ATTACHMENT 1 

Generic Flow Diagrams for PVC Production 
 06/25/08 Fig 1. Suspension and Dispersion Processes Flow Diagram 

SD1

VC 

Storage 

Unloading 

Holding Tank 

Weighing 

Tank 

Polymerization 

Reactor 

Polymer 

Stripping 

Vessel 

Knock-out 

Pot 

VC Recovery 

System 

Blend Tanks 

Cyclone & or Drying 

Screening 

PVC Storage 

& Shipping 

Process Steps

SD1. VC Unloading and Storage SD2. Mixing, Weighing and Holding SD3. Polymerization Reaction SD4. Resin Stripping SD5. Recovery System SD6. Blending SD7. Drying SD8. PVC Storage SD9. “In Process” Wastewater Stripping SD10. Control Device System (e.g. Incinerator) 

To 

Wastewater 

Stripper 

Centrifuge 

To W

Nat. 

“In Process” wastewater 

1) H2O from Double Mechanical Seals 

on all Pumps, Compressors and Agitators 

2) H2O from Reactor Evacuating Prior 

to Opening 

3) Knock-Out Pots 

“In Process” Wastewater 

Stea

SD6

SD3

SD2 SD5

SD7

SD10

SD4

SD9

SD8
06/25/08 Fig 2. Bulk Process Flow Diagram

B1

VC 

Storage 

Unloading 

Holding Tank 

Weighing 

Tank 

PrePolymerization 

Reactor 

PostPolymerization 

Reactor 

Knock-out 

Pot 

VC Recovery 

System 

Blend Tanks 

PVC Storage 

& Shipping 

Process Steps

B1. VC Unloading and Storage B2. Mixing, Weighing and Holding B3. Pre-Polymerization Reaction B4. Post-Polymerization B5. Recovery System B6. Blending and Screening B7. “In Process” Wastewater Stripping B8. PVC Storage B9. Control Device System (e.g. Incinerator) 

To 

Wastewater 

Stripper 

Nat. 

“In Process” wastewater 

4) H2O from Double Mechanical Seals 

on all Pumps 

5) Condensed Steam from Reactor 

Evacuating Prior to Opening 

6) Condensed steam from Polymer 

Stripping 

“In Process” Wastewater 

To 

Stea

B6 

B7

B9

B4

B8

B3

B2 SD5

Reflux Condenser 

Course 

Screening 

Fine 
Attachment 2 

1

06/25/08 

Production of Polyvinyl Chloride: Process Description 

Note: The majority of the information represented in this document is taken from EPA’s February 1982 

document entitled: Vinyl Chloride- A Review of National Emission Standards (EPA-450/3-82-003). 

Where necessary, minor changes were made to represent current operations. 

In the United States, four polymerization processes are being used currently to manufacture PVC 

resins: 

1. Suspension 

2. Dispersion (emulsion) 

3. Bulk (mass); and, 

4. Solution. 

Figure 1 in Attachment 1 shows a generic flow diagram for PVC production by the suspension and 

dispersion processes. The process steps, which are numbered, are described below. The potential 

emission points for each of the process steps shown in Figure 1 are listed in Table 1 along with a 

summary of VCM NESHAP requirements for control of emissions. 

Figure 2 shows a generic flow diagram for PVC production by the bulk process. The potential 

emission points for each of the process steps shown in Figure 2 are listed in Table 2 along with a 

summary of VCM NESHAP requirements for control of emissions. 

Note that it is the Vinyl Institute’s understanding that Dow, Freeport, TX operates the only solution 

PVC production process in the United States. Dow, the only US PVC producer who is not a Vinyl 

Institute member, has been contacted and information has been shared. 

Many companies have licensed some phase of their particular process such as stripping technology 

or clean reactor technology. The licensing of these process phases has evolved from the intensive 

research work done to reduce residual vinyl chloride monomer (RVCM) levels in finished resins, limit 

worker exposure, and reduce emissions to the atmosphere. 

After polymerization, VCM may be present in any of three forms in the polymerization reactor 

depending on the particular process. VCM will always be present separately as a gas or liquid in the 

reactor and will also be trapped within the newly formed polymer resin. In the suspension, dispersion, 

and solution processes, VCM will be trapped in the process water. 

The resins produced by a process are categorized as to the “type” of resins. Those processes 

responsible for more than one variation of their type of resin are further subdivided into “grades.” The 

resin grade is developed to allow compounding and fabrication to yield the desired product. 

 

A plant manufacturing polymers containing any amount of polymerized VCM is subject to the current 

VCM NESHAP at 40 CFR Part 61 Subpart F. 

Free Radical Polymerization

Polymerization is the chemistry of combining simple molecules (monomers) into long chains of 

repeating molecular units (polymers). There are two types of polymerization – addition and 

condensation. PVC resins are commercially produced by addition polymerization and, in general, 

polymerization is induced by the use of free radical initiators (Nass, 1977, p. 34). Thermal 

decomposition of the initiator, which is combined with the VCM and other constituents in the 

polymerization reactor, yields free radical molecules having one unshared electron. This free radical 

reacts with additional VCM molecules by removing an electron from the VCM double covalent bond 
Attachment 2 

2

and sharing an electron with the free radical. The remaining unshared electron moves along the 

chain becoming the new radical bond site. Another VCM molecule may then become a part of the 

polymer chain by reacting with the polymer radical. 

