Preheater Research Articles

Effects of Pyrolysis Bio-Oils on Fuel Atomisation—A Review

Bio-oils produced by biomass pyrolysis are substantially different from those produced by petroleum-based fuels and biodiesel. However, they could serve as valuable alternatives to fossil fuels to achieve carbon neutral future. The literature review indicates that the current use of bio-oils in gas turbines and compression-ignition (diesel) engines is limited due to problems associated with atomisation and combustion. The review also identifies the progress made in pyrolysis bio-oil spray combustion via standardisation of fuel properties, optimising atomisation and combustion, and understanding long-term reliability of engines. The key strategies that need to be adapted to efficiently atomise and combust bio-oils include, efficient atomisation techniques such as twin fluid atomisation, pressure atomisation and more advanced and novel effervescent atomisation, fuel and air preheating, flame stabilization using swrilers, and filtering the solid content from the pyrolysis oils. Once these strategies are implemented, bio-oils can enhance combustion efficiency and reduce greenhouse gas (GHG) emission. Overall, this study clearly indicates that pyrolysis bio-oils have the ability to substitute fossil fuels, but fuel injection problems need to be tackled in order to insure proper atomisation and combustion of the fuel.

PREDICTION SULPHURIC ACID AND WATER VAPOUR DEW POINT TEMPERATURES OF FLUE GASES AND COMBUSTION ANALYSIS FOR SOLID FUELS IN TURKEY

In the study, the combustion analysis is examined for the solid fuels in Turkey. The principal aim of the analysis is determined the limits and obstacles in the design heat exchanger to avoid the corrosion risk on the heat exchanger surfaces in the latent heat recovery applications from waste flue gas. To do this, in which regions of the heat exchanger the flue gas temperature reached to the sulphuric acid and water vapour dew point temperatures are required to predict. In order to predict the condensing zone, an air preheater for the coal-fired boiler in a heating system is designed using finite difference method. Designed the air preheater is consists of the counter-cross flow, Ushaped stainless steel tube bundle. The tube is discredited 200 cells to one-dimensional during the flow. The heat transfer rates, the flue gas and air inlet and outlet temperatures, surface temperatures of the tube wall, the mole fractions of water and sulphuric acid vapour, the other non-condensing gases in the flue gas are calculated in each discrete cell. According to the results of the study, while the dew point temperature of the water vapour changes over the range 30-40 °C, the acid dew point temperature waves to 125 °C from 140 °C for the coal types mined in Turkey.

Integration of biomass gasification with a supercritical CO2 and Kalina cycles in a combined heating and power system: A thermodynamic and exergoeconomic analysis

A novel cogeneration system based on a combination of a gas turbine cycle, a supercritical CO2 cycle, and a Kalina cycle is devised for heating and power generation. Energy, exergy, and exergoeconomic analysis are performed to assess the system’s performance and feasibility. According to the findings, the energy and exergy efficiencies of the system are obtained by 78.15% and 40.97%, respectively. In addition, heating capacity enhanced with the increment of air preheater’s terminal temperature difference (ΔTAP), air compressor’s pressure ratio (r1p), and pressure ratio of S–CO2 compressor (r2p). The system’s sum unit cost of the product (SUCP) decreased with the increment of ΔTAP and with the decrement of ammonia concentration. Besides, the minimum value of SUCP is obtained at the air compressor pressure ratio of r1p=13.24 and r2p=2.63. The maximum value of exergy efficiency is evaluated at ΔTAP=262K, r1p=14.5, and r2p=4.21. Moreover, the maximum net output power is obtained where the design parameters are set as ΔTAP=262K, r1p=14.5, and r2p=3.5. Furthermore, the economic analysis revealed that the payback period and net present value are evaluated to be 6.9 years and 5.374×10+6 $, respectively, for the electricity price of 0.07 $/kWh and fuel cost of 2 $/GJ.

