17 replies to this topic

[Bambang Wahyu Pramono]

hi all,,
my name is Bambang, I'm working on my final task for my bachelor degree at university of north sumatra Indonesia,

I need a little help..
my final task is "manufacture ofphosgenefromcarbon
monoxideandchlorine"
so for the raw material I used carbon monoxide and chlorine both at 1 atm,
and both at gases phase,
it make the temperature of carbon monoxide is -185 C and chlorine is -40 C
to make sure temperature stable I used liquid propane as refrigerant at temperature -188 C,
from material balance I've got the product phosgene at flow rate 3156,5656 kg/hr,
carbonmonoxide at flow rate 2000 kg/hr, and chlorine about 1156,5656 kg/hr

so the problem is, I didn't know how much propane I must used for both of those raw material for it's storage tanks..
I've searched many literature and I couldn't find any of them..
so could you all help me for this problem..?
thx a lot for your help..
I really appreciate for all of your help..

[MrShorty]

I'm not sure I fully understood your question, but I'd like to suggest something for you to think about.

I used carbon monoxide and chlorine both at 1 atm,
and both at gases phase,
it make the temperature of carbon monoxide is -185 C and chlorine is -40 C
to make sure temperature stable I used liquid propane as refrigerant at temperature -188 C, ...
I didn't know how much propane I must used for both of those raw material for it's storage tanks.

Those temperatures are correct, if you are intending to store them as liquid at their normal boiling points. I will admit that I work exclusively with things on a laboratory scale, so I don't know that much designing such a process. I could be wrong, but I get the impression from your post that you have accepted those temperatures without really thinking about what they mean and whether they really apply to what you are doing.

I guess it "boils" down to two things I want to be sure you have thought about:

1) Why do you want to refrigerate CO down to its boiling point? I think I would want to have some specific and well-thought-out reasons for storing/delivering liquid CO to justify the costs of refrigeration.
2) Recognize that you really can't mix liquid CO and liquid Cl2. The critical point of CO is so far below the freezing point of Cl2 that you would either freeze out the Cl2 or you would vaporize the CO. Either scenario suggests to me that you really aren't trying to mix them as liquids. Which brings me back to my first question -- what do these temperatures really mean, and do they really apply to what you are doing?

[Bambang Wahyu Pramono]

thank you for reply sir,
I'm sorry if at first my english isn't that good enough....

here's the condition :
---> I was at my last year at chemical engineering faculty, the final task was to make a manufacture of phosgene making from carbon monoxide and chlorine
---> capacity 25000 ton/year
it equals 3156,56 kg/hr

Quote :
1. I used both raw materials carbonmonoxide and chlorine were in GASES PHASE.
----> I search for literature to confirm melting and boiling point of both raw materials
----> I used vapour pressure table from Perry to confirm the value of pressure and temperature
Both raw materials were at 1 atm, CAUSE my lecture suggest me that.
at first discussion with her I used both raw material at room temperature 30 ⁰C,
but from the table, I got both pressure at room temperature 30 ⁰C were very high, about 185 atm.
other people must be laugh if I used gases raw material at that high temperature.
So, she suggest me to play with temperature, that means the pressure of both raw materials
shoul be 1 atm.
----> it means that like my previous quote it make temperature of carbon monoxide -185 ⁰C
and chlorine -40 ⁰C
----> both at GASES PHASE
2. I stored both raw materials at different storage tanks that must be flowed by refrigerant to make temperature stable.
Flowrate of each raw material such as carbon monoxide and chlorine I've told you at previous quote



Now the problem :
1. At each flowrate and storage tank, how much I must used LIQUID PROPANE as refrigerant to keep
the temperature stable?



p.s : I choose propane as refrigerant because propane has melting point about -188 ⁰C.
it's just a little above carboon monoxide temperature that -185 ⁰C




first and last thank you for all your help sir..
best regards..

