Reasons and Solutions for Black Smoke from Ship Boiler Combustion

The combustion device (also known as the burner) consists of fuel injectors, air regulators, and igniters.

1. Fuel injector

The task of the fuel injector is to atomize the fuel into very fine droplets, which facilitates rapid and complete combustion of the fuel. There are three main types of fuel injectors: pressure type, return type, and rotary cup type.

2. Air regulator

The task of the air conditioner is to generate swirling flow and distribute air reasonably, so that the air supplied into the furnace is evenly mixed with the injected oil mist to improve combustion efficiency. The air volume supplied by the air conditioner is appropriate. Insufficient air can cause poor combustion, while excessive air can lower the furnace temperature, which is not conducive to combustion and weakens heat transfer efficiency. It will also increase waste heat loss due to increased exhaust volume, thereby reducing the thermal efficiency of the boiler. The supplied air cannot be fully utilized, so the actual supply should be slightly higher. The ratio of actual air supply to theoretical demand is called the excess air coefficient. The smaller the excess air coefficient under the condition of ensuring good combustion, the better, generally between 1.1 and 1.4.

3. Igniter

The igniter consists of two heat-resistant aluminum magnesium alloy electrode rods, with a distance of 3-4mm between the two ends. When the two electrode rods are subjected to a high voltage of 5000-10000V, an arc spark is generated between the ends to ignite the fuel injected into the furnace. In order to ensure ignition effect and prevent conical oil mist from spraying on the electrodes, it is required that the two electrode rods be 11mm higher than the centerline of the fuel injector and 2.5mm beyond the front end face of the fuel injector. The two electrode rods cannot be staggered. Reasons for Black Smoke from Oil fired Boilers

1. Poor fuel quality

If the fuel added contains many impurities and poor viscosity, it is easy to cause nozzle blockage, poor atomization, and other phenomena.

2. Incomplete fuel combustion

Incorrect setting of the air intake baffle, poor air oil ratio, dirty air distributor, and insufficient air intake to fully burn the fuel will result in incomplete combustion of the fuel.

3. Poor quality of fuel atomization

Low fuel pressure, low fuel oil temperature, aging and clogged nozzles can all cause poor atomization.

4. The furnace and supply air temperature are too low

When igniting a cold furnace, low inlet air temperature in winter can also cause poor combustion.

5. Fuel pump supply system malfunction

Malfunctions and aging of the fuel supply pump result in unstable fuel supply, fluctuating oil pressure, and poor atomization, leading to poor combustion.

6. Secondary combustion accident occurred in the flue

Excessive accumulation of ash in the flue and secondary combustion can also cause black smoke from the boiler.

Solution to black smoke emission from fuel boilers

1. When installing regular fuel, if it is found that the boiler nozzle is easily blocked by oil residue, and the fuel injector and air distributor are prone to dirt, the fuel quality should be promptly reported to the company and qualified fuel should be installed.

2. Correctly set the air oil ratio to avoid insufficient and excessive air supply, clean the air distributor on time to ensure thorough mixing of air and oil.

3. Set the fuel pressure and start stop temperature of the fuel heater according to the instructions, and clean and replace dirty and clogged fuel injectors in a timely manner.

4. When igniting a cold furnace, first use light diesel with good ignition effect for combustion, and then convert it into heavy oil after the furnace temperature rises. In winter, pay attention to the insulation of the engine room and increase the engine room temperature.

5. Regularly check the fuel pump and replace the fuel pump components according to the instructions to ensure that the fuel pump is always in good working condition.

6. Regularly clean the ash accumulation in the flue to prevent excessive ash accumulation. Ships with boiler soot blowing function can choose suitable sea areas for regular soot blowing. During shipyard repairs, the flue should be cleared to ensure smooth operation.

7. Regularly inspect and clean the filters in the fuel supply system and injection system to ensure normal fuel supply. Replace the pressure gauges in the system in a timely manner in case of any malfunction to prevent incorrect analysis of related faults.

8. If the boiler load is automatically controlled, it is appropriate to increase the oil tank heating valve or partially release steam during low load to increase the boiler load, reduce or even avoid low load operation.