A process for improving conversion gas efficiency in a sodium and sodium production device

Abstract

The present invention discloses a process for improving the efficiency of conversion gas in two sodium production devices, characterized in that it includes: the conversion gas in the two sodium production devices goes to the acid-making process in one way, and goes to the alkali absorption process in the other way; the alkali absorption process includes at least two processes, the first process performs pretreatment reaction absorption on the NO gas, the second process mixes the unreacted mixed gas of NO in the first process, the tail gas discharged in the acid-making process and the neutralization tower tail gas for reaction absorption, and after the alkali solution absorption reaches a specified concentration, it is discharged to the sodium nitrate evaporation process; in the sodium nitrate evaporation process, most of the sodium nitrate is precipitated from the solution through evaporation crystallization, and the crystal mother liquor is pumped into the conversion process, and the conversion process is respectively linked with the second process of the acid-making process and the alkali absorption process. The present invention can not only reduce the final tail gas nitrogen oxide content, so that it meets the emission standards, but also increase the sodium nitrate output and obtain a higher yield.

Description

Technical Field

[0001] The invention belongs to the technical field of sodium nitrate production devices, and in particular relates to a process for improving conversion gas efficiency in sodium nitrate production devices. Background Art

[0002] In the production process of sodium nitrate, the conversion process is to react the sodium nitrite mother liquor (containing sodium nitrate, sodium nitrite and water) after the evaporation of the two-sodium neutralization liquid with dilute nitric acid in a conversion tower, mainly to produce sodium nitrate solution and conversion gas, that is, a nitrogen oxide gas mainly composed of NO. Then the sodium nitrate solution is sent to the nitrate section for evaporation, crystallization, centrifugation, drying and other operations to produce sodium nitrate products. After purification, the conversion gas is added to the alkali absorption system and continues to react with soda ash to prepare a qualified neutralization solution in preparation for the production of sodium nitrite. The unreacted conversion gas in the alkali absorption process enters the exhaust gas treatment system for treatment.

[0003] In this process, since the conversion gas is mainly sodium nitrite reacting with nitric acid, NO gas is mainly generated. The reaction formula is as follows:

[0004] 3NaNO2+2HNO3=3NaNO3+H2O+2NO↑

[0005] A small amount of side effects may also occur:

[0006] 2HNO2+NO=3NO2↑+H2O

[0007] At present, in the production process of sodium and sodium, the impurities such as nitric acid mist, droplets and fine foam of nitrate solution brought out by the conversion gas when it leaves the conversion tower pass through the gas-liquid separator system and then enter the alkali absorption process. However, in the alkali absorption process, since sodium carbonate and NO cannot react directly, the conversion rate of NO gas in the conversion gas is reduced; in addition, since the NO content in the conversion gas is relatively small, due to the balance limitation of the absorption process, it is difficult for simple alkali absorption to absorb NO to meet the standard, resulting in an increase in the load of the ammonia reduction process in the subsequent tail gas treatment process, resulting in an increase in ammonia consumption. In addition, it may also cause the tail gas to fail to meet the emission standards, which is not only very unfavorable to production, but also causes environmental pollution. Therefore, the effective treatment and utilization of the conversion gas has become a difficult problem to be solved urgently in the production of nitrate. Summary of the invention

[0008] The purpose of the present invention is to provide a process for improving the conversion gas efficiency in a sodium production device, and to effectively utilize the conversion gas generated by the device. The conversion gas can have three options. The first option is similar to the existing device and can be sent to an alkali absorption system, which has a general effect on the absorption of nitrogen oxides. The second option is that all the conversion gas can be sent to an acid production process to produce nitric acid to increase the output of nitric acid. The third option is that according to the actual operating conditions of the device, a part of the conversion gas can be used to assist in the joint production of nitric acid, and a part of the conversion gas can be used to accurately distribute gas to each tower in the alkali absorption process, thereby reducing the nitrogen oxide content of the tail gas absorbed by the alkali tower, making it easier to meet the emission standards. After the conversion gas treatment process, the NO utilization rate in the final conversion gas reaches more than 99.9%, effectively reducing the ammonia reduction tail gas treatment load, and even directly meeting the emission standards.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A process for improving the conversion gas efficiency in a sodium and sodium production device, characterized in that it comprises:

[0011] In the two sodium production units, the conversion gas goes to the acid production process in one way and to the alkali absorption process in the other way;

[0012] The alkali absorption process includes at least two processes, the first process performs pre-treatment reaction absorption on the NO gas, and the second process mixes and reacts and absorbs the unreacted mixed gas of NO in the first process, the tail gas discharged from the acid making process, and the tail gas from the neutralization tower, and after the alkali solution absorption reaches a specified concentration, it is discharged to the sodium sulfate evaporation process;

[0013] In the sodium nitrite evaporation process, most of the sodium nitrite is precipitated from the solution through evaporation and crystallization, and the crystallization mother liquor is pumped into the conversion process, and the conversion process is then linked with the second process of the acid production process and the alkali absorption process respectively.

[0014] In a preferred embodiment of the present invention, the conversion gas in the two-sodium production device is compressed air and mixed with gaseous ammonia, which then enters the ammonia oxidation process to generate a mixed gas mainly containing NO, N2, O2, CO2 and H2O.

[0015] In a preferred embodiment of the present invention, the nitrogen oxide content of the tail gas after multiple rounds of alkali absorption process, acid production process, sodium sulfite evaporation crystallization process, and conversion process is reduced to 100 mg / m 3 The following can be discharged.

[0016] In a preferred embodiment of the present invention, the acid production process mainly involves oxidizing a mixed gas containing NO to generate NO2, which is then absorbed by water to produce dilute nitric acid.

[0017] In a preferred embodiment of the present invention, the concentration of the dilute nitric acid is controlled by controlling the NO oxidation temperature and oxidation time. The lower the oxidation temperature and the longer the oxidation time, the higher the nitric acid concentration.

[0018] In a preferred embodiment of the present invention, the conversion process includes a conversion tower, and the conversion tower includes an absorption section and a conversion section. The conversion gas produced by the conversion tower is extracted from the top of the tower and the middle of the tower in two ways, one part returns to the acid production process, and the other part goes to the alkali absorption process.

[0019] In a preferred embodiment of the present invention, the operating pressure of the conversion tower is controlled at 150-300 kPa, the tower top temperature is 30-45°C, and the tower bottom temperature is 65-100°C.

[0020] In a preferred embodiment of the present invention, the conversion gas extracted from the middle of the conversion tower is mixed with a certain ratio of air and then enters each level of alkali absorption tower. The temperature after mixing is controlled at 45-70°C. The ratio of air and conversion gas is adjusted according to the molar ratio of O2:NO. After adjustment, the molar ratio of O2:NO is in the range of 0.5-5.

[0021] Specifically, the conversion gas extracted from the top of the conversion tower is pressurized by a booster and mixed with the mixed gas produced in the ammonia oxidation process, and the temperature is controlled at 30-70°C before entering the acid making process; the conversion gas extracted from the middle of the conversion tower is cooled and then enters a separator for gas-liquid separation. After the gas phase is pressurized, it is mixed with air and enters each level of alkali absorption tower for absorption.

[0022] In a preferred embodiment of the present invention, the alkali solution in the alkali absorption step is a Na2CO3 aqueous solution with a mass percentage concentration of 10-45%.

[0023] In a preferred embodiment of the present invention, the first step of the alkali absorption step includes at least 4 alkali absorption towers, and the second step includes at least 4 alkali absorption towers.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The two routes of conversion gas are respectively supplied to the acid-making process and the alkali absorption process. Through reasonable distribution and precise air matching, not only the nitrogen oxide content of the final tail gas can be reduced, but also the output of sodium nitrate can be increased to obtain a higher yield; the above-mentioned processes are reacted and nested in sequence, and the products or tail gas of the reaction process are also linked to each other, so that through reasonable distribution and precise air matching, not only the nitrogen oxide content of the final tail gas can be reduced to meet the emission standards, but also the output of sodium nitrate can be increased to obtain a higher yield.

[0026] 2. The present invention can be used for the transformation of existing sodium-sodium devices or for the construction of new devices. For the transformation of old devices, it can effectively reduce the final tail gas treatment process, such as the ammonia reduction treatment load, and reduce energy consumption; for new devices, it can directly meet the emission standards, reduce the tail gas treatment process, reduce equipment costs and operating costs, and ultimately achieve energy conservation and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of the present invention.

