Medium Pressure Steam Research Articles

Dynamic simulation and control strategy development of molten salt steam generation system for coal-fired power plant flexible retrofit

The coal-fired power plant (CFPP) coupled with the molten salt thermal energy storage system is a potential way to improve its flexibility and peak-shaving ability. The steam generation system (SGS) is a suitable choice to convert the feed water into hot steam by using the heat from the molten salt. In this paper, the schematic of an SGS coupled with the CFPP is presented. A dynamic model of the SGS basing lump parameter method is established and validated to investigate its dynamic response characteristics. Five different disturbance experiments including feed water inlet parameters, molten salt inlet parameters and medium pressure steam valve, are conducted and analyzed. The dynamic response curves of molten salt and steam are obtained. Moreover, the load adjustment process of SGS with three different load changing rates (3 %, 6 %, 10 % Pe/min) under the rated conditions is compared and its influence on the SGS is analyzed. The temperature changing rates in the thick-wall components of SGS are within 2 °C/min which meets the safe operating standard. Based on the above results, the three elements control strategy with excellent robustness for the SGS safety operation is proposed and demonstrated. The results show that the response time for the SGS load regulation process and the water level fluctuation have been significantly improved as the three elements control strategy is imposed. The water level can be stabilized in 200 s with tiny fluctuation when the SGS loads down 10 % thermal load with 10 % Pe/min load changing rate. These results could provide useful references for the design and control strategy making of the CFPP coupled with the molten salt thermal energy storage system.

Exergy analysis of process configurations for phenol recovery from wastewater

Wastewater with high phenol content, primarily generated by the petrochemical, coal, oil, and gas industries, must be treated before disposal to meet global regulations and prevent environmental harm. Liquid-liquid extraction is a well-studied method employed to address this need. Despite the extensive focus on to energy performance, exergy analysis has not yet been incorporated. Therefore, this study aims to compare four process configurations by integrating an exergetic approach with economic and emissions analyses to quantify thermodynamic efficiency, total annual cost, and CO2 emissions. Process simulations were conducted using Aspen Plus V.12, and the economic analysis was performed using the Aspen Process Economic Analyzer. The input streams of all configurations were 100 ton/h of wastewater containing 275 kg/h of phenol and 266 kg/h of hydroquinone, with pure methyl iso-butyl ketone (MIBK) as the makeup solvent. Extraction and mixing exhibited the lowest exergy destruction, while distillation accounted for approximately 55 % of the total exergy destruction. Configurations that incorporated direct medium-pressure steam input resulted in greater exergy destruction, leading to reduced exergy efficiency, but a lower total annual cost. The most economical configuration was achieved by heat integration of De Dietrich® process with low-pressure steam (C-IE lps), benefiting from exergy analysis insights. The exergy efficiency of this configuration increased from 33 % to 38 %, and the total annual cost decreased by 183 thousand USD per year compared to the initial De Dietrich® process (configuration C). Similarly, CO2 emissions were reduced to the lowest level, reaching 4.87 kg CO2 /h.

Cross-level steam load smoothing and optimization in industrial parks using data-driven approaches

This study focuses on the integrated energy production system in industrial parks, addressing the problem of stable load dispatch of equipment under demand fluctuations. A cross-level method for steam load smoothing and optimization is proposed, aiming to achieve stable production and optimal economic performance through three levels of integration: load forecasting, load dispatch, and load regulation. Unlike traditional methods that directly use load forecasting values, heat network elasticity is presented as a buffer between demand and supply. Constraints for minimal changes in equipment load and operational parameters are established for smooth regulation. Industrial cases demonstrate that the load forecasting model has mean absolute percentage errors of 2.44% and 1.68% for medium-pressure and low-pressure steam, respectively, meeting accuracy requirements. The modified supply-side load smoothness is effectively improved by considering heat network elasticity. The method increases boiler efficiency by 1.92%, reducing average coal consumption by 0.92 t/h. Compared to manual operation, the proposed model leads to an average increase of 5.69 MW in power generation and an average reduction of 10.81% in coal-to-electricity ratio. This study verifies the importance of smooth integration across different levels and analyzes the effective response of the proposed method to the uncertainty in load forecasting. The method demonstrates the enormous potential of data-driven methods in achieving safe, economical, and sustainable production in industrial parks.

