Apparatus and method for cleaning gas streams from biomass combustion

1. A horizontal scrubber system for removing sulfur dioxide and particulate matter from a gas stream comprising:

a housing including an inlet configured to receive a gas stream derived from the combustion of sugar cane bagasse and an outlet, wherein a bulk flow of the gas stream flows substantially horizontally from said inlet to said outlet;

a manifold of liquid nozzles disposed within said housing and configured to provide a spray of liquid droplets in a co-current orientation to said gas stream; and

an array of tubular members oriented adjacent said manifold of liquid nozzles;

wherein each individual nozzle included among said manifold of liquid nozzles is substantially centered with respect to a respective tubular member of said array of tubular members;

wherein the tubular members of said array of tubular members extend lengthwise in a direction substantially parallel to the bulk flow of the gas stream.

2. The horizontal scrubber system of claim 1 wherein the tubular members of said array of tubular members include circular walls with a substantially uniform cross section along their length.

3. The horizontal scrubber system of claim 1 wherein the tubular members of said array of tubular members are arranged in a grid of rows and columns.

4. The horizontal scrubber system of claim 1 wherein the tubular members of said array of tubular members are packed together in a closest packing geometry.

5. The horizontal scrubber system of claim 1 wherein said manifold of liquid nozzles is offset from said array of tubular members; and

wherein said nozzles are configured to provide a cone of liquid spray, the spray from adjacent nozzles intersecting outside of respective openings of respective tubular members of said array of tubular members.

6. The horizontal scrubber system of claim 1 wherein said manifold of liquid nozzles is offset from said array of tubular members; and

wherein said nozzles are configured to provide a cone of liquid spray that directs fluid inside of respective openings of respective tubular members of said array of tubular members.

7. The horizontal scrubber system of claim 1 wherein the tubular members of said array of tubular members have a substantially circular cross section with a diameter of about 15 inches to about 25 inches;

wherein a length of the tubular members of said array of tubular members is between about 2 feet to about 5 feet.

8. The horizontal scrubber system of claim 1 wherein said outlet includes a cross sectional area that is up to about 50% greater than that of said inlet.

9. The horizontal scrubber system of claim 1 wherein said outlet includes a cross sectional area that is about 10% to about 40% greater than that of said inlet.

10. A system for processing flue gas comprising:

an electrostatic precipitator configured to receive an exhaust gas stream from a biomass boiler;

a manifold of liquid nozzles;

a housing including an upstream and a downstream flow path that is substantially horizontal;

wherein said manifold of liquid nozzles is disposed within the upstream flow path of said housing;

wherein the manifold of liquid nozzles is configured to provide scrubber liquid in a co-current orientation to said exhaust gas stream; and

an array of tubular members oriented adjacent said manifold of liquid nozzles and configured to receive said scrubber liquid and said gas stream;

wherein tubular members of said array of tubular members include substantially circular walls with a cross sectional diameter of between about 15 inches to about 25 inches;

wherein tubular members of said array of tubular members have a length of about 2 feet to about 5 feet; and

a demister disposed along the downstream flow path of said housing and configured to remove said scrubber liquid from the exhaust gas stream.

11. The system of claim 10 further comprising one or more spray bars located between said electrostatic precipitator and said manifold of liquid nozzles.

12. The system of claim 10 wherein the downstream flow path of said housing includes a cross sectional area that is up to about 50% greater than a cross sectional area of said upstream flow path of said housing.

13. A method of cleaning an exhaust gas stream derived from combustion of biomass comprising:

directing exhaust gas from a biomass boiler to an electrostatic precipitator for treatment and removal of particulate matter;

directing the exhaust gas past a nozzle array configured to spray a scrubbing liquid into said exhaust gas;

wherein the nozzle array is aligned adjacent to a group of low flow resistance tubular members;

directing the exhaust gas and scrubbing liquid through said group of tubular members;

wherein the tubular members are configured to encourage mixing of the exhaust gas with the scrubbing liquid to produce a mixture of cleaned gas and contaminated scrubbing liquid; and

separating the cleaned gas from the contaminated scrubbing liquid.

14. The method of claim 13 wherein said biomass is sugar cane bagasse.

15. The method of claim 13 wherein said tubular members comprise cylindrical tubes of substantially uniform cross section of between about 15 inches and about 25 inches in diameter and having a length of about 2 feet to about 5 feet.

16. The method of claim 15 further comprising directing the mixture of cleaned gas and contaminated scrubbing liquid through a housing positioned adjacent said low flow resistance tubular members;

wherein said housing increases in cross sectional area by up to about 50% along the flowpath for the cleaned gas; and

wherein said housing and said low flow resistance tubular members are configured to increase a drop in pressure across said low flow resistance tubular members.