[0028] In the figure: 1 is an ammonia oxidation gas cooler;

[0029] 2 is a mixed gas cooler;

[0030] 3 is an acid-making tail gas absorption tower;

[0031] 4 is a circulating pump for the tail gas absorption tower;

[0032] 5 is a tail gas absorption tower cooler;

[0033] 6, 7, 8, 9, 18, 19, 20, and 21 are alkali absorption towers;

[0034] 10, 11, 12, 13, 22, 23, 24, 25 are circulation pumps for the alkali absorption tower;

[0035] 14, 15, 16, 17, 26, 27, 28 and 29 are circulating liquid heat exchangers of the alkali absorption tower;

[0036] 30 is a conversion tower;

[0037] 31 is a reformed gas cooler;

[0038] 32 is a separator;

[0039] 33 and 34 are superchargers;

[0040] 35 is an air compressor;

[0041] 36 is an air heat exchanger;

[0042] 37, 38, 39 and 40 are mixers. DETAILED DESCRIPTION

[0043] 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.

[0044] Reference Figure 1As shown, a process for improving the conversion gas efficiency in a sodium production device is characterized in that it includes: the conversion gas in the sodium production device goes to an acid-making process in one way and to an alkali absorption process in the other way; the alkali absorption process includes at least two processes, the first process performs pretreatment reaction absorption on the NO gas, the second process mixes the unreacted mixed gas of NO in the first process, the tail gas discharged in the acid-making process and the tail gas of the neutralization tower for reaction absorption, and after the alkali solution absorption reaches a specified concentration, it is discharged to the sodium nitrite evaporation process; in the sodium nitrite evaporation process, most of the sodium nitrite is precipitated from the solution through evaporation and crystallization, and the crystallization mother liquor is pumped into the conversion process, and the conversion process is then linked with the second processes of the acid-making process and the alkali absorption process respectively.

[0045] The above-mentioned processes are carried out in sequence and nested, and the products or exhaust gases of the reaction process are also linked to each other, so that through reasonable distribution and precise air matching, not only can the nitrogen oxide content of the final exhaust gas be reduced to meet the emission standards, but also the sodium nitrate production can be increased to obtain a higher yield.

[0046] Specifically, a process for improving the conversion gas efficiency in a sodium production device is described in detail, including an acid production process, an alkali absorption process, a sodium nitrate evaporation and crystallization process, a conversion process, and a sodium nitrate evaporation process, wherein the conversion process is mainly composed of a conversion tower.

[0047] The high-temperature NO gas generated from the ammonia oxidation process is heat exchanged in the heat exchanger and then goes to the acid production process and the alkali absorption process respectively. The proportion of NO gas entering the two processes is adjusted according to the nitric acid production and nitrate salt production targets.

[0048] In the acid production process, NO is oxidized with air to NO2, which is then absorbed by water to generate 30-50% dilute nitric acid. The concentration of the nitric acid is controlled by controlling the NO oxidation temperature and oxidation time. The lower the oxidation temperature and the longer the oxidation time, the higher the nitric acid concentration.

[0049] In the alkali absorption process, NO can react with oxygen to generate NO2 or N2O3 before reacting with Na2CO3 aqueous solution to generate two-sodium neutralization liquid of sodium nitrite and sodium nitrate solution; the two-sodium neutralization liquid is subjected to an evaporation and crystallization process to obtain a sodium nitrite mother liquor, which enters a conversion tower and is mixed with dilute nitric acid generated in the previous acid production process to convert the sodium nitrite in the mother liquor into sodium nitrate, and at the same time generate a conversion gas mainly containing NO gas.

