The polypropylene (PP) plant is an industrial complete equipment system used for producing polypropylene resin through the polymerization reaction of propylene monomers, and is one of the core devices in the petrochemical industry. By precisely controlling the reaction conditions, catalyst system, and process flow, it produces polypropylene products of different grades (such as homopolymer PP, copolymer PP, random copolymer PP, etc.) to meet the needs of various fields such as packaging, automotive, home appliances, and building materials.
Polypropylene plants typically consist ofRaw material pretreatment unit、Aggregation reaction unit、Separation and recycling unit、Granulation unitandauxiliary systemComposed of five major parts, each unit collaborates to complete the entire production process from propylene raw materials to PP finished products.
Raw material pretreatment unitResponsible for the purification of propylene raw materials, removing impurities such as water, oxygen, carbon monoxide, sulfides, etc. (which can poison the catalyst), usually using processes such as molecular sieve dehydration and hydrogenation deoxygenation to ensure that the purity of propylene is ≥ 99.5%.
Aggregation reaction unitThe core unit involves the polymerization reaction of propylene monomer to produce polypropylene powder through the action of a catalyst, including a reactor, catalyst injection system, circulation system, etc.
Separation and recycling unitSeparate unreacted propylene monomers, solvents (if any), and catalyst residues, recycle the recovered propylene back to the reaction unit for reuse, and reduce raw material consumption.
Granulation unitMix the polymerized polypropylene powder with additives (such as antioxidants, lubricants, color masterbatch, etc.), melt, extrude, and cut them into granular products for easy storage, transportation, and processing.
auxiliary systemIncluding public utilities (such as steam, circulating water, nitrogen), automatic control system (DCS distributed control), safety system (such as emergency shutdown system ESD), etc., to ensure stable operation of the equipment.
The polymerization process of polypropylene can be classified according to the reaction phase and reactor typeSlurry method, liquid-phase bulk method, gas-phase method, and composite processThe core differences between different processes lie in the reaction medium, reactor structure, and product adaptability.
| Process Type |
Core Features |
Typical Process Examples |
Product scope of application |
| slurry |
Using inert solvents (such as hexane) as a medium, propylene polymerizes in the solvent, with a mild reaction that is easy to control and a wide molecular weight distribution of the product |
Spheripol process (Basel), Hypol process |
Homopolymer PP, copolymer PP, suitable for injection molding, fiber |
| Liquid phase ontology method |
Solvent free, propylene monomer itself serves as the reaction medium, with simple equipment, low energy consumption, and high reaction pressure |
China Environmental Management Law (such as Shanghai Petrochemical) |
Mainly made of homopolymer PP, suitable for wire drawing and injection molding |
| gas-phase method |
Acrylic polymerizes in the gas phase, solvent-free, with a short process and good environmental friendliness, and can flexibly produce multiple grades of products |
Unipol process (Dow), Innovene process |
Homopolymer, copolymer, and random copolymer PP, suitable for films and pipes |
| composite process |
By combining the advantages of two or more processes (such as "liquid phase+gas phase"), product performance can be precisely controlled |
Spherizone process (Basel), Novolen process |
High performance copolymer PP (such as high impact PP) |
withGas phase method (Unipol process)For example, its core process is:
The purified propylene and catalyst (such as Ziegler Natta catalyst or metallocene catalyst) enter the gas-phase fluidized bed reactor;
Under the conditions of 60-80 ℃ and 2.0-3.0MPa, propylene polymerizes under the action of a catalyst to produce PP powder, and the fluidized bed is maintained in a laminar state by circulating gas;
After the powder is discharged from the reactor, unreacted propylene is removed by a degassing unit;
After degassing, the powder is mixed with additives and enters the granulator for melting and cutting to obtain the finished product.
The core equipment of the polypropylene plant directly affects reaction efficiency, product quality, and energy consumption, mainly including:
reactorThe core sites of polymerization reactions are divided into kettle reactors (slurry method), loop reactors (liquid-phase bulk method), fluidized bed reactors (gas-phase method), etc. due to different processes. For example, a loop reactor mixes materials evenly through high-speed circulation, removes reaction heat through jacket cooling water, and maintains precise temperature control.
Catalyst injection systemIncluding catalyst storage, metering, and transportation equipment (such as screw pumps and nitrogen pipelines), precise control of catalyst dosage (usually 0.001% -0.01% of propylene mass) is required to regulate polymerization rate and product molecular weight.
Circulating compressorUsed to compress the separated and recovered propylene gas and send it back to the reactor to maintain stable pressure in the reaction system, usually using centrifugal or reciprocating compressors.
GranulatorMost of them are twin-screw extrusion granulators, which melt and mix powder and additives through screw shearing. After extrusion through the die, the granulator cuts them into particles with a diameter of 2-4mm. The melting temperature (200-230 ℃) and cutting speed need to be controlled to ensure that the particles are uniform