Waste Heat Boiler Research Articles

Exergoeconomic analysis of a steam turbine power plant in a sulfuric acid factory

This study presents an exergoeconomic analysis of a steam turbine power plant (STPP) implemented within a sulfuric acid production facility. The plant harnesses waste heat from an exothermic chemical reaction to generate electricity. A detailed mathematical model was developed in Engineering Equation Solver (EES) to perform the exergoeconomic assessment on individual components and the overall system.The STPP generates 4.7 MW of electricity, with an exergoeconomic factor of 33 %. The exergy cost and unit exergy cost of the electricity are 455.8 $/h and 26.94 $/GW, respectively. The turbine represents the highest capital cost within the system. The steam produced incurs an exergy cost of 640.7 $/h, with a unit exergy cost of 2.2 $/GW. The waste heat boiler exhibits the highest exergy destruction cost at 112 $/h, and the major exergy destruction cost ratios are observed for the waste heat boiler (0.23 W/$) and the turbine (0.51 W/$). Additionally, the impact of variations in steam inlet temperature and pressure on the exergoeconomic performance was analyzed.These findings provide valuable, cost-based indicators such as exergy destruction cost, exergoeconomic factor, and exergy destruction cost ratio, which can guide the optimization and practical implementation of STPPs in the sulfuric acid industry.

Разработка методики расчета составляющих резерва тепловой экономичности парогазовых установок

The components of the thermal efficiency reserve of thermal power plant equipment are the overexpenditure or savings of fuel due to the deviation of the actual values of the equipment performance from their nominal values. They are determined in tons of reference fuel for a certain period. The components of the thermal efficiency reserve are the most essential element of the technical record-keeping and reporting systems of power plants. They allow us to quantitatively assess the technical condition of the equipment and, on this basis, effectively plan repair programs. The methods to calculate the components of the thermal efficiency reserve of steam power plants are well developed and regulated according to the regulatory documents. Regulatory requirements for combined-cycle plants in this area contain inaccuracies and do not cover a full list of the components of the thermal efficiency reserve. Thus, it is necessary to develop a method that allows us to calculate the components of the thermal efficiency reserve of combined-cycle plants. When developing the methodology for combined-cycle plants, the authors have applied the approaches to calculate the components of the thermal efficiency reserve that are used for steam power plants. In addition, available methods for assessing the thermal efficiency of thermal power plant equipment have been used. The developed methods have been tested based on actual data on the operation of combined-cycle plant PGU-116. A methodology to calculate the components of the thermal efficiency reserve of combined-cycle plants with waste-heat boilers without fuel afterburning has been developed. The methodology has been tested in assessing the thermal efficiency indicators of combined-cycle plant in operation. Shortcomings in regulatory documents of the energy industry in terms of calculating the components of the thermal efficiency reserve of combined-cycle equipment have been identified. The developed methodology can be recommended for use in the systems of technical record-keeping and reporting of power plants when monitoring the indicators of thermal efficiency of combined-cycle plants. To ensure the objectivity of the results of the analysis of the efficiency of operated combined-cycle power units in Russia, it is necessary to adjust industry regulatory documents. They should contain uniform scientifically substantiated methods for calculating the components of the reserve of thermal efficiency of combined-cycle equipment.

