4 replies to this topic

[Mukund Balachandran]

Hi,

We are in the process of finalizing the flare system for our upcoming refinery in India. After identifying the controlling load we have found that flare load is very high from the Cracker complex (for cooling water failure case). Our primary motive is to avoid additional cost incuured via having a seperate flare header for the cracker complex. in line with this can you suggest ways of mitigating flare load giving examples of case studies.

Thanks

B Mukund
M A M Krishnen
Process Engineers
HMEL

[Dacs]

HIPPS comes to mind in minimizing relief loads.

You might as well consider that option.

[Zauberberg]

HIPPS philosophy - as seen in Oil&Gas production facilities - is not applicable in refinery environment. As an ultimate protection, configure the flare system in such manner it can handle full process load. And, in my opinion, this step should be done after configuring ESD systems and power/utility supply system modes of operation; or even before that, but at least having the idea what it will look like.

1. Power supply network should be redundant - having at least two, or three independent sources. In the case of power grid failure, alternative power supply is automatically provided, and your pump/compressor/fan motors will continue to run.

2. Equipment sparing philosophy. A good practice is to provide different (motive) sources for equipment in critical service. For example, consider having both electrical and steam turbine-driven pumps, compressors etc. It's not very likely that two systems will both fail at once.

3. Configure plant ESD systems in such way they respond fast and logical, ensuring maximum protection. This means you need to account for automatic shutdown of all process equipment which generates heat and takes it into the system (i.e. fired heaters), while heat removal sections should be fully relaxed (i.e. 100% opening of louvres in air-coolers, pumparound control valves etc.)

After assessing these items, you'll see that estimated (the most conservative load) is very high, as compared with the one resulting from the optimum power/utility/sparing/ESD philosophy. And early design stage is the right moment to deal with all these subjects.

[Qalander (Chem)]

HIPPS philosophy - as seen in Oil&Gas production facilities - is not applicable in refinery environment. As an ultimate protection, configure the flare system in such manner it can handle full process load. And, in my opinion, this step should be done after configuring ESD systems and power/utility supply system modes of operation; or even before that, but at least having the idea what it will look like.

1. Power supply network should be redundant - having at least two, or three independent sources. In the case of power grid failure, alternative power supply is automatically provided, and your pump/compressor/fan motors will continue to run.

2. Equipment sparing philosophy. A good practice is to provide different (motive) sources for equipment in critical service. For example, consider having both electrical and steam turbine-driven pumps, compressors etc. It's not very likely that two systems will both fail at once.

3. Configure plant ESD systems in such way they respond fast and logical, ensuring maximum protection. This means you need to account for automatic shutdown of all process equipment which generates heat and takes it into the system (i.e. fired heaters), while heat removal sections should be fully relaxed (i.e. 100% opening of louvres in air-coolers, pumparound control valves etc.)

After assessing these items, you'll see that estimated (the most conservative load) is very high, as compared with the one resulting from the optimum power/utility/sparing/ESD philosophy. And early design stage is the right moment to deal with all these subjects.

Dear Mukund Balachandaran Hello/Good Afternoon,
Just adding slightly to what has been justifiabely pointed out/suggested by Zauberberg
A thorough conceptual Overall 'Vented to Flare system' loads survey be conducted and wherever their diversion to Fuel gas or Flaregas recovery systems is possible should be routed to such destinations/eqipments.
Moreover the Most Important/Critical Cooling System/reflux Streams Pumps and other Finfan coolers Power must be kept secured as rightly pointed out by Zauberberg.
The overall control valve Failure to close and Open stratagy is also to be very thoroughly checked/reviewed to serve this objective.
Hope this helps
Qalander

[kishor senjaliya]

I would create a table listing all countable flare loads for a cooling water failure scenario. Then I can add up the frequency and the load for every flare source. I can use a safety instrumented function (SIF) to mitigate the flare load by stopping heat addition to the flare source vessel or tower. The probability of the failure of the SIF is directly related to the size of the possible flare mitigation will be achieved by preventing the heat addition using SIF.

If you have more frequent probability of larger load then the heat cut out SIF will get higher Safety Integrity Level (SIL).

Common use of SIL-2 and if the consequence of not stopping heat addition is realy a big hazard and the risk assessment results shows very high level of fatalities, environment and equipment damage then it may qualify for HIPPS as per the corporate risk criteria.

Let me know, if I answered your questions.

Kishor Senjaliya, CFSE, PE

Hi,

We are in the process of finalizing the flare system for our upcoming refinery in India. After identifying the controlling load we have found that flare load is very high from the Cracker complex (for cooling water failure case). Our primary motive is to avoid additional cost incuured via having a seperate flare header for the cracker complex. in line with this can you suggest ways of mitigating flare load giving examples of case studies.

Thanks

B Mukund
M A M Krishnen
Process Engineers
HMEL