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long term solutions for industrial wastes a proposed approach Paulo von Krüger Professor of the Metallurgy and Materials Department – Escola de Minas/lJFOP – Ouro Preto – Brazil, ABSTRACT 3 p Waste generation is industrial process. nce from any Among the shortcomings from that, environment impairing and underutilization of non- renewable natural resources can be emphasized. Generally speaking it can be said that the adopted solutions aims only the attending of regulatory constraints from official agencies. Normally, when these solutions result in economic benefits, it is not more than a coincidence.

This comes from the misconception that wastes are unrecoverable losses and those who generate it are villains that must be permanently watched. In this paper another point of view is proposed. In it, wastes are considered as raw materials/products and generators as businessmen looking for marketing it in sound commercial basis. Besides that, from this same point of view, La generación de residuos es el proceso inevitable de cualquier proceso industrial. En las consecuencias resultantes, se destacan la agresión al medio ambiente y el bajo provecho de los recursos naturales non renovables.

Las soluciones adoptadas normalmente contemplan casi exclusivamente el atender a las reglas ambientales impuestas por el gobierno. Los ejemplos de alternativas de reciclaje que generan beneficios económicos son apenas felices coincidencias. Esto es el resultado natural de una concepción que considera una pierda irrecuperable y los generadores los que deben ser controlados. La propuesta de este trabajo es la mudanza de este enfoque. Acá los residuos son considerados una materia prima o producto y los generadores de residuo los empresarios responsables por su colocación en el mercado, en forma comercialmente ceptable.

De esta forma si no existen, en el presente, tecnologias adecuadas de recuperación, los generadores deberían tener la responsabilidad de formar estoques de modo que sean utilizables en futuro. Dentro de este enfoque se proponen los conceptos de “planta de efluentes” y “yacimientos de efluentes”. INTRODUCTION As it is well known any activity, both natural and artificial, generates some kind ofwaste. This is well stated by the thermodynamic laws. Based on that, it can be said that it is impossible to develop a technology for any industrial process with complete elimination of wastes.

In other words the “zero waste” condition is an unreachable benchmark- Therefore all searches and develo ments lead to 20F waste” condition is an unreachable benchmark. Therefore all searches and developments lead to minimization, and not elimination, of the impact to the environment. Three approaches are considered on that purpose. The first one is, of course, the attempt to reduce the waste generation level. That results in both lowering the impact to the environment and improving the recovery from the starting materials.

However, as far as even the best technology doesn’t imply in a complete elimination, this approach never comes lone. Therefore the second and/or third approaches are always present. These are recycling and dumping, respectively. As a general rule, it can be said that in the first approach the main concerns are the technical and economical ones whereas in the other two, the enwronmental side is emphasized. Waste minimizing is already a concern in any plant and, in principie, there is no need on regulations to stimulate it.

In fact, the less waste is generated the higher are the yields, productivities and as a consequence, the better the technical and economical results. The environmental concern is a mere consequence. An example of that is the recovery of oxidized copper from the cover of sulfide ore bodies by means of heap leaching – SX – electrowinning improves the ratio metal/ore. That means that, for the same metal output, less ore must be mined, grinded and concentrated. These are the goals. As a consequence, fewer wastes are generated, but that wasn’t the main purpose for using that technology.

By far, the main concern was economical an 30F that wasn’t the main purpose for using that technology. By far, the main concern was economical and not ecological. Should this route doesn’t achieve the economical requirements it wouldn’t be pplied. For instance, the carbothermic reduction of aluminum in submerged arc furnaces is a proven processa Its adoption would avoid the generation of the hazardous SPL (Spent PotLining) and emissions of fluoride bearing fumes. However, the cost of the metal is greater than that produced by the Hall-Héroult process. Because of that the carbothermic way is not used.

Examples like these are copious in all kinds of industrial activities. Waste recycling can be considered from two points of view. The first one considers the ecological approach as a chief concern. The economics is a mere consequence. Should the operation bring some economical benefits, that would be good but it is just a coincidence. If not, there Will be an extra cost to be added, reducing or even impairing profits. Many plants shutdowns are a consequence of that. In a second point of view recycling is considered as a wayto generate new products or as a manner to recover lost values.

The term “product” means a good that can be used or sold in suitable technical and commercial conditions. Illustrating spent potlining from aluminum smelters can be used in cement kilns. In the present condition, the smelter pays to the ement plant for each ton burned. That is the first instance, as far as this means a cost addition to the metal. Even being a less worse alternative to stockpiling, is a co 40F means a cost addition to the metal. Even being a less worse alternative to stockpiling, is a cost increase factor.

On the other hand, if this material could be sold at a Price based on its energy content, this would result in earnings that would reduce the smelter costs. In that condition, the waste “SPL” would be turned to another product of the plant Waste dumping practice depends on the kind and amount of the waste. Here, dumping means any kind of disposal, from landfilling through storage in tight sealed buildings. It can be said that dumping is a last alternative i. e. , in an ideal situation this alternative would be adopted only in cases when, in the state of the art, there wouldn’t be a suitable appliance available.

Dumping can be done in two ways: in a selective manner, when the wastes are disposed separately, according to their characteristics or in a mixed form, when the wastes are put together or, at most, separated according to their pollutant potential. In the first instance, the possibilities of a future recovery, when arket conditions would be favorable and when available processing technologies would be avallable, Will be better. However, if there is an uncontrolled mix of diferent materials, that recovery Will be more difficult and more distant. n the following some proposed approaches on recycling and dumping are discussed.

