大学化工专业英语Lesson

Chlor-Alkali and Related Processes氯碱工业与相关过程Historically the bulk chemical industry was built on chlor-alkali and related processes.纵观历史，大部分化学工业是建立在氯碱工业及其相关过程之上。

The segment is normally taken to include the production of chlorine gas, caustic soda（sodium hydroxide）, soda-ash（derivatives of sodium carbonate in various forms）and, for convenience, lime-based products.该部分通常包括氯气、苛性钠（氢氧化钠）、无水碳酸钠（以各种形式存在的碳酸钠的衍生物），以及以石灰为基础的产品。

Soda-ash and sodium hydroxide have competed with each other as the major source of alkali ever since viable processes were discovered for both.作为碱的主要来源，自从发现很多过程对于纯碱和火碱都是可行的，它们就相互竞争。

The peculiar economics of electrolytic processes mean that you have to make chlorine and caustic soda together in a fixed ratio whatever the relative demand for the two totally different types of product, and this causes swings in the price of caustic soda which can render soda-ash more or less favorable as an alkali.电解过程的特殊经济性意味着，不管对氯气和氢氧化钠这两种不同类型的产品的相对需求量如何，你只有以固定的比例同时制备氯气和氢氧化钠。

这引起了氢氧化钠的价格的摇摆不定，从而使得纯碱作为一种碱或多或少有利。

Both chlorine/caustic soda and soda-ash production are dependent on cheap readily available supplies of raw materials.氯气/氢氧化钠和纯碱的生产都依赖于廉价的现成的原材料供应。

Chlorine/caustic soda requires a ready supply of cheap brine and electricity, soda-ash requires brine, limestone and lots of energy.氯气/氢氧化钠需要廉价的现成的卤水和电力的供应，纯碱需要卤水、石灰石和大量的能量。

Soda-ash plants are only profitable if their raw materials do not have to be transported far.如果纯碱厂的原材料不需要运输的话，它们是盈利的。

The availability of such supplies is a major factor in the location of many of the chemical industry ’s great complexes.在许多化学工业的重大复合物的位置中，这种供货的可行性是一个主要因素。

1. Lime-Based Products1. 基于石灰的产品One of the key raw materials is lime.一种重要的原料是石灰。

Limestone consists mostly of calcium carbonate （CaCO 3） laid down over geological time by various marine organisms.石灰石主要由CaCO 3组成，CaCO 3是多种多样的海洋生物经过整个地质年代留下来的。

High quality limestones are often good enough to be used directly as calcium carbonate in further reactions.高质量的石灰石可以作为CaCO 3直接用于下一步反应。

Limestone is usually mined in vast open-cast quarries, many of which will also carry out some processing of the materials.石灰石通常在大型露天采石场开采，其中，许多还将进行一些材料的处理。

The two key products derived from limestone are quicklime （CaO ） and slaked lime[Ca(OH)2]. 来自于石灰石的两个主要的产品是生石灰（CaO ）和熟石灰[Ca(OH)2]。

Quicklime is manufactured by the thermal decomposition （1200~1500℃） of limestone according to the equation ：32CaCO CaO+CO →石灰石在1200~1500℃下热分解即可制得生石灰，反应方程式如下：32CaCO CaO+CO → Typically limestone is crushed and fed into the higher end of a sloping rotating kiln where the decomposition takes place and quicklime is recovered from the end.通常，将石灰石打碎，然后将它放入倾斜的旋转窑较高的末端，在那里，石灰石将会分解，从这个窑的末端将会得到生石灰。

Most frequently, however, the quicklime is not isolated for further reactions, rather, other compounds are fed in with the lime to give final products at the low end of the kiln.然而，最常见的是生石灰并不是下一步反应唯一的反应物，而是，其他的化合物也会和石灰一起放入，这样在窑的较低的末端得到最终的产品。

For example, alumina, iron ore and sand can be fed in to give Portland cement.例如，将氧化铝、铁矿石和沙子放入后，能够得到硅酸盐水泥。

Soda-ash manufacture often adds coke to the limestone which burns to give extra carbon dioxide needed for soda-ash manufacture.纯碱的生产通常是在石灰石中添加焦炭，它可以通过燃烧来提供制备纯碱所需的额外的二氧化碳。

Slaked lime which is more convenient to handle than quicklime——is manufactured by reacting quicklime with water.熟石灰的生产比生石灰的生产更方便一些，它通常是通过生石灰与水反应制得。

About 40% of the output of the lime industry goes into steel-making. where it is used to react with the refractory silica present in iron ore to give a fluid slag which floats to the surface and is easily separated from the liquid metal.大约40%的石灰工业的产品用于钢铁制造业。

在钢铁制造业中，纯碱用来与铁矿石中难溶的硅酸盐反应，生成流态矿渣，矿渣漂浮于表面上，很容易从液态金属中分离。

Smaller, but still significant, amounts are used in chemical manufacture, pollution control and water treatment. The most important chemical derived from lime is soda-ash.较少量但重要的石灰工业的产品用于化学品的制造、污染控制和水处理。

从石灰石得到的最重要的化学品是纯碱。

2. Soda Ash2. 纯碱The Solvay Process. The process, which was perfected by Ernest Solvay in 1865, is based on the precipitation of NaHCO3when an ammoniated solution of salt is carbonated with CO2from a coke-fired lime kiln.索尔维工艺。

该工艺发现于1865年由ES优化：工艺是以当氨化的盐溶液经来自于石灰窑中焦炭燃烧产物CO2碳化时，NaHCO3沉淀析出为基础。

The NaHCO3 is filtered, dried, and calcined to Na2CO3.NaHCO3经过滤、干燥和煅烧生成Na2CO3。

The filtered ammonium chloride process liquor is made alkaline with slaked lime and the ammonia is distilled out for recycle to the front end of the process.过滤后的NH4Cl溶液与熟石灰反应后，呈碱性，为了循环利用，蒸馏出的NH3放回到该过程的前端。