The previous issue discussed the impact of poor atomization effect of the sulfur burner on the sulfur incinerator. This issue will focus on the chain hazards it causes to the subsequent conversion system and absorption system, as well as the problem of severe over-limit of sulfur dioxide emissions in the tail gas during start-up.

1. Damage to the conversion system

Poor atomization results in uneven injection of the sulfur gun, with large liquid sulfur particles that are difficult to fully combust. Unburned sulfur vapor passes through the waste heat boiler with the gas flow. At this point, the flue gas temperature at the outlet of the waste heat boiler drops to approximately 380°C, which is lower than the vaporization temperature of sulfur (444.6°C).

The sulfur vapor condenses into liquid sulfur particles, which are carried by the flue gas and collide with the flue gas pipeline from the waste heat boiler to the inlet of the first stage of the conversion. Liquid sulfur adheres to the carbon steel flue gas pipeline. In an oxygen-deficient and high-temperature environment, liquid sulfur reacts with carbon steel to form iron sulfide. As iron sulfide continuously forms and falls off, it is blown onto the surface of the first-stage catalyst, irreversibly covering the catalyst's permeability and significantly increasing the system resistance. This may even cause local overheating and sintering deactivation of the catalyst. More seriously, iron sulfide particles accumulate in the first-stage conversion bed, forming a "sulfur blockage", directly blocking the gas flow channel, causing the fan to surge and forcing the system to shut down.

Poor atomization causes the liquid sulfur particles ejected from the sulfur gun to be relatively large, making it difficult to fully combust. A large amount of unburned sulfur droplets enter the converter, adhering to the surface of the catalyst and blocking the pores of the catalyst surface, resulting in a decrease in catalyst activity and an increase in bed pressure drop. At the same time, free sulfur vapor enters the high-temperature superheater, adhering to the heat exchange fins and affecting the heat exchange efficiency, leading to an increase in resistance.

2. Harm to the absorption system

Unburned sulfur vapor passes through the converter along with the gas flow. After contacting with sulfuric acid in the primary absorption tower, it forms tiny particles of sulfur, which adhere to the packing walls and the tower walls, significantly reducing the efficiency of gas-liquid mass transfer.

At the same time, the tiny sulfur particles circulate in the acid, exacerbating the clogging of the packing. This causes the pressure drop inside the tower to gradually increase. Since the tiny sulfur particles are yellow in color, it affects the color of the finished sulfuric acid, making it appear cloudy and yellowish.

The tiny sulfur particles continuously accumulate in the circulating acid and are carried out by the flue gas and enter the fiber demisting device, blocking its microporous structure, resulting in a sharp decline in demisting efficiency and an acid mist escape exceeding the standard.

3. Problem of excessive SO₂ emissions during driving stage

When the sulfuric acid production unit restarts after a temporary shutdown， it often encounters situations where the atomization of the sulfide gun is poor， resulting in unstable liquid sulfur spraying and insufficient combustion. A large amount of unburned sulfur vapor directly enters the conversion system， causing a sharp decline in conversion rate. Due to the poor atomization effect of the sulfide gun， the liquid sulfur vaporizes at high temperatures， causing a sulfur vapor explosion phenomenon， which leads to a sudden increase in the SO₂ concentration at the inlet of the first section， far exceeding the design value， and causing the catalyst to be overloaded instantaneously.

At the same time， the condensed sulfur carried by the low-temperature flue gas will accelerate the accumulation of sulfur in the bed， further inhibiting the catalytic reaction activity. This will result in continuous SO₂ concentration exceeding the limit， and in severe cases， it will exceed the 2000 mg/Nm³ limit， preventing the exhaust gas treatment system from achieving standard emissions， and triggering environmental protection alerts.

This situation will cause the unit to take a longer time to start up， usually requiring 6 - 8 hours to gradually return to the standard level. During this period， not only will fuel and electricity consumption increase， but also due to repeated adjustments of the sulfide gun parameters， switching of backup guns， and sulfur blowing operations， the frequency and operational risks of manual intervention will significantly increase.

Summary

All of this seems to be an imbalance between equipment and process, but in fact, it is due to a slight deviation in the core step of sulfide gun atomization. It is like knocking over a domino, which broke the stable balance of the entire sulfuric acid production system.

The quality of atomization directly determines the specific surface area of liquid sulfur, the vaporization rate, and the uniformity of combustion, and thereby affects the generation intensity of SO₂, the distribution of the temperature field, and the evolution path of the sulfur vapor phase state. Due to the poor atomization effect, it often leads to problems such as the burning through of the incinerator, the accumulation of sulfur deposits on the catalyst bed of the converter, the blockage of the packing in the absorption tower, and the emission exceeding the standard.

Solving the problem of sulfide gun atomization is the fundamental breakthrough to solve this series of problems. It needs to start from optimizing the nozzle structure and upgrading the performance of the sulfide gun.

In the next issue, we will share the practical path for optimizing sulfide gun atomization, including the precise regulation of the swirling atomization structure of the new Laval nozzle on the particle size distribution of liquid sulfur.