At present, the leading vulcanization process in the domestic tire industry adopts a dual-mode vulcanizing machine. The external temperature and external pressure are provided by high-pressure (1.6MPa~1.9MPa) saturated steam; while the internal temperature and internal pressure are provided by superheated water, and the thermal energy of both comes from the coal-fired boiler.

This kind of device causes great pollution to the environment, and many equipments (such as transmission pipes, valves, etc.) need to be configured in the process of heat energy transmission. This traditional process consumes a lot of resources. Calculated by a 20T coal-fired boiler, it needs 480T of water and 16.7T of coal a day. Nitrogen vulcanization is an innovation of the above-mentioned traditional heating and pressurization methods. According to the information, 3/4 of the car tires, light truck tires and 1/4 of the truck tires of major foreign tire companies have been changed to nitrogen as the main heating medium, which reflects the two advantages of energy saving and prolonging the service life of the bladder. The new process has begun to be applied and promoted in China.

At present, the relatively mature "nitrogen vulcanization" process is used, which mainly fills the bladder with nitrogen to replace the original superheated water. The advantage of nitrogen is that the heat capacity and molecular weight are small, and the temperature will not be lowered due to heat absorption after charging. The specific operation procedure is to use low-pressure (0.03MPa~0.3MPa) steam to fill the shape and close the mold, and then use high-pressure (1.4MPa~1.7MPa) steam to blow into the capsule, and the blowing time generally lasts 2min~ 8min, wait until the steam is filled to ensure that the temperature in the capsule is not lower than 150 ℃ before the end of the vulcanization cycle.

Next, immediately fill the capsule with nitrogen as the pressure-holding medium to ensure the pressure required for the entire vulcanization process. After the vulcanization is completed, the mixed gas is discharged, the mold is opened, and the tire is unloaded. It can be seen from this that the so-called "nitrogen vulcanization" is not actually pure nitrogen vulcanization, but is first heated by saturated steam, and then filled with pure nitrogen to increase and maintain the pressure. After the vulcanization is completed, the nitrogen and steam mixed gas is discharged together .
Since "nitrogen vulcanization" adopts the "separated" heating and pressurizing method, it has the following advantages:
1. There is no need to configure superheated water heating and pressurization systems, thereby reducing investment, energy consumption and post-processing configuration costs.
2. Since nitrogen is an inert gas, it can delay the aging process of the capsule and increase the service life of the capsule by 25% to 100%. At the same time, erosion of the pipeline is also eliminated, reducing downtime and routine maintenance workload.
3. The exhaust gas after vulcanization does not contain harmful substances, which can be directly discharged into the atmosphere, saving the cost of sewage treatment and environmental protection.
The quality requirements of nitrogen for sulfidation are relatively high, and its purity must reach at least 99.99%, preferably 99.999%.

In recent years, my country's tire industry has made new improvements and attempts to the "nitrogen vulcanization" process. Compared with the current "nitrogen vulcanization", there are two differences:
1. The charged nitrogen is preheated to the temperature required for vulcanization, so that there is no need to charge saturated steam first, and the heating, pressure boosting and pressure maintaining tasks of the capsule are completed by pure hot nitrogen.
2. The external temperature is changed to far-infrared heating, which is far simpler than steam heating, and does not require a pressure vessel, and there is no problem of explosion or heat leakage.