RU2592008C2 - Method of two-stage delivery water heating - Google Patents

Abstract

FIELD: energy.

SUBSTANCE: invention relates to heat engineering and can be used to increase efficiency of extraction turbines with two-stage heating of delivery water in modes with increased direct delivery water system temperature relative to nominal one. Method involves stem extraction from extraction turbine and its delivery to network water heaters, wherein steam delivery to second stage of heating is performed with its switching from two chambers of said turbine with different pressures. Switching is carried out under condition of heat flow reduction from fuel combustion at equal production of heat and electric energy, determined at heat consumption dependence diagrams to turbine from direct delivery water system temperature for both said chambers, wherein straight direct delivery water system temperature and steam flow control is performed by turning control diaphragm and steam distribution unit of turbine high pressure cylinder.

EFFECT: invention increases both efficiency and reliability of turbine blade system.

1 cl, 2 dwg

Description

The invention relates to a power system and can be used to increase the efficiency of cogeneration turbines with two-stage heating of network water in modes with increased direct network water relative to the nominal temperature.

The flow part of the cogeneration turbine is selected from the operating conditions at the nominal cogeneration and condensation modes. At the same time, the turbine operating modes vary over a wide range of operating parameters, primarily depending on the outdoor temperature and, accordingly, the flow rate, the temperature of the return and direct network water. According to the technical conditions, the maximum pressure in the upper sampling chamber can reach 0.25 ... 0.3 MPa at its nominal value of 0.1 MPa, that is, it changes by 3 times. Under these conditions, the redistribution of the sampling occurs between the first and second stages of heating the network water and the operation of the near-sampling stages occurs with low efficiency.

There are several ways to improve efficiency at elevated pressures in the upper sampling chamber, which corresponds to temperatures of direct network water of 120 ... 150 ° C. For example, it is proposed to change the number of steps in a compartment between selections according to the patent of the Russian Federation 2307941 C2, published on 10.10.2007, bull. No. 28. The disadvantage of this method is obvious, when switching to another mode, disassembly and assembly of the cylinder is required.

For the prototype we accept the patent of the Russian Federation No. 2204724, BI 2003, No. 14, p. 467, where it is proposed to use the connection of the upper selection to two chambers and switch the selection depending on the temperature of the direct supply water. The disadvantages of the proposed method are:

- By measuring the pressure and, accordingly, the saturation temperature in each chamber, the selection is connected to the chamber, where the saturation temperature is closer to the set one, which is an approximate estimate, because the saturation temperature in the heater is significantly affected by the pressure loss in the sampling pipelines for each of the network heaters, which is quite large and depends on the consumption for sampling.

- The proposed scheme at certain temperatures requires steam throttling, which, as you know, reduces efficiency.

- The proposed scheme has a complex control and hardware structure (transducers, pressure sensors, adders, etc.)

The objective of the claimed invention is to remedy these disadvantages.

The problem is achieved by a method of two-stage heating of network water, including the selection of steam from the cogeneration turbine and its supply to the network water heaters, and steam is supplied to the second stage of heating by switching it from two chambers of the said turbine with different pressures, characterized in that the said switching is carried out subject to a decrease in heat consumption from fuel combustion with equal generation of heat and electric energy, determined from the diagrams of the dependence of heat consumption the turbine temperature direct network water to both of said chambers, wherein the temperature control direct mains water and steam flow is performed by turning the regulating diaphragm and the body high pressure turbine steam distribution cylinder. For this, two regulating bodies available in the cogeneration turbine are used: the regulating rotary diaphragm behind the lower bleed and the steam distribution of the high-pressure cylinder. To determine the most economical option for connecting the upper selection, fuel (heat) saving is taken as the main criterion with equal generation of heat and electric energy (Barinberg G.D., Brodov Yu.M., Goldberg AA, etc. Steam turbines and turbine units Ural Turbine Plant, Yekaterinburg: Aprio, 2007, p. 86).

The essence of the claimed invention is illustrated by the following drawings:

FIG. 1 is a heat flow diagram of a method of two-stage heating of network water;

FIG. 2 is a diagram of the dependence of the heat consumption on the Q _tour turbine on the temperature of the direct network water t _pr for two variants of the circuit using the example of the T-250-240 turbine.

