DESULPHURIZATION OF A TURKISH LIGNITE BY PYROLYSIS COMPARISION OF SLOW AND FLASH PYROLYSIS

To observe the effect of the heating rate on the desulphurization. Bolu- Mengen lignite was desulphurized in the temperature range of 450-750 °C using flash and slow pyrolysis methods. A reduction of 57.6 % and 34.2 % In the total sulphur was obtained for the slow and flash pyrolysis at a pyrolysis temperature of 750 °C. respectively. It was observed that the flash pyrolysis is shifted toward higher temperatures with respect to the slow pyrolysis. The flash pyrolysis having high thermal efficiency has a potential as a desulphurization process.     

RAPID PYROLYSIS OF EASTERN CANADIAN COALS BY FREE FALL REACTORS

Abstract

The effect of temperature was investigated on the rapid pyrolysis of Prince, Lingan and No. 26 coals in the temperature range of 525^° to 750^°C using a 600 cm high stainless-steel free fall reactor at atmospheric pressure.

The yields of char, condensibles and gaseous products were determined at 25^°C intervals. Gaseous products were analysed for H₂, CO, CO₂, CH₄ and C₂+.

Volatile product (condensible and gas) yields exceeded the volatile product in the A.S.T.M. methods at and above 700^°C.

Some experiments using Prince coal were repeated at reduced pressure (50 mm mercury) in both the 600 cm height stainless-steel and a 140 cm height quartz reactor in order to find out the effect of pressure and retention time.

The experimental results indicated that the condensable yield was higher at the lower pressure and at the shorter retention time. The effect of retention time was far more pronounced.     

EFFECTS OF HEATING RATE AND PARTICLE SIZE ON THE PRODUCTS YIELDS FROM RAPID PYROLYSIS OF BEECH-WOOD

ABSTRACT

Effects of pyrolysis temperature (300–1000 ^°C), heating rates (100, 500, 1000, and 10,000 ^°C/s), and particle sizes (53–63,104–120,177–270, and 270–500 urn) on the yields and formation rates of tar, light oils, total gases, and char from pyrolysis of beech-wood under 1 atm helium pressure were studied. Wood particles were pyrolyzed in strips of stainless steel wire mesh in a captive sample apparatus; and yields of products were measured in weight percent of original wood as a function of temperature for different heating rates and particle sizes. The overall weight loss achieved from pyrolysis of this wood was about 90%. The total yields of tar and light oils from pyrolysis of this wood accounted for up to 80% of the original wood above 400 ^°C. Due to the post-pyrolysis reactions of tar and light oils, the tar and light oils yields go through a maximum with pyrolysis temperature for all particle sizes and most heating rates studied here. As particle size increases from 53–63 μm to 270–500 μm the maximum tar yield decreases from 53% to about 38%. The maximum tar yield also decreases with increasing the heating rate from 70% at 100 ^°C/s to 48% at 10,000 ^°C/s heating rate. Theses results indicate that as the intra-panicle post-pyrolysis cracking reactions of tar increases at higher heating rates and with larger particles the tar yield decreases. Tar was also analyzed with GPC for the effects of above pyrolysis parameters on the tar molecular weight. The tar average molecular weight. remains relatively constant (M_w = 300 amu, M_n = 155 amu, and M_z = 483 amu) under helium atmosphere with pyrolysis temperature at 1000 ^°C/s heating rate and with 53/63 u m particle size. The average molecular weight of tar does not significantly varies with heaung rate, but it decreases as the particle size increases.     

KINETICS FOR FAST PYROLYSIS OF HAZEL NUT SHELL

Abstract

In this article, the potential utilization of hazel nut shell as a combustible residue was studied. To obtain liquid and gaseous products, the hazel nut shell was subjected to pyrolysis and it was converted to 49.3 % (w) gaseous and 20.0 % (w) liquid products at 475 °C for 7.5 minutes in a simple pyrolysis device The kinetic model used in the present study was based on fractional weight loss for each pyrolysis step. The simple fast pyrolysis was compared with TGA technique.     

