SO3 related Automation and Controls
Breen Energy Solutions has developed a set of advanced technologies to help manage SO3 related Balance-of-Plant impacts (BOP). The output of the AbSensor-SO3/AbS device is fed into these control processes for optimized systems controls.
Rotating Air Heater Thermodynamic Model
The residual enthalpy in the flue gas post-economizer is extracted into the Primary and Secondary Air using Air Pre Heaters. These Air Heaters can be of a rotating basket type or a tubular design. In the rotating basket design there are 2-3 layers of baskets filled with metal elements. These baskets rotate between the Flue gas duct and the air duct, picking up heat on the flue gas side and giving up heat on the air side. The typical flue gas temp at the inlet to the air heater is about 650-750 DegF. The typical flue gas temp exiting the air heater is in the 275 to 350 DegF. The air flow direction is counter to the flue gas flow. The typical air inlet temp is 60 to 120 DegF based on local ambient temperatures and the air outlet temperature is typically in the 550 to 650 DegF range.
While it is possible to measure the Flue gas and Air temperature at the inlet and outlet of the Air heater, it is not possible to measure the actual metal matrix temperature in the Air Heater. The sulfur condensables in the flue gas condense on any surface that is at a temperature below the kinetic dewpoint of the condensables concentration. The depth to which these condensables deposit determines if the Air Heater will foul over time causing balance-of-plant impacts.
EPRI, in association with Lehigh University, has developed a thermodynamic heat transfer model of the rotating air heater which takes in the physical dimensions and properties of the Air heater and then based on the flow rates and temperatures of the Air and Gas, can calculate the 2-dimensional metal matrix temperature grid. Breen Energy has licensed this technology and implemented this in a real-time application that can communicate with the Plant DCS or PI system and calculate these temperatures in real time.
By overlaying the AbSensor - Condensables device reported Formation and Evaporation temperatures we can now report the estimated depth at which the condensate is beginning to form and foul the Air Heater.
Heat Rate Improvement System - Average Cold End Temp (ACET) Control
Once the Air Heater Thermodynamic Model reports the estimated depth at which the condensables are forming, the Heat Rate Improvement system can then adjust the Average Cold End Temperature to maintain the deposition depth within the effective range of the cold end Air Heatersootblower. This can be accomplished by manipulating Air Side Steam coils that keep the Air Inlet temperature artificially higher or, if equipped, by adjusting the Air Bypass dampers that control the amount of air that flows through the Air Heater. Typically, the steam coils and air bypass dampers are set conservatively to keep the Air Heater away from fouling, however this conservatism has a negative impact on Unit Heat rate as the stack temperature and stack heat losses increase..
The Breen heat rate improvement system minimizes stack heat losses by estimating the condensation depth and keeping it within theeffective range of the air heater sootblower.
It is also possible in many cases to influence the Formation and Evaporation temperatures by lowering the condensables fouling potential. In the case of an Ammonium Bisulfate condensable, it is possible to mitigate fouling potential by reducing SCR/SNCR Ammonia/Urea flow. The Breen Heat Rate - Ammonia optimization system can adjust the Ammonia/Urea injection rate in addition to manipulating the ACET. One has an impact on NOx tons reduced and the other has an impact on Heat-Rate. The power producer is given the ability to balance these objectives.
Dynamic Speed Controlled (DySC) Air Heater Sootblowing Control System
Air Heaters are designed to allow some level of sulfuric acid to condense in the cold end and use air or steam sootblowers to clean the cold end. The original air heaters were designed based on a lower level of estimated coal sulfur. And they were certainly not designed to handle higher temp condensables such as Ammonium Bisulfate.
A typical sootblower cycle, when initiated, moves at a constant speed from the outermost diameter of the Air Heater to the Innermost diameter of the Air Heater. As the sootblower lance moves across the metal basket channels, the sootblowing media penetrates with pressure thereby cleaning the channels. As the Air Heater is rotating, the stream of media gets clipped at each channel interface.
There are two fundamental flaws in this standard design: 1) Thesootblower lance does not station itself at a particular position through the entire rotation of the Air Heater. This results in a spiral cleaning action as the sootblower travels while the Air heater rotates and 2) the tangential velocity at the sootblower position is 5 to 10 times higher at the outermost diameter as it is at the innermost diameter because the circumference is larger. More distance traveled in the same time elapsed results in less residence time for cleaning the channels further away from the air heater's center axis. This reduces media penetration and therefore allows fouling depositions to remain onthe Air Heater baskets towards the outside of the Air Heater.
The DySC system solves this problem by a) moving in an indexed fashion by a small increment equal to the cleaning zone of the lance, b) staying stationary at each index position for one full rotation of the Air Heater and c) adjusting (lowering) the Air Heater rotational speed to maintain uniform tangential velocity and therefore maximum media penetration. This results in full cleaning of the cold end all the way through from the innermost diameter to the outermost diameter in the most time-effective manner.
The DySC system is designed to use a dual-redundant Vector drive setup with various safeguards to ensure that under all circumstances, the Air Heater continues to turn.