The thermal diagram of the two-stage heating of the mains water in one cylinder 9 is shown in FIG. 1. Heating of network water 12 in network heaters (SP) of the first stage 1 and second stage 2 is possible in two ways (circuit options):

1. At low temperatures of direct network water, the valve 6 closes and the valve 5 opens and the second stage 2 is selected for the joint venture by pipeline 3 from the chamber 10 with a lower pressure, and accordingly we get less heating of the network water.

2. At elevated temperatures of direct network water, the valve 5 closes and the valve 6 opens and the second stage 2 is selected for the joint venture by pipe 4 from the chamber 11 with a higher pressure, and accordingly we get more heating of the network water.

When working on a thermal schedule, i.e. when the thermal load is set and the steam flow is not regulated, the regulating rotary diaphragm 8 is closed, and the pressure in the chambers 10, 11 is regulated by the main steam distribution body 7 of the cylinder 9.

When working on an electrical schedule, i.e. when the thermal load and steam flow rate are set, the pressure in the chamber 10 or 11 is regulated by the rotary diaphragm 8, and the steam flow rate is regulated by the main steam distribution body 7 of the cylinder 9.

, а во втором

, т.е. без изменений, где q_кес - удельный расход теплоты замещающей турбины, за которую можно принять самую экономичную конденсационную турбину или теплофикационную турбину на конденсационном режиме.The difficulty of comparing the two options is that even with equal heat load Q _{t, there} will be different turbine power N and heat consumption per turbine Q _tour , and specific heat consumption q _e = (Q _tour -Q _t ) / N is not applicable for comparing these options. The criterion may be fuel economy with equal generation of heat and electricity. Instead of fuel consumption B and specific fuel consumption b, the diagrams usually operate on the heat consumption Q and the specific heat consumption q, respectively, when converting these values to the CHP, it is recommended to take the heat of combustion of the equivalent fuel q _cg = 7000 kcal / kg (29308 kJ / kg). The recalculation formulas will be as follows: Q = B × q _cg ; q = b × q _cg . For different capacities N ₁ and N ₂ (hereinafter, index 1 refers to the first option, and index 2 to the second), to compare the economics of the regimes, add the heat necessary to generate additional power in the replacement condensing turbine In _kes = b _kes × (N ₂ -N ₁ ), where b _kes is the specific fuel consumption on a condensing turbine (see the cited book, formula 3.2, p. 86). Thus, the heat consumption in the first embodiment will be equal to

, and in the second

, i.e. unchanged, where q _kes is the specific heat consumption of the replacement turbine, for which you can take the most economical condensing turbine or a cogeneration turbine in condensing mode.

, N₁,

, N₂ берутся из результатов расчетов на переменный режим турбоустановки, которые проводятся для построения диаграмм режимов. При этом по оси абсцисс обычно откладывают температуру прямой сетевой воды t_пр. На фиг. 2 показаны эти зависимости для турбины Т-250-240. На пересечении кривой 14 (вариант 1) и кривой 15 (вариант 2) находим температуру переключения t_пер=98°С. То есть до температуры прямой сетевой воды t_пр=98°С надо использовать подключение к камере 10 с более низким давлением и соответственно при более высоких температурах t_пр использовать подключение к камере 11 с более высоким давлением. Из фиг. 2 следует также, что режимы с t_пр>120°С не реализуются в варианте 1.Typically, the heat load Q _{t of the} temperature of the forward and reverse network water t _pr , t _rev , which depend on one parameter - the outdoor temperature t _nv (see Fig. 1.1, Fig. 1.2, p. 6-7 of the cited book), is usually given. In this case, the dependences Q ₁ and Q ₂ are plotted in a given interval of t _tv changes. Required data

, N ₁ ,

, N ₂ are taken from the results of calculations for an alternating mode turbine, which are carried out to build mode diagrams. In this case, the temperature of direct network water t _ave . Is usually plotted on the abscissa axis. In FIG. 2 shows these dependences for the T-250-240 turbine. At the intersection of curve 14 (option 1) and curve 15 (option 2) we find the switching temperature t _per = 98 ° C. That is, up to the temperature of direct network water t _pr = 98 ° C, it is necessary to use a connection to the chamber 10 with a lower pressure and, accordingly, at higher temperatures t _pr, use a connection to the chamber 11 with a higher pressure. From FIG. 2 it also follows that modes with t _ol > 120 ° C are not implemented in option 1.