Radicals are transferred from the polymer by a reaction with the VCM to yield a polymer and a free 

radical. The transfer reaction increases with increasing temperature. This characteristic of the 

reaction kinetics allows a desired molecular weight to be obtained by controlling reaction temperature 

(Cameron, 1979, pg 39). Radicals are also transferred by reacting with hydrogen atoms obtained 

from VCM or solvent in the reactor. Another way of transferring radical sites from the growing 

polymer chain is by using chain transfer agents (CTA). These CTAs are used to regulate the 

molecular weight of the polymer to a desired level. In all transfer reactions, the radical is released and 

able to initiate another polymerization reaction. The reaction is terminated when two polymers with 

radical sites are combined. Polymerization rate is controlled by choice of the appropriate initiator. 

The polymerization reaction is exothermic and the reaction rate must not be allowed to accelerate to 

the extent that the heat of reaction cannot be removed by reactor control devices. Reaction rates 

tend to increase as the temperature increases. If the heat of reaction is not removed, a runaway 

reaction can develop and the rapid increase in temperature will increase the pressure inside the 

reactor vessel beyond safe limits. 

The monomer structure of VCM is capable of several variations in chain structure, but free radical 

polymerizations generally produce atactic structures, (random orientation of monomer unit in the chain 

structure) (Nass, 1977, p. 46). Tendency towards syndiotactic structure (regular alternating 

orientation of the monomer unit in the chain structure) and crystallinity are both increased by reduced 

polymerization temperatures. 

Suspension Polymerization

Process Step SD1: Unloading at PVC Plant Sites 

Under the current VCM NESHAP, VCM emissions from loading and unloading lines, which are 

opened to the atmosphere, must be reduced in the opened lines to 0.0038 cubic meters (0.13 cubic 

feet) or less at standard temperature and pressure (STP). Also, the VCM removed from loading and 

unloading lines in order to meet this requirement of the VCM NESHAP must be vented to a control 

device system from which the concentration of VCM in the exhaust gas does not exceed 10 ppm. 

When PVC plants are not located close enough to receive VCM by pipeline, it is shipped by railcar, 

tank car, barge, or marine vessels. 

The VCM is normally unloaded at PVC plants by displacement. This is accomplished by pumping 

vapor from storage tanks into the transfer vessel which displaces the liquid VCM from the transport 

vessel through the unloading line. When the liquid VCM is displaced, the compressor line is reversed 

and used as suction to evacuate remaining liquids as vapor. The remaining liquid VCM is allowed to 

boil during tank car evacuation for its removal as a gas. This vaporization of the VCM usually takes 

20 to 30 minutes (Mukerji, 1977, p. 155). Lines between tank car compressor and storage tank can 

be switched without disconnection by incorporating a 4-way valve in the pumping lines. 

Instrumentation of the system usually incorporates a turbine meter, a flow totalizer to measure the 

VCM flowrate and quantities unloaded, and storage tank level indicators. 

Unloading and transfer lines may be purged with nitrogen to reduce VCM to the required level before 

disconnection of the unloading lines. In some cases, the portion of the unloading line which is opened 

to the atmosphere has been reduced to diminish the amount of VCM that will escape to the levels 

below those required by the VCM NESHAP. 

Unloading of relatively small amounts of additive materials can involve various containers, such as 

drums or totes. 
Attachment 2 

3

Process Step SD2: Mixing, Weighting and Holding Vessels 

Storage spheres, storage tanks, gasholders, wastewater storage tanks, knockout pots, and surge 

tanks are representative of vessels covered under sections 61.64(c) of the VCM NESHAP for mixing, 

weighing, and holding vessels. These vessels are used to hold liquid or gaseous VCM and PVC 

slurry during various stages of the PVC process. Some of these vessels were open to the 

atmosphere prior to promulgation of the VCM NESHAPs, but have since been enclosed and are 

usually ducted to the recovery system and/or the primary control device. The number and types of 

vessels will vary from plant to plant depending on the size and type of process used to produce the 

PVC resin. The majority of small additive tanks or totes are open to atmosphere, but emissions are 

minor and/or may be exempt from control under other Maximum Achievable Control Technology 

(MACT) Standards, such as the Organic Liquids Distribution MACT. 

Section 61.64(c) of the VCM NESHAP requires the concentration of VCM in all exhaust gases 

discharged to the atmosphere from mixing, weighing, and holding containers “in VCM Service” not to 

exceed 10 ppm. Any piece of equipment that contains or contacts a fluid that is 10 percent by weight, 

VCM, or gas that is at least 10% by volume, is considered “in VCM Service.” There are no 

requirements in the VCM NESHAP for mixing, weighing or holding containers used in the process 

after the stripping of the PVC resins providing resin stripping is used. This not unlike the recently 

promulgated Miscellaneous Organic NESHAP (MON) regulation (see MON’s definition of 

Miscellaneous organic chemical manufacturing process at 40 CFR 63.2550). 

