- Published on Tuesday, 17 June 2014 09:53
- Written by Kate Kunkel
The VMA’s recent Technical Seminar focused in large part on fugitive emissions, and with good reason. Plant and community safety, air quality and loss of product are all affected by emissions, so it is in the best interests of refiners, chemical companies, valve manufacturers and citizens to keep them as low as possible.
Sources of fugitive emissions include flares, flanges, pumps, tanks, relief valves and valves. In fact, more than 50% of fugitive emissions come from valves, and more than 75% of valve leaks come from the valve stem. Other sources of leaks include other fittings on the valves, but most leaks are from the flanges.
One of the presenters at the technical seminar was Ken Garing, who is with the National Enforcement Investigations Center of the Environmental Protection Agency (EPA). According to data shown in his presentation, it is generally only 1 to 2 % of valves in any one facility that are actually leaking. And while it is true that relatively few valves are actually leaking and many of those leaks are small, the amount of emissions that come from that small percentage of valves can range from a few pounds up to a ton of emissions from one valve in a year. If a facility has a couple of hundred thousand valves, 1 or 2% still means that 2,000 valves could be leaking. If each valve leaks anywhere from a few pounds to several hundred pounds per year per valve, that equals a lot of emissions.
Garing said that monitoring results are used in calculations for state emission inventories. According to the terms of their permits, facilities have to pay per ton of emissions. If they have a lot, then they have to pay for them, based on the kind of emission.
These figures also end up in reports that go to regulators, and citizens also have access to see those figures. “Citizens keep very close tabs on toxic release inventory,” said Garing. “If figures are high, this can get citizens fired up, but it also means a loss for producers.”
Leak Detection and Repair
Since the 1980’s when it first went into force, leak detection and repair (LDAR) has remained a high priority item for the EPA because air quality protection is part of the EPA’s mandate. The goal is to monitor, find and fix any sources of emissions.
Many of the large refineries and chemical plants in the U.S. list between 10 and a 100 tons of fugitive emissions. “One of the most memorable examples,” said Garing, “was a refiner that had leaks in 50% of the valves in one part of the refinery. Of 350 valves, 170 of them were leaking.”
Garing pointed out that it is a misperception that, just because a valve leaks, it is a violation of the regulations. That is not necessarily true. States like California have other rules, but usually, particularly for federal regulations, it is only a violation if it’s not fixed in the right amount of time.
There are multiple regulations dealing with LDAR. They are all based on when the facility was built, what chemical it makes and whether it’s a hazardous air pollutant. Each facility must monitor valves, flanges, connectors, compressors and pumps. Generally, this must be done either quarterly or annually, but for facilities operating under consent decrees, it is quarterly. Garing said that currently, there are nearly 70 LDAR regulations; he recommended that anyone go to Sub part F for the latest, state-of-the-art requirements.
Monitoring Under Method 21
Method 21 monitoring is probably the single most expensive thing that plants do, according to Garing. Someone must physically take a testing instrument into the facility and actually touch every valve, flange, and connector in the facility, “vacuum” the air around it and analyze for leaks. If a leak is found, the operator must stay at that spot for twice the response time of the instrument. Typically it takes 30 seconds to a minute or two for each valve, to find the right spot to take a reading.
“In some of the bigger refineries in Texas and California,” said Garing, ‘”there could be up to 15 people full time going around the facility looking at valves, monitoring for leaks. Companies could be paying half a million dollars or more a year to monitor leaks.”
The device normally used for testing (see photo) is called a TVA. It weighs 18 pounds and works basically like a vacuum, sucking up the air around the valve at about a liter of air per minute. To ensure the instrument is working correctly, calibration must be done daily in the facility, and it must be sent to manufacturer quarterly to be sure that it is accurate. Also, every year, every TVA must be sent in to be certified by the manufacturer.
The rule of thumb is that, when a valve shows leaks, it should be taken out of service and fixed. “In the case of chronically leaking valves,” said Garing, “in many of the consent decrees, the EPA has imposed that they drill and tap them. The facility cannot wait until the next turnaround when the valve is out of service to do the repair. Some of them have four, five, or six of these procedures done, at a cost of about $250 each, but it is a way to repair the valve while it still is in service instead of shutting down the entire process unit.”
A hydrocracker cannot be shut down every time there is a leaking valve, but the regulations do stipulate how long a facility has to repair a valve. Garing said that generally, the regulations allow 15 days to repair a valve, but it also says that if it can’t be done in that period, the valve can put on delay repair list, to be fixed on the next turnaround. A late repair or never repaired valve is usually a compliance issue.
Garing indicated that, since refiners and chemical plants have a huge financial incentive for keeping leaks to a minimum, this is also reflected in the way they purchase valves. A lot of refiners are moving toward a purchasing practice in which suppliers must be on an approved vendor’s list. They must be certified as low emission valves. If the manufacturer does not have that certification, chances are, they may not be able to bid on plants.
Nearly all facilities now have all of the test results in computer databases. This facilitates better reporting and compliance and in fact the EPA is moving toward requiring that all facilities turn in all of their results electronically. This is partially to be sure that data does not get lost. In the past, there were so many people involved, data could be misplaced. Now the EPA and the state will be able to analyze and monitor the electronic data.
There are also companies dedicated to collating the databases for individual facilities. Such companies can recommend follow-ups and even do calculations for reporting. While this is a very sophisticated way of ensuring compliance, according to Garing, it is also prone to errors.
Advances in Monitoring
Garing was enthusiastic in discussing new monitoring technology. “Now there are new infrared (IR) cameras that show exactly where emissions are coming from. You can actually see the hydrocarbons leaking,” he said. The IR cameras look only at a very narrow band of the infrared spectrum where most of the hydrocarbons absorb energy: at 3.2 to 3.4 Hz. That is where benzene, propane and methane absorb energy and give off heat.
Garing warned that, while the IR camera is a very powerful tool because you can look at many things, it cannot see leaks as small as users are required to find. That means they must monitor more frequently. “The theory is that if you find a bigger leak sooner, you cut the emissions sooner,” he said.
Another development that Garing found interesting is that now there are consultants working in the facilities who keep track of who has what valve in these different facilities. With this information, they can actually track the leak rates of specific valves from specific manufacturers, so the different valve manufacturers are being tracked. “It’s a powerful incentive for manufacturers to be especially vigilant,” he said.
Garing was also excited about the new vehicle the EPA has, which is outfitted with equipment that can suck in the air around a facility. With analysis much like that from the TVA, the emissions can be measured and the EPA can plot methane or benzene. “While they cannot find out which valve is leaking,” he said, “they can literally see which unit has the leaks.”
While there are many advances in detection and sealing technology, the bottom line is that there are still enough fugitive emissions that the EPA has just proposed changes in refinery emissions rules. The proposed changes would, according to the EPA, reduce toxic air emissions by an estimated 5,600 tons per year. They would compel operators to upgrade storage tank emission controls, adopt new emission standards for delayed coking units, monitor benzene emissions along their fence lines and ensure waste gases are properly destroyed. These changes are in an 870-page document that came about as a result of a lawsuit filed on behalf of people directly affected by emissions from refineries in California, Louisiana and Texas.
All images copyright and courtesy of the Environmental Protection Agency and were included in Ken Garing’s presentation at VMA’s 2014 Technical Seminar.