WO2014040491A1

WO2014040491A1 - Tower-type boiler with primary reheater and secondary reheater

Info

Publication number: WO2014040491A1
Application number: PCT/CN2013/082333
Authority: WO
Inventors: 姚丹花; 诸育枫; 徐雪元; 倪建军
Original assignee: 上海锅炉厂有限公司
Priority date: 2012-09-11
Filing date: 2013-08-27
Publication date: 2014-03-20
Also published as: PL409128A1; PL237933B1; CN102889570A; MY176444A; ZA201406664B; CN102889570B

Abstract

A tower-type boiler with a primary reheater and a secondary reheater is provided. A super heater of the boiler comprises a low-temperature super heater and a high-temperature super heater (31). A main steam system flow of the boiler comprises the following steps: firstly, feeding water enters into a front flue coal economizer and a rear flue coal economizer (10) which are arranged in parallel, then water came from the outlets of the coal economizers (10) enters into water-cooling walls (1, 2) from the lower part of a hearth (6), wherein the outlets of the water-cooling walls (1, 2) are connected to a separator (19), and at last, the steam came out of the separator (19) enters into the low-temperature super heater and the high-temperature super heater (31) successively. Along the steam flow direction which is from a low temperature to a high temperature at the side of the steam, the primary reheater successively comprises a primary reheating low-temperature reheater (11) and a primary reheating high-temperature reheater, and the secondary reheater successively comprises a secondary reheating low-temperature reheater (12) and a secondary reheating high-temperature reheater. Furthermore, the primary reheater and the secondary reheater are in parallel with each other in a perpendicular flue.

Description

Tower boiler with two reheaters

Technical field

The invention relates to a boiler having two reheaters for the power industry. Background technique

In the power plant, the steam becomes a relatively low pressure after working in the high pressure cylinder of the steam turbine, is discharged by the high pressure cylinder, enters the boiler and is heated in a reheater, and is supplied to the steam turbine for one reheating medium pressure cylinder to be discharged after work, and enters the boiler. The secondary reheater is heated and supplied to the secondary reheating intermediate cylinder and the low pressure cylinder of the steam turbine for work. This thermodynamic cycle with two reheats is more efficient than a reheating thermodynamic cycle. The above boiler with secondary reheat is used in a power plant.

The factors affecting the thermal cycle efficiency are mainly the steam pressure, steam temperature and reheating number used for work. The steam temperature of the current reheat unit is generally 600 °C. However, the temperature of the existing secondary reheat unit superheater and reheater is generally low, not exceeding 580 °C. In order to further improve the efficiency of the thermodynamic cycle, the present invention proposes a secondary reheat boiler in which both the superheated steam temperature and the reheated steam temperature reach 60 CTC or more.

Usually, the heat absorption ratio of the primary reheat boiler superheater and reheater is about 80:20. The reheater has a lower heat absorption ratio, and only one reheat outlet temperature reaches 60 CTC or more. Usually, the reheater is arranged in a region where the smoke temperature region is from loocrc to 8oo °c, and convection heat is used. The heat absorption ratio of the secondary reheat boiler superheater and the primary reheater and the secondary reheater of the present invention is about 71:17:12. The reheater has a large heat absorption ratio, and the reheating outlet temperature reaches 60 CTC or more. Since there is sufficient heat transfer temperature difference due to heat transfer, a large amount of heat exchange area needs to be arranged, which not only increases the cost but also in a limited space. It is difficult to arrange and increase the size of the boiler. Therefore, how to arrange the heating surface with the three steam temperatures of 600 ° C including the superheater, the primary reheater and the secondary reheater becomes a difficult point in the design of the high-parameter secondary reheat boiler.

In addition, the adjustment of the primary reheat steam temperature generally adopts one of the means of swinging the burner and adjusting the flue gas baffle to satisfy the requirement. How to adjust the steam temperature of the two reheaters is another difficulty due to the presence of two reheaters.

