A dry desulfurization system and a dry desulfurization method

Abstract

The present invention discloses a dry desulfurization system and a dry desulfurization method, which are applicable to the dry desulfurization process of Claus tail gas coupled with coal-fired boiler flue gas. The dry desulfurization system comprises a coal-fired boiler, a flue gas mixer, a flue gas circulating fluidized bed device and a Claus process system. The flue gas output pipeline of the coal-fired boiler is connected to the flue gas mixer, the tail gas output pipeline of the Claus process system is connected to the flue gas mixer, the flue gas mixer is used to mix the Claus tail gas and the coal-fired boiler flue gas, and input the mixed flue gas into the flue gas circulating fluidized bed device for desulfurization treatment. The present invention can make the Claus tail gas meet the higher requirements of the ultra-low emission standards of coal-fired boiler flue gas with lower investment and operating costs.

Description

Technical Field

[0001] The present invention relates to the field of chemical technology, and in particular to a dry desulfurization system and a dry desulfurization method, which are applicable to a dry desulfurization process of Claus tail gas coupled with coal-fired boiler flue gas. Background Art

[0002] In recent years, the coal chemical industry has ushered in a period of rapid development. The by-products of coal liquefaction contain a certain concentration of H 2 If acidic gases such as S are discharged directly, on the one hand, direct discharge of acidic gases will cause a large amount of sulfur resources to be wasted, and on the other hand, it will cause serious atmospheric pollution.

[0003] The Claus process is a mature and widely used 2 The acid gas treatment process converts S into sulfur. During the conversion process, H 2 S. SO 2 The exhaust gas temperature is usually 250℃~300℃, and the excess H in the exhaust gas is burned in an incinerator. 2 S, methane, methanol and other excess gases, eventually generating high concentrations of SO 2 The main components of the tail gas are N 2 , O 2 , CO 2 , H 2 O, SO 2 These main components account for more than 99%, and some contain very small amounts of SO 3 , H 2 S, argon, etc. The existing Claus tail gas complies with GB31571-2015 "Petrochemical Industry Pollutant Emission Standard" "General Area SO 2 <100 mg / m 3 (3%O 2 ), key areas SO 2 <50mg / m 3 (3%O 2 )”.

[0004] Usually, the sulfur recovery efficiency of the two-stage Claus process (compared to the multi-stage process) can reach 92-95%. If the number of stages is increased or the super Claus or super-optimal Claus process is used, the sulfur recovery efficiency can reach more than 99%. In the past, under the relatively loose requirements of the Claus tail gas emission standards, there are many conventional methods to improve the sulfur recovery rate and ensure that the Claus tail gas can meet the emission standards, such as increasing the number of Claus reaction stages (three or four or more multi-stage Claus processes), or further absorbing and regenerating the tail gas through alcohol amine solvents (SCOT process), or reducing and absorbing the tail gas (super / super-optimal Claus process). In fact, after the sulfur is recovered in the two-stage Claus process, it is not very economical to recover sulfur from the tail gas, which only accounts for a few percent of the total sulfur in the original acid gas. Even if these process routes are considered to be the optimization solutions for the tail gas treatment of the Claus process at that time, they are not based on economic considerations, but mainly for the stable and standard emission of Claus tail gas. However, with the promulgation of more stringent Claus tail gas emission standards, the tail gas using the traditional Claus process can no longer meet the requirements of GB31571-2015 "Petrochemical Industry Pollutant Emission Standard" "SO 2 <100mg / Nm 3 (3%O 2 ), key areas SO 2 <50Nmg / m 3 (3%O 2 )". It is now common to use separate tail gas alkali washing or ammonia washing methods and other desulfurization processes to further remove Claus tail gas to meet the existing and future potentially more stringent Claus tail gas emission standards.

[0005] Circulating fluidized bed dry desulfurization process technology has the advantages of low investment cost, low operating cost, good adaptability to boiler load and coal quality, no wastewater discharge, no corrosion, simple process and simple operation. More and more coal chemical companies are using circulating fluidized bed dry desulfurization process as a solution for coal-fired boiler flue gas treatment. Although the circulating fluidized bed dry desulfurization process has many advantages, it is difficult to treat high-concentration SO 2 Flue gas, the absorbent consumption of circulating fluidized bed dry desulfurization process is relatively large. Secondly, high temperature flue gas greater than 260℃ can easily affect the stability of the circulating fluidized bed dry desulfurization system, and easily cause equipment damage such as bag burning or bag sticking in the circulating fluidized bed dry desulfurization system.

[0006] Therefore, how to reduce SO in Claus tail gas 2 concentration and reduce the equipment cost of Claus tail gas desulfurization process, which is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0007] In view of this, the object of the present invention is to provide a dry desulfurization system and a dry desulfurization method suitable for a dry desulfurization process of Claus tail gas coupled with coal-fired boiler flue gas, which can make Claus tail gas meet the higher requirements of ultra-low emission standards of coal-fired boiler flue gas with lower investment and operating costs.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A dry desulfurization system, which is applicable to the dry desulfurization process of Claus tail gas coupled with coal-fired boiler flue gas, and comprises a coal-fired boiler, a flue gas mixer, a flue gas circulating fluidized bed device and a Claus process system, wherein:

[0010] The flue gas output pipe of the coal-fired boiler is connected to the flue gas mixer, and the tail gas output pipe of the Claus process system is connected to the flue gas mixer. The flue gas mixer is used to mix the coal-fired boiler flue gas output by the flue gas output pipe and the Claus tail gas output by the tail gas output pipe to obtain mixed flue gas, and input the mixed flue gas into the flue gas circulating fluidized bed device for desulfurization treatment.

