双滚筒干燥器设计.docx
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双滚筒干燥器设计.docx
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双滚筒干燥器设计
摘要·····································································································1
第一章绪论······································································································2
1.1滚筒干燥器概述·······························································································2
1.2滚筒干燥过程中的传热与传质············································································2
1.3提高滚筒干燥器干燥效果的途径·········································································2
第二章滚筒干燥机滚筒部件设计····································································3
1.1干燥器结构参数的计算·····················································································3
1.1.1物料和热量衡算····························································································3
1.1.2滚筒干燥机干燥面积、滚筒直径、长度确定························································4
1.1.3滚筒干燥器功率的计算··················································································4
1.1.4传动装置设计·······························································································8
1.1.5滚筒组件的强度与刚度校核··········································································12
1.1.6刮刀装置计算······························································································20
1.1.7密封罩及通气管设·······················································································25
1.2结构设计·······································································································26
1.2.1筒体的设计·································································································26
1.2.2端盖和端轴的结构设计················································································27
设计总结··········································································································28
致谢··················································································································29
参考文献··········································································································30
第一章绪论
1.1滚筒干燥器概述
滚筒干燥器是通过转动的滚筒,以热传导的形式,将附在筒体外壁的液相物料或带状物料进行干燥的一种连续操作设备。
滚筒干燥过程的操作过程如下:
需干燥处理的酵母预热至60C后,通过泵将料液从底部打入料槽内。
干燥滚筒在传动装置驱动下,按规定的转速转动,由于滚筒底部浸料,旋转的烘缸表面便沾涂上一层均匀的酵母乳,烘缸内连续通入水蒸气,加热筒体,由筒壁传热料膜的湿分气化,再通过刮刀将达到干燥要求的物料刮下,再通过刮刀螺旋输送器将干燥产品输送至储存槽内。
蒸发除去的湿分,根据其性质可通过排气罩引入相应的处理装置内;一般为水蒸气,可直接由罩顶排气管放至大气中。
滚筒干燥器具有以下优点:
(1)操作连续,能够得到均匀的产品;