[kkala]

"but from the table, I got both pressure at room temperature 30 ⁰C were very high, about 185 atm"
Banbang, this phrase is not clear (to me) and the pressures of 185 atm are not understood. Cl2, CO, COCl2 are gases at atmospheric pressure and 30 oC. Phosgene is produced at 50-150 oC temperature, see http://en.wikipedia.org/wiki/Phosgene. You can find useful elements by searching the Web, although pressure during production was not found (higher pressure would help equilibrium). Let us accept that industrial synthesis occurs at atmospheric pressure, as your instructor suggested.
Let us look at Temp - Enthalpy diagram of CO (Perry, 7th ed, p. 2-226, thermodynamic properties). Vapor pressor of liquid at about -190 oC is 1 Atm a indeed. But this does not mean that CO at 1 Atm a has necessarily a temperature of -190 oC. Following the line of p=1 Atm a, we can see that it can have values from -190 oC to 27 oC and even more, if we could extend the diagram. CO need not be saturated, and then it can have any temperature higher than -190 oC at atmospheric pressure.
So gases can be at atmospheric pressure and far from saturation temperature; this is the case of the two gases CO and Cl2. COCl2 has a boiling point of 8.3 oC, so it has to have higher temperature to avoid condensation. The reaction is understood to be between gases and the product is gas.
I do not know whether above has hit any target, but can you think of them? Check stoichiometry of the reaction too.

[kkala]

Further to previous posts, following notes might be useful
1. You can store raw materials at higher than atmospheric pressure, then heat and pressure reduce them upstream of the COCl2 reactor.
2. For Cl2 storage see http://www.chlorinei...ItemNumber=3638, http://www.google.gr...iw=1152&bih=740.
3. For CO storage data is difficult to find, http://www.lindecana...Monoxide_EN.pdf indicates storage of gas in cylinders, under rather high pressure (Like e.g. N2 gas).
4. Both substances are harmful, phosgene product is much more harmful (normally produced where it is used), so special measures are needed for handling.
5. Phosgene synthesis require high purity raw materials, is it related to low temperatures mentioned (-185 oC, -40 oC)? But a purification process should have followed. I am not aware of such cases (well, liquid N2 did some purification on NH3 synthesis gas, if I remember well).

Edited by kkala, 31 December 2011 - 04:00 AM.

[Bambang Wahyu Pramono]

first of all I would like to say thank you very much for any concept, information, of link that you gave to me sir..

hmmm...
I could understand your offer concept to me..
I've found 2 handbook literature before about phosgene production that say the produce of phosgene should be at atmospheric pressure and between 50 - 150 oC like you said..


your quote :
"Let us look at Temp - Enthalpy diagram of CO (Perry, 7th ed, p. 2-226, thermodynamic properties). Vapor pressor of liquid at about -190 oC is 1 Atm a indeed. But this does not mean that CO at 1 Atm a has necessarily a temperature of -190 oC. Following the line of p=1 Atm a, we can see that it can have values from -190 oC to 27 oC and even more, if we could extend the diagram. CO need not be saturated, and then it can have any temperature higher than -190 oC at atmospheric pressure.
So gases can be at atmospheric pressure and far from saturation temperature; this is the case of the two gases CO and Cl2. COCl2 has a boiling point of 8.3 oC, so it has to have higher temperature to avoid condensation. The reaction is understood to be between gases and the product is gas."

i've understand the concept and i've seen the diagram too...
and my question now is : are you saying that i can store both of this gases at atmospheric pressure at temperature 27 oC or about room temperature at 30 oC..?
based on the diagram it would say to, but based on the table 2.243 at perry too right before the diagram, there was clarified pressure and it's temperature value.
this was very essential for me..
cause my lecture told me first that I must clarified at which pressure, how much the temperature and what was the phase..
at this point that you and me have cleared that all this gases must be at gas phases, such as CO, Cl2 and COCl2
if you suggest me that I can store this raw materials such as CO, Cl2 at atmospheric pressure and 27 or 30 oC temperature, that means I must not use any refrigerant, right?
then..how you can explain that to me..?
so I can explain this theory you gave to me to my lecture at campus..
because first off all my question to you was ratio of refrigerant used...
and now, since you gave me that theory, how you can explain that...
thank you very much before sir..

