A low-temperature coal-fired flue gas desulfurization and denitrification system and method

Abstract

The present application belongs to the field of flue gas treatment, and discloses a low-temperature coal-fired flue gas desulfurization and denitrification system and method. The system comprises an electrostatic precipitator, a denitration liquid regenerating device, a NO complex absorber, a desulfurizer, a power induced draft device and a chimney; the denitration liquid regenerating device comprises a regenerator and a jacket layer; the NO complex absorber is provided with denitration liquid; the flue gas outlet of a coal-fired equipment is connected with the lower gas inlet of the jacket layer through the electrostatic precipitator; the upper gas outlet of the jacket layer is connected with the lower gas inlet of the NO complex absorber; the desulfurizer is provided with desulfurization liquid; and the top gas outlet of the NO complex absorber is connected with the lower gas inlet of the desulfurizer. The present application completes efficient removal of nitrogen oxides under the condition of lower flue gas temperature through the process of wet absorption, and simultaneously links calcium-calcium desulfurization technology to complete desulfurization and denitrification purification treatment of low-temperature flue gas.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of flue gas treatment, and more particularly relates to a low-temperature coal-fired flue gas desulfurization and denitrification system and method. BACKGROUND

[0002] With the rapid development of industrialization, energy resources represented by coal account for more than 60% of total resource consumption. Power plants, industrial coal-fired boilers, coal chemical industry and other industries all have the problem of flue gas treatment. Coal releases a large amount of ash and pollutants such as sulfides, nitrogen oxides and hydrocarbons during combustion. Nitrogen oxides and sulfur dioxide will form corresponding acid substances when they come into contact with water, and form acid rain when it rains, which will have a great corrosive effect on buildings, soil and other things on the ground. Nitrogen oxides in flue gas are a kind of greenhouse gas, which can destroy the ozone layer and enhance ultraviolet radiation.

[0003] The main pollutants in coal-fired flue gas are nitrogen oxides and sulfur dioxide. Nitrogen oxides are divided into components such as nitric oxide and nitrogen dioxide, and the proportion of nitric oxide in nitrogen oxides is more than 90% due to the influence of combustion conditions. The main desulfurization and denitrification technologies on the market are as follows: 1. The main desulfurization technology is wet desulfurization, and the limestone-gypsum method is the most widely used wet desulfurization technology at present. Its principle is that the slurry made of limestone powder contacts with sulfur dioxide in flue gas to generate calcium sulfite, and the calcium sulfite is then oxidized to form stable gypsum. 2. The denitrification technology is divided into selective catalytic reduction method (SCR), which uses ammonia to selectively reduce nitrogen oxides into nitrogen and water under the catalysis of noble metal and vanadium oxide. 3. The non-selective catalytic reduction method (SNCR) is to reduce nitrogen oxides into nitrogen and water without catalyst under the condition of 900-1200℃ with ammonia.

[0004] In actual production process, these desulfurization and denitrification methods have certain limitations. Wet desulfurization has the disadvantages of easy plugging and easy disintegration in the operation process. SCR is mainly restricted by cost, and has high investment and high catalyst cost. In some industrial production, the temperature of flue gas generated after the waste heat utilization of coal-fired boiler and coal-fired power plant cannot reach the SCR denitrification reaction temperature, and the dust and sulfur dioxide in the flue gas can cause catalyst poisoning, resulting in poor denitrification effect and high overall operation cost. SNCR has a relatively harsh reaction temperature, and the flue gas is generally difficult to reach the reaction temperature, resulting in low denitrification efficiency. In addition, in the field of power plant and the like, SNCR mainly sprays urea (ammonia water) in the furnace to specifically reduce nitrogen oxides to achieve the effect of denitrification, but the mass transfer effect of the sprayed ammonia substances is general, and the ammonia substances have a great corrosive effect on the furnace. Considering comprehensively, the effect of SNCR is general. At the same time, ammonia water or urea is also used as a reducing agent in SCR, which is easy to corrode the equipment in the production process, causing equipment damage and increasing maintenance cost.

[0005] Therefore, there is an urgent need to propose a new low-temperature coal-fired flue gas desulfurization and denitrification system and method. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a low-temperature coal-fired flue gas desulfurization and denitrification system and method. The present application completes the efficient removal of nitrogen oxides at a lower flue gas temperature through the process of wet absorption, and simultaneously completes the desulfurization and denitrification purification treatment of low-temperature flue gas by linking calcium-calcium desulfurization technology.

[0007] In order to achieve the above-mentioned purpose, the present application provides a low-temperature coal-fired flue gas desulfurization and denitrification system, which comprises an electrostatic precipitator, a denitrification liquid regenerator, a NO complex absorber, a desulfurizer, a power induced draft device and a chimney.

[0008] The denitrification liquid regenerator comprises a regenerator and a jacket layer arranged on part of the body of the regenerator; the jacket layer is provided with a lower gas inlet and an upper gas outlet; the NO complex absorber is provided with a lower gas inlet and a top gas outlet, and the NO complex absorber is provided with denitrification liquid; the flue gas outlet of the coal-fired equipment is connected with the lower gas inlet of the jacket layer through the electrostatic precipitator; the upper gas outlet of the jacket layer is connected with the lower gas inlet of the NO complex absorber;

[0009] The desulfurizer is provided with a lower gas inlet and a top gas outlet, and the desulfurizer is provided with desulfurization liquid; the top gas outlet of the NO complex absorber is connected with the lower gas inlet of the desulfurizer; the top gas outlet of the desulfurizer is connected with the chimney through the power induced draft device;

[0010] The denitrification liquid is a mixture of ferrous sulfate, EDTA and a reducing agent.

[0011] The desulfurization liquid is calcium sulfite slurry with a concentration of 20-30%.

[0012] In the application, the main component of the denitration liquid is Fe(II)-EDTA (ethylenediamine tetraacetic acid), Fe(II)-EDTA reacts with NO to form ferrous ferriyl compound through chelation, and the chelation reaction is as follows:

[0013] Fe 2+ -EDTA + NO → Fe 2+ (NO)EDTA,

[0014] The chelation reaction is a rapid pseudo-first-order reaction, and the rate constant can reach 10 6 L / (mol·s) at normal temperature, and can efficiently capture low-concentration NO.

