CN110917869A - Method for reducing NOx emission in incompletely regenerated flue gas in catalytic cracking process - Google Patents
Method for reducing NOx emission in incompletely regenerated flue gas in catalytic cracking process Download PDFInfo
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Abstract
The invention belongs to the field of catalytic cracking, and discloses a method for reducing NOx emission in incompletely regenerated flue gas in a catalytic cracking process3And the like reduced nitrides. The invention provides a catalytic cracking device by using a near-field catalytic cracking unitThe method is characterized in that high-temperature catalyst coking flue gas containing CO in a regenerator is introduced into an independent denitration auxiliary agent tank system, the addition amount of an auxiliary agent is automatically controlled, so that active components in the auxiliary agent are partially converted into carbides and reduced states from oxides under the high-temperature reductive CO atmosphere, the activity of the auxiliary agent is improved, the amount of NOx discharged by a catalytic device is reduced by 20-30%, and the control process is flexible.
Description
Technical Field
The invention relates to a method for reducing the emission of NOx in incompletely regenerated flue gas in a catalytic cracking process, belonging to the field of catalytic cracking.
Technical Field
Catalytic cracking plays a major role in refineries as an important means for processing heavy oil in refineries, and is not only a main means for balancing heavy oil in refineries and producing clean fuel, but also an attention point for energy conservation and efficiency improvement of refineries. In the process of Fluid Catalytic Cracking (FCC), raw oil and a regenerated catalyst are in rapid contact in a riser to carry out catalytic cracking reaction, coke generated by the reaction is deposited on the catalyst to cause the deactivation of the catalyst, the coke-formed deactivated catalyst enters a regenerator after being stripped and contacts with regenerated air or air rich in oxygen entering the bottom of the regenerator to carry out coke-burning regeneration. The regenerated catalyst is circulated back to the reactor to participate in the catalytic cracking reaction again. According to the content of the surplus oxygen in the flue gas in the regeneration process or the sufficient degree of CO oxidation, the catalytic cracking device can be divided into complete regeneration operation and incomplete regeneration operation.
During incomplete regeneration, the flue gas from the regenerator has a very low NOx concentration and reduced nitrides such as NH due to low excess oxygen content and high CO concentration3And higher concentration of HCN and the like. These reduced nitrides flow downstream with the flue gas, and if they are sufficiently oxidized in the CO boiler for energy recovery, NOx is formed; if not sufficiently oxidized, residual NH3And the ammonia nitrogen in the wastewater of the downstream washing tower exceeds the standard easily, or the ammonia nitrogen reacts with SOx in the flue gas to generate ammonium salt which is separated out to cause salt deposition of a residual boiler or other flue gas post-treatment equipment (such as SCR), so that the long-period operation of the device is influenced. Thus, the incomplete regeneration process catalytically converts NH in the regenerator using a catalyst promoter3And the NOx emission in the flue gas can be reduced, and the operation period of the device is prolonged.
The denitration auxiliary agent denitration technology is that a denitration catalyst is added into a regenerator in an auxiliary agent mode, and a precursor NH of NOx is added into the regenerator3And HCN to harmless N2The method can radically reduce NOx precursors entering a CO boiler so as to reduce the emission of NOx in flue gas, is considered to be one of the most effective methods, and is also an emergency emission reduction measure for dealing with the over-standard emission of NOx caused by the fluctuation of the nitrogen content of the catalytic raw material. The action mechanism is as follows: firstly, catalytic hydrolysis of HCN to NH3(ii) a Second, NH3Catalytic decomposition to N2And H2And O. The reactions involved are as follows:
HCN+2H2O＝HCOOH+NH3
HC≡N+H2O→NH3+CO
2NH3→N2+H2
2H2+O2→2H2O
various technical companies have made extensive research and development efforts for this purpose, but for controlling the flue gas NH of incomplete regenerators3And NOx emissions, relatively few research and application reports have been reported.
US5021144 discloses a method for reducing NH in flue gas of incomplete regeneration FCC device3The method of discharging is to add excess CO combustion improver into the regenerator in an amount 2-3 times the minimum addition to prevent lean bed afterburning. The method can reduce NH in flue gas of incomplete regeneration FCC device3But the emission is large, the energy consumption is high, and the environmental protection is not facilitated.
