Hi DKF,

Flaring in refineries is practised as a last easy avaialble option in emergencies. In refinery most of the processes are interconnected , with or without intermediate storage available. For example refinery / off gases from bitumen coker or distillation towers have to be used in either H2 production or to be fired as fuel in boliers , but what happen if H2 plant trips off and no refinery gas storage is available,  refinery doesnot / cannot sut down its distillation unit to stop the production of refinery gas so in this case refinery gas is diverted to FLARE.
This is just one example and as I mentioned a lot of processes are interconnected in refinery , if one goes down the product of its upstream process is diverted to FLARE, if no suitable storage is available.

I hope this help you in understanding about the flaring in refineries, however there are ways to minimise these.

This is first time I am writing in ENG-TIPS forum , if any body more experienced in this field gets a chance to review this please do correct me ( as I am a fresh graduate and new in refinery ).

Muhammad Ehtisham
B.S ( Applied Chemistry & Chemical Technology )
ehtisham3@yahoo.com
 

Hi Ehti
Thanks for your reply. You justified the existence of the flares, what I wanted to know is a listing of things that refinery can do to minimize the energy waste. Is there any new technology, new process concept being used anywhere?
I am a new neighbor of a refinery, and the waste and pollution deeply annoys me.
Further help will be welcome.
Regards
DKF

    

In Oil Refineries you have vessels and colums which contain hydrocarbons in liquid and vapor form under pressure. All these equipment are connected to a flare header which actually acts like a pressure relief valve. If there is some abnormal pressure build up somewhere in the process, the gas is vented to the flare, where it is burned.

In case of normal operation the flare header must be under a slight positive pressure, to maintain oxygen out of the process. The combination hydrocarbons, pressure, heat and oxygen leads to explosions.

The pressure on the flare header is mainted by spiking in lpg or some other combustible gas. That is why there will be always a flare on a working Refinery.

If the flare is to big, it can be that there is a process upset and they need to vent the overproduction of gas.

Regards

Steven van Els
SAvanEls@cq-link.sr

Steven

Thank you for your attention. I do understand the reason of the FLARE, and why sometimes there are 4 or 5 in open flame.
But when I lok at it, I see a big waste of energy. My question is why don´t they burn these effluents in a steam boiler(may be its a stupid idea, but I´m looking for alternatives)maybe there is technology available to avoid this waste. Do you know of any alternatives being used elsewhere?

Regards

DKF

Hi Guys ,

On my request one of my company's well experienced manager replied to this flaring issue as follows :

This feedback is from Coleen West ( Manager Site Wide Energy & GHG Coordination & Management )

......Flares are installed to protect the equipment in the refinery from overpressuring and thereby eliminate the potential for associated ruptures, release and fire/explosion.  A good way to think of the refinery is to compare it to a train moving along a track at high speed.  If one car in the train was to suddenly stop, the cars behind it would continue to push, and the cars ahead of it would continue to pull.  Many of the cars would likely derail - leave the track and be destroyed.

To prevent a similar "derailment" in the refinery and keep the refinery on track, the "cars" behind the one that stop are redirected to another track immediately... and that track leads to a flare where the material being diverted can be safely combusted in an emergency situation.

The less justifiable, and more annoying, type of flaring is that which occurs because of inefficient operation.  Refineries should be very motivated to eliminate unnecessary flaring.  The material being flared is potentially gas which could be used to fire the heaters that the refinery needs in order to process oil into saleable products!  Without it, they must import natural gas for fuel or for hydrogen plant feed, and this increases their operating cost.

Refineries can reduce unnecessary flaring by:
- Making sure equipment is properly maintained  / modified to improve it's reliability so that overpressuring doesn't occur due to equipment or instrumentation failure.  (Newer refineries tend to have more reliable and efficient equipment, and less flaring.  Older refineries cost more to operate, so the priority may be on spending money to make production vs energy efficiency and reduced flaring.)
- Operating in such a manner as to prevent overpressuring equipment... sometimes this conflicts with "pushing rates" to make as much production as possible, and the refinery may be reluctant to invest capital to solve the problem.
- Making sure that the instrumentation control logic on fuel gas systems works properly i.e. avoid situations where they are importing natural gas while at the same time flaring excess gas from the fuel gas system.

In some cases, the gas being flared is going to flare because it is at too low of a pressure to be used in the fuel gas system.  The refinery could collect the gas, and install a compressor to boost the pressure back up to a usable level... again, this requires capital to resolve the situation.......

