内燃机积炭的危害及清除

积炭是内燃机的燃料和润滑油在高温及氧化作用下的生成物。当燃料及窜入燃烧室的润滑油不能完全燃烧时,未燃部分的胶质粘附在零件表面上,被高温烤灼及氧化成为沥青质、油焦质和炭青质等复杂混合物,于是形成了积炭。积炭是一种有害有毒的物质。 积炭的危害 1.导致早燃。积炭粘附在组成燃烧室的各零件表面,缩小了燃烧室容积,改变了压缩比及工作性能。同时积炭成为许多炽热点,容易诱发早燃。

内燃机积炭的危害及清除

积炭是内燃机的燃料和润滑油在高温及氧化作用下的生成物。当燃料和窜入燃烧室的润滑油不能完全燃烧时,未燃部分的胶质粘附零件表面上,被高温烤灼及氧化成为沥青质、油焦质和炭青质等复杂混合物,于是形成了积炭。积炭是一种有害有毒的物质。

Effect of coke properties and its blending recipe on performances of carbon anode for aluminium electrolysis

The properties and blending recipe of petroleum cokes used to make high quality carbon anodes for aluminium electrolysis were studied. Three kinds of green cokes were selected for bench scale study to illustrate the effects of cokes properties and its blending recipe on anode performances. The results show that impurities derived mainly fi＇om cokes remarkably affect the CO2 reactivity and air reactivity of carbon anodes. Ca, Na and V can increase CO2 reactivity of calcined cokes but S has the contrary effect, and the cokes of high V level generally present high air reactivity. The anodes with good quality can be made by properly selecting and scientifically blending of cokes, some poor quality cokes can also be used to produce high quality anodes with a reasonable blending recipe. Na contaminated anodes have high CO2 reactivity and air reactivity, so the recycled anode butts should be well cleaned to reduce Na content before being introduced into anode production, which is especially important to the low S cokes.

Catalytic cracking mechanisms of tar model compounds

B3LYP/6-31G(d,p) method was used to investigate the catalytic cracking mechanism of biomass tar model compound.Phenol,toluene and benzene were selected as the tar model compounds and CaO was selected as the catalyst.The pathways of tar compound radical absorbed by CaO were determined firstly through comparing enthalpy changes of the absorption,and then Mulliken population changes were analyzed.The results show that the absorption of tar model compound radical and CaO is an exothermic reaction.Formation of C—O—Ca is more easily than that of C—Ca—O and formation of Caromatic—Caromatic—Ca—O is more easily than that of Caromatic—C(O)—Ca—O.The C—C bond Mulliken populations in tar model compound radicals are reduced by 11.9%,10.5% and 15.5% in the case of a hydrogen atom removed,and those are 15.7%,14.3% and 16.3% in the case of two hydrogen atoms removed through the absorption of CaO.Catalytic ability of CaO acting on the tar model compound is in an order of phenol>benzene>toluene.

Ni nanoparticles supported on carbon as efficient catalysts for steam reforming of toluene(model tar)

This paper investigated the influences of surface properties of carbon support and nickel precursors(nickel nitrate, nickel chloride and nickel acetate) on Ni nanoparticle sizes and catalytic performances for steam reforming of toluene. Treatment with nitric acid helped to increase the amount of functional groups on the surface and hydrophilic nature of carbon support, leading to a homogeneous distribution of Ni nanoparticles. The thermal decomposition products of nickel precursor also played an important role, Ni nanoparticles supported on carbon treated with acid using nickel nitrate as the precursor exhibited the smallest mean diameter of 4.5 nm. With the loading amount increased from 6 wt% to 18 wt%, the mean particle size of Ni nanoparticles varied from4.5 nm to 9.1 nm. The as-prepared catalyst showed a high catalytic activity and a good stability for toluene steam reforming: 98.1% conversion of toluene was obtained with the Ni content of 12 wt% and the S/C ratio of3, and the conversion only decreased to 92.0% after 700 min. Because of the high activity, good stability, and low cost, the as-prepared catalyst opens up new opportunities for tar removing.

