Sulfur is one of the most common elements of the earth's crust. Most often, it is found in minerals containing metals besides it. Very interesting are the processes that occur when the boiling and melting points of sulfur are reached. We will analyze these processes, as well as the difficulties associated with them, in this article. But first, let's plunge into the history of the discovery of this element.
History
In its native form, as well as in the composition of minerals, sulfur has been known since antiquity. Old Greek texts describe the toxic effects of its compounds on the human body. Sulfur gas released during the burning of compounds of this element can indeed be deadly to humans. Around the 8th century, sulfur began to be used in China for the preparation of pyrotechnic mixtures. It is not surprising, because it is in this country, as it is believed, that gunpowder was invented.
Even in Ancient Egypt, people knew the method of roasting copper-based sulfur-containing ore. Thus, this metal was mined. Sulfur was removed as a toxic gas, SO 2 .
Despite the fame from ancient times, the knowledge of what constitutes sulfur came from the work of the French naturalist Antoine Lavoisier. It was he who established that it is an element, and its combustion products are oxides.
Here is such a brief history of the acquaintance of people with this chemical element. Next, we will talk in detail about the processes taking place in the bowels of the earth and leading to the formation of sulfur in the form in which it is now.
How does sulfur appear?
There is a common misconception that most often this element is found in a native (i.e. pure) form. However, this is not quite true. Native sulfur is most often found as interspersed in another ore.
At the moment, there are several theories regarding the origin of the element in its purest form. They suggest a difference in the time of formation of sulfur and ores into which it intersperses. The first, the theory of syngenesis, involves the formation of sulfur together with ores. According to her, some bacteria that live in the ocean, reduced sulfates in the water to hydrogen sulfide. The latter, in turn, went up, where it was oxidized to sulfur using other bacteria. It fell to the bottom, mixed with silt, and subsequently they formed ore together.
The essence of the epigenesis theory is that sulfur in the ore was formed later than itself. There are several branches. We will only talk about the most common version of this theory. It consists in this: groundwater, flowing through accumulations of sulfate ores, is enriched by them. Then, passing through oil and gas fields, sulfate ions are reduced to hydrogen sulfide due to hydrocarbons. Hydrogen sulfide, rising to the surface, is oxidized by oxygen in the air to sulfur, which deposits in the rocks, forming crystals. This theory has recently found more and more evidence, but so far the question of the chemistry of these transformations remains open.
From the process of the origin of sulfur in nature, we turn to its modifications.
Allotropy and polymorphism
Sulfur, like many other elements of the periodic table, exists in nature in several forms. In chemistry, they are called allotropic modifications. There is sulfur rhombic. Its melting point is slightly lower than that of the second modification: monoclinic (112 and 119 degrees Celsius). And they differ in the structure of unit cells. Rhombic sulfur is more dense and stable. When heated to 95 degrees, it can go into the second form - monoclinic. The element we are discussing has analogues in the periodic table. Scientists are still discussing the polymorphism of sulfur, selenium, and tellurium. They have a very close relationship with each other, and all the modifications that they form are very similar.
And then we will analyze the processes that occur during the melting of sulfur. But before you start, you should plunge a little into the theory of the structure of the crystal lattice and the phenomena that occur during phase transitions of matter.
What does a crystal consist of?
As you know, in a gaseous state, matter is in the form of molecules (or atoms) moving randomly in space. In a liquid substance, its constituent particles are grouped, but still have a sufficiently large freedom of movement. In a solid state of aggregation, everything is a little different. Here, the degree of ordering increases to its maximum value, and the atoms form a crystal lattice. In it, of course, oscillations occur, but they have a very small amplitude, and this can not be called free movement.
Any crystal can be divided into unit cells - such sequential compounds of atoms that are repeated in the entire volume of the sample compound. It is worth clarifying that such cells are not a crystalline lattice, and here the atoms are located inside the volume of a certain figure, and not at its nodes. They are individual for each crystal, but they can be divided into several main types (syngonium) depending on the geometry: triclinic, monoclinic, rhombic, rhombohedral, tetragonal, hexagonal, cubic.
We briefly analyze each type of lattice, because they are divided into several subspecies. And we begin with how they can differ from each other. Firstly, it is the ratio of the lengths of the sides, and secondly, the angle between them.
Thus, the triclinic syngony, the lowest of all, is an elementary lattice (parallelogram) in which all sides and angles are not equal to each other. Another representative of the so-called lower category of syngonium is monoclinic. Here, two corners of the cell are 90 degrees, and all sides have different lengths. The next species belonging to the lower category is rhombic syngony. It has three unequal sides, but all the corners of the figure are 90 degrees.
Let's move on to the middle category. And its first member is tetragonal syngony. Here, by analogy, it is easy to guess that all the angles of the figure that it represents are 90 degrees, and also two of the three sides are equal to each other. The next representative is rhombohedral (trigonal) syngony. Everything is a little more interesting here. This type is defined by three identical sides and three angles that are equal to each other but not straight.
The last option of the middle category is hexagonal syngony. Its definition is even more complex. This option is built on three sides, two of which are equal and form an angle of 120 degrees, and the third is in a plane perpendicular to them. If we take three cells of hexagonal syngony and attach them to each other, then we get a cylinder with a hexagonal base (which is why it has such a name, because "hexa" in Latin means "six").
Well, the peak of all syngonies, which has symmetry in all directions, is cubic. She is the only one in the highest category. Here you can immediately guess how it can be characterized. All angles and sides are equal and form a cube.
So, we have finished the analysis of the theory for the main groups of syngonies, and now we will talk more about the structure of various forms of sulfur and the properties that follow from this.
