A high-parameter industrial steam supply system and method suitable for large coal-fired units

Abstract

The present invention discloses a high-parameter industrial steam supply system and method suitable for large coal-fired units, including a superheater, a temperature and pressure reducer, a high-pressure cylinder, a low-pressure cylinder, a high-pressure heater, a booster pump and a flash device: the outlet of the superheater is respectively connected to the inlet of the high-pressure cylinder and the temperature and pressure reducer; the temperature and pressure reducer reduces the temperature and pressure of the main steam and then supplies high-pressure gas to the outside; the outlet of the high-pressure cylinder is sequentially connected to the reheater, the medium-pressure cylinder and the low-pressure cylinder; the condensate return water or make-up water is respectively connected to the temperature and pressure reducer, the flash device and the inlet of the reheater through a booster pump. The present invention does not require irreversible modification of the heating surface of the boiler reheater, and there is no obvious modification risk; finally, the system of the present invention is simple, reliable in operation, and can flexibly adapt to the situation of fluctuations in steam supply, reduction in supply or even suspension of supply, ensuring that the outlet steam temperature of the boiler reheater is maintained in a relatively stable range, and ensuring that the safety of the unit operation is not affected by fluctuations in steam supply.

Description

[Technical field]

[0001] The invention belongs to the technical field of high-efficiency cogeneration of large-scale thermal power generating units, and relates to a high-parameter industrial steam supply system and method suitable for large-scale coal-fired units. [Background technology]

[0002] In recent years, according to the relevant requirements of energy conservation and environmental protection, a large number of self-owned small units and self-owned boilers of chemical and smelting enterprises have been shut down, resulting in the inability to effectively guarantee the industrial steam required in their process production. In order to maintain normal production of enterprises, it is usually necessary to purchase a large amount of high-temperature industrial steam from surrounding large thermal power plants. This move is in line with energy conservation and environmental protection policies and is also conducive to achieving a win-win situation for enterprises and power plants.

[0003] For general large-scale thermal power units, 0.5-1MPa low-pressure industrial steam can be supplied by the exhaust steam of the medium-pressure cylinder of the unit, and the steam supply capacity of the medium-pressure cylinder is relatively large, which has almost no effect on the axial thrust and boiler of the unit; 1-3MPa medium-pressure industrial steam can be supplied by the low-temperature reheat steam or high-temperature reheat steam of the unit. Generally, when the steam supply is small, low-temperature reheat steam can be given priority. However, a large amount of low-temperature reheat steam can cause the boiler reheater to overheat, affecting the safe operation of the unit. When the steam extraction volume is large, high-temperature reheat steam can be used for steam supply. The reason is that high-temperature reheat steam has little effect on the boiler. For high-parameter industrial steam supply above 4MPa, the reheat steam pressure of the general unit can no longer meet the steam supply requirements, and a higher pressure main steam needs to be used for steam supply by cooling and reducing pressure. However, a large amount of main steam supply by cooling and reducing pressure faces the limitation of boiler reheater overheating, resulting in a sharp drop in heating capacity. Taking a conventional 300MW subcritical unit as an example, the maximum industrial steam supply capacity of a single unit at 0.5-1MPa low pressure can reach 300t / h-400t / h, the maximum industrial steam supply capacity of 1-3MPa medium pressure can reach 200-300t / h, while the maximum industrial steam supply capacity of 4MPa and above high pressure can only reach 50-70t / h.

[0004] It can be seen that in the heating transformation of conventional large-scale coal-fired units, the high-parameter steam supply transformation is limited by the overtemperature of the boiler reheater, resulting in an obvious lack of steam supply capacity. This poses a great threat to the production capacity and survival ability of some industrial enterprises that have a large demand for high-pressure steam but do not have sufficient steam sources nearby. [Summary of the invention]

[0005] The purpose of the present invention is to solve the problem in the prior art that high-parameter steam supply modification is limited by boiler reheater overtemperature, resulting in obviously insufficient steam supply capacity, and to provide a high-parameter industrial steam supply system and method suitable for large coal-fired units. The present invention can effectively solve the difficult problem of obviously insufficient high-parameter industrial steam supply capacity of large coal-fired units. Under the premise of not making irreversible modifications to the boiler heating surface, the problem of boiler reheater overtemperature caused by high-parameter steam extraction is effectively solved, thereby significantly improving the high-parameter industrial steam supply capacity and steam supply reliability of the unit.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A high-parameter industrial steam supply system suitable for large coal-fired units, comprising:

[0008] Superheater, the outlet of the superheater is connected to the inlet of the high-pressure cylinder and the temperature and pressure reducing device respectively;

[0009] The desuperheater and pressure reducer reduces the temperature and pressure of the main steam and then supplies high-pressure steam to the outside;

[0010] High-pressure cylinder, the outlet of which is connected to the reheater, the medium-pressure cylinder and the low-pressure cylinder in sequence;

[0011] Low-pressure cylinder, the outlet of which is connected in sequence to the condenser, condensate pump, low-pressure heater, deaerator, feedwater pump and high-pressure heater;

[0012] a high pressure heater, wherein an outlet of the high pressure heater is connected to an inlet of the superheater;

[0013] Booster pump, condensate return water or make-up water is connected to the desuperheater, flash evaporator and reheater respectively through the booster pump;

[0014] Flash device, the outlet of the flash device is mixed with the exhaust steam of the high-pressure cylinder and then connected to the inlet of the reheater.

[0015] The present invention is further improved in that:

[0016] A first regulating valve and a first stop valve are arranged on the pipeline between the boosting pump and the temperature reducing and pressure reducing device, and a second regulating valve and a second stop valve are arranged on the pipeline between the boosting pump and the flash evaporation device; the outlet of the superheater is divided into two paths, one path is connected to the inlet of the high-pressure cylinder, and the other path is connected to the inlet of the temperature reducing and pressure reducing device through a fourth regulating valve and a fourth stop valve.

[0017] A third regulating valve and a third stop valve are arranged on the pipeline between the booster pump and the reheater.

[0018] A high-parameter industrial steam supply method suitable for large coal-fired units comprises the following steps:

[0019] i. When no high-pressure steam is supplied to the outside;

[0020] Close all regulating valves and stop valves, and the unit operates in pure condensing mode; the main steam at the superheater outlet enters the high-pressure cylinder to perform work, the exhaust steam enters the reheater for secondary heating, the outlet reheated steam enters the medium-pressure cylinder to perform work, the exhaust steam enters the low-pressure cylinder to perform work, and the exhaust steam enters the condenser to condense. After the condensate passes through the condensate pump, it enters the low-pressure heater, deaerator, feed water pump and high-pressure heater in turn. After passing through the high-pressure heater, the feed water enters the superheater to become high-temperature steam and then enters the high-pressure cylinder to continue to perform work;

[0021] ii. When supplying high pressure steam to the outside:

[0022] Open all regulating valves and stop valves. When the unit operates normally in pure condensing mode, part of the main steam enters the temperature and pressure reducing device through the fourth regulating valve and the fourth stop valve. After the condensate return water or make-up water passes through the booster pump, part of it passes through the first regulating valve and the first stop valve and then enters the temperature and pressure reducing device. The temperature and pressure reducing device cools and reduces the pressure of the incoming main steam and then supplies high-pressure steam to the outside; the other part enters the flash evaporation device through the second regulating valve and the second stop valve for pressure reduction and flash evaporation. The flashed steam is mixed with the exhaust steam of the unit's high-pressure cylinder and then enters the boiler reheater to make up for the reduction in the original high-pressure cylinder steam inlet flow rate. The remaining part is sprayed into the boiler reheater through the third regulating valve and the third stop valve to mix and cool the reheated steam to prevent the reheater from overheating.

[0023] The further improvement of the above method is:

[0024] The remaining condensate return water or make-up water from the booster pump is sprayed into the boiler reheater through the third regulating valve and the third stop valve to mix and cool the reheated steam to prevent the reheater from overheating.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention can significantly improve the external steam supply capacity of the unit's main steam, and meet the high-parameter industrial steam demand of steam-using enterprises. Taking a 300MW unit as an example, the main steam heating extraction capacity can be increased from 50 to 70 t / h to 200 t / h to 300 t / h; the investment added by the present invention is relatively low, and the investment added to solve the boiler reheater overtemperature problem is generally 2 to 3 million yuan, which increases the transformation cost by about 10% compared with the conventional steam supply transformation project, but can increase the steam supply capacity of a single unit by about 4 times; the present invention does not require irreversible transformation of the heating surface of the boiler reheater, and there is no obvious transformation risk; finally, the system of the present invention is simple, reliable in operation, and can flexibly adapt to the situation of fluctuations in steam supply, reduction in supply, or even suspension of supply, ensuring that the outlet steam temperature of the boiler reheater is maintained in a relatively safe and stable range, and ensuring that the safety of the unit operation is not affected by fluctuations in steam supply.

