Using crystallizer and press to produce refined naphthalene from naphthalene cake is more complex, more equipment, more investment and poor working conditions, so the adoption of this process is gradually reduced.
              

　　根据萘的用途，如生产邻苯二甲酸酐时，也可以不用精萘，而用高于95%的含萘量的工业萘。我国必须用精萘生产的品种或生产苯酐的工艺设备要求的数量约占萘产量的30%左右，大部分可用工业萘生产萘酐。因此萘油馏分经脱酚和脱吡啶后，采用连续精馏工艺来生产工业萘（也可采用间歇精馏）得到了发展。目前国内主要有两种流程，即单炉单塔连续生产工业萘和双炉双塔生产工业萘。

　　According to the use of naphthalene, for example, in the production of phthalic anhydride, the industrial naphthalene containing more than 95% naphthalene can be used instead of refined naphthalene. In China, about 30% of naphthalene output must be produced with refined naphthalene or the required quantity of process equipment for phthalic anhydride production. Most of naphthalene can be used to produce naphthalene anhydride. Therefore, after dephenolization and depyridization of naphthalene oil fraction, the continuous distillation process (or batch distillation) is developed. At present, there are two main processes in China, i.e. single furnace single tower continuous production of industrial naphthalene and double furnace and double tower production of industrial naphthalene.