化工热力学(第三版)答案陈钟秀

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2-1.使用下述方法计算1kmol甲烷贮存在体积为0.1246m3、温度为50℃的容器中产生的压力:(1)理想气体方程;(2)R-K方程;(3)普遍化关系式。

解:甲烷的摩尔体积V=0.1246 m3/1kmol=124.6 cm3/mol

查附录二得甲烷的临界参数:Tc=190.6K Pc=4.600MPa Vc=99 cm3/mol ω=0.008

(1) 理想气体方程

P=RT/V=8.314×323.15/124.6×10-6=21.56MPa

(2) R-K方程

22.522.560.5268.314190.60.427480.427483.2224.610ccRTaPamKmolP

53168.314190.60.086640.086642.985104.610ccRTbmmolP

∴0.5RTaPVbTVVb

50.5558.314323.153.22212.462.98510323.1512.461012.462.98510

=19.04MPa

(3) 普遍化关系式

323.15190.61.695rcTTT 124.6991.259rcVVV<2

∴利用普压法计算,01ZZZ

∵ crZRTPPPV

∴ crPVZPRT

654.61012.46100.21338.314323.15crrrPVZPPPRT

迭代:令Z0=1→Pr0=4.687 又Tr=1.695,查附录三得:Z0=0.8938 Z1=0.4623

01ZZZ=0.8938+0.008×0.4623=0.8975

此时,P=PcPr=4.6×4.687=21.56MPa

同理,取Z1=0.8975 依上述过程计算,直至计算出的相邻的两个Z值相差很小,迭代结束,得Z和P的值。

∴ P=19.22MPa

2-2.分别使用理想气体方程和Pitzer普遍化关系式计算510K、2.5MPa正丁烷的摩尔体积。已知实验值为1480.7cm3/mol。

解:查附录二得正丁烷的临界参数:Tc=425.2K Pc=3.800MPa Vc=99 cm3/mol ω=0.193 (1)理想气体方程

V=RT/P=8.314×510/2.5×106=1.696×10-3m3/mol

误差:1.6961.4807100%14.54%1.4807

(2)Pitzer普遍化关系式

对比参数:510425.21.199rcTTT 2.53.80.6579rcPPP—普维法

∴ 01.61.60.4220.4220.0830.0830.23261.199rBT

14.24.20.1720.1720.1390.1390.058741.199rBT

01ccBPBBRT=-0.2326+0.193×0.05874=-0.2213

11crcrBPBPPZRTRTT=1-0.2213×0.6579/1.199=0.8786

∴ PV=ZRT→V= ZRT/P=0.8786×8.314×510/2.5×106=1.49×10-3 m3/mol

误差:1.491.4807100%0.63%1.4807

2-3.生产半水煤气时,煤气发生炉在吹风阶段的某种情况下,76%(摩尔分数)的碳生成二氧化碳,其余的生成一氧化碳。试计算:(1)含碳量为81.38%的100kg的焦炭能生成1.1013MPa、303K的吹风气若干立方米?(2)所得吹风气的组成和各气体分压。

解:查附录二得混合气中各组分的临界参数:

一氧化碳(1):Tc=132.9K Pc=3.496MPa Vc=93.1 cm3/mol ω=0.049 Zc=0.295

二氧化碳(2):Tc=304.2K Pc=7.376MPa Vc=94.0 cm3/mol ω=0.225 Zc=0.274

又y1=0.24,y2=0.76

∴(1)由Kay规则计算得:

0.24132.90.76304.2263.1cmiciiTyTK

0.243.4960.767.3766.445cmiciiPyPMPa

303263.11.15rmcmTTT 0.1011.4450.0157rmcmPPP—普维法

利用真实气体混合物的第二维里系数法进行计算

011.61.610.4220.4220.0830.0830.02989303132.9rBT

114.24.210.1720.1720.1390.1390.1336303132.9rBT 016111111618.314132.90.029890.0490.13367.378103.49610ccRTBBBP

021.61.620.4220.4220.0830.0830.3417303304.2rBT

124.24.220.1720.1720.1390.1390.03588303304.2rBT

016222222628.314304.20.34170.2250.03588119.93107.37610ccRTBBBP

又0.50.5132.9304.2201.068cijcicjTTTK

331313131331293.194.093.55/22cccijVVVcmmol

120.2950.2740.284522cccijZZZ

120.2950.2250.13722cij

6/0.28458.314201.068/93.55105.0838cijcijcijcijPZRTVMPa

∴ 303201.0681.507rijcijTTT 0.10135.08380.0199rijcijPPP

0121.61.6120.4220.4220.0830.0830.1361.507rBT

1124.24.2120.1720.1720.1390.1390.10831.507rBT

∴01612121212126128.314201.0680.1360.1370.108339.84105.083810ccRTBBBP

2211112122222mByByyByB

26626630.247.3781020.240.7639.84100.76119.931084.2710/cmmol∴1mmBPPVZRTRT→V=0.02486m3/mol

∴V总=n V=100×103×81.38%/12×0.02486=168.58m3

(2) 1110.2950.240.10130.0250.2845cmZPyPMPaZ 2220.2740.760.10130.0740.2845cmZPyPMPaZ

2-4.将压力为2.03MPa、温度为477K条件下的2.83m3NH3压缩到0.142 m3,若压缩后温度448.6K,则其压力为若干?分别用下述方法计算:(1)Vander Waals方程;(2)Redlich-Kwang方程;(3)Peng-Robinson方程;(4)普遍化关系式。

解:查附录二得NH3的临界参数:Tc=405.6K Pc=11.28MPa Vc=72.5 cm3/mol ω=0.250

(1) 求取气体的摩尔体积

对于状态Ⅰ:P=2.03 MPa、T=447K、V=2.83 m3

477405.61.176rcTTT 2.0311.280.18rcPPP—普维法

∴01.61.60.4220.4220.0830.0830.24261.176rBT

14.24.20.1720.1720.1390.1390.051941.176rBT

010.24260.250.051940.2296ccBPBBRT

11crcrBPPVBPPZRTRTRTT→V=1.885×10-3m3/mol

∴n=2.83m3/1.885×10-3m3/mol=1501mol

对于状态Ⅱ:摩尔体积V=0.142 m3/1501mol=9.458×10-5m3/mol T=448.6K

(2) Vander Waals方程

222262627278.314405.60.4253646411.2810ccRTaPammolP

53168.314405.63.737108811.2810ccRTbmmolP

22558.314448.60.425317.659.4583.737103.73710RTaPMPaVbV

(3) Redlich-Kwang方程

22.522.560.5268.314405.60.427480.427488.67911.2810ccRTaPamKmolP

53168.314405.60.086640.086642.591011.2810ccRTbmmolP

0.550.5558.314448.68.67918.349.4582.5910448.69.458109.4582.5910RTaPMPaVbTVVb (4) Peng-Robinson方程

∵448.6405.61.106rcTTT

∴220.37461.542260.269920.37461.542260.250.269920.250.7433k

220.50.51110.743311.1060.9247rTkT

22226268.314405.60.457240.457240.92470.426211.2810cccRTaTaTTPammolP

53168.314405.60.077800.077802.3261011.2810ccRTbmmolP

∴aTRTPVbVVbbVb

510108.314448.60.42629.4582.326109.4589.4582.326102.3269.4582.32610 19.00MPa

(5) 普遍化关系式

∵ 559.458107.25101.305rcVVV<2 适用普压法,迭代进行计算,方法同1-1(3)