[kkala]

and my question now is : are you saying that i can store both of this gases at atmospheric pressure at temperature 27 oC or about room temperature at 30 oC..?
based on the diagram it would say to, but based on the table 2.243 at perry too right before the diagram, there was clarified pressure and it's temperature value.
this was very essential for me..cause my lecture told me first that I must clarified at which pressure, how much the temperature and what was the phase.. at this point that you and me have cleared that all this gases must be at gas phases, such as CO, Cl2 and COCl2
if you suggest me that I can store this raw materials such as CO, Cl2 at atmospheric pressure and 27 or 30 oC temperature, that means I must not use any refrigerant, right? then..how you can explain that to me..?
so I can explain this theory you gave to me to my lecture at campus.... because first off all my question to you was ratio of refrigerant used... and now, since you gave me that theory, how you can explain that........

Glad to see that our thinking is converging. Perry's table 2-243 concerns "saturated carbon monoxide" and indicates that e.g. at 1.01 bar a and T=81.62 oK= -191.5 oC liquid and gas CO coexist. Suppose you heat this total at constant pressure; there will be only CO gas, as soon as temperature gets higher. For T > 132.91 oK = -140.2 oC (critical temperature of CO), CO cannot be liquid at any applied pressure and this is far lower than ambient temperature.
Concerning Cl2 http://en.wikipedia.org/wiki/Chlorine indicates: critical temperature=143.75 oC, boiling point (at 1 Atm a)=-34.04 oC. For min ambient temp=20 oC it will remain gas for pressures=6.7 bar a or lower (Perry, 7th ed, Table 2-47).
Theoretically CO gas and Cl2 gas could be stored at atmospheric pressure at ambient temperature; but this is not economic, they can occupy much lower volume under pressure. Both fluids can be reduced to (almost) atmospheric pressure and heated to required temperature (50-150 oC) upstream of the phosgene reactor. Refer to previous post No 5 (and its web references). CO seems to be stored under high pressure, Cl2 in liquid form under pressure (see also http://en.wikipedia....rine_production). Liquid Cl2 would facilitate transportation to the factory. Recommended pressures for storage of CO and Cl2 have not been found in the Web at first look, but should be specified through further investigation, even from information of local market.
A rough simplified scheme of the COCl2 plant per above could be according to attached "phosg.doc". Phosgene storage and transportation could be a problem, due to its toxicity and normal boiling point of 8.3 oC; let it be for later on.

Attached Files

•  phosg.doc   25KB   14 downloads

[Bambang Wahyu Pramono]

hmm....
thx for your phosgene flowsheet you gave to me,
I had discuss about your process too..
and I a little bit understand the concept of critical temperature (previously I don't even understand it..haha)
and now I got confused by recommended pressure too..

I've discussed with my partner just now, and we both agreed with your concept, because we didn't need any refrigerant..
At very first our discuss with our lecture, we got this concept too, Cl2 as liquid and CO as gases,
but she told us we must clarified at which temperature, what was the phases and what was the pressure..
maybe our value wasn't same like yours..
based on your flowsheet, I must store CO as gases and Cl2 as liquid.,
that means liquid Cl2 must be vaporized before enter the reactor,
If I should store CO at ambient temperature,
could you suggest to me what's the temperature of both CO and Cl2 that you gave..?
and how about the pressure too..?
(I'm sorry for bothering you again...=P)

I'll attach our flowsheet too as your comparison..
there's set temperature and pressure too at each of flowrate..  flowsheet.xlsx   374.9KB   17 downloads

[kkala]

