Abstract
Natural gas plays a growing role in the energy mix by displacing coal due to its relative economic and/or environmental advantages A process of natural gas liquid (NGL) recovery utilizing internally generated energy to achieve energy efficiency was designed. The process utilizes heat generated from the compressor end of the turbo-expander to provide heat energy required to maintain the appropriate operating conditions at the intermediate and bottom sections of the demethanizer column, rather than utilizing dedicated steam generators that requires additional construction, installation, operations and maintenance cost. Simultaneously, the temperature of the hot residue gas is also dropped to the required range for export, rather than utilizing dedicated process gas coolers. The various unit operations such as heat exchangers, liquid separators, Joules Thompson Valve coefficient, demethanizer column, reflux condenser, and bottom reboiler were designed, and cost evaluation performed for each unit, while models were solved using MatLab software. The quality and composition of NGL and residue gas produced are consistent with industrial process plant data. In addition, condenser and reboiler showed that the heat removed from the condenser is 3.180.5kW and 1.65m 2 area was exchanged, while the heat for the reboiler is 474.5kW at 47.25m 2 exchanged area. Also, the temperature profile of the demethanizer column is not uniform as lower temperature is required for the rectifying section (cryogenic absorption). Thus, temperature of -90 o C to – 95 o C favours the production of sales gas as the top product stream, while a temperature range of 30 o C to 36 o C at the bottom favours the recovery of NGL product as the bottom stream. The height and diameter of demethanizer column for distillation and absorption sections are 28m and 1.55m and 7.24m and 3m respectively. Keywords: Natural Gas Liquid, Heat Exchanger, Separator, J-T Valve, Demethanizer Column, DOI: 10.7176/CPER/64-04 Publication date: January 31 st 2022
Highlights
The current renaissance in oil and natural gas production worldwide has provided economic benefits globally, through higher employment and lower energy prices(USEIA, 2018)
This study focuses on utilizing heat energy generated from hot process gas in the natural gas liquid (NGL) recovery process, to serve as hot fluid for the reboilers and heat www.iiste.org exchangers of the Demethanizer Column, thereby eliminating additional cost of installing and maintaining steam generators, and process fan coolers
4.1 Sales Gas and NGL Produced The produced residue gas is mainly methane gas with a molecular weight of 16.16Kg/kmol, flow rate of 57.28Kg/s, temperature of -90°C, pressure of 24bar and compositions of C1 (99.17%) and nitrogen gas (0.08%), while the NGL produced from the bottom of the demethanizer column has specific gravity of 0.470, flow rate of 27Kg/s, temperature of 28°C, pressure of 24bar and compositions are C1 (0.45%), C2 (31.94%), C3 (31.66%), iC4 (8.9%), nC4 (11.57%), iC5 (4.39%), nC5 (3.42%), C6 (3.06%) and C7+ (4.61%)
Summary
The current renaissance in oil and natural gas production worldwide has provided economic benefits globally, through higher employment and lower energy prices(USEIA, 2018). Natural gas plays a growing role in the energy mix by displacing coal due to its relative economic and/or environmental advantages in some markets. The application of horizontal drilling and hydraulic fracturing techniques in oil and gas production is among other technological factors that has revolutionized the energy system(USDE, 2018).Natural gas is a key component of global energy supply and the cleanest fossil fuel. It is the safest and most useful of all sources of energy(Kidnay et al, 2006). Increasing from an estimated value of 130.8trillion standard cubic meter (tscm) in 1998 to about 170.2tscm in 2008, 196.1tscm in 2017, and has further increased to about 196.9tscm in 2018(Statistical Review, 2019)
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