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1737 King Street, Suite 390, Alexandria, VA 22314 (571) 970-3392 Fax (571) 970-3271 

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September 17, 2010

Ms. Jodi Howard

U.S. EPA - Office of Air Quality Planning and Standards 

Sector Policies and Program Divisions 

Coatings and Chemicals Group 

Mail Code: E143-01 

Research Triangle Park, NC 27711

RE: PVC MACT Rulemaking—Stripping Technology is MACT for the PVC Industry

Dear Ms. Howard,

During our August 24, 2010 meeting, Agency staff indicated that they might find it 

helpful for the polyvinyl chloride (“PVC”) industry to identify emission control technology 

that could be practically implemented downstream of the resin stripper. VI members 

have considered the request and herein provide the Environmental Protection Agency 

(“EPA”) with: 

(1) Information on the characteristics of exhaust streams downstream of the resin 

strippers;1and

(2) A brief summary of potential alternative control technologies and their potential 

impracticalities and tradeoffs. 

VI and its members appreciate EPA’s continuing willingness to receive and consider our 

technical submissions in support of the PVC and copolymer source category maximum 

achievable control technology rulemaking (hereinafter, “PVC MACT”). We are confident 

that throughout this effort, the exchange of information and ideas will serve to enhance 

the effectiveness and success of the resultant standard. 

I. Characteristics of Exhaust Dryer Steams

PVC Units reduce vinyl chloride monomer (VCM) emissions and other organic 

hazardous air pollutant (HAP) emissions from PVC resin through the use of steam 

stripping technology. The ultimate level to which resin can be stripped is determined by 

several factors including reactor and stripper design; operating conditions (such as 

temperature and pressure); polymerization recipe chemistry; and the morphology (e.g., 

 

1

Information on resin emissions and exhaust streams downstream of the resin strippers also was provided in response to the information 

collection request issued pursuant to the Agency’s Clean Air Act section 114 authority (hereinafter, “114 Request”).
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particle size distribution and porosity) of the particular type and grade of PVC resin 

being produced. 

Note that during the steam stripping operation, HAP-containing exhaust waste gases 

from the strippers themselves are vented through a closed vent system to a control 

device (e.g., thermal oxidizer). This particular waste gas stream is not the subject of 

today’s memo.

PVC resin emission reductions are measured by the amount of residual VCM (RVCM) 

in the PVC resin. Once a PVC Unit meets the RVCM limit, emission sources beyond 

the stripper are not regulated under Part 61 Subpart F, based on EPA’s past 

determinations that add-on control devices would reduce the already reduced emissions 

by a fraction of a percent. These downstream emission sources include slurry blend 

tanks, centrifuges, dryers and PVC silos. For this summary, PVC dryers were selected 

to illustrate the challenges of designing and operating potential add-on control devices 

to this downstream equipment.

Generally, the gas stream exhausted from a PVC dryer is moist, hot waste air with 

practically no heat value (i.e., low HAP content) but a very high volumetric flow rate 

when compared to typical waste gas streams exhausted to a control device. 

Conversely, waste gas streams from PVC production equipment that vent to a control 

device have high heat values and low volumetric flow rates. Table 1 provides a general 

comparison of waste air from a Polyethylene (PE) resin dryer and two PVC dryers and 

their associated waste process gases from production equipment.

As Table 1 illustrates, a comparison of PVC waste gas streams with dryer vent streams 

reveals the critical differences in both HAP concentrations (3-4 orders of magnitude 

higher) and flows (3 orders of magnitude lower). These differences help explain why 

the industry anticipates that a requirement to further treat dryer vent streams at PVC 

units could prove to be significantly difficult and complex to implement. 

