Flue Gas Heat Recovery Research Articles

Using Air for Increasing the Depth of the Flue Gas Heat Recovery

The methods of flue gas heat recovery have been reviewed and carried out their effectiveness analysis. Revealed a theoretical limit of flue gas deep heat recovery and suggested possible ways to achieve them. The possibility of using air as a heated medium is discussed in more detail.

The role of outlet temperature of flue gas in organic Rankine cycle considering low temperature corrosion

This paper gives a special focus on the role of outlet temperature of flue gas (Tgo) in organic Rankine cycle (ORC) system for low tem- perature flue gas waste heat recovery. The variations of performance indicators: net work (Wnet), exergy efficiency (ηex) and levelized energy cost (LEC) versus Tgo are discussed. Considering the corrosion of low temperature flue gas, the necessity and reasonability of limiting Tgo at its minimum allowed discharge temperature (355.15 K) are analyzed. Results show that there exist optimal Tgo (Tgo,opt) for Wnet and LEC, while Tgo,opt for ηex does not appear under the investigated range of Tgo. Moreover, the Tgo,opt for Wnet is always lower than 355.15 K, the Tgo,opt for LEC, despite being greater than the one for Wnet, is just slightly higher than 355.15 K when the inlet temperature of flue gas varies from 408.15 K to 463.15 K. For the waste heat recovery of low temperature flue gas, it is reasonable to fix Tgo at 355.15 K if Wnet or LEC is selected as primary performance indicator under the pinch point temperature difference of evaporator (ΔTe) below 20 K.

Mechanism and Condensation Heat Transfer Characteristics Research on the Depth of the Flue Gas Heat Recovery from Burning Natural Gas

This article probe into the depth of the flue gas heat recovery from the burning of natural gas. It explore the mechanism of the way to control the temperature of the flue gas from the burning of natural gas below the dew point temperature. It expounds the absorption way of sensible heat and latent heat from the vaporization in flue gas. After the study on the condensation heat transfer characteristics of the flue gas from the burning of natural gas, we can find that the dropwise condensation is more conducive to the heat exchange between flue gas and cooling water. And to find the method of dropwise condensation.

Efficiency improvement strategies for the feedwater heaters network designing in supercritical coal-fired power plants

Coal will continue playing a major role in worldwide electricity generation during next years. This trend will augment CO2 emission to the atmosphere. Improving power plant efficiency could alleviate the negative effect of coal consumption on CO2 emissions. Main efforts have been focused on supercritical boiler technology (once-through units) and materials development (austenitic steels) with the aim of accomplishing high steam parameters that allow this efficiency enhancement. However, improvement in supercritical steam parameters should be followed by an exhaustive review of the steam cycle design. This paper shows a strategy for the optimization of the feedwater heaters network and the flue gas heat recovery system design. Starting with the lay-out of a supercritical steam cycle using the best available technology, this paper analyses not only the steam cycle itself, but also its integration with the boiler cold-end. By means of thermodynamic optimization it is possible to propose new feedwater heat exchanger network configurations and reducing steam consumption from turbine bleeds, achieving optimum power plant efficiency. Simulations have been carried out using Aspen Plus software and optimization procedure is based on a sequential quadratic programming method that maximized overall plant efficiency taking turbine bleeds pressure as independent variables. Results show a feasible improvement of the overall plant efficiency of 0.7 points in comparison with state-of-the-art reference plant. This increase implies a direct reduction of CO2 emissions of about 1.3% compared with the best plant currently available. Moreover, an economic analysis confirms the feasibility of the proposals analysed and shows important additional yearly incomes.

