Vinyl chloride and polyvinyl chloride

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Vinyl chloride and polyvinyl chloride presents about company profile; the Vinnolit VCM process (EDC distillation, EDC cracking, VCM distillation, waste water treatment,...); the Vinnolit S-PVC process (Description of the S-PVC process, advantages of the S-PVC process,...).

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Nội dung Text: Vinyl chloride and polyvinyl chloride

3 Vinyl chloride and polyvinyl chloride lutions e is ustr ia l S o n a m ew Ind com Our n enKrupp o l u t ions. s ial-s Thys dustr in kr upp- . t h yssen w ww ThyssenKrupp Uhde
2 Table of contents 1. Company profile 3 2. The Vinnolit VCM process 4 2.1 General process description 5 2.2 Direct chlorination 6 2.3 Oxychlorination 8 2.4 EDC distillation 10 2.5 EDC cracking 11 2.6 VCM distillation 12 2.7 Measures to recover by-products and to protect the environment 13 2.7.1 HCl recycling with waste gas heat recovery 13 2.7.2 Waste water treatment 13 2.7.3 Liquid and waste gas collection systems 13 2.8 Cumulated capacity of reference plants 14 3. The Vinnolit S-PVC process 16 3.1 Description of the S-PVC process 17 3.2 Advantages of the S-PVC process 18 3.3 The new Vinnolit High-Performance Reactor for suspension PVC 19 3.4 The Vinnolit MST Cyclone Drier 20 3.5 Products and applications 21 4. References 22
3 1. Company profile With its highly specialised workforce of more than 5,600 employees Vinnolit is one of Europe’s leading EDC, VCM and PVC producers and its international network of subsidiaries and branch offices, Uhde, with a capacity of 780,000 t/year of PVC, 665,000 t/year of VCM a Dortmund-based engineering contractor, has to date successfully and upstream chlorine plants. They enhance and optimise their completed over 2,000 projects throughout the world. process technology on a permanent basis. Vinnolit was founded in 1993 as a 50/50 joint venture between Hoechst AG and Wacker Uhde’s international reputation has been built on the successful Chemie GmbH. The new company drew on the experience of its application of its motto Engineering with ideas to yield cost-effective two founders, both active in the vinyl sector for almost 60 years. high-tech solutions for its customers. The ever-increasing demands In 2000 Advent International acquired Vinnolit. Advent is one of placed upon process and application technology in the fields of the world’s largest and most experienced private equity invest- chemical processing, energy and environmental protection are met ment firms. through a combination of specialist know-how, comprehensive service packages, top-quality engineering and impeccable punctuality. Since 1964 the licensor has granted licences for a capacity of more than 14 million tonnes of EDC, approx. 6.5 million tonnes Uhde and Vinnolit – Partners for vinyl chloride and polyvinyl chloride of VCM and about 2.9 million tonnes of S-PVC. Our licensor for the Ethylene Dichloride (EDC), Vinyl Chloride Mono- The cooperation between the licensor and Uhde has been success- mer (VCM) and for the Polyvinyl Chloride (PVC) process is Vinnolit ful for some 40 years. Uhde is the sole basic engineering partner for GmbH & Co. KG. Vinnolit’s EDC, VCM and PVC processes.
