Operating Conditions Gas Research Articles

Atom economy or product yield to determine optimal gasification conditions in biomass-to-olefins biorefinery

Biorefinery design uses various metrics for achieving biomass conversion with process efficiency and biochemical selectivity. A common optimization strategy targets the product yield expecting favorable waste reductions. As a green-chemistry metric, atom economy offers a novel approach to achieving mass efficiency by simultaneously computing products and waste. A comparison between the product yield and atom economy presumes different optimal operating conditions. This study applied atom economy to a biomass-to-olefins process to elucidate metric differences. An initial revision of the stoichiometric conditions determined the ideal product and waste generations. A realistic simulation predicted the mass flows to olefins via gasification, methanol synthesis, and methanol-to-olefins conversion. The gasifier operating conditions were modified to clarify interactions among the atom economy, reaction temperature, and steam-to-biomass mass ratio (S/B). The optimal atom-economic and product-yield conditions differed; a lower gasification temperature and atom-economic (S/B) ratio enhanced the olefins-to-waste ratio. The atom economy indicated that CO2 and H2O are inefficient transport molecules for releasing oxygen in biomass. Both wastes consume at best 33% g/g of feedstock carbon or hydrogen, complying to olefin and intermediate H/C ratios. A comprehensive revision of the energy performance is required to complement the atom economy as a performance indicator.

Mathematical modeling of tar conversion on downdraft biomass gasification processes

AbstractThe article concerns some problems associated with the use of low‐grade fuels for the production of syngas in fixed‐bed gasifiers. Syngas is typically used to feed internal combustion engines in small power systems. Gas quality can be understood as its various characteristics, such as calorific value, the content of individual components (for example, hydrogen), low tar and soot content, and so forth. Achieving these quality criteria often requires specific conditions for the gasification process, in addition, some of them may be limited by additional requirements that are associated with thermal stability or fuel conversion requirements. When evaluating the technical and economic characteristics of gasification‐based power plants, the optimal efficiency does not always correspond to the higher efficiency of the gasification process and the quality of producer gas. In this regard, the aim is to develop optimization methods for different criteria and to create regime maps that cover physically achievable options. Novel mathematical models of tar conversion are proposed, allowing investigation of the dependencies of tar yield on gasification conditions, including the addition of catalysts or staged air supply. Computational tools based on thermodynamic and kinetic models make it possible to solve some of these problems, first of all, to consider and compare the efficiency of various methods for reducing tar content in producer gas (staged gasification, fuel mixing, thermal, and catalytic methods of tar elimination). The choice of relatively simple mathematical models allows us to conduct numerical calculations in a wide range of conditions and to optimize the parameters of biofuel conversion plants. This approach allows a more flexible choice of gasifier operating conditions, including its work as a part of a power unit. Optimal parameters are calculated for specific conditions: secondary air ratio (1–20%) and fraction of catalytic material (5–10%). The results may be used in the analysis and choice of biofuel gasification conditions at small power plants.

A Review of Factors Affecting Gasifier Performance

AbstractThe Physico‐chemical characteristics are inherent properties of fuel and their behaviour changes in different gasification conditions. The critical properties of the coal impede the gasifier's performance, and hence, a proper study is needed to develop and further enhance the gasification systems. A proper assessment of factors influencing gasifier performance and their optimization enables to select, alter, and adjust the conditions. The present paper reviews the effect of important coal properties and gasifier operating conditions on gasification performance parameters. Further, the suitability of gasifiers (moving bed, fluidized bed, and entrained flow) according to the physico‐chemical properties of fuel along with proper operating parameters has also been studied.

Performance Testing and Case Studies of Rural Household Biogas Micro-CHP Systems

Against the backdrop of clean rural heating and dual carbon targets, this paper investigates and develops a household combined heat and power (CHP) unit. The performance of the unit under natural gas operating conditions was tested and evaluated in the laboratory. The test results show that at rated operating conditions the unit has an electrical efficiency of 29% and an overall efficiency of 96%. The micro-CHP was then tested in a civil building in a demonstration site in Xuzhou, Jiangsu province, for trial operation under biogas working conditions. The test results show that when the unit in biogas working condition is heating the room, the unit has a rated working condition power generation of 3.2 KW and still has an average electrical efficiency of about 26.8% and a thermal efficiency of 65.6%, which remains at a high level. And the room temperature data shows that the heat supply meets the heating demand. Finally, this paper compares the performance with micro-CHP units available in the European and American markets. The results show that the performance of this unit is superior to many micro-CHP units available overseas. This paper demonstrates through test results that rural micro-CHP system can meet the daily energy needs of farmers, improve energy use efficiency and reduce carbon emissions.

