Fluidized Bed Combustion Research Articles

Assessing the impact of wet and dry flue gas recycling on heat transfer in oxygen-fired circulating fluidized bed furnaces

Oxygen-driven circulating fluidized bed combustion (oxy-CFB) has been suggested as a potential technique for facilitating carbon capture in large-scale power generation. Precise modeling of radiative heat transfer is vital for forecasting the thermal performance of such processes. This research examines the impact of wet and dry flue gas recycling on the thermal behavior of a large-scale oxy-CFB furnace, utilizing a combined modeling strategy that merges a three-dimensional furnace process model with a thermal radiation solver. The semi-empirical furnace model operates in steady-state conditions, accounting for fluid dynamics, reactions, and heat transfer phenomena. The radiation solver, based on the zone method, employs novel correlations for radiative heat exchange between optically thick zones. The radiation solver employs a weighted sum of the gray gases model, developed specifically for oxy-combustion, and geometric optics to determine the radiative characteristics of combustion gases and particles, respectively.This research covers various process conditions and boiler loads to evaluate the influence of wet versus dry flue gas recycling on heat transfer and temperature profiles. Model results were successfully compared against small-scale oxygen-fired CFB tests and large-scale measurements in a supercritical air-fired CFB. Utilizing an external radiation solver allows for a more precise representation of radiative heat transfer and the influence of varying process conditions. The insights from this research can aid in the design of large-scale oxy-CFB facilities, and the demonstrated modeling approach can be employed for additional model development, such as integrating the external radiation solver with other modeling tools.

Numerical investigation of mixing and heat transfer of mixed biomass and silica sand particles in a bubbling fluidized bed combustor

Using fluidized bed combustion technology, biomass is being promoted for electricity production. However, a lack of biomass in a particular location or season poses a problem, leading to low thermal efficiency when using a single biomass. Thus, mixed biomass is considered a potential solution. This study uses CFD-DEM simulation to investigate the effects of various biomass types, loadings, and blending ratios on hydrodynamics and heat transfer in a bubbling fluidized bed. Coarse bagasse size provides the most efficient mixing behavior for a single biomass mixture. A blending ratio of 1:3 wood chip to coarse bagasse with 5% biomass loading, using 1 mm silica sand, is the appropriate condition. The primary factor for mixing is the difference in biomass sizes, while different biomass loadings have no significant influence. Smaller sand particles enhance the mixing and heat transfer. These findings provide useful guidelines for efficient biomass conditions in fluidized bed combustors.

Design and development of waste heat re-utilisation technology by using artificial intelligence at thermal power plant

ABSTRACT The primary goal of this research paper is to inculcate AI approaches in thermal power plants to raise automation at power plants by expanding the integrated control idea to thermal power plants and implementing it using AI approaches. The recommended control method will be analysed and contrasted with established strategies. The crucial condition will be evaluated even though the suggested type of control system doesn’t come up with an effective result. The development of the conceptual model is predicated on the state of power generation technologies. There will be no suggestion to use newer or different technology, such as fluidised bed combustion, sliding pressure units or ultra-supercritical plants, in the process of producing electricity. This study specifically focuses on the operational features of the control system instead of the hardware technologies.

Non-traditional aluminosilicate based alkali-activated mortars - statistical optimization of solution parameters and processing conditions for optimal compressive strength, workability and setting time

The recent shortage of traditional fly ash and slag, commonly used precursors in alkali-activated binders, prompted a rigorous search for alternative materials. This study evaluated four groups of currently underused supplementary cementitious materials (SCMs) as precursors for producing alkali-activated mortars. The materials evaluated include three calcined clays, three ground bottom ashes, three volcanic ashes, and two fluidized bed combustion ashes, collectively named non-traditional and natural pozzolans (NNPs). Firstly, the compositions of the NNPs were optimized using trial-and-error methods to minimize the concentration of the activating solution. Then, the two solution parameters i.e., silica modulus and Na2O% were optimized for compressive strength using a central composite design. The compressive strength (ASTM C109), the workability (ASTM C1437), and the setting time (ASTM C191) of the mortar were determined. The results show that all 11 materials could produce mortar mixtures with compressive strength in the 20–40 MPa range at 28 days, satisfactory workability of at least 50 % (flow value), and at least 30 min of initial setting time without heat curing and without blending with conventional SCMs. Most of the materials were activated with lower solution parameters than those used in the literature. The binder optimization suggested Si/Al range 1.0–3.0 and a minimum Ca/Al of 0.25 as favorable molar ratios for potentially reactive aluminosilicate precursors. Multiple linear regression models validated by higher R2 and minimum RMSE and MAE could accurately predict the compressive strength of NNP mortar. Furthermore, calcium hydroxide and shrinkage-reducing admixtures were identified as set regulators in alkali-activated NNP mortars.