Engineering acid dew temperature: the limitation for flue gas heat recovery

In order to study how deep we can reduce the temperature of exhaust flue gas, an experiment focusing on the combined influence of ash deposition and acid condensation on the heat transfer characteristics of the heat exchanger was carried out in a 300-MW boiler unit. An annular tube was inserted into the flue gas duct between the air preheater and the electrostatic precipitator. The water with given temperature firstly entered the inner tube and then flowed into the outer tube at the end of the inner tube. It is found that heat transfer performance drops sharply at fixed temperature range under given coal quality. The turning temperature is defined as the engineering acid dew temperature (EADT). When the inlet water temperature is under the EADT, ash sticks to the tube and is difficult to blow off, and thus the flow resistance rises. Furthermore, the corrosion can be observed obviously. From the point of economy and reliability, EADT is the limitation for flue gas heat recovery. The EADT is at least 30 °C lower than ADT calculated by traditional empirical and theoretical equations.

Techno-economic study of a heat pump enhanced flue gas heat recovery for biomass boilers

An active condensation system for the heat recovery of biomass boilers is evaluated. The active condensation system utilizes the flue gas enthalpy exiting the boiler by combining a quench and a compression heat pump. The system is modelled by mass and energy balances. This study evaluates the operating costs, primary energy efficiency and greenhouse gas emissions on an Austrian data basis for four test cases. Two pellet boilers (10 kW and 100 kW) and two wood chip boilers (100 kW and 10 MW) are considered. The economic analysis shows a decrease in operating costs between 2% and 13%. Meanwhile the primary energy efficiency is increased by 3–21%. The greenhouse gas emissions in CO2 equivalents are calculated to 15.3–27.9 kg MWh−1 based on an Austrian electricity mix. The payback time is evaluated on a net present value (NPV) method, showing a payback time of 2–12 years for the 10 MW wood chip test case.

실증운전을 통한 배가스 열회수 히트펌프 시스템의 성능 분석

Abstract A field test of a 70 ㎾ heat pump system with flue gas heat recovery was performed by an experiment at theKorea Institute of Energy Research. The flue gas is exhausted from a 320 RT absorption chiller-heater in the heating season.Using this flue gas, source water of the heat pump is heated by a condensed-type heat exchanger in the chimney. Theoperating characteristics of the heat recovery heat pump system were analyzed. Based on the results of the experiments, operating maps were obtained, and an optimum operating range is suggested, in which the return and heat source watertemperature are 51 ℃ and 31 ℃ , respectively. Additionally, economic analysis of this system was conducted and about 50%energy cost savings can be expected in the heating season. Key words Condensing heat recovery(응축열회수), Flue gas(배가스), Heat recovery system(열회수 시스템), Latent heat(잠열), Condensation(응축)†Corresponding author, E-mail: yslee@kier.re.kr 기호설명COP H ： 난방성능계수 Q cond ： 응축(난방)열량 [ ㎾ ] Q evap ： 증발열량 [ ㎾ ]

Flue Gas Recirculation and Enhanced Performance of Waste Incinerators under Waste Uncertainty

Variations in waste quantities and composition affect incinerator operating conditions and performance. Fluegas volumes consititute a dominant environmental and financial consideration for efficient waste incinerator (WI) operation, since they affect the temperature, throughput, air pollution control system (APCS) residence time, and pollutant emissions, when the charging rate or composition of any waste is varying. Fluegas recirculation (FGR) in WI is an effective technique for reducing WI atmospheric pollution, mainly NOx emissions, albeit affecting WI throughput, temperature and destruction/removal efficiency. FGR refers to mass recirculation of a possibly cooled fraction of fluegases and differs substantially from fluegas heat recovery. The present work shows that, besides emission control, suitable manipulation of FGR enhances WI performance under waste uncertainty, enabling higher throughput, at the desired temperature and within the allowed APCS residence time range. A dimensionless parameter related to the uncertain wastes' net enthalpy contribution is isolated, which encompasses heat of reaction and enthalpy outflows from fluegas and solids and which reveals whether throughput is decreasing or increasing with temperature and FGR ratio. Normalized throughput and total fluegas volume isotherms manifest the interdependence and enable manipulation for enhanced environmental and economic performance.

