March 29, 2024, 03:55:16 AM
Forum Rules: Read This Before Posting


Topic: Coke in iron extraction/Nitrogen oxidation?  (Read 7035 times)

0 Members and 1 Guest are viewing this topic.

Offline AlwaysQuestioning

  • Regular Member
  • ***
  • Posts: 15
  • Mole Snacks: +1/-1
Coke in iron extraction/Nitrogen oxidation?
« on: November 12, 2013, 11:50:51 PM »
Hi guys. Just a few questions on how coke is used for iron extraction and about air.

On a website about iron extraction, they mentioned how :"A high quality coke should be able to support a smooth descent of the blast furnace burden with as little degradation as possible while providing the lowest amount of impurities, highest thermal energy, highest metal reduction, and optimum permeability for the flow of gaseous and molten products. Introduction of high quality coke to a blast furnace will result in lower coke rate, higher productivity and lower hot metal cost."

What does the smooth descent of the blast furnace burden (what's that?) refer to? And how will the coke degrade in this descent? Also, what is coke rate? And in the quote it states that it should have an optimum permeability for the gaseous and molten products. What do these products refer to? And why should the coke be permeable to them since most of it will react with the oxygen in the hot air injected to form carbon monoxide anyway? Or does the gaseous product refer to the carbon dioxide gas that will further react with more carbon to form carbon monoxide?


Also, regarding nitrogen combusting in air, according to wikipedia, "Nitrogen is not considered to be a combustible substance when oxygen is the oxidant, but small amounts of various nitrogen oxides (commonly designated NOx species) form when air is the oxidant." Why is this so? Shouldn't pure oxygen be better since given a volume of gas there will be more oxygen to react in pure oxygen as compared to air? And also since all the heat will go into heating the oxygen gas instead of having to "waste" energy heating the other gases to the same temperature as well? Or are there certain catalyst in the air that facilitate the reaction of nitrogen with oxygen? And lastly as for the reason why this reaction has to take place at high temperatures because nitrogen molecules are held together by triple covalent bonds so presumably the activation energy/heat required to overcome these bonds are very high ? (N2 used as gas in some lightbulbs? )

Thanks! ;D

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27633
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #1 on: November 13, 2013, 02:58:27 AM »
What does the smooth descent of the blast furnace burden (what's that?) refer to?

Do you know how the blast furnace operates?

Quote
And how will the coke degrade in this descent?

Do you know how the blast furnace operates?

Quote
Also, what is coke rate?

I wonder if they don't mean coke consumption rate.

Quote
And in the quote it states that it should have an optimum permeability for the gaseous and molten products. What do these products refer to?

Do you know how the blast furnace operates?

Quote
And why should the coke be permeable to them since most of it will react with the oxygen in the hot air injected to form carbon monoxide anyway?

You want the reactions to take place in whole volume, you need the mixture to be permeable for that.

Most of the questions you asked refer just to the way blast furnace works, read about it and the answers should become more or less obvious.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline curiouscat

  • Chemist
  • Sr. Member
  • *
  • Posts: 3006
  • Mole Snacks: +121/-35
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #2 on: November 13, 2013, 04:12:27 AM »
Quote
Also, what is coke rate?

I wonder if they don't mean coke consumption rate.

Yep sort of.

In blast furnace ops. the coke rate typically refers to how much coke you dump down the bell in a given hour I think.

Offline curiouscat

  • Chemist
  • Sr. Member
  • *
  • Posts: 3006
  • Mole Snacks: +121/-35
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #3 on: November 13, 2013, 04:14:07 AM »

Also, regarding nitrogen combusting in air, according to wikipedia, "Nitrogen is not considered to be a combustible substance when oxygen is the oxidant, but small amounts of various nitrogen oxides (commonly designated NOx species) form when air is the oxidant." Why is this so? Shouldn't pure oxygen be better since given a volume of gas there will be more oxygen to react in pure oxygen as compared to air? And also since all the heat will go into heating the oxygen gas instead of having to "waste" energy heating the other gases to the same temperature as well? Or are there certain catalyst in the air that facilitate the reaction of nitrogen with oxygen? And lastly as for the reason why this reaction has to take place at high temperatures because nitrogen molecules are held together by triple covalent bonds so presumably the activation energy/heat required to overcome these bonds are very high ? (N2 used as gas in some lightbulbs? )

Thanks! ;D

This part of your question isn't making much sense to me. No one burns N2 in air on  purpose. It's a by product. What are you trying to ask. 

Offline AlwaysQuestioning

  • Regular Member
  • ***
  • Posts: 15
  • Mole Snacks: +1/-1
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #4 on: November 14, 2013, 04:17:45 AM »
Oh sorry @Borek will read up more. Thanks!

@CuriousCat Sorry if it seems unclear, the main thing i wanted to ask was (ignoring the purpose of burning nitrogen in air) why such a phenomenon occurs (the fact that somehow nitrogen isn't combustible in oxygen if oxygen is the only oxidant and somehow in air it is able to take place)

Thanks~

Offline curiouscat

  • Chemist
  • Sr. Member
  • *
  • Posts: 3006
  • Mole Snacks: +121/-35
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #5 on: November 14, 2013, 04:57:58 AM »

@CuriousCat Sorry if it seems unclear, the main thing i wanted to ask was (ignoring the purpose of burning nitrogen in air) why such a phenomenon occurs (the fact that somehow nitrogen isn't combustible in oxygen if oxygen is the only oxidant and somehow in air it is able to take place)


Where have you read this? I think your facts are wrong.

