Supercritical water process to upgrade petroleum

1. A method for upgrading a petroleum feedstock with supercritical water while preventing plugging in equipment process lines, the method comprising the steps of:

priming an upgrading reactor to receive the petroleum feedstock, the priming of the apparatus comprising the steps of:

supplying a heated and pressured water stream to a first mixing device, wherein the water stream is heated and pressurized to a temperature and pressure greater than the critical point of water;

supplying a heated and pressurized start-up hydrocarbon stream to the first mixing device, wherein the start-up hydrocarbon stream is heated and pressurized to a temperature of between about 10 and 250° C.;

mixing the heated and pressurized water stream and the heated and pressurized start-up hydrocarbon stream in the first mixing device to produce a water and start-up hydrocarbon containing primer stream;

supplying the water and start-up hydrocarbon containing primer stream to the upgrading reactor, said reactor being maintained at a temperature that is between about 380 and 550° C. to produce a treated primer stream, wherein the primer stream has a residence time in the upgrading reactor of between about 10 seconds and 60 minutes;

cooling the treated primer stream to a temperature of less than about 150° C., depressurizing the cooled treated primer stream;

separating the cooled treated primer stream into treated primer gas and treated primer liquid phase streams;

separating the treated primer liquid phase into a recycle start-up hydrocarbon stream and a recycle water stream;

continuing the priming step until the temperature of the streams within a heater, supercritical upgrading reactor and cooling devices are maintained to within 5% of their set point for a period of at least 10 minutes;

stopping the flow of the start-up hydrocarbon containing primer stream to the upgrading reactor and then supplying a heated and pressurized petroleum feedstock to the first mixing device, wherein the heated and pressurized petroleum feedstock is maintained at a temperature of between about 10 and 250° C.;

mixing the heated and pressurized water stream and the heated and pressurized petroleum feedstock in the first mixing device to produce a mixed water and start-up petroleum feedstock stream;

supplying the mixed water and start-up petroleum feedstock stream to the upgrading reactor, said reactor being maintained at a temperature that is between about 380 and 550° C. to produce an upgraded petroleum containing stream, wherein the mixed water and start-up petroleum feedstock stream has a residence time in the upgrading reactor of between about 10 seconds and 60 minutes;

cooling the upgraded petroleum containing stream to a temperature of less than about 150° C.,

depressurizing the cooled upgraded petroleum containing stream;

separating the cooled upgraded petroleum containing stream into a gaseous phase upgraded and desulfurized petroleum containing stream and liquid phase upgraded and desulfurized petroleum containing stream;

separating the liquid phase upgraded and desulfurized petroleum containing stream into an upgraded and

desulfurized petroleum product stream and a recycle water stream.

2. The method of claim 1 , wherein the start-up hydrocarbon is selected from benzene, toluene, xylene, and ethylbenzene.

3. The method of claim 1 , wherein the start-up hydrocarbon is selected from reformate from a catalytic reformer, light cracked naphtha from an FCC unit, visbreaker naphtha, coker naphtha, and pyrolysis gasoline from a steam cracker.

4. The method of claim 1 , wherein the start-up hydrocarbon has an aromatic content of at least about 30% by volume.

5. The method of claim 1 , wherein the start-up hydrocarbon has a solid content of less than about 10 ppm.

6. The method of claim 1 , wherein the petroleum feedstock is selected from the group consisting of whole range crude oil, topped crude oil, the product stream from a petroleum refinery, the product stream from a steam cracker, liquefied coal, the liquid product recovered from oil sand, bitumen, asphaltene, and hydrocarbons that originate from biomass.

7. The method of claim 1 , wherein the water, start-up hydrocarbon and petroleum feedstock streams are each pressurized to a pressure that is greater than the critical pressure of water.

8. The method of claim 1 , wherein the volumetric flow rate of the start-up agent and water is between 1:5 and 1:1.

9. The method of claim 1 , wherein the water is heated to a temperature of between about 300 and 550° C.

10. The method of claim 1 , wherein the reactor is maintained at a temperature of between about 400 and 450° C.

11. The method of claim 1 , the mixed water and start-up petroleum feedstock stream has a residence time in the upgrading reactor of between about 20 and 30 minutes.

12. The method of claim 1 , wherein the step of cooling the upgraded petroleum containing stream exiting the upgrading reactor comprises supplying the stream to a heat exchanger wherein the stream is heat exchanged with a start-up hydrocarbon or water stream.

13. The method of claim 1 , wherein the upgraded petroleum containing stream is cooled to a temperature of between about 25 and 75° C.

14. The method of claim 1 , wherein the pressure of upgraded petroleum containing stream exiting the upgrading reactor is reduced to between about 0.1 and 0.5 MPa.

15. The method of claim 1 , further comprising recycling the recycle start-up hydrocarbon stream to the first mixing device.

16. The method of claim 1 , further comprising recycling the recycle water stream to the first mixing device.