[0011] In the above-mentioned dry desulfurization system, the flue gas mixer is provided with a mixing device made by the injection grid technology, and the Claus tail gas and the coal-fired boiler flue gas are mixed in the mixing device.

[0012] In the above-mentioned dry desulfurization system, a pre-electrostatic precipitator (ie, a device for dust removal using pre-charging technology) is provided between the outlet of the flue gas mixer and the bottom inlet of the absorption tower in the flue gas circulating fluidized bed device.

[0013] In the above dry desulfurization system, the Claus process system includes a Claus reactor, an incinerator and the tail gas output pipeline arranged in series, and a windshield assembly is provided in the tail gas output pipeline. The windshield assembly includes an electric windshield and a manual windshield arranged in series to avoid high concentration SO 2 The high-temperature exhaust gas has an adverse effect on the flue gas circulating fluidized bed device 600, ensuring the stable operation of the system.

[0014] In the above-mentioned dry desulfurization system, a waste heat utilization device is arranged between the incinerator and the windshield assembly to recover and utilize the waste heat of the Claus tail gas after incineration.

[0015] Specifically, the waste heat utilization device 703 is a waste heat utilization boiler or a flue gas heat exchanger (ie, GGH); the coal-fired boiler is a circulating fluidized bed boiler or a pulverized coal boiler.

[0016] In the above-mentioned dry desulfurization system, the medium-pressure steam produced by the waste heat utilization device can be: used to heat the dry desulfurization ash hopper in the flue gas circulating fluidized bed device; and / or used to heat the fluidizing air in the flue gas circulating fluidized bed device; and / or, incorporated into the plant's medium-pressure steam pipeline network.

[0017] In addition, the Claus process system of the above-mentioned dry desulfurization system also includes a liquid sulfur storage tank and a sulfur granulator. The liquid sulfur is stored in the liquid sulfur storage tank and then passes through the sulfur granulator to form a sulfur product; the coal-fired boiler of the above-mentioned dry desulfurization system can also be equipped with an SNCR denitrification device, an in-furnace desulfurization system, and an SCR denitrification device according to actual needs; the above-mentioned flue gas circulating fluidized bed device includes an absorption tower, a bag filter, an induced draft fan and a chimney arranged in sequence, as well as a material circulation device, a silo pump, an ash storage, a load adjustment device, an absorbent supply system and a process water supply system.

[0018] A dry desulfurization method is applicable to the dry desulfurization process of Claus tail gas coupled with coal-fired boiler flue gas. The dry desulfurization method comprises: generating Claus tail gas by a Claus process system; generating coal-fired boiler flue gas by a coal-fired boiler; mixing the Claus tail gas and the coal-fired boiler flue gas to obtain mixed flue gas, and performing a dry desulfurization process on the mixed flue gas through a flue gas circulating fluidized bed device.

[0019] Specifically, the Claus process adopted by the Claus process system may be any one of two-stage Claus, three-stage Claus, two-stage Claus+SCOT process, and super-optimal Claus.

[0020] In the above dry desulfurization method, the SO 2 The concentration is controlled at 1000mg / m 3 Within.

[0021] In the above dry desulfurization method, the SO at the outlet of the absorption tower in the flue gas circulating fluidized bed device is 2 Concentration not more than 35mg / Nm 3 (Dry basis, 6%O 2 ).

[0022] In the above dry desulfurization method, if the SO 2 If the concentration exceeds the preset value, the SO in the flue gas of the coal-fired boiler is reduced by improving the desulfurization efficiency in the furnace of the coal-fired boiler. 2 concentration.

[0023] In the above dry desulfurization method, the outlet tail gas temperature of the Claus reactor in the Claus process system is controlled at 250°C to 300°C, and the outlet tail gas temperature of the incinerator is controlled at 350°C to 900°C.

[0024] In the above dry desulfurization method, the flue gas temperature at the outlet of the air preheater of the coal-fired boiler is controlled at 120°C to 180°C, and the mixed flue gas temperature at the inlet of the absorption tower in the flue gas circulating fluidized bed device is controlled at 120°C to 180°C.

[0025] In the above dry desulfurization method, the temperature of the mixed flue gas at the outlet of the absorption tower is 10° C. above the water dew point. The water dew point refers to the temperature at which water vapor reaches the maximum saturation value under specific pressure conditions, also known as the dew point.

[0026] In the above dry desulfurization method, if the temperature of the mixed flue gas is calculated to be greater than 160°C, a waste heat utilization device is provided between the incinerator and the windshield assembly. During the production process, the temperature of the Claus tail gas after waste heat utilization is controlled to be 120°C to 180°C, which is equivalent to the flue gas temperature at the outlet of the air preheater of the coal-fired boiler;

[0027] If it is calculated that the temperature of the mixed flue gas is less than 160° C., the waste heat utilization device is not provided between the incinerator and the windshield assembly.

