How to choose a boiler burner

News     |      2023-11-10 16:07

Part One: Calculate the parameters required for the burner based on the boiler and fuel.

1. Determine relevant information about the boiler

• Boiler capacity and efficiency

• Furnace back pressure

• Fuel

• Burner fuel inlet pressure

2 .Calculate burner capacity. Burner capacity = Boiler capacity/efficiency

Example: Boiler capacity 6,500 kW, efficiency 90 % → Burner capacity = 6,500 kW / 0.9 = 7,220 kW.

3 .Gas burner: required gas flow [m3n/h] = (burner capacity [kW] x 3.6)/gas calorific value [MJ/m3n].

Example: Burner capacity = 7,220 kW → Required gas flow = (7,220 kWx 3.6)/35.8 MJ/m3n

= 726 m3n/h, where 35.8 MJ/m3n is the calorific value of natural gas.

4. Oil burner: Calculate the required oil flow rate [kg/h]. Required oil flow [kg/h] = (burner capacity [kW] x 3.6)/heating value of oil [MJ/kg].

Example: Required burner capacity = 7,220kW → Required oil flow = (7,220 kW x 3.6)/42.7 MJ/kg = 609

kg/h, of which 42.7MJ/kg is the calorific value of light oil.

5. Check that the external dimensions of the burner, especially those of the burner head, are suitable for the application; the length of the burner head should be such that when installed, the burner head is flush with the furnace wall or inside the furnace by approximately 10 to 20 mm.

6. Check the flame size in the flame size chart. Please note that the flames must not come into contact with the wall stove.

7. Accessory requirements must also be considered: gas pressure regulator, pumping unit, boiler thermostat/barostat.

Part 2. Common parameters and convenient algorithms

1. Burner capacity = boiler capacity/0.9 (when boiler efficiency is 90%)

2. Steam boiler: 1 ton/hour steam ≈ 700kW boiler capacity

3. Light oil: 1 kg/h ≈ 11.86 kW burner capacity

Calorific value 42.7 MJ/kg

4. Heavy oil: 1 kg/h ≈ 11.22 kW burner capacity

Calorific value 40.5MJ/kg

5. Natural gas: 1 cubic meter n/h ≈ 10 kW burner capacity

Calorific value 35.84 MJ/m3n

6. Combustion air volume:

• Gas burner: required combustion air volume

The burner capacity per 10kW is 12~13m3/H.

• Oil burner: required combustion air volume

The oil burned per kilogram [kg/h] is 13.5 m3/H.

7. Oil pumping, filtering and preheating devices

Required when burning heavy fuel oil. When the burner capacity is greater than 2MW, a transfer pump unit is always required, including when used with light fuel oil.

The minimum pump output [kg/h] required for this can be calculated as:

Minimum required output [kg/h] = (Oil flow rate as combustion kg/h + 150 to 200 kg/h)* 1.25 to 1.3, where the expression inside the parentheses indicates the preheated oil flow to each burner.