Modulatable heat exchanger with restraint to avoid condensation

Claim 2

A modulatable heat exchanger system for cooling hot dustladen flue gas having an elevated dew point which comprises, a heat exchanger unit formed of a bank of tubes coupled to tube manifolds such that the bank of tubes communicates with a hot gas inlet and a hot gas outlet coupled respectively to said manifolds, each of said tubes being surrounded by a tube to provide annular spaces having manifolds communicating therewith through which air is circulated in said heat exchanger in concurrent flow with said hot flue gas, means for maintaining a flow of hot flue gas through said heat exchanger to a downstream line, a closed circuit air line including a blower for maintaining a flow of air through said heat exchanger in concurrent flow and heat exchanging relationship with said hot flue gas, first valve means for feeding fresh air into said air line when needed, first temperature-sensing means for sensing the temperature of the flue gas downstream of said heat exchanger, second valve means in said aiR line operable in accordance with the temperature sensed by said first temperature sensing means for controlling the rate of flow of said air through said heat exchanger according to the temperature sensed by said first temperatures-sensing means, second temperature-sensing means associated with a portion of the heat exchanger in contact with said flue gas for sensing the temperature of the heat exchanger at said portion, said second temperature-sensing means being operably coupled to said first valve means for controlling the feeding of fresh air to said air line, and a pressure-sensing device in said air line coupled to a third valve means comprising an exit air gas valve for opening said valve to expel air from said line when a pressure above a predetermined pressure is sensed in the air line, whereby the flow of air through the heat exchanger is independently controlled relative to the flow of said flue gas so as to maintain the temperature of said heat exchanger above the dew point of said hot flue gas during the cooling thereof in accordance with the temperature sensed by the temperaturesensing means of the system.

Claim 3

The heat exchanger system of claim 1, wherein, said second temperature-sensing means coupled to said first valve means is also operably coupled to a fourth valve means located in said air line, said fourth valve means being mechanically linked to first valve means, such that when said first valve means is caused to open in response to said second temperature-sensing means, the mechanically linked valve is caused to move towards the closed position, and when the first valve means is caused to move to the closed position, the mechanically linked valve is caused to move towards the open position.

Claim 4

The heat exchanger system of claim 1, wherein a manually operable valve means is coupled to the air line to provide a fixed maximum air flow setting for the system below which the air flow rate through the heat exchanger unit is automatically controlled.

Claim 5

The heat exchanger system of claim 1, including a heater coupled to a portion of the air line for preheating the air to a predetermined temperature, said air line portion being connected to said third air valve means for bleeding air from the system when the air pressure increases above the predetermined air pressure set point.

Claim 6

A modulatable heat exchanger system for cooling hot dust-laden flue gas having an elevated dew point which comprises, a heat exchanger formed of a vertical cylindrical shell containing a bank of tubes vertically disposed therein coupled to tube manifolds at opposite ends thereof such that the bank of tubes communicates with a hot gas inlet and a hot gas outlet coupled respectively to said manifolds, each of said tubes being surrounded by a tube to provide annular spaces having manifolds communicating therewith through which air is circulated in said heat exchanger in concurrent flow with said hot flue gas, means for maintaining a flow of hot flue gas through said heat exchanger to a downstream line, a closed circuit air line including a blower for maintaining a flow of air through said heat exchanger in concurrent flow and heat exchanging relationship with said hot flue gas, first valve means for feeding fresh air into said air line when needed and another valve means in said air line mechanically linked with said first valve means, such that when the first valve means opens, said other valve means closes and when said first valve means is caused to move to the closed position, the mechanically linked valve is caused to move towards the open position, first temperature-sensing means for sensing the temperature of the flue gas downstream of said heat exchanger, second valve means in said air line operable in accordance with the temperature sensed by said first temperature-sensing means for controlling the rate of flow of said air through said heat exchanger according to the temperature seNsed by said first temperature-sensing means, second temperature-sensing means associated with a portion of the heat exchanger in contact with said flue gas for sensing the temperature of the heat exchanger at said portion, said second temperature-sensing means being operably coupled to said first valve means for controlling the feeding of fresh air to said air line and for controlling the flow of air through said valve means mechanically linked to said first valve means, a manually operable valve means in said air circuit to provide a fixed maximum air flow setting to said air line, a heater coupled to a portion of said air line for preheating the air to a predetermined temperature, and a pressure-sensing device in said air line coupled to a third valve means comprising an exit air gas valve for opening said valve to expel heated air from said line when a pressure above a predetermined pressure is sensed in said line, whereby the flow of air through the heat exchanger is independently controlled relative to the flow of said flue gas so as to maintain the temperature of said heat exchanger at above the dew point of said hot flue gas during the cooling thereof in accordance with the temperature sensed by the temperature-sensing means of the system.

Claim 7

A modulatable heat exchanger system for cooling hot dust-laden flue gas having an elevated dew point which comprises, a heat exchanger formed of a vertical cylindrical shell containing a bank of tubes vertically disposed therein coupled to tube manifolds at opposite ends thereof such that the bank of tubes communicates with a hot gas inlet and a hot gas outlet coupled respectively to said manifolds, each of said tubes being surrounded by a tube to provide annular spaces having manifolds communicating therewith through which air is circulated in said heat exchanger in concurrent flow with said hot flue gas, means for maintaining a flow of hot flue gas through said heat exchanger to a downstream line, a closed circuit air line including a blower for maintaining a flow of air through said heat exchanger in concurrent flow and heat exchanging relationship with said hot flue gas, first valve means for feeding fresh air into said air line when needed and another valve means in said air line mechanically linked with said first valve means, such that when the first valve means opens, said other valve means closes and when said first valve means is caused to move to the closed position, the mechanically linked valve is caused to move towards the open position, first temperature-sensing means for sensing the temperature of the flue gas downstream of said heat exchanger, second valve means in said air line operable in accordance with the temperature sensed by said first temperature-sensing means for controlling the rate of flow of said air through said heat exchanger according to the temperature seNsed by said first temperature-sensing means, second temperature-sensing means associated with a portion of the heat exchanger in contact with said flue gas for sensing the temperature of the heat exchanger at said portion, said second temperature-sensing means being operably coupled to said first valve means for controlling the feeding of fresh air to said air line and for controlling the flow of air through said valve means mechanically linked to said first valve means, a manually operable valve means in said air circuit to provide a fixed maximum air flow setting to said air line, a heater coupled to a portion of said air line for preheating the air to a predetermined temperature, and a pressure-sensing device in said air line coupled to a third valve means comprising an exit air gas valve for opening said valve to expel heated air from said line when a pressure above a predetermined pressure is sensed in said line, whereby the flow of air through the heat exchanger is independently controlled relative to the flow of said flue gas so as to maintain the temperature of said heat exchanger at above the dew point of said hot flue gas during the cooling thereof in accordance with the temperature sensed by the temperature-sensing means of the system.

Claim 10

The method of claim 6, wherein as the input of fresh air into said air line is varied by means of said first valve means in response to the temperature-sensing means at the heat exchanger, the flow rate of the air in the air line is oppositely varied simultaneously through a valve means in said air line mechanically linked to said first valve means, such that as the fresh air input to the air line is being increased, the flow rate of the air in the air line through the mechanically linked valve is decreased and vice versa.

Claim 11

The method of claim 6, including the step of fixing the maximum flow rate of the air through the air line by means of a manually operable air valve in said air line.

Claim 12

The method of claim 6, including the step of heating the circulating air to a predetermined temperature.