Sodium alkali flue gas desulfurization and its absorption liquid regeneration system

Abstract

The present application relates to a kind of sodium base method flue gas desulfurization and its absorption liquid regeneration system, comprising the following steps: absorption liquid is in main tower and is contacted with flue gas in counter current absorption SO2 in flue gas, absorption liquid and SO2 Reaction generated NaHSO3 And Na2SO3 Oxidized to Na2SO4, And transport to desulfurizer regeneration device;Ammonia water absorbs CO2 In gas generated NH4HCO3;Separate out NH4HCO3 Crystal as Na2SO4 Regeneration agent;Transport to desulfurizer regeneration device and Na2SO4 Double decomposition reaction generated NaHCO3.The beneficial effects of the present application are: sodium carbonate and sodium bicarbonate have no volatility, and the absorption system and the regeneration system are used for the chemical reagent that is easily dissolved in water, so not only effectively avoid the fouling and plugging problem of the existing technology center sodium-calcium double base method desulfurization system, and there is no aerosol in flue gas desulfurization system, effectively avoid the problem of secondary pollution in ammonia method desulfurization process in the prior art;(NH4)2SO4 Can be separated out, can be used as compound fertilizer raw material or directly as chemical fertilizer sold out.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of flue gas desulfurization, and particularly relates to a sodium alkali method flue gas desulfurization and an absorption liquid regeneration system thereof. BACKGROUND

[0002] In the existing industrial production process, coal-fired boilers, industrial kilns, waste incinerators and the like will produce flue gas containing SO2 and other pollutants, SO2 is one of the main pollutants causing air pollution and acid rain, which causes great harm to people's health, economic development, ecological beauty and social progress. It is one of the important tasks of current air pollution control to take effective measures to control the emission of SO2 and realize the resource utilization of SO2. Current flue gas desulfurization technologies mainly include limestone-gypsum flue gas desulfurization, ammonia flue gas desulfurization, sodium-calcium dual alkali flue gas desulfurization and the like.

[0003] The ammonia flue gas desulfurization technology uses ammonia as the absorbent of SO2, ammonia reacts with SO2 to generate ammonium sulfite and ammonium bisulfite, and ammonium sulfite is oxidized to generate ammonium sulfate which is crystallized out of the desulfurization system and sold as a by-product. The absorbent utilization efficiency of ammonia desulfurization is high, the desulfurization efficiency is high, and the by-product ammonium sulfate can be used as a compound fertilizer raw material or directly used as a chemical fertilizer, but ammonia has strong volatility, which increases the consumption of the absorbent, and a large amount of aerosol particulate matter is generated in the ammonia desulfurization process, which causes secondary pollution to the environment.

[0004] The sodium-calcium dual alkali flue gas desulfurization first uses sodium hydroxide, sodium carbonate or sodium bicarbonate solution as the absorbent to absorb SO2, and then uses lime milk or lime to regenerate the absorption liquid. The sodium-calcium dual alkali flue gas desulfurization has small liquid-gas ratio and high reliability, but due to the extremely low reaction conversion rate of the oxidation by-product sodium sulfate in the regeneration process, the absorption liquid regeneration effect is poor, and the alkali solution needs to be supplemented regularly, in addition, calcium sulfite and calcium sulfate cannot be completely precipitated and enter the main tower with the absorption liquid, which causes fouling in the tower.

[0005] Therefore, a new flue gas desulfurization system is needed to overcome the above problems. SUMMARY

[0006] The purpose of the present application is to overcome the deficiencies in the prior art, and to provide a sodium alkali method flue gas desulfurization and an absorption liquid regeneration system thereof.

[0007] The sodium alkali method flue gas desulfurization and the absorption liquid regeneration system thereof comprise a main tower and an auxiliary tower, a main tower oxidation tank is arranged below the main tower, the main tower oxidation tank is connected to the top of the main tower through an absorption liquid circulation pipe, and the main tower oxidation tank is connected with a desulfurizer regeneration device through an external discharge pipe.

[0008] The desulfurizer preparation tank is connected with the desulfurizer regenerating device through an absorption liquid pipe, and the desulfurizer regenerating device is connected with a by-product recovery system through an overflow pipe.

[0009] The auxiliary tower is provided with ammonia water and carbon dioxide gas containing input pipes, and is provided with an ammonia water circulation pipe.

[0010] The crystallizer, the clarifier and the solid-liquid separator are respectively connected with a carbon ammonium mother liquor tank through pipes.

[0011] The main tower is provided with a pipe for inputting flue gas above the liquid surface and a pipe for inputting oxidizing air below the liquid surface.

