Youqing Wu

CO2-Gasification Reactivity of Different Carbonaceous Materials at Elevated Temperatures

Abstract At the atmospheric pressure and at the temperatures between 1,223 and 1,673 K, the CO2 gasification reactivity of seven different carbonaceous materials comprising coal tar pitch coke, petroleum coke, natural graphite, carbon black and three coal chars was investigated by using thermogravimetric analysis. Their crystalline structures were analyzed by X-ray diffraction (XRD). It is found that the reactivity of the chars, pitch coke and petroleum coke produced from liquid-phase carbonization, is several times poorer than that of the coal chars produced from solid-phase carbonization and even lower than that of natural graphite. At the same time, it is obtained that under the condition of the chemical reaction control, the apparent activation energies of the former are in the range of 135.82–174.92 kJ/mol, while those of the latter are between 89.95 kJ/mol and 110.05 kJ/mol. Besides, the reactivity of the sample has a certain correlation with the crystalline structure of the sample, i.e., the larger the fraction of the relatively better crystalline structure is, the poorer the reactivity of the sample is.

Effect of Charring Temperature on the Composition and Solubility of Chars Formed from Rapid Heating of Shenfu Coal

Abstract A series of chars were prepared by rapidly heating Shenfu coal, a Chinese bituminous coal, to different temperatures. Ash, volatile matter, and elemental contents of the chars were compared. The chars were extracted with carbon disulfide, benzene, and tetrahydrofuran sequentially, and the extraction solutions were analyzed with gas chromatography/mass spectrometer (GC/MS). The results show that raising charring temperature increases the ash and carbon contents, but decreases the hydrogen and nitrogen contents as well as the solubility, while change in sulfur content is very small with charring temperature. A series of alkanes and polycyclic arenes were detected in the extraction solutions.

The physicochemical properties and catalytic characteristics of different biomass ashes.

Steam gasification of petroleum coke catalyzed by different biomass ashes and different biomass ash loadings were investigated to examine the catalytic effects not only on the gasification activity but also on the H2 production characteristics, and the physicochemical properties of three biomass ashes (rice straw ash, wheat straw ash, and cotton straw ash) were also analyzed. The total contents of alkali metals (K and Na), alkaline earth metals (Ca and Mg), and transition metal (Fe) in RSA, WSA, and CSA were separately up to 22.63, 43.88, and 55.68%, and a large quantity of catalytic components (such as KCl, K2SO4, etc.) were contained in these biomass ashes. The biomass ashes could not only enhance the gasification activity of petroleum coke effectively, but also promote the H2 production greatly. The ordering of the catalytic action of various biomass ashes was CSA > WSA > RSA. The increasing loading of biomass ash was favorable for elevating the gasification activity of petroleum coke and promoting the H2 production, and the effects of the redundant biomass ash loading on those were very little. The mineral matters in biomass was conducive to improve the gasification activity of petroleum coke during the co-gasification processes and to promote the H2 production to produce syngas with high purity H2 (up to 61%) and no virtual CH4 at relatively low temperatures.

A Semi-empirical Kinetic Model for Simulating the Steam Gasification of Petroleum Coke Catalyzed by K2CO3

K2CO3-catalyzed steam gasification of petroleum coke at 650–850°C was performed using a laboratory fixed-bed reaction system with an on-line quadruple mass spectrometer. Due to the catalytic effect of K, the catalytic gasification rate exhibited a maximum in the high carbon conversion range, which was different from that in the case of non-catalytic gasification. When the random pore model was used to simulate the catalytic gasification process of petroleum coke, great deviations were found at high carbon conversions. A semi-empirical model (extended random pore model) was proposed on the base of the random pore model. It was found that the extended random pore model could describe well the catalytic gasification profile in the whole carbon conversion range, and the two empirical parameters (α and β) introduced in the extended random pore model could be well correlated with the gasification temperature.

CO2 Gasification Characteristics of Biomass Residues from Agricultural and Woody Production

In this article, various chars were prepared at the pyrolysis temperature of 973–1,273 K, using the biomass residues (rice shell, rapeseed shell, and wood scrap) from agricultural and woody production as raw materials, and their CO2 gasification characteristics were mainly investigated from room temperature to 1,673 K by a non-isothermal method. The residues presented a very high content of volatile matters and their de-volatilization process was very easy. The order of the gasification activity of the three biomass residues was as follows: rapeseed shell > wood scrap > rice shell. The residues wholly presented quite high activity and their gasification activity was far higher than that of coal. Consequently, the residues were suitable to be used as fuels for the median temperature gasification. The apparent activation energies for the CO 2 gasification reaction of chars from these residues ranged from 282.05 to 363.72 kJ/mol. In addition, it was found that a marked compensation effect was also presented between the activation energy and the pre-exponential factor for the gasification reaction of chars from these residues.

