降膜蒸发器改造热平衡计算.docx
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降膜蒸发器改造热平衡计算
蒸发热平衡计算
计算的原始数据
1)新蒸汽使用压力P=5bar(绝压),T=155°C,潜热2102kJ/kg;
3
2)原液Nd75g/I,质量分率13.8%,比热0.825KCal/kgC,to=85C,p=1270kg/m;
3)出料浓度NK255g/l,质量分率18.5%,比热0.766Kcal/kgC,t出=90C,p
3
=1375kg/m;
4)末效(第VI效)压力P=0.1bar(绝压),二次蒸汽温度Te=46C,汽化热2387kJ/kg;
5)传热系数(W/m2C):
Ki=1980,Kii=1580,Kiii=1580,Kiv=1400,Kv=917,
Kvi=1024,
K强=750;
6)传热面积(m):
Fi=1500,Fii=1500,Fiii=1500,Fiv=1500,Fv=3750,Fvi=3750,F强=580;
7)温度损失:
蒸发器
III
III
IV
V
VI
沸点升咼
13
11
9
9
8
15
沿管损失
1
1
1
1
1
合计
14
12
10
10
9
15
总温度损失70C;
8)为简化计算过程,计算时没有考虑冷凝水自蒸发产生的二次汽及热损失,而把它们考虑为相互抵消;
9)按处理流量1000kg/h进行计算。
计算
1、蒸水量
W总=1000[1-(175/1270)/(255/1375)]=235.8kg/h
2、总温度差
△t总=155-46=109C
3、蒸发水量的分配(第一次逼近值)
W1=(W1+W2+W3+W4+W5+W6)XKi/(Ki+Kii+Kiii+Kiv+Kv+Kvi)
=235.8X1980/(1980+1580X2+1400+917+1024)=55.1kg/h
W2=W3=W1XKii/Ki=55.1X1580/1980=44.0kg/h
W4=W1XKiv/Ki=55.1X1400/1980=39.0kg/h
W5=W1XKv/Ki=55.1X917/1980=25.5kg/h
W6=W1XKvi/Ki=55.1X1024/1980=28.5kg/h
4、有效温差
△t有=△t总-△t损=109-70=39C
5、有效温差分配(第一次逼近值)
△t1=△t2=△t3=△t4=△t5=△t6=39/6=6.5C
I
II
III
IV
V
VI
I闪
II闪
III闪
加热蒸汽
J曰由
155
134.5
116
99.6
83.1
67.6
温度
161
123
106
94
81
66
106.5
97
90
有效温差
6.5
6.5
6.5
6.5
6.5
6.5
沸点升咼
13/30
11/13
9/6
9/4
8/2
15/3
二次汽温
135.5
117
100.5
84.1
68.6
46.1
度
124
107
95
82
67
57
沿管损失
1
1
1
1
1
加热蒸汽
658
651
645.8
638.8
632
625.6
热焓
KCal/kg
加热蒸汽
502
516
530
540
549.2
557.4
潜热
KCal/kg
溶液沸点
148.5
128
109.5
93.1
76.6
61.1
130
111.5
95.1
二次汽焓
656
649
644
636
629.7
623
650.6
644
637.6
二次汽潜
508
522
533
543
553
561
520.1
532.1
542.0
热
6各效浓度%
a=GB始/(G-W)=1000X175/1270/(1000-28.5)=14.6%
o5=0.5X(1000-28.5)X0.146/[0.5X(1000-28.5)-25.5]=15.4%(送入蒸发系统的原液全部进入切效蒸发器,经切效蒸发浓缩后,分别各以50%的液量送入V效和川效。
)o4=[0.5X(1000-28.5)-25.5]X0.154/[0.5X(1000-28.5)-25.5-39]=16.8%
03=0.5X(1000-28.5)X0.146/[0.5X(1000-28.5)-44.0]=16.1%
o2=[0.5X(1000-28.5)-44]X0.161/[0.5X(1000-28.5)-44-44]=17.9%
a1=[0.5X(1000-28.5)-44-44]X0.179/[0.5X(1000-28.5)-44-44-55.1]=20.8%
7、各效蒸水量
1)第VI效热平
1
W5r5=W6「6+F0C0(t6-t0)
w5=[w6X561+1000X0.825(61.1-85)]/557.4=W6-35.4
W5=W6-35.4
2)第V效热平
11
W4r4=W5「5+0.5F6C3(t5-t6)=W5「5+0.5(F°C0-W6)X(t5-t6)
=(W6-35.4)X553+0.5(1000X0.825-W6)X(76.6-61.1)
