Foreword

In the production process of sulfur acid making plant, the body of the sulfonate gun may be bent, especially after the device is stopped. Normally, the body of the gun curves upward.

First, Theoretical analysis of bending:

The gun is usually made of 316L or 310S. In order to ensure the mechanical strength and stability of the material, its use temperature is usually controlled. For example, 316L can be used continuously below 750 ° C; 310S can be used continuously below 1150℃. These two materials can meet the requirements of sulfur burning furnace. However, the coefficient of thermal expansion of metals varies with temperature. According to the data, the thermal expansion coefficient of 310S is: 66.9&mu for every 100℃ temperature rise; m/m, 124.4&mu at 200℃; m/m, 289.3&mu per 500℃ temperature rise; m/m, 496.0&mu at 800℃; m/m, 722.8&mu at 1100℃; m/m. It can be seen that with the increase of temperature, the expansion amount of the material increases significantly. In the case of uneven heating of the gun, the temperature difference on both sides will cause the material expansion amount to be different, resulting in the bending of the gun. When the gun is bent upward, it indicates that the lower part of the gun is warmer than the upper part, and the expansion of the lower part is therefore greater than the expansion of the upper part.

Two, the use of sulfuric gun insulation steam:

1. The steam system with thermal jacket was designed at the beginning of manufacture. Before driving, the main function of the heat preservation steam of the sulphate gun is to dredging the sulphate pipe to ensure the smooth flow of liquid sulphur; After stopping, its function is to take away the radiant heat of the sulfur burner to the sulfonate gun, so as to protect the sulfonate gun from damage.

2, in the preparation stage of driving, in order to quickly melt the sulfur in the sulfur gun, the amount of steam through the sulfur gun should be increased as much as possible, and to ensure that there is sufficient heat transfer time. Therefore, it is not appropriate to set a trap at the outlet of the sulfogun heat preservation steam, but the valve can be slightly closed to ensure that the steam evenly passes through the sulfogun and provides sufficient heat transfer time.

3, during the operation of the device, liquid sulfur continues to flow in the sulfonate gun, so there will be no blockage. At the same time, dry air will also enter the sulfur burner along the direction of the sulfonate gun. The temperature of the dry air depends on the setting of the fan: if the fan is in front of the tower, the temperature is usually about 65 ° C (depending on the control of the drying acid temperature is slightly different); If the tower behind the fan, the temperature will not exceed 120℃. This air cools the gun and protects it from being burned out. Therefore, during the operation of the device, the effect of the sulfuric gun insulation steam is relatively small, and you can choose to close or keep it open.

4, after the device stops, the dry air stops entering, and the radiant heat of up to 900 degrees from the sulfur burning furnace will be quickly transferred to the sulfur gun. At this time, the sulfogun insulation steam must be passed in time to take away the heat and prevent the sulfogun from being burned. It should be noted that the thermal insulation steam will become superheated steam after heating, so it is strictly prohibited to set the trap at the outlet, otherwise the steam will not be able to pass through and the heat can not be taken away. The amount of steam flowing in should be large enough, and the outlet should be slightly turned off to ensure that the entire gun is full of steam.

5, in the early stage of discharging the insulation steam, because the steam is saturated, white smoke can be observed. When the steam is heated to superheated steam, the white smoke will disappear, which may give the appearance that no steam has passed through. If no white smoke can be seen, the thermal insulation steam should be turned on again until there is white smoke. This is because only when the superheated steam is discharged, it is impossible to judge the degree to which the heat of the sulfonate gun is taken out, and the sulfonate gun may still be in a higher temperature range. The white smoke discharge indicates that the steam has not been completely overheated, and the temperature of the sulfonate gun has been effectively guaranteed.

Three, possible causes of bending:

1, the uneven distribution of thermal insulation steam inside the gun is mainly due to the insufficient amount of steam through. Heat trapping steam accumulates in the upper area, while the lower area has little or no steam. Because there is steam in the upper area for heat exchange, the temperature is relatively low; On the contrary, due to the lack of steam for heat exchange in the lower region, the temperature is higher, resulting in the thermal expansion of the lower region is greater than that of the upper region, and eventually the sulfonate gun bends.

2. After the device is stopped, the butterfly valve at the inlet of the sulfur burner may not be opened due to lax sealing or easy sticking after stopping, or it is not completely closed due to human reasons. At this time, the high-temperature flue gas in the furnace will spread to the inlet flue gas pipe along the opposite direction of the sulfonate gun, thus forming a bottom-up temperature gradient, that is, the lower temperature is higher than the upper temperature. In addition, if the heat insulation steam is not turned on in time (especially during the process of disassembling the gun, which takes a long time), or the amount of heat insulation steam is not enough, or the steam outlet is installed at the steam trap, so that the radiant heat of the gun body cannot be removed in time (the amount of removal is not enough), the gun will also produce temperature differences, and eventually cause the gun to bend.