RECYCLING/DUMPING/STORING There is no doubt that recyclin is the best alternative to unavoidable wastes. OF However, to take full advantage of this tool, it must be used cautiously. As pointed out herebefore, there are two kinds of recycling: those that implies in expenses and those that implies in proflts. The first one is based on the thinking that wastes are nothing but wastes and all that must be done is to get rid of it in a way that satisfies the regulations. In this case, the choice of the recycling way au lieu of the dumping one was based simply on the fact that the former was cheaper than the later.

Anyway, the production costs increase and so the consumers Price of the product. Unfortunately this is the prevailing condition in the industry. This comes both from misconceptions and some of what was called elsewhere Paranoia-Generation-Regulations (1 ). According to those, wastes are Iike outlaws that must be permanently atched. According to this conception, recycling would be like hiring an ex-outlaw. Like in the human version, the use of the waste looks more for the solution of a social problem and seldom takes into account its “skill”.

As a consequence, the use of natural resources is not optimized as well as the health of the industrial activity and, last but not least, this stimulates the trend of the potentially pollutant industries to move to regions where the regulations are sofrer. Naturally, this Will lead to a worsening of the Earth’s environment. Of course in many cases the “social solutions” are the best ones in he state of the art. What must be avoided is To consider that as a final solution and st 6 OF the art. What must be avoided is To consider that as a final solution and stopping the searching for the second kind of recycling. the second kind the waste IS considered like a material that has “skills”, that could be useful in the same facility or elsewhere. In other words it is a conventional good and is evaluated like this, taking into account its properties and shortcomings. In other words, it has its “rights” and “dutles”, as all common materials. The difference ofthis approach, compared to the previous, is hat if it is competitive both technically and commercially with its conventional concurrent, he Will be also a conventional good, doesn’t matter its origin.

In this condition, it Will be another product of the generator facilities that Will contribute to the industry revenues. This is a long-term solution. On the other hand if it does not achieve these requirements, in the state ofthe art, it Will keep on the condition of a non- profitable material, in the present conditions. In this case solutions as those referred previously. The difference is that these solutions are considered as provisory ones until the echnological development and/or the economical conditions turn it in a marketable product. There are many examples of the aforesaid situations.

Among them are the iron ore fines and the copper orebodies. In the past, the product of iron ore resources was the lump and pebble fractions. The size fractions below were mining wastes. With the purpose ofimprove the yields of the extraction, agglomeration techniques were develope With the purpose ofimprove the yields ofthe extraction, agglomeration techniques were developed. These are sintering and palletizing. New products were included to the mining mix: inter feed and pellet feed. Nowadays neither the most radical activist nor the tighter environment regulation thinks in those materials as wastes.

It is interesting to point out that when these solutions that are for good came on stream when the environmental subject wasn’t even taken into account. By the time ofWW II, the copper ores in the USA, to be considered as so, should have copper contents of about 1,5%. Forty years later this reference number dropped to 0,5%. In other words What was a non profitable material became a product. The same can be said about the offshore oil, slags from old opper smelters, etc. From the above comments, it can be pointed out that the dump policy should be reviewed.

The offshore petroleum and the low- grade copper ore bodies were made by the Nature and there is nothing to do about them. But the industrial wastes are manmade deposits and so those that made them are able to influence on their characteristics. If a natural copper ore body has an abnormal content of bismuth, this brings constraints for its use, but nobody can be charged for that. But if a rich slag is dumped together with a bismuth bearing converter dust that means a contamination that could be avoided nd Will make a future copper recovery more problematic.

This suggest that non profit wastes should have its characteristics preserved in their disposal places in ord 80F suggest that non profit wastes should have its characteristics preserued in their disposal places in arder to turn easier and earlier their recovery. n the following, considered the herebefore statements two new concepts are proposed. These are the “*fluent Mine” and the “Effiuent Plant” EFFLUENT MINE / EFFLUENT PLANT f the effluent is considered as a conventional good it comes from a resource and is processed In a plant.

Figure 1 shows that, comparing a natural raw material processing with one with an effluent. As can be seen in both cases the processing starts on the place were the ore was generated (by the nature or by the man), were it is mined (or collected) ending in its conditioning for use (ore or effluent dressing). n both cases, the technical and economical feasibility of their use is checked. Ifthe conclusions of these studies are positive, they are commercial products. If not they are respectively mineral occurrence and waste. If the conditions are changed further, the material looses or achieves the status of product.

Figure 1 – Comparison between natural and man made raw materials (2) done in a similar manner than a conventional raw material. A way to develop this was proposed by Professor Kazuhlro Ueta, from Kyoto University (3). According to him, a successful utilization of the residues as products, would depend on the four conditions, as follows: – The waste generated should be large in quantity – The waste should contain useful properties – The proper recycling technology should be available – There should be a market for the product As can be seen any conventional material must achieve these four conditions.

For illustrating purposes those steps Will be shown for a selected waste from the aluminum industry. This is the Red Mud from the alumina refinery. As known this is a hazardous wastes for which there is not a suitable solution at present. The uses considered in the example are in the iron and steel plants. Case Study – Red Mud n the Bayer Process, bauxite is leached in autoclaves by caustic soda. In this process aluminium goes in solution whereas the gangue material remains in an insoluble form. This fraction is the waste called Red Mud. The mechanism of formation of the Red Mud Mine is presented in figure 2. 0 DF 13