Acid Gas & Halogenated Thermal Oxidizer

Acid gases formed during oxidation, HCl, HF, SO₂ and other acid-forming species, are handled by a quench and wet scrubbing section after the combustion chamber. The quench cools the hot exhaust rapidly with water spray or recirculated scrubber liquid, which also limits dioxin and furan formation on chlorinated streams. A packed tower or venturi scrubber then neutralises the acid gases with caustic soda, lime slurry or soda ash, with a second stage for trace polishing and a mist eliminator. The effluent is pH-neutralised and solids are removed before discharge. CRA engineers the oxidiser and the acid gas control section together.

A properly engineered acid gas and halogenated thermal oxidiser is designed for destruction efficiency above 99.99% for halogenated VOCs, acid gases and complex halogenated and hazardous emissions under controlled operating conditions. The targets usually come from hazardous waste combustion rules such as US EPA RCRA, MACT requirements for chemical manufacturing, semiconductor emission limits and local air permits. Reaching these levels requires a combustion temperature high enough to break the halogen bonds, enough residence time, precise oxygen control, a refractory chamber that holds a uniform temperature and continuous emissions monitoring.

An acid gas and halogenated thermal oxidiser is the right choice for corrosive, chlorine-, fluorine-, bromine- and sulphur-bearing waste streams that a conventional oxidiser cannot handle. Typical sources are vinyl chloride production, fluorochemical manufacturing, semiconductor fabrication with halogenated etching and chamber cleaning gases, agrochemical and pharmaceutical synthesis with chlorinated intermediates, mixed halogenated solvent waste and speciality bromine and fluorine chemistry. What makes the unit different is the acid-resistant refractory, corrosion-resistant materials in the wetted sections, the integrated quench and scrubbing for HCl, HF and SO₂, and instrumentation that tolerates the corrosive environment. CRA designs the combustion and scrubbing sections together for these streams.

Temperature, residence time, refractory, metallurgy and scrubber chemistry decide performance. The combustion temperature and residence time are set high enough to break the halogen bonds, and they are often written into the permit. The refractory, the quench and the scrubber use materials suited to the acid gases in the stream, and the reagent feed is matched to the acid load. The controls cover temperature, oxygen, scrubber chemistry and stack monitoring, with safety interlocks.

The figures in these FAQs are general guidance for acid gas and halogenated service, and the performance of a specific unit depends on the composition of the waste stream, its halogen and sulphur content, flow and concentration swings, the emission limits in the permit and the site utilities. CRA reviews the stream data, including upset and turndown cases, before sizing the combustion chamber, quench, scrubber and controls. For a specific application, send the waste gas analysis, flow cases and the emission limits that apply, and CRA's engineering team reviews the design basis with you before any proposal is prepared.