An Ejector and Flashbox-Integrated Approach to Flue Gas Waste Heat Recovery: A Novel Systematic Study

In this study, a comprehensive examination was conducted to explore the technology involved in the recovery of waste heat from flue gas emitted by a 1000 MW unit. Traditional methods are constrained in their ability to harness waste heat from flue gas solely for the purpose of generating medium-temperature water. The system being examined not only recovers waste heat but also utilizes it to generate steam, thereby greatly improving resource efficiency. The process entails utilizing the flue gas to heat water to a certain temperature, followed by subjecting it to flash evaporation. This process leads to the generation of low-pressure waste heat steam. Within the steam ejector, the waste heat steam combines with high-pressure motive steam extracted from the source, resulting in the formation of medium-pressure steam. Within the steam ejector, the waste heat steam blends with high-pressure motive steam drawn from the source, forming medium-pressure steam that eventually feeds into the A8 steam extraction pipe (low-pressure turbine pumping pipe). The present study examines the fluctuation patterns in motive steam flow, suction coefficient, waste heat steam volume, and outlet temperature of the flue water heat exchanger when different motive steam sources are used. Additionally, the research calculates the reduction in CO2 emissions, the coal consumption for power supply, and the cost savings in fuel for the retrofitted system. The findings indicate that maximizing energy utilization can be achieved by operating the retrofitted unit at the lowest feasible waste heat steam pressure. The implementation of the new system has resulted in a substantial decrease in coal consumption for power supply. When employing main steam as the extraction steam source, the consumption of coal for power generation decreases in proportion to the decrease in waste heat steam pressure while maintaining a constant unit load. When the waste heat steam pressure reaches 0.0312 MPa, the recorded coal consumption for power generation varies between 289.43 g/kWh at 100% turbine heat acceptance (THA) and 326.94 g/kWh at 30%THA. When comparing this performance with the initial thermal power plant (TPP) unit, it demonstrates reductions of 2.26 g/kWh and 1.52 g/kWh, respectively. After implementing modifications to this 1000 MW unit, it is projected that the annual CO2 emissions can be effectively reduced by 6333.97 tons, resulting in significant cost savings of approximately USD 0.23 million in fuel expenses. This system exhibits considerable potential in terms of emission reduction and provides valuable insights for thermal power plants aiming to decrease unit energy consumption.

Coupling a small modular molten salt reactor with desalination

To respond to the increasing water demand worldwide, especially in coastal cities and islands, nuclear desalination becomes a potential solution. SmTMSR-400 is a small modular molten salt reactor, which can be easily transported and has inherent safety. This paper analyzes the options of coupling SmTMSR-400 with desalination with parametric studies. SmTMSR-400 is integrated with multi-effect distillation (MED) and reverse osmosis (RO), respectively. In the MED options, the high-pressure, medium-pressure, or low-pressure steam from the steam Rankine power cycle can be used to generate the process steam for desalination. After evaluating and comparing the four options, it is found that: a) the RO option has the best performance of energy utilization and a higher upper limit of water production; b) the RO option is not suitable for water sources containing a large amount of organic matter, and the quality of the water produced is lower than that of the thermal desalination options; c) the low-pressure steam option has the best performance of energy utilization among the MED options, but its water production and power generation cannot be adjusted according to the local demand; d) when the performance of energy utilization, production flexibility, and water quality are all required, the medium-pressure steam option could be an alternative.

Process Simulation and Optimization of Fluid Catalytic Cracking Unit’s Rich Gas Compression System and Absorption Stabilization System

In a fuel-based refinery, rich gas in the fluid catalytic cracking (FCC) unit is further processed to separate dry gas and refinery products (i.e., stabilized gasoline and liquified petroleum gas). The process is utility-intensive and costly and includes a two-stage compressor, pumps, an absorber, a stripper, a stabilizer, and a re-absorber. The optimization was conducted with respect to the compressor outlet pressure from the gas compression system (GCS) and the flow rate of absorbent and supplementary absorbent from the Absorption-stabilization System (ASS) using the process simulation software Aspen Plus. Compared to the base case of a 725 kt/a rich gas FCC unit, a refinery can save 2.42% of utility costs under optimal operation. Through optimized operation, medium-pressure steam consumption has been reduced by 2.4% compared to the base case, resulting in a significant improvement in total operational cost. The optimization strategy can provide insightful guidance for the practical operation of GCS and ASS.

