CN110645586A - A power plant boiler de-whitening device and its working method - Google Patents

Abstract

The invention provides a power station boiler whitening device and a working method thereof. The invention adopts the artificial graphite material with acid corrosion resistance and high heat transfer coefficient as the heat exchange element, and the graphite has the advantages of high heat conduction performance, corrosion resistance, stable chemistry, moderate strength and the like, so that the heat transfer effect and the practicability of the heat exchange element are superior to those of various existing boiler tail devices at home and abroad, the heat exchange is carried out on the flue gas at the tail of the boiler more efficiently, the low-temperature corrosion problem is effectively solved with lower device manufacturing cost, and the dual purposes of energy conservation and environmental protection are achieved.

Description

A power plant boiler de-whitening device and its working method

technical field

The invention belongs to the technical field of industrial process environmental protection, and in particular relates to a power plant boiler dewhitening device and a working method thereof.

Background technique

It is a special equipment with high energy consumption on the power station boiler. The power station boiler uses coal as the fossil fuel. Generally, lump coal is crushed and pulverized and sent to the furnace of the power station boiler to burn and generate heat. After the fossil fuel is burned and desulfurized, the flue gas is released from the boiler chimney. Exhaust, and the saturated or near-saturated wet flue gas diffuses in the air. When it contacts with the ambient air with a lower temperature, the saturated or near-saturated wet flue gas condenses and condenses due to the decrease in temperature, and a large amount of condensation is formed in the flue gas. The water droplets refract and scatter the light, thus appearing white or gray, which is called "smoke plume", commonly known as "white smoke".

The vast majority of domestic coal-fired power plants or cogeneration thermal power plants have undergone wet desulfurization before boiler flue gas discharge. The saturated or nearly saturated wet flue gas has high salt content and contains more dissolved salts and SO2. _3. Gel dust, fine dust, etc., these are the main components of atmospheric haze.

"Bleaching" should not only improve the visual effect of the city, but also reduce the emission of harmful substances that form atmospheric smog. At present, mainly due to material reasons, the operation of the existing technical devices is unstable, and the maintenance workload is large. The overall "whitening" of power plant boilers The effect is not satisfactory.

At present, the "dewhitening" is carried out by the condensation technology after flue gas desulfurization. A steel condensing device is installed on the flue after the flue gas desulfurization of the boiler to condense part of the water vapor with high salt content in the wet flue gas, so that the water vapor The harmful substances contained in the desulfurization tower, and the desulfurization slurry that escaped from the desulfurization tower (the desulfurization tower demister is difficult to efficiently capture the desulfurization slurry) are also condensed to reduce the harmful substances in the flue gas discharged after desulfurization (including harmful substances that form atmospheric haze). substance). This "whitening" method has the following disadvantages: 1. The flue gas condensation technology reduces the water vapor content in the flue gas, but the flue gas exhaust temperature is further reduced, which intensifies the corrosion of the chimney, and the exhaust flue gas is still saturated or Near saturated wet flue gas, the whitening effect is very limited. 2. Since the flue gas after desulfurization contains desulfurization slurry, the salt content in the flue gas after desulfurization can reach about 130mg/ ^m3 , which is extremely corrosive. The service life of the steel condensing device is very short, and some are less than 1 month. Corrosion and perforation affect the continuous operation of power plant boilers and the economic benefits of power plants.

Another "whitening" device currently used is the GGH (Gas Gas Heater) device. In order to "whiten" the flue gas in the power plant, the GGH device is used for two-way heat exchange, that is, the flue gas after desulfurization is used for the flue gas before desulfurization. Heating is carried out so that the exhaust gas temperature basically reaches above the dew point, the dryness of the flue gas is increased, and there is no condensation of water vapor at the exhaust port of the chimney, thereby "whitening". There are the following defects: 1. The use of GGH device for two-way heat exchange increases the exhaust gas temperature after desulfurization, but basically does not reduce the harmful substances in the flue gas after desulfurization, and the escaped desulfurization slurry is heated and vaporized, which not only does not affect the atmospheric haze. Improvements may even exacerbate. 2. Because the GGH heat exchanger is also made of steel, the low temperature corrosion is extremely serious, the air leakage and smoke and other reasons, the maintenance workload is very large, and it is rarely used at present.