A. Specific value of temperature was not given, but storage should be considered at maximum ambient temperature. Let us suppose that local max ambient temperature (that you have to find) is 45 oC.
1. For Cl2: Vapor pressure of liquid is 13 bar a (see attached Cl2.xls) at (supposed) max ambient temperature, so for the Cl2 storage drum we can assume max operating pressure =12 barg and design pressure=12*1.1=13.2 barg. Transportation could be realized through trucks, specific for this.
2. For CO: Market research has to define storage conditions and transport.
If you cannot find data (but first search for it), transportation in cylinders could be assumed under high pressure, say 150 barg at 25 oC. So at 45 oC pressure will be higher. However small capacity of cylinders is a disadvantage.
Once we referred to "standard" N2 metallic bottles (cylinders) as having pressure=200 Atm and capacity=50 lt. Such a 50 lt bottle carrying CO at 150 barg (*) would carry about 39 kg CO, too small for your needs. It is necessary to know max capacity of commercial cylinders storing CO, even ways of transporting CO. Cylinders have been reported, based on a phrase of Material Safety Data Sheet (MSDS) by BOC ( web reference in post No 5). But the transported quantities indicate now that liquid CO transport and storage could be more feasible, if liquid CO handling is applied in practice. Sorry that I have not seen it before. After all critical conditions of CO are close to those of N2, transported and stored in liquid form; see http://www.cheresour...as-storage-tank.
On the other hand CO cylinders may be locally available, liquid CO may be not. Matter may need much of your patience, if looked into, but instructor may be able to give a simplifying assumption, e.g. multiple CO cylinders in parallel. It is necessary to have a decision, affecting the flowsheet .
(*) Note: CO seems not to be chemically affected by high pressures, at least up to 1000 bar http://www.pdas.com/refs/tnd6807.pdf.
3. Flow diagram shall be based on final decisions. Some comments from reactor and downstream currents:
α. Cl2 and CO streams enter the reactor from same side (why counter currently?) and product from other side.
β. You have to verify that COCl2 downstream E-310 is liquid (normal boiling point = 8.3 oC, so at 1 Atm there is liquid and vapor at 8.3 oC).
γ. Gas from E-310 to waste gas treatment is noted.
δ. SOCl2 storage under pressure (F-410) is noted. Product vapor pressure will be higher than 1 Atm at max ambient temperature. Where PSV shall go?
ε. Transportation of SOCl2 is dangerous, better to be consumed by factories at the same area (post No 7)

Editing note, 17 Jan 12: CO2 corrected to CO.

Attached Files

•  Cl2.xls   22KB   19 downloads

Edited by kkala, 17 January 2012 - 10:54 AM.

[Bambang Wahyu Pramono]

1. For Cl2 : based on my flowsheet diagram, are you saying that I could store it in liquid phase..? Because on my flowsheet diagram it was at gases phase.
at my ambient temperature is about 30 oC.
If I store Cl2 as liquid phase that means I must vaporize it too like CO, right?
and next I can calculate with it's laten heat because there was a phase change from liquid to gases, same as CO..

2. For CO : assumed that my ambient temperature here is about 30 oC, then from table 2.243 perry, if we extend the table we can get CO at 30 oC it's pressure is about 137 atm.
From MSDS BOC you gave yesterday, storage tank was possible as long as it didn't reach 50 oC.
Is it possible to storage CO at that condition? 30 oC and 137 atm?
and what phase are you suggesting..?
shall I use liquid or gases though..?
and, I've looked for properties of nitrogen such as Tc,Pc,mp,bp and others it looks alike CO that we've been talking for like you said,
so if you suggest me to use CO as a liquid, can I use that calculate on that nitrogen discussion thread as comparison to my calculate..?

3. that's our final diagram before I discuss with you sir, and it may change according to your suggest to me..
a. it's looked like that because all of my senior assignment looked like that too..=)
b. from 2 handbooks of phosgene I got, there was clarified prossedure that I didn't know if that assumption or real that the phase is liquid..
c. from handbook too, waste gas treatment would have contacted with NaOH to bury all waste gas
d. I will discuss it with my partner sir..
e. yes, I got a theory and book about it too sir..

[kkala]

1. An investigation has to be made by you, checking how Cl2 and CO are handled in local market, since they have to be transported to COCl2 plant.
-Yes, liquid Cl2 can be stored in drums under pressure, as explained, just like LPG. Then you have to vaporize it / superheat it upstream of the reactor.
2.1 The simplest (but probably not economical) way is to use high pressure cylinders filled with CO. Nothing is anticipated against storing CO in cylinders at ambient temperature and p=137 Atm or even more, thinking of the example of N2. Table 2-243 of Perry (saturated CO) holds up to critical temperature (-140.2 oC) and pressure (34.96 bar). Market will tell you about the usual pressure in cylinders, as previously said.
2.2 Liquid CO is expected to be more economical in your case, but it may not be locally available. This is to investigate or discuss with your instructor for a decision. If you decide liquid CO, storage can be in an insulated vessel, as described for liquid N2 storage in the web reference of post No 9 (Sizing nitrogen gas storage tank, mainly post No 9). The vessel needs no refrigeration, simply evaporated CO will go to reactor, unless reactor is idle (then it can go to a flare, if discharge to atmosphere from safe location is not permitted). Additional CO may have to be evaporated, in addition to the boil off CO gas.
3b phosgene can be liquid at 40 oC under some pressure, a table or diagram for COCl2 is needed similar to this for CO or Cl2 (not found so far).