[0015] Moreover, after the cooling flue gas enters the NO complex absorber, part of the sulfur dioxide in the cooling flue gas is dissolved to generate sulfite, which can reduce the trivalent iron in the denitration liquid to divalent iron, thereby indirectly maintaining the absorption activity of the denitration liquid and promoting the absorption of NO.

[0016] Considering that the denitration liquid is affected by the oxygen content in the flue gas, and the divalent iron in the denitration liquid will be oxidized to trivalent iron to cause the denitration liquid to be deactivated after a period of absorption, the application sets that the main component of the denitration liquid is Fe(II)-EDTA, and a small amount of reducing agent (NaSO3) is added to inhibit the oxidation of Fe(II)-EDTA to Fe(III)-EDTA during the absorption of NO, thereby delaying the deactivation time of the denitration liquid.

[0017] According to the application, preferably, the jacket layer is further provided with a condensed water outlet connected to the outside of the system through a hydrophobic valve.

[0018] According to the application, preferably, an online flue gas detection device is arranged on the pipeline connected between the top gas outlet of the NO complex absorber and the lower gas inlet of the desulfurizer, and the online flue gas detection device is used to detect the NO content in the top gas outlet of the NO complex absorber.

[0019] According to the application, preferably, the NO complex absorber is further provided with a bottom liquid outlet and a middle-lower liquid inlet.

[0020] The regenerator is a sealed tank provided with stirring, and the part of the body of the regenerator without the jacket layer is provided with an upper regenerated liquid inlet, a lower material supplementing port, a middle-upper protective gas inlet, a controllable exhaust port, and a bottom liquid outlet.

[0021] The system further comprises a reducing agent tank, an activated carbon tank, a pH regulator tank, a protective gas storage tank and a denitration liquid storage tank; the denitration liquid storage tank is provided with a lower liquid supplement outlet and an upper protective gas inlet;

[0022] The bottom liquid outlet of the NO complexing absorber is divided into two paths, one of which is connected with the upper liquid inlet of the regenerator to be regenerated, and the other is connected to the outside of the system.

[0023] The outlet of the reducing agent tank, the outlet of the activated carbon tank and the outlet of the pH regulator tank are all connected with the lower material supplement port of the regenerator.

[0024] The outlet of the protective gas storage tank is connected with the upper protective gas inlet of the regenerator and the upper protective gas inlet of the denitration liquid storage tank respectively; the protective gas in the protective gas storage tank is inert gas such as nitrogen.

[0025] The middle and lower liquid inlets of the NO complexing absorber are connected with the bottom liquid outlet of the regenerator and the lower liquid supplement outlet of the denitration liquid storage tank respectively.

[0026] In the present application, the regenerator and the denitration liquid storage tank both need to be protected by protective gas.

[0027] According to the present application, preferably, the content of the reducing agent in the denitration liquid is 4.5-5.5‰ based on the total weight of the denitration liquid, the reducing agent in the denitration liquid is sodium sulfite, and the molar ratio of ferrous sulfate to EDTA in the denitration liquid is (0.8-1.2):(0.8-1.2).

[0028] According to the present application, preferably, the reducing agent in the reducing agent tank is sodium sulfite aqueous solution.

[0029] According to the present application, preferably, the substance in the activated carbon tank is a coconut shell powder activated carbon suspension, which is prepared by mixing coconut shell powder activated carbon with water.

[0030] In the present application, the regeneration function system in the regenerator can not only reduce Fe(III)-EDTA into Fe(II)-EDTA, but also reduce Fe(II)-EDTA(NO) into Fe(II)-EDTA. 2+ -EDTA+NO→Fe 2+ EDTA(NO).

[0031] The regeneration function system is an activated carbon-sulfite coupled catalytic reduction regeneration system, which realizes the efficient reduction regeneration of Fe(III)-EDTA and Fe(II)-EDTA(NO) by the strong adsorption catalysis of activated carbon, and the reduction regeneration reaction is as follows:

[0032] Fe(II)-EDTA(NO) + SO3 2- Fe(II)-EDTA + SO3(NO)2 2- ;

[0033] EDTA-Fe(III) + SO3 2- EDTA-Fe(II) + SO4 2- + 2H + ;

[0034] The regenerator of the denitration liquid of the application realizes efficient regeneration of the denitration liquid by introducing N2 gas protection, controlling the indexes of pH and temperature, etc.

[0035] In the application, the NO complex absorber takes the form of a packed tower, according to the application, preferably, the middle part of the NO complex absorber is filled with packing, the packing being at least one of ceramic Raschig rings, glass springs and stainless steel Pall rings;

[0036] The upper middle part of the NO complex absorber is provided with a spray water distributor; the NO complex absorber is also provided with a bottom denitration liquid circulating outlet and a middle upper denitration liquid circulating inlet; the system further comprises a first circulating pump (variable frequency); the bottom denitration liquid circulating outlet of the NO complex absorber is connected with the first circulating pump, the middle upper denitration liquid circulating inlet of the NO complex absorber and the inlet of the spray water distributor in sequence.

[0037] According to the application, preferably, the desulfurizer is also provided with a bottom liquid outlet, a middle lower liquid inlet and a middle material supplement inlet;

[0038] The system further comprises a calcium circulating tank, a first calcium supplement tank and a second calcium supplement tank; the calcium circulating tank is a sedimentation tank provided with stirring, and is provided with an upper liquid inlet, a middle lower material supplement port, a bottom liquid outlet and a residue discharge port;

[0039] The bottom liquid outlet of the desulfurizer is connected with the upper liquid inlet of the calcium circulating tank; the bottom liquid outlet of the calcium circulating tank is connected with the middle lower liquid inlet of the desulfurizer;

[0040] The outlet of the first calcium supplement tank is connected with the middle material supplement inlet of the desulfurizer, and the desulfurization liquid is arranged in the first calcium supplement tank;

[0041] The outlet of the second calcium supplement tank is connected with the middle lower material supplement port of the calcium circulating tank, and a regenerant is arranged in the second calcium supplement tank; the regenerant is lime milk with a concentration of 5%-10%.