The thermal conductivity of graphite is 116.3-183.7W/(m·K), which is 2.5 times that of carbon steel and 7 times that of stainless steel, which is a good heat exchange element material. After years of practical verification in the chemical industry, graphite equipment has a series of excellent properties: good heat transfer performance, simple structure, convenient manufacture, low cost and outstanding corrosion resistance, widely used in chemical industry, fertilizer, medicine, food , light industry, chemical fiber, metallurgy and other industrial fields, has rich experience in use, the main heat exchange element of the device is graphite heat exchange tube, using impregnated impermeable artificial graphite material. Artificial graphite is an ideal non-metallic corrosion-resistant and thermally conductive material, and its thermal conductivity exceeds that of many existing corrosion-resistant materials and chemically stable metals.

With the continuous development of society and economy, the "whitening" of the flue gas of power station boilers has also attracted more and more attention. How to beautify the urban environment, realize the efficient "whitening" of power station boilers, and reduce the emission of harmful substances that form atmospheric haze is extremely important. .

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a power plant boiler whitening device and a working method thereof, which adopts impermeable artificial graphite material to make a power station flue gas condensation-heating system, which "whitens" the flue gas and captures the escaping gas at the same time. Desulfurization slurry, which condenses harmful substances in flue gas, is an environmental protection measure that does not increase energy consumption.

In order to solve the above technical problems, the embodiments of the present invention provide a dewhitening device for a power plant boiler, including a heat exchange component, a dust collector, a desulfurization tower, a condenser and a heater, the heat exchange component, the dust collector, the desulfurization tower, the condensation The boiler and the heater are sequentially connected between the boiler outlet and the chimney through the flue, a circulating water pipeline is communicated between the heat exchange component and the heater, and the heat exchange component is composed of a plurality of parallel tubular graphite heat exchange The tubular graphite heat exchanger is provided with a heat exchange tube bundle, and the heat exchange tube of the heat exchange tube bundle is an artificial graphite tube.

Wherein, the circulating water pipeline includes a circulating water outlet pipe and a circulating water return pipe, the circulating water outlet pipe has high temperature circulating water flowing from the heat exchange component to the heater, and the circulating water return pipe has a self-heater flowing in the circulating water outlet pipe. The low-temperature circulating water that flows to the heat exchange component is provided with a circulating water tank on the circulating water return pipe. The circulating water tank is also provided with an external hot water supply pipe or a heating water supply pipe.

Wherein, an induced draft fan is arranged on the flue between the dust collector and the desulfurization tower.

Wherein, the upper end of the condenser is connected with a condenser water inlet pipe, and a condenser water outlet pipe is connected between the lower end and the circulating water tank.

Wherein, the heat exchange assembly includes an ash accumulation hopper, a flue gas inlet distribution box, 8 to 12 tubular graphite heat exchangers and a flue gas outlet collection box arranged in order from bottom to top, and the flue gas inlet distribution box The flue gas inlet is communicated with the boiler outlet through the flue, the ash hopper is communicated with the lower dust outlet of the flue gas inlet distribution box, and the flue gas inlet distribution box communicates with the heat exchange at the lower end of each tubular graphite heat exchanger. The flue gas outlet collection box is connected to the heat exchanger smoke outlet at the upper end of each tubular graphite heat exchanger, and the smoke outlet of the flue gas outlet collection box is connected to the dust collector through the flue. Connected.

Further, the tubular graphite heat exchanger includes a conical heat exchanger lower shell, a heat exchanger shell and a conical heat exchanger upper shell, and the lower end of the heat exchanger lower shell is provided with a The heat exchanger smoke inlet, the upper end of the heat exchanger upper shell is provided with a heat exchanger smoke outlet, the heat exchanger shell is provided with a heat exchange tube bundle, and the lower part of the heat exchange tube bundle is fixedly connected with a lower part. Tube sheet, the lower part is connected with the upper tube sheet, the lower tube sheet is supported and positioned in the heat exchanger shell by the support plate ring, the upper tube sheet is a floating tube sheet, and the tube side of the tubular graphite heat exchanger is The inside is flue gas, and the inside of the shell is circulating water.

The lower shell of the heat exchanger is provided with a lower manhole, and the upper shell of the heat exchanger is provided with an upper manhole. The joints between the upper tube sheet and the lower tube sheet and the heat exchanger shell are sealed by packing combination.

Preferably, the lower tube sheet and the upper tube sheet are circular tube sheets with a diameter of Ф1200mm, and the heat exchange tube bundle is composed of 309 artificial graphite tubes with an outer diameter/inner diameter of Ф50/36mm. The length is 2560mm, and the total height of the tubular graphite heat exchanger is 6400mm.