Laboratory Research on Tahe AR Fluid Coking on Weak Acid Catalysts

Fluid coking on micro-spherical particles with acid sites on them could produce more light oils from Tahe AR.The conversion rate could increase by about 20% on the catalyst B compared to that obtained on the catalyst A and the light oil yield could increase by about 12%.The yield of gasoline and diesel was more than 50% from Tahe AR over the catalyst B.Tests on acidity of the catalyst B by pyridine FT-IR spectrometry showed that the total acid content and the ratio of weak acid number to total acid number were higher than other catalysts.

Separation of arenols from a high-temperature coal tar

A high-temperature coal tar collected from Xuzhou Coking Plant, Saint-Gobain Pipelines （Xuzhou） Co., Ltd. was exhaustively extracted with petroleum ether （PE）. The extract was sequentially eluted through silica gel with PE and PE/ethyl acetate （EA） mixed solvents （volume ratio 2：1 ） to afford two eluted frac- tions. The extract and eluted fractions were analyzed with gas chromatography/mass spectrometry. In total, 14 arenols were detected, including phenol, cresols, xylenols, fluorenols, phenanthren-3-ol and pyren-l-ol.

Decomposition of Toluene as a Biomass Tar through Partial Combustion

One way for reducing tar is oxidative and thermal cracking by partial combustion of the biomass producer gas in the gas reformer. Cracking and polymerization of the tar occur simultaneously at the proximity of inverse diffusion flame. Experimental study has been performed to clarify the effect of hydrogen concentration on soot formation and the growth of polycyclic aromatic hydrocarbons. In the present study, hydrogen concentration is controlled by the small amount of hydrogen addition to the oxidizer. The main results are as follows. Soot formation is suppressed by the small amount of hydrogen addition. The suppression of soot formation is caused by higher concentration of hydrogen. Carbon yield increases by hydrogen addition since carbon content in the undetectable components by the integrated gas chromatograph decreases. In addition, the increase in carbon yield is caused mainly by the increase in carbon monoxide stemmed from reforming of high-boiling components.

Effect of Green and Carbonized Mesocarbon Microbeads on Development of Carbonaceous Mesophase

Two types of mesocarbon microbeads(MCMB), one of which was green sphere and the other carbonized at 1000 ℃, were used to modify coal tar pitches, and their influences on the development of carbonaceous mesophase in coal tar pitches were investigated. Optical microscopy was used to observe the changes caused by the additives. The green MCMB could promote the growth of mesophase spheres. When the holding time at the final temperature was prolonged to 100 min, the green MCMB-modified pitch would produce excellent bulk mesophase. Carbonized MCMB prohibited the coalescence of mesophase spheres and was beneficial to forming super large mesophase spheres. In the green MCMB-modified pitch, mesophase spheres grew up using the added MCMB spheres as nuclei, i.e. the green MCMB continued to grow during heat-treatment, which accelerated the formation, growth, and coalescence of mesophase spheres. For carbonized MCMB, their active sites were passivated and they could not continue to grow. These inert spheres could aggregate around the newly-formed mesophase spheres, prohibiting the growth and coalescence of the mesophase spheres.

Separation of Acearylenes from High-Temperature Coal Tar

High-temperature coal tar was extracted with petroleum ether （PE） under ultrasonic irradiation and the extracts were analyzed with gas chromatograph/mass spectrometer. The acearylene fractions including acenaphthylene, aceanthrylene and cyclopentapyrene were enriched together and named E, which was then transferred to a car- tridge in Isolera-One flash chromatography. Three groups of compounds were eluted out with ethyl acetate/PE mixed solvent （volume ratio 1：9） and named E1, E2 and E3 according to their main components. Acenaphthylene accounted for 78.2% in El, aceanthrylene 71.6% in E2 and cyclopentapyrene 75.9% in E3, respectively. The three groups of acearylenes were purified by Sephadex LH-20 column chromatography with ethanol/cyclohexane mixed solvent （vol- ume ratio 1：4）, and then confirmed with nuclear magnetic resonance spectrometer. This method indicates that flash chromatography has a good effect on separating the compounds with a similar structnre after extraction under ultrasonic irradiation.