Yes

Do you have any idea how?

Vasiis,

The point of my previous post is that your question is so vague that we can’t really help. Can you be more specific about what you are trying to achieve? Is this a waste stream that just needs to be combusted? Are you looking for an oxidizer-type design or a flare? Do you want to combust this stream to make steam? Etc, etc, etc.

Sorry you are right.
I'm working on a power plant that uses a reformer and a fuel cell. The gases that come out of the fuel cell(containing hydrogen and hydrocarbons) need to be combusted so the flue gases will be used to heat the inlets of the plant in heat exchangers. I have been looking everywhere to find ho to do the sizing of a gas combustor.
Thank you

Okay, that helps a bit. Designing a combustion nozzle / chamber is a rather specialized field, and NOT something that you should attempt to do yourself. There are vendors who specialize in thermal systems design - Maxon is a reputable and respected name in the industry. Given you have a non-standard fuel feed to the nozzle, you will want to work in-depth with a specialist to design specifically to your process. You may want to look up thermal oxidizer companies or gas-fired vaporizer companies as well to explore your options.

I say this because when you work with combustion, things can go BOOM, and you really don’t want to learn by doing with this one.

Thank you so much for your help, i'll do my research. Wish you all the best!

Agree with post above, thermal oxidizer design is a very specialized field. The performance of these sorts of devices is highly regulated for safety and air permitting.
If you're hoping to make steam or recover heat, I would suggest looking into recuperative thermal oxidizers. This is a style of thermal oxidizer that recovers heat after combustion via integral heat exchangers. The big differentiator when looking at vendors is destruction/reduction efficiency (DRE). Some can combust 95-98% of the incoming hydrocarbons. Then in a completely different category is the vendors that can do 99-99.9% DRE (they will offer "three 9s"). Understanding your air permitting situation will help you decide which DRE to design around, which will drive which vendors you should speak to.

Thank you very much ChemE2014, this is very helpful!!

For starters, look up the Maxon Burner catalogue. Heaps of burners in various styles, type of flame, and more. They've got you covered.