N'OG??Y1'?mX21?ln?(1?S)'?S?1?S?Y2?mX2?
OGN'OG?N'???10.04?2?0.001ln?(1?0.75)'?0.75??6.2331?0.75?Y2?2?0.001?
?3解得Y2?4.375?10
Y1'?Y2'0.04?4.375?10?3????0.8906?89.06%'Y10.04
'X2?0时:
原工况 S?0.75 Y2?Y1(1??)?0.05(1?0.9)?0.005
NOG?
??Y?mX21ln?(1?S)1?S?1?S?Y2?mX2?
10.05??ln?(1?0.75)?0.75??4.7151?0.75?0.005?
NOG?''HOG?HOG新工况 Z?Z
N'OG??Y1'1?ln?(1?S)'?S?1?S?Y2?
OGN'OG?N'???10.04ln?(1?0.75)'?0.75??4.7151?0.75?Y2?
?3解得Y2?4.00?10
Y1'?Y2'0.04?4.00?10?3????0.9?90%'Y10.04
' 从计算结果看,塔高一定,当用纯溶剂吸收混合气体中的溶质时,入塔气体组成变化,其它条件不变,其吸收率不变。
19.在一逆流操作的填料塔中,用纯溶剂吸收混合气体中溶质组分,当液气比为1.5时,溶质的吸收率为90%,在操作条件下气液平衡关系为Y?0.75X。如果改换新的填料时,在相同的条件下,溶质的吸收率提高到98%,求新填料的气相总体积吸收系数为原填料的多少倍?
*解:原工况:
S?mV0.75??0.5L1.5
NOG?
??Y?mX21??11ln?(1?S)1?S??ln?(1?S)?S?1?S?Y2?mX21???1?S??
NOG?新工况: S?S
'11??ln?(1?0.5)?0.5??3.411?0.5?1?0.90?
N'OG?
11??ln?(1?0.5)?0.5??6.4771?0.5?1?0.98?
HOG?VZVZ?H'OG??'KYa?NOG KYa?N'OG
'KY'aNOG6.477???1.900KYaNOG3.41
20. 在一填料吸收塔内用洗油逆流吸收煤气中含苯蒸汽。进塔煤气中苯的初始浓度为0.02
*(摩尔比,下同),操作条件下气液平衡关系为Y?0.125X,操作液气比为0.18,进塔
洗油中苯的浓度为0.003,出塔煤气中苯浓度降至0.002。因脱吸不良造成进塔洗油中苯的浓度为0.006,试求此情况下(1)出塔气体中苯的浓度; (2)吸收推动力降低的百分数? 解:原工况:
S?mV0.125??0.6944L0.18
NOG??Y1?mX21?ln?(1?S)?S?1?S?Y2?mX2?
10.02?0.125?0.003??ln?(1?0.6944)?0.6944?4.837?1?0.6944?0.002?0.125?0.003?
NOG??Ym?新工况: H''Y1?Y20.02?0.002??0.003721NOG4.837
OG?HOG Z'?Z S'?S
NOG?NOG???10.02?0.125?0.006ln?(1?0.6944)'?0.6944??4.8371?0.6944?Y2?0.125?0.006?' 解得Y2?0.002344
'?YmY1?Y'20.02?0.002344???0.003650NOG4.837
?Ym??Y'm0.003721?0.003650??0.01908?1.91%?Ym0.003721
21.在一塔径为880m的常压填料吸收塔内用清水吸收混合气体中的丙酮,已知填料层高度为6m,在操作温度为25℃时,混合气体处理量为2000m3/h,其中含丙酮5%。若出塔混合物
气体中丙酮含量达到0.263%,每1kg出塔吸收液中含61.2kg丙酮。操作条件下气液平衡关
*系为Y?2.0X,试求:
(1)气相总体积传质系数及每小时回收丙酮的kg数; (2)若将填料层加高3m,可多回收多少kg丙酮?
