A wet scrubber is an air pollution control device that removes gaseous pollutants and particulate matter from industrial exhaust by bringing the contaminated gas stream into contact with a scrubbing liquid — usually water or a chemical solution. The liquid captures, dissolves, or chemically reacts with the pollutants, and the cleaned gas exits the system while the contaminated liquid is treated or recirculated. Removal efficiencies of 95‑99% are standard for properly designed systems, with outlet concentrations below 10 ppm achievable for most acid gases, ammonia, and hydrogen sulfide. This guide covers all 10 wet scrubber types we manufacture — 3 categorized by engineering design and 7 by target contaminant or use case — so you can match the right system to your exhaust conditions.

Wet Scrubber Types by Design

Spray Tower Scrubber

A spray tower scrubber — also called a spray tower wet scrubber or simply a spray tower — is the simplest industrial wet scrubbing design: a vertical cylindrical vessel with no internal packing, where scrubbing liquid is atomized through full‑cone nozzles into the rising gas stream. The contaminated gas enters at the bottom and flows upward through the spray zone, contacting fine droplets that capture soluble gases and coarse particulate.

The spray tower achieves 90‑95% removal of highly soluble gases such as HCl and NH₃. Pressure drop is the lowest of any wet scrubber design — typically 100‑250 Pa — because there is no packing to resist gas flow. Spray towers handle inlet gas temperatures up to 800°C with a quench section upstream, making them the preferred choice for hot exhaust from furnaces, incinerators, and kilns.

Packed Bed Scrubber

A packed bed scrubber — also called a packed bed scrubbers system or packed bed scrubber design unit — is a vertical counter‑current tower filled with packing media (typically PP Pall rings or structured packing) that maximizes the gas‑liquid contact surface area. The scrubbing liquid is distributed over the top of the packing and flows downward as a thin film, while contaminated gas flows upward through the wetted packing surface.

A packed bed scrubber design achieves 95‑99% removal of acid gases, ammonia, H₂S, chlorine, and VOCs — the widest contaminant range of any wet scrubber design — because the 110‑220 m²/m³ of packing surface area provides orders of magnitude more mass transfer than an open spray chamber. Packing depth ranges from 0.6 m for highly soluble HCl and HF to 1.8 m for moderately soluble H₂S and Cl₂. Gas velocity is held to 1.0‑1.5 m/s to prevent flooding.

Crossflow / Horizontal Scrubber

A crossflow scrubber — also called a cross flow scrubber or crossflow scrubbers system — arranges the gas flow horizontally through a vertical packed bed, while the scrubbing liquid flows downward by gravity. This configuration reduces total system height by 40‑60% compared to a vertical counter‑current tower.

Crossflow scrubbers handle the same contaminant range as a vertical packed bed — HCl, HF, H₂SO₄, HNO₃, Cl₂, H₂S, NH₃ — and achieves comparable 95‑99% removal at L/G ratios of 0.5‑0.9 L/m³. The packing section is typically 0.6‑1.0 m thick in the gas flow direction; multiple stages can be arranged in series when higher efficiency is required. Access for packing inspection and media replacement is a major advantage — the packed section can be withdrawn as a cartridge without entering the vessel.

Wet Scrubber Types by Application

Acid Fume Scrubber

An acid fume scrubber — also called a chemical fume scrubber or acid scrubber system — removes corrosive acid gases from industrial exhaust using a caustic scrubbing solution. The scrubber system targets HCl, H₂SO₄ mist, HF, and HNO₃ from pickling lines, electroplating tanks, chemical reactors, and battery manufacturing. The standard chemistry is NaOH at 5‑20% concentration.

Reactions are fast and essentially irreversible — HCl + NaOH → NaCl + H₂O and HF + NaOH → NaF + H₂O — achieving 99%+ removal at L/G ratios of 0.5‑0.7 L/m³ with only 0.6 m of PP packing. PP construction is mandatory: HF etches glass, and HCl vapor corrodes stainless steel at concentrations above 10 ppm in the gas phase. For mixed acid streams (HCl + HF from stainless steel pickling), a two‑stage system with separate sumps prevents cross‑contamination.

Ammonia Scrubber

An ammonia scrubber — also called an ammonia scrubber system or ammonia NH₃ scrubber — uses a dilute sulfuric acid solution (H₂SO₄ at 5‑10% concentration) to capture ammonia from exhaust streams. The reaction 2NH₃ + H₂SO₄ → (NH₄)₂SO₄ produces ammonium sulfate, a water‑soluble salt that can be concentrated and sold as liquid fertilizer (21% nitrogen, 24% sulfur).

