Gas-fired boiler burner is a device that converts combustible components of fuel and oxygen in air into heat energy after fully mixing combustion. The oxygen required for fuel combustion comes from air, the volume percentage of oxygen in air is about 21%, and the theoretical air required for full combustion of 1 m3 natural gas in standard state is about 9.64 m3. However, the atmospheric pressure, air density and oxygen content in high altitude areas will be different from the standard state with the change of altitude.
As altitude increases, atmospheric pressure decreases, air density decreases and oxygen content decreases. Because the oxygen content in the air has changed, the theoretical air volume value calculated under the standard state is not suitable for the calculation of high altitude areas.
The ratio of the relative oxygen density at different altitudes to the standard oxygen density is equal to the unit volume oxygen of the two.
The mass ratio of air content, which is actually the revised value of actual air quantity required for combustion at different altitudes, is K= p0'/p0.
Formula: K-plateau correction coefficient; oxygen density under p0-P-standard condition, kg/m3.
Altitude Correction Value of Commonly Used Altitude (15℃)
Elevation H(m) 1O00 2O00 3O00 4O00
Plateau correction coefficient K 0.908 0.823 0.744 0.6
Oil-fired and gas-fired boilers are usually equipped with imported burners, which have their own blowers. Its output characteristics can be obtained from the characteristic curve of each model. The abscissa in the figure is the output power of the burner and the longitudinal coordinate is the pressure of the blower. For a point on the characteristic curve, the abscissa value represents not only the output power of the burner, but also the amount of air that the blower carried by the burner can supply for the complete combustion of fuel corresponding to the output power. The longitudinal coordinate value is the ability of the burner to overcome the total resistance of the flue gas side of the boiler under the output power condition. Therefore, when burners are used in plain or near standard conditions, we usually follow the following steps to determine the type of burner:
(1) Calculating the output power of burner Qb=Q/η
Type: Q is boiler rated output power, MW; η is boiler thermal efficiency.
(2) Determine the total resistance of flue gas side of matching boilers △P
(3) Check the pressure of blower in burner
According to the burner characteristic curve, from the output power Qb upward drawing line intersects with the characteristic curve at a point, the burner type corresponding to the P >△P characteristic curve is selected to complete the burner selection. Because the altitude correction coefficient K is less than 1, that is, the oxygen content in the air is only equal to K times of the standard state, the air quantity corresponding to Q/k point on the characteristic curve can satisfy the complete combustion of fuel quantity when the output power of the burner is Qb, and the longitudinal coordinate value of this point must be greater than the total resistance △P of the flue gas side of the boiler. The selection steps of burners under plateau conditions are as follows:
(1) Calculating Plateau Correction Coefficient K = p0'/p0
(2) Calculating the actual output power of the burner Qb =Q/η
(3) Calculating the output power of the burner when it meets the plateau air volume
Qbh=Q／η／K
(4) Check the pressure of burner blower
According to the burner characteristic curve, a point Pm intersecting the characteristic curve from Qbh upward is obtained. The burner type corresponding to Pm>△P characteristic curve is selected, that is, the burner type selection under plateau operating conditions is completed.
