Simulation of a Plug Flow Reactor

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Simulation of a Plug Flow Reactor

Postby arvind.prasad » 22 September 2017, 14:16

In the Plug Flow reactor Edit menu, under packings, and sub section empty bed we have a text box to enter the Wall dimension. I have gone through the help file but am not so sure, if the information to be supplied is the wall diameter or the wall thickness? How will wall thickness affect the calculations? Also, the wall diameter will always be equal to the reactor diameter for an empty bed. This information is already supplied in the edit> reactor > Reactor Diameter text box. :?:
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Re: Simulation of a Plug Flow Reactor

Postby jasper » 22 September 2017, 20:14

The label in front of the edit field is a bit too short and truncates the second word. I corrected the layout for the next update. The word is "wall roughness". It is parameter 'e' in the Colebrook equation:

http://cocosimulator.org/index_help.php?page=COUS/pfr.htm
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Re: Simulation of a Plug Flow Reactor

Postby arvind.prasad » 10 November 2017, 06:35

Dear Jasper,
The attached flowsheet is simulation of PFR for methanol synthesis from CO,CO2 and H2O. The wall heat transfer coefficient and tube heat transfer coefficient have been set to zero. On running the simulation, it is found that the enthalpyF balance is not zero. Can you explain this? I guess it should be zero.
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Re: Simulation of a Plug Flow Reactor

Postby jasper » 10 November 2017, 08:59

Thank you for reporting that. For the heat balance, the inert component flow was not taken into account for the d xi / dl term.

The issue is fixed now - fix is available via CUP. In your case it makes a big difference on the enthalpy balance.
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Re: Simulation of a Plug Flow Reactor

Postby arvind.prasad » 10 November 2017, 10:11

Thanks for the update. Now it is working fine.
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Re: Simulation of a Plug Flow Reactor

Postby arvind.prasad » 10 November 2017, 16:14

Please find the attached flowsheet. I have connected the energy stream to the PFR, and selected tube heat duty option. The energy stream shows incorrect value of the heat to be removed from the reactor. Also the heat balance of the reactor shows that the reactor is working adiabatically.
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Re: Simulation of a Plug Flow Reactor

Postby jasper » 14 November 2017, 09:10

The answer looks correct to me.

Total enthalpyF in:

-5.93459e+08 W on feed.

Total enthalpyF out:

-6.24261e+08 W on product + 30.801896 MW on tube duty energy stream 12, = -5.93459e+08 W

The same 30.8 MW tube duty is reported in the last run report, and is taken into account in the energy balance when double clicking the unit.

Below is a table doing a first order integration of the heat transfer to the tubes using the temperature profile along the length (see Profiles report). Works out ok.

Code: Select all

K       796         W/m2/K     
T out   523.15      K       
nTube   4801           
dTube   0.0445      m       
A tube  671.1839917 m2/m       
               