Sulfur structure
As already mentioned, sulfur has two modifications: rhombic and monoclinic. After a section with the theory, it probably became clear how they differ. But the whole point is that, depending on the temperature, the lattice structure can change. The whole point is in the very process of transformations that occur when the melting point of sulfur is reached. Then the crystal lattice is completely destroyed, and atoms can more or less freely move in space.
But back to the structure and characteristics of such a substance as sulfur. The properties of chemical elements largely depend on their structure. For example, sulfur, by virtue of the characteristics of the crystal structure, has the property of flotation. Its particles are not wetted by water, and air bubbles adhering to them pull them to the surface. Thus, lump sulfur floats when immersed in water. This is the basis for some methods of separating this element from a mixture of the like. And then we will analyze the main methods of extraction of this compound.
Production
Sulfur can occur with various minerals, and therefore, at different depths. Depending on this, different production methods are chosen. If the depth is shallow and there are no accumulations of gases underground that interfere with production, then the material is mined in an open way: layers of rocks are removed and, finding ore containing sulfur, they are sent for processing. But if these conditions are not met and there are dangers, then the downhole method is used. It is necessary that the melting point of sulfur is reached. For this, special installations are used. A lump sulfur melting apparatus is simply necessary in this method. But about this process, a little later.
In general, when sulfur is extracted in any way, there is a great risk of poisoning, because most often along with it there are hydrogen sulfide and sulfur dioxide, which are very dangerous for humans.
To better understand what disadvantages and advantages this or that method has, we will get acquainted with the methods of processing sulfur-containing ore.
Extraction
There are also several tricks based on completely different properties of sulfur. Among them, thermal, extraction, steam-water, centrifugal and filtration are distinguished.
The most proven of them are thermal. They are based on the fact that the boiling and melting temperatures of sulfur are lower than that of ores into which it "wedges". The only problem is that a lot of energy is spent. To maintain the temperature, earlier it was necessary to burn part of the sulfur. Despite all its simplicity, this method is ineffective, and losses can reach a record 45 percent.
We are following the branch of historical development, so we move on to the steam-water method. Unlike thermal, these methods are still used in many factories. Oddly enough, they are based on the same property - the difference between the boiling and melting points of sulfur from similar indicators for related metals. The only difference is how the heating occurs. The whole process goes to autoclaves - special installations. Enriched sulfur ore is supplied there, containing up to 80% of the mined element. Then, hot water vapor is pumped into the autoclave under pressure. Warming up to 130 degrees Celsius, sulfur melts and is removed from the system. Of course, the so-called tails remain - particles of sulfur floating in the water formed due to condensation of water vapor. They are removed and put back into the process, since it also contains a lot of the element we need.
One of the most modern methods is centrifugal. By the way, it was developed in Russia. In short, its essence is that the melt of the mixture of sulfur and minerals with which it accompanies is immersed in a centrifuge and spins up at a high speed. The heavier rock, due to centrifugal force, tends from the center, and the sulfur itself remains higher. Then the obtained layers are simply separated from each other.
There is another method that is still used in production to this day. It consists in the separation of sulfur from minerals through special filters.
In this article, we will consider exclusively thermal methods for extracting an element that is undoubtedly important for us.
Melting process
The study of heat transfer during the melting of sulfur is an important issue, because it is one of the most economical ways of extracting this element. We can combine the system parameters when heated, and we need to calculate their optimal combination. For this purpose, heat transfer research and analysis of the features of the sulfur melting process are carried out. There are several types of installations for carrying out this process. A sulfur melting boiler is one of them. Obtaining the desired element using this product is only an auxiliary method. However, today there is a special installation - a lump sulfur melting apparatus. It can be effectively used in production to produce high-purity sulfur in a large volume.
For the above purpose, in 1890, an installation was invented that allowed melting sulfur at a depth and pumping it to the surface using a pipe. Its design is quite simple and effective in action: two pipes are in each other. Overheated up to 120 degrees (melting point of sulfur) steam circulates through the outer pipe. The end of the inner pipe reaches the deposits of the element we need. Heated with water, sulfur begins to melt and go outside. Everything is quite simple. In the modern version, the installation contains another pipe: it is inside the pipe with sulfur, and compressed air flows through it, which makes the melt rise faster.
There are several more methods, and in one of them the melting point of sulfur is reached. Two electrodes are lowered into the ground and a current is applied through them. Since sulfur is a typical dielectric, it does not conduct current and begins to heat up very much. Thus, it is melted and, using the pipe, as in the first method, is pumped out. If they want to send sulfur to the production of sulfuric acid, then it is burned underground and the resulting gas is taken out. It is oxidized to sulfur oxide (VI), and then dissolved in water, obtaining the final product.
We examined the melting of sulfur, sulfur melting plants and methods for its extraction. Now it's time to find out why such complex methods are needed. In fact, an analysis of the sulfur melting process and a temperature control system are needed in order to clean and effectively apply the final product. After all, sulfur is one of the most important elements that play a key role in many areas of our lives.
Application
It makes no sense to say where sulfur compounds are used . It’s easier to say where they do not apply. Sulfur is found in any rubber and rubber products, in the gas that is supplied to the house (there it is needed to identify a leak in case of such). These are the most common and simple examples. In fact, there are countless applications for sulfur. Listing them all is simply unrealistic. But if we take it upon ourselves, it turns out that sulfur is one of the most essential elements for humanity.
Conclusion
From this article, you learned what is the melting point of sulfur, why this element is so important to us. If you are interested in this process and its study, then you must have learned something new for yourself. For example, it may be features of the melting of sulfur. In any case, there is no limit to perfection, and none of us will be hindered by knowledge of the processes occurring in industry. You can independently continue to master the technological subtleties of the processes of extraction, extraction and processing of sulfur and other elements contained in the earth's crust.