[0028] In the above dry desulfurization method, the flue gas output pipeline of the coal-fired boiler is connected to the flue gas mixer, and the tail gas output pipeline of the Claus process system is connected to the flue gas mixer, and the flue gas mixer is used to mix the flue gas of the coal-fired boiler outputted by the flue gas output pipeline and the Claus tail gas outputted by the tail gas output pipeline to obtain mixed flue gas; a windshield assembly is arranged in the tail gas output pipeline. If the Claus tail gas causes the bag filter in the flue gas circulating fluidized bed device to be damaged, or the flue gas emission index exceeds the standard, the Claus tail gas is shut off by the windshield assembly.

[0029] In the above dry desulfurization method, the amount of Claus tail gas generated by the Claus process system and the amount of coal-fired boiler flue gas generated by the coal-fired boiler are calculated, and the process parameters of the flue gas mixer are designed so that the temperature of the mixed flue gas is controlled at 120°C to 150°C.

[0030] It can be seen that in the dry desulfurization system and dry desulfurization method provided by the present invention, since the amount of Claus tail gas is relatively small compared to the amount of coal-fired boiler flue gas, and the SO 2 The concentration is low, so a large amount of coal-fired boiler flue gas can be used to dilute and assimilate the Claus tail gas, so that the mixed flue gas composed of Claus tail gas and coal-fired boiler flue gas in the coal chemical industry can be treated by the flue gas circulating fluidized bed device, which reduces the desulfurization difficulty of Claus tail gas, expands the application scope of the flue gas circulating fluidized bed dry desulfurization process, and solves the problem that the flue gas circulating fluidized bed device is not suitable for treating high-concentration SO 2The technical barriers of high-temperature Claus tail gas make SO in Claus tail gas 2 The ultra-low emission standard of flue gas from coal-fired boilers is achieved, and the Claus tail gas desulfurization efficiency reaches more than 99%, while saving the investment and operation and maintenance costs of Claus tail gas desulfurization equipment. Moreover, a certain amount of Claus tail gas coupled with the flue gas desulfurization system of coal-fired boilers can increase the influence of the flue gas circulating fluidized bed device on boiler load fluctuations, which is conducive to improving the stability of system operation and reducing the adjustment frequency of the load adjustment device in the flue gas circulating fluidized bed device.

[0031] In addition, H 2 S, sulfur dust, etc. are explosive gases, and sulfur recovery process equipment belongs to chemical equipment, which must be designed and selected according to explosion-proof standards. The Claus tail gas at the tail of the incinerator is led to the flue gas desulfurization layout area of ​​the coal-fired boiler, which belongs to the non-explosion-proof area, through the flue, which can greatly save the investment cost and operation and maintenance cost of post-furnace dry desulfurization.

[0032] Moreover, through the dry desulfurization system and dry desulfurization method provided by the present invention, the requirements for the sulfur conversion rate of the front-stage Claus tail gas can be appropriately simplified and reduced, the sulfur output can be appropriately reduced, and the range of selection of the process route of the Claus tail gas itself can be increased (such as selecting only a secondary Claus process), thereby saving the investment cost and operating cost of Claus tail gas treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A schematic structural diagram of a dry desulfurization system for Claus tail gas coupled with coal-fired boiler flue gas provided in a first specific embodiment of the present invention;

[0035] Figure 2 A schematic structural diagram of a dry desulfurization system suitable for Claus tail gas coupled with coal-fired boiler flue gas provided in a second specific embodiment of the present invention.

[0036] in:

[0037] 701- Claus reactor, 702- incinerator, 703- waste heat utilization device (optional), 704- electric windshield,

[0038] 705-manual windshield, 706-flue gas mixer, 707-liquid sulfur storage, 708-sulfur granulator;

[0039] 601-coal-fired boiler, 602-SNCR denitration device (optional), 603-furnace desulfurization system (optional), 604-SCR denitration device (optional), 605-pre-electrostatic precipitator (optional),

[0040] 606-absorbent supply system, 607-process water supply system, 608-absorption tower, 609-bag dust collector, 610-induced draft fan, 611-chimney, 612-load regulating device, 613-material circulation device, 614-silo pump, 615-ash storage. DETAILED DESCRIPTION

[0041] First of all, it should be noted that the sulfur recovery scale of the Claus process unit is about 5,000 t / a at a small scale and about 10,000 t / a at a large scale. The amount of Claus tail gas after the incinerator is as small as several thousand m 3 / h, up to 100,000 m 3 / h. Compared with most coal-fired boiler flue gas, the amount of Claus tail gas is relatively small. Depending on the needs, the tail gas temperature after the incinerator is usually between 350 and 900 °C. The acid gas of the sulfur-restricted raw material contains H 2 Affected by factors such as S concentration and acid gas volume, the Claus process is usually divided into normal operating conditions and special conditions. Claus tail gas SO under special conditions 2 The concentration is as high as about 60g / m 3 , exhaust gas SO under normal operating conditions 2 The concentration is usually in the range of several hundred to tens of thousands of mg / m 3 In summary, the tail gas composition of the Claus exhaust from the incinerator is basically the same as that of the flue gas from the coal-fired boiler, with a small amount of Claus exhaust gas, high temperature, and SO 2 Characteristics of high concentration.