W4=[(w6-35.4)X553+0.5(1000X0.825-w6)X(76.6-61.1)]/549.2
W4=0.993W6-24
3)I闪热平
F1c1t1=FIcItI+wIHI
FIcI=f1c1-wI
F1c1(t1-tI)=wIrI
F1c1=0.5F6c6-w1-w2-w3=0.5(F0c0-w6)-w1-w2-w3(忽略闪蒸进入的水量)[0.5(F0c0-w6)-w1-w2-w3](t1-tI)=wIrI
wi=[0.5(1000X0.825-W6)-W1-W2-W3](148.5-130)/520.1
wi=14.7-0.018ws-0.036(w什W2+W3)
wi=14.7-0.018X28.5-0.036X143.1=14.7-0.018X28.5-0.036X143.1=9kg/h
4)ii闪热平
Ficiti=Fiiciitii+wiiHii
Fiicii=fici-wii
Fici(ti-tii)=wiirii
[0.5(F0c0-w6)-w1-w2-w3-wi](ti-tii)=wiirii
wii=[0.5(1000X0.825-w6)-w1-w2-w3-wi](130-111.5)/532.1
wii=14.3-0.017w6-0.035(w1+w2+w3+wi)
wii=14.34-0.0172X8.5-0.035(X55.1+44+44+9)=8.5kg/h
5)iii闪热平
Fiiciitii=Fiiiciiitiii+wiiiHiii
Fiiiciii=fiicii-wiii
Fiicii(tii-tiii)=wiiiriii
[0.5(F0c0-w6)-w1-w2-w3-wi-wii](tii-tiii)=wiiiriii
wiii=[0.5(1000X0.825-w6)-w1-w2-w3-wi-wii](111.5-95.1)/542
wiii=12.5-0.015w6-0.03(w1+w2+w3+wi+wii)
wiii=12.5-0.0152X8.5-0.03(5X5.1+88+9+8.5)=7.3kg/h
6)第iV效热平
1
w3r3+wiiiHiii=w4r4+F5c5(t4-t5)
w3r3+wiiiHiii=w4r41+F5c5(t4-t5)
w3r3+wiiiHiii=w4r41+[0.5(F0c0-w6)-w5](t4-t5)
1
w3r3=w4r4+[0.5(F0c0-w6)-w5](t4-t5)-wiiiHiii
=543(0.993w6-24)+[0.5(1000X0.825-w6)-w6+35.4](93.1-76.6)-7.3X637.6
=539.2w6-13032+6806.3-8.25w6-16.5w6+584.1-4654.5
=514.45w6-10296
w3=(514.45w6-10296)/540
w3=0.953w6-19.1
7)第iii效热平
11
w2r2+wiiHii=w3r3+0.5F6c6(t3-t4)=w3r3+0.5(F0c0-w6)(t3-t6)
w2r2=w3r31+0.5(F0c0-w6)(t3-t4)-wiiHii
=533(0.953w6-19.1)+0.5(1000X0.825-w6)(109.5-61.1)-8.5X644
=508w6-10180.3+19965-24.2w6-5474=483.2w6+4310.7
w2=(483.2w6+4310.7)/530=0.91w6+8.1
8)第ii效热平
1
w1r1+wiHi=w2r2+F3c3(t2-t3)
F3c3=0.5F6c6-w3=0.5(F0c0-w6)-w3
w1r1+wIHI=w2r21+[0.5(F0c0-w6)-w3](t2-t3)
=522(0.91W6+8.1)+[0.5(1000X0.825-W6)-0.953W6+19.1](128-109.5)
=475w6+4228.2+7631.3-9.25w6-17.6w6+353.4
=448.2w6+12212.9w1r1=448.2w6+12212.9-9X650.6=448.2w6+6537.5
w1=(448.2w6+6537.5)/516=0.869w6+12.3
9)第I效热平
1
Dr=w1r1+F2c2(t1-t2)
F2c2=0.5(F0c0-w6)-w3-w2
Dr=w1r11+[0.5(F0c0-w6)-w3-w2](t1-t2)
=508(0.869w6+12.3)+[0.5(1000X0.825-w6)-0.953w6+19.1-0.91w6-8.1](148.5-128)=441.5w6+6248.4+8456.3-10.25w6-19.5w6+391.6-18.7w6-166.1
=393.1w6+14930.2
D=(393.1w6+14930.2)/502=0.783w6+29.7
10)蒸水量
w1+w2+w3+w4+w5+w6=w
