Waste Minimization in Gas Treating and Processing Operations
Waste minimization has been proven to be an effective and beneficial operating procedure. You will find that there are many economically and technically feasible waste minimization techniques that can be used in natural gas plant treating and processing operations. In fact, many oil and gas operators have implemented waste minimization techniques and have enjoyed benefits such as:
- reduced operating and waste management costs;
- increased revenue;
- reduced regulatory compliance concerns;
- reduced potential liability concerns; and
- improved company image and public relations.
Choosing feasible source reduction and recycling options (i.e., waste minimization) is a smart business decision.
Waste minimization is part of the concept of the "Waste Management Hierarchy." The Waste Management Hierarchy sets out a preferred sequence of waste management options. The first, and most preferred option is source reduction. Source reduction is any activity that reduces or eliminates either the generation of waste at the source or the release of a contaminant from a process. The next preferred option is recycling. Recycling is the reclamation of the useful constituents of a waste for reuse, or the use or reuse of a waste as a substitute for a commercial feedstock or as a feedstock in an industrial process. Together, source reduction and recycling comprise waste minimization. The last two options, and least preferred of the hierarchy, are treatment and disposal.
This document will provide a general but comprehensive overview of waste minimization techniques for wastes arising from natural gas treating and processing operations. In addition to a discussion of waste minimization techniques for these wastes, the document provides case histories of successful waste minimization projects and a bibliography of useful technical references. Many of the references listed in the bibliography provide detail on the successful application the waste minimization opportunities discussed in this document.
The Railroad Commission also provides the publication Waste Minimization in the Oil Field. Waste Minimization in the Oil Field provides a general overview of waste minimization as a waste management practice and how to include it in an area-specific waste management plan. It also includes chapters on waste generation in oil and gas operations, identification of hazardous oil and gas waste, and the principles of waste minimization.Waste Minimization in the Oil Field is available from the RRC's Waste Minimization Program. Call (512) 463-6804 to obtain a free copy.
Waste Minimization in Natural Gas Treating and Processing Operations
As noted in the introduction, there are many economically and technically feasible waste minimization techniques that may be applied to natural gas treating and processing operations. An operator should consider all costs, including waste management and disposal costs, when evaluating the feasibility of a waste minimization option. For example, a substitute product or chemical may cost more, but the savings in waste management and disposal costs will make the substitution cost-effective.
The following discussion will consider the various source reduction opportunities for wastes arising from natural gas treating and processing operations.
The best place to start waste minimization efforts for natural gas treating and processing operations is in the planning stages. This is true whether you are preparing to build a new facility or preparing to work on smaller projects within an existing facility. An important component of the initial concept of the plan should be a discussion of the anticipated waste generation and waste management. As the project plan is developed it should be continually evaluated for potential waste generation and adjusted to take advantage of source reduction and recycling opportunities. This type of planning can significantly impact waste management requirements for the facility.
- Site Construction - A preplanning opportunity for a new facility is the preparation of the site and the construction of associated roads. The site and roads should be planned so that they are constructed such that stormwater runoff is diverted away from the site and erosion is minimized. Stormwater runoff from the site itself, which may be contaminated, should be collected in an appropriate location on the site. These steps will help minimize the volume of contaminated stormwater runoff to be managed. Also, the site size should be only as large as absolutely necessary. Site construction costs, including the cost of the disposition of cleared trees and vegetation, can be reduced. As well, the image of such an operation, as perceived by the general public, is enhanced.
- Installation of New Equipment - When planning for the installation of new equipment (e.g., to replace old equipment, expand a facility, or modify a process), consider the potential for waste generation in your selection of the equipment. For example, design glycol dehydrators with vapor recovery to control VOC emissions. If possible the equipment should be installed with a containment structure appropriately located to contain any spills, leaks , or drips. Also, if waste generation cannot be reduced, try to select a process that generates waste amenable to recycling.
Product substitution is one of the easiest and most effective source reduction opportunities. Vendors are becoming more attuned to operators' needs in this area and are focusing their efforts on providing less toxic, yet effective, substitutes. Some operators have found that vendors and suppliers will start offering less toxic substitutes in response to a company's establishing inventory control procedures. A few examples of effective and beneficial product substitution for natural gas treating and processing operations are provided below.
