Document ID: EPA-HQ-OW-2008-0667-0597
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2011-04-20T04:00Z

Site Visit Report

Union Carbide -- St. Charles Operations (SCO)
355 State Highway 3142
Hahnville, LA 70057
January 13, 2010

1.0	Background and Objectives

      The Environmental Protection Agency (EPA) is in the process of developing 316(b) cooling water intake structure requirements that reflect the best technology available (BTA) for minimizing adverse environmental impact for all existing power plants and manufacturing facilities. As part of this process, EPA staff is visiting electric generators and manufacturers to better understand the cooling water intake structure (CWIS) technologies in use at facilities, including the site-specific characteristics of each facility and how these affect the selection and performance of CWIS technologies.  EPA is also visiting facilities to better understand cooling water use and specific issues or technologies that can affect 316(b) compliance.  Dow's St. Charles Operations (SCO) facility was selected for a site visit because it utilizes cooling water in manufacturing a wide variety of basic and specialty chemical products.

2.0	Facility Description

      SCO is located on a 2000 acre site on the shore of the Mississippi River near Hahnville, LA.  The facility began operations in 1966 and employs approximately 1100 personnel, plus as many as 1000 contractors.  The facility's NPDES permit (NPDES permit number LA0000191) expired June 30, 2009 and has been administratively continued as the facility submitted its permit application and is awaiting a renewed permit.  

3.0	Manufacturing Information

      Dow SCO is an integrated petrochemical plant with 23 operating units that produce primarily intermediate chemical products.  These products end up in a variety of consumer goods such as plastics, insecticides, films and fabrics, antifreeze and brake fluid, paints and adhesives, pharmaceuticals, personal care products , and cleaning agents.  According to the company's website, the facility is capable of producing over 10 billion pounds of chemical product per year.
      
      The site is arranged in a series of complexes (e.g., hydrocarbons complex, oxide complex) that may contain multiple plants.  This site is also home to four other companies:  Air Liquide, Air Products, Praxxair, and Western.

4.0	Cooling Water System and Intake Structure

      SCO's CWIS is located along the shoreline of the Mississippi River near a receiving pier.  Seven inlet pipes each lead to an inlet bay (each with one single speed intake pump), where a coarse mesh (3/8" mesh, ~48% porosity) traveling screen removes debris and aquatic organisms.  Each screen bank is 10 ft wide and 36 feet in height.  Screens are typically rotated twice per day by a high pressure wash and discharge to a common trough, which empties into a pit that drains back into the river.  Facility representatives stated that the screens are refurbished approximately every 5 years.  The through-screen intake velocity is 2 feet per second (fps) at average water level of 20.5 ft and 4.6 fps at low water level of around 9 ft.
      
      The design intake flow (DIF) of the CWIS is 907 million gallons per day (mgd).  The average intake flow (AIF) is 773 mgd, which has remained relatively constant for the previous 4-5 years.
      
      The CWIS provides cooling and process water to a system of internal canals that transport water throughout the facility.  As many as twenty plants withdraw from the canal, use the water (or distribute it to other process units), and discharge to a similar series of return canals that connect to a discharge pumping station.  This station is the primary outfall for the facility and pumps effluent back to the Mississippi River.
      
      The facility's fire suppression system withdraws from the cooling water canals.
      
      Facility representatives stated that sedimentation is not a significant problem at this site.  Occasionally, dredging is required at the discharge point, but operators adjusted the discharge velocity to correct the settling problem.
      
      The facility uses quaternary amine as a biofouling agent to treat for clams.
      
      The CWIS also provides cooling water for Air Liquide and Praxair facilities.
      
5.0	Flow Diagram

      A general flow diagram is provided in Attachment C.  Facility representatives stated that 98.9% of the water withdrawn is for once-through cooling.  The remaining water is clarified and then used for cooling tower makeup (0.4%, ~3 mgd) and other process uses (0.7%, ~5 mgd).
      
      There are five pump stations throughout the plant that feed 20 of the plant units. Canal water is returned via 8 pumps at a rate of 720,000 gpm.  

6.0	Electricity Generation and Transmission
      
      SCO operates two cogeneration power plants (i.e., produces both power and steam).  Both were built in 1995, use once-through cooling, and use natural gas and plant-produced fuel gas (a by-product of production).  The electric generating capacity is a total of 240MW and the steam generating capacity is a total of 80 MW. 
      
      Facility representatives also noted that SCO's steam generation is heavily integrated into the facility, as any change in steam production ripples through and affects production at multiple process units.  Integrated chemical facilities (especially those with basic process units) are often good candidates for cogeneration power plants.  In fact, Dow has previously built "package" plants with a chlorine unit, a caustic unit, and a power plant.
      
      Facility representatives stated that the power plants are not operated for profit, but for facility reliability.  SCO can produce its own electricity cheaper than it can purchase it from the grid and also has a constant need for both steam and electricity.