Offline AlwaysQuestioning

  • Regular Member
  • ***
  • Posts: 15
  • Mole Snacks: +1/-1
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #6 on: November 14, 2013, 07:40:51 AM »
Oh perhaps i may have interpreted it wrongly ? I read it from wikipedia , their page on combustion.

Link:en.wikipedia.org/wiki/Combustion‎
What they mentioned was:"Nitrogen is not considered to be a combustible substance when oxygen is the oxidant, but small amounts of various nitrogen oxides (commonly designated NO
x species) form when air is the oxidant."

Thanks in advance! :D

Offline curiouscat

  • Chemist
  • Sr. Member
  • *
  • Posts: 3006
  • Mole Snacks: +121/-35
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #7 on: November 14, 2013, 07:51:47 AM »

Link:en.wikipedia.org/wiki/Combustion‎
What they mentioned was:"Nitrogen is not considered to be a combustible substance when oxygen is the oxidant, but small amounts of various nitrogen oxides (commonly designated NO
x species) form when air is the oxidant."


I may be wrong then. I've never heard of this and still sounds bizarre to me.

All I know is the reaction of N2 & O2 isn't easy & needs high temps. & even then NOx is formed in ppm amounts.

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27633
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #8 on: November 14, 2013, 07:55:36 AM »
I don't see any contradiction here. Nitrogen doesn't easily react with oxygen, which doesn't mean it never does. The higher the temperature, the easier the reaction gets. That's why you have some small amounts of nitrogen oxides produced during thunderstorms or in car engines, conditions in the blast furnace are similar enough. ppm IS a small amounts, isn't it?
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline curiouscat

  • Chemist
  • Sr. Member
  • *
  • Posts: 3006
  • Mole Snacks: +121/-35
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #9 on: November 14, 2013, 08:11:45 AM »
I don't see any contradiction here. Nitrogen doesn't easily react with oxygen, which doesn't mean it never does. The higher the temperature, the easier the reaction gets. That's why you have some small amounts of nitrogen oxides produced during thunderstorms or in car engines, conditions in the blast furnace are similar enough. ppm IS a small amounts, isn't it?

It's this snippet which sounds iffy:

"Nitrogen is not considered to be a combustible substance  when oxygen is the oxidant, but small amounts of various nitrogen oxides form when air is the oxidant."

Maybe I'm misreading it, but I'd take it to imply an oxidant = air versus oxidant = oxygen distinction which is the wrong way of looking at things.

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27633
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #10 on: November 14, 2013, 08:21:48 AM »
If seen this way it is wrong, no doubt about it. But as the phrase comes from wikipedia, I would not treat it too literally.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline curiouscat

  • Chemist
  • Sr. Member
  • *
  • Posts: 3006
  • Mole Snacks: +121/-35
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #11 on: November 14, 2013, 08:24:58 AM »
If seen this way it is wrong, no doubt about it. But as the phrase comes from wikipedia, I would not treat it too literally.

True. I agree.

Offline AlwaysQuestioning

  • Regular Member
  • ***
  • Posts: 15
  • Mole Snacks: +1/-1
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #12 on: November 14, 2013, 09:50:17 AM »
Guess so. Thanks so much!!!!

Offline billnotgatez

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 4399
  • Mole Snacks: +223/-62
  • Gender: Male
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #13 on: November 14, 2013, 11:05:19 AM »
I thought that in car engines oxygen and nitrogen will combine to make a compound.
In fact enough so it is considered a significant pollutant.
My impression was it had to do with the combination of pressure and temperature in the engine chamber.
It seems to me we have a definitional situation here.
Since WIKI is patrolled by ACS members it seems that the article mentioned has some relevance and accuracy.
I am stating the above from memory since I am in a hurry.
I will concede that the blast furnace scenario would be different from the car engine and I am not as familiar with the blast furnace environment.
But, it seems to me that one could create and environment sufficient to combine nitrogen and oxygen in air with heat involved.
Is it not only a matter of degree of effort you are willing to undertake to make the reaction happen.
I guess I am easily confused and do not grasp what was said before in this post.



 

Offline curiouscat

  • Chemist
  • Sr. Member
  • *
  • Posts: 3006
  • Mole Snacks: +121/-35
Re: Coke in iron extraction/Nitrogen oxidation?
« Reply #14 on: November 14, 2013, 11:41:44 AM »
I thought that in car engines oxygen and nitrogen will combine to make a compound.
In fact enough so it is considered a significant pollutant.
My impression was it had to do with the combination of pressure and temperature in the engine chamber.
It seems to me we have a definitional situation here.
Since WIKI is patrolled by ACS members it seems that the article mentioned has some relevance and accuracy.
I am stating the above from memory since I am in a hurry.
I will concede that the blast furnace scenario would be different from the car engine and I am not as familiar with the blast furnace environment.
But, it seems to me that one could create and environment sufficient to combine nitrogen and oxygen in air with heat involved.
Is it not only a matter of degree of effort you are willing to undertake to make the reaction happen.
I guess I am easily confused and do not grasp what was said before in this post.

I'll recap ( @Borek: correct me if I err! )

(1) O2 and N2 can indeed combine to yield NOx

(2) Reaction indicated in (1) isn't easy & only happens at high T or other special conditions

(3) Even when (2) prevails the NOx formed is in small amounts

(4) The oxidant can be either air or pure O2. Both will work. Nothing special about air. 

(5) In spite of (1) through (4) no one usually will refer to N2 as "combustible". That'd be somewhat silly. Thinking of N2 as "combustible" in air but not in O2 is also silly.

Sponsored Links