22解: Ω?0.785?0.88?0.61m
V?2000?273(1?0.05)?77.71kmol/h22.4?298
0.0561.2/58?0.0526X1??0.0202X?01?0.05938.8/18 2
Y1??Y1?Y1?Y1*?0.0526?2?0.0202?0.0122
?Y1?Y1?Y1*?0.0526?2?0.0202?0.0122 ?Y2?Y2?Y2*?0.00263 ?Ym??Y1??Y20.0122?0.00263??0.00624?Y10.0122lnln0.00263?Y2
NOG?HOG?KYa?Y1?Y20.0526?0.00263??8.008?Ym0.00624
VZ?KYaΩNOG
V77.7NOG??8.008?170kmol/(m3?h)ZΩ6?0.61
W?V(Y1?Y2)?77.7?(0.0526?0.00263)?3.883kmol/h?225.19kg/h
(2)
HOG?VZ6???0.749m3KYaΩNOG8.008
'N'OG?ZHOG?6?3?12.020.7493
Y?Y2L0.0526?0.00263?1??2.474VX1?X20.0202?0
S'?S?2/2.474?0.8084
N
'OG??10.0526?ln?(1?0.8084)?0.8084??12.021?0.8084?Y2'?
'Y2解得?0.001096
W'?V(Y1?Y'2)?77.7?(0.0526?0.001096)?4.002kmol/h?232.11kg/h
?W?W?W'?225.19?232.11?6.918kg/h
22.用纯溶剂在一填料吸收塔内,逆流吸收某混合气体中的可溶组分。混合气体处理量为1.25Nm3/s,要求溶质的回收率为99.2%。操作液气比为1.71,吸收过程为气膜控制。已知
*10℃下,相平衡关系Y?0.5X,气相总传质单元高度为0.8m。试求:
(1)吸收温度升为30℃时,溶质的吸收率降低到多少? (30℃时,相平衡关系Y?1.2X) (2)若维持原吸收率,应采取什么措施(定量计算其中的2个措施)。 解:
*(1)原工况:
S?mV0.5??0.292L1.71
NOG?
??Y?mX21??11ln?(1?S)1?S??ln?(1?S)?S?1?S?Y2?mX21???1?S??
11??ln?(1?0.292)?0.292??6.341?0.292?1?0.992?
NOG?Z?NOG?HOG?6.34?0.8?5.072m
''HOG?HOG新工况: Z?Z
m'1.2S?S??0.292?0.7008m0.5
'
'NOG?N'OG???11ln?(1?0.7008)?0.7008??6.341?0.7008?1??'?
解得??0.95
(2)温度升高,平衡线上移,推动力减小,保持吸收率不变,可采取措施:
1)L/V增加,即增加溶剂量;
S?S'mVm'V?'LL
m'1.2L?L?L?2.4Lm0.5
'2)增加填料层高度
m'1.2S?S??0.292?0.7008m0.5 L/V不变,温度升高,,推动力减小靠增加塔高弥补。
'N'OG?
11??ln?(1?0.7008)?0.7008?12.17?1?0.7008?1?0.992?
'H温度改变,对气膜控制吸收过程,传质单元高度不变,OG?HOG?0.8
Z'?N'OG?HOG?12.17?0.8?9.736m
?Z?9.736?5.072?4.664m
23.在一塔高为4m填料塔内,用清水逆流吸收混合气中的氨,入塔气体中含氨0.03(摩尔比),混合气体流率为0.028kmol/(m2·s), 清水流率为0.0573kmol/(m2·s)要求吸收率为98%,气相总体积吸收系数与混合气体流率的0.7次方成正比。已知操作条件下物系的平衡关系为
Y*?0.8X,试求:
(1)当混合气体量增加20%时,吸收率不变,所需塔高?
(2)压力增加1倍时,吸收率不变,所需塔高?(设压力变化气相总体积吸收系数不变) 解:
y1? 原工况:
Y10.03??0.0291?Y11?0.03
2V?0.028?(1?0.029)?0.0272kmol/(m?s)
S?mV0.8?0.0272??0.38L0.0573
NOG?NOG?HOG???11ln?(1?S)?S?1?S?1???
11??ln?(1?0.38)?0.38??5.561?0.38?1?0.98? VZ4???0.720mKYa?NOG5.56
(1)气体流量增加20%
因水吸收氨为气膜控制,所以V增加,传质单元高度变化
HOG?VV?0.7?V0.3KYaΩV
H'OGV'0.30.3?()??1.2??1.056HOGV
H'OG?1.056?0.720?0.760m
mV'0.8?0.0272?1.2S???0.456L0.0573
'N'OG?11??ln?(1?0.456)?0.456??6.1031?0.456?1?0.98?
Z'?N'OG?H'OG?6.103?0.760?4.64m
m'?(2)压力加1倍
p0.8m??0.4p'2