Journal Pre-proof Effects of Non-hydrocarbons Impurities on the Typical Natural Gas Mixture Flows through a Pipeline Ammar Ali Abd, Samah Zaki Naji, Atheer Saad Hashim PII: S1875-5100(20)30072-X DOI: https://doi.org/10.1016/j.jngse.2020.103218 Reference: JNGSE 103218 To appear in: Journal of Natural Gas Science and Engineering Received Date: 30 November 2019 Revised Date: 13 February 2020 Accepted Date: 13 February 2020 Please cite this article as: Abd, A.A., Naji, S.Z., Hashim, A.S., Effects of Non-hydrocarbons Impurities on the Typical Natural Gas Mixture Flows through a Pipeline, Journal of Natural Gas Science & Engineering, https://doi.org/10.1016/j.jngse.2020.103218. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier B.V. Effects of Non-hydrocarbons Impurities on the Typical Natural Gas Mixture Flows through a Pipeline a Ammar Ali Abd Samah Zaki Naji a Atheer Saad Hashim a b b Chemical Engineering Department, Curtin University of Technology, Perth, Australia. Mechanical Engineering Department, Nottingham University, Nottingham, United Kingdom. Abstract Natural gas mixture flowing in the transportation pipeline is impure owing to the presence of various impurities. The presence of non-hydrocarbons impurities in natural gas mixture impacts the natural gas properties at different extents. The effect of the existence of each impurity on the natural gas mixture has not been sufficiently studied and widely understood. In this study, various mixtures containing typical natural gas compositions and one impurity at maximum allowable concentration, flowing in the pipeline are evaluated to elaborate their effect on the pipeline performance. A pipeline string of Rodersdorf to Lostorf taken from the Trasitgas project with 55 km is simulated using Aspen Hysys and validated by Aspen plus. The molar flow rate is 30382.32 kgmole/h, the internal and external diameters specified to be 875.4 mm and 900 mm. 67.5 bar and 63.29 bar were deployed as input and minimum pressures with 55 ℃ as input temperature, to keep the fluid in the supercritical phase. The impact of each impurity is studied and the deviation from the typical natural gas mixture is determined. These deviations were classified to grade the impurities in order of degree of impact on each parameter. All the impurities came with at least one negative impact on the typical natural gas mixture fluid flow. 10% of nitrogen had the highest impact on the pressure drop, temperature drop, viscosity, and phase envelope. 5% of carbon dioxide had the highest impact on the density of the mixture while 5% of hydrogen sulfide had the highest impact on the critical temperature and the critical pressure of the mixture. 0.05% of argon, 0.01% of oxygen, 147 ppm water, and 0.5% helium had the lowest impact, hardly affecting the properties of the typical natural gas mixture. Keywords: Natural gas properties; Phase envelope; Impact of impurities; Natural gas pipelines; pressure losses. Corresponding Author: Ammar Ali Abd E-mail: [email protected] 1. Introduction Worldwide, the natural gas industry is taking more attention as a source of clean energy that can replace petroleum. The demand for natural gas will record an explosive growth due to the flourishing of the world economy and growing population. A quarter of the consumed energy in the United State is from using natural gas while more than 20% of consumed energy is relying on natural gas in the European Union per year [1]. Globally, natural gas considers now a common primary source of energy accounting 22.1% of the total energy supply and contributes with 23.2% as a source of energy in power generation [2]. Girgin and Krausmann (2016) stated that the demand for natural gas is foreseeable to grow by 10% between 2007 and 2035 [3]. The natural gas industry includes different sections and components for production, treatment, sweetening, transportation, storage and distribution of the product to customers. The pipeline network is one of the most important parts of the process due to huge economic losses and serious environmental destruction that may result in any failure. Tan et al. (2016) mentioned that about 664 billion cubic meters of natural gas which consists of 66.5% of the world trade are transported through pipelines [4]. The natural gas pipelines classify into three types depending on the pipe