Gas expansion cooling method

1. A gas expansion cooling method for reducing hydrocarbon emissions, comprising the steps of:

a) feeding a cooling gas through a valve, wherein the valve decreases a temperature of the cooling gas by decreasing the pressure of the cooling gas;

b) feeding the cooling gas into a heat exchanger, wherein the cooling gas is drawn from a preexisting high pressure gas system, and wherein the high pressure gas system serves a purpose other than supplying a coolant to the heat exchanger;

c) diverting a hydrocarbon gas into the heat exchanger such that the cooling gas decreases a temperature of the hydrocarbon gas, wherein a portion of the hydrocarbon gas is condensed by the cooling gas to form a hydrocarbon liquid; and

d) returning the cooling gas from the heat exchanger into the high pressure gas system.

2. The gas expansion cooling method of claim 1 , wherein in step (b), the cooling gas is fed into a shell portion of the heat exchanger; and wherein in step (c), the hydrocarbon gas is diverted into a tube portion of the heat exchanger.

3. The gas expansion cooling method of claim 1 , further comprising the steps of:

e) feeding the hydrocarbon gas and the hydrocarbon liquid from the heat exchanger into a separation vessel; and

f) allowing the hydrocarbon liquid to separate from the hydrocarbon gas in the separation vessel.

4. The gas expansion cooling method of claim 3 , further comprising the steps of:

g) feeding the hydrocarbon liquid from the separation vessel into a storage vessel; and

h) feeding the hydrocarbon gas from the separation vessel to a ventilation system;

wherein the hydrocarbon gas in step (h) contains less VOCs than the hydrocarbon gas fed into the heat exchanger in step (c).

5. The gas expansion cooling method of claim 3 , further comprising the steps of:

g) feeding the cooling gas from the heat exchanger into a second heat exchanger;

h) feeding the hydrocarbon gas from the separation vessel into the second heat exchanger such that the cooling gas again decreases the temperature of the hydrocarbon gas, wherein a portion of the hydrocarbon gas is condensed by the cooling gas in the second heat exchanger to form a second hydrocarbon liquid.

6. The gas expansion cooling method of claim 5 , further comprising the step of:

i) feeding the second hydrocarbon liquid into the separation vessel.

7. The gas expansion cooling method of claim 6 , further comprising the steps of:

j) feeding the hydrocarbon liquid and the second hydrocarbon liquid from the separation vessel into a storage vessel; and

k) feeding the hydrocarbon gas from the second heat exchanger to a ventilation system;

wherein the hydrocarbon gas in step (k) contains less VOCs than the hydrocarbon gas fed into the heat exchanger in step (c).

8. The gas expansion cooling method of claim 3 , further comprising the step of:

g) feeding a cool liquid through an atomizer, the atomizer spraying the cool liquid onto the hydrocarbon gas before it is fed into the heat exchanger such that the cool liquid reduces the temperature of the hydrocarbon gas, thereby creating a vacuum in the hydrocarbon gas.

9. The gas expansion cooling method of claim 8 , wherein the cool liquid comprises a portion of the hydrocarbon liquid; and wherein step (g) further comprises: feeding the portion of the hydrocarbon liquid from the separation vessel and through the atomizer, wherein the atomizer sprays the portion of the hydrocarbon liquid onto the hydrocarbon gas before it is fed into the heat exchanger such that the portion of the hydrocarbon liquid reduces the temperature of the hydrocarbon gas, thereby creating a vacuum in the hydrocarbon gas.

10. The gas expansion cooling method of claim 3 , further comprising the step of:

g) feeding a cool liquid through an atomizer, the atomizer spraying the cool liquid onto the hydrocarbon gas as it is fed into the heat exchanger such that the cool liquid reduces the temperature of the hydrocarbon gas, thereby creating a vacuum in the hydrocarbon gas.

11. The gas expansion cooling method of claim 10 , wherein the cool liquid comprises a portion of the hydrocarbon liquid; and wherein step (g) further comprises: feeding the portion of the hydrocarbon liquid from the separation vessel and through the atomizer, wherein the atomizer sprays the portion of the hydrocarbon liquid onto the hydrocarbon gas as it is fed into the heat exchanger such that the portion of the hydrocarbon liquid reduces the temperature of the hydrocarbon gas, thereby creating a vacuum in the hydrocarbon gas.

12. A gas expansion cooling method for reducing hydrocarbon emissions, comprising the steps of:

a) providing a gas expansion cooling system comprising: a cooling gas input line leading to a heat exchanger, a valve disposed on said cooling gas input line, a hydrocarbon input line leading to the heat exchanger;

b) feeding a cooling gas through the cooling gas input line, the valve, and into the heat exchanger, wherein the cooling gas is drawn from a preexisting high pressure gas system, wherein the high pressure gas system serves a purpose other than supplying a coolant for the gas expansion cooling system, and wherein the valve decreases a temperature of the cooling gas by decreasing the pressure of the cooling gas;

c) diverting a hydrocarbon gas into the heat exchanger such that the cooling gas decreases a temperature of the hydrocarbon gas, wherein a portion of the hydrocarbon gas is condensed by the cooling gas in the heat exchanger to form a hydrocarbon liquid; and

d) returning the cooling gas from the heat exchanger into the high pressure gas system.

