外文翻译-甲醇精馏采用高效塔板和工艺路线的改进

外文翻译 1、英文原文 Methanol distillation trays with high efficiency and process improvements in line Abstract Brief description of the methanol distillation tower internals rehabilitation programs: micro-hole width efficient composite plate, more suitable than the regular packing, superior; analysis of three towers of methanol distillation tower process than the advantages of technology and economic benefits. Keywords Tray efficiency Process Route Improve For many chemical elements, the energy consumption of the technology is always an important factor in economic indicators. Save energy, reduce consumption and speed up the pace of technological transformation, the implementation of product structure adjustment, the survival of every business dispute, and development of important measures. Now after my factory technical transformation described by methanol distillation trays and improved high technology route to reducing energy consumption play an important role. Practice shows, for the methanol distillation separation, not just rely on highly efficient distillation column internals used in order to achieve significant reduction in energy consumption of alcohol distillation, and methanol distillation process improvements can be made to the system consumption decreased significantly. 1 A methanol distillation tower process Currently, most of the twin towers of methanol distillation separation processes are used. My factory has a set of 3 104t / a methanol tower distillation unit, in December 2002 to be expanded to 8 104t / a methanol tower distillation unit, the process shown in Figure 1. This process constituted by the two distillation columns: pre-tower and the main tower. Come from the methanol synthesis section in the crude methanol containing 86% methanol, the first into the pre-tower, is actually a pre-column extractive distillation column, in the top of the tower by adding the equivalent of 20% crude methanol feed. 30% of the water, water as extractant the crude methanol into dimethyl ether and other compound contained in the separate light components, thus pre-column based products mainly light components such as dimethyl ether, and the tower bottom product mainly a mixture of methanol and water. Pre-column conditions are generally operated under normal pressure, the top temperature of 65. 75 or so, bottom of the column temperature is about 80 . Pre-tower trays usually installed 45.60, can achieve a theoretical separation step 25-35. Since the tower was extracted by methanol and water tower to tower bottom, so crude methanol feed opening position is relatively high, generally up from the bottom of the column number of the first 36-40 block board feed. Pre-Tata bottom outflow of methanol and water mixture immediately into the main tower, in the main tower of methanol and fusel achieve water separation. Usually installed in the main tower block tray 65-85, needs 36,050 a theoretical series (as the back flow of size). Many plant products are often stressed the tower of methanol concentration, while the outflow of water on the bottom of the column with methanol content less importance, so the pre-column to a mixture of methanol and water are in the lower half into the tower main tower. Location of the feed used by several bottom of the column 20 about a 26 plate. The main methanol distillation tower generally operate at atmospheric pressure. Tower operating temperature of 65-66 , bottom of the column operating temperature of 105 1IO. C. Tower refined methanol product generally require moisture 0.1%, methanol content 99.5%, while the bottom of the column with methanol content in the discharged water must be 0.5%. To prevent pre-tower with a light component to the main tower and moved with methanol on top of the tower was purified methanol product out of towers, the main tower from the top, generally in the first 10 or so side draw tray purified methanol product. High energy consumption of such processes, I plant steam consumption per ton of methanol in 2.1. 