Oxidation Of Natural Gas Research Articles

Experimental study and modeling of the liquid phase hydrogenation of acetylene

Selective hydrogenation of acetylene is an important process for both ethylene purification and ethylene production from acetylene in the industry. Herein, we proposed liquid phase acetylene hydrogenation for high feed concentrations of C2H2 (8 %) and CO (20 %), which is used to produce ethylene as a subsequent process of partial oxidation of natural gas. The experiments were carried out in a stirred tank reactor using N-methylpyrrolidone (NMP) as solvent and PdAg/SiO2 as catalyst. The liquid phase process obtained a much higher selectivity to ethylene (92 %) with only 8 % selectivity to green oil (GO) and C4, compared to 71 % ethylene selectivity in gas phase hydrogenation. Furthermore, in the liquid phase ethylene selectivity increased with increasing acetylene conversion, especially in the conversion range of 80–100 %. We developed a model incorporating reaction kinetics, mass transfer and reactor model to predict the acetylene conversion and ethylene selectivity in liquid phase hydrogenation. The calculation results indicated that hydrogenation in the liquid phase operated at a lower acetylene concentration and a higher H2/C2H2 ratio, especially under high acetylene conversions. This explains why the liquid phase hydrogenation of acetylene has a much higher selectivity to ethylene than the gas phase process.

Non-Catalytic Partial Oxidation of Hydrocarbon Gases to Syngas and Hydrogen: A Systematic Review

The review contains a comparative analysis of studies on the production of hydrogen and syngas based on the processes of partial oxidation of natural gas and other types of gas feedstock. The results presented in the literature show the high potential of non-catalytic autothermal processes of partial oxidation of hydrocarbons for the development of gas chemistry and energetics. The partial oxidation of hydrocarbons makes it possible to overcome such serious shortcomings of traditional syngas production technologies as technological complexity and high energy and capital intensity. The features of non-catalytic partial oxidation of hydrocarbon gases, the obtained experimental results and the results of kinetic modeling of various options for the implementation of the process, which confirm the adequacy of the kinetic mechanisms used for the analysis, are considered in detail. Examples of industrial implementation of processes based on partial oxidation and proposed alternative options for its organization are considered. Designs of reactors used to ensure stable conversion of rich mixtures of hydrocarbons with an oxidizer are presented. The possibility of obtaining other chemical products by partial oxidation of hydrocarbons is discussed.

Improving the energy-efficiency of small-scale methanol production through the use of microturboexpander units

The issue of improving the energy-efficiency of container-based gas chemical plants for methanol production in field conditions is considered. The relevance of the direction is determined by the necessity for development of remote Arctic hydrocarbon fields. The object of research is energy-efficient conversion of waste gases energy and surplus thermal energy in small-scale system of methanol production using technology of synthesis gas generation by non-catalytic partial oxidation of natural gas. Approaches to the design and analysis of structural solutions for microturboexpander units are considered. A technique combining traditional approaches to the calculation of equipment and modeling by the finite element method in ANSYS is proposed. The developed methodology facilitates calculation of design parameters for microturboexpanders and allows taking into account peculiarities of working medium, thermobaric conditions and gas flow characteristics.

Kinetic investigation of the ozone-assisted partial oxidation of fuel-rich natural gas mixtures at elevated pressure

The partial oxidation of natural gas in HCCI engines in terms of a polygeneration process could be a promising technology to flexibly produce useful chemicals, heat, and work, depending on demand. Because natural gas is relatively inert, high intake temperatures or compression ratios are required to initiate its conversion which can result in a lower lifetime of the engine. Alternatively, small amounts of more reactive species such as ozone can be added to the initial mixture to provide radicals at more moderate conditions and initiate the main ignition. In this study, plug-flow reactor experiments are performed to assess the influence of ozone on the fuel conversion and product formation during the partial oxidation of methane and natural gas. Experiments are performed in the temperature range of 373 K to 973 K at 4 bar and equivalence ratios of 2. Molecular-beam mass spectrometry coupled with electron ionization is used as analytical technique to detect the mixture composition at the outlet of the reactor. The results show that even very small amounts of ozone can help to shift the conversion onset to much lower temperatures and increase the yields of useful chemicals. The data can further be used to improve reaction mechanisms describing the conversion of hydrocarbons in the presence of ozone. A literature ozone reaction mechanism has been implemented in two recent hydrocarbon mechanisms and the results of simulations using these mechanisms are compared to the experimental data with respect to the low-temperature intermediates which influence ignition. Predictions differ substantially from the experimental results identifying starting points for further investigations. The speciation data provided in this work contribute to extending the reaction kinetics of ozone assisted fuel conversion to higher pressure.