US4755282 discloses a process for reducing NH in flue gas of a partially or incompletely regenerated FCC unit3A method of venting. TheThe method comprises adding ammonia decomposition catalyst with particle size of 10-40 μm into regenerator, maintaining the catalyst in dilute phase bed layer at a certain concentration, and adding NH3Conversion to N2And water. The active component of the ammonia decomposition catalyst may be a noble metal dispersed on an inorganic oxide support.
CN101024179A discloses a NOx reducing composition for use in FCC processes comprising (i) an acidic metal oxide substantially free of zeolite, (ii) an alkali metal, an alkaline earth metal and mixtures thereof and (iii) an oxygen storage component. The prepared composition is impregnated by noble metal to convert gas phase reduced nitrogen substances in the flue gas of an incomplete regeneration catalytic cracking unit and reduce the emission of NOx in the flue gas.
Because the difference between the smoke composition of the incomplete regeneration device and the complete regeneration device is obvious, the existing catalytic auxiliary agent suitable for the complete regeneration device has undesirable application effect on the incomplete regeneration device. The auxiliary composition for incomplete regeneration disclosed in the above technology can catalyze and convert NH in flue gas to some extent3Nitride in reduced state, but for NH in flue gas3The catalytic conversion activity of the nitride in reduced state is still to be improved to slow down NH3And the influence of deposited salt on the operation of equipment is avoided, so that the development and improvement of the activity of the flue gas pollutant emission reduction auxiliary agent of an incomplete regeneration device are needed, and the emission of flue gas NOx is further reduced.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide a method for reducing the emission of NOx in incompletely regenerated flue gas in a catalytic cracking process, the method comprises the steps of pretreating a denitration auxiliary agent by utilizing high-temperature CO-containing flue gas generated by a catalytic cracking device, obviously improving the activation performance of the auxiliary agent, and quantitatively conveying the denitration auxiliary agent into a catalytic cracking regenerator through the pressure difference between an auxiliary agent tank and the regenerator and the opening and closing of an electromagnetic valve, so that the emission of NOx in discharged flue gas is reduced by 20-30%.
In order to achieve the technical purpose, the invention provides a method for reducing the emission of NOx in incompletely regenerated flue gas in a catalytic cracking process, which comprises the following steps: guiding the flue gas containing CO from the catalytic cracking regeneratorThe flue gas containing CO enters a denitration auxiliary agent tank, the denitration auxiliary agent in the denitration auxiliary agent tank is subjected to activation pretreatment by the flue gas containing CO, the denitration auxiliary agent subjected to activation pretreatment is quantitatively pressed into a catalytic cracking regenerator through the pressure difference between the auxiliary agent tank and the regenerator and the opening and closing of an electromagnetic valve, and the denitration auxiliary agent is used for catalytic conversion of the flue gas containing NH in the catalyst regeneration process3The internal reduction state nitride is used for reducing the content of NOx in the discharged flue gas;
the denitration auxiliary agent consists of an inorganic oxide carrier and Fe and Co loaded on the inorganic oxide carrier, wherein the inorganic oxide carrier accounts for 60-95 wt% of the denitration auxiliary agent, and the Fe and Co account for 5-40 wt% of the denitration auxiliary agent. Preferably, the inorganic oxide carrier accounts for 75-92% by weight based on the total amount of the denitration auxiliary agent, and the weight percentage of Fe and Co calculated by oxide accounts for 8-25%. More preferably, the inorganic oxide carrier accounts for 84-99 wt% of the total amount of the denitration auxiliary agent, and the weight percentage of Fe and Co calculated by oxide accounts for 10-16 wt%.
In the present invention, unless otherwise specified, Fe in terms of oxide means Fe in terms of Fe2O3In terms of Co in oxide, Co means Co in Co2O3And (6) counting.
