Throttling device for deep cracking of heavy petroleum products

Abstract

To deepen the cracking of crude and heavy petroleum products, they are heated in tube furnaces, and the decomposition products are subsequently held in an external reaction chamber [1,2]. Disadvantages of tube furnaces result from combined heating and thermal decomposition of the petroleum products (this eliminates their mutual regulation, and optimization), as well as vigorous carbon deposition on the walls of the tubes. Additional holding of high-temperature decomposition products exiting from the furnace in an external reaction chamber does not ensure their complete thermal decomposition as a result of secondary reactions.Let us examine the possibility of deepening the cracking of petroleum products and destructive processing of polymeric wastes by organizing those conditions for which the heating and thermal decomposition of the products are separated in time and space, while heating of the liquid products will ensure attainment of the boundary of the phase state by the most thermally stable components. At this boundary, all nonvolatile fractions go over into the gaseous phase, and cooling occurs due to absorption of the heat liberated by the decomposition reaction. This process takes place as a result of heating of the reaction mixture at a temperature and pressure, which are sufficient to throttle the evaporation processes and the reaction in the tube furnace, and which are required to convert the mixture to a state of attainable superheat of the most thermally stable components in the reaction chamber. For this purpose, the pressure at the end of the coil should exceed the pressure in the chamber. Provision for attainable superheat of nonvolatile components that proceed into the chamber is a requisite condition in selecting the pressure differential and the temperature of the reaction in the coil and chamber. A pressure increase in the coil will lead to an increase in the temperature of the mixture, and to a reduction in the content of gaseous phase, which prevents rapid heating of the mixture in the coil, as a result of which the thermal flux through the wall of the coil and the amount of heat accumulated in the products being heated will increase, and, accordingly, coke formation will decrease. The thermal-decomposition reaction takes place as a result of a pressure drop when the mixture enters the reaction chamber, whereupon the increased reserve of thermal energy intensifies thermal decomposition of the mixture in the chamber, and ensures increased output of volatile fractions.It is known that the rates of the decomposition reaction are lower in the liquid phase than in the gaseous phase owing to the so-called cage effect. As the molecules dissociate, a pair of radicals that has been formed in the liquid phase, exists for a certain time (10 -9 -10 -10 sec) in a single cage; intracage recombination, and equilibrium shift in the direction of the initial compound are therefore possible. If the mixture goes over into a state of attainable superheat as a result of a pressure drop, the components of the mixt...