METHANOL PRODUCTION UNITS OF MODULAR TYPE FOR INDUSTRY DECARBONIZATION

The production of carbon-containing chemicals is a way to decarbonize gas emissions. In particular, methanol (CH3OH) can be produced from associated petroleum gas, which is currently flared. It makes sense to use simple methods of hydrocarbon gas conversion into synthesis gas, such as partial oxidation of methane to create small modular plants for direct operation in oil and gas fields. The numerical modelling of partial oxidation is considered, taking into account the kinetics of chemical processes and the design of the equipment. In this workthe several models have been built to describe partial oxidation of natural gas with air -the equilibrium and complete 3D models which take into account the phenomena of mass and energy transfer, as well as chemical transformation. The main conclusion of the model comparison is that the full numerical model predicts incomplete oxidation quite well, while the simpler equilibrium model does not. In the future, the results of the numerical modelling of oxygen methane conversion will be investigated and presented.

Shock tube study of natural gas oxidation at propulsion relevant conditions

Global climate change and rising crude oil prices have motivated search of clean, sustainable and economic fuel. Methane, having the highest hydrogen to carbon ratio is ideally the best option towards carbon neutral emissions and reduce greenhouse gas emissions. However, there the economic benefits are minimal when using pure methane because of purification costs. Natural gas primarily consists of methane but with appreciable amounts of C2C4 alkanes which significantly impact oxidation performance, especially when compared to pure methane at high pressures and temperatures, studies of natural gas have been scarce and there is new interest in studying natural gas for its application to propulsion devices. This single pulse shock tube study investigates the effect of natural gas composition on species yields as a function of temperature at various stoichiometric conditions (φ ≈ 0.5, 1.0, 2.0) and high pressure (240 atm) over a nominal reaction time of 2.5 ms. The experimentally measured speciation results for one real natural gas sample from Boise, ID (USA) and a reference natural gas sample are compared to species yield predictions using well established chemical kinetic mechanisms, to check the feasibility of using these mechanisms in the design of propulsion devices. The chemical kinetic simulations are carried out using the constant pressure approach as well as the changing pressure approach which considers the exact measured pressure change in the shock tube. The experiments provide a large speciation data set for optimizing chemical kinetic mechanisms for natural gas applications and to understand the effect of composition on natural gas chemical kinetics. The predictions vary significantly between models tested and effect of composition variation was evident. Aramco Mech 3.0 could predict the experiments almost perfectly, especially at fuel rich conditions.

Reduced order modeling and large-scale validation for non-catalytic partial oxidation of natural gas

• Reduced order modeling of non-catalytic partial oxidation of natural gas. • Low computational effort through a physics-based and compact model. • Validation against semi-industrial test plant experiments and CFD. • Demonstrated exibility and reliability of the model for a broad spectrum of operating parameters. • Analysis of conversion processes in different reactor zones. A reduced order model (ROM) for the non-catalytic partial oxidation (POX) of natural gas was developed and validated against large-scale numerical and experimental results. The ROM utilizes a network of perfectly stirred reactors, each describing a distinctive reactor zone and corresponding conversion processes. The zone definition is based on the CFD calculation of reactive flow, resulting in a compact, physics-based model that is valid for a broad range of POX reactors. The ROM is capable of predicting global reactor characteristics and flow field pattern within a short period of time, enabling the optimization of reactor geometry and the boundary and operating conditions. Additionally, the ROM can be used to evaluate detailed chemical reactions mechanisms. The ROM is validated against semi-industrial process data, and used to analyze the influence of each reactor zone on the overall species conversion. A new correlation between the fuel slip from the burner to the downstream reactor zones, the steam injection, and the λ value is built.

Purification and reuse of carbon black wastewater of acetylene production from natural gas by microchannel filtration

Carbon black wastewater is a by-product of partial oxidation of natural gas to acetylene and can cause serious pollution to the environment. In this study, the effect of deep bed filtration (microchannel filtration) in the synergistic separation of particulate pollutants and organic pollutants in carbon black wastewater were investigated. The results indicated that the separation efficiency of carbon black particles with a mean diameter of 6.88 µm was 95%− 98%, 95–97%, and 95%− 96% when the filter material was quartz sand + quartz sand, quartz sand + activated, and quartz sand + anthracite, respectively. The solid content of inlet was 300 mg/L and 145 NTU, respectively, and those of the purified effluent were below 15 mg/L and 14 NTU, which meet the first-class B standard of China sewage discharge. The total kinds of organics were reduced from 29 to 2. The separation efficiency of C6-C24 all higher than 97%. A 150 m3/h full-closed treatment process for carbon black wastewater was designed to replace the original open sedimentation tank. The carbon black wastewater could be efficiently purified by this method, the purified carbon black wastewater could be reused, and the carbon black was used to make a filter cake for recycling in rubber without discharge. Finally, the possibility of achieving zero discharge of carbon black wastewater is shown.