An NH₃ scrubber achieves 95‑99% removal at L/G ratios of 0.7‑1.2 L/m³ with 1.0‑1.2 m of PP packing depth. pH control is critical — maintain pH 2‑4 in the sump for optimal absorption; above pH 5, ammonia breakthrough occurs. Ammonia scrubbers are installed in fertilizer plants, cold storage facilities, semiconductor fabs, livestock housing, and chemical manufacturing.

H2S Scrubber

An H2S scrubber — also called a hydrogen sulfide scrubber — removes H₂S from industrial exhaust, biogas, and wastewater foul air using chemical absorption in a packed column. An H2S scrubber system operates with one of three chemistries: caustic (NaOH: H₂S + 2NaOH → Na₂S + 2H₂O), oxidative (NaOCl: H₂S + NaOCl → S↓ + NaCl + H₂O), or chelated‑iron catalyst for continuous high‑load applications above 200 kg H₂S/day.

Removal efficiency is 95‑99% at L/G 0.7‑0.9 L/m³ with 1.0‑1.2 m of PP packing. Caustic requires spent sulfidic caustic oxidation before sewer discharge; oxidative produces sewer‑acceptable sulfate directly; chelated‑iron regenerates with air for near‑zero chemical cost. H2S scrubbers are deployed in wastewater treatment, biogas purification, petroleum refining, and natural gas processing. PP construction resists both H₂S and the sulfuric acid formed by secondary oxidation.

Chlorine Scrubber

A chlorine scrubber — also called a chlorine gas scrubber or chlorine gas Cl₂ scrubber — captures Cl₂ gas from water treatment plants, chemical manufacturing, bleach production, and cylinder storage areas using a sodium hydroxide solution. The reaction Cl₂ + 2NaOH → NaOCl + NaCl + H₂O is fast and exothermic, producing sodium hypochlorite and common salt as byproducts.

A single packed bed with 0.8‑1.0 m of PP packing at L/G 0.7‑1.0 L/m³ achieves 99%+ removal, reducing outlet Cl₂ below 1 ppm. For safety‑critical applications — such as a chlorine cylinder storage area — an emergency scrubber sized for the full cylinder contents within 30 minutes is required by EPA RMP fire codes. Key design requirements include dual‑redundant caustic pumps, backup power, fail‑open inlet valves, and automatic actuation from Cl₂ detectors.

Emergency Vent Scrubber

An emergency vent scrubber — also called an emergency gas scrubber or emergency vent scrubber — is a safety‑critical standby system designed to capture a sudden, high‑volume release of toxic gas from a storage tank rupture, cylinder failure, or reactor over‑pressure event. Unlike a process scrubber that runs continuously, an emergency scrubber sits on standby and must activate within seconds of a release detection signal.

It is sized for the worst‑case scenario: the full contents of the largest storage vessel at maximum discharge rate. For chlorine, this means neutralizing a 1‑ton cylinder within 30 minutes per EPA Risk Management Program fire code requirements. The standard chemistry is NaOH at 15‑20% with the sump sized for no‑makeup operation. Key requirements include dual‑redundant pumps, backup generator power, fail‑open inlet valves, and automatic actuation from gas detectors. Emergency scrubbers achieve up to 99.995% removal for chlorine, SO₂, and ammonia releases.

Odor Control Scrubber

An odor control scrubber — also called an odor control scrubbers unit or industrial odor control scrubber — removes hydrogen sulfide, ammonia, mercaptans, and volatile organic compounds from foul air at wastewater treatment plants, food processing facilities, and rendering operations. An industrial odor control scrubber typically uses a two‑stage configuration: a caustic stage (NaOH) removes the bulk H₂S and acid gases, followed by an oxidizing stage (NaOCl or H₂O₂) that oxidizes residual odor compounds.

Multi‑stage systems reduce chemical consumption by up to 50% through staged pH control compared to single‑stage caustic‑only scrubbers. Flow rates range from 2,000 CFM for a single pump station vent to over 80,000 CFM for a large headworks building. Because odor complaints — not ppm numbers — are the primary compliance driver, the performance metric is a polished outlet with no detectable odor at the property line. For zero‑odor discharge, an activated carbon polishing stage is added downstream.

Laboratory Scrubber

A laboratory scrubber — also called a laboratory wet scrubber or laboratory fume scrubber — is a compact gas cleaning system designed for fume hood exhaust from university research labs, pharmaceutical R&D facilities, hospital pathology labs, and industrial quality control laboratories. A laboratory fume scrubber handles flow rates from 200 to 3,000 CFM with an unpredictable contaminant mix: HCl, HNO₃, H₂SO₄, HF, NH₃, and organic solvent vapors through the same exhaust duct.

