R134a生產(chǎn)工藝

1、production of r-134abackgroundin the 1930s, chlorofluorocarbons (cfcs) were developed as a supposedly safealternative to ammonia and sulfur dioxide refrigerants. while sulfur dioxide is toxic and ammoniais both toxic and highly flammable, cfcs were found to be nonflammable, nonexplosive, andnoncorro

2、sive. cfcs quickly became the compounds of choice for refrigeration as well as forcleaning and foam blowing agents.however, the discovery of a hole in the ozone layer over antarctica in 1985 led to amovement to reduce the use of cfcs. due to their high ozone depleting potential, cfcs werescheduled t

3、o be phased out completely by 1996. this led to the need to find alternativerefrigerants that are not ozone depleting substances. some experts have suggested the use ofhydrochlorofluorocarbons (hcfcs) for this use. unfortunately, hcfcs also have some ozonedepleting potential, and are scheduled to be

4、 banned by 2030. with this in mind, one replacementfor cfc s in refrigeration is cf3ch2f (r-134a). r-134a is very attractive as a refrigerantbecause it has zero ozone depleting potential as well as a low direct global warming potential(gwp).one factor limiting the use of r-134a had been the fact tha

5、t conventional lubricants are notmiscible with r-134a. however, new lubricants have been developed which allow r-134asystems to run efficiently and reliably long-term. this, along with the need to find refrigerantswith a low ozone depleting potential, will greatly increase the market for r-134a in t

6、he future.environmental significanceproduction of an environmentally-friendly product alternativeprocess descriptionthe bfd and two pfds shows a process to produce r-134a1. liquid hydrogen fluoride (hf)enters the system at 25c and 2 atm in stream 1. it is pumped up to 3 atm by p-201 before beingmixe

7、d with a recycle stream (stream 16) consisting of hf, r-133a (cf3ch2cl), r-134a(cf3ch2f), and trichloroethylene (tce). the mixed stream (stream 3) then enters h-201 whereit is heated to 400c before being fed to the r-134a reactor r-201. this isothermal plug-flowreactor converts 99.3% of the r-133a t

8、o r134a. the heat of reaction is removed from theprocess by means of a dowthermtm a cooling loop.the product stream of r-201 (stream 5) is then mixed with a feed of tce (stream 8). themixed stream (stream 9) is then fed through e-203 where it is cooled to 290c. r-202 nextconverts hf and tce to r-133

9、a and hydrochloric acid (hcl). r-202 is quite similar in operationto r-201, including the use of a dowtherm loop to remove the heat of reaction.stream 10 leaves r-202 and is then sent to e-205 where it is cooled to 30c to reduce thecosts associated with c-201. c-201 compresses the stream adiabatical

10、ly to 9.8 atm, with atemperature increase to 595c. the stream is then cooled to 30c by e-206. the cooled stream(stream 13) is then fed to t-201, the first of three distillation towers. t-201 operates at 9 atm,with the distillate temperature being 0.1c and the bottoms temperature being 88.5c. therebo

11、iler uses low-pressure steam, with the bottom stream being recycled and mixed with the hffeed. the condenser uses a refrigerant mixture produced on site and processed in a refrigerationloop (not shown). in the loop, the refrigerant mixture removes heat from the process in thecondensers of the towers

12、. it is then compressed, cooled, and throttled back to the initial pressure.the distillate (stream 14) from t-201 consists mainly of r-134a, hcl, r-125, r-143a, and r-23. this stream is next compressed in c-202 to 20 atm before being fed into t-202. here, r-134a and trace amounts of hcfc-1133 are re

13、moved from the rest of the refrigerants and the hcl.the 99.99% pure r-134a bottom stream (stream 20) is then fed to a zeolite column (a-201 a/b)where the toxic hcfc-1133 is adsorbed. a-201 a/b is two zeolite columns in parallel. thisallows for continuous operation, with one operating while the other

14、 is being regenerated. e-207then cools the r-134a to 40c before p-205 pumps the stream to 28 atm (stream 23) for storage.the distillate from t-202 (stream 19) is then sent to t-203 where hcl and r-23 are removedfrom the refrigerant mixture. the refrigerant mixture obtained as the bottoms from t-203

15、(stream25) is cooled in e-208 to 15c and pumped to 25 atm in p-206. it is then stored.the distillate of t-203 (stream 24) contains mainly hcl and r-23. the hcl is absorbed intowater in t-204. the result is a stream of hcl in water that is 99.99% pure hcl at a concentrationof 35.12 weight percent (st

16、ream 30) which is stored. the unwanted r-23 stream (stream 29) issent to the waste incineration facility.necessary information and simulation hintsr-134a is produced by the following series of reactions:3133223223hftce hc clra h c clfhcl+-+()()ra h c clfhfra h c fhcl-+-+133134223224()()these reactio

