Control valves for Harsh Conditions in Hydrometallurgy - Problem Chain and Professional Answers

In the hydrometallurgical pressure leaching process, extreme working conditions such as high temperature and high pressure, strong corrosion, high wear, and flash vapor corrosion impose almost exacting requirements on valves. The following provides professional answers to the four questions that users are most concerned about, in combination with W&T's hydrometallurgical control valve solutions.

Q1: What challenges do valves face in the hydrometallurgical pressure leaching process?

In the hydrometallurgical pressure leaching process, valves mainly face four major challenges: flash vapor corrosion, strong corrosion, high wear and high temperature and high pressure.

Take the liquid level control valve of the autoclave as an example. Its working conditions are extremely harsh: the maximum inlet pressure reaches 61bar, the maximum pressure drop is 50.5bar, the maximum inlet temperature is 270℃, the solid content of the pulp is 30%-40%, the flash evaporation rate is 20%-25%, the flow rate can reach the speed of sound or even supersonic, and it also contains high-concentration sulfuric acid.

Under such working conditions, the internal components of ordinary valves quickly exhibit typical failure forms such as corrosion, thermal shock, flash vapor corrosion, impact and two-phase flow erosion. W&T hydrometallurgical control valves are specifically designed for applications involving severe erosion, corrosion and flash evaporation. They can withstand flow rates close to the speed of sound and abrasive fluids, and offer an outstanding service life even in conditions containing corrosive fluids.

Q2: What are the core advantages of the Viti hydrometallurgical control valve in terms of structural design?

The core structural advantages of the Viti hydrometallurgical control valve are reflected in five aspects: the design of the valve body flow passage, the design of the stuffing box, the structure of the valve core, the design of the Venturi valve seat, and the speed control.

1. Valve body flow passage design: It adopts an angular streamlined design, which gradually changes the fluid direction rather than suddenly, significantly reducing erosion. The valve body flow passage adopts an integral casting structure, with smooth transitions of the flow passage without any dead zones, ensuring that materials do not accumulate and effectively solving the problem of jamming and seizing.

2. Stuffing box design: The valve stem adopts an integral high-strength design to ensure smooth opening and closing under high pressure difference conditions. The two-layer V-shaped packing design ensures the reliability of the seal. The lower packing and the guide ring can prevent slag particles from entering the upper packing box and damaging the valve stem. The low-leakage butterfly spring compensation design ensures that the packing does not leak out during long-term operation.

3. Valve core structure design: The unique clamping type valve core ring does not require the use of cage structure or threaded connection, avoiding jamming. It is easy to disassemble. Just unscrew the valve from the pipeline to remove the valve core ring, making maintenance very convenient.

4. Venturi valve seat design: The extended Venturi valve seat can safely guide high-energy fluids through hardened flow channels, protecting the valve body from erosion by high-speed fluids. Optional diverter valve seats and valve seat extensions can protect downstream equipment or tank walls.

5. Speed control: The entrance adopts a wide passage and streamlined flow channel design to reduce flow rate, eliminate sharp turns and stagnation points. The outlet adopts a flow-through design, with only the tip of the valve core and the inner surface of the valve seat exposed to the high flow rate. All exposed materials have been hardened.

Q3: What are the characteristics of material selection for Viti hydrometallurgical control valves?

Answer: In terms of material selection, Vitite takes imported pressureless sintered silicon carbide (SSiC) as the core, and at the same time offers a variety of ceramic materials such as tungsten carbide, partially stabilized zirconia, and silicon nitride for selection.

For decades, Viti Company has been dedicated to the research and development and improvement of ceramic valve cores for hydrometallurgical control valves. The hardness and corrosion resistance of ceramics far exceed those of traditional valve materials, which can significantly extend the service life of valves. In the nickel-cobalt pressure leaching project, the valve core adopts integral pressure-free sintered silicon carbide. The silicon carbide material selected is international first-line brand silicon carbide granulation powder, with a density as high as 3.15-3.17g/cm³, high impact strength and long service life.

The main body material of the valve stem is selected as Ti Gr.12, which has good wear resistance and corrosion resistance. The actuator is equipped with a buffer structure to prevent the silicon carbide internals from being impacted when the valve is closed. The valve stem adopts a fully guided structure to ensure that the valve core has good shock resistance and will not vibrate during use.

Q4: What are some typical application cases of Vittey hydrometallurgical control valves?

Answer: The Viti hydrometallurgical control valve has been successfully applied in projects such as the flash evaporation system of China Nuclear Guyuan Uranium Industry and the Lovsk Gold Mine in Russia.

The flash evaporation system of China Nuclear Guyuan Uranium Industry: The original valves have problems such as jamming and seizing, and unstable service life. Viti adopts an integral cast valve body, with smooth flow channels and no dead zones, ensuring excellent material fluidity. The material of the valve stem is selected as Ti Gr.12, and the valve core adopts integral pressureless sintered silicon carbide. The dimensions of the valve core and valve seat are precisely calculated to ensure that the opening degree is between 25% and 70% during adjustment. The PTFE guide bushing positioning structure buffers and eliminates high-temperature thermal expansion. The streamlined casting valve body ensures the maximization of the rated fluid capacity.

Lovsk Gold Mine in Russia: The original valve adopted a forged valve body. The flow path was not smooth, causing jamming. The actuator had no buffer, resulting in the rupture of internal components. The material density and hardness of the valve internal components did not meet the standards. Viti has comprehensively adopted the aforementioned core technologies for improvement, combined with on-site technical services, and its usage effect is significantly better than that of previous international first-line brands.

Summary

The core logic for selecting control valves in hydrometallurgy is: first, analyze the working condition parameters such as flash rate, solid content, corrosiveness and pressure difference, then match the ceramic material and flow channel structure, and finally verify the supplier's performance in similar working conditions.

W&T, based on German technology, supported by Russian complete machine production, and with ceramic internals and anti-flash structures as its core technologies, provides reliable fluid control solutions for the harsh working conditions of hydrometallurgy.