Analysis of the Combustion Air Preheater from the Aluminum Melting Furnaces

2016 ◽  
Vol 14 (11) ◽  
pp. 27-32
Author(s):  
Aurel Gaba ◽  
Vasile Bratu ◽  
Dorian Musat ◽  
Ileana Nicoleta Popescu ◽  
Maria Cristiana Enescu
Keyword(s):  
Mathematical Model ◽  
Heat Exchanger ◽  
Computer Program ◽  
Flue Gas ◽  
Heat Recovery ◽  
Melting Furnace ◽  
Operating Conditions ◽  
Air Preheater ◽  
Constructive Version ◽  
Scrap Aluminum

Abstract This paper presents solutions and the equipment for preheating combustion air from scrap aluminum melting furnaces through flue gas heat recovery. For sizing convection pre-heaters, there has been developed a mathematical model which has been transcribed into a computer program in C + +. A constructive version of the pre-heater was drawn up and a recovery heat exchanger was manufactured and mounted on an aluminum melting furnace. Both the functional parameters values and the reasons causing the pre-heater worning out, as well as the steps taken for sizing and the achievement of a new air pre-heater able to bear the operating conditions of the aluminum melting furnace are shown.

scholarly journals How to Construct a Combined S-CO2 Cycle for Coal Fired Power Plant?

Entropy ◽  
2018 ◽  
Vol 21 (1) ◽  
pp. 19 ◽  
Author(s):  
Enhui Sun ◽  
Han Hu ◽  
Hangning Li ◽  
Chao Liu ◽  
Jinliang Xu
Keyword(s):  
Power Plant ◽  
Flue Gas ◽  
Heat Recovery ◽  
Water Cycle ◽  
Combined Cycle ◽  
Exergy Destruction ◽  
Generation Efficiency ◽  
Air Preheater ◽  
Recompression Cycle ◽  
Residual Heat

It is difficult to recover the residual heat from flue gas when supercritical carbon dioxide (S-CO2) cycle is used for a coal fired power plant, due to the higher CO2 temperature in tail flue and the limited air temperature in air preheater. The combined cycle is helpful for residual heat recovery. Thus, it is important to build an efficient bottom cycle. In this paper, we proposed a novel exergy destruction control strategy during residual heat recovery to equal and minimize the exergy destruction for different bottom cycles. Five bottom cycles are analyzed to identify their differences in thermal efficiencies (ηth,b), and the CO2 temperature entering the bottom cycle heater (T4b) etc. We show that the exergy destruction can be minimized by a suitable pinch temperature between flue gas and CO2 in the heater via adjusting T4b. Among the five bottom cycles, either the recompression cycle (RC) or the partial cooling cycle (PACC) exhibits good performance. The power generation efficiency is 47.04% when the vapor parameters of CO2 are 620/30 MPa, with the double-reheating-recompression cycle as the top cycle, and RC as the bottom cycle. Such efficiency is higher than that of the supercritical water cycle power plant.

A study on air-cooling waste heat recovery from molten slag of slag-tap boilers

2017 ◽  
Vol 231 (5) ◽  
pp. 371-381
Author(s):  
Lei Deng ◽  
Chunli Tang ◽  
Xiaowen Tan ◽  
Ke Sun ◽  
Song Wu ◽  
...  
Keyword(s):  
Flue Gas ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Molten Slag ◽  
Waste Heat ◽  
Ash Content ◽  
Air Cooling ◽  
Air Preheater ◽  
Hot Air ◽  
Secondary Air

For a better utilization of Zhundong coals which have high fouling and slagging tendency, the slag-tap boiler has attracted much attention. To avoid the high sensible heat loss of discharged molten slag, an air-cooling waste heat recovery system is proposed. Energy and economic analyses are conducted to investigate the effectiveness of heating the desulfurized flue gas by hot air and the influences of partially substituting the secondary air by hot air on heat transfer of air preheater and thermal efficiency of boiler. A case study is performed by referring to a typical 50 MW cyclone boiler with nine types of low fusion temperature coals. The results show that for coals with low ash content, the temperature increment of desulfurized flue gas can be over 7 ℃. While for coals with high ash content, the flue gas temperature can be heated to more than 70 ℃, and the surplus hot air can be sent to the furnace. When the hot air is introduced to partially substitute the secondary air, an instantaneous impact on the air preheater will give rise to a decrement of quantity of heat transferred and increments of temperatures of exit flue gas and hot secondary air. The variations of these thermodynamic parameters become smaller with increasing hot air temperature. After introduction of hot air, the thermal efficiency of boiler can increase, resulting in a decrease of fuel consumption rate. In addition, the heating surface area of air preheater can be reduced.

