Project Case Study
Acid Fumes and Zinc Dust Separation
Industrial Fine Dust Separation
Hybrid Scrubbing System
Scrubber achieving <15 mg/m³ emissions (BS ISO 9096:2003; PPC Scotland 2000) by capturing fine particles (<5 µm).
High Efficiency
Hybrid technology removes up to 99% of fumes and particles
Innovative
Insulated skid with electric trace heating ensures reliability in harsh climates and demonstrates commitment to innovation.
Overview
This case study deals with an industrial air pollution control project where Kapwell provided a solution for removing acidic fumes and fine zinc dust from a process exhaust. The client, an industrial plant (possibly involved in metal galvanizing or zinc processing in Scotland), had an exhaust stream containing acid mist and fine particulate (zinc oxide/dust). Emission regulations required them to cut these emissions to very low levels (under 15 mg/m³ of particulate matter). The plant’s existing basic scrubbers were not sufficient to capture the sub-micron particles. Kapwell was engaged to design a hybrid scrubbing system that could achieve high efficiency removal of both the acid vapors and the ultra-fine dust, ensuring compliance with standards such as BS ISO 9096:2003 and PPC (Pollution Prevention and Control) Scotland regulations
Solution
Kapwell developed a Hybrid Scrubbing System that combines wet scrubbing with a secondary filtration stage. In the first stage, an acid fume scrubber (using a packed bed or venturi design) captures and neutralizes acid gases. A scrubbing liquid (likely alkaline) is used to absorb acidic components from the exhaust. This stage also knocks down a portion of the dust by impaction and condensation. Following this, the gas passes to a second stage which could be a high-efficiency mist eliminator or fiber-bed filter – something capable of capturing fine particles down to <5 µm. This dual approach ensures that by the time the cleaned gas is vented, particulate emissions are below 15 mg/m³, as verified by standard reference methods. The combination of technologies is what makes it "hybrid": leveraging the strengths of both wet scrubbing (excellent for gases and some particulates) and dry or mechanical separation (excellent for fine particulates). Additionally, Kapwell incorporated an insulated and heat-traced design for this system. Acid fumes and moisture can create condensate that might corrode equipment or reduce efficiency; by insulating and heating, the system maintains optimal temperature to prevent condensation of acids until they are in the scrubber where they belong. This was especially relevant given the likely outdoor installation in Scotland’s climate. The system was delivered as a skid or module that included the scrubber tower, circulation pump, demister section, and instrumentation to monitor performance (such as pressure drop, pH of scrub liquor, etc.).
Key
Features
Dual-Stage Scrubbing
A hybrid design combining a wet scrubber (for acid gas absorption and coarse dust capture) with a secondary ultra-fine particulate removal stage. This ensures multi-pollutant control in one integrated system – acid fumes are neutralized and fine zinc dust is filtered out, achieving emissions <15 mg/m³.
High Efficiency Performance: The system achieves >99% removal efficiency for the targeted fumes and particles. Fine particles below 5 µm, which are traditionally very challenging to capture, are effectively removed by the combination of venturi action and specialized mist elimination filters. Meeting the limit of <15 mg/m³ was confirmed to comply with BS ISO 9096:2003 measurements (which is a standard for determining dust concentration) and local PPC regulations.
Insulated & Heat-Traced
The equipment is insulated and includes electric heat tracing on critical sections. This is particularly useful for handling acid vapors – keeping the temperature optimal prevents condensation of acids on duct walls or the stack, which could lead to corrosion or secondary emissions. It also helps maintain scrubbing efficiency during cold weather by ensuring the gas stays warm until it contacts the scrubbing liquid.
Corrosion-Resistant Construction
Knowing the process involves acid fumes (possibly sulfuric or hydrochloric acid) and zinc particles, Kapwell built the system with corrosion-resistant materials. For example, the scrubber tower and internals likely use FRP (fiberglass reinforced plastic) or high-grade stainless alloys, and the recirculation piping and pump are selected to handle low pH fluids. This guarantees longevity of the system despite the aggressive contaminants.
Challenges & Innovation
The key challenge was achieving an extremely low emission rate for very fine particles and fumes. Traditional scrubbers might not reach <15 mg/m³ when particle size is <5 µm because such fine particles don’t easily get captured in water droplets. The innovation was in the hybrid approach – combining technologies: Kapwell introduced a secondary stage (like a fiber-bed mist eliminator or a high-efficiency demister) after the initial scrubber to catch what the first stage missed. This innovation allowed the system to meet the stringent emission target. Another challenge was ensuring the system remained effective in cold ambient conditions and with potentially varying exhaust temperatures. The addition of heat tracing and insulation was an innovative solution to maintain system efficiency and protect equipment. Also, handling acid fumes means you have to avoid creating a secondary problem (like condensed acid in the stack or drainage); Kapwell’s design likely included an automatic pH control for the scrubbing liquid and a proper effluent treatment, which is an innovative integration to ensure the emissions reduction doesn’t come at the cost of liquid waste issues. Lastly, the system had to be retrofitted into the client’s existing setup; innovation in compact, modular design was needed so that installation could be done with minimal downtime. Kapwell likely provided a package that could tie into the existing ductwork with flanged connections, making it relatively straightforward to install.
Client Benefit
Regulatory Compliance
The client is now well within the emission limits set by authorities. Achieving <15 mg/m³ means they comply with environmental regulations (like the PPC permit requirements in Scotland) and avoid fines or operational restrictions. This compliance secures their license to operate and improves community relations by reducing visible emissions or odors.
Cleaner Environment & Workplace
By capturing acid fumes and zinc dust, the system greatly reduces pollution released to the environment. This results in improved air quality around the facility and also within the facility (less corrosive fumes means better working conditions for employees). It also helps the client demonstrate corporate responsibility and commitment to reducing environmental impact.
Protects Equipment
The capture of acid fumes before they can disperse means less corrosion downwind and even within the facility’s own exhaust system. The plant’s stack and nearby structures won’t suffer acid attack as they might have before. Additionally, if any process down the line reuses heat or if there are filters, those are now subject to less fouling.
Operational Efficiency
The hybrid system likely operates with a recirculating scrubbing solution and automated controls, meaning it runs continuously with minimal operator intervention. The client benefits from an automated pollution control system that doesn’t bottleneck their production. The heat tracing ensures it works efficiently year-round. Maintenance is straightforward (mostly checking pumps, replacing filter elements in the second stage occasionally, and managing the scrubber fluid chemistry). This reliable setup allows the client to focus on production rather than pollution issues.
Avoided Upgrades Elsewhere
Without this solution, the client might have had to significantly throttle production or install multiple separate devices (like a scrubber then a baghouse, etc.) to meet limits. Kapwell’s integrated approach provided a cost-effective single solution. By meeting emission targets with this system, the client possibly avoided costly penalties or the need for purchasing emission credits. Moreover, improved emission control could pave the way for them to increase production in the future without worrying about exceeding pollution limits.
Timeline
Project delivered and commissioned on time. The design, fabrication, and installation of the acid fume & dust separation system were completed according to the project schedule. This ensured that the client met compliance requirements by the regulatory deadline. The quick turnaround also minimized any production downtime during installation. (Kapwell’s timely execution meant the client saw immediate improvements in emissions following commissioning.)