The functions of ultra-high temperature ball valves are as follows:
(1) Purging and anti-blocking in the central cavity
The titanium dioxide industry, chemical industry and other large boilers such as the bottom slag discharge or the top high-temperature liquid outlet have extremely high requirements on the temperature resistance of the valve, and also have good wear resistance and anti-blocking of the valve. In order to solve the blocking of the previous valve after using for some time, the valve is designed with a purge interface, which uses liquid or gas to purge the medium in the valve cavity when the valve is fully closed or fully opened, and discharges the medium in the cavity, such as slags or powder and other easily blocked substances and easily scaled substances at the purging area, solving the problem of blockage in such working conditions.
(2) Ultra-high temperature protection structure
The valve is in a high-temperature working temperature of above 800℃ for a long time, which affects the service life of the valve. Therefore, a casing is set outside the valve body to form a closed circulation space between the valve body and the casing. Set up a water inlet and a water outlet, so that the valve can be cooled by water circulation during high-temperature operation, which has a certain cooling effect, effectively protects internals and sealing parts of valves, and improves the service life of the valve.
(3) High-temperature protection of packing
The valve stem packing is made of high-temperature resistant materials, and the valve stem is designed with an extended stem. The bonnet is extended, and a heat sink is designed to ensure that the temperature of the packing is far lower than the high-temperature oxidation failure temperature; the valve can be sealed effectively when it is at a high temperature.
(4) Unique valve body design
The top entry valve body is used, which is convenient for maintenance. A boss is designed at the seat hole for the installation of preload screws and set screws. The pre-tightening screw pushes the elastic sealing ring, and the elastic sealing ring pushes the valve seat, so that the valve seat and the ball are sealed; the sealing pre-tightening pressure is achieved. At this time, the tightening screw connects the valve seat to the boss, fixes the valve seat and elastic sealing ring, and keeps the sealing ring in a sealed state.
Working principles
The high-temperature and high-pressure ball valve is a top entry floating hard-sealed ball valve. The initial sealing specific pressure of the valve is provided by the adjusting screw, and the medium pushes the ball to press the outlet valve seat to completely seal the outlet. The flexible rotation of the ball is ensured under the joint adjustment of the adjustment screws at the inlet end and the outlet end. After the adjustment screw is adjusted, tighten the locking screw, so that the elastic seal forms a wedge seal between the valve seat and the valve body, forming a high-temperature resistant valve seat sealing structure. In this way, a real hard sealing ball valve is formed, that is, the dynamic hard sealing between the ball and the valve seat. When the valve is in an ultra-high temperature condition, the valve body, ball, valve seat and elastic seal are under different external conditions. The valve body is cooled by external water or low-temperature gas, and the temperature is low; the valve seat and elastic seal are in contact with the valve body, and the temperature is lower than that of the sphere. Therefore, a temperature difference is formed between the parts of the valve, resulting in inconsistent deformation, so the relative expansion of the sphere is greater. At this time, the ball has a high-level expansion force pressed on the valve seat, and the valve seat is transmitted to the elastic seal. The elastic seal cannot move under the limit of the adjusting screw, but the elastic seal has a cantilever structure. The cantilever undergoes a small amount of elastic deformation, which can effectively absorb the uneven force of high-level expansion, so that the sphere can still flexibly rotate, and will not be stuck by high-temperature expansion. The elastic seal plays the role of the graphite seal and preload spring of the traditional hard-sealed ball valve, and at the same time solves the problem of these two components being prone to high-temperature failures when the temperature exceeds 600°C. In the opening and closing process of the valve, the force applied by the ball on the valve seat is also transmitted to the elastic seal. The elastic seal cannot move after being limited by the adjusting screw. At this time, the cantilever structure is slightly deformed, which absorbs excessive force, ensures the flexible opening and closing, and prolongs the service life of the ball and valve seat sealing pair. The key design difficulty of this structure is the design of the elastic seal.
(1) Designing the elastic force of the cantilever
Ensure that sufficient elastic force can be provided while absorbing the uneven expansion at ultra-high temperatures, and make sure that the valve can be flexibly opened and closed at a temperature of about 1000°C.
(2) Selecting the wedge angle among the elastic seal and the valve body and the valve seat
Ensure that self-locking and not being able to slide under force won't happen so as to form an effective deformation and bending at the cantilever, which acts as a spring.
(3) The hardening treatment and anti-scratch treatment of the valve seat, the valve body and the wedge angle contact part
Ensure that the surface roughness and hardness meet the requirements to achieve the effect of flexible sliding and sealing. When the valve operates under ultra-high temperatures, it needs to be cooled by water to ensure the safety of the valve body of the pressure-bearing parts at a high temperature. Under the working conditions of high-temperature slags, high-temperature powder, and easily scaled media, when the valve is fully opened or fully closed, the middle cavity can be purged with steam to prevent the valve from being blocked due to the blockage of the middle cavity, and to avoid the ball and valve seat sealing from easy failing caused by scaling.
Conclusion
The ultra-high-temperature ball valve is an on-off valve designed for the top outlet of the reaction boiler in the titanium dioxide industry, and is also used for the bottom discharge and slag discharge of the boiler. The valve has a working temperature of 800℃ for a long time; occasionally, the temperature will rise to about 1000℃. Through the special high-temperature-resistant structure design, the selection of seals and springs that the traditional structure cannot have a breakthrough under the working condition of 600℃is solved. It also solves the problem of expansion and jamming of the valve in all directions and latitudes under ultra-high temperatures. The special purging design also solves the problems of slag discharge of ball valves and sticking and clogging of powder. Through a series of structural innovative designs, the ball valve can be used in the inlet and outlet of the high-temperature reaction furnace at a temperature of about 1000℃ and even the slag discharge, which solves the problem of having a short life, easy jamming, and not being able to be opened and closed at a critical time of the traditional valve under the same working conditions. Ultra-high temperature ball valves have been widely used in the inlet and outlet of boilers in the titanium dioxide industry, phosphate fertilizer industry and acid production industry.
