Patent Grant
7749308
The invention relates generally to reducing emissions of volatile compounds. More particularly, the invention is a method for reducing emissions of highly reactive volatile organic compounds from pipeline operations associated with oil and gas recovery, production, refining, and petrochemical manufacture, processing, and transportation.
Many oil, gas, and petrochemical pipeline operations, including pigging, swabbing, changes of meter parts, pipeline inspection maintenance (PIM), and the like, produce emissions of volatile organic compounds in associated venting or flaring operations. Pipeline operations also generally cover considerable distances, making it difficult and expensive to deal with these types of emissions.
Over the past few years, there has been more and more regulation of emissions of contaminants into the air. The passage of the Clean Air Act Amendments of 1990, the Kyoto Accord, and other regulations have set the stage for the reduction of air emissions worldwide. Reduction of air emissions is a priority for both countries and companies.
Air emissions in the United States are regulated by the Environmental Protection Agency (EPA). The EPA is the agency directly responsible for regulating air emissions in many states; however, in certain states the responsibility for regulatory compliance has been delegated to state agencies, e.g., in California, Texas, Louisiana, and others. Each state that has the responsibility for regulatory compliance must submit a State Implementation Plan (SIP) to the EPA for approval. The goal of the SIP is to implement federal standards in a manner that reflects the priorities and conditions of air emissions within the state. The SIP can be more stringent than the federal standards but not less so.
The Clean Air Act Amendments of 1990, and earlier legislation, divide a state or region into “attainment” and “non-attainment” areas. The “attainment” areas are those geographic areas considered capable of meeting federal standards for air quality. The “non-attainment” areas are those geographic areas that cannot meet or attain air quality standards. Those that emit pollutants into the air in “non-attainment” areas have to implement more stringent performance standards to reduce emissions. These more stringent standards extend to businesses in certain “SIC” code categories and can even extend to the general public for automobiles to meet certain emissions standards.
“Non-attainment” areas generally have more stringent criteria for certain air emissions. These criteria can include reduced allowable emissions of the oxides of nitrogen (NOx) or reduced allowable emissions of smog precursors such as VHAP's or HRVOC's. A “VHAP” is an acronym/abbreviation for ‘Very Hazardous Air Pollutant’ and HRVOC is an acronym/abbreviation for ‘Highly Reactive Volatile Organic Compound’. Since VHAP's and HRVOC's are smog precursors, recent SIP proposals to the EPA have stated that smog, a criteria pollutant, may be limited by controlling the amount of VHAP's and HRVOC's that are emitted to the atmosphere. Indeed, many regulated areas are beginning to place emissions “caps” on identified atmospheric pollutants, a “cap” meaning that there is a certain amount that a business entity can emit without an economic penalty and when the “cap” is exceeded then economic penalties are incurred.
With the introduction of the allowable emission “cap”, long-standing practices in the production, manufacturing, refining, transportation, and distribution of chemical and refined products must be examined. Recent SIP documents have resulted in regulations for HRVOC materials that define, limit, and establish the basis for documenting HRVOC emissions. HRVOC emissions events can be categorized as any of the following activities: a) venting HRVOC material to the atmosphere; b) flaring HRVOC material to the atmosphere; and c) fugitive emissions from equipment.
Venting and flaring of hydrocarbons has been done since the earliest days of oil and gas production. Early oil production had excess natural gas co-produced with the oil. Since there was no market for this co-produced gas, the gas was vented or flared. Old stories abound that the sky was lighted so brightly at night by flared gas that one could read a newspaper virtually anywhere oil was being produced.
As refining and petrochemical industries began to process “deeper into the barrel”, flaring and venting continued to play a primary role in plant safety. Pressure relief, with the accompanying venting and flaring, was then and continues to be one of the primary methods of assuring safety in refining and petrochemical facilities. Venting and flaring have long been accepted and unquestioned practices in the refining and chemical industries.
Over the past several years there has been increased environmental awareness that has resulted in laws and regulations implementing those laws to promote “cleaner” air and reduced earth-warming gases. Man has finally achieved a level of activity in emissions to the atmosphere and energy consumption that the earth's atmosphere is being profoundly affected. Regulatory response has been ever more stringent regulation of emissions to the atmosphere of “criteria” pollutants, including oxides of nitrogen, oxides of sulfur, earth-warming gases, carbon dioxide, volatile organic compounds, volatile hazardous air pollutants, and highly reactive volatile organic compounds. It should be noted that regulations generally do not eliminate certain activities, but rather promote regulatory “complexities” in the form of more stringent specifications and reporting requirements that create incentives to “do things a different way”. This is the case with both flaring and venting operations in industrial applications.