The metal elements in the auxiliary agent adopted by the invention mostly exist in an oxidation state, and are added into a catalyst bed layer of a regenerator after being treated by high-temperature CO-containing flue gas, compared with the flue gas which is not treated by high-temperature CO-containing flue gas, the reduction of the content of NOx in the discharged flue gas is obvious, and the improvement of the activity of the auxiliary agent is related to the conversion of an oxide into a carbide and the reduction state of an active component under the high-temperature reductive CO atmosphere. According to the invention, the denitration auxiliary agent is pretreated by using the high-temperature flue gas containing CO generated by the catalytic cracking device, so that the heat of the high-temperature flue gas can be recovered, the CO content in the discharged flue gas can be reduced, the activation performance of the auxiliary agent can be obviously improved, and the NOx content in the discharged flue gas can be reduced.
Preferably, the flue gas containing CO of the catalytic cracking unit comprises 4-8% by volume of CO and 13-18% by volume of CO20.15 to 0.18% by volumePercentage of O2(ii) a The temperature of the flue gas is 670-680 ℃. The pressure is 0.14 to 0.16 MPa.
Preferably, the activation pretreatment means that the flue gas containing CO is introduced from the top of the catalytic cracking regenerator to the bottom of the denitration auxiliary agent tank to be in countercurrent contact with the denitration auxiliary agent, and then the flue gas is discharged from a catalyst cyclone separator connected with the denitration auxiliary agent tank and then is recycled by a flue gas turbine.
Preferably, the pressure difference between the auxiliary agent tank and the regenerator is achieved by cutting off an introduction line of the flue gas containing CO, and then pressurizing the denitration auxiliary agent tank by using a non-purified air line provided at the top of the denitration auxiliary agent tank. After the activation pretreatment is finished, a lead-in pipeline of the flue gas containing CO is cut off, the electromagnetic valve is opened, and a non-purification air line matched with the top of the denitration auxiliary agent tank is communicated, so that the denitration auxiliary agent tank is pressurized, and the pressure difference between the auxiliary agent tank and the regenerator is caused.
Preferably, the addition amount of the denitration auxiliary agent accounts for 2-3 wt% of the total amount of the catalyst in the regenerator, and the denitration auxiliary agent is realized by repeatedly opening and closing an electromagnetic valve. For example, in the activation pretreatment, the electromagnetic valve is closed to stop adding the auxiliary agent; after the activation pretreatment is finished, opening the electromagnetic valve, quantitatively pressing the auxiliary agent into the catalytic cracking regenerator through the pressure difference between the auxiliary agent tank and the regenerator according to the addition amount required by the denitration auxiliary agent, and circulating in this way.
Preferably, the inorganic oxide support is selected from at least one of alumina, silica-alumina, zeolite, spinel, kaolin, diatomaceous earth, perlite and perovskite; more preferably, the inorganic oxide support is selected from at least one of alumina, spinel and perovskite; most preferably, the inorganic oxide support is alumina.
The alumina may be at least one selected from the group consisting of γ -alumina, δ -alumina, η -alumina, ρ -alumina, κ -alumina and χ -alumina, and the present invention is not particularly limited thereto.
The alumina may be derived from various sols or gels of aluminum, or aluminum hydroxide. The aluminum hydroxide may be selected from at least one of gibbsite, surge dam, nordstrandite, diaspore, boehmite, and pseudoboehmite. Preferably, the alumina source is selected from pseudoboehmite.
The inorganic oxide support may be commercially available or may be prepared by a conventional method.
In the present invention, the NH content of the composition can be increased by using Fe and Co as the metal elements3In order to further exhibit the synergistic effect of Fe and Co, the catalytic conversion activity of the reduced nitrides is preferably such that the weight ratio of Fe to Co, calculated as oxides, is 1: (0.1 to 10), and more preferably 1: (0.3 to 3), more preferably 1: (0.4-2). The inventor of the invention finds that Fe and Co in a specific ratio can generate better synergistic effect, and are more beneficial to improving the performance of the composition.
Preferably, Fe in the denitration auxiliary agent is at least partially in the form of iron carbide; the Co in the composition is at least partially present in the form of elemental cobalt.
