第十一章 浸出与萃取

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设溶质A原来呈固态，且足够 多，则A在S中必有一饱和溶解度。 该饱和溶解度即图中的G点所代 表的组成，则BG线把相图分为两 个区域，其中位于BG线下方的区 域为未饱和区，亦即A与S量之比 小于饱和溶解度，而位于BG上方 的区域为饱和区。 只有在不饱和区才能进行浸出。
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The ways of operation used in extraction processes can be continuous or batch连续或间歇操作. Once or more stages can be employed for batch operation, with new solvent in each stage 平 流 （ 错 流 ） , or under countercurrent逆流. A simple stage consists of an agitated mixer搅拌混合器, where the solid and the solvent are in contact for at given time. Then the mixture is transferred to a separator分离器, where the phases, called extract and exhausted solids, are obtained after a specified standing time. The extraction and separation stages can be carried out in one piece of equipment instead of two; this type of equipment is called an extractor萃取器.
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二．浸出理论 1．浸出体系组成的表示方法——三角形坐标图triangular diagram 认为一个浸出体系由三种成分组成：溶质、萃取剂和原溶 液（稀释剂）。
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每个顶点分别代表一个纯组分，即顶点A表示纯溶质A，顶点B表示 纯原溶剂（稀释剂）B，顶点S表示纯萃取剂S。 AB边以A的质量分率作为标度，BS边以B的质量分率作为标度，SA 边以S的质量分率作为标度。 三条边上的任一点代表一个二元混合物系，第三组分的组成为零。 三角形坐标图内任一点代表一个三元混合物系。 xA+ xB+xS =1.0
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三．浸出过程与影响因素 （一）浸出过程 浸出过程一般可被分解为以下四个阶段： 1、溶剂浸润与渗透阶段：溶剂被吸附在固体物料表面， 由于液体静压力和固体物料的毛细作用，被吸附的溶剂 渗透到物料组织内部的过程。溶剂渗透到物料细胞组织 中后使干皱的细胞膨胀，恢复细胞壁的通透性，形成通 道，能够让目标产物从细胞内扩散出来。 2、解吸与溶解阶段：由于固体物料中有些成分对其他 成分有较强的吸附作用（亲合力），使这些成分不能直 接溶解在溶剂中，需要解除这种吸附作用，即解吸，才 能使目标成分进入溶剂即溶解。
separation process involves two phases. The two phases may be solid and liquid, immiscible liquid phases, or solid and gas.
萃取 分类
固-液萃取（Solid-Liquid Extraction ）：用液态 萃取剂溶解提取固体物料中某组分的单元操 作。又称为浸出、浸提等。 液-液萃取（Liquid-liquid extraction ）：是用液态 萃取剂处理与之不互溶的溶液，实现组分分离 的单元操作，又简称萃取。 超临界萃取（supercritical extraction ）：用超临 界流体作为萃取剂的萃取操作 。
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Solid-liquid extraction has different names depending on the objective of the process. Thus, it may be known as lixiviation浸滤, washing洗涤, percolation浸透, etc. It is usually described as “leaching 滤 取 、 滤 去 ” in English-language literature . The purpose of this operation can be diverse, since in some cases it is necessary eliminate from a solid an undesirable component by dissolving it into a liquid, which is called washing. However, in other cases, it is desired to obtain a valuable component contained in a solid by dissolving it into a liquid, which is called lixiviation. The term“percolation” refers to the way that the operation is carried out, which is by pouring a liquid onto a solid. 国内常称为浸出、 提取等。
萃取获得的物质不是纯物质，为了获得纯物质还须作进一步的处理，通常 可借蒸馏、蒸发、结晶或干燥等方法，以去除萃取剂。为了经济的原因， 一般萃取剂须回收再用。
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11.2 固-液萃取
Solid-Liquid Extraction


一、概述 1、概念：Solid-liquid extraction is a basic operation to separate one or more components contained in a solid phase by a liquid phase or solvent. The components transferred from the solid to the liquid phase are called solutes 溶 质 , while the insoluble solid is called inert 惰性物质.
2013-8e） 假设原混合物量为M，其组成为zA、zB 、zS ；溢流E组 成为yA 、yB 、yS ；设底流的组成为BE联线上的R状态点， 其组成为xA、xB、xS，则 总物料衡算： M=E+R 对组分A的物料衡算： MzA=EyA+RxA
式中：E、R分别为溢流和底流量，单位为kg或kg/s ； RM、ME分别为线段的长度，代表溢流和底流的量。
溶质
原溶剂 （稀释剂）
萃取剂
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（惰性固体）
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2．浸出系统的平衡关系
当固体与溶剂经过充分长时间的接触后，溶质A 溶解进和萃取剂，固体空隙中液体的浓度将等于 固体周围液体的浓度，液体的组成将不再随接触 时间延长而改变，即达到平衡。这样的接触级称 为理论级或理想级。平衡时的溶液不一定已达到 饱和。 It is evident that mass transfer takes place until equilibrium is reached. Equilibrium is reached when the solute is dissolved, thus obtaining a solution with uniform concentration. When the solute content in the solid is high enough, it is considered that equilibrium is reached when the solution in contact with the solid is saturated.
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2、应用： Important applications of the solid-
liquid extraction in the food industry include: obtaining extracts from animal or vegetable materials：extraction of animal and vegetable oils 动植物油（soybean, corn, and rice bran， rapeseeds, sunflower seeds ）；spice oils and natural flavor extracts 香 精 油 和 风 味 物 质 ； obtaining sugar （ cane or beet ） 糖 ； manufacturing tea and instant coffee速溶茶和 咖啡；to separate useful ingredients from food processing waste and medicinal plants功能成分. washing precipitates ； Washing occurs so frequently as to need no specific examples. 除杂
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3、操作：This type of operation may be performed in one or multiple stages单级或多级. A stage refers to equipment in which the phases are in contact for a determined time, so that the mass transfer among the components of the phases are carried out, tending to equilibrium over time. Once the equilibrium is reached, a mechanical separation of phases is applied. It is difficult to reach equilibrium in one stage, so it is necessary to define the efficiency 效 率 in order to calculate the real stages. Efficiency of one stage is the quotient商数 between the change in composition actually achieved and the change that should have been achieved for an equilibrium situation under the working conditions.