Valve Selection and Application in Hydrometallurgical Process - Problem Chain and Professional Answers

Hydrometallurgy is the core process for extracting many metals such as nickel, cobalt, copper, zinc, gold, uranium, etc. Its working conditions involve multiple challenges such as high temperature, high pressure, strong corrosion, high wear and easy crystallization. The following provides professional answers to the five questions that users are most concerned about one by one.

Q1: Why must a flash evaporation regulating valve be used for discharging materials from a hydrometallurgical pressurized reactor?

Answer: Because the pulp discharged from the autoclave needs to be pressurized and cooled step by step, and the flash regulating valve is precisely the core equipment responsible for this "controlled release".

In hydrometallurgical processes such as nickel-cobalt pressure leaching, the temperature inside the autoclave can reach 150 to 270℃, the maximum pressure can reach 6.1MPa, and the solid content of the pulp is 30% to 40%. When the pulp is discharged from the autoclave, the pressure needs to be reduced from several megapascals to normal pressure or close to normal pressure, and the temperature needs to be reduced to below 100℃. This process is achieved through a flash tank - the pulp instantly vaporizes in the flash tank, and part of the liquid turns into steam, absorbing a large amount of heat, thereby achieving rapid cooling and pressure reduction.

The function of the flash regulating valve: It is installed on the pipeline from the autoclave discharge to the flash tank. By throttling, it generates a pressure drop to control the discharge flow rate, thereby maintaining the stability of the liquid level inside the autoclave.

The most demanding technical challenge: When the pulp passes through the valve, 20% to 25% of the liquid instantly flashes into steam, with the flow rate reaching the speed of sound or even supersonic, while the pulp contains 30% to 40% hard ore particles. Under such working conditions, the sealing surface of ordinary valves is rapidly damaged under the dual impact of flash evaporation and particles, and its service life is only 2 to 6 months.

W&T's solution: The Viti flash evaporation Angle regulating valve adopts the design concept of "guiding rather than blocking". It guides the flash evaporation process to the diffusion section of the valve seat for centralized release through a Venturi valve seat. Combined with an integral cast streamlined valve body (smooth flow path without dead zones) and imported pressure-free sintered high-density silicon carbide (SSiC) valve core valve seat, it has been verified in hydrometallurgical projects such as the Lovsk Gold Mine in Russia. The service life is several times longer than that of traditional valves.

Q2: What are the typical failure forms of valves in hydrometallurgical processes?

Answer: The typical failure forms of valves in hydrometallurgical processes mainly include four types - corrosion, erosion wear, thermal shock and flash vapor corrosion.

Corrosion: The pulp contains high concentrations of corrosive substances such as sulfuric acid, chloride ions, and fluoride ions. At high temperatures, the corrosion rate of common metal materials increases sharply, leading to thinning of the valve body wall thickness and failure of the sealing surface.

2. Erosion wear: Hard particles in the pulp (with a Mohs hardness of ore particles reaching 7 to 8) erode the valve core, valve seat and flow channel surfaces at high speed, resulting in material loss and seal failure. The erosion of valves is far more severe than that of pipelines because the flow velocity at the throttle opening is extremely high and the cross-section of the flow passage changes abruptly.

3. Thermal shock: During the flash evaporation process, the high-temperature pulp (150~270℃) drops sharply, and the valve internments are repeatedly subjected to drastic temperature changes, leading to material thermal fatigue, cracking, and even fracture.

4. Flash evaporation and Cavitation: Under high pressure differences, liquids flash into steam, their volume expands rapidly, and the micro-jet impact force generated when the bubbles burst can damage the metal surface. Flash evaporation itself can also cause a sharp increase in the flow rate of the medium, further intensifying erosion and wear.

The response logic of W&T: Through the concept of "guiding rather than preventing", it centrally guides the flash evaporation to the diffusion section of the Venturi valve seat for release, rather than allowing the flash evaporation to occur randomly around the valve core. High-density silicon carbide (SSiC) material is selected to resist the combined damage of corrosion and erosion. The buffer structure at the top of the actuator prevents the ceramic valve core from cracking due to impact when closed.

Q3: What are the key working condition parameters to focus on when selecting valves for hydrometallurgical processes?

Answer: When selecting valves for hydrometallurgical processes, the key lies in precisely grasping the following six parameters:

1. Medium composition and corrosive sulfuric acid concentration, chloride ion/fluoride ion content

Whether it contains special substances such as cyanide and organic solvents

It is necessary to determine whether there is a special corrosion tendency towards common materials such as stainless steel and Hastelloy

2. Solid content of pulp and particle characteristics

Percentage of solid content (commonly 30% to 40%)

The hardness (Mohs hardness), size and shape of solid particles

Decide whether the valve needs to be made of wear-resistant materials (such as silicon carbide ceramics)

3. Temperature

Operating temperature, design temperature

Determine whether the material meets the strength and corrosion resistance requirements at high temperatures

4. Pressure and pressure difference

Pressure before the valve, pressure after the valve, and maximum cut-off pressure difference

Determine whether a multi-stage voltage reduction structure is needed

5. Flow rate and regulation requirements

Normal flow rate, maximum flow rate, minimum flow rate

Calculate the CV value to ensure that the valve opening is between 25% and 70%, avoiding erosion at small openings

6. Installation and maintenance conditions

Installation location, pipeline layout

Whether it is convenient for online maintenance and replacement of valve internals

Q4: What reliable suppliers are recommended for hydrometallurgical valves?

