Diploma project on vinyl chloride polymerisation

Contents

Introduction

1. General concept of polymerization process

2. Physicochemical characteristics of raw materials, auxiliary materials, finished products

3. Block - "PVC Production" Diagram

Block Description - "PVC Production" Diagram

4. Description of "PVC production" process diagram

5. Calculation of material balance of the VC polymerization reactor

6. Environmental protection. Solid waste, wastewater, air emissions

7. Safe operation of production. Characteristics of fire hazardous and toxic properties of raw materials, semi-products, finished products and production wastes

Conclusion

Introduction

The wide development of the chemical industry will allow the maximum replacement of non-ferrous metals with synthetic materials in the chemical, electro-radio industry, oil engineering; use plastic masses instead of alloyed metals and special alloys in the design of machines and devices, with lower weight and increased performance, in the creation of new processes in atomic, reactive and radar technology; to introduce polymers more widely in construction, agriculture, medicine and other areas of the national economy.

The rapid development of chemistry and physics of high molecular weight compounds contributed to the synthesis of hundreds of new polymers. In addition, methods have been developed to change the properties of polymers as a result of oxidative, radiation, chemical-mechanical and other processes, and plastic modification has been obtained essential materials in a number of branches of technology.

Characteristics of raw materials, finished products and auxiliary materials

1. The PVC product is a capillary porous material whose properties (molecular weight, molecular weight distribution, chain structures) significantly determine the behavior of the polymer when it is processed into products. According to the morphological characteristic of the grain of suspension PVC, it is divided into:

a) homogeneous (monolithic with a predominance of transparent grains or opaque grains);

b) heterogeneous porous (there is no predominance of grains of any one type)

The feasibility of producing PVC grains of one type or another is determined by the specific purpose of this class of PVC.

PVC is a white, well-sieved powder. It is physiologically harmless in the absence of monomeric or oligomeric impurities, combustible. When burned, hydrogen chloride is released, which at elevated concentrations irritates and burns the airways.

It is resistant to acids and bases, and is unstable to polar organic solvents (ketones, ethers, chlorocarbons). Soluble in cyclohexane and tetrahydrofuran.

Glass transition temperature 8085 0С

Decomposition temperature is more than 120 0С

Flash point 624 0С

1. PVC suspension is a milk-colored aqueous suspension.

The solid content in the suspension is 25-35%;

VC content in suspension is not more than 20 • 104% (wt) relative to PVC.

Suspension density 1.09 - 1.12 g/cm3

The toxicity and flammability of PVC suspension depends on the presence of VC. The suspension is prone to sedimentation, so they should be washed with water to avoid clogging of pipelines. Suspension collectors shall be equipped with stirrers, pipelines shall not have "dead knots" or strong bends.

2. Demineralized water is a colorless liquid. Not combustible, not explosive. Not toxic. pH = 6.5-7.5.

3. Vinyl chloride - under normal conditions, a colorless gas with a relative air density of 2.18 g/l, is highly soluble in organic solvents, and is practically insoluble in water. It has polymerization activity with the release of significant heat.

Molecular weight - 62.5

Density of liquid BX at 30 0С - 0.89 g/cm3

Boiling point (at 760 mm hg) = 13.9 0С

Flash point = 78 0С

Ignition temperature = 472 0С

4. Liladox (dicetyl peroxydicarbonate) is a white powder. Polymerization initiator.

Mass fraction of the main substance 75-90% (wt.)

Structural formula:

C16N33 - C - O - O - C - C16 H33

OO

6. Metocel (hydroxypropimethylcellulose) is a white hygroscopic powder that is very dusty. Soluble in water. Emulsifier of reaction mixture.

7. Kluzel (hydroxypropyl cellulose) is a white hygroscopic powder that is very dusty. Soluble in water. Emulsifier of reaction mixture.

8. Spahn - 20 (monosorbit ester of lauric acid) is a clear viscous liquid, oily. Soluble in water. Stabilizer - PVC plasticizer.

9. Ionol (2,6 ditretbutyl paracresol) is a pale yellow crystalline powder used as an antioxidant additive to control the reaction rate in the final stage.

10. Nigrosin is a black dye obtained by prolonged heating of aniline and nitrobenzene with metallic iron or its chloride. It is used as an anti-anticoeducer.

11. Stopper (tert-butyl pyrocatechin) is a dark brown fluid of sharp smell. Breaker

polymerisation.

12. Hydrogen peroxide is a colorless and transparent liquid. Caustic. It is used to reduce foaming in the reactor.

13. Calcium hydroxide is a highly dusting powder of white color. It is used to absorb hydrogen chloride released from PVC; higher thermal stability of PVC.