Brief Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0028] Among them: 1-high-pressure cylinder; 2-medium-pressure cylinder; 3-low-pressure cylinder; 4-superheater; 5-temperature and pressure reducing device; 6-reheater; 7-first regulating valve; 8-first stop valve; 9-second regulating valve; 10-second stop valve; 11-third regulating valve; 12-third stop valve; 13-boosting pump; 14-high-pressure heater; 15-deaerator; 16-feedwater pump; 17-low-pressure heater; 18-condensate pump; 19-condenser; 20-fourth regulating valve; 21-fourth stop valve; 22-flash device. [Specific implementation method]

[0029] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all embodiments, and is not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0030] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0031] In the context of the present disclosure, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or an intervening layer / element may exist between them. In addition, if a layer / element is "on" another layer / element in one orientation, the layer / element may be "under" the other layer / element when the orientation is reversed.

[0032] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0033] Principle of the present invention:

[0034] In order to solve the problem of insufficient high-parameter industrial steam supply capacity of large coal-fired units, the key is to solve the problem of boiler reheater overheating caused by large main steam extraction. For normal units, in order to ensure long-term safe and reliable operation of the boiler, the allowable main steam extraction is about 5% to 7% of the reheat extraction flow. If the main steam extraction is to be further increased, the boiler needs to be adaptively modified.

[0035] In order to solve this problem and significantly improve the main steam supply capacity, some power plants have partially cut off and renovated the heating surface of the boiler reheater. By reducing the heating surface area of ​​the boiler reheater, the problem of overheating of the boiler reheater after a large amount of steam extraction can be solved. This renovation plan has a very serious defect: if the steam consumption of the steam-using enterprise fluctuates greatly, or if there is a reduction or shutdown of production, the steam supply will drop sharply or even stop. At this time, the reheat steam of the unit will be seriously under-temperatured, which will significantly affect the economic operation of the unit, and cause the moisture loss and water erosion of the low-pressure cylinder of the steam turbine to increase, seriously affecting the economic operation and safety and reliability of the unit. Once the steam-using enterprise stops production due to poor operating conditions or relocates for other reasons, it will directly lead to the termination of steam use. At this time, if the power plant wants to maintain normal, efficient and safe operation, it must re-renovate the boiler and restore the heating surface area of ​​the reheater, which will lead to huge renovation investment. For secondary reheat units of 300MW and above, the cost of this renovation may be as high as millions or even tens of millions of yuan, causing huge economic losses to the power plant. It can be seen that in order to achieve high-parameter industrial steam supply with large flow rate, there is a huge market risk in adopting the solution of cutting off the heating surface of the reheater.

[0036] To this end, a new, efficient, high-parameter industrial steam supply solution suitable for large coal-fired units has been specially developed. Without irreversible transformation of the boiler heating surface, the condensate return or water replenishment solution is optimized and improved to solve the boiler reheater overtemperature problem at a relatively low cost, thereby greatly improving the unit's main steam supply capacity to the outside without affecting the unit's low steam supply or pure condensing operating conditions. The economic benefits of the unit are significantly improved. Without increasing the risk of major transformation, the problem of insufficient high-parameter industrial steam supply capacity of power plants is effectively solved, and at the same time, the problem of insufficient high-parameter industrial steam sources for a large number of domestic industrial enterprises is solved.

[0037] The present invention is further described in detail below with reference to the accompanying drawings

[0038] See also Figure 1 The present invention is applicable to a high-parameter industrial steam supply system of a large coal-fired unit, comprising a high-pressure cylinder 1, an intermediate-pressure cylinder 2 and a low-pressure cylinder 3; the outlet of the superheater 4 is respectively connected to the inlet of the high-pressure cylinder 1 and the temperature-reducing and pressure-reducing device 5, and the temperature-reducing and pressure-reducing device 5 reduces the temperature and pressure of the main steam and supplies high-pressure steam to the outside; the outlet of the high-pressure cylinder 1 is connected to the reheater 6, the intermediate-pressure cylinder 2 and the low-pressure cylinder 3 in sequence; the outlet of the low-pressure cylinder 3 is connected to the condenser 19, and the outlet of the condenser 19 is connected to the condensate pump 18, the low-pressure heater 17, the deaerator 15, the feed water pump 16 and the high-pressure heater 14 in sequence, and the outlet of the high-pressure heater 14 is connected to the inlet of the superheater 4.