The inventors have found that the Fe of the selected promoter is at least partially present in the form of iron carbide, preferably Fe3C and/or Fe7C3(ii) a However, the amount of iron carbide present is not particularly limited, and the ability to reduce NOx emissions can be effectively improved if some iron carbide is present. The Co in the selected promoter is at least partially present in the form of elemental cobalt, the amount of said elemental cobalt present being not particularly limited, as long as part of the elemental cobalt is present, which is effective in improving the performance of reducing NOx emissions. The existence of the iron carbide and/or the simple substance cobalt can enable the auxiliary agent to better promote the decomposition of the nitrogen-containing compound in the reduction state, reduce the generation of nitrogen oxides and promote the reduction of the nitrogen oxides to a certain extent.
The preparation method of the denitration additive comprises the steps of mixing and pulping a precursor of an inorganic oxide carrier, a precursor of Fe, a precursor of Co and water to obtain slurry, carrying out spray drying on the slurry, and then roasting;
the denitration catalyst comprises an inorganic oxide carrier and a denitration auxiliary agent, wherein the amount of the precursor of the inorganic oxide carrier, the amount of the precursor of Fe and the amount of the precursor of Co are such that the denitration auxiliary agent accounts for 60-95% by weight based on the total amount of the denitration auxiliary agent, and the weight percentage of Fe and Co is 5-40% by weight based on the oxide; preferably, the weight percentage of the inorganic oxide carrier is 75-92%, and the weight percentage of Fe and Co is 8-25% calculated by oxide; more preferably, the weight percentage of the inorganic oxide carrier is 84-99%, and the weight percentage of Fe and Co calculated by oxide is 10-16%.
The dosage of the Fe precursor and the Co precursor is such that in the prepared denitration auxiliary agent, the weight ratio of Fe to Co is 1: (0.1 to 10), preferably 1: (0.3 to 3), and more preferably 1: (0.4-2).
The precursor of Fe and the precursor of Co are respectively selected from water-soluble salts of Fe and Co, such as nitrate, chloride, chlorate or sulfate; the precursor of the inorganic oxide support includes various substances that can be obtained by subsequent calcination treatment to obtain the inorganic oxide support, and the present invention is not particularly limited thereto, and may be selected from various sols or gels of aluminum, or aluminum hydroxide; the aluminum hydroxide may be selected from at least one of gibbsite, surge dam, nordstrandite, diaspore, boehmite, and pseudoboehmite; most preferably, the precursor of the alumina is pseudoboehmite.
Preferably, the slurry has a solid content of 8 to 30 wt%.
According to the present invention, the method of mixing and beating the precursor of the inorganic oxide carrier, the precursor of Fe, the precursor of Co, and water is not particularly limited, and the method of mixing and beating the precursor of the inorganic oxide carrier, the precursor of Fe, the precursor of Co, and water is not particularly limited, as long as the three are mixed and then beaten to obtain a slurry.
Preferably, before mixing and beating, the precursor of the alumina is subjected to acidification peptization treatment, further preferably, the acid used in the acidification peptization treatment is hydrochloric acid, and the conditions of the acidification peptization treatment comprise: aluminum sulfate ratio of 0.12-0.22: 1, the time is 20-40 min. The acidification peptization treatment can be carried out according to the conventional technical means in the field, for example, the pseudoboehmite is added into water for pulping and dispersion, and then hydrochloric acid is added for acidification for 30min, and the acid-aluminum ratio is 0.18.
In the present invention, the aluminum acid ratio refers to a mass ratio of hydrochloric acid calculated as 36% by weight of concentrated hydrochloric acid to a precursor of alumina on a dry basis, unless otherwise specified. The spray drying may be carried out according to a conventional technique in the art, and the present invention is not particularly limited thereto, and preferably the spray drying conditions are such that the average particle size of the spray-dried particles is 60 to 75 μm and the particle size distribution range is mainly 20 to 100 μm, and more preferably the spray drying conditions are such that 50% or more of the particles having a particle size of 40 to 80 μm are contained in the spray-dried particles.
Preferably, the conditions of the calcination include: the temperature is 400-1000 ℃, preferably 450-650 ℃, and the time is 0.1-10 h, preferably 1-3 h.