Performance degradation analysis of a medium pressure superheater due to tube deactivation

Steam is essential in petrochemical industries for the transportation of thermal energy and usage in some reforming process. Superheaters are heat exchangers that convert saturated steam to dry steam by utilizing waste heat from the flue gas stream. Medium pressure steam superheaters are prone to tube deterioration due to service at elevated temperatures and erosion from the presence of liquid phase in the steam, leading to tube plugging after tube failure. This reduces the overall surface heating area of the superheater. Relations between the tube plugging practice and the energy dynamics of the superheaters are important for engineers to identify the responses of the superheater for operation planning, and this issue has not been extensively explored academically. This article analyses the deterioration of superheater performance due to reduction of surface heating area based on operational data of a petrochemical steam generation line. The objective is to find relations between the effect of tube plugging on the states of both steam and flue gas streams, as well as its impact on the overall energy exchange. The operating conditions of a superheater at two separate service years, before (year 2014) and after (year 2017) tube plugging, were compared through the first law energy analysis. The average steam inlet temperatures were between 248 °C and 250 °C, at flow rates between 70 and 90 ton/hour. The analysis indicated that 0.3 to 0.8 % increase in inlet energy is required for every plugged tube to compensate for the reduction of heating surface. At 3 % reduction of heating surface area, the heat exchanger effectiveness decreases by an average of 11 % that also leads to a lower steam temperature output by approximately 6% from the design operating temperature. These results would assist steam engineers to analyse changes to the energy economics of the whole plant and decide the feasibility of replacing existing superheaters with new ones. Also, another significant finding to be considered by steam engineers is that the current practice of increasing the steam flow rate does not offset the loss of energy effectiveness due to tube plugging.

Process simulation of cassava cellulosic ethanol production with low to medium-pressure steam heat integration

Energy demand tends to increase by 80% in 2050 due to the rapid growth of the global population. However, the energy resources rapidly decrease for responding to the global need. Many previous researchers suggest the ideas for solving this situation and the most interesting solution is the heat integration which intends to produce cost-effective energy with minimal impact on the environment. Energy integration thus should be noticeable for the industry process to minimize the loss along the industrial process. The ethanol production process is interested in this study because it can add value to agricultural products like cassava which is an industrial crop in several countries and produces ethanol products that can decrease the usage of gasoline. Here, the heat integration model was developed for the ethanol production process by using low to medium-pressure steam. For the simulation model, the ethanol production process used the cellulose content as the main inlet component to be easy for applicable corresponding to feed casava cellulosic substances. The process contained three sections including enzymatic hydrolysis, simultaneous saccharification fermentation (SSF), and fractional distillation. The quality and quantity of low to medium-pressure steam were investigated for maintaining the operation of the enzymatic hydrolysis reactor by varying steam pressure between 1–2 atm and steam temperature between 100–105 °C. The results achieved the methodology to find optimum conditions by the ratio between steam flow rate and product quantity. The best case could reduce 6.49% of the excessive usage of low to medium-pressure steam which pointed out the way to use the energy efficiently.

Optimised coker unit design integrating heat exchange network and exergy analysis

Two approaches are applied for reducing energy consumption in an actual delayed coking plant converting vacuum residue into lighter and higher value hydrocarbon products. Pinch analysis is applied with a view to optimising the pinch temperature approach and structure of the existing seven heat exchangers' network. This resulted in about 27% reduction of the total annual cost corresponding to an annual saving of about US$1.9 million. Exergy analysis is also conducted on other main process plant equipment which revealed a possible annual saving of US$0.75 million through generation of medium pressure steam in the blowdown tower.

Design and Optimization of Coal to Hydrogen System Coupled with Non-Nominal Operation of Thermal Power Unit

In an actual thermal power plant, deep peak shaving will cause thermal power units to run under non-nominal conditions for an extended period, resulting in serious problems such as increased equipment wearing, low equipment utilization efficiency and decreased benefits. To this end, in this work, both the design and optimization method for a coal to hydrogen system which is coupled with the expected non-nominal operation of thermal power units are proposed. Aiming towards maximum profit in the context of thermal power plants, a mathematical optimization model for a coal to hydrogen system based on the multi-period operating conditions of thermal power plants is established. The corresponding optimal design scheme of the coal to hydrogen system is determined using variable operating conditions. The superiority of the integrated system compared with an independent system is explored and the feasibility of the proposed method is verified by using the case study of an actual thermal power plant. The results show that compared with the independent system, the economic benefits of the integrated system can increase by 13.56%, where the sale of hydrogen in the coal to hydrogen system accounts for 60.3% of the total benefit. The main expenditure associated with the system is the purchase cost of feedstock coal, accounting for 91.8%. Since the required power and medium-pressure steam in the coal to hydrogen process are provided by thermal power units, the minimum operating load of the thermal power plant in the integrated system increases from 40% to 60.1%, which significantly improves the utilization efficiency and service life of the generator units. In addition, the proposed integration scheme of the system is simple and controllable, which can contribute to the maintenance of the safe and stable operation of power generation and hydrogen production processes. These results are expected to provide the necessary methodological guidance for the integration and optimization of coal-fired power plants and coal to hydrogen systems.