Physicochemical Properties and Gasification Reactivity of Chars from Different Carbonization Processes

Three kinds of high temperature carbonization chars (gas-phase carbonization chars [GPCCs], solid-phase carbonization chars [SPCCs], and high temperature calcination chars from liquid-phase carbonization cokes [HLPCCs]) were prepared at the carbonization temperature of 800–1,600°C, and their physicochemical properties and CO2 gasification reactivity were mainly investigated. The increasing carbonization temperature was favorable for chars produced from different carbonization processes to form more ordered carbon crystallite structures. At the same carbonization temperature, the regularity of carbon crystalline structures of different chars presented the following order: GPCCs > HLPCCs > SPCCs. The increasing carbonization temperature resulted in the increase of surface areas of HLPCCs as a whole and the decrease of surface areas of SPCCs, while those of GPCCs initially increase and then decrease with the increasing carbonization temperature. Brunauer-Emmett-Teller surface areas of different chars, as a whole, presented the following order: SPCCs > GPCCs ≥ HLPCCs. The increasing carbonization temperature was adverse to the gasification activities of SPCCs and GPCCs, while those of HLPCCs initially decrease and then increase with the increasing carbonization temperature. The ordering of the gasification reactivity of different chars was SPCCs > GPCCs > HLPCCs.

The Reactivity and H2 Production Characteristics of Petroleum Coke-steam Gasification Catalyzed by Potassium Salts

Potassium salts-catalyzed steam gasification of petroleum coke for H2 production was performed using a laboratory fixed-bed reaction system with an on-line quadruple mass spectrometer. The gasification reactivity and H2 production characteristics of petroleum coke-steam gasification catalyzed by potassium salts were investigated mainly. The potassium salt catalysts could not only enhance effectively the gasification reactivity of petroleum coke, but also promote greatly the H2 production. The catalytic action of various potassium salts was ordered as K2CO3 > KAc > KNO3 > K2SO4 > KCl. The increasing catalyst loading could promote the H2 production of petroleum coke gasification. However, different potassium salts almost had no effect on the distribution of product gases. It was feasible to produce syngases with high H2 (up to 60%) and no virtual CH4 (below 0.1%) through the catalytic steam gasification of petroleum coke at relatively low temperatures.

The Effect of Heterogeneous Catalysts on Hydrothermal Liquefaction of Corn Stalk under CO Atmosphere

Hydrothermal liquefaction of corn stalk under CO atmosphere with three commercial heterogeneous catalysts was performed in a high pressure autoclave. The structure and reducibility of the catalysts were studied by X-ray diffraction and differential thermal gravity under H2 atmosphere. The results indicated that the catalysts greatly increased the conversion of cornstalk yield and heating value of liquid product. The activity order of the catalysts is as follows: JT203 > JT201 > JB-1, which is consistent with the high surface area and low reduction temperature of JT203. The catalysts might favor a hydrothermal liquefaction process through the active H produced by water-gas shift reaction.

The Effect of Wood Vinegar on Hydrothermal Liquefaction of Cotton Stalk Under CO Atmosphere

High pressure liquefaction of cotton stalk under carbon monoxide atmosphere in water and two kinds of wood vinegar was performed in a high pressure autoclave. The results indicated that the conversion of cotton stalk and yield of liquid product were increased by using wood vinegar as the solvent. Using wood vinegar as the solvent, the hydrothermal liquefaction of cotton stalk under carbon monoxide atmosphere was investigated and it was found that, compared with water, wood vinegar could improve the conversion of cotton stalk and yield and heating value of liquid product from 91.56%, 35.75%, and 34.14 MJ/kg to 94.98–97.37%, 48.26–54.23 MJ/kg, and 35.45–37.58 MJ/kg, respectively.

Characteristics of liquid products from hydrothermal liquefaction of typical crop straws under CO atmosphere

The hydrothermal liquefaction of three typical crop straws (corn, wheat and cotton straws) under CO atmosphere was carried out in a 500 mL autoclave. Simultaneously, the main properties and chemical compositions of the liquid products (LPs) were investigated by the elemental analysis, gas chromatography–mass spectrometry and 1 H nuclear magnetic resonance. In the hydrothermal liquefaction under CO atmosphere, the conversion of typical crop straws and the yield of LPs are respectively up to 82?4–91?6% and 35?8–39?5%, and the LPs with low O content (10?64–14?01%), high H/C ratio (1?05–1?28) and trace amounts of S and N have a high heating value between 34?14 and 36?73 kJ g 21 . The results of gas chromatography–mass spectrometry and 1 H nuclear magnetic resonance analyses show that the LPs are mainly composed of phenol derivatives, long chain alkanes and other O containing compounds (carboxylic acids, ketones and esters) and also contain a large amount of aliphatic fractions, suggesting that the LPs might be potentially valuable resources as renewable fuel and chemical feedstocks. In addition, it has been found that the cleavage of C–O bond in alkoxyl groups is easy in the hydrothermal liquefaction process, while the removal of O from phenolic hydroxyl group is difficult.