1. Conversion reaction equation 

The characteristics of the reaction equation are reversible, exothermic, and volume reduction. Theoretically, increasing the oxygen content, reducing the content of the product sulfur trioxide, lowering the reaction temperature, and increasing the reaction pressure can all make the conversion proceed in the forward direction. 

2. Balance Conversion Rate 

The percentage of the amount of reacted sulfur dioxide to the initial total amount of sulfur dioxide is called the conversion rate. When the reaction conditions remain unchanged and regardless of the duration, the reactants no longer decrease and the product sulfur trioxide no longer increases. At this point, the reaction reaches a chemical equilibrium state, and the reaction rate is equal to zero. The concentrations of each component are called equilibrium concentrations. At this time, the conversion rate of sulfur dioxide is called the equilibrium conversion rate. The higher the equilibrium conversion rate, the higher the actual achievable conversion rate. The equilibrium conversion rate is only related to the temperature, pressure and initial components when the sulfur dioxide is converted. No matter how good the catalyst is or how it is adjusted, the theoretical upper limit of the sulfur dioxide conversion rate - the equilibrium conversion rate - exists, and the actual conversion rate is always less than the equilibrium conversion rate. 

3. Factors Affecting Conversion Rate 

Changing the reaction temperature, pressure, and gas composition can alter the equilibrium conversion rate. If the equilibrium conversion rate increases, the conversion rate can also be increased accordingly. 

3.1 The influence of temperature: 

This reaction is an exothermic reaction. Lowering the reaction temperature is beneficial for increasing the conversion rate. However, during the reaction process, a high reaction rate also needs to be considered. The reaction rate is affected by temperature; the lower the temperature, the slower the reaction rate. Therefore, during the conversion process, the same temperature range cannot be maintained throughout. In the initial stage, when the distance from the equilibrium state is far, it is advisable to convert the gas at a higher temperature to obtain a larger reaction rate; in the later stage, when the distance from the equilibrium state is closer, it is advisable to convert the gas at a lower temperature to achieve the highest conversion rate. Thus, the gas is cooled through a superheater and heat exchanger before reacting, enabling segmented conversion reactions and achieving a higher conversion rate and a faster reaction speed. 

3.2 Component Influence 

From the reaction equation, it can be seen that increasing the content of oxygen and sulfur trioxide both facilitate the forward reaction of the transformation. 

Increase the oxygen content in the flue gas to ensure there is sufficient oxygen in the conversion section, which is beneficial for improving the conversion rate. In the sulfuric acid production process, the oxygen comes from the residual oxygen in the flue gas after sulfur is burned in the sulfur incinerator (some installations have a supplementary air supply pipeline). It is necessary to ensure an adequate supply of oxygen. The concentration of sulfur dioxide in the sulfur incinerator should be controlled. Generally, the concentration should not exceed 11%. To ensure that the oxygen concentration in the tail gas is above 5%. However, the concentration of sulfur dioxide should not be too low. A lower concentration of sulfur dioxide will result in a decrease in the temperature of the sulfur incinerator, making the sulfur combustion insufficient and prone to the formation of sublimated sulfur. If the concentration of sulfur dioxide continues to decrease, the thermal equilibrium in the conversion section cannot be maintained. Therefore, the concentration of sulfur dioxide should generally be maintained above 8%. Therefore, monitoring the sulfur dioxide concentration at the outlet of the sulfur incinerator is a necessary measure to ensure the conversion rate of the system. 

Online SO2 analyzer 

Excluding the product SO3, the reverse reaction rate will definitely significantly decrease, and the equilibrium state will be immediately disrupted. The reaction will then become more favorable for the forward reaction to proceed, further increasing the conversion rate. Therefore, the device adopts a two-stage forward and two-stage reverse process. The sulfur trioxide from the initial reaction is absorbed by one absorption tower and then undergoes a second conversion, followed by another absorption process, ensuring a relatively high total conversion rate. 

3.3 Impact of Pressure 

This reaction is a volume-reducing reaction. Under the same conditions of temperature and gas composition, increasing the pressure is beneficial for the forward progression of the reaction. Therefore, in the sulfuric acid production system, the conversion and absorption processes, when carried out under pressure, have advantages, but the construction and operation costs must also be taken into consideration.