[0042] According to the application, preferably, the power induced draft device is an induced draft fan.

[0043] In the present application, the desulfurizer takes the form of a spray tower, according to the present application, preferably, a plurality of layers of nozzle water distributors are vertically arranged in the upper middle part of the desulfurizer; the desulfurizer is further provided with a bottom desulfurization liquid circulation outlet and a middle upper part desulfurization liquid circulation inlet; the system further comprises a second circulation pump; the bottom desulfurization liquid circulation outlet of the desulfurizer is sequentially connected with the second circulation pump, the middle upper part desulfurization liquid circulation inlet of the desulfurizer and the inlet of the plurality of layers of nozzle water distributors.

[0044] According to the present application, preferably, the plurality of layers of nozzle water distributors are 3-5 layers.

[0045] In the present application, the connecting pipelines between the electrostatic precipitator, the denitration liquid regenerator, the NO complex absorber, the desulfurizer, the power induced draft device and the chimney are made of stainless steel material, and a compensator for preventing thermal expansion and cold contraction is arranged on each connecting pipeline.

[0046] The present application further provides a low-temperature coal-fired flue gas desulfurization and denitrification method, which adopts the above-mentioned system and comprises the following steps:

[0047] S1: The low-temperature coal-fired flue gas discharged from the flue gas outlet of the coal-fired equipment is introduced into the electrostatic precipitator for treatment by the power induced draft device to obtain dust-removal flue gas; the dust-removal flue gas is sent into the jacket layer of the denitration liquid regenerator to realize heat exchange between the dust-removal flue gas and the regeneration system in the regenerator, and to obtain cooled flue gas and condensed water in the jacket layer;

[0048] S2: The cooled flue gas is sent into the NO complex absorber from the lower gas inlet of the NO complex absorber, the denitration liquid reacts with NO in the cooled flue gas to remove NO in the cooled flue gas, and to obtain denitration flue gas;

[0049] S3: The denitration flue gas is sequentially sent into the desulfurizer from the top gas outlet of the NO complex absorber and the lower gas inlet of the desulfurizer, the desulfurization liquid reacts with sulfur dioxide and nitrogen dioxide in the denitration flue gas to remove sulfur dioxide and nitrogen dioxide in the denitration flue gas, and to obtain desulfurization and denitration flue gas, which is sequentially discharged to the outside of the system through the power induced draft device and the chimney.

[0050] According to the present application, preferably, the temperature of the low-temperature coal-fired flue gas is 200-400℃.

[0051] According to the present application, preferably, the method further comprises sequentially discharging the condensed water in the jacket layer to the outside of the system through the condensed water outlet and the drain valve.

[0052] In step S1 of the present application, low-temperature coal-fired flue gas generated by a coal-fired device (coal-fired burner) is drawn to an electrostatic precipitator by an induced draft fan. In the electrostatic precipitator, after the low-temperature coal-fired flue gas passes through a discharge area, the dust and other particles in the flue gas are enriched with electrons, the dust is negatively charged, and under the action of electric field force, the dust particles with negative charge move to a dust collection chamber, so that more than 99% of the dust particles in the low-temperature coal-fired flue gas are removed.

[0053] According to the present application, preferably, in step S2, the denitration liquid in the NO complex absorber is sequentially lifted by a bottom denitration liquid circulation outlet of the NO complex absorber, a first circulation pump to a middle-upper denitration liquid circulation inlet of the NO complex absorber, and then uniformly falls to the filler in the NO complex absorber by a spray water distributor; at the same time, the cooled flue gas is sent into the NO complex absorber from a lower gas inlet of the NO complex absorber, so that the cooled flue gas and the denitration liquid form countercurrent mass transfer from bottom to top, and the reaction of the denitration liquid and NO in the cooled flue gas is realized.

[0054] According to the present application, preferably, the liquid-gas ratio in the NO complex absorber is controlled to be 10-20:1 L / m 3 .

[0055] According to the present application, preferably, in step S3, the desulfurization liquid in the desulfurizer is sequentially lifted by a bottom desulfurization liquid circulation outlet of the desulfurizer, a second circulation pump to a middle-upper desulfurization liquid circulation inlet of the desulfurizer, and then uniformly sprayed downward by a multi-layer nozzle water distributor; at the same time, the denitration flue gas is sequentially sent into the desulfurizer from a top gas outlet of the NO complex absorber and a lower gas inlet of the desulfurizer, so that the denitration flue gas and the desulfurization liquid form countercurrent mass transfer from bottom to top, and the reaction of the desulfurization liquid and sulfur dioxide and nitrogen dioxide in the denitration flue gas is realized.

[0056] According to the present application, preferably, the liquid-gas ratio in the desulfurizer is controlled to be 5-10:1 L / m 3 .

[0057] According to the present application, preferably, the method further comprises: detecting the NO content in the denitration flue gas discharged from the top gas outlet of the NO complex absorber by using an online flue gas detection device, when the NO content in the denitration flue gas exceeds a threshold value, judging that the denitration liquid in the NO complex absorber is deactivated, sending a part of the deactivated denitration liquid as a to-be-regenerated liquid into the regenerator for regeneration treatment, and discharging the remaining part of the deactivated denitration liquid from the system; the threshold value is 50 mg / m 3 .

[0058] The regeneration treatment method of the to-be-regenerated liquid in the regenerator comprises:

[0059] The reducing agent in the reducing agent tank, the coconut shell powder activated carbon suspension in the activated carbon tank and the pH adjusting agent in the pH adjusting agent tank are sent into the regenerator to form a regeneration system in the regenerator with the liquid to be regenerated; the protective gas in the protective gas storage tank is sent into the regenerator and the denitration liquid storage tank respectively;

[0060] The dust removal flue gas in the jacket layer exchanges heat with the regeneration system in the regenerator, so that the liquid to be regenerated reacts with the reducing agent under the adsorption catalysis of the coconut shell powder activated carbon suspension and the protection of the protective gas to obtain regenerated denitration liquid; the regenerated denitration liquid and the fresh denitration liquid in the denitration liquid storage tank are sent to the NO complexing absorber together to reach the working liquid level in the NO complexing absorber;

[0061] The temperature of the regeneration reaction is 35-45 DEG C, and the pH adjusting agent controls the pH of the regeneration reaction to be 6-6.5.

