A large amount of research publications and analytical data, concerning gypsum-bearing wastes (GSW) gives an understanding of their huge volumes in many countries, as well as the urgent need to find solutions and opportunities that open up in the development and implementation of effective technologies for the disposal of GSW in various areas of the construction industry. In this paper, the review of actual technological approaches for recycling of GSW in the framework of such field of utilization as a gypsum binder production. It was found, that application of traditional technologies of synthesis of binders, containing natural raw materials is not reasonable for GSW-bearing binders due to variation in component composition, high concentration of impurities, and high dispersion. For this reason, the most advanced technologies proposed by various researchers provide for measures to correct these shortcomings or involve the synthesis of the final product - a high-quality gypsum binder, which is based on different principles - growing crystals of the desired geometry and properties in salt and acid solutions. These technologies are characterized by complexity, a negative impact on equipment, and personnel. In addition, they lead to the formation of secondary waste, which reduces the attractiveness of their practical implementation. Synthesis of GSW-bearing binders using the method of calcining is the simplest technologically and organizationally, but the binders are characterized by unsatisfactory physical and mechanical properties. The desired way to increase their profitability and investment attractiveness is the possibility of providing comprehensive processing of raw materials, where the final product will be not only binders but also other conditioned products, taking into account the minimum formation of secondary waste. The development of such technology of GSW recycling and its implementation on a commercial scale will allow increasing the volume of GSW recycling as well as to solve the ecological aspects and to expand the raw materials source base in regions where this problem is actual
rational environmental management is one of the priorities of the technological development of the Russian Federation and most countries of the world. Particularly important in this area is the work undertaken with previously generated and accumulated waste, a whole group of which is gypsum-bearing wastes (GBW), which includes by-products of various industries: phosphogypsum, borogypsum, chlorogypsum, ferrogypsum, citrogypsum, vitamin gypsum, etc. GBW features are similar compositions, prevalence, perennial volumes of stored reserves with stable dynamics of annual growth. This determines the relevance of research on the development of a unified methodology for converting GBW of various types into target products particularly for construction purposes, providing maximum energy efficiency and minimal generation of secondary waste. The starting point of the research is the monitoring of approaches developed by the scientific community which are presented in the article. It is shown that researchers are exploring several main areas of GBW conversion: components of Portland cement and clinker; single and multicomponent binders; direct raw materials for the production of building materials; and road construction. The latter two directions have the greatest potential capacity for the consumption of GBW. The general level of research on the issue is not exhaustive, but has the potential to improve on existing methods of processing and application and promote the search for new and more efficient methods
Gypsum binders are among the most environmentally friendly from the point of view of their production. The raw material base for their production is represented not only by natural raw materials, but also by a wide variety of technogenic materials, phosphogypsum is the most multi-ton and studied of them. At the same time, citrogypsum is also a promising raw material for the production of gypsum binders and, in comparison with phosphogypsum, does not contain toxic impurities that require the development of additional measures for their removal. Synthesis of the binder from gypsum-containing waste is possible with the use of various technologies using autoclaves, chemical reagents and at elevated temperature and atmospheric pressure. Each method has its own advantages and disadvantages. The most acceptable from the point of view of industrial production is the method of calcination at atmospheric pressure, but it does not allow producing high-strength binders and products based on them. It is possible to increase the efficiency of using such binders for the production of small-piece products by applying special molding modes with increased pressing pressure. The possibility of obtaining a binder from the waste of citric acid – citrogypsum production by calcination in a semi-industrial plant is shown. Using standard methods, a complete analysis of the resulting binder was performed: granulometry, grain shape and morphology, normal density and setting time. A comparison was made with construction gypsum (G5) and high-strength gypsum (G16). The possibility of obtaining small – piece products from a synthesized binder with a dry compressive strength of 20 MPa is shown by using the semi-dry pressing method at high pressures.
In the modern world, outer space is an object of research in various fields of scientific activity. One of these spheres is plant breeding, i.e. cultivation of higher plants, as they are the most promising from the side of use as photosynthetic organisms. The use of nutrient media in which agar-agar, basalt wool, microcellulose can be used as a thickener is considered for plant life support. Also, 1.5 ml of 2-ip hormone was added to all substrates to stimulate plant growth. It was found that using agar-agar as a nutrient thickener in an amount of 15 g/l, allows the best growth and development of plants obtained by microclonal propagation under microgravity conditions. In addition, mechanical tests of nutrient media with agar-agar as a thickener determined the resistance to external factors, because the resulting substrate does not yield to indentation, deformation and fluidity.
The paper proposes a method for calculating the main design parameters and operational characteristics of the HPEC using the Helmholtz equations of state. N-pentane, freon R11, and acetone were considered as the working fluid. The calculations were performed using the CoolProp 6.3.0 library. It was found that the most profitable for HPEC operating on the Rankin cycle with low-potential sources is n-pentane. LD expander operation and mass flow rate of the working fluid are calculated. The calculations were performed using the freely distributed open source library CoolProp 6.3.0. The calculations show that the most profitable WF for HPEC running on the Rankin cycle with low-potential sources is n-pentane. It is determined that the increase in costs when the temperature decreases before the SD is due to a decrease in the level of operation of the Lд expander, which in turn depends on the value of the steam enthalpy at the entrance to the ex-pander.
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