- Organic Solvents - Organic solvents, such as trichloroethylene, and carbon tetrachloride, are commonly used for cleaning equipment and tools. These solvents, when spent, become listed hazardous oil and gas wastes and are subject to stringent regulation. Alternative cleaning agents, such as citrus-based cleaning compounds and steam may be substituted for organic solvents. By doing so, a hazardous waste stream may be eliminated, along with the associated waste management and regulatory compliance concerns. Another solvent commonly used is Varsol (also known as petroleum spirits or Stoddard solvent). While most Varsol has a flashpoint below 140oF, which is a characteristically hazardous wastes when spent, some suppliers may provide a "high flash point Varsol" with a flash point greater than 140o F. Ask for non-toxic cleaners that reduce your regulatory compliance concerns.
- Mechanical Cleaning - Mechanical cleaning techniques are related to product substitution in that they may eliminate the need for organic solvents. There are commercial products which use high pressure and/or high temperature water based solvents to clean equipment. This type of equipment in many cases recycles the cleaning fluid to get the maximum use out of the solvent being used and minimize the volume of the waste generated.
- Paints and Thinners - Oil-based paints and organic solvents (i.e., thinners and cleaners) are used less frequently today, nonetheless they are still used. These paints and thinners provide an excellent product substitution opportunity. Water-based paints should be used whenever feasible. The use of water-based paints eliminates the need for organic thinners, such as toluene. Organic thinners used for cleaning painting equipment are typically listed hazardous waste when spent. This substitution can eliminate a hazardous waste stream and reduce waste management costs and regulatory compliance concerns.
- Amine Process Sludges - Amine sludges can contain a high sodium content. To eliminate sodium in amine process waste substitute potassium hydroxide for sodium hydroxide to maintain high pH in the process. Amine sludges have also been shown to have elevated levels of nickel and copper, probably as a result of corrosion while gas is being processed. The addition of potassium hydroxide to maintain pH during the process also helps minimize corrosion and the presence of these metals in the sludge.
- Flash Tank Separators on Dehydrators - Dehydrators remove water from gas by bringing the gas into contact with a desiccant (e.g. glycol) which absorbs water in the gas. The glycol water mixture is then sent to a regeneration unit where it is heated to drive off the absorbed water. The glycol also contains quantities of volatile organic compounds (VOCs) which are driven off with the water and vented to the air. A flash tank separator (FTS) can be installed on the dehydrator to reduce the amount of VOCs released to the air. The FTS removes gas absorbed in the desiccant by a rapid pressure reduction which causes the gas to "flash out" of the desiccant. The gas may then be recovered and used to fuel the regenerating unit.
- High-Bleed Pneumatic Control Devices - Many devices used throughout gas processing facilities use pneumatic devices such as valves and instruments to control and monitor the flow of gas. These devices need a pneumatic supply to drive their operating mechanisms. The most convenient supply is usually the natural gas in the line the device is monitoring or controlling. The typical pneumatic device uses a large volume of gas as a driving mechanism and then vents the gas to the atmosphere (thus the term "high-bleed"). There are two options to reduce the amount of gas which is vented. First, the supply could be changed to compressed air. This is not always a practical solution since supplying compressed air may not be feasible. The second option is to replace "high bleed" devices with "low bleed" devices to minimize the amount of vented gas. Generally, low-bleed devices operate slower than high-bleed devices and a replacement is not feasible in all cases.
- Lubricating Oil Purification Units - Power plants (i.e., engines) typically generate large volumes of waste lubricating oil and lubricating oil filters. A lube oil testing program combined with extended operating intervals between changes is effective in reducing waste lube oil generation. However, an equipment modification also can effectively reduce the volume of waste lubricating oil and filters. Commercial vendors offer a device called a lube oil purification unit. These units use 1 micron filters and fluid separation chambers and are attached to the lube oil system of an engine. The unit remove particles greater than 1 micron in size and any fuel, coolant, or acids, that may have accumulated in the oil. The unit does not affect the functional additives of the lube oil. The lube oil is circulated out of the system and through the purifier. The purified lube oil is then returned to the engine's lube oil system. Many operators have found that use of lube oil purification units has significantly reduced the need for lube oil changes, waste lube oil management, and concurrently, the cost of replacement lube oil. Also, a new engine that has been fitted with a lube oil purification unit will break in better and operate more efficiently over time, in part because bearing surfaces and piston rings seat better due to the polishing by particles less than 1 micron in size.
- Conventional Filters - A good target for waste minimization are the conventional filters that typically comprise a large part of an operations waste stream. An operator can replace conventional filter units with reusable stainless steel filters or centrifugal filter units (spinners). These devices generate only filtrate as waste and eliminate from the waste stream the conventional filter media and filter body. Operators have found that the reduced costs of replacing lost oil, maintenance requirements, new filter purchases, and waste filter management recover the expense of installing these alternative filtering units.