[0062] According to the application, preferably, after the desulfurization liquid reacts with sulfur dioxide and nitrogen dioxide in the denitration flue gas, the desulfurizer also obtains regenerated desulfurization liquid, and a regeneration treatment method of the regenerated desulfurization liquid comprises the following steps: the regenerated desulfurization liquid is sent into the calcium circulation pool; in the calcium circulation pool, the regenerated desulfurization liquid reacts with a regenerant from the second calcium supplement tank to obtain regenerated desulfurization liquid and a precipitate residue; the regenerated desulfurization liquid and fresh desulfurization liquid in the first calcium supplement tank are sent to the desulfurizer together to reach the working liquid level in the desulfurizer; and the precipitate residue is discharged from the system through a residue discharge port.

[0063] The technical scheme of the application has the following beneficial effects:

[0064] The application completes efficient removal of nitrogen oxides at a lower flue gas temperature (200-400 DEG C) through a wet absorption process, and simultaneously completes desulfurization and denitration purification treatment of low-temperature flue gas through a calcium-calcium desulfurization technology.

[0065] The content of NO in flue gas accounts for more than 95% of the total content of nitrogen oxides, so the application focuses on removal of NO, and removal of NO can achieve removal of most of the nitrogen oxides. Compared with traditional SCR and SNCR denitration methods, the application adopts a complexing denitration process, and realizes stable absorption and removal of NO by configuring NO denitration liquid.

[0066] Regeneration of denitration liquid is greatly affected by temperature, and the application realizes simple heat exchange between the front-end flue gas and the regeneration system in the regenerator through a jacket layer, which not only utilizes waste heat of the flue gas, reduces heating cost of the denitration liquid regeneration device, but also reduces the temperature of the flue gas, avoids decomposition of the denitration liquid in the NO complexing absorber caused by excessively high flue gas temperature, and guarantees efficient operation of the NO complexing absorber.

[0067] The application comprises a flue gas dust removal device, which adopts a dry electrostatic dust removal process, can remove more than 99% of dust, greatly avoids the pollution of dust to the denitration liquid, and maintains the activity of the denitration liquid.

[0068] The application adopts a calcium-calcium and double-alkali desulfurization process, calcium sulfite absorbs sulfur dioxide to generate calcium bisulfite with high solubility, solves the scaling and plugging problem of the desulfurizer, through step-by-step reaction, calcium hydroxide reacts with calcium bisulfite to generate calcium sulfite in the calcium circulation pool, realizes the regeneration of the desulfurization liquid (calcium sulfite), and reduces the consumption of the desulfurization liquid.

[0069] Other features and advantages of the application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0070] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the several views, and in which:

[0071] Figure 1 A structure schematic diagram of a low-temperature coal-fired flue gas desulfurization and denitrification system provided by the embodiment 1 of the application is shown.

[0072] The reference signs are explained as follows:

[0073] A low-temperature coal-fired flue gas; B desulfurization and denitrification flue gas;

[0074] 1 electrostatic precipitator, 2 regenerator, 3 NO complex absorber, 4 desulfurizer, 5 induced draft fan, 6 chimney;

[0075] 1.1 lower air inlet of the jacket layer, 1.2 upper air outlet of the jacket layer;

[0076] 2.1 upper liquid inlet of the regenerator to be regenerated, 2.2 lower material supplementing port of the regenerator, 2.3 middle upper protective gas inlet of the regenerator, 2.4 bottom liquid outlet of the regenerator, 2.5 reducing agent tank, 2.6 activated carbon tank, 2.7 pH adjuster tank, 2.8 protective gas storage tank, 2.9 denitration liquid storage tank, 2.10 lower liquid supplementing outlet of the denitration liquid storage tank, 2.11 upper protective gas inlet of the denitration liquid storage tank;

[0077] 3.1 lower inlet of NO complexing absorber, 3.2 top outlet of NO complexing absorber, 3.3 bottom liquid outlet of NO complexing absorber, 3.4 middle lower liquid inlet of NO complexing absorber;

[0078] 4.1 lower inlet of desulfurizer, 4.2 top outlet of desulfurizer, 4.3 bottom liquid outlet of desulfurizer, 4.4 middle lower liquid inlet of desulfurizer, 4.5 middle material supplement inlet of desulfurizer, 4.6 calcium circulation tank, 4.7 first calcium supplement tank, 4.8 second calcium supplement tank, 4.9 upper liquid inlet of calcium circulation tank, 4.10 middle lower material supplement inlet of calcium circulation tank, 4.11 bottom liquid outlet of calcium circulation tank. DETAILED DESCRIPTION

[0079] The preferred embodiments of the present application will be described in more detail below. Although the preferred embodiments of the present application are described below, it is understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present application will be more thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0080] In the following examples:

[0081] The coconut shell powdered activated carbon is selected from Chengde Lijing Activated Carbon Manufacturing Co., Ltd.

[0082] The EDTA is selected from Hebei Chuangzhengyuan Biological Technology Co., Ltd.