TREATMENT OF COPPER FLUE DUST FROM FLASH FURNACE WASTE HEAT BOILER FOR IMPURITIES CONTROL

During the pyrometallurgical processing of copper sulphide raw materials, part of the charge leaves the furnace space together with the exhaust gases in the form of dust entrainment. Volatile components also pass into the dust-gas flow, due to which it is enriched with impurities, some of which are harmful to the technological process. The formed dust-gas flow passes through dust collection equipment, where the main part of it is captured. Most often, the captured dust is recirculated, which leads to a decrease in the productivity of the furnace unit and a gradual increase in the content of impurities in the condensed products of the smelting. To overcome these disadvantages, it is necessary to take part or all the recirculating dust out of the melting cycle and process it independently to extract the valuable metals and dispose of the harmful substances. In metallurgical practice, industrial application for the processing of recirculating dust entrainment has mainly been accomplished by hydrometallurgical methods based on treating the flue dust in aqueous solutions of acid or alkaline reagents. In the present research work, laboratory results on hydrometallurgical leaching of flue dust from a flash furnace waste heat boiler (FF-WHB) are presented. The effect of the main technological parameters affecting the degrees of recovery of the main metals in solution was studied. Based on the experimental results, the optimal conditionsfor hydrometallurgical treatment of the FF-WHB flue dust were determined. By treating the dust under optimal conditions, the main tasks of the research are achieved - removal of impurities harmful to the technological process and reduction of the amount of flue dust processed in the flash furnace.

Increasing the Economic Efficiency of Marine Power Plants Using Waste Heat Boilers with Controlled Flow Separation

Abstract Heat recovery of exhaust gases from main and auxiliary marine diesel engines is an effective way to improve the technical and economic parameters of marine power plants. Improvements in engine efficiency necessitate an increase in the weight-size parameters of the waste heat boilers, which makes it difficult to recover heat. Intensification of the heat transfer process is considered to be an effective way to reduce these indicators. By utilising mathematical modelling, this paper shows the effectiveness of using profiled heating surfaces of waste heat boilers for this purpose. The use of elliptical heating surfaces with a mechanism of controlled flow separation, in the form of a triangular notch, is proposed. This will reduce surface drag and increase the overall thermal-hydraulic efficiency of the heat transfer processes. It is shown that the use of such surfaces in waste heat boilers makes it possible to increase the efficiency of marine power plants in tankers with a deadweight of about 45,500 tons up to 1.5% absolute and container ships with a deadweight of about 122,000 tons up to 2.5% absolute.

Flue gas-dust two-phase heat transfer characteristics and corrosion behavior in industrial-scale waste heat boilers

Waste heat boiler (WHB) has been extensively utilized across various industries due to the high efficiency in heat recovery and robust adaptability. This study employs the multiphase particle-in-cell approach to investigate the heat transfer behavior between flue gas and dust, as well as the in-furnace corrosion behavior in an industrial-scale WHB. Upon validation of the model, the flow dynamics of flue gas, the distribution characteristics of dust particles, corrosion behavior together with the effect of structure are examined. The findings reveal that excessive vortex formation significantly disrupts the flow uniformity of flue gas, with 0.87 % of the particles backflowing into the rising flue, and 51.6 % of the particles settling in the WHB. The heat transfer coefficient of dust particles reaches its peak at velocities ranging from 2 to 4 m/s, with a maximum value of 204 W/(m2K). Increasing the baffle spacing diminishes the vortex intensity in the radiation chamber and improves the flow uniformity of flue gas. Expanding the radiation chamber size not only enhances the heat exchange efficiency of flue gas, resulting in a temperature decrease of 24 K at the chamber exit, but also increases the particle sedimentation rate by 3.1 %.

Corrosion of Waste Heat Boiler Tubes in Methanol Plant

A thorough failure investigation was conducted into a failure of waste heat boiler tubes in a methanol plant to determine the failure mechanism, and contributing factors. The investigation was performed utilizing different characterization techniques, including optical light microscopy, scanning electron microscopy, mechanical testing and chemical analysis techniques. The investigation findings showed that the tubes failure is attributed to corrosion under deposit. Details of the failure’s contributing factors, and recommendations to avoid similar failures, are discussed in this article.

Numerical Investigation of Shell-Side Flow Behavior and Vapor Distribution in Waste Heat Boilers.

