Troubleshooting of Heavy Oil Combustion System in Asphalt Mixing Plant

One asphalt mixing plant (hereinafter referred to as mixing plant) used by a certain unit uses diesel as fuel in production. As the price of diesel in the market continues to rise, the operating cost of the equipment is getting higher and higher, and the benefit is decreasing. In order to reduce the production cost, it was decided to use a special combustion oil (heavy oil for short) with low price, good combustion performance and meeting requirements to replace diesel oil as fuel.

1. Fault phenomenon

In the process of using heavy oil, the asphalt mixing equipment has the phenomenon of black smoke from combustion, blackening of recovered mineral powder, dark combustion flame and odor of hot aggregate, and the consumption of fuel oil is relatively large (7kg heavy oil is required to produce 1t of finished material) . After producing 3000t of finished material, the imported fuel high-pressure pump used for it was damaged.

After dismantling the fuel high-pressure pump, it was found that its copper sleeve and screw were severely damaged. Through the analysis of the structure and material of the pump, it is known that the copper sleeve and screw used in the pump are not suitable for burning heavy oil. After replacing the imported high-pressure fuel pump with a domestic high-pressure fuel pump, the phenomenon of burning black smoke still exists.

The analysis believes that the black smoke is caused by insufficient combustion of the mechanical burner. There are three main reasons: one is the uneven mixing of air and oil, the other is poor fuel atomization, and the third is that the flame is too long. Insufficient combustion will not only cause the generated residues to stick to the gaps of the dust collector bag and hinder the separation of dust from the flue gas, but also make it difficult for the dust to fall off the bag, affecting the dust removal effect. In addition, the sulfur dioxide generated during the combustion process will also cause serious corrosion to the cloth bag. In order to solve the problem of incomplete combustion of heavy oil, we take the following improvement measures.

2. Improvement measures

(1) Control the viscosity of the oil

When the viscosity of heavy oil increases, the oil particles are not easy to disperse into fine droplets, which will cause poor atomization, resulting in black smoke when burning. Therefore, the viscosity of the oil must be controlled.

(2) Increase the injection pressure of the burner

The function of the burner is to atomize the heavy oil into finer particles, and inject them into the drum to mix with the air to form a good combustible mixture. Therefore, we increase the injection pressure of the burner, which effectively improves the quality of the combustible mixture and improves the fuel condition.

(3) Adjust the air-oil ratio

Properly adjusting the ratio of air and oil can make the fuel and air form a good mixture, avoid incomplete combustion and cause black smoke and increase fuel consumption.

(4) Add a fuel filter device

Replace the high-pressure fuel pump with a new one, keep the original circuit, pressure gauge, safety valve and other components untouched, and set up multi-stage filtering devices on some fuel pipelines to reduce impurities in heavy oil and ensure sufficient combustion.