US1954101A - System for stabilizing light hydrocarbons - Google Patents

Description

April 10, 1934. ROBERTS ET AL 1,954,101

SYSTEM FOR STABILIZING LIGHT HYDROCARBONS Filed Aug. 19, 1931 Patented Apr. v1934 UNITED STATES PATENT OFFICE;

SYSTEM FOR STABILIZING LIGHT HYDROCAR-BONS Application August 19, 1931, Serial No. 558,114

- '7 Claims.

This invention relates to a method and means for controlling the temperature of a light hydrocarbon stabilizer and to a new and improved system comprising a stabilizer tower, heating means, and automatic interrelated thermostatic regulators and/or controls therefor.

The object of our invention is to remove objectionable gases (such as ethane and propane) from light hydrocarbons (such as gasoline) without sacrificing desirable volatile constituents.

A further object of our invention is to provide an automatically controlled stabilizer system in which the amount of heat supplied is varied with the'amount and nature of the light hydrocarbon which is to be stabilized so that there will be a maximum retention of volatile products and a minimum retention of dissolved gases.

In carrying out our invention we employ a stabilizer tower and a heater, each of which is equipped with a thermocouple. The thermocouple in the heater is connected to a temperature regulator which actuates a valve-operating motor, and the setting of the temperature regulator is automatically controlled by an electrical device connected to a second thermocouple in the stabilizer tower. The regulator maintains a constant temperature in the heater, and the control raises or lowers thistemperature in accordance with the nature of the hydrocarbons which are being stabilized.

The terms regulator and control are often used synonymously, but in this specification and in the following claims the word regulator refers to the thermostatic device for causing the opening and closing of the valve which admits the heating fluid. This regulator may be set by hand at any desired temperature, but in accordance with our invention we set it automatically by means of a second thermostatically operated device which will be, referred to as a control. The regulator causes the valve to be opened and closed, and the control changes the setting of the regulator.

The invention will be more clearly understood from the following description of a preferred embodmient, which is diagrammatically illustrated in the accompanying drawing.

A stabilizer system of this type may be designed and operated for the stabilization of any hydrocarbon oil or similar compound. In the present description we will refer to the stabilization of gasoline which contains dissolved gases. The light hydrocarbon oil (gasoline) is pumped into the system through pipe 10, passed through heat exchanger 11 and orifice meter 12, and introduced into stabilizer tower 13 at an intermediate point thereof. The stabilizer tower per se may be equipped with bubbleplates or equivalent means for obtaining rectification. The specific structure of the gas-liquid contact means forms no part of the present invention, and it will therefore not be described in detail.

Gases'and vapors leave the top of stabilizer tower 13 through pipe 14 in which they are conducted to condenser 15 wherein the heavier fractions thereof are liquefied. The liquids and gases are then introduced by pipe 16 into separator 17, the gases being discharged through pipe 18 and the liquids being returned to the stabilizer tower by means of pipe 19, pump 20, and volume controller 21. The amount of cooling fluid flowing through the condenser 15 is regulated by a float or other suitable means in separator. 17, the float being connected by electrical or mechanical means 22 to the valve which regulates the flow of cooling fluid through the condenser. The volume controller 21 assures the return of a constant ratio of light condensed hydrocarbons (reflux liquids) which are introduced in the stabilizer tower at a point above the introduction of unstabilized oil, the amount of reflux being proportioned to the amount of feed by suitable means 23.

In order to maintain constant pressure in the system weprovide a pressure control 24 on gas discharge pipe 18. To maintain the temperature in the' stabilizer tower we transfer the oil from the base thereof through pipe 25 to heater 26 and return the vapors through pipe 2'7 to the stabilizer tower. Stabilized oil may be withdrawn from the bottonf of heater 26, conveyed to exchanger 11 by pipe 28, and finally dischargedthrough pipe 29.

The heater in the present instance may consist of a heat exchange device wherein the oil is heated by steam coils, the steam being admitted In the present instance the heater should be maintained at about 245 F. This temperature varies with the nature of the oil which is introduced into the system. Such variations cause temperature changes at the top of stabilizer tow er 13, which is preferably about 110 F. in this instance, and unless this tower temperature is held constant, valuable gasoline components will be lost or objectionable gases will remain in the solution. To avoid this difliculty we provide an automatic control for setting the temperature regulator. v

A thermocouple 40 is inserted in the stabil'mer tower near the top thereof and is connected by wires 41 and 42 to temperature indicator and control 43. This thermostatic temperature control 43 is in turn connected by wires 44 and 45 to electromagnetic or equivalent means for setting the thermostatic regulator 35. If the tower temperature is too high thermostatic control 43 sets thermostatic regulator 35 to maintain a lower temperature; when this lower temperature is exceeded in heater 26 the thermostatic regulator causes the motor to close valve 39 and when the heater temperature is too low the same mechanism causes the valve to be opened. Should the tower top temperature drop below 110, the same mechanism will cause a higher temperature to be held in the heater 26, thus preventing the retention' of objectionable gases in the liquid prodnot.