[0083] Example 1

[0084] The present embodiment provides a low-temperature coal-fired flue gas desulfurization and denitrification system, as shown in the figure, the system comprises an electrostatic precipitator 1, a denitrification liquid regenerating device, a NO complexing absorber 3, a desulfurizer 4, a power induced draft device and a chimney 6. Figure 1

[0085] ​The denitration liquid regeneration device comprises a regenerator 2 and a jacket layer (not shown) arranged on part of the body of the regenerator 2; the jacket layer is provided with a lower gas inlet 1.1, an upper gas outlet 1.2 and a condensed water outlet (not shown); the NO complex absorber 3 is provided with a lower gas inlet 3.1 and a top gas outlet 3.2, and the NO complex absorber 3 is provided with a denitration liquid, which is a mixture of ferrous sulfate, EDTA and a reducing agent, the content of the reducing agent in the denitration liquid is 5 ‰ based on the total weight of the denitration liquid, the reducing agent in the denitration liquid is sodium sulfite, the molar ratio of ferrous sulfate to EDTA in the denitration liquid is 1:1; the flue gas outlet of the coal-fired equipment is connected with the lower gas inlet 1.1 of the jacket layer through the electrostatic precipitator 1; the upper gas outlet 1.2 of the jacket layer is connected with the lower gas inlet 3.1 of the NO complex absorber; the condensed water outlet is connected to the outside of the system through a hydrophobic valve.

[0086] The desulfurizer 4 is provided with a lower gas inlet 4.1 and a top gas outlet 4.2, and the desulfurizer 4 is provided with a desulfurization liquid, which is a calcium sulfite slurry with a concentration of 20%-30%; the top gas outlet 3.2 of the NO complex absorber is connected with the lower gas inlet 4.1 of the desulfurizer, and an online flue gas detection device is arranged on the pipeline connected between the top gas outlet 3.2 of the NO complex absorber and the lower gas inlet 4.1 of the desulfurizer, which is used for detecting the content of NO in the top gas of the NO complex absorber; the top gas outlet 4.2 of the desulfurizer is connected with the chimney 6 through the power induced draft device.

[0087] The middle part of the NO complex absorber 3 is filled with fillers, which are ceramic Rasching rings; the upper middle part of the NO complex absorber is provided with a spray water distributor; the NO complex absorber is also provided with a bottom denitration liquid circulation outlet and a middle upper denitration liquid circulation inlet; the system further comprises a first circulation pump; the bottom denitration liquid circulation outlet of the NO complex absorber is connected with the first circulation pump, the middle upper denitration liquid circulation inlet of the NO complex absorber and the inlet of the spray water distributor in sequence.

[0088] The upper middle part of the desulfurizer is vertically provided with 3-5 layers of nozzle water distributors; the desulfurizer is also provided with a bottom desulfurization liquid circulation outlet and a middle upper desulfurization liquid circulation inlet; the system further comprises a second circulation pump; the bottom desulfurization liquid circulation outlet of the desulfurizer is connected with the second circulation pump, the middle upper desulfurization liquid circulation inlet of the desulfurizer and the inlets of the 3-5 layers of nozzle water distributors in sequence.

[0089] The NO complex absorber is also provided with a bottom liquid outlet 3.3 and a middle-lower liquid inlet 3.4; the regenerator 2 is a sealed tank provided with stirring, and the part of the body of the regenerator 2 without the jacket layer is provided with an upper liquid inlet 2.1 to be regenerated, a lower material supplementing port 2.2, a middle-upper protective gas inlet 2.3, a controllable exhaust port and a bottom liquid outlet 2.4; the system further comprises a reducing agent tank 2.5, an activated carbon tank 2.6, a pH regulator tank 2.7, a protective gas (nitrogen in this embodiment) storage tank 2.8 and a denitration liquid storage tank 2.9; the denitration liquid storage tank 2.9 is provided with a lower liquid supplementing outlet 2.10 and an upper protective gas inlet 2.11; the bottom liquid outlet 3.3 of the NO complex absorber is divided into two routes, one of which is connected with the upper liquid inlet 2.1 to be regenerated of the regenerator, and the other of which is connected to the outside of the system; the outlet of the reducing agent tank 2.5, the outlet of the activated carbon tank 2.6 and the outlet of the pH regulator tank 2.7 are all connected with the lower material supplementing port 2.2 of the regenerator; the outlet of the protective gas storage tank 2.8 is connected with the middle-upper protective gas inlet 2.3 of the regenerator and the upper protective gas inlet 2.11 of the denitration liquid storage tank respectively; the middle-lower liquid inlet 3.4 of the NO complex absorber is connected with the bottom liquid outlet 2.4 of the regenerator and the lower liquid supplementing outlet 2.10 of the denitration liquid storage tank respectively; the reducing agent in the reducing agent tank 2.5 is sodium sulfite aqueous solution; the substance in the activated carbon tank 2.6 is coconut shell powder activated carbon suspension, which is mixed by coconut shell powder activated carbon and water.

[0090] The desulfurizer 4 is also provided with a bottom liquid outlet 4.3, a middle-lower liquid inlet 4.4 and a middle material supplementing inlet 4.5; the system further comprises a calcium circulation tank 4.6, a first calcium supplementing tank 4.7 and a second calcium supplementing tank 4.8; the calcium circulation tank 4.6 is a sedimentation tank provided with stirring, and is provided with an upper liquid inlet 4.9, a middle-lower material supplementing port 4.10, a bottom liquid outlet 4.11 and a residue discharging port; the bottom liquid outlet 4.3 of the desulfurizer is connected with the upper liquid inlet 4.9 of the calcium circulation tank; the bottom liquid outlet 4.11 of the calcium circulation tank is connected with the middle-lower liquid inlet 4.4 of the desulfurizer; the outlet of the first calcium supplementing tank 4.7 is connected with the middle material supplementing inlet 4.5 of the desulfurizer, and the first calcium supplementing tank 4.7 is provided with the desulfurization liquid; the outlet of the second calcium supplementing tank 4.8 is connected with the middle-lower material supplementing port 4.10 of the calcium circulation tank, and the second calcium supplementing tank 4.8 is provided with a regenerating agent; the regenerating agent is lime milk with a concentration of 8%.

[0091] The power induced draft device is an induced draft fan 5.

