Steam heat supply system based on steam pressure conversion

Abstract

The invention relates to a steam heat supply system based on steam pressure conversion, and belongs to the technical field of cogeneration of thermal power generating units. The steam heat supply system based on steam pressure conversion comprises a water storage tank and a once-through steam furnace, the once-through steam furnace comprises a shell and a heat exchange tube bundle arranged in the shell, the input end of the heat exchange tube bundle is connected with a water storage tank pipeline through a water inlet pipe, and a water feeding pump is arranged on the water inlet pipe. Through countercurrent flow heat exchange of low-pressure high-temperature steam and demineralized water in the once-through steam furnace, the low-pressure steam exhausted by the medium-pressure cylinder of the steam turbine is effectively utilized and converted into available high-pressure steam, the steam exhaust amount of the medium-pressure cylinder is increased, meanwhile, the steam exhaust amount of the high-pressure cylinder is reduced, and then the axial thrust of rotors of the two cylinders is balanced.

Description

Technical Field

[0001] The invention belongs to the technical field of heat and power cogeneration of thermal power units, and in particular relates to a steam heating system based on steam pressure conversion. Background Art

[0002] The cogeneration cycle is achieved by utilizing the low-grade heat energy of thermal power plants and sending the heat energy to various heat users through the steam network. It can save fuel for power production, reduce consumption, and obtain comprehensive economic benefits of heat products. It is an important measure for the development of the power industry.

[0003] However, industrial heat users generally have higher requirements for heating pressure, and often use high-pressure cylinder exhaust steam output by steam turbines for heating. However, in order to avoid overload of high-pressure cylinder blades and excessive difference in axial thrust of rotors between high-pressure cylinders and medium-pressure cylinders, the existing technology results in limited heating suction capacity and is unable to meet the growing demand of the heating market. Therefore, there is an urgent need for a heating system that can effectively utilize the exhaust steam from the medium-pressure cylinder and participate in heating. Summary of the invention

[0004] The object of the present invention is to provide a steam heating system based on steam pressure conversion which can effectively improve the current situation that the exhaust steam pressure of the intermediate pressure cylinder is insufficient and difficult to utilize, and only requires the modification of the existing heating system.

[0005] In order to achieve the above object, the present invention provides the following technical solutions: A steam heating system based on steam pressure conversion, comprising a water storage tank and a direct current steam furnace, wherein the direct current steam furnace comprises a shell and a heat exchange tube bundle arranged inside the shell, wherein the input end of the heat exchange tube bundle is connected to the water storage tank pipeline through a water inlet pipe, and a water supply pump is arranged on the water inlet pipe; The top of the direct current steam boiler is input with low-pressure and high-temperature steam discharged from the intermediate-pressure cylinder of the steam turbine, the bottom of the shell is connected with a return pipe, the other end of the return pipe is connected to the top of the water storage tank, and the return pipe is provided with a condensate pump and a cooler.

[0006] Furthermore, the direct current steam furnace is a heater, a steam-water heat exchanger, a steam generator or any form of equipment for steam-water heat conversion.

[0007] Furthermore, the direct current steam furnace comprises, from bottom to top, a heating section, an evaporation section and a superheating section.

[0008] Furthermore, a water supply pipe is connected to the top of the water storage tank.

[0009] The present invention uses countercurrent heat exchange between low-pressure and high-temperature steam in a direct current steam boiler and desalted water, which not only effectively utilizes the low-pressure steam discharged from the intermediate-pressure cylinder of the steam turbine and converts it into usable high-pressure steam, but also increases the exhaust steam usage of the intermediate-pressure cylinder and reduces the exhaust steam usage of the high-pressure cylinder at the same time, thereby balancing the axial thrust of the rotors of the two cylinders.

[0010] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of a steam heating system based on steam pressure conversion shown in one embodiment of the present invention.

[0012] Explanation of the accompanying drawings: 1. Water storage tank; 2. Cooler; 3. Water feed pump; 4. Condensate pump; 5. DC steam boiler; 51. Heating section; 52. Evaporation section; 53. Superheating section; 6. Low-pressure and high-temperature steam; 7. Export high-pressure steam. DETAILED DESCRIPTION

[0013] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0015] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0016] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] See also Figure 1 A steam heating system based on steam pressure conversion shown in a preferred embodiment of the present application includes a water tank 1 and a direct current steam furnace 5. The direct current steam furnace 5 includes an outer shell and a heat exchange tube bundle arranged inside the outer shell. The heat exchange tube bundle includes a heating section 51, an evaporation section 52 and a superheating section 53 from bottom to top. The input end of the heat exchange tube bundle is connected to the water tank 1 through a water inlet pipe, and a water supply pump 3 is arranged on the water inlet pipe.