Accordingly, there exists a need for a method for reducing emissions of volatile organic compounds in pipeline and other operations and that is the subject of the present invention.
The present invention provides a system of recovering and recycling the otherwise vented or flared volatile and non-volatile reactive organic materials from pipeline and plant operations associated with oil and gas recovery, refining and petrochemical manufacture, processing and transportation.
Emissions of organic compounds that include the HAP, VHAP, and HRVOC compounds from such operations have in the past been disposed of by venting. To avoid putting such “hazardous air pollutants” (HAP) and “very hazardous air pollutants” (VHAP) into the atmosphere, such emissions are typically flared, that is, they are disposed of by burning. This invention/process provides an alternative to flaring and recycles products to a useful purpose rather than sending such products to the atmosphere.
There are many operations in which this invention is applicable. Typically, these operations are those in which flaring is performed during some operational procedure. The invention is applicable in virtually every instance that requires equipment to be “blown down”, including pipeline and equipment maintenance and startup and shutdown operations and filter and flow meter servicing. The invention is specifically applicable in any pipeline and plant operations that include a system of piping and valves adapted to be opened and closed without disturbing product flow in the main system, for example, to insert or remove pipeline pigs or swabs.
The invention comprises, in part, a set of pipes, valves, pumps, and associated equipment to connect operatively with the drain valves and blowdown valves that are typically associated with a pig trap or other isolation vessel associated with a maintenance or service operation that has a set of blocking valves and the necessary drainage and blowdown valves. Through these connections, organic compounds that are isolated between the blocking valves are caused to flow into a product recovery tank that may be located on a truck bed or some other suitable portable carrying means.
Once the products have been essentially completely recovered from the pig trap or other isolation vessel, the entire recovery system may be purged of organic materials so that it is safe to close and disconnect.
It should be noted that the initial flow from the pig trap or isolation vessel will ordinarily be due to the existing pressure as well as product volatility of some (but not all) of the products being handled by the main system. Thereafter, nitrogen or any other appropriate purging gas (even methane or natural gas could also be used to advantage in some processes), may be employed to complete the product recovery phase.
The final part of the product recovery phase is typically performed under pressure. First, a “purging” phase is conducted, to “push” the organic materials through the collection system with a suitable gas, such as nitrogen. Thereafter, where appropriate, a suitable vacuum may be applied to help vaporize and remove the remaining hydrocarbons. This is especially helpful with volatile organic compounds, the preferred target of this process. On materials like crude oil with considerably lower vapor pressures, applying a vacuum accomplishes very little. However, on materials such as propylene, butenes (alkenes), and the lighter alkanes (defined as having eight or fewer carbon atoms), which products tend to vaporize relatively easily, a vacuum is advantageously applied. The equipment used in the process of the invention is adapted to handle both positive and negative pressures.
The method of the invention basically involves:
The method of the invention requires at least one trained operator and a portable unit that may be affixed on the bed of a truck but can also be transported to the appropriate location by other mobile transport means, as will be understood by those skilled in this art. The method sometimes also requires the cooperation of those employed at the specific pipeline operation at which the method is to take place.
The portable unit used in this invention method may comprise:
The purging means and the recycling means used as described above may be powered by an internal combustion engine that is no larger than that typically found on motor vehicles, specifically automobiles. The engine, suitably sized to accomplish the desired purging and pumping operations, is adapted to generate the determined negative or positive pressure by any means suitable and well within the skill of those having ordinary skill in this art. It will also be noted and understood by those skilled in this art that the engine may also be adapted to run on the particular volatile hydrocarbon that is being recovered, or a mixture of such a hydrocarbon mixed with a suitable natural gas, gasoline, or diesel fuel.
The recovery of the products and the subsequent combustion/oxidation of the vapors of the VOC's, further reduces the “potential to emit”.