3.1. description of the block of the production diagram

The block diagram of PVC production includes the stage of DCE production by the combined method. Oxygen, ethylene, chlorine and the same hydrogen chloride from the separation step will be fed to this step. Further, DCE enters the purification stage, where polychlorides are separated, and DCE goes to the pyrolysis stage (T = 500 ° C). After passing through the furnaces, the cracked gas enters the separation stage from where HCl is withdrawn to the DCE production stage, and VC from additional purification is sent to the polymerization stage. Also, liladox (initiator of the polymerization process) is supplied to this stage - its own production, aqueous components (demineralized water, emulsifiers - clucel, metocel, trellis 20), loading of solid components (ionol - antioxidant additive, calcium hydroxide - hydrogen chloride acceptor, medium regulator). The resulting PVC suspension is sent to the final stage of PVC production - drying, here the aqueous phase is separated from the finished PVC, which goes to the batch, then to the consumer.

4. description of the polymerization flow chart in

VC polymerization is carried out periodically in polymerization reactors equipped with a jacket for heating and cooling the reaction mass and a reflux condenser located directly on the reactor. To mix the reaction mass, reactor R is equipped with an impeller three-bladed stirrer with a lower drive.

Preparation of raw material includes purification (filtration) of BX, production of demineralized water by ion-exchange purification (E 5), dissolution of stabilizers - metocel (E 3 - E4), clucel (E1 - E2), frame 20 (E 6) in water, preparation of polymerisation regulators and pHsreda - calcium hydroxide and hydrogen peroxide (E 7 - E 8).

Capacity E 10 is filled with 10% breaker solution (800 liters) and is under nitrogen pressure of 1.71.8 MPa. Before the reactor start-up, the pressure of the tank E 9 is checked, if it is less than the standard one, then the reactor stirrer cannot be put into operation. When the reactor is operating in the stage of VC dosing, heating, polymerization, it is necessary to monitor the pressure of the tank E 10.

Control of liquid flows during stirring in the reactor is carried out by side counter-mixers (wave cutters) installed in the upper part of the reactor. All operations for loading liquid components in the polymerization reactor R, maintaining the polymerization process, hydrotreating are carried out by a computer according to a given program in accordance with the requirements of the brand of PVC produced. Ionol, Calcium hydroxide, liladox, in the listed sequence, are loaded through the hatch into a lock - a vertical cylindrical apparatus equipped with a cooling jacket, where river water is supplied. After loading the solid components, the computer loads the aqueous components of clucel, metocel, hydrogen peroxide, frame 20, demineralized water. After the dosing of the aqueous components is completed, the computer turns on the stirrer and controls its operation. Before BX dosing, the following is checked: shutter water pressure, stirrer operation, a circulation pump is started to supply cooling water, which circulates through the reactor jacket and the return cooler; VC dosing station is checked.

The VC enters the reactor R through a lock previously loaded with solid components, while the VC washes the solid components into the reactor R.

Simultaneously with the loading of VC into the reactor R, the heating of the reaction mass begins, the supply of steam with a pressure of 1.2 MPa to the cooling water pipeline. When the polymerization temperature is reached, the steam supply is stopped and the cooling water supply is started, hot water is displaced from the reactor jacket. When the temperature of the reaction mass reaches a predetermined value inside the reactor R, the computer detects the temperature value in the reactor jacket and activates the temperature control circuit in the return cooler for a predetermined temperature value of the reaction mass inside the reactor R. From this moment, the polymerization process begins, in which the temperature of the reaction mass and the pressure in the reactor are constantly controlled. To avoid exceeding the permissible value of the pressure in the reactor R, it is equipped with safety valves that release pressure to the atmosphere at 1.65 MPa. When the pressure in the reactor drops, the computer fixes this and reports a pressure drop, the process of additional polymerisation begins, which proceeds due to the heat of the reaction and heating through the reactor jacket.

After the additional polymerisation time expires, the computer issues a message about the end of the polymerization operation and reduces the temperature in the reactor jacket and in the refrigerator. After the polymerization process, the suspension from reactor R is discharged to the degassing vessel of the unit. The suspension is discharged from reactor R at a pressure of 0.3-0.6 MPa in the reactor, filter F 1 (cylindrical horizontal apparatus, inside of which there is a plate with holes with a diameter of 25 mm, demineralized water is supplied for washing from clogging, which is removed to the waste water collector after washing through the waste water line).

Before the reactor R is discharged, the filter F 1 and the discharge line must be filled with water to avoid deflection of the filter plate. The degree of reactor unloading is controlled by the level in the degassing unit. After the slurry is discharged to reactor R, 6,000 liters of water (demineralized) are dosed to wash the reactor R cooler after discharge. Flushing water is pumped by pump H 8 to degasser U. After washing the reactor, its cleaning with high-pressure water begins. Degassing is carried out in two steps: degassing under pressure of the degassing vessel of the unit, then degassing in the PRZ column.

