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To increase the efficiency of a combined cycle power plant, it was suggested in a double-pressure heat recovery steam generator to carry out a reheat of water steam that had been spent in a high pressure cylinder of a steam turbine. The researchers introduce a mathematical algorithm and calculation methodology of the waste-heat boiler. It is proved that after re-superheat of water vapour in a double-circuit waste-heat boiler after the high-pressure superheater (with vapour already used in the high-pressure cylinder of a condensing steam turbine), a CHP-plant efficiency and reliability increase. Calculations for the combined cycle gas turbine unit PGU-450 were performed. It is shown that when the reheater is installed in the recovery steam generator, its efficiency increases by 2.15%. At the same time the efficiency of CCGT for power generation is increased by 3.36%, the degree of dry water steam used in the turbine is increased by 0.082. Consequently, the specific consumption of conventional fuel for electric power generation is reduced by 6.1%. Re-superheating of the total flow of water vapour allows to increase CGP-450 steam-gas unit efficiency by increasing the parameters of the steam entering the low-pressure cylinder of the steam turbine.

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Methods are proposed for utilization of the heat of heated air emerging from the air channel of smokestacks. Numerical calculations for a 240-m-high smokestack at the Samara thermal power plant are used to determine the economic effect of recirculating the air heated in the air heater.In order to increase their operational reliability, some designs for reinforced concrete smokestacks have an annular air ventilation channel rather than thermal insulation between the reinforced concrete body of the smokestack and the refractory lining, In order to avoid cracking of the lining, the air introduced into the air channel is heated in an air heater to temperatures such that the temperature drop across the lining structure is acceptable [1,2].The Samara thermal power plant of the firm JSC "Volzhskaya TGK," which is mainly fired with natural gas, has 5 type BKZ-420-140 power generation boilers (units No. 1 --5), 8 type PTVM-100 (units No. 1 -3) and KVGM-180-150-2 (units No. 4 -8) water heating boilers. The combustion products from the power generation boilers in units 4 and 5 and the water heater boilers in units 4 -8 are discharged to the atmosphere through the 240-m-high smokestack at unit No. 2. The flue gas temperature is 130°C. The smokestack at unit No. 2 consists of a supporting reinforced concrete body and an inner acid resistant refractory lining, separated by an annular air ventilation channel of varying width. The lining is made of type 200 acid-resistant straight and radial bricks. At the base of the stack (elevation 0 m) the outer diameter of the stack body is 24.1 m and its walls are 600 mm thick. The inner diameter at the top of the stack is 8.4 m and at its base, 20.8 m. At elevation 5 m, the reinforced concrete body has two windows of size 16,700 × × 8,800 mm for gas ducts. Beginning at a height of 5 m, the reinforced concrete body has an air channel whose width at 5 m height is 380 mm and at 25 m, 490 mm. Then, with increasing height the width of the channel gradually decreases; up to H = 150 m it exceeds the thickness of the supporting body of the smokestack. At a height of 220 m, the thickness of the stack body wall is 200 mm and the channel width is 60 mm. At a height of 236.5 m there are 12 ventilation ports with windbreak boxes. Viewing ports of size 640 × 350 mm in the body and 400 × 250 mm in the lining have been made at heights of 56 and 176 m.In order to protect the reinforced concrete body from corrosion, the static pressure in the air channel should be greater than the pressure in the gas outlet channel over the entire height of the stack. The difference in these pressures is referred to as the counterpressure. The counterpressure is created by the entry of heated air into the air channel by natural draft or force ventilation. Two heating ventilator systems are provided, each of which consists of an air intake chamber, a heater and a ventilator fan unit. The latter includes a type Ts4-76-10 blower with a capacity of 27,000 m 3 /h. However, despite the presence of the fan units, the smokestack f...

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