If conventional filters must be used, an operator should change filters based on differential pressure across the unit. Differential pressure is a good indicator of the effectiveness of a filter unit and can be used to determine the actual need for replacement. This is a simple change that can significantly reduce waste filter generation.
- High Energy Ion Plating - Magnetic ion coating is a technology that has been advanced in recent years. The process uses impingement of metals such as chrome/gold alloy or pure copper. The high energy application of these metals to a steel surface causes them to penetrate the steel surface, thus forming superior adhesion and slip (low friction) properties (sort of a "metal lubricant"). The metal plating reduces friction such that valve stem packing may be tightened to essentially eliminate fugitive emissions, and the valve packing/stem unit lasts up to seven times longer than a conventional untreated unit.
- Chemical Metering, or Dosing, Systems - The occasional bulk addition of treating chemicals, such as inhibitors, can result in poor chemical performance and inefficient use of the chemical. A chemical dosing system that meters small amounts of the chemical into a system continuously can reduce chemical usage and improve its performance in the system. In many instances, this equipment modification can result in cost savings due to reduce chemical purchases and more efficient operation of the system.
Process or Procedural Modifications
- Lubricating Oil Reduction -The Alaska Health Project (partially funded by the U.S. EPA) conducted a program to study the feasibility of determining oil change intervals for diesel engines by using a portable field monitor. Incidents of normal and abnormal oil degradation were recorded and correlated between field and laboratory tests.. The result of the study indicated that oil change intervals can be extended with analysis and monitoring. The study concluded that one facility in the study could save over 2,000 gallons of lubricating oil per year, based on a 5,000 hour/year operational period.
- VOC Emissions - Operators can reduce the VOC emissions from a glycol dehydration unit by optimizing the operation of the unit. In many cases, glycol dehydration units are over-sized, and the glycol circulation rate is too high. Many of these units can be optimized by reducing the glycol flow rate, though in some cases a glycol pump may need to be replaced with a smaller pump. A study conducted in Louisiana found that a dehydration unit with a glycol flow rate of 0.90 gal/min was too high for the gas flow through the unit. The glycol flow rate was reduced to 0.23 gal/min and the VOC emissions in the unit decreased proportionally to the reduction in the glycol rate.
Reduction In Water Use
Cooling tower blowdown generates large volumes of wastewater. In many instances, an operator can make modifications to the operation of the cooling water system that will reduce blowdown frequency, thus reducing the need for make-up water. One operator reduced the volume of cooling tower blowdown by using a substitute scale inhibitor and installing a chemical metering system.
Good Housekeeping and Preventative Maintenance
- Drip Pans and Other Types of Containment - Tanks, containers, pumps, and engines all have the tendency to leak. A good housekeeping practice that can help reduce the amount of soil and water contamination that an operator has to remediate is installing containment devices. Even though a small investment is required, containment devices save money and regulatory compliance concerns in the long run. Also, they can capture valuable released chemicals that can be recovered and used. Some examples of containment include: drip pans beneath lubricating oil systems on engines; containment vessels beneath fuel and chemical storage tanks/containers; drip pans beneath the drum and container storage area; and containment, such as a half-drum or bucket beneath chemical pumps and system valves/connections. Numerous companies have implemented good housekeeping programs to reduce the amount of hydrocarbons, chemicals, products, and wastes that reach the soil or water. These companies have found these programs to be cost effective in the long run (i.e., less lost chemical and product plus reduced cleanup costs). Also, their regulatory compliance concerns and potential future liability concerns are reduced.
- Preventive Maintenance - The companion of good housekeeping is preventive maintenance. Regularly scheduled preventive maintenance on equipment, pumps, piping systems and valves, and engines will minimize the occurrence of leaks and releases of chemicals and other materials to containment systems, or if there are no containment systems, to the environment. Numerous companies have implemented preventive maintenance programs and found them to be quite successful. The programs have resulted in more efficient operations, reduced regulatory compliance concerns, reduced waste management costs, and reduced soil and/or ground water cleanup costs.
- Chemical and Materials Storage - Another important aspect of good housekeeping is the proper storage of chemicals and materials. Chemicals and materials should be stored such that they are not in contact with the ground (e.g., on wooden pallets). Preferably, the raised storage area will include secondary containment and be protected from weather. All drums and containers should be kept closed except when in use. It is very important that all chemical and material containers always be properly labeled so that their contents may be identified at any time. Also, material data safety sheets (MSDSs) and other manufacturer information should be kept on file for all stored chemicals and materials. The use of bulk storage, rather than 55-gallon drums or smaller containers is a preferable way to store chemicals and materials. Proper storage and labeling of containers allows quick and easy identification and classification of released chemical or material in the event of a leak or release. In some instances, that could save hundreds of dollars in soil sampling and laboratory analysis costs.