Numerical and experimental assessment of a micro-combined cooling, heating, and power (CCHP) system based on biomass gasification

The goal of this paper is to analyse an innovative micro-combined cooling, heating, and power (CCHP) system, whose power generation unit is composed of an internal combustion engine fuelled with syngas coming from a woody biomass gasification process. The internal combustion engine is directly coupled to the gasifier. The analysis of the existing plant, realized in South Italy, was carried out experimentally. Moreover, a numerical model was developed. The model, in particular, considers the impact of gasifier operating conditions, i.e., biomass feed rate and equivalence ratio (ER) on engine performance: electric, thermal, and overall efficiency of the micro-CCHP system, running on woody biomass at full and partial loads conditions. Modelling the coupled system at partial load with real thermophysical properties of the syngas produced by the gasification process is surely a novel contribution but even more relevant is the presentation of experimental data on an existing plant. Once the model was validated, the system performance was evaluated by comparing two different biomass compositions: W1, characterized by a lower heating value of 14.5 MJ/kg and W2, having a lower heating value of 16.8 MJ/kg. Results show that the biomass composition affects more significantly the gasifier efficiency (72.4–82.6 %) and the engine thermal efficiency (55.3–50.6 %), while the engine electric efficiency is weakly affected (26–27 %). An overall efficiency of the entire micro-CCHP system amounting to 55.2 % and 61.1 % for W1 and W2, respectively, was estimated. Lastly, the economic feasibility of the micro-CCHP system was investigated and includes a sensitivity analysis of the current costs of energy vectors. The results demonstrate the affordability of the biomass based CCHP system, which is further increased in this period of contingent international political crisis and a payback period of about 2 years is currently predictable.

Mathematical Justification for Optimizing Operating Conditions of Gas and Gas Condensate Producing Wells

The paper investigated the problem of selecting/finding the optimal process conditions for gas condensate wells. The well process conditions imply a set of parameters that characterize its operation. The optimization of process conditions provides for the efficient operation of an oil and gas field while meeting the defined boundary and initial conditions, and allows for the process/production goal to be achieved. This paper proposed using the tree-structured Parzen estimator (TPE), which allows for the results from previous iterations to be considered, in order to identify the most promising region of conditions, thereby increasing the optimization efficiency. The movement of multiphase fluid inside the pipeline system (also in the borehole) must be calculated to solve the process optimization problem. The optimization module was integrated into the hydraulic and unsteady state multiphase flow calculations inside the well and the pipeline. The platform created allows for the process conditions at gas condensate fields to be identified via the use of numerical methods. The proposed optimization algorithm was tested in delivering the task of optimizing the process conditions in 13 producing wells in a part of a real gas condensate field in Western Siberia. The engineering problem of optimizing the production of gas and the gas condensate was solved as a consequence of the calculations performed.

Rate-based modeling approach for High Pressure Water Scrubbing with unsteady gas flowrate and multicomponent absorption applied to biogas upgrading

Biogas upgrading aims to increase the methane concentration in biogas by removing carbon dioxide. Upgraded biogas can then be used as a renewable energy resource. Among the technologies used for biogas upgrading, High Pressure Water Scrubbing (HPWS) is one of the most widespread. HPWS is identified as fulfilling all the requirements for farm-scale anaerobic digesters, presenting several levers to reduce operational and installation costs. One possible remedy is to optimize operating parameters to reach targeted gas specifications, without applying excessive treatment or energy consumption. The purpose of this study is to develop an efficient modeling tool that can predict methane purity and its recovery for different operating conditions of gas and liquid. This original model integrates the decrease of gas flow along the packing height and the concomitant absorption of carbon dioxide and methane. The model is based on mass transfer and hydrodynamics to explain and anticipate the performance of HPWS in order to facilitate its implementation on the field. Model results retrieved from a homemade environment on Excel are compared to those of experiments conducted on a farm-scale biogas upgrading plant and show very good agreement. The model demonstrates great adaptability regarding variations of parameters. It can thus be used to anticipate HPWS performance and to optimize running parameters in order to reach targeted purities while making energy consumption more flexible. Water regeneration is identified as the key parameter for compliance with gas injection standards, achieving a purity over 97% and a recovery ratio of 93% at a desorption pressure of 0.2 bar. Results highlight that a rate-based model giving access to molar fraction variation along the column is crucial to adjust operating parameters in order to reach optimal economic and environmental performances. More accurate operating conditions could be the key to lowering costs of production and attaining financial viability for biogas upgrading at farm scale.