Wherein, the heat exchange assembly further includes an automatic monitoring system and a safety protection system, each of the tubular graphite heat exchangers is provided with an automatic monitoring system and a safety protection system, and the automatic monitoring system includes flue gas A humidity alarm system and a circulating water pressure alarm system, the circulating water pressure alarm system includes a pressure sensor and an alarm set on the heat exchanger shell, and the flue gas humidity alarm system includes a flue gas outlet collection box. A flue gas humidity detector; the safety protection system includes a water outlet valve on the circulating water outlet pipe, a water return valve on the circulating water return pipe, a flue gas inlet flap valve at the smoke inlet of the heat exchanger, and a heat exchange valve. The flue gas outlet flapper valve at the smoke outlet.

The invention provides a working method of a power plant boiler dewhitening device, comprising the following steps:

(1) Flue gas heat exchange: the flue gas from the boiler outlet enters the flue gas inlet distribution box, and then enters the tubular graphite heat exchanger of the heat exchange component through the flue gas inlet of the heat exchanger. After the heat exchange of the heat exchanger, the flue gas temperature is reduced from 175-180°C to 130-135°C, and the circulating water temperature in the shell side is increased from 60-65°C to 90-95°C;

(2) The flue gas cooled in step (1) enters the dust collector through the flue gas outlet collecting box and the flue to remove the dust in the flue gas, and the falling dust enters the ash hopper;

(3) The flue gas after dedusting in step (2) enters the desulfurization tower through the induced draft fan, and the SO ₃ in the flue gas is removed in the desulfurization tower;

(4) The flue gas after desulfurization in step (3) enters the condenser through the flue, and is condensed by cold water. The temperature of the cold water is raised from 20-25℃ to 35-40℃, and then flows into the circulating water tank;

(5) The flue gas condensed in step (4) enters the heater through the flue, and the circulating water heated up in step (1) flows into the heater through the circulating water outlet pipe, and the circulating water entering the heater conducts heating on the flue gas. Heating, the temperature of circulating water is lowered from 90-95°C to 75-80°C, and flows through the circulating water return pipe into the circulating water tank; the flue gas temperature is raised from 40-45°C to 70-75°C, and the humid saturated flue gas is heated to After the dry flue gas is discharged into the chimney through the flue, the whitening of the flue gas is completed.

Wherein, in steps (4) and (5), the desulfurization slurry escaped in step (3) is condensed and captured in the graphite tubes of the condenser and the heater.

In step (5), the low-temperature circulating water in the circulating water tank flows into the tubular graphite heat exchanger of the heat exchange assembly through the circulating water return pipe.

The beneficial effects of the above-mentioned technical solutions of the present invention are as follows:

The invention adopts the artificial graphite material with acid corrosion resistance and high heat transfer coefficient as the heat exchange element. Because graphite has the advantages of high thermal conductivity, corrosion resistance, chemical stability, moderate strength, etc., its heat transfer effect and practical performance are superior to those already used at home and abroad. Some types of boiler tail equipment can more efficiently exchange heat for the boiler tail flue gas, and at a lower equipment cost, effectively solve the problem of low temperature corrosion and achieve the dual purpose of energy saving and environmental protection.

Description of drawings

Fig. 1 is the structural block diagram of the present invention;

Fig. 2 is the structural representation of the tubular graphite heat exchanger in the present invention;

Figure 3 is an enlarged view of the structure at the tube sheet of the tubular graphite heat exchanger in Figure 2;

Fig. 4 is the front view of the heat exchange assembly in the present invention;

Fig. 5 is the left side view of the heat exchange assembly in the present invention;

Fig. 6 is the top view of the heat exchange assembly in the present invention;

Fig. 7 is the safety control schematic diagram of the heat exchange assembly in the present invention;

FIG. 8 is an enlarged view of a part of the structure at A in FIG. 7 .

Description of reference numbers:

1. Heat exchange components; 100, tubular graphite heat exchanger; 101, ash hopper; 102, flue gas inlet distribution box; 103, flue gas outlet collection box; 2, dust collector; 3, desulfurization tower; 4, Condenser; 400, condenser inlet pipe; 401, condenser outlet pipe; 402, cold water pump; 5, heater; 6, boiler outlet; 7, chimney; 8, circulating water pipeline; 800, circulating water outlet pipe; 801 , circulating water return pipe; 802, circulating pump; 803, supply pump; 9, circulating water tank; 10, induced draft fan.

Detailed ways

In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

As shown in Figure 1, a power plant boiler dewhitening device includes a heat exchange component 1, a dust collector 2, a desulfurization tower 3, a condenser 4 and a heater 5. The heat exchange component 1, the dust collector 2, and the desulfurization tower 3 , The condenser 4 and the heater 5 are sequentially connected between the boiler outlet 6 and the chimney 7 through the flue, and a circulating water pipeline 8 is communicated between the heat exchange assembly 1 and the heater 5, and the heat exchange assembly 1 consists of multiple It consists of two tubular graphite heat exchangers 100 arranged in parallel. The tubular graphite heat exchanger 100 is provided with a heat exchange tube bundle, and the heat exchange tubes of the heat exchange tube bundle are artificial graphite tubes.

