Second, polypropylene control program 2.1 batch method bulk polypropylene control Batch liquid phase bulk (abbreviated type) polypropylene production process is China's independent development of China's national conditions of polypropylene production technology. Its main technical process is liquid propylene in the polymerization reactor, under the action of the catalyst polymerization reaction, and adding hydrogen to adjust the relative molecular mass. After the completion of the polymerization reaction, the polymerization product enters the flash evaporator, removes the unreacted propylene, enters the extruder, is extruded and pelletized, and is weighed, packaged, and delivered to the product warehouse. The recovered propylene is recycled after being condensed.
2.1.1 Routine Control of Batch Process The propylene and initiator feeds, polypropylene polymerization, flash deactivation, and propylene recovery of the polypropylene production process are complicated, and the equipment is complex. In addition, there are many analog control and cumulative measurement, and many control objects have characteristics such as strong lag, large inertia, and multiple disturbances, such as the temperature of the polymerizer. Based on the advantages of DCS products, Zhongzhong used DCS's powerful analog processing functions and unique control algorithms and strategies to successfully implement the difficult-to-difficult control of the batch process polypropylene process and to satisfy the batch process. Polypropylene process control requirements.
1. Accurate measurement of feed control propylene monomer, initiator, and hydrogen feed amount. Sequence operation of each valve during feeding of each material. Cm feed valve open, interlocked shut-off propylene return valve; conversely, interlock Open propane return valve
2. Control key controls in the transition phase:
The pressure and temperature curve in the polymerizer control the temperature in the kettle to a predetermined temperature within a short period of time. At the same time, the temperature cannot rise too fast, resulting in the control of the pressure in the kettle during the thermostat phase.
The company has built a mathematical model for the control of the temperature increase of propylene polymerization, and on the basis of the model, it has achieved the best optimization of the control effect of the temperature increase process time and the constant temperature stage. 3. Constant temperature control features control strategy:
The central control adopts a cascade control method in which the pressure of the polymerization vessel is the main ring and the jacket water temperature is the secondary ring. With the jacket temperature sub-circuit, the pressure and temperature disturbances before the cooling water valve can be overcome quickly, that is, the temperature secondary circuit acts as a rapid coarse adjustment, and the pressure main circuit plays a role of fine tuning.
The control of the cascade predictive function, which is similar to the traditional cascade PID control method, is used for control (ie APC-PFC control engineering software package), which makes the temperature and pressure control effect more ideal.
Zhongzhong built a mathematical model for formulating and hydrogenation control, which can accurately control the amount of hydrogen added.
Conversion rate online measurement, combined with the polymerization reaction time and temperature changes, in order to determine the end of the polymerization reaction.
4. Key controls for spray, flash, recovery process control:
The pressure of the recovery system controls the pressure of the flash tank, and the pressure of the temperature of the propylene recovery valve of the interlocking flash vaporization tank is high. The characteristic control strategy of propylene recovery during pressure relief is as follows:
The establishment of an automatic control model for the propylene recovery process can effectively ensure the safety of the recovery system, reduce the time of the recovery process, and increase the production efficiency.
2.1.2 batch control Batch liquid phase bulk polypropylene (PP) production process Another feature is batch control, the need to combine the actual production of the entire polymerization reactor batch control according to the formula to modify and transferred to achieve from the monomer, Add initiators, polymerization to the entire process of flash control. In the entire control strategy, Zhongzhong will divide the feeding, batching, heating, insulation, spray material, flash tank displacement vacuum, and flash tank feed into several sub-function units, each of which is programmed independently. Both include unit initialization startup program, human-computer dialogue program, unit interlock protection program, unit equipment failure detection/fault handling program, and control main program. In this way, the unit program can be individually modified and debugged, initialized separately, and started separately according to the preset conditions. The control logic of this unit is completed, and the operator starts the relevant program steps one by one according to the production sequence to complete the entire batch production. The modification and transfer of recipes are the key to the entire batch control. It is directly related to the accuracy of feeding, the safety of production and the effect of control. The recipe selection and aggregation control screens are shown in Figure 4 and Figure 5:
2.2 Continuous Process Control Strategy for Bulk Polypropylene Production Process The continuous process bulk polymerization process is divided into a tank polymerization process and a tubular polymerization process according to the different polymerization reactors used. This process is characterized by its simple structure, heat transfer area per unit volume, high overall heat transfer coefficient, high single-pass conversion rate, and short product brand switching time. In the world and in the domestic production of polypropylene devices, the use of the loop process is the most. The reaction system and related processes are required for the measurement and control system of the entire process production process. It includes pre-contact tanks, pre-polymerization reactors and loop reactors. Throughout the reaction process, the detection and control requirements for temperature, pressure, propylene feed, hydrogen addition amount, buffer tank liquid level, and polymer content of the loop reactor are relatively strict, and the control of each parameter is interrelated.
1. Catalyst and additives configuration unit features control strategy:
A method of adjusting the ratio of propylene feed was used to automatically adjust the feed of triethylaluminum. The flow rate of the electron donor and the flow rate of triethylaluminum are controlled.
Based on the mathematical model constructed, the temperature control of the main catalyst dispersion tank can fully meet the design requirements of the process.