Cold End Corrosion Avoiding by Using a New Type of Air Combustion Pre-Heater

2017 ◽  
Vol 907 ◽  
pp. 157-163 ◽  
Author(s):  
Maria Cristiana Enescu ◽  
C. Marius Vlădulescu ◽  
Aurel Gaba ◽  
Vasile Bratu ◽  
Elena Valentina Stoian ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Sulfur Dioxide ◽  
Computer Program ◽  
Skin Temperature ◽  
Fuel Economy ◽  
Flue Gas ◽  
Heat Recovery ◽  
Sulfur Trioxide ◽  
Dew Point ◽  
New Type

This paper analyzes the possibility of reducing the cold end corrosion in boilers and furnaces by using a new type of air combustion pre-heater. Cold end corrosion appears due to catalytic oxidation of the sulfur dioxide to sulfur trioxide and then due to the sulfuric acid condensation at dew point. Calculating dew points of various acid gases and options for reducing cold end corrosion of heat recovery exchangers are presented. For avoiding the cold end corrosion we design a new type of air combustion pre-heater for boilers and furnaces. Also, the tube skin temperature of the first row of pipes of the actual air pre-heater was simulated with this computer program, in order to determine whether this temperature is lower than acid dew point of flue gas. With the simulation for this configuration of the actual combustion air pre-heater, the skin temperature for the first row (for the combustion air flow) of tubes from the upper bundle was TS = 134 °C. A way to reduce the cold end corrosion in the combustion air pre-heaters is raising the temperature of the combustion air at the air pre-heater entrance. This solution involves taking a quantity of preheated air, recirculation and then reintroducing it in the air pre-heater. In the same time, this solution avoiding to use the steam radiator, mounted after the fan, for pre-heating the combustion air from 1°C to 45°C. Thus, the furnaces equipped with the new combustion air pre-heater and modern low NOx burners made a fuel economy about 3%.

Exhaust Heat Recovery Unit Equipped With Nanofluid and Helical Tapes, a Solution for Cleaner Energy Production

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
M. Sheikholeslami ◽  
A. Arabkoohsar ◽  
M. Jafaryar
Keyword(s):  
Nusselt Number ◽  
Heat Exchanger ◽  
Environmental Impacts ◽  
Flue Gas ◽  
Heat Recovery ◽  
Internal Combustion Engines ◽  
Waste Heat ◽  
Physical Parameters ◽  
Twisted Tape ◽  
Exhaust Heat

Abstract In internal combustion engines (ICE), a major part of the generated energy via burning the fuel is wasted. The cooling fluid controlling the temperature, the reclaimed hot gases for reducing the environmental impacts, and the hot combustion productions leaving the engine from the exhaust are the main origins of energy waste in such a machine. Waste heat recovery and flue gas condensation are the methods by which the overall efficiency of a thermal engine is enhanced, and its environmental impacts are mitigated. In this paper, the utilization of the exhaust waste energy of ICE by using a heat exchanger with nanofluid and helical tape, in order to augment the thermal performance of the engine and reduce its environmental impact, is investigated numerically. In this heat exchanger, the flue gas of the engine at high temperature and H2O-CuO nanofluid are considered as the primary and secondary working fluids, and the twisted tape makes the flow further disturbed so that a larger overall heat transfer coefficient is obtained. The finite volume method has been applied to scrutinize the impacts of Reynolds number as well as the twisting-tape turns number on the operation and performance of the tube. As such, suitable correlations for the prediction of some of the thermos-physical parameters of the problem (such as Nusselt number and Darcy factor) are extracted regarding the obtained data. The results of the study reveal that Nusselt number is higher for larger numbers of the tape turn and higher Reynolds numbers, while a lower friction factor is achieved as the number of the turns is reduced.

scholarly journals Advance Exergo-Economic Analysis of a Waste Heat Recovery System Using ORC for a Bottoming Natural Gas Engine

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 267 ◽  
Author(s):  
Guillermo Valencia Ochoa ◽  
Jhan Piero Rojas ◽  
Jorge Duarte Forero
Keyword(s):  
Heat Exchanger ◽  
Economic Analysis ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Operating Conditions ◽  
Cost Rate ◽  
Waste Heat Recovery System ◽  
Recovery System ◽  
Heat Recovery System