Breen Energy Solutions has developed a set of advanced technologies to help manage SO3 related Balance-of-Plant impacts (BOP). The output of the AbSensor-SO3/AbS device is fed into these control processes for optimized systems controls.
Rotating Air Heater Thermodynamic Model
The residual enthalpy in the flue gas post-economizer is extracted into the Primary and Secondary Air using Air Pre Heaters. These Air Heaters can be of a rotating basket type or a tubular design. In the rotating basket design there are 2-3 layers of baskets filled with metal elements. These baskets rotate between the Flue gas duct and the air duct, picking up heat on the flue gas side and giving up heat on the air side. The typical flue gas temp at the inlet to the air heater is about 650-750 DegF. The typical flue gas temp exiting the air heater is in the 275 to 350 DegF. The air flow direction is counter to the flue gas flow. The typical air inlet temp is 60 to 120 DegF based on local ambient temperatures and the air outlet temperature is typically in the 550 to 650 DegF range.While it is possible to measure the Flue gas and Air temperature at the inlet and outlet of the Air heater, it is not possible to measure the actual metal matrix temperature in the Air Heater. The sulfur condensables in the flue gas condense on any surface that is at a temperature below the kinetic dewpoint of the condensables concentration. The depth to which these condensables deposit determines if the Air Heater will foul over time causing balance-of-plant impacts.
EPRI, in association with Lehigh University, has developed a thermodynamic heat transfer model of the rotating air heater which takes in the physical dimensions and properties of the Air heater and then based on the flow rates and temperatures of the Air and Gas, can calculate the 2-dimensional metal matrix temperature grid. Breen Energy has licensed this technology and implemented this in a real-time application that can communicate with the Plant DCS or PI system and calculate these temperatures in real time.
By overlaying the AbSensor - Condensables device reported Formation and Evaporation temperatures we can now report the estimated depth at which the condensate is beginning to form and foul the Air Heater.
Heat Rate Improvement System - Average Cold End Temp (ACET) Control
Once the Air Heater Thermodynamic Model reports the estimated depth at which the condensables are forming, the Heat Rate Improvement system can then adjust the Average Cold End Temperature to maintain the deposition depth within the effective range of the cold end Air Heatersootblower. This can be accomplished by manipulating Air Side Steam coils that keep the Air Inlet temperature artificially higher or, if equipped, by adjusting the Air Bypass dampers that control the amount of air that flows through the Air Heater. Typically, the steam coils and air bypass dampers are set conservatively to keep the Air Heater away from fouling, however this conservatism has a negative impact on Unit Heat rate as the stack temperature and stack heat losses increase..The Breen heat rate improvement system minimizes stack heat losses by estimating the condensation depth and keeping it within theeffective range of the air heater sootblower.
It is also possible in many cases to influence the Formation and Evaporation temperatures by lowering the condensables fouling potential. In the case of an Ammonium Bisulfate condensable, it is possible to mitigate fouling potential by reducing SCR/SNCR Ammonia/Urea flow. The Breen Heat Rate - Ammonia optimization system can adjust the Ammonia/Urea injection rate in addition to manipulating the ACET. One has an impact on NOx tons reduced and the other has an impact on Heat-Rate. The power producer is given the ability to balance these objectives.
Dynamic Speed Controlled (DySC) Air Heater Sootblowing Control System
Air Heaters are designed to allow some level of sulfuric acid to condense in the cold end and use air or steam sootblowers to clean the cold end. The original air heaters were designed based on a lower level of estimated coal sulfur. And they were certainly not designed to handle higher temp condensables such as Ammonium Bisulfate.A typical sootblower cycle, when initiated, moves at a constant speed from the outermost diameter of the Air Heater to the Innermost diameter of the Air Heater. As the sootblower lance moves across the metal basket channels, the sootblowing media penetrates with pressure thereby cleaning the channels. As the Air Heater is rotating, the stream of media gets clipped at each channel interface.
There are two fundamental flaws in this standard design: 1) Thesootblower lance does not station itself at a particular position through the entire rotation of the Air Heater. This results in a spiral cleaning action as the sootblower travels while the Air heater rotates and 2) the tangential velocity at the sootblower position is 5 to 10 times higher at the outermost diameter as it is at the innermost diameter because the circumference is larger. More distance traveled in the same time elapsed results in less residence time for cleaning the channels further away from the air heater's center axis. This reduces media penetration and therefore allows fouling depositions to remain onthe Air Heater baskets towards the outside of the Air Heater.The DySC system solves this problem by a) moving in an indexed fashion by a small increment equal to the cleaning zone of the lance, b) staying stationary at each index position for one full rotation of the Air Heater and c) adjusting (lowering) the Air Heater rotational speed to maintain uniform tangential velocity and therefore maximum media penetration. This results in full cleaning of the cold end all the way through from the innermost diameter to the outermost diameter in the most time-effective manner.
The DySC system is designed to use a dual-redundant Vector drive setup with various safeguards to ensure that under all circumstances, the Air Heater continues to turn.