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] First specific embodiment

[0044] The first specific embodiment of the present invention provides a dry desulfurization system and a dry desulfurization method, which are applicable to the dry desulfurization process of Claus tail gas coupled with coal-fired boiler flue gas.

[0045] See also Figure 1 , Figure 1A schematic structural diagram of a dry desulfurization system suitable for Claus tail gas coupled with coal-fired boiler flue gas provided in the first specific embodiment of the present invention.

[0046] The dry desulfurization system includes a coal-fired boiler 601, a flue gas mixer 706, a flue gas circulating fluidized bed device 600 (i.e., a flue gas circulating fluidized bed dry desulfurization device) and a Claus process system. Among them:

[0047] The Claus process system includes a Claus reactor 701, an incinerator 702, an electric windshield 704, a manual windshield 705, a liquid sulfur storage 707, a sulfur granulator 708, and whether to set up a waste heat utilization device 703 can be selected according to actual conditions;

[0048] On the coal-fired boiler 601, it can be selected whether to install the SNCR denitration device 602, the furnace desulfurization system 603, and the SCR denitration device 604 according to the actual situation;

[0049] The flue gas circulating fluidized bed device 600 includes an absorbent supply system 606, a process water supply system 607, an absorption tower 608 (i.e., a circulating fluidized bed dry desulfurization absorption tower), a bag filter 609, an induced draft fan 610, a chimney 611, a load regulating device 612, a material circulation device 613, a silo pump 614, and an ash storage 615;

[0050] In addition, between the flue gas mixer 706 and the absorption tower 608, it is also possible to choose whether to install a pre-electrostatic precipitator 605 according to actual conditions.

[0051] During the production process, the dry desulfurization method adopted by the dry desulfurization system is: Claus tail gas is generated by the Claus process system; coal-fired boiler flue gas is generated by the coal-fired boiler; the Claus tail gas and the coal-fired boiler flue gas are mixed to obtain mixed flue gas, and the mixed flue gas is subjected to a dry desulfurization process through a flue gas circulating fluidized bed device.

[0052] The dry desulfurization method is as follows (see Figure 1 ):

[0053] Combustion gas (i.e. fuel gas and air) and acid gas are fed into the Claus reactor 701. After the Claus process, liquid sulfur is stored in the liquid sulfur storage 707 and then passes through the sulfur granulator 708 to produce sulfur products.

[0054] The outlet tail gas temperature of Claus reactor 701 is usually 250°C to 300°C. The tail gas contains H 2 S and SO 2 After entering the incinerator 702, the H 2 S is converted to SO 2The temperature of the Claus tail gas discharged from the outlet of the incinerator 702 is between 350°C and 900°C. The Claus tail gas generated by the combustion in the incinerator 702 has different components according to the different components of the combustion-supporting gas. The main components of the Claus tail gas discharged from the outlet of the incinerator 702 are N 2 , O 2 , CO 2 , H 2 O、SO 2 These main components account for more than 99%, and some contain very small amounts of SO 3 , H 2 S, argon, etc.

[0055] Whether the waste heat utilization device 703 needs to be set after the incinerator 702 is determined according to the amount of Claus tail gas, the amount of combustion-supporting gas and the demand of the incinerator. The waste heat utilization device 703 is used to recover and utilize the waste heat of the Claus tail gas after incineration. It is assumed that the waste heat utilization device 703 can produce 0.7Mpa medium-pressure steam, which can be used to heat the dry desulfurization ash hopper in the flue gas circulating fluidized bed device 600, and can also be used to heat the fluidizing air. The excess steam is incorporated into the medium-pressure steam network in the plant area to play the role of waste heat utilization. The temperature of the Claus tail gas after waste heat utilization is controlled to be 120℃ to 180℃, which is equivalent to the flue gas temperature at the outlet of the coal-fired boiler air preheater. Among them, the amount of Claus tail gas is relatively small compared to the coal-fired boiler flue gas coming out of the coal-fired boiler air preheater. If the proportion of Claus tail gas to the coal-fired boiler flue gas is small, and the theoretical mixed flue gas temperature is not greater than 160℃ after calculation, the waste heat utilization device 703 can be omitted.

[0056] The tail gas output pipeline in the Claus process system is used to input the Claus tail gas into the flue gas mixer 706. The tail gas output pipeline is provided with an electric damper 704 and a manual damper 705 to prevent the high concentration of SO2 from entering the flue gas mixer 706 under special working conditions. 2 The high-temperature Claus tail gas damages the bag filter 609 in the flue gas circulating fluidized bed device 600 and is used to prevent the flue gas emission index from exceeding the standard.

[0057] After the flue gas from the coal-fired boiler comes out of the air preheater, it is mixed evenly with the Claus tail gas in the flue gas mixer 706. 2 The concentration is usually controlled at 1000 mg / m 3 If the SO in Claus exhaust gas 2 Too high a concentration leads to SO in the mixed flue gas 2 If the concentration is too high, the SO in the flue gas of coal-fired boilers can be reduced by improving the desulfurization efficiency in the furnace. 2 Concentration, in-furnace desulfurization technology is one of the front-end desulfurization technologies for coal-fired boilers.

[0058] By calculating the amount of Claus tail gas and the amount of coal-fired boiler flue gas, a suitable flue gas mixer 706 is designed. For example, the mixing device in the flue gas mixer 706 is manufactured by the injection grid technology. Its function is to quickly mix two gases with different temperatures and different proportions, that is, to mix the Claus tail gas and the coal-fired boiler flue gas evenly, so that the temperature of the mixed flue gas is controlled between 120°C and 150°C. Specifically, the mixed flue gas after passing through the injection grid enters the absorption tower 609 in the flue gas circulating fluidized bed device 600 from the bottom. Here (i.e., the bottom of the absorption tower), the mixed flue gas is fully mixed with the calcium-based absorbent and the circulating desulfurization ash to carry out a preliminary desulfurization reaction. Among them, the calcium-based absorbent is provided by the absorbent supply system 606, and the circulating desulfurization ash is provided by the material circulation device 613. The calcium-based absorbent can be purchased slaked lime, or it can be made of slaked lime of suitable quality on site through a digester.

[0059] After the initial desulfurization, the mixed flue gas enters the absorption tower 608. The circulating fluidized bed in the absorption tower 608 contains a high-density, violently turbulent absorbent and material particle bed. The process water is sprayed into the absorption tower 608 by the atomizing spray gun in the process water supply system 607, and adheres to the surface of the absorbent and material particles to form a liquid film. The SO in the mixed flue gas 2 It is captured by the liquid membrane and reacts with the absorbent to generate the by-product CaSO 3 1 / 2H 2 O. In addition, atomized water is sprayed into the absorption tower 608 to reduce the temperature of the mixed flue gas in the desulfurization reactor. The reaction temperature in the absorption tower 608 is usually controlled at about 80°C. At the same time, the temperature of the mixed flue gas is always higher than the dew point temperature by more than 10°C. Therefore, the exhaust gas does not need to be heated again, and the entire system does not require any anti-corrosion treatment. The water sprayed in to reduce the temperature of the flue gas is fully evaporated in the tower with violently turbulent material particles with a large surface area as a carrier, ensuring that the fly ash entering the subsequent dust collector is dry and has a good flow state. SO in the flue gas 2 、SO 3 , HCl, HF, etc. and Ca(OH) 2 An ionic reaction occurs, thus achieving efficient removal, and heavy metals in the flue gas are also adsorbed and captured by the high-density bed.

[0060] The flue gas leaving the absorption tower 608 enters the subsequent high-efficiency dust collector, that is, the dust is captured by the bag filter 609.

[0061] Finally, the desulfurized flue gas is discharged from the chimney 611 under the action of the induced draft fan 610 .

[0062] Since the exhaust temperature of dry flue gas is always more than 10°C higher than the dew point temperature and multiple pollutants are removed efficiently and synergistically, the exhaust gas is transparent and the entire system does not require any anti-corrosion treatment.

[0063] Specifically, the Claus process can be any one of two-stage Claus, three-stage Claus, two-stage Claus + SCOT (tail gas hydrogenation technology) process, super Claus, etc.; the Claus reactor 701 can be used to implement any one of two-stage Claus, multi-stage Claus, two-stage Claus + SCOT, two-stage Claus + catalytic oxidation, two-stage Claus + hydrogenation reduction + catalytic oxidation.

[0064] Specifically, the waste heat utilization device 703 may be a waste heat utilization boiler or a GGH (flue gas reheater).

[0065] Specifically, the coal-fired boiler 601 may be a circulating fluidized bed boiler or a pulverized coal boiler.

[0066] Specifically, at the inlet of the absorption tower 608, the temperature of the mixed flue gas is 120°C to 180°C.

[0067] Specifically, at the outlet of the absorption tower 608, the flue gas temperature is 10° C. above the water dew point, usually 60° C. to 80° C. The water dew point refers to the temperature at which water vapor reaches the maximum saturation value under specific pressure conditions, also known as the dew point.

[0068] Specifically, at the outlet of the absorption tower 608, SO 2 Concentration not more than 35mg / Nm 3 (Dry basis, 6%O 2 ).

[0069] The dry desulfurization system and dry desulfurization method provided in the first specific embodiment of the present invention have the following advantages and effects: In the dry desulfurization system, the differences in explosion-proof design and selection between chemical plants and coal-fired boiler power plants are fully combined, and the mixing temperature and component ratio of the two different gases of Claus tail gas and coal-fired boiler flue gas are comprehensively considered, as well as the applicable treatment gas of the flue gas circulating fluidized bed device. Through the interaction between the flue gas mixer 706, the Claus tail gas concentration and the pre-desulfurization process of the coal-fired boiler, the Claus tail gas meets the ultra-low emission standards of the coal-fired boiler industry. At the same time, the redundancy of the Claus tail gas desulfurization device of the coal chemical enterprise is achieved, and the investment and operating expenses of the Claus tail gas desulfurization equipment are saved by only including relatively small investment costs such as the windshield component, the tail gas output flue, and the flue gas mixer. It provides a practical and feasible new preferred technical solution for further promoting the field of coal chemical enterprises and Claus tail gas treatment.