Investigation of the potential of thermophotovoltaic heat recovery for the Turkish industrial sector

Thermophotovoltaics (TPV) are the use of the photovoltaic effect to generate electricity from a high-temperature thermal (infrared) source. This study deals with to provide an overview of heat recovery by TPV from industrial high-temperature processes in Turkish industrial sector. The paper reviews the relevant facts about TPV technology and the high-temperature industry and identifies three principle locations for TPV heat recovery. For each location, one example process is assessed in terms of applicability of TPV impact on the existing process and power scale. Knowledge of these factors should contribute to the design of an optimum TPV system. In the TIS, the total technical–potential energy recovery in the high-temperature industry using deployed and demonstrated heat recovery devices for product, flue gas, and wall heat recovery was estimated as 447.8PJ/year. However, an estimation from 22.40PJ/year to 67.45PJ/year can be achieved according to the TPV efficiencies. Also, the paper estimates the range of possible energy savings and the reduction in CO emission using TPV in the high-temperature industry. It is expected that this study will be very beneficial in developing energy policies of countries in terms of the usage of waste energy efficiency.

Techno-economic analysis and optimization of the heat recovery of utility boiler flue gas

Coal-fired power plants in China consume nearly half of available coals, and the resulting CO2 emissions cover over 40% of total national emissions. Therefore, reducing the energy expenditure of coal-fired power plants is of great significance to China’s energy security and greenhouse gas reduction programs. For coal-fired power plants, the temperature of a boiler’s exhaust gas reaches 120–150°C or even higher. The thermal energy of boiler’s exhaust accounts for approximately 3–8% of the total energy of fuel input. Given these factors, we conducted a techno-economic analysis and optimization design of the heat recovery system using boiler exhaust gas. This research is conformed to the principles of thermodynamic, heat transfer, and hydrodynamics. Based on the data from an existing 1000MW typical power generation unit in China, four typical flue gas heat recovery schemes are quantitatively analyzed from the thermodynamics perspective. The impacts of flue gas heat recovery on net work output and standard coal consumption rate of various schemes are performed. Furthermore, the transfer area of heat recovery exchanger and the draft fan work increment due to the flue gas pressure drop are analyzed. Finally, a techno-economic analysis of the heat recovery schemes is conducted, and some recommendations on optimization design parameters are proposed, with full consideration of various factors such as the decrease on fuel cost due to energy conservation as well as the investment cost of heat recovery retrofitting. The results revealed that, high-stage steam substitute scheme of flue gas heat recovery in power plant can obtain higher energy-saving effects than that of low-stage steam substitute scheme. And the energy-saving benefit of flue gas heat recovery, especially with high-stage steam substitute scheme, is weakened by large heat exchange areas and flue gas pressure drop caused by lower temperature differentials. Therefore, the techno-economic performance of the flue gas heat recovery in power plant may not always increase with the increment of the recovered heat but have an optimum point.

Effect of Flue Gas Heat Recovery on Plume Formation and Dispersion

Effect of Flue Gas Heat Recovery on Plume Formation and Dispersion

Flue gas purification and heat recovery: A biomass fired boiler supplied with an open absorption system

A new technique for energy recovery combined with particle separation from flue gas has been tested in this project. A conventional small boiler for biofuel produces besides heat also particles to the environment through the flue gas. Decreasing the impact on the environment is desirable. Increased efficiency can be obtained if the temperature and water content of the flue gas can be further reduced. Installing an open absorption system in the heat production unit fulfils both these demands. An experimental unit has been built and tested in the last 2years. The results show a reduction of particles in the flue gas by 33–44% compared to the ordinary system. At the same time the heat production from the unit increased by 40% when fired with wet biofuels.