The heat exchange components, condensers and heaters of the present invention all use artificial graphite materials as heat exchange elements, and all are composed of artificial graphite tube heat exchange modules, inlet and outlet flues and flue gas distribution boxes, ash hoppers and ash discharge devices, and brackets. It is composed of operating platform, pipeline system, etc., and has automatic control and detection and safety protection system.

In order to ensure the reliability, safety, stability of the device and the convenience of maintenance of the entire device, the present invention adopts a modular design, that is, the heat exchange components are made into a whole, and each tubular graphite heat exchanger ( Vertical) as a module, the flue gas and circulating water (or cold water) of each module are connected in parallel to form a heat exchange component, each module can be isolated separately, the flue gas goes to the tube side, and the water goes to the shell side.

The design pressure of the present invention is 0.8 MPa, the test pressure is 1.0 MPa, and the design temperature is 220°C. The invention adopts the artificial graphite material with acid corrosion resistance and high heat transfer coefficient as the heat exchange element. Because graphite has the advantages of high thermal conductivity, corrosion resistance, chemical stability, moderate strength, etc., its heat transfer effect and practical performance are superior to those already used at home and abroad. Some types of boiler tail equipment can more efficiently exchange heat for the boiler tail flue gas, and at a lower equipment cost, effectively solve the problem of low temperature corrosion and achieve the dual purpose of energy saving and environmental protection.

The circulating water pipeline 8 includes a circulating water outlet pipe 800 and a circulating water return pipe 801. The circulating water outlet pipe 800 flows high temperature circulating water from the heat exchange component 1 to the heater 5, and the circulating water return pipe 801 There is low-temperature circulating water flowing from the heater 5 to the heat exchange assembly 1. The circulating water return pipe 801 is provided with a circulating water tank 9, and the circulating water return pipe 801 between the circulating water tank 9 and the heat exchange assembly 1 is provided with Circulation pump 802. The upper end of the condenser 4 is connected with a condenser water inlet pipe 400 , a cold water pump 402 is arranged on the condenser water inlet pipe 400 , and a condenser water outlet pipe 401 is connected between the lower end and the circulating water tank 9 . The circulating water tank 9 is also provided with an external hot water supply pipe or a heating water supply pipe, so the hot water in the circulating water tank can provide hot water to users. 803 external heat water supply or as boiler feed water.

An induced draft fan 10 is arranged on the flue between the dust collector 2 and the desulfurization tower 3 .

As shown in FIGS. 4 to 6 , the heat exchange assembly 1 includes an ash hopper 101 , a flue gas inlet distribution box 102 , 8 to 12 tubular graphite heat exchangers 100 and flue gas, which are arranged in sequence from bottom to top. The outlet collection box 103, the smoke inlet of the flue gas inlet distribution box 102 is communicated with the boiler outlet 6 through the flue, the ash accumulation hopper 101 is communicated with the lower dust outlet of the flue gas inlet distribution box 102, and the flue gas inlet The distribution box 102 is in communication with the heat exchanger smoke inlet at the lower end of each tubular graphite heat exchanger 100 , and the flue gas outlet collecting box 103 is connected to the heat exchanger at the upper end of each tubular graphite heat exchanger 100 to discharge smoke The smoke outlet of the flue gas outlet collecting box 103 is communicated with the dust collector 2 through the flue.

As shown in FIG. 2 and FIG. 3 , the tubular graphite heat exchanger 100 includes a conical heat exchanger lower shell, a heat exchanger shell and a conical heat exchanger upper shell. The heat exchange The lower end of the lower shell of the heat exchanger is provided with a heat exchanger smoke inlet, the upper end of the heat exchanger upper shell is provided with a heat exchanger smoke outlet, and the heat exchanger shell is provided with a heat exchange tube bundle. The lower part of the heat pipe bundle is fixedly connected with a lower tube sheet, and the lower part is connected with an upper tube sheet. The lower tube sheet is supported and positioned in the heat exchanger shell by the support plate ring. Release the thermal stress caused by temperature; the heat exchange area (in inner diameter) of a single tubular graphite heat exchanger is 78㎡.

The tube side of the tubular graphite heat exchanger is flue gas, and the shell side is circulating water. The joints between the upper tube sheet and the lower tube sheet and the heat exchanger shell are sealed by packing combination. The lower shell of the heat exchanger is provided with a lower manhole, and the upper shell of the heat exchanger is provided with an upper manhole.

