We live in the industrial age, when the materiality of the world around us is being more and more impetuously involved into the bottomless scope of consumer interests. There are more things around us made of radically transformed elements of inanimate nature. They are plastics, and metals, and glass, and various composites. They are in a huge amount, but insatiable consumption thirst requires more and more...
Consuming delightedly the environment converted for their needs, people don’t think a lot about the price of such a global alteration. But they really should. Because in the process of getting 1 ton of material with improved consumer characteristics up to 10 tons of much degraded material – so-called industrial waste – are inevitably formed. This inevitability is dialectical by its nature, and with the existing human approach to the material resources it is impossible to circumvent it. As a result, very soon industrial humanity will definitely drown in its own life wastes. The first paroxysms of this are already shaking inhabited world. The red sludge reservoir spill in Hungary, land poisoning by sprawling oil shale ash in the Baltics, dust storms attacking cultivated fields from the coal TPP ash damps, moon landscape of spoil tips and lifeless slagheaps – that is a non-exhaustive list of attributes of industrial prosperity seamy side, which increasingly spoil its attractive face.
What is the fundamental problem of human present approach to resources? It consists in utility in a narrow sense: every element of the material world is considered like a source of a single useful product. Aluminum oxide is extracted from bauxite, iron oxide – from iron ore, combustibles – from coal. All the rest – even if there were gold with diamonds – is ruthlessly sent to the dumps. It is easier and, until recently, it was cheaper.
Today humanity is beginning to pay off for this simplicity and cheapness of yesterday humanity. People are starting to realize that they have to do something with these millions of tons of wastes. The attempts to solve this problem are even being made, but, as before, the narrow understanding of the issue considerably narrows the range of possible solutions. The most commonly taken decision is to bury! Just to remove out of sight. And then – let tomorrow humanity worry about this.
We claim that the only way to solve the problem of industrial waste drastically is their complete separation into market demanded products. The key concept here is "complete", because if during the waste processing some other wastes are produced, we simply replace at the dump one hazardous waste by another one, often more dangerous. Furthermore, this is the only way that makes waste control profitable, unlike knowingly non-profitable attempts to use waste as a source of one valuable product (or properties), in accordance with the old paradigm.
We propose to consider our approach in the context of utilization of some widespread kinds of waste.
Ash and slag from coal burning.
(Ash is a polymineral source of the future)
It is not a secret that the industrial revolution became possible due to development of coal as an energy source. Moreover, since the beginning of this revolution and up to date coal has been the main, and until the 20th century – the only highly concentrated source of energy for the needs of industry and energy production. Widespread use of coal has led to the fact that the world has accumulated huge amounts of coal burning residues – ash and slag. These wastes are traditionally stored in ash dumps, which tend to grow, reducing the already scarce habitable land area. They are trying to use ash and slag mainly for backfilling of the waste pits and abandoned mines, bedding of the road bases, as an aggregate to concrete – like an inert material such as sand and gravel. But ash is not inert, it is a very active substance. Under the influence of rain water, air and sun many chemical processes run in it. Some of them can destroy concrete where ash was imprudently added. Others lead to the extraction of toxic heavy metals soluble compounds – in particularly, mercury. These compounds get into the water and poison the agricultural lands.
At the same time, the ash contains practically all the elements of the periodic table, including rare and precious metals. It is often unprofitable to extract them according to the old paradigm – as the only target product – because of their low content, and it is not solving the problem of ash as a waste.
The picture changes if we consider the ashes as a multicomponent source. As a result of its processing by our proposed technologies the oxides of silicon, aluminum, iron and calcium are obtained as the main products, being of sufficiently high purity. It is very important and significantly increases their market value. Thus, the value of technical silicon oxide is a few dollars per ton. And a value of pure silicon oxide in the form of "white carbon" is 1000 times higher.
Except the basic oxides, during complete separation of ash by components it becomes possible to select and utilize minority impurities. And they include more interesting compounds: these are titanium dioxide, and vanadium oxides, and compounds of scandium, and rare earth metals, and platinum group metals, and silver and gold...
According to conservative estimation, the products obtained during the separation of 1 ton of ash have a market value of about $ 2,000. But some ashes contain so many impurities that the value of recycled ash exceeds $ 10,000 per ton.
Red sludge.
Red sludge is a large tonnage waste generated during the obtaining of alumina from bauxites by the method of Bayer: obtaining of 1 ton of alumina is accompanied by the formation of more than 2 tons of red sludge. This waste is an aggressive highly alkali slurry which is stockpiled in the large sludge reservoirs; there are no ideas what to do with it. The storages are periodically destroyed, which leads to big environmental catastrophes.
Today the main way of red sludge disposal, taking into account the high content of iron in it, is the processing of red sludge into cast iron. But this process is complicated because, unlike iron ore, sludge is very difficult to enrich, it has to be remelted with the "empty" mineral part, which leads to the accumulation of new waste – metallurgical slag. Furthermore, other valuable components are not selected in this process.
But red sludge contains valuable components, and they are very interesting ones. These are platinum group metals, and scandium, and titanium, and zirconium, and rare earth elements. Depending on the origin of the bauxites, the price of the elements contained in red sludge (upon condition that they separated into the pure substances) is approximately from 5 to 12 thousand dollars.
Shale ash.
Unlike oil and coal, containing a lot of energy, but quite rare, oil shale is rather widespread, but is relatively poor of energy. If the ash content in quality coal is less than 10-15%, such index for shale is 3-4 times as high. Accordingly, the quantity of ash produced during shale burning is 3-4 times higher than during coal burning. In addition, shale ash contains a lot of lime and free calcium oxide that makes it highly aggressive substance.
Originally there were two directions of shale ash utilization: production of building materials (high content of calcium oxide allows to consider shale ash as a kind of lime analogue, though not of very high quality – a large number of impurities spoils color) and swamp soils deoxidation. However, the second way demonstrated soon its fallacy: because of the high content of heavy metals in the ash and ease of their assimilation by plants in acidic soils, among the people who used these plants the epidemic of chronic poisoning had began, up to the mass cases of children’s alopecia. So, today such application is abandoned.
Our technology allows dividing shale ash into high-quality pure snow-white lime, pure silicon, aluminium and iron oxides, as well as separating in pure form impurity elements, such as titanium, zirconium, molybdenum and other substances worth a total of 5000 dollars per ton.
Thus the concept of processing we propose consists in complete separation of industrial waste into its constituent elements. All of these substances, being obtained in pure form, are in demand and have a high market value, which provides a profitability of processing. In addition, the territory of the former waste storage becomes completely free and can be reshaped for the construction or agriculture, which significantly increases the value of the land.
The concept is based on the package of technologies basing on hydrometallurgical processes with the mandatory recycling of active reagents. One of the main characteristics of our solutions is refusing to use highly aggressive reagents, like concentrated acids, which reduces the risk of man-made environmental disasters in case of emergency situations. Another important quality is complete absence of wastes and effluents; the processing material is separated and recycled completely. For each type of waste we select its processing sequence allowing optimizing the processing and minimizing time and energy expenditure.