Shell-and-tube waste heat boilers (STWHBs) are essential in the recovery of waste heat from high-temperature industrial processes. Kettle-type STWHBs are known to experience failures due to hold-up of steam, a significant concern in the industry. Multiphase computational fluid dynamics (CFD) simulations are used to study the effect of tube layout on the steam hold-up of an industrial-scale STWHB. Different design specifications are simulated including tube layout, heat flux, and pitch to predict steam hold-up performance and analyze thermo-hydrodynamic phenomena within the tube bundle. Simulation results show that, for similar tube bundle shape and size, 45° rotated square tube bundle layouts perform better, with respect to steam hold-up, than the square and triangle layouts for a range of heat flux duties. It is found that steam hold-up increases linearly with increasing heat flux and decreasing tube pitch, for the conditions simulated. The turbulent kinetic energy of the bubbly flow is greatly influenced by increasing phase fraction. Visualizations of the flow of water and steam within and around the tube bundle show that there is a vertical flow deviation for both staggered tube patterns (rotated square and triangle). These results motivate further multiphase CFD-based study of the thermo-hydrodynamics of STWHBs for improved understanding, retrofit, and new designs.

Analysis of the causes of waste heat boiler leakage in large-scale chemical plants

A waste heat boiler is a kind of high-temperature and high-pressure heat exchanger in a large chemical plant, and its safe operation is directly related to the production efficiency and safety risk of a chemical plant. In this paper, the leakage failure analysis of a waste heat boiler in an ethylene plant is carried out, and the analysis methods such as field observation, macro observation of fracture, metallographic analysis, micro observation of fracture, phase analysis, and energy spectrum analysis are adopted respectively. The results show that the direct cause of the leakage of the waste heat boiler is the thinning of the wall thickness of the heat exchange tube caused by alkali corrosion, which leads to the overload and fracture of the heat exchange tube. The pits on the outer surface of some heat exchange tubes are caused by mechanical reasons, which are related to this leakage and closure. The corrosion failure of heat exchange tubes is widespread, which has a great influence on safety production and serious consequences. Through this comprehensive analysis, the failure mechanism is clarified, which can provide a reference for the maintenance of similar equipment. At the same time, preventive measures are put forward from the aspects of technology, structure, and detection to reduce the occurrence of similar accidents.

A Novel Designation of Solid Oxide Fuel Cell-Integrated System Using LPG as Fuel for Marine Vessels

A Novel Designation of Solid Oxide Fuel Cell-Integrated System Using LPG as Fuel for Marine Vessels

An improved methodology for thermal calculation and design optimization of a thermosiphon waste heat boiler for CCPP

The study is dedicated to enhancing design and computational methodologies for thermosiphon waste heat boilers (WHB) within combined cycle power plants (CCPP). The optimized WHB design and an improved thermal calculation approach are shown. The efficiency of the proposed WHB has been improved by optimizing the area and arrangement of the surface. The novel method incorporates considerations for the internal thermal resistance within thermosyphons and the graded velocity of natural circulation within the evaporation circuit. To refine the calculation method, empirical and experimental data concerning internal temperature gradient in thermosiphon functioning within a heat load spectrum of up to 17 kW/m2, were used. Important findings include three categories. Firstly, increasing the number of sections will slightly increase capital costs and decrease WHB gas temperature, which could be neglected by the unification of thermosiphon sections. Secondly, by applying this modified methodology to a power plant facility featuring a 6700 kW gas turbine engine (GTE), notable adjustments in thermal power were realized, amounting to 157 kW (approximately 6 %), along with corresponding electrical power adjustments of 149 kW (approximately 2 %). Third, the new method is limited to a GTE power of up to 10 MW due to the experimental data used for validation.