Process Step SD3: Suspension Polymerization 

The suspension process for producing PVC resins (see Figure 1) is characterized by the formation of 

polymers in droplets of the liquid VCM (or other co-monomers) suspended in water. These droplets 

are formed by agitation and the use of protective colloids or suspending agents. Protective colloids 

commonly used are water-soluble polymers such as modified cellulose or partially hydrolyzed 

polyvinyl acetate. The process is started by evacuating the polymerization reactor to remove oxygen 

and other contaminants that may inhibit the reactor initiator. Water and VCM may be simultaneously 

added to the reactor with the protective colloids, or they may be added separately (water and colloids 

first, followed by the liquid monomer). The water used is deionized and deaerated in order not to 

inhibit free radical initiator formation. Water and other ingredients charged to the reactors must be 

carefully measured prior to charging. In some cases the reactor is on a scale and the amount of 

material charged is weighed in the reactor. More often, a separate weigh tank is used to measure 

materials charged to the reactor. A flow meter can be used to record the amount of water added. 

Reactor operators manually charge additives that are used in small proportions. The initiator is 

usually the last ingredient charged to the reactor. Initiators commonly used in the suspensions 

process are peresters, peroxycarbonates, peroxides, or azo compounds. The initiators are soluble in 

VCM and allow formation of PVC in the monomer droplets. Some initiators have low levels of 

impurities and can produce low levels of decomposition products. 

After all the materials are in the reactor, the batch is brought up to reaction temperature by passing 

steam through the reactor jackets which allows free radical initiators to be formed. Reaction 

temperatures are varied in order to produce a resin grade of a particular molecular weight. Once 

polymerization is initiated, the reaction becomes exothermic and cooling water must be circulated 

through the reactor jacket to remove heat of reaction. In some instances reflux condensers have also 

been used to control reaction temperature and remove excess heat. 

After approximately 6 hours in the reactor, the batch temperature and pressure drop. This signifies 

that nearly all the VCM has reacted (75% to 90% of the VCM usually reacts) and the remaining or 

residual VCM (RVCM), which is in the liquid or gaseous state or trapped in the resin particles, must be 

stripped. This RVCM is usually stripped with steam under vacuum. The suspension process yields a 
Attachment 2 

4

particle size distribution of a much wider range than other polymerization processes. Particle size 

may range from 90 micrometers to 130 micrometers (0.0035 inches to 0.0050 inches) with low to 

medium molecular weights. 

Process Step SD4: Resin Stripping 

The VCM NESHAP requires that RVCM levels for suspension resins not exceed 400 ppm of the PVC 

product. PVC resin, unreacted VCM (in the water, in the headspace, and trapped in the resin) and 

water are the constituents remaining in the reactor after polymerization. This polymer slurry may be 

steam-stripped of RVCM batch wise in the reactor or is a separate vessel. B. F. Goodrich has 

developed a continuous stripping operation which strips the resin with steam running countercurrent 

to the PVC slurry. Most plants strip batch wise with steam in separate vessels or in the continuous 

stripping column. In all cases, water accompanying the PVC product is stripped with the slurry and 

then removed by centrifugation. 

Batch stripping procedures use temperatures up to 87 deg. C (190 deg. F) and a vacuum of 91 

kilopascals (27 inches of mercury) or more (Nass, 1977, pg 83). Heat is applied by steam injected 

directly into the batch or by steam passed through the reactor wall jackets. If stripping is used to meet 

RVCM levels, any downstream processes or equipment (e.g., water treatment, vents from mixing 

tanks, centrifuges, dryers, etc.) are not required to meet any other requirements of the VCM NESHAP. 

Process Step SD6: Blending 

After stripping, the batch is transferred to blend tanks which mix the batch with other batches to 

ensure product uniformity. The mixed batches are then fed to a continuous centrifuging operation that 

separates the polymer from the water in the slurry. Both mixing tanks and centrifuges are vented to 

the atmosphere if stripping is utilized. The water from centrifuging is not required to be stripped of 

VCM because most of the VCM is removed during resin stripping. Therefore, the centrifuge water is 

recycled back to the process or discharged to the plant’s wastewater treatment system. 

Process Step SD7: Drying 

The wet cake from centrifuging is conveyed to a rotary dryer for further removal of the remaining 

(usually 25 percent) moisture (Nass, 1977, p 83). Most of the RVCM not removed during stripping will 

be released during the drying operation. Counter-current air temperatures in the dryer range from 65 

deg. C to 100 deg. C (150 deg. F to 201 deg. F). Drying time is generally short, but large volumes of 

air containing RVCM are released. 

Process Step SD8: PVC Storage 

After drying, the resin may be screened to remove agglomerates. The resin is then bagged or stored 

in silos for bulk shipment by trucks or rail car. Uniformity of suspension resin batches is dependant on 

control of variable such as: 

 Impurities (noncondensable gases present in the reactor prior to polymerization or impurities in 

raw materials charged to the reactor), 

 Rate of temperature increase to reaction temperature, 

 Agitation speed and schedule (speed varies as the slurry becomes more dense), 

 Charging rate of raw materials, and 

 Temperature of raw materials charged. 

In some of the newer PVC facilities, these variables are closely monitored by level of computer 

control. In the older plants, many variables such as cooling water flow rates, pump operation, agitator 

motors, temperature, and pressure are monitored and controlled manually from the control room 

panel or at the reactor. More versatility is possible with computer assistance. A reactor linked to 

computerized control elements can produce different grades of resin by using programs designed to 

yield specific reactor conditions (e.g., agitation, temperature, amount, and type of materials charged) 
Attachment 2 

5

that will produce the desired resin product. Computers can also monitor operating conditions and 

respond to emergencies (such as high pressure in the reactor). They can be programmed to take 

necessary action to bring an upset condition under control (e.g., choosing the best compensatory 

action.) 

