A systematic experiment has been conducted to obtain the ignition delay of fine fuel droplets in a hot and pressurized gas stream to examine the effects of ambient pressure and additional oxygen on the ignition delay and moreover the relationship between the evaporation rate and the ignition delay. An array of free fine droplets of paraffin hydrocarbon, whose mean diameter is close to that of droplets in a fuel spray, was discharged into a high temperature and high pressure gas flow. It was confirmed from the results that the ignition delay reduces with the increase in ambient pressure and additional oxygen and, moreover the more the number of carbon atom in the hydro-carbon are, the longer the delay becomes. In the case of multiple composition droplets of n-heptane and n-hexadecane, the evaporation rate constant increases and the ignition delay reduces as the proportion of n-heptane increases, and also the trend changes at the point of 50% in the proportion.
In the previous paper, the initial stage liquefaction of several coals was examined by using a pipe reactor which was designed to recover six heat-treated samples in the heating process up to ca. 450°C and the yield of pyridine insolubles (PI) of the heat-treated slurry was shown to depend on the coal rank and decrease to less than % in some coals. In this paper, solid-state 13C-NMR spectroscopy of PI is applied to examine the mechanism of the initial stage liquefaction of Lingan bituminous coal, Illinois and Wandoan subbituminous coals and Wabamun lignite. The followings are derived from the analysis of NMR spectra. The spectra of PI samples of Lingan coal heat-treated up to 423°C are almost the same and those of Illinois and Wandoan coals are scarcely changed up to 372°C and 409°C, respectively. It is therefore considered that PS (pyridine solubles) of each coal is composed of the compounds with almost the same functional group distribution as that of PI of the raw coal. The PI values of the three coals decrease largely at higher temperatures than the above-mentioned as previously presented. The followings are discussed in this temperature range. It is shown in Lingan coal that the compounds relatively rich in aromaticity become PS and the components with relatively low aromaticity remain as PI. In the case of Illinois coal, the small aromatics with side chains such as alkyl groups become PS and the components composed of the relatively large aromatic ring crosslinked by alkyl chains remain as PI. In the case of Wandoan coal, the compounds with the long alkyl chains are changed to PS and the components relatively rich in aromaticity crosslinked by alkyl chains are recovered as PI. Wabamun coal shows a completely different behavior from these three coals, that is, the aliphatic compounds become PS successively with increasing tempera-ture without an abrupt change and the components with high aromaticity remain as PI.
This paper describes the newly developed simple-quick method for evaluation of metal-uptake capacity of various catalysts. Adsorption of Ni-naphthenates on catalysts in the dilute xylene solution can be just indicated by linear equation (1). log (X/M) =1/n*ogC k (1) where X: amount of adsorbate M: amount of adsorbent (catalyst) C: concentration of adsorbate in the solution n, k: constant Inverse of gradient, i. e. n-value, has a good correlation with physical properties of catalyst, especially with mean pore diameter and pore volume. The catalysts having large n- and k-value are suitable for demetallation catalyst. Metal tolerance and demetallation selectivity of catalysts can be evaluated through reaction behavior to high-metal Boscan crude oil. n-Values measured by simple adsorption method have a good correlation with allowable metals on catalyst (metal tolerance) measured by hydrogenation of high-metal Boscan crude oil. Therefor, metal tolerance of catalyst can be evaluated easily and quickly by measuring n-value in equation (1) through simple adsorption of Ni-naphthenates in xylene solution at room temperature.