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Natural Gas Reservoirs

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1 Natural Gas Reservoirs
Commercialization of Nitrogen-Rich Natural Gas Reservoirs Albert Curtis & Monique Wess Low Quality Natural Gas Statistics Introduction Engelhard Corporation’s Molecular Gate PSA Abstract Natural gas is one of the most vital sources of energy in the United States. It supplies approximately one half of all energy used in residential areas, and is one of the most promising fuel sources for industrial and commercial applications making up 18% of U.S. electricity generation by fuel sources1. Natural gas is a fossil fuel made up of primarily methane along with traces of heavier hydrocarbons such as ethane, propane, and butane. The gas is colorless and odorless, but generates a great deal of energy when combusted. Natural gas is favored because unlike other energy sources, the combustion of natural gas is clean and does not emit harmful substances into the atmosphere. The table below displays general composition percentiles of natural gas. With the natural gas supply in the United States not being able to support the nations demand for natural gas, the US will either have to find more sources for natural gas or import more natural gas from foreign countries. One of the potential sources to increase natural gas supply is to use nitrogen rich natural gas. The objective of this study is to identify and analyze potential uses for nitrogen rich natural gas reserves. An economic analysis will be shown on the feasibility of production and commercialization of nitrogen rich natural gas. The separation options include the purification of natural gas by cryogenic distillation, pressure swing adsorption, membranes, and molecular gate technology. The commercialization options include conversion of methane to synthesis gas and its derivates and combustion of natural gas for power generation. A mathematical model was built to determine the best process combination based on maximizing net present worth. - - A mathematical model was coded and run using the Generic Algebraic Modeling System (GAMS) as interface based on Mixed Integer Linear Programming (MILP) (Cplex is the solver used). Chemical Formula Composition Percentile Methane CH4 70-90% Ethane C2H6 0-20% Propane C3H8 Butane C4H10 Carbon Dioxide CO2 0-8% Oxygen O2 0-0.2% Nitrogen N2 0-5% Hydrogen sulfide H2S Rare gases A, He, Ne, Xe trace The molecular gate pressure swing adsorption process, originally developed by Engelhard Corporation, has proven to be more cost effective than the traditional process. This adsorption is unique from other adsorption processes, as the nitrogen is adsorbed instead of the methane. The simplicity and reliability of this new technology has made it a leading option for upgrading nitrogen contaminated steams since its commercialization in The molecular gate nitrogen system is capable of handling flow rates as low as 0.5 MMscfd with the economics of scale increasing with flow rate. The Molecular GateTM adsorbent is titanium silicate (CTS-1) designed with size selective pore openings to remove nitrogen from methane. The molecular sieve with a pore size of 3.7Å is custom designed to allow smaller nitrogen molecules (3.7 Å) to adsorb into the bed, penetrating the crystalline structure while larger methane molecules (3.8 Å) are excluded exiting the column at feed pressure6. Figure 6 illustrates separation by use of the Molecular Gate. Results Low Quality Natural Gas Reservoir Molecular Gate Pressure Swing Adsorption Low Quality Natural Gas Pipeline Quality Natural Gas N2 <4% Q > 5 MMscf/d Low Quality Natural Gas Reservoir Molecular Gate Pressure Swing Adsorption Steam Reforming Water Gas Shift Haber-Bosch Bosch-Meiser Boiler Steam Turbine Central Utility Plant Usage Low Quality Natural Gas Steam Electricity Urea Methane/Nitrogen Stream mixture - Pipeline Quality Natural Gas Syn Gas Hydrogen Ammonia 15%< N2 > 30% Q > 5 MMscf/d Low Quality Natural Gas Defined Low Quality Natural Gas Reservoir Boiler Steam Turbine Central Utility Plant Usage Steam Reforming Water Gas Shift Haber-Bosch Bosch-Meiser 4%< N2 > 15% Q > 5 MMscf/d Low Quality Natural Gas Steam Hydrogen Electricity Synthesis Gas Ammonia Urea Approximately 30% of all natural gas reserves in the United States contain low quality natural gas (LQNG). LQNG is gas from any reservoir containing excessive amounts of non-hydrocarbon components which place the gas outside of pipeline specifications. The most common contaminates of natural gas are carbon dioxide, nitrogen, and hydrogen sulfide. These non-combustible contaminates lower the heating value of natural gas and must be removed prior to use. Aside from lowering the heating value, the contaminants are toxic, corrode pipe lines, and harm the environment1. While there is no universal standard or government regulation for LQNG, the most commonly used specifications between gas purchasers and suppliers are as follows. Natural gas cannot contain2: greater than 2% carbon dioxide greater than 4% nitrogen