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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 MAC T 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 re sin strippers; 1 

### and

(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 o f 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 l evel 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 p orosity) 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., ther mal 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 stripp er 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, d ryers 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

de vice 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 anticipat es 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 res in 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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www.vinylinfo.org www.vinylindesign.com Table 1: PVC Dryer Vent Stream vs. Waste Gas Stream

Example Unit Description Dryer Vent Stream (Waste air from res in drying step) Waste Gas Stream to Control (Off

- gas resin production equipment)

S

- PVC Unit #2 Exhaust Volume 11,000,000 d scf/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 HA Ps 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 chal lenging (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 inc rease 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 con straints, 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 Descri ption 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 malfunc tions); given the TO’s operating environment, i.e., 1800 o F with excess air, it would be prudent to assess fire safety issues, including the potential for combustible dust hazards

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

rather than “con tinuous”

2 Actual dryer v ent 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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www.vinylinfo.org www.vinylindesign.com Table 2: Potential Alternative Control Technologies

# Control Technology Descri ption 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 h eating 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, periodi c 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 a nd 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 an d/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 effi ciency

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 fo r 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 t he 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 pl ans.

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)

Annu al 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 consi der:

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 concentratio ns 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 ca lculations 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 othe r 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 manufactur ers 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 app licable 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