Novel rotary regenerative heat exchanger using cascaded phase change material capsules

A novel rotary regenerative heat exchanger with cascaded phase change material (PCM) capsules was proposed and proved to be a better alternative to the traditional one. The rotary regenerative air preheater used in coal-fired power plant was taken as an example to comparatively analyze the performance characteristics of the rotary regenerative heat exchanger with latent heat storage material and the one with sensible heat storage material. The latent rotary regenerative air preheater (LRAPH) can achieve more uniform outlet temperature of air at low rotating speed than the sensible one (SRAPH), which is conductive to the measurement and process control in application. PCM capsule functions as both a latent heat storage material at its phase change temperature and as a sensible heat storage material at other temperature values. At lower rotating speed, more PCM capsules in LRAPH will work at the phase change temperature resulting in small temperature swings of fluid and matrix. The heat exchanger effectiveness is comparatively analyzed for SRAPH and LRAPH with different matrix parameters. The replacement of sensible heat storage materials by the latent ones would lead to an efficiency improvement of RAPH as large as 11% especially at lower rotating speed. The LRAPH is more capable to counter the entrainment leakage and the problems induced by temperature swings than traditional SRAPH. The cascaded distribution of PCM capsules with different phase change temperatures should be reasonably set according to the specific characteristics of temperature distribution in application to make full use of advantages of cascaded PCMs.

Experimental Performance of an Advanced Air-Type Photovoltaic/Thermal (PVT) Collector with Direct Expansion Air Handling Unit (AHU)

In addition to electrical energy generation, photovoltaic/thermal (PVT) systems utilize heat from building-integrated photovoltaic (BIPV) modules for domestic hot water and space heating. In other words, a PVT system can improve the electricity efficiency of BIPVs while using the waste heat of BIPVs as a source of thermal energy for the building. By generating thermal and electrical energies simultaneously, PVT systems can improve the utilization of solar energy while enhancing the energy performance of buildings. To optimize the performance of an air-type PVT collector, it is necessary for the system to extract more heat from the PV module. Consequently, this approach decreases PV temperature to improve PV electrical energy generation. The thermal and electrical performance of an air-type PVT collector depends on its design, which affects airflow and heat transfer. Moreover, the performances of the PVT collector can differ according to the coupled facility in the building. In this study, the thermal and electrical performances of an advanced air-type PVT collector with a direct expansion air handling unit (AHU) were analyzed experimentally. For this purpose, six prototypes of an advanced air-type PVT collector were developed. Furthermore, a direct expansion AHU with a heat recovery exchanger (HRX) was designed and built. The advanced PVT collectors with a total capacity of 740 Wp were installed in an experimental house and were coupled to the direct expansion AHU system with a maximum airflow of 700 CMH. The performance of PVT collectors was analyzed and compared with the BIPV system. Results showed that building-integrated photovoltaic/thermal (BIPVT) collectors produced 30 W more power than the BIPV system. When operating the AHU system, the temperature of the BIPVT collector was generally lower than the BIPV. The maximum difference in temperature between BIPVT and BIPV was about 22 °C. During winter season, the BIPVT collector supplied preheated air to the AHU. The supplied air temperature from the BIPVT collector reached 32 °C, which was 15 °C higher than outdoor air temperature.

Cost-effective fault diagnosis of a multi-component dynamic system under corrective maintenance

Maintenance planning and execution are challenging tasks for every system with complex structure. Interdependent nature of the components that builds up the system may have significant effect on system integrity. While preventive maintenance actions can be carried out in a more planned fashion, corrective actions are more time sensitive as they directly affect the availability of the system. This study proposes a cost-effective dynamic Bayesian network modeling scheme to be used in the planning of corrective maintenance actions on systems having hidden components which have stochastic and structural dependencies. In such context, the regenerative air heater system which is a key element of a power plant is taken into consideration. The proposed maintenance framework offers several methods, each aiming to balance the cost with the probability effect using a normalization procedure. The methodologies are extensively simulated for sensitivity analysis under various downtime cost values. Fault effect methods with worst state probability efficiency measures give the least total cost for all downtime cost values and their distinction becomes significant as this value increases. Further statistical analysis concludes that considerable gains on maintenance costs can be achieved by the proposed approach.