The ultra-supercritical boiler or supercritical boiler referred to in the present invention refers to the pressure of the working fluid in the boiler. The working fluid in the boiler is water. The critical pressure of water is: 22.115MPa, 374°C. At this pressure and temperature, the density of water and steam is the same, it is called the critical point of water, the working medium pressure in the furnace. Below this pressure is called Asia For critical boilers, more than this pressure is a supercritical boiler. The steam temperature in the furnace is not lower than 593 °C or the steam pressure is not lower than 31 MPa. It is called ultra-supercritical, and ultra-supercritical is also in the supercritical range.

BACKGROUND OF THE INVENTION The invention has been filed on April 7, 2011 by the applicant. The invention is entitled: A tower-type boiler with flue-divided and adjustable flow rate, application number 201110085966.6.; The invention name applied for on December 21st was 350MW supercritical tower type lignite boiler, application number 201110432324.9.

Summary of the invention

The object of the present invention is to provide a boiler with two reheaters, the outlet temperature of the superheater, the primary reheater and the secondary reheater can reach 600 ° C - 695 ° C, according to the engineering It is desirable that the temperature is preferably 610 ° C - 620 ° C and 630 ° C - 650 ° C.

In order to achieve the object of the present invention, the technical solution of the present invention is:

A tower type boiler with two reheaters, the boiler is a supercritical boiler, the heating surface of the boiler comprises a heat exchanger, a primary reheater and a secondary reheater; the superheater comprises a low temperature superheater and a high temperature superheater;

The main steam system flow is: feed water enters the front and rear flue economizers, and the front and rear flue economizers are arranged in parallel. The economizer outlet water enters the water wall from the lower part of the furnace, the water wall outlet is connected to the separator, and the separator outlet steam Enter the low temperature superheater and the high temperature superheater in turn, and finally enter the steam turbine to do work;

The steam of the primary reheater comes from the steam exhaust of the steam turbine. From the low to high flow direction of the steam side, the primary reheater includes a reheating low temperature reheater and a reheating high temperature reheater in sequence; finally, the steam enters the steam turbine. Do work;

The steam of the primary reheater becomes the exhaust of the steam turbine after the work of the steam turbine; the steam of the secondary reheater comes from the steam exhaust of the steam turbine, and the temperature from the steam side is viewed from low to high, including secondary reheating and low temperature. Heater, secondary reheating high temperature reheater; finally the steam enters the steam turbine to do work;

The primary reheater and the secondary reheater are arranged in parallel in the vertical flue of the furnace. Preferably, the primary reheating high temperature reheater is divided into a cold section and a hot section, and the secondary reheating high temperature reheater is divided into a cold section and a hot section;

The low temperature superheater is viewed from the steam flow direction, including the low temperature superheater suspension inlet pipe, the low temperature superheater vertical section heating surface and the low temperature superheater screen pipe section; 1. The secondary reheating high temperature reheater cold section is arranged in advance, that is, placed under the high temperature superheater, in the area with strong radiation characteristics, absorbing part of the radiant heat, and the second reheating high temperature reheater hot section Arranged above the high temperature superheater;

The upper vertical flue of the furnace is arranged in series along the flue gas flow with a low temperature superheater screen pipe section, one and two reheating high temperature reheater cold section, a high temperature superheater, a secondary reheating high temperature reheater hot section, one , secondary reheat low temperature reheater, economizer and low temperature superheater suspension inlet pipe; primary reheater cold section and secondary reheater cold section are arranged in parallel, primary reheater hot section and secondary reheat The hot sections are arranged in parallel, and the primary reheat low temperature reheater and the secondary reheat low temperature reheater are arranged in parallel. Preferably, the low temperature superheater screen tube section has a large distance between the screen and the screen, and is capable of transmitting heat radiation; the low temperature superheater vertical section heating surface can also be suspended above the economizer and reheater of the low temperature superheater screen tube section. , high temperature superheater;

The first and second reheating high temperature reheater cold section is designed as a screen tube type, and some are arranged above the gap between the screen and the screen of the low temperature superheater to receive heat radiation;

