Neutralising acidic gases is a critical step in rare earth refining and many chemical processes. Wet scrubbers are commonly used to remove and neutralise contaminants such as HCl, SO₂, and HF by bringing the gas stream into contact with an aqueous or alkaline solution. These reactions convert harmful gases into stable salts and safer by-products before discharge.
Reliable scrubber performance depends on more than chemistry alone. The scrubber configuration, material compatibility, and—critically—the circulation pump all play a major role in maintaining efficiency and uptime.
Challenge
Reliable circulation of corrosive scrubber acid in a continuous-duty acid scrubber system.
Solution
ISO 2858/ISO 5199 process pump with double mechanical seals and an API Plan 52 thermosiphon system.
Outcome
Stable scrubber performance, longer seal life, and reduced maintenance.
How acid scrubbers work
In a typical wet scrubber, contaminated gas enters the tower and flows through packed sections designed to maximise gas–liquid contact. A recirculating liquor—often caustic soda or lime—absorbs and reacts with acidic components. Mist eliminators remove entrained droplets, and the treated gas exits at the top of the tower.
Removal efficiency and operating reliability are driven by good packing selection, correct reagent dosing, stable pH control, and sound hydraulic design throughout the system.
The pumping challenge
Scrubber circulation pumps operate continuously in hot, corrosive conditions. They often handle acidic liquids with entrained air and fluctuating solids content, making pump selection critical. The application demands:
- chemical compatibility of all wetted parts with acids/alkalis
- dimensional interchangeability and maintainability for long life
- mechanical robustness and reliable sealing under continuous duty.
These requirements are typically met using ISO process pump standards. ISO 2858 provides dimensional interchangeability, while ISO 5199 adds enhanced requirements for shaft stiffness, bearing life, and sealing—making it well suited to demanding chemical services.
The solution
For this acid scrubber system, Global Pumps supplied an Affetti CGI-T long-coupled process pump built to ISO 2858 and ISO 5199 standards. The pump features solid thermoplastic wetted components (PP, PVDF, or PE-UHMW), with seal elastomers selected specifically for the process chemistry.
This configuration delivers excellent resistance to aggressive acids and alkalis while maintaining the interchangeability and ease of maintenance expected from ISO equipment.
The Affetti CGI-T was selected because it offers:
Materials designed for corrosive service: Solid polymer hydraulic components provide strong chemical resistance and good abrasion tolerance in scrubber recirculation duties.
A true process-duty design: Compliance with ISO 5199 ensures shaft rigidity, bearing capacity, and sealing support suitable for continuous operation and predictable reliability.
What makes a scrubber system reliable?
Pump selection is only part of the equation. Long-term scrubber reliability also depends on correct pump positioning, proper suction piping, compatible materials, and a seal support system matched to the duty.
In this installation, the CGI-T operates with double mechanical seals supported by an API Plan 52 system. The system is configured as a thermosiphon arrangement using an unpressurised buffer fluid, providing effective seal cooling, lubrication, and controlled leakage management.
What API Plan 52 involves
API Plan 52 circulates a clean buffer fluid between the inboard and outboard seals. Circulation is driven by an internal pumping ring during operation and by natural convection in the thermosiphon loop when the pump is stopped.
Although no external pump is required, correct seal pot sizing, piping layout, cooling provisions, and instrumentation are essential for reliable performance.
When to consider API Plan 53
If the process fluid is toxic, highly volatile, or regulations require zero leakage, a pressurised barrier system such as API Plan 53 is usually the better option. Global Pumps engineers both Plan 52 and Plan 53 systems, selecting the appropriate hardware and buffer or barrier fluids to meet process and compliance requirements.
ISO vs ANSI: which standard suits your process?
Both ISO (2858/5199) and ANSI/ASME B73.1 are proven standards for chemical process pumps. ISO standards focus on global dimensional interchangeability and robust process-duty design, while ANSI is more common in North America.
The choice is typically driven by site standards, spares strategy, and ease of integration—not by inherent performance differences. For this Queensland-based client, ISO pumps provided the simplest fit and met both material and sealing requirements.
The results
By combining the Affetti CGI‑T with an engineered API Plan 52 seal support system and scrubber‑appropriate materials, the client achieved:
- stable, continuous neutralisation performance
- extended seal life and reduced maintenance intervention
- straightforward servicing thanks to ISO dimensional standards.
Why partner with Global Pumps?
Global Pumps specialises in challenging pumping applications, including aggressive chemicals, slurries, and abrasive services. We deliver custom-engineered, skid-mounted systems complete with pipework, valves, instrumentation, controls, and seal support hardware.
All systems are factory assembled and tested, reducing commissioning time and on-site risk.
Whether you’re upgrading an acid scrubber, addressing seal leakage in chemical service, or standardising ISO or ANSI process pumps across your plant, our team can engineer a complete, fit-for-purpose solution—from materials and seal plans to baseplates, guards, and site integration.
Ready to improve your scrubber reliability?
Send us your enquiry and our engineers will recommend the right pump, materials, and seal support system for your process here.