4 2. The Vinnolit VCM process Knapsack (Cologne), which have a com- bined capacity of 665,000 t/year, as well as at many other plants worldwide. The modern Vinnolit process for the pro- duction of VCM has the following major distinctive features: High operational reliability: • Reliable reaction control • Time-proven materials and equipment • State-of-the-art process control system High economic efficiency: • Low energy consumption due to the utilisation of reaction and waste gas heat and integration with PVC or caustic soda plants • High yields • Optimised reaction conditions and Qatar Vinyl Company (QVC), Vinyl chloride (VCM), which is made from reaction control Mesaieed, Qatar ethylene and chlorine, is used as feedstock • Utilisation of by-products containing Capacities of the complex: in the production of the standard plastic Cl2 along with the recycling of HCl gas 360,000 t/year of DC-EDC material PVC. • High on-stream factor 175,000 t/year of Oxy-EDC • Low personnel requirement 230,000 t/year of VCM The market for PVC and hence VCM has • Low maintenance costs continued to grow, thus dispelling the fore- • High flexible, wide range of load casts made in the 80s, according to which PVC would be substituted by other plastics. Extremely low pollution levels: • ≤ 0.01 ppm VCM (annual average) The reasons for this were not only the mani- in working areas fold applications and properties of PVC, but • Extremely low VCM emissions also the progress made in limiting emissions • Small waste water quantities and by-products during production. PVC pro- with EDC/VCM contents ≤ 1 ppm duction capacity attained growth rates of • In-plant disposal of low-boiling approx. 6% per year, accounting for approx. and high-boiling constituents in conjunc- 47 million tonnes worldwide in 2010. For the tion with HCl gas recycling and steam next few years, growth rates in the order of generation 4% per year are again expected. • Special facilities for preventing emissions when the plant is shut down As a chemical engineering contractor, Uhde • Thermal waste gas treatment added VCM to its range of processes some 40 years ago and has to date designed and Expected consumption figures for raw constructed plants with a total nominal ca- materials and utilities per 1,000 kg VCM pacity of approx. 6 million tonnes. product Ethylene (100 %) 459 kg The VCM process applied by Uhde is licen- sed by Vinnolit. The current high technologi- Chlorine (100 %) 575 kg cal standard was reached through intensive Oxygen (100 %) 139 kg development work on the part of Vinnolit Steam 250 kg1 in collaboration with Uhde. The process has been successfully applied at Vinnolit’s ex- Fuel gas 2.7 GJ isting plants at Gendorf (Bavaria) and at 1) Combined figure for VCM / PVC plant: 435 kg
5 2.1 General process description Biggest VCM plant in China SINOPEC Qilu Petrochemical Corp. Linzi, Zibo, Shandong Prov., China 400,000 t/year of VCM (balanced) 1st section: C2H4 + Cl2 C2H4Cl2 + 218 kJ/mole 2nd section: C2H4 + 2HCl + ½O2 C2H4Cl2 + H2O + 238 kJ/mole 3rd section: C2H4Cl2 C2H3Cl + HCl - 71 kJ/mole The process for the production of vinyl chlo- ride monomer (VCM) from ethylene proceeds in several process sections. In the first process section, ethylene dichlo- ride (EDC; 1,2 dichloroethane) is produced by direct chlorination, in the second section by oxychlorination. Both reactions are exo- thermal. The EDC produced by direct chlorination is fed straight into the cracking section without In the third process section, the EDC is well as liquid by-products are fed to the HCl any further purification. cracked, and the VCM formed there, as well recovery unit and converted to HCl, CO2 and as the hydrogen chloride and unconverted water. The heat of this exothermic reaction can be EDC, are separated in a VCM distillation unit. used for PVC drying in the PVC plant or for The VCM is temporarily stored in a tank, The recovered HCl is reused in the oxychlo- heating of columns in the EDC distillation while the HCl is returned to the oxychlorina- rination process, which leads to a complete unit depending on the individual plant con- tion unit and the unconverted EDC to the conversion of the input chlorine. figuration. cracking section. The diagram shows the individual sections The EDC formed by oxychlorination passes Any process water obtained undergoes treat- of the overall process which are described through a purification stage (EDC distillation). ment. Waste gases containing pollutants as on the following pages. VCM synthesis: 2 C2H4 + Cl2 + 1⁄2 O2 2 C2H3Cl + H2O Schematic diagram of a VCM plant Chlorine Direct EDC VCM Vinyl chloride EDC Cl2 chlorination cracking distillation VCM Cat ΔH C2H4 + Cl2 C2H4Cl2 C2H4Cl2 + 218 k J/mole C2H3Cl + HCl – 71 k J/mole Ethylene EDC recycle EDC liquid + gaseous C 2H 4 distillation chlorination by-products HCl Oxygen by-product Oxychlorination HCl O2 recovery Cat C2H4 + 2 HCl + 1⁄2 O2 C2H4Cl2 + H2O + 238 k J/mole