Based on the above research, the inventor proposes that a newly-built denitration auxiliary agent tank and an automatic denitration auxiliary agent addition control system are used for introducing high-temperature flue gas containing CO in a regenerator of a catalytic cracking unit into the tank containing the auxiliary agent from the bottom of the denitration auxiliary agent tank nearby, the denitration auxiliary agent and the high-temperature flue gas are in countercurrent contact to carry out activation pretreatment on the denitration auxiliary agent, the auxiliary agent in the denitration auxiliary agent tank is subjected to activation pretreatment for a period of time by utilizing the characteristics of CO contained in catalytic regeneration flue gas and high temperature, so that the partial active component in the auxiliary agent is converted into carbide and a reduction state from oxide in the high-temperature reductive CO atmosphere, the residual flue gas is discharged from a tank top catalyst cyclone separator to be recovered by a flue gas turbine with lower pressure, a guide pipeline of the flue gas containing CO is cut off after the activation pretreatment is finished, a non-purification air line matched with the top of the denitration auxiliary agent tank is communicated, an electromagnetic valve is opened, according to the required addition amount of the auxiliary agent, the auxiliary agent is quantitatively pressed into the catalytic cracking regenerator through the pressure difference between the auxiliary agent tank and the regenerator and is used for catalytically converting NH in the flue gas in the catalyst regeneration process3Reducing the nitride in an equal reduction state so as to reduce the content of NOx in the discharged flue gas.
The invention has the advantages that:
the auxiliary agent is pretreated by high-temperature flue gas containing CO in a catalytic cracking device to improve the activity, a newly-built denitration auxiliary agent tank and an automatic denitration auxiliary agent addition control system can be used as a pretreatment device before industrial application of the denitration auxiliary agent, the flue gas can be introduced from the catalytic cracking device nearby, the investment is saved, the process is simple, the pre-activation performance is high, and the corresponding NOx emission is reduced by 20-30%; compared with the common method that the auxiliary agent is mixed into the catalytic cracking main catalyst and then added into the regenerator, the independent automatic control system for the addition amount of the denitration auxiliary agent can control the content of NOx in the discharged flue gas through the control of the addition amount according to the change of the catalytic feeding property and the operation condition and/or the change of the content of NOx in the discharged flue gas, and the control process is flexible.
Drawings
FIG. 1 is a schematic flow chart of the technical scheme of the invention.
Detailed Description
The present invention and its effects are further described below by examples.
Example 1
Preparation of a denitration auxiliary agent:
adding 2.62kg of pseudo-boehmite into 14.2kg of deionized water, pulping and dispersing, then adding 238mL of hydrochloric acid, acidifying for 15min to obtain aluminum-aluminum colloid, and adding ferric nitrate (calculated as Fe) calculated by metal oxide2O3Calculated as Co) 100g, cobalt nitrate (calculated as Co)2O3Calculated by the following steps) 100g of the denitration aid is added into 3500mL of water and stirred until the denitration aid is fully dissolved, the aluminum-aluminum colloid is added into the water and stirred for 20min to obtain slurry, the slurry is subjected to spray drying, 100g of particles obtained by spray drying (the average particle size is 65 μm, the particles with the particle size of 40-80 μm account for 60%, the same is applied below) are treated for 1.5h at 600 ℃ in an air atmosphere, and the denitration aid is obtained.
As shown in figure 1, high-temperature flue gas with the temperature of 670 ℃, the pressure of 0.158MPa (gauge pressure) and the CO volume percentage content of about 5.6 percent is introduced from a regenerator of a catalytic device to the bottom of a denitration auxiliary agent tank to enter the tank, the high-temperature flue gas and the denitration auxiliary agent are in countercurrent contact in the tank and then are discharged to the low-pressure end of an outlet of a flue gas turbine through a tank top catalyst cyclone separator, the top of the denitration auxiliary agent tank is provided with a non-purified air line, non-purified air with the pressure of 0.45MPa (gauge pressure) is used for pressurizing the denitration auxiliary agent tank, and the pressure is automatically controlled by openingThe denitration auxiliary agent is added into a regeneration system of a catalytic cracking device quantitatively and uniformly, so that the denitration auxiliary agent amount reaches 2 wt% of the total amount of the catalyst in the regenerator, the NOx content in the discharged flue gas is detected, and the result is about 114mg/m3。
Comparative example 1
The flow and the device for adding the denitration auxiliary agent are the same as those in the example 1, under the condition that the reaction and regeneration operation conditions of the catalytic cracking device and the properties and the treatment capacity of the processing raw materials are the same as those in the example 1, the high-temperature flue gas pretreatment with the CO volume percentage content of 5.6 percent, the temperature of 670 ℃ and the pressure of 0.158MPa (gauge pressure) is not introduced, the content of NOx in the discharged flue gas is detected, and the result is about 150mg/m3。
Compared with the example 1, the denitration auxiliary agent is not pretreated by high-temperature CO-containing flue gas, the denitration effect is poorer than that of the denitration auxiliary agent after pretreatment, and the content of NOx in discharged flue gas is increased by about 24%.