0.869w6+12.3+0.91w6+8.1+0.953w6-19.1+0.993w6-24+w6-35.4+w6=235.8
5.725w6-58.1=235.8
w6=51.3kg/h
w5=51.3-35.4=15.9kg/h
w4=0.993X51.3-24=27.0kg/h
w3=0.953X51.3-19.1=29.8kg/h
w2=0.91X51.3+8.1=54.8kg/h
w1=0.869X51.3+12.3=56.9kg/h
D=0.783X51.3+29.7=69.9kg/h
10)蒸汽单耗
D/w=69.9/235.8=0.296kg汽/kg.水
8、热负荷
Q1=Dr=69.9X502=35089kcal
Q2=w1r1=56.9X516=29360kcal
Q3=w2r2=54.8X530=29044kcal
Q4=w3r3=29.8X540=16092kcal
Q5=w4r4=27.0X549.2=14828kcal
Q6=w5r5=15.9X557.4=8863kcal
9、相对热负荷
g2=Q2/Q1=29360/35089=0.837
g3=Q3/Q1=29044/35089=0.828
g4=Q4/Q1=16092/35089=0.459
g5=Q5/Q1=14828/35089=0.423
g6=Q6/Q1=8863/35089=0.253
10、精确分配有效温差
△ti=39/(1+g2XFiXKi/F2XK2+g3XFiXKi/F3XK3+g4XFiXKi/F4XK4+g5XFi
XKi/F5XK5
+g6XFiXKi/F6XK6)
=39/[i+0.837Xi955Xi980/(ii06Xi580)+0.828Xi955Xi980/(ii06Xi580)+0.459Xi955Xi980/(ii06Xi400)+0.423Xi955Xi980/(i800X9i7)+0.253Xi955Xi980/(4000Xi024)]]
△ti=5.5°C
△t2=5.5X0.837Xi955Xi980/(ii06Xi580)=i0.2C
△t3=5.5X0.828Xi955Xi980/(ii06Xi580)=i0.iC
△t4=5.5X0.459Xi955Xi980/(ii06Xi400)=6.3C
△t5=5.5X0.423Xi955Xi980/(i800X9i7)=5.5C
△t6=5.5X0.253Xi955Xi980/(4000Xi024)=i.4C
ii、计算结果列表
I
II
III
IV
V
VI
I闪
II闪
III闪
加热蒸汽
i55
i35.5
ii3.3
93.2
76.9
62.4
温度
有效温差
5.5
i0.2
i0.i
6.3
5.5
i.4
沸点升咼
i3
ii
9
9
8
i5
二次汽温
i36.5
ii4.3
94.2
77.9
63.4
46
度
沿管损失
i
i
i
i
i
加热蒸汽
658
652.5
644.8
636
630
623
热焓
加热蒸汽
502
5i6
532
544
553
56i
潜热
溶液沸点
i49.5
i25.3
i03.2
86.9
7i.4
6i
i27.3
i05.2
88.9
二次汽焓
657
649
640.5
634
627.5
623
649.5
64i.5
635
二次汽潜
506
523
538
547
556
56i
522
536
546
热
i2、第二次逼近计算
/1)蒸水量
1)第VI效热平
i
W5r5=W6r6+F0C0(t6-t0)
W5=[W6X56i+i000X0.825(6i.0-85)]/56i=W6-35.3
W5=W6-35.3
2)第V效热平
ii
W4r4=W5「5+0.5F6C3(t5-t6)=W5「5+0.5(F°C0-W6)X亿5才6)
=(W6-35.3)X556+0.5(i000X0.825-w6)X(7i.4-6i.0)
W4=[(w6-35.4)X556+0.5(1000X0.825-w6)X(76.6-61.1)]/553
w4=0.991w6-24
3)I闪热平
F1c1t1=FIcItI+wIHI
FIcI=f1c1-wI
F1c1(t1-tI)=wIrI
F1c1=0.5F6c6-w1-w2-w3=0.5(F0c0-w6)-w1-w2-w3(忽略闪蒸进入的水量)
[0.5(F0c0-w6)-w1-w2-w3](t1-tI)=wIrI
wi=[0.5(1000X0.825-W6)-wi-w2-w3](149.5-127.3)/522
wi=14.7-0.021ws-0.043(w什W2+W3)
wi=仃.5-0.021X51.3-0.043X141.5=10.3kg/h
4)ii闪热平
Ficiti=Fiiciitii+wiiHii
Fiicii=fici-wii
Fici(ti-tii)=wiirii
[0.5(F0c0-w6)-w1-w2-w3-wi](ti-tii)=wiirii
wii=[0.5(1000X0.825-w6)-w1-w2-w3-wi](127.3-105.2)/536
