holding time increased. Thus, it can be concluded that carbon infiltration will significantly reduce the porosity, and improve the ceramic properties, of zirconia-toughened alumina (ZTA).

Dynamic Heat Transfer Characteristic of Heat Exchanger for Sensible Heat Recovery of Raw Coke Oven Gas

Abstract A simplified hybrid-dimensional unsteady heat transfer model for the ascension-pipe heat exchanger with a helically coiled tube embedded in the jacket and supported by high conductivity particles is established based on the non-thermal equilibrium theory of porous medium. This idea can also be used in the design of other heat exchange devices involving the helically coiled tube. According to calculations, the wall temperature of the ascension-pipe heat exchanger periodically varies due to the periodic variations of flow rate and temperature of raw coke oven gas. A great thermal stress will be produced due to this reason. The coal tar precipitation mainly occurs in the late stage of the coking period due to the continuous cooling of molten salt. Based on the detailed analysis, thermal conductivity of packing layer, heat capacity per unit volume of packing layer, volume of packing layer, flow rate of molten salt and inlet temperature of molten salt are important factors that should be scientifically designed in the design of this type of heat exchanger to reduce thermal stress and coal tar precipitation. Cutting off molten salt in the late stage of the coking period is an effective measure to control the wall temperature of the ascension pipe above the dew point of coal tar vapor.

Modeling and Numerical Simulation of the Inlet Velocity on Oil–Water Two-Phase Vapor Separation Efficiency by the Hydrocyclone

The density of tar vapor and water vapor produced by coal pyrolysis is different. Different centrifugal forces will be generated when they flow through the hydrocyclone. The water vapor and tar vapor are divided into inner and outer layers. According to this phenomenon, the moisture in the tar can be removed. In this paper, a Eulerian gas–liquid two-phase flow model is established by numerical simulation to study the effect of inlet velocity on the separation effect of a designed hydrocyclone (split ratio 0.2). The results show that the inlet velocity and moisture content have an influence on the volume distribution characteristics, tangential velocity, axial velocity, pressure drop distribution, and separation efficiency of tar vapor and water vapor in the hydrocyclone. When the inlet velocity increases from 2.0 to 12.0 m/s, the central swirl intensity increases, and the negative pressure sweep range at the overflow outlet increases. The axial velocity increased from 2.8 to 14.9 m/s, tar vapor content at the overflow outlet decreased from 74% to 37%, and at the underflow outlet increased from 89% to 92%. When the moisture content is lower than 10%, the hydrocyclone with the split ratio of 0.20 is no longer suitable for the separation of oil–water two-phase vapor. However, when the water content is higher than 20%, the purity of tar vapor at the underflow outlet can reach 92%, and the overflow outlet needs multistage separation to realize tar purification.

Integration of pyrolysis – tar decomposition over porous low grade iron ore

The objective of this research was to investigate the effect of low grade iron ore as catalyst on pyrolysis process of using palm empty fruit bunch. The process was conducted in fixed bed reactor at 450-600 °C. During experiment, the biomass placed within the first stack underwent pyrolysis process was pyrolyzed to produce char, tar and gases. Tar vapor and gases passed through the catalyst bed located within the second stack to conduct catalytic reaction. Furthermore, the vapor left the reactor and entered the cooling system. The catalyst after experiment was weighed to calculate total carbon deposited into catalyst pores. The results showed that the presence of low grade iron ore catalyst increased the gas yield with the yield reduction of liquid fraction. The gas yield was also increased with increasing temperature.

TGA analysis of tobacco rob pyrolysis and release characteristics of noncondensable gas in a fixed-bed reactor

ABSTRACTIn this study, the size of tobacco rob (TR) particle was considered as a major factor in determining the mass loss in thermogravimetric analysis (TGA) and product yield and composition at different reactor temperatures in the fixed-bed reactor. The TGA results showed that the conversion rate increased and the activation energy (ranged from 53.29 to 58.25 kJ/mol) decreased with a decrease in particle size. The experiments demonstrated that fuel gas yield (from 0.76 to 0.82 Nm3/kg at 900 °C) increased with a decrease in particle size while char and tar yield decreased. Smaller particle sizes resulted in higher H2 (25.68%) and CO (27.36%) contents. Minimizing the size of raw materials is an alternative method to improve the gas quality of TR pyrolysis. The increase of gas yield was attributed to the decomposition of char and tar vapor as temperature increased.

