CN201636884U - A boiler flue gas deep cooling waste heat recovery device - Google Patents

Abstract

A boiler flue gas deep cooling waste heat recovery device with an independent operating system, including a flue gas cryogenic cooler, a heater and an independent water circulation system composed of it, using the flue gas after dust removal by an electrostatic precipitator to cool the flue gas The cold water is heated in the cooler to recover the waste heat of the flue gas, and the hot water at the outlet of the flue gas cryogenic cooler is sent to the heater to preheat the air to increase the temperature of the combustion-supporting air of the boiler; the flue gas passes through the flue gas cryogenic cooler and then directly enters the desulfurization Tower, for desulfurization recovery treatment, and finally discharged through the wet chimney; this device does not need to change the existing thermal system of the unit, while recovering the waste heat of the flue gas, it does not affect its long-term safe operation, not only reduces the exhaust gas temperature, but also saves Desulfurization water consumption improves unit efficiency and increases unit output.

Description

A boiler flue gas deep cooling waste heat recovery device

technical field

The utility model belongs to the technical field of waste heat recovery and utilization, in particular to a waste heat recovery and utilization device for deep cooling of flue gas of power station boilers and industrial boilers.

Background technique

Exhaust heat loss is the largest item among various heat losses of boilers, generally ranging from 5% to 12%, accounting for 80% or more of the total heat loss of boilers. In order to recycle the exhaust heat of boilers, the following two forms are mainly adopted for different units:

1) For traditional coal-fired units that are not equipped with a desulfurization system, the existing technology usually installs a low-pressure economizer between the air preheater and the electrostatic precipitator of the boiler, and uses the waste heat of the flue gas to heat the condensate in the reheating system. After the water absorbs heat, it returns to the low-pressure heater, and then the low-pressure cylinder uses this part of the flue gas heat to drive the generator to generate electricity, resulting in huge economic benefits. However, the fly ash content between the air preheater and the electrostatic precipitator is very high, and the dust removal efficiency is calculated according to 99.4% to 99.6%. Wear and tear, the service life of the heat exchange tube is shortened, and the safety factor of the equipment is reduced. For this reason, it is necessary to control the wear of the pipe within a reasonable range, and the wear rate of the fly ash on the pipe wall is proportional to the third power of the flue gas flow rate, and the control of wear requires the control of the flue gas flow rate. Usually, by increasing the heat transfer area of the low-pressure economizer to increase the flue gas resistance, the purpose of limiting the flue gas flow rate is achieved, but the equipment investment cost is increased.

At the same time, in order to avoid low-temperature corrosion, the inlet pipe wall temperature of the low-pressure economizer is controlled above the acid dew point of the flue gas, and the outlet flue temperature is controlled at 130°C to 150°C, which severely restricts heat recovery. However, after the flue gas passes through the low-pressure economizer, the temperature drops, and the specific resistance of the smoke and dust increases more, which will have a great impact on the performance and life of the electrostatic precipitator, and the dust removal efficiency will drop significantly. Even if the flue gas temperature is kept above the acid dew point temperature, the possibility of flue gas condensation cannot be completely avoided. Pipe conditions, etc. will cause condensation on the pipe wall of the low-pressure economizer. Once condensation occurs, the calcium in the fly ash will combine with the acid and moisture in the flue gas to form a cement-like substance that is deposited on the pipe wall and is difficult to remove. Over time, these cement-like substances can easily block the pipe row, which brings serious hidden dangers to the safe operation of the unit. Once blockage occurs, the flue gas channel will be reduced, the flow resistance will increase, and the power consumption of the plant will increase. In severe cases, it will cause the unit to drop its output or even be forced to stop. In addition, the low-temperature economizer in front of the static precipitator is susceptible to wear and corrosion. Once the pipe is perforated and leaks, the condensed water sprayed out will become a disaster for the electrostatic precipitator or bag filter.

2) For coal-fired units equipped with a desulfurization system, a gas-gas heat exchanger (GGH) flue gas reheating device is usually installed in the desulfurization system to recover the waste heat of the flue gas. In order to save energy, it is usually installed before the desulfurization tower.