Optimization of Cogeneration Power-Desalination Plants

The design of new dual-purpose thermal desalination plants is a combinatory problem because the optimal process configuration strongly depends on the desired targets of electricity and freshwater. This paper proposes a mathematical model for selecting the optimal structure, the operating conditions, and sizes of all system components of dual-purpose thermal desalination plants. Electricity is supposed to be generated by a combined-cycle heat and power plant (CCHPP) with the following candidate structures: (a) one or two gas turbines; (b) one or two additional burners in the heat recovery steam generator; (c) the presence or missing a medium-pressure steam turbine; (d) steam generation and reheating at low pressure. Freshwater is supposed to be obtained from two candidate thermal processes: and (e) a multi-effect distillation (MED) or a multi-stage flash (MSF) system. The number of effects in MED and stages in MSF are also discrete decisions. Different case studies are presented to show the applicability of the model for same cost data. The proposed model is a powerful tool in optimizing new plants (or plants under modernization) and/or improving existing plants for desired electricity generation and freshwater production. No articles addressing the optimization involving the discrete decisions mentioned above are found in the literature.

Modeling and analysis for cleaner operation of a process to remove BTX from coke oven gas

Coke oven gas (COG) is a by-product of the coke production process which can be used as a fuel or in the production of chemicals such as methanol. In this research, a model of a BTX (Benzene, Toluene, Xylene) removal process for COG purification is developed, validated with commercial-scale plant data, and applied to improve performance and reduce energy consumption. The process includes a BTX scrubbing column and a distillation column for regeneration of the washing oil. Washing oil is represented as a mixture of BTX, naphthalene and pseudo-components.Three important phenomena with implications for energy conservation were identified using the model. First, the scrubbing efficiency is higher when the ASTM D20 distillation curve of the washing oil is lower. This phenomenon can be explained by the phase equilibrium and the difference in molar volume of the washing oil components. Second, it was found that if the setpoint of the distillation column top temperature exceeds 95 °C, the temperature in the upper portion of the column will increase significantly, which increases the amount of naphthalene in the light oil and decreases its quality. Third, the total energy consuption of the distillation column can be reduced without compromising the purification efficiency if feed temperature is decreased and the low-pressure steam flowrate is increased. Plant test result and model analysis showed that for an exisiting plant with a large vapor heat exchanger and small washing oil heat exchanger, the medium-pressure steam flowrate to the preheater can be reduced without modifying any equipment.

Creep Damage in Steam Pipelines and the Use of Metallography in Verifying the Possibilities of Testing

With high operating parameters of the medium in medium-pressure and high-pressure steam pipelines of fossil power plants, creep damage occurs, especially in welded joints leading to complete rupture of the pipe wall in the last phase. Detection of creep damage at an early stage before major cracks may occur can prevent these accidents. For these purposes, phased array ultrasonic testing was performed using a high frequency probe. This testing was performed on real welded joints cut from the power plant. To verify the possibility of detection, metallographic analysis on the tested locations was performed. When comparing the results, it is possible to refine the interpretation of the ultrasonic data and the metallographic results can also be used in the eventual qualification of non-destructive testing.

Life cycle assessment of liquefied natural gas production from coke oven gas in China

Producing liquefied natural gas (LNG) from coke oven gas (COG) is a promising option to partly alleviate the shortage of natural gas supply and effectively utilize the byproduct of coking production in China. In order to systematically evaluate the energy consumption and environmental impact of COG-based LNG process, the life cycle assessment (LCA) method was introduced in this study. Two synthesized approaches were considered and compared, namely decarbonization process and methanation process. Besides, whether with or without H2 extraction in methanation process is also discussed. Inventory data are obtained from onsite investigations of representative enterprises in China. The results indicate that, LNG production stage is the dominated unit in the overall environmental impacts of decarbonization process, next is LNG evaporation stage, while coking stage only contributes 2.38%. The reason is that COG is only responsible for less upstream environmental burdens as a byproduct. In LNG production stage, medium pressure steam, COG and electricity are the key substances. Comparative LCA shows that methanation process shows better environmental performance than decarbonization process in COG-based LNG production since more LNG product are produced. It is suggested that methanation process with H2 extraction is more desirable considering economic performance. This work intends to provide useful insights on the sustainability development of COG utilization in coking industry.