Muhammad Ehtisham,
Applied Chemistry & Chemical Technology
ehtisham3@yahoo.com

As you have seen most of the ideas on the flare, they  all are viable.  

To your specific Q i.e. to avoid the wastage of energy:

Flaring in upset plant is un avoidable. This option you would like to have, otherwise you being the neighbour of refinery will be effected as well.

2. Whereas Continous flaring can be avoided there are few methods
a. Balance the plant in such a way that you avoid the excess production of fuel gas (gas streams).
b. Use whatever gas is produced in the boilers, heaters, tankage etc. You may use dual fuel heaters to be  able to better manage the fuel gas/ natural gas/ liquid fuel.
c. In a scenario if you produce more than the required fuel gas then there could be one option to cool it down/ or expand to liquify it  and then you can use that liquid in the  refinery as part of feed or oil etc..

Once again the  key thing is one must do a thermal review of the refinery every few years.  This will help the refinery to understand their energy consumption  which  add value to the refinery economics anyways. You must optimize the energy use in the refinery.
If you need any further info on these things you may e mail.
Thanx.
  

Mr Sandeep1970, some remarks, your explanation is good but 2 things:

You will have always a flare, if the plant is every eficient, you will maybe not notice it. We use our fuel gases in 3 heaters, and sometimes you have to look for the flare, but it is allways there. Continous flaring is unavoidable. A big black smoking yellow flare indicates that pure hydrocarbons are being burned, and money is wasted. Like Enti said, there are a lot of factors contributing to this (instrumentation, maintenance, plant age, etc.)

Let's say you buy a boiler to be fired on the excess gas. You make an investment, and connect more equipment to this boiler.

If your excess gas is caused by defect equipment, the day this is in place, you will need to buy fuel for your newly installed Boiler, and all the savings you calculated by justify the installation of your boiler, will be lost and increase your production cost.

Like you said an anual thermal review or assessment is the only way to determine if you will have the required conditions to make environmental, technical and economical sound investment

My last remark, it is very difficult to send an e-mail if I do not see an address.

Kindly Regards

Steven van Els
SAvanEls@cq-link.sr

Hi Steven Van ,

I really liked your example of the bolier ( fired on excess gas ) but on the same token Sandeep 's option of liquifying excess refinery gases or extracting CH4 or propane out of it is also good option to minimise flaring( by such an extraction you reduce the volume of your refinery gas and get liquified butane / ( some of ) naphtha as one of your fuel or product).

Multiple fuel boilers is also a very good option for minimum flaring but a lot of constraints are there to bring this in effective operations.

Finally, no matter whatever we manage to do, we can minimise flaring but cannot email someone , without having email address. We have to wait for some ultrascientific technology ( Just kidding Sandeep1070 ) ( Donot mind ).

Thanks all of you for contributing in this thread.

Looks like that you all guys are from rfineries can any one of you discuss different ways of incresing efficiency of H2 production plant.

Muhammad Ehtisham
B.Sc ( Applied Chemistry & Chemical Technology )

Good points.  Steven's example is good, In the moderen refineries to addresss that issue quite often people install at least one utility boiler with multiple fuel option ( as this  does not cost that much as far as fixed capital is concerned) because this gives a very  good  operational flexibilty.  

The other thing refineries do is to have at least one of their heaters which can use both liquid as well as gaseous fuels.

Regarding e-mail, good point. Here it is "Sandeep1970@hotmail.com".  You are welcome to email re this topic or other topics related to refineries/ power industries.

Re H2 plant you got to send more info. you can send what technology you are using what is hte layout and what is the concerns.  What is the current efficiency. What is the location. You can start that as new thread even.

Hi all,

I am new to this forum, I work at a natural gas plant and have heard of compression systems out there that eliminate the need for sending all that energy up the stick. I am just wondering if any one else has heard of these systems.

Compression recovery systems on flares are common but handle recovering the normal daily flow rate of gas out to the flare or perhaps minor upsets depending how much you want to spend in equipment costs.  

When you have a major upset, that flare is going to light up.  You can minimize the visual and noise effect of a conventional above ground flare with alternate designs.  Totally enclosed ground flares work very well, have a very small footprint but cost significantly more.  If land isn't available for a conventional flare or you want to minimize the visual effect or noise, they are a good choice.