Generally speaking, the optimum desulfurization working temperature for boiler flue gas wet desulfurization is 80-90°C. For this reason, use GGH to reduce the exhaust gas temperature of boilers at 130°C to 150°C to about 90°C before passing it into the desulfurization tower for desulfurization, and the temperature drops to about 50°C after desulfurization. In order to increase the flue gas lift height and prevent the flue and the inner wall of the chimney from being corroded by the low-temperature wet flue gas at the outlet of the desulfurization tower, the gas-gas heat exchanger (GGH) is used to heat the net flue gas at the outlet of the desulfurization tower from about 50°C to 80°C to 100°C. ℃, and finally discharged through the chimney. It can be seen that the installation of a gas-gas heat exchanger (GGH) does not bring significant economic benefits, and the waste heat of the flue gas at more than 100 degrees is wasted in vain, and the structure of the gas-gas heat exchanger (GGH) is complex and reliable in operation. Low, the installation cycle is long, the initial investment of the equipment is large, and the gas-gas heat exchanger (GGH) cannot be widely used.

With the development of desulfurization technology and the in-depth understanding of the role of gas-gas heat exchanger (GGH), it is found that gas-gas heat exchanger (GGH) does not have the effect of increasing environmental protection, even if the gas-gas heat exchanger is installed (GGH) The flue gas temperature is still not high, and anti-corrosion measures still need to be taken on the inner wall of the flue and chimney, and if the gas-gas heat exchanger (GGH) is not installed, the phenomenon of a large amount of water mist in the chimney exhaust will not increase the atmospheric pressure. pollute. Therefore, nowadays developed countries and regions tend not to install gas-gas heat exchangers (GGH), and new desulfurization projects in my country in recent years have also begun to accept designs without gas-gas heat exchangers (GGH).

In view of this, how to recover the waste heat of the flue gas and reduce the corrosion of the flue and chimney behind the desulfurization tower without installing a gas-gas heat exchanger (GGH) has become an urgent technical problem to be solved.

Contents of the invention

In order to overcome the above-mentioned shortcomings of the prior art, the purpose of this utility model is to provide a boiler flue gas deep cooling waste heat recovery device with an independent operating system, which reduces the temperature of the flue gas to about 90°C through the flue gas deep cooling cooler, and recovers The heat of the flue gas heats the air through the heater to increase the temperature of the combustion-supporting air. While recovering the waste heat of the flue gas, it not only does not affect the long-term safe operation of the existing thermal system, reduces the exhaust gas temperature, but also saves the consumption of the desulfurization tower. The amount of water improves the efficiency of the unit and increases the output of the unit.

In order to achieve the above purpose, the technical solution of the utility model is achieved as follows: a boiler flue gas deep cooling waste heat recovery device, comprising:

A flue gas cryogenic cooler 8, the inlet flue of the flue gas cryogenic cooler 8 is connected through the outlet flue of the electrostatic precipitator 3, and the outlet flue of the flue gas cryogenic cooler 8 is connected through the inlet flue of the desulfurization tower 9 ,

A heater 4, the cold air inlet of the heater 4 is connected with the blower 5, the hot air outlet of the heater 4 is connected with the air preheater 2, and the cold water outlet of the heater 4 is cooled with the flue gas through the water pump 6 The cold water inlet of the cooler 8 is connected, and the hot water outlet of the flue gas cryogenic cooler 8 is connected with the hot water inlet of the heater 4, thereby forming an independent water circulation system.

A booster fan 7 can be installed between the inlet flue of the flue gas cryogenic cooler 8 and the outlet flue of the electrostatic precipitator 3 .

The essence of the utility model is to use the gas-water heat exchange device used as the flue gas cryogenic cooler 8 to use the waste heat of the flue gas at the outlet of the electrostatic precipitator 3 to heat the cold water in the independent water circulation system, and then the flue gas cryogenic cooler 8 The hot water from the hot water outlet is sent to the air heater 4 to heat the cold air and increase the temperature of the air entering the air preheater 2, thereby achieving the purpose of improving boiler efficiency and increasing the net efficiency of the unit.