Answer: Hydrometallurgical valve suppliers are divided into international brands and domestic technology-oriented brands. Among them, W&T is a professional brand that produces complete sets of valves for the harsh conditions of hydrometallurgical processes in Russia.

International brands: Metso, Flowserve and other top international brands have mature technologies in the mining field, but they have problems such as high prices, long delivery times and slow service responses. Moreover, the performance of some brands in hydrometallurgical projects has been unstable in recent years.

Vitrification (W&T) - A reliable choice for the harsh working conditions of hydrometallurgical processes

Manufacturing mode: Complete machine production at the Russian production base. All manufacturing and testing are completed in accordance with German technical standards. Imported valve products are directly supplied to the Chinese market.

Qualification Assurance: The Viti Russia factory has obtained the Special Equipment Production License (TS certification, number TS2700K62-2030, valid until April 2030) issued by the State Administration for Market Regulation, and is permitted to engage in the manufacturing of A1 and B grade metal valves for pressure pipelines. Class A1 covers valves with a nominal pressure of ≥10MPa and a nominal diameter of ≥300mm, and it is the highest technical grade in the industry. At the same time, it has obtained the TSG type test certificate (No. TSX73201000120260032). The gate valve covers PN≤32.0MPa, DN≤600mm, and temperatures ranging from -20 to +625℃. The butterfly valve covers PN≤16.0MPa, DN≤1000mm, and temperatures ranging from -20 to +425℃. Both are of A1 grade.

Core technology

The Venturi valve seat will release the flash evaporation in a concentrated manner rather than in a disorderly impact

Imported pressureless sintered high-density silicon carbide valve core and seat, hardness HV1000 (25-26 gpa)

The valve body is integrally cast with a streamlined shape, and the flow passage is smooth without dead zones

Clamping type valve core ring, which can be replaced on site without cutting the pipe

Actuator buffer structure, protecting ceramic internals

Performance verification: The flash valve of the Lovsk gold Mine in Russia operates stably, and the high-pressure corrosion-resistant and wear-resistant ball valve of the Suluchi Mine in Russia performs better than those of international first-line brands.

Q5: How to determine whether the selection of a hydrometallurgical valve project has been successful?

Answer: To determine whether the selection is successful, it can be evaluated from two core indicators: operational stability after commissioning and maintenance cycle.

The sign of successful selection

Within six months after the valve was put into operation, there was no jamming, no internal leakage, and the regulating linearity remained good

The maintenance cycle reaches or exceeds the design life promised by the supplier (such as more than 12 months)

There are no obvious erosion grooves on the sealing surface, and there is no leakage of the valve stem packing

Typical manifestations of failed selection

Frequent valve jamming and seizing affect the flow stability of the discharge system

Severe cavitation or erosion grooves appeared on the valve core and valve seat within a short period of time

The lack of a buffer structure in the actuator leads to severe impact between the valve core and the particulate matter

The internal flow passage of the valve body is not smooth, causing material accumulation and accelerating wear

The selection logic of W&T:

First, understand the process: continuous discharging or intermittent discharging? Is liquid level adjustment needed?

Re-analyze the working conditions: Are the temperature, pressure, pressure difference, and pipeline layout complex?

Then confirm the medium: what is the solid content, particle hardness and corrosiveness?

Following this logic, the Viti technical team ensures that the valves are precisely matched with the working conditions during the selection stage, rather than using a "general model hard fit".

Summary

The core logic for valve selection in hydrometallurgical processes is: first, clarify the process requirements; then, analyze the working condition parameters; next, match the medium characteristics; and finally, choose a professional brand with imported quality and compliance qualifications.

Scientific selection steps

First, understand the process: continuous discharging/intermittent discharging? Is liquid level adjustment needed?

Re-analyze the working conditions: temperature, pressure, pressure difference, and pipeline layout

Then confirm the medium: solid content, particle hardness, and corrosiveness

Finally, choose the brand: Do you have similar performance? Does it meet the domestic access qualifications?

W&T, with complete machine production at its Russian production base, manufacturing in accordance with German technical standards, and complete A1-level TS/TSG qualifications, provides imported valve solutions for the harsh working conditions of hydrometallurgy. The core products, such as flash regulating Angle valves and wear-resistant and corrosion-resistant ball valves, have been verified by multiple hydrometallurgical projects both at home and abroad.