The heat exchange assembly of the present invention also includes an automatic control and detection system, an automatic monitoring system and a safety protection system. Each of the tubular graphite heat exchangers is provided with an automatic monitoring system and a safety protection system. The monitoring system includes a flue gas humidity alarm system and a circulating water pressure alarm system, the circulating water pressure alarm system includes a pressure sensor and an alarm set on the heat exchanger shell, and the flue gas humidity alarm system includes a flue gas humidity alarm system. The flue gas humidity detector on the outlet collection box; the safety protection system includes a water outlet valve on the circulating water outlet pipe, a water return valve on the circulating water return pipe, and a flue gas inlet plug at the smoke inlet of the heat exchanger. Plate valve, flue gas outlet plug-in valve at the flue gas outlet of the heat exchanger.

The automatic control system of the heat exchange components is as follows:

The operation control of cold water pump, circulating pump and supply pump should be connected to the power station boiler control (DCS or PLC control) system, which can be interlocked with the boiler induced draft fan to realize 1. When the boiler induced draft fan is started, the cold water pump, circulating pump and supply pump Automatic start; 2. When the boiler induced draft fan stops running, the cold water pump and the circulating pump stop running; when the water level of the water tank is detected normally, the boiler induced draft fan stops running, and the cold water pump stops running.

An electrode type water level detection sensing system is installed in the circulating water tank. 1. Detect the water level of the circulating water tank, and interlock with the supply pump (the supply pump adopts frequency conversion speed regulation). The supply pump adjusts the external water supply flow to keep the circulating water tank at a certain water level . 2. The circulating water tank is set to detect the extremely low water level, and the signal is connected to the boiler control system. However, when the water level of the circulating water tank is lower than the extremely low water level, the cold water pump will supply water to ensure that the circulating water tank will not be short of water. When the circulating water tank is short of water ( When the water level is detected to be lower than the extremely low water level) the induced draft fan of the boiler shall not be started. This ensures the safe and efficient operation of the circulatory system.

The technical solutions of the present invention are further described below with specific embodiments.

1. Technical solutions

The plurality of tubular graphite heat exchangers in the heat exchange assembly of the present invention are divided into 2 rows, each row has 4-6 tubular graphite heat exchangers, and a set of 8-12 tubular graphite heat exchangers in total (For power station boilers with cogeneration of 75t/h—130t/h, power station boilers greater than 130t/h can increase the number of modules according to the flue gas flow), the total heat transfer area of the whole set of heat exchange components is each column of tubular graphite The sum of the heat transfer area of the heat exchanger.

The lower tube sheet and the upper tube sheet of the tubular graphite heat exchanger are circular tube sheets with a diameter of Ф1200mm. The heat exchange tube bundle consists of 309 artificial graphite tubes with an outer diameter/inner diameter of Ф50/36mm. The length is 2560mm, and the total height of the tubular graphite heat exchanger is 6400mm.

The boiler flue gas enters the tube side through the flue gas inlet distribution box at the bottom of the heat exchange assembly, flows vertically from bottom to top, and flows into the top flue gas outlet collection box after heat exchange, and then enters the flue. The circulating water (or cold water) is distributed to the branch pipes through the main pipe and enters the shell of each tubular graphite heat exchanger, and flows laterally through the shell side (outside the tube) through the baffle. The flow direction of flue gas and circulating water is countercurrent, and the temperature of circulating water (or cold water) and flue gas is changed through heat exchange.

The heat exchange component is equipped with a bypass flue, which can be isolated during maintenance without affecting the continuous operation of the power station boiler. The function of the device system is reasonably set. Without increasing energy consumption, the flue gas emitted by the boiler is first condensed, and a large number of harmful substances that can form atmospheric haze are condensed, and then the exhaust flue gas is heated. , reducing the corrosion of flue gas to the chimney.

2. Operation and Control

The normal operation of the whitening device of the utility boiler of the present invention is automatic control operation, a reliable program is designed, and high-quality and reliable automatic control elements are selected. The detection of each tubular graphite heat exchanger is also carried out automatically, and there are two sets of monitoring systems (flue gas humidity alarm system and circulating water or cold water pressure alarm), which can ensure the safe and stable operation of the bleaching device, and will not It will not affect the subsequent process, nor will it affect the normal operation of the boiler. The flue gas inlet and outlet of the tubular graphite heat exchanger are equipped with automatic flue plug-in valves, and the inlet and outlet of circulating water or cold water are equipped with automatic valves and manual valves, which can be controlled independently. The main pipe is also equipped with manual valves, and has Bypass and valve, as shown in Figure 7.

