Behind the scenes of a CNG station
Published: May 21, 2013
ATHENS TWP. — When a driver pulls into a mini mart for gas, there is usually a small building as well as gas pumps. The vehicle gets fueled at the pumps and the driver and passengers often will go into the building for coffee for their own refueling. That building, depending on which company owns it, will have anything from one coffee pot to a whole selection of flavors and types of brews, as well as breakfast and/or dinner menus plus a small selection of groceries.
Times are changing. At least that is so in Towanda and in Athens. Some vehicles aren’t refueling on gasoline. And there are no gas pumps at the new station in Athens Township at the corner of Elmira and Pine streets. What looks like pumps there are actually dispensers, and they are dispensing compressed natural gas (CNG).
How is CNG different from gasoline? The most obvious answer is that gasoline is a liquid; CNG is just as it says -- a gas. As a fossil fuel substitute for gasoline, diesel fuel or propane gas, according to the website CNGNOW.com, CNG is much safer than other fuels because in the case of a spill, it dissipates into the air rather than pooling on the ground. Natural gas is primarily methane (CH4), which is a greenhouse gas that could contribute to global climate change if leaked. CNG is made by compressing natural gas to less than 1 percent of the normal volume it occupies at standard atmospheric pressure. CNG is stored in cylindrical or spherical containers at a pressure of about 2,900 – 3,600 psi or pounds per square inch. Compare this pressure to the normal average pressure in a car’s tire, which is 35 to 45 psi. Compressed natural gas is colorless, odorless and tasteless. On average, it costs about 50 percent less than gasoline or diesel. Depending upon make and model of vehicles, it emits up to about 90 percent fewer emissions than gasoline.
The new Dandy Mini Mart in Athens Township is an unmanned CNG station. The concrete block building that is across the lot from the dispensers is not a mini mart. You won’t be able to enter and buy a cup of coffee.
So, what actually lies behind those concrete block walls? Cody Wenzel and Adam Girardi, of Beavers Petroleum & Alternative Fuels in Horseheads, who were contracted to build the station, gave this writer a tour and explained how the system works.
According to Wenzel, there are several tanks that hold the CNG and store it and keep it dry before it makes its way across the parking lot underground through high-pressure, stainless steel tubing. The natural gas comes into the concrete block building through a large diameter, gray, metered line. Then it goes through the PSB dryer that removes any moisture from the natural gas before it enters the compressor.
The PSB dryer, which is a very large, aluminum-colored tank manufactured by PSB Industries in Erie, Pa., is filled with a type of desiccant which acts as a drying agent. A desiccant is a hygroscopic (ability of a substance to attract and hold water molecules from the surrounding environment) substance that sustains or induces a state of dryness in the area surrounding it. Wenzel explained this very well in layman’s terms. The desiccants used in the PSB dryer are very similar to those little packets you often find in a shoe box when you purchase a new pair of shoes, or the packets found in a container of pills. But there are lots more desiccants in this PSB dryer than in the little packets. They both do the same job; they keep moisture out.
As Wenzel continued the tour he explained that the drying process is so important because any moisture in the gas has to be removed before the gas is compressed. He gave an example to help better understand this. Imagine 100 gallons of natural gas with 1 percent liquid in it that will be compressed down to only about a tablespoon. If the moisture isn’t removed, there would be a lot of moisture in that tablespoon of gas. The gas is compressed, but the amount of moisture stays the same; unless it is removed.
After the moisture is removed, the natural gas enters the compressor, which compresses the natural gas from about 50 psi to close to 4,000 psi. According to Wenzel, this change in compression is necessary in order to quickly fill a vehicle’s tank.
After being compressed, the gas flows into large white cylindrical storage containers ready for use.
From the storage containers it runs through a line that contains several filters. These filters remove particulates from the gas before it goes out to the dispensers.
The last leg of the journey for the CNG takes it out through the wall of the concrete block building through high-pressure, stainless steel tubes that run underground across the lot to the dispensers.
The dispensers operate pretty much the way gasoline pumps operate. Use a credit card and follow the directions on the dispenser. There are a few more instructions to follow, but most of them are precautions for safety.
The only thing that CNG users won’t be able to do right now at this Dandy station in Athens Township is buy a cup of coffee. But perhaps they can find one down the road.