Analysis of regulatory requirements for the assessment of carbon dioxide corrosion at gas production facilities

Aim.In many fields, the produced gas contains corrosive CO2, which, in combination with moisture and other factors, stimulates the intensive development of corrosion processes, including local ones, which requires careful attention to the assessment of the corrosiveness of operating fluids in order to select effective anti-corrosion protection. Ensuring reliable and safe operation of equipment and pipelines prevents not only man-made risks, but also no less important environmental risks, which are especially dangerous for marine underwater facilities for Arctic coastal facilities.Methods.The analysis of normative and technical documentation in the field of assessment of corrosion risks, aggressive factors of internal corrosion and operating conditions of gas and gas condensate fields has been carried out.Results.One of the criteria for assessing the corrosion hazard is the corrosion rate of steel under operating conditions. However, the normative documents predominantly regulate the general corrosion rate, which evaluates the uniform thinning of the metal. But the rate of local corrosion is in no way taken into account, which is most relevant precisely for the conditions of carbon dioxide corrosion of steel. Another tool for identifying risks can be a corrosion allowance to the pipe wall thickness, which should be selected at the design stage and which is provided to compensate for corrosion losses during the operation of gas pipelines. It is shown that the minimum corrosion allowance (3 mm) specified in the main regulatory documents is insufficient, especially for offshore facilities.Conclusion.The experience of operating gas production facilities confirms that the rate of local corrosion can reach several mm/year. To limit this, effective anti-corrosion measures should be chosen, for example, the use of corrosion inhibitors, and a reasonable level of corrosion allowance should be provided that would take into account the corresponding level of corrosion risks at the gas production facility.

Control of Fossil Fuel Gas Operating Conditions on the Performance of Carbon Dioxide Capture Process

The emission of Carbon dioxide (CO2) from combustible flue gases is now seen as the key instrumental factor to global warming. The process of post-combustion capture from industrial flue gases via reactive absorption have the capability of substantially reducing the emissions of the greenhouse effect. This paper presents the modelling and simulation of flue gas conditions for carbon dioxide capture process utilizing post-combustion process. The obtained models were simulated using SCILAB 5.5.2 code based software. The results shows a good relevance of the modeling procedure with the fact that the volumetric flow rate of the flue gas and the Amine temperature governs the dynamics of CO2 absorption at the bottom region of the column. It is also noted in the findings that the increase in the volume of the flue gas gives rise to the concentration of CO2 at low temperatures.

Thermal degradation characteristics and gasification kinetics of camel manure using thermogravimetric analysis

In this work, the sustainable valorisation of camel manure has been studied using thermogravimetric analysis. The gasification tests were performed from ambient conditions to 950 °C at 10, 20, and 50 °C/min under an O2 environment. The TGA data were applied to determine the kinetics of the O2 gasification. Single-heating rate models (Arrhenius and Coats-Redfern) and multi-heating rate models (Distributed activation energy, Friedman, Flynn-Wall-Ozawa, Starink, and Kissinger-Akahira-Sunose) were applied to estimate the kinetics of the process. Between the two single-heating rate models, the Coats-Redfern method fitted best with the experimental data. Among the multi-heating rate models, the Flynn-Wall-Ozawa model fitted best with the experimental results. The kinetic parameters-frequency factor, activation energy, and order of reaction were estimated using the Flynn-Wall-Ozawa model (the best-fitting model) and the estimated kinetic parameters were used to calculate the thermodynamic properties-Gibbs free energy, enthalpy, and entropy. The information on these kinetic and thermodynamic properties can be useful for the design of gasifiers and for optimising the O2 gasification operating conditions.