[0092] The embodiment also provides a low-temperature coal-fired flue gas desulfurization and denitration method, which adopts the system of the embodiment and comprises the following steps:

[0093] S1: low-temperature coal-fired flue gas A discharged from the flue gas outlet of the coal-fired equipment is introduced into the electrostatic precipitator 1 for treatment by the induced draft fan 5 to obtain dust-removal flue gas; the dust-removal flue gas is sent into the jacket layer of the denitration liquid regenerator to realize heat exchange between the dust-removal flue gas and the regeneration system in the regenerator 2, and to obtain cooled flue gas and condensed water in the jacket layer; the condensed water in the jacket layer is discharged to the outside of the system through the condensed water outlet and the drain valve in sequence;

[0094] S2: the denitration liquid in the NO complex absorber 3 is lifted to the middle-upper denitration liquid circulation inlet of the NO complex absorber through the bottom denitration liquid circulation outlet of the NO complex absorber and the first circulation pump in sequence, and then uniformly falls to the packing in the NO complex absorber 3 through the spray water distributor, forming a liquid film on the surface of the ceramic Raschig ring packing; at the same time, the cooled flue gas is sent into the NO complex absorber 3 from the lower gas inlet 3.1 of the NO complex absorber, so that the cooled flue gas and the denitration liquid form countercurrent mass transfer from bottom to top, the reaction of the denitration liquid and NO in the cooled flue gas is realized to generate ferrous acyl compounds, the removal of NO in the cooled flue gas is realized, and denitration flue gas is obtained; the liquid-gas ratio in the NO complex absorber 3 is controlled to be 15:1 L / m 3 ;

[0095] S3: the desulfurization liquid in the desulfurizer 4 is lifted to the middle-upper desulfurization liquid circulation inlet of the desulfurizer through the bottom desulfurization liquid circulation outlet of the desulfurizer and the second circulation pump in sequence, and then uniformly sprayed downward through the multi-layer nozzle water distributor; at the same time, the denitration flue gas is sent into the desulfurizer 4 from the top gas outlet 3.2 of the NO complex absorber and the lower gas inlet 4.1 of the desulfurizer in sequence, so that the denitration flue gas and the desulfurization liquid form countercurrent mass transfer from bottom to top, the reaction of the desulfurization liquid and sulfur dioxide and nitrogen dioxide in the denitration flue gas is realized (sulfur dioxide reacts with calcium sulfite sprayed by the nozzle water distributor to generate bisulfite solution; a small amount of nitrogen dioxide in the flue gas also reacts with calcium sulfite to generate calcium sulfate), the removal of sulfur dioxide and nitrogen dioxide in the denitration flue gas is realized, desulfurization and denitration flue gas and desulfurization liquid to be regenerated (bisulfite solution + calcium sulfate) are obtained, and the desulfurization and denitration flue gas B is discharged to the outside of the system through the power induced draft device and the chimney 6 in sequence.

[0096] The liquid-gas ratio in the desulfurizer 4 is controlled to be 10:1 L / m 3 .

[0097] The denitration liquid is gradually deactivated by the oxygen content in the flue gas and the gradual absorption reaction of NO. Therefore, the method further comprises: detecting the NO content in the denitration flue gas discharged from the top outlet 3.2 of the NO complex absorber using an online flue gas detection device. When the NO content in the denitration flue gas exceeds a threshold value, it is determined that the denitration liquid in the NO complex absorber 3 is deactivated. 80% of the deactivated denitration liquid is sent to the regenerator 2 for regeneration treatment, and the remaining 20% of the deactivated denitration liquid is discharged from the system. The threshold value is 50 mg / m 3 The regeneration treatment method of the regenerated liquid in the regenerator 2 comprises: sending the reducing agent in the reducing agent tank 2.5, the coconut shell powdered activated carbon suspension in the activated carbon tank 2.6, and the pH adjuster (acid) in the pH adjuster tank 2.7 into the regenerator 2 to form a regeneration system in the regenerator 2; sending the protective gas in the protective gas storage tank 2.8 into the regenerator 2 and the denitration liquid storage tank 2.9, respectively; the dust-containing flue gas in the jacket layer exchanges heat with the regeneration system in the regenerator 2, so that the regenerated liquid reacts with the reducing agent under the adsorption and catalysis of the coconut shell powdered activated carbon suspension and the protection of the protective gas, and the regenerated denitration liquid (Fe(II)-EDTA) is obtained; the regenerated denitration liquid and the fresh denitration liquid (supplementing the deactivated denitration liquid discharged) in the denitration liquid storage tank 2.9 are sent together to the NO complex absorber 3 to reach the working liquid level in the NO complex absorber 3; the temperature of the regeneration reaction is 35-45°C, and the pH adjuster controls the pH of the regeneration reaction to be 6-6.5.

[0098] The regeneration treatment method of the regenerated liquid in the regenerator 2 comprises: sending the reducing agent in the reducing agent tank 2.5, the coconut shell powdered activated carbon suspension in the activated carbon tank 2.6, and the pH adjuster (acid) in the pH adjuster tank 2.7 into the regenerator 2 to form a regeneration system in the regenerator 2; sending the protective gas in the protective gas storage tank 2.8 into the regenerator 2 and the denitration liquid storage tank 2.9, respectively; the dust-containing flue gas in the jacket layer exchanges heat with the regeneration system in the regenerator 2, so that the regenerated liquid reacts with the reducing agent under the adsorption and catalysis of the coconut shell powdered activated carbon suspension and the protection of the protective gas, and the regenerated denitration liquid (Fe(II)-EDTA) is obtained; the regenerated denitration liquid and the fresh denitration liquid (supplementing the deactivated denitration liquid discharged) in the denitration liquid storage tank 2.9 are sent together to the NO complex absorber 3 to reach the working liquid level in the NO complex absorber 3; the temperature of the regeneration reaction is 35-45°C, and the pH adjuster controls the pH of the regeneration reaction to be 6-6.5.

[0099] The temperature of the low-temperature coal-fired flue gas A of the present embodiment is 220°C, the NO content therein is 650 mg / Nm 3 , the SO2 content is 870 mg / Nm 3 , the NO x content is 730 mg / Nm 3 , and the dust concentration is 840 mg / Nm 3 .

[0100] The NO content of the desulfurized and denitrated flue gas B obtained in the present embodiment is 18 mg / Nm3 SO2 content is 30 mg / Nm 3 NO x content is 32 mg / Nm 3 Dust emission concentration is 4 mg / Nm 3 .