Energy efficiency analysis and optimization of a pressurized oxy-fuel circulating fluidized bed combustion system

The commercial application of oxy-fuel combustion technology is limited by energy deduction which is caused by addition of air separation unit (ASU) and carbon dioxide compression and purification unit (CPU). Pressurized circulating fluidized bed (CFB) oxy-fuel combustion technology is one option to improve the net electric generation efficiency. In this research, a series of simulations and optimizations were carried out to analyze the energy efficiency of a pressurized oxy-fuel combustion system. The boiler structure and heat exchange surface arrangement under different pressure were calculated. The cross-sectional area of the furnace and tail flue were both reduced up to 10 % of the original size and the floor space of the boiler was considered to be the lowest at 1.1 MPa. The energy efficiency and exergy analysis were used to explore the influence of pressure on the net efficiency and the optimization potential of system. The net electric generation efficiency reached a maximum value of 24.16 % at 1.1 MPa, which is 5.4 % higher than that at atmospheric pressure. Finally, four parameters, i.e. preheat temperature, oxygen concentration, ASU outlet oxygen purity and CPU compressor outlet pressure, were optimized to improve the system net efficiency to 26.67 %, 29.04 %, 25.87 % and 24.36 %, respectively.

NOx and SO2 emission of oxygen carrier aided combustion in fluidized bed

Oxygen carrier aided combustion (OCAC) has been established as an innovative concept for improving fuel combustion in fluidized bed (FB) combustors. OCAC uses the particles of oxygen carrier (OC) to partly or completely replace the inert bed materials within the FB, which can make the oxygen distribution in the combustor more uniform and subsequently enhance combustion efficiency. However, the fundamental study on SO2 and NOx emissions during the OCAC is still not sufficient and controversial. In this work, the OCAC of coal and petroleum coke has been evaluated under different operating conditions on a lab-scale FB combustor with a special focus on the SO2 and NOx emissions. The conversion ratios of volatile-N (XV-N) and char-N (XC-N) have been quantitatively decoupled, and the influence of operating parameters on XC-N and XV-N has been revealed. Results showed that the OCAC concept has significantly reduced CO emission, enhanced NOx emission, and increased nitrogen conversion (XN). However, the NOx emission decreased by reducing the ilmenite ore proportion in the bed materials. This was attributed to the presence of ilmenite ore, which reduced the reducing regions and weakened the NOx reduction. Under OCAC operation, the XV-N increased significantly with the increase of O2 concentration and primary air ratio (A); and the variation of A shows a most decisive effect on XV-N. However, the XC-N was insensitive to the change of O2 concentration and A, when the XC-N was in the range of 31.01–34.89 % for all OCAC operations. The significant reduction of the SO2 emission during OCAC is mainly due to the employment of the ilmenite ore as bed materials that not only can absorb S element, but also lead to more uniform distribution of both oxygen and bed temperature, thereby improving the self-desulfurization of ash and reducing the sulfate decomposition.

Combustion of polyethylene and polypropylene in the fluidized bed with a variable vertical density profile

A new type of fluidized bed with a variable vertical density profile was developed. A mixture of sand (Ønominal = 100–140 μm, 2.6 g/cm3) and cenospheres (Ønominal = 140–160 μm, 0.85 g/cm3) was used to form a binary fluidized bed. The minimum fluidization velocity of the binary fluidized bed was determined experimentally. Two points of inflection on the fluidization curve were observed. Additionally, a measurement of the pressure as a function of height was used to determine the profile of fluidized bed density. It was proven that the fluidized bed made out of cenospheres and sand can be characterized by a variable vertical density profile. The binary fluidized bed was used for the combustion of polyolefins. The results were compared to combustion in a conventional fluidized bed made out of sand. The surface of the fluidized bed was video recorded and the changes in the image brightness were used to identify diffusion combustion in the freeboard. A Fourier Transform Infrared (FTIR) analyzer with high spectral resolution (1 cm−1) was used to record the IR spectra of flue gases. In-house software was used to deconvolve complex IR spectra. In the process performed in the fluidized bed made out of sand, regardless of temperature, around 30 % of the polymeric carbon left the reactor in the form of soot. The lack of dependence on the temperature results from the fact that in such an organized process combustion did not take place inside the fluidized bed but on its surface. The binary fluidized bed eliminated the problem of the presence of diffusion flames and soot formation. High fuel conversion to CO2 (above 90 %) was observed at temperatures above over 800 °C during polyolefin combustion in the binary fluidized bed.