Position    Temperature     dT              dT(av)          dH
m           K               K               K               W
0           498.15          -25     
0.0726      500.8425576     -22.30744239    -23.65372119    -917467.6324
0.1452      503.328647      -19.82135296    -21.06439768    -817034.3644
0.2178      505.6288988     -17.52110117    -18.67122706    -724209.3684
0.2904      507.7616042     -15.38839582    -16.45474849    -638237.807
0.363       509.7429874     -13.40701255    -14.39770419    -558450.2948
0.4356      511.5874086     -11.5625914     -12.48480198    -484253.6875
0.5082      513.3075284     -9.842471581    -10.70253149    -415123.9522
0.5808      514.91464       -8.235360014    -9.038915797    -350596.5344
0.6534      516.418799      -6.731200996    -7.483280505    -290257.4014
0.726       517.8289632     -5.321036831    -6.026118914    -233737.8126
0.7986      519.1530708     -3.996929227    -4.658983029    -180710.0918
0.8712      520.3981953     -2.751804707    -3.374366967    -130883.1049
0.9438      521.5706226     -1.579377384    -2.165591045    -83997.76394
1.0164      522.6760135     -0.473986485    -1.026681934    -39822.37872
1.089       523.7192098     0.569209844     0.04761168      1846.735848
1.1616      524.7047913     1.55479127      1.062000557     41192.29818
1.2342      525.6364139     2.48641385      2.02060256      78374.02967
1.3068      526.51771       3.36770999      2.92706192      113533.2808
1.3794      527.3515812     4.201581158     3.784645574     146796.7676
1.452       528.1408239     4.990823929     4.596202544     178274.9966
1.5246      528.8879212     5.737921158     5.364372544     208070.3554
1.5972      529.5950348     6.445034782     6.09147797      236272.924
1.6698      530.2641369     7.114136869     6.779585826     262962.8761
1.7424      530.8969618     7.746961806     7.430549338     288212.0936
1.815       531.4949759     8.344975911     8.045968859     312082.6502
1.8876      532.0595278     8.909527765     8.627251838     334629.1373
1.9602      532.5917685     9.441768465     9.175648115     355900.0329
2.0328      533.0927237     9.942723741     9.692246103     375937.5538
2.1054      533.5633534     10.41335342     10.17803858     394780.2074
2.178       534.0045038     10.85450379     10.63392861     412463.0211
2.2506      534.4169621     11.26696208     11.06073294     429017.6746
2.3232      534.8014865     11.6514865      11.45922429     444474.1397
2.3958      535.15873       12.00872995     11.83010822     458859.7834
2.4684      535.489366      12.33936597     12.17404796     472200.3303
2.541       535.7939918     12.64399175     12.49167886     484520.4244
2.6136      536.0732089     12.92320887     12.78360031     495843.3143
2.6862      536.3276119     13.17761188     13.05041038     506192.1975
2.7588      536.5577931     13.40779308     13.29270248     515590.0914
2.8314      536.7643613     13.61436132     13.5110772      524060.2908
2.904       536.9479503     13.79795027     13.7061558      531626.893
2.9766      537.1092074     13.95920738     13.87857882     538314.7434
3.0492      537.248808      14.09880801     14.02900769     544149.4963
3.1218      537.3674482     14.21744819     14.1581281      549157.7481
3.1944      537.4658386     14.31583858     14.26664338     553366.7798
3.267       537.5447417     14.39474175     14.35529017     556805.1628
3.3396      537.6049326     14.45493264     14.4248372      559502.715
3.4122      537.6471754     14.49717536     14.476054       561489.2845
3.4848      537.6723091     14.52230907     14.50974221     562795.9645
3.5574      537.6811827     14.53118266     14.52674586     563455.4929
3.63        537.6745791     14.52457906     14.52788086     563499.5164
3.7026      537.653376      14.503376       14.51397753     562960.2415
3.7752      537.6184631     14.46846308     14.48591954     561871.9435
3.8478      537.5706712     14.42067122     14.44456715     560267.9896
3.9204      537.5108079     14.36080785     14.39073954     558180.1536
3.993       537.4397843     14.28978434     14.3252961      555641.7692
4.0656      537.3584611     14.20846107     14.24912271     552687.1973
4.1382      537.2675313     14.11753125     14.16299616     549346.5679
4.2108      537.1678809     14.01788094     14.0677061      545650.5088
4.2834      537.0603255     13.91032551     13.96410323     541632.0172
4.356       536.9455334     13.79553339     13.85292945     537319.8695
4.4286      536.8242391     13.67423909     13.73488624     532741.2739
4.5012      536.6971845     13.54718448     13.61071179     527924.8628
4.5738      536.5650238     13.41502379     13.48110413     522897.7119
4.6464      536.4283304     13.27833038     13.34667708     517683.6288
4.719       536.2877496     13.13774962     13.20804        512306.2493
4.7916      536.1438602     12.99386016     13.06580489     506789.3115
4.8642      535.9971414     12.84714142     12.92050079     501153.3352
4.9368      535.848117      12.69811698     12.7726292      495417.7727
5.0094      535.6972536     12.54725359     12.62268528     489601.8299
5.082       535.5449776     12.39497755     12.47111557     483722.8265
5.1546      535.3916845     12.24168454     12.31833104     477796.7037
5.2272      535.2377412     12.08774115     12.16471284     471838.2448
5.2998      535.0834857     11.93348567     12.01061341     465861.1201
5.3724      534.9292412     11.77924123     11.85636345     459878.1568
5.445       534.7752757     11.62527575     11.70225849     453900.8176
5.5176      534.6218343     11.47183435     11.54855505     447939.0523
5.5902      534.4691835     11.31918352     11.39550893     442002.7832
5.6628      534.3175117     11.16751175     11.24334763     436100.8337
5.7354      534.1669924     11.01699241     11.09225208     430240.2216
5.808       534.0178057     10.86780573     10.94239907     424427.8049
5.8806      533.8701112     10.7201112      10.79395847     418670.1718
5.9532      533.7240141     10.57401413     10.64706267     412972.4577
6.0258      533.5796206     10.42962058     10.50181735     407338.7618
6.0984      533.4370646     10.2870646      10.35834259     401773.7409
6.171       533.2964001     10.14640014     10.21673237     396281.041
6.2436      533.1576831     10.00768306     10.0770416      390862.7916
6.3162      533.0210022     9.871002183     9.93934262      385521.7987
6.3888      532.886392      9.736391986     9.803697085     380260.4537
6.4614      532.7538731     9.603873127     9.670132557     375079.8256
6.534       532.6234787     9.473478676     9.538675902     369980.9566
6.6066      532.4952439     9.345243934     9.409361305     364965.1726
6.6792      532.3691596     9.219159581     9.282201757     360032.9775
6.7518      532.2452234     9.095223442     9.157191512     355184.1482
6.8244      532.123475      8.973475044     9.034349243     350419.4093
6.897       532.0038844     8.85388438      8.913679712     345738.9454
6.9696      531.8864325     8.736432534     8.795158457     341141.8076
7.0422      531.7710912     8.621091233     8.678761884     336627.0809
7.1148      531.6578225     8.507822462     8.564456848     332193.4795
7.1874      531.5466666     8.396666587     8.452244525     327841.0491
7.26        531.4375735     8.28757351      8.342120049     323569.601
                        total                           30793707.28

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Re: Simulation of a Plug Flow Reactor

Postby arvind.prasad » 14 November 2017, 12:09

Thanks for the clarification.
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