Table 1: PVC Dryer Vent Stream vs. Waste Gas Stream

Example Unit Description Dryer Vent Stream

(Waste air from resin drying step)

Waste Gas Stream to Control

(Off-gas resin production equipment)

PE Unit

Exhaust Volume 1,800,000 dscf/hr 27,000 dscf/hr

Exhaust VOC Content 2,500 ppmv 560,000 ppmv

Inlet Line to Control Device 60” (Diameter of Dryer Stack) 6”

S-PVC Unit #1

Exhaust Volume 3,400,000 dscf/hr 3,200 dscf/hr (PVC Waste gas only)

Exhaust VOC Content 0.979 ppmv VCM 

4.46 ppmv VOC

~54,000 ppmv VCM

Inlet Line Size 66” (Diameter of Dryer Stack) 2” to 16”
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Table 1: PVC Dryer Vent Stream vs. Waste Gas Stream

Example Unit Description Dryer Vent Stream

(Waste air from resin drying step)

Waste Gas Stream to Control

(Off-gas resin production equipment)

S-PVC Unit #2

Exhaust Volume 11,000,000 dscf/hr 21,000 dscf/hr (PVC Waste gas only)

Exhaust HAP Content 15 ppmv HAP ~600,000 ppmv VCM

Inlet Line Size 24”-60” (Diameter of Dryer Stack) 4”

S-PVC Unit #2 was selected in order to provide an upper-bound range estimate of 

emissions from sources following the stripping operation. Potential emissions were 

estimated by combining the available HAP concentrations in both the water and wet 

slurry fractions of the resin stream exiting the stripping operation and entering the dryers 

and assuming all HAPs were emitted through the dryer exhausts.

As indicated above, the estimate for the S-PVC Unit #2 resulted in a dryer vent stream 

HAP concentration of 15 ppmv in a flow of 11,000,000 dscf/hr. This relatively low HAP 

concentration in a very large and challenging (particulate containing, wet) vent stream 

would most likely require huge amounts of supplemental fuel, e.g. natural gas, to reduce 

the HAP concentration any further.2 The trade-off for this relatively small HAP reduction 

would be a significant increase in greenhouse gas emissions from the source.

II. Brief Assessment of Alternative Control Technologies

The purpose of this section is to provide the PVC industry’s initial evaluation of 

alternative emission control technologies for dryers. Given time constraints, we were 

unable to fully review these approaches. Accordingly, we have in Table 2 identified the 

various “add on” control technologies that can be considered in addition to the use of 

stripping technology, and summarized our initial environmental and safety concerns. 

Additional research and consideration is needed to fully evaluate the feasibility of 

implementing these technologies pursuant to Clean Air Act mandates.

Table 2: Potential Alternative Control Technologies

# Control Technology Description Hurdles

1. Flare Dedicated Vent Line to a Flare 

Header

a. Prohibited in other MACTs: Halogenated HAPs will not be 

destroyed/removed by flare; 

b. Cannot install a scrubber on a Flare.

2. Thermal Oxidizer (TO) Burn residual HAPs by heating 

in an enclosed chamber. 

Optimal temperature 1400-

2000 deg F with residence 

times of 0.5-2 seconds. 

a. Fire and/or Explosion Concern: PVC resin can carry over 

into TO (e.g., cyclones on dryer vent malfunctions); given 

the TO’s operating environment, i.e., 1800oF with excess 

air, it would be prudent to assess fire safety issues, including 

the potential for combustible dust hazards.

b. TO needs steady state gas flow: PVC operations are “batch” 

rather than “continuous”

 

2

Actual dryer vent stream concentrations are most likely lower than shown for S-PVC Unit #2 as measurements below detection limit were 

treated as present at the detection limit. 
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Table 2: Potential Alternative Control Technologies

# Control Technology Description Hurdles

Auxiliary fuel is necessary to 

maintain combustion 

temperatures

c. High velocity dryer vent stream can “snuff” out TO firebox 

flame

d. Once flame out, would slowly have to bleed moist dryer air 

back into TO.

e. Increased shutdowns and subsequent startup: potential for 

more excess emission events.

f. If waste gas has low heating value (i.e., low organic VOC 

content), then stream needs to be supplemented with fuel; 

commonly done with natural gas.

g. Additional emissions will be created, (e.g., NOx, CO, 

possibly HCl and dioxin/furans), which on this large volume 

of gas would be more difficult to recapture in such dilute 

concentrations.

3. Catalytic Oxidizer The use of catalysts can lower 

the oxidization temperatures of 

VOCs; by lowering the 

oxidation temperature, less 

supplementary fuel is needed

Reaction takes place in 

catalyst; no residence time.