Erratum to: Managing of agglomerate formation in a utility scale pressurized fluidized bed combustor. Chem. Process Eng., 2010, 31, 767–788

Erratum to: Managing of agglomerate formation in a utility scale pressurized fluidized bed combustor. Chem. Process Eng., 2010, 31, 767–788

Alternative sorbents for mercury capture in flue gas from lignite combustion

This paper presents an experimental study of two of alternative sorbents for mercury capture from the lignite combustion flue gas. The sorbents are based on calcium hydroxide and aluminosilicate, using different modifications. A commercially available activated carbon (AC) with bromine impregnation was selected as the reference sorbent. This sorbent is a state-of-the-art solution for mercury removal in industrial combustion facilities. However, its application is costly for power plants because of the market price of the AC and because the presence of carbon in the fly ash can complicate its further use, which gives a strong motivation for exploring new alternatives. Experimental investigation was carried out in a 500 kW pilot-scale bubbling fluidized bed combustor using a lignite with naturally high mercury content. A injection system of our own design and construction was used to supply the sorbents to the flue gas downstream of the combustor at a flow rate in the range of 100–500 mg/m3N of the flue gas. Continuous measurement of mercury concentration was used upstream the sorbent injection and downstream the fabric filter, simultaneously. Different sorbent injection rates and flue gas temperatures at the sorbent injection point were examined.The mercury capture ratio was evaluated considering the Hg balance in the combustor. It was shown that the mercury self-capture by the fly ash in the fluidized bed combustion system varies approximately from 30 to 90 %, depending on the SO2 concentration. The Hg capture ratio for calcium hydroxide was in a range of approximately 15–25 %, while for aluminosilicate it was 25–45 %, determined by the actual conditions of the flue gas and the initial Hg concentration. This is in the range of the reference AC, which typically reaches from 25 – 95%. The increased injection rate of the sorbents was reflected in the Hg capture ratio, but its promotion was observed only in the case of the aluminosilicate sorbent. A correlation of the Hg capture ratio with the flue gas temperature at the injection point was also clearly identified only for the aluminosilicate sorbent, when an increase in the temperature led to increasing in the capture ratio.

Effect of back pressure on gas-solid distribution characteristics of cyclone distributor applied in powdered coal-fired circulating fluidized bed combustion system

The cyclone distributor is an essential part of the powdered-coal-fired circulating fluidized bed (PC-CFB) combustion system, and its gas-solid distribution characteristics are significantly affected by the back pressure of the lower outlet. A four-way coupling method using a dense discrete phase model (DDPM) was adopted to simulate the cyclone distributor. The results indicate that the effect of the back pressure on the axial gas velocity is more pronounced compared to that on the tangential gas velocity. With the increase in the back pressure, the particle separation efficiency decreases monotonically, while the rate of change gradually increases. Meanwhile, the gas separation efficiency increases as the back pressure becomes higher. Furthermore, increasing back pressure improves the particle concentration at the outlets of the cyclone distributor. To maintain high particle separation efficiency and ensure the safe operation of the boiler, it is recommended to set the back pressure between 1000 Pa and 2000 Pa.

Bubbling fluidized bed co-combustion and co-gasification of sewage sludge with agricultural residues with a focus on the fate of phosphorus