Design and Performance Analysis of New Ultra-Supercritical Double Reheat Coal-Fired Power Generation Systems

In order to solve the existing problems of large mean heat transfer temperature differences of regenerative air heaters and high superheat degrees of regenerative extraction steam in double reheat coal-fired power generation systems, two new design schemes of ultra-supercritical double reheat cycles are proposed, which can realize the deep boiler-turbine coupling among the heat transfer processes of air, feeding water and regeneration extraction steam on the base of the principle of energy level matching. A typical 1000 MW ultra-supercritical double reheat cycle system is selected as the reference system and the overall system model is built by using the Ebsilon simulation software. The performances of two new systems are analyzed by using both the exergy method and energy equilibrium method. The results show that net output powers of both new systems 1 and 2 increase by 6.38 MW and 6.93 MW, respectively, and the standard coal consumptions of power generation decrease by 1.65 g/kWh and 1.79 g/kWh, respectively. The off-design performances of new systems and the reference system are analyzed, and the results show that performances of two new systems are better than that of the reference system. The system flow of the new system 2 is more complex compared with that of the new system 1. Generally speaking, the performance of new system 1 is better than that of new system 2. On the basis of new system 1, new system 3 is further optimized and its full operating condition performance characteristics are analyzed. The standard coal consumption rate of new system 3 is reduced about 1 g/kWh at higher load, and around 0.2 g/kWh at low load.

Analysis of Leakage and Corrosion of Air Preheater in Coal-Fired Power Plant

A unit of a coal-fired power plant (300MW) in North China was selected to study. The flue gas parameters (NH3, O2 and flue gas temperature) at the outlet of denitration system, oxygen content at the inlet and outlet of air preheater, and composition of combustion coal were tested. Then, the air leakage and corrosion of air preheater were evaluated from the operation of denitration system, air preheater leakage detection, and acid dew point calculation of flue gas. The influence of ammonium hydrogen sulfate from denitration system on the downstream air preheater is limited due to the low ammonia escaping. The air leakage rates of the air preheater at the side A and B were 8.45% and 3.01%, which are higher than the normal value (< 3%). Due to the air leakage of air preheater on side B, the cold end temperature of air preheater is significantly lower than the acid dew point of flue gas, resulting in the condensation of sulfuric acid mist in flue gas on the air preheater and the sulfuric acid corrosion on the air preheater.

Research on Ash Clogging of Rotary Air Preheater in Coal-fired Power Plant

The air preheater of coal-fired units has the problem of ash blocking. Combining the working principle and ash blocking mechanism, FLUENT uses the porous media model to simulate the air preheater, and the corresponding mass flow rate at different speeds or air side inlets is obtained. The temperature results are compared and analyzed, and a reasonable air preheater is used to reduce ash clogging.

Modelling of dew point operating conditions in a rotary regenerative air heater

Dew point related fouling of regenerative rotary air heaters contributes to efficiency reduction of coal-fired boilers. This fouling commonly causes high pressure differences over the air heater steel matrix, along with elevated leakage rates, resulting in increased loading of draught group fans. These increases also conduce to excessive erosion rates, introducing premature failure of element packs and draught group components. The research problem aimed to develop, and validate, a modelling tool to predict the onset of dew point related fouling for regenerative rotary air heaters (VBA RAH model). A modelling tool equip system engineers with the knowledge to enhance operating conditions and maintenance strategies, to prevent the onset of dew point related fouling. The results yielded that the cold end of the air heater packs experience sulphuric acid dew point related fouling for at 670MW(90% MCR), at 544MW(80% MCR) and at 468MW(68% MCR) of the exposure time to the flue gas stream. Different operating and design change configurations were simulated to find potential solutions to minimize dew point related fouling and improving boiler efficiency. The tool provides a platform for identifying methods to reduce maintenance costs and production losses, which will contribute to improved and sustainable operating of coal fired power generation plants.

Stable Operation of Rotary Stoker Furnace for Industrial Waste

Incineration is one of the most common methods for the treatment of industrial waste. Large amounts of bottom ash are buried without being reused. By reducing components such as toxic metals contained in bottom ash under suitable incineration conditions, landfill waste can be reduced, and re-use of bottom ash can be increased. In this study, effects of the air supplied to the bottom of a commercialy used rotary stoker furnace was investigated as the first step to improve incineration conditions. Bottom ash content must be controlled against various types of industrial waste whose content changes from day to day. The characteristics of industrial waste containing typical components were numerically investigated using a combustion simulation program. It was found that if the primary air used for combustion is not preheated, auxiliary fuel is required to burn waste. Preheated primary air increases the drying rate of the input material, and allows burning of waste without auxiliary fuel. At the furnace, components and calorific values of input raw material are controlled by mixing different types of waste together. Preheated primary air enables reduction of bottom ash, reduction of auxiliary fuel consumption, and stabilization of furnace operation.