Compared with the unit system installed with low-pressure economizer or gas-gas heat exchanger (GGH) flue gas recovery device, the utility model has the following characteristics:

1) The utility model has an independent operating system and an independent water circulation system, so the active units only need to add this system without changing other equipment and systems to complete the transformation, so as to achieve the recovery and utilization of boiler exhaust heat and reduce the exhaust temperature , to improve boiler efficiency, increase unit output, and achieve high efficiency, energy saving, and emission reduction goals. Even if a fault occurs during the use of the utility model, it is only necessary to stop repairing the faulty equipment without affecting the normal operation of the unit.

2) The flue gas cryogenic cooler 8 has all the advantages of the low-pressure economizer and the gas-gas heat exchanger (GGH) flue gas recovery device. The flue gas cryogenic cooler 8 is installed between the electrostatic precipitator 3 and the desulfurization tower 9 to ensure that the flue gas cryogenic cooler 8 works in a low-dust area, and the flue gas corrosion wear, adhesion and blockage are relatively light, and the work is reliable and efficient The booster fan 7 is installed before the flue gas cryogenic cooler 8, which ensures that the addition of the flue gas cryogenic cooler 8 does not change the original system of the unit, and the installation period is short, the investment is small, and the effect is quick; After the gas cryogenic cooler 8, the exhaust gas temperature decreases, the waste heat of the flue gas can be recycled, the boiler efficiency is improved, and the output of the unit is increased; the large water consumption of wet desulfurization is mainly due to the large water consumption in the adiabatic evaporation process of the absorption tower, and the flue gas passes through After the flue gas cryogenic cooler 8, the temperature drops to near the optimal desulfurization temperature and then passes into the desulfurization tower 9, which not only has high desulfurization efficiency, but also greatly reduces the amount of evaporated water. Emissions and disposal costs are greatly reduced.

3) The heat exchange medium of traditional air heaters is steam and air, while the air heater 4 in the utility model involves heat exchange between hot water and air. Since the heat recovered by the flue gas cryogenic cooler 8 is not too large, the heat load of the air heater 4 is small, and the design principle and method of an ordinary heat exchanger can be adopted, and the structure is simple and reliable. The air heater 4 is installed to preheat the air, which improves the inlet temperature of the air preheater 2 and prevents low-temperature corrosion. Because the heat transfer capacity of the air heater 4 is not too large, the temperature of the cold air does not rise much (generally <50°C), and the utility model is independent from the original system of the unit, and has an independently adjustable water circulation system, which ensures that the installation of a heater The wall temperature of the heated surface of the air preheater 2 behind the air device 4 is higher than the acid dew point temperature of the flue gas and has little influence on the heat exchange effect of the air preheater 2, so there will be no flue gas condensation on the surface of the heated surface of the air preheater 2 Sulfuric acid corrosion does not affect the normal use of the air preheater 2.

4) After passing through the flue gas cryogenic cooler 8, the flue gas is directly passed into the desulfurization tower 9, and finally discharged through the wet chimney 11. Since most thermal power plants have desulfurization towers 9, and the existing desulfurization technology is relatively mature, it is capable of dealing with the problem of flue gas condensation corrosion, and the follow-up flue and wet chimneys have undergone anti-corrosion treatment. There is an acid pool at the bottom of the wet chimney 11, and the smoke The gas condenses in the wet chimney 11 to form sulfuric acid and falls into the acid tank, and is sent to the desulfurization tower 9 through the acid-resistant pump 10 for treatment, so the flue gas at the outlet of the flue gas cryogenic cooler 8 can be directly passed into the desulfurization tower 9 for subsequent treatment. There is no potential safety hazard.

Description of drawings

Accompanying drawing is the system structure diagram of the utility model.

Detailed ways

Below in conjunction with accompanying drawing, structural principle and working principle of the present utility model are described in detail.