The use of large reactor systems has increased quality control and allowed incorporation of 

equipment and procedures that reduce VCM emissions. Large reactors, approximately 8,000 gallons 

(30 cubic meters) and up, offer lower plant cost, improved product uniformity, and increased 

productivity. However, certain PVC units utilize smaller reactors. 

Process Step SD9: “In Process” Wastewater 

Water used in the PVC process can become contaminated with VCM and be a source of secondary 

emissions if not contained and controlled. Even though the requirements of the VCM NESHAP for 

fugitive emission controls (equipment specifications, operational procedures and leak detection and 

elimination programs) are not applicable to inprocess wastewater, it is still categorized as a fugitive 

emissions source. The VCM NESHAP requires the concentration of VCM in each wastewater stream 

containing greater than 10 ppm VCM measured immediately as it leaves a piece of equipment, and 

before being mixed with other wastewater, be reduced to 10 ppm VCM or less. This concentration in 

the water must be attained prior to mixing with other inprocess wastewater containing 10 ppm or less 

VCM, before being discharged to a wastewater treatment process or plant, or before being discharged 

untreated to a body of water. 

There are several sources of inprocess wastewater in PVC plants. VCM contaminated inprocess 

wastewater is generated from the following sources: 

 Water used to evacuate reactors prior to opening in order to meet reactor opening loss 

(ROL) requirements; 

 Water used as sealing fluid for double mechanical seals on pumps, compressors and 

agitators; 

 Water removed by knock-out pots used in the monomer recovery system; and, 

 Water used to seal gasholders. 

Depending on the methods used to attain the ROL requirement, large quantities of inprocess 

wastewater can be generated. 

Inprocess wastewater from ROL methods, seals, and knock-out pots is usually collected in a vessel 

and then steam stripped of VCM. Water used to seal gasholders is in contact with VCM contaminated 

gases and by definition is an inprocess wastewater. This water is always exposed to atmosphere 

without treatment. Actual VCM concentrations of this seal water are generally not available, but for 

one plant using a water-sealed gasholder, emissions to the atmosphere from the seal were calculated 

to be approximately 0.79 kilograms (1.75 pounds) per year (Battye, 1978). 

Removal of VCM dissolved in water is usually accomplished by a distillation column. The water 

collected by fugitive emission sources, and usually held in a vessel prior to the column, is close to 

saturation. Thus, separation in the stripping column is simple because the vapor pressure of VCM is 

much greater than water. 

Process Step SD10: Control Device 

Most of the requirements of the VCM NESHAP pertain to PVC plants because these facilities 

contribute proportionality more emissions than VCM plants. The characteristics inherent in the batch 

processes of PVC plants account for the relative difficulty in emission control implementation. 
Attachment 2 

6

Control devices, applied to reduce VCM emissions when exhaust gases are discharged to the 

atmosphere, include: 

Incineration – This method represents the most prevalent means of primary control and is the only 

method used by both VCM and PVC plants (collocated). (Solvent absorption and carbon adsorption 

are also used as primary controls in PVC plants, but in VCM plants they are used on a smaller scale 

as part of the process or as a means to reduce fugitives). 

Although thermal incineration is most commonly used, in the past, two plants used catalytic oxidation 

systems. At least one of those plants has been shutdown. In most cases, thermal incineration is 

reducing emissions below the required 10 ppm. Most units have scrubbers to prevent HCl emissions. 

Solvent Absorption – This method is effective in reducing emissions below 10 ppm. It is used as 

primary control only in PVC plants. VCM is recovered by this method, rather than destroyed (as with 

incineration). 

Dispersion Polymerization

The Process Steps for dispersion resins are similar to those of suspension resins. 

Although dispersion (emulsion) resins are formed in reactors similar to those used for suspension type 

resins, reaction kinetics of polymer formation vary greatly. In general, dispersion resins are of a high 

density with small particle size. The process is initiated by charging the necessary ingredients (water, 

liquid, VCM, emulsifiers, and a free radical initiator) to an evacuated reactor. Proportions of these 

ingredients and other minor additives will vary depending on the type of resin and the resin grade. 

Emulsifiers (soaps and surfactants) are used to disperse VCM in the water phase. Soap micelles 

(i.e., colloidal aggregates that are formed above a critical emulsifier concentration) also contain small 

amounts of VCM and are the site of polymer formation. Initiators used are water soluble (versus VCM 

soluble initiators used in suspension polymerization) and penetrate soap micelles to begin 

polymerization. Commonly used initiators are hydrogen peroxide, organic peroxide, and 

peroxydisulfates. 

Two general types of resins are produced by the dispersion process- latex and dispersion. If the latex 

type resin is to be produced, only a small amount of VCM and initiator are normally charged. The 

reactor is heated by injecting steam into the reactor jackets to initiate formation of free radicals. 