[0050] The sodium nitrate solution at the bottom of the conversion tower enters the neutralization tower, where it is mixed with an alkali solution that is slightly in excess of the nitric acid content, and reacted with excess air (Na2CO3:HNO3 molar ratio is 1.3-1.0; air:HNO3 molar ratio is 50-80) to neutralize the nitric acid and sodium carbonate in the solution. In this process, the role of the air is to fully mix the solution and further oxidize the generated nitrogen oxides, so that tail gas containing nitrogen oxides will be generated at the top of the neutralizer. This part of the tail gas returns to the alkali absorption process for treatment. The generated conversion gas can be divided into two parts according to the actual production situation. One part is extracted from the conversion gas at the top of the conversion tower and mixed with the NO generated in the ammonia oxidation section. It is sent to the acid production section through the NOx fast cooler. After the nitric acid is produced, the tail gas that has not been absorbed from the top of the nitric acid tower enters the tail gas absorption tower;

[0051] The other part is extracted from the middle of the conversion tower, cooled, and accurately mixed with appropriate air by a booster compressor so that most of the NO reacts with the air to form NO2. It is then sent to the alkali towers in the alkali absorption process to react with sodium carbonate to form a two-sodium neutralization solution of sodium nitrite and sodium nitrate.

[0052] The two sodium neutralization liquids enter the sodium nitrate evaporation crystallization process, and the produced crystallization mother liquor is sent to the conversion tower. The conversion liquid goes to the neutralizer from the bottom of the conversion tower. In the neutralizer, the conversion liquid is neutralized with alkaline solution and a certain amount of air is added to promote neutralization. The tail gas from the upper part of the neutralizer is sent to the alkali absorption process for treatment, and the solution produced at the bottom of the neutralization tower is sent to the sodium nitrate evaporation crystallization process.

[0053] See the attached for the specific process flow Figure 1 :

[0054] After the air passes through the air filter, the compressed air is mixed with gaseous ammonia and enters the ammonia oxidation process to generate a mixed gas mainly containing NO, N2, O2, CO2 and H2O.

[0055] After passing through the cooler 1, the mixed gas is divided into two paths. One part is pressurized with the conversion gas from the top of the subsequent conversion tower 30 by the supercharger 34, mixed by the mixer 40, and then adjusted by the heat exchanger 2 to a temperature below 35°C before entering the acid making process.

[0056] The acid-making process mainly involves the oxidation of a mixed gas containing NO to generate NO2, which is then absorbed by water to produce dilute nitric acid with a concentration of 45-50%. After the nitric acid is produced, the acid-making process will produce acid-making tail gas, which mainly contains unconverted NO (mass fraction <5%), and the remaining is a large amount of N2 gas, a small amount of O2 and CO2 gas. The acid-making tail gas enters the tail gas absorption tower 3, and after the sodium carbonate solution is forced to circulate by the pump 4 and the temperature is adjusted by the heat exchanger 5, it is sprayed above the tower 3 for further absorption, and is discharged from the top of the tail gas absorption tower 3 to the alkali absorption process for further treatment. The alkali absorption process generally consists of 4-8 alkali absorption towers. The dilute nitric acid produced in the acid-making process enters the conversion tower 30, reacts with the sodium nitrite crystal mother liquor, and converts the sodium nitrite in the mother liquor into sodium nitrate.

[0057] The other part of the mixed gas after ammonia oxidation directly enters the alkali absorption process for reaction absorption. The mixed gas enters the bottom of absorption towers 6, 7, 8, and 9 in turn, and is forced to circulate sodium carbonate solution by pumps 10, 11, 12, and 13 respectively. The temperature is adjusted to less than 75°C by heat exchangers 14, 15, 16, and 17. After spray absorption at the top of each tower, sodium nitrate and sodium nitrite products are generated, and the unreacted mixed gas and the absorption reaction product CO2 are discharged from the top of tower 17.

[0058] After the gas from the top of tower 17 is mixed with the tail gas discharged from the top of tail gas absorption tower 3 and the tail gas from the neutralizer, the main components are still unreacted NO gas, a small amount of unabsorbed NO2 produced by alkali absorption, a large amount of N2, and a small amount of O2 and CO2. The mixed gas continues to enter the bottom of the absorption towers 18, 19, 20, and 21 of the alkali absorption process in turn, and the sodium carbonate solution is forced to circulate by pumps 22, 23, 24, and 25 respectively. After the temperature is adjusted to less than 75°C by heat exchangers 26, 27, 28, and 29, sodium nitrate and sodium nitrite products are generated after spray absorption at the top of each tower. The unreacted mixed gas and the absorption reaction product CO2 are discharged from the top of tower 29. After the alkali solution absorption of each tower in the alkali absorption section reaches the specified concentration, it is discharged from the bottom of the tower to the sodium nitrite evaporation process.

