About the NewChem-method and the NewChem-technologies
Why is it relevant?
A common disadvantage of the majority of modern chemical and hydrometallurgical technologies is their high material and energy consumption. To a great extent, this is a consequence of the imperfection of those mass-exchange processes that underlie them. Let us explain what this is about.
In order to carry out a chain of redistributions and to obtain chemical products from raw materials, it is necessary, as it is known, to first carry out leaching, i.e. transfer of mineral components of this raw material into solution. The majority of the processing methods widely used in hydrometallurgy are based on the decomposition of mineral raw materials by concentrated acids, with subsequent separation of target components from the resulting solution. In this case, inevitably, it becomes necessary to remove excess acidity from the reaction system to create conditions for precipitation and filterability of the working media. The process of neutralizing the resulting highly acidic productive solution by traditional methods means irreversible losses of both a significant part of the acid and an expensive alkaline agent. In addition, there is an additional secondary contamination of the solution by the products of their interaction. As a result, the quality of the resulting products suffers, and the whole process becomes energy-consuming, multi-stage and labor-intensive.
Experts know that more than 30% of all energy consumption in the chemical industry is just that “extra” energy, which is forcedly spent due to the discrepancy between the real industrial process and the theoretically possible (perfect one). This situation is typical for a number of industries where “wet” chemistry is widely used, in particular, for non-ferrous metallurgy.
A typical example is acid technologies for processing of low-quality aluminum-containing raw materials to obtain pure metallurgical alumina. Due to the existing large-scale shortage of high-quality bauxite suitable for processing by the classical “Bayer” method, such technologies are now very relevant both for Russia and for many other countries of the world. Despite a number of attractive qualities, acidic methods in the aluminum industry still haven’t not got industrial application due to the increased consumption of chemical reagents, as well as increased energy consumption.
Similar problems are observed in the production technologies of some other non-ferrous metals, as well as strategically important rare and rare earth elements. In the production of metals by the electrochemical method, as it is known, it is difficult to obtain pure elements that meet international requirements in one conversion. For example, almost all enterprises of the former Soviet Union producing refined copper cannot get registered now at the LME with the official status of "Good Delivery" due to the insufficient quality of their products. The reason of the quality problems mainly lies in the usual technological contamination of their working electrolytes at the refining stage. At the same time, due to the presence of free sulfuric acid in these electrolytes, their purification is a very difficult task. As a rule, copper producers solve it in a fairly simple but costly way - by periodical replacement of the contaminated electrolyte with a new one.
Another example. In the production of mineral fertilizers, as well as in the chemical industry as a whole, the traditionally weak point is the formation of mixed acidic solutions that require further processing and disposal. In some cases, large volumes of liquid wastewater and sludge have to be stored in sedimentation tanks, allocating special areas for them with the threat of their destruction and negative impact on the surrounding ecosystem, or spending considerable additional costs to neutralize them.
Thus, today, the improvement and optimization of mass-exchange processes in acidic media is one of the most pressing relevant chemical and technological problems, the solution of which is of general industrial importance.
How has the problem been solved until today?
If we talk about the effectiveness of the above mass-exchange processes, it is determined by the following interrelated factors:
• how close is the consumption of reagents, in particular - acids, to the stoichiometric one?
• how the regeneration of the used acids and the removal of free acid from the working solution are organized?
For decades, the efforts of several generations of scientists and specialists, chemical engineers, technologists have been aimed at finding an effective solution to these problems.
One of such potentially attractive directions is thermohydrolysis of metal salts formed during acid decomposition of mineral raw materials. In the elaborations of the Tananaev KSC RAS devoted to the development of the nitric acid method of nepheline processing (Zakharov V.I., Matveev V.A.) it is proposed, for example, to carry out the hydrolysis of sodium and potassium nitrates and the subsequent synthesis of nitric acid in a special high-tech device - a plasmatron - at the temperatures above 1000 ⁰С. A significant drawback of this approach is the obvious complexity and high cost of the special equipment involved, as well as the high energy consumption required for its operation.
Several years ago, the Canadian company Orbite Aluminae Inc announced the development of an acidic process for processing of aluminum-containing raw materials based on thermohydrolysis of chloride salts with hydrochloric acid recycling. Publicly available data and publications on this issue are still insufficient to draw final conclusions about the effectiveness of the Canadian process. However, given the high aggressiveness of hydrochloric acid vapors generated during thermohydrolysis of chloride salts, it is clear that its implementation will require very expensive corrosion-resistant equipment. In addition, the method is only applicable to the hydrochloric acid processes.
In the 60s of the last century, in an attempt to solve the characteristic problems of traditional acidic methods of processing mineral raw materials in the United States (Hatch M.J., Dillon J.A.), a new interesting approach was discovered, which is called the “Ion exchange method” or “Acid retardation”. The method consists in the fact that when a mixture of acid and its salts is passed through the anion exchanger, the latter are separated due to the effect of stronger retention of the acid in the ion exchanger. The separation of the solution is carried out on the surface of the granules of the sorption material. In this case, however, a significant part of the useful product still remains in solution.