6 2.2 Direct chlorination In the direct chlorination process, EDC is Gaseous chlorine is added via an injector The process is particularly produced by means of a highly exothermal nozzle to a relatively small circulating EDC environment-friendly, because: reaction of ethylene and chlorine. side stream withdrawn in the downcomer • The energy recovery options lead to a section of the CNC reactor and cooled to significant reduction of CO2-emissions The main feature of the Vinnolit direct allow the chlorine to be better pre-dissolved. • The formation of high-boiling chlorination process is an innovative boil- This cooling provides another opportunity to constituents is significantly reduced ing reactor with natural convection flow. recover the heat of reaction. • Extremely small quantities of low-boiling Recently, as a result of a joint development constituents are formed (only a few ppm) project of Uhde and Vinnolit, the compact The ethylene solution and the completely • No scrubbing water is required and natural circulation (CNC) reactor was devel- predissolved chlorine are mixed in the reac- • No catalyst is discharged with the product. oped and now is ready for introduction on tion zone of the riser and react to EDC in a the market. In the CNC reactor, the natural fast liquid-phase reaction which significantly The catalyst has no corrosive properties be- circulation is established in an internal loop lowers by-product formation. cause of its complex structure, and therefore consisting of a riser section and a down- the process equipment can be made mainly comer section, leading to a more comact Due to the reduced static pressure head in of ordinary carbon steel. Existing plants can and cost-saving reactor design. the top section of the riser, the EDC starts be converted without any difficulty. boiling. The product amount and some ex- The Vinnolit Direct Chlorination process cess EDC are withdrawn from the upper The advantages of the process can be operates at boiling conditions with a tem- part of the CNC reactor and passed on to summarised as follows: perature of 120°C. The heat of reaction is the product vessel and a stripping column • Nearly no consumption of catalyst removed by boiling off EDC from the boiling to achieve 'Sales EDC' quality, if required. • High raw material yields reactor. A big portion of this heat can be The excess EDC is recycled to the main • High EDC purity: 99.9 % recovered by several heat recovery options, reactor loop. • Utilisation of reaction heat, e.g. for e.g. heating of distillation columns in the heating of distillation columns or drying EDC distillation unit or heating of a fluidised In contrast to competitive direct chlorination of PVC, leading to a reduction in steam bed PVC drier in the PVC plant yielding a processes, the Vinnolit Direct Chlorination consumption of up to 700 kg / tonne reduction of steam consumption of up to process does not use FeCl3, but a complex of EDC. 700 kg / tonne of EDC. compound as catalyst. The catalyst sup- • Low investment costs presses the formation of by-products and • Complete reaction in only one reactor The reaction is carried out in the riser sec- ensures higher selectivity to EDC. • Proven materials and reliable and simple tion of the CNC reactor. In contrast to other equipment processes, gaseous ethylene is first com- Thus the Vinnolit Direct Chlorination process • High active and selective catalyst pletely pre-dissolved in the lower part of the combines the energy efficiency of a high- riser section of the CNC reactor. temperature chlorination (HTC) process with Utilising the reaction heat saves energy and the EDC purity of a low-temperature chlorin- reduces emissions of CO2 by an amount ation (LTC) process. The catalyst is fed to the equivalent to the energy savings. Thus, car- reactor loop before start-up and does not bon certificate trading has a positive effect have to be topped up in normal operation. on production costs.
7 Refrigerant Direct chlorination process using a boiling reactor Waste gas to incineration CW Heat recovery Chlorine Product Stripping vessel column Ethylene Sales - EDC Heat N2 recovery CNC Reactor Furnace feed EDC