wii=17.0-0.021w6-0.041(w1+w2+w3+wi)
wii=17.0-0.0215X1.3-0.041(X56.9+54.8+29.8+10.3)=9.7kg/h
5)iii闪热平
Fiiciitii=Fiiiciiitiii+wiiiHiii
Fiiiciii=fiicii-wiii
Fiicii(tii-tiii)=wiiiriii
[0.5(F0c0-w6)-w1-w2-w3-wi-wii](tii-tiii)=wiiiriii
wiii=[0.5(1000X0.825-w6)-w1-w2-w3-wi-wii](105.2-88.9)/522
wiii=12.9-0.016w6-0.03(w1+w2+w3+wi+wii)
wiii=12.9-0.0165X1.3-0.031(5X6.9+54.8+29.8+10.3+9.7)=7.1kg/h
6)第iV效热平
1
w3r3+wiiiHiii=w4r4+F5c5(t4-t5)
w3r3+wiiiHiii=w4r4+F5c5(t4-t5)
w3r3+wiiiHiii=w4r41+[0.5(F0c0-w6)-w5](t4-t5)
w3r3=w4r41+[0.5(F0c0-w6)-w5](t4-t5)-wiiiHiii
=547(0.991w6-24)+[0.5(1000X0.825-w6)-w6+35.3](86.9-71.4)-7.1X635=542.7w6-13128+6393.8-7.75w6-15.5w6+547.2-4508.5
=519.45w6-10695.5
w3=(519.45w6-10695.5)/544
w3=0.955w6-19.7
7)第iii效热平
11
w2r2+wiiHii=w3r3+0.5F6c6(t3-t4)=w3r3+0.5(F0c0-w6)(t3-t6)
1
w2r2=w3r3+0.5(F0c0-w6)(t3-t6)-wiiHii
=538(0.955w6-19.7)+0.5(1000X0.825-w6)(103.2-61.0)-9.7X641.5=513.8w6-10598.6+17407.5-21.1w6-6222.6=492.7w6+586.3
w2=(492.7w6+586.3)/532=0.926w6+1.1
8)第II效热平
1
w1r1+wIHI=w2r2+F3c3(t2-t3)
F3c3=0.5F6c6-w3=0.5(F0c0-w6)-w3
1
w1r1+wIHI=w2r2+[0.5(F0c0-w6)-w3](t2-t3)
=523(0.926W6+1.1)+[0.5(1000X0.825-w)-0.955W6+19.7](125.3-103.2)
=484.3w6+575.3+9116.25-11.05w6-21.1w6+435.4
=452.2w6+10127
wiri=452.2we+10127-10.3X649.5=452.2w6+3437.2
W1=(452.2W6+3437.2)/516=0.876W6+6.66
9)第I效热平
i
Dr=wiri+F2c2(ti-t2)
F2c2=0.5(F0c0-w6)-w3-w2
Dr=wirii+[0.5(F0c0-w6)-w3-w2](ti-t2)
=506(0.876w6+6.66)+[0.5(1000X0.825-W6)-0.955W6+19.7
-0.926w6-i.i](i49.5-i25.3)
=443.3w6+3370+9982.5-12.1w6-23.1w6+476.7-22.4w6-26.6
=385.7w6+13802.6
D=(385.7w6+13802.6)/502=0.768W6+27.5
10)蒸水量
w1+w2+w3+w4+w5+w6=w
0.876W6+6.66+0.926W6+1.1+0.955W6-19.7+0.991W6-24+W6-35.3+W6=235.8w6=53.5kg/h
w5=53.4-35.3=18.2kg/h
w4=0.991X53.4-24=28.9kg/h
w3=0.955X53.4-19.7=31.3kg/h
w2=0.926X53.4+1.1=50.5kg/h
w1=0.876X53.4+6.66=53.4kg/h
D=0.768X53.4+27.5=68.5kg/h
11)蒸汽单耗
D/w=68.5/235.8=0.291kg汽/kg.水
13)热负荷
Q1=Dr=68.5X502=34378kcalQ2=w1r1=53.4X516=27554kcalQ3=w2r2=50.5X532=26866kcalQ4=w3r3=31.3X544=17027kcalQ5=w4r4=28.9X553=15981kcalQ6=w5r5=18.1X561=10154kcal
14)相对热负荷
g2=Q2/Q1=27554/34378=0.801
g3=Q3/Qi=26866/34378=0.781
g4=Q4/Q