7.0	Impingement and Entrainment Information

      Dow has not conducted any biological studies at the site. 

8.0	Cooling Tower Feasibility
      
      SCO utilizes closed-cycle cooling (with mechanical draft cooling towers) at three plants, with helper cooling towers (i.e., supplemental cooling along with once through cooling) at two other plants.  When the facility was originally designed, all of the cooling water needs were met with once-through cooling water from the canal system.  However, as the plant expanded, water needs exceeded the capacity of the canal system and newer process units were built with closed-cycle cooling.  As a result, process units built since the late 1990s (typically in locations further from the river) tend to use cooling towers; therefore the DIF has not changed because of the additional units.  Facility representatives stated that 4% of the facility's heat load is processed through cooling towers; without the cooling towers, the facility's intake flows would be slightly higher.
      
      Facility representatives noted that retrofitting remaining process units to closed-cycle cooling would present a number of challenges.  First, much of the piping used throughout the plant is operating at the upper end of the range for its design pressure.  Adding cooling towers would require additional pumps and likely require widespread replacement of piping throughout the facility.  Second, product reactivity of water in certain process units could make both quality and safety would be an issue: the increase in pressure could adversely affect some process lines that operate at lower pressures, leading to either a lower quality product, or in some cases, potentially dangerous chemical reactions.  Third, the difference in the cooling water temperature itself could have a negative effect on process and product capacity.  Anytime the process is condensing water, the cooler the better.
      
      For the two cogeneration gas turbines, facility representatives indicated the pump station and distribution header would need to be re-engineered.  The facility also indicated that shell pressure issues may require retrofit of the heat exchangers.  
      
      Facility representatives also discussed the role of cost in selecting the design of a cooling system: at a recently constructed facility in Saudi Arabia, the cost of the cooling system (approximately $2 billion) was higher than the costs for all other environmental infrastructure combined.  As such, they noted that cooling system retrofits would not simply be an issue of cost and affordability, but could even be a barrier to being competitive.  
	
      Facility representatives stated that while individual process lines are periodically taken offline for maintenance, the entire facility rarely shuts down.  In general, there is sufficient redundancy within the facility to prevent widespread downtime; for example, boilers can be rotated to continue to provide steam.  Each cogeneration unit is taken offline once per year and other process units go offline as often as twice per year or as infrequently as every 2-3 years.

9.0	Future Activities
      
      SCO representatives were not aware of any plans for significant changes or increases in operations.

10.0	Cooling Ponds
	
      There are no cooling ponds onsite.

11.0	316(a)

      The facility has no permit limitations for temperature or 316(a) permit conditions.

12.0	Ash Handling

      There are no coal ash wastes generated onsite.

13.0	Air Emissions Controls

      EPA did not review air emissions controls.

14.0	Issues with Debris
      
      No significant problems with debris were noted.

15.0	Additional Information

      Facility representatives believe that 316(b) should be implemented on a case by case basis as compliance should be customized to the site specific situation.  
      Facility representatives stated that, if forced to meet impingement requirements through use of a technology, they would consider evaluating installing cylindrical wedgewire screens, as these have been successfully implemented at Dow sites in West Virginia.  They added that there are not many other technologies that would be viable candidates at this site other than Ristroph screens.  If a cost benefit alternative is available for IM requirements, the facility stated they would use this alternative.  
      
      The facility has not evaluated entrainment reduction at this facility because it believes the costs of such controls would considerably outweigh any benefits.  However, they noted that they were not aware of any available technologies to reduce entrainment at this site.   
      
      The facility also discussed ways in which waste heat recovery could be used to give cooling water credits.  The difference in waste heat from the base case as compared to the heat rejected and recovered could be 10 to 20%.  For example, if the BTU could be quantified, and the source cooling is known, then the BTU could be converted to a quantity of cooling water that would have been needed.  
      
      As a general comment, stand alone plants may have less dependence on fully integrated site power as opposed to larger integrated manufacturers and utilities that generate power for sale.
      

Attachments

Attachment A		List of Attendees
Attachment B		Aerial Photos
Attachment C		PowerPoint Presentation (January 13, 2010)

Attachment A--List of Attendees

Paul Shriner, EPA
Jan Matuszko, EPA
Kelly Meadows, Tetra Tech
Christine Baldridge, Dow
John Hill, Dow
Tim Finley, Dow
Ed Keough, Dow
Qingzhong Wu, Dow
Sarah Thigpen, Dow
Bryce Chord, Dow
Maria Valdez, Dow (via telephone)
Jim-Bob Williams (via telephone)

Attachment B--Aerial Photo

Please see DCN 10-6556A accompanying this document.

Attachment C--PowerPoint Presentation (January 12, 2010)

Please see DCN 10-6556B accompanying this document.