Heating Value Of Natural Gas Research Articles

ASSESSMENT OF METHODS FOR DETERMINING THE NATURAL GAS HEAT OF COMBUSTION

The shortage of fuel and energy resources, the increase in natural gas prices and the continuous increase in gas consumption indicate the relevance of the issues of measuring the natural gas amount and assessing its quality indicators. Ukraine is implementing the European methodology for calculating gas consumption based on its quality and efficiency. The problem of determining the gas quality in Ukraine requires a thorough assessment and research.
 The main physical and chemical indicator of the natural gas quality, which characterizes its energy value, is the specific volumetric gas heat of combustion. The value of this parameter differs for different gas fields. The gas heat of combustion determines the efficiency of its use both in everyday life and in industry.
 The aim of the work is to analyze the main methods for determining the calorific value of natural gas.
 The gas heat of combustion is determined by calorimetric, chromatographic and correlation methods.
 The calorimetric method is characterized by the complexity of the measurement process, complete combustion of the test gas, and long term process. This ensures the objectivity of the results, which is based on taking into account the moisture content of the gas and the presence of non-combustible components in it.
 The basis of the chromatographic method is the separation of the components of a gas sample in a chromatographic column. The result is a chromatogram that shows the percentage composition of hydrocarbons in the gas. The characteristic properties of the method are the identification of a wide range of components and the repeatability of the results.
 When using correlation methods for determining the heating value of natural gas, various physicochemical parameters of samples are measured (such as total hydrocarbon concentration, heat capacity, acoustic wave propagation velocity, carbon dioxide concentration, thermal conductivity, dielectric constant, dynamic viscosity, and others).
 Correlation dependence is based on the choice and association of such parameters. This dependence is studied on different test gas mixtures and allows us to determine the empirical dependence. The mixtures correspond to gases with different calorific values. The obtained empirical dependence is used to register the heat of combustion of real natural gas. The paper evaluates the features of these methods application and instruments based on them.

Increasing the heating value of natural gas by reducing CO2 concentration using vortex tube: A new method

Natural gas (based on methane) is one of the most popular fossil fuels used in the world's energy industries, so, any progress in increasing its heating value can have impressive impacts on the energy efficiency around the world and specially on global warming. Separation of carbon dioxide is one of the most important actions that can increase the heating value of natural gas. For the first time, this experimental investigation is designed to apply thermodynamic performance of a vortex tube for improving the heating value of natural gas through the separation process. Furthermore, this research investigates the effects of the internal structural parameters of the navigator on the separation level of CO2 from the injected natural gas (Pin = 0.5, 0.7 and 0.9 MPa). The considered structural factors are; the middle part diameter (Ø=12, 13 and 14 mm), the convergence angle (θ = 0°, 1°, 2°, 3° and 4°) and the divergence angle (β = 0°, 1°, 2°, 3° and 4°), and the results show that there are optimum values (Ø=13 mm, θ = 3°, β = 1°) which lead to the maximum level of carbon dioxide separation from the natural gas stream. The results show that the optimum VT decreases the concentration of CO2 at the cold outlet to 1.30 % (P = 0.5 MPa), 1.16 % (P = 0.7 MPa) and 0.79 % (P = 0.9 MPa) via the thermodynamic separation process.

Asymmetric pore windows in MOF membranes for natural gas valorization

To use natural gas as a feedstock alternative to coal and oil, its main constituent, methane, needs to be isolated with high purity1. In particular, nitrogen dilutes the heating value of natural gas and is, therefore, of prime importance for removal2. However, the inertness of nitrogen and its similarities to methane in terms of kinetic size, polarizability and boiling point pose particular challenges for the development of energy-efficient nitrogen-removing processes3. Here we report a mixed-linker metal-organic framework (MOF) membrane based on fumarate (fum) and mesaconate (mes) linkers, Zr-fum67-mes33-fcu-MOF, with a pore aperture shape specific for effective nitrogen removal from natural gas. The deliberate introduction of asymmetry in the parent trefoil-shaped pore aperture induces a shape irregularity, blocking the transport of tetrahedral methane while allowing linear nitrogen to permeate. Zr-fum67-mes33-fcu-MOF membranes exhibit record-high nitrogen/methane selectivity and nitrogen permeance under practical pressures up to 50 bar, removing both carbon dioxide and nitrogen from natural gas. Techno-economic analysis shows that our membranes offer thepotential to reduce methane purification costs by about 66% for nitrogen rejection and about 73% for simultaneous removal of carbon dioxide and nitrogen, relative to cryogenic distillation and amine-based carbon dioxide capture.

