source: mso/sample/reactors/fogler/chap9/cstr_startup.mso @ 28

Last change on this file since 28 was 28, checked in by Rodolfo Rodrigues, 16 years ago
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1#*---------------------------------------------------------------------
2* Hydrolysis of propylene glycol in a unsteady-state CSTR
3*----------------------------------------------------------------------
4* Solved problem from Fogler (1999).
5* Problem number: 9-4, 9-5, and 9-7
6* Page: 504 at 517 (Brazilian version, 2002)
7*----------------------------------------------------------------------
8*
9*   Description:
10*               The propylene glycol is produced for hydrolysis reaction of
11*       propylene oxide in a CSTR:
12*                       CH3(O)CHCH3 + H2O -> CH2(OH)CH2(OH)CH3
13*               This sample calculates the outlet molar concentration and
14*       temperature as function of the time in a CSTR jacketed. It is
15*       possible to identify the MSS (Multiple Steady-State).
16*
17*   Assumptions
18*               * elementary reactions
19*               * unsteady-state
20*               * heat exchange
21*       * isobaric system
22*       * gaseous phase
23*
24*       Specify:
25*               * the inlet stream
26*               * the kinetic parameters
27*               * the components parameters
28*
29*----------------------------------------------------------------------
30* Author: Christiano D. Wetzel Guerra and Rodolfo Rodrigues
31* GIMSCOP/UFRGS - Group of Integration, Modeling, Simulation, Control,
32*                                       and Optimization of Processes
33* $Id$
34*--------------------------------------------------------------------*#
35
36using "types";
37
38
39#*---------------------------------------------------------------------
40* Example 9-4 : Startup of a CSTR
41*--------------------------------------------------------------------*#
42
43Model CSTR_startup
44        PARAMETERS
45        NComp           as Integer              (Brief="Number of components");
46        stoic(NComp)as Real             (Brief="Stoichiometric number");
47        UA              as Real             (Brief="Exchange heat", Unit="Btu/h/degR");
48        V               as volume           (Brief="Volume of the reactor");
49        Ta1             as temperature  (Brief="Cooling temperature");
50        DH              as enth_mol     (Brief="Molar reaction enthalpy");
51        rho(NComp)      as dens_mol     (Brief="Molar density");
52        cp(NComp)       as cp_mol               (Brief="Molar heat capacity");
53        # Rate of reaction
54        ko                      as frequency    (Brief="Frequency factor");
55        E                       as energy_mol   (Brief="Activation energy");
56        R                       as Real                 (Brief="Universal gas constant", Unit="Btu/lbmol/degR", Default=1.987);
57       
58        VARIABLES
59        C(NComp)        as conc_mol     (Brief="Molar concentration", Unit="lbmol/ft^3", Lower=0);
60        N(NComp)        as mol                  (Brief="Molar holdup", Unit="lbmol");
61        Co(NComp)       as conc_mol     (Brief="Initial molar concentration", Unit="lbmol/ft^3", Lower=0);
62        Fo(NComp)       as flow_mol     (Brief="Initial molar flow", Unit="lbmol/h");
63        T               as temperature  (Brief="Reactor temperature", Unit="degR");
64        To              as temperature  (Brief="Initial reactor temperature", Unit="degR");
65        Ta2             as temperature  (Brief="Temperature of heat exchange", Unit="degR");
66        r(NComp)        as reaction_mol (Brief="Rate of reaction", Unit="lbmol/ft^3/h");
67        k               as frequency    (Brief="Specific rate of reaction", Unit="1/h", Upper=1e5);
68        mc              as flow_mol     (Brief="Molar flow of cooling water", Unit="lbmol/h");
69        Q               as heat_rate    (Brief="Heat exchange", Unit="Btu/h");
70        Theta(NComp)as Real                     (Brief="Parameter Theta");
71        vo              as flow_vol     (Brief="Volumetric flow", Unit="ft^3/h");
72        tau             as time_h       (Brief="Residence time", Unit="h");
73
74        EQUATIONS
75        "Molar balance"
76        diff(C) = r + (Co - C)/tau;
77       
78        "Energy balance"
79        diff(T)*sumt(N*cp) = (Q - Fo(1)*sumt(Theta*cp)*(T - To) + DH*r(1)*V);
80       
81        "Rate of reaction"
82        r = stoic*k*C(1);
83       
84        "Specific rate of reaction"
85        k = ko*exp(E/(R*T));
86       
87        "Residence time"
88        tau = V/vo;
89       
90        "Volumetric flow"
91        vo = sumt(Fo/rho);
92       
93        "Temperature of heat exchange"
