Current production facility is giving away a diluted aqueous ammonia solution which is a by-product from one of their chemical reactors.

engineering

Description

Problem Statement

Current production facility is giving away a diluted aqueous ammonia solution which is a by-product from one of their chemical reactors. However, another reactor in their facility, which operates in batch mode, requires ammonia with a minimum concentration of 87 mol% NHin water. Instead of giving away the aqueous ammonia and then re-purchasing pure ammonia, the plant proposes:

  • to install a 30,000 US gallon intermediate storage tank for the diluted aqueous ammonia solution,

  • to install a continuous distillation system with bubble cap trays to recover the ammonia from a 1.5 to 25 mol% NHin water solution (i.e., “diluted aqueous ammonia stream”), and

  • to install a 25 mconcentrated aqueous ammonia product storage tank (indicate the desired orientation of the tank, i.e., vertical vs. horizontal installation).

    Diluted aqueous ammonia conditions entering the feed pump:

  • Concentration: 1.5 to 25 mol% NHin water

  • Temperature: 40 to 75F

  • Pressure: the pressure gauge is broken, but the operator mentioned that the diluted aqueous

    ammonia entering the pump is in a liquid state.

  • Mass flow rate: 1600 kg/h

    The environmental engineer emphasized that the water treatment facility cannot accept any effluent from the new process that contains more ‘than a few ppm of NHin water’.

    Additional Information

    Utilities:

  • Cooling tower water supply: 25C; max. 800 USGPM

  • Glycol supply: 20 vol% mono-ethylene-glycol in water; 45F; available in a very limited quantity.

  • Heating medium: Dowtherm G; 570F, max. 12,000 USGPH

  • Plant air: max. 150 psig

  • Instrument air: max. 150 psig

1. Draw a P&ID of the system, i.e., the P&ID can be neatly drawn by hand.

o You may wish to exclude the following from the P&ID: the waste water treatment facility, the diluted aqueous ammonia storage tank, and the heat tracing of pipes and equipment.

2. Determine:

o the heating medium flow rate to the reboiler,
o the cooling medium flow rate to the condenser, and
o the reflux pump type, model number, and manufacturer.

  1. Indicate all instruments (e.g. flow, pressure, temperature) on the P&ID.

  2. Show all valves and pressure relief devices.

  3. Perform Hazard and Operability (HAZOP) analysis.


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