[0039] The condensate return water or make-up water is connected to the desuperheater 5, the flash device 22 and the reheater 6 respectively through the booster pump 13; the outlet of the flash device 22 is mixed with the exhaust steam of the high-pressure cylinder 1 and connected to the inlet of the reheater 6.

[0040] A first regulating valve 7 and a first stop valve 8 are provided on the pipeline between the boosting pump 13 and the temperature reducing and pressure reducing device 5, a second regulating valve 9 and a second stop valve 10 are provided on the pipeline between the boosting pump 13 and the flash evaporation device 22, and a third regulating valve 11 and a third stop valve 12 are provided on the pipeline between the boosting pump 13 and the reheater 6; the outlet of the superheater 4 is divided into two routes, one route is connected to the inlet of the high-pressure cylinder 1, and the other route is connected to the inlet of the temperature reducing and pressure reducing device 5 through a fourth regulating valve 20 and a fourth stop valve 21.

[0041] The present invention is applicable to a high-parameter industrial steam supply method for large coal-fired units, comprising the following steps:

[0042] i. When no high-pressure steam is supplied to the outside;

[0043] Close all regulating valves and stop valves, and the unit operates in pure condensing mode. The main steam at the outlet of superheater 4 enters the high-pressure cylinder 1 to perform work, the exhaust steam enters the reheater 6 for secondary heating, the outlet reheated steam enters the medium-pressure cylinder 2 to perform work, the exhaust steam enters the low-pressure cylinder 3 to perform work, and the exhaust steam enters the condenser 19 to condense. After the condensate passes through the condensate pump 18, it enters the low-pressure heater 17, the deaerator 15, the feed water pump 16 and the high-pressure heater 14 in sequence. After passing through the high-pressure heater 14, the condensate enters the superheater 4 and becomes high-temperature steam, and then enters the high-pressure cylinder 1 to continue to perform work.

[0044] ii. When supplying high pressure steam to the outside:

[0045] All regulating valves and stop valves are opened. When the unit operates normally in pure condensing mode, part of the main steam enters the desuperheater 5 through the fourth regulating valve 20 and the fourth stop valve 21. After the condensate return water or make-up water passes through the booster pump 13, part of it passes through the first regulating valve 7 and the first stop valve 8 and enters the desuperheater 5. The desuperheater 5 desuperheats and reduces the pressure of the incoming main steam and then supplies high-pressure steam to the outside; the other part enters the flash device 22 through the second regulating valve 9 and the second stop valve 10 for decompression and flash evaporation. The flashed steam is mixed with the exhaust steam of the high-pressure cylinder 1 of the unit (i.e., low-temperature reheat steam) and then enters the boiler reheater 6 to make up for the part of the steam flow rate entering the reheater 6 that is reduced due to the original reduction in the steam flow rate of the high-pressure cylinder; the remaining part is sprayed into the boiler reheater 6 through the third regulating valve 11 and the third stop valve 12 to mix and reduce the temperature of the reheated steam to prevent the reheater 6 from overheating.

[0046] The present invention optimizes and improves the condensate return or replenishment system (the condensate return is for the case of heating steam condensate recovery, and the replenishment is for the case of heating steam condensate not recovery) to avoid overheating of the boiler reheater when a large amount of main steam is extracted. In the traditional scheme, the condensate return or replenishment generally directly enters the deaerator or condenser. In the present invention, a booster pump is required to be added for the condensate return or replenishment to increase the pressure of part of the condensate return or replenishment to above the steam supply pressure: one part is used as the main steam supply desuperheating water and is sprayed through the steam supply desuperheating pressure reducer; the other part is decompressed and flashed through the newly added flash evaporation device, and the flashed steam is mixed with the low-temperature reheat steam of the unit and enters the boiler reheater to make up for the part of the steam flow entering the reheater caused by the reduction of the high-pressure cylinder steam inlet; the remaining part is sprayed into the boiler low reheat steam for mixing and desuperheating, and is used as water to suppress the overheating of the boiler reheater. In order to ensure a good mixing effect, a desuperheating bypass and corresponding isolation valve are added for the boiler low-temperature reheat steam. When the industrial steam supply is terminated, the temperature reduction bypass can be shut down without causing irreversible negative impact on the boiler.

