14.06?161.73?12.95?14.6.15?11.10?152.94?11.11?129.08=148.28m2
49.22S1161.73146.15?14.06=15.34℃, △t2''=?12.95=12.76℃ △t1''=?t1'=
S148.28148.28152.94129.08?11.10=11.45℃, △t4''=?11.11=9.67℃ △t3''=
148.28148.28∑△t''= 15.34+12.76+11.45+9.67=49.22℃
S=
重新核算各效浓度及各沸点升高 X1=0.5
FX046014.83?27.56%==0.40
F?W4?W3?W246014.83-4216.05-4445.46-5337.4FX046014.83?27.56%X3===0.34
F?W4?W346014.83?4216.05?4445.46FX046014.83?27.56%X4===0.30
F?W446014.83?4216.05由经验公式:△i=1.78Xi+6.22Xi2 得各效沸点升高
X2=
△1,=1.78×0.5+6.22×0.52=2.45℃ △2,=1.78×0.40+6.22×0.602=1.71℃ △3,=1.78×0.34+6.22×0.342=1.32℃ △4,=1.78×0.30+6.22×0.302=1.09℃
重新核算各效加热蒸汽温度,二次蒸汽温度及各效沸点
T1=120.2℃, t1=T1-△t1''=120.2-15.34=104.86℃, T1'=t1-△1'=102.41℃ T2=101.41℃, t2=T2-△t2''=101.41-12.76=89.65℃, T2'=t2-△2'=87.94℃ T3=86.94℃, t3=T3-△t3''=86.94-11.45=76.49℃, T3'=t3-△3'=75.17℃ T4=74.17℃, t4=T4-△t4''=74.17-9.67=65.5℃, T4'=t4-△4'=64.41℃ 查表得:
r1=2204.6kJ/kg r1'=2252.13kJ/kg r2=2254.73kJ/kg r2'=2288.09kJ/kg r3=2290.51kJ/kg r3'=2319.10kJ/kg r4=2321.44kJ/kg r4'=2344.80kJ/kg 各效沸点和有效温差计算
公式:Cp0=1.6×糖的百分比+C水×水的百分比 T0=60℃,Cpw水=4.178kJ/kg. ℃
Cp0=1.6×0.2756+4.178×0.7244=3.47kJ/(kg?℃) Cp2=1.6×0.40+4.178×0.60=3.15kJ/(kg?℃) Cp3=1.6×0.34+4.178×0.66=3.30 kJ/(kg?℃) Cp4=1.6×0.30+4.178×0.70=3.40kJ/(kg?℃) 将以上数值带入焓平衡方程解得:
W1=6220.92kg/h W2=5444.50kg/h W3=4704.99kg/h W4=4283.59kg/h D=7041.39kg/h
求传热面积:(取K=2000W/(m2?℃))
2204.6?7041.39S1==140.55m2
3.6?2000?15.342254.73?6220.92S2==152.67m2
3.6?2000?12.762290.51?5444.5S3==151.27m2
3.6?2000?11.452321.44?4704.99S4==156.88m2
3.6?2000?9.67Smin相对偏差εs=1->3%,故进行第四次核算
Smax重新分配有效温差
15.34?140.55?12.76?152.67?11.45?151.27?9.67?156.88S==149.39m2
49.22140.55152.67?15.34=14.43℃, △t2'''=?12.76=13.04℃ △t1'''=
149.3914.9.39151.27156.83?11.45=11.59℃, △t4'''=?9.67=10.15℃ △t3'''=
149.39149.39∑△t'''=14.43+13.04+11.59+10.15=49.21℃ 重新核算各效浓度及各沸点升高 X1=0.5
FX046014.83?27.56%==0.40
F?W4?W3?W246014.83-4283.59-4704.99-5444.50FX046014.83?27.56%X3===0.34
F?W4?W346014.83?4283.59?4704.99FX046014.83?27.56%X4===0.30
F?W446014.83?4283.59由经验公式:△i=1.78Xi+6.22Xi2 得各效沸点升高
X2=
△1,=1.78×0.5+6.22×0.52=2.45℃ △2,=1.78×0.40+6.22×0.402=1.71℃ △3=1.78×0.34+6.22×0.342=1.32℃
,
△4,=1.78×0.30+6.22×0.302=1.09℃
重新核算各效加热蒸汽温度,二次蒸汽温度及各效沸点
