Patent Application
20100032344
The present invention relates to a process for the removal of mercury from crude oil. In another aspect, this invention relates to a process for the removal of mercury from crude oil at the well site using produced gas.
Since the presence of mercury in crude oil can cause problems with downstream processing units, as well as health and environmental issues, there is an incentive to remove mercury from crude oil.
Therefore, development of an improved process for effectively removing mercury from crude oil before downstream processing into products would be a significant contribution to the art.
In accordance with a first embodiment of the present invention, a process is provided including the following:
a) extracting a crude oil stream comprising elemental mercury, hydrocarbons and water from a crude oil well;
b) separating the crude oil stream into a gaseous hydrocarbon stream comprising hydrocarbons, mercury and water, and a liquid hydrocarbon stream comprising hydrocarbons and elemental mercury, and which can also include water;
c) charging a mercury-containing gas feed, including in part at least a portion of the gaseous hydrocarbon stream, to a mercury removal unit for removal of mercury from the mercury-containing gas feed, thereby forming a treated gas stream;
d) contacting a recycle gas stream comprising a portion of the treated gas stream with at least a portion of the liquid hydrocarbon stream for transfer of at least a portion of the elemental mercury contained in the liquid hydrocarbon stream to the recycle gas stream; thereby forming a mercury rich gas stream, and a treated liquid hydrocarbon stream; and
e) passing the mercury rich gas stream to the mercury removal unit as a portion of the mercury-containing gas feed.
In accordance with a second embodiment of the present invention, a process is provided including the following:
a) extracting a crude oil stream comprising elemental mercury, hydrocarbons and water from a crude oil well;
b) separating the crude oil stream into a gaseous hydrocarbon stream comprising hydrocarbons, mercury and water, and a liquid hydrocarbon stream comprising hydrocarbons and elemental mercury, and which can also include water;
c) removing water from a mercury-containing gas feed, including in part at least a portion of the gaseous hydrocarbon stream, prior to charging to a mercury removal unit for removal of mercury from the mercury-containing gas feed, thereby forming a treated gas stream;
d) contacting a recycle gas stream comprising a portion of the treated gas stream with at least a portion of the liquid hydrocarbon stream for transfer of at least a portion of the elemental mercury contained in the liquid hydrocarbon stream to the recycle gas stream; thereby forming a mercury rich gas stream, and a treated liquid hydrocarbon stream; and separating water from the liquid hydrocarbon stream; and
e) passing the mercury rich gas stream to the mercury removal unit as a portion of the mercury-containing gas feed.
According to the first embodiment of the present invention, the process of the present invention will be described with reference to
Referring to
According to the second embodiment of the present invention, the process of the present invention will be described with reference to
Referring to
The crude oil stream of the present invention comprises, consists of, or consists essentially of a broad range crude oil. More particularly, the crude oil stream comprises hydrocarbons containing at least one carbon atom per molecule.
The gaseous hydrocarbon stream comprises, consists of, or consists essentially of hydrocarbons containing from about 1 to about 6 carbon atoms per molecule.
The temperature at which the crude oil stream is separated into the gaseous hydrocarbon stream and the liquid hydrocarbon stream is preferably at least about 50° C., more preferably at least about 60° C. The pressure at which the crude oil stream is separated into the gaseous hydrocarbon stream and the liquid hydrocarbon stream is preferably at least about 0.5 Bars, more preferably at least about 1 Bars.
The mercury removal unit has a fixed bed comprising any mercury sorbent material capable of removing mercury from gases.
The treated gas stream preferably comprises less than about 20 wt. % of the mercury contained in the mercury-containing gas feed, and more preferably less than about 10 wt. % of the mercury contained in the mercury-containing gas feed.
The treated liquid hydrocarbon stream preferably comprises less than about 50 wt. % of the elemental mercury contained in the liquid hydrocarbon stream, and more preferably less than about 20 wt. % of the elemental mercury contained in the liquid hydrocarbon stream.
The liquid hydrocarbon stream typically comprises at least about 10 ppb elemental mercury, and more particularly comprises at least about 200 ppb elemental mercury.
The recycle gas stream is contacted with the liquid hydrocarbon stream at a temperature in the range of from about 70° C. to about 300° C., preferably from about 150° C. to about 200° C., a pressure in the range of from about 0.5 Bars to about 15 Bars, preferably from about 1 Bar to about 10 Bars, and more preferably from about 2 Bars to about 7 Bars; and a gas to liquid ratio in the range of from about 50 to about 300 standard cubic feet of gas/bbl of liquid (SCF/bbl), preferably from about 100 to about 200 SCF/bbl.
The following examples are provided to further illustrate this invention and are not to be considered as unduly limiting the scope of this invention.
To test the idea, a simulation of the liquid/gas contactor was constructed using an equation of state thermodynamic prediction model for mercury partitioning between gas and liquid using data for elemental mercury in a commercially obtained crude oil blend. The results of the calculation are shown in
This simulation shows that 90% mercury removal is achievable at the temperature and pressure conditions commonly present at the crude oil well site. That is, wherein the pressure of the Low Pressure Coalescer/Separator typically present at the well site (which is redeployed in the invention as a gas/oil contactor) ranges from about <1 to ˜3 Bars, and the reservoir temperature of high mercury crude oils is normally greater than about 150° C.
An experiment was run to test the removal of Hg (elemental) from a hydrocarbon by sparging with a lighter hydrocarbon. Elemental mercury was dissolved in decane at about 1,300 ppbw.
A third experiment was run wherein, prior to adding the elemental mercury, the decane was water washed and passed over a silica gel column to remove trace levels of chloride, oxide or sulfur compounds that could, at the conditions of the experiment, oxidize the mercury and cause it to form non-spargable mercury compounds.
Also shown in
While this invention has been described in detail for the purpose of illustration, it should not be construed as limited thereby but intended to cover all changes and modifications within the spirit and scope thererof.
