The hydrodynamics in an unbaffled stirred vessel were simulated in order to highlight the effect of gravity on pressure and velocity distributions. Two fluids with different viscosity were studied for the laminar and turbulent flow regimes, respectively. The simulation results were compared with experimental data from the literature. Results indicate that for the higher-viscosity fluid, gravity only affects static pressure and that the effects of gravity on velocity and dynamic pressure are negligible. For the lower-viscosity fluid, however, gravity imposes a pronounced impact on static pressure, dynamic pressure, velocity, and turbulent kinetic energy. These findings indicate that careful consideration is necessary for the role that gravity plays in the study of free-surface hydrodynamics in unbaffled stirred vessels.

Effect of Gravity on the Hydrodynamics in an Unbaffled Stirred Vessel

The invention discloses a high-viscosity polymerization plant and a method for producing polylactic acid by using the device. The high-viscosity polymerization plant comprises a base and a horizontal cylinder, wherein the horizontal cylinder comprises a reaction cylinder and a discharge cylinder; an operating hole, a circulating inlet and a circulating outlet are formed in the horizontal cylinder; a support frame is arranged at the lower end of the horizontal cylinder; the section of the reaction cylinder is in similar oval shape, a jacket and a runner are arranged between the inner wall and the outer wall of the reaction cylinder, and a heat transfer medium circulates in the jacket; two stirring shafts are arranged in the reaction cylinder, a stirring paddle is arranged on the stirring shaft, and the section of the stirring paddle is fusiform; the discharge cylinder is cylindrical, a discharge screw matched with the discharge cylinder is arranged in the discharge cylinder; a motor for providing power is arranged on the base. According to the invention, the stirring paddle plays the roles of stirring, scraping and cleaning the inner wall of the cylinder, and the heat transfer medium circulates in the cylinder circularly, so that the polymerization reaction efficiency is improved. The high-viscosity polymerization plant is convenient to install and simple and convenient to operate, and can be used for saving same and manpower and material resources.

High-viscosity polymerization plant and method for producing polylactic acid by using same

The invention relates to a system and a process for preparing polycarbonate sheets. The process comprises the following steps: at first, a polycarbonate dichloromethane solution with a certain concentration is prepared in a solution pre-preparation device, the polycarbonate dichloromethane solution is mixed with superheated steam, then the mixture is loaded in a condenser tube, dichloromethane is gasified under the action of the superheated steam, and polycarbonate condenses into small droplets on the wall of the condenser tube; when the friction force between the polycarbonate droplets and the wall of the condenser tube is not enough to support the weight, the polycarbonate sheets are blown out from the condenser tube by steam and dichloromethane steam, the polycarbonate sheets enter a cyclone separator for gas-solid separation, and the polycarbonate sheets after gas-solid separation are then subjected to impurity removal by a steam stripping tower to obtain pure polycarbonate sheets; after dichloromethane and steam are separated by a phase separator, dichloromethane is conveyed in the solution pre-preparation device, and waste water enters a sewage treatment plant.

System and process for preparing polycarbonate sheets

The invention discloses p-tert-butyltoluene rectification separation equipment which comprises a rectifying still, wherein a rectifying tower is arranged at the top of the rectifying still; a seal head is arranged at the top of the rectifying tower; a reflux distributor is arranged at the lower part of the rectifying tower; a gas phase hole is formed in the seal head, and a tower top temperature measuring hole is formed close to the gas phase hole; a feeding hole is formed in one side of the top of the rectifying still; a heat-conducting oil return pipe is arranged on the side wall of the rectifying still and stretches into the rectifying still; multiple internal coil pipes are arranged in the rectifying still; a heat-conducting oil inlet pipe is arranged at the bottom of the rectifying still and is communicated with the internal coil pipes; the internal coil pipes are communicated with the heat-conducting oil return pipe; and multiple external coil pipes are arranged on the outer wall of the rectifying still and are communicated with the heat-conducting oil return pipe. The invention also discloses a process for distilling and separating p-tert-butyltoluene. The rectification time is short, the energy consumption is low, the separation effect is good, the purification percentage of the p-tert-butyltoluene is improved, the original purity only can be 98.5-99 percent, and the purity reached by the equipment can be more than 99.5 percent.

