Distillation: processes – separatory – Vaporization zone under positive pressure or vacuum
Reexamination Certificate
1998-12-21
2001-08-28
Manoharan, Virginia (Department: 1764)
Distillation: processes, separatory
Vaporization zone under positive pressure or vacuum
C196S138000, C196S140000, C196S114000, C203S026000, C203S024000, C203SDIG001, C203S100000, C208S357000, C208S366000, C208S368000
Reexamination Certificate
active
06280578
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention pertains to the field of jet technology, primarily to installations for producing a vacuum in rectification columns destined for the distillation of various separable liquid products.
A method of operation of a pumping-ejector vacuum system for crude oil rectification is known, which consists of feeding of a separable liquid product into a vacuum rectification column, separation of the liquid product into a vapor fraction and at least one liquid fraction, delivery of the liquid fraction into the nozzle of a liquid-gas jet apparatus by a pump, evacuation of the vapor fraction by the liquid-gas jet apparatus, mixing of the vapors with a motive liquid in the jet apparatus and condensation of easy-condensable components of the vapors in the motive liquid, and separation of the motive liquid from vapors in a separator (see U.S. Pat. No. 1,567,429, M cl. C 10 C7100, 1925).
However, this method of operation of a pumping-ejector installation is characterised by high power inputs and high consumption of the motive liquid, which must be purified before discharge to drainage.
There is also another known method of operation of a pumping-ejector installation for the distillation of a liquid product. This method includes delivery of a separable liquid product into a vacuum rectification column, separation of the liquid product into a vapor phase and at least one liquid fraction, delivery of the liquid fraction into the nozzle of a liquid-gas jet apparatus by a pump, evacuation of the vapor phase by the liquid-gas jet apparatus, mixing of the vapour phase with a motive liquid in the jet apparatus with simultaneous compression of the vapor phase and forming of a liquid-vapor mixture, and separation of the mediums' mixture into a liquid medium and a compressed gaseous component in a separator (see RU patent, 2048156, cl. B01 D3/10, 1995).
According to this method, evacuation of the vapor phase from the rectification column is effected by the liquid-gas jet apparatus. However, evacuation of the vapor phase by the liquid-gas jet apparatus is not accompanied by complete condensation of easy-condensable components of the vapor phase, which reduces output of a light fraction as the base product of the vacuum rectification column. Such is conditioned by the fact that correlation between pressure in the vacuum rectification column, pressure in the separator and saturated vapour pressure of the motive liquid, which is delivered into the nozzle of the liquid-gas jet apparatus, is not optimal.
SUMMARY OF THE INVENTION
The present invention is aimed at an increase of efficiency of a pumping-ejector system for the distillation of a liquid product, which can be achieved due to optimal correlation between pressure in a rectification column, pressure in a separator and saturated vapour pressure of a motive liquid of the pumping-ejector system.
The solution of above mentioned problem is provided by an operating process of a pumping-ejector system for the distillation of a liquid product, including feeding of a separable liquid product into a vacuum rectification column, fractionation of the liquid product into a vapor phase and at least one liquid fraction, delivery of the liquid fraction into the nozzle of a liquid-gas jet apparatus by a pump, evacuation of the vapor phase by the liquid-gas jet apparatus, mixing of the vapour phase with a motive liquid in the jet apparatus with simultaneous compression of the vapor phase and forming of a liquid-vapor mixture, separation of the mediums' mixture into a liquid medium and a compressed gaseous component in a separator, which is modified as follows:
a liquid, having a saturated vapour pressure not less than the pressure at the top of the rectification column, is delivered into the nozzle of the liquid-gas jet apparatus as the motive liquid;
the pressure maintained in the separator represents from 1.1 to 160 times the pressure of the vapor phase at the inlet of the liquid-gas jet apparatus;
condensation of easy-condensable components of the vapor phase in the motive liquid and forming of the liquid-vapor mixture take place after mixing of the vapor phase with the motive liquid and exit of the mixture from the liquid-gas jet apparatus, but before entry of the mixture into the separator, then the liquid-vapor mixture is separated in the separator into the compressed gaseous component and a liquid medium, where the latter is bled from the separator as the motive liquid.
This process enables one to change the composition of the motive liquid of the liquid-gas jet apparatus directly in the pumping-ejector system subject to the composition of the feed stock of the rectification column. After mixing of the vapor phase and the motive liquid, feeding of the liquid fraction under pressure from the rectification column into the mediums' mixture is possible and the outlet pressure of the liquid-gas jet apparatus can be reduced consequently. Condensation of easy-condensable components of the vapour phase in the liquid fraction and in the motive liquid can be provided during mixing of the two liquids (the liquid fraction and the motive liquid). A liquid-gas flow is formed as a result of feeding of the liquid fraction into a condenser and then into the separator. Further the liquid-gas mixture is separated in the separator into the compressed gaseous component and a liquid medium. The latter is delivered from the separator to the suction port of the pump as the motive liquid. Besides, feeding of the liquid fraction under pressure into the liquid medium is accompanied by partial transfer of kinetic energy from the liquid fraction to the liquid medium. As a result of mixing of both liquids, the final composition of the motive liquid, which passes further to the suction port of the pump, is formed.
Experimental research revealed that a correlation between saturated vapor pressure of the motive liquid and pressure in the top section of the rectification column, wherefrom the vapor phase proceeds into the liquid-gas jet apparatus, has great importance.
As a matter of fact, the saturated vapour pressure of the motive liquid is a factor which governs density, working temperature and partly the chemical durability of the motive liquid under rated operating conditions.
Maintaining such operating parameters and selecting such a motive liquid, which provides for implementation of the condition when the saturated vapour pressure of the motive liquid is not less than the pressure at the top of the rectification column, allow one to achieve the highest possible (near-design) capacity of the liquid-gas jet apparatus. It is necessary to signify, that pressure in the rectification column, more precisely—the pressure of the vapor phase at the inlet of the liquid-gas jet apparatus, has considerable influence on the quality of separation of mediums in the separator and, consequently, on efficiency of the pumping-ejector system, because performance of the liquid-gas jet apparatus depends on the thoroughness of the separation of the liquid-gas mixture in the separator. Besides, the required makeup supply of the motive liquid also depends on such pressure.
It was determined, that maintaining of the pressure in the separator within the range from 1.1 to 160 times that of the pressure of the vapor phase at the inlet of the liquid-gas jet apparatus ensures such a working mode of the pumping-ejector system when makeup supply of the motive liquid is not necessary because of effective degassing of the liquid medium in the separator. At the same time, conditions, when there are neither ebullition nor changing of physical and chemical parameters of the liquid medium, are generated in the separator due to the above described matching of pressures. Thus, one may deliver the motive medium with precisely adjusted physical and chemical parameters into the nozzle of the liquid-gas jet apparatus.
There is a variant of the introduced method which occurs when the required correlation of above mentioned pressures in the pumping-ejector system is kept automaticall
Manoharan Virginia
Oathout Mark A.
Petroukhine Evgueni D.
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