2.5t 2 Transformation of methanol distillation line The transformation of methanol distillation system, can be used two ways: First, high efficient distillation column internals to improve the separation efficiency, reduce back flow, thereby reducing energy consumption; Another way is to change the separation line, and reduce energy consumption. Efficient use of methanol distillation tower internals can improve yield and reduce energy consumption with the role, but the magnitude does not meet expectations. At the same time changing the distillation process route to the greater effect of reducing energy consumption. The most commonly used pieces of high-Distillation Column with structured packing and efficient main tray two categories. According to the actual situation in our factory, structured packing does not apply to our plant expansion transformation of methanol distillation. Reasons are as follows. (1) The high separation efficiency of structured packing is mainly expressed in the hydrocarbon class system. For this type of material system, the liquids surface tension is very low, easy-to-the structured packing has a large number of surface area on the stretch, resulting in significant gas-liquid interfacial surface area, to achieve excellent separation efficiency. In the methanol distillation system is completely different. The liquid in the two towers contain a lot of water, so much higher than the surface tension of liquid organic hydrocarbon class. Thus the liquid surface in the filler dispersion is severely reduced, gas-liquid mass transfer efficiency is bound to fall significantly. Such as methanol distillation tower in the second half, close to 100% water content, surface tension is also close to 56dyn/cm (0.056N / m), as used in this condition, the structured packing, the separation is not satisfactory . I plant 3 104t / a methanol distillation device be transformed into an 8 104t / a methanol production capacity, regulatory (2) structured packing bed, the bed floor to the top always install the appropriate liquid distributor, so that downward flow of liquid to achieve uniform distribution along the tower section. However, the gradual downward flow of liquid, the initially uniform distribution along the tower section of the liquid will gradually accumulate to the tower wall. This phenomenon is known as wall flow (wall flow). When the wall of flow occurs, most of the liquid along the column wall to the downstream region, while most of the gas in the central region of upward flow tower. This has resulted in the separation of gas-liquid flow. Greatly reduced the contact between gas and liquid. One can imagine that at this time The structured packing distillation column can not have a good separation efficiency. To overcome this problem, generally when in the design of structured packing distillation column, a packed bed is only 6 seek to achieve a series of 10 theory, if a theory of distillation process requires far more than the number of series, they should be structured packing bed is divided into several sections, each distributor installed between the liquid and then to achieve uniform distribution of liquid flow again. However, this arrangement would allow the complex structure of the distillation column, expensive. By this analysis, using structured packing factory methanol distillation column transformation is not feasible. Can I use the highly efficient transformation of plant trays to methanol distillation column, in order to significantly reduce the energy consumption of methanol distillation system do? A variety of