Advantageously, the present invention provides for the reduction of venting and flaring in pipeline operations associated with oil and gas production and petrochemical manufacturing and refining. This is accomplished by operating several systems together to accomplish the stated objectives of: i) reducing venting and flaring to the atmosphere; ii) maximizing product recovery; iii) documenting the operation to assure regulatory agencies that objectives were accomplished.
An example is used below of a “pigging” operation, where a “pig” or “swab” is received into a pipeline “pig trap”. A pig trap is a system of piping and valves constructed to receive a “pig” or “swab” and is generally arranged as shown in
Description of Normal Pig Trap Operation
In normal operation of a pipeline 100, a trap bypass valve 102 is open and a trap valve 101 and a trap jump over valve 103 are closed. The trap valve 101 and the trap jump over valve 103 serve to isolate a pig trap 107. The system also includes a test valve 108 up to 1500 feet upstream of the pig trap 107.
When the pigging operation is initiated, the trap valve 101 and the trap jump over valve 103 are both opened and the trap bypass valve 102 is closed. Once a pig (not shown) is captured within the pig trap 107, the trap bypass valve 102 is opened and the trap valve 101 and the jump over valve 103 are closed. This action isolates the pig in the pig trap. Before a trap closure 106 can be opened and the pig removed from the pipeline system, a drain valve 105 is opened for the isolated pipeline product material to be vented or flared to the atmosphere through a discharge line 110. Once the drain valve 105 is opened, the trap can be purged by attaching a nitrogen connection to a blow down valve 104. The nitrogen purge then purges the excess material from the pig trap through the drain valve 105. Once the pig trap has been purged, the trap closure 106 can be opened to remove the pig.
When the trap closure 106 is opened, in many cases, personnel working in the area must be in personnel protective equipment (PPE) that may include protective clothing or special breathing apparatus to insure the health and safety of the personnel in the area. Indeed, in many cases, liquid is trapped behind the pig and this liquid is spilled on the ground or a container on the ground and must be placed in drums later. This trapped liquid is easily handled by placing a “T-handle” (like a pipeline location probe) in the trap 107 with the “T-handle” butting up to the closure 106 and the length of the “T-handle” that extends from the pig trap closure flange past the jump over piping connection including jump over valve 103. This enables the pig to end its journey in the pig trap slightly higher and allowing trapped liquids to pass into the drain. This helps assure that the pig trap is properly emptied in the purge procedure and makes a safer entry of the pig into the pig trap with a minimum of trapped hydrocarbons.
Description of Pig Trap Operation and the Invention
The method of the present invention eliminates the waste of the fluid that would otherwise result from the operation of the prior art as just described. The method of this invention may define different operating modes. These modes can be described as follows:
As previously described, in normal pipeline operation, the trap bypass valve 102 is open and the trap valve 101 and the trap jump over valve 103 are closed. When the pigging operation is initiated the trap valve 101 and the trap jump over valve 103 are both opened and the trap bypass valve 102 is closed. Once the pig has been received in the pig trap 107, the trap bypass valve 102 is opened and the trap valve 101 and the jump over valve 103 are closed. This action isolates the pig in the pig trap along with remaining product. The invention is ready to be attached to the components in the pig trap.
Connecting the Invention and Taking Safety Precautions
The purpose of the following safety precautions section is to set up the invention, preferably at a shop prior to moving the invention to a work site, and then to connect the invention properly to operating equipment. This section provides a checklist and a description of all of the valve positions and equipment states that should exist for the invention when operations are initiated.
Once the pig is isolated in the pig trap as described above, the following should be accomplished:
a) A responsible operations person should check the trap valve 101 and the jump over valve 103 to make sure both valves are closed. If either of the valves is motor operated, the valve operator should be placed in the manual mode so that the valve cannot be remotely operated. Both valves are then appropriately “locked out and tagged out” for the duration of the time the pig trap (or other equipment) is being maintained. For the duration of the time the invention is in use, the invention operator should have the “lock out tag out” keys that lock the valves 101 and 103.