Agitation is used to disperse the monomer and other ingredients in the water medium. Once 

polymerization begins, the heat of reaction is removed by circulation of cooling water through the 

reactor jackets. Small amounts of initiator and monomer are then continuously added during 

polymerization until the correct particle size is attained. Conversion of VCM to latex polymer is almost 

complete. Latex resin particle sizes range from 0.05 micrometer to 2 micrometers. 

The residual VCM is removed from the latex resins by completely reacting the free VCM with 

additional catalyst (post-catalysis). This is done in the reactor or in a separate vessel. The VCM 

NESHAP requires that latex resins be stripped to 400 ppm RVCM. Latex resins are usually sold in 

solution, and drying or separation of resin from the polymer slurry is not necessary. 

The process for formation of dispersion type resins follows that described for latex except that some 

monomer is added to allow particles to grow to a larger size. In some cases the process may call for 

“seed” latex. The “seed” latex is formed by starting a batch in a separate reactor. Before this batch 

reaches 60 percent conversion it is transferred to other reactors with more VCM and emulsifiers. This 

allows formation of larger emulsion particles which are used in plastisol and stir-in resins. These 

dispersion type resins range from 0.2 micrometers to 5 micrometers in particle size and are more 

sensitive to heat and mechanical agitation than suspension resins. Because the dispersion resins are 
Attachment 2 

7

more sensitive, stripping the resin may take longer because lower stripping temperatures are used. 

The VCM NESHAP requires that dispersion type resins be stripped to 2,000 ppm RVCM. 

After polymerization is complete, the dispersion resins are usually spray dried. Spray-dried resins 

contain emulsifiers that inhibit the absorption of plasticizers. In many applications where heat is 

applied during fabrication, this property is acceptable because the heat melts the resins which allows 

plasticizer absorption. In some fabrication processes (such as calendaring), plasticizers must be 

absorbed prior to fabrication because temperatures used are not high enough to melt the resin. If 

removal of the soaps from the dispersion resin is desired, coagulation of emulsifiers with salts is 

usually performed. The salts (calcium or magnesium) are added to the polymer slurry and the 

emulsifiers precipitate and are rinsed out with water. The resin and water are then separated and the 

resin is dried in a rotary or pan dryer (Erdman, 1980). 

Bulk Polymerization

The following Process Steps for bulk resins are similar to those of suspension and dispersion resins: 

B1: Unloading at PVC Plant Sites 

B2: Mixing, Weighing and Holding Vessels 

B5: Recovery System 

B7: “In Process” Wastewater Stripping 

B8: PVC Storage 

B9: Control Device 

Bulk (mass) polymer resins are produced by a two-stage polymerization process. A simple diagram 

of the bulk process is shown in Figure 2 and requirements of the VCM NESHAP for bulk plants are 

summarized in Table 2. The first stage is the formation of a “seed” resin in a vertical prepolymerization (Pre-Po) reactor. The “seed” resin is transferred to a horizontal post-polymerization 

(Po-Po) reactor in the second stage of the process. More VCM is added to the Po-Po which allows 

the “seed” resin to grow in size to the finished resin product. The bulk process differs from the 

dispersion process in that no water is used in the reaction – the process is anhydrous. The bulk 

process used in this country is licensed by Rhone-Poulenc of France. A new version of the RhonePoulenc process utilizing a vertical Po-Po reactor is now available, but is not currently being used in 

the United States. 

Process Step B3. Pre-Polymerization 

The Pre-Po reactor is charged with liquid VCM and enough initiator to carry the reaction to 

approximately seven to twelve percent conversion. Initiators used are those commonly used in the 

suspension process – an oil soluble, free radical catalyst (Nass, 1977). The Pre-Po reactor is brought 

to an operating temperature of 40°C to 70°C (130°F to 184°F) by injecting steam into the reactor 

jackets. Strong agitation is used to form small particles of approximately 1 micrometer (Nass, 1977, 

p. 75). These small particles provide the “seed” that grows in size to form resin beads in the Po-Po 

reactor. The remaining liquid VCM and seed resin are pumped to the Po-Po reactor at approximately 

7 to 12 percent conversion. 

Total cycle time for the Pre-Po is 2 hours (Dubec, 1980) which is normally one-fifth the duration of the 

Po-Po cycle. Thus one Pre-Po reactor can be used to feed as many as six Po-Po reactors. 

Process Step B4. Post-Polymerization

After the “seed” polymer and remaining liquid VCM is pumped from the Pre-Po to the Po-Po, more 

VCM and initiator are added to the Po-Po for completion of the reaction. Small amounts of additional 

additives may be charged to the reactor for heat stability and particle size control (Dubec, 1980). The 

number of PVC particles in the Po-Po is determined by the amount of seed resin charged from the 
Attachment 2 

8

Pre-Po. The “seed” resin absorbs the VCM and at about 20 percent conversion the batch becomes 

solid and powdery, thus the agitator in the Po-Po must be of rugged construction. When the 

conversion to PVC has reached 70 percent to 90 percent, the jacket is heated with steam and a 

vacuum is pulled on the reactor to remove RVCM from the PVC resin particles. This represents the 

bulk stripping procedure that takes place in the Po-Po reactor. Exhaust gases from this stripping 

procedure are vented to recovery and the primary control so that VCM emissions do not exceed 10 

ppm. VCM recovered from the reactors is sent back to the charge tank for reuse. The VCM NESHAP 

requires bulk resins be stripped to 400 ppm RVCM as determined on a dry solids basis. 

