Russian generation spans gamut of equipment, experience

Russian generation spans gamut of equipment, experience

Reliance on fossil fuels is pushing R&D for efficiencies and innovations

A.F. Armor

EPRI Fossil Power Plants

In the fall of 1989, EPRIstaff members made a series of visits to electric utilities, fossil plants, manufacturers, research and development (R&D) labs and universities in what was then the Soviet Union. A subsequent visit was made in August 1992 to scope out potential research projects and development testing that might offer significant benefits to the US electric power industry. More than two dozen opportunities were identified for potential collaboration, and several have already produced valuable data and technology. Others are ongoing or in planning stages.

The initial list of potential projects included tests on 300 MW superconducting generators, supercritical boilers featuring full variable-pressure operation, low-slagging lignite-fired boilers that emit low levels of nitrogen oxides, water-cooled gas turbine blades, and steam turbines employing thyristor-controlled startup techniques. Two of the projects that were identified–hydraulic recirculation pumps and advanced district-heating turbines–have been the subject of recent in-plant testing.

The fact-finding visits which stimulated this work were carried out by A.F. Armor, W. Piulle and I. Oliker of the Electric Power Research Institute (EPRI). There is, in both the US and the Newly Independent States (NIS), a heavy reliance on fossil fuels. The NIS has an installed fossil fuel power base of about 239 GW, representing about 70 percent of total electric generating capacity, compared with about 500 GW in the United States, also accounting for about 70 percent of the total. Hydroelectric is 19 percent of the total capacity and nuclear, 11 percent. NIS relies heavily on oil and natural gas, which account for half the total installed capacity. The export value of these fuels, however, is moving NIS toward greater use of coal–a change that can be seen in stepped-up research on pulverized coal and fluidized-bed boilers.

Of the 239 GW of installed fossil power, about 40 percent produces both heat and electricity. More than 1,000 cogeneration plants supply nearly 40 percent of the heat to the former Soviet cities. In 1989 NIS plants generated 1,705 million MWh. This represented 16 percent of total electric generation in the world.

Of this, fossil fuel plants contributed about 75 percent, hydro plants, 13 percent; and nuclear plants, 12 percent. Annual electric generation in the NIS reached 6,000 kWh per capita by 1990, and the new emphasis on production of consumer goods, housing construction, and the need for reduction of power plant pollution emissions calls for a substantial increase in electric generation. In fact, electric generation between 1990 and 2000 has been predicted to grow by 3 percent annually, bringing the total to 2,400 million MWh per year. However, growth has been curtailed by an overall slowdown in industrial output in the past five years.

Nuclear power

Plans for expansion of power capacity in the NIS have been seriously affected by the Chernobyl accident and the resultant reduction in the construction rate of nuclear power plants. Such plants had long been planned for the European part of the NIS, which houses about 80 percent of the population and has limited fossil fuel resources. At the beginning of 1990, NIS nuclear plant capacity was 37 GW, consisting of 46 units installed at 15 plants. Since 1987 only seven nuclear units entered commercial operation, and two units at an Armenian plant were shut down for safety reasons. Predictions now indicate that nuclear capacity will reach 50 GW by the year 2000.

Hydro power

The NIS has substantial hydro potential, 90 percent of which is in Siberia; and a 50 percent increase in electric generation from hydro power plants by the year 2000 is expected. Other renewable energy resources are expected to contribute very little to total electric generation. During a 1992 visit to the Krasnoyarsk hydro plant, the immense hydro potential of the Siberian rivers flowing into the Arctic was apparent. The 6,000 MW Krasnoyarsk hydro plant is located on the Yenisei River, 40 km from Krasnoyarsk.

The 3,300 km long Yenisei has the most flow of any river in Russia, draining a territory five times the size of France with a maximum flow of 180,000 m3/sec. The dam head is 101 m; powers 12 by 500 MW units, and has generated a new town of 30,000 people and spawned new local industries in metals, wood and chemicals. Several other major dams are in operation or planned on the Yenisei for a total of 34,000 MW of power.

At Krasnoyarsk, 11 of the 12 hydro units were running at the time of the visit, all seemingly well maintained, although no machine diagnostics were evident and the control room was entirely analog. It is notable that this dam (and its sister plant on the Yenisei, the 6,400 MW Sayano-Shushenskoye) are the second and third largest in the world, after Itaipu in Brazil. All the water from the river goes through the turbines, only four times in 20 years have the spillways been used in times of heavy flooding.

Coal-fired plants

Coal in the former Soviet Union generates about 33 percent of all electricity, and steam plants consume about 176,000 metric tons (t) of coal annually. The NIS possesses abundant reserves of coal, and proven reserves are estimated at 290 billion t. Major explored coal reserves are concentrated in several basins including Kansk-Achinsk, 80 billion t; Kuznetsk, 60 billion; Donetsk, 50 billion; Ekibastuz, 11 billion; Pechora, 8 billion; and Karaganda, 8 billion. About 75 percent of the coal reserves are concentrated in the eastern regions of the country (Figure 1). The major coal developments for the utility industry are in the Ekibastuz and Kansk-Achinsk basins.