Experimental determination of the worker’s clothing surface temperature during the ceramic gas heater operation

Providing regulated comfortable thermal conditions for workers and engineers working in large-sized industrial premises is a rather energy-consuming process in many cases. It is necessary to heat not only large volumes of air very often, but also the enclosing structures. One of the most promising options for reducing energy costs is the use of gas infrared heaters as heat sources. However, such radiant heaters are still little used, because no relationship has been established between the characteristics of the heat supply object – the operating one and the parameters of the radiator. The purpose of the study is to establish, based on the results of the experimental studies, the functional relationships of the surface temperature of the worker’s clothing and the parameters of a typical gas infrared heater. The experiments have been carried out to register the temperature fields of the material surface of the working model, as well as in the immediate vicinity of the model. A substantially inhomogeneous distribution of the temperatures of the surface of the fabric of the model’s clothing has been established depending on the orientation of this surface relative to the direction of the radiation flux. Based on the results of the experiments, the conclusions have been drawn about the regularities of heat transfer of a heat supply object – working with the external environment under the operating conditions of gas infrared heater (GIH). Recommendations for the formation of thermal conditions for those working with radiant heating were formulated.

Bio-methanol production from oil palm residues: A thermodynamic analysis

The thermodynamic analysis of bio-methanol production from oil palm residues was performed using a process model developed in Aspen Plus. Among the different types of oil palm residues, i.e., trunk, frond, and empty fruit bunch, the trunk residue offers the highest synthesis gas (syngas) (H2 and CO) yields via the gasification process; therefore, it was selected as the biomass model compound. The effect of gasification operating conditions on the syngas composition, yield, bio-methanol production, energy consumption, and exergy performance was examined. The yield of syngas increased with increasing gasifying temperature, whereas that of bio-methanol exhibited the opposite trend due to the decrease in H2 concentration of the syngas. The gasifier was an important unit for enhancing the exergy efficiency of the system, which was decreased when the equivalent ratio (ER) and gasifying temperature increased. Recirculating pressure swing adsorption offgas to the gasifier did not benefit bio-methanol production, nor did it improve energy and exergy performance. The maximum yield of bio-methanol was achieved by a once-through process that maintained the gasifying temperature at 750 °C and ER at 0.25. Under these conditions, the maximum energy and exergy efficiencies were 38.57 and 25.44%, respectively.

Exploring the sustainable production of ammonia by recycling N and H in biological residues: Evolution of fuel-N during glutamic acid gasification

In this work, the recycling of nitrogen and hydrogen from nitrogen-rich (N-rich) biological residues via autothermal gasification has been proposed as a process suitable for the sustainable production of ammonia (NH3). Two N-rich biological residues, sewage sludge and meat and bone meal, were used and analyzed in this work and glutamic acid was selected as the model compound of the protein-fuel-N in these residues. Glutamic acid gasification experiments were carried out in order to study the effect of temperature (800–900 °C) and steam-to-carbon ratio (0.5–1.0 g g−1) on the conversion of fuel-N into the most typical N-containing gasification products: NH3, molecular nitrogen (N2), hydrogen cyanide (HCN), nitrogen monoxide (NO), tar-N and char-N. Sewage sludge and meat and bone meal were also gasified under selected operating conditions with the main aim of assessing the NH3 production. The most abundant N-containing compounds obtained in the gasification of glutamic acid were NH3 (35–51% over fuel-N) and N2 (45–63% over fuel-N). The highest conversion of fuel-N to NH3–N in the glutamic acid gasification experiments (51%) was obtained at the lowest temperature (800 °C) and the lowest S/C ratio (0.5 g g−1). The increase in the temperature caused a decrease in the yield of NH3, as a consequence of its decomposition into N2. A similar fuel-N distribution was found when sewage sludge and meat and bone meal were gasified, obtaining joint yields of HCN–N, NO–N, tar-N and char-N lower than 5%, and being NH3–N (30–67%) and N2–N (28–68%) the majority products. The yields of NH3–N obtained from glutamic acid (51%), sewage sludge (30%), and meat and bone meal (67%) under the same gasification operating conditions were significantly different. These differences were attributed to the catalytic effect of the metals present in these residues and point to the need to optimize the operating conditions specifically for each residue. In summary, gasification of sewage sludge and meat and bone meal may be able to produce around 10% of the NH3 produced annually in Europe and between 102 and 262 GJ·ton−1 NH3 thanks to the combustion of the syngas generated.