Catalytic Cracking of Primary Tar Vapor from Biomass over High Ash-Containing Paper Sludge Ash

High ash-containing paper sludge ash (PSA) has been investigated in terms of its use as a low-cost catalyst for primary pyrolysis tar cracking in the two-stage pyrolysis of biomass. Experimental results showed that tar yields decreased significantly using PSA as catalyst in comparison with the thermal cracking experiments. A consequent increase in total gas yield was obtained. The yields of H2, CH4, and CO2 increased significantly under the catalytic effect of PSA, particularly the H2 yield almost doubled, while CO yields showed a slight decrease due to the consumption reactions. Thermogravimetric analysis of the fresh and spent PSA showed that carbon particles formed along with the tar decomposition, while the catalytic reactivity of the PSA was not reduced because of the participation of carbon particles in tar reforming. XRD spectrograms revealed that calcium-ferrite oxide (Ca2Fe2O5) was formed in PSA, which has excellent stability and catalytic effect on tar cracking and H2 production. The PSA still s...

Innovative Process to Enrich Carbon Content of EFB‐Derived Biochar as an Alternative Energy Source in Ironmaking

This paper describes the mechanism of a developed process—an integrated pyrolysis‐tar decomposition process—to produce oil palm empty fruit bunch‐ (EFB‐) derived biochar with additional solid carbon within the biochar bodies, produced by decomposition of tar vapor on its pore surface, using the chemical vapor infiltration (CVI) method. The product, carbon‐infiltrated biochar, was characterized to investigate the possibility to be used as partial coke breeze replacement in ironmaking. Carbon‐infiltrated biochar is proposed to be utilized for a sintering process that could reduce the consumption of coke and CO2 emission in iron‐steel industry.

Development of an ultra-small biomass gasification and power generation system: Part 1. A novel carbonization process and optimization of pelletization of carbonized wood char

Small-scale, distributed and low cost biomass power generation technologies are highly required in the modern society. The biomass pretreatment process, that is, a combination of carbonization and pelletization processes of cedar wood were explored in this study. For the carbonization process, a novel carbonizer composed of one carbonization chamber and one combustion chamber was tested, and the mass and energy balances during cedar wood carbonization at 400–500°C were analyzed, respectively. During the initial heating stage, about 22kg of wood with dry basis should be supplied into the combustion chamber through several batches. When the temperature in the carbonization chamber reached to the range of 200–220°C, the combustion chamber could be self-heated by burning the pyrolysis gas (tar vapor, CH4, H2, CO) sent from the carbonization chamber. The specific wood consumption for producing 1kg of wood char was within 3.6–4.4kg, which presented an increase trend with increasing the carbonization temperature. Moreover, this carbonization system can deal with different kinds of biomass with various water contents and shapes. For the pelletization process, effects of adding amount of the binder (poval solution), water and the carbonization temperature on the pellet quality were studied so as to explore the optimal condition for making high quality pellets from the crushed wood char. The results indicated that there was an optimal ratio among char, added water, and the binder for making high quality pellets. Considering the energy transfer efficiency and pellet quality, the mass ratio of 0.93:0.32:0.10 for 450°C-char in the dry basis: added water plus water in char: poval solution was the optimal condition for making high quality pellets.

An approach for on-line analysis of multi-component volatiles from coal pyrolysis with Li+-attachment ionization mass spectrometry

Ion-attachment mass spectrometry (IAMS) is a technique used for measuring easily ionized organic compounds in a non-fragmenting mode by softly attaching a Li+ or another type of alkaline ion to the gaseous molecule. In this study, a prototype device for Li+ IAMS is developed for real-time quantitative monitoring of the vapor produced from thermochemical conversion of coal. Simulated tar vapor containing a suite of aromatics and the real vapor produced from the pyrolysis of coal are monitored by IAMS with a Li+ source. It is confirmed that both the simulated and real vapors are ionized without undergoing fragmentation and the sensitivities of these detected aromatic molecules are similar to one another. In addition, when the feeding rate of the coal sample is changed from 0.5 to 1.0g/min, the peak intensities increase nearly twice as much. These results show the possibility of applying IAMS to the quantitatively monitoring of coal-derived volatiles.

