Technologies for the Comprehensive Exploitation of the Geothermal Resources of the North Caucasus Region

Technology for the integrated development of low-temperature geothermal resources using the thermal and water potentials for various purposes is proposed. The heat of the thermal waters is utilized in a low-temperature district heating system and for heating the water in a hot water supply system. The water cooled in heat exchangers enters a chemical treatment system where it is conditioned into potable water quality and then forwarded to the household and potable water supply system. Efficient technologies for removal of arsenic and organic contaminants from the water have been developed. For the uninterrupted supply of the consumers with power, the technologies that use two and more types of renewable energy sources (RESs) have the best prospects. Technology for processing organic waste using the geothermal energy has been proposed. According to this technology, the geothermal water is divided into two flows, one of which is delivered to a biomass conversion system and the other is directed to a geothermal steam-gas power plant (GSGP). The wastewater arrives at the pump station from which it is pumped back into the bed. Upon drying, the biogas from the conversion system is delivered into the combustion chamber of a gas-turbine plant (GTP). The heat of the turbine exhaust gases is used in the GSGP to evaporate and reheat the low-boiling working medium. The working medium is heated in the GSGP to the evaporation temperature using the heat of the thermal water. High-temperature geothermal brines are the most promising for the comprehensive processing. According to the proposed technology, the heat energy of the brines is utilized to generate the electric power at a binary geothermal power station; the electric power is then used to extract the dissolved chemical components from the rest of the brine. The comprehensive utilization of high-temperature brines of the East-Precaucasian Artesian Basin will allow to completely satisfy the demand of Russia for lithium carbonate and sodium chloride.     

Technologies for the exploration of highly mineralized geothermal resources

The prospects of the integrated processing of the high-parameter geothermal resources of the East Ciscaucasia of artesian basin (ECAB) with the conversion of their heat energy into electric energy at a binary geoPP and the subsequent extraction of solved chemical compounds from thermal waters are evaluated. The most promising areas for the exploration such resources are overviewed. The integrated exploration of hightemperature hydrogeothermal brines is a new trend in geothermal power engineering, which can make it possible to significantly increase the production volume of hydrogeothermal resources and develop the geothermal field at a higher level with the realization of the energy-efficient advanced technologies. The large-scale exploration of brines can solve the regional problems of energy supply and import substitution and fulfill the need of Russia in food and technical salt and rare elements. The necessity of the primary integrated exploration of the oil-field highly mineralized brines of the South Sukhokumskii group of gas–oil wells of Northern Dagestan was shown in view of the exacerbated environmental problems. Currently, the oil-field brines with the radioactive background exceeding the allowable levels are discharged at disposal fields. The technological solutions for their deactivation and integrated exploration are proposed. The realization of the proposed technological solutions provides 300 t of lithium carbonate, 1650 t of caustic magnesite powder, 27300 t of chemically precipitated chalk, 116100 t of food salt, and up to 1.4 mln m³ of desalinated water from oil-field brines yearly. Desalinated water at the output of a geotechnological complex can be used for different economic needs, which is important for the arid North Caucasus region, where the fresh water deficiency is acute, especially in its plain part within the ECAB.     

Heat Exchangers for Utilization of the Heat of High-Temperature Geothermal Brines

The basic component of two-circuit geothermal systems is the heat exchanger. When used in geothermal power systems, conventional shell-and-tube and plate heat exchangers cause problems related to the cleaning of the latter from salt-deposition and corrosion products. Their lifetime does not exceed, as a rule, 1 year. To utilize the heat of high-temperature geothermal brines, a heat exchanger of the “tube-in-tube” type is proposed. A heat exchanger of this design has been operated for several years in Ternair geothermal steam field; in this heat exchanger, the thermal potential of the saline thermal water is transferred to the fresh water of the secondary circuit of the heating system for apartment houses. The reduction in the weight and size characteristics of the heat exchangers is a topical problem that can be solved with the help of heat transfer enhancers. To enhance the heat transfer process in the heat exchanger, longitudinal ribbing of the heat exchange surface is proposed. The increase in the heat exchange surface from the heat carrier side by ribbing results in an increase in the amount of the heat transferred from the heating agent. The heat exchanger is easy to manufacture and is assembled out of components comprised of two concentrically positioned tubes of a definite length, 3–6 m, serially connected with each other. The method for calculation of the impact of the number and the size of the longitudinal ribs on the heat transfer in the well heat exchanger is presented and a criterion for the selection of the optimal number and design parameters of the ribs is formulated. To prevent the corrosion and salt deposition in the heat exchanger, the use of an effective OEDFK (oxyethylidenediphosphonic acid) agent is proposed. This agent has a long-lasting corrosion-inhibiting and antiscaling effect, which is explained by the formation of a strongly adhesive chelate layer difficult to wash off the surface. The passivating OEDFK layer is restored by periodical pulsed introduction of the agent solution into the brine at the heat exchanger inlet.     

