Perchloric Acid Digestion Hood with Scrubber

What is the Perchloric Acid Digestion Hood with Scrubber?

A perchloric acid digestion hood with scrubber adds a wet scrubbing stage to the washdown duct to capture acid mist before discharge. It is used where perchloric acid emissions are limited and acid volumes are large.

Overview

This design combines the mandatory washdown system with a packed-column wet scrubber on the dedicated exhaust path. The washdown keeps the duct free of perchlorate deposits, while the scrubber absorbs perchloric acid mist in a water-irrigated packed bed before the air reaches the stack. Removal of 90–99 % is typical depending on packing, liquid-to-gas ratio and mist loading. A circulation pump, reservoir, pH monitoring and a demister are added, and the scrubber itself is drained and flushed as part of the washdown routine so salts cannot collect in the scrubber. Face velocity at the sash remains 0.4–0.6 m/s, and fan pressure must cover the hood, duct and scrubber resistance. Materials are polypropylene or PVC for the wetted parts and stainless for structural elements where compatible.

How does it work?

Perchloric acid hoods work like other fume hoods but add a washdown system that periodically sprays water through the interior, the rear baffle and the entire exhaust duct. Heated perchloric acid vaporises, and its vapour can condense with organic material to form perchlorate salts in the duct, which are shock-sensitive and can explode. Water washdown dissolves these deposits before they accumulate. The hood and duct are constructed from non-combustible, chemically resistant materials with smooth, coved and crevice-free interiors and no sharp bends or horizontal runs where liquid or salt could collect. The washdown cycle runs for several minutes, typically daily or after each use, and drains to a dedicated chemical waste line. A dedicated exhaust system, separate from other hoods, prevents cross contamination and dilution problems.

What are the key features?

• Packed-column wet scrubber on dedicated duct
• Removal of 90–99 % of perchloric acid mist
• Scrubber flushed as part of washdown routine
• Circulation pump with pH monitoring
• Demister to limit mist carry-over
• Face velocity 0.4–0.6 m/s at the sash

What are the technical specifications?

A typical perchloric acid digestion hood with scrubber configuration offers scrubber type of Packed column, wet, removal efficiency of 90–99 % for acid mist, face velocity of 0.4–0.6 m/s, airflow of 600–2000 m3/h, washdown cycle of 3–10 min, duct and scrubber and liquid-to-gas ratio of 2–10 L/m3. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Perchloric Acid Digestion Hood with Scrubber is used in large-volume perchloric digestion, environmental testing with emission limits, geological and metallurgical assay and institutional labs with strict stack limits. Across the wider Perchloric Acid Hoods class, laboratories also deploy it for trace-metal digestion with perchloric acid, environmental and geological analysis and food and biological sample decomposition.

Which standards and certifications apply?

Relevant standards and methods include EN 14175-2 (fume cupboards, safety and performance), EN 14175-3 (type test methods), ASHRAE 110 (method of testing performance of laboratory fume hoods), NFPA 45 (fire protection for laboratories using chemicals), GB/T 34269 and IEC 61010-1. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Never share the duct with other hoods, and never use the hood for organic solvents or for drying organic material, since perchloric acid and organics can form explosive mixtures. Run the washdown cycle before and after work and keep a log of cycles and cleaning. Inspect the duct interior for salt deposits on a defined schedule, using a borescope where needed, and clean any deposit with water rather than scraping. Keep all surfaces smooth and free of ledges, gaskets or insulation that could collect salts. Verify face velocity and alarms regularly, and train users to keep glassware away from baffles. Treat washdown effluent as acidic waste and confirm the trap and drain are compatible.

How do I select the right Perchloric Acid Digestion Hood with Scrubber?

Choose a scrubber when perchloric acid emission limits apply and acid volumes are large. Confirm the scrubber is included in the washdown routine so salts cannot collect. RFQ: acid volumes, required removal, stack limit, liquid supply and waste handling.

How does it compare with other Perchloric Acid Hoods variants?

Every perchloric acid hood must have a full washdown system covering the interior and the whole duct, because partial washdown leaves deposition sites. Choose a dedicated exhaust path with no shared ductwork, and specify smooth, all-welded construction with coved corners and no internal fasteners or ledges. Select the liner for the acids used: polypropylene or PVC for mixed acid work, and stainless steel or special alloys where hot concentrated perchloric acid is handled. Match the internal height to reflux glassware and the digestion block, and select airflow so face velocity stays at 0.4–0.6 m/s. Include a washdown timer or automatic cycle, drainage with an acid-resistant trap, and airflow monitoring with an alarm. Confirm the duct material, slope and washdown coverage in writing.