Monetization of the Nigeria Flared Associated Natural Gas Stream in Real-Time Via Conversion to Multiple Utilization Options Using Modular Units

Abstract

The previous nine research investigations on this series for the monetization of the associated stranded natural gas in Nigeria, discussed the quantitative conversion of the entire flare stream from a single processing facility to one specificend product such as CNG, LNG, LPG, NGH (GTH), GTW, GTL, NGLs and various petrochemicals including nitrogenous fertilizer (ammonia/urea). In this concluding publication, the flare stream from a given facility is divided into five fractions and each fraction is used for the production of different specific end products via various skid mounted processing units.

 For this study, the 20 MMscfd flow rate flare stream, is composed of 0.492MMscfd impurities,3.8 MMscfd ofnon-methane hydrocarbons and15.708 MM scfd methane. The extracted natural gas liquids (NGLs), containing ethane, propane, butane and natural gasoline (C₅+ hydrocarbons), could be used directly as ethane, commercial propane, commercial butane, propane- butane mixture (LPG), and natural gasoline or as a feedstock for petrochemical/ chemical end products. The purified methane stream is divided into 5 fractions in the ratio (4: 4: 4: 2: 1.708) for electric power generation, synthetic fuel production, nitrogenous fertilizer production, LNG/CNG/NGH production and petrochemicals/chemicals production respectively, using various technologies available from different licensors for small-scale natural gas modular monetization facilities. Applying the heat of reaction concept for the combustion of methane (when one mole of methane burns, 212.8 kcal of heat are released to the environment) and the relation (one standard cubic foot represents 1.19804 moles or 0.0026412-pound moles). For 4MM scfd, it is 4,000,000 x 1.19804    =   4,792,160 moles, and the overall heat energy or internal potential chemical energy on the fraction becomes 4,792,160 x212.8 k cal = 1, 019,771,648 k cal or (1, 019,771,648 x 4.184   = 4,266,724,575.232 KJ) while the equivalent conversion to power electricity energy is 14,654.16 kW (approximately   15 MW).

Existing GTL processes convert between 8,500 -12,000 scf of natural gas to about one barrel of synfuel depending on scale of the plant, or between 15MM Btu to 20MM Btu, to about one barrel, but the conventional standard is 10,000 scf, with 80% selectivity for nC₅+ . Therefore 0.8 x 4 MMscfd   = 3,200,000 scfd, which yields: 3,200,000 scf/10,000 scf    = 320 barrels, equivalent to 42 x 320 = 13,440 US gallons or 160 x 320 = 51,200 liters.In the Haber-Bosch process balanced equation, the 4 MMscfd fraction, which is equivalent to 4,792,160 moles or 76,674,560grams of methane, reacted with steam to produce 14,376,480 moles or 28,752,960 grams of hydrogen. Subsequent reaction of this quantity of hydrogen with nitrogen from the air produced 162,933,440 grams of ammonia which then reacted with carbon dioxide to produce 287,529.600 kg of urea, equivalent of about 5,750.592 bags of 50kg fertilizer per day.  Applying their different thermal efficiencies, the available retail heat energy for each of the gas to gas options, using the 2 MMscfd fraction is (CNG      2MMM Btu x 0.93 = 1,860,000,000 Btu),     (LNG      2MMM Btu x 0.91 = 1,820,000,000 Btu), and (NGH   2MMM Btu x 0.85 = 1,700,000,000 Btu).

The use of assorted petrochemicals and chemicals plants yields various products from the 1.708 fraction such as plastics of all descriptions, cleaning agents (e.g.  soaps and detergents), solvents, dyestuffs, greases waxes, paints, synthetic textiles (e.g. artificial fibers, polyester clothes), synthetic rubbers, epoxy resins, flooring, insulating materials, and products as diverse as aspirin and other drugs, luggage, boats, automobiles, aircraft, adhesives, refrigerants, antifreeze, aerosols, alcohols, explosives, recording discs and tapes etc. This approach is designed to satisfy the various needs of the immediate communities/states for the products, create numerous job opportunities as well as earn very huge revenue from surplus products sales.