In producing PVC resins by the bulk process, temperature is the major control variable for determining 

the molecular weight of the polymer. One disadvantage of the bulk process is that there is not a good 

medium for heat transfer from the polymer reaction to the reactor wall. Reflux condensers are used to 

help control the reactor vessel temperature. The condensers remove gas from the reactor 

headspace, condense the gas, and then return the liquid VCM to the reactor. Heat from the gas is 

removed by cooling water in the reflux condensers. 

The Po-Po is opened monthly for cleaning. 

Process Step B6: Blending 

VCM concentrations that are emitted when the Po-Po reactor is opened may be determined by actual 

measurement or by calculation as approved by the Administrator. Polymer removed from the Po-Po 

reactor (already dry) is pneumatically conveyed to screens that remove oversize particles. Batches 

may be blended to improve product uniformity. 

Bulk resins range in size from 0.1 to 1.0 micrometers and exhibit excellent qualities for dry-blending 

compounds. The beads are of uniform size and porosity which allows uniform adsorption of 

plasticizer. Also, because suspending agents and surfactants are not used, the finished resin has a 

higher purity and therefore better heat stability than suspension or dispersion resins (Nass, 1977, p. 

75). 
Attachment 2 

9

Table 1: 

Point Source Emissions Typical Of Suspension And Dispersion PVC Plants 

Process Step Potential Emission Points VCM NESHAP Requirements 

SD1 VCM Unloading 

and Storage 

Loading lines, VCM Storage Tank Emissions from loading lines must be 

reduced so that upon opening of line to the 

atmosphere emissions do not exceed 

0.0038m3

 of VCM at Standard Temperature 

and Pressure (STP) 

VCM removed from lines to meet this 

criteria must be controlled to < 10 ppm upon 

exhaust to the atmosphere. Concentration 

of exhaust gases discharged to the 

atmosphere from storage tanks must not 

exceed 10 ppm. 

SD2 Mixing, weighing 

and holding tanks 

before stripping 

operation 

Mixing, weighing and holding tank 

vents 

Concentration of VCM exhaust gases 

discharged to the atmosphere must not 

exceed 10 ppm 

SD3 Polymerization Polymerization reactor opening 

loss (ROL) 

Polymerization reactor relief valve 

discharges 

Polymerization reactor rupture 

disc discharge 

ROL from each reactor is not to exceed 

0.02 g VCM/kg PVC product 

No discharge to the atmosphere except for 

an emergency relief discharge 

Concentration of the VCM exhaust gases 

discharged to the atmosphere must not 

exceed 10 ppm. Not required to be 

reported. 

SD4 Stripping Stripping vessel vent Concentration of VCM exhaust gases 

discarded to the atmosphere must not 

exceed 10 ppm. 

SD5 Monomer recovery 

system 

Recovery system exhaust vent 

knock-out pot 

Concentration of VCM exhaust gases 

discharged to the atmosphere must not 

exceed 10 ppm. 

SD6 Blending (mixing, 

weighing and 

holding tanks after 

stripping operation) 

Slurry blend tanks and holding 

tank vents 

Not regulated under the VCM NESHAP if 

the PVC Unit is using stripping to control 

VCM emissions. 

SD7 Drying, sizing, 

screening of 

dewatered resin 

Centrifuge vents, dryer vent 

stacks, storage silos, baghouse 

vents, screening operation vents 

Not regulated under the VCM NESHAP if 

the PVC Unit is using stripping to control 

VCM emissions. 

SD8 PVC loading and 

storage 

Storage silos Not regulated under the VCM NESHAP if 

the PVC Unit is using stripping to control 

VCM emissions. 

SD9 “In process” 

wastewater stripper 

Wastewater storage tank and 

wastewater stripper column 

VCM removed from “In process“ water is 

ducted to a control system from which the 

concentration of VCM in exhaust gas does 

not exceed 10 ppm. 

SD10 Control Device 

System 

Incinerator, carbon adsorber, 

and/or scrubber 

VCM emissions must be reduced to 10 

ppm. 
Attachment 2 

10

Table 2: 

Point Source Emissions Typical of Bulk PVC Plants 

Process Step Potential Emission Points VCM NESHAP Requirements 

B1 VCM Unloading and 

storage 

Loading lines, VCM storage tank Emissions from loading lines must be 

reduced so that upon opening of line 

to the atmosphere emissions do not 

exceed 0.0038 m3 of VCM at STP. 

B2 Mixing, weighing and 

holding tanks before 

stripping operation 

Mixing, weighing and holding tank 

vents 

Concentration of VCM exhaust gases 

discharged to the atmosphere must 

not exceed 10 ppm. 

B3 Pre-polymerization Polymerization reactor opening 

loss (ROL) 

Polymer reactor relief valve 

discharges 

Polymerization reactor rupture 

disc discharges 

ROL from each reactor is not to 

exceed 0.02 g VCM/kg PVC products. 

No discharge to the atmosphere 

except for an emergency relief 

discharge 

Concentration of VCM exhaust gases 

discharged to atmosphere must not 

exceed 10 ppm. Not required to be 

reported. 