Electromagnetic Disturbed Mechanism of Electronic Current Transformer Acquisition Card under High Frequency Electromagnetic Interference

The electronic current transformer (ECT) acquisition card is widely used in smart grids with many advantages. However, with the continuous improvement of the power grid and localized intelligent electronic devices, the electromagnetic environment under the operating conditions of gas insulated switchgear (GIS) substations is becoming more complicated. The reliability and safety of the ECT acquisition card will be endangered due to the complicated electromagnetic environment. In order to solve these problems, this paper investigates the electromagnetic disturbed mechanism of the ECT acquisition card. The effects of different grounding methods on the electromagnetic interference of the ECT acquisition card were studied. A platform based on IEC 61000-4-4 was built, and the electromagnetic interference (EMI) of the ECT acquisition card with different grounding methods was measured. The results show that the lower grounding impedance of the ECT acquisition system increased the internal EMI. Further, the high frequency electrical fast transient/burst coupling mechanism was analyzed. The parasitic parameters of the acquisition card were extracted based on the critical circuit by using the finite element method. Then, the high-frequency EMI coupling model of the ECT acquisition card was established.

Fabrication and Performance Evaluation of Industrial Alumina Based Graded Ceramic Substrate for CO2 Selective Amino Silicate Membrane.

The present study mainly focuses on the careful design of an amino-silicate membrane integrated on an asymmetric graded membrane substrate, comprised of a cost-effective macroporous industrial alumina based ceramic support with a systematic graded assemblage of sol-gel derived γ-alumina intermediate and silica-CTAB sublayer-based multilayered interface, specifically dedicated for the separation of CO2 gas from the binary gas mixture (CO2/N2) under nearly identical flue gas atmospheric conditions. The tailor-made industrial α-alumina-based porous ceramic support has been characterized in terms of apparent porosity, bulk density, flexural strength, microstructural feature, pore size, and its distribution to demonstrate its application feasibility toward the evolution of the subsequent membrane structure. The near surface morphology of the subsequent intermediate and submembrane layer has been carefully controlled via precisely scheming the colloidal chemistry and consequently implementing it during the deposition process of the respective γ-alumina and silica-CTAB precursor sols, whereas the potentiality of the quarantined amine groups in the final amino-silicate membrane has been methodically optimized by the appropriate heat treatment process. Finally, the real-time applicability of the hybrid amino-silicate membrane has been evaluated in terms of systematic analysis of the binary gas (CO2/N2) separation performance under variable operating conditions. The investigated ceramic membrane exhibited optimum CO2 permeance of 46.44 GPU with a CO2/N2 selectivity of 12.5 at 80 °C under a trans-membrane pressure drop of 0.8 bar having a feed and sweep side water flow rate of 0.03 mL/min, which shows its performance reliability at nearly identical flue gas operating conditions.

A new semi-empirical correlation for driving mass-flow rate calculation through ejectors for CO2 heat pumps. Comparison with predictions of other methods.

Carbon dioxide (CO2) is an interesting substitute of traditional HFCs in vapor compression systems, due to its environmentally friendly characteristics: zero ODP and extremely low GWP. Nevertheless, the use of CO2 heat pumps in residential heating and cooling applications actually is still limited, due to the different operating conditions of gas cooling, they can perform significantly worse than conventional.The use of ejection systems for the fluid expansion in a refrigeration cycle can contribute to recovery part of the mechanical energy otherwise dissipated as friction, leading to significant benefits in terms of performance. The ejector sizing is a critical point for the balancing of components and the correct operation of the CO2 heat pump; in this regard, the availability of reliable methods for calculating the motive flow rate would be useful. In recent years, ENEA Laboratory DTE-PCU-SPCT of the Casaccia research center, along with the Industrial Engineering Department of Federico II University of Naples, carried on a project aimed at evaluating experimentally the effect of several ejectors geometries on the global performance of a CO2 heat pump working with a transcritical cycle.This paper presents a new semi-empirical correlation for the ejector primary mass flow rate calculation, developed by the experimental data, based on the hypothesis of isentropic and choked flow. The correlation is then tested on other experimental data available in the literature for different ejectors. Finally, the predictions are compared to others semi-empirical correlations present in the literature.