The operation of our improved system will be apparent from the above description. The oil to be stabilized (gasoline) is introduced into the stabilizer tower at a temperature of 185 F. The stabilizer is maintained at a pressure of about 250 pounds and the temperature in the top of the tower is preferably about 110 F. The heater is maintained at 245 F. The separator is held at about 85 F. and it is' at substantially the same pressure as the stabilizer tower. As rectification proceeds in the stabilizer tower gases and vapors are discharged through pipe 14, and partially condensed in condenser 15,-the objectionable gases and undesirable light vapors being discharged from the system through pipe 18. The condensed components are reintroduced by pump 20 into the stabilizer tower, the rate of pumpback being controlled by the valve of the volume controller 21. This controller may be a ratio controller to maintain a constant relation between the feed and reflux.

The gasoline drawn from the bottom of the heater is substantially free from objectionable light components and it is passed through heat exchanger 11 to give up its heat to the incoming oil.

If the temperature in the tower rises above 110 F. a current is set up in wires 41 and 42 by means of thermocouple 40 whereby the temperature control 43 automatically resets the temperature regulator 35. The heater is held at the tempera ture for which the regulator is set; valve 39 being closed if the heater is too hot and being opened if the heater is too cold.

We claim:

1. A system for stabilizing light hydrocarbon oils, such as gasoline, whichcomprises a stabilizer tower, means for introducing hot oil at an intermediate point in said tower, means for withdrawing and partially condensing gases and vapors from the top ofsaid tower, means for introducing condensed vapors into said tower at a point above the introduction of hot oil, means for heating the oil in the base of the tower, thermostatic means responsive to the temperature in theheating means for regulating the temperature of the heating means, and separate thermostatic means responsive to the vapor temperature at the top of the tower for controlling the regulating means.

2. In combination, a stabilizer tower, means for introducing hydrocarbon oils at an intermediate point in said tower, means for heating the liquid at the base of said tower, means for withdrawing gases and vapors from the top of said tower, means for discharging uncondensed vapors and gases from the system, means for returning condensate into said tower at a point above the introduction of the oil, and means for maintaining a constant temperature in the top of said tower, the said last named means comprising a temperature control actuated by the vapor temperature at the top of the tower, a temperature regulator actuated by the temperature in said heating means, and connections whereby said control varies said temperature regulator.

3. A system for stabilizing light hydrocarbons, such as gasoline, which comprises a stabilizer tower, a heater, means for introducing oil from the base of said tower to said heater and from said heater to said tower, a thermocouple in said tower, a thermocouple in said heater, a thermostatic temperature control, electrical connections from said tower thermocouple to said temperature control, a thermostatic temperature regulator, electrical connections from said heater thermocouple to said temperature regulator, means whereby said temperature control sets said temperature regulator, and means whereby said temperature regulator regulates the amount of heat introduced into said heater.

4. The method of stabilizing a light hydrocarbon oil such as gasoline, which comprises preheating said oil, fractionating it under pressure in a stabilizer tower for separating dissolved gases and light condensable vapors therefrom, condensing said condensable vapors and returning a portion thereof as reflux in the fractionation, reboiling the fractionated liquid, removing part thereof from the system, introducing the vapors from the reboiled liquid to assist in rectification, and automatically regulating the heat input in the reboiler in accordance with the vapor temperature in the tower at the outlet thereof and in accordance with the temperature in the reboiler.

5. In a stabilizing system wherein a liquid is rectified in a stabilizer tower and liquid is withdrawn from the base of said tower, reboiled in a heater and a vaporized part thereof reintroduced into said tower to maintain the temperature thereof, the method of automatically regulating the temperature at the top of said tower which comprises thermostatically regulating in accordance with the temperature in the heater the amount of heat introduced into said heater to maintain a constant heater temperature and thermostatically controlling or setting said regulator in accordance with the temperature in the top of the tower.

6. In apparatus of the class described, a stabilizer tower, a heater, means for introducing liquid from said tower into said heater and for introducing heated vapors from said heater to said tower, means for supplying heating fluid to said heater, a thermocouple in said heater, a thermostatic regulator connected to said thermocouple, means controlled by said regulator for regulating the amount of heating fluid introduced into said heater, a thermocouple in said tower, a thermostatic control connected with said thermocouple,

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