A novel designation of LNG solid oxide fuel cells combined system for marine application

This paper presents a pioneering multigeneration system for marine vessel applications, involving the integration of solid oxide fuel cells (SOFCs) fueled by liquefied natural gas (LNG), coupled with LNG cold energy utilization cycles and exhaust gas heat recovery systems. The system comprises a tandem arrangement of organic Rankine cycle (ORC) and trans-critical carbon dioxide cycle (TCO2), specifically engineered to harness the cold energy released during LNG regasification process. The elevated temperature exhaust gases emanating from the SOFC are efficiently recuperated through a series of components including a gas turbine (GT), regenerative, steam Rankine cycle (SRC), and waste heat boiler (WHB). The proton exchange membrane fuel cells (PEMFC) is designed to enhance the overall operational flexibility and responsiveness of the multigeneration system. The Aspen Hysys V12.1 is used to simulate the propose system and numerical method is employed to parameter optimize of system. The first and second laws of thermodynamics are applied to establish the thermodynamics equations and calculated the system performances. The described system is estimated to obtain energy efficiency of 69.32 % and exergy efficiency of 33.85 %. The high-temperature exhaust gas harvesting integrated systems are sufficiently generated 2091.24 kW which accounted 35.49 % of entire power generate. Furthermore, the parametric researches are implemented to examine the influence of current density, β values to the performance indicators of systems. The WHB is designed to generate 1081 kg/h of superheated vapor at 170 °C and 405 kPa for various purposes of seafarers and equipment's onboard ship. The economic feasibility is performed to view the possibility of investment, maintenance cost and payback period for the described system.

Study on the Application of a Multi-Energy Complementary Distributed Energy System Integrating Waste Heat and Surplus Electricity for Hydrogen Production

To improve the recovery of waste heat and avoid the problem of abandoning wind and solar energy, a multi-energy complementary distributed energy system (MECDES) is proposed, integrating waste heat and surplus electricity for hydrogen storage. The system comprises a combined cooling, heating, and power (CCHP) system with a gas engine (GE), solar and wind power generation, and miniaturized natural gas hydrogen production equipment (MNGHPE). In this novel system, the GE’s waste heat is recycled as water vapor for hydrogen production in the waste heat boiler, while surplus electricity from renewable sources powers the MNGHPE. A mathematical model was developed to simulate hydrogen production in three building types: offices, hotels, and hospitals. Simulation results demonstrate the system’s ability to store waste heat and surplus electricity as hydrogen, thereby providing economic benefit, energy savings, and carbon reduction. Compared with traditional energy supply methods, the integrated system achieves maximum energy savings and carbon emission reduction in office buildings, with an annual primary energy reduction rate of 49.42–85.10% and an annual carbon emission reduction rate of 34.88–47.00%. The hydrogen production’s profit rate is approximately 70%. If the produced hydrogen is supplied to building through a hydrogen fuel cell, the primary energy reduction rate is further decreased by 2.86–3.04%, and the carbon emission reduction rate is further decreased by 12.67–14.26%. This research solves the problem of waste heat and surplus energy in MECDESs by the method of hydrogen storage and system integration. The economic benefits, energy savings, and carbon reduction effects of different building types and different energy allocation scenarios were compared, as well as the profitability of hydrogen production and the factors affecting it. This has a positive technical guidance role for the practical application of MECDESs.

Kinetic modeling of a Claus reaction furnace and waste heat boiler: Effects of H2S/CO2 and H2S/H2O ratio on the production of hazardous gases in an industrial sulfur recovery unit

In this study, the reaction furnace (RF) and waste heat boiler (WHB) were modeled using a kinetic model developed from key reactions to determine how the input feed in the various acid gas scenarios affects the Sulfur Recovery Unit's (SRU's) thermal stage for industrial application. The modeling results showed that, while keeping other parameters constant, a decrease in the H2S/CO2 and H2S/H2O ratios leads to an increase in the production of hazardous gases such as CO, SO2, and COS in the Waste Heat Boiler (WHB). Consequently, this leads to a decrease in the efficiency of the Sulfur Recovery Unit (SRU). When the temperature profile is altered, the Claus reaction pathway changes unfavorably, consequently affecting the overall efficiency of the Claus process. The accuracy of the kinetic model decreases as the acid gas becomes more dilute, significantly impacting the temperature profile. The accuracy of these results was confirmed through industrial data spanning from typical acid gas to sweet gas, with a Mean Absolute Percentage Error (MAPE) ranging from 26.18 to 47.37.