Example 2
Preparation of a denitration auxiliary agent:
adding 2.34kg of pseudo-boehmite into 12.7kg of deionized water, pulping and dispersing, then adding 212mL of hydrochloric acid, acidifying for 15min to obtain an aluminum-stone colloid, adding 100g of ferric nitrate and 200g of cobalt nitrate in terms of metal oxide into 4000mL of water, stirring until the ferric nitrate and the cobalt nitrate are fully dissolved, adding the aluminum-stone colloid into the water, stirring for 20min to obtain slurry, performing spray drying on the slurry, and treating 100g of particles obtained by spray drying at 650 ℃ for 1h in an air atmosphere to obtain the denitration aid.
Introducing high-temperature flue gas with the temperature of 680 ℃, the pressure of 0.154MPa (gauge pressure) and the CO volume percentage content of about 7.2% from a regenerator of a catalytic device to the bottom of a denitration auxiliary agent tank to enter the tank, after the high-temperature flue gas and the denitration auxiliary agent are in countercurrent contact in the tank, removing the low-pressure end of an outlet of a flue gas turbine through a top catalyst cyclone separator, wherein the top of the denitration auxiliary agent tank is provided with a non-purified air line, pressurizing the denitration auxiliary agent tank by using 0.45MPa (gauge pressure) non-purified air, automatically controlling the opening and closing of an electromagnetic valve, and pressurizing the pretreated denitration auxiliary agent to a regeneration system of a catalytic cracking device to realize the quantitative and uniform addition of the denitration auxiliary agent, so that the denitration auxiliary agent amount reaches 2 wt% of the total amount of the catalyst in the regeneratorThe fruit is about 105mg/m3。
Comparative example 2
The flow and the device for adding the denitration auxiliary agent are the same as those in example 2, under the condition that the reaction and regeneration operation conditions of the catalytic cracking device and the properties and the treatment capacity of the processing raw materials are the same as those in example 2, the high-temperature flue gas pretreatment with the CO volume percentage content of 7.2%, the temperature of 680 ℃ and the pressure of 0.154MPa (gauge pressure) is not introduced, the NOx content in the discharged flue gas is detected, and the result is about 150mg/m3。
Compared with the example 2, the denitration auxiliary agent is not pretreated by high-temperature CO-containing flue gas, the denitration effect is poorer than that of the denitration auxiliary agent after pretreatment, and the content of NOx in discharged flue gas is increased by about 30%.
Example 3
Preparation of a denitration auxiliary agent:
adding 2.62kg of pseudo-boehmite into 14.2kg of deionized water, pulping and dispersing, then adding 238mL of hydrochloric acid, acidifying for 15min to obtain an aluminum-stone colloid, adding 50g of ferric nitrate and 150g of cobalt nitrate in terms of metal oxide into 3500mL of water, stirring until the ferric nitrate and the cobalt nitrate are fully dissolved, adding the aluminum-stone colloid into the water, stirring for 20min to obtain slurry, performing spray drying on the slurry, and treating 100g of particles obtained by spray drying at 600 ℃ for 1.5h in an air atmosphere to obtain the denitration aid.