Comparative evaluation of Ru-coated fecralloy and SiC monolithic catalysts in catalytic partial oxidation of natural gas for hydrogen production

The catalytic activity of structured catalysts comprising Fecralloy and SiC monoliths coated with Ru/Mg-Al oxide by deposition–precipitation was evaluated in the partial oxidation of natural gas and compared with that of a conventional pellet catalyst. The geometric surface area (GSA) of the Fecralloy and SiC monolithic catalysts were 377.0 × 10-4 and 118.5 × 10-4 m2, respectively; significantly larger than that of the 0.5% Ru/Al2O3 pellet catalyst (89.6 × 10-4 m2). Owing to the high GSA of the structured catalysts, a small amount of Ru (0.070–0.12 wt%) resulted in highly dispersed uniform loading. Thus, the structured catalysts exhibited higher performance for catalytic partial oxidation at varying C/O2 ratio, inlet temperature, and gas hourly space velocity (GHSV) than the pellet catalyst. However, in a stability test at high GHSV (50,000 h−1), the CH4 conversion of the Fecralloy monolithic catalyst decreased rapidly from 90% to less than 70% in 150 min. In addition, the Mg-Al oxide layer of the Fecralloy monolithic catalyst was damaged owing to material deterioration, resulting in a loss of Ru particles. In contrast, CH4 conversion catalyzed by the SiC monolithic catalysts remained above 85% even after 1000 min, and the material or support layer was not damaged even under severe conditions.

Small-Scaled Production of Blue Hydrogen with Reduced Carbon Footprint

This article reviews a method of hydrogen production based on partial non-catalytic oxidation of natural gas in an original synthesis gas generator. The working principles of the unit are similar to those of liquid-propellant rocket engines. This paper presents a description of the operation and technical characteristics of the synthesis gas generator. Its application in the creation of small-scaled plants with a capacity of up to 5–7 thousand m3/h of hydrogen is justified. Hydrogen production in the developed installation requires a two-stage method and includes a technological unit for producing a hydrogen-containing gas. Typical balance compositions of hydrogen-containing gas at the synthesis gas generator’s outlet are given. To increase the hydrogen concentration, it is proposed to carry out a two-stage steam catalytic conversion of carbon monoxide contained in the hydrogen-containing gas at the synthesis gas generator’s outlet using a single Cu–Zn–cement-containing composition. Based on thermodynamic calculations, quasi-optimal modes of natural gas partial oxidation with oxygen are formulated and the results of material balance calculation for the installation are presented. In order to produce “blue” hydrogen, the scheme of carbon dioxide separation and liquefaction is developed. The conclusion section of the paper contains the test results of a pilot demonstration unit and the recommendations for improving the technology and preventing soot formation.

Structural design and performance evaluation of industrial-scale C2H2 reactor by partial oxidation of natural gas

In this study, industrial-scale reactors are designed and the reactions are numerically simulated by computational fluid dynamics coupled with detailed chemical reaction mechanism. The results show that the mole fraction of C2H2 at the outlet is 9.93% under industrial scale production conditions, whereas it is lower than 8.0% in the industrial production process. This indicate that the designed reactor is competitive. Studies shows that decreasing the number of inlet tubes will lengthen the flame and thus reduce the reaction degree under the same flow rate. The role of oxygen-supply tube is only to stabilize the flame. There is a dependent relationship between the optimal oxygen-hydrocarbon ratio and the preheating temperature. For the target product C2H2 only, at 923 K, the optimal oxygen-hydrocarbon ratio is 0.56. The best preheating temperature range is 823–923 K. These results deepen the understanding of C2H2 production by partial oxidation of natural gas, and provide help for optimizing the process.