b) Once the trap valve and jump over valves have been secured, the protecting blind flanges or bull plugs should be removed from the drain valve 105 and a blow down valve 104. Once the blinds or plugs are removed, a flexible hose or line is attached to the pipe 110 at the drain valve 105 to connect the system of the present invention at a system block valve 200 as shown in
c) All systems, motors and test equipment should be checked before transporting the system of
d) While the motors and test equipment are warming up, a nitrogen blanket should be established on a product recovery vessel 240 by opening a nitrogen valve 340 and a nitrogen pressure regulator 320 that provides nitrogen to the product recovery tank 240. The product recovery tank 240 may include an internal vaporization exchanger 360 inside the product recovery tank 240 to vaporize liquid nitrogen and thereby cool higher vapor pressure products in the product recovery tank 240, such as ethylene, for example.
e) Next, the product recovery tank regulator 320 should be adjusted so that the regulator 320 will hold roughly 100 pounds per square inch gauge back pressure, depending on the product to be recovered, before relieving to a purge system liquid knockout drum 440. This regulator may require adjustment to adjust the back pressure to be higher or lower depending upon the ambient conditions and the product material being recovered.
f) A purge system block valve 430 should be closed and “lock out-tag out” procedures should be used to make sure this valve is closed until needed in the purging process.
g) A product recovery block valve 210 should be in the closed position but not locked out and a product recovery tank block valve 230 should be in the open position. A flow meter 227 should be reset to zero and a reading of the total flow noted. A flow reversal valve 223 should be in the closed position.
h) All connections between the invention and the pipeline operating equipment of
i) Other valve positions and component states in the system are listed by number in the table below:
Operating in the Product Recovery Mode
The purpose of the product recovery mode is to recover as much of the isolated product as possible so that the isolated product is not vented to the atmosphere; it is not flared to the atmosphere; and it can be returned to the pipeline or plant facility or the product can be carried to an offsite location and be beneficially recycled.
Product recovery, as considered in this invention, has distinct operational phases: a) in a first phase, 98% to more than 99% of the product is recovered while the pipeline system is under pressure (propane, for instance will be under roughly 200 to 250 psig of pressure) either from the pipeline due to product volatility or from nitrogen (from the storage area of the invention) applied to “chase” the pipeline product out of the pig trap; b) in a second phase, residual product that cannot be recovered is “sucked” out using vacuum and is combusted; c) a purge phase where the pipeline equipment is purged to the point that the system is safe to open, and finally d) recycling of the product that occurs when the recovery stage is complete. The recycle phase can be performed either onsite based on the instructions from the operations person or be performed offsite at an arranged location.
Once the equipment in the invention is set up, connected, and operating as defined in the prior section, the equipment operator can initiate the product recovery mode and follow the steps as outlined as follows:
1) Open the pig trap drain valve 105 and allow the flexible connecting tubing (not shown) to fill with the pipeline product previously isolated in the pig trap 107. Then open the system block valve 200. At this point there should be a reading of the pressure in the pig trap 107 on a pressure indicator 205. Once the pressure on the pressure indicator 205 has been noted, slowly open the product recovery block valve 210. At this point there should be a sound of product liquid entering the product recovery tank 240. The operator should watch a level indicator 250 on the product recovery tank 240 and the pressure indicator 250 while product is being recovered.
2) Once the sound of the flow of recovered product diminishes, the flow meter 227 can be monitored. Once flow stops due to the pressure equalization between the pig trap 107 and the product recovery tank 240, the nitrogen purge valve 380, which was originally connected to the pig trap blow down valve 104, can be opened to blow nitrogen through the pig trap 107. This will chase out any remaining liquid in the trap 107 to the product recovery tank 240. The equipment operator should now check the flow that has occurred through the flow meter 227 and compare the flow meter 227 reading to a calculation of the volume of fluid isolated in the trap 107. If the flow meter 227 reading and the pig trap 107 volume calculation are reasonably close, say within 5%, the product can be considered recovered and the purge mode can begin. Otherwise, the pig trap 107 should be chased with nitrogen until more product is recovered.
At this point the pig trap is considered to be empty of free flowing product and the purge cycle can begin.
The Product Purge Mode
The purpose of the purge mode of operation of the invention is to scavenge and purge the remaining hydrocarbon products, generally less than 2% of the original isolated volume, from the pig trap 107 without releasing or venting to the atmosphere or utilizing a flare. Meeting these two conditions of no venting and no flaring meets and exceeds the most stringent environmental regulations. Venting has stringent monitoring and reporting requirements that require expensive equipment and extensive reporting. Flaring is subject to complex regulations under the Code of Federal Regulations, 40 CFR §60.18, that requires the equipment operator to install expensive monitoring equipment, requires periodic testing, and requires extensive reporting. Since no flare is used in the purging process, the operator does not have to incur the capital costs, high maintenance costs, recordkeeping requirements, and manpower required to comply with 40 CFR §60.18.