8 2.3 Oxychlorination In the oxychlorination process, EDC is formed mixture, consisting of C2H4, HCl and O2, is by a highly exothermal catalytic reaction of catalytically converted in the fluidised-bed ethylene with hydrogen chloride and oxygen. reactor to EDC in a highly exothermal reac- tion at a temperature of > 200°C. The heat The reaction takes place in a fluidised- is dissipated via internal cooling coils and bed reactor, and the reaction heat is used recovered to generate steam. Independent for steam generation. In the downstream of load the generated steam has a constant quench column, a major portion of the reac- pressure level. tion water is removed by condensation. To remove small quantities of chlorinated hydro- The excellent distribution in the fluidised-bed carbons from the reaction water, it is trans- makes it possible to maintain a constant tem- ferred to the effluent treatment facilities. perature, to ensure low by-product formation and to achieve optimum process control. By cooling the reaction gases further by means of cooling water (CW) and refrigerant The reaction gas passes a filter unit in (R), the raw EDC is removed by condensation which the catalyst fines are separated from and fed to the EDC distillation unit, where it the gas. Depending on customer's require- is purified to obtain “feed EDC quality”. ments, also a waste water treatment section comprising a precipitation and sludge filtra- The Vinnolit oxychlorination process can tion step can be implemented. To remove use oxygen from air separation units as well the reaction water, the hot reaction gases as oxygen from pressure swing adsorption are quenched and the EDC is condensed units (PSA oxygen). In the reactor the cata- with the aid of chilled water in a multi-stage lyst is fluidised with circulation gas. Just condensation unit. The crude EDC is puri- enough oxygen is added to the reactor to fied in an EDC distillation unit to obtain keep the concentration of the circulation gas “feed EDC quality”. outside the flammable range (oxygen lean operation). The very small off-gas stream The reaction water obtained is passed to of inerts and carbon oxides which is formed the waste water treatment facilities to re- in the process is fed to the HCl recycle unit move the small quantities of chlorinated without further treatment. The reaction hydrocarbons it contains. Refrigerant Waste gas to incineration Steam CW HCl from TDI / MDI possible Hydrogenation Catalyst reactor filtration Boiler feedwater Hydrogen Oxychlorination Hydrogen chloride Quench reactor column Crude EDC Oxygen Circulating-gas Ethylene compressor Effluent to waste water treatment
9 Oxychlorination reactor Erection of oxychlorination reactor BorsodChem Rt., Hungary The modern oxychlorination process of Vinnolit has the following distinctive features: • Fluidised-bed reactor with good reaction heat distribution: no hot spots, no catalyst stickiness • Proven materials and reliable and simple equipment • Reactor and cooling coils made of carbon steel • Crude EDC purity: 99.6 % • High conversion of C2H4 to EDC: 99.0 % • Low catalyst consumption • Removal of catalyst fines either by simple waste water treatment or by catalyst filtration • High flexibility of the plant, wide range of load • Production of 10 bar steam for distillation units possible • High safety standard, O2 content < 1 %
10 2.4 EDC distillation To produce pure feed EDC, both the EDC The dry bottom product from the heads obtained in the oxychlorination process column together with the unconverted EDC and the EDC not converted in the cracking from the cracking process are separated process (recycle EDC) are treated in the EDC from the high-boiling compounds in the distillation unit in order to remove water as high-boil and vacuum columns. These high- well as low-boiling and high-boiling com- boiling compounds are withdrawn from the ponents. bottom of the vacuum column and sent to the incineration unit. The wet raw EDC from the oxychlorination unit is fed to the heads column in order to By default, the high-boil column is oper- remove the water and low-boiling substanc- ated at elevated pressure and the overhead es by distillation. The water phase of the vapours of this column are used to heat head product containing small quantities the heads column and the vacuum column. of chlorinated hydrocarbons and sodium Depending on customer's requirements chloride is transferred to the waste water also other heat recovery options can be treatment unit. The organic phase and the realized. off-gas are fed to the incineration unit. EDC evaporator and cracking furnace Waste gas to incineration Recycle EDC CW from VCM distillation CW CW R Heads column High-boils Vacuum column column Crude EDC from oxychlorination from cracking Steam High-boiling Cond. components to incineration Cracking EDC Low-boiling components to incineration Effluent to waste water treatment
