The Challenge of Gold Refining Exhaust
If you are designing a gold refining line using nitric acid and aqua regia, you already know: the fumes generated are among the most aggressive and hazardous in the entire metallurgical industry.
Gold refining with aqua regia and nitric acid produces a complex mixture of toxic, corrosive gases that demand a purpose-engineered treatment solution. The process involves:
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Nitric acid reactions generating nitrogen oxides (NO, NO₂) — brown, highly toxic fumes
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Aqua regia (HCl + HNO₃) producing chlorine gas (Cl₂), nitrosyl chloride (NOCl), and additional NOx compounds
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Sodium metabisulfite precipitation releasing SO₂ fumes
These gases are not only hazardous to personnel and the environment but also highly corrosive to equipment. A standard ventilation system is insufficient—you need a specialized acid gas scrubbing system designed specifically for precious metals refining applications.
Why Gold Refining Requires Specialized Scrubber Design
Unlike general industrial exhaust, gold refining fumes present unique challenges:
| Challenge | Impact |
|---|---|
| Multiple gas types | NOx, Cl₂, SO₂ require different treatment chemistries |
| Concentration spikes | Batch refining creates sudden fume surges |
| High corrosivity | Unscrubbed gases destroy fans, ductwork, and equipment instantly |
| Temperature variations | Exothermic reactions can elevate exhaust temperatures |
A standard “off-the-shelf” scrubber will fail in this environment. What you need is a custom-engineered system designed specifically for the chemistry of precious metals refining.
Yuanfang EP’s Engineered Solution for Gold Refining Applications
At Henan Yuanfang Environmental Protection Equipment Co., Ltd., we have extensive experience designing acid gas scrubbing systems for precious metals operations. Our approach combines correct chemistry, sufficient retention time, and corrosion-resistant engineering to deliver systems that perform reliably for decades.
Multi-Stage Scrubbing Chemistry
Based on the proven chemistry required for gold refining fumes, our systems typically incorporate:
Stage 1: Oxidizing Scrubber (H₂O₂ Solution)
Converts NO to NO₂, making it soluble and ready for neutralization . Hydrogen peroxide is the preferred oxidizer as it’s effective and decomposes to water and oxygen.
Stage 2: Alkaline Scrubber (NaOH/Na₂CO₃ Solution)
Neutralizes acidic gases including NO₂, Cl₂, and SO₂. Sodium hydroxide or sodium carbonate reacts with these gases to form harmless salts.
Stage 3: Polishing Scrubber (Optional)
Final capture of any remaining contaminants, often with pH monitoring to verify complete neutralization .
Engineered for Efficiency: Packed Tower Technology
Laboratory-scale bubbling systems—like gas washing bottles—are ineffective for production-scale refining . The industrial solution is a packed tower wet scrubber , which our company designs and fabricates in-house.
Key design features we implement:
| Feature | Function |
|---|---|
| Random packing media | Maximizes gas-liquid contact surface area |
| Counter-current flow | Fumes rise against descending scrubbing solution for maximum efficiency |
| Mist eliminator | Removes entrained droplets from exhaust gas |
| Recirculation system | Continuous chemical distribution for consistent performance |
| pH/ORP monitoring | Real-time control of scrubbing chemistry |
Material Selection: Critical for Longevity
Aqua regia and nitric acid fumes will destroy carbon steel and standard metals within hours. Our scrubbers are constructed from corrosion-resistant materials:
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PP (Polypropylene) – Exceptional resistance to acids and alkalis, ideal for most refining applications
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FRP (Fiberglass Reinforced Plastic) – Superior strength for larger systems, excellent chemical resistance
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CPVC/PVC – For interconnecting ductwork and piping
As noted in industry discussions, even vacuum pumps must be protected, which is why we recommend PVC eductors rather than pulling fumes through mechanical pumps -1-5.
Complete System Scope: What We Deliver
For your gold refining line, our quotation and technical proposal will include a comprehensive engineered system:
1. Packed Tower Wet Scrubber
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Custom-sized for your airflow requirements
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Multi-stage design with dedicated packing sections
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Corrosion-resistant PP/FRP construction
2. Complete Auxiliary Systems
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Recirculation pump with magnetic drive (no seals to leak)
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Liquid reservoir with level control
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Chemical dosing system for automated pH maintenance
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Mist eliminator section
3. Air Moving Equipment
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Corrosion-resistant fan (located AFTER the scrubber to handle clean air only)
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Variable frequency drive for airflow control
4. Interconnecting Components
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CPVC/PVC ductwork
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Instrumentation (differential pressure, flow, pH)
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Control panel with PLC for automated operation
5. Documentation & Support
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P&ID diagrams
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Installation manual
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Start-up assistance
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Operator training
Our Track Record: Serving the Precious Metals Industry
While every application is unique, our team has successfully delivered scrubbing systems for:
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Gold refining operations using aqua regia and nitric acid processes
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Silver refining and parting operations
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Base metal leaching facilities
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Precious metals recovery from electronic scrap
We understand the specific challenges of your industry, from the intermittent nature of batch refining to the extreme corrosivity of the gases involved.
Technical Considerations for Your Proposal
To provide you with an accurate quotation and optimized technical proposal, we will need:
| Parameter | Why It Matters |
|---|---|
| Maximum airflow (CFM/m³/h) | Determines scrubber diameter and fan sizing |
| Batch size and frequency | Affects chemical consumption and peak loads |
| Peak gas concentrations | Influences packing height and recirculation rate |
| Available utilities | Power, water, drain access |
| Site constraints | Space, access for installation |
Why Partner with Yuanfang EP for Your Gold Refining Scrubber?
1. Deep Understanding of Your Chemistry
We don’t just build scrubbers—we understand the NOx, chlorine, and SO₂ chemistry of precious metals refining
2. Engineered for Longevity
Our PP and FRP construction stands up to the most aggressive acid fumes, providing decades of reliable service .
3. Complete System Responsibility
From design through fabrication to startup support, we take single-source responsibility for your system’s performance.
4. Proven Efficiency
Our packed tower designs achieve the 99%+ removal efficiencies required to meet environmental regulations and protect personnel .
Ready to Move Forward?
We understand you’re in the design phase of your gold refining line—this is the ideal time to integrate a properly engineered scrubbing system. Retrofitting later is always more expensive and disruptive.
Contact our engineering team today to discuss your specific requirements and receive a detailed quotation and technical proposal tailored to your gold refining operation.
Specializing in acid gas scrubbing systems for precious metals refining applications