Raman Natural Gas Analyzer: Effects of Composition on Measurement Precision.

Raman spectroscopy is a promising method for analyzing natural gas due to its high measurement speed and the potential to monitor all molecular components simultaneously. This paper discusses the features of measurements of samples whose composition varies over a wide range (0.005–100%). Analysis of the concentrations obtained during three weeks of experiments showed that their variation is within the error caused by spectral noise. This result confirms that Raman gas analyzers can operate without frequent calibrations, unlike gas chromatographs. It was found that a variation in the gas composition can change the widths of the spectral lines of methane. As a result, the measurement error of oxygen concentration can reach 200 ppm. It is also shown that neglecting the measurement of pentanes and n-hexane leads to an increase in the calculated concentrations of other alkanes and to errors in the density and heating value of natural gas.

Insights on Cryogenic Distillation Technology for Simultaneous CO2 and H2S Removal for Sour Gas Fields.

Natural gas demand has dramatically increased due to the emerging growth of the world economy and industry. Presently, CO2 and H2S content in gas fields accounts for up to 90% and 15%, respectively. Apart from fulfilling the market demand, CO2 and H2S removal from natural gas is critical due to their corrosive natures, the low heating value of natural gas and the greenhouse gas effect. To date, several gas fields have remained unexplored due to limited technologies to monetize the highly sour natural gas. A variety of conventional technologies have been implemented to purify natural gas such as absorption, adsorption and membrane and cryogenic separation. The application of these technologies in natural gas upgrading are also presented. Among these commercial technologies, cryogenic technology has advanced rapidly in gas separation and proven ideally suitable for bulk CO2 removal due to its independence from absorbents or adsorbents, which require a larger footprint, weight and energy. Present work comprehensively reviews the mechanisms and potential of the advanced nonconventional cryogenic separation technologies for processing of natural gas streams with high CO2 and H2S content. Moreover, the prospects of emerging cryogenic technologies for future commercialization exploitation are highlighted.

Experimental Study on Increasing the Heating Value of Natural Gas by Reducing the Concentration of Carbon Dioxide Using Vortex Tube with Different Cold Orifice Geometries

Experimental Study on Increasing the Heating Value of Natural Gas by Reducing the Concentration of Carbon Dioxide Using Vortex Tube with Different Cold Orifice Geometries

Techno-Economic and Feasibility Assessment of Cryogenic Distillation Membrane (CDM) for Purification Natural Gas from CO2

It is estimated that the energy demand in the world at 2050 will increase by 52% relative to 2017. In Indonesia, it was predicted the deficit energy at natural gas sector occurred as much as 17.5 BSCF in 2020 and the deficit will increase to 3,327 BSCF in 2050. Nevertheless, the natural gas that Indonesia produced has impurities of 70% CO2 and 0.6% H2S, while the hydrocarbon only 28.1%, that makes the heating value of natural gas become lower compared to common natural gas. Therefore, the process of separating the impurities of CO2 and H2S from hydrocarbon is needed to increase the heating value and to get pure natural gas. One of alternatives that can solve the problem is Cryogenic Distillation Membrane (CDM). The CDM process integrates the process of cryogenic distillation and cryogenic membrane to separate impurities from hydrocarbon. It has been proven that cryogenic distillation can decrease CO2 concentration from 70% to 3%, and rise up hydrocarbon purity from 70% to 95%. Moreover, cryogenic membrane can increase the purity of natural gas from 95% to 98%. Therefore, CDM process is expected as appropriate process to get rid the impurities and give high purity of natural gas. Based on the calculation through simulation using software ASPEN HYSYS, the CDM process is beneficial because it gives capture rate CO2 up to 99%, decreases the purity CO2 from 70% to 0.001%, reduces the purity H2S from 0.6% to 0.02%, increases natural gas purity from 28.1% to 98%, raises the heating value from 284.5 Btu/SCF to 988.4 Btu/SCF and can generate valuable byproduct CO2 liquid.

