Patent Application
20110099128
Not Applicable
These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:
Natural gas is an essential energy source in the United States. It is one of the cleanest, safest and most useful of all energy sources. It is used both commercially and residentially and is a major source of energy for the power generation industry.
Natural gas extracted from the ground is made up primarily of methane gas. Raw natural gas exists in mixtures with other hydrocarbons, such as ethane, propane, butane and pentanes. These other hydrocarbons are in vapor and liquid form. Typically, raw natural gas from shallow wells is composed of the following components:
Marcellus Shale natural gas fields which are typically found primarily in the northeastern United States yield a natural gas that has a slightly (but economically significant) different makeup of hydrocarbons than that of shallow wells:
Thus, by comparing
Prior to any raw natural gas being transported via pipeline, it must be processed at or near the well head through a field processing “Extraction Plant.” The Extraction Plant removes the various hydrocarbons from the methane gas, which are also referred to a “Y-grade liquids.” The methane is sent directly to the gas pipeline for commercial and residential sales.
This extraction process recovers a large percentage of the ethane in the gas stream, along with the other hydrocarbons. A small percentage of ethane can be re-introduced into the sales gas stream (which is made up primarily of methane); however, great care must be taken that the pipeline content does not exceed imposed restrictions on the final gas composition. Regulations require that the natural gas pipeline have a British Thermal Unit (“BTU”) value maximum of 1,100 BTU with an average value of 1,000 BTU. The normal expected BTU from methane is 1,000 and the normal expected BTU of ethane is almost 1,800. Thus, by adding too much ethane to the methane gas pipeline, the overall BTU will be too high and unusable for either commercial or residential use.
Typically, once the Y-grade liquids are removed from the raw natural gas stream by extraction, this liquid must be further separated down into their base components (e.g., ethane, propane, butane and pentanes). These separated components have a higher market value than they do as part of the Y-grade liquid. The Y-grade liquids are broken down by a Fractionation Process.
Under most circumstances, current technologies and distribution modalities utilize virtually all of the propane and butane from the Y-grade liquid. As previously stated, ethane can sometimes be added back into the natural gas pipeline, but only in limited amounts due to its high BTU value. To further compound the ethane problem, the only current alternative to ethane use (other than being added back into the natural gas pipeline) is to mix the ethane with the Y-grade liquids for further processing at a fractionation facility. However, shipments to fractionation facilities that exceed 4% ethane are either rejected or the extraction plant is penalized creating additional cost. Accordingly, current stocks of Marcellus Shale Y-grade liquid are ripe with ethane that has no real substantive market for its use.
One embodiment of the current invention is applicable in the landfill industry. The ethane gas is mixed with a landfill's waste gas stream (usually primarily composed of methane) and sent to an incinerator or flare to burn residual and commercial waste products at the landfill or to help burn afluents separated from the landfill gases.
The method of the current invention requires that ethane-laced Y-grade liquid be transferred to a fractionation facility near or at a landfill via truck or train. As set forth in
The vapor from the Y-grade liquid (made up primarily of ethane and traces of propane) is maintained 53 at 200 to 215 pounds per square inch to control boil off and is then sent directly to the landfill's flares 54 for incineration of landfill materials.
The Y-grade liquid is pumped 41 to a maximum pressure of 230 pounds per square inch. Then it is pumped into a heating unit 42 and heated to 150 degrees Fahrenheit. The heated fluid then passes into a de-ethanizer tower 43 where ethane 48 is vaporized out of the fluid. Once the ethane is separated out as a gas, natural expansion occurs 49. The ethane gas can then be mixed with methane gas 51 which originates from the landfill itself. The mixture is then adjusted to achieve a BTU level 52 of 1,100, which yields a temperature of 1,600 to 2,100 degrees Fahrenheit. A gas chromatograph is used to read the BTU of the mixture. This mixture is then sent to customers as sales gas 53. The mixture can be sent directly to a stream to mix with other gasses for use as a fuel in many industries. Ethane not mixed with methane is simply sent to the landfill 50 for use in flare burn.
The liquid product resulting from the de-ethanizer process 43 is then further fractionated in a de-propanizer/de-butanizer 44. This fractionation will make pure propane 45, pure butane 46 as well as hexanes 47 for wholesale commercial and residential sales of propane and butane.
Thus, by using ethane to aid in the incineration process, a landfill can decrease its reliance on methane it gets from the gas pipeline and realize a decrease in its incineration costs.
From the descriptions above, a number of advantages of the methods become evident:
The present application claims the benefit of U.S. Provisional Application No. 61/255,118 filed on Oct. 27, 2009, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61255118 | Oct 2009 | US |
