Conversion of Steam Turbine Plants to Adiabatic Phase Formation as a Condition for Technical Progress in Power Engineering

S. V. Polozhii

(Presented by the scientific seminar of the Department of Thermal Power Plants)

A distinctive potential feature of the development of domestic power engineering is the development at the Tomsk Polytechnic Institute of steam turbine plants with adiabatic phase formation, as the only method known so far for eliminating the degradation of the traditional second-law cycle; the presence of theoretical studies of the traditional cycle and the establishment of its degradation as an objective law of development of modern power engineering, as well as of the causes of erroneous technical decisions and forecasts in power engineering [1, 2, 3].

The theoretical studies, conclusions, and forecasts of TPI in the field of the development of power engineering with the traditional second-law cycle over the last one and a half decades are well confirmed by the entire practice of development of world power engineering.

The formulation of the problem of the STP APF and its development throughout these years have fully justified themselves and have been enriched with new advantages of steam turbine plants with adiabatic phase formation for the power engineering of the future.

For the first time, a new type of power plant has been discovered and developed in which the increase in thermal efficiency, in and of itself, without concentration of generating capacities and centralization of power supply, is associated with a reduction in material and labor costs, with the cheapening and simplification of power equipment, the thermal scheme and the technological process, operating conditions and mode of operation, with a sharp reduction in the calculated costs of producing electric power under the real conditions of developing power systems in comparison with known power plants using organic and nuclear fuels.

For the first time, an effective power plant of maximum universality has been developed. Complete universality with respect to fuel—for solid, liquid, and gaseous fuel, both high-grade and low-grade fuel, as well as nuclear fuel.

Broad universality with respect to capacity and purpose—from effective low-capacity plants to plants of enormous capacity for regional power stations and combined heat-and-power plants, stationary and marine plants, for thermal power stations and nuclear power stations.

High universality with respect to operating modes and maneuverability, for both low and high capacities, with a high level of efficiency in generating electric power not only in the base-load portion, but also in the variable portion of the load schedules of power systems; in para-

parameters, thermal, technological, and startup schemes, and in the main and auxiliary equipment—uniformity in design, in production technology, and in the metal used.

The efficiency of thermal power plants with adiabatic phase formation considerably exceeds the efficiency of modern block-type supercritical-pressure thermal power plants in the base operating mode, owing to the low cost of the power equipment and the high thermal economy of installations with adiabatic phase formation. In the variable part of the load schedules, the calculated costs of producing electric energy in installations with adiabatic phase formation are reduced still more substantially, by one and a half to two times, and the specific fuel consumption by 50–200 g/kWh, as compared with modern thermal power plants.

The conversion of the power-machine-building industry to the production of installations with adiabatic phase formation will lead to technical progress in this branch of industry—the production of low-temperature supercritical-pressure boilers from carbon steel instead of expensive once-through boilers made of alloy steel, single-shaft low-temperature AF turbines instead of the cylinders for supercritical steam parameters of modern block-type thermal power plants, and the abandonment, in block-type thermal power plants, of equipment for superhigh and supercritical parameters made of high-alloy steel.

The conversion of power engineering to adiabatic phase formation eliminates the need to solve numerous problems in the development of thermal power plants and power systems with the traditional second-region cycle at the stage of its degradation, problems connected with the incompatibility of block-type supercritical-pressure thermal power plants with the conditions and requirements of power systems in different operating modes.

The introduction of adiabatic phase formation into power engineering can be carried out in the shortest possible time not with additional capital investments, but with the release of material and labor resources associated with the modern path of development of power engineering with the traditional second-region cycle. The degree of readiness of AF steam-turbine plants for their introduction is at a level that excludes the element of risk or the impossibility of achieving the calculated operating indicators of such installations within the shortest possible time.

The continuing delay in solving the problem of converting thermal power plants to adiabatic phase formation, and in developing on an industrial scale and introducing steam-turbine installations with adiabatic phase formation into power engineering, is causing great damage, the magnitude of which continuously increases as power engineering and the scale of electric-power production in the country develop further, with the ever increasing degradation of the traditional second-region cycle.

The idea of converting steam-turbine installations to adiabatic phase formation and work on this problem evoked the most negative attitude from the proponents of the traditional direction of thermal-power-plant development with the modern steam-power cycle. Only thanks to the support of the scientific and technical community of Siberia, and especially of the power systems of Siberia, which financed these studies at TPI under contractual topics, was it possible to complete these works up to the stage of industrial testing and implementation, to publish the basic materials, and to register the results at the Center in the form of research reports under contractual and state-budget topics and informational bulletins of TPI.

In working on this problem it was necessary to generalize numerous data on the shortcomings and difficulties in the development of modern power engineering with the traditional second-region steam-turbine cycle abroad and in our country. This is one of the initial questions for the conversion of thermal power plants to adiabatic phase formation. Herein lies the essence of the historical neces-

necessity of replacing the traditional cycle with the AP cycle in present-day and future power engineering. These studies ultimately made it possible to discover the law of the inevitable complete degradation of the traditional steam-turbine cycle of region II in future power systems, of the inevitable regress in the development of classical thermal power engineering in the next 15–20 years, with the complete transfer of steam-turbine TPPs into the variable part of electric-power-system load schedules.

Knowledge of this law plays a major role in the rational development of modern power engineering; it indicates the necessity of an immediate rejection of the construction of only unit-type TPPs for base-load purposes with supercritical pressure, and of the development and introduction of special maneuverable TPPs that are uneconomical but cheaper for the variable part of electric-power-system load schedules, which in 10–15 years must become the principal type of power installations in thermal power engineering in combination with base-load nuclear power-plant units. This law also indicates the impossibility of solving the problem of technical progress in thermal power engineering on the basis of modern cycles and installations without converting power engineering to adiabatic phase formation.