Thermal behavior and kinetic study on the pyrolysis of Shenfu coal by sectioning method

According to the physical and chemical characteristics of Shenfu coal pyrolysis process, the kinetics process is divided into three parts at the temperature where the variation of mass loss rate reaches the maximum. First of all, the adsorbed gas and crystal water are removed in the low temperature range; secondly, with a large amount of coal gas and tar vapors evaporating off, coal is transformed into semi-coke in the middle temperature range; thirdly, the semi-coke is further coked with the obvious volume shrinkage in the high temperature range. And then, interfacial chemical reaction model, internal diffusion model with the constant volume of resultant and internal diffusion model with the shrinking volume of resultant are developed to describe the different ranges of pyrolysis process. The results illustrate that the experimental data are fitted well, and all the correlation coefficients (r 2) exceed 0.95. Finally, the kinetic parameters of each temperature range are obtained for the utilization of coal resource.

Reduction of primary tar vapor from biomass by hot char particles in fixed bed gasification

This study investigated the reduction of primary tar vapor from biomass pyrolysis over a bed of hot char particles, focusing on the effect of different operating conditions and char properties. The char samples were prepared from wood, paddy straw, palm kernel shell, and activated carbon. The primary tar was produced from fir wood by pyrolysis at 500 °C and passed through a reactor filled with char particles with different lengths and temperatures.The tar cracking reactions became active above 700 °C, and the presence of hot char particles promoted more tar reduction compared with thermal cracking alone. The mass yield of the primary tar was reduced from 24.8% by pyrolysis to 13.7% by thermal cracking at 800 °C, and further to 7.7% by hot char particles in a reactor volume of 1.48 cm3/gwood. In terms of carbon yield, these values correspond to 32.1%, 19.9% and 11.8%, respectively. The tar with smaller molecular weights was quickly decomposed to gases, whereas the heavy tar was resistant to cracking, even when the reactor volume was increased to 6.90 cm3/gwood. The tar cracking behaviors were similar for four char types despite differences in microscopic surface areas, pore-size distributions, and inorganic contents. The results suggest that creating a tar-cracking zone using char particles situated between the pyrolysis and gasification zones could be helpful in converting the primary tar vapor in a downdraft fixed-bed gasifier, but the degree of conversion is not high enough to eliminate tar issues completely.

Enhancement of oil palm empty fruit bunch char by impregnation of pyrolytic carbon from tar vapor decomposition

This paper describes a technology for condensable vapor from pyrolysis (often referred to as “tar”) of oil palm empty fruit bunch, EFB, to be collected—by EFB char substrate—in the form of pyrolytic carbon to produce a value-added EFB char and to make EFB able to be utilized as a supplementary solid fuel. Chemical vapor infiltration method was employed at atmospheric pressure for tar vapor to undergo secondary decomposition to produce pyrolytic carbon to be deposited within porous char. Porous char in a packed bed was used as the substrate, and impregnated with pyrolytic carbon using tar vapor as a reactant. Char substrate was prepared by slowly heating coarse EFB particles in the packed bed to 400 °C in nitrogen atmosphere. Tar vapor was obtained from fast pyrolysis of fine EFB particles at 400–700 °C, and the weight ratio of fine EFB particles—the tar source—to char substrate was increased from 0.5 to 4.0. The amount of carbon contents of the resultant products by this process was compared to those without carbon deposition. After carbon deposition, EFB char has substantially increased in carbon contents which promise higher heating values than those of EFB char with no carbon deposition. The resultant products can be used as a partial substitute to the now depleting fossil fuels.

Carbon Deposition from Biotar by Fast Pyrolysis of Palm Empty Fruit Bunch

This paper presents a technology to recover carbon available in tar vapor produced from fast pyrolysis of oil palm empty fruit bunch, EFB using porous biochar pellets by employing chemical vapor infiltration, CVI method. By combining slow and fast pyrolysis of EFB, a process was developed employing CVI method, to produce a value-added EFB product. In this developed process, porous biochar produced from slow pyrolysis of EFB pellet was introduced as a medium for tar decomposition to take place. Tar vapor infiltrated within biochar pores and then decomposed into carbon and gases where carbon was deposited on the pore surface. Non-condensable gases can be collected and biotar can be recovered in the form of carbon deposit before being utilized as a renewable energy source by itself. The purpose of this work is to investigate the possibility of using EFB-derived biochar as a medium for tar decomposition and carbon deposition during secondary pyrolysis reaction. Temperature 450°C was found to be the optimum temperature for this secondary pyrolysis reaction to take place within the EFB-derived biochar leaving solid carbon within the available pores. The product of this tar filtering process was carbon-deposited biochar – a potential candidate to be used as an alternative fuel source.