[0070] Second specific embodiment

[0071] The second specific embodiment of the present invention provides a dry desulfurization system and a dry desulfurization method, which are applicable to the dry desulfurization process of Claus tail gas coupled with coal-fired boiler flue gas. Figure 2 , Figure 2 A schematic structural diagram of a dry desulfurization system suitable for Claus tail gas coupled with coal-fired boiler flue gas is provided for the second specific embodiment of the present invention; the dry desulfurization method can refer to the above-mentioned first specific embodiment.

[0072] The second specific embodiment of the present invention provides a dry desulfurization system as a transformation project, as described below.

[0073] The Claus tail gas desulfurization device in a coal chemical enterprise has a Claus process flow of traditional two-stage Claus process + SCOT (hydrogenation reduction + MDEA selective absorption) + incinerator + Claus tail gas chimney emission. The sulfur output of the Claus process system is 34t / d (annual output is about 12,000t / a), and the sulfuric acid raw gas processing is 3800Nm 3 / h. Before the Claus tail gas desulfurization device was modified, the amount of Claus tail gas after the incinerator was 6700Nm 3 / h, SO under normal operating conditions of Claus tail gas 2 The emission concentration is about 600mg / m 3 , SO under special conditions 2 Emission concentration 11500mg / m 3 , the exhaust gas temperature of the chimney is 250℃ (there is no waste heat utilization device after the incinerator, and the Claus exhaust gas is discharged from the chimney). Before the transformation, the Claus exhaust gas can meet the "SO 2 ≤960mg / m 3 ” emission requirements, but does not meet the current “Petrochemical Industry Pollutant Emission Standards” “General Area SO 2 <100mg / Nm 3 (3%O 2 )” emission requirements.

[0074] The existing coal-fired power boilers in the plant are two 160t / h pulverized coal boilers, the flue gas temperature at the air preheater outlet is 140℃, and the air preheater outlet SO 2 Concentration 1900mg / m 3 Before the transformation, the coal-fired boiler used an ammonia desulfurization process. The flue gas emissions of the coal-fired boiler could not meet the national ultra-low emission requirements. At the same time, there were phenomena such as severe corrosion of the desulfurization equipment and chimney gas tailing.

[0075] Due to the above problems, the enterprise carried out Claus tail gas desulfurization and coal-fired boiler flue gas ultra-clean emission desulfurization renovation projects. The renovation plan adopted the dry desulfurization system and dry desulfurization method suitable for Claus tail gas coupled with coal-fired boiler flue gas dry desulfurization process provided by the second specific embodiment of the present invention. Please refer to the structural schematic diagram of the dry desulfurization system Figure 2 The dry desulfurization system includes a coal-fired boiler 601, a flue gas mixer 706, a flue gas circulating fluidized bed device 600 (i.e., a flue gas circulating fluidized bed dry desulfurization device) and a Claus process system. Among them:

[0076] The Claus process system includes a Claus reactor 701, an incinerator 702, an electric windshield 704, a manual windshield 705, a liquid sulfur storage 707, and a sulfur granulator 708;

[0077] On the coal-fired boiler 601, it can be selected whether to install the SNCR denitration device 602, the furnace desulfurization system, and the SCR denitration device according to the actual situation;

[0078] The flue gas circulating fluidized bed device 600 includes an absorbent supply system 606, a process water supply system 607, an absorption tower 608 (i.e., a circulating fluidized bed dry desulfurization absorption tower), a bag filter 609, an induced draft fan 610, a chimney 611, a load regulating device 612, a material circulation device 613, a silo pump 614, and an ash storage 615.

[0079] In this dry desulfurization system, Claus tail gas is led to the coal-fired boiler flue gas desulfurization equipment area through a DN500 flue of about 160m, and then enters the absorption tower 608 of a flue gas circulating fluidized bed device 600 after passing through the flue gas mixer 706. The absorption tower 608 is designed to process 400,000 Nm of mixed flue gas. 3 / h (wet basis), the treatment design of the mixed flue gas in the inlet of the absorption tower 608 is SO 2 Concentration 2800mg / m 3 , the design mixed smoke temperature is 140℃~150℃, the chimney outlet is designed to be SO 2 Concentration 35mg / m 3 The exhaust temperature at the chimney outlet is 80℃.

[0080] After the device was built and put into operation, the actual operation situation was: the actual amount of Claus tail gas was 3900m 3 / h (wet basis), coal-fired boiler flue gas is 296400m 3 / h (wet basis); actual SO in Claus tail gas 2 The concentration is 428 mg / m 3 , coal-fired boiler flue gas SO 2 The actual concentration is 764 mg / m 3 , the mixed flue gas SO after the Claus tail gas passes through the flue gas mixer 7062 The actual concentration is 760mg / m 3 (The actual SO 2 The concentration is lower than the design value, and the actual SO in Claus tail gas 2 The concentration is also lower than the design value); the Claus tail gas temperature is 260℃, the coal-fired boiler flue gas temperature is 145℃, and the actual mixed flue gas temperature is 146℃; the actual coal-fired boiler flue gas chimney outlet SO 2 Concentration 6mg / m 3 The actual exhaust temperature at the chimney outlet is 85°C. The desulfurization rate of Claus tail gas reaches 99.1% and is stable at less than 35mg / m 3 Run below.