Inventory control is one of the most effective ways to reduce waste generation, regulatory compliance concerns and operating costs. Especially, when combined with proper chemical and materials storage. An inventory control system is easy to implement, especially with the use of computer programs now available. An operator who tracks his chemicals and materials can use them more efficiently and reduce the volume of unusable chemical that must be managed as waste. (Note: Commercial chemical products that are returned to a vendor or manufacturer for reclamation or recycling are not solid wastes. Therefore, it is to the operator's advantage to require vendors to take back empty and partially filled containers for reclamation or reuse.)
Selection of Contractors
Operators should choose contractors who recognize the value of waste minimization and make efforts to apply it in their service. Any oil and gas waste generated at the operator's facility is the operator's regulatory responsibility. Therefore, an operator who uses contractors who practice waste minimization can expect reduced waste management concerns, reduced regulatory compliance concerns, and reduced operating costs.
The next preferred waste management option is recycling. Recycling is becoming a big business and more recycling options are available every day The following discussion offers some tips on recycling natural gas treatment and processing wastes.
- Reuse of Spent Natural Gas Liquid Sweetening Solutions - Many gas plant facilities use sour gas fuel in their operations. These facilities use exhaust gas scrubbers to control sulfur dioxide (SO2) emissions from units burning sour gas. SO2 scrubbing units can use partially spent caustic solutions from natural gas sweetening processes as a reagent. A major oil company conducted a study in which partially spent caustic natural gas liquid sweetening solution was used in place of soda ash solution as a reagent in an SO2 scrubber. To achieve acceptable performance using partially spent caustic solutions, they found that necessary changes to the scrubber operation were reagent feed rate, scrubber liquid pH and specific gravity, and blowdown rate. A cost savings was realized due to reduced off-site disposal and purchases of reagent. It was demonstrated that the SO2 scrubber could be operated without negative effects on performance, compliance, or operating costs.
- Lubricating Oil and Filters - Currently, waste lube oil and waste lube oil filters are generally banned from landfill disposal. Recycling is now the primary method of managing these wastes. Companies that handle lube oil and filters for recycling are located in every area of Texas, so finding one is not difficult. The Waste Minimization Program will provide upon request a listing of these companies.
- Paint Solvent Reuse - A simple technique for reducing the volume of organic paint solvents is to reuse it in stages. An organic solvent, such as toluene, may be used for cleaning painting equipment, but eventually it will become spent and ineffective. The "spent" solvent is not a waste if it is used for another intended purpose. A solvent spent from cleaning painting equipment is still suitable for use in thinning paint. This simple technique can greatly reduce the volume of waste paint solvent that may be subject to stringent hazardous waste regulation.
- Commercial Chemical Products - An operator should implement procedures that recycle any unused chemical products. Whenever a vendor is contracted to supply chemicals, the vendor should be required to take contractual responsibility for unused chemical products and the containers in which they were delivered. As noted under the source reduction opportunity, "Inventory Control," commercial chemical products that are returned for reclamation or recycling are not solid wastes. An operator that manages chemical products properly will avoid the unnecessary generation of unused chemicals that must be disposed of. In many instances, those chemical wastes would be hazardous and subject to stringent regulation.
- Sorbent Pads and Booms - When cleaning up spills of hydrocarbons and chemicals, use recyclable sorbent pads or booms. Try to avoid using granular adsorbent materials that must be disposed of. Several vendors offer sorbent pads and booms that are designed for repeated reuse.
- Spent organic solvents and other miscellaneous spent chemicals -Many companies accept spent chemicals for recycling. In many instances the spent chemicals (especially organic solvents) are reclaimed for reuse or blended to make fuels for energy recovery. See "Recycling Information" below to learn how to find these companies.
- Scrap Metal and Drums - Scrap metal is a relatively easy waste to recycle. Many operators have found that scrap metal recycling companies will collect and remove materials such as tanks, drums, and other types of scrap metal from the lease or facility at no charge to the operator. An additional consideration is regulatory requirements. Scrap metal that is recycled is not subject to hazardous oil and gas waste regulations; but it is if disposed of. For example, an old steel tank coated with lead-based paint would likely be determined hazardous if disposed of; however, if recycled it is excluded from regulation as a hazardous oil and gas waste.
An excellent way to ensure that steel 55-gallon drums are recycled is to require in the contract with a vendor the requirement that the vendor take back any delivered drum, including drums that still contain some chemical or product. Note that empty drums and commercial chemical product that is recycled are generally excluded from regulation as hazardous oil and gas waste. (Also, see the discussions in "Good Housekeeping" and "Inventory Control.")