The discovery of this law also makes it possible to reveal empiricism in the development of power engineering, the causes of erroneous technical decisions and forecasts in the past for the present time and in the present time for the future. As a result, it becomes obvious that already at present power systems are operating irrationally, that there is a need to transfer and operate base-load units with high and supercritical steam conditions in semipeak load, for which these units are technically unsuitable and techno-economically inexpedient. For this reason a catastrophic situation is maturing for the Unified Energy System—the power systems of the Center and of the Northwest, which are saturated with base-load TPPs and have flattened load schedules.

Modern thermal power engineering is developing in accordance with this law of degradation of the traditional cycle of region II, and failure to take it into account leads to great material damage, to a nonoptimal structure of generating capacities, hampers the operation of power systems, and reduces the reliability of power supply.

In foreign practice, as in our country, at present all the forces of scientific and technical potential are directed toward seeking, within the framework of the traditional cycle, a more rational development of power engineering under the new conditions, with the task of avoiding an excessively negative effect when unit-type base-load TPPs are transferred into the variable part of electric-power-system load schedules, and of preventing a sharp decline in the reliability and efficiency of electricity production in the variable operating mode of unit-type TPPs.

For modern steam-turbine installations with the traditional cycle of region II, the new conditions of development of power engineering and electric power systems require abandonment of the basic principle of classical thermodynamics, of the successes achieved in power engineering over previous decades and realized in modern high-capacity unit-type TPPs with high and supercritical steam conditions, and, in particular, of the maximum increase in the thermal efficiency of steam-turbine installations, which was the driving force of technical progress throughout the past history of thermal-power development. At the present stage, and still more so for the power engineering of the future, in installations with the traditional cycle of region II the principle is being implemented of a deliberate reduction in the thermal economy of TPPs and in the thermal efficiency of the cycle by returning to lower steam parameters, lowering the reheat temperature or completely abandoning reheat, increasing the exhaust steam pressure, and simplifying or abolishing regenerative heating of feedwater. Only in this way is it possible to increase the efficiency of modern and especially

future thermal power engineering with the traditional cycle of region II, at the stage of its final degradation, as TPPs move into the variable portion of the load schedules of power systems.

This is explained by the fact that, for a small number of hours of utilization of installed capacity when operating in the variable part of the load schedule, PPSs require a comprehensive reduction in capital investments, simplification and cheapening of installations, which can be accomplished for modern TPPs only by abandoning the thermodynamic achievements of contemporary power engineering, as well as the heat-engineering and design achievements in power-machine building embodied in base-load supercritical-pressure units. To this end, simultaneously with the rejection of high thermal efficiencies, the thermal economy of the boiler unit is reduced: the temperature of the exhaust gases is lowered, the velocities of the heat carrier and the temperature differences are increased. For the same reason, the relative internal efficiency of the turbine is reduced: the number of stages is decreased, the governing stage is abandoned, and a number of design measures are taken that cheapen and simplify the steam turbine at the expense of its thermal economy. As a result of all these measures, the reliability of such TPPs increases and their cost decreases; such installations acquire maneuverability and mobility—the basic requirements for TPPs in future power systems.

The development of unit TPPs with supercritical pressure and the traditional cycle of region II has concentrated within itself the entire scientific and technical potential of the developed countries of the world, the highest scientific authorities and research institutes in the field of power engineering and other branches of industry connected with the traditional direction of power development. Nevertheless, the development of power engineering proceeds with allowance for errors both in forecasts and in technical decisions, in everyday practice as well as in the strategic direction: the creation of power units technically unsuitable for operation, and the planning of technical progress without sufficient anticipation of the deterioration in the efficiency of electric-power production in future power systems.

The point is that this entire established system, the entire scientific and technical potential and technical policy in the field of power engineering in the developed countries of the world, are directed toward the implementation of an ineffective path of thermal-power development, one that is incapable of ensuring genuine technical progress in the power engineering of the future at the stage of final degradation of the traditional cycle of the second region.

From the standpoint of the modern direction of development of steam-turbine TPPs with the traditional cycle of region II, obtaining a net efficiency in a condensing steam-turbine installation with a temperature of only 380–390°C, without primary and secondary steam superheating, equal to the efficiency of modern supercritical-pressure units, is incredible.

No less incredible, from the standpoint of the traditional path of power-engineering development, is the possibility of achieving in AP installations the record thermal economy of modern supercritical-pressure units by means of many-fold (by tens of times for individual elements of power equipment) reduction in the cost of equipment in comparison with modern supercritical-pressure TPPs with the traditional cycle of region II. The same assessment also applies to the achievement of high maneuverability and reliability of large units with adiabatic phase formation.

The practical realization of steam-turbine installations with adiabatic phase formation will lead, as we see it, to positive changes, the essence of which consists in a return to very

low steam temperature in the cycle of the steam-power plant (380–390°C), the abandonment of the use of superheated steam in power engineering, and the reduction of requirements imposed on the metal of power installations, which were characteristic of power engineering at the end of the last and the beginning of the present century, with a simultaneous increase in the efficiency of electric-power production in comparison with the contemporary technical-and-economic level of its production in the most developed countries of the world.

REFERENCES

1. S. V. Polozhii. Degradation of the traditional steam-turbine cycle—the principal trend in the development of world power engineering. This collection.

2. S. V. Polozhii. Degradation of the traditional cycle of the second region in domestic power engineering. This collection.

3. L. A. Melent’ev, K. D. Lavrenenko. On the selection of efficient equipment in the variable part of load schedules of electric-power systems. Teploenergetika, 1971, No. 3.