Maleic anhydride (MA), also known as 2,5-furanedione, maleic anhydride and dehydrated malic anhydride, is the third largest anhydride in the world after phthalic anhydride and acetic anhydride. It is a colorless acicular crystal at room temperature, with an irritating smell and sour taste. Its melting point is 52.8 ℃, and its boiling point is 202 ℃. It is easily sublimated, flammable, sublimated, and soluble in water to generate maleic acid (maleic acid), which is also soluble in benzene, acetone Ethanol and other organic solvents are commonly used as important organic chemical raw materials. The downstream application fields are extensive, including dozens of industries such as unsaturated polyester resin (UPR), paint, coating, curing agent, organic acid, dye, water treatment agent, lubricating oil additive, rosin, etc.

目前可降解塑料根据原料主要分为PLA、PBS、PCL、PHA、PHB等，其中PBS（聚丁二酸丁二醇酯）以低廉、力学性能优异、加工耐热性能好等特点成为目前具有产业化前景的通用型生物可降解塑料之一，生产PBS主要原料丁二酸的基础原料是顺酐。

At present, degradable plastics are mainly divided into PLA, PBS, PCL, PHA, PHB, etc. According to raw materials, PBS (polybutylene succinate) has become one of the universal biodegradable plastics with industrialization prospects because of its low price, excellent mechanical properties, and good processing heat resistance. The basic raw material for producing succinic acid, the main raw material of PBS, is maleic anhydride.

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虽然国内顺酐起步于上世纪90年代，因顺酐项目建设伊始是由苯法工艺兴起的，主要得益于国内焦化苯资源丰富，以及下游产业发展缓慢，但是随着苯法项目的不断上新，迅速导致顺酐产能过剩。2000年前后因素影响苯法顺酐工艺发展，尤其是焦化苯快速被加氢苯所取代，苯法生产成本较大幅度提升，加速了苯法工艺的衰退。而2012年前后开始齐翔腾达，江宁化工等丁烷法项目陆续投产，因其产能较大，快速抢占了市场份额，在2015年前后，丁烷法与苯法工艺完成了“交接”，目前顺酐市场流通货源76%以上为丁烷法工艺,其主要流程如下所示：

Although domestic maleic anhydride started in the 1990s, because the construction of maleic anhydride project was started by benzene process, mainly due to the rich coking benzene resources in China and the slow development of downstream industries, the continuous upgrading of benzene process projects quickly led to overcapacity of maleic anhydride. Environmental protection factors affected the development of benzene maleic anhydride process around 2000, especially coking benzene was rapidly replaced by hydrogenated benzene, which greatly increased the production cost of benzene process and accelerated the decline of benzene process. Qixiang Tengda started around 2012, and Jiangning Chemical and other butane process projects were put into production successively. Because of their large capacity, they quickly seized the market share. Around 2015, the butane process and benzene process completed the "handover". At present, more than 76% of the circulating goods in the maleic anhydride market are butane process, and the main processes are as follows:

化工行业之顺酐产业研究：边际需求爆发，行业格局重塑

Research on Maleic Anhydride Industry in Chemical Industry: Outburst of Marginal Demand, Reshaping of Industry Pattern

①进料及反应工序

① Feeding and reaction process

常温、常压下的空气经空气过滤器过滤后，由电动鼓风机组、蒸汽透平机驱动的鼓风机组压缩，再经空气加热器加热一定温度。正丁烷液体经输送泵加压后送入到正丁烷蒸发罐，然后使用正丁烷蒸发器使其汽化，再经正丁烷过热器加热一定温度。过热的正丁烷气与空气混合成一定浓度反应气体进入立式管/壳型反应器中，在反应器壳程中采用熔盐混合物通过熔盐泵往复循环用作冷却介质；反应气体进入管程在催化剂的作用下进行氧化反应，反应过程中加入助催化剂。反应热通过熔盐移走，部分熔盐经过熔盐冷却器的壳程，通过与熔盐冷却器管的锅炉水换热产生蒸汽并使其冷却。反应器温度靠控制流经熔盐冷却器的熔盐流量进行控制。反应后的热反应气体经气体冷却器和切换冷却器管程冷却之后送吸收工序。气体冷却器和切换冷却器壳程中的锅炉水被加热并部分气化，和熔盐冷却器中产生的蒸汽在蒸汽包中分离出来或过热后供装置内蒸汽透平机及其它用户做为热源使用。

