Chemistry of hydrocarbon compounds – Purification – separation – or recovery – By addition of extraneous agent – e.g. – solvent – etc.
Reexamination Certificate
2002-06-06
2004-10-19
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Purification, separation, or recovery
By addition of extraneous agent, e.g., solvent, etc.
C585S833000, C585S836000, C585S850000, C585S856000, C208S25100H, C208S253000
Reexamination Certificate
active
06806398
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for removing mercury from a mercury-containing liquid hydrocarbon.
BACKGROUND ART
Natural gas liquids (NGL) obtained from natural gas field, i.e., liquid hydrocarbons such as liquefied petroleum gas and condensates, contain mercury in an amount of 2 to several thousands ppb although it varies depending upon the production area. Therefore, light hydrocarbons obtained by distilling NGL tend to still contain mercury.
When a liquid hydrocarbon containing mercury is used as a raw chemical material, the mercury corrodes apparatus by forming amalgam with aluminum which constitutes the apparatus, or reduces the activity of a reforming catalyst. Therefore, it has been strongly demanded to develop a technique for removing mercury from the liquid hydrocarbon.
To meet such a demand, Japanese Patent Application Laid-Open No. 10-251667 proposes a method of removing a trace amount of mercury in a hydrocarbon fraction by a combination of hydrogenation and adsorption, in which a hydrocarbon fraction containing mercury is first subjected to hydrogenation, and then the hydrogenated hydrocarbon fraction is contacted with a porous carbonaceous material.
In this method, however, the hydrogenation must be performed under high-temperature and high-pressure conditions, i.e., at 100 to 400° C., preferably 250 to 350° C. under 1 to 5 MPa, preferably 2.5 to 3.5 MPa. Therefore, the method is energy-intensive because a lot of energy is required for heating and pressurizing. Further, the preparation process of the porous carbonaceous material used as an adsorbent is extremely complicated because the adsorbent is required to have strictly controlled properties such as a specific surface area of 100 to 2,500 m
2
/g, preferably 500 to 1,500 m
2
/g; an average pore radius of 5 to 30 Å; and a pore volume of 0.2 to 1.2 mL/g with respect to pores having a pore radius of 50 Å or smaller.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a process for efficiently removing mercury from a mercury-containing liquid hydrocarbon in a continuous and simple manner or in a semi-continuous and simple manner at around ordinary temperature under around ordinary pressure.
As a result of extensive research in view of the above object, the inventors have found that mercury is effectively removed from a mercury-containing liquid hydrocarbon in a continuous and simple manner by continuously introducing the mercury-containing liquid hydrocarbon into a mercury-ionization zone and then a sulfur compound-treatment zone.
The inventors have further found that mercury is effectively removed from a mercury-containing liquid hydrocarbon in a semi-continuous manner by continuously feeding the mercury-containing liquid hydrocarbon into a mercury-ionization column, and then feeding into a sulfur compound-treatment tank to convert the mercury to a solid mercury compound in a batch manner.
Thus, in a first aspect of the present invention, there is provided a process for removing mercury from a liquid hydrocarbon, comprising:
(A) continuously feeding a mercury-containing liquid hydrocarbon into an ionization zone where the liquid hydrocarbon is contacted with an ionizing substance capable of ionizing elementary mercury, thereby ionizing the elementary mercury in the liquid hydrocarbon;
(B) continuously feeding the resultant liquid hydrocarbon containing the ionized mercury into a sulfur compound-treatment zone where the liquid hydrocarbon is contacted with a sulfur compound represented by the general formula:
MM′S
wherein M and M′ may be the same or different and are each independently a hydrogen atom, an alkali metal or an ammonium group, or contacted with a liquid containing the sulfur compound, thereby converting the ionized mercury into a solid mercury compound; and
(C) removing the solid mercury compound from the liquid hydrocarbon.
