苯酐是重要的化工原料，目前国内外苯酐的方法主要有萘氧化法和邻二甲苯氧化法，两种方法在苯酐净化过程中都有黑褐色精馏残渣产生。该废料中含有大量苯酐，同时含有部分黑色焦油和高聚物，无法进行直接利用。
Phthalic anhydride is an important chemical raw material. At present, the main production methods of phthalic anhydride at home and abroad are naphthalene oxidation and o-xylene oxidation. In the purification process of phthalic anhydride, black brown distillation residue is produced in both methods. The waste contains a large amount of phthalic anhydride, part of black tar and high polymer, which can not be used directly.
目前有各种回收方法，其中比较多的有溶剂萃取法、升华法和反应深加工处理法等。但各种工艺均不能很好的满足实际要求。本研究按某厂提出的产品不含焦油、收率高、成本低的要求，采用简单合理的回收工艺可回收几乎废料中的全部苯酐，产品质量好。
At present, there are a variety of recovery methods, including solvent extraction, sublimation and deep processing. But all kinds of production processes can not meet the actual requirements. According to the requirements of tar free, high yield and low cost of the product proposed by a factory, almost all phthalic anhydride in the waste can be recovered by simple and reasonable recovery process, and the product quality is good.
采用该法处理回收某厂苯酐废料600吨，可年产粗苯酐近500吨，再结合工厂的需要将该苯酐返回到苯酐装置出工业优级品，不影响苯酐装置的正常。
By using this method, 600 tons of phthalic anhydride waste can be recovered from a factory, with an annual output of nearly 500 tons of crude phthalic anhydride. Combined with the needs of the factory, the phthalic anhydride can be returned to the phthalic anhydride production unit to produce industrial high-grade products without affecting the normal production of the phthalic anhydride unit.
该技术可降低苯酐成本，为工厂带来一定的经济效益。目前国内苯酐能力估计为70万吨，按2%计算可年产废料1.4万吨，估计可回收1万多吨苯酐。若该技术推广全国或向国外转化技术将具有很好的经济和社会效益。该技术成熟，达到水平。
This technology can reduce the production cost of phthalic anhydride and bring certain economic benefits to the factory. At present, the domestic production capacity of phthalic anhydride is estimated to be 700000 tons. Based on 2%, the annual output of waste material is 14000 tons, and it is estimated that more than 10000 tons of phthalic anhydride can be recovered. If the technology is extended to the whole country or transformed to foreign countries, it will have good economic and social benefits. The technology is mature and has reached the international advanced level.
