Help me in selection of PRS station for 400 Kg/hr steam boiler

[Asisraja D]

Hi professionals
We have purchased a steam boiler with capacity of 400 kg/hr at maximum operating pressure of 10 kg/cm2 and now we have planned to install a pressure reduction station. i will add some information below for better understanding.

1) Steam outlet nozzle size : 1"
2) Main steam line header size : 3"
3) PRS Station nozzles size : 1.5" X 2"

As the vendor suggest us to go for PRS station from 10 kg/cm2 to 3-4 Kg/cm2 for the header.

he just asked me a few questions to conclude this those are just
*how many branches you have planned for ?
*how much pressure you expect at the equipment side ?
* and he roughly says at 1" line you could have get 150 - 160 kg/hr steam flow rate.

my answer to that question is

we have planned for taking one secondary header (2") from the main header (3") then we planned for 6 branches at (1") nozzle.
we need 2 kg/cm2 at equipment side. (reactor jacket side)

can anyone please explain me a bit how exactly he could decide the factors here ?
i have attached the vendor quote and GA drawing of the boiler.

i need to some explanation for the conclusion made by him.


if anyone have few basics to make be clear on this please send me your valuable comments on this.


Thank you.

 

[Asisraja D]

TBP​

Why wouldn't you simply install a steam boiler that operates at the required lower pressure.

we have not designed properly for the steam demand required by the process but for all i know we have selected the more demand for the reactors because the maximum reactor capacity is 1.0 KL.

 

[TBP]

The boiler of course needs the capacity to deliver the amount of steam required for your process, but my question is why operate a boiler at 10 kg/cm2 when the only steam load you have appears to require a header pressure of 3-4 kg/cm2? Why spend a lot of money installing a pressure reducing valve station for your one and only steam load? Simply select a boiler that can generate 400 kg/hr steam, that operates at 3-4 kg/cm2.

 

[pierreick]

Hi,
How do you manage the steam flow rate and temperature on these reactors?
A better description is needed to understand what you are doing. To me we get only half of the story.
Why did you purchase a boiler supplying 10 bars g pressure?
Ask a process engineer to support you.
Pierre

 

[Asisraja D]

Snickster​

i could not understand your calculations and if you don't mind can i get to know how did you get these steps and procedures ?

and you have mentioned the velocities, did you consider them from your point of view ?

i am very glad to have reading your comments and it will take for me a little bit knowledge to get them.

thank you.

 

[Asisraja D]

TBP​

Why spend a lot of money installing a pressure reducing valve station for your one and only steam load? Simply select a boiler that can generate 400 kg/hr steam, that operates at 3-4 kg/cm2.

This decision has taken by portfolio managers level and those level of authority person involves in project level. It creates an unwanted conflicts with the project managers and team so i could not get what is our business strategy to meet them so i hope at least i could help from my level to verify the design level aspects.

 

[Asisraja D]

pierreick​

Why did you purchase a boiler supplying 10 bars g pressure?
Ask a process engineer to support you.

We don't have a process engineer in our greenfield project so we are getting all the communication related to the project is only from business level authorities to satisfy the needs of stakeholders but in between our project manager also relies on them but no proper chemical process engineer.

 

[TBP]

"... so i hope at least i could help from my level to verify the design level aspects."

I believe - based on the information discussed here - that the design as it stands will leave the operations & maintenance people with significant and ongoing challenges.

It's entirely possible that my assessment is incorrect.

Best of luck to all involved.

 

[LittleInch]

Looks like a recipe for disaster if people who have no idea what they are doing are imposing technical design onto you.

Good luck.

And start looking for alternative employment.

 

[georgeverghese]

Looking at table 29-8 in Perry Chem Eng Handbook 7th ed, we get roughly 20kW for dropping this 400kg/hr of steam down to 50psig through a small steam turbine, which is one way of reducing the degree of superheat in this LP steam. Dresser Rand appear to have a ST for this power range, which they list can be used as a substitute for pressure reduction station - see page 7 of this link

https://p3.aprimocdn.net/siemensenergy/58f4a16c-f9e0-4071-9798-b036011798de/SE-Brochure-Dresser-Rand-Steam-Turbines-2021-pdf_Original%20file.pdf

You could use this to generate electric power or run some utility pump etc - interested? Ask them about turndown

 

[pierreick]

Hi,
To add to George's suggestion:

https://www.energy.gov/sites/prod/files/2014/05/f16/steam20_turbogenerators.pdf

Pierre

 

[goutam_freelance]

Please check with similar process plants for the steam pressure of the boiler.

If the steam demand is highly variable, boiler pressure should be somewhat higher than the process steam pressure. This is for better transient response due to the stored energy in the boiler and HP steam line. Boiler load response alone, in general, may be sluggish.

 

[georgeverghese]

Steam turbine idea for this application is most likely not suitable - moisture content in turbine exit stream is too high, which will lead to premature blade erosion failure - there is no superheat in the turbine feedstream.