Agglomeration Phenomena During Fluidized Bed Combustion/gasification of Biomass Fuels

The objective of this research is to investigate the occurrence of agglomeration phenomena during fluidized bed processing of biomass fuels. These are to be ascribed to the alkali content in biomass materials that gives rise to low melting compounds in combination with SiO2, normally present in bed materials. The results obtained in a lab scale facility under operating conditions of gasification highlight that other materials may be adopted (e.g. olivine and chromite), despite they have higher density with respect to silica sand, affecting the bed fluid-dynamics. As alternative the addition of metakaolin is effective in order to delay the occurrence of bed agglomeration, as demonstrated by experiments carried out in alumina crucible at 900 °C and complemented by electronic scanning microscopy (SEM) and x-ray diffraction (XRD) analyses. The results are reported and discussed in the article, with the sake of providing further insights for contrasting the undesired agglomeration behavior in practical applications.

Comparison of different ORC typologies for heavy-duty trucks by means of a thermo-economic optimization

This study focuses on the design phase of ORC systems recovering the heat wasted from two of the sources available on a Heavy-Duty Truck (HDT): the exhaust and recirculated gases. From these heat sources and their combinations, 5 possible architectures are considered. The main components (i.e. the heat exchangers, the pump and the expander) of the WHR systems are investigated and modeled. Plate type heat exchangers are considered for both the hot and cold sides of the system. Regarding the expansion devices, 5 positive displacement machine technologies, the scroll, screw, piston, vane and roots expanders, are considered and modeled while, among the turbo-expanders, the radial-inflow turbine is taken into consideration. A semi-empirical model is proposed to simulate a volumetric pump. The models of components are first confronted with experimental data. The validated models are then used as references for the design of the new components, which is achieved following similitude rules. This ultimately leads to 30 typologies that will be used with 6 of the various investigated working fluids. In order to identify the most promising system(s), a 3-step optimization tool is developed. First, the most suitable conditions are identified for the design of the ORC systems using a simplified model of an expansion machine. In the second step, the design phase, using more detailed models for the expanders and a proposed economic model for the overall system, a thermo-economic optimization is performed. In the third step, the output power for each of the obtained system models is maximized, optimizing the evaporating pressure and the superheating degree for various off-design conditions. The average power weighted using the frequency distribution of the gas operating conditions is computed and used to compare the 180 systems. Finally, because power is not the only criterion to select the most suitable system topology, additional criteria are taken into consideration.

Fly Ash From Poultry Litter Gasification – Can it be Utilised in Agriculture Systems as a Fertiliser?

Fly ash from a poultry litter gasification process and the potential of application of the fly ash as a fertiliser in line with the poultry litter protocol is investigated. The fines collected in the cyclone are mainly formed by ash which comprises between 70-83 wt.% of the fines on a dry basis, and to a lesser extent of carbon (elutriated char). The effect of the gasification operating conditions on the concentration of ash forming elements (inorganic compounds) in the fly ash, are discussed. In addition, the enrichment factor which defines the volatility, has been used and fly ash elements were categorised as Class I (non-volatile), Class II (semi-volatile with the possible occurrence of condensation) and Class III (highly volatile elements). Inorganic elements in fly ashes from poultry litter gasification experiments are categorised as Class I: Ca, Co, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, P, Class II: Cd, Cr, Mo and Class III: Pb and Se. It has been found that the fly ash from the poultry litter gasification exceeds the upper acceptable limit set by Poultry Litter Protocol to be used as a fertiliser in agriculture systems.

Effects of gasification condition on the overall performance of methanol-electricity polygeneration system

The operating conditions of coal gasifier have significant effects on the overall system performance of an associated process. This study designs a methanol-electricity polygeneration system and presents a comprehensive discussion about the effects of the ratio of steam to coal, the ratio of O2 to coal, the ratio of carrier gas (CO2) to coal and the CO2 concentration in methanol synthesis gas on different performance indicators. The results show that the steam/coal ratio has slight effects on the overall system performance due to the offset in different sections. An optimal O2/coal ratio exists in the range of 0.84–0.86 to achieve the minimum unit water consumption and the maximum methanol production and energy efficiency, which is almost consistent with the range that the H2 concentration in gasifier syngas reaches the maximum value. The amount of carrier gas CO2 and the CO2 concentration in methanol synthesis gas should be kept at a low level to just meet the requirements of coal pressurization and synthesis reaction. This comprehensive sensitivity analysis can provide some significant guidance for the system design.