[0101] Example 2

[0102] The difference between this example and Example 1 is only that:

[0103] The liquid-gas ratio in the NO complex absorber 3 is controlled at 20:1 L / m 3 .

[0104] The temperature of the low-temperature coal-fired flue gas A in this example is 285°C, and the NO content therein is 1050 mg / Nm 3 SO2 content is 1550 mg / Nm 3 NO x content is 1250 mg / Nm 3 Dust concentration is 930 mg / Nm 3 .

[0105] The NO content of the desulfurized and denitrated flue gas B obtained in this example is 12 mg / Nm 3 SO2 content is 24 mg / Nm 3 NO x content is 33 mg / Nm 3 Dust emission concentration is 4 mg / Nm 3 .

[0106] The above has described various embodiments of the present application, and the above description is exemplary, is not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A low-temperature coal-fired flue gas desulfurization and denitrification system, characterized in that, The system comprises an electrostatic precipitator, a denitration liquid regenerator, a NO complex absorber, a desulfurizer, a power induced draft device and a chimney. The denitration liquid regenerator comprises a regenerator and a jacket layer arranged on part of the body of the regenerator; the jacket layer is provided with a lower gas inlet and an upper gas outlet; the NO complex absorber is provided with a lower gas inlet and a top gas outlet, and the NO complex absorber is provided with a denitration liquid; the flue gas outlet of the coal-fired equipment is connected with the lower gas inlet of the jacket layer through the electrostatic precipitator; the upper gas outlet of the jacket layer is connected with the lower gas inlet of the NO complex absorber. The desulfurizer is provided with a lower gas inlet and a top gas outlet, and the desulfurizer is provided with a desulfurization liquid; the top gas outlet of the NO complex absorber is connected with the lower gas inlet of the desulfurizer; the top gas outlet of the desulfurizer is connected with the chimney through the power induced draft device. The denitration liquid is a mixture of ferrous sulfate, EDTA and a reducing agent; the content of the reducing agent in the denitration liquid is 4.5-5.5‰ based on the total weight of the denitration liquid; the reducing agent in the denitration liquid is sodium sulfite; the molar ratio of ferrous sulfate to EDTA in the denitration liquid is (0.8-1.2):(0.8-1.2). The desulfurization liquid is a calcium sulfite slurry with a concentration of 20-30%. The NO complex absorber is further provided with a bottom liquid outlet and a middle-lower liquid inlet. The regenerator is a sealed tank provided with stirring, and part of the body of the regenerator which is not arranged with the jacket layer is provided with an upper to-be-regenerated liquid inlet, a lower material supplementing port, a middle-upper protective gas inlet, a controllable gas outlet and a bottom liquid outlet. The system further comprises a reducing agent tank, an activated carbon tank, a pH regulator tank, a protective gas storage tank and a denitration liquid storage tank; the denitration liquid storage tank is provided with a lower liquid supplementing outlet and an upper protective gas inlet. The bottom liquid outlet of the NO complex absorber is divided into two routes, one of which is connected with the upper to-be-regenerated liquid inlet of the regenerator, and the other of which is connected to the outside of the system. The outlet of the reducing agent tank, the outlet of the activated carbon tank and the outlet of the pH regulator tank are all connected with the lower material supplementing port of the regenerator. The outlet of the protective gas storage tank is connected with the middle-upper protective gas inlet of the regenerator and the upper protective gas inlet of the denitration liquid storage tank, respectively. The middle-lower liquid inlet of the NO complex absorber is connected with the bottom liquid outlet of the regenerator and the lower liquid supplementing outlet of the denitration liquid storage tank, respectively. The reducing agent in the reducing agent tank is an aqueous sodium sulfite solution. The substance in the activated carbon tank is a coconut shell powder activated carbon suspension liquid, which is obtained by mixing coconut shell powder activated carbon with water.

2. The low-temperature coal-fired flue gas desulfurization and denitration system according to claim 1, wherein, The jacket layer is further provided with a condensate water outlet connected to the outside of the system through a hydrophobic valve; An online flue gas detection device is arranged on the pipeline connected between the top gas outlet of the NO complex absorber and the lower gas inlet of the desulfurizer, and the online flue gas detection device is used for detecting the content of NO in the top gas outlet of the NO complex absorber.

3. The low-temperature coal-fired flue gas desulfurization and denitrification system according to claim 2, wherein, The middle part of the NO complex absorber is filled with a filler, which is at least one of ceramic Rasching ring, glass spring and stainless steel Pall ring; The upper middle part of the NO complex absorber is provided with a spray water distributor; the NO complex absorber is further provided with a bottom denitration liquid circulation outlet and an upper middle part denitration liquid circulation inlet; the system further comprises a first circulation pump; the bottom denitration liquid circulation outlet of the NO complex absorber is connected with the first circulation pump, the upper middle part denitration liquid circulation inlet of the NO complex absorber and the inlet of the spray water distributor in sequence.

4. The low-temperature coal-fired flue gas desulfurization and denitrification system according to claim 1, wherein, The desulfurizer is further provided with a bottom liquid outlet, a middle lower part liquid inlet and a middle part material supplement inlet; The system further comprises a calcium circulation tank, a first calcium supplement tank and a second calcium supplement tank; the calcium circulation tank is a sedimentation tank provided with stirring, and the calcium circulation tank is provided with an upper liquid inlet, a middle lower part material supplement port, a bottom liquid outlet and a residue discharge port; The bottom liquid outlet of the desulfurizer is connected with the upper liquid inlet of the calcium circulation tank; the bottom liquid outlet of the calcium circulation tank is connected with the middle lower part liquid inlet of the desulfurizer; The outlet of the first calcium supplement tank is connected with the middle part material supplement inlet of the desulfurizer, and the first calcium supplement tank is provided with the desulfurization liquid; The outlet of the second calcium supplement tank is connected with the middle lower part material supplement port of the calcium circulation tank, and the second calcium supplement tank is provided with a regenerant; the regenerant is lime milk with a concentration of 5%-10%; The power induced draft device is an induced draft fan.

