PROCEEDINGS

of the Tomsk Polytechnic Institute named after S. M. Kirov,
holder of the Order of the October Revolution and the Order of the Red Banner of Labor

Volume 205

1972

REVISITING THE APPLICATION OF ADIABATIC PHASE FORMATION IN STEAM-TURBINE UNITS

S. V. Polozhii

(Presented by the Department of Thermal-Power Installations)

Technical progress in world and domestic power engineering over the last 15–20 years has been determined by the modern steam-power cycle—through the transition of thermal power engineering to superhigh and supercritical steam parameters, the use of complex regenerative heating of feedwater, one or two reheatings of steam, along with the broadest progress in the production of the main and auxiliary equipment of unit-type thermal power stations, and the exceptionally high concentration and centralization of electric-power production in unit installations of enormous capacity. As a result, there has been a sharp improvement in the technical and economic indicators of electric-power production at thermal power stations—a reduction in the specific fuel consumption, in the initial and current capital investments for the construction and operation of thermal power stations, and in the cost of producing electric power. The development of Soviet power engineering is proceeding at an especially high rate. In our country, electric-power production doubles every 6–7 years—2–3 years faster than the world doubling time for electric-power production.

Within the framework of the existing steam-power cycle, the modern direction of development of thermal power engineering and the technical policy in this field are, undoubtedly, correct and have been proven by the entire course of development of world and domestic power engineering over the past two decades. The low technical level of development of thermal power engineering in the previous period is especially vividly emphasized by the high technical and economic indicators of powerful unit-type thermal power stations with superhigh and supercritical parameters. The latter circumstance is one of the reasons for satisfaction with this path of development of thermal power engineering and for an uncritical attitude toward the shortcomings of the modern steam-power cycle. This largely accounts for the underestimation, by supporters of the modern steam-power cycle, of the work of the Tomsk Polytechnic Institute on steam-turbine units with adiabatic phase formation, as well as for the development of modern unit-type thermal power stations in the initial period of world power engineering at practically unsuitable steam temperatures. As a result, U.S. power engineering, as early as the beginning of the 1960s, after 6–8 years of mastering and operating such high-temperature units at 600–650°C, was forced to abandon them completely and subsequently proceed to the construction of powerful units with a low initial steam temperature on the order of

538°C. The same happened with the power industry of the FRG, and later with the power industry of the USSR.

The Seventh World Energy Conference (Moscow, 1968) in fact summed up the present state of development of large unit thermal power plants of superhigh and supercritical pressure, gave an objective assessment of the modern steam-power cycle and of its limited possibilities for ensuring a further increase in the thermal economy of thermal power plants.

The work of the World Energy Conference in this respect must be assessed positively for the development of thermal power plants with adiabatic phase formation, as more effective for the development of domestic and world power engineering [1—4].

Enormous difficulties and high costs were involved in mastering in our country a steam temperature of 565°C—lower than that previously used in the USA—in superhigh-pressure units of 150 and 200 MW in the last seven-year period. Still greater efforts and additional material expenditures were required for the development and operation of 300 MW units at a steam temperature of 560°C under supercritical pressure, introduced into service in the last seven-year period, the main units of the current and subsequent five-year plans.

As a result of the impossibility of achieving the design performance indicators of such units (in terms of thermal economy, number of hours of utilization of installed capacity, operating reliability and cost, and other indicators), in 1968, after many years of operation of such units, a decision was made temporarily to reduce the steam temperature in supercritical-pressure units of 300, 500, and 800 MW to 540°C. This decision in fact summed up the discouraging results of the many-year stage of mastering and operating 300 MW units with a steam temperature of 560°C and marked the transition of the domestic power industry, as had previously happened in the power industry of the USA and other countries, to a low steam temperature in large units of supercritical and superhigh steam pressure. An even more striking example of the shortcomings of the modern steam-power cycle may be the stagnation in the reduction of specific fuel consumption over the last 5–6 years in a number of developed capitalist countries, and above all in the USA—the leading power-engineering country of the world. The saturation of the U.S. power industry with the most powerful and modern units in the world did not lead to the expected reduction in the country’s specific fuel consumption. Over the last five years, the specific fuel consumption in the U.S. power industry not only did not decrease, but even rose somewhat—from 361 g/kWh in 1963 to 363 g/kWh in 1967.

In England, over the last six years, the substantial commissioning of large units also did not provide a reduction in the country’s specific fuel consumptions, which have remained stable at the level of 440–445 g/kWh.

It is especially noteworthy that abroad there has been a reassessment of the capabilities of modern units. Many power engineers of the world now regard new units as the final stage in the development of classical thermal power engineering before its replacement by nuclear power stations and MHD installations; they have also arrived at the conclusion that the capabilities—the “ceiling”—of modern units at a low steam temperature of 535–540°C are limited. Enormous material expenditures and many years of varied work on the development, mastery, and operation of units with superhigh steam temperature were required in order to convince the world power industry of the erroneousness of developing such units for a superbarrier initial steam temperature. This “barrier” temperature of the modern steam-power cycle proved to be 90–110°C lower than that which had begun to be mastered a decade and a half ago, and 150–200°C lower than that predicted by thermal power engineers in the past-

...as a whole at the present time—the 1960s and 1970s. This is the regression of the modern steam-power cycle, the absolute untenability of any further substantial technical progress in thermal power engineering on the basis of such a cycle, and the objective conditions for transferring thermal power engineering to adiabatic phase formation as a more progressive path for the development of thermal power engineering.

