Apparatus and Method For Reducing Fouling In Crude Refining By Reduction Of Phosphorus

Abstract

A method and apparatus for the reduction of fouling in a crude unit. Chemicals containing Phosphorous are understood to be utilized in the production or transportation of certain types of crude oils. It is believed that the elevated levels of phosphorus are contributing to the excessive fouling observed in the preheat exchanger circuits and crude heaters.

Claims

1. A method for reducing the levels of phosphorus in the process of refining oil comprising the steps of: heating crude to the temperature exceeding 450° F. transferring the heated crude oil to a flash tower; separating light hydrocarbons and contaminants from the crude oil; condensing the heavier of the light hydrocarbons at the upward portion of the flash tower; collecting the heavier of the condensed light hydrocarbons and transferring the recondensed heavier light hydrocarbons directly to a crude tower for processing; transferring the flashed crude to a crude heater; and transferring the heated flashed crude to the crude tower for processing.

2. The method of claim 1 further including the step of transferring the tighter of the light hydrocarbons to a naphtha stripper for separating light naphtha from heavy naphtha.

3. The method of claim 2 further including the step of sending the light naphtha to a debutanizer for separating propane and butane.

4. An apparatus of claim 4 further including use in reducing the levels of phosphorus in the process of refilling oil comprising in combination a flash tower for receiving crude oil heated above 450° F. wherein the crude oil is separated into light hydrocarbons, heavy hydrocarbons, and flashed crude; a total draw tray positioned below the fractionation trays to catch condensed light hydrocarbons and heavy hydrocarbons, preventing the light and heavy hydrocarbons from remixing with the flashed crude; piping engaged with the total draw tray for removing the flashed heavy hydrocarbons and contaminants and transferring the flashed heavy hydrocarbons and contaminants directly to a crude tower;

Description

IN THE DRAWINGS

[0009] FIG. 1 is a schematic drawing a typical crude unit, including a flash separator with a draw tray, of the present invention.

[0010] FIG. 2 is a cross section view of a flash tower having a total draw tray.

[0011] FIG. 3 is a cross section view of a flash tower showing the metal draw tray in more detail.

DETAILED DESCRIPTION OF THE INVENTION

[0012] Referring now to FIGS. 1-3, the crude oil 1, or raw crude, enters the refinery from a pipeline at ground temperature of about 50-70° F. The crude oil 1 is stored in tanks (not shown) until it is transferred to the crude unit 20, where it is heated by passage through a plurality of heat exchangers (not shown) to increase the temperature of the crude oil 1 to approximately 300° prior to entering a desalter 2. The heat exchangers increase the temperature of the crude oil 1 while, reducing the temperature of the finished product. Crude oil enters a desalter 2 where salt is removed, or washed, from the crude. The crude oil, now called desalted crude, is pumped through additional heat exchangers, raising the temperature to above 450° F., before entering a flash tower 6. In the flash tower 6, light and heavy hydrocarbons and contaminants contained in the crude oil are vaporized, or flashed, and are thus separated from the desalted crude. Naphtha or light hydrocarbons are then separated from the heavy hydrocarbons, such as kerosene.

[0013] The flashed light hydrocarbons carrying some heavy hydrocarbons containing contaminates, including kerosene and phosphorous rise through the flash tower 5 while the flashed desalted crude falls to the bottom of the flash tower. The upper portion of the flash tower 6 contains a plurality of fractionation trays 22 wherein the vaporized hydrocarbons will condense based on their boiling points and contamination levels. The higher fractionization trays condense the lighter hydrocarbons.

[0014] The heavier hydrocarbons containing the contaminants such as phosphorous will condense and begin to fall back down through the fractionation trays 22, toward the bottom of the flash tower 6. A total draw tray 25 is in position below the fractionation trays 22 to catch any falling condensed hydrocarbons before they remix with the flashed desalted crude. The total draw tray 25 is designed such that vapors can pass upward through chimneys 27 but condensed hydrocarbons cannot pass downward. The condensed hydrocarbons are prevented from passing through the chimneys 27 by means of chimney caps 29. The chimney caps direct condensed hydrocarbons away from the chimneys 27 and up to the total draw tray 25. The condensed hydrocarbons contained by the total draw tray 25 pool at exit point 30 for further processing. Thus, the heavy condensed hydrocarbons containing the contaminants such as phosphorus bypass downstream vessel, including the crude heater 8. The light hydrocarbons or naphtha are transferred to a naphtha stripper 14 where light naphtha and heavy naphtha are separated. The light naphtha is further sent to debutanizer 12 intended to separate the propane and butane contained in the light naphtha.

[0015] The crude oil from the flash tower 6, now called flashed crude, is pumped through additional heat exchangers, and on to a crude heater 8. By removing kerosene and ensuring that all of the water content is reduced from the crude, the phosphorous fouling of the heat exchanger and crude heater is reduced significantly. The outlet of the crude heater 8 is piped directly to the crude tower 10, where the crude oil is separated into finished products.

[0016] The above detailed description of the present invention is given for explanatory purposes. It will be apparent to those skilled in the art that numerous changes and modifications can be made without departing from the scope of the invention. Accordingly, the whole of the foregoing description is to be construed in an illustrative and not a limitative sense, the scope of the invention being defined solely by the appended claims.