Ind. Eng. Chem. Process Des. Dev. 1983, 22, 436-447
436
available upon request from the authors. Acknowledgment The authors are grateful to the Danish Consul for Scientific and Technical Research for financial support and to the Ben Gurion University of the Negev, Israel, for granting Osnat Ben Yair leave of absence for this investigation. In addition, we thank Torben Jensen and Peter Rasmussen of Instituttet for Kemiteknik for many helpful discussions. Nomenclature am,,= UNIFAC group interaction parameter Ah = parameter in Gibbs energy function for group k B,(T) = second virial coefficient of component i Agk = Gibbs energy function for group k AG ", = sum of structure-dependent contributions for component i M'k, = structure dependent contribution j for group k AHvi = heat of vaporization of component i N(') = number of different groups in molecule i P,"= vapor pressure of pure component i Qk = van der Waals surface area of group k R = gas constant
HYdW
T = absolute temperature Greek Letters rk(i)= activity coefficient of group k in pure component i 4; = saturation fugacity coefficient of component i $m = UNIFAC parameter related to a,,,,, omfi = surface area fraction of group m in molecule i vk(i) = number of groups k in molecule i vkj(i) = number of structure contributions of type j in groups
k Indices and Superscripts i = component molecule k , m, n, = group 1 = parameter number j = structure contribution type number s = saturation
Literature Cited Jensen, T.; Fredenslund, Aa.; Rasmwsen, P. I n d . Eng. Chem. Fundam. 1961, 20, 239. Gmehllng, J.; Rasmussen P.; Fredenslund, Aa. Ind. Eng. Chem. Process BS. B V . i982,21, i t a .
Received for review May 10,1982 Accepted January 3, 1983
atlon of Heavy Oils Dennis E. Walbh and NaEYuen Chen' Mob11 Research and Development Corporation, prlnceton, New Jersey 08540
Thermal hydrogasiflcatkm of heavy petraleum dls was lnvestlgated under conditions of short reaction tlme (0.5-15 s products residence tlme) and varied heating rates to elevated temperatures (50-850 OC/s to >550 "C). Total pressures and hybogen partial pressures up to 1500 psig were examined. Products consisted of a residual carbon fraction, light gases (primarily CH,), and BTX. Carbon residue was minimized by increasing hydrogen pressure up to 700 psig, final reaction temperature up to 700 O C , and the oil reaction time up to 8 s. The amount of carbon residue produced is a function of the C/H ratio of the charge. For San Ardo crude, the highest carbon conversion to light products was 82 wt % corresponding to 18 wt % carbon as residue, 67 wt % carbon as gas, and 15 wt % as BTX. Over a wMe range of conversion, gas and BTX were produced in fairly fixed proportions (-82% gas, 18% BTX).
-
-
Introduction It has long been recognized that raw coal can provide substantial yields of gaseous hydrocarbons under conditions of high temperature and hydrogen pressure (Dent, 1944). It has also been established that substantial liquid yields can be realized from the hydrogasification of coal under purely thermal conditions or in the presence of a catalyst (Schroeder, 1962). An extensive review of coal devolatilization and hydrogasification was presented by Anthony and Howard (1976). Pelofsky et al. (1977) presented data on the influence of heating rate, product vapor residence time, and reaction temperature on the yield and quality of gas and liquid products obtained in the thermal hydrogasification of coal. Graff et al. (1976) and Dobner et al. (1976) reported data indicating thermal gasification conditions which yielded essentially methane, ethane, and BTX as the sole light hydrocarbon products, the balance of the coal carbon becoming char. Finn et al. (1980) studies the production of C8and lighter aromatics from the hydropyrolysis of coal, noting that volatiles evolution and their cracking to BTX were se-
-
quential reactions. By optimizing separately both the cracking temperature and vapor residence time, they obtained yields of up to 12 wt % benzene from a high volatile bituminous coal. Fynes et al. (1980) reviewed work carried out at various laboratories on the production of BTX from the thermal hydroconversion of coal. Assessing the impact of the several process variables on product yields, they noted that the maximum production of BTX obtained from bituminous coal and lignite was about 15 w t %. Coproduction of BTX is quite desirable since it reduces hydrogen consumption, and the BTX products have value both for blending into the gasoline pool and as chemicals. Consequently, a substantial yield of BTX from a proposed hydrogasification process can enhance its economic attractiveness. Information obtained from the references cited above indicates that the most desirable operating conditions for maximum conversion of coal carbon to light produds with maximum production of BTX include: (1)rapid heating of the material to be hydrogasified (several hundred degrees centigrade per second); (2) final reaction tempera-
0796-430518311122-0436801.5010 0 1983 American Chemical Society
Ind. Eng-Chem. Process Des. Dev., Vol. 22, No. 3, 1983 437
tures in the vicinity of 7OCb800 "C where CHI and monoaromatics would be the most stable compounds; (3) controlled vapor residence time (not longer than several seconds) to prevent product degradation to coke; and (4) hydrogen pressure, 500 psig. Thompson and Conway (1972) published results from pilot plant scale investigations of the hydrogasification of hydrocarbon oils. Their main concern was with methane producti0n:and their interest in the direct thermal reaction of H2with oils was predicated on the fact that hydrocarbon feedstocks with C/H weight ratios >-6 do not lend themselves readily to direct reaction with steam. Their studies, however, did not include any heavy feedstocks, all of the materials reported having C/H weight ratios
