Phasing out PAH
Elkem Carbon’s main R&D priority is to develop products that are PAH (polycyclic aromatic hydrocarbons) free.
Elkem Carbon is a world-leading supplier of carbon electrode materials, lining materials and specialty carbon products to metallurgical processes for the production of ferroalloys, base metals and primary aluminium.
Elkem Carbon uses coal tar pitch as a binder in its products. Coal tar pitch contains PAHs - polycyclic aromatic hydrocarbons. Several of the PAH compounds are classified as health hazards and substances of very high concern. The large volumes of such binders (4 million tonnes annual consumption worldwide) also constitute a substantial contribution to greenhouse gases, since it is oxidized to CO₂ during metal production. In December 2016 the European Union made the use of coal tar pitch subject to authorisation. Intermediate use, like in electrode paste for use in smelting processes, is exempted from authorisation.
Research to find alternatives to coal tar pitch is a priority for Elkem Carbon. By developing products that do not contain coal tar pitch, Elkem Carbon will minimise PAH exposure and emissions both from its own production and from the customer’s production of aluminium, ferroalloys and other metals.
A consortium of 14 European companies using EU funding under the Horizon 2020 programme, is planning to demonstrate the conversion of woody biomass to value adding chemical building blocks. Elkem Carbon will focus on demonstrating the application of the chemicals as binders in their products.
Knowledge and experience from Elkem’s work on ELSEAL® Type G will be used in this project to verify if different materials available from the bio refineries can be used as binders in carbon materials for the metallurgical industry.
Green binder for carbon products – supported by the Norwegian Research Council
The overall goal of the ‘Green binder for carbon products’ project is to develop biobased binders for carbon products to replace today’s fossil based coke tar binders. This will, if successful, reduce the CO₂ ENVIRONMENT PAH emissions to water from Elkem Carbon Fiskaa, Norway from 650 kg in 2004 to around 2 kg per year in 2016.
Elkem Carbon and the Norwegian bio refinery Borregaard have joined forces in this project. Borregaard will tailor-make bio based binders with optimized properties for use in carbon products. Elkem Carbon will test the new binders in both their pilot and full scale facilities, and make the necessary adjustments and optimizations to make use of these novel green binders in their commercial manufacturing processes possible.
To avoid unnecessary disposal of waste containing PAHs, Elkem Carbon is working systematically to recycle scrap production in the production of new products. It has invested in new equipment to handle and process off-spec materials. The rejected products are crushed, sieved and fed in controlled quantities into the production process through a separate silo.
Reduction of PAH emissions to air
Elkem Carbon Fiskaa, Norway, aims to keep its emissions of PAH under 50% of what is permitted in their environmental permit, even with increased production. A stable production process in a well-maintained facility is important to reach this goal. Systematic work to reduce dust has had a strong positive impact on Elkem Carbon’s PAH emissions to air. The vast improvements have given room for less use of personal respiratory protection, as the air in the working environment is safe to breathe.
Elkem Carbon, Fiskaa, Norway is participating in a national survey on moss quality in the areas around Norwegian production facilities. This includes determination of PAHs and metals in moss and PAHs in air. Since 1983 and every year from 2010 Elkem Carbon Fiskaa, Norway has been monitoring the water and sediment quality for PAHs in the neighbouring fjord (Kristiansandsfjorden). After 30 years of warning against eating fish from the fjord, the Norwegian Food Safety Authorities now considers fish from the Kristiansandsfjord safe to eat. Results for blue mussels and sediments are also improving.
Reduction of PAH emissions to water
Efforts are ongoing at all Elkem Carbon plants worldwide to reduce the amount of water used in production. The reduction of PAH from 650 kg to less than 2 kg have been achieved through extensive maintenance on the water pipes to avoid leaks, and new piping has been installed, in order to separate water streams into clean cooling water and contaminated water. This makes it possible to treat the contaminated surface water and measure emissions.
Elkem Carbon Ferroveld in South Africa has an integrated process-water treatment system on site. Contaminated water from the extruder facility is transferred to process-water used for cooling chrome slag at another production facility in the industrial park. In this process contamination is destroyed and water evaporates instead of being discharged.
In tropical regions, biological methods for water purification can be used to remove PAHs and other contamination from rainwater and other storm water. At Elkem Carbon’s plant in Brazil, water that may be contaminated is fed through three basins: one containing old wood materials, one containing plants, and one containing bacteria. This purification method is also adopted at Elkem’s new plant in Malaysia.