It is now especially obvious that the recommendations of the leading research organizations of our country—ENIN, TsKTI, VTI, MEI, and others—made back in the 1950s, to convert the national power industry to “superhigh” steam temperatures of 580–650°C were erroneous. In this connection, it is also worth recalling the unjustified optimism of the participants in the 1965 meeting on steam-turbine units with adiabatic steam formation at ENIN in Moscow (ENIN, TsKTI, VTI, MEI), who asserted that there were broad prospects for further raising the initial parameters and the thermal economy of modern domestic units, and on this basis denied the relevance of TPI work on converting the power industry to adiabatic phase formation. The transition of the power industry to unit installations, both abroad and in our country, was formerly based on the technically and economically unjustified high thermodynamic efficiency of the modern steam-power cycle with a superhigh initial steam temperature, and on the calculated (theoretical) performance indices of such units under base load, without a corresponding in-depth analysis of the real possibilities of achieving and the feasibility of realizing such calculated indices for units, without scientifically substantiated forecasts, and without sufficient analysis of new problems and ways of solving them both for the units themselves and for power systems and the country as a whole.

In ensuring this new stage in the development of thermal power engineering in the highly developed countries of the world, enormous work has been done in all directions, before which the scale and scientific achievements of the previous period pale. However, neither the high level of organization of scientific research, nor the unprecedented scale of these studies in the past, nor the great efforts of the operating personnel of thermal power stations and power systems, of installation, commissioning, and other organizations and of the power-engineering industry, nor the high technical level of the developed countries made it possible to overcome the shortcomings of the modern steam-power cycle and to realize the high theoretical efficiency of the cycle with a superhigh temperature of 580–650°C and pressures of 300–350 ata, with which the new stage in the development of power engineering in the developed countries of the world began.

The difficulties and shortcomings in the development of unit installations with the modern steam-power cycle, as well as of power systems and thermal power engineering as a whole, are now well known.

1. The periods required to master the design performance indices of unit installations proved to be many times greater than had been assumed and accepted when the units were designed. Moreover, units with a steam temperature above 560°C, with which the new stage in the development of thermal power engineering began in the developed countries of the world, proved to be economically inexpedient and technically unjustified.

2. An unprecedentedly low reliability of unit operation in the history of power engineering, an inadmissibly high accident rate, and a small number of hours of utilization of installed capacity over many years and even a decade; enormous underproduction of electric power, large additional capital investments in the power industry, and losses in industry over long periods of mastering and operating unit installations.

3. The complete unsuitability, inapplicability, and inexpediency of unit operation under variable conditions and partial loads.

sharply worsens the economic performance of the units themselves, of the country’s power systems and power industry as a whole; leads to the widespread use, for peak and semi-base loads, of uneconomical thermal power plants of the previous period of construction and of special low-efficiency peak thermal power plants; and makes it impossible to reduce the specific fuel consumption over many years, despite the intensive annual increase in unit capacity in the country (USA, England, etc.).

1. Optimization of the efficiency of unit installations did not precede the introduction of units, but in the overwhelming majority of cases was carried out and revealed itself in the process of mastering and operating the units, and has dragged on for many years and has still not been completed:

a) initial steam parameters—the introduction of units in the past—12–15 years ago—began with steam temperatures of 600–650°C and pressures of 300–350 ata, with these parameters subsequently being abandoned and a transition in recent years to units with a low steam temperature;

b) development of two-shaft units of comparatively low capacity, 200–350 MW, in the initial period, and abandonment of two-shaft units up to capacities of 800–900 MW (USA, USSR) at the present time;

c) widespread use of double units earlier (USSR) and abandonment of them at present and in the future;

d) excessive multiplicity of steam-pipeline strings and a large number of auxiliary-equipment sets in high-capacity units at the beginning, and abandonment and enlargement in new units;

e) construction in the past of complex turbines with a large number of stages, and the transition recently to simpler ones;

f) complication of thermal schemes in the past and their simplification in a number of countries at the present time.

Such is the objective reality of the development of modern thermal power engineering, and it must serve as the basis for assessing the possibilities of steam-turbine installations with adiabatic phase formation, the negative attitude of supporters of the modern steam-power cycle toward this problem, and also for a radical reconsideration of the existing situation with the aim of comprehensively developing work in this direction and implementing the transition of power engineering to adiabatic phase formation.

The delay in transferring the power industry of our country to adiabatic phase formation leads to enormous material damage, calculated in recent years alone in billions of rubles of overspent funds, in tens of millions of tons of fuel, in underproduction of tens of billions of kilowatt-hours of electric energy, and also in major losses in industry.

