Optimizing Material of Construction for Agitators in High-Temperature, High-Pressure Leach Reactors Handling Abrasive Mineral Slurries

High-pressure and high-temperature reactors used in hydrometallurgical processes often face operational challenges due to highly abrasive and chemically aggressive leach slurries derived from mineral ores. The agitators used in these systems play a crucial role in maintaining slurry homogeneity and enhancing leaching efficiency. However, they are prone to rapid wear and failure due to mechanical abrasion and chemical corrosion.

Material challenges in agitator applications

Agitators operate under extreme conditions, encountering:
a) Temperatures >200 °C
b) Pressures >20 bar
c) Slurry solids content >30%
d) Highly acidic/alkaline or oxidative chemical environments

This demands MOC selections that balance abrasion resistance, corrosion resistance, and mechanical strength. A recent study emphasized the failure of conventional rubber linings in leaching circuits due to slurry abrasion and thermal degradation [1]. Figure 1 represents custom figures (agitator cross-sections and wear contour maps):

Figure 1:Custom figures (agitator cross-sections and wear contour maps).

Advances in MOC for agitators Metallurgical solutions:

a) Super Duplex Stainless Steels (e.g., SAF 2507): Enhanced corrosion resistance with moderate wear strength
b) Nickel Alloys (e.g., Inconel 625, Hastelloy C276): Excellent corrosion properties but limited wear resistance
c) High Chromium White Cast Irons: Used as claddings for their hardness (>600HV)

Coating and composite solutions:

a) Ceramic-Polymer Composites: Applied as protective overlays; e.g., alumina or silicon carbide-based coatings
b) Thermal Spray Coatings (HVOF): Provide surface hardness >1000HV with corrosion stability
c) Chao’an [2] explored the use of abrasion-resistant linings for agitators in hydrochloric acid leaching circuits, reporting a 40% increase in service life.

Design optimization

Agitator design also contributes to durability:
a) Blade profile affects slurry turbulence and wear zones
b) CFD simulations show that hydrodynamically optimized impellers reduce wear concentrations near blade tips.

A CFD-based redesign trial [3] resulted in a 25% lower maintenance frequency in polymetallic nodule reactors.

Case studies and field data

Table 1

Table 1:Comparative performance of agitator MOC in pilot trials.

a) For leach slurries with >30% solids and pH <2, use ceramic-reinforced duplex or Inconel-blended coatings.
b) Use CFD-optimized blade geometry to limit erosion zones.
c) Schedule Non-Destructive Testing (NDT) intervals to predict failure [4-6].

Advancements in MOC especially hybrid and coated materials show promise in extending agitator lifespan in harsh mineral leaching conditions. However, material choice must be coupled with design optimization and operational strategy for best performance outcomes.

1. Akan AKM (2005) Abrasion failure of lining rubber on agitator blades in the leaching circuit of mineral processing industries. Doctoral dissertation, CQ University.
2. Chao’an D (2024) Concentrator design. In: Kuangdi X (Ed.), The ECPH encyclopedia of mining and metallurgy. Springer, Singapore.
3. Mittal NK, Sen PK (2003) India's first medium-scale demonstration plant for treating poly-metallic nodules. Minerals Engineering 16(9): 865-868.
4. Nazari G, Lamotte J, Ries M, Agin J, Tizon E, et al. (2018) Development of a metallurgical process for Eramet’s Mabounié Nb-REE project. Extraction 2018: Proceedings of the First Global Conference on Extractive Metallurgy, pp. 2353-2366. Springer International Publishing.
5. Rao LK, Sriharsha P, Sarkar S, Rao MS (2025) Process intensification in precipitation of uranium from post alkali leach liquor using re-dissolution of sodium diuranate slurry: A short review of laboratory and pilot scale test results. Hydrometallurgy 235: 106491.
6. Thamida SK, Sharma VK, Reddy BNK (2024) Carbonation and modeling study for process liquor in batch mode using flue gas in the mining and mineral processing industry. Chemical Papers 78(7): 4189-4199.