熔融結晶法的原理是基于混合物中各組分在相變時有重分布現(xiàn)象。并且實際生產(chǎn)中采用熔融結晶法的較多，主要幾種熔熔融結晶法如下：

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)間歇式分布結晶法—prosbd法，20世紀60年代法國prosbd公司開發(fā)。本法在捷克烏爾克斯焦油加工廠實施。主要設備是8個結晶箱，分4步進行。結晶箱的升溫和降溫通過一臺泵、一臺加熱器和一臺冷卻器與結晶箱串聯(lián)起來實現(xiàn)。

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.

分步結晶法制取精萘的特點是：原料單一，不需要輔助原料。工藝流程和設備及操作都比較簡單。設備投資少。操作時僅需泵的壓送、冷卻結晶、加熱熔融，操作費用和能耗都比較低。生產(chǎn)過程中不產(chǎn)生廢水、廢氣、廢渣，對環(huán)境無污染。原料可用工業(yè)萘也可用萘油組分，產(chǎn)品質量可用結晶循環(huán)次數(shù)加以調節(jié)，靈活性較大。生產(chǎn)工藝較成熟，產(chǎn)品質量穩(wěn)定，也可用于生產(chǎn)工業(yè)萘。寶鋼三期精萘裝置從法國befs公司引進，也是分步結晶法。

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)連續(xù)式多級分步結晶法—brodie法，又稱萘區(qū)域熔融精制。70年代澳大利亞聯(lián)合碳化物公司研制了此工藝。主要由晶析精制、精萘蒸餾、制片包裝和溫水循環(huán)4個系統(tǒng)組成。此法的特點是：連續(xù)生產(chǎn)過程，產(chǎn)品質量穩(wěn)定。因其基建投資和操作費用高，操作條件要求較嚴。所以在中國目前還沒有得到普遍應用。上海寶鋼化工1985年采用此裝置運行。

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)立管降膜結晶法—mwb法，80年代末瑞士sulzer公司開發(fā)。此法由于采用獨特的降膜結晶技術，有效地強化了萘熔體的傳染與傳質過程，設備處理能力提高。我國鞍山化工總廠92年引進蘇爾壽精萘加工裝置，1994年投產(chǎn)，年產(chǎn)2萬噸。其他熔融結晶法還有80年代初德國呂特格公司開發(fā)的鼓泡式熔融結晶法，70年代末日本新日鐵化學公司開發(fā)的連續(xù)結晶法(bmc法），投資較大。

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.