Promotion of Low-Carbon Economy through Efficiency Analysis: A Case Study of a Petrochemical Plant

Over the past few decades, industrial development has caused a dramatic increment in greenhouse gas (GHG) emissions, as a leading cause of climate change. Modifying the industrial plants' environmental performance is the main pillar of improving efficiency that can reduce the waste of resources and make achieving lower-cost global emission reduction targets of the Kyoto protocol's clean development mechanism (CDM) possible. Considering the essentiality of knowledge-based research in increasing the awareness of policymakers by providing better access to accurate and reliable information, an analytical survey on efficiency in oil, gas, and petrochemical industries has been conducted by applying data envelopment analysis (DEA). For this purpose, comprehensive evaluations were elaborated on monthly data for Zagros Petrochemical Company (ZPC), from 2011 to 2017, as a case study. The CO2 equivalent emissions of fuel combustion in the petrochemical plant's furnaces were calculated according to standard guidelines for calculation and reporting GHG to be used for environmental efficiency estimations. The data envelopment analysis program (DEAP) was applied to estimate efficiencies through the data envelopment analysis-materials balance principle (DEA-MBP) approach, which is a robust approach employed in this study to provide practical solutions to both economic and environmental concerns. Since DEA-MBP is based on the materials balance principle and incorporates by-products, it can reliably explain the best relationship between product quantities, carbon emissions, and external costs. The outcomes revealed that the lower heating value of natural gas and CO2 emission factor and CO2 equivalent emissions were 32.87 × 10–3 GJ/Sm3, 55.73 × 10–3 ton/GJ, and 2,376,449 tons, respectively. DEAP analysis also exhibited the technical, environmental, and environmental allocative efficiency scores as 0.976, 0.861, and 0.881, respectively, and estimated distances to efficiency frontiers were 0.024, 0.139, and 0.119, respectively. Ultimately, the carbon prices were found to be about US$83,175,715 and US$71,531,110 under two scenarios (A and B).

Research of the Influence of Temperature Factor on Express Control of Natural Gas Combustion Heat

The article is devoted to the study of the influence of the qualitative and quantitative composition of gas environments on the flame temperature of the combusted gas at different values of gas flow rate and changes volume ratio gas-air in its combustion. The functional scheme of the developed labo­ratory stand (Fig. 1), which provides temperature measurement during combustion of natural gas or propane-butane mixture, is considered. The design of the developed burner is described and the expe­rimental researches are carried out when measuring the flame temperature of the combusted gas during the operation of the laboratory stand. The opera­ting conditions of different thermocouples in measuring the temperature of the flared gas are investigated (Fig. 2). The temperature instability in the lower and upper flames was experimentally determined (Fig. 3) and its difference from the reference data [12, 13]. The measurement of the flame temperature with
 a uncased thermocouple and two thermocouples of different types with protective housings is reali­zed. Methodical error of temperature measurement by different thermocouples was estimated (Fig. 5). An algorithm for the implementation of measurement control in determining the heat of combustion of natural gas according to the patented method is outlined [11]. Experimental studies of temperature changes of combusted gas mixtures at different gas flow rates and different ratios with air, which is additionally supplied for gas combustion, were carried out (Figs. 4, 7). The computer simulation (Figs. 6, 8) of the change in the flame temperature was performed on the basis of the experimental data, which allowed to obtain approximate equations of the functional dependence of the flame temperature on the gas flow rate and the ratio of the additional air and gas consumption. The possibility of realization of the device of express control of the heating value of natural gas by measuring the combustion temperature of the investigated gases, which is based on the expe­rimentally confirmed increase in the flame temperature of the investigated gases with increasing their calorific value, is substantiated (Fig. 9). The necessity of further investigation of the optimization design characteristics of the burner and the operating conditions of combustion of the gases under rapid cont­rol of their combustion heat was established (Fig. 9).

Modeling and Simulation of the Absorption of CO2 and NO2 from a Gas Mixture in a Membrane Contactor

The removal of undesirable compounds such as CO2 and NO2 from incineration and natural gas is essential because of their harmful influence on the atmosphere and on the reduction of natural gas heating value. The use of membrane contactor for the capture of the post-combustion NO2 and CO2 had been widely considered in the past decades. In this study, membrane contactor was used for the simultaneous absorption of CO2 and NO2 from a mixture of gas (5% CO2, 300 ppm NO2, balance N2) with aqueous sodium hydroxide solution. For the first time, a mathematical model was established for the simultaneous removal of the two undesired gas solutes (CO2, NO2) from flue gas using membrane contactor. The model considers the reaction rate, and radial and axial diffusion of both compounds. The model was verified and validated with experimental data and found to be in good agreement. The model was used to examine the effect of the flow rate of liquid, gas, and inlet solute mole fraction on the percent removal and molar flux of both impurity species. The results revealed that the effect of the liquid flow rate improves the percent removal of both compounds. A high inlet gas flow rate decreases the percent removal. It was possible to obtain the complete removal of both undesired compounds. The model was confirmed to be a dependable tool for the optimization of such process, and for similar systems.

