Neutralization of cement-asbestos waste by melting in an arc-resistance furnace

Our plain-English summary of Neutralization of cement-asbestos waste by melting in an arc-resistance furnace, by J. Witek, R. Kusiorowski (Waste Management, 2017).

The study

• Authors: J. Witek, R. Kusiorowski
• Journal: Waste Management
• Published: 2017;69:336-345
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The paper presents the results of research on asbestos waste disposal by the melting process. The tests were carried out in a laboratory arc-resistance electric furnace. The obtained results showed that the fibrous structure of asbestos contained in cement-asbestos waste was completely destroyed. This led to the formation of new mineral phases without dangerous properties. The melting test was conducted on raw cement-asbestos samples without any additives and with a content of mineral compounds, the aim of which was to support the melting process. The additives were selected among others on the basis of the computer simulation results carried out using FactSage database computing system. The research results indicate that the melting process of asbestos wastes is a potential and interesting method of neutralizing hazardous asbestos waste, which allows for further treatment and material recycling.

Copyright © 2017 Elsevier Ltd. All rights reserved.

In plain English

This was a laboratory materials experiment, not a health study. The authors tested whether melting destroys the asbestos in cement-asbestos waste ("eternit"). The waste contained about 10 wt% asbestos, and chrysotile was the only asbestos mineral identified. Crushed waste was melted for about 100 minutes in a laboratory arc-resistance furnace. It was melted once alone and once with two fluxes, sodium carbonate and potassium feldspar, in a ratio of 85:10:5 (waste to sodium carbonate to feldspar). The fluxes were chosen partly by computer simulation to lower the melting temperature. In the melted products, X-ray diffraction showed no chrysotile. Light microscopy found no fibrous asbestos and no particles more than three times as long as they were wide. With fluxes, about 60 wt% of the starting material could be poured out, compared with about 20 wt% without them. Energy use per kilogram fell by about 20%, from 3.1 to 2.6 kWh. Without fluxes, the cooled product crumbled into powder. The furnace lining corroded, adding aluminium to the products. The authors concluded that the asbestos was completely transformed into new non-fibrous phases and that the product might be recycled.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory experiment: melting tests of cement-asbestos waste in an electric arc-resistance furnace, run for about 100 minutes, with chemical, mineralogical, thermal and microscopic analysis and computer simulations (FactSage) to choose melting additives
• Who was studied: No people were studied. The test material was cement-asbestos waste ("eternit", Portland cement and asbestos fibers) left over from asbestos-containing materials used in civil engineering. The furnace chamber held about 50 kg of material.
• Exposure: Cement-asbestos waste melted alone, or mixed with sodium carbonate (soda) and potassium feldspar as fluxes in a ratio of 85:10:5 (cement-asbestos to soda to feldspar).
• Main results:
  • The waste tested contained about 10 wt% asbestos.
  • Chrysotile was the only asbestos mineral identified in the raw waste.
  • None of the melted products, with or without fluxes, contained asbestos minerals. No chrysotile reflection appeared on the X-ray diffraction patterns.
  • Under the light microscope, the fibrous form of asbestos was not seen in the melted material, and no particles with an aspect ratio over three were detected.
  • The raw cement-asbestos waste had a refractoriness of 151 sP, corresponding to 1510 degrees C.
  • Without fluxes, only about 20 wt% of the initial material could be cast into a mould. The rest stayed in the furnace.
  • With fluxes, the cast amount reached about 60 wt%.
  • Adding fluxes reduced energy consumption per kg of melted material by about 20%, from 3.1 to 2.6 kWh.
  • The product melted without additives broke down spontaneously on cooling. This did not happen when fluxes were added, and that product formed a solid block.
  • The products became enriched in aluminium because the melt corroded the furnace's alumina-based refractory lining.
• The authors' conclusion: The authors concluded that melting in a laboratory arc-resistance furnace destroyed the asbestos minerals in cement-asbestos waste, transforming them into new high-temperature phases without the dangers of fibrous asbestos. They added that fluxes lowered the melting temperature and that the product could possibly be recycled, for example as aggregate, binding material or ceramics.
• Limitations the authors state:
  • The energy figures come from a small laboratory furnace. The authors note that energy use in a large industrial furnace is usually several times lower.
  • Without fluxes, far less melt could be cast than the furnace design assumed, probably because of the melt's high density and viscosity.

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