摘要:

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 (Mw= 300 amu, Mn= 155 amu, and Mz= 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.

ISSN:0884-3759    

DOI:10.1080/08843759608947593

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The perchloroethylene coal refining process was used on North Dakota lignite coal. Effects of extraction time, perchloroethylenexoal ratio and artificial weathering were studied to determine their effects on the removal of organic sulfur. The artificial weathering conditions used were found to be too harsh and caused a decrease in the amount of organic sulfur removed, unlike normal weathering conditions. Additional studies were done involving various ligands, and showed that the addition of certain ligands during the process aided in the extraction of organic sulfur from the coal.

ISSN:0884-3759    

DOI:10.1080/08843759608947594

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Texas lignites are a low-Btu, high-ash and moderately high-sulfur fuel that can be readily upgraded before combustion using physical and microbial desulfurization technology. Although physical and chemical processes and some microbial processes are effective in removing pyritic sulfur, they are ineffective for removing organic sulfur. Microbial processing of Texas lignite with sulfur content of up to 15 wt.% was investigated using laboratory shake-flask experiments. Organisms of the genusThiobucillus ferrooxiduns, Leptospirillum Jerrooxidans and Pseudomonas putidawere investigated. It was found that up to 77% of the sulfur compounds present in the Texas lignite with more than 90% of the pyritic sulfur could be removed by the use of these microbes. Texas lignite samples were pulverized to pass through 149-μim sieve.Thiobucillus ferrooxidunsreduced up to 54% of the total sulfur and 78% of the pyritic sulfur in 14 days andLeptospirillum ferrooxidansremoved up to 41% and 60%, respectively. A mixed culture of these two bacteria was also studied for sulfur removal The lignite was retreated withP.putidu which further removed 50% of the total sulfur in 7 days.P.puiidu could successfully remove up to 37% of the organic sulfur in 7 days.

ISSN:0884-3759    

DOI:10.1080/08843759608947595

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The absorption of H2S by large particles of limestone, dolomitic limestone and dolomite (average mass-radius of 0·40 mm) was tested under simulated coal gases. Below the calcination temperature of CaCO3(about 900°C under 1 bar of CO2), complete conversion of the calcium carbonate to calcium sulfide can only be achieved with dolomite. Above the calcination temperature of CaCO3, the conversion to CaS is complete for all three sorbents in about one hour when 10,000 ppm H2S is present in the gas phase. Large particles of limestone thus appear to be a suitable sorbent for high-temperature coal-gas desulfurization (above about 900°C). A mathematical model based on the kinetic information collected in this work predicts the desulfurization performance of a packed or moving bed of limestone particles. Finally, a low-temperature regeneration scheme for the spent sorbent (CaS) in which sulfur can be subsequently recovered as the element is suggested.

ISSN:0884-3759    

DOI:10.1080/08843759608947596

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

U.S. Department of Energy (DOE) has been supporting an indirect coal liquefaction program aimed at developing improved technologies to convert coal based synthesis gas into economically competitive and environmentally clean hydrocarbon and oxygenate transportation fuels. A key element of this program is the development of a liquid phase reactor technology which could offer improved economics and operational flexibility over the conventional gas phase reactors. This paper will review the accomplishments of liquid phase methanol technology development at the proof-of-concept (POC)scale unit in LaPorte, Texas and the advancement of this technology to commercial demonstration which has been underway since 1993 under the support of DOE Clean Coal Technology program. The POC facility has recently been upgraded to allow for developing liquid phase reactor technologies for Fischer-Tropsch synthesis and the production of other oxygenate fuels and chemicals from synthesis gas. The upgraded POC unit, now known as the Alternative Fuels Development Unit (AFDU)as well as the results of new campaigns that have been conducted at this unit will also be reviewed.

ISSN:0884-3759    

DOI:10.1080/08843759608947597

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A promising method for cleaning coal involves suspending the finely ground material in water and selectively agglomerating the more hydrophobic and oleophilic components with oil or a hydrocarbon such as heptane. In order to study the effect of coal surface properties and other parameters on the rate of agglomeration, a number of agglomeration tests were conducted in which a batch of coal was agglomerated with either heptane or hexadecane, and the rate of change in the turbidity of the suspension was determined. Two types of bituminous coal were utilized, and the surface properties of each type were varied by exposing the ground materials to air at 150°C for periods ranging from a few hours to 84 hr. Measurements made by means of FT-IR photoacoustic spectroscopy showed that the concentration of oxygen functional groups increased with increasing oxidation time. Furthermore, the apparent rate of agglomeration of either type of coal decreased with increasing oxidation time. Therefore, the rate of agglomeration depended on both the rank of the coal and the extent of oxidation of the coal. The rate was also found to depend on the type of agglomerant and its dosage. While the rate tended to increase in direct proportion to agglomerant dosage, the rate of increase with respect to the dosage fell as the coal became more heavily oxidized.

ISSN:0884-3759    

DOI:10.1080/08843759608947598

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Biomass pyrolysis oils were produced from stored biomass feedstocks by rapid pyrolysis in a fluidized bed reactor. The feedstocks used for these studies were switchgrass, com stover, and hybrid poplar. The woody and herbaceous feedstocks were stored in chip piles and bales, respectively, unprotected in an open field for 6 months. At the end of the storage period, biomass samples were taken from the interior of bales and the centers of chip piles for pyrolysis studies. The materials were ground to pass −20/+80 mesh and dried to less than 10% moisture content before pyrolyzing in the fluidized bed reactor. Pyrolysis was conducted at 500°C and with less than 0·4 s. vapor residence time. Total liquid yields were as high as 66% for the hybrid poplar and as low as 58% for the com stover. Moisture content of the oils was between 10% and 13%. Gas and char/ash yields were 10-15% and 12-22%, respectively. The char/ash yields were feedstock dependent, but storage influence was significant for only the com stover feedstock. Gas and liquid yields were not influenced by storage time. The oils were highly oxygenated and had higher heating values (HHV) of 23-24 MJlkg that decreased slightly with storage time for all the feedstocks except the switchgrass. The oils, as currently produced, are high in ash and alkali metals. Ultimately, they will be upgraded and used as boiler and turbine fuels.

ISSN:0884-3759    

DOI:10.1080/08843759608947599

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0884-3759    

DOI:10.1080/08843759608947592

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor