Energy and exergy system analysis of thermal improvements of blast-furnace plants

Abstract

SUMMARYThe blast-furnace process dominating in the production of steel all over the world is still continuously improved due to its effectiveness (exergy efficiency is about 70%). The thermal improvement consist in an increase of the temperature of the blast and its oxygen enrichment, as well as the injection of cheaper auxiliary fuels. The main aim is to save coke because its consumption is the predominating item of the input energy both in the blast-furnace plant and in ironworks. Besides coke also other energy carriers undergo changes, like the consumption of blast, production of the chemical energy of blast-furnace gas, its consumption in Cowper-stoves and by other consumers, as well as the production of electricity in the recovery turbine. These changes affect the whole energy management of ironworks due to the close connections between energy and technological processes. That means the production of steam, electricity, compressed air, tonnage oxygen, industrial water, feed water undergo changes as well. In order to determine the system changes inside the ironworks a mathematical model of the energy management of the industrial plant was applied. The results of calculations of the supply of energy carriers to ironworks can then be used to determine the cumulative energy and exergy consumption basing on average values of cumulative energy and exergy indices concerning the whole country. Such a model was also used in the system analysis of exergy losses.

Exergo-Ecological Assessment Of Auxiliary Fuel Injection Into Blast-Furnace

“…For the purpose of Exergy and TEC analysis the "input-output" model [7,8] has been applied for prediction of PCI direct effects and zone balance model [14] for simulation of direct effects of top-gas recirculation. The scheme of blast furnace with assumed temperature zones for modelling purposes has been presented in Fig.…”

“…The I-O model let to predict the influence of operational parameters changes x 0 → x 1 on energy characteristic of BF plant including: consumption of coke (K) and blast (D), production of top-gas (G) and its chemical energy (E), as well as, the chemical energy of the top-gas feeding the gas-system (E Z ). Moreover the model of top-gas expansion turbine [7,8,14] let to evaluate the production of electric energy by the recovery turbine of top-gas (E el ). For example the carbon element balance is presented by Eq.…”

“…The exergy efficiency of the whole blast furnace plant, including Cowper stoves, (Fig. 2) reaches the level of about 65 % [7,8]. Such high thermodynamic effectiveness of the process is possible because the counter flow of heat and substance is realised in the shaft of this furnace [9].…”

“…These models in details has been discussed e.g. in [7,8,14]. Results of modelling, so called energy characteristics of blast furnace plant represents input data for both -direct and cumulative exergy analysis by means of TEC.…”

Energy Efficiency Improvement and Cost Saving Opportunities for the U.S. Iron and Steel Industry An ENERGY STAR(R) Guide for Energy and Plant Managers

“…A compressor unit is required for COG injection, resulting in an additional energy consumption of about 185 kWh/ton COG (204 kWh/tonne) (IPPC, 2008). Analysis by Ziębik and Stanek (2006) indicated that injection of pulverized coal leads to higher energy effectiveness than that of coke oven gas.…”