In addition, much of the cost of the product recovery and purging process is offset by the beneficial use of the product that was vented or flared in operations prior to the invention.
The previously described recovery process extracts and saves to the product recovery tank 240 about 98% of the hydrocarbon product isolated in the trap 107. A 6 inch pipeline pig trap, which will have an 8 inch diameter trap barrel some 6 feet in length with and 2 feet of 6 inch pipe will contain roughly 20 gallons of isolated product. The objective of the purging operation is therefore to remove less than 0.5 gallon of product remaining in the equipment without letting any product go to the atmosphere. Much of the product will be in the bottom of the trap 107 and will freely drain through the drain valve 105.
Once the product recovery mode is complete, the following operations should be performed for system purging and scavenging for remaining hydrocarbon vapors and residual liquids:
a) The product recovery block valve 210 should be closed and the lock should be removed from the purge system block valve 430 and placed on the product recovery block valve 210. The product recovery tank block valve 230 should be left open to prevent any pocketing of hydrocarbon vapors, in the event a highly volatile product has been recovered. The nitrogen valve 380 can be shut or throttled to low flow—shut being the generally preferred condition at the outset of the purge operations;
b) The invention operating personnel should make sure that the nitrogen test meter is running and connected to a sample point 550, that the engine emissions analyzer 670 is running and connected to a sample point 570 and may be easily connected to a sample point 590. In addition, the computer 660 should be running and able to acquire data from the engine analyzer 670 measuring the unburned hydrocarbon emissions from the sample points 570 and 590;
c) The engine 560, which functions as an oxidizer for the invention, should be running and the emissions analyzer 670 and the computer 660 should be calculating lambda (λ) for the operating engine;
d) A liquid accumulator drain valve 450 should be open and a nitrogen valve 470 should be closed a drain valve 490 to a liquid accumulator 480 should be closed;
e) Begin purging material to the vacuum pump 540 by slowly opening the purge system block valve 430. Stop opening when the ball valve handle is between an angle of 30 degrees to 45 degrees. Wait about a minute and listen if the vacuum pump 540 begins to load and feel the line with the hand between the purge system block valve 430 and the liquid knock out drum 440. This segment of line should become noticeably cooler over the next 60 to 120 seconds.
f) If the line segment described above becomes cooler, the liquid should be scavenged from the isolated portion of the pipeline equipment 107 in roughly 10 to 15 minutes.
g) At the end of the purging and scavenging portion of the operation, the person in charge of operating the pipeline 100 equipment may desire to further purge the pipeline equipment with additional nitrogen 350. If this is desired, open the nitrogen purge block valve 380 and allow enough nitrogen to flow to turn over two to three times the volume of the isolated product. This purging with nitrogen will normally be enough so that the pig trap 107 may be opened to remove a pig trapped in the pig trap.
h) At the end of the purging process, shut down the engine 560, the vacuum pump 540, shut the nitrogen valves 340 and 380, open the liquid accumulator drain valve 490 and allow any accumulated liquid to flow into the product recovery tank 240. Once the liquid in the accumulator is sent to the product recovery tank 240, then the accumulator drain valve 490 should be closed again. The purge system block valve 430 should be closed and locked. The system block valve 200 should be closed and the flexible line removed from the system block valve 200 and the trap drain valve 105. The nitrogen line should be removed from the nitrogen purge block valve 380 and the trap blow down valve 104.
Operating in the Product Return or Recycle Mode
Based on the product purity and contamination specifications, the recovered product in the product recovery tank 240 may now be returned to the pipeline system 100 or beneficially recycled to an offsite facility.
The procedure to return the product to the pipeline system can be performed as follows:
At this point the product recovery, purging and product return operations at this site are complete.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
This application claims the benefit of U.S. Provisional Patent Application No. 60/755,929 filed Jan. 3, 2006.
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| Number | Date | Country | |
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| 20070151603 A1 | Jul 2007 | US |
| Number | Date | Country | |
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| 60755929 | Jan 2006 | US |