Coal-fired, mine-mouth power plants with design capacity of 4,000 MW, made of eight 500 MW units, have been constructed in the Ekibastuz basin in the last decade. A 6,400 MW plant of eight 800 MW units is now being constructed in western Siberia to burn coal from the Kansk-Achinsk basin. Most of these coals are low grade, with heat value of less than 7,300 Btu/lb.; and they contain large amounts of water and/or ash. Some bituminous coals with heat value of 8,600 Btu/lb. are also classified as low grade because of high ash content, intensive slagging, low reactivity and poor grindability.

Unique combustion

Some unique coal combustion methods have been developed, and two examples are noted here. In a spiraling fireball furnace for low temperature combustion developed by the Leningrad Politechnic Institute, spiral recirculation of nonpulverized coal chunks is achieved by injection of two streams of air and gas mixtures above the burners (Figure 2). The advantage of this furnace is intensive recirculation of coke particles. This permits stabilization of ignition and intensification of combustion. Field tests of this method were conducted in a 420 t/h boiler at the Ust-Ilimskaja plant firing Irsh-Borodin coal. The crushed coal is supplied directly to eight burners by four air ejectors. The boiler has no mills. Heat flux in the furnace cross section was 2.9 MW/m2 and in the furnace volume, 137 kW/m3.

In general, the test results indicated that the furnace is capable of reliably firing low-grade coals. A 215 MW tangential-fired annular boiler (Figure 3) is being tested at the Novo-Irkutzk cogeneration plant. This 820 t/h boiler fires Kansk-Achinsk coal. The annular furnace is formed by external and internal octagonal radian sections, and the furnace is equipped with 24 burners located at three levels in eight burners at each level. The heat fluxes in the furnace are 4.4 MW/m2 and 130 kW/m3. After testing, the boiler design will be adapted for an 800 MW unit. It is estimated that this design will permit reduction of boiler height by 30 m, which should result in a substantial reduction in plant capital cost.

Supercritical units

An important factor in Russian efforts to improve the thermal efficiency of power plants is the use of supercritical boilers for more than 35 percent of their fossil fuel plant capacity. The former Soviet Union installed its first 100 MW supercritical unit in 1966, and Russia has since emerged as the world`s largest supercritical power producer. Today there are more than 200 supercritical units in operation at both cogeneration and electric-only plants, with standardized ratings of 300, 500, 800 and 1,200 MW. The US, for comparison, has about 170 units; and Japan has approximately 60.

In fact, the NIS and their trade partners in Eastern Europe, Cuba and mainland China have now installed more supercritical boilers for electric power production than the rest of the world combined. The increased steam pressures and temperatures in supercritical units can improve the thermal efficiency of fossil plants by up to 5 percent over a good subcritical unit; yet operation with supercritical steam conditions requires careful startup and control practices to avoid severe stresses on boiler and turbine components. In addition, supercritical units demand exacting attention to water chemistry if the supercritical fluid is to be kept from carrying corrosive impurities to the boiler and turbine.

The Russians inject oxygen into the feedwater of supercritical units to control corrosion. This oxygenated water chemistry treatment, using high concentrations of oxygen and maintenance of a pH between 7 and 8, represents an alternative approach to the all-volatile treatment (AVT) used in most supercritical units in the US, where hydrazine and ammonia are injected into the feedwater to reduce oxygen concentrations. Rather than fighting oxidation with AVT, the oxygenated treatment encourages it. This practice was identified as an area for follow-up during a 1989 EPRI trip to Russia; and since then, more than 60 US units have been converted to the oxygenated water treatment method with excellent results.

District heating

The wide use of cogeneration plants for district heating is a remarkable feature of the Russian utility landscape. Cogeneration in Russia is a large-scale, centralized activity encompassing more than one-third of all steam-electric power plants. First established in the 1920s, Russian district heating has always been at the center of efforts to conserve fuels; and now as environmental awareness grows, it is increasingly viewed as a way to minimize emissions.

At the Southern heat and power station of Lenenergo (the utility of St. Petersburg) and at Power Station 26 of Mosenergo (Moscow`s utility), EPRI visitors observed two different approaches to district heating. The 500 MWe, 1,100 MW Southern station, one of several plants in St. Petersburg`s open district heating system, delivers hot water directly to the residences of more than 150,000 people for everyday uses, such as bathing, and for space heat.

Morning and evening bath times are the peak hours in such a system, which must constantly draw on a flow of makeup water from the city`s main supply. Lenenergo, the first Russian utility to use district heating, now supplies 35 billion thermal kWh of heat per year to 13,000 buildings, 45 percent of St. Petersburg`s heat load. Lenenergo maintains 10,000 MW of installed power, including 12 cogeneration plants, 6 hydroelectric facilities and a 4,000 MW nuclear station.

