Retrofitting Research On Heating And Recovery Of Flue Gas Waste Heat From Aluminum Hydroxide Roasting Furnace

In accordance with the requirements of the original city government to enhance economic efficiency of the company,China Light and Power Investment Shanxi Aluminum Co.,Ltd.intends to use roaster flue gas waste heat and surplus steam from the power plant to the original city heating in response to the national call for energy-saving emission reduction.Based on the principle of "using energy and using cascade",thermodynamic analysis is used to analyze the different levels of flue gas at different temperature levels.At the same time,under the way of waste heat recovery and utilization of flue gas to be focused on,macroscopically for the selection of flue gas waste heat recovery program to provide a reference.According to the requirements of Yuanping city heating and the specific conditions of this project,three technical schemes are selected according to the principle of technological advancement,applicability and economy.Respectively,the first program:the use of water and heat exchanger waste heat recovery flue gas;Option two:the use of steam-type flue gas waste heat recovery unit and flue gaswater wall heat recovery roaster flue gas heat,heat network backwater;Option three:The use of open absorption heat pump technology recovery roaster flue gas heat,heating heat network backwater.Through comparative analysis,the third scheme of open absorption heat pump technology has obvious advantages over other technologies and is the preferred technology of the project.The basic principle of flue gas waste heat recovery technology is:the use of a strong hygroscopic inorganic salt solution directly countercurrent contact with the flue gas in the low-temperature energy converter,the solution has a strong dehumidification and destruction of flue gas "aerosol" so as to adsorb the smoke in the flue gas,so as to realize the function of removing the flue gas and reducing the dew point temperature of the flue gas,thereby achieving the deep purification of the flue gas;meanwhile,the solution vapor is absorbed by the solution through the circulating spraying of the solution.A large amount of latent heat of vaporization is released in the flue gas,and the waste heat recovery of the low-temperature flue gas is realized.At the same time,flue gas purification and waste heat recovery are realized.The project consists of 2 sets of waste heat recovery units for flue gas,of which 1 set of waste heat recovery unit processes flue gas from#1,#2 and#3 roaster and another set of waste heat recovery unit treats#4,#5 and#6 roaster gas;at the same time the construction of a hot site(arranged with a heating network circulation pump and heating network heater,the use of steam directly heating network circulating water),as a waste heat recovery unit standby.The main processes of waste heat recovery system,the selection of major equipment,the corrosion protection of equipment and pipeline,the safeguard of heat supply,the impact on alumina production and the utilization of waste heat recovery system during non-heating period are introduced.After the transformation,the total heat capacity of the system is 2.16 million GJ,which can heat 3600 t/h primary pipe network water from 55℃ to 95℃ to meet the heating area of 3.34 million m2(the heating index is 50 W/m2).The company can obtain a net income of 30.4517 million yuan from the 2018 to 2019.