AUTOMATED SETUP PROCESS FOR METERED COMBUSTION CONTROL SYSTEMS

• US 20110212404A1
• Filed: 11/25/2008
• Published: 09/01/2011
• Est. Priority Date: 11/25/2008
• Status: Active Grant

• Current Assignee: UTC Fire & Security Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: UTC Fire & Security Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Lelic, Muhidin A., Fan, Junqiang
• Granted Patent: US 9,028,245 B2
• Time in Patent Office: Days
• US Class Current: 431/12
• CPC Class Codes: F23N 1/022 using electronic means
• CPC Class Codes: F23N 1/082 using electronic means
• CPC Class Codes: F23N 2223/44 Optimum control
• CPC Class Codes: F23N 2225/18 feedwater temperature
• CPC Class Codes: F23N 2225/19 outlet temperature water heat-exchanger
• CPC Class Codes: F23N 2227/20 Calibrating devices
• CPC Class Codes: F23N 2233/08 with variable speed
• CPC Class Codes: F23N 2235/06 at the air intake
• CPC Class Codes: F23N 2235/14 electromagnetically operated
• CPC Class Codes: F23N 2237/26 oxygen-air ratio
• CPC Class Codes: F23N 2241/04 Heating water
• CPC Class Codes: F23N 5/006 the detector being sensitive to oxygen

Abstract

A method is provided for the automated setup of a metered combustion control system for controlling operation of a boiler combustion system. The automated setup process includes both commissioning and controller tuning, rather than tuning the carbon monoxide and/or oxygen trim controller after the commissioning process has been completed. The oxygen trim controller or the carbon monoxide trim controller is used to identify the air/fuel ratio.

Claims

1. A setup method for a metered combustion control system for controlling operation of a boiler combustion system having a burner, a fuel flow control device and a fuel flow controller operatively associated with said fuel flow control device for supplying fuel to said burner and an air flow control device and an air flow controller operatively associated with said air flow control device for supplying air to said burner, the method comprising the steps of:

identifying a lower limit air/fuel mass flow ratio and an upper limit air/fuel mass flow ratio through a negative feedback control method at a plurality of selected firing rate points between a minimum firing rate and a maximum firing rate;

calculating a setpoint air/fuel ratio as the average of the lower limit air/fuel ratio and the upper limit air/fuel ratio at each selected firing rate point of the plurality of firing rate points;

developing a relationship between the average air/fuel ratio and firing rate between the minimum firing rate and the maximum firing rate;

tuning the air flow controller and the fuel flow controller; and

tuning an oxygen trim controller and a carbon monoxide trim controller.

2. A setup method as recited in claim 1 wherein the negative feedback control method used in identifying a lower limit air/fuel mass flow ratio and an upper limit air/fuel mass flow ratio at each selected firing rate point comprises a carbon monoxide trim control loop.

3. A setup method as recited in claim 1 wherein the negative feedback control method used in identifying a lower limit air/fuel mass flow ratio and an upper limit air/fuel mass flow ratio at each selected firing rate point comprises an excess oxygen trim control loop.

4. A setup method as recited in claim 1 wherein the step of identifying a lower limit air/fuel mass flow ratio and an upper limit air/fuel mass flow ratio through a negative feedback control method at a plurality of selected firing rate points between a minimum firing rate and a maximum firing rate comprises identifying a minimum and a maximum air flow rate setpoint at each selected firing rate at a respective selected fuel flow control device controller setting associated with said each selected firing rate.

5. A setup method as recited in claim 1 wherein the step of identifying a lower limit air/fuel mass flow ratio and an upper limit air/fuel mass flow ratio through a negative feedback control method at a plurality of selected firing rate points between a minimum firing rate and a maximum firing rate comprises identifying a minimum and a maximum fuel flow rate setpoint at each selected firing rate at a respective selected air flow control device controller setting associated with said each selected firing rate.

6. A setup method for a metered combustion control system for controlling operation of a boiler combustion system having a burner, a fuel flow control device and a fuel flow control device controller operatively associated with said fuel flow control device for supplying fuel to said burner and an air flow control device and an air flow control device controller operatively associated with said air flow control device for supplying air to said burner, the method including defining a lower limit air/fuel mass flow ratio and an upper limit air/fuel mass flow ratio at a plurality of selected firing rate points between a minimum firing rate and a maximum firing rate, said setup method comprising the steps of:

(a) selecting a firing rate point between the minimum firing rate and the maximum firing rate;

(b) at a initial setting of the fuel flow control device controller associated with the selected firing rate point, selecting a first setting of the air flow control device controller and incrementally resetting the air flow control device controller;

(c) operating the burner at the selected firing rate point at each air flow control device controller setting in step (b) to generate a flue gas and measuring at each air flow control device controller setting;

the mass air flow, the oxygen content in the flue gas, and the carbon monoxide content in the flue gas;

(d) identifying and saving a lower limit air/fuel ratio at the selected firing rate at which the measured carbon monoxide content in the flue gas is equal to an upper limit carbon monoxide target level;

(e) identifying and saving an upper limit air/fuel ratio at the selected firing rate at which the measured carbon monoxide content in the flue gas is equal to a lower limit carbon monoxide target level;

(f) repeating steps (a) through (e) at a plurality of selected firing rate points between a minimum firing rate and a maximum firing rate; and

(g) calculating a set point air/fuel ratio as the average of the lower limit air/fuel ratio and the upper limit air/fuel ratio at each selected firing rate point of the plurality of selected firing rate points and developing a relationship between the average air/fuel ratio and firing rate between the minimum firing rate and the maximum firing rate.