The first and second reheating high temperature reheater cold section also includes a vertical section heating surface, and the cold section and the hot section are connected by a vertical section heating surface disposed in the vertical flue. Preferably, after the flue gas flows through the hot section of the reheating unit of the first and second reheating, the flue gas passage is separated into the front and rear flue by the separated flue partition wall, and the front flue is arranged with a reheating low temperature reheater. And the front flue economizer, the rear flue is arranged with a secondary reheat low temperature reheating and a rear flue economizer; the separated flue partition wall extends to the second flue inlet, and a flue gas block is arranged here The plate is used to adjust the flue gas flow before and after the flue;

The separating flue partition wall is composed of a suspended tubular membrane wall which is taken as part of the low temperature superheater from the low temperature superheater inlet header, returned to the low temperature superheater outlet header or returned to the intermediate mixing Container

The primary reheater is placed close to the front wall, and the secondary reheater is placed close to the rear wall. Preferably, the steam temperature of the superheater, the primary reheater and the secondary reheater reaches 600 ° C to 695 ° C ;

The percentage of heat absorption of the secondary reheat boiler superheater and the primary reheater and the secondary reheater is, the superheater sucks The heat is 65%_75%, the heat absorption of the primary reheater is 15%-25%, the heat absorption of the secondary reheater is 10%_15%, and the sum of the three is 100%. Preferably, the steam pressure in the superheater is 28 MPa-35 MP _a; the steam pressure in the secondary reheater is 5 MPa-14 MPa _;

The steam pressure in the secondary reheater is 2 MPa _ 5 MPa. Preferably, the furnace is composed of a membrane water wall, the lower water wall adopts a spiral tube; and the upper water wall adopts a vertical tube arrangement;

After the feed water enters the front and rear flue economizers, it then enters the lower part of the furnace spiral around the pipe ring, enters the intermediate mixing header, the upper vertical pipe screen of the furnace, the separator, the low temperature superheater and the high temperature superheater, and finally the steam enters the high pressure of the turbine. The cylinder works. Preferably, the superheater steam temperature is controlled by the coal-water ratio adjustment and the two-stage water spray; 1. The secondary reheater steam temperature is synchronously adjusted by the burner swing, and the first and second reheater chambers are adjusted by the flue gas baffle Endothermic balance; a small amount of water spray is placed on the outlet pipe of the low temperature reheater. Therefore, the present invention places a part of the reheater heating surface in the flue near the furnace portion, thereby absorbing the radiant heat of a part of the furnace, thereby achieving a sufficient temperature rise with a small area. At the same time, the reheating device has the characteristics of the radiant heating surface, which is also beneficial for ensuring the reheater outlet rated temperature when the load is reduced.

Since the radiant heat is greatly reduced after passing through the heated surface. In order to make the reheater with two outlet temperatures above 60CTC, it can absorb part of the radiant heat and ensure a high heat transfer temperature difference. The present invention does not employ the commonly used series type, but employs a method in which two reheaters are arranged in parallel.

The difference between this secondary reheating scheme and the conventional primary reheating scheme is to increase the steam required to reach 600 °C or more. That is to say, in general, the temperature of the flue gas generated by the combustion of the boiler is constant, and a hot surface with a high temperature is required. Endothermic, how to arrange? Because the heat transfer is to have a certain temperature difference, generally two series of outlet surfaces with an outlet temperature of 60 CTC are placed in series, and the subsequent flue gas temperature is insufficient to heat the third heating surface to 600 ° C. Therefore, the present invention adopts A parallel scheme allows the two heated surfaces to share a relatively high smoke temperature. The purpose of the reheater part is to improve the heat transfer efficiency, and the second is to oscillate the burner. Has a higher sensitivity. However, it is not easy to advance the reheater in advance, but it is risky. In the current selection of conventional ultra-supercritical materials, in order to ensure safety, the steam temperature of the radiant heat reheater should not be too high, otherwise the metal wall temperature will be high, resulting in no alternative materials. As for the low temperature superheater, there is no safety problem. This is because the superheater has a higher pressure than the reheater, and the steam heat transfer characteristics are better. The steam characteristics determine the same steam temperature. The temperature of the metal tube wall is higher than that of the superheater, so the reheater cannot be blindly advanced. However, the current high-parameter secondary reheating scheme must accurately calculate the heating surface layout, which not only meets the temperature but also achieves safety and reliability.