geometry and the operating conditions namely gathering, transportation and distribution pipelines. Generally, the transportation pipelines are deployed to transfer a large amount of natural gas from the production section to the distribution section. The transportation network operates with high pressure to transfer natural gas a long way. Lanzano et al. (2013) mentioned that the large-scale transportation pipelines include about 300,000 km with a design diameter ranging between 24 to 36 inches and operating pressure 3.4 to 9.7 MPa in the United States [5]. In 2013, China executed more than 62,000 km of the natural gas pipelines [6], where the total pipeline’s length reached 100,000 km at the end of 2015 [7]. The national transmission system in the UK consists of 7660 km of transmission steel pipelines with a design diameter between 63 mm to 1200 mm and operation pressure around 85 bar [8]. While the overall length of the distribution pipelines network is 267,750 km with a design diameter between 300 to 600 mm [8]. The interstate natural gas association of Americans reported that between 160 and 210 billion dollars are the required investments in the natural gas pipeline infrastructure to finance the execution of 1200 to 1300 miles per year [9]. The materials of construction of natural gas pipelines are commonly cast iron, steel, and plastic. More specifically, the transportation pipelines are made from steel while the distribution pipelines are made from polyethylene [10]. Natural gas compositions can be considered as an important factor in the design of the framework and the operating conditions of the pipelines. Chaczykowski et al. (2018) stated that it is important to identify the quantities of natural gas constituents and contaminants for an accurate evaluation of energy delivery and/or flow assurance [11]. The compositions of the natural gas depend significantly on the period of extraction during the year, the production source, and the level of treatments. All the mentioned factors strongly influence the octane number of the natural gas mixture. Natural gas predominantly consists from methane as a major contributor, with the amount of ethane up to 14% as in natural gas from Abu Dhabi in the United Arab Emirates, and propane can reach 5% as in natural gas from Indonesia besides some other heavy hydrocarbons like i&n-butane, i&n-pentane, and hexane [12]. In the same vein, natural gas contains different non-hydrocarbons which can be classified diluents, contaminations, and solid matter. These components i.e N2, He, CO2, H2S, Ar, O2, H2O, and H2O consider impurities with typical maximum percent shown by Table 1, while other impurities with low concentrations do not significantly affect fluid properties and ignored in this study. These impurities can reduce the heating value of the natural gas as well as H2S and CO2 forms acid in the presence of water that causes corrosion problems in pipelines. The variation of the natural gas compositions affects the flame temperature and the thermophysical properties of the natural gas [13]. The component and the percentage of these impurities influence density, viscosity, critical properties, pressure and temperature drop over the pipeline, and phase envelope of the natural gas to a great extent. Proper evaluation of these properties can help in the design and optimization of the natural gas pipelines. Additional studies to understand more completely the key tenets of the impact of nonhydrocarbons impurities on the typical natural gas mixture (TNGM) flow through the transportation pipelines are required. This paper seeks to address the effect of nitrogen, carbon dioxide, hydrogen sulfide, argon, helium, oxygen, water, and hydrogen content on the TNGM properties (density and viscosity), pressure and temperature drop, phase envelope, and critical pressure and critical temperature. The pipeline specifications are taken from the Transitgas pipeline string from Rodersdorf to Lostorf and the data collected using Aspen Hysys version 8.8. The natural gas compositions with maximum allowable percentages reproduced from Speight (2015a) [14]. This paper presents a good opportunity for understanding the impact of non-hydrocarbons on the typical natural gas mixture flow in the pipelines in terms of properties and the operating conditions. Table 1: Typical compositions