The transfer of domestic power engineering to adiabatic phase formation has been fully prepared for all types of steam-turbine installations, both on organic and on nuclear fuel, and can be carried out on a broad front and at a rapid pace, with a significant reduction in capital expenditures and with high efficiency in operation.

The transfer of power engineering to adiabatic phase formation is based on well-mastered power equipment of moderate steam pressures: ordinary series-produced turbines for industrial thermal power plants, the medium- and low-pressure cylinders of modern units, steam pipelines and steam superheaters of moderate pressure, with the simultaneous organization in power-machine building of the production of specific inexpensive elements of such installations with adiabatic phase formation (single-stage turbines with adiabatic phase formation at low temperature and pressure of the working medium; boilers of subcritical pressure with low temperature of the working medium—375–385°C at the boiler outlet—with a low-pressure steam superheater for the modern temperature of initially or reheat-superheated steam), with simultaneous discon—

... of the output of modern boilers with superhigh and supercritical steam parameters, turbine equipment in the supercritical, superhigh, and high-pressure sections—the SKD, SVD, and VD cylinders—as well as steam pipelines for superhigh and supercritical steam parameters made of high-grade alloy steels—metal-intensive and costly elements of modern unit installations [1–5].

The conversion of power engineering to adiabatic phase formation eliminates the shortcomings of the present path of development of thermal power stations of both small [8] and large capacity and, in particular, those enumerated above.

The features of power units, thermal power stations, and heat-power engineering with adiabatic phase formation are as follows:

1. High thermal efficiency of power units, exceeding the calculated thermal efficiency of modern units with superhigh and supercritical steam pressures and a limiting initial steam temperature of 540–560°C.

2. Broad universality of installations with adiabatic phase formation in terms of unit capacity at high thermal efficiency—from small-capacity installations of several MW to very large units of up to 800–900 MW in a single-shaft arrangement and up to 1200–1500 MW in a two-shaft arrangement.

3. Low specific cost of power equipment, both of especially large and of small capacity, relative to modern steam-turbine installations: boiler units, steam pipelines, turbine units.

4. Broad demand for low-grade metals in highly efficient large-capacity units—carbon-steel units—and low consumption of alloy steels, many times lower than in modern units at the same initial steam temperature.

5. High operational reliability of the units—significantly lower accident rate of the main equipment compared with modern units, relative simplicity of operation, comparable to a considerable degree with the corresponding indicators of modern thermal power stations of medium or high pressure.

6. High maneuverability of operation of large units, and the expediency and effectiveness of operation under peak and variable load schedules (high mobility, low cost, high reliability, and thermal efficiency)—great universality of units with respect to operating modes in power systems, eliminating the need to use uneconomical thermal power stations and to create special installations of low thermal efficiency for peak and variable loads; a sharp increase in the average annual efficiency of power systems and of the country’s heat-power engineering as a whole.

7. High thermal efficiency of thermal power stations with adiabatic phase formation of small and medium capacity, industrial thermal power stations and combined heat-and-power plants, peak and semi-peak thermal power stations, with a significant reduction in material costs for the construction and operation of such thermal power stations, together with high reliability and mobility of their operation.

8. High integral efficiency of heat-power engineering with adiabatic phase formation—an increase in the reliability of operation of thermal power stations, power systems, and the country’s power engineering; a sharp reduction in the average annual specific fuel consumption in power systems; a significant additional increase in electricity generation in the country; improvement in the quality of power supply in power systems; a sharp reduction in initial and current capital investments in the development and operation of power engineering; reduction in the cost of energy production in power systems; increase in labor productivity in power engineering and in power...

in machine building; the overall positive effect on the development of the national economy and technical progress in the country.

The use of adiabatic phase formation is also more effective in the new cycles now being developed—in steam-and-gas thermal power plants, in MHD installations, and also in the creation of binary and ternary cycles based on the steam-power cycle and, especially, in nuclear power engineering.

REFERENCES

1. K. D. Lavrenenko. The Seventh World Power Congress. Teploenergetika, No. 8, 1968.

2. V. B. Pakshver. Problems of thermal power engineering at the VII World Power Conference. Energeticheskoe khozyaistvo za rubezhom, No. 5, 1968.

3. V. G. Zhilin, A. M. Nekrasov, A. S. Pavlenko. Power engineering of the USSR and the nearest prospects for its development. Elektricheskie stantsii, No. 8, 1968.

4. D. G. Zhimerin. Problems in the development of thermal power engineering in the USSR. Teploenergetika, No. 8, 1968.

5. S. V. Polozhii. Steam-power installations with adiabatic steam formation. Izv. vuzov SSSR — Energetika, No. 1, 1965.

6. S. V. Polozhii. Steam-power cycles with adiabatic steam formation. Izvestiya TPI, Vol. 150, 1968.

7. S. V. Polozhii. Evaporator-generators of steam-power installations with adiabatic steam formation. Izv. TPI, Vol. 150, 1968.

8. S. V. Polozhii. Increasing the efficiency of industrial power stations by means of adiabatic steam formation. Izv. TPI, Vol. 150, 1968.

9. S. V. Polozhii. The state and prospects of scientific research on the problem of adiabatic steam formation. Izv. TPI, Vol. 150, 1968.