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• (January 12, 2023, 01:18:11 AM)

[Evonus]

Well, at least there's no danger of this becoming a "do my homework for me" thread.

At least not from me!

That saddens me.  I have a test on this stuff next Wednesday and I need to know how to do it.

[TheJudge]

Do you have a blackeberry with web browsing enabled?

[ivan]

That saddens me.  I have a test on this stuff next Wednesday and I need to know how to do it.

Look, bub. This is a two-level problem. First, to correctly construct the equations, you have to know what is being required. Since I don't have a background in -- what is this, some kind of chemical engineering? -- I can't make head nor tail of this problem. However, once the equations are constructed, it's only a matter of simple algebra to solve them. I'll lay down cash money I can do the algebra, as can you. The problem is understanding how to construct the equations. In that sense, this is not really an algebra problem, but a chemical engineering problem. If you come up with garbage after doing the algebra, then either you screwed up the engineering bit, or it's not garbage.

Or you may have screwed up the algebra.

[Evonus]

Look, bub. This is a two-level problem. First, to correctly construct the equations, you have to know what is being required. Since I don't have a background in -- what is this, some kind of chemical engineering? -- I can't make head nor tail of this problem. However, once the equations are constructed, it's only a matter of simple algebra to solve them. I'll lay down cash money I can do the algebra, as can you. The problem is understanding how to construct the equations. In that sense, this is not really an algebra problem, but a chemical engineering problem. If you come up with garbage after doing the algebra, then either you screwed up the engineering bit, or it's not garbage.

Or you may have screwed up the algebra.

I'll give you the equations I got and you can tell me what you get for values. I kept getting y = 0 which makes no sense within the context of the problem.

1 = x + y
.01 = x(1-4z)
.495 = 2xz + y

.1 = x/(r+x)

F = r +1

q = (xz + .2475)/F

n = 2(F)(q)(.20)

c = n/.2475

That should be a little easier to work with, and those should be the equations, unless of course I have no idea what I'm doing which may also be the case.

[xolik]

Well the homework was already due, but just to humor you I'll post the problem I couldn't figure out.

*what follows is a bunch of stuff that makes my head hurt*

This right here is why I hate math.

[ivan]

I'll give you the equations I got and you can tell me what you get for values. I kept getting y = 0 which makes no sense within the context of the problem.

1 = x + y
.01 = x(1-4z)
.495 = 2xz + y

.1 = x/(r+x)

F = r +1

q = (xz + .2475)/F

n = 2(F)(q)(.20)

c = n/.2475

That should be a little easier to work with, and those should be the equations, unless of course I have no idea what I'm doing which may also be the case.

All right, I don't understand what you did there.

In the first equation, if x is the fraction of fresh feed, and y is the fraction of purge, and they are both fractions of the total mols fed to the reactor, then x + y = 1 is not true, because the total mols fed to the reactor (r) also includes the fraction of recycled unreacted gases. No?

Also, what are z, q and c?

[Evonus]

You can isolate the entire thing as a system, and so I can basically set What goes in equal to what goes out. So I set the fresh feed (1) equal to the purge + the product stream.

Also, I know that no Inert is recycled because that would cause a buildup of inert, and none exits in the product stream, so Inert in in the fresh feed = inert out in the purge stream. I wrote the fraction of inert out in terms of z(moles N2). Basically how I figured that out, was the hydrogen + Nitrogen + inert is always equal to 1 because its fractional amounts. And hydrogen is always 3 times Nitrogen because that's how their stoichiometry lines up. So it was 1 = 3z + z + I

Finally, the last thing I did was write a balance for nitrogen atoms. 2 times 0.2475 which is how much nitrogen comes in should equal the nitrogen out in the product feed(in the form of Amonium) + 2 times the nitrogen out in the purge stream in the form of nitrogen gas.

F is the feed to the reactor.

Q is the fraction of nitrogen in the feed to the reactor

n is nr in the problem the amount of NH3 produced per pass.

c is fov.

[ivan]

I'm speaking from complete ignorance on this, but here is the part that made me think all 3 gases are in the recycle stream:

...and a gas stream containing the inerts and the unreacted  hydrogen and nitrogen leave the condenser. The gas stream is split into two fractions with the same composition: one is removed from the process as a purge stream, and the other is the recycle stream combined with the fresh feed.

