Draft control method and apparatus for material processing plants

In a material processing apparatus having a burner supplied with fuel and air, means to establish an open chamber through which material to be processed is passed into contact with a flame of combustion products extending into said chamber from said burner, a draft exhaust system for maintaining said chamber under a negative pressure adequate to ensure a continuous flow of gas through said chamber and to discharge to the atmosphere, as stack gases, the products of fuel combustion and other gaseous materials, the improvement comprising:

• means for measuring the percent oxygen in said stack gases;
• means for measuring the carbon monoxide content of said stack gases in reference to the percent oxygen in said stack gases;
• and
• means for varying the draft of said exhaust gas system to maintain the carbon monoxide content within a predetermined maximum level and to obtain maximum combustion efficiency of fuel supplied to said burner, said means for varying the draft of said exhaust system comprising:
• means for correcting the measured carbon monoxide content in reference to a predetermined stack gas oxygen percentage to obtain a corrected CO content;
• means for determining when said corrected CO content exceeds a predetermined maximum allowable CO content;
• and
• means for trimming said draft to reduce the CO content in said stack gases when said corrected CO content exceeds said predetermined maximum allowable CO content in response to deviation of the measured oxygen percentage from an ideal percentage.

In a material processing apparatus having a burner supplied with fuel and air, the air supplied to said burner being less than that required for complete combustion of said fuel, means to establish an open chamber through which material to be processed is passed into contact with a flame of combustion products extending into said chamber from said burner, a draft exhaust system for maintaining said chamber under a negative pressure adequate to ensure a continuous flow of gas through said chamber and to discharge to the atmosphere, as stack gases, the products of fuel combustion and other gaseous materials, the improvement comprising:

• means for measuring the percent oxygen in said stack gases;
• means for measuring the carbon monoxide content of said stack gases in reference to the percent oxygen in said stack gases;
• and
• means for varying the draft of said exhaust gas system to maintain the carbon monoxide content within a predetermined maximum level and to obtain maximum combustion efficiency of fuel supplied to said burner, wherein said means for varying the draft of said exhaust system operates to draw into said chamber, the remainder of air needed for complete combustion of fuel.

In a material processing apparatus having a burner supplied with fuel and air, means to establish an open chamber through which material to be processed is passed into contact with a flame of combustion products extending into said chamber from said burner, a draft exhaust system for maintaining said chamber under a negative pressure adequate to ensure a continuous flow of gas through said chamber and to discharge to the atmosphere, as stack gases, the products of fuel combustion and other gaseous materials, the improvement comprising:

• means for measuring the percent oxygen in said stack gases;
• means for measuring the carbon monoxide content of said stack gases in reference to the percent oxygen in said stack gases;
• means for varying the draft of said exhaust gas system to maintain the carbon monoxide content within a predetermined maximum level and to obtain maximum combustion efficiency of fuel supplied to said burner;
• and
• means defining a leakage source of tramp air between said chamber and said draft exhaust system, said means for varying the draft of said exhaust system operating to minimize the leakage of tramp air into said exhaust system.