Intermittency-friendly and high-efficiency cogeneration: Operational optimisation of cogeneration with compression heat pump, flue gas heat recovery, and intermediate cold storage

This paper develops, implements, and applies a mathematical model for economic unit dispatch for a novel cogeneration concept (CHP-HP-FG-CS (CHP with compression heat pump and cold storage using flue gas heat)) that increases the plant’s operational flexibility. The CHP-HP-FG-CS concept is a high-efficiency and widely applicable option in distributed cogeneration better supporting the co-existence between cogenerators and intermittent renewables in the energy system. The concept involves integrating an efficient high-temperature compression heat pump that uses only waste heat recovered from flue gases as low-temperature heat source, and an intermediate cold thermal storage allowing for non-concurrent operation of the cogeneration unit and the heat pump unit. The model is applied for a paradigmatic case study that shows how the integration of a heat pump affects the operational strategy of a cogeneration plant. It is found that CHP-HP-FG-CS offers significant reductions in fuel consumption (−8.9%) and operational production costs (−11.4%). The plant’s fuel-to-energy efficiency increases from 88.9 to 95.5%, which is state-of-the-art. The plant’s intermittency-friendliness coefficient Rc improves only marginally due to the constrained nature of the low-temperature heat source and the associated small capacity of the heat pump unit. Significant improvements in Rc are found when increasing the heat pump capacity assuming the availability of an unconstrained heat source.

Process design and performance of a microstructured convective steam–methane reformer

We describe the design and operation of a microstructured steam–methane reformer in which the heat transfer area and reaction volume demands for the reforming process are decoupled to yield a high degree of process intensification relative to conventional tubular reformer design. The plant design incorporates intensive process integration without steam export. With 80% hydrogen recovery from the syngas in a PSA, and use of the PSA offgas as the only fuel source, the reformer system has a fuel energy efficiency of 78.6% as designed, corresponding to a hydrogen production rate of 2.69 mol H 2 per mol NG. Based on printed-circuit heat exchanger techniques, the demonstration plant incorporates 17 stages of reforming at nominally 15 bar. Heating for the individual adiabatic stages is provided by combustion stages and by flue-gas heat recovery. The plant incorporates design features to minimise potential for carbon deposition and metal dusting. It displays intrinsic autoregulation over a wide range of turn-down, from 34% to 125%. Start-up is very rapid, approximately 2 h from cold to syngas production at full rate. With these features, this process and plant design is well suited for standalone operation, for example to substitute for merchant hydrogen delivery in small or isolated facilities. While the present plant has a capacity of 5 Nm 3 H 2 h −1, the multichannel printed circuit architecture is scalable without loss of precision to very large throughputs.

Waste Heat Recovery and Reuse of Flue Gas in Copper Pyrometallurgy

In the paper, we take current relatively advanced, the most widely used flash smelting furnace, converter and rotary anode furnace as the examples, the waste heat resources of the process of matte smelting, the process of matte converting and the process of fire refining of blister copper in copper pyrometallurgy are analyzed respectively. Meanwhile, based on the way of using waste heat reasonably to suitable heat consumer in production process and the grade recovery principle of energy level matching, the model of waste heat recovery and reuse of flue gas in copper pyrometallurgy is constructed.

Identifying and quantifying energy savings on fired plant using low cost modelling techniques

Combustion in fired heaters, boilers and furnaces often accounts for the major energy consumption on industrial processes. Small improvements in efficiency can result in large reductions in energy consumption, CO2 emissions, and operating costs. This paper will describe some useful low cost modelling techniques based on the zone method to help identify energy saving opportunities on high temperature fuel-fired process plant.The zone method has for many decades, been successfully applied to small batch furnaces through to large steel-reheating furnaces, glass tanks, boilers and fired heaters on petrochemical plant. Zone models can simulate both steady-state furnace operation and more complex transient operation typical of a production environment. These models can be used to predict thermal efficiency and performance, and more importantly, to assist in identifying and predicting energy saving opportunities from such measures as:•Improving air/fuel ratio and temperature controls.•Improved insulation.•Use of oxygen or oxygen enrichment.•Air preheating via flue gas heat recovery.•Modification to furnace geometry and hearth loading.There is also increasing interest in the application of refractory coatings for increasing surface radiation in fired plant. All of the techniques can yield savings ranging from a few percent upwards and can deliver rapid financial payback, but their evaluation often requires robust and reliable models in order to increase confidence in making financial investment decisions. This paper gives examples of how low cost modelling techniques can be applied to improve confidence in implementing energy efficiency improvements whilst safeguarding manufacturing output and quality.