[0012] The main tower circulation pump is arranged in the absorption liquid circulation pipe, and the main tower discharge pump is arranged in the discharge pipe.

[0013] The carbon ammonium mother liquor circulation pump is arranged in the pipe between the carbon ammonium mother liquor tank and the auxiliary tower.

[0014] The use method of the sodium alkali flue gas desulfurization and the absorption liquid regenerating system comprises the following steps:

[0015] Step one, NaHCO3 solution or Na2CO3 solution is used as the absorption liquid and is input from the top of the main tower, and is contacted with the flue gas in the main tower to absorb SO2 in the flue gas.

[0016] Step two, air is blown into the main tower oxidation tank to oxidize NaHSO3 and Na2SO3 generated by the reaction of the absorption liquid and SO2 into Na2SO4, and is transported to the desulfurizer regenerating device.

[0017] Step three, ammonia water is input from the top of the auxiliary tower, and is contacted with the gas containing CO2 in the auxiliary tower to generate NH4HCO3 by absorbing CO2 in the gas.

[0018] Step four, the solution at the bottom of the auxiliary tower is input into the crystallizer to obtain NH4HCO3 crystal slurry, the crystal slurry is transported to the clarifier for further concentration and then is transported to the solid-liquid separator, and NH4HCO3 crystals are separated out as the Na2SO4 regenerant.

[0019] Step five, the NH4HCO3 crystals are transported to the desulfurizer regenerating device to generate NaHCO3 by double decomposition reaction with Na2SO4, the NaHCO3 is transported to the desulfurizer preparation tank to prepare the absorption liquid, and the absorption liquid is transported to the main tower.

[0020] As preferred, in step two, part of the absorption solution in the oxidation tank of the main tower is transported to the top of the main tower for recycling, and part of the absorption solution is transported to the desulfurizer regenerating device; in step three, part of the solution at the bottom of the auxiliary tower is transported to the top of the auxiliary tower for recycling, and another part enters the crystallizer to implement step four; in step four, the overflow liquid of the crystallizer, the overflow liquid of the clarifier and the filtrate of the solid-liquid separator enter the ammonium bicarbonate mother liquor tank, and the solution in the ammonium bicarbonate mother liquor tank is transported to the top of the auxiliary tower for recycling.

[0021] As preferred, in step three, the concentration of the ammonia water is 10% to 28%, and the volume fraction of CO2 in the CO2-containing gas is 40% to 99.9%.

[0022] As preferred, in step five, the Na2SO4 and NH4HCO3 undergo a double decomposition reaction to obtain NaHCO3 and a double decomposition mother liquor, the NaHCO3 is directly transported to the desulfurizer preparation tank to prepare the absorption solution or is calcined into Na2CO3 and then transported to the desulfurizer preparation tank to prepare the solution; the double decomposition mother liquor enters the by-product recovery system to separate out (NH4)2SO4 as a by-product.

[0023] As preferred, in step five, the absorption solution prepared in the desulfurizer preparation tank is transported to the oxidation tank of the main tower or is combined with the absorption solution recycling pipe and then is input into the top of the main tower for flue gas desulfurization, and steps one to five are repeated.

[0024] The present application has the following beneficial effects:

[0025] 1) In the desulfurization process of the present application, ammonium bicarbonate is used as a regenerant to regenerate the sodium alkali absorbent, the conversion efficiency is high in the regeneration process of the sodium alkali absorbent, the amount of the newly supplemented absorbent is small, and the operation cost is reduced; the present process uses the alkali sodium salt which is easily soluble in water as the desulfurization absorbent, the desulfurization efficiency is high, the system operation is reliable, and the liquid-gas ratio is small.

[0026] 2) The sodium carbonate and sodium bicarbonate used in the present application have no volatility, and the chemical agents used in the absorption system and the regeneration system are all easily soluble in water, so not only the scaling and plugging problems in the existing sodium-calcium double alkali desulfurization system are effectively avoided, but also no gas aerosol is generated in the flue gas desulfurization system, and the problem of secondary pollution in the ammonia desulfurization process in the existing technology is effectively avoided.

[0027] 3) The double decomposition mother liquor after the double decomposition reaction in the desulfurizer regenerating device enters the by-product recovery system, and (NH4)2SO4 can be separated out, the (NH4)2SO4 is a high-value ammonium sulfate by-product which can be used as a compound fertilizer raw material or directly sold as a chemical fertilizer, so the present application has good economic benefits on the basis of desulfurization. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 This is a schematic diagram of the structure of the sodium alkali flue gas desulfurization system and its absorbent regeneration system.