Characterization of particulate matter formed during wood pellet gasification in an indirect bubbling fluidized bed gasifier using aerosol measurement techniques

This study characterizes particulate matter, organic compounds, and inorganic compounds formed in an atmospheric indirect bubbling fluidized bed gasifier at two different steam-to-fuel ratios using wood pellets as fuel. The sampling and conditioning system consisted of a high-temperature dilution probe to quench aerosol dynamics and condense inorganic vapors, a primary thermodenuder to adsorb tar components, and a secondary thermodenuder to investigate the volatility/thermal stability of the remaining aerosol. Both online and offline instruments were used to characterize the aerosol in terms of number size distribution, mass size distribution, particle mass concentration, particle number concentration, morphology, and elemental analysis. Size distributions with three distinct modes were established. The fine and intermediate modes were mainly formed by tar and alkali vapors that had condensed in the sampling and conditioning systems. The coarse mode mainly consisted of the original particles, which are char, fly ash, and fragmented bed material. At the higher steam-to-fuel ratio, tar components seem to be reduced and more coarse-mode particles emitted compared to the low steam case. Furthermore, a possibility for online monitoring of heavy tar is suggested.

Development of Carbon-infiltrated Bio-char from Oil Palm Empty Fruit Bunch

This paper presents a technology to utilize bio-char and bio-tar from the pyrolysis of oil palm empty fruit bunch, EFB. In this study, tar vapor from pyrolysis of EFB was infiltrated within porous bio-char and carbon deposition occurred on the pore surface by chemical vapor infiltration process. For preparation, EFB particles were made into pellets. In the first part of experiments, porous bio-char pellets were produced by slowly heating the EFB pellets in a tube furnace in argon atmosphere to terminal temperatures of 500– 800°C. In the second part, the porous bio-char pellets were used as precursor for tar decomposition process to deposit carbon within the bio-char pores. Tar vapor was obtained from the pyrolysis of EFB at 400–500°C at a fast heating rate for tar decomposition to occur. The purpose of this research is to investigate the amount of carbon deposited within bio-char by this tar carbonization process as compared to carbon contents of metallurgical coke. We showed how EFB bio-char was used as the tar filter and in the process to produce carbon-infiltrated bio-char, a useful renewable energy source for ironmaking process.

D213 循環流動層ガス化における低品位石炭タールの低減と組成変化におよぼす操作条件の影響(OS5 バイオマス・新燃料・環境技術(1))

This paper examined possibility of reduction and/or reforming of tar emitted during gasification of low rank coal in low-temperature gasification. During low temperature gasification, large amount of tar emitted and then interact with carbonaceous solid residue, i.e., char. This interaction is called as volatile-char interaction (VCI), and VCI results in inhibition of char gasification. Therefore, it is important to examine effect of operating conditions on VCI in continuous reactor. In the present study, we developed a circulating fluidized bed reactor that consisted of pyrolyzer and combustor. Coal was fed in the pyrolyzer and then volatiles including tar and inorganic gas etc. and char were formed. The char and silica sand bed material were transported to the combustor to be partially combusted. It means that char was recycled to the pyrolyzer and then contacted with tar in the pyrolyzer. In our previous study, we reported reduction of heavy tar and light tar when coal was fed onto the bubbling bed (top feeding). On the contrary to the previous study, we fed coal into pyrolyzer at the bottom of the bubbling bed. The heavy tar and light tar yield decreased in comparison with the top feeding condition, because tar vapor could be cracked in the bed (secondary cracking). Furthermore, we applied Kendrick mass diagram method that was frequently used in analysis of heavy oil to detailed analysis of heavy tar. According to the Kendrick mass diagram method it was found that deoxygenation was enhanced during char recycling in the bottom feeding condition.