greater than a 4% combination of carbon dioxide and nitrogen. Minor contaminates of natural gas include helium, argon, hydrogen, and oxygen, however these typically act as inert gases and pose no major problems in processing LQNG. Methane/Nitrogen Stream mixture Converted From Synthesis Gas Product General Production Formula Uses Methanol Simplest alcohol, light, volatile steam-methane reforming 2H2 +CO →CH3OH antifreeze, solvent, fuel, intermediate in the production of other products Acetic Acid weak carboxylic acid methanol carbonylation CO + CH3OH → CH3COOH vinyl acetate monomer and acetic anhydride Formaldehyde simplest aldehyde oxidation and dehydrogenation of methanol CH3OH → H2CO + H2 polymers and a wide variety of specialty chemicals Dimethly Ether Gaseous ether methanol dehydration 2CH3OH → CH3OCH3 + H2O aerosol spray propellant or a refrigerant The mathematical model produced three results depending on the nitrogen concentration of the natural gas as well as the size of the reservoir. With small natural gas reservoirs it is not profitable for additional processing of the natural gas due to the high startup capital costs of the equipment. If the reservoir size is greater than 5 MMscf/day the most profitable product is urea, the difference in the second and third results is that one keeps the nitrogen in the natural gas stream, which reduces the feed cost, however it increases the reactor sizes and capital costs. Urea Market Major markets: ≈90% of urea goes into fertilizers ≈10% in other commodity markets such as cigarettes, toothpaste, pretzels ect… The twenty-three processes examined as monetization options for LQNG are shown above. These options include: The removal of nitrogen to obtain pipeline quality natural gas. The combustion of natural gas as a fuel source to generate and sell electricity. The conversion of natural gas to synthesis gas by methane steam reforming. Several chemicals and fuels can be developed from synthesis gases that have potentially promising markets. Product General Production Formula Uses Ammonia colorless alkaline gas with penetrating odor Haber-Bosch process 3H2 + N2 → 2NH3 nitrogen source in fertilizer and the manufacture of urea Urea solid produced as prills or granules Bosch- Meiser 2NH3 + CO2 → NH2CONH2 + H2O fertilizers, plastics, and protein supplement in animal feed Hydrogen Colorless, odorless gas Steam reforming / Water gas shift reaction CH4 +H2O → 3H2 + CO processing of fossil fuels and to produce ammonia or methanol Synthetic Fuel liquid hydrocarbons Fischer-Tropsch process 3H2 + CO → CH4 +H2O diesel and naptha Summary Acknowledgements References The evaluation of nitrogen rich natural gas lead to two major conclusions. The first being that the most economical way of separating the nitrogen from natural gas is using pressure swing adsorption with molecular gate technology. The second is that the most economical product produced from nitrogen rich natural gas varies by reserve capacity and nitrogen content. If reserve capacity is low the natural gas is most profitable by removing the nitrogen using the PSA process and selling the natural gas via pipeline. If reserve capacity is high the most profitable product produced is urea and is most economically produced by separating the nitrogen out of the natural gas before processing at high nitrogen contents and keeping the nitrogen in when processing at low nitrogen contents. Quang Nguyen Shi Liu Roman Voronov Dr. Miguel J. Bagajewicz OAchenson W.P, Hackworth J.H, Kasper S., McIlvried H.R, “Utilization of Low-Quality Natural Gas – A Current Assessment,” K & M Engineering and Consulting Corporation. January 1993. Bailey K., Farberow C., “Green is Seen in Fertilizers - A New Approach to Municipal Solid Waste Management,” University of Oklahoma. 1 May 2007. Lavaja J., Lawson B., Lucas A., “Upgrading Low BTU Gas of High Nirtogen Content to Power of Pipeline,” University of Oklahoma. Kidnay A., Parrish W., “Fundamentals of Natural Gas Processing,” 21 June 2006. Molecular Gate® Adsorption Technology, Guild Associated Inc., Copyright 2007. Processing Natural Gas, NaturalGas.org, Copyright 2004. Electrical Generation using Natural Gas, NaturalGas.org, Copyright 2004.

2 Pipeline Quality Natural Gas Synthesis Gas Hydrogen Ammonia
Low Quality Natural Gas Methanol Steam Pipeline Quality Natural Gas Synthesis Gas Hydrogen Ammonia Electricity Urea Formaldehyde Acetic Acid Dimethly Ether Diesel and Naphtha Methane/Nitrogen Stream mixture Low Quality Natural Gas Reservoir Molecular Gate Pressure Swing Adsorption Steam Reforming Water Gas Shift Haber-Bosch Bosch-Meiser Methanol Synthesis Methanol Oxidation Carbonylation Dehydration Fischer-Tropsch Boiler Steam Turbine Central Utility Plant Usage Sold in Market Diesel and Naphtha Talk about selling intermediates

3 Low Quality Natural Gas Pipeline Quality Natural Gas
Low Quality Natural Gas Reservoir Molecular Gate Pressure Swing Adsorption Low Quality Natural Gas Pipeline Quality Natural Gas Talk about selling intermediates

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