analysis shows that this approach to improve the system capacity, product purity methanol and methanol yield The effect is obvious, but the effect on reducing energy consumption, but also not very satisfactory. Distillation Technology Co., Ltd. Nanjing Canning production efficiency of composite hole miniature valve trays, is currently the only company approved by the U.S. research company distillation efficient industrial scale pilot test trays, the tower is equipped with a composite hole-board micro-valve, triangle to promote and multiple bubble hem downcomer, see Figure 2. With high flux, high separation efficiency, operating flexibility and so on. The tray efficiency than conventional tray more than 25%, using the plate transformation of factory pre-towers and methanol distillation tower, the original diameter of column under the conditions of constant expansion to meet the 8 104t / a methanol demand investment than the 50% reduction in use of structured packing, and can reduce the pre-tower water and back flow of the main tower. Which can reduce the energy consumption of methanol distillation system purposes. But the process simulation analysis shows that under these conditions methanol distillation system, lowering energy consumption is only about 5%, this rate is still relatively small, I still can not meet the methanol plant to expand output without increasing coal-fired boiler requirements. 2Canning affected companies around the three-dimensional map tray efficiency significantly reduce energy consumption from the point of view, only the replacement of high efficiency internals of this line is not enough, so it must be from the distillation point to find a better solution to the problem Methods. 3 3 Tati can significantly reduce the energy consumption of pure alcohol In many distillation system, people tend to unity of the two or three towers and two towers, and strive to reduce energy consumption. This means reducing energy consumption of machines is to reduce the number of evaporation and condensation of materials to reduce energy consumption. However, for methanol distillation, the people are the opposite of a tower will be divided into two towers, but they can make a lot of lower energy consumption. Addressed before the methanol distillation tower is a pre-extractive distillation. In the top of the tower by adding extractant - water, methanol and dimethyl ether and other light components separately. The towers energy consumption depends on water and feed composition, feed composition is a synthetic process (catalyst type. Synthesis of pressure, etc.) decisions, distillation section in not at liberty to demand for changes. The water is determined by methanol - dimethyl ether - water vapor-liquid equilibrium of three substances. Tower operating at atmospheric pressure as long as the pre-conditions, the vapor-liquid equilibrium is basically fixed, basically the size of water is fixed. Thus, the methanol distillation column at atmospheric pressure conditions expected little to change the process conditions to reduce energy consumption possibilities. Only by adopting high efficiency plate, increase the separation efficiency, reduce return flows to reduce energy consumption. However, the methanol distillation tower distillation process is not the case. Methanol distillation tower tower feed from the bottom of pre-mixture of methanol and water. In the methanol distillation tower for the separation process is actually heating of methanol evaporation from the water out of the process. In the process of distillation towers, the main tower of the role of distillation tower bottom is put in enough calories to make methanol out of the water completely evaporated, condensing in the top of the tower be refined methanol product. German Lurgi Company in the development of its low pressure methanol synthesis process, the use of the three columns of methanol purification process. This process will be methanol distillation tower is divided into two towers: the Pressurized and atmospheric distillation column distillation. The process shown in Figure 3. 