(2)干燥时间短,一般约为7-30s,干燥产品没有处于高温的危险,适合于热敏性物料的干燥,但壁面也有可能产生过热;(3)料浆粘度高或低均能干燥;(4)热效率高;(5)因干燥内不会剩余残留的产品,少量物料也可以干燥;(6)滚筒干燥的操作参数调整范围广,并易于调整;(7)机内易于清理,改变用途容易;(8)废气不带走物料,因此不需用除尘设备等。
1.2滚筒干燥过程中的传热与传质
筒体表面上料膜干燥的基本原理,是基于筒体与料膜传热间壁的热阻,形成温度梯度,筒内的热量传导至料膜,引起料膜内湿分向外转移,当料膜外表面的蒸汽压力超过环境空气的蒸汽分压时,则产生蒸发和扩散作用。
滚筒在连续转动的过程中,每转一圈所粘附的料膜,其传热与传质的作用始终由里至外,同一方向地进行。
料膜干燥的全过程,可分为预热、等速和降速三个阶段。
干燥作用开始时,膜表面气化,并维持恒定的气化速度。
当膜内扩散速度小于表面气化速度时,则进入降速阶段的干燥。
随着料膜内湿含量降低,气化速度大幅度下降,降速阶段的干燥时间占总停留时间的80%-98%。
1.3提高滚筒干燥器干燥效果的途径
决定干燥效果的主要因素是料液的干燥性质,工艺操作的控制指标和环境的条件。
料液的性质也通常可通过操作条件的改变而使之有利于干燥过程的进行。
在控制的操作条件下,最重要的是决定料液与产品的湿含量,滚筒的转速和筒壁温度。
要提高滚筒干燥效果,需通过改变料液含湿量,产品湿含量,料液温度,筒内蒸汽压力等手段来实现。
第二章淀粉干燥的流程
操作流程为:
需干燥处理的料液由高位槽流入滚筒干燥器的受料槽内。
干燥滚筒在传动装置驱动下,按规定的转速转动。
物料由布膜装置,在滚筒壁面上形成料膜。
筒内连续通入供热介质,加热筒体,由筒壁传热使料膜的湿分汽化,再通过刮刀将达到干燥要求的物料刮下,经螺旋输送最后干燥器将成品输至贮槽内,然后进行包装。
蒸发除去的湿分,视其性质可通过密闭罩,引入相应的处理装置内;一般为水蒸汽,可直接由罩顶的排气管放至大气中。
第三章双滚筒干燥机——滚筒部件设计
要求:
淀粉干燥前悬浮液固相物含量为30%,干燥后含水量为14%,生产能力为500kg/h,进料料液温度t=85C,刮料点的温度t=105,供热介子为p=0.3Mpa(表压)饱和水蒸汽
3.1干燥器结构参数的计算
3.1.1物料和热量衡算
干燥器的产品的生产负荷:
500kg/h
G=500kg/h
W=1-30%=70%
W=14%
蒸发水分量:
W=G2=500=933.3kg/h
W——干燥前淀粉的含水量
W——干燥后淀粉的含水量
料液处理能力:
G=W+G=933.3+500=1433.3(kg/h)
干燥器的有效热负荷:
Qm=Wr+GCt-GCt-WCt
=933.3539.4+5000.39375-5000.39385-933.3185
=422.126kcal/h
r-水的汽化潜热,(kJ/kg)
C2、Cw—干燥淀粉、水的比热(kJ/kgC)
t1、tw—淀粉溶液和干淀粉的温度(在刮料点处)(C)
干燥器的总热负荷Q
取滚筒干燥的热效率为75%
Q===5.6kcal/h
查P=4kgf/cm(表压)蒸汽的t=151C,i=656kcal/kg,c=1kcal/kgC。
取蒸汽利用系数=0.85
G===1311.47kg/h
3.1.2滚筒干燥机干燥面积、滚筒直径、长度确定
干燥面积:
根据设计条件提供的蒸发强度,可计算如下:
A===12.44(m)
R—滚筒蒸发强度,取R=75
取设计面积为13m
筒径和直径的计算
设计保证滚筒料膜有效干燥弧面角270,设取筒体的长径比=L/D=1、1.5、2,计算结果如下:
=L/D
筒径D=(m)
筒体L=D(m)
1.0
D==1.7
L=1.7
1.5
D==1.4
L=1.4
2.0
D==1.2
按上表计算结果,考虑筒体加工和受力情况,设计取=1.5时的计算参数。
圆整取筒径D=1400mm,筒长L=2100mm。
计算实际受热A=4兀RL=(m)
A>A满足条件
当有效干燥弧面角270时的有效加热面积A18.46=13.85(m)>4.39(m)
3.1.3滚筒干燥器功率的计算
滚筒驱动状态下的功率消耗,由刮刀、进气头轴封和支承阻力的功率等3部分组成:
(1)刮刀作用力矩M的确定:
考虑筒体较长,设计分成4组刮刀。
每组刮刀的长度分配如下图所示:
组合刀片长度(mm)
刮刀顶紧力取q=3kgf/cm(最大为5kgf/cm)
刮刀接触筒体总长度L=257.4+62.5+40=217.5cm
染料固态膜剥离筒壁的作用力取q=2kgf/cm
固态料膜附在筒壁上的轴线长度L=210cm
刮刀材料设计取1Cr18Ni9Ti,筒体材料设计取1Cr18Ni9Ti,刮刀和筒体之间的摩擦系数f=0.15。
滚筒的阻力矩计算(最不利条件下的刮刀受力):
正常条件下(q=3kgf/cm)
M=(Pf+P)R
=[(q)+(qL)]R
=(3)70
=36251.25kgfcm
最大作用力顶紧时(q=5kgf/cm)
M=(Pf+P)R
=[(q)+(qL)]R
=(5)70
=40818.75kgfcm
(2)进气头填料函的阻力矩计算:
蒸汽进管内外径确定
蒸汽体积流量
设计取正常操作压力下的蒸汽状态计,P=5kgf/cm(大气压),t=151C。
V=
=
=0.113m/s
G—蒸汽消耗量按热量衡算计算为1311.1kg/h
冷凝液排出管设计取无缝钢管,d=2.5cm。
取饱和蒸汽在进气头处的流速W=20m/s。
求蒸汽管内径:
d=
=
=0.089(m)
设计取无缝钢管。
填料函结构尺寸确定:
选用10优质石棉填料。
确定:
填料室外径
D=d+2s
=10.2+2
=12.2(cm)
填料室轴向长度H=(4~6)s,设计取H=6=60(mm)
式中,s为填料
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