2. Characteristics of liquid phase polymerization unit control strategy:
Propylene flow control adopts a cascade method with the density of the slurry in the reactor. The slurry density serves as the main loop of the cascade circuit, and the propylene flow rate serves as a secondary loop of the cascade circuit. In this way, the feed adjustment in the loop reactor is realized, the slurry density in the reactor is controlled, and the production is in a state of smooth operation.
The pressure in the loop reactor is controlled by the flow of liquid propylene into the propylene evaporator, while at the same time the pressure is high alarm and interlock protection.
A cascade control method is adopted in which the temperature of the slurry in the loop reactor is the main ring and the water temperature of the jacket is the secondary ring.
In order to ensure that the density of the slurry in the loop reactor is relatively stable, the discharge of the loop reactor is controlled continuously by controlling the level of the reactor buffer tank. In order to ensure the continuity of the discharge, one is set at the same time. Manual operation controller.
The flow rate of hydrogen gas is controlled by using a tandem circuit in which the hydrogen concentration in the propylene gas flow measured by gas chromatography is the main ring and the flow rate is adjusted to the sub-ring.
Interlock control is divided into three situations:
1) System logic determines that when a rapid termination of the reaction is required, the program automatically injects a mixture of nitrogen and carbon monoxide into the bottom of each reactor leg.
2) When the slurry circulation pump malfunctions and the inhibition is ineffective, the solids that sink are discharged to the high pressure discharge tank by opening the pressure switch under the reactor.
3) Interlock open the upper safety valve of the reactor.
2.3 The control strategy of the gas phase method polypropylene device The gas phase technology is based on the technology of no deashing, no off random matter, and the gas-phase fluidized polymerization process adopting the high-efficiency catalyst. The polymerization reactor used in this process usually has a fluidized bed, a vertical stirring bed, and a horizontal stirring bed. It has the characteristics of a general high-efficiency bulk process, but it has some special advantages over the bulk method.
1.Feeding system control characteristic control strategy An online algorithm for calculating the reactor load was constructed. The production load can be set by the operator online.
The load of the reactor was controlled by controlling the amount of the main catalyst added. With the reactor load control as the main loop, the flow control of the main catalyst is cascaded as a secondary loop.
The flow rate of the cocatalyst and the modifier is adjusted with the ratio of the main catalyst.
2. Reaction system control features control strategy:
In the four zones of the reactor, there are three temperature measurement points in each zone, and the temperature in the reactor is controlled by three quench liquid flow control valves.
The control of the gas/liquid ratio control in the reactor is mainly to control the circulating gas volume, and the ratio of the total flow of the quench liquid to the reactor is controlled.
There are two kinds of material level control methods in the reactor: radiation mode or motor power mode. The liquid level is controlled by the opening time and opening interval of the reactor outlet valve. The cycle opening time and interval time of the valve are given by the control logic.
Hydrogen/propylene ratio control is cascaded with hydrogen flow. Hydrogen flow control is divided into two types: when the flow deviation is large, a large flow control valve is used to adjust, and when the flow deviation is small, a small flow control valve is used to adjust, so that the hydrogen flow is maintained in a stable state.
The ethylene/propylene ratio control also uses cascade control. Ethylene flow is controlled as the inner ring, and the ethylene/propylene ratio is the outer ring.
The top separator level and fresh propylene feed flow are cascade controlled.
Jining Union Machinery And Parts Co.,Ltd is very professional in doing cylinders for Excavator. The arm cylinder, bucket cylinder and boom cylinder are for all brands of excavators.
Excellent Production Process for the hydraulic cylinders
1.Raw material process
2.Tempering steel
3.Induction hardended steel
4.Chrome plating rod
5.Rod finish machining
6.Painted rod
We can supply arm cylinder, bucket
cylinder and boom cylinder for the following excavators:
For Komatsu PC30 PC40 PC45 PC60 PC75 PC100 PC120 PC130 PC200 PC220 PC240 PC300 PC350 PC400 PC450
For Cater E70B E110 E120B E215 E235 E307 E311 E312 E322 E180 E240 E200B E320 E300 E300B E330 E325
For DAEWOO DH55 DH130 DH180 DH200 DH220 DH280 DH300 DH320 DH330 DH360 DH400 DH450 DH500 For HITACHI EX30 EX40 EX60 EX100 EX120 EX200 EX220 EX270 EX300 EX350 EX400 EX450 ZX230 ZX240 ZX250 ZX270 ZX280 ZX330 ZX350 ZX370 ZX450 ZX470 ZX520 ZX600 ZX650 ZX670 ZX800
For HYUNDAI R55 R60 R70 R80 R110 R130 R150 R170 R190 R200 R205 R210 R220 R230 R290 R300 R360 R450
For KATO HD140 HD250 HD400 HD450 HD550 HD700 HD820 HD850 HD880 HD900 HD1220 HD1250
For KOBELCO SK60 SK100 SK120 SK200 SK220 SK230 SK250 SK280 SK330 SK350 SK400 SK450
For SUMITOMO SH70 SH100 SH120 SH160 SH200 SH220 SH240 SH260 SH265 SH280 SH300 SH330 SH340 SH350 LS2650 LS2800
Excavator Hydraulic Cylinder,Excavator Telescopic Hydraulic Cylinder,Excavator Hydraulic Steering Cylinder,Pc200 Excavator Hydraulic Cylinder
JINING UNION MACHINERY AND PARTS CO., LTD. , http://www.vmpmachineryparts.com