[0029] Explanation of reference numerals in the attached drawings: 1. Main tower; 2. Main tower oxidation tank; 3. Main tower circulation pump; 4. Main tower discharge pump; 5. Desulfurizing agent regeneration device; 6. Desulfurizing agent preparation tank; 7. Desulfurizing agent metering pump; 8. By-product recovery system; 9. Auxiliary tower; 10. Auxiliary tower circulation pump; 11. Crystallizer; 12. Clarifier; 13. Solid-liquid separator; 14. Ammonium bicarbonate mother liquor tank; 15. Ammonium bicarbonate mother liquor circulation pump. Detailed Implementation

[0030] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0031] Example 1

[0032] As one example, such as Figure 1 As shown, this sodium alkali flue gas desulfurization and absorbent regeneration system includes a main tower 1, a main tower oxidation tank 2, a desulfurizing agent regeneration device 5, a desulfurizing agent preparation tank 6, an auxiliary tower 9, a crystallizer 11, a clarifier 12, and a solid-liquid separator 13.

[0033] A chimney is located at the top of the main tower 1. A pipe for inputting flue gas is located above the liquid surface of the main tower 1, and a pipe for inputting oxidizing air is located below the liquid surface. The main tower oxidation tank 2 is located below the main tower 1. The outlet pipe interface at the bottom of the main tower oxidation tank 2 is connected to the inlet of the main tower discharge pump 4, and the outlet of the main tower discharge pump 4 is connected to the solution inlet of the desulfurizing agent regeneration device 5.

[0034] The auxiliary tower 9 is equipped with input pipes for ammonia water and carbon dioxide gas. The bottom outlet of the auxiliary tower 9 is connected to the inlet of the crystallizer 11. The crystal slurry outlet of the crystallizer 11 is connected to the inlet of the clarifier 12. The bottom outlet of the clarifier 12 is connected to the inlet of the solid-liquid separator 13. The solid separated by the solid-liquid separator 13 is transported to the desulfurizing agent regeneration device 5 as a regenerator.

[0035] The absorbent regenerated by the desulfurizing agent regeneration device 5 is transported to the desulfurizing agent preparation tank 6 for internal circulation in the main tower 1.

[0036] Example 2

[0037] As another embodiment, this embodiment two proposes a more specific sodium alkali flue gas desulfurization and absorbent regeneration system based on embodiment one, and also includes a by-product recovery system 8.

[0038] The desulfurizer regeneration device 5 is provided with an overflow pipe connected with the feed inlet of the by-product recovery system 8.

[0039] The main tower 1 and the auxiliary tower 9 are also provided with a loop for circulation, the absorption liquid circulation pipe interface at the bottom of the main tower oxidation tank 2 is connected with the inlet of the main tower circulation pump 3, and the outlet of the main tower circulation pump 2 is connected with the absorption liquid circulation pipe interface at the top of the main tower 1; the ammonia water circulation pipe interface of the auxiliary tower 9 is connected with the inlet of the auxiliary tower circulation pump 10, and the outlet of the auxiliary tower circulation pump 10 is connected with the ammonia water circulation pipe interface at the top of the auxiliary tower 9.

[0040] The overflow port of the crystallizer 11, the overflow port of the clarifier 12 and the filtrate outlet of the solid-liquid separator 13 of the desulfurizer preparation tank 6 are respectively connected with the feed inlet of the carbon ammonium mother liquor tank 14 through pipelines; the discharge outlet of the carbon ammonium mother liquor tank 14 is connected with the inlet of the carbon ammonium mother liquor circulation pump 15, and the outlet of the carbon ammonium mother liquor circulation pump 15 is connected with the top of the auxiliary tower 9.

[0041] The absorption liquid pipe interface of the desulfurizer preparation tank 6 is connected with the inlet of the desulfurizer metering pump 7, and the outlet of the desulfurizer metering pump 7 is connected with the outlet pipe of the main tower oxidation tank 2 or the main tower circulation pump 3.

[0042] It should be noted that the same or similar parts in this embodiment as in embodiment one can be mutually referred to, and will not be described herein again.