Regeneration of Soot Produced from Partial Oxidation of Natural Gas.(Dept.P)

Regeneration of Soot Produced from Partial Oxidation of Natural Gas.(Dept.P)

Rate-enhancement effect of CO in magnetite concentrate particle reduction by H2+CO mixtures

ABSTRACT The kinetics of the reduction of magnetite concentrate particles by H2+CO mixtures have been investigated in drop-tube reactors (DTRs) to obtain rate expressions for the design of novel flash ironmaking reactors. The experimental temperature varied from 1423 K (1150°C) to 1873 K (1600°C). The H2/CO ratio was varied from 0.5 to 2, which is the typical composition range of the product gas from the partial oxidation of natural gas. The experimental data were analysed separately in two temperature ranges 1423 K (1150°C)–1623 K (1350°C) and 1623 K (1350°C)–1873 K (1600°C), as the magnetite concentrate particles tend to fuse and melt at temperatures above 1623 K (1350°C) changing the reduction mechanism. CFD (Computational Fluid Dynamics) simulations were used to more accurately account for temperature and concentration variations. Synergistic effects were observed in the reduction by H2+CO mixtures compared with the simple summation of contributions of the individual component gases.

Experimental speciation study of natural gas oxidation using a single pulse shock tube

AbstractAn experimental shock tube study of natural gas (NG) oxidation for several NG samples was carried out at nominal reaction pressures of 50–60 atm and temperatures ranging from 1100 to 1750 K over a nominal reaction time of 2.5 ms. As NG has no standard specified composition, various samples of NGs taken from the gas supply system across the United States were studied near stoichiometric conditions. In addition, a speciation study at equivalence ratios ranging from fuel lean (φ ≈ 0.5) to pyrolysis of a representative NG sample was carried out to provide a comprehensive but nonexhaustive set of experimental data, which will be useful in optimizing chemical kinetic models for NG. Temperature‐dependent species yields measured in these experiments were compared with predictions from four well established chemical kinetic models. The agreement with model predictions was found to be largely inconsistent from experiment to experiment, reinforcing the need for optimization of models using comprehensive experimental data before their use predicting the oxidation products of NG.

Plug-flow reactor and shock-tube study of the oxidation of very fuel-rich natural gas/DME/O2 mixtures

A polygeneration process with the ability to provide work, heat, and useful chemicals according to the specific demand is a promising alternative to traditional energy conversion systems. By implementing such a process in an internal combustion engine, products like synthesis gas or unsaturated hydrocarbons and very high exergetic efficiencies can be obtained through partial oxidation of natural gas, in addition to the already high flexibility with respect to the required type of energy. To enable compression ignition with natural gas as input, additives such as dimethyl ether are needed to increase the reactivity at low temperatures. In this study, the reaction of fuel-rich natural gas/dimethyl ether (DME) mixtures is investigated to support the further development of reaction mechanisms for these little studied reaction conditions. Temperature-resolved species concentration profiles are obtained by mass spectrometry in a plug-flow reactor at equivalence ratios ϕ = 2, 10, and 20, at temperatures between 473 and 973 K and at a pressure of 6 bar. Ignition delay times and product-gas analyses are obtained from shock-tube experiments, for ϕ = 2 and 10, at 710 – 1639 K and 30 bar. The experimental results are compared to kinetic simulations using two literature reaction mechanisms. Good agreement is found for most species. Reaction pathways are analyzed to investigate the interaction of alkanes and DME. It is found that DME forms radicals at comparatively low temperatures and initiates the conversion of the alkanes. Additionally, according to the reaction pathways, the interaction of the alkanes and DME promotes the formation of useful products such as synthesis gas, unsaturated hydrocarbons and oxygenated species.

Impact of low concentration hydrocarbons in natural gas on thermal partial oxidation in a micro-flow reactor for solid oxide fuel cell applications

The increase in production and decrease in cost of natural gas have made it a viable alternative fuel to petroleum and coal power-based systems. The thermal partial oxidation of natural gas has been investigated previously, but few have investigated the effects of lower concentration hydrocarbons on reforming characteristics; especially at low temperatures (<1000 °C). This study investigates the microcombustion reforming of methane/air and natural gas/air utilizing heat recirculation to achieve high synthesis gas production. Maximum wall temperatures of 800–1000 °C at total flow rates of 10 and 50 mL min−1 are investigated. Equivalence ratios 1–5 are investigated with no soot formation present in the reactor at 800 °C and 900 °C. Natural gas is found to reform ⁓130% more than methane at 800 °C and 50 mL min−1 total flow rate due to low concentration hydrocarbons found in natural gas. A micro-tubular solid oxide fuel cell (mT-SOFC) is integrated into the natural gas/air microcombustion exhaust and characterized. The mT-SOFC operating in microcombustion exhaust achieves a high fuel utilization of 60% and 84% of the power density of a natural gas baseline. Three short-term tests are performed comparing the stability of natural gas and natural gas microcombustion in a mT-SOFC.