Evaluation of heat transfer performance of a laboratory-scale polymer rotary air preheater

Regenerative heat exchangers, which increase the temperature of newly supplied air using the waste heat of exhaust gas, are installed in large thermal systems, such as thermal power plants and industrial boilers, to improve their thermal efficiency. These devices are also known as air preheaters, and the rotary regenerative type has been widely used. The heat transfer performance of a rotary regenerator is enhanced as the heat capacity, which is the product of the density and specific heat, increases rather than the thermal conductivity of heat exchanging plates (HEPs). Studies to replace the existing metal materials with polymers, which are resistant to corrosion and inexpensive, have garnered attention. In this study, the heat transfer performance of HEPs fabricated using polytetrafluoroethylene, Mono Cast nylon, stainless steel, and aluminum is experimentally compared using a laboratory-scale experimental setup. It is confirmed that the polymer materials have similar or larger effectiveness compared to metals within the experimental error.

Energy performance analysis of pasta and macaroni factory-a case study

The great expansion of industries in Ethiopia has significantly increased the demand for the limited energy source of the country. Hence, effective and efficient way of utilizing the available energy is a crucial issue in all industries. This study investigates the energy consumption performance and possible energy saving potentials of Pasta and Macaroni Factory-a case of Africa PLC which is located in Adama city. It is the biggest pasta and macaroni producing factory in the city and consuming a very large amount of energy. The thermal and electrical energy consumption of the factory has been analyzed based on the actual data measured. The thermal performances of the two boilers (steam generators) are analyzed using an indirect method (i.e., calculating the different losses) and the typical boiler efficiency obtained are 81% and 80% for boiler #1 and #2 respectively. It is found that the major heat loss from the boilers is due to the dry exhaust gas. Similarly, water chiller, air compressor, electrical motors, pumps and lighting system equipment energy utilization have been analyzed. The various energy saving measures are analyzed and it is found that the industry can save 2,301 GJ/year of electrical energy by using high efficient motors instead of the existing normal standard motors, 782.6 GJ/year of heat energy can be recovered from the dry exhaust gas by using air preheater and 1,221 GJ/year of heat energy can be recovered by controlling the air to fuel ratio which is a significant energy saving potential. Finally this study reveals that the total possible annual bill saving potential of the factory is 1,676,871 ETB.

Performance improvement of a sugar mill through EXERGY analysis

EXERGY is the idea of thermodynamics that facilitates articulation that get past with every single working part of a system framework. The sugar business in India assumes critical role in Indian economy. Considering its wide client space and the volume of generation, it is essential to enhance the execution and proficiency of the segments in the sugar business. Thus explained EXERGY investigation of a sugar process plant through the EXERGY adjusts of an open framework. The scientific plans displayed for different types of EXERGY and the EXERGY effectiveness elements. This review connected EXERGY investigation to existing boiler, economizer, air pre-heater, juice heater and evaporator of a 3000TCD sugar plant. In light of the after effects of this paper, authors prescribed proposal for enhancing the productivity of different subcomponents. For instance, in one of subcomponent, heat loss observed in the existing set-up of raw juice heaters because of ineffective insulation.

Development of Advanced Biomass Cookstove and Performance Comparisons Using the Modified Star Rating Methodology

A disruptive approach to a fundamental process has been applied in a biomass combustion device with two variable speed fans to supply air for gasification and another for combustion processes, separately. Besides, the preheating of secondary air, required for combustion process was also ensured through annulus chamber before being fed into the combustion chamber. The turbulent flow and homogenous mixing were also ensured by controlling the flow rate resulting in the reduced emissions of carbon monoxide (CO) and fine particulate matter (PM 2.5, particulate matter having aerodynamic diameter

Efficient CO2 Capture from Lime Production by an Indirectly Heated Carbonate Looping Process

Lime production is associated with unavoidable process CO2 emissions that can only be avoided by CO2 capture technologies. The indirectly heated carbonate looping (IHCaL) is a promising post-combustion carbon capture technology that can be applied to lime plants with high potential for heat and mass integration. In this work, two concepts for efficiently integrating the IHCaL into lime plants are proposed and evaluated. To study and characterize these concepts, heat and mass balances were established, sensitivity analyses were performed, and key performance indicators were calculated by means of process simulations. The results show an increase of 63% in the direct fuel consumption for a highly integrated concept, but almost 30% of the entire heat input can be converted into electric power via heat recovery steam generation. Direct CO2 emissions are reduced by up to 87% when coal is used as fuel in the IHCaL process, but net negative CO2 emissions could be achieved when using biogenic fuels. Critical points for integration are the preheating of the combustion air, the efficiency of the sorbent solid-solid heat exchanger, and the utilization of the sorbent purge as lime product. The developed models and the obtained results will be used to further develop the integration of the IHCaL into lime plants through both experimental and numerical methods.