of natural gas (adopted from [14], [15]. [16], [17]). Natural gas Components mol% Non-hydrocarbons components mol% Methane 96 Argon ≤ 0.05 Ethane 2 Nitrogen ≤ 10 Propane 0.6 Hydrogen sulfide ≤5 Isobutane 0.18 Helium ≤ 0.5% n-butane 0.12 Carbon dioxide ≤5 Isopentane 0.14 Oxygen ≤ 0.01 n-Pentane 0.06 Water ≤ 147 ppm Hexanes 0.1 Hydrogen ≤ 0.02 Heptanes 0.8 2. Methodology Aspen Hysys simulation tool (version 8.8, chemical processes simulator) is used to modeling the process of the natural gas flow in pipelines. The simulation includes the estimation of natural gas properties (viscosity and density), phase envelope, critical properties (temperature and pressure), and the drop-in temperature and pressure. To build confidence, Aspen Plus is used to simulate the process and validate the results where the two simulators reached similar results with some minor differences in the results which are ignored in this study. Aspen Hysys offers a wide range of fluid packages like Acid Gas, Peng-Robinson, SRK, Glycol package, General NRTL, Sour PK, PRSV, and Lee-Kesler-ploker. Peng-Robinson is recommended for hydrocarbons and applicable with a high level of accuracy over a wide range of conditions, it has been therefore chosen [6][18]. The specifications of the hypothetical pipeline used in this simulation shown in Table 2, which is taken from the Trasitgas pipeline string of Rodersdorf to Lostorf which is operated by FluxSwiss and Swissgas AG. The 55 km string of Rodersdorf to Lostorf chosen to avoid the effect of boosting stations. Each impurity is evaluated at the maximum allowable percentage and the deviations from the typical natural gas mixture are reported. Later, the deviations are analyzed to rank the effect of each impurity on the flow features. To simplify the simulation complexity, it is customary to justify some assumptions i.e steady-state, horizontal pipeline, flow direction prespecified, and the pipeline buried in 1 m depth. Table 2: Natural gas pipeline specifications (Transitgas Pipeline System) [19]. Length, m 55,000 Thermal conductivity of Pipeline, w/m. k 45 Inner diameter, mm 875.4 Inlet pressure, bar 67.5 Outer diameter, mm 900 Inlet temperature, ℃ 55 Pipeline Material Mild Steel Molar Flowrate, kgmole/h 30382.32 Pipeline Roughness, m 4.572 *10-5 Pipeline Elevation Horizontal 3. Results and discussion All the non-hydrocarbons impurities influence the natural gas flows in different ways. Some of these impurities have a positive effect on a certain parameter while others have a negative effect. Throughout this section, a simulation study has been executed to investigate the impact of the non-hydrocarbons impurities with their maximum content on the typical natural gas mixture (TNGM) properties, pressure and temperature drop, temperature drop, phase envelope, and the critical pressure and temperature. This study aims to identify the changes in the properties and the performance of natural gas flow in the pipeline due to the presence of the nonhydrocarbon impurities. 3.1. Impact on natural gas viscosity The viscosity of natural gas plays a vital role in pressure losses through transportation pipelines and fluid flow dynamics. The viscosity is the measurement of the fluid flow resistance. Generally, viscosity is a function of temperature, pressure, and compositions of the gas. The pressure losses depend on the friction factor which can be estimated using Reynold’s number that is a function of viscosity. Sanjari et al. (2011) reported that the viscosity of a gas increases with increasing the temperature at low and moderate pressures while the gas viscosity approaches the viscosity of liquid which decreases as the temperature increases [20]. Hassaballah et al. (2003) studied the effect of temperature and pressure on the natural gas viscosity with different API gravities [21]. They concluded that temperature and pressure have strong effects on viscosity behavior. Jarrahian et al. (2015) proposed a new model to estimate the viscosity of sour natural gas mixture at a wide range of high temperature and pressure with different mixtures [22]. Their results revealed that increasing the pressure at constant temperature increases the viscosity of the natural gas up to 0.0197 cP at 4.6 ℃ and 10.34 MPa. A simulation study has been executed to evaluate the impact of non-hydrocarbons impurities