If the heat load does not depend unambiguously on t _nv , which is possible with forced redistribution of heat loads between several turbines at the station, as well as with deviation of the initial steam parameters, it is necessary, as is customary in the mode diagrams for turbines, to construct a correction depending on the changing parameter . But, as calculations show, the selection switching temperature, taking into account the amendment, changes by no more than 3 ° C. Selection switching should be performed when the deviation from the switching temperature is 5 ° C or more, since with smaller deviations the economic effect will be negligible.

можно вычислить из результатов двух расчетов на переменный режим, проведенных непосредственно на ТЭЦ с учетом всех отклонений, в частности принятого на ТЭЦ значения q_кес.The use of diagrams is generally accepted, but introduces an additional error. Currently, thermal power plants are equipped with computers and a thermal calculation program for a turbine installation for a variable mode (thermal balances) of the manufacturer's plant can be installed, therefore, heat saving

It can be calculated from the results of the two calculations on alternating operation performed directly on the CHP considering all the deviations, in particular, adopted at the TPP values of q _CES.

Table 1 shows the calculation results (n _k is the number of the sampling chamber, t _pr is the temperature of the direct network water, Gt is the steam consumption for the turbine, Ne is the power, G ₁ , G ₂ are the samples for network heaters, P _reg is the pressure in front of the control the diaphragm, i.e. in the selection chamber for the first network heater, q _e is the specific heat consumption, ΔТ ₁ , ΔТ ₂ is the heating of water in the network heaters, ΔВ is the equivalent fuel saving with a heat of combustion of 7000 kcal / kg with equal heat and electric energy) for turbines operated at the CHP with sampling from chamber 10 and with switching selection from chamber 11.

Thus, at a temperature t _ol = 120 ° C for a T-120-130 turbine, we have a standard fuel economy of 490 kg / h, and for a T-250-240 turbine, 992 kg / h. Relative fuel economy with equal generation of heat and electricity is 0.95-1.05%. The saving of fuel equivalent with the equal generation of heat and electric energy is the most universal indicator of the operation of a cogeneration turbine, because reflects the perfection of not only the thermal circuit, but also the flow part of the turbine.

The specific heat consumption q _e does not fully reflect the efficiency of the cogeneration turbine, because It does not take into account the additionally generated electric energy, which must be estimated according to the conditions of its receipt at the replacement condensing power station.

EFFECT: invention makes it possible to increase the heating coefficient α of a _{thermal power station} , and at moderate peak loads, to abandon a peak boiler or boiler. The value of α _TPP adopted in Russia = 0.5-0.6 is due to the impossibility of heating the mains water in cogeneration turbines above 110-120 ° C. The use of switchable selection to the second stage allows you to get the temperature of direct network water 140-150 ° C and exclude the use of peak boilers and boilers, which will bring even greater economic effect, since it will significantly increase the generation of electricity for heat consumption.

For turbines of the T-120-12.8 family, in modes with a high temperature of direct network water, we obtain a saving of about 1% in specific fuel consumption. At a direct water temperature of 120 ° C for the T-120-130-8MO turbine, the fuel economy is 11.75 t / day, and for the T-250-240 turbine, the saving is 23.8 t / day.

Switching the selection at elevated temperatures of direct network water improves other indicators. The difference between the screenings for network heaters of the first and second stages is reduced, as well as the maximum heating of water in the heater, which, as you know, increases the efficiency of the turbine, as well as the reliability of its operation.

Table 1 shows the data when heating network water to 140 ° C. According to some indicators (water heating in one heater is not more than 50 ° C, maximum pressure in the upper sampling, etc.), these modes are not possible in the existing T-120-130 turbine when sampling from chamber 10, but when sampling from chamber 11, these figures approach to allowed, and with a small change in stages 13, these modes become valid.

The organization of selection from the chamber 11 requires its expansion, which, as a rule, is not provided for in existing structures. Therefore, switching the selection of the second stage of heating must be provided for in the new design of the turbine.

Claims (1)

A method of two-stage heating of network water, including the selection of steam from a cogeneration turbine and supplying it to the network water heaters, the steam being supplied to the second heating stage being switched from two chambers of the said turbine with different pressures, characterized in that said switching is carried out under condition of reduction heat consumption from fuel combustion with equal generation of heat and electric energy, determined from the diagrams of the dependence of heat consumption on a turbine on the temperature of a straight line with net water for both of these chambers, while the temperature of the direct network water and the steam flow are controlled by means of a rotary control diaphragm and a steam distribution organ of the high pressure cylinder of the turbine.

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