[0043] Embodiment three

[0044] As another embodiment, the use method of the sodium alkali method flue gas desulfurization and the absorption liquid regeneration system thereof in embodiments one and two comprises the following steps:

[0045] Step one, NaHCO3 solution or Na2CO3 solution is used as the absorption liquid and enters from the top of the main tower 1, and is in countercurrent contact with the flue gas in the main tower 1 to absorb SO2 in the flue gas, and the absorption liquid after absorbing SO2 enters the main tower oxidation tank 2;

[0046] Step two, air is blown into the main tower oxidation tank 2 to oxidize NaHSO3 and Na2SO3 generated by the reaction of the absorption liquid with SO2 into Na2SO4, part of the absorption liquid in the main tower oxidation tank 2 is transported to the top of the main tower 1 by the main tower circulation pump 3 for circulation, and part of the absorption liquid is transported to the desulfurizer regeneration device 5 by the main tower discharge pump 4.

[0047] Step three, ammonia water enters from the top of the auxiliary tower 9, and is in countercurrent contact with the gas containing CO2 in the auxiliary tower 9 to generate NH4HCO3 by absorbing CO2 in the gas;

[0048] Step four, part of the solution at the bottom of the auxiliary tower 9 is transported to the top of the auxiliary tower 9 by the auxiliary tower circulating pump 10 for recycling, and the other part of the solution enters the crystallizer 11 to obtain NH4HCO3 crystal slurry, which is transported to the clarifier 12 for further concentration and then to the solid-liquid separator 13, and NH4HCO3 crystals are separated out as Na2SO4 regenerant; the overflow liquid of the crystallizer 11, the overflow liquid of the clarifier 12 and the filtrate of the solid-liquid separator 13 enter the ammonium carbonate mother liquor tank 14; the solution in the ammonium carbonate mother liquor tank 14 is transported to the top of the auxiliary tower 9 by the ammonium carbonate mother liquor circulating pump 15 for recycling.

[0049] Step five, the NH4HCO3 crystals are transported to the desulfurizer regenerating device 5 to react with Na2SO4 to generate NaHCO3, and the NaHCO3 is transported to the desulfurizer preparation tank 6 to be prepared into an absorption liquid, which is transported into the main tower 1.

[0050] Example four

[0051] As another embodiment, this embodiment four proposes a more specific use method of the sodium alkali method flue gas desulfurization and the absorption liquid regenerating system based on the embodiment three.

[0052] In step three, the ammonia concentration is 10% to 28%, and the volume fraction of CO2 in the CO2-containing gas is 40% to 99.9%. In step four, the Na2SO4 regenerant is NH4HCO3 prepared by reacting ammonia with CO2 in the CO2-containing gas, and the regeneration mode of the absorption liquid is the double decomposition reaction of Na2SO4 and NH4HCO3 to obtain NaHCO3 and double decomposition mother liquor.

[0053] In step five, the NH4HCO3 crystals are transported to the desulfurizer regenerating device 5 to react with Na2SO4 in the solution to generate NaHCO3, and the NaHCO3 is directly transported to the desulfurizer preparation tank 6 to be prepared into a solution, or is calcined into Na2CO3 and then transported to the desulfurizer preparation tank 6 to be prepared into a solution, and the absorption liquid in the desulfurizer preparation tank 6 is transported to the main tower oxidation tank 2 or the outlet pipe of the main tower circulating pump 3 by the desulfurizer metering pump 7 for flue gas desulfurization.

[0054] The double decomposition reaction mother liquor of NH4HCO3 and Na2SO4 enters the by-product recovery system 8 to separate out (NH4)2SO4 as a by-product.

[0055] It should be noted that the same or similar parts in this embodiment and embodiment three can be referred to each other, and will not be described in detail in this application.

[0056] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the embodiments can be referred to each other.