A compact packed bed scrubber (0.5‑0.8 m of PP packing, 200‑500 mm vessel diameter) with water or dilute NaOH handles the acid gases. Acid‑impregnated activated carbon downstream captures residual solvent vapors. PP construction handles the mixed acid environment without corrosion risk. Fan speed is commonly controlled by a VFD linked to fume hood sash position to reduce energy consumption and noise when hoods are closed. For full‑scale pilot plant applications, a scaled‑down industrial packed bed scrubber provides the same chemistry in a smaller footprint.

Materials and Construction

The material you choose for the scrubber vessel, packing, and internals determines the system’s service life, maintenance cost, and capital cost. Three materials cover the majority of industrial wet scrubber applications:

PP is the default choice for most of our scrubber systems — it handles NaOH, H₂SO₄, HCl, HF, H₂S, Cl₂, and NaOCl without measurable degradation at operating temperatures below 80°C. At 3× the corrosion resistance of 304 stainless steel at roughly half the material cost, it is the most cost‑effective material for acid gas scrubbing. The entire vessel wall is corrosion‑resistant — there is no internal coating to blister or re‑apply. For temperatures above 80°C, we switch to FRP or dual‑laminate. For structural spans above 2 m diameter, FRP provides the rigidity PP cannot. Our engineering team specifies the material based on your gas temperature, contaminant chemistry, and site conditions — not our inventory.

How to Select the Right Wet Scrubber

Five inputs determine which scrubber type and configuration fits your application:

1. Gas flow rate (Qg): m³/hr or CFM. Determines vessel diameter and fan size. Under 2,000 CFM → compact packed bed or lab scrubber. Over 50,000 CFM → spray tower or multi‑stage packed bed
2. Contaminant type and inlet concentration: Determines scrubbing chemistry. Acid gases → NaOH. Ammonia → H₂SO₄. Mixed contaminants → multi‑stage
3. Required outlet concentration: Per your air permit. Determines packing depth, L/G ratio, and whether a polishing stage is needed
4. Gas temperature and moisture: PP ≤80°C, FRP ≤120°C. Hot gas → quench section upstream of the packed section
5. Site constraints: Height limited → horizontal crossflow. Indoor → compact packed bed. Explosion hazard → ATEX‑rated fans and N₂‑blanketed sump

With those five inputs, you can narrow the options to one or two designs. The table below maps the most common industrial scenarios to the recommended scrubber type.

Frequently Asked Questions

What is a wet scrubber and how does it work?

A wet scrubber is an air pollution control device that removes gaseous pollutants and particulate matter from industrial exhaust by contacting the contaminated gas with a scrubbing liquid — usually water or a chemical solution. The liquid captures, dissolves, or chemically reacts with the pollutants inside a tower containing packing media or spray nozzles. The cleaned gas exits to atmosphere; the contaminated liquid is recirculated or treated. Wet scrubbers achieve 95‑99% removal efficiency for most acid gases, ammonia, and hydrogen sulfide. They are the most widely used industrial air pollution control technology because they handle corrosive gases, high temperatures (with quench), and variable loads — all in a single device with no consumable media beyond the scrubbing chemical.

What are the main types of wet scrubbers?

Wet scrubbers divide into two categories. By design: spray tower (open vessel, low pressure drop), packed bed (tower filled with PP Pall rings or structured packing for maximum gas‑liquid contact), and crossflow/horizontal (packed bed with horizontal gas flow for low‑headroom sites). By application: acid fume scrubber (HCl, HF, H₂SO₄), ammonia scrubber (NH₃ with H₂SO₄), H2S scrubber (NaOH or oxidative), chlorine scrubber (NaOH), emergency vent scrubber (safety‑critical standby system), odor control scrubber (two‑stage for municipal and food processing), and laboratory scrubber (compact system for fume hood exhaust). Any design type can be configured for any application — the key difference is the scrubbing chemistry and operating parameters.

How much does a wet scrubber cost?

A pre‑engineered PP packed bed scrubber for 5,000 CFM with automated pH control costs approximately $20,000‑35,000 installed. Operating cost is dominated by chemical consumption: roughly $0.50‑1.50 per kg of pollutant removed for NaOH or H₂SO₄. Annual maintenance (pH probe replacement, pump seal inspection, packing inspection) adds $3,000‑6,000. A 50,000 CFM multi‑stage system with FRP construction, redundant pumps, and continuous emissions monitoring typically ranges from $150,000‑300,000 depending on the contaminant complexity and automation level. Every system we build is custom‑quoted based on your gas flow rate, contaminant concentration, and site conditions — contact our team with your operating data for a budget proposal within 48 hours.

