How to determine the quality of industrial naphthalene and what are the influencing factors

1、塔頂溫度的影響:

1. Influence of tower top temperature:

前已述及，工業(yè)萘的生產(chǎn)過程是以萘洗三混餾分為原料，經(jīng)過精餾過程而完成的。而精餾操作恰恰是利用混合液中各組分揮發(fā)度的不同而達到分離的目的，溶液中各組分的揮發(fā)度的差異是隨溫度的改變而變化的，因而溫度的變化可影響精餾操作的正常進行。

As mentioned earlier, the production process of industrial naphthalene is completed through distillation process with naphthalene washing three mixture fraction as raw material. The distillation operation achieves the purpose of separation by using the different volatilities of each component in the mixed liquid. The difference of volatilities of each component in the solution changes with the change of temperature, so the change of temperature can affect the normal operation of distillation.

1.1初餾塔塔頂溫度的影響

1.1 effect of overhead temperature of primary distillation tower

在通常情況下，初餾塔塔頂溫度需控制在185-195℃左右。主要是因為萘洗三混餾分中只有酚油的溫度小于200℃，而為182℃，在這個溫度下，只有酚油作為輕組分而從塔頂溢出，其余餾分作為重組分而從塔底流出;若初餾塔塔頂溫度過高，則萘洗餾分中的一部分很容易作為輕組分隨酚油一起從塔頂溢出，使酚油中萘含量增加從而使萘的提取率下降;若初餾塔塔頂溫度過低則一部分酚油將隨萘洗混合餾分流入塔底，使后續(xù)工藝過程中萘油的酚油含量升高，從而使產(chǎn)品質(zhì)量下降。

Under normal circumstances, the top temperature of the primary distillation tower needs to be controlled at about 185-195 ℃. This is mainly because the temperature of only phenol oil in the naphthalene washing three mixture fraction is less than 200 ℃ but 182 ℃. At this temperature, only phenol oil overflows from the tower top as a light component, and the rest of the fraction flows out from the tower bottom as a heavy component; If the temperature at the top of the primary distillation tower is too high, part of the naphthalene washing fraction can easily overflow from the top of the tower as a light component with the phenol oil, increasing the content of naphthalene in the phenol oil and reducing the extraction rate of naphthalene; If the temperature at the top of the primary distillation tower is too low, part of the phenol oil will flow into the tower bottom with the naphthalene washing mixed fraction, which will increase the phenol oil content of naphthalene oil in the subsequent process, so as to reduce the product quality.

1.2精餾塔塔頂溫度的影響

1.2 influence of distillation tower top temperature

同理，精餾塔塔頂溫度一般都應控制在218℃到220℃之間。若高于這個溫度，則洗油中的一部分易作為輕組分隨萘油從塔頂溢出,使萘油中洗油含量增加，從而使產(chǎn)品質(zhì)量下降，若塔頂溫度過低則萘油中的一部分易作為重組分流入塔底，因而使萘的提取率下降。

Similarly, the top temperature of distillation column should be controlled between 218 ℃ and 220 ℃. If the temperature is higher than this, a part of the washing oil is easy to overflow from the tower top as a light component with the naphthalene oil, increasing the washing oil content in the naphthalene oil, so as to reduce the product quality. If the tower top temperature is too low, a part of the naphthalene oil is easy to be diverted into the tower bottom as a reorganization, so as to reduce the extraction rate of naphthalene.

故在工業(yè)萘的生產(chǎn)的過程中，需要嚴格控制塔頂溫度使其在一定溫度范圍之內(nèi)，嚴禁出現(xiàn)偏高或偏低現(xiàn)象，從而使柰的提取率或質(zhì)量下降。

Therefore, in the production process of industrial naphthalene, it is necessary to strictly control the tower top temperature to make it within a certain temperature range, and it is strictly prohibited to be high or low, so as to reduce the extraction rate or quality of Nai.

2、回流量對產(chǎn)質(zhì)量的影響

2. Effect of return flow on Yield and quality

由蒸餾過程的原理可知，將液體混合物進行一次部分汽化(或部分冷凝)的過程，對于輕組分只能起到部分分離的效果。然而要想使混合物中的各組分都得到近乎完全的分離，需要進行多次部分汽化和部分冷凝過程，但如果采用多級分離則在分離過程中不但設備龐雜，能耗嚴重，同時因為得到許多中間餾分，而使純產(chǎn)品的收率也很低。因而只有采用將上級液相回流與下級的氣相直接接觸,這樣就解決了中間產(chǎn)品,提高了產(chǎn)品的收率;同時由于液相溫度低于氣相溫度，因而高溫蒸汽將直接加熱低溫液體，從而使液體部分汽化，而蒸汽自身則被同時部分冷凝，故省去了中間加熱器和部分冷凝器。上述情況對于難揮發(fā)組分亦上如此。所以采用回流不僅可以提高收率,而且是精餾過程進行的必不可少的條件。

According to the principle of distillation process, the process of partial vaporization (or partial condensation) of liquid mixture can only partially separate the light components. However, in order to achieve almost complete separation of each component in the mixture, multiple partial vaporization and partial condensation processes need to be carried out. However, if multistage separation is adopted, not only the equipment is complicated and the energy consumption is serious, but also the yield of pure products is very low because many middle fractions are obtained. Therefore, only by directly contacting the upper liquid phase reflux with the lower gas phase, the intermediate product is solved and the yield of the product is improved; At the same time, because the liquid phase temperature is lower than the gas phase temperature, the high-temperature steam will directly heat the low-temperature liquid, so as to vaporize part of the liquid, while the steam itself is partially condensed at the same time, so the intermediate heater and part of the condenser are omitted. The above situation is also true for non-volatile components. Therefore, reflux can not only improve the yield, but also be an essential condition for the distillation process.