[0047] In the present invention, the amount of water entering the booster pump is determined by the external steam supply of the main steam, the steam desuperheating water supply and the water required to suppress overheating of the boiler reheater, and is intelligently controlled according to the operating conditions of the unit.

[0048] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A high-parameter industrial steam supply system suitable for large coal-fired units, characterized in that: include: A superheater (4), wherein an outlet of the superheater (4) is respectively connected to an inlet of the high-pressure cylinder (1) and a temperature reducing and pressure reducing device (5); A temperature reducing and pressure reducing device (5), the temperature reducing and pressure reducing device (5) reduces the temperature and pressure of the main steam and then supplies high-pressure steam to the outside; A high-pressure cylinder (1), wherein an outlet of the high-pressure cylinder (1) is connected in sequence to a reheater (6), an intermediate-pressure cylinder (2), and a low-pressure cylinder (3); A low-pressure cylinder (3), wherein an outlet of the low-pressure cylinder (3) is sequentially connected to a condenser (19), a condensate pump (18), a low-pressure heater (17), a deaerator (15), a feedwater pump (16), and a high-pressure heater (14); A high-pressure heater (14), wherein an outlet of the high-pressure heater (14) is connected to an inlet of the superheater (4); A booster pump (13), condensate return water or make-up water is connected to the temperature reducing and pressure reducing device (5), the flash evaporation device (22) and the reheater (6) respectively through the booster pump (13); A flash device (22), wherein an outlet of the flash device (22) is mixed with exhaust steam from the high-pressure cylinder (1) and then connected to an inlet of a reheater (6); A first regulating valve (7) and a first stop valve (8) are provided on the pipeline between the booster pump (13) and the temperature reducing and pressure reducing device (5), and a second regulating valve (9) and a second stop valve (10) are provided on the pipeline between the booster pump (13) and the flash evaporation device (22); the outlet of the superheater (4) is divided into two paths, one of which is connected to the inlet of the high-pressure cylinder (1), and the other of which is connected to the inlet of the temperature reducing and pressure reducing device (5) through a fourth regulating valve (20) and a fourth stop valve (21). A third regulating valve (11) and a third stop valve (12) are provided on the pipeline between the booster pump (13) and the reheater (6); The amount of water entering the booster pump is determined by the main steam supply to the outside, the amount of steam cooling water and the amount of water required to suppress overheating of the boiler reheater, and is intelligently controlled according to the operating conditions of the unit.

2. A high-parameter industrial steam supply method for large coal-fired units using the system of claim 1, characterized in that: The following steps are involved: i. When no high-pressure steam is supplied to the outside; All regulating valves and stop valves are closed, and the unit is operated in pure condensing mode; the main steam at the outlet of the superheater (4) enters the high-pressure cylinder (1) to perform work, the exhaust steam enters the reheater (6) for secondary heating, the outlet reheated steam enters the medium-pressure cylinder (2) to perform work, the exhaust steam enters the low-pressure cylinder (3) to perform work, the exhaust steam enters the condenser (19) to condense, and the condensate passes through the condensate pump (18) and then enters the low-pressure heater (17), the deaerator (15), the feed water pump (16) and the high-pressure heater (14) in sequence. The feed water after passing through the high-pressure heater (14) enters the superheater (4) and becomes high-temperature steam, and then enters the high-pressure cylinder (1) to continue to perform work; ii. When supplying high pressure steam to the outside: All regulating valves and stop valves are opened. When the unit is operating normally in a pure condensing mode, part of the main steam enters the temperature reducing and pressure reducing device (5) through the fourth regulating valve (20) and the fourth stop valve (21). After the condensate return water or make-up water passes through the booster pump (13), part of it passes through the first regulating valve (7) and the first stop valve (8) and enters the temperature reducing and pressure reducing device (5). The temperature reducing and pressure reducing device (5) reduces the temperature and pressure of the entering main steam and then supplies high-pressure steam to the outside. The other part enters the flash evaporation device (22) through the second regulating valve (9) and the second stop valve (10) to be reduced in pressure and flash evaporated. The flash evaporated steam is mixed with the exhaust steam of the high-pressure cylinder (1) of the unit and then enters the boiler reheater (6), thereby compensating for the part of the steam flow rate entering the reheater (6) that is reduced due to the original reduction in the steam flow rate of the high-pressure cylinder. The remaining part is sprayed into the boiler reheater (6) through the third regulating valve (11) and the third stop valve (12) to mix and reduce the temperature of the reheated steam, thereby preventing the reheater (6) from overheating.

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