This manuscript presents an advanced exergo-economic analysis of a waste heat recovery system based on the organic Rankine cycle from the exhaust gases of an internal combustion engine. Different operating conditions were established in order to find the exergy destroyed values in the components and the desegregation of them, as well as the rate of fuel exergy, product exergy, and loss exergy. The component with the highest exergy destroyed values was heat exchanger 1, which is a shell and tube equipment with the highest mean temperature difference in the thermal cycle. However, the values of the fuel cost rate (47.85 USD/GJ) and the product cost rate (197.65 USD/GJ) revealed the organic fluid pump (pump 2) as the device with the main thermo-economic opportunity of improvement, with an exergo-economic factor greater than 91%. In addition, the component with the highest investment costs was the heat exchanger 1 with a value of 2.769 USD/h, which means advanced exergo-economic analysis is a powerful method to identify the correct allocation of the irreversibility and highest cost, and the real potential for improvement is not linked to the interaction between components but to the same component being studied.

The latent heat recovery from boiler exhaust flue gas using shell and corrugated tube heat exchanger: A numerical study

Heat Transfer ◽  
2020 ◽  
Vol 49 (6) ◽  
pp. 3797-3815 ◽  
Author(s):  
Sharare Mohammadi ◽  
Seyed Soheil Mousavi Ajarostaghi ◽  
Mohsen Pourfallah
Keyword(s):  
Heat Exchanger ◽  
Latent Heat ◽  
Flue Gas ◽  
Heat Recovery ◽  
Numerical Study ◽  
Tube Heat Exchanger ◽  
Corrugated Tube

A Novel Flue Gas Heat Recovery System Integrated With Air Preheating in a Utility Boiler

2013 ◽  
Author(s):  
Cheng Xu ◽  
Gang Xu ◽  
Luyao Zhou ◽  
Yongping Yang ◽  
Yuanyuan Li ◽  
...  
Keyword(s):  
Flue Gas ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Power Plants ◽  
Energy Savings ◽  
Waste Heat ◽  
The Novel ◽  
Air Preheater ◽  
Recovery System ◽  
Condensed Water

Exhaust gas temperature in coal-fired power plants can reach approximately 120 °C to 140 °C, with the thermal energy accounting for approximately 3% to 8% of the total input energy. Therefore, the heat recovery of exhaust flue gas can improve the thermal efficiency of coal-fired power plants. Currently, the waste heat of flue gas can be recovered by installing an extra heat exchanger, also called low-temperature economizer (LTE), at the end of the boiler flue to heat a part of the condensed water. Extra work can then be obtained by saving the extracted steam and using it to heat the condensed water. However, the temperature of exhaust flue gas is only about 130 °C, which causes the flue gas to heat only the condensed water in the #7 and #8 regenerative heaters. Thus, the energy savings are inconspicuous. This paper proposes a novel flue gas heat recovery system to dramatically increase the temperature of flue gas in the LTE by comprehensive optimization of the air preheater and the LTE. A low-temperature (LT) air preheater can be installed after the LTE in the novel system so that the flue gas can be divided into two parts to heat the air. Simultaneously, the LTE can be installed between the two air preheaters, causing the temperature of flue gas in the LTE to reach above 170 °C. Hence, the temperature of condensed water in the LTE can be increased significantly. In addition, the LTE can replace the high-pressure extracted steam from the turbine, resulting in better energy savings. We also conduct case studies based on a typical 1,000 MW supercritical power generation unit in China. The results indicate better performance of the novel system, with a decrease in exergy loss and improvement in heat transfer characteristics. The reduction in standard coal equivalent of the novel system can reach 3.31g/kWh, nearly 2.4 times that of the system that uses conventional waste heat recovery. Our achievements provide a promising waste heat recovery methods of the utility boiler flue gas.

A total heat recovery system between the flue gas and oxidizing air of a gas-fired boiler using a non-contact total heat exchanger

2017 ◽  
Vol 207 ◽  
pp. 613-623 ◽  
Author(s):  
Sheng Shang ◽  
Xianting Li ◽  
Wei Chen ◽  
Baolong Wang ◽  
Wenxing Shi
Keyword(s):  
Heat Exchanger ◽  
Flue Gas ◽  
Heat Recovery ◽  
Total Heat ◽  
Recovery System ◽  
Heat Recovery System
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