Claims

1. A method of using a sodium-alkali flue gas desulfurization system and its absorbent regeneration system, characterized in that, The sodium alkali flue gas desulfurization and its absorbent regeneration system includes: a main tower (1) and an auxiliary tower (9). The main tower (1) is equipped with a main tower oxidation tank (2) below it. The main tower oxidation tank (2) is connected to the top of the main tower (1) through an absorbent circulation pipe. The main tower oxidation tank is connected to a desulfurizing agent regeneration device (5) through an external discharge pipe. The outlet end of the desulfurizing agent regeneration device (5) is connected to a desulfurizing agent preparation tank (6). The desulfurizing agent preparation tank (6) is connected to the main tower oxidation tank (2) or the absorption liquid circulation pipe through the absorption liquid pipe. The desulfurizing agent regeneration device (5) is connected to a by-product recovery system (8) through the overflow pipe. The auxiliary tower (9) is equipped with an input pipe for ammonia water and carbon dioxide gas. The auxiliary tower (9) is equipped with an ammonia water circulation pipe. The bottom of the auxiliary tower (9) is connected to a crystallizer (11). The outlet end of the crystallizer (11) is connected to the desulfurizing agent regeneration device (5) through a clarifier (12) and a solid-liquid separator (13) in sequence. The usage method includes the following steps: Step 1: NaHCO3 solution or Na2CO3 solution is used as the absorbent and enters from the top of the main tower (1). It comes into countercurrent contact with the flue gas in the main tower (1) to absorb SO2 in the flue gas. The absorbent after absorbing SO2 enters the oxidation tank (2) of the main tower. Step 2: Air is blown into the main tower oxidation tank (2) to oxidize the NaHSO3 and Na2SO3 generated by the reaction of the absorbent with SO2 into Na2SO4, and then transported to the desulfurizing agent regeneration device (5). Step 3: Ammonia water enters from the top of the auxiliary tower (9) and comes into countercurrent contact with the gas containing CO2 inside the auxiliary tower (9), absorbing the CO2 in the gas to generate NH4HCO3; Step 4: The solution at the bottom of the auxiliary tower (9) enters the crystallizer (11) to obtain NH4HCO3 crystal slurry. The crystal slurry is sent to the clarifier (12) for further concentration and then sent to the solid-liquid separator (13) to separate NH4HCO3 crystals as Na2SO4 regenerator. Step 5: NH4HCO3 crystals are transported to the desulfurizer regeneration device (5) to undergo a metathesis reaction with Na2SO4 to generate NaHCO3. NaHCO3 is then transported to the desulfurizer preparation tank (6) to prepare an absorbent. The absorbent is then transported to the main tower (1). In step 5, Na2SO4 and NH4HCO3 undergo a metathesis reaction to obtain NaHCO3 and a metathesis mother liquor. The NaHCO3 is directly transported to the desulfurizer preparation tank (6) to prepare an absorbent or calcined into Na2CO3 before being transported to the desulfurizer preparation tank (6) to prepare a solution. The metathesis mother liquor enters the by-product recovery system (8) to separate (NH4)2SO4 as a by-product.

2. The method of using the sodium alkali flue gas desulfurization and absorbent regeneration system according to claim 1, characterized in that, The crystallizer (11), clarifier (12) and solid-liquid separator (13) are connected to the ammonium bicarbonate mother liquor tank (14) via conduits. The ammonium bicarbonate mother liquor tank (14) is connected to the top of the auxiliary tower (9) via a pipeline.

3. The method of using the sodium alkali flue gas desulfurization and absorbent regeneration system according to claim 1, characterized in that, The main tower (1) has a pipe for inputting flue gas above the liquid surface and a pipe for inputting oxidizing air below the liquid surface.

4. The method of using the sodium alkali flue gas desulfurization and absorbent regeneration system according to claim 1, characterized in that, The absorption liquid circulation pipe is equipped with a main tower circulation pump (3), and the external discharge pipe is equipped with a main tower discharge pump (4); the ammonia water circulation pipe is equipped with an auxiliary tower circulation pump (10).

5. The method of using the sodium alkali flue gas desulfurization and absorbent regeneration system according to claim 2, characterized in that, An ammonium bicarbonate mother liquor circulation pump (15) is installed in the pipeline between the ammonium bicarbonate mother liquor tank (14) and the auxiliary tower (9).

6. The method of using the sodium alkali flue gas desulfurization and absorbent regeneration system according to claim 1, characterized in that, In step two, part of the absorbent in the main tower oxidation tank (2) is transported to the top of the main tower (1) for recycling, and part of the absorbent is transported to the desulfurizer regeneration device (5); in step three, part of the solution at the bottom of the auxiliary tower (9) is transported to the top of the auxiliary tower (9) for recycling, and the other part enters the crystallizer (11) to implement step four; in step four, the overflow liquid of the crystallizer (11), the overflow liquid of the clarifier (12) and the filtrate of the solid-liquid separator (13) enter the ammonium bicarbonate mother liquor tank (14), and the solution in the ammonium bicarbonate mother liquor tank (14) is transported to the top of the auxiliary tower (9) for reuse.

7. The method of using the sodium alkali flue gas desulfurization and absorbent regeneration system according to claim 1, characterized in that, In step three, the concentration of ammonia water is 10% to 28%, and the volume fraction of CO2 in the CO2-containing gas is 40% to 99.9%.

8. The method of using the sodium alkali flue gas desulfurization and absorbent regeneration system according to claim 1, characterized in that, In step five, the absorbent prepared in the desulfurizing agent preparation tank (6) is transported to the oxidation tank (2) of the main tower or merged with the absorbent circulation pipe and then input into the top of the main tower (1) for flue gas desulfurization, and steps one to five are repeated.

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