7. A method as recited in claim 6 wherein at steps (d) and (e) a negative feedback control loop is used to identifying the maximum and minimum air flow setpoint at each firing rate.

8. A method as recited in claim 7 wherein the negative feedback control loop comprises a carbon monoxide trim control loop.

9. A method as recited in claim 7 wherein the negative feedback control loop comprises an oxygen trim control loop.

10. A method as recited in claim 6 further comprising the steps of:

comparing the measured oxygen content at the air flow control device controller setting at which the measured carbon monoxide content in the flue gas is equal to an upper limit carbon monoxide target level to a lower limit oxygen target level;

if the measured oxygen content is less than the lower limit oxygen target level, incrementally resetting the air flow control device controller setting until the measured oxygen content exceeds the lower limit oxygen target level; and

identifying and saving the air/fuel ratio at the air flow control device controller setting until the measured oxygen content first exceeds the lower limit oxygen target level as the lower limit air/fuel ratio at the selected firing rate point.

11. A setup method for a metered combustion control system for controlling operation of a boiler combustion system having a burner, a fuel flow control device and a fuel flow control device controller operatively associated with said fuel flow control device for supplying fuel to said burner and an air flow control device and an air flow control device controller operatively associated with said air flow control device for supplying air to said burner, the method including defining a lower limit air/fuel mass flow ratio and an upper limit air/fuel mass flow ratio at a plurality of selected firing rate points between a minimum firing rate and a maximum firing rate, said setup method comprising the steps of:

(a) selecting a first firing rate point;

(b) at a initial setting of the fuel flow control device controller associated with the selected firing rate point, selecting a first setting of the air flow control device controller and incrementally resetting the air flow control device controller;

(c) operating the burner at the selected firing rate point at each air flow control device controller setting in step (b) to generate a flue gas and measuring at each air flow control device controller setting;

the mass air flow, the oxygen content in the flue gas, and the carbon monoxide content in the flue gas;

(d) identifying at the selected firing rate;

a model relating;

the air mass flow to the air flow control device controller setting, a model relating the oxygen content in the flue gas to the air flow control device controller setting, and a model relating the carbon monoxide content in the flue gas to the air flow control device controller setting;

(e) calculating a set of control parameters for an air mass flow rate feedback loop controller, for a oxygen trim feedback loop controller, and for a carbon monoxide trim feedback loop controller;

(f) resetting the air flow control device controller at the first setting and incrementally resetting the fuel flow control device controller;

(g) measuring the fuel mass flow at each fuel flow control device controller setting in step (f) and identifying a model relating the fuel flow mass to the fuel flow control device controller setting;

(h) calculating a set of control parameters for a fuel mass flow rate feedback loop controller;

(i) selecting a new firing rate point;

(j) at a initial setting of the fuel flow control device controller associated with the selected firing rate point, selecting a first setting of the air flow control device controller and incrementally resetting the air flow control device controller;

(k) operating the burner at the selected firing rate point at each air flow control device controller setting in step (b) to generate a flue gas and measuring at each air flow control device controller setting;

the mass air flow, the oxygen content in the flue gas, and the carbon monoxide content in the flue gas;

(l) identifying and saving a lower limit air/fuel ratio at the selected firing rate at which the measured carbon monoxide content in the flue gas is equal to an upper limit carbon monoxide target level;

(m) identifying and saving an upper limit air/fuel ratio at the selected firing rate at which the measured carbon monoxide content in the flue gas is equal to a lower limit carbon monoxide target level;

(n) repeating steps (i) through (m) at a plurality of selected firing rate points between a minimum firing rate and a maximum firing rate; and

(o) calculating a set point air/fuel ratio as the average of the lower limit air/fuel ratio and the upper limit air/fuel ratio at each selected firing rate point of the plurality of selected firing rate points and developing a relationship between the average air/fuel ratio and firing rate between the minimum firing rate and the maximum firing rate.

12. A method as recited in claim 11 wherein at steps (l) and (m) a negative feedback control loop is used to identifying the maximum and minimum air flow setpoint at each firing rate.

13. A method as recited in claim 12 wherein the negative feedback control loop comprises a carbon monoxide trim control loop.

14. A method as recited in claim 12 wherein the negative feedback control loop comprises an oxygen trim control loop.

15. A method as recited in claim 11 wherein at steps (l) and (m), the method includes the further step of selectively activating one of a negative feedback oxygen trim control and a negative feedback carbon monoxide trim control for use in identifying the maximum and minimum air flow setpoint at each firing rate.