(1) Circulating water or cold water pressure alarm and detection

There is a pressure sensor on the shell of each tubular graphite heat exchanger. When the pressure of the outer pipeline drops or the pressure drops caused by the leakage of the module, the program controller receives the pressure drop signal sent by the pressure sensor in the module, and automatically adjusts the pressure. The tube type graphite heat exchanger is subjected to pressure detection. The detection method is to automatically close the inlet and outlet water pipe valves of the tube type graphite heat exchanger and stop for 1-2 minutes (program setting). If the pressure is further reduced, it means that there is water leakage in the tubular graphite heat exchanger, the valve will no longer be opened, and the inlet and outlet flap valves of the flue will be automatically closed immediately, and an alarm will be issued at the same time; if the pressure does not decrease, the boiler feed water valve will automatically open to continue normal operation. . The program can be set to perform automatic inspection on all tubular graphite heat exchangers on a regular basis (for example, automatic inspection every eight hours is set).

(2) Flue gas humidity alarm system

There is an online flue gas humidity detector on the flue gas outlet collection box. Once there is water leakage, the leaked water enters the flue gas, and its humidity will increase. The pressure detector is used for pressure detection, and the detection method is the same as before. After the problem is confirmed by testing, the flap valve at the inlet and outlet of the flue is automatically closed.

For the faulty tubular graphite heat exchanger, immediately close the water inlet and outlet manual valves and lock the flue plug valve, open the purge valve and exhaust valve on the shell, check the appearance first, and then seal the seal. Carry out inspection and find faults and eliminate them in time. If there is no fault in the appearance, it means that there is a problem with the heat exchange tube. It is necessary to open the manhole cover on the flue gas inlet and outlet pipes of the tubular graphite heat exchanger, enter from the manhole, and find the leaking water. heat exchange tube. The leaking heat exchange tubes can be quickly blocked on site and then resume normal operation.

During normal operation, all the multiple tubular graphite heat exchangers can be opened, or one or several (generally no more than three) can be closed according to the flue gas temperature or circulating water temperature.

Before the device is put into operation, carry out detailed technical disclosure and operation training on the structure, performance, characteristics, precautions, etc. of the device, and write product instruction manuals and operation manuals, so that users can fully understand the characteristics, use, control, and maintenance requirements of the device until they are proficient. until operation.

3. Equipment cleaning and maintenance

The ash discharge system of the ash hopper adopts the same automatic control and conveying method as that of the dust collector. The ash conveying pipe is connected with the existing system, and there is no need to increase the vacuum equipment; the outlet of the ash hopper is equipped with a plug-in valve and an electric discharge valve. The control of the ash discharge system needs to be integrated with the existing control system of the utility boiler.

Since the flue gas flows through the heat exchange tube from bottom to top, the heat exchange tube with a higher flow rate has a larger inner diameter and a smooth inner wall, so the possibility of dust accumulation in the heat exchange tube is very small, and soot blowing is usually not required in the heat exchange tube. There will be a small amount of ash accumulation at the non-pipe hole of the flue gas outlet of the upper tube sheet, but it will not increase to a certain extent, and it will be taken away by the flue gas. Manual cleaning or periodic cleaning module by module.

If there is adhesion inside the heat exchange tube, a single tubular graphite heat exchanger can be isolated for manual cleaning, or the tubular graphite heat exchanger can be cleaned regularly one by one. The cleaning method depends on the bonding situation. Brushes, high-pressure air, high-pressure steam, etc. can be used, but hard tools such as steel brushes, steel pipes, and drills cannot be used to dredge.

The present invention also provides a working method of a power plant boiler dewhitening device, comprising the following steps:

(1) Flue gas heat exchange: the flue gas from the boiler outlet enters the flue gas inlet distribution box, and then enters the tubular graphite heat exchanger of the heat exchange component through the flue gas inlet of the heat exchanger. After the heat exchange of the heat exchanger, the flue gas temperature is reduced from 175-180°C to 130-135°C, and the circulating water temperature in the shell side is increased from 60-65°C to 90-95°C;

(2) The flue gas cooled in step (1) enters the dust collector through the flue gas outlet collecting box and the flue to remove the dust in the flue gas, and the falling dust enters the ash hopper;

(3) The flue gas after dedusting in step (2) enters the desulfurization tower through the induced draft fan, and the SO ₃ in the flue gas is removed in the desulfurization tower;

(4) The flue gas after desulfurization in step (3) enters the condenser through the flue, and is condensed by cold water. The temperature of the cold water is raised from 20-25℃ to 35-40℃, and then flows into the circulating water tank;

(5) The flue gas condensed in step (4) enters the heater through the flue, and the circulating water heated up in step (1) flows into the heater through the circulating water outlet pipe, and the circulating water entering the heater conducts heating on the flue gas. Heating, the temperature of circulating water is lowered from 90-95°C to 75-80°C, and flows through the circulating water return pipe into the circulating water tank; the flue gas temperature is raised from 40-45°C to 70-75°C, and the humid saturated flue gas is heated to After the dry flue gas is discharged into the chimney through the flue, the whitening of the flue gas is completed.