B4 Post-polymerization 

(stripping in reactor) 

Polymerization reactor opening 

loss (ROL) 

Polymerization reactor relief valve 

discharges 

Polymerization reactor rupture 

disc discharges 

ROL from each reactor is not to 

exceed 0.02 g VCM/kg PVC products. 

No discharge to the atmosphere 

except for an emergency relief 

discharge. 

Concentration of VCM exhaust gases 

discharged to atmosphere must not 

exceed 10 ppm. Not required to be 

reported. 

B5 Monomer recovery 

system 

Recovery system exhaust vent 

knock-out pot 

Concentration of VCM exhaust gases 

discharged to atmosphere must not 

exceed 10 ppm. 

B6 Blending (mixing, 

weighing and holding 

tanks after stripping 

operation) 

Dry resin blend tanks and 

screening operation baghouse 

vents 

Not regulated under the VCM 

NESHAP if the PVC Unit is using 

stripping to control VCM emissions. 

B7 “In-process” 

wastewater stripper 

Wastewater storage tank 

Wastewater stripper column 

VCM removed from in process water 

is to be ducted to a control system 

from which concentration of VCM in 

exhaust gas does not exceed 10 ppm.

B8 PVC loading and 

storage 

Storage silos Not regulated under the VCM 

NESHAP if the PVC Unit is using 

stripping to control VCM emissions. 

B9 Control Device 

system 

Incinerator, carbon adsorber, 

and/or scrubber 

VCM emissions must be reduced to 

10 ppm. 
Vinyl Institute, Inc.

(Lb/hr) (T/Y) (Lb / mmLb PVC)

SD7

Dryer Scrubber, Centrifuge 

Vent, fugitive emissions from 

additive

0.007 - 1.30 0.03 - 33.28 0.06 - 39.38 1, 2, 3, 4: LDAR 

monitoring

SD2, SD6, SD7, 

SD9

Additive Make-up tanks, Blend 

Tank Vents, Centrifuge and 

Dryer Stacks, WW Treatment 

Plant

0.057 - 1.38 0.092 - 35.42 0.50 - 39.38 2, 3

SD1-10

Incinerator; Dryer & Centrifuge 

Vents and Wastewater 

Treatment Plant; VCM Railcar 

Disconnect & Area fugitive 

emissions, ROL, EOL; Blend 

Tanks Vent emissions; PVC 

Silo Storage emissions; 

Wastewater Emissions

7.49E-09 - 

0.53 1.48E-07 - 2.32 1.48E-07 - 3.40 1, 2, 3, 4: lab data / modeling

SD7, 9, 10

Dryer & Centrifuge Vents; 

Wastewater Treatment Plant; 

Cooling Tower; Fugitives; 

Incinerator

< Limit of 

Detection - 

0.13

< Limit of 

Detection - 

0.57

< Limit of Detection - 

1.08 1, 2, 4: lab data

SD1-10

Incinerator; Dryer & Centrifuge 

Vent and Wastewater 

Treatment Plant; VCM Railcar 

Disconnect & Area fugitive 

emissions, ROL, EOL; Blend 

Tanks Vent emissions; PVC 

Silo Storage emissions; 

Wastewater Emissions

 3.00E-09 - 

0.16 1.31E-08 - 0.71 5.90E-08 - 1.30 1, 2, 3, 4: lab data / 

modeling

SD1 - 10

Incinerator; Dryer & Centrifuge 

Vent and Wastewater 

Treatment Plant; VCM Railcar 

Disconnect & Area fugitive 

emissions, ROL, EOL; Blend 

Tanks Vent emissions; PVC 

Silo Storage emissions; 

Wastewater Emissions

7.49E-09 - 

2.22 1.48E-07 - 9.52 1.48E-07 - 12.53 1, 2, 3, 4: lab data / 

modeling

SD1-10

Incinerator; Dryer & Centrifuge 

Vents and Wastewater 

Treatment Plant; VCM Railcar 

Disconnect & Area fugitive 

emissions, ROL, EOL; Blend 

Tanks Vent emissions; PVC 

Silo Storage emissions; 

Wastewater Emissions

1.19E-09 - 

0.26 2.36E-08 - 1.15 2.36E-08 - 7.9 3

Compound Emission Ranges Across All Facilities

Basis for Estimate Key: 1 = Stack Test; 2 = Material Balance based on liquid/solid samples; 3 = Estimate from usage rate; 4 = other

Incinerators = As used here the term includes all exhaust gas control devices, primarily thermal oxidizers

Ethyl Chloride (Chloroethane)

Chloroform

Ethylene Dichloride (1,2 Dichloroethane)

Additive decomposition 

product; impurity, initiator 

delivery

Suspending agent diluent; 

impurity

VCM Impurity

Methyl Chloride (Chloromethane)

1-3 Butadiene

VCM Impurity

Basis 

for Estimate

Estimated Emission Rate Ranges

Methanol

VCM Impurity

Process 

Step Emission Source Description ofPossible HAP Source

VCM Impurity

VCM Impurity

June 26, 2008 Page 1 of 3
Vinyl Institute, Inc.