CHARACTERIZATION OF COAL CHARS FROM A FLASH PYROLYSIS PROCESS BY CROSS POLARIZATION/MAGIC ANGLE SPINNING 13C NMR

ABSTRACT

Chars from the Illinois Springfield (No. 5) Coal are prepared by flash pyrolysis at progressively higher charring temperatures. The results of a study of these chars by ¹³C NMR with CP/MAS indicate that the initial stage of heating (300^°C) produces a char with aromatic carbon fraction (f_ar) of 68%, and successive heating gives chars with f_ar of 70% (400^°C), 73% (500^°C), 89% (600^°C), 95% (700^°C), and 96% (800^°C). However, the actual amount of aromatic and aliphatic carbon in the char can be calculated by using the NMR measurements, the organic carbon content of the char, and the weight of the char. The calculated values show that the amount of aromatic carbon in char remains relatively constant at each temperature, but the amount of aliphatic carbon in char is reduced during higher temperature charring. At 600^°C, both a large reduction of the aliphatic carbon content and a maximum weight loss occur. Evidently, the aliphatic-bond carbon in coal is the principal source of volatiles derived from coal. The apparent increase in aromaticity (f_ar) of the char heated to progressively higher temperatures is due to the loss of aliphatic-bond moieties and reduction in volume of materials.     

PRODUCTS FROM FLASH PYROLYSIS OF A TURKISH LIGNITE IN A FREE-FALL REACTOR UNDER VACUUM

ABSTRACT

Flash pyrolysis of a Turkish lignite under vacuum in a free-fall reactor was examined at a temperature range of 400 - 800 °C. Gaseous products were analysed with an on-line GC equipped with a manuel injection valve. Solvent fractionation was applied to the liquid product to separate preasphaltenes, asphaltenes and oils fractions. Two particle distributions of the lignite were used: ?0.315+0.2 mm and ?0.1 mm. The liquid yield increased with temperature up to 650 °C and, thereafter decreased for the larger particles. The maximum liquid yield, excluding pyroltic water, was found to be 8 % wt (dal) at 650 °C. In the case of the smaller particles the liquid yield increased steadily with temperature and the yield of liquid, excluding pyrolytic water, was 5.9 % wt (da) at 850 °C. The gaseous product yield also increased with temperature for both size fractions, and CO and CO₂ in the gaseous products were present in large amounts.     

PYROLYSIS OF SUNNYSIDE (UTAH) TAR SAND: CHARACTERIZATION OF VOLATILE COMPOUND EVOLUTION

ABSTRACT

Sunnyside (Utah) tar sand was subjected to programmed temperature pyrolysis and the volatile products were detected by tandem on-line mass spectrometry (MS/MS) in real time analyses. A heating rate of 4°C/min from room temperature to 900°C was employed.

Evolution of hydrogen, light hydrocarbons, nitrogen-, sulfur-, and oxygen-containing compounds was monitored by MS or MS/MS detection. Evolution of volatile organic compounds occurred in two regimes: 1) low temperature (maximum evolution at 150 to 175°C), corresponding to entrained organics, and 2) high temperature (maximum evolution at 440 to 460°C), corresponding to cracking of large organic components. Alkanes and alkenes of two carbons and higher had temperatures of maximum evolution at approximately 440°C, and methane at approximately 474°C. Aromatic hydrocarbons had temperatures of maximum evolution slightly higher, at approximately 450° C. Some nitrogen-, sulfur-, and oxygen-'ccntaining compounds were also detected in the volatile products.

Comparing the Sunnyside pyrolysis to the pyrolysis of other domestic tar sands indicated the following for hydrocarbon evolution: 1) the evolution of entrained organics relative to the total evolution was much less for Sunnyside tar sand, 2) the temperatures of maximum evolution of hydrocarbons due t o cracking reactions were slightly lower, and 3) the temperatures of maximum evolution for benzene and toluene are slightly higher than observed for other tar sands.

In general, the noncondensible gases, H₂, CO, and CO₂, exhibited evolution associated with hydrocarbon cracking reactions, and high temperature evolution associated with mineral decomposition, the water-gas shift reaction, and gasification reactions. Pyrolysis yields were dominated by the evolution of carbon oxides and water. The CO₂ primarily appeared t o cane from the decomposition of carbonate minerals. Compared t o other domestic tar sands, the gas evolution reflected more mineral decomposition character for Sunnyside tar sand.     

NON-ISOTHERMAL PYROLYSIS OF TWO KINDS OF CHINESE OIL SHALE

Abstract

Non-isothermal pyrolysis of two kinds of Fushun oil shale with particle sizes, <0·075 mm, 0·3 - 0·5 mm, 0·75 - 1·0 mm and 1·5 - 2·0 mm, has been investigated in stream (nitrogen) at the flow rate of 100 ml/min by thermo-gravimetric analyzer with a linear heating rate 6·8K/min. It has been found that the temperaturee intervals of oil-generation from rich grade shale ( 9·8 % Fisher Assay oil yield ) and poor grade shale ( 3·9% Fisher Assay oil yield ) with particle size less than 2·0 mm are 400 - 500 °C and 400 - 520° C respectively. The kinetic treatment of the thermo gravimetric data reveals that pyrolytic reactions of the two kinds of Fushun oil shale are both of the first order, but with different activation energy E and pre-exponential factor A in different temperaturee regions during pyrolysis. This is different from what was described in general terms as global first order reaction for oil shale pyrolysis by other anthers. The kinetic parameters for pyrolysis of the two kinds of Fushun oil shale with different particle sizes were calculated by means of least square curve fitting, and the influence of particle size on pyrolysis was also discussed.     