11 2.5 EDC cracking The cracking of 1,2 dichloroethane takes The advantages of Vinnolit’s modern EDC place in a cracking furnace heated by fuel. cracking process can be summarised as VCM and HCl are formed at temperatures of follows: 480°C, the reaction being endothermic and incomplete. • High reliability due to low coke formation • High savings in primary and secondary In addition to VCM and HCl, by-products of energy, due to: various chemical structures and coke are - External EDC pre-evaporation using formed. cracking gas heat The external EDC pre-evaporation facility - Utilisation of flue gas and cracking reduces the formation of coke in the crack- gas heat to preheat combustion air, ing furnace considerably. The operating to generate steam or to preheat EDC periods between two decoking intervals are • Low maintenance costs very long (up to 2 years). • Proven materials and reliable equipment 3D model of one of the world's largest PVC complexes ARVAND Petrochemical Co., Bandar Imam, Iran On the left: The EDC cracking furnaces Capacities of the complex: 570,000 t/year of chlorine 329,000 t/year of sales EDC 343,000 t/year of VCM 340,000 t/year of PVCa Cracking EDC CW HCl Combustion air Cond. Steam to VCM distillation Cracking product to VCM distillation Fuel Fuel Recyle EDC to EDC distillation
12 2.6 VCM distillation The product from the cracking unit consists The Vinnolit EDC distillation unit can do of VCM, HCl, unconverted EDC and by-prod- without a low-boil column for recycle EDC ucts of various chemical structures. with all its related problems. Hydrogen chloride is recovered in the HCl Advantages of the VCM column: column and fed to the oxychlorination unit. • HCl content in VCM < 1 ppm without Vinyl chloride is obtained at the top of the using caustic VCM column. • Long on-stream time of VCM distillation unit, because of no coke carry over from Any traces of HCl are removed from the VCM hot quench system in the HCl stripper. The overhead product of • Vapor feed of HCl stripper overhead the HCl stripper is recycled to the HCl col- product to the HCl column, no conden- umn via a H2O removal unit which removes sation system necessary moisture from the distillation process and • Lower power consumption for HCl con- protects against moisture build-up. densation compared to low pressure HCl column The bottom product of the VCM column, i.e. un-converted EDC, is returned to the Advantages of the recycle EDC chlorination: EDC distillation process after the low-boiling • No separation of low-boiling compounds compounds have been converted by chlo- necessary rination to high-boiling compounds. Thus • Low investment cost in comparison to the difficult and energy-consuming separa- a low-boil column tion of recycle EDC from other low-boiling • Easy operation components is avoided. • No steam consumption • Low maintenance cost HCl to oxychlorination H2O removal CW Refrigerant from Cracking HCl column VCM column HCl stripper quench Cracking unit product Steam Steam Steam CW Cond. Cond. Cond. Heat Product recovery VCM EDC chlorination unit Recycle EDC to EDC distillation Cl2
13 2.7 Measures to recover by-products and to protect the environment HCl recovery unit The treated waste gas complies with all applicable German statutory regulations in force since 3.5.2000, including those con- cerning the concentration of dioxins and furanes (< 0.1 ng TE/m3). The advantages of the HCl recycling process are: • Recovery of hydrogen chloride from the by-products • Optimum utilisation of the input chlorine to produce VCM • Utilisation of the energy content of the by-products in the form of steam • Use of proven technology and materials • Environment-friendly process 2.7.2 Waste water treatment The process effluent from the VCM plant and any splash water are sent to a waste water treatment unit. Chlorinated hydrocar- bons are removed by distillation, hydrogen chloride by neutralisation with caustic soda solution. A copper content of less than 1 ppm is ensured either by dry catalyst filtration in the oxychlorination or by treat- ment of the waste water using flocculation, sedimentation and filtration. The treated effluent, which meets the statu- tory purity requirements, is subsequently fed to a biological treatment unit. The sludge obtained as a waste product is dumped or incinerated. 2.7.1 HCl recycling oxidation process to form CO2, water and with waste gas heat recovery hydrogen chloride. This process operates 2.7.3 Liquid and waste gas collection with an excess of air at approx. 1,150°C. systems In the production of VCM, not only 1,2 dichloro-ethane is produced as a desirable The heat of the hot combustion gases is ex- Liquid EDC and VCM from drains, cleaning of intermediate product, but also further by- ploited to generate steam, and the hydrogen filters, reboilers etc. are collected in closed products, consisting of a mixture of high- chloride is recovered as a valuable feed- systems and returned to the process loop to boiling and low-boiling compounds, are stock which is returned in gaseous form to protect the environment. obtained in liquid or gaseous form. the oxychlorination process. Sources of continuous waste gas streams In a new modified Vinnolit process, these Alternatively, aqueous HCl of 25 to 30% can are connected to waste gas headers and by-products are completely converted in an be produced. the gas is sent to the HCl recovery unit.