The temperature regulation characteristics of the reheater are combined by adjusting the excess air ratio and the flue gas baffle adjustment by the oscillating burner. The center of the flame in the furnace is raised or lowered by the oscillation of the burner, and the outlet temperature of the reheater having the radiation characteristics is thus increased or decreased. Since the two reheaters are arranged in parallel and in the same smoke temperature region, their trends are the same. Increasing the excess air ratio increases the flow rate of the flue gas passing through the heated surface, and also has the effect of increasing the heat exchange of the reheater. The upper flue is divided into two flue front and rear flue by the partition wall of the suspended membrane wall, and the low temperature section of the primary reheater and the low temperature section of the secondary reheater are arranged in the two flues respectively, the hanging duct membrane As part of the low temperature superheater, the wall is drawn from the low temperature superheater inlet header, back to the low temperature superheater outlet header or back to the intermediate mixing header. The middle partition wall extends all the way to the tail flue inlet, where two flue gas flow regulating baffles are placed. The purpose is to control the flue gas flow of the two flue gases before and after by adjusting the opening degree of the baffle to achieve the purpose of adjusting the steam temperature rise of the first and second low temperature reheaters in the two flue gases before and after. When the temperature rise of the reheating low temperature section is increased, the temperature rise of the secondary reheating low temperature section is lowered, and vice versa. In combination with the oscillating burner, adjusting the excess air ratio and adjusting the flue gas baffle, it is ensured that the two reheaters reach the rated temperature at low load or fuel change.

Preferably, the primary reheater is arranged near the front wall, and the secondary reheater is arranged close to the rear wall. Since the rear wall flue is close to the horizontal flue, the flow rate is faster than the front wall flue, and the steam of the secondary reheater The pressure is lower than the pressure of the primary reheater, and the heat transfer characteristics are worse. Therefore, the secondary reheater is arranged close to the back wall, which is beneficial to heat absorption, so that the primary and secondary reheaters absorb heat. The heat absorption percentage of the secondary reheat boiler superheater and the primary reheater and the secondary reheater of the present invention is that the heat absorption of the superheater is 65%-75%, and the heat absorption of the primary reheater is 15%- 25%, the secondary reheater absorbs 10%-15%, the sum of the three is 100%, the preferred ratio is about 71: 17: 12, each ratio is floating within plus or minus 1 And for 100. The steam pressure in the superheater is 30MP _a -35MPa, the steam pressure in the primary reheater is 5MPa_13MPa, and the steam pressure in the secondary reheater is 2MPa_5MPa. One, The secondary reheater is of the same material and is of high grade stainless steel. The grades are, for example, SA-213TP347HFG, SA-213TP310HcbN, SA-213S304H, SA-335pgl, 15CrMoG, 12CrlMoVG, SA213T12, SA213T23, SA-335T9U SA210C. DRAWINGS

Figure 1 is a side view of the boiler; the reference numerals indicate: front wall water wall 1, rear wall water wall 2, intermediate mixing box 3, water wall inlet header 4, furnace roof 5, furnace 6, burner 7, Horizontal flue of the second flue, vertical flue of the second flue 9, economizer 10, primary reheat low temperature reheater 11, secondary reheat low temperature reheater 12, reheating and high temperature reheating Heat section 13, primary reheating high temperature reheater cold section 14, low temperature superheater screen section 15, low temperature superheater vertical section heating surface 16, lower part of partition (without fins) 17, partition wall with fins 18 , separator 19, low temperature superheater inlet header 20, flue gas baffle 21, low temperature superheater suspension inlet pipe 22, upper suspension pipe 23, low temperature superheater outlet header 24, vertical section heating surface 25, coal saving The inlet box 26, the economizer outlet header 27, the water wall outlet header 28, the secondary reheating high temperature reheater section 29, the secondary reheating high temperature reheater section 30, the high temperature superheater 31, Furnace vertical flue 32. detailed description

The present invention will be further described in detail below with reference to the drawings and specific embodiments, but the invention is not limited to the following examples.