In this work, the fate of the ash-forming elements during bubbling fluidized bed combustion and gasification of P-rich sewage sludge (SS) and mixtures with either Si-K-rich wheat straw (WS) or K-Ca-rich sunflower husks (SH) were investigated. The focus of the study was assessing the feasibility of using fuel blends in fluidized bed systems and potential P recovery from the resulting ashes. The used fuels were pure SS and mixtures including 90 wt.% WS (WSS) and 85 wt.% SH (SHS). The analyzed operating conditions were combustion (930–960 °C, λ: 1.2–1.5) and gasification (780–810 °C, λ: 0.4–0.7) in a 5 kW bench-scale reactor. Residual ash and char fractions were collected from different parts of the 5 kW bubbling fluidized bed (bed, cyclone, filter) and analyzed by CHN, SEM/EDS, XRD, and ICP-AES.The conversion of the fuel mixtures achieved a steady state under the used process conditions except for the combustion of WSS, which led to the formation of large bed agglomerates with the bed material. The morphology of ash samples after combustion showed that SS fuel pellets mostly maintained their integrity during the experiment. In contrast, the ash and char particles from fuel mixtures were fragmented, and larger quantities were found in the cyclone, the filter, or on interior reactor surfaces. The fate of P was dominated by crystalline Ca-dominated whitlockites in all ash fractions, partially including K for the fuel mixtures SHS and WSS. 76–81 % of ingoing P was found in the bed residue after combustion and gasification of the SS-fuel. After conversion of the fuel mixtures SHS and WSS, the share was lower at 22–48 %, with larger shares of P in the entrained fractions (25–34 %). The quantity of identified crystalline compounds was lower after gasification than combustion, likely due to the limited interaction of ash-forming elements in the residual CHN matrix. Altogether, the results show that fuel mixtures of sewage sludge with agricultural residues could expand the fuel feedstock and enable P recovery. This may be used in the fuel and process design of upscaled fluidized bed processes or systems employing both combustion and gasification.

Improvement of coal and Petroleum coke combustion in a fluidized bed by using ilmenite ore as bed material

Oxygen carrier-aided combustion (OCAC) is an innovative technology that adopts the reactive oxygen carrier (OC) particles as bed materials instead of inert ones, which improves the uniformity of temporal and spatial oxygen distribution in the fluidized bed combustor. However, the existing research of OCAC mainly focuses on high-volatile fuels, less attention has been paid to high-ash and low-volatile fuels (such as coal), which are widely used in the world. In this work, three kinds of solid fuels have been comprehensively evaluated in a lab-scale fluidized bed reactor. Results show that compared to quartz sands as bed material, the OC as bed material shows an apparent “oxygen buffering capacity”, improving combustion stability and reducing the unburnt gas. The promotion effect of OCAC increases with the increase of volatile content in fuel, which indicates that OCAC mainly improves combustion through the redox reaction between volatile and OC particles. The solid-solid reaction between OC and char was negligible. The OCAC experiment was carried out for more than 20 h and found that due to the abrasion of the OC surface, the generated fly ash has a significantly higher Fe content than that using quartz sand as bed material at the initial stage of the experiment, and the abrasion of OC decreases with the increase of experimental time. Interestingly, during a 20-h continuous operation, the reactivity of ilmenite ore increased gradually, which was attributed to the development of pore structure and Fe diffusion of ilmenite ore. In addition, the content of unburnt carbon in the fly ash is similar regardless of the bed materials.

Role of surface morphology in bed particle layer formation on quartz bed particles in fluidized bed combustion of woody biomass

The influence of quartz bed particle surface morphology on the bed particle layer and crack layer formation process in fluidized bed combustion of woody biomass was investigated in this work. Bed material samples were collected at different sampling times from the startup with a fresh bed in industrial scale bubbling fluidized bed (BFB) and circulating fluidized bed (CFB) boilers, both utilizing woody biomass. X-ray microtomography (XMT) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) were employed to characterize bed particle layers and crack layers in the samples. Results showed that there is a noticeable difference between the bed layer characteristics over the so-called “concave” and “convex”-shaped morphologies on the bed particle surface with respect to layer formation. The concave areas are mainly covered with a thin inner layer, whilst the convex display a comparably thick inner layer and an outer layer. In addition, 3D images of the particles revealed that the crack layers mainly originate from concave areas where the particle is less protected by an outer bed particle layer in conjunction with cracks in the inner layer.

Development of emission reduction measures of trace gas emissions from coal-fired power plants in Indonesia

Most of Indonesia’s electricity demand is supplied by coal fired power plants (CFPPs) which can potentially emit huge amounts of air pollutant gases such as NOx and SO2 gas. The country has committed to reduce Greenhouse Gases (GHGs) emission by 2030 through Nationally Determined Contributions but some emission reduction measures may also reduce air pollutant gases. Flue Gas Desulfurization (FGD) and Atmospheric Fluidized Bed Combustion (AFBC) are the leading control technologies for reducing SO2 and NOx emissions that can be installed in the CFPPs. This study aims to determine the pollution load of SO2 and NOx gases in 2030 generated from CFPPs operation with (reduction scenario) and without FGD and AFCB control technology (business as usual (BAU)). The gas pollution load was calculated using the Atmospheric Brown Clouds- Emissions Inventory Manual (ABC-EIM) procedure. Based on the BAU scenario, the emission load accounted of 1,440,192 tons/year for NOx and 613,121 tons/year for SO2 in 2030. After implementing the control technology scenarios in 2030, the NOx emission load is projected to decrease to 579,610 tons/year, and the SO2 emission load decrease to 77,920 tons/year. The application of AFBC and FGD control technologies can potentially reduce NOx and SO2 emissions load from CFPPs operation in 2030 thus it can help to improve air quality in the future.