Same as Items 2.a, 2.b and 2f. In addition:

a. High operating expense with catalysts replacement.

b. Catalysts need to be reactivated, sometimes continuously, 

which could create a new set of HAPs (e.g., HCl)

c. Catalysts need regular, periodic regeneration, which leads to 

periods of operations without this control, which must be 

accounted for. 

d. Catalysts regeneration could create other emissions.

4. Adsorption Using activated carbon, VOC 

recovery is possible, 

depending on molecular 

weights and carbon adsorption 

properties. 

a. Useful for recovery of VOCs with intermediate molecular 

weights (typically 45-130); smaller compounds do not 

adsorb well; larger compounds cannot be removed during 

carbon regeneration

b. Depending on VOC; could cause fire and/or explosion

c. Adsorption is most effective at lower temperatures, hence, 

hot exhaust gas streams may have to be cooled.

d. Does not handle humid streams.

5. Misc. VOC Recovery 

Systems

Condenser; Membrane 

Recovery, Refrigeration 

System

a. Lower HAP removal efficiency

b. Gas volume is too large to effectively reduce already 

highly dilute concentrations, high-energy consumption 

devices needed (e.g., compressors, which increase 

overall greenhouse gas emissions. 

6. Baghouses Particulate Filtration Devices 

(in use on some existing 

dryers for particulate control)

a. Inefficient removal of volatile organic HAP

b. Higher temperature and humidity concerns

c. Potential explosion/fire hazard.

7. Absorbers Water absorption devices 

(e.g., scrubbers; in use on 

some existing dryers for 

particulate control)

a. Ineffective removal of volatile organic HAPs

b. Generates large amount of wastewater

c. May require higher pressure drop

A. Costs of “Add On” Control Technologies

The PVC industry has not at this point had an opportunity to fully evaluate the 

implications of the technologies discussed above, nor has it had the opportunity to 

obtain and review estimates of costs to implement and operate such controls. We 

understand that EPA believes costs are not to be considered in establishing floor 

values. However, when estimating costs to implement technical alternatives, the Agency 

should consider:
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Capital for Add On Control Device(s)

Retrofitting existing structures, which in most cases may not be practical, given 

physical constraints of current plot plans.

Additional energy consumption needed to drive certain control technologies

Wasted supplemental fuel (e.g., during Section 114 testing of PVC-only waste 

gas stream supplemental fuel (Natural gas) to the TO cost between $150,000 to 

$250,000/ month)

Annual Operational and Maintenance Costs

B. Significant HAP Reduction from Alternative Technologies

Currently, detailed emission reductions through the use of alternative “Add on” control 

technologies are not available. Emission reduction estimates need to consider:

HAP concentration of PVC dryer stream

Velocity and low atmospheric pressure of PVC dryer vent stream

Moisture content

Particulate matter content

Demonstration of add-on control technologies downstream of the stripper for 

highly dilute HAP concentrations should be completed in pilot units before 

emission rules could incorporate such new, lower limits as being achievable. We 

note that in past MACT standards (e.g. HON and MON MACTs) EPA has relied 

on use of the Total Resource Effectiveness (TRE) index calculations as an 

approach to identify high volume low concentration streams that did not warrant 

further treatment. 

* * *

Stripping technology should remain the essential HAP emission control mechanism for 

PVC resins for a variety of reasons. Unlike other add-on control devices, stripping 

technology results in a lower residual HAP content of the final PVC resin product going 

to processors, fabricators, and ultimately the consumer. PVC stripping technology has 

been continually improved by resin manufacturers allowing more VCM and other 

organic HAPS to be recovered and less to remain with the resin. This is consistent with 

the approach employed in the Vinyl Chloride NESHAP that minimizes emissions for 

sources following the strippers through RVCM limits applicable to the stripping 
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operation, thus protecting workers, the environment and public health.

If after review of the above information that EPA would like further discussion or 

clarification on this subject, please do not hesitate to contact me. Thank you for the 

opportunity to submit this important additional documentation. 

Sincerely, 

Richard P. Krock

Technical Director

e-mail: rkrock@vinylinfo.org

phone: 571-970-3392

cell: 571-216-4474