Thermal performance evaluation of a bioclimatic ventilated wall using a Hot Box

Nowadays, external isolation is highly recommended for both building renovation and new building construction. This isolation requires the installation of structure protecting the insulating materials from the humidity and weather variations. One of the current techniques is the installation of ventilated facades. The recovered energy by this process could be used in winter for the preheating of ventilated air or could be evacuated in summer to protect the building from potential overheating. This study describes the design and application of Hot Box developed specifically to test the thermal performance of a ventilated bioclimatic wall. Based on experiments test, this paper discusses the experimental set-up and the thermal metrology. Data collected from testing a ventilated wall were used to estimate the convection heat transfer coefficients of the ventilated wall.

Analysis and Treatment of High Differential Pressure of Boiler Air Preheater for 630 MW Unit

Analysis and Treatment of High Differential Pressure of Boiler Air Preheater for 630 MW Unit

СКОРОЧЕННЯ ЧАСУ ПРОГРІВАННЯ ДВИГУНА ЛЕГКОВОГО АВТОМОБІЛЯ ЗА ВИКОРИСТАННЯ ДОДАТКОВОГО ДЖЕРЕЛА ТЕПЛОТИ

The article presents the results of additional experimental studies about the effect of heat supply to the intake air on the parameters and characteristics of the process of warming up the engine of a car. The aim of the work is to accelerate the car engine warming after starting at low temperatures. The research method is an experimental determination of the characteristics of active idling and concentrations of pollutants in the exhaust gases of the engine. The tests were performed when the car's engine was idling without heating the inlet air and with heating the inlet air through the air intake under the hood of the car and through the pipe in front of the intake manifold. Comparison of engine operation in active idling mode without heating the inlet air and with heating the air before inlet through the air intake, did not show significant differences. The long passage of preheated air through the air duct to the air filter, through the air filter and the air duct after the filter, causes cooling of the heated air and does not provide the efficiency of additional heat supply. For efficient use of additional heat supply, it is necessary to carry out this supply directly in front of the intake pipe. Most of the parameters that characterize the process of warming up the engine are obtained by direct measurement. Also, the dependences on which total indicators of economy and toxicity of the car were calculated are resulted in the article. According to the results of experimental studies, it is established that the operation of the car in low ambient temperatures leads to a deterioration of its fuel economy and environmental performance. For an internal combustion engine, with garage-free maintenance of the car in low ambient temperatures and with long periods of downtime, it is important to find and implement measures that allow, with minimal consumption of fuel and energy resources, to ensure warm-up of the cold engine. Additional heat supply to the inlet air provides rapid warming of the car engine to operating temperature, which provides a short period of preparation for the perception of the load. Intake air heating reduces fuel consumption during engine idling by an average of 4%. With additional heat supply, the concentrations of pollutants are being reduced, especially in the first 50 seconds of engine warm-up, and the total toxicity of the engine, determined by the two components (carbon monoxide and hydrocarbons) is being reduced by an average of 6%. KEY WORDS: ENGINE, HEAT, HEATING, FUEL CONSUMPTION, COOLANT TEMPERATURE, POLLUTANTS

Heat transfer studies at different speeds and loads of regenerative air preheater in thermal power plant

Regenerative air preheater is one of the largest heat recovery systems in thermal power plants. There are various factors, which determine the heat transfer rate in regenerative air preheaters (RAPH) such as, material of heating elements, temperature difference between air and flue gas, quantity of flue gas, amount of air passing through the RAPH and its rotational speed. In all power plants, RAPH is designed to operate at constant speed where the maximum heat transfer is achieved in full load operation. The rate of heat transferred to the air is compared at different loads and speeds of the RAPH and the optimum speed at which maximum heat transfer rate occurs is found in this experimental study. Speed is varied using a Variable Frequency Drive (VFD) power supply to the RAPH motors. Based on the study, it is inferred that the optimum speed varies with load of the power plant. A cost benefit analysis is also carried out, which clearly indicates that more amount of energy could be conserved by operating the RAPH at various speeds rather than at constant speed.