Volatile Organic Compounds from Coal Tar and Soil Vapor Samples at MGP Sites

This study characterized organic compounds found in New York State manufactured gas plant (MGP) coal tar vapors using controlled laboratory experiments from four separate MGP sites. In addition, a limited number of deep (0.3–1.2 m above coal tar) and shallow (1.2–2.4 m above coal tar) soil vapor samples were collected above the in situ coal tar source at three of these sites. A total of 29 compounds were consistently detected in the laboratory-generated coal tar vapors at 50°C, whereas 24 compounds were detected at 10°C. The compounds detected in the field sample results were inconsistent with the compounds found in the laboratory-generated samples. Concentrations of compounds in the shallow soil vapor sample were either non-detectable or substantially lower than those found in deeper samples, suggesting attenuation in the vadose zone. Laboratory-generated data at 50°C compared the (% non-aromatic)/(% aromatic) ratio and indicated that this ratio may provide good discrimination between coal tar vapor and common petroleum distillates.

Carbon Deposition Using Various Solid Fuels for Ironmaking Applications

In this paper, we describe an innovative process involving iron reduction through chemical vapor deposition for applications in the ironmaking industry. In our experiment, we produced tar vapors from pyrolysis of various solid fuels, including high-grade bituminous coal (HGC), low-grade lignite coal (LGC), and biomass palm kernel shell (PKS), and decomposed these vapors into gases, carbon, and light hydrocarbon. Carbon was deposited within the pores of pisolite ore (low-grade ore), which became porous during the dehydration process at 450 °C. We determined that the amount of tar produced during pyrolysis strongly affected carbon deposition, and HGC produced the highest carbon deposition because of its large tar product. In addition to tar amount, surface area and pore volume also played important roles in this process. PKS had the highest ratio of deposited carbon because it produced the smallest quantities of reacted tar and, consequently, the largest numbers of vacant pores. The amount of carbon deposition decreased at higher temperatures because tar was easily converted to a gaseous phase. The deposited carbon within iron ore showed potential as a reducing agent because it was highly reactive and reduced at lower temperatures. Carbon deposited within iron pores dramatically reduced the contact distance between the iron ore and carbon. Thus, these results show that our proposed methodology could have important applications as an alternative low-energy approach for producing metallic iron using low-grade materials.

Catalytic coal-tar decomposition to enhance reactivity of low-grade iron ore

Effective utilization of low-grade iron ore and coal can be one of the solutions for avoiding the high cost of raw materials and solving the problem of resource shortages in the steelmaking industry. This paper describes the behavior of reduction reaction during tar decomposition over low-grade iron ore. Pisolite ore, containing 5.9mass% of combined water, was dehydrated at 450°C to obtain porous ore. Tar vapor and pyrolysis gas of low-grade coal were introduced to porous ore for tar decomposition and carbon deposition. The iron ore effectively decomposed 22.1mass% of tar component into gas product and deposited carbon at 600°C. Besides tar decomposition, the ore was also reduced to magnetite and wustite by gas product which was produced from coal pyrolysis and tar decomposition. The reactivity of deposited carbon within ore was evaluated by reduction reaction using thermogravimetry method. The reduction of the carbon-deposited ore began at 750°C, while that of the reference mixture of Fe3O4 and coke began at 1100°C. The carbon-deposited iron ore was more reactive because nanoscale contact between iron ore and carbon enhanced reaction rate. These results revealed attractive utilization and reduction process of low-grade iron ore with coal tar decomposition.

Carbon Deposition from Biotar by Fast Pyrolysis Using the Chemical Vapor Infiltration Process within Porous Low-Grade Iron Ore for Iron-Making

This paper presents a technology for iron-making using biomass and a low grade iron ore by implementing chemical vapor infiltration (CVI) for the tar carbonization process. In this process, tar vapor from pyrolysis of biomass was infiltrated within a porous ore and carbon deposition occurred on the pore surface. For preparation, ore sample was heated in an electric furnace to decompose combined water in the sample, creating nanosized pores. In the experiments, the traditional slow pyrolysis was compared with fast pyrolysis to determine which condition is better for maximizing carbon deposition. Tar vapor from the pyrolysis process was introduced into the porous ore and trapped inside it, where tar decomposed and carbonized within the pores. The product of this process which is a carbon−magnetite composite with close arrangement of iron ore and carbon is useful for reduction of iron by carbon and is able to lower the temperature needed for reduction of iron to occur, as compared to that in steelworks. The purpose of this research is to compare the effects of slow pyrolysis and fast pyrolysis processes on the amount of carbon deposited within iron ore by the tar carbonization process and to observe the reduction reactivity of the carbon-deposited iron ore.