P-tert-butyltoluene rectification separation equipment and p-tert-butyltoluene rectification separation process

The invention discloses a horizontal double-shaft stirring reaction kettle with a star-shaped stirrer. The horizontal double-shaft stirring reaction kettle comprises a kettle body, a motor and a speed reducer, wherein the speed reducer is connected with the motor, a material inlet, a gas outlet and a hand hole are respectively arranged in the top of the kettle body, a plurality of material outlets are arranged in the side wall and at the bottom of the kettle body, two rotating shafts connected with an output shaft of the speed reducer are arranged in the kettle body, a plurality of stirring discs are respectively arranged on each of the two rotating shafts at intervals, the stirring discs are star-shaped polygon stirring discs, or a part of stirring discs are polygon stirring discs, and the other part of stirring discs are star-shaped polygon stirring discs, the star-shaped polygon stirring discs are in a structure that an arc-shaped groove is formed along each polygon side wall, and a stirring rod is respectively arranged at the turning corner part of each polygon stirring disc and each star-shaped polygon stirring disc. The kettle has the advantages that the axial flowing blockage on materials is greatly reduced, the axial impelling force is further enhanced, and the stirring mixing effect is enhanced.

Horizontal double-shaft stirring reaction kettle with star-shaped stirrer

Sensitivity of pressure and velocity fields to gravity

The invention discloses a method and device for recovering mixed dibasic dimethyl from a horizontal double-shaft stirring re-boiler. The method comprises the following steps: (a) adding the heated heat-conducting oil into a jacket outside the horizontal double-shaft stirring re-boiler and introducing cooling circulating water into a condenser; (b) feeding the to-be-processed liquid containing the mixed dibasic dimethyl into the horizontal double-shaft stirring re-boiler, and meanwhile, starting a motor, stirring the materials in the horizontal double-shaft stirring re-boiler by a stirring shaft under the driving of the motor so as to heat and vaporize the mixed dibasic dimethyl in the materials, causing the mixed dibasic dimethyl to enter into the bottom of a rectifying tower, and purifying by the rectifying tower, thereby obtaining the high-purity mixed dibasic dimethyl; and (c) condensing the high-purity mixed dibasic dimethyl into liquid by the condenser, causing the liquid to flow into a liquid collecting tank, and discharging the solid residues in the re-boiler from a residue discharging port under the driving of the stirring shaft and causing the solid residues to flow into a residue receiving tank. The method and the device provided by the invention are used for obtaining more recovered products, the yield is increased and the residual emission load is reduced.

Method and device for recovering mixed dibasic dimethyl from horizontal double-shaft stirring re-boiler

The invention discloses a continuous desolventizing method and a device for polycarbonate resin. The continuous desolventizing method comprises the following steps: (a) adding conduction oil into a jacket out of a stirred tank; (b) starting a vacuum pump, inputting parts of the colloidal solution of polycarbonate and dichloromethane, which is to be processed, into the stirred tank from the feeding liquid hole of the stirred tank, and simultaneously starting a motor; (c) when the stirred tank temperature of the feeding hole of the stirred tank reaches 150-180DEG C, the sticky area stirred tanktemperature reaches 180-250DEG C and the stirred tank temperature of a material outlet reaches 250-300DEG C, continuously adding the colloidal solution of polycarbonate and dichloromethane, which is to be processed, into the stirred tank; and (d) stirring materials in the stirred tank, wherein dichloromethane in the material in the stirred tank is heated to vaporize, the vaporized dichloromethaneenters a recovery tower via a gaseous phase pipeline, and non-volatile polycarbonate solid particles or powders in the stirred tank are discharged from a product discharging hole after being propelled by a stirring shaft to flow into a product receiving tin. With the continuous desolventizing method disclosed by the invention, a qualified polycarbonate (PC) product can be obtained in one time.

Continuous desolventizing method and device for polycarbonate resin

The invention discloses a method for recovering maleic anhydride from maleic anhydride distillation kettle residues. The method comprises intermittent operation and continuous operation, wherein the intermittent operation comprises the following steps that maleic anhydride distillation kettle residues are added from a feeding opening of a double-shaft stirring reboiler, the kettle temperature of the double-shaft stirring reboiler is controlled to be 140 DEG C to 200 DEG C through controlling the heat conducting oil flow rate, the operation pressure of the double-shaft stirring reboiler and a distillation tower is controlled to be 10 to 50 KPa, the maleic anhydride distillation kettle residues are heated to be 150 to 180 DEG C, steam enters the distillation tower and is condensed by a condenser, one part of steam flows back to the distillation tower and is distributed to a lower mass transfer unit by a liquid distributor, and one part of steam enters a collecting device by a production pipeline until no gas phase is produced. The method has the advantages that the residue discharge quantity can be reduced by more than 50 percent.

Wei Jin

Papers

Horizontal double-shaft stirring reaction kettle with star-shaped stirrer

Sensitivity of pressure and velocity fields to gravity

Method and device for recovering mixed dibasic dimethyl from horizontal double-shaft stirring re-boiler

Continuous desolventizing method and device for polycarbonate resin

Method for recovering maleic anhydride from maleic anhydride distillation kettle residues