Scrubber-Equipped Acid Digestion Hood

What is the Scrubber-Equipped Acid Digestion Hood?

A scrubber-equipped acid digestion hood includes a packed-column scrubber that neutralises acid vapour before discharge to atmosphere. It is chosen where acid volumes are high or stack emission limits are strict for the site.

Overview

The hood combines an acid-resistant enclosure with a wet scrubber mounted on the exhaust path. Acid fume passes through a packed bed irrigated with water or dilute alkali, where absorption and neutralisation remove nitric, hydrochloric and sulfuric acid vapour before the air is discharged. Scrubbing efficiency of 90–99 % is typical depending on packing, liquid-to-gas ratio and acid type. The system adds a circulation pump, liquid reservoir, pH control and a demister. Face velocity at the sash is 0.4–0.6 m/s, and total fan pressure must overcome both the hood and the scrubber resistance. Media or packing is cleaned periodically, and the reservoir is drained as acidic waste. A washdown system keeps the hood liner clean. This design is common in mining, metallurgical and environmental laboratories with multiple digestion positions.

How does it work?

An acid digestion hood encloses the hotplate or block digester on a chemically resistant work surface and draws acid vapours away through a rear baffle and exhaust duct. The body, liner and sash are made from polypropylene, PVC or acid-resistant stainless steel so that nitric, hydrochloric and hydrofluoric acid vapours do not corrode the surfaces. Face velocity at the sash is held at 0.4–0.6 m/s, and a corrosion-resistant fan, usually plastic or PVC-coated, moves air to atmosphere. Because digestion releases dense acid fumes and heat, larger air volumes and deeper baffles are used than in a general-purpose hood. Some models add a scrubber that neutralises acid in a packed column before discharge, reducing emissions to the stack. Water washdown and low dead volume help prevent salt accumulation and cross contamination between trace-metal samples.

What are the key features?

• Packed-column wet scrubber on exhaust path
• Scrubbing efficiency 90–99 % for acid vapour
• Circulation pump with pH control
• Demister to limit liquid carry-over
• Face velocity 0.4–0.6 m/s at the sash
• Washdown spray for liner cleaning

What are the technical specifications?

A typical scrubber-equipped acid digestion hood configuration offers scrubber type of Packed column, wet, scrubbing efficiency of 90–99 % (per acid), scrubbing liquid of Water or dilute alkali, face velocity of 0.4–0.6 m/s, airflow of 600–2000 m3/h 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 Scrubber-Equipped Acid Digestion Hood is used in large-volume acid digestion, mining and metallurgical assay, environmental testing with emission limits and battery and alloy analysis. Across the wider Acid Digestion Hoods class, laboratories also deploy it for trace-metal sample digestion, environmental soil and water analysis and food and feed elemental analysis.

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), GB/T 34269, ASTM D1193 (reagent water used in digestion blanks) 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.

Install the hood away from doors and air supply diffusers, and provide corrosion-resistant ducting with the correct slope and drainage. Commission face velocity and, where required, containment by tracer gas at the sash. Establish a hotplate and acid-usage log, and inspect the liner, sash and fittings monthly for etching or discoloration. Replace exhausted scrubber media on the schedule set by the acid load, and treat scrubber effluent as acidic waste. Keep the work surface clean and free of salt deposits, especially around the inside of the duct connection. Provide secondary containment trays and confirm the fan, duct and roof discharge are rated for the acids in use.

How do I select the right Scrubber-Equipped Acid Digestion Hood?

Choose a scrubber when acid volumes are large or local stack emission limits apply. Confirm the fan can overcome combined hood and scrubber pressure drop, and plan liquid supply, drainage and waste handling. RFQ: acid types and volumes, required removal efficiency, emission limit and service availability.

How does it compare with other Acid Digestion Hoods variants?

Choose the construction from the acids used. Hydrofluoric acid attacks glass and requires polypropylene or special liners; nitric and hydrochloric acid work needs polypropylene, PVC or acid-grade stainless steel. Decide whether a scrubber is required by local emission limits and the acid volumes handled. Match the internal height to the hotplate, rack and reflux glassware, and choose depth for tall condensers. Consider a dedicated water washdown system if the duct could collect salts. Select face velocity monitoring and alarms, and a work surface with a spill lip. Confirm the fan is corrosion-resistant rather than mild steel, and plan for acid-resistant duct material and drainage. Large multi-position digestions may need a walk-in or dual-duct layout.