Choice of optimal working fluid for binary power plants at extremely low temperature brine

The geothermal energy development problems based on using binary power plants utilizing lowpotential geothermal resources are considered. It is shown that one of the possible ways of increasing the efficiency of heat utilization of geothermal brine in a wide temperature range is the use of multistage power systems with series-connected binary power plants based on incremental primary energy conversion. Some practically significant results of design-analytical investigations of physicochemical properties of various organic substances and their influence on the main parameters of the flowsheet and the technical and operational characteristics of heat-mechanical and heat-exchange equipment for binary power plant operating on extremely-low temperature geothermal brine (70°С) are presented. The calculation results of geothermal brine specific flow rate, capacity (net), and other operation characteristics of binary power plants with the capacity of 2.5 MW at using various organic substances are a practical interest. It is shown that the working fluid selection significantly influences on the parameters of the flowsheet and the operational characteristics of the binary power plant, and the problem of selection of working fluid is in the search for compromise based on the priorities in the field of efficiency, safety, and ecology criteria of a binary power plant. It is proposed in the investigations on the working fluid selection of the binary plant to use the plotting method of multiaxis complex diagrams of relative parameters and characteristic of binary power plants. Some examples of plotting and analyzing these diagrams intended to choose the working fluid provided that the efficiency of geothermal brine is taken as main priority.     

Combined cycle power unit with a binary system based on waste geothermal brine at Mutnovsk geothermal power plant

The Russian geothermal power systems developed in the last few decades outperform their counterparts around the world in many respects. However, all Russian geothermal power stations employ steam as the geothermal fluid and discard the accompanying geothermal brine. In reality, the power of the existing Russian geothermal power stations may be increased without drilling more wells, if the waste brine is employed in combined cycle systems with steam and binary turbine units. For the example of the 50 MW Mutnovsk geothermal power plant, the optimal combined cycle power unit based on the waste geothermal brine is considered. It is of great interest to determine how the thermodynamic parameters of the secondary steam in the expansion unit and the pressure in the condenser affect the performance of the equipment in the combined cycle power unit at Mutnovsk geothermal power plant. For the utilization of the waste geothermal brine at Mutnovsk geothermal power plant, the optimal air temperature in the condensers of the combined cycle power unit is +5°C. The use of secondary steam obtained by flashing of the geothermal brine at Mutnovsk geothermal power plant 1 at a pressure of 0.2 MPa permits the generation of up to 8 MW of electric power in steam turbines and additional power of 5 MW in the turbines of the binary cycle.     

World Geothermal Congress WGC-2015

This article discusses materials and results of the World Geothermal Congress that was held in Melbourne (Australia) from April 19 to April 25, 2015. Information on the extent and technological features of utilization of geothermal resources for heat supply and power production, as well as in other economic areas, is given. A stable growth in the capacity and number of geothermal power systems that is determined by ecological cleanliness, economic efficiency, and the highest (among renewable energy sources) indicators of installed capacity utilization is shown. It was noted that combined schemes of geothermal power plants (GPPs), such as turbine units of different type (binary units, units with one or two separation pressures, etc.), have become more frequently used to increase the efficiency of utilization of geothermal heat carrier. Actual data determining room heating systems with the total worldwide capacity of nearly 50000 MW thermal (MWt) as the most currently significant segment of consumption of geothermal waters are given. In addition, geothermal resources are also utilized in soil pumps, balneological and sports basins, greenhouse complexes, and other manufactures. It was noted that geological studies were carried out in more than 40 countries, with the development of methods of simulation of tanks for the existing and new geothermal fields. Trends of development and the role of geothermal power engineering in the energy supply of many countries are shown. It was shown that prospects for the development of geothermal power generation are significantly associated with utilization of low-temperature geothermal sources in binary power generating units, as well as with the increase in installed capacity of operating geothermal power plants (GPPs) without drilling additional wells, i.e., by using waste geothermal heat carrier in binary-cycle or combined-cycle power plants. The article provides data on a pilot binary power unit at Pauzhetka GPP and on a promising Russian geothermal project to increase the installed capacity of Mutnovsk GPP (whose current capacity is 50.0 (2 × 25.0) MW of electric power) by 25% by constructing a combined binary-cycle power generating unit on the basis of waste separate utilization.     

