A pigment manufacturer operates batch reactors that emit very low volumes of highly concentrated ammonia. Batches occur over a 20-hour period and ammonia concentrations varies from <1 to 96%.
Ammonia is an odorless gas with a permissible exposure limit (PEL) of 50 ppm. Ammonia can also form explosive mixtures in air with a lower explosive limit (LEL) of 15% and upper explosive limit (UEL) of 28%.
The customer needs to recover a 25-28% (w/w) aqueous solution of ammonia for re-use as a raw material while meeting air emission limits. The recovered ammonia can have no potential silicone due to sensitivity of the end-product. The system must be robust and safe to operate.
The customer selected a custom designed Envitech ammonia recovery system based on Envitech’s proprietary design for low flow rate applications. The scope of supply includes a compressor, a packed bed concentrator, a packed bed absorber, instruments, PLC and HMI control system, and an equipment skid containing pre-assembled vessels, instruments, control system, pumps, piping, valves, fitting, and instruments with pre-wiring. Panel and components are explosion proof. Vessels are 316SS fabricated to pressure vessel ASME code for 90 PSI. All components are specially selected to ensure no possible silicone contamination.
The gas is drawn out of the reactor using a specially selected compressor ideally suited to handle corrosive, low flow rate gases and to generate high pressures while generating an upstream vacuum.
The concentrator uses recirculated water to absorb and concentrate ammonia. A 2nd stage absorber recovers residual ammonia to meet air emission limits.
Blowdown from both stages purge concentrated ammonia for re-use as raw material.
The recovery system will be commissioned in early 2020 and will meet the design parameters and performances below.
- Inlet flow rate: 50 acfm
- Inlet temperature: 68oF
- Carrier gas composition: N2
- Peak ammonia concentration: 96%
- Concentration of recovered ammonia: > 25%
- Ammonia removal: > 98%
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