The air under normal temperature and pressure is filtered by air filter, compressed by electric blower unit and blower unit driven by steam turbine, and then heated to a certain temperature by air heater. The n-butane liquid is pressurized by the delivery pump and sent to the n-butane evaporation tank, then vaporized by the n-butane evaporator, and heated to a certain temperature by the n-butane superheater. The superheated n-butane gas is mixed with air to form a reaction gas with a certain concentration and enters the vertical tube/shell reactor. In the shell side of the reactor, molten salt mixture is used for reciprocating circulation through the molten salt pump as the cooling medium; The reaction gas enters the tube side to conduct oxidation reaction under the action of catalyst, and cocatalyst is added in the reaction process. The reaction heat is removed through molten salt, and part of the molten salt passes through the shell side of the molten salt cooler to generate steam and cool it by exchanging heat with the boiler water of the molten salt cooler tube. The reactor temperature is controlled by controlling the molten salt flow through the molten salt cooler. The thermal reaction gas after reaction is sent to the absorption process after being cooled by the gas cooler and switching cooler tube side. The boiler water in the shell side of the gas cooler and switching cooler is heated and partially gasified, and the steam generated in the molten salt cooler is separated from the steam package or superheated for the steam turbine and other users in the device to use as the heat source.

在反应器进料系统中设有增湿系统和助剂添加系统以保证催化剂的更佳转化率和选择性。增湿系统是通过调节低压蒸汽加入量以达到工艺要求；助剂添加是通过氮气鼓泡方法加入到过热正丁烷气体中。

A humidification system and a promoter adding system are set in the reactor feed system to ensure better conversion and selectivity of the catalyst. The humidification system achieves the process requirements by adjusting the amount of low-pressure steam added; The additive is added to the superheated n-butane gas by nitrogen bubbling.

②吸收、解吸、精制

② Absorption, desorption and refining

在吸收系统，被贫溶剂（DIBE）从切换冷却器排出的顺酐富气中的顺酐被贫溶剂（DIBE）吸收出来。之后，在解吸段，顺酐通过真空蒸馏从富溶剂中解吸出来，含有少量有机物的尾气送到尾气处理系统。

In the absorption system, maleic anhydride in the rich gas of maleic anhydride discharged from the switching cooler by the lean solvent (DIBE) is absorbed by the lean solvent (DIBE). Then, in the desorption section, maleic anhydride is desorbed from the rich solvent through vacuum distillation, and the tail gas containing a small amount of organic matter is sent to the tail gas treatment system.

由于顺酐吸收过程和冷凝过程在同一时间发生，在气相流股被冷却时，顺酐绝大部分被从气体中移走。为了使这一过程的热量被全部移出同时维持一个较低的贫溶剂流量，吸收塔下部塔盘在一个带冷却循环回路的直联式冷却器条件下操作。从塔下部上升的气体被冷却后在塔内部塔盘得到吸收，在吸收塔内，富气从塔底进入并上升，同时贫溶剂从塔顶进入，富溶剂用吸收塔循环泵一部分输送到吸收塔循环，另一部分输送到富溶剂贮罐，吸收塔顶排出的尾气送到尾气处理系统。

Since the absorption and condensation of maleic anhydride occur at the same time, most of the maleic anhydride is removed from the gas when the gas stream is cooled. In order to remove all the heat in this process and maintain a low lean solvent flow, the lower tray of the absorption tower is operated under the condition of a direct cooler with a cooling circulation loop. The gas rising from the lower part of the tower is absorbed in the tray inside the tower after being cooled. In the absorption tower, rich gas enters and rises from the bottom of the tower, while lean solvent enters from the top of the tower. The rich solvent is transported to the absorption tower for circulation by the circulating pump of the absorption tower, and the other part is transported to the rich solvent storage tank. The tail gas discharged from the top of the absorption tower is sent to the tail gas treatment system.

富溶剂从富溶剂贮罐经闪蒸塔进行闪蒸后进入到解吸塔中部,蒸汽喷射系统（顺酐真空系统）保持了塔内真空，解吸塔底部以再沸器加热，顶部出口气回到解吸塔。

The rich solvent enters the middle of the desorption tower after flashing from the rich solvent storage tank through the flash tower. The steam injection system (maleic anhydride vacuum system) maintains the vacuum in the tower. The bottom of the desorption tower is heated by a reboiler, and the top outlet gas returns to the desorption tower.

