熔融结晶法的原理是基于混合物中各组分在相变时有重分布现象。并且实际生产中采用熔融结晶法的较多，主要几种熔熔融结晶法如下：

The principle of melt crystallization method is based on the phenomenon of redistribution of each component in the mixture during phase transition. And in actual production, there are many methods that use melting crystallization, and the main types of melting crystallization methods are as follows:

l)间歇式分布结晶法—prosbd法，20世纪60年代法国prosbd公司开发。本法在捷克乌尔克斯焦油加工厂实施。主要设备是8个结晶箱，分4步进行。结晶箱的升温和降温通过一台泵、一台加热器和一台冷却器与结晶箱串联起来实现。

l) Intermittent distributed crystallization method - ProsBD method, developed by ProsBD company in France in the 1960s. This law is implemented at the Urks tar processing plant in Czech Republic. The main equipment consists of 8 crystallization boxes, which are divided into 4 steps. The heating and cooling of the crystallization box are achieved by connecting a pump, a heater, and a cooler in series with the crystallization box.

分步结晶法制取精萘的特点是：原料单一，不需要辅助原料。工艺流程和设备及操作都比较简单。设备投资少。操作时仅需泵的压送、冷却结晶、加热熔融，操作费用和能耗都比较低。生产过程中不产生废水、废气、废渣，对环境无污染。原料可用工业萘也可用萘油组分，产品质量可用结晶循环次数加以调节，灵活性较大。生产工艺较成熟，产品质量稳定，也可用于生产工业萘。宝钢三期精萘装置从法国befs公司引进，也是分步结晶法。

The characteristic of stepwise crystallization method for producing refined naphthalene is that the raw materials are single and do not require auxiliary materials. The process flow, equipment, and operation are relatively simple. Low equipment investment. During operation, only pump pressure, cooling crystallization, and heating melting are required, resulting in lower operating costs and energy consumption. During the production process, no wastewater, exhaust gas, or waste residue is generated, and there is no pollution to the environment. The raw materials can be industrial naphthalene or naphthalene oil components, and the product quality can be adjusted by the number of crystallization cycles, with greater flexibility. The production process is relatively mature, the product quality is stable, and it can also be used to produce industrial naphthalene. The refined naphthalene unit of Baosteel Phase III was imported from Befs Company in France, which is also a step-by-step crystallization method.

2)连续式多级分步结晶法—brodie法，又称萘区域熔融精制。70年代澳大利亚联合碳化物公司研制了此工艺。主要由晶析精制、精萘蒸馏、制片包装和温水循环4个系统组成。此法的特点是：连续生产过程，产品质量稳定。因其基建投资和操作费用高，操作条件要求较严。所以在中国目前还没有得到普遍应用。上海宝钢化工1985年采用此装置运行。

2) Continuous multi-stage fractional crystallization method - Brodie method, also known as naphthalene region melting refining. In the 1970s, the Australian Union Carbide Company developed this process. It mainly consists of four systems: crystallization refining, refined naphthalene distillation, film packaging, and warm water circulation. The characteristics of this method are: continuous production process and stable product quality. Due to its high infrastructure investment and operating costs, the operating conditions are relatively strict. So it has not yet been widely applied in China. Shanghai Baosteel Chemical adopted this device for operation in 1985.

3)立管降膜结晶法—mwb法，80年代末瑞士sulzer公司开发。此法由于采用独特的降膜结晶技术，有效地强化了萘熔体的传染与传质过程，设备处理能力提高。我国鞍山化工总厂92年引进苏尔寿精萘加工装置，1994年投产，年产2万吨。其他熔融结晶法还有80年代初德国吕特格公司开发的鼓泡式熔融结晶法，70年代末日本新日铁化学公司开发的连续结晶法(bmc法），投资较大。

3) Vertical tube falling film crystallization method - MWB method, developed by Swiss company Sulzer in the late 1980s. This method, due to the use of unique falling film crystallization technology, effectively enhances the contagion and mass transfer process of naphthalene melt, and improves the equipment processing capacity. In 1992, China's Anshan Chemical Plant introduced the Sulzer refined naphthalene processing unit, which was put into operation in 1994 with an annual output of 20000 tons. Other melt crystallization methods include the bubbling melt crystallization method developed by the German company Luteger in the early 1980s, and the continuous crystallization method (BMC method) developed by Nippon Steel Chemical Company in Japan in the late 1970s, which requires significant investment.