The “Acid retardation” method has not found industrial application for a long time due to problems with longitudinal dispersion inside the sorption column. As was further shown by K. Brown, the acid retardation method becomes effective for practical use only if special conditions for the process are provided, which make it possible to exclude the free volume in the ion exchanger layer available for the processed electrolytes.
Further development of the ion extraction method took place, thus, through reducing the free volume of the processed solution in the space between the sorbent granules. To this end, the Canadian Company EcoTec Inc. (K. Brown et al.) modernized the method and developed special equipment in which a sorbent of a special quality with similar small grains was used.
An increase in the efficiency of separation of the solution and the extraction of a useful product is achieved with a significant (up to 30 atm.) increase in the pressure inside the column with the sorbent.
As a result, the sorbent granules are flattened from a spherical shape almost into cubes, thereby increasing the sorption surface, and the free space between the sorbent granules is significantly reduced.
The disadvantages of this modernization of the “Acid retardation” method, called by its authors the “Recoflo Method”, are the cumbersomeness, complexity and high energy consumption of the installation for its implementation, as well as the high consumption of expensive sorption material.
What is the approach of the NewChem Technology LLC?
A quantum leap in the development of acidic methods for processing of mineral raw materials became possible several years ago in Russia, after the specialists from the NewChem Technology (Moscow) invented a new unique method for carrying out mass-exchange sorption processes for the separation of electrolytes and other aqueous solutions of inorganic substances (the “NewChem” method), which is devoid of the above disadvantages of the AR-method.
A distinctive feature of the "NewChem" method in comparison with the "Acid retardation" method is the use of a sorption system with two liquid phases: aqueous and organic, which makes it possible to eliminate the free space in the separating sorption column in a much simpler way, thereby avoiding erosion effects due to longitudinal dispersion.
In the Newchem method, unlike the EcoTec method, the problem of extending the contact area of the solution and the sorbent and reducing the intergranular free space is solved at normal atmospheric pressure by filling the space between the granules with a special liquid organic substance that repels the solution. When an acid-salt solution is passed through a sorption system organized in such a way, the electrolyte is infused at the interface between the organic liquid and the granule surface, forming a nanoscale dynamic film that envelops each sorbent granule and flows down through the points of contact between the granules. In fact, this leads to an increase in the contact area of the solution and the sorbent by hundreds and thousands of times, as well as to a reduction in the sorption cycle. In this case, there are no blurring effects associated with the influence of longitudinal dispersion, and the sorption layer is stabilized in a rather narrow range of linear values. The use of this mechanism makes it possible to achieve the reagent-free separation of acid from salts at an early stage (with its return to the cycle) in the concentrated solutions of electrolyte mixtures formed after leaching, which radically changes the picture of the ongoing chemical process. Thus, previously unattainable conditions are created for the subsequent selective low-reagent effect on the working solution in order to separate the contained chemical components stage-by-stage (for the technology of processing of aluminum-containing raw materials, for example, separation of iron as the component closest in properties and polluting aluminum).
The advantage of our approach is also the possibility of working with colloidal systems, provided by the use of the phenomenon of stabilization of supersaturated solutions of slightly soluble substances in micropores and dense layers of sorption materials (the IXISS-effect).
The NewChem method helps to reduce the energy intensity of the processes in two ways: on the one hand, it allows using the above phenomenon of isothermal supersaturation and work with supersaturated solutions - without additional energy consumption for the phase formation, and on the other hand, it is deprived of the drawbacks of the Brown’s “clamped layer” described above, requiring high pressure and high energy consumption.
In practical terms, the application of the NewChem method provides a key to a significant simplification of many technological schemes for chemical processing of mineral raw materials using acids and significantly increases the economic attractiveness of such processes.
Another important result achieved by the NewChem Technology and which is complementary to the NewChem method - is the development of an original “acid-salt” method of opening mineral raw materials with subsequent regeneration of the leaching agent. The peculiarity of this method is that the decomposition process is carried out not with the help of an acid, but with the help of a certain composite based on a mixture of this acid and its salt. In combination with the NewChem-method, this approach makes it possible to practically create reagent-free closed processing cycles in many important hydrometallurgical and chemical processes, including those mentioned above. Now the promising “acid-salt” method of processing mineral raw materials has already been patented in Russia and is being patented in a number of other countries.
What can our innovations give?
It is well known that breakthrough technical innovations are possible only on the basis of qualitatively new scientific ideas and approaches. The NewChem Technology fully shares this idea, therefore, we are trying to develop competitive chemical technologies, relying on the most advanced scientific achievements.
In this sense, the NewChem method, as an effective technological method based on the use of a fundamentally new mass-exchange process, is a good example of how a sound scientific idea can lead to very useful practical results, in fact, to the improvement of the entire group of chemical technologies dealing with acid-salt solutions.
Over the past several years, the Newchem Technology has carried out a significant work both on the development of the theoretical aspects of the new proposed mass-exchange processes, and on the engineering design of the developed technological solutions in relation to various industrial problems.
The result of this work was the original scientific, technical and engineering solutions embodied in more than 10 Russian and foreign patents, as well as applied technological products that can become an effective tool in the hands of production workers in the future.
For more information on the technological developments of the NewChem Technology LLC with the use of the NewChem method see sections “Technological developments”, “Patents