Using Reduced Kinetic Model for the Multi-Objective Optimization of Thermal Section of the Claus Process Leading to a More Cost-Effective and Environmentally Friendly Operation

The Claus process is a sulfur recovery unit wherein hydrogen sulfide is converted into the elemental sulfur. This study aims to model the thermal section of the Claus process, which consists of a reaction furnace and a waste heat boiler, as a configuration of two reactors, and subsequently optimize the entire section. Two different reduced kinetic schemes were provided for both units. Using the validated kinetics, mathematical models were developed. The waste heat boiler was modeled as a plug flow reactor with heat transfer, instead of a heat exchanger. The main objective was to maximize the amount of elemental sulfur at the end of the thermal section. Additionally, maximizing the amount of steam generated in the WHB was considered as a secondary objective, and the multi-objective optimization problem was solved. The sulfur production was improved 14.1% and 30% as a result of single- and multi-objective optimization studies. In addition, as an alternative, the Taguchi method was also used for optimization studies, and optimum values were determined. Using the Taguchi method, we determined that an increase in sulfur production by 24% is possible.

New green and low-carbon technology for all-sensible heat recovery of converter gas

The smelting process of converter determines the explosive, dusty and intermittent nature of gas itself. Therefore, either the way of water (oxygen converter gas recovery system) or mist spraying (Lurgi-Thyssen system) is usually adopted to treat the converter gas after passing through the vaporization cooling flue for further reducing temperature and removing dust. This will lead to a waste of gas sensible heat resources of approximately 800–1000 °C. In this paper, an all-sensible heat recovery technology for converter gas, that is completely different from the oxygen converter gas recovery and Lurgi-Thyssen system, is proposed and implemented in an actual converter with a capacity of 100 tons. For the implementation, the new process is paralleled with the original Lurgi-Thyssen system, and successfully recovers the waste heat of converter gas through a gas-solid separator and waste heat boiler instead of an evaporative cooler. The main advantages of the all-sensible heat recovery process are reflected in the increased steam yield, the reduced energy consumption and the improved calorific value of converter gas. Obviously, this process can be used to further improve the negative energy consumption level of converter, and is expected to become the development trend of converter gas treatment in the future.

Сухе гасіння коксу: утилізація надлишкового циркулюючого газу

The article is devoted to a practical solution to the problem of improving the environmental safety of a coke dry quenching unit by means of a new technology developed to reduce CO and coke dust emissions by introducing of the utilisation of excess circulating gas using a special utilisation unit, the main element of which is a special utilisation boiler. It is shown that the need to discharge harmful substances into the atmosphere during the operation of the coke dry quenching unit is associated with the fact that during the operation of the unit, repeated circulation of gases through hot coke leads to a change in the gas composition in the direction of increasing the amount of carbon monoxide (CO). This makes the plant explosive and the gas highly toxic. To reduce the explosion hazard of the plant, it is necessary to reduce the concentration of combustible components in the circulating gas. This is done by diluting the mixture with nitrogen. This article discusses the method developed by GIPROKOKS to utilise excess circulating gases by burning CO to CO2 using a special utilisation unit. The equipment of the utilisation unit can be located directly in the boiler house of the coke dry quenching unit or in a separate building near the coke dry quenching unit. The operation of the utilisation unit is controlled by a modern process control system. The concentration and gross carbon monoxide emissions are reduced in a special reactor. In the process of refining the implemented technology, it became necessary to make changes and improve some solutions. In particular, the operation of the gas path of the unit was changed, which increased the potential for receiving excess circulating gas, stabilised the combustion mode and became a key solution to ensure the aerodynamic operation of the coke dry quenching unit. A mixing device was also installed at the circulating gas inlet to the waste heat boiler, which, by controlling the flow rate and composition of the circulating gas, allowed to stabilise the reactor operation and somewhat improve the conditions for the utilisation (combustion) of combustible components when circulating gas of ‘ballasted’ composition is supplied. It is shown that the implementation of this technology by SE “GIPROKOKS” can significantly reduce the concentration of harmful substances and provides additional steam generation, which can be used for the technological needs of the enterprise or for generating electricity. Keywords: coke, dry quenching, afterburning, waste heat boiler, circulating gas, surplus, utilisation, CO content, carbon monoxide, coke quality. Corresponding author: A.A. Kogtin, e-mail: kogtin.giprokoks@gmail.com