[0081] Among them, the flue gas mixer 706 in the dry desulfurization system fully mixes the high-temperature Claus tail gas and the coal-fired boiler flue gas. The Claus tail gas passes through the mixing device (i.e., the injection grid) manufactured by the injection grid technology in the flue gas mixer 706 to avoid the high-temperature flue gas from flowing sideways and causing damage to the desulfurization equipment in the flue gas circulating fluidized bed device 600.

[0082] If Claus tail gas combined with tail gas desulfurization process route transformation is adopted, no matter whether sodium alkali wet method, ammonia washing method, electrodialysis method, etc. are adopted, the investment cost of Claus tail gas desulfurization equipment in the transformation project will increase by about 8 million yuan, and the annual absorbent cost and personnel management cost are not taken into account. According to the second specific embodiment of the present invention, the investment cost of Claus tail gas transformation project including windshield, flue and injection grid is less than 300,000 yuan, which greatly saves the investment cost of Claus tail gas desulfurization equipment. After the transformation, the redundancy of the enterprise in the management and operation of Claus flue gas desulfurization equipment and coal-fired boiler flue gas desulfurization equipment is also reduced.

[0083] In summary, the dry desulfurization system and dry desulfurization method provided by the specific embodiment of the present invention have the following advantages:

[0084] 1. With lower investment and operating costs, Claus tail gas can meet the ultra-low emission requirements of flue gas in the coal-fired boiler field and stabilize at "SO 2 <35mg / Nm 3 "Emissions are far better than the emission requirements of Claus tail gas "Petrochemical Industry Pollutant Emission Standards".

[0085] 2. Claus tail gas treatment and coal-fired boiler process are matched with each other. By adding technical measures such as electric dampers, manual dampers and flue gas mixers, and relying on the dilution and assimilation of a large amount of coal-fired boiler flue gas, the application scope of flue gas circulating fluidized bed desulfurization process is expanded, so that the circulating fluidized bed process that is not suitable for treating Claus tail gas can be applied to both Claus tail gas and coal-fired boiler flue gas. With the advantages of circulating fluidized bed desulfurization technology, the requirements for sulfur conversion rate of the previous Claus process can be simplified and reduced, and the selection range of Claus tail gas process routes can be expanded. On the one hand, the investment cost of the remaining process equipment of Claus tail gas is reduced, and on the other hand, the overall operation and maintenance cost of Claus tail gas process equipment is greatly reduced.

[0086] 3. Secondly, the relatively small amount of high-temperature and high-sulfur concentration Claus tail gas has no effect on the design and selection of the circulating fluidized bed dry desulfurization device for coal-fired boiler flue gas, and is very suitable for both Claus tail gas treatment renovation projects and new projects.

[0087] 4. A certain amount of Claus tail gas coupled with the flue gas desulfurization system of a coal-fired boiler can increase the impact of the flue gas circulating fluidized bed device on boiler load fluctuations and reduce the adjustment frequency of the load adjustment device of the flue gas circulating fluidized bed.

[0088] 5. The present invention realizes the integrated treatment of Claus tail gas and coal-fired boiler flue gas through the circulating fluidized bed dry desulfurization process. The process flow is simple, the operation is easy, the operation is stable, and there is no wastewater in the whole flow, no secondary pollution is generated, and no anti-corrosion treatment is required.

[0089] 6. The matching and interactivity of the two processes have been solved. The Claus tail gas in the coal chemical industry has basically no impact on the design and selection of coal-fired boilers and flue gas circulating fluidized bed dry desulfurization devices. It is very suitable for both Claus tail gas treatment renovation projects and new projects.

[0090] 7. Claus process is a chemical equipment, each equipment is compactly arranged and must be designed and selected according to chemical explosion-proof standards. Claus tail gas is connected to a non-explosion-proof coal-fired boiler flue gas circulating fluidized bed dry desulfurization device through a flue duct, which is equivalent to saving the investment and operation and maintenance costs of a set of Claus process equipment designed according to explosion-proof standards for tail gas desulfurization equipment, and at the same time solves the redundancy of desulfurization process personnel management in the same coal chemical enterprise. The investment and operation costs of the Claus tail gas treatment process route and scheme of this invention are low, and only include the addition of an electric adjustable windshield, a manual adjustable windshield and a flue gas mixer, which can save about 90% of the investment cost compared with the existing Claus tail gas treatment device, and has obvious technical and economic application advantages.

