Brochures Available for Download WAHLCO has brochures available for immediate download. Aftermarket Parts & Services AOD® Ammonia On Demand Aqueous Ammonia Systems DeNOx Systems Flue Gas Conditioning Fast Response Thermocouples Fuel Control Valve Trains U2A® Urea to Ammonia Systems High Pressure Duct Heaters Ammonia Systems for SRC microSCR Applications for NOx Reduction Immersion and Pipe Heaters