on the viscosity of the typical natural gas mixture. It is observed by Fig. 1, 10% of nitrogen has the highest increase impact on the natural gas viscosity of 3.67% deviation from the typical natural gas mixture, while 0.05% of argon has the lowest increase impact of 0.235%. Nitrogen content results in an increase of the molar density of the mixture, which corresponds to an increase in the natural gas mixture viscosity. Low viscosity reduces the friction factor between the gas mixture molecules and the surface of the pipeline and allows the gas mixture flows free. Therefore, the fluid with high viscosity comes with high-pressure losses. Based on the results, all the impurities have a negative impact on the natural gas flow in terms of viscosity. Fig. 1. Viscosity of natural gas mixture with different impurities and deviation from typical natural gas mixture at 67.5 bar and 55 ℃. 3.2. Impact on the natural gas density Gas density can be termed as the number of gas molecules in the volume of the material. Temperature and pressure have a direct impact on the density of the gas, where the temperature has a negative correlation with gas density while the pressure has a positive correlation with gas density. The gas can have density and other properties approach the liquid properties with temperature and pressure above its critical values. Patil et al. (2007) measured the density of natural gas over a temperature range of -3 to 67 ℃ with methane content up to 91% to conclude that the density of the gas mixture increases as the pressure increases to reach 101.844 kg/m3 at 67 ℃ and 13.8 MPa [23]. According to the molecular weight, each impurity has a different impact on the density of natural gas. Light impurities reduce the natural gas mixture density while the heavy impurities increase the natural gas density. Fig. 2 displays the density of the typical natural gas mixture and the impact of the impurities on the natural gas density. 5% of CO2 has the highest increase of natural gas density with 8.98% percent above the density of the typical natural gas mixture. While 0.05% of He reduces the density of the natural gas by -0.51% below the density of the typical natural gas mixture. The impurities that increase the natural gas mixture density lead to reduce pressure drops while those that reduce the density of the natural gas mixture increase the pressure losses in the transportation pipelines. Therefore, helium, hydrogen, and oxygen with low molecular weight have a negative impact. The smallest impact records to the 147 ppm H2O with only a 0.003% increase in density. Followed by 0.05% Ar which increases it by 0.066%. Fig. 2. Density of typical natural gas mixture with different impurities and deviation from typical natural gas mixture. 3.3. Impact on pressure drop Natural gas loses momentum by flowing through the transportation pipeline due to the friction between the pipeline wall and the fluid. Transportation of natural gas for long distances can result in significant pressure losses over the transportation pipeline length. Compressor stations are deployed at specific points along the pipeline to make up the operating pressure and guarantee the transported gas meets the specifications of the customers. The compression process consumes about 3 to 5% out of the total energy required for transportation, where it is reported that the efficient design of transportation pipelines minimizes the compression energy by 20% [24]. Impurities lighter than the natural gas mixture increases pressure drop while denser impurities minimize the pressure drop. This result supports by the fact that more amount of lighter gases required to tune the same flow rate which is, in turn, raises the velocity of the mixture. Higher pressure losses in the transportation pipeline result in more boosting stations which consequently increases the capital cost. A simulation study has been conducted to investigate the impact of different non-hydrocarbons impurities on the pressure drop in the natural gas pipelines. Fig. 3 shows the pressure drop over the pipeline with different impurities. The results reveal that 0.5% of helium only reduces the pressure drop in the pipelines by 0.2% while all the other impurities increase the pressure drop. 10% of nitrogen records the highest pressure drop of 8.83% while 0.05% argon records the lowest pressure drop of 0.094%. The most remarkable result to emerge from the findings is that there is no pressure drop in the presence of 0.02% hydrogen. For inclined pipelines, the impact of density may overtop the effect of velocity owing to the elevation parameter. The fluid with high velocity will lead to a high-pressure drop in inclined transportation pipelines, however, it may result in higher gain pressure in declined pipelines. To calculate the pressure drop between two points Bernoulli’s equation can be used as in equation 1 [25]. ∆ = 2 + ∆ . 