A novel process for ultra-low emission of flue gas by adding waste heat steam

This work offers a new process for removing fine particles from converters by adding steam from a waste heat boiler. The fine particles were enlarged using the pre-technique of water vapor condensation which was initially validated its available in a lab-scale experimental system. Following the steam was introduced into the secondary scrubber system to reform converter dust removal system, the mass concentration of the dust at the stack outflow decreased from approximately 30 ∼ 40 mg/m3 to 6 mg/m3. The morphology and elemental content of the fine particles released from the chimney vents, with and without steam injection, were analyzed by SEM and EDS, respectively, to further investigate the particle size range and chemical composition of the fine particles eradicated by steam injection. It was discovered that the growth and removal of the 200–300 nm iron–rich fine particles can be facilitated by vapor condensation. This work provides a new idea for achieving ultra-low emission transformation of the converter wet dust removal process.

Exergy analysis of a steam power station in a sulfuric acid plant

This study presents energy and exergy analyses of a Steam Power station of a sulfuric acid plant. A heat recovery system is implemented in the plant to recover waste heat from an exothermic chemical reaction of the sulfuric acid production process. This research aims to analyze system components to determine where energy losses are. A mathematical model was developed using the EES software to perform the calculations. Exergy analysis is computed for real ranges of the main operating parameters. It was found that the key sources of exergy destruction are the waste heat boiler 41 %, followed by the heaters 24.7 % then the steam turbine 18.6 %, and the condenser 13.8 % of the total exergy destruction. The 2nd law efficiency obtained for the waste heat boiler, the steam turbine, and the condenser is 80 %, 82 %, and 37.4 % respectively, while the overall plant exergy efficiency is 68.7 %. The effect of varying different parameters such as reference environmental temperature on main plant components is investigated. The effect of increasing steam inlet temperature, pressure, and mass flow rate on plant exergetic efficiency and exergy destruction is also presented. Results showed that lowering condenser vacuum pressure leads to a 7 % improvement in overall system exergetic efficiency.

Performance analysis and multi-objective optimization of organic Rankine cycle for low-grade sinter waste heat recovery

In order to enhance the sinter waste heat recovery (WHR) rate efficiently, the organic Rankine cycle (ORC) for power production was applied to take the low-grade sinter cooling flue gas (SCFG) expelled from the waste heat boiler as the heat source. The system thermodynamic, thermo-economic and multi-objective optimization models were constructed firstly, and then R245fa was chosen as the ORC working fluid. Furthermore, the variations of system thermodynamic and thermo-economic performances with the ORC thermal parameters under different inlet temperatures of SCFG were analyzed in detail, and the ideal parameter combination was established through the multi-objective optimization approach. The results show that, the optimal inlet temperature of SCFG is determined to be 160 °C, and under the aforementioned condition of inlet temperature of SCFG, the optimal ORC thermal parameters are determined to be 95 °C for the working fluid evaporation temperature, 10 °C for the working fluid superheat degree, 28 °C for the working fluid condensation temperature and 9 °C for the pinch-point temperature difference in evaporator by considering the system thermodynamic and thermo-economic performances comprehensively. Meanwhile, the WHR rate of SCFG under the above ORC parameter combination could reach 64.86 %, showing remarkable energy-saving effect.

A state-of-the-art review of heat recovery steam generators and waste heat boilers

A state-of-the-art review of heat recovery steam generators and waste heat boilers