In a second aspect of the present invention, there is provided a process for removing mercury from a liquid hydrocarbon, comprising:
(A) feeding the liquid hydrocarbon into an ionization column where the liquid hydrocarbon is contacted with a substance capable of ionizing elementary mercury, thereby ionizing the elementary mercury contained in the liquid hydrocarbon;
(B) feeding the resultant liquid hydrocarbon containing the ionized mercury to a sulfur compound-treatment tank where the liquid hydrocarbon is contacted with a sulfur compound represented by the general formula:
MM′S
wherein M and M′ may be the same or different, and are each independently a hydrogen atom, an alkali metal or an ammonium group, or contacted with a liquid containing the sulfur compound, thereby converting the ionized mercury to a solid mercury compound; and
(C) removing the solid mercury compound from the liquid hydrocarbon.
BEST MODE FOR CARRYING OUT THE INVENTION
The mercury-containing liquid hydrocarbons to be treated by the process of the present invention are not particularly restricted, and may include any hydrocarbons which are liquid at ordinary temperature. Examples of the liquid hydrocarbons include crude oil, straight run naphtha, kerosene, gas oil, vacuum distillates, topped crude, and natural gas condensate (NGL). Of these liquid hydrocarbons, preferred is the natural gas condensate (NGL).
The mercury to be removed by the process of the present invention may be in either of elementary form or ionic form. The concentration of mercury in the liquid hydrocarbon to be treated is not particularly restricted, and is usually 2 to 1,000 W/V ppb, preferably 5 to 100 W/V ppb.
The crude oil to be treated in the present invention is not particularly restricted. Examples of the crude oil are those produced in Saudi Arabia, United Arab Emirates, Nigeria, Algeria, Canada, Mexico, Iran, Iraq, China, Kuwait, Malaysia, Venezuela, America, Australia, Russia, Libya, Philippines, Indonesia, Norway, Thai Land, Qatar, Argentina, England, and Japan. These crude oils may be used in combination of two or more.
The straight run naphtha, kerosene, gas oil, vacuum distillate and topped crude are obtained by processing the crude oil by known methods.
(1) First Embodied Process
In the first embodied process of the present invention, the liquid hydrocarbon is continuously supplied to the ionization zone, thereby bringing the elementary mercury in the liquid hydrocarbon into contact with the substance capable of ionizing elementary mercury.
Examples of the substance capable of ionizing elementary mercury (hereinafter occasionally referred to as “mercury-ionizing substance”) include an iron compound such as iron sulfate, iron chloride, iron sulfide, iron oxide, iron nitrate and iron oxalate, preferably iron(III) compounds; a copper compound such as copper sulfate, copper chloride, copper oxide, copper nitrate and copper sulfide; a vanadium compound; a manganese compound, preferably manganese dioxide; a nickel compound; an inorganic or organic peroxide such as hydrogen peroxide and peracetic acid; and a sludge in crude oil tank. These mercury-ionizing substances may be used alone or in combination of two or more. Elemental analysis of a typical crude oil tank sludge are shown below.
Fe: 36 wt %; Si: 1.3 wt %; Na: 3,600 wt ppm; Al: 2,700 wt ppm; P: 2,200 wt ppm; Zn: 2,100 wt ppm; Cu: 950 wt ppm; Ca: 720 wt ppm; Mg: 550 wt ppm; V: 350 wt ppm; K: 350 wt ppm; Cr: 290 wt ppm; Mn: 230 wt ppm; Ni: 120 wt ppm; C: 32.0 wt %; H: 3.0 wt %; N: 0.9 wt %; S: 3.0 wt %; and Cl: 0.4 wt %.
The manganese compounds such as manganese oxide may be of any shape such as powdery form, pulverized form, columnar form, spherical form, fibrous form and honeycomb form. In addition, the manganese compounds may be supported on a carrier such as silica, alumina, silica-alumina, zeolite, ceramic, glass, resin and activated carbon. The supporting amount is not particularly restricted, and is preferably 0.1 to 30% by weight based on the weight of the carrier.
In the process of the present invention, the elementary mercury in the liquid hydrocarbon is brought into contact
Ito Hajime
Mase Jun
Sakai Tsunenori
Griffin Walter D.
Idemitsu Petrochemical Co. Ltd.
Nguyen Tam M.
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