Heat and Mass Transfer Processes in Scrubber of Flue Gas Heat Recovery Device

Heat and Mass Transfer Processes in Scrubber of Flue Gas Heat Recovery DeviceThe paper deals with the heat and mass transfer process research in a flue gas heat recovery device, where complicated cooling, evaporation and condensation processes are taking place simultaneously. The analogy between heat and mass transfer is used during the process of analysis. In order to prepare a detailed process analysis based on heat and mass process descriptive equations, as well as the correlation for wet gas parameter calculation, software in the Microsoft Office Excel environment is being developed.

Fouling Reduction Characteristics of a No-Distributor-Fluidized-Bed Heat Exchanger for Flue Gas Heat Recovery

Heat exchangers and heat exchanger networks are extensively used for the purpose of recovering energy. In conventional flue gas heat recovery systems, the fouling by fly ashes and the related problems such as corrosion and cleaning are known to be major drawbacks. To overcome these problems, a single-riser no-distributor-fluidized-bed heat exchanger is devised and studied. Fouling and cleaning tests are performed for a uniquely designed fluidized bed-type heat exchanger to demonstrate the effect of particles on the fouling reduction and heat transfer enhancement. The tested heat exchanger model (1 m high and 54 mm internal diameter) is a gas-to-water type and composed of a main vertical tube and four auxiliary tubes through which particles circulate and transfer heat. Through the present study, the fouling on the heat transfer surface could successfully be simulated by controlling air-to-fuel ratios rather than introducing particles through an external feeder, which produced soft deposit layers with 1 to 1.5 mm thickness on the inside pipe wall. Flue gas temperature at the inlet of heat exchanger was maintained at 450°C at the gas volume rate of 0.738 to 0.768 CMM (0.0123 to 0.0128 m3/sec). From the analyses of the measured data, heat transfer performances of the heat exchanger before and after fouling and with and without particles were evaluated. Results showed that soft deposits were easily removed by introducing glass bead particles, and also heat transfer performance increased two times by the particle circulation. In addition, it was found that this type of heat exchanger had high potential to recover heat of waste gases from furnaces, boilers, and incinerators effectively and to reduce fouling related problems.

Multicriteria decision making in process integration

The goal of this work was to study the potential of multicriteria decision making performance in plant design with the aid of process integration. Generally, the industrial process plant design problems are multiobjective, because there is a need to fulfill different criteria at the same time. In this paper, the hierarchical decision making methodology is presented, where environmental and safety regulations, and growing demand of the product quality were also taken into account. A case study of calcination kiln, followed by flue gas cleaning and heat recovery systems, is given as an example.

Simulation of fixed bed regenerative heat exchangers for flue gas heat recovery

Fixed-bed regenerators are used to provide high temperature process gases in the glass and steel industries, in power plants and in waste heat recovery systems. In all these situations the temperature levels require the regenerator packing to be made from the low thermal conductivity materials such as ceramic. Simulation of the operation of fixed bed heat exchangers must accommodate the heat transfer from the gas to the packing surface and the temperature distribution within the core of the ceramic spheres. Most of the mathematical models employed in theory and practice assume either that the internal thermal resistance to heat flow within the core is negligible, or that the resistance can be incorporated in a lumped convective heat transfer coefficient at the surface. This investigation considers both approaches in the analysis of the experimental data obtained for a regenerator packed with alumina balls. Unifying theory and practice in this way allows the influence of flow rate and periodicity of operation to be investigated free from the effect of misleading interactions. The difference between the effectiveness results is firstly due to the experimental errors in the parameter measurements and secondly due to the heat losses from the main bed which has not been taken into account in the mathematical model.