Energy benchmarking of thermal power plants using Pinch Analysis

Benchmarking of process industries with respect to energy consumption has always been a challenging issue for effective management of energy resources. Having developed a precise model for estimating the energy consumption, we have a powerful tool to measure and identify the opportunities for improvements through a plant. In this study, a mathematical-conceptual model is presented for one-way benchmarking of thermal power plants applying Pinch concepts. Using the environmental variables of the ambient air and relative load of gas turbine, the model presented for the combined cycle power plants provides a standard for the functional parameters of the unit. Another model is presented for the conventional steam cycle power plants enabling the prediction of the results of energy retrofit projects on these power plants based on combined Pinch and Exergy Analysis. By this model, the relationships between minimum temperature difference in heat exchanger networks and the enhanced efficiency, heat transfer area increment, and energy consumption decline are specified. A mathematical model is also proposed for estimating the natural gas heating value and CO2 emission based on natural gas composition. The proposed models have been validated using data of other existing power plants and showed enough accuracy of given targets.

Cascade refrigeration systems in integrated cryogenic natural gas process (natural gas liquids (NGL), liquefied natural gas (LNG) and nitrogen rejection unit (NRU))

Heavy components in the natural gas itself can feed downstream units and also due to the low temperature process may be formed solid. Therefore heavy components separation is a necessity and can produce useful products. Virtually all natural gases are containing nitrogen that would lower the heating value of natural gas. This study investigates design and optimization of integrated process recovery of natural gas liquids, natural gas liquefaction, and nitrogen remove unit. In this integrated process, design of low temperature processes is started from the core process and continued by heat exchangers network design and cooling system based on MFC. Design and integration processes of units at the same time reduces the number of required equipment and energy consumption. The results show that the new integrated process has specific power around 0.343–0.33 (kW-h/kg-LNG) and its thermal efficiency equal to 62.82%, compared to other integrated systems have the lowest and highest values. Exergy analysis shows that towers has the highest Exergy destruction among other equipment. Sensitivity analysis shows that the structure of the integrated process capable of removing nitrogen from natural gas at a concentration of between 5% and 15%. By analyzing the operating parameters shows reduction in the Total specific power from 19.5% to 24% and the Specific power from 2.57% to 11%, yet surging in the Ethane recovery from 2.5% to 17%. Sensitivity analysis is the method to identification of the Decision variables, finally Genetic Algorithm used to identify optimum of objective function (minimization of Specific Power) and reduction of it to 6%.

The Potential and Approach of Flue Gas Waste Heat Utilization of Natural Gas for Space Heating

After the combustion of natural gas, the flue gas contains large amounts of water vapor. The latent heat of the water vapor in the flue gas account for 10%-11% of the lower heating value of natural gas, that is, if the condensing heat of the flue gas were recovered, the energy efficiency could be improved greatly. In order to improve the efficiency of the space heating system by natural gas, the potential of waste heat of the flue gas were analyzed, and the problems of the conventional space heating system were proposed. A new approach was proposed, which could decrease the temperature of the flue gas, and recover the waste heat of the flue gas simultaneously. The flue gas outlet temperature could be reduced to below 25°C. The different processes were proposed for gas boiler, distributed energy system, and natural gas cogeneration systems. The energy saving analysis and economic evaluation were investigated. A remarkable economic advantage can be achieved in this technology. The payback year is within 4 years. It provides the important reference for reasonable application of the technique.