Introducing high-temperature flue gas with the temperature of 672 ℃, the pressure of 0.148MPa (gauge pressure) and the CO volume percentage content of about 6.4% from a regenerator of a catalytic device to the bottom of a denitration auxiliary agent tank to enter the tank, after the high-temperature flue gas and the denitration auxiliary agent are in countercurrent contact in the tank, removing the low-pressure end of an outlet of a flue gas turbine through a top catalyst cyclone separator, wherein the top of the denitration auxiliary agent tank is provided with a non-purified air line, pressurizing the denitration auxiliary agent tank by using 0.45MPa (gauge pressure) non-purified air, automatically controlling the opening and closing of an electromagnetic valve, and pressurizing the pretreated denitration auxiliary agent to a regeneration system of a catalytic cracking device to realize the quantitative and uniform addition of the denitration auxiliary agent, so that the denitration auxiliary agent amount reaches 2.4 wt% of the total amount of the catalyst in the regenerator, detecting the NOx content3。
Comparative example 3
The procedure and apparatus for adding denitration aid were the same as those in example 3, and the reaction and regeneration operation were carried out in a catalytic cracking apparatusUnder the same conditions as those of example 3, the properties and the treatment amounts of the processing raw materials were the same, and the content of NOx in the discharged flue gas was measured without introducing high-temperature flue gas pretreatment in which the volume percentage content of CO was 6.4%, the temperature was 672 ℃, and the pressure was 0.148MPa (gauge pressure), and the result was about 150mg/m3。
Compared with the example 2, the denitration auxiliary agent is not pretreated by high-temperature CO-containing flue gas, the denitration effect is poorer than that of the denitration auxiliary agent after pretreatment, and the content of NOx in discharged flue gas is increased by about 20%.
Example 4
Preparation of a denitration auxiliary agent:
adding 2.62kg of pseudo-boehmite into 14.2kg of deionized water, pulping and dispersing, then adding 238mL of hydrochloric acid, acidifying for 15min to obtain an aluminum-stone colloid, adding 150g of ferric nitrate and 50g of cobalt nitrate in terms of metal oxide into 3500mL of water, stirring until the ferric nitrate and the cobalt nitrate are fully dissolved, adding the aluminum-stone colloid into the water, stirring for 20min to obtain slurry, performing spray drying on the slurry, and treating 100g of particles obtained by spray drying at 600 ℃ for 1.5h in an air atmosphere to obtain the denitration aid.
Introducing high-temperature flue gas with the temperature of 672 ℃, the pressure of 0.154MPa (gauge pressure) and the CO volume percentage content of about 6.8 percent from a regenerator of a catalytic device to the bottom of a denitration auxiliary agent tank to enter the tank, after the high-temperature flue gas and the denitration auxiliary agent are in countercurrent contact in the tank, removing the low-pressure end of an outlet of a flue gas turbine through a top catalyst cyclone separator, wherein the top of the denitration auxiliary agent tank is provided with a non-purified air line, pressurizing the denitration auxiliary agent tank by using 0.45MPa (gauge pressure) non-purified air, automatically controlling the opening and closing of an electromagnetic valve, and pressurizing the pretreated denitration auxiliary agent to a regeneration system of a catalytic cracking device to realize the quantitative and uniform addition of the denitration auxiliary agent, so that the denitration auxiliary agent amount reaches 2.5 wt% of the total amount of the catalyst in the regenerator, detecting the NOx content3。
Comparative example 4
The flow and the device for adding the denitration auxiliary agent are the same as those in example 4, under the condition that the reaction and regeneration operation conditions of the catalytic cracking unit and the properties and the treatment capacity of the processing raw materials are the same as those in example 4, the high-temperature flue gas pretreatment with the CO volume percentage content of 6.8 percent, the temperature of 672 ℃ and the pressure of 0.154MPa (gauge pressure) is not introduced, and the discharged flue gas is detectedNOx content, results about 150mg/m3. Compared with the example 4, the denitration auxiliary agent is not pretreated by high-temperature CO-containing flue gas, the denitration effect is poorer than that of the denitration auxiliary agent after pretreatment, and the content of NOx in discharged flue gas is increased by about 18%.