13. The gas expansion cooling method of claim 12 , wherein in step (b), the cooling gas is fed into a shell portion of the heat exchanger; and wherein in step (c), the hydrocarbon gas is diverted into a tube portion of the heat exchanger.

14. The gas expansion cooling method of claim 12 , wherein the gas expansion cooling system further comprises a hydrocarbon fluid output line leading from the heat exchanger to a separation vessel, wherein the method further comprises the steps of:

e) feeding the hydrocarbon gas and the hydrocarbon liquid from the heat exchanger, through the hydrocarbon fluid output line, and into the separation vessel; and

f) allowing the hydrocarbon liquid to separate from the hydrocarbon gas in the separation vessel.

15. The gas expansion cooling method of claim 14 , wherein the gas expansion cooling system further comprises a hydrocarbon liquid output line running from the separation vessel to a storage vessel, and a vent line running from the separation vessel to a ventilation system;

wherein the method further comprises the steps of:

g) feeding the hydrocarbon liquid from the separation vessel, through the hydrocarbon liquid output line, and into the storage vessel; and

h) feeding the hydrocarbon gas from the separation vessel, through the vent line, and to the ventilation system;

wherein the hydrocarbon gas in step (h) contains less VOCs than the hydrocarbon gas fed into the heat exchanger in step (c).

16. The gas expansion cooling method of claim 14 , wherein the gas expansion cooling system further comprises a hydrocarbon gas output line leading from the separation vessel to a second heat exchanger, and a cooling gas output line leading from the heat exchanger to the second heat exchanger, wherein the method further comprises the steps of:

g) feeding the cooling gas from the heat exchanger, through the cooling gas output line, and into the second heat exchanger;

h) feeding the hydrocarbon gas from the separation vessel, through the hydrocarbon gas output line, and into the second heat exchanger such that the cooling gas again decreases the temperature of the hydrocarbon gas, wherein a portion of the hydrocarbon gas is condensed by the cooling gas in the second heat exchanger to form a second hydrocarbon liquid.

17. The gas expansion cooling method of claim 16 , further comprising the step of:

i) allowing the second hydrocarbon liquid to drain from the second heat exchanger, through the hydrocarbon gas output line, and into the separation vessel.

18. The gas expansion cooling method of claim 17 , wherein the gas expansion cooling system further comprises a hydrocarbon liquid output line running from the separation vessel to a storage vessel, and a vent line running from the second heat exchanger to a ventilation system;

wherein the method further comprises the steps of:

j) feeding the hydrocarbon liquid from the separation vessel, through the hydrocarbon liquid output line, and into the storage vessel; and

k) feeding the hydrocarbon gas from the second heat exchanger, through the vent line, and to the ventilation system;

wherein the hydrocarbon gas in step (k) contains less VOCs than the hydrocarbon gas fed into the heat exchanger in step (c).

19. The gas expansion cooling method of claim 14 , wherein the gas expansion cooling system further comprises an atomizer positioned on the hydrocarbon input line, and wherein the method further comprises the step of:

g) feeding a cool liquid through the atomizer and into the hydrocarbon input line such that the cool liquid reduces the temperature of the hydrocarbon gas flowing through the hydrocarbon input line, thereby creating a vacuum in the hydrocarbon input line.

20. The gas expansion cooling method of claim 19 , wherein the gas expansion cooling system further comprises an atomizer feed line leading from the separation vessel to the atomizer; wherein the cool liquid comprises a portion of the hydrocarbon liquid from the separation vessel; and wherein step (g) further comprises: feeding the portion of the hydrocarbon liquid from the separation vessel, through the atomizer feed line, through the atomizer, and into the hydrocarbon input line such that the portion of the hydrocarbon liquid reduces the temperature of the hydrocarbon gas flowing through the hydrocarbon input line, thereby creating a vacuum in the hydrocarbon input line.

21. The gas expansion cooling method of claim 14 , wherein the gas expansion cooling system further comprises an atomizer positioned at an inlet to the tube portion of the heat exchanger, and wherein the method further comprises the step of:

g) feeding a cool liquid through the atomizer and into the inlet to the tube portion of the heat exchanger such that the cool liquid reduces the temperature of the hydrocarbon gas flowing through the inlet to the tube portion of the heat exchanger, thereby creating a vacuum in the inlet to the tube portion of the heat exchanger.

22. The gas expansion cooling method of claim 21 , wherein the gas expansion cooling system further comprises an atomizer feed line leading from the separation vessel to the atomizer; wherein the cool liquid comprises a portion of the hydrocarbon liquid from the separation vessel; and wherein step (g) further comprises: feeding the portion of the hydrocarbon liquid from the separation vessel, through the atomizer feed line, through the atomizer, and into the inlet to the tube portion of the heat exchanger such that the portion of the hydrocarbon liquid reduces the temperature of the hydrocarbon gas flowing through the inlet to the tube portion of the heat exchanger, thereby creating a vacuum in the inlet to the tube portion of the heat exchanger.

23. The gas expansion cooling method of claim 12 , wherein step (c) further comprises: diverting a gas mixture into the heat exchanger such that the cooling gas decreases a temperature of the gas mixture, wherein the gas mixture comprises steam and a hydrocarbon gas, and wherein a portion of the gas mixture is condensed by the cooling gas in the heat exchanger to form a liquid mixture comprising water and a liquid hydrocarbon.