This invention concerns a process for producing gaseous hydrocarbons and distillates from heavy oils, atmospheric or vacuum residues, asphalts produced by deasphalting petroleum residues, bitumen extracted from bituminous sands or bituminous shale oils, by hydropyrolysis of said heavy oils in the presence of a previously hydrogenated recycle cut and of a gas containing hydrogen and carbon monoxide produced by oxyvapogasification of the hydropyrolysis heavy residue.
Many techniques for upgrading such heavy oils to lighter products have already been proposed.
The processes commonly used in petroleum refining involving a catalytic treatment in the presence of hydrogen, such as catalytic hydrocracking, are not convenient owing to the rapid poisoning of the catalysts by organometallic compounds and asphaltenes contained in said heavy charges.
The processes making use of a thermal treatment such as thermal cracking or cokefaction also are not convenient since they give a low yield of distillable hydrocarbons, moreover of bad quality, and a high yield of coke or tar difficult to upgrade.
Different solutions have been proposed to improve the quality of the formed products and to reduce the formation of coke or tar.
A first solution consists of effecting a thermal cracking in the presence of a hydrogen donor diluent containing partially hydrogenated polyaromatic hydrocarbons. This technique, known as "Hydrogen Donar Diluent Cracking" is described particularly in U.S. Pat. No. 2,953,513. Many patents describe variations of this technique. Thus, the U.S. Pat. No. 4,115,246 describes a process for cracking heavy oils in the presence of a hydrogen donor diluent, wherein the cracking products are separated into a gas oil fraction recycled after hydrogenation as hydrogen donor diluent and a residue or tar used for producing the hydrogen required for the oxyvapogasification. The operating conditions of the cracking step are generally a temperature from 370.degree. to 538.degree. C., a sufficient pressure to maintain a liquid phase and a residence time of 0.25 to 5 hours.
A second technique consists of effecting a quick heating of the carbonaceous material under hydrogen pressure (flash hydropyrolysis) followed with a quench so as to avoid reactions of recombination of the cracking products. The U.S. Pat. Nos. 2,875,150 and 3,855,070 describe two ways of making use of this principle. The cracking is generally effected at a temperature from 600.degree. to 900.degree. C., under a pressure higher than 5 bars and for a residence time lower than 10 seconds.
In spite of the improvements brought by these innovations, the amounts of formed residue, coke or tar, remain high as compared to the yield of the desired light products. Moreover, the adopted technological solutions, particularly as concerns the quick heating of the charge, are heavy and/or expensive in power consumption.
The process of the invention avoids these disadvantages and provides means for converting a heavy oil or a petroleum residue to gaseous products and distillates with an optimized yield in terms of the consumed power.