Direct conversion of an agricultural solid waste to hydrocarbon gases via the pyrolysis technique

The increased awareness toward the global warming and the environmental pollution problems has stimulated the utilization of the alternative energy sources since they can positively take part in minimizing such problems. Among these sources, biomass based solid wastes is counted as one of the most promising in the field of energy production. Thus, the current research work focuses on the conversion of rice straw (a biomass-based solid waste) into hydrocarbon gases in general and methane (main constituent of natural gas) in particular. The reduction of the operational temperature and the elevated rate of solid-to-gas conversion are newly presented approaches in this research. Specifically, the used operating temperature, in this study, had been 250?°C while the well-known temperature range for slow pyrolysis is 380–550?°C. Another approach is represented in this work via the orientation of the obtained biogas to become mainly hydrocarbon gases instead of CO, CO₂ and CH₄ mixture, as the common for such pyrolysis processes. The attained high rate of solid-to-gas conversion (80%) while at low temperature is also a new approach of this study since such high rate is just possible in the flash pyrolysis (750–900?°C). The increased conversion rate was achieved via reducing the particles size of the used solid-biomass to a nano-sized range.     

PYROLYSIS OF SOME TURKISH LIGNITES BETWEEN 200 - 600°C

Abstract

This study was undertaken to examine the effect of pyrolysis between 200-600°C on sulphur content, proximate and ultimate analyses of four (Seyitomer, Tuncbilck, Elbistan and Kangal) lignite samples. A decrease in semi-coke yield and an increase in tar and gas yields with increasing temperature were observed for all samples. Percent reduction of volatile matter was the same up to 400°C for the lignites. It has been observed that total sulphur contents were reduced significantly during carbonization. The highest sulphur reduction, 45%, was obtained with Elbistan lignite. By increasing temperature, hydrogen, carbon dioxide, methane and hydrogen sulphur yields increased notably but ethane and propane yields increased only slightly for all samples. In order to study effect of C, H and O contents of the original lignites on the yield and the distribution of the products, a linear regression analysis has been carried out and the model relations have been obtained. Experimental data and the model values from the relations have been compared. Yield values appear to be in good agreement with the model values for all samples.     

CHARACTERISTICS OF PYROBITUMEN AND OIL OBTAINED FROM GREEN RIVER OIL SHALE PYROLYSIS

ABSTRACT

Pyrobitumens and oils generated from the isothermal pyrolysis of Green River oil shale at 400° 425°, and 440° C for different times were characterized. Elemental contents, average molecular weights, and hydrocarbon contents were determined for the pyrobitumens and oils. The pyrobitumens, a major initial pyrolysis product, had an average molecular weight exceeding 1200 and contained about 85% polars. The atomic hydrogen-to-carbon ratio, nitrogen content, and average molecular weight of the pyrobitumens changed with pyrolysis temperatures and times. The variable composition of the pyrobitumens suggests that pyrobitumen should not be considered as a single intermediate for kerogen decomposition. In contrast, oils contained 60% hydrocarbons and had a constant atomic hydrogen-to-carbon ratio and average molecular weight of about 250. However, the nitrogen content of the oils increased with increasing reaction time. The ratios of normal heptadecane/ pristane and normal octadecane/phytane, and odd-even predominance of oils were sensitive to pyrolysis temperatures and times. The rate constants, frequency factors, and activation center, for funding this work under cooperative Agreement Number DE-FE21-86MC11076.     

13C-N.M.R. STUDIES OF A FLASH PYROLYSIS TAR AND A SUPERCRITICAL GAS EXTRACT USING MODERN PULSE SEQUENCES

ABSTRACT

The oil and the asphaltene obtained from a flash pyrolysis tar of an Australian sub-bituminous coal and the oil and asphaltene from a supercritical gas extract of an Australian bituminous coal were studied by ¹³;c-n.m.r. apectroscopy using modern pulse sequences which distinguish between primary (CH₃), secondary (CH₂), tertiary )CH( and quaternary (C) carbons. The oil from the flash pyrolysis tar was further separated into three fractions by elution chromatography and these were also studied. All the samples studied contained considerable amounts of long unsubstituted aliphatic chains. In the flash pyrolysis tar, a sizeable proportion of the long chains had a CH = CH₂ end group pertaining to both 1-alkenea and those chains attached to aromatic rings (w-aryl-1-alkenes), but this was much less in the supercritical gas extract. From the quaternary and tertiary carbon subspectra, it appears that the division of the aromatic carbon signal at 129-130 ppm between aromatic CH and C carbons is not valid for polar fractions of coal liquids. Though these pulse sequences are very useful for obtaining information on well resolved signals, broad featureless signals often found in coal liquids pose considerable problems.     

