Split pass economizer bank with integrated water coil air heating and feedwater biasing
View Patent ↗An apparatus for using a water coil air heater with a single bank economizer. A boiler economizer arrangement includes an economizer bank which has separate hot pass bank and cold pass bank economizer portions in a parallel arrangement, each facing the same flow of hot flue gas. Feedwater enters the cold pass bank economizer where it is heated by the hot flue gas, and then flows to a water coil air heater away from the hot flue gas. The feedwater dissipates heat energy in the water coil air heater which may be used to heat air bound for combustion. The feedwater continues into the hot pass bank economizer portion of the economizer arrangement where it absorbs additional heat from the flue gas. The heated feedwater flows out of the economizer arrangement and may be subject to additional heating by a boiler or other heat exchanger.
1. A boiler economizer arrangement comprising:
a single cavity for conveying heated flue gas flow, the single cavity including a first economizer side wall and a second economizer side wall, wherein the first and second economizer side walls are opposite each other to define the single cavity therebetween;
the single cavity having an upstream direction which receives a stream of heated flue gas flow, and a downstream direction for exiting flue gas;
an economizer bank stretching substantially from the first economizer side wall to the second economizer side wall, the economizer bank comprising a cold pass bank economizer and a hot pass bank economizer, and wherein the cold pass bank and the hot pass bank are positioned in a parallel arrangement relative to the stream of heated flue gas such that each bank receives a different portion of the stream of heated flue gas;
a split collection header comprising a hot pass split collection header for the hot pass bank economizer, a cold pass split collection header for the cold pass bank economizer, the cold pass split collection header extending between a first end and a second end, the hot pass split collection header extending between a third end and a fourth end, and a split at a location between the second end and the third end cold pass split collection header and the hot pass split collection header, said location being within the single cavity such that a portion of the stream of heated flue gas passes through the split;
a water coil air heater positioned outside of the cavity and adapted for transferring heat from a flow of feedwater flowing inside the water coil air heater to a stream of air outside of the water coil air heater; a feedwater inlet for receiving the flow of feedwater into the economizer arrangement from outside the cavity;
a feedwater outlet for the flow of feedwater exiting the economizer arrangement; and at least one valve adapted for controlling the flow of feedwater between the cold pass bank economizer and the water coil air heater;
wherein the economizer arrangement is adapted to route the flow of feedwater from the feedwater inlet, then to the cold pass bank economizer, then outside the cavity to the water coil air heater, then back into the cavity into the hot pass bank economizer, and then to the feedwater outlet and out of the economizer arrangement;
wherein the flow of feedwater is routed away from the economizer bank to the water coil air heater at the split between the cold pass split collection header and the hot pass split collection header; and
wherein the cold pass bank economizer and the hot pass bank economizer are connected in series relative to the flow of feedwater.
2. The economizer arrangement of claim 1 , wherein the cold pass bank economizer is adjacent to the first economizer side wall and the hot pass bank economizer is adjacent to the second economizer side wall.
3. An economizer arrangement comprising:
a single cavity for conveying heated gas flow, the single cavity having a first economizer side wall and a second economizer side wall to define the single cavity therebetween;
the single cavity having an upstream direction which receives a stream of heated gas and a downstream direction for exiting gas flow;
an economizer bank stretching substantially from the first economizer side wall to the second economizer side wall, the economizer bank comprising a plurality of sections including at least a cold pass bank economizer and a hot pass bank economizer, and wherein the cold pass bank and the hot pass bank are positioned in a parallel arrangement such that each bank receives a different portion of the stream of heated gas;
a split collection header comprising a hot pass split collection header for the hot pass bank economizer, a cold pass split collection header for the cold pass bank economizer, and a split at a location between the cold pass split collection header and the hot pass split collection header, said location being within the single cavity such that a portion of the stream of heated gas passes through the split;
a water coil air heater positioned outside of the cavity and adapted for transferring heat from a flow of feedwater flowing inside the water coil air heater to a stream of air outside of the water coil air heater;
wherein the economizer arrangement is adapted to route the flow of feedwater into the cold pass bank economizer, then outside the cavity to the water coil air heater, then back into the cavity into the hot pass bank economizer, and then out of the economizer arrangement;
wherein the flow of feedwater is routed away from the economizer bank to the water coil air heater at the split between the cold pass split collection header and the hot pass split collection header; and
wherein the cold pass bank economizer and the hot pass bank economizer are connected in series relative to the flow of feedwater.
4. The economizer arrangement of claim 3 , further comprising: a feedwater inlet for receiving the flow of feedwater entering the economizer arrangement; and a feedwater outlet for the flow of feedwater exiting the economizer arrangement.
5. The economizer arrangement of claim 3 , wherein the water coil air heater is adapted to warm the stream of air on its way to a furnace.
6. The economizer arrangement of claim 3 , further comprising at least one valve adapted for controlling the flow of feedwater including between the cold pass bank economizer and the water coil air heater.
7. The economizer arrangement of claim 3 , wherein the single cavity is part of a boiler, and wherein the first economizer side wall and the second economizer side wall are directly opposite each other.
8. The economizer arrangement of claim 7 , wherein the cold pass bank economizer is adjacent to the first side wall and the hot pass bank economizer is adjacent to the second side wall.