Referring to the accompanying drawings, a boiler flue gas deep cooling waste heat recovery device includes: a flue gas cryogenic cooler 8 and an air heater 4, and the flue gas cryogenic cooler 8 includes a cold water inlet and a hot water outlet , 1 flue gas inlet and 1 flue gas outlet to realize heat exchange between flue gas and cold water. The inlet flue of the flue gas cryogenic cooler 8 is connected through the outlet flue of the electrostatic precipitator 3 , and the outlet flue of the flue gas cryogenic cooler 8 is connected through the inlet flue of the desulfurization tower 9 . The air heater 4 includes 1 hot water inlet, 1 cold water outlet, 1 cold air inlet, and 1 hot air outlet to realize heat exchange between hot water and cold air. The cold air inlet of the air heater 4 and the blower 5 connected, the hot air outlet of the heater 4 is connected through the air preheater 2, the cold water outlet of the heater 4 is connected with the cold water inlet of the flue gas cryogenic cooler 8 through the water pump 6, and the flue gas cryogenic cooler 8 is hot water The outlet is connected with the hot water inlet of the air heater 4, thereby forming an independent water circulation system.

The booster fan 7 is placed between the electrostatic precipitator 3 and the flue gas cryogenic cooler 8, the desulfurization tower 9 is arranged next to the flue gas cryogenic cooler 8, and finally the wet chimney 11; the air heater 4 is arranged in the air preheating before device 2.

The cooling water enters the flue gas cryogenic cooler 8 from the cold water inlet, and exchanges heat with the flue gas to become hot water. The wind device 4, after heat exchange with the cold air, becomes cold water; the cold water is sent from the cold water outlet of the air heater 4 to the flue gas cryogenic cooler 8 through the water pump 6, thereby forming an independent water circulation system.

The cold air is sent to the heater 4 by the blower 5 through the cold air inlet of the heater 4 for preheating; the hot air enters the air preheater 2 through the hot air outlet of the heater 4 for further preheating; the air preheater 2 The outlet hot air is sent to the furnace of boiler 1 to support combustion and improve the combustion condition; the flue gas at the outlet of boiler 1 enters the air preheater 2 to preheat the air through the flue; the flue gas at the outlet of air preheater 2 directly passes into the electrostatic precipitator 3 Flue gas dust removal; the flue gas at the outlet of the electrostatic precipitator 3 is sent to the flue gas cryogenic cooler 8 through the booster fan 7 to reduce the temperature of the flue gas and recover the waste heat of the flue gas; the flue gas at the outlet of the flue gas cryogenic cooler 8 is directly fed into the desulfurization The tower 9 performs desulfurization treatment; the flue gas at the outlet of the desulfurization tower 9 is discharged through the wet chimney 11 . The wet chimney 11 is lined with Ti alloy through the explosive expansion method. There is _an acid tank at the bottom of the chimney. Sulfuric acid corrosion problem.

In the accompanying drawings, 1 is a boiler; 2 is an air preheater; 3 is an electrostatic precipitator; 4 is a heater; 5 is a blower; 6 is a water pump; 7 is a booster fan; 8 is a flue gas cryogenic cooler; 9 is a desulfurization tower; 10 is an acid pump; 11 is a wet chimney.

Claims (2)

1. A boiler flue gas deep cooling waste heat recovery device, comprising: A flue gas cryogenic cooler (8), the inlet flue of the flue gas cryogenic cooler (8) is connected through the outlet flue of the electrostatic precipitator (3), and the flue gas cryogenic cooler (8) outlet flue is connected to the desulfurization The inlet flue of tower (9) connects through; A heater (4), the cold air inlet of the heater (4) links to each other with the blower (5), the hot air outlet of the heater (4) is connected through the air preheater (2), and the heater ( 4) The cold water outlet communicates with the cold water inlet of the flue gas cryogenic cooler (8) through the water pump (4), and the hot water outlet of the flue gas cryogenic cooler (8) communicates with the hot water inlet of the air heater (4). 2. A boiler flue gas deep cooling waste heat recovery device as claimed in claim 1, characterized in that: between the flue gas cryogenic cooler (8) inlet flue and the electrostatic precipitator (3) outlet flue can be added Install booster blower (7).

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