As shown in Fig. 1, the boiler comprises a furnace 6, the first flue is the vertical flue 32 of the furnace, the upper flute is divided into a split flue and a main flue, and the partition of the flue is divided by a fin. For the front and rear flue; below the finned partition 18 is a heated surface tube 17 without fins. Since there is no fin separation, the smoke is not blocked, and the finned partition 18 is Membrane water wall; the second flue is divided into a horizontal flue 8 and a vertical flue 9. The boiler is, for example, a boiler that uses pulverized coal.

The high temperature gas from the plurality of burners 7 in the lower portion of the furnace 6 passes through the furnace 6, enters the first flue 32 in the vertical direction, then enters the horizontal flue 8 of the second flue, and then enters the vertical flue 9 of the second flue. .

The upper vertical flue of the furnace is arranged in series along the flue gas flow with a low temperature screen superheater, a secondary reheating high temperature reheater cold section, a high temperature superheater, a secondary reheating high temperature reheater hot section and a Second reheat Low temperature reheater, front and rear wall economizer, low temperature superheater suspension inlet pipe; primary reheater cold section and secondary reheater cold section parallel arrangement, primary reheater hot section and secondary reheater hot section Parallel arrangement, one reheat low temperature reheater and two reheat low temperature reheaters are arranged in parallel.

The upper suspension pipe 23 is a non-circulating medium for suspending the low temperature superheater to suspend the inlet pipe 22. As shown in Figure 1, the boiler is a 1000MW class coal-fired steam turbine generator set, a super-supercritical parameter variable-pressure operation spiral tube ring DC furnace, a single furnace, a secondary intermediate reheat, a tangential combustion method, a balanced ventilation, and a solid-state discharge. Slag, all-steel suspension tower boiler, open-air coal-fired boiler.

As shown in Figure 1 and Table 1, the main steam system flow is: After the feed water enters the economizer inlet header 26, it enters the front and rear flue economizers 10, and the front and rear flue economizers are arranged in parallel, and the water is saved in the coal. After heating, the device enters the economizer outlet header 27, and the water in the economizer outlet header is merged by the lower water wall inlet header 4 of the furnace, and then enters the front and rear water wall 1, 2, and is heated in the water wall to enter the water wall. The outlet header 28, the water wall outlet header is connected to the steam separator 19, and the separator outlet steam sequentially enters the low temperature superheater 15 and the high temperature superheater 31, and finally enters the steam turbine to perform work. Six steam separators are arranged vertically in the width direction of the boiler front, and the inlet and outlet are respectively connected with the water wall and the low temperature superheater. When the unit starts and the boiler load is lower than the minimum DC load by 30% BMCR, the medium exiting the heating surface exits through the distributor before the separator and enters the separator for steam-water separation. The steam passes through the upper pipe joint of the separator and enters the two distributors. After entering the first-stage superheater, the saturated water passes through one connecting pipe under the barrel of each separator and enters the lower one of the storage tanks, and the water tank is provided with water level control. A drain pipe below the storage tank leads to a connection piece. The connection is made hydrophobic to the recirculation system and the other to the atmospheric expansion vessel.

