An accurate empirical correlation for predicting natural gas viscosity

Natural gas viscosity is an important parameter in many gas and petroleum engineering calculations.This study presents a new empirical model for quickly calculating the natural gas viscosity.The model was derived from 4089 experimental viscosity data with varieties ranging from 0.01 to 21,and 1 to 3 of pseudo reduced pressure and temperature,respectively.The accuracy of this new empirical correlation has been compared with commonly used empirical models,including Lee et al.,Heidaryan et al.,Carr et al.,and Adel Elsharkawy correlations.The comparison indicates that this new empirical model can predict viscosity of natural gas with average absolute relative deviation percentage AARD (%) of 2.173.     

An efficient correlation for calculating compressibility factor of natural gases

Compressibility factor (z-factor) values of natural gases are necessary in most petroleum engineering calculations. Necessity arises when there are few available experimental data for the required composition, pressure and temperature conditions. One of the most common methods of calculating z-factor values is empirical correlation. Firstly, a new correlation based on the famous Standing-Katz (S-K) Chart is presented to predict z-factor values. The advantage of this correlation is that it is explicit inzand thus does not require an iterative solution as is required by other methods. Secondly, the comparison between new one and other correlations is carried out and the results indicate the superiority of the new correlation over the other correlations used to calculate z-factor.     

A novel correlation approach for prediction of natural gas compressibility factor

Gas compressibility factor (z-Factor) is one of the most important parameters in upstream and downstream calculations of petroleum industries. The importance of z-Factor cannot be overemphasized in oil and gas engineering calculations. The experimental measurements, Equations of State (EoS) and empirical correlations are the most common sources of z-Factor calculations. There are more than twenty correlations available with two variables for calculating the z-Factor from fitting in an EoS or just through fitting techniques. However, these correlations are too complex, which require initial value and more complicated and longer computations or have magnitude error. The purpose of this study is to develop a new accurate correlation to rapidly estimate z-Factor. Result of this correlation is compared with large scale of database and experimental data also. Proposed correlation has 1.660 of Absolute Percent Relative Error (E_(ABS)) versus Standing and Katz chart and has also 3.221 of E_(ABS) versus experimental data. The output of this correlation can be directly assumed or be used as an initial value of other implicit correlations. This correlation is valid for gas coefficient of isothermal compressibility (c_g) calculations also.     

Experimental determination and prediction of the compressibility factor of high CO_2 content natural gas with and without water vapor

In order to study the effect of different CO2 contents on gas compressibility factor(Z-factor),the JEFRI-PVT apparatus has been used to measure the Z-factor of dry natural gas with CO2 content range from 10.74 to 70.42 mol%at the temperature range from 301.2 to 407.3 K and pressure range from 7 to 44 MPa.The results show that Z-factor decreases with increasing CO2 content in natural gas at constant temperature and increases with increasing temperature for natural gas with the same CO2 content.In addition,the Z-factor of water-saturated natural gas with high CO2 content has been measured.A comparison of the Z-factor between natural gas with and without saturated water vapor indicates that the former shows a higher Z-factor than the latter.Furthermore,Peng-Robinson,Hall-Yarborough,and Soave-Benedict-Webb- Rubin equations of state(EoS)are used for the calculation of Z-factor of high CO2 content natural gas with and without water vapor.The optimal binary interaction parameters(BIP)for PR EoS are presented.The measured Z-factor is compared with the calculated Z-factor based on three models,which shows that PR EoS combined with van der Waals mixing rule for gas without water and Huron-Vidal mixing rule for water-saturated gas,are in good agreement with the experimental data.     

Initial estimation of hydrate formation temperature of sweet natural gases based on new empirical correlation

Production,processing and transportation of natural gases can be significantly affected by clathrate hydrates.Knowing the gas analysis is crucial to predict the right conditions for hydrate formation.Nevertheless,Katz gas gravity method can be used for initial estimation of hydrate formation temperature (HFT) under the circumstances of indeterminate gas composition.So far several correlations have been proposed for gas gravity method,in which the most accurate and reliable one has belonged to Bahadori and Vuthaluru.The main objective of this study is to present a simple and yet accurate correlation for fast prediction of sweet natural gases HFT based on the fit to Katz gravity chart.By reviewing the error analysis results,one can discover that the new proposed correlation has the best estimation capability among the widely accepted existing correlations within the investigated range.     

