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How to arrange the reasonable combination of gas/oil burners and boilers
How to arrange the reasonable combination of gas/oil burners and boilers
The reasonable combination of gas/oil burners and boilers can perfectly reduce fuel consumption and reduce nitrogen oxides emissions.Therefore, how should one choose an appropriate gas/oil burner for a boiler? Here are the following points summarized by the European-based combustion equipment manufacturer:
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Power
The combustion device's power refers to the amount of fuel that can be burned per hour at a specific combustion rate (kg/h or thousand calories per hour) and provides corresponding heat output (kw/h or cal/hour).The boiler is also calibrated for both steam production and fuel consumption. When selecting the gas/oil burner, both must be matched. -
Matching of gas-to-air flow characteristics
A unit of fully automated burners acts like a flame sprayer, spraying the flame into the furnace (combustion chamber), achieving complete combustion and outputting heat; the combustion device manufacturer measures the overall performance of its product in a specific standard combustion chamber; therefore, the selection of the gas/oil burner and boiler is generally based on standard operating conditions.These conditions can be summarized as:
(1) Power;
(2) Furnace air flow pressure;
(3) Furnace spatial size and geometric shape (diameter and length).
The term "gas-to-air flow characteristics" refers to the degree to which these three conditions are met. -
The impact of furnace size and geometric shape
For a boiler, the size and shape of the furnace's combustion chamber are initially determined during the design process based on the selection of the furnace's heat load intensity. This allows for a preliminary determination of the furnace's capacity.Once the furnace's capacity is determined, its geometric shape and size should also be determined. The design principle is to utilize the furnace's capacity to the fullest extent possible and avoid dead corners, a certain depth, and a reasonable flow direction, ensuring sufficient reaction time, ensuring complete combustion of the fuel in the furnace.This means allowing the flame sprayer to spray out the flame with sufficient dwell time in the furnace because although oil mist particles are very small (<0.01mm), they are already ignited and burning before being sprayed out by the burner, but this is still not enough.If the furnace is too shallow, the dwell time is not enough, resulting in incomplete combustion. The lighter tail gas CO exceeds the standard, and the heavier smoke pollutes the smoke stack, resulting in failure to meet the requirements of the burner. Therefore, the geometric shape of the furnace mainly affects the flow resistance and uniformity of the airflow.The boiler must be repeatedly adjusted before it can be matched with the burner to achieve a good performance.
- Gas pressure in the furnace
In oil and gas boilers, hot air flows from the burner start, pass through the furnace, heat exchangers, smoke collection devices, and exhaust pipe to the atmosphere, forming a flow-based heat transfer process.After combustion, the hot air flow generated flows upward in the furnace channel, just like water flowing in a river. The water level difference (drop, head) flows downward due to the resistance of walls, passages, bends, barriers, spurs, and chimneys to the gas flow, resulting in pressure losses.If the pressure head does not overcome the pressure losses along the route, the flow rate cannot be achieved. Therefore, the smoke pressure inside the furnace must be maintained at a certain level, which is referred to as backpressure. For boilers without an air intake device, the pressure inside the furnace must be higher than atmospheric pressure after considering the pressure losses along the route.The size of the backpressure directly affects the output of the burner, and it is related to the size of the furnace, the length of the smoke duct, and the geometric shape of the chimney. The larger the flow resistance, the higher the pressure required for the burner.For a specific burner, its pressure head has a maximum value corresponding to the maximum airflow gate and maximum gas flow condition. When the inlet throttle valve changes, the air flow and pressure also change, resulting in a change in the output of the internal combustion engine.When the inlet air flow is small, the pressure head is small. When the inlet air flow is large, the pressure head is high. For a specific boiler, when the inlet air flow is large, the flow resistance increases, increasing the backpressure inside the furnace.The increase in backpressure inside the furnace will inhibit the airflow of the burner. Therefore, when selecting a burner, it is necessary to understand how its power curve can be matched with a good performance automatic oil (gas) burner installed on the boiler.Whether it still has the same excellent combustion performance is largely dependent on the airdynamic characteristics of the two. Only by matching them well can the performance of the burner be fully developed, ensuring stable combustion inside the furnace, achieving expected heat output, and obtaining a good heat efficiency of the boiler.Whether it still has the same excellent combustion performance is largely dependent on the airdynamic characteristics of the two. Only by matching them well can the performance of the burner be fully developed, ensuring stable combustion inside the furnace, achieving expected heat output, and obtaining a good heat efficiency of the boiler.