Degassing of the suspension under pressure occurs in the degassing vessel of the unit (a vertical cylindrical apparatus with a capacity of 300 m3, equipped with a three-bladed stirrer with a lower drive to prevent subsidence of the suspension) there is a partial removal of unreacted VC by equalizing the pressure in the container of the unit and separator C, from 0.3-0.25 to 0.02 MPa. In the separator, the suspension particles are separated from the BX gas. The slurry flows down the walls to the bottom of the separator and through the drain pipeline flows into the unit tank. Separator C is equipped with a circular sprayer for washing it with demineralized water. Suspension from PIECE capacity via the F 2 filter, centrifugal pump H 9 moves in a column of decontamination of Cd. The filter is a vertical cylindrical apparatus with a removable perforated plate inside, on which the suspension is filtered from crusts and large PVC particles. When cleaning the filter, its contents are drained into a pit of waste water. In case of filling of pipelines (PVC crusts), flushing with demineralized water in place is performed.

For suspension heating, steam with pressure of 0.5 MPa cleaned from mechanical impurities is used at degassing stage.

To better remove the remaining VC suspension, it is heated to 105-115 0C before being supplied to the column. The remaining VC is separated from the suspension up to the mass fraction of 20٠104% in the CD-degassing column. The degassing column is a vertical cylindrical apparatus. Inside the column, a set of 27 horizontal trays is installed, in which a significant number of holes are located along the entire surface. Overflow tubes are used to drain the liquid and adjust its level on the tray. The upper ends of the tubes are 20 cm below the tray and immersed in the slurry layer. Odd trays have one central overflow pipe with a diameter of 360 mm, and even trays have 12 overflow pipes with a diameter of 107 mm, diametrically located on the tray. At the bottom tray, the overflow device ends with a drain pipe reaching almost to the bottom of the column. A set of trays is installed on a support grille welded to the column body.

The bottom temperature of the column is maintained at 110-115 0C by supplying steam to the bottom of the column.

PVC suspension enters the first tray and enters the cube through the trays, moving countercurrent to the rising steam. Steam passes into the hole of the trays and is distributed in the liquid in the form of small jets, only at a certain distance to the bottom of the tray a layer of foam and spray is formed - the main area of ​ ​ mass exchange and heat exchange on the tray. The pressure and velocity of the vapor passing through the opening of the tray should be sufficient to overcome the pressure of the liquid layer on the trays and prevent the liquid from flowing through the openings. In case of violation of the column operation mode, foam formation in the upper part is possible. In separator C 2 there is partial condensation of water vapor and separation of BX vapors from liquid particles (condensate, suspension).

Next, the PVC slurry from the degassing step is sent to the centrifugation and drying step.

6. environmental protection

Emissions to the atmosphere

Abgases from stage 1500 are released into the atmosphere through a dispersal candle with a height of 49.5 meters. The concentration of vinyl chloride in abgas shall not exceed 20483 mg/m3.

In order to ensure the protection of the air basin against volley emissions containing vinyl chloride, in case of emergency in the polymerization compartment, the following measures are provided:

- emissions containing vinyl chloride from all safety valves installed on equipment and pipelines are made on the gas holder;

-when the pressure increase in reactor RC1201AG (3rd and 5th level of reactor overpressure protection) is released to the emergency condensation stage (st.1800). Condensed vinyl chloride is collected in tank VS1803, from where, depending on the level, it can be blown onto a gas holder or pumped out to the building 205 of workshop No. 30.

Gaseous vinyl chloride from the gas holder is compressed and used in loading into the reactor.

When stopped for repair, vinyl chloride from the tanks and pipelines is blown onto the gas holder, then compressed, collected into the tank VS1502 and pumped into the housing 205 of the workshop 30.

Solid waste

Polyvinyl chloride crusts after cleaning of polymerization reactors and suspension filters are transported by road to the landfill.

The polyvinyl chloride slurry after cleaning the waste water pit VS1325 is transported by road to the landfill.

Paper bags, cardboard drums after the use of raw materials are transported by road to the landfill of construction waste.

Wastewater

The organo-containing wastewater of the polymerization compartment is supplied for further treatment to the wastewater treatment stage - stage 1900.

The cooling water from EX1801 condensers is drained in the stormwater sewerage (well No. 179).

Household effluents are drained into wells No. 92, No. 93 and further into the general reservoir of household sewage.

RC-1201A.dwg

Полимеризация.dwg