A first contact reactor, mechanical separator device, one or more second contact reactors, silo, filter, one or more fans each equipped with one or more vibration dampers, an optional wet scrubber and stack are each integrated into a single compact air quality control system (AQCS) compartment. Additionally, a process gas cooling system may be integrated into the compact AQCS compartment. Benefits of the subject compact AQCS compartment includes footprint reduction, operating cost reduction from reduced pressure drop due to reduced ductwork, capital cost reduction from reduced ductwork, noise reduction, weather protection and increased adaptability to meet specific system requirements.