Effects of ammonia co-firing ratios and injection positions in the coal–ammonia co-firing process in a circulating fluidized bed combustion test rig

Ammonia (NH3) co-firing is a promising technology for reducing greenhouse gas emissions in coal-fired power plants. Prior to commercialization, an experimental study on coal–NH3 co-firing in a pilot-scale circulating fluidized bed (CFB) combustion test rig was conducted for technical verification. The comprehensive combustion characteristics, including pollutant emission, combustion efficiency, and ash properties, of NH3 co-firing with sub-bituminous coal in a CFB combustion test rig and the CO2 reduction according to NH3 co-firing ratios under two different injection positions (dense bed zone (DBZ) and wind box (WB) with primary air) were investigated. When NH3 was injected at the DBZ, NO emissions decreased as the NH3 co-firing ratio increased and CO emissions increased more rapidly than with only coal-fired combustion. Compared with only coal-fired combustion, a 25.4% NH3 co-firing ratio at the WB position simultaneously reduced NO and CO concentrations, achieving the highest combustion efficiency without ash-related problems. However, N2O emissions increased by > 1.5 times, indicating the formation of N intermediates during NH3 burning. Therefore, with minor retrofitting, coal–NH3 co-firing at the WB position is a feasible solution for simultaneously reducing CO2, NO, and CO emissions in commercial CFB combustion plants.

Development and combustion characteristics of microwave plasma-assisted fluidized bed combustor

A novel waste treatment method that can efficiently decompose waste, suppress by-product generation, and operate at a low cost is urgently required. Herein, a microwave plasma-assisted combustor was developed and its combustion characteristics were investigated for application in solid waste treatment. The experimental conditions for obtaining good states of fluidization, mixing, and plasma formation were examined prior to the combustion experiments. Subsequently, the optimal experimental conditions, such as the filling amount of bed particles, bed particle diameter, microwave irradiation position, and microwave output, required for good combustion were achieved. Combustion experiments based on these conditions revealed that a good fluidization state is required to obtain a good combustion state in this device, although the combustion condition does not necessarily depend on the system pressure at each O2 flow rate. Comparison of the conditions with similar fluidization states at O2 flow rates of 1–4 L/min revealed a maximum fuel conversion ratio at 4 L/min owing to the combustion promotion caused by increased O2 partial pressure. The fuel did not remain in the fluidized bed combustor after the combustion experiments.

The Characteristics of Self-Hydration and Carbonation Reaction of Coal Ash from Circulating Fluidized-Bed Boiler by Absorption of CO2.

The by-products of the circulating fluidized-bed boiler combustion (CFBC) of coal exhibit self-hardening properties due to the calcium silicates generated by the reaction between SiO2 and CaO, and the ettringite generated by the reaction of gypsum and quicklime with activated alumina. These reactions exhibit tendencies similar to that of the hydration of ordinary Portland cement (OPC). In this study, the self-hydration and carbonation reaction mechanisms of CFBC by-products were analyzed. These CFBC by-products comprise a number of compounds, including Fe2O3, free CaO, and CaSO4, in large quantities. The hydration product calcium aluminate (and/or ferrite) of calcium aluminate ferrite and sulfate was confirmed through instrumental analysis. The CFBC by-products attain hardening properties because of the carbonation reaction between calcium aluminate ferrite and CO2. This can be identified as a self-hardening process because it does not require a supply of special ions from the outside. Through this study, it was confirmed that CFBC by-products generate CaCO3 through carbonation, thereby densifying the pores of the hardened body and contributing to the development of compressive strength.