(Lb/hr) (T/Y) (Lb / mmLb PVC)

Compound Emission Ranges Across All Facilities

Basis for Estimate Key: 1 = Stack Test; 2 = Material Balance based on liquid/solid samples; 3 = Estimate from usage rate; 4 = other

Incinerators = As used here the term includes all exhaust gas control devices, primarily thermal oxidizers

Basis 

for Estimate

Process Estimated Emission Rate Ranges

Step Emission Source Description ofPossible HAP Source

SD1-10

Incinerator; Dryer & Centrifuge 

Vent and Wastewater 

Treatment Plant; VCM Railcar 

Disconnect & Area fugitive 

emissions, ROL, EOL; Blend 

Tanks Vent emissions; PVC 

Silo Storage emissions; 

Wastewater Emissions

1.50E-10 - 

0.18 6.56E-10 - 0.80 2.95E-09 - 5.50 1, 3

SD6, 7, 9

Centrifuges; Blend Tanks; 

Dryers; Cooling Tower; Waste 

Water Stripper; Dryer Stacks 

& Centrifuge Vents 

0.01 - 2.75 0.02 - 3.48 0.09 - 7.10 1, 2

SD1-10

Incinerator; Dryer & Centrifuge 

Vent and Wastewater 

Treatment Plant; VCM Railcar 

Disconnect & Area fugitive 

emissions, ROL, EOL; Blend 

Tanks Vent emissions; PVC 

Silo Storage emissions; 

Wastewater Emissions

5.99E-09 - 

1.36E-06

2.62 E-08 - 

1.34E-06 1.18E-07 - 1.09E-05 1, 3

SD7, 9 Waste Water treatment, Dryer 

and Centrifuge Vent, Fugitives 0.00 - 0.61 0.00 - 2.67 0.00 - 1.55 1, 2

SD9, 10, Utilities 

Area

Control Device Vent; Cooling 

Tower; Waste Water 

Treatment Plant; Fugitives

7.00E-04 - 

0.59 0.00 - 2.30 5.50 - 15.90 1, 3, 4: lab data

B9, SD9-10

Control Device Vent; 

incineration (located in VCM 

plant); Scrubber; Caustic 

scrubber; Incinerator Stack; 

Thermal Oxidizer

0 - 0.12 0 - 3.7 0 - 5.12 1, 2, 3

SD7, 10 Incinerator 0.00 0.00 0.00 1

SD7, 9, 10

Dryer and Centrifuge Vents; 

Waste Water Treatment Plant; 

Dryer Stacks; Fugitives

0 - 0.46 0 - 11.68 0 - 25.98 1, 2, 4

SD1, 2 Fugitives, 3 Dryers, Catalyst 

make-up tanks 0 - 0.17 0 - 0.75 0 - 3.37 3

SD7, 9 Waste Water treatment; Dryer 

and Centrifuge Vent 0 - 0.2 0 - 5.04 0 - 5.88 2, 4

SD7, 9, 10

Incinerator; Dryer & Centrifuge 

Vent and Wastewater 

Treatment Plant; Fugitives

VCM Impurity No Data No Data No Data No Data

Initiator Impurity

Initiator decomposition 

product

Additive decomposition 

product

VCM combustion 

decomposition product

Initiator decomposition 

product

VCM Impurity

Formaldehyde

Hydrochloric Acid

Chloroprene

Acetophenone

Vinyl Bromide

Cumene

VCM Impurity

Chlorine

Acetaldehyde

Vinylidene Chloride

VCM Impurity

Additive decomposition 

product

VCM Combustion, 

Disinfectant for cooling tower 

and treatment plant effluent

June 26, 2008 Page 2 of 3
Vinyl Institute, Inc.

(Lb/hr) (T/Y) (Lb / mmLb PVC)

Compound Emission Ranges Across All Facilities

Basis for Estimate Key: 1 = Stack Test; 2 = Material Balance based on liquid/solid samples; 3 = Estimate from usage rate; 4 = other

Incinerators = As used here the term includes all exhaust gas control devices, primarily thermal oxidizers

Basis 

for Estimate

Process Estimated Emission Rate Ranges

Step Emission Source Description ofPossible HAP Source

SD5, 7, 9

Recovery System, Waste water 

treatment plant; Dryer and 

Centrifuge Vent

0.00 - 0.063 0.00 - 0.278 No data / Insignificant 3

SD7, 9 Dryer and Centrifuge Vent; 

Waste Water Treatment Plant 0 - 0.01 0 - 0.02 0 - 0.09 2, 4

SD7, 9, 10 7 Dryer Stacks & Centrifuge 

Vents; Vent Gas Absorber 0.00 - 0.62 0.00 - 2.72 0.00 - 12.24 ND

SD5, 7 Dryer and Centrifuge Vent; 

Added by small timed pump

< Limit of 

Detection - 

0.03

< Limit of 

Detection - 

0.13

< Limit of Detection - 

0.90 2, 3

No Data No Data No Data No Data No Data No Data

Copolymer SD2, 7, 9 Storage, Drying 0 - 15.70 0 - 13.50 0 - 344 2

2,2,4 Trimethylpentane

Coolant in vent gas absorber 

& seal fluid in double 

mechanical seals

Initiator decomposition 

product; Vent gas absorbing 

fluid 

Vinyl Acetate

Methyl Ethyl Ketone

Phenol

Corrosion/Water Chemistry 

Additive

Ethylene Glycol

VCM Recovery; Initiator 

decomposition product

Hydroquinone

Initiator decomposition 

product

June 26, 2008 Page 3 of 3