[Evonus]

I'm speaking from complete ignorance on this, but here is the part that made me think all 3 gases are in the recycle stream:

Oh, all 3 gases are in the recycle stream, but the recycle stream is part of the inside of the system. You can ignore it and focus on only inputs and outputs of the system as a whole. These problems would be impossible if you couldn't bisect them.

[Demosthenes]

Are you sure you aren't trying to pick up on Detta?  Because you're using the oldest lines in the book on her in this thread.

[Min]

He just said it would be his dream if I did him all day...wait, were you talking to ivan?

[ivan]

Oh, all 3 gases are in the recycle stream, but the recycle stream is part of the inside of the system. You can ignore it and focus on only inputs and outputs of the system as a whole. These problems would be impossible if you couldn't bisect them.

But you're being asked to build an equation for the total moles fed to the reactor, which is not just what was put into the system. If it was, the answer would be the given 1 mol.

The way I read it was this: The single-pass conversion (Fsp) = .20, which I took to mean that 20% of the gas feed is converted to amonia. The fraction of purge is .10 of the total feed, which meant to me that 10% of the gas fed to the converter ends up being purged. The remaining 70% is recycled, or fed back to the converter. Of that 70% recycled gas, 20% gets converted, 10% gets purged, and 70% gets recycled. And so on, until the recycled stream dwindles to nothing. So I would need a recursion formula for this.

[ivan]

Are you sure you aren't trying to pick up on Detta?  Because you're using the oldest lines in the book on her in this thread.

Yes.

I know.

[jeee]

I tried picking up on Detta but there was a distance problem. And then there was Enrique.

[Crystalmonkey]

I tried picking up on Detta but there was a distance problem. And then there was Enrique.

Was this the distance problem?

    *  A 555-mile, 5-hour plane trip was flown at two speeds. For the first part of the trip, the average speed was 105 mph. Then the tailwind picked up, and the remainder of the trip was flown at an average speed of 115 mph. For how long did the plane fly at each speed?


This was taken from another website, google search distance problem...

[pbsaurus]

What were you flying, a Helio Courier or something?

[Chris]

Was this the distance problem?

    *  A 555-mile, 5-hour plane trip was flown at two speeds. For the first part of the trip, the average speed was 105 mph. Then the tailwind picked up, and the remainder of the trip was flown at an average speed of 115 mph. For how long did the plane fly at each speed?


This was taken from another website, google search distance problem...

x = time spent flying at 115mph
y = time spent flying at 105mph

The system of equations looks like the following:
115x + 105y = 555
x + y = 5

When solved, the ordered pair that satisfies both equations is (3, 2).

[Evonus]

But you're being asked to build an equation for the total moles fed to the reactor, which is not just what was put into the system. If it was, the answer would be the given 1 mol.

The way I read it was this: The single-pass conversion (Fsp) = .20, which I took to mean that 20% of the gas feed is converted to amonia. The fraction of purge is .10 of the total feed, which meant to me that 10% of the gas fed to the converter ends up being purged. The remaining 70% is recycled, or fed back to the converter. Of that 70% recycled gas, 20% gets converted, 10% gets purged, and 70% gets recycled. And so on, until the recycled stream dwindles to nothing. So I would need a recursion formula for this.

It doesn't work like that. 0.10 is the relation of the purge to recycle + purge. Not to mention, as stuff recycles around you have more feed coming in. Stuff is being recycled while new stuff is being fed in. That's why I was trying to ignore the inside of the system, find out the purge, so I could use the 0.10 to find the recycle, then add that to 1 to give me what's fed into the reactor.

It doesn't dwindle to zero, the system is at steady state, which means constant inflows and constant outflows.

[TheJudge]

I think he's trying to puck me up with all this gas talk 

[Evonus]

I think he's trying to puck me up with all this gas talk 

puck?

[Anyanka_was_framed]

Pucking asshat.


Nah, it's not the same.  Fuck has the "f" and "uh" and the "kuh" (as per Dane Cook).