The practical value of the work is to solve problems related to the reduction in the cost of hardware design production process: the development of cheaper ways to clean the inner surface of the pipes from the sediments, increasing the productivity of pipe leaching, to find optimal balance between rising temperatures, decreasing consumption of alkali and increasing output of alumina (up to 2 -3%) due to improvement output. Main results Aluminum is prevalence in nature among metals it ranked first on the practical use - the second (after iron). abundance aluminum is 8.05%, which is equivalent to Al2O3 is about 15%. For the production of alumina in the world, the following ores: bauxite, nepheline, alunite, kyanite and kaolin. However, the principal ore is bauxite. Depending on what aluminum hydroxides predominate, bauxite divided into hydroxide (Al₂O₃ • H₂O) - and bemtomite diaspore and trinitride (Al₂O₃ • 3H₂O) - gibbsite. Under the terms of the field of education, divided into lateritic bauxite (65% of total world reserves), or polygenic crust (20%) and sedimentary (15%) Literite bauxite often have a Cenozoic age and were formed in the tropical countries where it concerns Nigeria. Nigeria is located on the west end of the Guinea shield, within which more than 640 known lateritic bauxite deposits and occurrences. Total reserves of the region are estimated at 13 billion tons with an average grade of about 48% Al2O3. The mineral composition of ores mainly gibbsite in addition, in this area and found the field too polygenic gibbsite structure. Geological exploration of bauxite deposits in Nigeria has been nearly three decades ago. However, due to lack of equipment and, primarily, instruments for chemical analysis of ores seriously this issue developed last 5-6 years. At present, developed and mastered several fields. Of which the Ore is one of them (taken for study) has the average composition of the main components,%: Al₂O₃ - 48,08; SiO₂ - 18,90; TiO₂ - 1,26; Fe₂O₃ - 7,71. Silicon module of this ore is 2.53 (almost one of the lowest in the world for use of bauxite). In addition, it contains a minimal number of other impurities such as zirconium, manganese, potassium, etc. This greatly reduces the cost of alumina production. In the mining and metallurgical complex of Nigeria for the production of alumina using the Bayer process
The process consists of the following technological process stages: milling, leaching, sedimentation of red mud; expansion aluminate solution, filtering the hydrate of aluminum oxide, drying and calcining aluminum hydroxide to produce alumina residue other solutions and to obtain solids. The main stage production of alumina from bauxite ore is ripped out of her aluminum hydroxide. It is based on the following chemical property of aluminum oxide hydrate: crystalline aluminum hydroxide, which is part of bauxite, is highly soluble at high temperature in a solution of sodium hydroxide (caustic lye, NaOH), high concentration and with decreasing temperature and concentration of the solution re-crystallizes. Useless to produce aluminum materials that are part of bauxite (the so-called ballast) is not transferred at the same time in a soluble form or recrystallized, and precipitated before the crystallization of aluminum hydroxide is produced. Therefore, after the dissolution of aluminum hydroxide ballast can be separated and removed in a dump. Purified from impurities in the aluminum hydroxide solution of alkali (representing mainly a solution of sodium aluminates NaAlO₂ undergoes crystallization. To this end, the concentration of alkali and the solution temperature is reduced to certain values that are optimal for obtaining crystalline aluminum hydroxide. Crystallization substantially accelerated if the solution already presents crystals of aluminum hydroxide of sufficient size (embryos). Therefore, at this stage in a solution specially introduced a certain amount of fine-crystalline aluminum hydroxide, which is called a seed. After a sufficient degree of crystallization is separation from the solid hydroxide solution. Alumina (Al₂O₃) is obtained from aluminum hydroxide (Al(OH)₃) calcinations in furnaces last (calcinations) to remove bound water of the hydrate, leaching autoclave used scheme. The purpose of further this research is the development of tubular leaching cheaper for hardware design. HIGH TUBULAR leaching. Leaching at temperatures above 280 ° C, commonly called high temperature. High-temperature autoclave leaching has not found distribution of the high cost of autoclaves operating at a pressure of 60-100 atm. High leaching began to spread only after the development of Installation of tubular leaching, in which leaching occurs when moving slurry in the pipe long (1 km). Pipe length is determined by performance and holding time. Heating is provided by heat exchange on a "pipe-in-tube" (the main pipe is enclosed in another tube). Coolant (hot steam or boiled pulp) is moving in the annulus.

Conclusions of research

The advantages of tubular autoclave leaching before the following: simplicity, since it uses the serial production of high pressure tubes, rather than the thick-walled vessels of stainless steel, designed and manufactured by special order; no need for mixing devices: the pulp is mixed due to turbulence moving through the pipes of small cross section; for heating the pulp is used almost the entire surface of the pipe, and not only the surface of heat exchangers tubes, as is the case in an autoclave. The disadvantages of tubular variant can include the following: A large area of the pipe placement (but it can be reduced if the tube placed in several levels); difficulty of cleaning the internal surfaces of precipitation; in this case malfunction a mechanical cleaning method is mainly used and chemical cleaning by special agents; but it increases the cost of production and causes environmental problems.