T1=120.2℃, t1=T1-△t1'''=120.2-14.43=105.77℃, T1'=t1-△1'=103.22℃ T2=102.22℃, t2=T2-△t2'''=102.22-13.04=89.28℃, T2'=t2-△2'=87.57℃ T3=86.57℃, t3=T3-△t3'''=86.57-11.59=74.98℃, T3'=t3-△3'=73.66℃ T4=72.66℃, t4=T4-△t4'''=72.66-10.15=62.51℃, T4'=t4-△4'=61.42℃ 查表得:
r1=2204.6kJ/kg r1'=2250.3kJ/kg r2=2252.63kJ/kg r2'=2288.98kJ/kg r3=2291.40kJ/kg r3'=2322.64kJ/kg r4=2324.98kJ/kg r4'=2351.78kJ/kg 各效沸点和有效温差计算
公式:Cp0=1.6×糖的百分比+C水×水的百分比 T0=60℃,Cpw水=4.178kJ/kg. ℃
Cp0=1.6×0.2756+4.178×0.7244=3.47kJ/(kg?℃) Cp2=1.6×0.40+4.178×0.60=3.15 kJ/(kg?℃) Cp3=1.6×0.34+4.178×0.66=3.30 kJ/(kg?℃) Cp4=1.6×0.30+4.178×0.70=3.40 kJ/(kg?℃) 将以上数值带入焓平衡方程解得:
W1=6268.12kg/h, W2=5423.11kg/h, W3=4689.92kg/h, W4=4367.20kg/h D=7142.64kg/h 求传热面积:(取K=2000W/(m2?℃))
2204.6?7142.64S1==151.56m2
3.6?2000?14.432252.63?6268.12S2==150.39m2
3.6?2000?13.045423.11?2291.4S3==148.91m2
3.6?2000?11.592324.98?4689.92S4==149.21m2
3.6?2000?10.15Smin148.91相对偏差εs=1-=1-<3%
Smax151.56 2
取传热面积为152m
蒸汽的经济程度为:W/D=20651.46/7142.64=2.89即1kg蒸汽可蒸发2.89kg水。 该工程蒸汽消耗总量=7142.64×24=171423.36kg
4.2.2 喷干工段
(1)蒸发量
W=G(X1-X2)
W150%W25%X1===1, X2===0.05
1?W11?50%1?W21?5%G=G1(1-W1)=304318.10×(1-50%)/24=6339.96kg绝干料/h W=G(X1-X2)=6339.96×(1-0.05)=6022.96kg水分/h (2)新鲜空气消耗量
WL=, H2?H1由图5—3查出当t0=20℃,φ0=60%时,H0=0.012kJ/kg绝干气 由空气离开干燥器时t2=45℃, φ0=30%时,H2=0.022kJ/kg绝干气
596.085L==602296kg绝干气/h 0.022?0.012新鲜空气消耗量为L0=602296×(1+0.012)=609523.55kg新鲜空气/h
, (3)风机的风量V,
V〃=LνH
νH=(0.773+1.244H0)×湿空气/kg绝干气
V〃=LνH=602296×0.85=509332.61 m3新鲜湿空气/h (4)预热器中消耗的热量Qp Qp=L(I1-I0)
当t0=20℃,φ0=60%时,查得I0=43kJ/kg绝干气,空气离开预热器时t1=90℃,H1=H0=0.012 kJ/kg绝干气,查得I1=115kJ/kg绝干气. 故Qp=602296×(115-43) =43365312KJ/h (5)向干燥器补充的热量QD
由空气离开干燥器时t2=45℃, φ0=30%时,H2=0.022kJ/kg绝干气 由图5—3查出I1=158kJ/kg绝干气 QD= L(I2-I1)+G(I2,+I1,)+QL = L(I2-I1)+GCm(θ2-θ1)+QL
=602292×(158-115)+6339.96×3.28×(60-20)+1.2×3600=26734850.75kg/h (6)干燥系统消耗的总热量Q
Q=QP+QD=43365312+26734850.75=70100162.75kJ/h (7)干燥器系统的热效率η η=
W(2490?1.88t2)6022.96?(2490?1.88?45)?100%=22.12% ?100%=
70100162.75Q273?t020?273=(0.773+1.244×0.012)×=0.85m3新鲜2732734.2.3 各工段耗气耗热计算
(1)调乳:15.5℃→50℃
Q=CM△t=0.9×970170.03×(50-15.5)=30123779.43kcal D=
Q(1?3%)30123779.43?1.03==51366.62kg
r?c△t511.24?1?(142.8?50)(2)一喷:50℃→105℃
Q=CM△t=0.9×1002372×(105-50)=49617414kcal
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