Measurement and calculation of gas compressibility factor for condensate gas and natural gas under pressure up to 116 MPa

The volumetric properties of two reservoir fluid samples collected from one condensate gas well and one natural gas well were measured under four groups of temperatures, respectively, with pressure up to 116 MPa. For the two samples examined, the experimental results show that the gas compressibility factor increases with the increase of pressure. But the influence of the temperature is related to the range of the experimental pressure. It approximately decreases with the increase of temperature when the pressure is larger than (45 to 50) MPa, while there is the opposite trend when the pressure is lower than (45 to 50) MPa. The dew point pressure was also determined for the condensate gas sample, which decreases with the increase of temperature. The capabilities of four empirical correlations and a thermodynamic model based on equation of state for describing gas compressibility factor of reservoir fluids under high pressure were investigated. The comparison results show that the thermodynamic model recommended is the most suitable for fluids whatever produced from high-pressure reservoirs or conventional mild-pressure reservoirs.     

A novel correlation for estimation of hydrate forming condition of natural gases

An inherent problem with natural gas production or transmission is the formation of gas hydrates, which can lead to safety hazards to production/ transportation systems and to substantial economic risks. Therefore, an understanding of conditions where hydrates form is necessary to overcome hydrate related issues. Over the years, several models requiring more complicated and longer computations have been proposed for the prediction of hydrate formation conditions of natural gases. For these reasons, it is essential to develop a reliable and simple-to-use method for oil and gas practitioners. The purpose of this study is to formulate a novel empirical correlation for rapid estimation of hydrate formation condition of sweet natural gases. The developed correlation holds for wide range of temperatures (265–298 K), pressures (1200 to 40000 kPa) and molecular weights (16−29). New proposed correlation shows consistently accurate results across proposed pressure, temperature and molecular weight ranges. This consistency could not be matched by any of the widely accepted existing correlations within the investigated range. For all conditions, new correlation showed average absolute deviation to be less than 0.2% and provided much better results than the widely accepted existing correlations.     

The effect of lattice compressibility on the thermodynamics of gas sorption in polymers

A compressible lattice model with holes, the glassy polymer lattice sorption model (GPLSM), was used to model the sorption of carbon dioxide, methane, and ethylene in glassy polycarbonate and carbon dioxide in glassy tetramethyl polycarbonate. For glassy polymers, an incompressible lattice model, such as the Flory–Huggins theory, requires concentration-dependent and physically unrealistic values for the lattice site volumes in order to satisfy lattice incompressibility. Rather than forcing lattice incompressibility, GPLSM was used and reasonable parameter values were obtained. The effect of conditioning on gas sorption in glassy polymers was analyzed quantitatively with GPLSM. The Henry's law constant decreases significantly upon gas conditioning, reflecting changes in the polymer matrix at infinite dilution. Treating the Henry's law constant as a hypothetical vapor pressure at infinite dilution, gas molecules in the conditioned polymer are less “volatile” than those in the unconditioned polymer. Flory–Huggins theory was used to model the sorption of carbon dioxide, methane, and ethylene in silicone rubber. Above the glass transition temperature, the criterion of lattice incompressibility for Flory-Huggins theory was satisfied with physically realistic and constant values for the lattice site volumes. © 1992 John Wiley & Sons, Inc.     

Comparison of three methods for natural gas dehydration

This paper compares three methods for natural gas dehydration that are widely applied in industry:(1) absorption by triethylene glycol, (2) adsorption on solid desiccants and (3) condensation. A comparison is made according to their energy demand and suitability for use. The energy calculations are performed on a model where 105 Nm3/h water saturated natural gas is processed at 30 °C. The pressure of the gas varies from 7 to 20 MPa. The required outlet concentration of water in natural gas is equivalent to the dew point temperature of -10 °C at gas pressure of 4 MPa.     

A new equation of state for studying the thermodynamic properties of real gases

In this study, based on the compressibility effect of gas molecules, a new three-parameter cubic equation of state (EOS) is derived. To validate this EOS, density predictions of methane, ethane, carbon dioxide and oxygen have been studied using the new EOS at the temperature of 373 K and at the pressures up to 100 MPa. The results show a good agreement with reference data and this suggests that the proposed EOS would help to improve the study of thermodynamic properties for real gases.     