Evaluating the Effect from Constructing Binary Geothermal Power Units Based on Spent Petroleum and Gas Boreholes in the South Regions of Russia

The article substantiates the possibility of efficiently harnessing the geothermal resources available in the North Caucasian region through constructing binary geothermal power plants (GeoTPPs) using idle petroleum and gas wells. The power capacities of GeoTPPs are evaluated, and the basic characteristics of these power plants in case of constructing them in the promising areas are determined. The overall useful GeoTPP capacity equal to approximately 330 MW can be obtained from using the entire fleet of idle wells available in these areas. Diagrams confirming the possibility of reaching the optimal flowrate of geothermal heat carrier circulating in the geothermal circulation system loop are presented. This flowrate corresponds to a binary GeoTPP’s maximal useful power output. The article shows, taking the Ternair geothermal field as an example, that it is inefficient to use medium-enthalpy thermal waters for generating energy at a binary GeoTPP involving reinjection of a spent heat carrier. It is shown that good prospects can be expected from applying a hybrid geothermal and combined-cycle technology, by means of which it is possible to use lowenthalpy (80–100°С) thermal waters for generating electricity in a highly efficient manner. In accordance with such technology, geothermal heat is used in the binary GeoTPP cycle for heating low-boiling working fluid to its evaporation temperature. The working fluid is evaporated and superheated by using the heat of exhaust gases from a gas turbine power unit. Owing to combined use of the thermal water heat potential and the heat of exhaust gases from a gas turbine power plant in a hybrid process system, it becomes possible to obtain high power performance indicators of hybrid geothermal and combined-cycle power plants. This conclusion is confirmed by the results from numerical evaluations carried out as applied to the Ternair geothermal field. With the fully harnessed resource potential of the Ternair field, the total capacity of hybrid geothermal and combined-cycle power plants may reach 60 MW, a level that would make it possible to relieve a significant part of energy, environmental, economic, and social problems faced by the city of Makhachkala.     

Modern geothermal power: GeoPP with geothermal steam turbines

The first part of the review presents information on the scale and specific features of geothermal energy development in various countries. The classification of geothermal power plant (GeoPP) process flow diagrams by a phase state of the primary heat source (a geothermal fluid), thermodynamic cycle, and applicable turbines is proposed. Features of geothermal plants using methods of flashing and steam separation in the process loop and a flowsheet and thermodynamic process of a geothermal fluid heat-to-power conversion in a GeoPP of the most widespread type using a double-flash separation are considered. It is shown that, for combined cycle power units, the specific power-to-consumption geothermal fluid ratio is 20–25% higher than that for traditional single-loop GeoPP. Information about basic chemical components and their concentration range for geothermal fluids of various formations around the world is presented. Three historic stages of improving geothermal energy technologies are determined, such as development of high-temperature geothermal resources (dry, superheated steam) and application of a two-phase wet-steam geothermal fluid in GeoPP power units with one or two expansion pressures and development of binary cycle GeoPPs. A current trend of more active use of binary power plants in GeoPP technological processes is noted. Design features of GeoPP’s steam turbines and steam separating devices, determined by the use of low-potential geothermal saturated steam as a working medium, which is characterized by corrosion aggressiveness and a tendency to form deposits, are considered. Most promising Russian geothermal energy projects are determined. A list of today’s most advanced geothermal turbine performance technologies is presented. By an example of a 25 MW steam turbine design, made by JSC Kaluga Turbine Works, advantages of the internal moisture separation with a special turbine-separator stage are shown.     

Improving the efficiency of nuclear and geothermal power stations by using low environment temperatures

The possibilities of improving the efficiency of geothermal and nuclear power stations through the use of low environmental temperatures are considered. It is shown that replacing water, which is traditionally used as a working medium for the thermal power cycle, by an ammonia-water mixture (the Kalina’s cycle) or another substance that does not freeze at condensation temperatures ranging from ?30 to ?40°C allows the capacity of both nuclear and geothermal power stations to be increased substantially during most of the year.     

Kinetics of growth of calcium carbonate deposits in geothermal systems

Results from field investigations into the processes through which suspended particles are formed in geothermal water as a consequence of upset in carbonic acid equilibrium, as well as processes through which solid deposits of calcium carbonate are formed on the inner surfaces of geothermal equipment, are reported.     

Chemical resistance of electrical insulating epoxyisocyanates compound

The chemical resistance of hardened epoxyisocyanate compound to alkalis, acids, sodium carbonate, and chloride solutions, as well as to hot water, is examined. According to the test results, the compound can be classified as a chemically resistant substance and recommended for application in the insulating systems of electrical machines that operate under conditions with increased chemical contamination, as well as for electrical machines used in seagoing ships.     

Problems relating to operation of geothermal power stations stemming from the presence of admixtures in the geothermal heat carrier

The effects the specific features of chemical composition and the thermophysical properties of geothermal heat carrier have on the metal erosion-corrosion processes and on the formation of deposits during operation of a geothermal power station are analyzed. Methods for preventing the formation of deposits and making the geothermal power station equipment more resistant to erosion and corrosion are considered. Results from calculation and experimental investigations aimed at studying how the concentration of silicic acid and other admixtures vary in the working loop and turbine flow path at the Verkhne-Mutnovsk geothermal power station are presented. The possibility of using surface-active inhibitors to prevent the formation of deposits and erosion-corrosion processes in the geothermal power station equipment is demonstrated.     

