3 replies to this topic

[Muhammad farhan]

Hello Every One

 

Recently we have commissioned non.phenolic sour water stripping unit  at national refinery limited.

 

The unit is design at higher throughput by considering future need. it is almost three times bigger than the current/present normal operating capacity. Due to this over sizing, huge amount of energy is spent to run unit and some to product is recycled/re-routed to again feed tank to maintain turn-down capacity..

 

Management wanted to save OPEX so we are now keep the unit shutdown till feed tank completely fill and then running the unit at higher troughput (design capacity). So in this way unit is running for 1 day and remian shutdown  for 2 days. Total running 12 days per month while it remain shutdown for 18 days per month. So the frequency of startup and shut down is 10-12 times per month.

 

We have calculated the OPEX after this optimization and it is saving our 70,000 ($)USD per month.

 

Your valuable opinion is required in the light of your huge experience. This way of optimization is good or not. Because we are thinking that frequent start-up and shutdown of units may challenged the equipment integrity and causing damage to equipment like reboiler (tube leakage) etc.

 

Kindly add your suggestion for improvement and negative impact of frequent start-up and shutdown of sour water stripping unit like salt deposition/corrosion or any catastrophic failure.

 

Best Regards

 

Muhammad Farhan

Process Engineer

National refinery Limited

Sulfur Block.   

Edited by Art Montemayor, 10 July 2018 - 11:26 AM.

[Bobby Strain]

You might not have done proper accounting for your savings. Low pressure steam is almost worthless. And your operators could be turning their attention to more important activities instead or startup and shutdown. I would opt to run the stripper continuously rather than batch. Or at least explore running the stripper at lower than design rates to minimize startups.

 

Bobby

[Muhammad farhan]

Dear Bobby strain

 

The LP steam consumption is 6 ton/hr. We convert HP to MP steam and then to LP steam. The cost of steam provided by utility department is 40 $(USD) / ton. 

 

Kindly if you can enlist the potential damages of unit or most common failure of equipment during frequent startup and shutdown practice.

 

Best Regards

 

Muhammad Farhan

Process Engineer

National refinery Limited

Sulfur Block.

[Technical Bard]

Are you really letting down HP steam all the way to LP to make this steam?  In most plants, the LP steam is sourced from LP Steam generators (exchangers cooling hot processes) or from steam turbine exhaust - in which case they are, as Mr. Strain states, essentially free.  If the plant is venting any LP steam at all, then LP steam actually has negative value.