The furnace is composed of a membrane wall, and the water wall is arranged by a spiral tube and a vertical tube. From the inlet of the furnace ash hopper to the end of the high temperature superheater, a spiral pipe ring is used around the furnace; above the end of the high temperature superheater is a vertical pipe ring. The superheater steam temperature is controlled by the coal-to-water ratio adjustment and two-stage water spray. The steam temperature of the first and second reheaters is synchronously adjusted by the burner swing, and the heat absorption balance between the first and second reheaters is adjusted by the flue gas baffle. A small amount of water spray is set on the outlet pipe of the low temperature reheater. Key technology of the invention 1. Heating surface layout

The secondary reheat boiler adds a set of high temperature heating surfaces compared with the primary reheat boiler, and has a high temperature superheater, a reheating high temperature reheater and a secondary reheating high temperature reheater, and the heat absorption ratio of the reheater Significantly increased, so in the design, it is necessary to consider the reasonable matching of the heating surface to meet the change of the heat absorption of the superheated steam and the reheated steam, and at the same time meet the safety requirements brought by the increase of the reheat steam outlet temperature.

According to the conventional one-time reheat design concept, the heat-receiving surfaces of each stage are arranged in series, which will result in a high-temperature heating surface that cannot obtain sufficient heat exchange temperature and pressure, so that a large number of inefficient heat exchange areas need to be arranged. Therefore, in the design of the secondary reheat heating surface, the partial reheater is boldly advanced, absorbing part of the radiant heat, and the two high reheating surfaces are arranged in parallel to achieve the best heat exchange, economy and safety. balance. Since the low-temperature superheater blocks part of the heat radiation before the cold section of the reheating reheater, the low-temperature superheater is designed as a screen-type superheater, and the distance between the screen and the screen is large, and the distance is about Yes

700mm- 1300 Preferably 900mm-1100 Part of the heat radiation can penetrate the low temperature superheater screen tube to reach the cold section of the first and second reheating high temperature reheater. 1. The secondary reheating high-temperature reheater cold section is designed as a screen tube type, partially arranged above the neutral position between the screen and the screen of the low-temperature superheater, capable of receiving heat radiation, where the temperature is also higher, exceeding 100 CTC. Even reaching 1300 ° C -1500 ° C, has higher heat radiation characteristics; First, the secondary reheat high temperature reheater cold section also includes vertical section heating surface (25), vertical section heating surface (25) and The secondary reheating high temperature reheater is connected to the hot section, and the vertical section heating surface (25) is disposed in the furnace, preferably in the middle of the furnace, and most preferably on both sides of the partition wall 17 without fins. Designed as a screen-type low-temperature superheater, the distance between the screen and the screen is large, and it can transmit heat radiation. The low-temperature superheater also includes a vertical section heating surface 16, and the vertical section heating surface 16 can also suspend the low-temperature superheater tube screen. The economizer, reheater, high temperature superheater, etc. above the section serve as the suspension point for these heating surfaces. In addition, the low temperature reheater and the reheating high temperature reheater cold section are connected through a header outside the furnace. More specifically, the low temperature reheater outlet header is connected to the reheating high temperature reheater cold section inlet header through the pipeline.

2 temperature adjustment method

During the operation of the unit, it is often necessary to achieve the design value of the superheated steam outlet temperature or the reheated steam outlet temperature, whether at full load or low load, so that the unit can obtain higher efficiency. In the unit with low steam outlet temperature, the choice of temperature regulation mode has been an important issue. For the selected steam outlet temperature above 600 °C, secondary reheating super-supercritical unit with secondary reheat, temperature adjustment Choice of mode Choice is even more important.

From the perspective of the function of the steam at all levels, the temperature level of the primary steam is higher than the temperature level of the secondary steam, and the temperature level of the secondary steam is higher than the temperature level of the tertiary steam. Separate control of steam at each stage is required when selecting a temperature control scheme.

3 reheat steam temperature adjustment program

In this embodiment, the reheat steam temperature adjustment mode: swing burner + flue gas baffle + water spray desuperheating.

The goal of temperature regulation: By using effective temperature regulation means to ensure a reheat steam outlet temperature is

Under the condition of 50%~100%BMCR and the secondary reheat steam outlet temperature can reach the design value under the condition of 65%~100%BMCR.