Erosion-corrosion of metals in multicomponent geothermal flows

A classification of mechanisms governing the destruction of the metals of equipment operating at geothermal power stations is proposed. Basic similarity criteria and regularities of the physicochemical processes pertinent to erosion-corrosion of metals in multicomponent geothermal flows are determined. Results obtained from field erosion-corrosion tests at geothermal power stations are presented.     

金属有机框架材料用于锂电池负极的研究进展

金属有机框架材料(MOFs)因高孔隙率、结构可控和氧化还原活性可调等特点被广泛应用于锂离子电池负极的研究。分析了近几年来MOF基材料在锂电池负极的研究进展;指出MOF基材料固有的多孔结构有利于锂离子迁移,金属中心和有机配体可以作为氧化还原物质使用,具有孔隙可逆储锂和可逆化学反应储锂两种不同的储锂机制;讨论了近几年来MOF基衍生物、复合物在锂电池负极的应用;展望了MOFs在锂电池负极的发展前景。     

Carbon film covering originated from fullerene C60 on the surface of lithium metal anode for lithium secondary batteries

Carbon films from fullerene C₆₀ were coated on the surface of lithium metal for the anode of lithium secondary battery. In order to investigate the relationship between the electrochemical characteristics of the carbon films and deposition technique, three different vacuum techniques were employed such as RF (radio frequency)—magnetron sputtering of C₆₀, plasma assisted thermal evaporation of C₆₀ and ion beam assisted thermal evaporation of fullerene C₆₀. From the physical and chemical characterization tests, we found that the carbon films produced by those above techniques mainly consist of sp²/sp³ hybridized amorphous carbons. Electrochemical tests implied that the cyclic performance was enhanced by the fullerene C₆₀ coating on lithium metal anode in comparison to the pure lithium metal one. This enhanced performance is due to the formation of thin carbon film on the surface of lithium metal anode which plays a role as a passive layer against the side reaction between lithium metal and the electrolyte.     

地热发电简述

目前世界上实际能利用的地热资源很少,主要限于蒸汽田和热水田,这两者统称为地热田。地热蒸汽田以蒸汽为主,温度较高,一般为160℃以上,可将地热蒸汽田的蒸汽直接引入普通汽轮机发电。地热热水田则以热水为主,温度较低,一般为50～160℃,这就需要将地热水中的热能转换成地热蒸汽引入普通汽轮机发电。地热电站既没有燃料运输设备,也没有庞大的锅炉设备,所以也就没有灰渣和烟气对环境的污染,是比较清洁的能源。地热发电站发电后排出的热水,可供诸如采暖、医疗、洗涤、提取化学物质和农业养殖。地热发电成本较水电、火电都低。     

锂离子电池中炭负极的表征手段

阐述了锂离子电池炭负极的表征手段，重点介绍了XRD、拉曼光谱、FTIR、XPS、XRF等分析方法在炭负极材料表征中的应用。     

油田抽油机智能节电器的设计与应用

抽油机是油田生产中的主要设备,一般抽油机的电动机功率都超过实际负载功率,即留有较大余量,在运行中处于大功率带小负载的情况。电动机在抽油机上行时处于有功工作状态,下行时处于发电状态,平均有功功率较低,造成很大浪费。主要对抽油机用新型智能节电器的原理及应用进行了分析。     

硅基负极材料预锂化技术研究进展

从物理预锂、化学反应预锂和电化学预锂等方面,综述硅基负极材料预锂化技术的研究进展.物理预锂包括:与金属锂粉末直接混合法,将气态的金属锂沉积在硅基负极材料或集流体上的真空热蒸发法,将金属锂负载在集流体上的电化学沉积法;化学反应预锂包括:溶液预锂法,将硅制成硅化锂的高能球磨法,将预锂化前驱体生成稳定LixSiyOz结构的高...     

纳米科学技术在化学电源领域的新进展

９０年代纳米科学技术特别是纳米材料的应用已经扩展到化学电源领域。本文举例介绍了用于镍－碱性电池的纳米相氢氧化镍、ＡＢ５型纳米晶态贮氢合金以及在锂离子电池中用作阴极材料的锰钡矿型ＭｎＯ２纳米纤维、聚吡咯包覆尖晶石型ＬｉＭｎ２Ｏ４纳米管、聚吡咯／Ｖ２Ｏ５纳米复合材料,用作阳极材料的碳纳米管、纳米掺杂碳材料、纳米二氧化锡,用作固态电解质的纳米填料修饰聚氧乙烯基复合材料等几种新型纳米化学电源材料的制备、结构、形貌以及电化学性质,并且简要介绍了厦门大学化学电源研究中心纳米材料的研究进展。