CONTINUOUS HYDROGENATION OF FLASH PYROLYSIS COAL TAR

ABSTRACT

High melting tars from the flash pyrolysis of Millmerran coal have been upgraded to mobile liquid products by continuous hydrogenation over a fluidized nickel molybdate catalyst. The hydrogenation unit developed specifically for this purpose la described and changes In properties of the tar during hydrogenation are discussed.     

KINETICS OF CORN COB CHAR GASIFICATION IN CARBON DIOXIDE

ABSTRACT

The Reactivity of corn cob char in CO₂ has been studied on a thermogravimetric balance to develop a rate equation for the design of biomass gasifiers operating on corn cob char. Experiments in the range of 650-1000^°C were conducted with cylindrical shaped pellets of 1 cm diameter having L/D=l. The average porosity of the pellets was 0.5. It was observed that the rate of the CO₂/char reaction decreased with increase in temperature from 650-750^°C and then increased with temperature upto 1000^°C.

The data obtained at temperatures 750^°C and above has been used to determine a rate equation for char gasification. It has been found that the reaction proceeds according to the Sharp Interface Model (SIM) with a first order chemical reaction as the rate controlling step. The activation energy is found to be 40 Kcal/mole with frequency factor being 1.2 × 10⁷ mm/sec. Analysis of the data obtained for the decreasing reaction rate regime (650-750^°C) indicates that the change in the ash structure result in this kind of behavior.     

PYROLYSIS STUDIES OF ORGANIC OXYGENATES VI. THERMAL CHEMISTRY OF LONG CHAIN ALIPHATIC ACIDS

ABSTRACT

The thermal chemistry of two long-chain fatty acids, decanoic acid and tetradecanoic acid (myr1st1c add), has been determined at temperatures of 400-450^°C under Inert {helium and nitrogen) and reactive (hydrogen) atmospheres. In general the thermal chemistry pathways are similar to those found with aromatic acids. Secondary cracking type reactions were found to be much more Important for the fatty acids, leading to a very complex product mix.

As expected, decarboxylation and subsequent radical reactions are Important whether the pyrolysis is carried out In the presence of an Inert gas such as helium or whether a hydropyrolysis occurs. Consistent with what was previously demonstrated with an aromatic acid⁽⁷⁾ and an aryl alkyl ether⁽⁵⁾, hydropyrolysis suppresses CO_x formation and tends to generate more aldehydes and alcohols than are produced under conventional pyrolysis conditions.

For fatty acids under Inert atmosphere pyrolysis conditions, the major initial products are the alkanes and alkenes derived from loss of CO₂, and CO₂ Itself. When hydrogen is present In the vapor phase, additional major products are formed. These Include the alkane, alkene and aldehyde derived from reduction of the fatty add. In all cases there is a substantial yield of the ketone     

UPGRADING OF PETROLEUM RESIDUES BY VACUUM PYROLYSIS

ABSTRACT

Vacuum pyrolysis of petroleum residues which are classified as hazardous materials was performed in a batch reactor and enabled us to separate an upgraded oil from water and residual solids. Conversion of petroleum wastes to reusable oils reached 85% on an organic basis.

The pyrolysis oils and solid products were analysed for maltene, asphaltene and sulfur content. We found a significant increase in the pyrolysis oil maltene content. Much less sulfur was detected in the pyrolysis oil compared with the original organic waste material. The resin content of the pyrolysis oil decreased and the aliphatic, alicyclic and monoaromatic hydrocarbon content increased. The heavy portion of the pyrolysis oil contained approximately 5% of undesirable n-alkenes ranging from n-C₁₄ to n-C₃₈. Only trace amounts of organic and inorganic contamination was found in the solid phase leachate. The aqueous phase contained a small quantity of soluble organics which will be easily removed in a standard refinery water treatment plant. Results showed the merits of vacuum pyrolysis for upgrading petroleum residues.     