Influence of the Preparation Method on the Physicochemical and Catalytic Properties of Platinum Catalysts Supported on Bayerite Alumina for the Partial Oxidation Reactions of Hydrocarbons

Platinum catalysts supported onto bayerite alumina were synthesized and studied. Alumina of the θ-Al2O3 type, which was prepared from metallic aluminum by an aluminate method, was used as a support, and platinum(IV) nitrate and hydrogen hexachloroplatinate(IV) precursors containing Pt4+ ions were used for supporting an active component. The catalysts were studied by physicochemical methods such as X-ray phase analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, and ultraviolet-visible diffuse reflection spectroscopy. It was found that platinum occurred in a finely dispersed state in both of the catalysts, and it was uniformly distributed over the support surface. The particle sizes were 2.8 and 0.9 nm in the samples synthesized from platinum(IV) nitrate and hydrogen hexachloroplatinate(IV), respectively. The most uniform surface distribution, high dispersity, and a narrow particle-size distribution were obtained with the use of hydrogen hexachloroplatinate(IV). The catalysts were tested in the partial oxidation of natural gas. The catalyst synthesized using platinum(IV) nitrate afforded an almost thermodynamically equilibrium distribution of the reaction products of partial oxidation at a temperature of 700–800°С.

Study on combustion and emission characteristics of a heavy-duty gas turbine combustor fueled with natural gas

In this paper, the ignition delay and laminar combustion characteristics of natural gas were tested in a chemical shock tube and a constant volume combustion reactor, respectively, and simulated with the Gri_3.0, USC_2.0 and NUI_Galway models, respectively. It is proved that the ignition delay and laminar combustion characteristics of natural gas simulated with the Gri_3.0 model are in better agreement with the experiment than the USC_2.0 and NUI_Galway models. Furthermore, the simulated variation trends of the mole fractions of main species, especially NO and NO2 with temperature by the Gri_3.0 model are in better agreement with the experimental data in the oxidation of natural gas. The combustion process and pollutants generation characteristics in a single flame tube of a heavy-duty gas turbine burning natural gas were simulated by coupling the Gri_3.0 model with the computational fluid dynamics. It is shown that the simulated average temperature and the NOx concentration at the outlet of the flame tube are slightly higher than the experimental value by 8.06% and 5.08%, respectively. Because the NOx emission is higher than the designed value, fuel flows in the annular, main, and pilot combustion zones of the flame tube were reassigned and effects of the fuel redistributions on the NOx emission characteristics were investigated. It is shown that the NOx concentration at the outlet of the flame tube increases from 157.1 mg/m3 to 175.5 mg/m3 when the fuel flow in the pilot combustion zone is redistributed to the main combustion zone, and decreases from 157.1 mg/m3 to 139.51 mg/m3 when the fuel flow in the pilot combustion zone is redistributed to the annular combustion zone. The research results will provide theoretical basis and technical support for the optimization of this gas turbine operation.

Simulation of partial oxidation of natural gas in a resource-saving reactor mixer

Modern industrial methods of producing hydrogen almost exclusively use fossil fuels, like natural gas, crude oil or coal, as raw materials. Methods such as steam reforming or partial steam oxidation to produce hydrogen from fossil hydrocarbons. This process chemically separates the carbon which is then converted to carbon monoxide (CO). These methods of hydrogen extraction are not ideal to actively protect the climate. There is currently a certain shortage of hydrogen in any refinery, so an additional source of hydrogen needed to stabilize the process. The work presents the results of simulating the processes in the homogeneous zone of the mixer and simulating the process of converting methane in the catalyst bed of the mine reactor using natural gas to produce hydrogen.

Effect of Hydrogen Addition on Noncatalytic Partial Oxidation of Natural Gas with Oxygen in a Flow Reactor with Increased Calorific Intensity

The effect of hydrogen addition on the partial oxidation of a natural gas/O2 mixture was studied in a flow reactor with increased calorific intensity. The addition of hydrogen (CH4/H2 = 3) to a fuel-rich natural gas/O2 mixture with the oxidizer excess ratio α = 0.34 leads to an increase in the yields of H2 and CO and in the H2/CO ratio and to a decrease in the yields of CO2, H2O, C2H4, and C2H2 and in ∆C. The hydrogen addition at CH4/H2 = 3 positively influences the hydrogen production in partial oxidation of natural gas/O2 mixtures.