Proppant blender

1. A vapor hood for attachment to a blender tub for mixing proppant with a hydrocarbon fluid, the blender tub having an opening for receiving proppant, the vapor hood comprising:

a vapor-containing chamber adapted to be secured around the opening of the blender tub;

a first pressure-tight seal on an end of the vapor-containing chamber for sealing the vapor-containing chamber onto the blender tub;

a proppant entrance port to the vapor-containing chamber for receiving proppant from a proppant supply source;

the proppant entrance port including a one-way valve for preventing the escape of vapor through the proppant entrance port when proppant is not entering the vapor-containing chamber through the proppant entrance port;

a second pressure-tight seal on the proppant entrance port for sealing with the proppant supply source;

a sleeve opening on the vapor-containing chamber for accommodating a motor shaft, the sleeve opening further comprising a shaft seal; and

a vapor extraction port for extracting vapor from the vapor-containing chamber,

wherein the vapor-containing chamber, the first pressure-tight seal and the shaft seal are configured to maintain a pressure differential between an interior of the vapor-containing chamber and an exterior of the vapor-containing chamber.

2. The vapor hood of claim 1 in which the vapor extraction port is connected to a flare system.

3. The vapor hood of claim 1 in which the vapor extraction port is connected to a vapor recovery system.

4. The vapor hood of claim 1 in which the one-way valve comprises a damper system to allow a flow of proppant to complete before the one-way valve closes.

5. The vapor hood of claim 1 further comprising a viewport in the vapor-containing chamber to allow a person outside the vapor-containing chamber to view the proppant entrance port from a direction interior to the vapor-containing chamber.

6. Apparatus for mixing proppant with a hydrocarbon fluid, comprising:

a blender tub for combining the hydrocarbon fluid and proppant, the blender tub having an opening for receiving proppant;

a vapor-containing chamber secured around the opening of the blender tub;

a proppant entrance port to the vapor-containing chamber for receiving proppant from a proppant supply source;

the proppant entrance port including a one-way valve for preventing the escape of vapor through the proppant entrance port when proppant is not entering the vapor-containing chamber through the proppant entrance port;

a motor installed above the vapor-containing chamber;

a drive shaft extending from the motor into the vapor-containing chamber to drive a mixer inside the blender tub;

a sleeve opening through the vapor-containing chamber for accommodating the drive shaft;

a seal between the drive shaft and the sleeve opening; and

a vapor extraction port for extracting vapor from the vapor-containing chamber,

the vapor-containing chamber configured to maintain a pressure differential between an exterior of the vapor-containing chamber and an interior within the vapor-containing chamber and the blender tub.

7. The apparatus of claim 6 in which the vapor extraction port is connected to a flare system.

8. The apparatus of claim 6 in which the vapor extraction port is connected to a vapor recovery system.

9. The apparatus of claim 6 in which the one-way valve comprises a damper system to allow a flow of proppant to complete before the one-way valve closes.

10. The apparatus of claim 6 further comprising a viewport in the vapor-containing chamber to allow a person outside the vapor-containing chamber to view the proppant entrance port from a direction interior to the vapor-containing chamber.

11. The vapor hood of claim 1 wherein the first pressure-tight seal is a gasket seal, the second pressure-tight seal is an air bag face seal and the shaft seal is an air bag shaft seal.

12. The vapor hood of claim 1 wherein the first pressure-tight seal is configured to hold a pressure differential of >2 PSI and <11 PSI.

13. The vapor hood of claim 1 wherein the end of the vapor-containing chamber is a lower end of the chamber, and the sleeve opening is positioned on an upper end of the vapor-containing chamber opposite the lower end.

14. The apparatus of claim 6 wherein the pressure differential is an overpressure within the interior.

15. The apparatus of claim 14 wherein the pressure differential is >2 PSI and <11 PSI.

16. The apparatus of claim 6 further comprising a pressure-tight seal on a lower end of the vapor-containing chamber for sealing the vapor-containing chamber onto the blender tub.

17. The apparatus of claim 16 further comprising a second pressure-tight seal on the proppant entrance port for sealing with the proppant supply source.

18. The apparatus of claim 17 wherein the pressure-tight seal is a gasket seal, the second pressure-tight seal is an air bag face seal and the seal is an air bag shaft seal and the seal between the drive shaft and the sleeve is an air bag shaft seal.