94        Ta2 =  T - (T - Ta1)*exp(-UA/(cp(2)*mc));
95       
96        "Exchange Heat"
97        Q = mc*cp(2)*(Ta1 - Ta2);
98       
99        "Inlet Concentration"
100        Co = Fo/vo;
101       
102        "Molar holdup"
103        N = C*V;
104       
105        "Relation among molar fractions of components"
106        Theta = Fo/Fo(1);
107       
108        SET
109        NComp = 4; # A, B, C and M
110        stoic = [-1, -1, 1, 0]; # A + 2B -> C + D
111       
112        UA      = 16000*"Btu/h/degR";
113        V       = 500*"gal";
114        Ta1     = (60 + 460)*"degR";
115        DH      =-3.6e4*"Btu/lbmol";
116        rho     = [0.923, 3.45, 1, 1.54]*"lbmol/ft^3";
117        cp      = [35, 18, 46, 19.5]*"Btu/lbmol/degR";
118       
119        ko = 16.96e12*"1/h";
120        E  = -32400*"Btu/lbmol";
121end
122
123
124FlowSheet CSTR_stopped
125        DEVICES
126        CSTR as CSTR_startup;
127       
128        SPECIFY
129        "Inlet molar flow"
130        CSTR.Fo = [80, 1000, 0, 100]*"lbmol/h";
131        "Inlet reactor temperature"
132        CSTR.To = (75 + 460)*"degR";
133        "Molar flow of cooling water"
134        CSTR.mc = 1e3*"lbmol/h";
135
136        INITIAL
137        "Molar concentration"
138        CSTR.C  = [0, 3.45, 0, 0]*"lbmol/ft^3";
139        "Reactor temperature"
140        CSTR.T  = CSTR.To;
141
142        OPTIONS
143        time = [0:0.05:4]*"h";
144end
145
146
147#*---------------------------------------------------------------------
148* Example 9-5 : Falling off the upper steady-state
149*--------------------------------------------------------------------*#
150
151Model CSTR_ss as CSTR_startup
152        VARIABLES
153        X                       as fraction             (Brief="Molar conversion");
154        XMB                     as fraction             (Brief="Molar conversion of Material balance");
155        XEB                     as fraction             (Brief="Molar conversion of Energy balance");
156
157        EQUATIONS
158        "Molar conversion"
159        X       = 1 - C(1)/Co(1);
160       
161        "Molar conversion of Material balance"
162        XMB = tau*k/(1 + tau*k);
163       
164        "Molar conversion of Energy balance"
165        XEB = (sumt(Theta*cp)*(T - To) + Q/Fo(1))/(-DH);
166end
167
168
169FlowSheet CSTR_stopped2
170        DEVICES
171        CSTR as CSTR_ss;
172       
173        SPECIFY
174        "Inlet molar flow"
175        CSTR.Fo = [80, 1000, 0, 100]*"lbmol/h";
176        "Inlet reactor temperature"
177        CSTR.To = (70 + 460)*"degR"; # Reduction of temperature: 75°F to 70°F
178        "Molar flow of cooling water"
179        CSTR.mc = 1e3*"lbmol/h";
180
181        INITIAL
182        "Molar concentration"
183        CSTR.C = [0.039, 2.12, 0.143, 0.226]*"lbmol/ft^3"; # Final values of SS in 9-4
184        "Reactor temperature"
185        CSTR.T = (138.5 + 460)*"degR"; # Final values of SS in 9-4
186
187        OPTIONS
188        time = [0:0.05:4]*"h";
189end
190
191
192#*---------------------------------------------------------------------
193* Example 9-7 : PI Controller
194*--------------------------------------------------------------------*#
195
196Model CSTR_control_PI as CSTR_startup
197        PARAMETERS
198        Tsp                     as temperature  (Brief="Reference temperature");
199        mco             as flow_mol     (Brief="Molar flow of cooling water");
200        kc                      as Real                 (Brief="Gain");
201       
202        VARIABLES
203        I                       as Real                 (Brief="Integral action");
204        X                       as fraction             (Brief="Fraction conversion", Lower=0);
205       
206        EQUATIONS
207        "Integral action"
208        diff(I) = T - Tsp;
209       
210        "Molar flow of cooling water"
211        mc = mco + kc/tau*I + kc*(T - Tsp);
212       
213        "Molar conversion"
214        X = 1 - C(1)/Co(1);
215end
216
217
218FlowSheet CSTR_stopped3
219        DEVICES
220        CSTR as CSTR_control_PI;
221       
222        SET
223        CSTR.mco = 1000*"lbmol/h";
224        CSTR.Tsp = (138 + 460)*"degR";
225        CSTR.kc = 8.5;
226
227        SPECIFY
228        "Inlet molar flow"
229        CSTR.Fo = [80, 1000, 0, 100]*"lbmol/h";
230        "Inlet reactor temperature"
231        CSTR.To = (70 + 460)*"degR";
232
233        INITIAL
234        "Molar concentration"
235        CSTR.C = [0.03789, 2.12, 0.143, 0.2265]*"lbmol/ft^3";
236        "Reactor temperature"
237        CSTR.T = (138.53 + 460)*"degR";
238        "Integral action"
239        CSTR.I = 0;
240
241        OPTIONS
242        time = [0:0.01:4]*"h";
243end
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