5. The low-temperature coal-fired flue gas desulfurization and denitrification system according to claim 4, wherein, The upper middle part of the desulfurizer is vertically provided with a multilayer nozzle water distributor; the desulfurizer is further provided with a bottom desulfurization liquid circulation outlet and an upper middle part desulfurization liquid circulation inlet; the system further comprises a second circulation pump; the bottom desulfurization liquid circulation outlet of the desulfurizer is connected with the second circulation pump, the upper middle part desulfurization liquid circulation inlet of the desulfurizer and the inlet of the multilayer nozzle water distributor in sequence.

6. A method for desulfurization and denitrification of low-temperature coal-fired flue gas, characterized by, The method adopts the system according to any one of claims 1-5, and comprises the following steps: S1: introducing the low-temperature coal-fired flue gas discharged from the flue gas outlet of the coal-fired equipment to the electrostatic precipitator for treatment by the power induced draft device to obtain dust removal flue gas; introducing the dust removal flue gas into the jacket layer of the denitration liquid regenerator to realize heat exchange between the dust removal flue gas and the regeneration system in the regenerator, and obtaining cooled flue gas and condensed water in the jacket layer; S2: introducing the cooled flue gas into the NO complex absorber from the lower gas inlet of the NO complex absorber, so that the denitration liquid reacts with NO in the cooled flue gas to remove NO in the cooled flue gas, and obtaining denitration flue gas; S3: introducing the denitration flue gas into the desulfurizer from the top gas outlet of the NO complex absorber and the lower gas inlet of the desulfurizer in sequence, so that the desulfurization liquid reacts with sulfur dioxide and nitrogen dioxide in the denitration flue gas to remove sulfur dioxide and nitrogen dioxide in the denitration flue gas, and obtaining desulfurization and denitrification flue gas, which is sequentially introduced into the system outside through the power induced draft device and the chimney.

7. The low-temperature coal-fired flue gas desulfurization and denitrification method according to claim 6, wherein, The temperature of the low-temperature coal-fired flue gas is 200-400℃; The method further comprises: sequentially discharging the condensed water in the jacket layer to the outside of the system through a condensed water outlet and a drain valve.

8. The low-temperature coal-fired flue gas desulfurization and denitrification method according to claim 6, wherein, In the step S2, the denitration liquid in the NO complex absorber is sequentially lifted to the middle-upper denitration liquid circulation inlet of the NO complex absorber through the bottom denitration liquid circulation outlet of the NO complex absorber and the first circulation pump, and then uniformly falls to the filler in the NO complex absorber through the spray water distributor; at the same time, the cooling flue gas is sent into the NO complex absorber from the lower gas inlet of the NO complex absorber, so that the cooling flue gas forms countercurrent mass transfer with the denitration liquid from bottom to top, and the reaction of the denitration liquid and NO in the cooling flue gas is realized; The liquid-gas ratio in the NO complexing absorber is controlled at 10-20:1 L / m 3 ; In the step S3, the desulfurization liquid in the desulfurizer is sequentially lifted to the middle-upper desulfurization liquid circulation inlet of the desulfurizer through the bottom desulfurization liquid circulation outlet of the desulfurizer and the second circulation pump, and then uniformly sprayed downward through the multi-layer nozzle water distributor; at the same time, the denitration flue gas is sequentially sent into the desulfurizer from the top gas outlet of the NO complex absorber and the lower gas inlet of the desulfurizer, so that the denitration flue gas forms countercurrent mass transfer with the desulfurization liquid from bottom to top, and the reaction of the desulfurization liquid and sulfur dioxide and nitrogen dioxide in the denitration flue gas is realized. The liquid-gas ratio in the desulfurizer is controlled at 5-10:1 L / m 3 .

9. The cryogenic flue gas desulfurization and denitrification method according to claim 6, wherein, The method further comprises: detecting the content of NO in the denitration flue gas discharged from the top outlet of the NO complexing absorber by using an online flue gas detection device; when the content of NO in the denitration flue gas exceeds a threshold value, judging that the denitration liquid in the NO complexing absorber is deactivated; and sending a part of the deactivated denitration liquid as the liquid to be regenerated into the regenerator for regeneration treatment, and discharging the remaining part of the deactivated denitration liquid from the system; the threshold value is 50 mg / m 3 . The regeneration treatment method of the liquid to be regenerated in the regenerator comprises: The reducing agent in the reducing agent tank, the coconut shell powdered activated carbon suspension liquid in the activated carbon tank and the pH adjuster in the pH adjuster tank are sent into the regenerator to form a regeneration system in the regenerator with the liquid to be regenerated; and the protective gas in the protective gas storage tank is sent into the regenerator and the denitration liquid storage tank respectively; After the dust-containing flue gas in the jacket layer exchanges heat with the regeneration system in the regenerator, the liquid to be regenerated reacts with the reducing agent under the adsorption catalysis of the coconut shell powdered activated carbon suspension liquid and the protection of the protective gas, and the regenerated denitration liquid is obtained; the regenerated denitration liquid and the fresh denitration liquid in the denitration liquid storage tank are sent to the NO complex absorber together to reach the working liquid level in the NO complex absorber; The temperature of the regeneration reaction is 35-45℃, and the pH of the regeneration reaction controlled by the pH adjuster is 6-6.

5.

10. The cryogenic flue gas desulfurization and denitrification method according to claim 6, wherein, After the desulfurization liquid reacts with sulfur dioxide and nitrogen dioxide in the denitration flue gas, the desulfurizer also obtains the desulfurization liquid to be regenerated, and the regeneration treatment method of the desulfurization liquid to be regenerated comprises: sending the desulfurization liquid to be regenerated into a calcium circulation pool; in the calcium circulation pool, the desulfurization liquid to be regenerated reacts with the regenerant from the second calcium supplement tank to obtain regenerated desulfurization liquid and precipitated slag; the regenerated desulfurization liquid and the fresh desulfurization liquid in the first calcium supplement tank are sent to the desulfurizer together to reach the working liquid level in the desulfurizer; and the precipitated slag is discharged from the system through a slag discharge port.

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