In steps (4) and (5), the desulfurization slurry escaped in step (3) is condensed and captured in the graphite tubes of the condenser and heater. In step (5), the low-temperature circulating water in the circulating water tank flows into the tubular graphite heat exchanger of the heat exchange assembly through the circulating water return pipe.

Compared with the prior art, the present invention has the following advantages:

1. The present invention reduces the emission of harmful substances in the flue gas discharged from the power station boiler, and "whitens" the flue gas, the boiler chimney will no longer emit white smoke, and the environmental protection effect is remarkable.

2. Without increasing energy consumption, the device system can provide hot water to heat users, and can also heat boiler feed water, so as to improve the thermal efficiency of power plant boilers.

3. In the present invention, the boiler flue gas can be preliminarily dedusted through the heat exchanger, which reduces the load of the dust collector, reduces the temperature of the flue gas entering the desulfurization tower, and reduces the amount of spray water.

4. The present invention increases the temperature of the chimney entering the boiler chimney, increases the dryness of the wet flue gas, greatly reduces the corrosion of the flue gas to the boiler chimney, and prolongs the service life of the chimney.

5. The corrosion resistance of the present invention is remarkable, and the device system adopts the artificial graphite tube as the heat exchange element, which fundamentally solves the problem of low temperature corrosion of flue gas that has been difficult to overcome for decades.

6. The present invention adopts a modular design, and the number of modules can be selected according to the demand of the power station boiler, which is convenient for large-scale production and replacement.

7. Safety control and protection devices such as flue gas humidity and water pressure detection are set in the present invention, which has a high degree of automation, is safe and reliable, and ensures the safe operation of the device system.

8. The dewhitening device of the present invention has a reasonable structure, the device system is equipped with a bypass flue, and the tubular graphite heat exchanger does not affect the continuous operation of the power station boiler during maintenance.

9. The present invention can condense and capture the escaping desulfurization slurry, greatly reduce the emission of harmful substances that cause atmospheric haze, and at the same time, it can heat the boiler feed water internally and provide a large amount of hot water externally, thus achieving both energy saving and environmental protection.

10. The invention has simple operation and maintenance, can realize automatic operation, does not increase the labor intensity of the stoker, and has stable physical and chemical properties of the graphite material, high durability and long service life.

The above are the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. The utility model provides a white device of power plant boiler takes off, its characterized in that, including heat exchange assembly, dust remover, desulfurizing tower, condenser and heater, heat exchange assembly, dust remover, desulfurizing tower, condenser and heater loop through the flue and connect between boiler outlet and chimney, the intercommunication has the circulating water pipeline between heat exchange assembly and the heater, heat exchange assembly comprises a plurality of shell and tube graphite heat exchangers that connect in parallel the setting, be equipped with heat exchanger tube bank in the shell and tube graphite heat exchanger, heat exchanger tube bank's heat exchange tube is artificial graphite pipe.

2. The utility boiler whitening device according to claim 1, wherein the circulating water pipeline comprises a circulating water outlet pipe and a circulating water return pipe, wherein high-temperature circulating water flowing from the heat exchange component to the heater flows in the circulating water outlet pipe, low-temperature circulating water flowing from the heater to the heat exchange component flows in the circulating water return pipe, and a circulating water tank is arranged on the circulating water return pipe.

3. The utility boiler de-whitening device according to claim 1, characterized in that an induced draft fan is arranged on the flue between the dust remover and the desulfurizing tower.

4. The utility boiler whiting device of claim 1 wherein the condenser has an inlet pipe connected to the upper end of the condenser and an outlet pipe connected to the circulating water tank.

5. The utility boiler whitening device according to claim 1, characterized in that the heat exchange assembly comprises an ash deposition hopper, a flue gas inlet distribution box, 8 ~ 12 tubular graphite heat exchangers and a flue gas outlet collection box which are arranged from bottom to top in sequence, wherein a flue gas inlet of the flue gas inlet distribution box is communicated with a boiler outlet through a flue, the ash deposition hopper is communicated with a lower dust outlet of the flue gas inlet distribution box, the flue gas inlet distribution box is communicated with a heat exchanger flue gas inlet at the lower end of each tubular graphite heat exchanger, the flue gas outlet collection box is communicated with a heat exchanger flue gas outlet at the upper end of each tubular graphite heat exchanger, and a flue gas outlet of the flue gas outlet collection box is communicated with a dust remover through a flue.