2、译文 甲醇精馏采用高效塔板和工艺路线的改进 摘要 简要说明了甲醇精馏塔的内件改造方案：复合孔微型阔高效塔板，比规整填料更适宜、更优越；分析了甲醇精馏三塔工艺比双塔工艺的优越性和经济效益。 关键词 高效塔板 工艺路线 改进 对许多化工单元来说，能耗总是其技术经济指标的一个重要因素。节约能源，降低消耗，加快技改步伐，实施产品结构调整，是每个企业争生存、求发展的重要措施。现就我厂技改后甲醇精馏阐述采用高效塔板和改进工艺路线，对降低能耗起到的重要作用。生产实践证明，对于甲醇精馏分离，不能仅依靠高效塔内件应用于精馏塔中，以达到明显地降低甲醇精馏能耗，而甲醇精馏工艺流程的改进也可以使该系统的能耗明显下降。 1 甲醇精馏双塔流程 目前，大部分甲醇精馏过程均采用双塔分离流程。我厂现有一套 3104t a甲醇双塔精馏装置， 2002 年 12 月拟扩建为 8104t a 甲醇双塔精馏装置，其流程见图 1。 这一流程主要由两个精馏塔构成：预塔和主塔。由甲醇合成工段来的粗甲醇含甲醇 86左右，首先进入预塔，预塔实际上是一个萃取精馏塔，在塔顶加入相当于粗甲醇进料 20。 30左右的水，以水为萃取剂将粗甲醇进料中所含的二甲醚等轻组份分开，因而预塔塔顶产品主要是二甲醚等轻组分，而塔底产品中则主要是甲醇与水的混合物。预塔一般都在常压条件下操作，塔顶温度为65。 75左右，塔底温度为 80左右。预塔内一般安装有 45 60 块塔板，能达到 2535 个理论分离级数。由于该塔是通过塔顶加水萃取甲醇至塔底，故粗甲醇进料口位置比较高，一般在由塔底向上数第 3640 块板上进料。 预塔塔底流出的甲醇与水的混合物立即进入主塔，在主塔内实现甲醇与杂醇、水的分离。主塔一般安装有 6585 块塔板，需要 36 0 50 个理论级数 (视回流量大小而定 )。许多生产装置往往强调塔顶甲醇产品浓度，而对塔底流出水中的甲醇含量不太重视，所以由预塔来的甲醇与水的混合物往往在主塔下半部分入塔。常用的进料位置在由塔底数起第 20 一 26 块塔板左右。甲醇精馏的主塔一般均在常压下操作。塔顶操作温度为 6566，塔底操作温度为 105 1IO。C。塔顶的精甲醇产品一般要求含水量 0 1，甲醇含量 99 5，而塔底排放水中的甲醇含量必须 0 5。为防止预塔中轻组份带至主塔并随甲醇上移至塔顶而被精甲醇产品带出塔，主塔一般均在距塔顶第 10 块塔板左右侧线采出精甲醇产品。此种流程能耗较高，我厂每吨甲醇耗蒸汽在 2 1。 2 5t。 2 甲醇精馏改造路线探讨 甲醇精馏系统的改造可以采用两种方法：一是采用高效精馏塔内件来提高分离效率，降低回流量，从而降低能耗；另一种方法则是改变分离路线，以降低能耗。采用高效精馏塔内件可提高甲醇收率兼具有降低能耗的作用，但其幅度不能满足人们的期望。同时改变精馏工艺路线对降低能耗有更大的效果。目前常用的高效精馏塔内件主要有规整填料和高效塔板两大类。根据我厂实际情况，规整填料不适用于我厂甲醇精馏扩产改造。原因分析如下。 (1)规整填料的高分离效率主要是表现在轻烃类系统中。对于这一类物料系统来说，液相的表面张力极低，易于在规整填料所具有的大量表面积上舒展开，从而造成极大的气液接触表面积，达到极佳的分离效率。而在甲醇精馏系统中则完全不一样。两塔的液相中均含有大量的水份，使得液相表面张力大大高于轻烃类有机物。因而液体在填料表面上的分散能力大大下降，气液传质效率也必然大幅度下降。如在甲醇精馏主塔的下半段，含水量接近 100，表面张力也趋近于 56dyn cm(0 056N m)，如在此条件下采用规整填料，则分离效果并不理想。在我厂 3104t a 甲醇精馏装置上改造成为 8104t a 甲醇生产能力，规 整填料很难完成此项任务。 (2)在规整填料床层中，床层最上方总要安装适当的液体分布器，以使向下流动的液体达到沿塔截面均匀分布。然而在液体逐渐向下流动时，起先沿塔截面均匀分布的液体会逐渐地向塔壁积累。这种现象称为“壁流” (wall flow)。当壁流发生时，大部分液体沿塔壁区域向下流，而大部分气体则在塔中心区域向上流。这就造成了气液流动的分离。从而大大削弱了气液之间的接触。可想而知，此时 的规整填料精馏塔不可能有很好的分离效率。为克服此问题，一般在设计规整填料精馏塔时，一段填料床层仅力求达到 6 一 10 个理论级数，如一精馏过程需要的理论级数远远超过此数，则应将规整填料床层分为若干段，每段之间安装液体再分布器，使液体流动再次达到均匀分布。但这种安排将使整个精馏塔的结构复杂，造价昂贵。通过以上分析，采用规整填料改造我厂甲醇精馏塔是不可行的。是否可以用高效塔板来改造我厂甲醇精馏塔，以大幅度降低甲醇精馏系统的能耗呢 ?各种分析表明，这一途径对提高系统处理能力、甲醇产品的纯度和甲醇收率的效果明显，但在降低能耗上的效果，还不能令人十分满意。南京凯宁精馏技术有限公司生产的复合孔微型阀高效塔板，是目前国内唯一一家经美国精馏研究公司工业规模试验测试的高效塔板，该塔板上装有复合孔微型阀、三角形鼓泡促进器和多折边降液管，见图 2。具有通量高，分离效率高，操作弹性大等特点。该塔板比常规塔板效率高 25以上，采用此塔板改造我厂甲醇精馏预塔和主塔，在原塔径不变的条件下能够满足扩产 8104t a 甲醇的要求，投资比采用规整填料降低 50，并且能够降低预塔用水量和主塔回流量。从而达到降低甲醇精馏系统能耗之目的。但工艺模拟分析表明，在这种条件下甲醇精馏系统能耗的降低也只不过是 5左右，这一幅度还是比较小的，仍然不能适应我厂扩大甲醇产量，而不增加燃煤锅炉的要求。围 2 凯宁公司商效塔板的立体图从大幅度降低能耗的角度考虑，仅更换高效塔内件这一路线还是不够的，所以还必须从精馏工艺的角度去寻找解决问题的更好方法。 3 三塔提纯甲醇可大幅降低能耗 在许多精馏系统中，人们往往将两塔合一或三塔并二，力求达到能耗的降低。这一途径降低能耗的机在于减少物料蒸发与冷凝的次数，以减少能量消耗。然而，对于甲醇精馏提纯来说，人们反其道而行之，将一塔分为二塔，却可以使能耗大量的降低。前已述及，甲醇精馏的预塔是一萃取蒸馏塔。通过在塔顶加入萃取剂 水，将甲醇与二甲醚等轻组份分开。该塔的能耗主要取决于用水量和进料组成，进料组成是由合成工艺 (催化剂类型。合成压力等 )决定的，精馏工段不能随意要求改变。而用水量则是取决于甲醇 二甲醚 水三种物质的气液平衡。只要预塔操作在常压条件下，这一气液平衡也是基本固定的，用水量的大小也基本被固定下来。因而，甲醇精馏预塔在常压条件下几乎没有改变工艺条件以降低能耗的可能性。只有采高效塔板，提高分离效率，减少回流量来降低能耗。然而，甲醇精馏主塔内的精馏过程却不是这样。甲醇精馏主塔的进料是来自预塔底部甲醇与水的混合物。在甲醇精馏主塔内进行的分离过程实际上是在加热条件下，甲醇从水中蒸发出来的过程。在双塔精馏过程中，精馏主塔内的作用就是在塔底施加足够的热量，使甲醇从水中完全蒸发出来，而在塔顶冷凝得到精甲醇产品。德国 Lurgi 公司在开发其低压合成甲醇的工艺时，采用了三塔精馏甲醇提纯流程。这一流程将甲醇精馏主塔分为两个塔：加压精馏塔和常压精馏塔。其工艺流程图见图 3。 从甲醇预精馏塔底部出来的甲醇与水的混合物先进入加压精馏塔，在此塔顶部采出约占总产量 50的精甲醇。加压精馏塔底部物料必然浓度稍低的甲醇与水的混合物，该混合物再进入常压精馏塔进一步将剩余甲醇与水分开。这一流程的设计和操作的关键在于适当确定加压塔的操作压力，从而使得加压塔塔顶蒸出的精甲醇气为常压塔塔底再沸器的热源，使得整个甲醇与水分离过程只需要在加压塔底部从外部输入热量，而在常压塔底部不需要从外部引进热量。从设备的角度上看，加压塔塔顶的冷凝器即为常压塔塔底的再沸器。 工艺分析表明，将甲醇精馏主塔一分为二，确实是可以节省相当的能量消耗。首先，对于常压精馏塔其塔底温度在 105110。 C 左右。要使得加压塔塔顶的精甲醇气成为常压塔底再沸器的热源，加压塔塔顶温度应在 120左右，塔顶压力约 0 56MPa(G)，考虑到加压塔内精馏塔板所造成的压降，加压塔底部压力应为 0 6MPa(G)左右，而塔底温度只有 130左右。为对这种温度下的甲醇液体加热气化，使用一般的低压蒸汽即可。换句话说，三塔流程加压塔再沸器所需蒸汽和双塔流程常压塔再沸器所需蒸汽基本上是同等级的。其二，在采用三塔流程后，加压塔和常压塔顶分别采出约 50的精甲醇。而这两塔回流比基本相同，因而，这两个塔内的蒸发量基本相同，