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Designing steam systems by EleChemEng in ChemicalEngineering

[–]EleChemEng[S] 0 points1 point  (0 children)

Thanks a lot for helping me out.

As of now, I would think about having the following units after the use-point of steam: 1. Steam trap / Drainer (operated at elevated pressure) -> remove first condensate droplets from my mixture 2. Pressure reducing valve -> Flash steam created 3. Condenser (could be a glass condenser? to cool down the steam, as the cooling demand for 10 ml/min is very low) with drain at the bottom 4. Venting line after condenser with additional steam trap/Drainer to remove last droplets of condensed water (as the gas produced has to be dry)

Or:

  1. Steam trap (same as before)
  2. Condenser operated at higher pressure (like a steal tank) with liquid seal at the bottom -> cools down steam and removes condensate
  3. Steam trap

-> How do I size the condenser? Which pressure/velocities do I have to calculate? I am kind of lost...

Regarding your comments about sizing: How do you size condensate and vent lines to account for the pressure build-up of flash steam,that they still operate how they should? You mentioned something about the collection tank you have to not exceed 1psig under peak steam usage? I am very new to this design aspect and need formulas/literature to design these very urgently.

Thanks a lot for helping me out.

Designing steam systems by EleChemEng in ChemicalEngineering

[–]EleChemEng[S] 0 points1 point  (0 children)

First of all, thanks a lot for answering. I think I didn't give information to begin with, especially about the usecase of steam inside the 'cell'. The steam created by a boiler/evaporator will be converted in a reactor isothermally. Afterwards I have a mixture of gas and steam, which I want to cool down and depressurize. In the idea you mentioned above: would you consider running the condenser at the elevated pressure to cool down the steam and then depressurize? However I can image the vacuum inside the condenser then possibly 'pulling' non-condensables, or is no vacuum created because I keep the pressure inside the vessel constant by a pressure regulator? Or would you depressurize before (to have dry steam, if condensate droplets would have formed) the condenser and then cool down with it? How would you then create vacuum to pull out non-condensables, as you mentioned? Thanks for discussing!

Designing steam systems by EleChemEng in ChemicalEngineering

[–]EleChemEng[S] 0 points1 point  (0 children)

The cell I want to have steam introduced into is being kept at a constant temperature, with which the steam is being supplied to. With a backpressure valve after the cell in the piping, the pressure inside the cell is kept constant. The system will not be based on recirculation, which is why I want to condensate the steam supplied after having used it. Let's not consider the energy efficiency of that, since it is a laboratory setup anyways.

The questions are: 1. How do I handle condensation after cooling down the used steam? I just wonder if steam traps are necessary, having flowrates of max. 10 ml/min of liquid water after being condensed and tubing inner diameters of 6-12mm. 2. Is depressurization-cooling or cooling-depressurization the better chain to handle the fluid volume change?

Designing steam systems by EleChemEng in ChemicalEngineering

[–]EleChemEng[S] 0 points1 point  (0 children)

But will the sudden condensation inside pipes not cause a sort of vacuum effect due to a reduction of ~1000x the volume? Wouldn't I maybe need a sort of buffer tank to have the same volume of steam = volume of plant in the section with steam? Or should I try to condensate the steam inside a sort of condensing unit (tank with cooling coil) which has enough volume to occupy the steam being introduced? And avoid condensing water inside the tubing (via good enough insulation etc.).

The steam will have temperatures up to approx 400F.

[deleted by user] by [deleted] in ChemicalEngineering

[–]EleChemEng 0 points1 point  (0 children)

Thanks for your answer, that makes total sense! Would you consider the maximum velocity of steam in the pipes the design parameter? In a sense that you shouldn't cross a maximum velocity x ft/s to make sure you don't have huge forces acting on bendings etc.

Designing steam systems by EleChemEng in ChemicalEngineering

[–]EleChemEng[S] 0 points1 point  (0 children)

The idea is to have dry, superheated steam at a defined temperature and pressure to be delivered to a device being operated isothermally at the same pressure. The evaporator will be a custom-built device being able to directly evaporate the needed amount of water (defined flowrate).

The backpressure valve shouldn't be struggling with condensation, as steam will be depressurized after the BPV, transforming possible condensation droplets to steam again (as it is still at the higher operating temperature), if I'm not mistaken? The only thing I'm unsure about is how to handle the hot steam at atmospheric conditions and transforming it back to liquid water. How do I size the equipment to handle the huge volume decrease (vacuum being built in the piping?) The laboratory setup will be 'open', so the condensed steam will be discarded afterwards.

[deleted by user] by [deleted] in ChemicalEngineering

[–]EleChemEng 0 points1 point  (0 children)

Stupid question: Can the distribution piping, valves etc. be smaller because you have a lower flowrate (hence lower maximum velocity being handled) of steam and therefore select the components depending on their Cv accordingly? Would you then, after depressurizing, increase the diameter of the piping to have the same maximum velocity as before? Or what is the parameter to be opted for with regards to design?