1 Where ∆ is the pressure change, f is friction coefficient, is the pipeline length, v is flow velocity, D is the inner pipeline diameter, is the mixture density, g is the acceleration due to gravity, and ∆ is the change in elevation. The pipeline profile is another factor influencing the pressure losses. The pressure drop over the pipeline length increases for all the mixtures for the uphill pipeline and decreases for all the impurities in the downhill pipeline as shown in Table 3. Fig. 4 is the elaboration of the pressure gradient over the length of the pipeline for the typical natural gas mixture and impurities. Table 3: Percentage of deviation of pressure drop for uphill, horizontal, and downhill pipelines. Elevation + 10 m 0m 10% Nitrogen 8.8 8.832 11.2 5% Carbon dioxide 7.8 7.78 7.76 5% Hydrogen Sulfide 4.2 4.1 4.05 0.05% Argon 0.07 0.095 0 0.5% Helium -0.187 -0.19 -0.29 0.01% Oxygen 0.0234 0.0712 -0.096 0 0 -0.096 0.235 0.024 -0.072 0.02% Hydrogen 147 ppm Water -10 m Fig. 3. Pressure drop of typical natural gas mixture with various impurities. Fig.4. Pressure gradient of the typical natural gas mixture and impurities over the pipeline. 3.4. Impact on phase envelope Phase envelope defines as the projection of pressure and temperature of the phase diagram that estimates whether gas exists in one or two phases at the operating conditions. It consists mainly of two sections namely bubble curve and dew curve, the intersection points of these two curves called the critical point. The phase envelope of the natural gas is a function of the natural gas mixture compositions and strongly affects by the concentrations of heavier hydrocarbons [26]. Wang and Economides (2009) stated that the natural gas phase envelope is depending on the production sources in a great extent [27]. A simulation study has been conducted to investigate the effect of different impurities on the phase envelope of natural gas. Fig. 5 shows the phase envelope formed by the presence of N2, CO2, H2S, Ar, O2, H2, He and H2O in the natural gas mixture where red points represent the bubble curve and the blue points represent the dew curve. Fig. 5(b) shows that 10 % of N2 records the widest two-phase envelope while 0.5% He recorded the smallest two-phase envelope as shown in Fig. 5 (e). The most remarkable result to emerge from Fig. 5 is the helium/natural gas phase envelope. A natural gas mixture containing helium is characterized by a bubble point branch extending to infinity, revealing that small content of helium has cleared impact on the phase envelope of the natural gas at low temperature, which is in good consistent with Nichita (2018) [28] findings. Gonzalez and Lee (1968) reported that helium content in natural gas increases the bubble point pressure over temperature below -128 ℃ [29]. The presence of the nonhydrocarbon impurities in the natural gas mixture increases the possibility of the formation of two-phase flow when the temperature and pressure drop over the transportation pipelines. Therefore, all the impurities have a negative effect on the phase envelope of the typical natural gas mixture. Fig. 5. Phase envelope of typical natural gas and various impurities, red line is bubble curve, blue line is dew curve, yellow point is critical point. 3.5. Impact on the temperature drop The transfer of heat from the pipelines to the surrounding is a crucial heat conduction problem over the length of the pipeline. The maximum temperature of the natural gas mixture presents immediately after leaving the natural gas the compressor unit. It is important to estimate the overall heat transfer coefficient of the pipeline wall to reach an accurate evaluation of the pipeline conditions and the materials of insulation [30]. A significant decrease in temperature from the fluid flow in the pipelines can result in the formation of wax and hydrate which causes flow problems [31]. A simulation study has been performed to investigate the effect of N2, CO2, H2S, Ar, He, O2, H2O, and H2 on the temperature drop over the natural gas transportation pipeline. Fig. 6 illustrates the temperature drop over the horizontal pipeline length and the percentage of change compared to the typical natural gas mixture. 