In contrast to Lenenergo, Mosenergo operates a closed system that pipes hot water through heat exchangers at residential and industrial sites, supplying both heat and electricity to more than 85 percent of the national capital`s 9 million people. The Moscow network also supplies heat to a huge outdoor bathing pool that covers more than eight acres. Another impressive landmark in the Mosenergo system is station 26, the world`s largest district heating plant, which occupies 90 acres and is typical of a Russian trend toward large, modularly constructed, multiunit power stations.

It contains two 80 MW subcritical and five 250 MW supercritical units with peak capacities of 1,410 MWe and 3,640 MW. Five pipes, each five feet in diameter, deliver hot water at 135 C from the station and wind through Moscow for more than 25 km. Makeup water flows from the Moscow River, 13 km away. The facility feeds electricity into the distribution grid and supplies heat to residential districts with a total population of 1.5 million. The plant operates at baseload during the winter season, using virtually all of its waste heat for heating. As a result, the midwinter heat rate of 6,000 Btu/kWh is close to the maximum attainable, contributing to the year-round average of 7,680 Btu/kWh for all Russian district heating plants.

Moscow Power Institute

Several state-of-the-art facilities for power plant research exist. Among them is the Moscow Power Institute (MEI), the training ground for technicians and engineers who run the power plants of the former Soviet Union. MEI, which currently has a study body of 12,000, has been an important supplier of key specialists in power technologies.

MEI continues as a key incubator of talent. The organization has its own power plant and a large, fully instrumented test turbine that runs on steam diverted from one of the power plant`s turbines. This offers a unique opportunity for in-depth study of the serious global problem of corrosion and erosion of turbine blades. The test turbine is configured to allow the insertion of probes between stationary and rotating blades during operations so realistic steam samples can be taken.

Other instrumentation allows for monitoring of chemical and physical conditions before and after each row of blades and at various points along each blade length. EPRI`s project on steam chemistry uses the test turbine at MEI to explore the formation of chemical species in steam that contributes to the corrosion of turbine components. The resultant data will be part of EPRI`s contribution to a broad international collaborative study of steam turbine chemistry and corrosion.

Conclusions

Economic difficulties in the NIS have not diminished opportunities for international scientific collaboration. In fact, EPRI researchers have maintained long-term working relationships with scientists in Russia and the other republics, and interest in working with Russian utilities has increased. Recently EPRI entered a new phase in its relationship with NIS scientists and engineers, going beyond the traditional information exchange agreements to initiate funded contracts. END

References:

“The Soviet Power Industry Opens Its Doors,” EPRI Journal, March 1990.

“Bonds of Science: Strengthening Ties with the CIS” EPRI Journal, December 1993.

Hydraulic Turbine-Driven Boiler Circulation Pump, Field Testing at Southern Power Plant, St. Petersburg, Russia, EPRI TR-105532, September 1995.

Field Testing of the T-180/210-130 District Heating Turbine at Vilnius Power Plant 3, Lithuania, EPRI TR-104958, February 1995.

Armor, A.F., and Oliker, I., “The Power Industry in the Soviet Union: A first-hand account,” American Power Conference, Vol. 53, April 1991.

Ponomarev-Stepnoi, N.N., “Nuclear Electric Generation in the USSR,” Teploenergetika, 37 (8), 1990.

Hammond, J.R., Sullivan, J.B., “The Huge Potential of the Old USSR,” Private Power Executive, May/June 1993.

Armor, A.F., Oliker, I., “Boiler Design for Low Rank Coals in the Commonwealth of Independent States,” American Power Conference, Chicago, Ill., USA, April 1992, Vol. 54-I, pp. 542-553.

Rundigin, V.A., et al., “Field Test of BKZ 420 t/h Boiler with Spiraling Fireball Furnace,” Teploenergetika, 35 (1), 1988.

Grigorjev, K.A., et al., “Investigation of Coal Preparation for Low Temperature Spiraling Fireball Furnace,” Teploenergetika, 35 (11), 1988.

Sepant, F.A., et al., “Investigation of Annular Furnaces and Boiler Development for Large Capacity Units,” Teploenergetika, 29 (10), 1982.

Boizov, U.V., et al., “Development of Boilers for Kansk-Achinsk Coals,” Energomashinostroenie, No. 11, 1985.

Armor, A.F., Oliker, I., “Design and Operation of Russian Supercritical Units,” American Power Conference, Chicago, Ill., USA, April 25, 1989.

Dooley, B., “Optimum Feedwater Chemistry,” EPRI Feedwater Heater Technology Symposium, Kansas City, Kansas, USA, Sept. 27-29, 1995.

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Author:

Tony Armor is director of fossil power plants at EPRI, Palo Alto, Calif., USA. His responsibilities cover a broad range of programs for fossil steam and combustion turbine-based power plants. He is a member of the American Society of Mechanical Engineers and the Institute of Electrical and Electronics Engineers, and holds bachelor`s of science and master`s of science degrees from the University of Nottingham, England. He holds 12 US patents for innovations in steam turbine-generator design and power plant maintenance and is the author of more than 150 technical papers.

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