Distillation: processes – separatory – Vaporization zone under positive pressure or vacuum
Reexamination Certificate
1998-12-21
2001-08-21
Manoharan, Virginia (Department: 1764)
Distillation: processes, separatory
Vaporization zone under positive pressure or vacuum
C196S114000, C196S132000, C202S160000, C202S182000, C202S205000, C203S001000, C203S002000, C203SDIG001, C208S184000, C208S357000, C208S366000
Reexamination Certificate
active
06277247
ABSTRACT:
BACKGROUND
The invention pertains to the field of the petrochemical industry, mainly to methods and systems for fractionation of oil derivatives in vacuum rectification columns.
An operational process of a system for distilling liquid products is known, which includes feeding of a stock product into a vacuum rectification column, fractionation of the stock product in the said column into a vapor phase and a liquid fraction and evacuation of the vapor phase by a steam jet apparatus (see U.S. Pat. No. 2,680,709, cl. 202-204, 1954).
The same U.S. patent introduces a system for distilling liquid products, which has a vacuum rectification column with pipelines for bleeding of the vapor phase and liquid fraction, and a steam jet apparatus.
This system implementing the above described operational process provides the vacuum distillation of liquid products, oil derivatives, as a rule. However, during operation the system produces a mixture of oil derivatives and water, which is formed during evacuation of the vapor phase from the column. Discharge of the mixture into drainage results in environmental pollution whereas purification of such waste water is very expensive.
The starting point for the method of operation of a system for liquid product distillation, which includes in feeding of a stock product into a vacuum rectification column, fractionation of the stock product in the said column into a gas-vapor phase and at least one liquid fraction, evacuation of the gas-vapor phase by a liquid-gas ejector, has been disclosed in RU patent 2048156, cl. B 01 D 3/10, 1995. According to this patent a motive liquid is delivered from a separator into a nozzle of the ejector. Flowing from the nozzle, the liquid entrains the gas-vapor phase. Then the motive liquid mixes with the gas-vapor phase and compression of the gas-vapor component of the mixture takes place.
The same RU patent describes a system for liquid product distillation, having a vacuum rectification column with pipelines for bleeding of gas-vapor phase and at least one liquid fraction, and a vacuum-producing device composed of a liquid-gas ejector, a separator and a pump.
SUMMARY OF THE INVENTION
This system implements the introduced method and provides for evacuation of the gas-vapor phase from the rectification column by the liquid-gas ejector. A liquid, which is cognate to the evacuated gas-vapor phase by its physical and chemical properties, is used as the motive medium. Such system reduces environmental discharge of harmful substances.
However, if the molecular weight of the motive liquid is more than 100 (in atomic mass units), it is impossible to achieve conditions, where mixing of the motive liquid and gas-vapor phase is completed in the ejector's flow-through canal. I.e. in this case phase equilibrium between the mixing components can not be attained in the ejector. The phase equilibrium occurs if a saturated solution of gaseous components of the gas-vapor phase in the motive liquid is obtained while mixing of the motive liquid and gas-vapor phase. Consequently, specific pressure and temperature in the flow-through canal of the ejector and also a certain period of time are required for attainment of the phase equilibrium. All required conditions can not be maintained in the ejector's flow-through canal without a reduction of the ejector's efficiency. An incomplete mixing process results in an extra power input for pumping of the gas-vapor-liquid mixture from the ejector to the separator and in an incremental loading of the separator, where completion of the mixing process takes place in addition to the main function—separation of the gas-liquid mixture into the motive liquid and compressed gas.
Besides, from ecological and economical points of view, the completeness of the condensation of easy-condensable components of the gas-vapor phase has great importance for reduction of harmful products' pollution on the one hand, and for recovery of valuable chemical product on the other hand. After separation the easy-condensable components can be bled from the system as a desired product of the rectification column. But in order to achieve an optimal mode of the separator's operation, condensation of the easy-condensable components must be completed before entry of the medium's mixture into the separator.
The present invention is aimed at increasing of efficiency, productivity and environmental safety of the process of fractionation of petroleum products.
The above mentioned objectives are achieved because the operational method of a system for the distillation of a liquid product, including delivery of a stock product into a vacuum rectification column, fractionation of the stock product in the column into a gas-vapor phase and at least one liquid fraction, evacuation of the gas-vapor phase by a liquid-gas ejector, delivery of a motive liquid from a separator into the nozzle of the ejector, entrainment of the gas-vapor phase by the motive liquid while it's flowing from the nozzle, mixing of the motive liquid with the gas-vapor phase and compression of the gas-vapor component of the formed mixture, is modified as follows:
a liquid having a molecular weight more than 100 (in atomic mass units) is delivered into the nozzle of the ejector as the motive liquid;
the mixture of the gas-vapor phase and the motive liquid is discharged from the ejector into a shaped reservoir, where flow velocity is reduced, static pressure is boosted and, therefore, conditions for condensation of easy-condensable components of the mixture, for attainment of phase equilibrium and for transformation of the gas-vapor-liquid mixture into a gas-liquid mixture are created;
the gas-liquid mixture is delivered from the shaped reservoir into the separator, where it is separated into the motive liquid and compressed gas.
As for the system as an object of the invention, the problem is solved by providing a system for the distillation of a liquid product, which has a vacuum rectification column with pipelines for bleeding of a gas-vapor phase and at least one liquid fraction, and a vacuum-producing device composed of a liquid-gas ejector, a separator and a pump, with a shaped reservoir. A gas inlet of the ejector is connected to the pipeline for bleeding of the gas-vapor phase, a liquid inlet of the ejector is connected to the discharge side of the pump, an outlet of the ejector is connected to the inlet of the shaped reservoir, an inlet of the separator is connected to the outlet of the shaped reservoir and a liquid outlet of the separator is connected to the suction side of the pump.
Research efforts have shown, that rational usage of all of the system's components, namely usage of each device exactly for its designated purpose, has great importance for operational stability of the system for the distillation of a liquid product.
In case a liquid with molecular weight more than 100 (in atomic mass units) is used as the motive liquid, the mixing process does not have enough time to be completed and phase equilibrium is not achieved in the liquid-gas ejector. Consequently, a gas-vapor-liquid stream with a high content of the gas-vapor phase enters a flowing channel following the ejector. This results in big hydraulic losses and requires a pipeline of greater diameter between the ejector and separator. Consequently, the system's mass rises. Additionally, both the mixture's separation into a compressed gas and a motive liquid, and the forming of a saturated solution of gas in the motive liquid being accompanied by condensation of easy-condensable components of the mixture take place in the separator. The simultaneous progression of these two processes, requiring different suitable conditions for their complete realization, results in that a phase equilibrium is not achieved and in the reduction of yield of light fraction from the system. Installing the shaped reservoir between the ejector's outlet and the separator's inlet slows the mixture's flow down and boosts static pressure in the mixture. As a res
Manoharan Virginia
Oathout Mark A.
Petroukhine Evgueni D.
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