Evaluation of Multi-Utility Models with Municipal Solid Waste Combustion as the Primary Source under Specific Geographical and Operating Conditions

Developments in waste incineration technology in terms of efficient fuel preparation, combustion, and emissions reduction, as well as the growing needs of the community in terms of electricity, water, and air conditioning loads, are the prime motive for this study. This study presents a novel approach, in which three models of the fluidized bed combustion of municipal waste for simultaneous power generation, freshwater production, and district cooling are analyzed for their energy and exergy performance. The three simultaneously evaluated utility models are different configurations of a fluidized bed combustion system with Rankine cycle power generation, cooling with a vapor absorption refrigeration system, and fresh water production using multiple effect desalination. The output from the turbine, cooling system, and desalination system is determined using the Engineering Equations Solver for different boiler operating pressures. Energy and exergy analysis data for different pressures are used to identify the best configuration. Two variants of the absorption cooling system, namely, single effect and double effect, are considered. The variants of the multiple-effect desalination are the three-stage and five-stage methods. Input parameters used in this study are municipal solid waste generation and composition data collected for an urban community in an arid climate zone with high demand for electric power, cooling, and fresh water. Model 2, which contains two turbines with the reheating and cooling systems connected to a high-pressure turbine and water desalination connected to a low-pressure turbine, gave the best overall performance. Significant savings in terms of the replacement of conventional energy were observed from these waste conversion plants with greater benefits in arid weather conditions. The results obtained by different models under different operating criteria constitute a guideline for municipal planners for the selection of appropriate waste utilization technology, as well as the appropriate operations.

Utilizing Sewage Sludge Slag, a By-Product of the Circulating Fluidized Bed Combustion Process, to Efficiently Remove Copper from Aquatic Environment

Currently, one of the greatest threats to the aquatic environment is industrial wastewater containing heavy metals and other toxic substances. Hence, it seems necessary to search for ecological and cheap technologies for removing metals from wastewater. In this research, slag was used as waste obtained in the circulating fluidized bed combustion technology (CFBC), which is considered to be a modern, clean, and very effective method of incineration of municipal sewage sludge. The physicochemical properties of the waste material were characterized using selected analytical techniques. Next, the processes of adsorption of Cu(II) ions on slag in aqueous solutions were investigated. The results showed a high metal removal efficiency of 98.8% at pH 1.8 and slag dosage 5 g/L. Numerous studies have demonstrated that high process efficiency at a level of at least 90% is attainable. Based on the Langmuir equation, the maximum adsorption capacity was calculated to be 70.3 mg/g. Kinetic analysis revealed that the process fits better into the pseudo-second-order reaction model and the Freundlich isotherm. The intraparticle diffusion model was considered as a rate-controlling step for Cu(II) adsorption. In summary, the slag waste produced in the CFBC technology seems to be a highly effective adsorbent for potential use in adsorption processes to remove heavy metals from the aquatic environment. This solution is in line with the current European ‘zero waste’ strategy and the assumptions of a sustainable development economy.

Exergy and Energy Analysis of the Shell-and-Tube Heat Exchanger for a Poultry Litter Co-Combustion Process

Increasing production of poultry litter, and its associated problems, stimulates the need for generating useful energy in an environmentally friendly and efficient energy system, such as the use of shell-and-tube heat exchangers (STHE) in a fluidized-bed combustion (FBC) system. A holistic approach which involves the integration of the First Law of Thermodynamics (FLT) and Second Law of Thermodynamics (SLT) is required for conducting effective assessment of an energy system. In this study, the STHE designed by the CAESECT research group, which was integrated into the lab-scale FBC, was investigated to determine the maximum available work performed by the system and account for the exergy loss due to irreversibility. The effects of varying operating parameters and configuration of the space heaters connected to the STHE for space heating purposes were investigated in order to improve the thermal efficiency of the poultry litter-to-energy conversion process. Exergy and energy analysis performed on the STHE using flue gas and water media showed higher efficiency (75–92%) obtained via energy analysis, but much lower efficiency (12–25%) was obtained when the ambient conditions were factored into the exergy analysis, thus indicating huge exergy loss to the surroundings. From the obtained experimental data coupled with the simulation on parallel arrangement of air heaters, it was observed that exergy loss increased with increasing flue gas flow rate from 46.8–57.6 kg/h and with increasing ambient temperature from 8.8 °C to 25 °C. To lower the cost of STHE during final design, a larger temperature difference between the hot and cold flue gas is needed throughout the exchanger, which further increases the exergetic loss while maintaining an energy balance. In addition, this study also found the optimal conditions to reduce exergy loss and improve energy efficiency of the designed STHE. This study shows the possibility to evaluate energy systems using integration of exergy and energy analysis.