Development of an Integrated Structure for the Tri-Generation of Power, Liquid Carbon Dioxide, and Medium Pressure Steam Using a Molten Carbonate Fuel Cell, a Dual Pressure Linde-Hampson Liquefaction Plant, and a Heat Recovery Steam Generator

Due to the increase in energy consumption and energy prices, the reduction in fossil fuel resources, and increasing concerns about global warming and environmental issues, it is necessary to develop more efficient energy conversion systems with low environmental impacts. Utilizing fuel cells in the combined process is a method of refrigeration and electricity simultaneous production with a high efficiency and low pollution. In this study, a combined process for the tri-generation of electricity, medium pressure steam, and liquid carbon dioxide by utilizing a molten carbonate fuel cell, a dual pressure Linde-Hampson liquefaction plant and a heat recovery steam generator is developed. This combined process produces 65.53 MW of electricity, 27.8 kg/s of medium pressure steam, and 142.9 kg/s of liquid carbon dioxide. One of the methods of long-term energy storage involves the use of a carbon dioxide liquefaction system. Some of the generated electricity is used in industrial and residential areas and the rest is used for storage as liquid carbon dioxide. Liquid carbon dioxide can be used for peak shavings in buildings. The waste heat from the Linde-Hampson liquefaction plant is used to produce the fuel cell inlet steam. Moreover, the exhaust heat of the fuel cell and gas turbine would be used to produce the medium pressure steam. The total efficiency of this combined process and the coefficient of performance of the refrigeration plant are 82.21% and 1.866, respectively. The exergy analysis of this combined process reveals that the exergy efficiency and the total exergy destruction are 73.18% and 102.7 MW, respectively. The highest rate of exergy destruction in the hybrid process equipment belongs to the fuel cell (37.72%), the HX6 heat exchanger (8.036%), and the HX7 heat exchanger (6.578%). The results of the sensitivity analysis show that an increase in the exit pressure of the V1 valve by 13.33% would result in an increase in the refrigeration energy by 2.151% and a reduction in the refrigeration cycle performance by 9.654%. Moreover, by increasing the inlet fuel to the fuel cell, the thermal efficiency of the whole combined process rises by 18.09%, and the whole exergy efficiency declines by 12.95%.

Research on Selection of Heating Extraction Point for H Class Gas-Steam Combined Cycle Unit in Zengcheng， Guangzhou

Introduction To find out the best extraction heating scheme according to the medium pressure heating steam parameters of large capacity combined cycle unit. Method Combined with the heat load characteristics of Zengcheng project， this paper discussed and analyzed in detail the system configuration， initial investment， load adaptability， unit efficiency and power output of various extraction heating schemes applied to gas steam combined cycle units. Result The analysis results showed that， compared with hot section extraction and IP cylinder extraction， cold section extraction has higher unit power generation output， power generation efficiency and comprehensive energy utilization， and the initial investment was the lowest. Conclusion Cold section steam extraction is a kind of medium pressure steam extraction heating scheme with better parameter matching adaptability， stronger ability to adapt to variable operating conditions of units， better thermal economy and initial investment， and more suitable for large capacity combined cycle units. This scheme can be used for reference for similar engineering designs.

Comparative analysis of power distribution, exergy losses and exergy efficiencies of the 200 MW steam turbine for three operating modes with and without turbine steam extraction

The paper calculates the power, exergy losses and exergy efficiencies of the high, medium and low pressure steam turbine, as well as the total exergy losses and exergy efficiency of the 200 MW steam turbine. The calculation was performed for three modes of operation of the steam turbine with a load of 100%, 90% and 80%. For all three operating modes, the calculation of the analyzed parameters includes the operation of the steam turbine with and without turbine steam extraction. Based on the obtained results, a comparative analysis of steam turbine parameters was performed for all three operating modes and for operation with and without turbine steam extraction. Comparative analysis of the obtained results will show the influence of different operating modes of steam turbine with and without turbine steam removal on power, exergy losses and exergy efficiency of each module individually, but also on the total values of analyzed steam turbine parameters. The comparative analysis will also include the influence of mass steam flows from all turbine subtractions on the total steam turbine power losses for the three operating modes.