Claims (10)
1. A method for reducing the NOx emission in incompletely regenerated flue gas in a catalytic cracking process is characterized by comprising the following steps: introducing CO-containing flue gas from a catalytic cracking regenerator into a denitration auxiliary agent tank, carrying out activation pretreatment on the denitration auxiliary agent in the denitration auxiliary agent tank by the CO-containing flue gas, quantitatively pressing the activated and pretreated denitration auxiliary agent into the catalytic cracking regenerator through the pressure difference between the auxiliary agent tank and the regenerator and the opening and closing of an electromagnetic valve, and using the activated and pretreated denitration auxiliary agent in catalytic conversion flue gas containing NH in the catalyst regeneration process3The internal reduction state nitride is used for reducing the content of NOx in the discharged flue gas;
the denitration auxiliary agent consists of an inorganic oxide carrier and Fe and Co loaded on the inorganic oxide carrier, wherein the inorganic oxide carrier accounts for 60-95 wt% of the denitration auxiliary agent, and the Fe and Co account for 5-40 wt% of the denitration auxiliary agent.
2. The method of claim 1 for reducing NOx emissions from incompletely regenerated flue gas in a catalytic cracking process, wherein: the flue gas containing CO of the catalytic cracking unit comprises 4-8% of CO by volume percentage and 13-18% of CO by volume percentage20.15 to 0.18% by volume of O2(ii) a The temperature of the flue gas is 670-680 ℃.
3. The method of claim 1 for reducing NOx emissions from incompletely regenerated flue gas in a catalytic cracking process, wherein: the flue gas containing CO is introduced from the top of the catalytic cracking regenerator to the bottom of the denitration auxiliary agent tank to be in countercurrent contact with the denitration auxiliary agent, and is discharged by a catalyst cyclone separator connected with the denitration auxiliary agent tank and then is recycled by a flue gas turbine.
4. The method of claim 1 for reducing NOx emissions from incompletely regenerated flue gas in a catalytic cracking process, wherein: the pressure difference between the auxiliary agent tank and the regenerator is realized by cutting off a leading-in pipeline of the flue gas containing CO and then pressurizing the denitration auxiliary agent tank by using a non-purified air line matched with the denitration auxiliary agent tank.
5. The method of claim 1 for reducing NOx emissions from incompletely regenerated flue gas in a catalytic cracking process, wherein: the addition amount of the denitration auxiliary agent accounts for 2-3 wt% of the total amount of the catalyst in the regenerator, and the denitration auxiliary agent is realized by repeatedly opening and closing an electromagnetic valve.
6. The method for reducing the amount of NOx emissions in incompletely regenerated flue gas from a catalytic cracking process according to claim 5, wherein: the repeated opening and closing of the electromagnetic valve means that the electromagnetic valve is closed to stop adding the denitration auxiliary agent in the activation pretreatment process; after the activation pretreatment is finished, the electromagnetic valve is opened, and the denitration auxiliary agent is quantitatively conveyed into the catalytic cracking regenerator through the pressure difference between the auxiliary agent tank and the regenerator according to the required addition amount of the denitration auxiliary agent.
7. A method of reducing NOx emissions from incompletely regenerated flue gas in a catalytic cracking process according to any one of claims 1 to 6, wherein: the inorganic oxide carrier is selected from at least one of alumina, silica-alumina, zeolite, spinel, kaolin, diatomaceous earth, perlite and perovskite.
8. A method of reducing NOx emissions from incompletely regenerated flue gas in a catalytic cracking process according to any one of claims 1 to 7, wherein: based on the total amount of the denitration auxiliary agent, the weight percentage of the inorganic oxide carrier is 75-92%, and the weight percentage of Fe and Co is 8-25% calculated by oxide;
preferably, the inorganic oxide support is present in an amount of 84 to 90 wt%, and the total amount of Fe and Co, calculated as oxides, is 10 to 16 wt%.
9. A method of reducing NOx emissions from incompletely regenerated flue gas in a catalytic cracking process according to any one of claims 1 to 8, wherein: the weight ratio of Fe to Co calculated by oxide is 1: (0.1 to 10); preferably 1: (0.3-3); more preferably 1: (0.4-2).
10. A method of reducing NOx emissions from incompletely regenerated flue gas in a catalytic cracking process according to any one of claims 1 to 9, wherein: at least part of Fe in the denitration auxiliary agent exists in the form of iron carbide; at least part of Co in the denitration auxiliary agent exists in the form of simple substance cobalt.
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