How do I choose between a spray tower and a packed bed scrubber?

Choose a spray tower when your contaminant is highly soluble (HCl, NH₃ at low concentration) and you have high gas volumes (above 20,000 CFM) where low pressure drop matters for operating cost. Choose a packed bed when you need 99%+ removal of moderately soluble gases (Cl₂, H₂S, SO₂), when space is limited (packed beds are more compact per unit of removal), or when the contaminant concentration is variable (packing provides a buffer). In practice, a packed bed scrubber is the default choice for industrial acid gas scrubbing — it delivers the best removal efficiency per meter of vessel height and handles the widest range of contaminants. Spray towers are preferred for high‑temperature exhaust (with quench) and high particulate loads that would clog packing.

Can one wet scrubber handle multiple contaminants?

Yes, but the design must account for the hardest‑to‑remove compound in the mix. A packed bed scrubber with a caustic solution will capture HCl, HF, SO₂, and Cl₂ simultaneously — the HCl and HF are removed first (fastest reaction), and the Cl₂ requires the most packing depth. For mixed acid + alkaline contaminants (e.g., HCl + NH₃ from a chemical reactor), a single scrubber cannot handle both — the caustic scrubs the acid, but the ammonia passes through unreacted. A two‑stage system — first stage H₂SO₄ for NH₃, second stage NaOH for HCl — is required. For mixed H₂S + odor compounds, a two‑stage caustic‑to‑oxidative system captures the H₂S in the first stage and oxidizes residual odors in the second.

Get a Wet Scrubber Proposal

We custom‑engineer every wet scrubber system to your gas flow rate, contaminant concentrations, outlet permit limits, and site constraints — in PP, FRP, or dual‑laminate construction. Contact our engineering team with your exhaust data and we will provide a preliminary sizing, budget price, and system P&ID within 48 hours. No obligation, no sales pressure — just engineering.

XICHENG EP LTD — 500+ wet scrubber installations across 30 countries. PP and FRP systems from 500 to 100,000 CFM.

About XICHENG EP

XICHENG EP LTD is an industrial air pollution control equipment manufacturer with 16+ years of production experience, 2,600+ systems shipped, and installations in 60+ countries. We manufacture in China, with in‑house PP sheet extrusion, CNC cutting, hot‑gas welding, and FRP filament winding — every scrubber component from raw material to finished vessel is fabricated under one roof. No outsourced fabrication, no subcontractor delays.

Certifications and Compliance

• CE Marking — Machinery Directive 2006/42/EC, EMC Directive 2014/30/EU
• RoHS — 2011/65/EU compliant materials throughout
• ISO 9001:2015 — Quality management system
• ISO 14001:2015 — Environmental management system
• SGS material testing — PP sheet, FRP laminate, weld integrity verified
• Design basis per EU 2010/75/EU Industrial Emissions Directive
• Engineered to meet US EPA NESHAP and OSHA 1910.94

How to Order

1. Send your operating data: Gas flow rate (CFM or m³/hr), contaminant type and inlet concentration (ppm), required outlet limit per your permit, gas temperature, and available site footprint. Contact our engineering team
2. Receive your proposal: Within 48 hours — preliminary sizing, process flow diagram, budget price, and delivery timeline. No obligation
3. Review and approve: Once the proposal meets your requirements, we issue a formal quotation with detailed technical specifications
4. Drawing approval: P&ID, general arrangement, and electrical schematic for your sign‑off before fabrication begins
5. Manufacturing and testing: 6‑10 weeks fabrication. Pre‑shipment water‑tightness test, recirculation test, and control system checkout
6. Shipping and commissioning: Containerized sea freight or air freight worldwide. Remote commissioning support via video call included; optional on‑site supervision available

Global Shipping

We ship wet scrubber systems worldwide from our manufacturing facility in China. Regular containerized sea freight to ports in North America (Los Angeles, Houston, New York), Europe (Rotterdam, Hamburg, Antwerp), the Middle East (Jebel Ali, Dammam), Southeast Asia (Singapore, Port Klang), and Australia (Sydney, Melbourne). Air freight available for urgent deliveries and smaller systems. All equipment is crated, shrink‑wrapped, and container‑loaded with desiccant for ocean transit.