6. The utility boiler whitening device according to claim 1 or 5, characterized in that the tube type graphite heat exchanger comprises a conical lower heat exchanger shell, a heat exchanger shell and a conical upper heat exchanger shell, wherein a heat exchanger smoke inlet is formed in the lower end of the lower heat exchanger shell, a heat exchanger smoke outlet is formed in the upper end of the upper heat exchanger shell, a heat exchange tube bundle is arranged in the heat exchanger shell, a lower tube plate is fixedly connected to the lower portion of the heat exchange tube bundle, an upper tube plate is connected to the lower portion of the heat exchange tube bundle, the lower tube plate is supported and positioned in the heat exchanger shell through a support plate ring, the upper tube plate is a floating tube plate, flue gas is in the tube pass of the tube type graphite heat exchanger, and circulating water.

7. The utility boiler whitening device according to claim 6, characterized in that the lower tube plate and the upper tube plate are circular tube plates with a diameter of phi 1200mm, the heat exchange tube bundle is composed of 309 artificial graphite tubes with an outer/inner diameter of phi 50/36mm, the tube length of the artificial graphite tubes is 2560mm, and the total height of the shell and tube graphite heat exchanger is 6400 mm.

8. The utility boiler whitening device according to claim 1 or 5, characterized in that the heat exchange assembly further comprises an automatic monitoring system and a safety protection system, each of the shell-and-tube graphite heat exchangers is provided with an automatic monitoring system and a safety protection system, the automatic monitoring system comprises a flue gas humidity alarm system and a circulating water pressure alarm system, the circulating water pressure alarm system comprises a pressure sensor and an alarm arranged on a shell of the heat exchanger, and the flue gas humidity alarm system comprises a flue gas humidity detector arranged on a flue gas outlet collection box; the safety protection system comprises a water outlet valve arranged on the circulating water outlet pipe, a water return valve arranged on the circulating water return pipe, a flue gas inlet gate valve at the flue gas inlet of the heat exchanger and a flue gas outlet gate valve at the flue gas outlet of the heat exchanger.

9. A method of operating a plant boiler de-whitening means as claimed in any of the claims 1 ~ 8, characterized by the steps of:

(1) flue gas heat exchange: the flue gas from the boiler outlet enters a flue gas inlet distribution box, then correspondingly enters a tube type graphite heat exchanger of a heat exchange assembly through a heat exchanger flue gas inlet, after heat exchange of the tube type graphite heat exchanger, the temperature of the flue gas is reduced from 175-65 ℃ to 130-135 ℃, and the temperature of circulating water in a shell pass is increased from 60-65 ℃ to 90-95 ℃;

(2) the flue gas cooled in the step (1) enters a dust remover through a flue gas outlet collection box and a flue, dust in the flue gas is removed, and the falling dust enters an ash deposition hopper;

(3) and (3) enabling the flue gas subjected to dust removal in the step (2) to pass through a draught fan and then enter a desulfurizing tower, and removing SO in the flue gas in the desulfurizing tower₃；

(4) The flue gas desulfurized in the step (3) enters a condenser through a flue, and is condensed by cold water, the temperature of the flue gas is reduced to 40-45 ℃ from 50-55 ℃, harmful substances are condensed, the temperature of the cold water in the condenser is increased to 35-40 ℃ from 20-25 ℃, and then the cold water flows into a circulating water tank;

(5) the flue gas condensed in the step (4) enters a heater through a flue, the circulating water heated in the step (1) flows through a circulating water outlet pipe and enters the heater, the circulating water entering the heater heats the flue gas, the temperature of the circulating water is reduced to 75-80 ℃ from 90-95 ℃, and the circulating water flows through a circulating water return pipe and enters a circulating water tank; the temperature of the flue gas is increased from 40-45 ℃ to 70-75 ℃, and the wet saturated flue gas is heated into dry flue gas and then enters a chimney through a flue to be discharged, so that the whitening of the flue gas is completed.

10. The method of claim 9, wherein in the steps (4) and (5), the desulfurized slurry escaping from the step (3) is condensed and captured in the graphite tubes of the condenser and the heater, and in the step (5), the low-temperature circulating water in the circulating water tank flows into the shell-and-tube graphite heat exchanger of the heat exchange unit through the circulating water return pipe.

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