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.
              

　　根據(jù)萘的用途，如生產(chǎn)鄰苯二甲酸酐時，也可以不用精萘，而用高于95%的含萘量的工業(yè)萘。我國必須用精萘生產(chǎn)的品種或生產(chǎn)苯酐的工藝設備要求的數(shù)量約占萘產(chǎn)量的30%左右，大部分可用工業(yè)萘生產(chǎn)萘酐。因此萘油餾分經(jīng)脫酚和脫吡啶后，采用連續(xù)精餾工藝來生產(chǎn)工業(yè)萘（也可采用間歇精餾）得到了發(fā)展。目前國內主要有兩種流程，即單爐單塔連續(xù)生產(chǎn)工業(yè)萘和雙爐雙塔生產(chǎn)工業(yè)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.