Waste Heat Utilization for the Energy Requirements of a Post Combustion CO <sub>2</sub> Capture Retrofit Study of a Cement Manufacturing Facility

This paper presents a preliminary investigation of utilizing waste heat available from a cement manufacturing facility for carbon dioxide (CO2) capture and compression processes. The cement manufacturing facility considered in this study emits 600,000 - 750,000 tonnes of CO2 annually while producing 800,000 – 1,000,000 tonnes of clinker. Determining an alternative energy source for amine regeneration will be a major deliverable and a challenging component of this study. Previously utilized methods from the power industry do not apply in this situation since cement plants do not normally produce steam. Cement manufacturing is an energy intensive process resulting in multiple high temperature exhaust gas streams. In this study, preliminary thermodynamic investigations of the utilization of thermal energy have been performed in two gas streams including kiln flue gas and clinker cooler air exhaust. The scenarios investigated in this study include (1) direct recovery of heat using heat recovery boilers and (2) employing of duct firing to increase the temperature of the flue gas prior to heat recovery. The recovered energy can be used for the amine regeneration process. The use of duct burning subsequently produced excess heat which exceeded the energy need for amine regeneration. However, this option can be utilized to produce medium pressure steam which can then be paired with the installation of a back pressure turbine to produce electricity. The results obtained in this study focused solely on the thermodynamic feasibility and efficiency. To justify whether the proposed strategies are practical or not, several factors including CAPEX and OPEX, requirements for modifications to the existing plant, impacts on the existing cement kiln process, and complexity and reliability of the proposed heat recovery system need to be further considered.

Energy and economic analysis of a hydrogen and ammonia co-generation system based on double chemical looping

In this work, a model of hydrogen production by double chemical looping is introduced. The efficiency benefit obtained was investigated. The chemical looping hydrogen generation unit is connected in series to the downstream of a chemical looping gasification unit as an additional system for 100 MW·h coal gasification, with the function of supplementary combustion to produce hydrogen. Using Aspen Plus software for process simulation, the production of H2 and N2 in the series system is higher than that in the independent Chemical looping gasification and Chemical looping hydrogen generation systems, and the production of hydrogen is approximately 25.63% and 12.90% higher, respectively; The study found that when the gasification temperature is 900 °C, steam-carbon ratio is 0.84 and oxygen-carbon ratio is 1.5, the hydrogen production rate of the system was the maximum. At the same time, through heat exchange between logistics, high-pressure steam at 8.010 × 104 kg·h−1 and medium-pressure steam at 1.101 × 104 kg·h−1 are generated, and utility consumption is reduced by 61.58%, with utility costs decreasing by 48.69%. An economic estimation study found that the production cost of ammonia is 108.66 USD·(t NH3)−1. Finally, cost of equipment is the main factors influencing ammonia production cost were proposed by sensitivity analysis.

Simulation and Economic Evaluation of Polygeneration System for Coproduction of Power, Steam, CH3OH, H2, and CO2 from Flare Gas

Today, one of the challenging issues all over the world is the appropriate use of flare gases in oil, gas, and petrochemical industries. Burning flare gases having high heating value results in economic losses and the pollution of the environment. There are several methods to use flare gases; the heat and power generation, the production of valuable fuels, or the separation of more precious components are examples of these methods. In this study, a polygeneration system is designed and simulated for the coproduction of power, steam, methanol, H2, and CO2 from the flare gases in South Pars and Assaluyeh gas fields. The polygeneration system has advantages such as reducing greenhouse gases and the coproduction and sales of energy-related products. The polygeneration system for converting flare gases to energy and various products includes an acid gas removal unit, a synthesis gas production unit, a methanol synthesis unit, a hydrogen purification unit, a combined heat and power generation unit, and a CO2 capture unit. The purpose of this study is to conduct an economic evaluation of the polygeneration system and obtain the total capital cost, the operating profit, and the payback period of this process. The simulation results show that using 9690 kg/h of flare gases produces 8133 kg/h methanol, 653.7 kg/h hydrogen, 46950 kg/h nitrogen, 9103 kg/h CO2, 109850 kg/h medium-pressure steam, and 3.7 MW power. The economic evaluation results show that in the polygeneration system, the total raw material cost and the total utilities consumption cost are $193.8 and $1859.5 per hour respectively, and the total product sales and the total utility sales are $12941.8 and $2243.5 per hour respectively; also, the operating profit is $13132 per hour. Also, the equipment cost, the installation cost, the total capital cost, and the total operating cost are $29.7 million per year, $39.2 million per year, $71 million per year, and $27.9 million per year respectively; finally, the payback period is 1.5 years.