In order to effectively solve the temperature regulation effect of reheat steam at low load, the burner design can swing up and down, adjust the height of the combustion center by the swing of the burner, change the temperature of the flue gas at the outlet of the furnace through the adjustment of the combustion center, and affect the high temperature reheat. The heat absorbed by the device regulates the reheat steam outlet temperature. Since a part of the second high is set a part of the heating surface that absorbs the radiant heat, the change of the flame center has a significant influence on the reheat steam temperature, which can ensure that the primary reheater reaches the rated steam temperature within a large load range. At the same time, the flue gas baffle temperature adjustment mode is adopted, the flue gas share in the front and rear separated flue is controlled by the baffle opening degree, and the heat absorption distribution ratio between the primary and secondary reheaters is changed to adjust the secondary reheater outlet temperature. The purpose of balance. At the same time, the water spray is desuperheated on the pipe of the reheater to prevent the occurrence of over-temperature and effectively control the deviation of the steam temperature on the left and right sides.

Four-point micro-spray water desuperheating is arranged between the low-temperature reheater and the high-temperature reheater, and two-point water spray desuperheating is arranged at the inlet of the low-temperature reheater. Under normal operating conditions, the water spray desuperheating is not put into operation, only in emergency Operating under accident conditions, the total water spray capacity is 3%, and the capacity of the pipes and valves is considered to be 250% of the designed water spray.

In this scheme, the steam inlet and outlet temperatures of the secondary reheat steam are relatively close. First, the ratio of the area of the heated surface of the secondary reheater to the ratio of the first and second reheating heat is basically the same. Therefore, the secondary reheater in the form of parallel arrangement of the heating surface can ensure that the trend of the heat absorption of the two reheaters changes with load is basically the same. By adjusting the flame center by the oscillating burner, it can be ensured that the steam temperature at the outlet of the primary and secondary reheaters reaches the rated value substantially, and the difference in the heat absorption between the two is achieved by the adjustment of the tail flue gas baffle. balance. In addition, the primary reheater is equipped with a part of the radiant heating surface, so that the boiler has the characteristics of a good reheat steam temperature at a lower load.

Claims

Rights request:

1. A tower boiler with two reheaters. The boiler is a supercritical boiler. The heating surface of the boiler includes a superheater, a primary reheater, and a secondary reheater; the superheater includes a low-temperature superheater. , high temperature superheater; It is characterized by:

The flow of the main steam system is: the feed water enters the front and rear flue economizers (10). The front and rear flue economizers are arranged in parallel. The outlet water of the economizer enters the water-cooled wall (1) from the lower part of the furnace. The outlet of the water-cooled wall is connected and separated. (19), the separator outlet steam enters the low-temperature superheater and the high-temperature superheater (31) in sequence, and finally enters the turbine to do work; the steam in the primary reheater comes from the turbine exhaust, and when viewed from the flow direction from low to high steam side temperature, The primary reheater includes a primary reheating low-temperature reheater (11) and a primary reheating high-temperature reheater; finally, the steam enters the turbine to perform work;

After the steam turbine performs work, the steam in the primary reheater becomes the exhaust steam of the turbine; the steam in the secondary reheater comes from the exhaust steam of the turbine, and the flow direction is from low to high temperature on the steam side, including secondary reheating and low-temperature reheating. Heater (12), secondary reheat high-temperature reheater; Finally, the steam enters the turbine to perform work;

The primary reheater and the secondary reheater are arranged in parallel in the vertical flue of the furnace.

2. The tower boiler with two reheaters according to claim 1, characterized in that: the primary reheat high-temperature reheater is divided into a cold section (14) and a hot section (13), and the secondary reheat high-temperature reheater The heater is divided into cold section (30) and hot section (29);

The low-temperature superheater, viewed from the steam flow direction, includes the low-temperature superheater suspended inlet pipe (22), the low-temperature superheater vertical section heating surface (16) and the low-temperature superheater screen tube section (15);

The cold section of the first and second reheat high-temperature reheaters is arranged in advance, that is, placed under the high-temperature superheater, in an area with strong radiation characteristics, and absorbs part of the radiant heat. The first and second reheat high-temperature reheaters The hot section of the device is placed above the high-temperature superheater;