[0018] The bottom of the shell is connected with a return pipe, the other end of which is connected with the top of the water storage tank 1 , and a condensate pump 4 and a cooler 2 are arranged on the return pipe.

[0019] Furthermore, a water supply pipe is connected to the top of the water storage tank 1 for replenishing desalted water.

[0020] Working principle: The temperature of the low-pressure and high-temperature steam 6 discharged from the intermediate-pressure cylinder of the turbine is at the level of 345°C, and the external heating temperature is at the level of 260°C. Although the pressure is relatively low, it is sufficient to serve as a heat source for a direct-current steam boiler.

[0021] During operation, on the one hand, the top of the direct current steam boiler 5 receives the low-pressure and high-temperature steam 6 discharged from the intermediate-pressure cylinder of the turbine, releases heat to the heat exchange tube bundle through the superheating section 53, the evaporation section 52, and the heating section 51 in sequence, and is finally cooled into condensate at about 40°C. The condensate is transported to the cooler 2 through the condensate pump 4 for further cooling, and then flows back to the water storage tank 1.

[0022] On the other hand, the desalted water in the water tank 1 is pumped into the heat exchange tube bundle by the water feed pump 3, and passes through the heating section 51, the evaporation section 52 and the superheating section 53 in sequence, and absorbs the heat of the low-pressure high-temperature steam 6, and is converted into an outlet high-pressure steam 7 with an output pressure of 1.2 MPa and a temperature of 260°C, and finally merges with the heating main pipe to supply heat to the outside.

[0023] The following provides the basic calculation of heat exchange of the direct current steam furnace 5: The enthalpy of desalted water at room temperature of 25°C is 104.85KJ / Kg; The enthalpy of steam at 1.2MPa and 260℃ is 2954.66KJ / Kg; The amount of heat required to convert 1 kg of normal temperature desalted water into heating steam is 2954.66-104.85=2849.81 KJ / Kg; When the power load is 150MW, the enthalpy value of low-pressure high-temperature steam 6 parameters is 0.3MPa and 345℃ steam is 3159.7KJ / Kg; The enthalpy of condensed water at normal pressure at 40°C is 167.53KJ / Kg; It can be obtained that the heat released by 1Kg of low-pressure and high-temperature steam 6 being cooled to 40°C normal-pressure condensed water is 3159.7-167.53=2992.17KJ / Kg; Assuming that the heat exchange efficiency of the direct current steam boiler is 95%, the heat available from 1 kg of low-pressure high-temperature steam 6 is 2992.17 × 0.95 = 2842.56 KJ / Kg; Then the amount of low-pressure and high-temperature steam 6 in the medium-pressure cylinder required to convert 1 kg of normal-temperature desalted water into heating steam is 2849.81÷2842.56=1.003 kg; It can be concluded that if the steam direct current boiler is designed to supply 100t / h of steam, it is necessary to extract 100.3t / h of low-pressure and high-temperature steam 6 discharged from the intermediate-pressure cylinder of the steam turbine, which greatly increases the amount of exhaust steam from the intermediate-pressure cylinder and reduces the amount of exhaust steam from the high-pressure cylinder, thereby balancing the axial thrust of the rotors of the two cylinders.

[0024] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0025] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A steam heating system based on steam pressure conversion, characterized in that: It comprises a water storage tank and a direct current steam furnace, wherein the direct current steam furnace comprises a shell and a heat exchange tube bundle arranged inside the shell, wherein the input end of the heat exchange tube bundle is connected to the water storage tank pipeline through a water inlet pipe, and a water supply pump is arranged on the water inlet pipe; The top of the direct current steam boiler is input with low-pressure and high-temperature steam discharged from the intermediate-pressure cylinder of the steam turbine, the bottom of the shell is connected with a return pipe, the other end of the return pipe is connected to the top of the water storage tank, and the return pipe is provided with a condensate pump and a cooler.

2. The steam heating system based on steam pressure conversion according to claim 1, characterized in that: The direct current steam furnace is a heater, a steam-water heat exchanger, a steam generator or any form of equipment used for steam-water heat conversion.

3. The steam heating system based on steam pressure conversion according to claim 1, characterized in that: The direct current steam furnace comprises, from bottom to top, a heating section, an evaporation section and a superheating section.

4. The steam heating system based on steam pressure conversion according to claim 1, characterized in that: The top of the water storage tank is also connected with a water supply pipe.

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