Miljøprojekt, 1115 – Brancheindsats for jern- og metalstøberier - Delprojekt 1 - Organiske bindere og tilsætningsstoffer Fase 1.2: Fastlæggelse af organiske binders og tilsætningsstoffernes miljømæssige fingeraftryk

Brancheindsats for jern- og metalstøberier

Summary and conclusions

Analyses of pyrolytic gases from moulds bound with organic binders or moulds with organic additives show that carbon monoxide and benzene have most impact on the environment. In addition to the mentioned agents, pyrolysis agents such as formaldehyde, phenol and sulphur dioxide are developed during the casting process and the additional cooling of the sand moulds. The development of all agents depends on the type of binder and additive, the amount of additives as well as the thermic exposure. That is the casting temperature of the metal, mould and metal weight.

Background and purpose

Pyrolytic gases from moulds, made with organic binders or organic additives, have a large impact on the working environment in the foundry industry.

The objective of the project is to develop an environmental appraisal system for organic binders and additives. The basis of the valuation system is based on an analysis of the pyrolysis products that develop during casting and cooling of moulds made with organic binders, or bentonite bounded sand, containing organic additives like coaldust. Another objective of the project was to generate data for the UMIP-data base.

The investigation

A prototype was developed with the purpose of making sand moulds with core and mould binders as well as extraction systems. The equipment is developed for continuous extraction of gas samples for online analysis of carbon monoxide from pyrolytic gases and the total amount of aromatic hydrocarbons. In addition gas samples can be extracted for filter analysis of phenol, formaldehyde, sulphur dioxide and polyaromatic hydrocarbon. The equipment has been developed by Danish Technological Institute and tested in cooporation with Technical University of Denmark.

Conclusion

With the test method developed for this study it was possible to establish that carbon monoxide and benzene are the two agents from pyrolytic gases, from the most applied organic binders and additives, with most impact on the environment. Evolution of carbon monoxide and benzene display the highest values irrespective of type of binder and additive.

Therefore it will be natural in the future to analyse for benzene and carbon monoxide in order to evaluate the environmental impact of binders and additives.

Depending on type of binder and additive, the analysis can be extended to include e.g. sulphur dioxide, phenol or formaldehyde.

Manufactures of organic binders and additives develop new binder systems and additives or modify their products continuously. When changing to a new product, foundries should request that suppliers document the results of environmental evaluations or require that they carry out tests of new products. With the result from an environmental evaluation it is possible for each foundry to evaluate the consequences of changing to another product.

Project results

For an evaluation of binders and additives’ environmental impact the ”Attenuation Factor” (evolution/limit value) is applied. From this it is established that the evolution of benzene has the greatest impact on the environment. This applies for a majority of the tested binders. The average attenuation factor for the examined furan binders is therefore for benzene and carbon monoxide 395 and 265 respectively. By comparison the attenuation factor for cold-box-binders for benzene has an average of 880 and for carbon monoxide 204. For the other binder types examined the ratio between benzene and carbon monoxide is 1 to 2. The environmental impact for agents like phenol, formaldehyde and sulphur dioxide is limited compared to benzene or carbon monoxide. The attenuation factor for these agents has an average of 4, 15 and 1 respectively.

For the organic additives the environmental impact from carbon monoxide is approx. 20 times greater than for benzene. Just as with binders, the environmental impact from e.g. phenol and sulphur dioxide is at a very low level.

During casting and cooling of moulds moulded in cast iron the development of carbon monoxide and all hydrocarbons is at its highest level approx two to five minutes after pouring. In the following 30 to 40 minutes the development of the pyrolytic gasses decreases gradually. The development curve for hydrocarbons changes at pouring of metals with lower casting temperature than cast iron, such as aluminium. In this case an upward curve is observed the first 30 minutes after pouring. The carbon monoxide development is at its highest level immediately after pouring. However, considerably lower levels of both were recorded. Dependent on binder type the environmental impact from benzene is approx. 40 to 120 times lower and for carbon monoxide between 20 to 90 times lower compared to cast iron.