The vertical flue at the upper part of the furnace is arranged in series along the flue gas flow direction with a low-temperature superheater screen tube section, a primary and secondary reheating high-temperature reheater cold section, a high-temperature superheater, a primary and secondary reheating high-temperature reheater hot section, and a , secondary reheat low-temperature reheater, economizer and low-temperature superheater suspended inlet pipe; primary reheater cold section and secondary reheater cold section are arranged in parallel, primary reheater hot section and secondary reheater The heating section of the reactor is arranged in parallel, and the primary reheating low temperature reheater and the secondary reheating low temperature reheater are arranged in parallel.

3. The tower boiler with two reheaters according to claim 2, characterized in that: the low-temperature superheater screen tube section has a large distance between the screens and can transmit thermal radiation; the low-temperature superheater screen section The heating surface (16) of the vertical section of the low-temperature superheater can also suspend the economizer, reheater and high-temperature superheater above the screen tube section of the low-temperature superheater;

1. The cold section of the secondary reheat high-temperature reheater is designed as a screen tube type, and is partially arranged above the gap between the screens of the low-temperature superheater to accept thermal radiation;

The cold section of the primary and secondary reheat high temperature reheater also includes a vertical section heating surface (25), and the cold section and the hot section are connected by a vertical section heating surface (25) provided in the vertical flue.

4. The tower boiler with two reheaters according to claim 3, characterized in that: after the flue gas flows through the hot section of the primary and secondary reheat high-temperature reheaters, the flue gas channel is separated by a flue partition wall It is divided into front and rear flues. The front flue is equipped with a primary reheat low-temperature reheater and a front flue economizer. The rear flue is equipped with a secondary reheat low-temperature reheater and a rear flue economizer. Separation The flue partition wall extends to the entrance of the second flue, and a flue gas baffle is provided here to adjust the flue gas flow of the front and rear flues; the dividing flue partition wall is composed of a suspended tube membrane wall, which is As part of the low-temperature superheater, the hanging tube membrane wall is led from the low-temperature superheater inlet header and returns to the low-temperature superheater outlet header or to the intermediate mixing header; the primary reheater is arranged close to the front wall, and the secondary reheater The device is placed close to the back wall.

5. The tower boiler with two reheaters according to claim 3, characterized in that: the outlet steam temperature of the superheater, primary reheater and secondary reheater reaches 60 CTC to 695°C; The heat absorption percentages of the reheat boiler superheater, primary reheater and secondary reheater are: the heat absorption of the superheater is 65%-75%, the heat absorption of the primary reheater is 15%-25%, and the heat absorption of the secondary reheater is 65%-75%. The heat absorbed by the reheater is 10 -15, and the sum of the three is 100%.

6. The tower boiler with two reheaters according to claim 4, characterized in that: the steam pressure in the superheater is 28MPa-35MPa; the steam pressure in the primary reheater is 5MPa-14MPa ; The steam pressure in the secondary reheater is 2MPa-5MPa;

7. The tower boiler with two reheaters according to claim 3, characterized in that: the furnace is composed of a membrane water-cooled wall, the lower water-cooled wall adopts a spiral tube; the upper water-cooled wall adopts a vertical tube Arrangement: After the feed water enters the front and rear flue economizers, it then sequentially enters the spiral surrounding tube ring in the lower part of the furnace, enters the middle mixing header, the vertical tube screen in the upper part of the furnace, the separator, the low-temperature superheater and the high-temperature superheater, Finally, the steam enters the high-pressure cylinder of the turbine to perform work.

8. The tower boiler with two reheaters according to claim 3, characterized in that: the superheater steam temperature is controlled by adjusting the coal-water ratio and two-stage water spraying; 1. The steam temperature of the secondary reheater is synchronized The burner swing adjustment is adopted, and the heat absorption balance between the primary and secondary reheaters is adjusted through the flue gas baffle; a small amount of water spray is installed on the outlet connecting pipe of the low-temperature reheater.