System and method for separating a trace element from a liquid hydrocarbon feed

Abstract

The present invention is generally directed to removing a trace element from a liquid hydrocarbon feed. The liquid hydrocarbon feed, containing the trace element, is mixed with the water along with a hydrocarbon-soluble additive. While being mixed, a compound, which in some cases is preferably insoluble, is formed by the hydrocarbon-soluble additive chemically reacting with the trace element. A phase separation device, such as a desalter or an oil-water separator, receives the oil-water emulsion containing the compound and resolves the mixture to produce the compound, effluent brine, and effluent liquid hydrocarbon with a reduced concentration of the trace element as compared to the liquid hydrocarbon feed. In some embodiments, the present invention is directed to removing elemental mercury from a liquid hydrocarbon feed. A hydrocarbon-soluble sulfur-containing additive, typically an organic polysulfide, is mixed with the liquid hydrocarbon feed and water. The hydrocarbon-soluble, sulfur-containing additive reacts with the mercury, rapidly forming an agglomeration of mercuric sulfide which is then dispensed with the effluent brine or the effluent liquid hydrocarbon.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of U.S. patent application Ser. No. 12 / 132,475 filed Jun. 3, 2008, which is hereby incorporated herein in its entirety by reference.TECHNICAL FIELD[0002]This invention relates generally to separating a trace element from a liquid hydrocarbon feed within a phase separation device, such as a desalting unit or oil-water separator.BACKGROUND OF THE INVENTION[0003]Liquid hydrocarbon feeds generally contain an assortment of trace elements in amounts generally ranging from several parts per billion (ppb) to several thousand ppb depending on the feed source. These elements often cause corrosion within equipment and may deteriorate or poison a catalyst of a subsequent treatment process. For example, mercury may amalgamate with a surface metal, such as copper or aluminum, collecting with time in piping, valves and even in larger structures such as fractional distillation columns. Equipment replacement or a...

AI Technical Summary

Benefits of technology

[0007]The present invention comprises removing a trace element from a liquid hydrocarbon, such as crude oil, natural gas, and other petroleum products. The liquid hydrocarbon is mixed or emulsified with water and a hydrocarbon-soluble additive. During mixing, the additive chemically reacts with the trace element forming a compound. This compound is typically an aqueous insoluble compound, such that the compound may easily be separated and removed in subsequent treatment processes. A phase separation device, such as a desalter or an oil-water separator, resolves, i.e., separates, the oil-water emulsion containing the compound. The resolved mixture produces the compound formed by mixing the additive with the trace element, effluent brine, and effluent liquid hydrocarbon with a reduced concentration of the trace element as compared to the liquid hydrocarbon feed. The compound may be dispensed from the phase separation device with the effluent brine or the effluent liquid hydrocarbon and may later be filtered out.

Problems solved by technology

These elements often cause corrosion within equipment and may deteriorate or poison a catalyst of a subsequent treatment process.

Equipment replacement or abstraction of this deleterious metal from the equipment can be very expensive and potentially hazardous.

However, due to the liquid hydrocarbon state of the feed prior to distillation being more chemically complex, current technologies for removing the trace elements prior to hydrocarbon distillation tend to be less developed.

While the approach of using fixed bed absorbents to extract trace elements, including mercury, from a hydrocarbon feed have shown to be successful, they also include a number of less than desirable attributes.

Absorbent beds tend to get clogged by solid particulates in the crude, thus impeding the flow of the feed.

Absorbents can also be very costly due to the large quantity needed, especially if there is a high concentration of the trace element or elements being extracted.

Due to the high partition coefficient of the sulfur compounds in the aqueous phase, the risk of contaminating the liquid hydrocarbons with sulfur is limited.

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