10% of nitrogen concentration increased the temperature drop by a maximum of 2.63% and 0.5% Helium concentration increased the temperature drop by a minimum of 0.03%. The single most conspicuous observation to emerge from results is that hydrogen and water presence in the typical natural gas reduces the temperature drop by -0.09%. Decreasing the temperature can result in increasing the volume of the transported natural gas through the pipeline and reduces the pressure drop [32]. It has been therefore implied that all the impurities that increase the temperature drop have a positive impact on pipeline performance. Fig. 6. Temperature drop of typical natural gas and various impurities. 3.6. Impact on critical properties of natural gas Supercritical flow means the temperature and the pressure should be more than the critical values to avoid the formation of a liquid-phase. To reach this, the natural gas is compressed and the heat transfer from the pipelines to the environment should be reduced by heating or insulation. The compression of the natural gas to increase the pressure or heating process to reduce the heat losses are costly. Low critical pressure requires less compression and consequently low energy requirements. Increase the critical pressure of the natural gas may increase the operating pressure of the pipelines. The operating pressure of the natural gas pipeline is specified to be slightly more than the critical pressure of the natural gas mixture. The impurities that increase the critical pressure of the natural gas mixture result in increasing the cost of transmission as additional energy required to keep the flow in the supercritical state. A simulation study has been executed to investigate the impact of different impurities on the critical properties of the typical natural gas mixture. The results reveal that all the impurities increase the critical pressure of the natural gas mixture where 5% H2S has the maximum increase of more than 10.5% while 0.01% O2 increases the critical pressure of 0.005% only. H2S, CO2, He, O2, and H2O increase the critical temperature of the typical natural gas mixture while N2, Ar, and H2 reduce the critical temperature of the mixture. The supercritical temperatures range decreases as the critical temperatures increases. 5% of H2S records the highest increase in the critical temperature of the mixture by 11.1% and 10% of N2 records the highest reduction in the critical temperature by -8.63 % with a critical temperature of -76.39 ℃. Table 4 illustrates the critical properties (temperature and pressure) of the natural gas mixture with different non-hydrocarbons impurities. Table 4: and of typical natural gas with different impurities. Impurity Critical pressure, (kPa) Critical temperature, (℃) TNGM 5695 -70.32 10% N2 6097 -76.39 5% CO2 5976 -65.24 5% H2S 6293 -62.51 0.5% He 5863 -70.28 0.05% Ar 5696 -70.33 0.01% O2 5695.3 -70.32 0.02% H2 5699.82 -70.32 147 ppm H2O 5695.63 -70.3 4. Grading of the non-hydrocarbon impurities All the impurities in the natural gas mixture reduce the molar volume of the typical natural gas mixture by occupying a portion of the total volume. The impurities graded from the lowest to the highest negative impact on the studied parameters. Table. 5 elaborates a summary of deviation percentages from typical natural gas mixture owing to each impurity. ∎ Pressure drop: Helium, Hydrogen, Water, Oxygen, Argon, Hydrogen sulfide, Carbon dioxide, Nitrogen. ∎ Temperature drop; Water, Hydrogen, Argon, Helium, Oxygen, Hydrogen sulfide, Carbon dioxide, Nitrogen. ∎ Viscosity: Oxygen, Argon, Water, Helium, Hydrogen, Hydrogen sulfide, carbon dioxide, Nitrogen. ∎ Density: Helium, Hydrogen, Oxygen, Water, Argon, Nitrogen, Hydrogen sulfide, Carbon dioxide. ∎ Critical temperature: Nitrogen, Argon, Hydrogen, Oxygen, Water, Helium, Carbon dioxide, Hydrogen sulfide. ∎ Critical pressure: Oxygen, Water, Argon, Hydrogen, Helium, Carbon