Available online Efficiency potential of indirectly heated solar reforming with different types of solar air receivers

In solar reforming, the heating value of natural gas is increased by utilization of concentrated solar radiation. Hence, it is a process for storing solar energy in a stable and transportable form that also permits further conversion into liquid fuels like methanol. This process has the potential to significantly decrease the natural gas consumption and the associated CO2-emissions of methanol production with only few open questions to be addressed prior to commercialization. In the medium and long term, it has the potential to generate methanol as an environmentally friendly fuel for both transport as well as flexible electricity production in combined cycle gas turbines, when biogas is used as reactant. In a previous study the high potential of indirectly heated solar reforming with solar air receivers was shown; however, the efficiency is limited when using state of the art open volumetric receivers. Therefore, different types of air receivers are implemented into an indirectly heated solar reforming process and the overall efficiency potential is assessed in the present study. The implemented receivers are an open volumetric cavity receiver, a closed volumetric cavity receiver and a tubular cavity receiver. The open volumetric cavity receiver and tubular cavity receiver achieve the best results due to their capability of operating efficiently at temperatures well above 700 °C. For these receivers peak efficiencies up to 29% and 27% respectively are predicted. As the utilization of an open volumetric cavity receiver constitutes an open heat transfer loop, the air return ratio together with air return temperature is identified as a major impact factor for overall efficiency. With an improved air return ratio, annual process efficiency of 18.4% is feasible. Considering its relative technical simplicity, this makes indirectly heated solar reforming a promising technology to efficiently provide renewable energy for methanol production and thereby diversify solar energy utilization.

Energy System and Thermoeconomic Analysis of Combined Heat and Power High Temperature Proton Exchange Membrane Fuel Cell Systems for Light Commercial Buildings

The United States Department of Energy’s Pacific Northwest National Laboratory is teaming with industry to deploy and independently monitor 5-kilowatt-electric (kWe) combined heat and power (CHP) fuel cell systems (FCSs) in light commercial buildings. Results of an independent evaluation of manufacturer-stated engineering, economic, and environmental performance of these CHP FCSs are presented here. An important contribution of this paper is the precise definition and development of these essential terms for quantifying distributed CHP generator energy use within buildings: (1) electricity and heat utilization, (2) electrical and heat recovery efficiencies, (3) in-use electrical and heat recovery efficiencies, (4) percentage usage of electricity, and (5) percent usage of recoverable heat. Key additional parameters evaluated include the average cost of the CHP FCSs per unit of power and per unit of energy, the change in greenhouse gas (GHG) and air pollution emissions with a switch from conventional power plants and furnaces to CHP FCSs, the change in GHG mitigation costs from the switch, and the change in human health costs from air pollution. CHP FCS heat utilization is expected to be under 100% at several installation sites; for six sites, during periods of minimum heating demand, the in-use CHP FCS heat recovery (HR) efficiency based on the higher heating value of natural gas is expected to be only 24.4%. From the power perspective, the average per-unit cost (PUC) of electrical power is estimated to span $15–19,000/kWe (depending on site-specific installation, fuel, and other costs), while the average PUC of electrical and HR power is $7,000–9,000/kW. Regarding energy, the average PUC of electrical energy is $0.38–$0.46/kilowatt-hour-electric, while the average PUC of electrical and HR energy is $0.18–$0.23/kWh. GHG emissions were estimated to decrease by one-third after replacing a conventional system with a CHP FCS. GHG mitigation costs were also proportional to changes in GHG emissions. Estimated human health costs from air pollution emissions decreased by a factor of 1000 with changing to CHP FCS. Reported for the first time here is the derivation of the PUCs of power and energy for a CHP device from both standard and management accounting (MA) perspectives. Results show that the average PUC of combined electrical and HR power is equal to the average PUC of electric power applying an MA approach, and also equal to the average PUC of HR power applying an MA approach. Similar relations hold for the average PUC of energy. Results presented here demonstrate the value of using the equations herein for economic analyses of CHP systems to represent the average PUC of electrical power, HR power, or both, and for energy.

Efficiency potential of indirectly heated solar reforming with open volumetric solar receiver

In solar reforming, the heating value of natural gas is increased by utilization of concentrated solar radiation. Hence, it is a process for storing solar energy in a stable and transportable form that also permits further conversion into liquid fuels like methanol. The feasibility of solar reforming is proved. However, its overall process efficiency potential has not been studied systematically. In this work, an indirectly heated solar reforming process with air as heat transfer fluid is designed and modelled to produce syngas suitable for subsequent methanol synthesis. For provision of solar high temperature heat, an open volumetric receiver is implemented into the process model and the overall performance is investigated. Results show the paramount significance of the air return ratio of the receiver and its ability to achieve high efficiencies at temperatures above 850 °C. For realistic air return ratios, design point process efficiencies of 19% can be achieved, for an increased air return ratio, values up to 23% are feasible. The determined corresponding annual efficiencies are 12% and 14% respectively. Considering its relative technical simplicity this makes indirectly heated solar reforming a promising technology to overcome the current limitations of solar energy in the medium term.