14 2.8 Cumulated capacity of reference plants Uhde is one of the world’s leading engineering companies in the fields of EDC and VCM, having built plants with a total capacity of more than 8 million tonnes per year of EDC and approx. 5 million tonnes per year of VCM (see diagram). Cumulated Capacity of EDC & VCM Plants Designed by Uhde 10 9 8 7 6 EDC 5 4 million tonnes per annum 3 VCM 2 1 1970 1980 1990 2000 2010 Year of commissioning
15 The view of Europe's biggest and most modern VCM plant at Vinnolit in Knapsack near Cologne. Capacity: 190,000 t/year of EDC 370,000 t/year of VCM
16 3. The Vinnolit S-PVC process 3D model of one of the world's The suspension polymerisation process Vinnolit technology is characterised by: largest PVC complexes ARVAND Petrochemical Co., for manufacturing polyvinyl chloride is the Bandar Imam, Iran most important way to produce a variety of • Vinnolit‘s proprietary technology for all units general-purpose and highly sophisticated • Clean and closed reactor technology Capacities of the complex: grades of PVC. This process was invented in • High productivity 570,000 t/year of chlorine 1935 and first patented by Wacker Chemie • Low raw materials consumption 329,000 t/year of sales EDC 343,000 t/year of VCM GmbH, one of the former parent companies • Low waste water amount 340,000 t/year of PVC of Vinnolit. Continuous developments had (waste water recovery) been made in recipes, product quality and • Low energy consumption technology. Due to this long experience and • Low investment cost continuous improvements, Vinnolit can offer • Low maintenance cost a modern and highly economic process • High safety level for the production of S-PVC worldwide. A Vinnolit team of specialists is available to • Leading in environmental tailor plant design according to licensee’s protection – DIN ISO 14001 certified requirements. • High product quality – DIN ISO 9001 certified
17 3.1 Description of the S-PVC process Vinyl chloride and hot water are fed to The wet PVC is dried by means of heated Consumption per 1,000kg of PVC the Vinnolit High-Performance Reactor by air in a fluidized bed drier or the Vinnolit powder at the production plant including means of a special charging program. MST Cyclone drier VCM recovery: Vinyl chloride 1,001 kg Once the polymerisation has been completed After drying, the PVC powder is conveyed the content of the reactor is discharged into pneumatically to the silo and bagging unit. Demineralised water 1.4 m3) a blowdown vessel and from here continu- Chemicals 2.5 kg ously fed to the Intensive Degassing System. Consumption figures for raw materials Steam 700 kg4) and energy 3) Without waste water recovery 2.3 m3 The nonconverted monomer is stripped out, 4) Combined figure for VCM and PVC plant: 435 kg condensed and fed back into the process. Low consumption of monomers, demin. water, chemicals and auxiliary materials, This data is based on average values. After degassing and recovery of the latent low energy consumption due to heat re- The consumption values depend on K heat, the water is separated by centrifuge covery, results in low production cost. values, on recipes and location. and the wet PVC leaving the centrifuge is fed into the drying section. A big part of the water Especially, the utilization of hot water gener- from the centrifuge is recovered in a waste ated in the VCM plant for heating of the PVC water recovery unit (for pipe grade) and sent drier yields very low energy consumption in back to the high performance reactors. the PVC plant. CW off-air Recovered VCM VCM Activator Demin. water Centrifuge Dispersing agent Fluidized bed drier Hot water CW Steam Hot water Slurry PVC powder to silo Air Waste water recovery to waste water treatment unit High-performance- Blowdown Pre-degassing Degassing reactor vessel vessel column Polymerisation Degassing Drying
18 3.2 Advantages of the S-PVC process Clean reactor technology • Excellent reproducibility of the process giv- ing extremely consistent product quality Scale-free operation is achieved through • High level of plant safety and reliability the use of reliable lining inhibitors, optimum • Low personnel requirement operating conditions during polymerisation and a reactor designed to suit the require- ments specified. Intensive Degassing System This means: Our own work on the development of an intensive column degassing technology has • High-Performance Reactor resulted in perfect, continuously operating • Clean and closed reactor technology processes with the following conditions: • Heat dissipation remains constant • Extremely low residual VCM content in the PVC slurry and in the PVC products It is therefore not necessary to frequently open the reactor for cleaning purposes. • Gentle degassing conditions • Grade change without opening the Process control system column • Extremely low VCM emissions Polymerisation Reactors The whole plant is controlled with the aid of a digital process control system. Drying The safety concept This results in: In a fluidized bed drier, the PVC is dried The whole safety concept, including its • Precise metering of the individual to the required moisture content. This op- computer process control system, permits components during reactor charging eration can be performed highly economic a particularly high level of operational • High constancy of the present process because of the possible heat integration safety. parameters with the VCM plant. In addition, the polymerisation system is completely safeguarded and can stop the PVC High-Performance Reactor (inside view) reaction under extreme conditions e.g. simultaneous failure of coolant and power supply. Emissions According to Vinnolit’s commitment with regard to environmental protection, the offered S-PVC process sets a new standard. Clean and closed reactor technology, pro- cess automation and effective degassing of product means that VCM emissions are kept at an extremely low level and under normal operating conditions are far lower than the figures required at present: • Less than 1 mg/m3 in drier off-air • Less than 1 mg/m3 in waste water • Less than 2 vol. ppm (shift average value in the air at the workplace). Effective measures keep PVC emissions in the drier off-air to less than 10 mg/m3.