解吸塔底部解吸后的贫溶剂经与解吸塔进料换热后返回吸收塔。解吸后的贫溶剂经过与解吸塔进料换热后返回吸收塔。解吸塔顶部导出的粗顺酐气体经冷凝后进入到精制部分。

The lean solvent desorbed at the bottom of the desorber returns to the absorber after heat exchange with the desorber feed. The desorbed lean solvent returns to the absorption tower after heat exchange with the desorber feed. The crude maleic anhydride gas from the top of the desorption tower enters the refining section after condensation.

在精制部分粗顺酐进入到脱轻组分塔，轻组分塔顶导出的轻组分经冷凝后一部分回流到塔顶；一部分输送焚烧炉。塔底排出的粗酐进入到成品塔，成品塔顶导出的顺酐气体经冷凝后输出成品中间罐；塔底含有顺酐的重组分输送到解吸塔。

The crude maleic anhydride in the refining section enters the light component removal tower, and part of the light components from the top of the light component tower will flow back to the tower top after condensation; Some of them are delivered to incinerator. The crude anhydride discharged from the bottom of the tower enters the finished tower, and the maleic anhydride gas from the top of the finished tower is condensed and then output to the finished intermediate tank; The heavy fraction containing maleic anhydride at the tower bottom is delivered to the desorption tower.

③溶剂贮存

③ Solvent storage

a、溶剂贮存

a. Solvent storage

溶剂贮存系统的目的是冷却和贮存贫溶剂，并将其提供给吸收塔、尾气洗涤塔。贫溶剂储存在贫溶剂储罐中，并以贫溶剂进料泵送入装置中。因在装置有少量损失, 新鲜的贫溶剂须不断与外界定期性的补充到装置中。

The purpose of solvent storage system is to cool and store lean solvent and provide it to absorption tower and tail gas scrubber. The lean solvent is stored in the lean solvent storage tank and pumped into the unit by the lean solvent feed pump. As there is a small amount of loss in the unit, fresh lean solvent must be regularly added to the unit with the outside world.

b、溶剂处理系统

b. Solvent treatment system

贫溶剂中含有的未被处理的富马酸酐等杂质，通过碱洗和水洗溶剂来实现从装置中除去，贫溶剂和水持续不断的加到搅拌预混罐中，之后进入多级碱洗和水洗倾析器，溶剂相之后进入贫溶剂缓冲罐，水相回用于洗釜。

Impurities such as untreated fumaric anhydride contained in the lean solvent can be removed from the unit through alkali washing and water washing solvent. The lean solvent and water are continuously added to the stirred premix tank, and then enter the multi-stage alkali washing and water washing decanter. The solvent phase then enters the lean solvent buffer tank, and the water phase is used for kettle washing.

④结片成型系统

④ Patch forming system

由顺酐成品罐来的精制后的熔融顺酐，用顺酐输送泵送到顺酐中间罐中。用结片进料泵送到液酐冷却器冷却后，送结片机中。液态顺酐在结片机转鼓表面被转鼓内的冷水冷却结晶并被刮刀切下，片状顺酐由重力经中间漏斗后，加定量包装机中称重包装。

The refined molten maleic anhydride from the finished maleic anhydride tank is sent to the maleic anhydride intermediate tank by the maleic anhydride delivery pump. The flake feed pump is used to send the liquid anhydride cooler to the flaker for cooling. The liquid maleic anhydride is cooled and crystallized on the surface of the flaker drum by the cold water in the drum and cut off by the scraper. The flake maleic anhydride is added to the quantitative packaging machine for weighing and packaging after passing through the middle funnel by gravity.

来自循环水罐的温水用于冷却顺酐和进料管、结片机的夹套保温。结片机装有排风系统，以防止顺酐升华气体的外漏。引风机排出的气体经尾气洗涤塔循环的工艺水洗涤后排入大气，洗涤液经泵输送工艺水罐。

Warm water from circulating water tank is used to cool maleic anhydride and jacket insulation of feed pipe and flaker. The flaker is equipped with an exhaust system to prevent the leakage of maleic anhydride sublimation gas. The gas discharged from the induced draft fan is washed by the process water circulating in the tail gas scrubber and then discharged into the atmosphere. The washing solution is pumped to the process water tank.