The RRC's Waste Minimization Program can help operators identify recycling options. The Texas Commission on Environmental Quality (TCEQ) publishes two useful documents: Recycle Texas and RENEW.Recycle Texas is a listing of many of the companies that take various wastes for recycling. Those wastes include many that are typical of oil and gas operations. RENEW is a waste exchange that is published quarterly. RENEW lists companies that have generated wastes and are making them available for recycling, and RENEW also lists companies that want certain wastes for recycling. Recycle Texas and RENEW are available free of charge from TCEQ and can be obtained by calling 1-800-648-3927.
Training is probably one of the best waste minimization opportunities. An operator's efforts to minimize waste and gain the associated benefits will be only be effective if the people in the field understand waste classification and the concept of waste minimization. Also, people in the field should be empowered to implement waste minimization techniques as they are identified. Waste minimization training is becoming more common. Oil and gas associations have begun publicizing waste minimization successes, and technical societies such as the SPE, are publishing more and more papers on effective waste minimization techniques.
RRC Waste Minimization in the Oil Field Manual
Waste Minimization in the Oil Field: This manual, developed with the assistance of the oil and gas industry, offers source reduction and recycling (i.e., waste minimization) concepts, cost effective and practical examples of source reduction and recycling opportunities in the oil field, and information on how to develop an individualized waste minimization plan. The manual also presents a discussion on how to identify hazardous and nonhazardous oil and gas wastes as defined by EPA regulations under the Resource Conservation and Recovery Act.
EPA's Natural Gas Star Program
An additional source for waste minimization techniques in natural gas treating and processing operations is the EPA Natural Gas STAR Program. The Natural Gas STAR Program is a voluntary government/industry partnership designed to accomplish environmental protection through cost-effective measures without regulation. The program was started in March of 1993 and it encourages natural gas companies to adopt "best management practices" that can reduce methane emissions.
Natural Gas STAR Partners sign a Memorandum of Understanding (MOU) with EPA agreeing to review and implement "best management practices" as appropriate. The company then implements the plan over the next three years. The EPA supports the partners by assisting in training, analyzing new technologies, and removing unjustified regulatory barriers.
SPE Technical Papers
Brost, D.F., at al "Optical Methods for Monitoring Treating Chemicals in Oilfield Water Systems", Society of Petroleum Engineers 22781 (October 1991)
Santamaria, et al, "Controlling Paraffin Deposition Related Problems by the Use of Bacteria Treatments", Society of Petroleum Engineers 22851 (October 1991)
Frederick & Tulloh, "Clean Air Act Title III and the Oil Industry", Society of Petroleum Engineers 23996 (March 1992)
Ballard, et al, "An Overview of Exhaust Emissions Regulatory Requirements and Control Technology for Stationary Natural Gas Engines", Society of Petroleum Engineers 24306
Mussig, S., "Possibilities for the Reduction of Emissions-In Particular the Greenhouse Gases CO2 and CH4 in the Oil and Gas Industry" Society of Petroleum Engineers 25041 (November 1992)
Grizzle, P.L., "Hydrocarbon Emission Estimates and Controls for Natural Gas Dehydration Units", Society of Petroleum Engineers 25950 (March 1993)
Benoit & Schuh, "Waste Minimization Program at Sour Gas Facilities," Society of Petroleum Engineers 26011; (March 1993)
Reuter, et al, "Measurement and Enhanced Monitoring of BTEX and VOC Emissions from Glycol", Society of Petroleum Engineers 29698 (March 1995)
Brandon, et al, "Corrosion and Inhibition Use in the Oil and Gas Industry: Effectiveness and Environmental Impacts", Society of Petroleum Engineers29735 (March 1995)
Wilhelm & McArthur, "Removal and Treatment of Mercury Contamination at Gas Processing Facilities", Society of Petroleum Engineers 29721 ( March 1995)
Resch, R.A., "EPA's Natural Gas Star Program", Society of Petroleum Engineers 29731 (March 1995)
Hahn et al, "Reuse of Spent Natural Gas Liquid Sweetening Solutions", Society of Petroleum Engineers 29733 (March 1995
Boyle, C.A. "Management of Amine Process Sludges", Proceedings from First International Symposium on Oil and Gas Exploration and Production Waste Management Practices (September 1990)
US EPA Environmental Report
Gibbs, Micheal; Hathiramani, Pradeep; Weynand, Gordon; "Opportunities to Reduce Anthropogenic Methane Emissions in the United States", United States Environmental Protection Agency-Report to Congress (October 1993)