19 3.3 The Vinnolit High-Performance Reactor for suspension PVC Step by step Vinnolit has realised all • High output of up to 600 mt/m3/year requirements for a high-performance poly- - Very short non-reaction time merisation reactor. The inner cooler reactor - Very short reaction time was developed as a last link in the optimi- • High quality of product grades sation. This completely new reactor design - Use of the Vinnolit recipes has been created and improved by Vinnolit - Wide range of licensed grades engineers. The inner cooler reactor has - Heat dissipation only in the liquid phase demonstrated its outstanding suitability for as in a conventional reactor the production of suspension PVC on an industrial scale for many years and is there- • Large reactor Volumes of up to 160 m3 fore a proven design. ensuring - Low investment costs In view of Vinnolit’s inner cooler reactor, the - Low maintenance costs choice was made for a combination of: • Large heat transfer area and high heat- • Increased heat transfer area due to the transition coefficient, providing a cooling half-pipe coil on the inner reactor wall capacity twice that of a conventional reac- tor; therefore no additional cooling area • Improved heat-transition coefficient due (such as a reflux condenser) is required to the reduced thickness of the half-pipe coil • Very simple and safe operation • Increased heat transfer due to higher - Closed and clean reactor technology: The requirements of a modern high-perfor- turbulences at the wall. using the Vinnolit anti-fouling tech- mance polymerisation reactor with a high nology dispenses with high-pressure productivity: cleaning or reactor opening This design combines high heat transfer • Short non-reaction time rate with safe operation in a closed mode. - Automatic catalyst charging to be reached by: Of course the other internal components - Simultaneous charging of hot water - Closed and clean reactor technology of the inner cooler reactor like the agitator, and VCM - Efficient anti-fouling technology baffles and nozzles are optimised as well to - No heating up by means of a heating - No reactor opening apply the reactor technology in the same jacket - No high-pressure cleaning way as in Vinnolit’s conventional reactors. • Low operating costs because of - No heating up of the batch - Adapted recipes - Optimised charging procedure, i.e. The essential advantages of the Vinnolit - Use of cooling water instead of chilled simultaneous hot water/VCM charging High-Performance Reactor are: water - Automatic catalyst charging • Minimal reaction time to be reached by: Heat transfer graph (typical) Heat transfer graph (typical) of conventional reactor cooling of Vinnolit’s High-Performance Reactor - Fast reaction-heat dissipation - Large reactor technology - Volumes up to 160 m3 - Adapted recipes To achieve a minimal reaction time, the A Cooling channel reaction heat has to be dissipated out of the reactor quickly. B Cladded steel wall • by increasing the heat transfer area by C PVC-suspension arrangement of half pipe coils inside D Half-pipe wall • by increasing the differential temperature E Cooling coil between inside reactor and jacket, e.g. Suspension using chilled water • by improving the heat-transition coef- ficient, e.g. using a thinner wall between A B C D E inside reactor and cooling water • by adding an external condenser
20 3.4 Waste Water Recycling Ultrafiltration unit for waste water in an S-PVC plant Description Suspension PVC is produced in an aque- content. But today the required purity can and is recycled into the polymerization pro- ous process. Approx. 2.3 m3 of precious be achieved by a tailor-made special filtra- cess in order to reduce the consumption of water are used in a conventional process tion process. fresh de-mineralized water and at the same per ton of PVC. Up to now this water could time the amount of waste water. The flux only be used for flushing purposes, but the Ultrafiltration through the membranes can be preserved demand for flush water in the downstream on an acceptable level by regular cleaning units is small compared with the water de- Ultrafiltration is employed to remove any operations for at least 1 year. mand for polymerisation. So the water is solids from the decantation waste water. usually after treatment in a biological waste Ceramic membranes compatible with the Features water treatment discharged to a recipient. other ingredients in the waste water are used in that process. The PVC contami- • Reduction of fresh water consumption Re-use of the waste water in the poly- nated waste water from the decantation to approx. 1.4 m3/t PVC (pipe grade) merisation was so far inhibited by quality centrifuge is treated in the special filtration • Reduction of waste water problems caused by the residual PVC solid unit. The treated water is free of PVC solids • Proven in production scale for pipe grade Re-use of waste water in the suspension PVC process Thermal PVC solid Drying PVC H20 vapor VC Recycling VC Poly- Centrifuge PVC Additives merisation Drying PVC separation H 20 H 20 Reuse