GAS FLARE SYSTEM AND METHOD OF DESTROYING A FLAMMABLE GAS IN A WASTE GAS STREAM

• US 20140147795A1
• Filed: 11/19/2013
• Published: 05/29/2014
• Est. Priority Date: 11/23/2012
• Status: Active Grant

• Current Assignee: RTJ Technologies Inc.
• Original Assignee: RTJ Technologies Inc.
• Inventors: TREMBLAY, Charles, JASMIN, Simon, ROY, Alain
• Granted Patent: US 9,464,804 B2
• Time in Patent Office: Days
• US Class Current: 431/5
• CPC Class Codes: F23G 7/085 in stacks

Abstract

The gas flare system includes a vertical flare stack having an opened top end and a bottom floor wall. A weatherproof protective hood arrangement prevents rain and snow from entering through the opened top end. The gas flare system also includes a burner arrangement provided through the bottom floor wall. The burner arrangement receives a waste gas stream from a waste gas circuit and also primary air. Secondary air orifices around the burner supply secondary air coming from a plenum housing located directly underneath the bottom floor wall. The gas flare system can destroy the flammable gas in the waste gas stream with a combustion efficiency of more than 99% under almost any operating conditions. It can start automatically and operate efficiently without any supervision under any possible atmospheric conditions. A method of destroying a flammable gas in a waste gas stream is also disclosed.

Claims

1. A gas flare system for destroying a flammable gas contained in a waste gas stream, the gas flare system including:

a flare stack defining a flare stack chamber extending vertically between a bottom floor wall and an opened top end of the flare stack;

a weatherproof protective hood arrangement including an overhead cap located vertically above the opened top end and covering more than an entire area of the opened top end, and a lateral peripheral shroud surrounding the opened top end and the overhead cap;

a plenum housing located directly underneath the bottom floor wall;

a burner arrangement provided through the bottom floor wall, the burner arrangement having at least one burner outlet including;

a top-opened combustion chamber extending above the bottom floor wall;

a primary air housing extending under the bottom floor wall and into the plenum housing;

a waste gas outlet located at a bottom of the combustion chamber; and

a primary air outlet extending between the primary air housing and the bottom of the combustion chamber, the primary air outlet being adjacent to the waste gas outlet;

a waste gas circuit in fluid communication with the waste gas outlet of the at least one burner outlet;

a primary pressurized air circuit in fluid communication with the primary air housing of the at least one burner outlet, the primary air circuit including a primary air circuit flow regulator;

a primary air pressure sensor provided on the primary air circuit;

a secondary pressurized air circuit in fluid communication with the flare stack chamber, the secondary air circuit passing inside the plenum housing and ending at a plurality of secondary air orifices provided through the bottom floor wall around the at least one burner outlet, the secondary air circuit including a secondary air circuit flow regulator;

a waste gas composition analyzer in fluid communication with the waste gas inlet pipe;

a waste gas pressure sensor provided on the waste gas inlet pipe;

a waste gas flow meter provided on the waste gas inlet pipe;

a flue gas composition analyzer in fluid communication with a location adjacent to the opened top end inside the flare stack chamber;

a flue gas temperature sensor located in the flare stack chamber and adjacent to the opened top end;

a first controller sending command signals to control at least the primary air circuit flow regulator in response to data signals received from at least the waste gas pressure sensor, the waste gas flow meter, the waste gas composition analyzer, the flue gas composition analyzer and the primary air pressure sensor; and

a second controller sending command signals to control at least the secondary air circuit flow regulator in response to data signals received from at least the flue gas temperature sensor.

2. The gas flare system as defined in claim 1, wherein the burner arrangement includes more than one burner outlet, the burner outlets being spaced apart from one another and each burner outlet being surrounded by a corresponding set of the secondary air orifices.

3. The gas flare system as defined in claim 2, wherein the secondary air orifices of each set are axisymmetric with reference to each burner outlet.

4. The gas flare system as defined in claim 1, wherein the primary air outlet includes a plurality of axisymmetric primary air orifices surrounding the waste gas outlet.

5. The gas flare system as defined in claim 4, wherein the primary air orifices are obliquely disposed to promote a first swirling gas motion in the combustion chamber of the at least one burner outlet.

6. The gas flare system as defined in claim 5, wherein the secondary air orifices are obliquely disposed to promote a second swirling gas motion above the combustion chamber of the at least one burner outlet, the second swirling gas motion being in an opposite direction than that of the first swirling gas motion.

7. The gas flare system as defined in claim 1, wherein the primary air circuit includes a primary air fan and a primary air duct, the primary air duct being provided between the primary air fan and the primary air housing of the at least one burner outlet.

8. The gas flare system as defined in claim 7, wherein the primary air circuit flow regulator includes an actuated primary air damper provided on the primary air duct.

9. The gas flare system as defined in claim 1, further including an ignition device to ignite the flammable gas coming into the combustion chamber of the at least one burner outlet.

10. The gas flare system as defined in claim 1, wherein the secondary air circuit includes a secondary air fan and a secondary air duct, the secondary air duct being provided between the secondary air fan and the plenum housing.

11. The gas flare system as defined in claim 10, wherein the secondary air circuit flow regulator includes an actuated secondary air damper provided on the secondary air duct.

12. The gas flare system as defined in claim 1, further including a flue gas sampling pipe located in the flare stack chamber and adjacent to the opened top end, the flue gas sampling pipe being in fluid communication with the flue gas composition analyzer.

13. The gas flare system as defined in claim 12, wherein the waste gas composition analyzer and the flue gas composition analyzer are the same device.

14. The gas flare system as defined in claim 1, further including a flame scanner located in the flare stack chamber between the bottom floor wall and the opened top end.

15. The gas flare system as defined in claim 1, wherein the flare stack includes an outer wall having a substantially circular inner cross section.

16. The gas flare system as defined in claim 1, wherein the burner arrangement has a turndown ratio of at least 40:

1.

17. The gas flare system as defined in claim 1, wherein the burner arrangement has a turndown ratio of at least 400:

1.

18. A method of destroying a flammable gas in flare system, the method including:

continuously preventing rain water and snow from entering through an opened top end of the flare system;

monitoring pressure, flow rate and flammable gas fraction of the waste gas stream received at the flare system;

supplying the waste gas stream to a burner arrangement provided inside the flare system; and

burning off the flammable gas by;

supplying pressurized primary air inside the burner arrangement, the primary air and the waste gas stream only mixing inside a combustion chamber of the burner arrangement;

supplying pressurized secondary air from underneath the burner arrangement;

ejecting the secondary air around the combustion chamber of the burner arrangement;

monitoring temperature and flammable gas fraction of the flue gas resulting from burning off the flammable gas;

controlling the primary air supplied to the burner arrangement at least in function of the flammable gas fraction in the waste gas stream, the waste gas stream pressure, the waste gas stream flow rate and the flammable gas fraction in the flue gas; and

controlling the secondary air at least in function of the flue gas temperature.

19. The method as defined in claim 18, wherein the steps of monitoring the flammable gas fraction of the waste gas stream, supplying the waste gas stream to the burner arrangement and burning off the flammable gas are automatically initiated even after a prolonged standby period.

20. The method as defined in claim 19, wherein the steps are automatically initiated upon receiving the waste gas stream at a waste gas inlet pipe above a threshold pressure detected by the waste gas pressure sensor.

21. The method as defined in claim 18, wherein the step of burning off the flammable gas includes creating a flame having a substantially cordiform pattern.