家用天然气催化燃烧热水器的研制

天燃气传统的火焰燃烧存在一系列缺点[1],催化燃烧能改善燃烧过程,促进完全燃烧,降低有毒物质的形成[2]。本文以过渡金属为活性组分,氧化铝为载体,制备了家用燃烧热水器燃烧催化剂,其ＮＯｘ排放仅为24ｐｐｍ,远低于国家标准(小于80ｐｐｍ)[3],而一般的燃烧热水器则高达76ｐｐｍ。并且该催化燃烧热水器在热量接收不是很充分的情况下,其热效率已超过了一般的燃烧热水器。1　实验部分1 1　催化剂样品的制备用添加助剂Ｆｅ,Ｃｏ,Ｍｎ的硝酸盐溶液浸渍Ａｌ2Ｏ3粉末,100℃水浴烘干、600℃空气中焙烧2ｈ,制成浆液涂覆在堇青石400孔/ｉｎｃｈ2,9…     

An alternative approach for predicting peak width in gas chromatography

Summary The linear relationship between natural logarithm of width factor (lnp′)and natural logarithm of retention factor (lnk) is demonstrated. This relationship is then used to establish the relationship between (lnp′), absolute temperature (T), and carbon number (z), as follows: Inp′=A+bz+c/T+dz/T where A, b, c and d are thermodynamically related constants. The above equation is used to predict the unadjusted widths (w _R ) ofn-alkanes, fatty alcohols and fatty acid methyl esters (FAMEs) at various temperatures, predicted values are in good agreement with experimental values. The above equation can be used to predict the width of FAMEs from rice bran oil. The largest difference between the experimental and predicted values is 0.66 s or 6.32%.     

An empirical method for predicting detonation pressure of CHNOFCl explosives

This paper describes a new method for prediction of the Chapman-Jouguet detonation pressures of CHNOFCl explosives using the heat of detonation, Q_det, the number of moles of gaseous products of detonation per gram of explosive, α, and the average molecular weight of gaseous products, M. The equation has the form: P_CJ=15.88α(MQ_det)^1/2ρ₀²−11.17, where P_CJ is the Chapman-Jouguet detonation pressure and ρ₀ the loading density. Calculated P_CJ by this procedure show good result with respect to measured detonation pressure for any pure or mixture of ideal and some of less ideal CHNOFCl explosives at ρ₀>0.8 g/cm³.     

Nanoporous carbons as promising novel methane adsorbents for natural gas technology

Nanoporous carbons were synthesized using furfuryl alcohol and sucrose as precursors and MCM-41 and mordenite as nanoporous templates.The produced nanoporous carbons were used as adsorbent for methane storage.The average pore diameter of the samples varied from 3.9 nm to 5.9 nm and the BET surface area varied from 320m2/g to 824m2/g.The volumetric adsorption experiments revealed that MCM-41 and sucrose had better performance compared with mordenite and furfuryl alcohol,correspondingly.Also,the effect of precursor to template ratio on the structure of nanoporous carbons and their adsorption capacities was investigated.The nanoporous carbon produced from MCM-41 mesoporous molecular sieve partially filled by sucrose shows the best methane adsorption capacity among the tested samples.     

合成气甲烷化反应积炭过程的热力学分析

建立了煤制替代天然气工艺中合成气甲烷化过程的热力学计算模型,并对该反应体系的10个反应进行了分析计算,得到了各组分的平衡组成和各反应的标准化学平衡常数.研究了反应温度、操作压力、原料气组分浓度和产品气循环比等对催化剂床层积炭的影响,发现容易导致积炭的热力学条件为550~800 ℃的反应温度和0.1~1.5 MPa的操作压力,且温度在700 ℃左右、操作压力低于1.0 MPa时催化剂床层积炭量最大.本研究针对催化剂床层积炭规律提出了低温、相对高压、合理的原料气组成是有利于缓解催化剂床层积炭、提高产品收率及保持催化剂活性的优化反应操作条件.     

火焰原子吸收光谱法测定天然气转化催化剂中的氧化钾

建立火焰原子吸收光谱法测定天然气转化催化剂中氧化钾的分析方法。该方法将催化剂样品和助溶剂四硼酸锂熔融后再用盐酸溶解定容,采用火焰原子吸收光谱仪对样品溶液进行测定。在优化的实验条件下,钾离子的质量浓度在0.05~0.50 mg/L范围内与吸光度呈良好线性关系,相关系数为0.9995。钾的方法检出限为0.001 mg/L,定量限为0.01 mg/L,测定结果的相对标准偏差为2.6%~4.3%(n=6),样品加标回收率为97.8%~102.3%。与HG/T 3543-2014中的酸溶制样法相比,该方法能够将催化剂样品中的难溶钾盐溶出,分析结果准确度更高,可用于天然气转化催化剂中氧化钾含量的测定。