Heat transfer unit for steam generation and gas preheating

1. A heat transfer unit comprising:

a shell;

a boiler;

a gas preheater wherein said gas preheater comprises a plurality of big coils;

a central tubing; and a rolled fin heat exchanger;

a first annular space;

a second annular space;

a plurality of inlets; and

a plurality of outlets wherein said heat transfer unit is located downstream of a combustor, wherein said combustor is an anode tailgas oxidizer.

2. The heat transfer unit of claim 1 , wherein said boiler comprises a boiler reservoir; a bell shape evaporator; a bell shape empty space zone; and a plurality of small coils.

3. The heat transfer unit of claim 1 , wherein said plurality of inlets comprises a unit inlet; and a water inlet.

4. The heat transfer unit of claim 1 , wherein said plurality of outlets comprises an exhaust outlet; a steam outlet; and a gas outlet.

5. The heat transfer unit of claim 4 , wherein exhaust from exhaust outlet is piped to reforming reactor for direct preheating of reformer bed and shift bed during start-up of said reforming reactor.

6. The heat transfer unit of claim 4 , wherein exhaust from exhaust outlet is piped to a secondary air preheater associated with said combustor.

7. A method for operating a heat transfer unit comprising:

providing a boiler and a gas preheater integrated into said heat transfer unit;

permitting hot exhaust gas to enter said heat transfer unit via a unit inlet;

routing hot exhaust gas to make a first pass through said heat transfer unit;

routing hot exhaust gas to make a second pass through said heat transfer unit;

routing hot exhaust gas to make a third pass through said heat transfer unit wherein said third pass comprises routing hot exhaust to flow upward through a rolled fin heat exchanger; and

permitting hot exhaust gas to exit said heat transfer unit via an exhaust outlet.

8. The method for operating the heat transfer unit of claim 7 , wherein said first pass comprises: routing hot exhaust gas to contact a boiler reservoir; deflecting hot exhaust gas into a first annular space; and routing hot exhaust gas to flow upward and to contact a plurality of small coils.

9. The method for operating the heat transfer unit of claim 7 , wherein said second pass comprises: routing hot exhaust gas to flow downward into a second annular space; and routing hot exhaust gas to contact a plurality of big coils.

10. The method for operating the heat transfer unit of claim 7 , further comprising providing hot exhaust gas from a combustor.

11. The method for operating the heat transfer unit of claim 10 , further comprising routing hot exhaust gas from said exhaust outlet to a secondary air preheater associated with said combustor.

12. The method for operating the heat transfer unit of claim 10 , further comprising routing hot exhaust gas from said exhaust outlet to a reforming reactor to directly preheat reformer bed and shift bed during start-up of said reforming reactor.

13. The method for operating the heat transfer unit of claim 10 , wherein said combustor is an anode tailgas oxidizer.