EFFECT OF SOLVOLYTIC EXTRACTION AND PYROLYSIS PRETREATMENTS ON THE TOEMPRATURE STEAM GASIFICATION REACTTVITY OF COAL AND REDUCTION OF TAR FORMATION IN PRODUCT GASES

ABSTRACT

Pre-extraction of Talcher coal ( a bituminous coal) in anthracene oil was found to be a beneficial treatment for enhancing the reactivity for steam gasification of coal. Similarly, anthracene oil followed by liquid paraffin extraction of coal was also found to be a-better pretreatment for the steam gasification of coal. Anthracene oil extraction at 270°Cand steaming of coal at 650°C had almost equal effect on steam gasification of coal. Pyrolysis in steam of pre-extracted coals was found to further enhance the reactivity of coal for steam gasification. The studies were further confirmed by carrying out thermogravimetric analysis of pretreated coals in steam atmosphere. Degree of cross-linking in pretreated coals was studied by measurement of swelling of coal in quinoline. The formation of tar in gaseous product was reduced as a result of pre-extraction and steam pyrolysis of coal prior to their gasification in steam.     

VARIATION IN THE CHEMICAL NATURE OF ASPHALTENES WITH THE PROCESS,THE COAL AND THE REACTION CONDITIONS

ABSTRACT

Average structure data for twelve asphaltenes are reported, based on ¹³C- and H- n.m.r. spectroscopy combined with elemental, molecular weight and functional group analyses. The asphaltenes were from supercritical gas extraction, flash pyrolysis and hydrogenation of a brown and a bituminous coal. The effect of the reaction temperature and, for hydrogenation, the catalyst and solvent on the nature of the asphaltene produced was studied. The asphaltene obtained from supercritical gas extraction of the brown coal at 350°C was the least aromatic (f_a = 0.44) with the highest H/C atomic ratio (1.16) and probably consists mainly of single ring aromatlcs with about half of the aromatic sites substituted. A significant proportion of the carbon in this asphaltene is in long alkyl chains and the hydroxyl content is high. Whereas, the asphaltenes produced by hydrogenatlon of the bituminous coal at 450°C were far more aromatic with more highly condensed but less substituted aromatic ring systems and few, if any, long alkyl chains, together with a lower hydroxyl content. The asphaltenes obtained from the brown coal are less aromatic with less condensed aromatic ring systems but a higher degree of aromatic substitution than those produced from the bituminous coal under the same conditions. The asphaltenes formed at 450°C had lower H/C atomic ratios, molecular weights and degree of aromatic substitution, but higher aromaticities Ohan those produced at 35O°C or 400°C under like processing conditions. The asphaltene produced in the presence of both stannous chloride catalyst and tetralin was less aromatic than when either of these species was absent.     

PYROLYSIS STUDIES OF ORGANIC OXYGENATES. IV. NAPHTHALENE METHYL ETHER PYROLYSIS UNDER BATCH AUTOCLAVE CONDITIONS

ABSTRACT

Aryl alkyl ethers undergo two major kinds of thermal reactions at temperatures of about 450^°C. They cleave homolytically at the C-H alkyl bond to produce phenols and they cleave homolytically at the C-H alkyl bond, and rearrange to an aryloxy radical leading to carbonyl compounds and ultimately to other products. Results obtained with the methyl ethers of 1- and 2-naphthol and with anisole show clearly that relative kinetics for these pathways differ for different substrates. Unimolecular decomposition rates at 400^°C and at 450^°C show that 1-methoxy naphthalene decomposes faster than 2-methoxy naphthalene which in turn is more thermally reactive than anisole.     

塔里木盆地煤岩在不同介质条件下热模拟实验中烷烃系列有机地球化学特征

对塔里木盆地侏罗系煤岩在不同介质下的热模拟实验和正构烷烃系列色质测试分析结果表明,在400℃前后煤岩成烃机理不同。结合对峰型、ΣC21-/ΣC22+值、OEP指数和P r/Ph值等地球化学参数的研究,指出了不同热演化阶段的成烃机理:在低温阶段(<350℃)煤岩主要是裂隙、晶格间吸附烃和结构边缘烃的排出;在350~400℃之间,脱甲基及链断裂效应使得煤岩排烃进入高峰期;在高演化阶段(≥450℃),大量内部结构烃发生断裂重排,550℃以上温度达到第二个热降解高峰,产出烃发生脱甲基、链断裂和开环效应。模拟实验还表明,OEP指数变化较大,其每次变化都伴随一次生烃高峰;P r/Ph值随着热演化程度呈降低趋势;有水、伊利石和蒙脱石存在时,会改变煤岩在热演化过程中高碳数烃的热降解速率,有利于液态烃的形成。