The major air pollutants that occur during the production of steel besides greenhouse gases (in particular CO2) are sulfur dioxide (SO2), nitrous oxide (NOX), and dust. Emissions of all of these pollutants comply with the statutory threshold limits. These parameters are measured and their annual loads recorded by means of continuous measurements, intermittent laboratory analyses, and material flow analysis.
voestalpine makes every effort to minimize to the greatest extent possible the air pollutants that occur during production for purely technical reasons related to the process. On one hand, this is done by optimizing of the technical process (process integrated measures) and on the other, through end-of-pipe measures utilizing state-of-the-art technology. Fundamentally, technical limitations prevent the process-related emissions, which result primarily from the raw materials required and from existing production processes, from being avoided entirely. Due to the environmental measures that were begun in the mid-1980s, and have continued since then with significant technical effort and financial expense, emission levels have reached the minimum currently technically achievable.
Therefore, no additional significant reduction is possible using currently available technologies, as illustrated below. For example, the specific emissions for CO2, SO2, and NOX in the last five years are within the production-based fluctuation range. During the last three decades, the specific emissions produced by the voestalpine Group (i.e., based on one ton of crude steel) have been reduced as follows: CO2 by 20%, SO2 by 75%, NOX by 27%, and dust by 95%.
Greenhouse gas emissions
Crude steel production using the blast furnace/LD process depends on the use of carbon as a reducing agent; the resulting process-related CO2 emissions are technically unavoidable.
Since fall 2016 voestalpine has operated a direct reduction plant for the production of high quality sponge iron (HBI–hot briquetted iron) in Corpus Christi, Texas. During this process natural gas is used to reduce ore pellets. As a result, the specific Greenhouse Gas emissions for the reduction process can be lowered compared to the coal-based smelting reduction process.
Operations at around 130 voestalpine production sites generated greenhouse gas emissions of around 14.3 million tons in 2017, with the majority consisting of process-related and currently unavoidable CO2 emissions.
Direct and indirect GHG emissions
In millions of tons of CO2e
Many raw materials contain sulfur which is consequently introduced into the production process. During certain processing steps and when byproducts (coke oven gas and blast furnace gas) are used for thermal recycling, sulfur is emitted in the form of sulfur dioxide (SO2).
The specific SO2 emissions in the calendar year 2017 were 0.45 kg per ton of crude steel. The reduction over previous years is due to optimization of the separation performance in the sintering plant at the site in Linz, as well as the altered product reference values (including HBI in Texas).
Specific SO2 emissions
kg/t of product
Nitrous oxides (NOX) are gaseous nitrogen compounds which are created during combustion processes. In steel production they result from operating the industrial facilities and from thermal recycling of the blast furnace gases. By deploying denitrification systems and improved combustion technologies, voestalpine has significantly reduced these emissions to a low level in a long-term comparison, and held them at this level over the past years. In calendar year 2017, the specific NOX emissions from operations were around 0.51 kg per ton of crude steel.
Specific NOX emissions
kg NOX /t of product
Captured dust emissions
Dust-laden exhaust gases and emissions occurring during production are captured and routed to a dedusting system using state-of-the-art measures and precautions. In calendar year 2017, a direct reduction plant for the production of sponge iron became fully operational in Corpus Christi (Texas, USA). This is the main reason for the increase in absolute dust emissions. The specific dust emissions at voestalpine continue to remain at a very low level.
Captured dust emissions
Specific captured dust emissions
g/t of product
Organic air pollutants
Organic air pollutants (VOC) are primarily process-related, the result of the thermal process stages in crude steel production and in the combustion processes. In order to reduce VOC emissions further, regenerative afterburning in connection with the drying of coal was introduced at the site in Linz in 2017. In terms of production quantities, VOC emissions amounted to around 34 grams per ton of crude steel.
Specific VOC emissions
g/t of product