17、ns are based on limited data found in us patent 5,243,105. it was determined thatthe activation energies for the two main reactions were as follows:167 kj/mol for tce to r-133a237 kj/mol for r-133a to r-134ausing data from the patent the rate constants were determined from the following equations:-r

18、a = kcacb-=aardxc0these were found to be:k = 10.94 l/(mol s) for r-133a to r-134ak = 11.82 l/(mol s) for tce to r-133aand the preexponential factors were found to be:a = 6.51018 l/(mol s) for tce to r-133aa = 5.51020 l/(mol s) for r-133a to r-134athese values account for the two primary reactions fo

19、r the process. however, the patentdemonstrated that side reactions also occur in the r-134a reactor. this has been accounted for byadding a component separator and a small feed stream to the simulation immediately followingthis reactor, specified to correlate with the patent.a major difficulty in si

20、mulating the process outlined in the patent is the lack of available datafor r-133a. the simulation is based on r-133a as a user-added component, with all propertiesbased on the normal boiling point2 and the unifac group contribution method. all simulationswere run using ideal vapor pressure for k v

21、alues and latent heat for enthalpy except for the hclabsorber (t-204). in t-204, ppaq (partial pressure aqueous) was used for the k values whichautomatically accesses the library heats of solution for enthalpies (in chemcad).the nomenclature for refrigerants is as follows. for saturated hydrocarbon

22、refrigerants, thenomenclature is r xyza. the a denotes a specific stereoisomer. the x is the number of carbonsminus one (which means x = 0 for old, single-carbon refrigerants). the y is the number ofhydrogens plus one, and the z is the number of fluorines. the remaining number of atoms neededto satu

23、rate the molecule are chlorines. therefore, r-134a has two carbons, two hydrogens, 4fluorines, and no chlorines. r-133a has two carbons, one hydrogen, one fluorine, and onechlorine. r-125 has two carbons, one hydrogen, and five fluorines.equipment descriptionsp-201 a/bhf pumpsh-201fired heaterp-202

24、a/btce pumpse-201tce vaporizerr-201r-134a reactorp-203 a/br-134a reactor dowtherm pumpe-202r-134a reactor dowtherm coolere-203r-133a reactor pre-coolerr-202r-133a reactorp-204 a/br-133a reactor dowtherm pumpe-204r-133a reactor dowtherm coolere-205reactor effluent coolerc-201compressore-206reactor ef

25、fluent coolert-201tce recycle towere-209tce tower condenserv-201tce tower reflux vesselp-207 a/btce tower reflux pumpse-210tce tower reboilerc-202compressort-202r-134a towere-211r-134a tower condenserv-202r-134a tower reflux vesselp-208 a/br-134a tower reflux pumpse-212r-134a tower reboilera-201hcfc

26、 1122 adsorbert-203mixed refrigerants towere-213mixed refrigerants tower condenserv-203mixed refrigerants tower reflux vesselp-209 a/bmixed refrigerants tower reflux pumpse-214mixed refrigerants tower reboilere-207r-134a coolerp-205 a/br-134a pumpse-208refrigerant mixture coolerp-206 a/brefrigerant

27、mixture pumpst-204hcl absorberreferences1. scott, john d. and racheal steven. u.s. patent 5,243,105. imperial chemical industries.19932. chemfinder web sitestream flow table for r-134a productionstream no.12345678910temperature (oc)25.025.151.3400.0399.325.025.0114.9290.0290.0pressure (kpa)202.6304.

28、0304.0263.4243.2202.6222.9222.9222.91.6vapor mole fraction0.00.00.11.01.00.00.01.01.01.0total flow (kg/h)1833.41833.47220.87220.87222.72924.82924.72924.710147.510147.6total flow (kmol/h)91.691.6236.2236.2234.722.322.322.3257.0234.7compenent flowrates(kmol/h)1112-4f-ethane-3.63.623.9-23.923.9tricl-et

29、hylene-0.20.20.222.322.322.322.40.2hydrogen fluoride91.691.6210.3210.3186.8-186.8120.1hydrogen chloride-0.0010.00121.8-21.866.3111-3f-ethane-0.0010.0010.2-0.20.2pentaf-ethane-0.0060.0061.5-1.51.5trifluoromethane-0.2-0.20.2water-r-133a-22.222.20.2-0.222.4stream no.11121314151617181920temperature (oc)30.0594.830.05.3892.850.192.875.6-6.278.3pressure (kpa)1.6993.0993.0932.2952.5304.0952.52026.52026.52046.8vapor mole fraction1.01.00.21.00.00.20.01.01.00.0total flow (kg/h)10147.610147.610147.64698.85447.95387.460.54698.82619.52079.3total flow (kmol/h)234.7234.7234.788.5146.2144.51