Edited by kkala, 17 January 2012 - 10:58 AM.

[Bambang Wahyu Pramono]

I've been asking some of my graduated senior, they said that I can or I should store Cl2 as liquid, cause that was easier to be found, I think they were same as you told me before..
ok..we'll have a discuss to talk about this suggest with our instructor this thursday, and we'll hope we'll get final decision to be made then..
the problem now is, back to the topic, this liquid Cl2 is available as liquid around it's melting point and it's boiling point right..?
mp of Cl2 is -100.98 oC
and it's bp is -34.04 oC
let us guess that we'll store it at temperature -36 oC like I've told before, if we stored it at ambient temperature at 30 oC it'll raise it's temperature too..
at this point; the keyword has to be using a refrigerant to make sure temperature is stable,
and the question is, how much the ratio of refrigerant use for...?
I've been searched so far and I couldn't found it........................

[kkala]

-For liquid Cl2 storage in pressure vessels, refer to post No 9. Ambient temperature, no refrigeration required. Similar to LPG storage under pressure.
-If you do not find liquid CO in the local market, you have to assume CO stored in cylinders under pressure. Similar to N2 storage in cylinders.
It is pointed out that liquid CO storage and transport has not been traced so far, it is supposed because of its similarity to liquid nitrogen handled in liquid form. Nitrogen is handled either in cylinders under pressure or in liquid form.
Storage of liquid CO (if available) does not require necessarily refrigeration, refer to post No 11, para 2.2 and the relevant web reference.
Probably it is useful to refresh the posts of the thread before discussing the matter with the instructor, as it has been developed. Several points can be of value.

Edited by kkala, 03 January 2012 - 12:45 PM.

[Bambang Wahyu Pramono]

all right sir..
I'll make several points of your posts as comparison for her tomorrow,
if needed I'll print out this whole thread too as evidence of our post here..
thx for all your help sir, and probably I'll ask you about more question next..
if that can't be bother your job sir..=)
thx a lot sir..=D

[Bambang Wahyu Pramono]

hello again sir..=)
i would like to ask you several more question for my assignment that I share with you the other day..
only if that won't bother you..


I've discussed with my lecture the other day..
and now our assignment have been made a decision for it.
as you told me before now our assignment was settled like this :
1. We used liquid chlorine at storage tank at temperature -34,72 oC, so we must vaporize it then upstream the reactor, and we weren't used refrigerant for it's storage tank
2. we used carbon monoxide as gas phase at pressure 1 atm and temperature -185 oC.
and we must used a refrigerant for it's storage tank.

now the problem is :
1. how much ratio of rafrigerant propane I must use at carbon monoxide storage tank?

as note :
- it's important to know the value of refrigerant I'll use in calculation of energy balance and spesification of equipments of in my assignment

[kkala]

1. Liquid Cl2 in storage tank shall have temperature close to ambient. Trucks seem to transport it under atmospheric pressure (about -35 oC), but stored Cl2 will take the ambient temperature. So storage should be a pressure drum. If max ambient temperature is 50 oC, design pressure has to be about (14.25-1.013)+2=15.3 barg.
2. Refrigerated atmospheric storage is usually applied for larger storage capacities and could be probably avoided (see post 11 para 2.2, as well as post 13). On the other hand something has to be assumed to proceed with this exercise. Unfortunately I have no experience on refrigeration to suggest quantity of propane refrigerant. Other members have experience and could give proper advice on the matter. Evidently CO will be transferred to this storage in liquid form, through trucks.
Wishing successful continuation of your task

Edited by kkala, 17 January 2012 - 11:28 AM.

[Bambang Wahyu Pramono]

hmm...
amen that..
ok...once again thx a lot sir for your help this far..=D
if you could suggest, which member do I must take advice from...?

[kkala]

Well, wait for other members to see the topic and decide if they can help.