천연가스 열량 변화에 따른 GHP 엔진의 성능 및 배출가스 특성

가스엔진구동 히트펌프(GHP : Gas Engine Driven Heat Pump)의 연료인 천연가스의 열량이 감소함에 따라 국내에서 생산되는 GHP에 미치는 영향을 평가하였다. 저열량가스(<TEX>$9,800kcal/Nm^3$</TEX>)를 연료로 사용하여 엔진 단체 실험 및 GHP 현장평가를 실시한 결과 약간의 출력감소가 확인되었으나 시동성, 운전안정성, 배출가스 특성 등은 거의 변화가 없음을 확인하였다. 따라서 천연가스 열량이 <TEX>$9,800kcal/Nm^3$</TEX>까지 감소하여도 별도의 조정없이 GHP가 정상운전될 수 있을 것으로 판단된다. In general, natural gas is used as GHP(Gas Engine Driven Heat Pump) fuel. On this study, the influences of different natural gas heating value on GHP were evaluated. As a result of engine test & field test using low heating value gas(<TEX>$9,800kcal/Nm^3$</TEX>) as fuel, the engine power was reduced slightly, however the performance of start-up, the stability of operation and the characteristics of emission gas were almost similar. So it is considered that the normal operation of GHP is possible without any tuning when the low heating value(<TEX>$9,800kcal/Nm^3$</TEX>) of natural gas was used as fuel.

Effect of Variation of Fuel Composition on Gas Turbine Off-Design Performance

The effects of fuel composition is investigated in a gas turbine for natural gas. Fuel composition is divided H/C ratio and heating value. There are three control schemes for gas turbine. In this study, TIT control and TET control is adopted. A full off-design analysis of the gas turbine was performed. Performance characteristics and maximum turbine blade temperature are the main interests. The power output is decreased while heating value of fuel is increased and H/C ratio of fuel is decreased both control scheme. As heating value of natural gas decreased and H/C ratio of fuel increased, turbine blade temperature is increased in TIT control. Otherwise, Blade metal temperature is little influenced by H/C ratio of fuel in TET control scheme.

A Review on Robustness of Covalent Organic Polymers for CO&lt;sub&gt;2&lt;/sub&gt; Capture

The presence of carbon dioxide (CO2) in natural gas stream is a critical problem; besides causing corrosion it also reduces the energy contents and heating value of natural gas. Various separation techniques are available to separate CO2 from natural gas, such as metal organic framework (MOF), covalent organic framework (COF) and Covalent Organic Polymer (COP) adsorbents. The criteria of adsorbent selection that need to be fulfilled include high adsorption capacity, high selectivity of CO2 and hydrothermal stability at operating conditions. COPs are crystalline porous materials having high CO2 capacity and selectivity in the presence of water vapors. However, the research on COP material development is new and scarce information is available in literature. In this prospect, the paper highlights the different types of COPs, their basic constituents and the adsorption capacities.

Flowsheet development, process simulation and economic feasibility analysis for novel suspension ironmaking technology based on natural gas: Part 2 – Flowsheet and simulation for ironmaking combined with steam methane reforming

A novel gas–solid suspension ironmaking process with much less energy consumption and carbon dioxide emissions than the current blast furnace technology is under development at the University of Utah. The proposed process is based on flash reduction of iron ore concentrate with a gaseous reagent, such as hydrogen, syngas and/or natural gas. This series of papers reports on the results of process simulation for the proposed process operated with natural gas. This Part 2 deals with simulation of a commercial scale ironmaking process combined with a steam methane reforming process. The steam methane reforming process was simulated to produce hydrogen or syngas to provide fuel/reductant for ironmaking. Ironmaking was simulated in one-step configuration. The results indicated that the proposed process would reduce carbon dioxide emissions by 31–35%, but energy consumption would be larger by 0–6%, based on the higher heating value of natural gas (28–29% lower, if the lower heating value is used), compared with the average blast furnace process. The sensitivity of the energy requirement to operating conditions was also examined.