dioxide, Nitrogen, Hydrogen sulfide. ∎ Phase envelope: Helium, Hydrogen sulfide, Carbon dioxide, Hydrogen, Argon, Oxygen, Water, Nitrogen. Table 5: Percentage of deviation of typical natural gas mixture due to impurities. Impurity 10% N2 5% CO2 5% H2S 0.05% Ar 0.5% He Pressure drop 8.83 7.79 4.18 0.095 -0.2 Temperature drop 2.634 2.03 1.998 0.03 0.03 -8.63 11.12 7.22 -0.014 0.57 7.06 10.5 4.93 0.02 2.95 Viscosity 3.67 1.91 0.94 0.24 0.515 Density 5.57 8.9 6.54 0.066 -0.51 5. Conclusion This work investigates the impact of various nonhydrocarbons impurities at maximum allowable concentrations on the performance of the natural gas pipeline. The impacts of impurities on the performance of natural gas pipelines and the deviation percentages were analyzed. The authors adjust that natural gas pipeline with single nonhydrocarbon impurity was not reported in the literature and that the impacts of the multiple impurities might be more complicated than single impurities illustrated in this work. From this study, nitrogen has the highest impact followed by carbon dioxide. 10% of nitrogen increased the pressure drop in the pipeline by 8.83%, temperature drop by 2.634%, critical pressure by 7.06%, mixture viscosity by 3.67%, mixture density by 5.57%, and reduced the critical temperature by -8.63%. Argon has the lowest impact followed by oxygen on the natural gas pipeline performance. 0.05% of argon increased the pressure losses by 0.095%, the temperature drops 0.03%, critical pressure by 0.02, viscosity by 0.24, density by 0.066%, and reduced the critical temperature by -0.014%. The findings in this study can be deployed to identify the impact of the common nonhydrocarbons impurities on the performance of natural gas transportation pipelines. For instance, the nitrogen content should be reduced owing to the strong effect on the pipeline performance. The effect of argon, oxygen, and helium records as the lowest impact, therefore a higher concentration of argon, oxygen, and helium may accept to save the cost of separation for lower concentrations. This study can serve as a guide through the design of the natural gas pipelines because it illustrates the negative and the positive impacts of the common impurities in the natural gas. A pipeline manufactures to transmission natural gas may be overdesigned for natural gas fluids with non-hydrocarbons impurities having a positive effect however under design for non-hydrocarbons impurities having a negative effect. It is therefore advisable to design the parameters of natural gas pipelines with knowledge of the impacts of the impurities present in the mixture. References [1] Liang, F.-Y., Ryvak, M., Sayeed, S., & Zhao, N. (2012). 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Energy Conversion and Management, 47(6), 702– 715. doi: 10.1016/j.enconman.2005.06.001. 1- All the impurities came with at least one negative impact on the typical natural gas mixture flow. 2- 10% of nitrogen had the highest impact on the pressure drop, temperature drop, viscosity, and phase envelope. 3- 5% of carbon dioxide had the highest impact on the density of the mixture. 4- 5% of hydrogen sulfide had the highest impact on the critical temperature and the critical pressure of the mixture. 5- 0.05% of argon, 0.01% of oxygen, 147 ppm water, and 0.5% helium had the lowest impact, hardly affecting the properties of the typical natural gas mixture. Conflict of Interest and Authorship Conformation Form Please check the following as appropriate: o All authors have participated in (a) conception and design, or analysis and interpretation of the data; (b) drafting the article or revising it critically for important intellectual content; and (c) approval of the final version. o This manuscript has not been submitted to, nor is under review at, another journal or other publishing venue. o The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript Author’s name Affiliation Ammar Ali Abd Chemical engineering department, Curtin university Samah Zaki Naji Chemical engineering department, Curtin university Atheer Saad Hashim Mechanical Engineering Department, Nottingham University, CRediT author statement Ammar Ali Abd: Conceptualization, Methodology, Software, Writing Samah Zaki Naji.: Data curation, Writing- Original draft preparation. Atheer Saad Hashim: Visualization, Investigation.