[0091] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0092] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0093] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A dry desulfurization system, It is characterized in that The dry desulfurization system is applicable to the dry desulfurization process of Claus tail gas coupled with coal-fired boiler flue gas. The dry desulfurization system comprises a coal-fired boiler (601), a flue gas mixer (706), a flue gas circulating fluidized bed device (600) and a Claus process system, wherein: The flue gas output pipeline of the coal-fired boiler (601) is connected to the flue gas mixer (706), and the tail gas output pipeline of the Claus process system is connected to the flue gas mixer (706). The flue gas mixer (706) is used to mix the coal-fired boiler flue gas outputted from the flue gas output pipeline and the Claus tail gas outputted from the tail gas output pipeline to obtain mixed flue gas, and to input the mixed flue gas into the flue gas circulating fluidized bed device (600) for desulfurization treatment; The coal-fired boiler (601) is provided with an in-furnace desulfurization system (603) for reducing the SO2 concentration in the flue gas of the coal-fired boiler (601) by improving the in-furnace desulfurization efficiency when the SO2 concentration in the Claus tail gas is too high; The Claus process system comprises a Claus reactor (701), an incinerator (702) and the tail gas output pipeline which are sequentially arranged in series, and a windshield assembly is provided in the tail gas output pipeline; The windshield assembly comprises an electric windshield (704) and a manual windshield (705) which are arranged in series.

2. The dry desulfurization system according to claim 1, It is characterized in that The flue gas mixer (706) is provided with a mixing device manufactured by injection grid technology, and the Claus tail gas and the coal-fired boiler flue gas are mixed at the mixing device.

3. The dry desulfurization system according to claim 1, It is characterized in that A pre-electrostatic precipitator (605) is provided between the outlet of the flue gas mixer (706) and the bottom inlet of the absorption tower (608) in the flue gas circulating fluidized bed device (600).

4. The dry desulfurization system according to claim 1, It is characterized in that A waste heat utilization device (703) is provided between the incinerator (702) and the windshield assembly.

5. The dry desulfurization system according to claim 4, It is characterized in that The medium-pressure steam produced by the waste heat utilization device (703) can: Used for heating the dry desulfurization ash hopper in the flue gas circulating fluidized bed device (600); and / or, used to heat the fluidizing air in the flue gas circulating fluidized bed device (600); and / or, incorporated into the plant’s medium-pressure steam network.

6. A dry desulfurization method, used in the dry desulfurization system according to any one of claims 1 to 5, It is characterized in that The dry desulfurization method is applicable to the dry desulfurization process of Claus tail gas coupled with coal-fired boiler flue gas, and the dry desulfurization method comprises: A Claus tail gas is produced by a Claus process system; A coal-fired boiler (601) generates coal-fired boiler flue gas; The Claus tail gas and the coal-fired boiler flue gas are mixed to obtain mixed flue gas, and the mixed flue gas is subjected to a dry desulfurization process through a flue gas circulating fluidized bed device (600).

7. The dry desulfurization method according to claim 6, It is characterized in that The SO in the mixed flue gas 2 The concentration is controlled at 1000mg / m 3 within; and / or, on a dry basis, 6% O 2 " state, in the flue gas circulating fluidized bed device (600), the SO at the outlet of the absorption tower (608) 2 Concentration not more than 35mg / Nm 3 .

8. The dry desulfurization method according to claim 6, It is characterized in that If the SO in the mixed flue gas 2 If the concentration exceeds a preset value, the SO in the flue gas of the coal-fired boiler is reduced by improving the desulfurization efficiency in the furnace of the coal-fired boiler (601). 2 concentration.

9. The dry desulfurization method according to claim 6, It is characterized in that In the Claus process system, the outlet tail gas temperature of the Claus reactor (701) is controlled at 250°C to 300°C, and the outlet tail gas temperature of the incinerator (702) is controlled at 350°C to 900°C; and / or, the flue gas temperature at the outlet of the air preheater of the coal-fired boiler (601) is controlled within a range of 120° C. to 180° C., and the mixed flue gas temperature at the inlet of the absorption tower (608) in the flue gas circulating fluidized bed device (600) is controlled within a range of 120° C. to 180° C.; And / or, the mixed flue gas temperature at the outlet of the absorption tower (608) is 10°C above the water dew point.

10. The dry desulfurization method according to claim 6, It is characterized in that If the temperature of the mixed flue gas is greater than 160° C., a waste heat utilization device (703) is provided between the incinerator (702) and the windshield assembly; If the temperature of the mixed flue gas is less than 160° C., the waste heat utilization device (703) is not provided between the incinerator (702) and the windshield assembly.

11. The dry desulfurization method according to claim 6, It is characterized in that The flue gas output pipeline of the coal-fired boiler (601) is connected to a flue gas mixer (706), and the tail gas output pipeline of the Claus process system is connected to the flue gas mixer (706), and the flue gas mixer (706) is used to mix the coal-fired boiler flue gas outputted by the flue gas output pipeline and the Claus tail gas outputted by the tail gas output pipeline to obtain mixed flue gas; A windshield assembly is provided in the exhaust gas output pipeline; If the Claus tail gas causes damage to the bag filter (609) in the flue gas circulating fluidized bed device (600), or the flue gas emission index exceeds the standard, the Claus tail gas is shut off by the windshield assembly.

12. The dry desulfurization method according to claim 6, It is characterized in that By calculating the amount of Claus tail gas generated by the Claus process system and the amount of coal-fired boiler flue gas generated by the coal-fired boiler (601), the process parameters of the flue gas mixer are designed so that the temperature of the mixed flue gas is controlled at 120°C to 150°C.

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