化工热力学(第三版)答案陈钟秀 下载本文

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

R2Tc2.5a?0.42748?Pcb?0.086642.58.314?190.260.42748?64.6?106Pa3.?2m22?K0.?5mol?

2RTc8.314?190.6?53?1?0.08664?2.985?10m?mol 6Pc4.6?10∴P?RTa?0.5

V?bTV?V?b?8.314?323.153.222??12.46?2.985??10?5323.150.5?12.46?10?5?12.46?2.985??10?5

? =19.04MPa (3) 普遍化关系式

Tr?TTc?323.1519?0.61.9r5?VVc?124.699?1.259<2 6 V∴利用普压法计算,Z∵ ∴

?Z0??Z1

ZRT?PcPr VPVZ?cPr

RTP?PV4.6?106?12.46?10?5cZ?Pr?Pr?0.2133Pr

RT8.314?323.15

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

Z?Z0??Z1=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:

1.696?1.4807?100%?14.54%

1.4807?TTc?510425.2?1.199 Pr?PPc?2.53.?80.6—普维法579

(2)Pitzer普遍化关系式 对比参数:Tr∴

B0?0.083?0.4220.422?0.08?3??0. 23261.61.6Tr1.199B1?0.139?0.1720.172?0.139???0.05874 Tr4.21.1994.2BPc?B0??B1=-0.2326+0.193×0.05874=-0.2213 RTcZ?1?BPBPP?1?crRTRTcTr=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:

1.49?1.4807?100%?0.63%

1.48072-3.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:

Tcm??yiTci?0.24?132.9?0.76?304.2?263.1K

iPcm??yiPci?0.24?3.496?0.76?7.376?6.445MPa

iTrm?TTcm?303263.1?1.15 Prm?PPcm?0.1011.44?5利用真实气体混合物的第二维里系数法进行计算

0.—普维法0157

B10?0.083?0.4220.422?0.083???0.02989 1.61.6Tr1?303132.9?0.1720.172?0.139??0.1336 4.2Tr4.2?303132.9?11B1?0.139?B11?RTc108.314?132.91B1??1B1??0.02989?0.049?0.1336???7.378?10?6 ??6?Pc13.496?100B2?0.083?0.4220.422?0.083???0.3417 1.6Tr1.6?303304.2?20.1720.172?0.139???0.03588 4.24.2Tr2?303304.2?1B2?0.139?B22?又TcijRTc208.314?304.21?6B??B??0.3417?0.225?0.03588??119.93?10 ???222?6Pc27.376?10??TciTcj?0.5??132.9?304.2?30.5?201.068K3

?Vc113?Vc123??93.113?94.013?Vcij?????93.55cm3/mol ??22????Zc1?Zc20.295?0.274??0.2845

22???20.295?0.225?cij?1??0.137

22Zcij?Pcij?ZcijRTcij/Vcij?0.2845?8.314?201.068/?93.55?10?6??5.0838MPa

Trij?TTcij?303201.068?1.507 Prij?PPci??38j0.10135.080. 01990B12?0.083?0.4220.422?0.083???0.136 1.6Tr1.61.507120.1720.172?0.139??0.1083 4.24.2Tr121.5071B12?0.139?∴B12?RTc1208.314?201.0681B12??12B12???0.136?0.137?0.1083???39.84?10?6 ??6Pc125.0838?10

2Bm?y12B11?2y1y2B12?y2B22?0.242???7.378?10?6??2?0.24?0.76???39.84?10?6??0.762???119.93?10?6???84.27?10?6cm3/mol∴Zm?1?BmPPV?RTRT→V=0.02486m3/mol

∴V总=n V=100×103×81.38%/12×0.02486=168.58m3 (2)

P1?y1PZc10.295?0.24?0.1013?0.025MPa Zm0.2845Zc20.274?0.76?0.1013?0.074MPa Zm0.2845P2?y2P2-4.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

Tr?TTc?477405.6?1.176 Pr?PPc?2.0311.28?0.18—普维法

∴B0?0.083?0.4220.422?0.083???0.2426 Tr1.61.1761.60.1720.172?0.139??0.05194 4.24.2Tr1.176B1?0.139?BPc?B0??B1??0.2426?0.25?0.05194??0.2296 RTcZ?1?BPPVBPP??1?crRTRTRTcTr→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

27R2Tc227?8.3142?405.626?2 a???0.4253Pa?m?mol664Pc64?11.28?10b?RTc8.314?405.6?53?1??3.737?10m?mol 68Pc8?11.28?10P?RTa8.314?448.60.4253?2???17.65MPa 2?5?5V?bV9.458?3.737?10???3.737?10?(3) Redlich-Kwang方程

R2Tc2.58.3142?405.62.5a?0.42748?0.42748?8.679Pa?m6?K0.5?mol?2 6Pc11.28?10b?0.08664P?RTc8.314?405.6?0.08664?2.59?10?5m3?mol?1 6Pc11.28?10RTa8.314?448.68.679?0.5???18.34MPa ?50.5?5?5V?bTV?V?b??9.458?2.59??10448.6?9.458?10?9.458?2.59??10(4) Peng-Robinson方程 ∵Tr?TTc?448.6405.6?1.106