[0059] In the sodium nitrate evaporation process, most of the sodium nitrate is precipitated from the solution through evaporation and crystallization, and the crystallization mother liquor is pumped into the middle of the conversion tower 30. A conversion section is set in the lower part of the conversion tower 30, and an absorption section is set in the upper part. The crystallization mother liquor reacts with dilute nitric acid in the conversion section of the lower part of the tower 30 to generate sodium nitrate. The gas after the reaction is further absorbed by the sprayed dilute nitric acid in the absorption section of the upper part of the conversion tower 30. After the gas is pressurized by the supercharger 34 and mixed with part of the mixed gas from the ammonia oxidation process through the mixer 40, it is adjusted to a temperature of less than 35°C by the heat exchanger 2, and enters the acid production process to recover nitrogen oxides such as NO and NO2 in the tail gas of the conversion tower. The sodium nitrate solution at the bottom of the conversion tower enters the neutralizer, and an appropriate amount of alkali solution is added to the neutralizer to neutralize the excess nitric acid in the sodium nitrate solution, and appropriate air is added to make the reaction complete. The tail gas of the neutralizer returns to the alkali absorption process alkali absorption tower 18 for nitrogen oxide reabsorption.

[0060] Since nitric acid and sodium nitrite react to generate NO gas in the conversion section of the conversion tower, part of the conversion gas is extracted from the side line in the middle of the conversion tower. The gas extracted from the side line is cooled by the heat exchanger 31 and enters the separator 32 for vapor-liquid separation. The liquid phase returns to the conversion tower, and the gas phase is pressurized by the supercharger 33 and then enters the mixers 37, 38, and 39. At the same time, after the air is pressurized by the supercharger 36, the temperature is adjusted by the heat exchanger and then the air is divided into the corresponding mixers 37, 38, and 39 to mix with the conversion gas from the supercharger 33. In the mixers 37, 38, and 39, the NO in the conversion gas reacts with the O2 in the air, so that most of the NO is converted into NO2, and then enters the corresponding alkali absorption towers 19, 20, and 21 for re-reaction absorption. After multi-stage absorption in the alkali absorption process, the gas is finally discharged from the top of the last alkali tower in compliance with the standards.

[0061] Embodiment 1:

[0062] Combination Figure 1 , taking a 100,000 tons / year sodium nitrate and sodium nitrite production device as an example, the implementation mode of the present invention is explained.

[0063] In this embodiment, after the air passes through the air filter, the compressed air is mixed with gaseous ammonia and enters the ammonia oxidation process to generate a mixed gas mainly containing NO, N2, O2, CO2 and H2O, totaling 51635 kg / h, with a composition of 6.528% O2, 71.1% N2, 11.361% H2O, 10.966% NO and 0.045% CO2.

[0064] After the mixed gas passes through the cooler 1, it is divided into two paths. A part of the mass flow rate of 3900kg / h is pressurized by the supercharger 34 with the conversion gas from the top of the subsequent conversion tower 30, mixed by the mixer 40, and then adjusted to 35°C by the heat exchanger 2 before entering the acid-making process. The acid-making process mainly generates NO2 by oxidizing the mixed gas containing NO, and produces dilute nitric acid with a concentration of 44.91% after being absorbed by water. After the nitric acid is produced, 6629kg / h of acid-making tail gas is generated by the nitric acid section, and the acid-making tail gas mainly contains unconverted NO (specifically composed of 5.881% O2, 87.151% N2, 2.887% H2O, 3.312% NO, 0.642% CO2, and 0.136% nitric acid). The acid production tail gas enters the tail gas absorption tower 3, and the sodium carbonate solution is forced to circulate by the pump 4 and the temperature is adjusted to 65°C by the heat exchanger 5. It is sprayed on the top of the tower 3 for further absorption, and discharged from the top of the tail gas absorption tower 3 to the alkali absorption process for further treatment. Its flow rate is 6875.3kg / h (specific composition is O2 is 5.184%, N2 is 85.434%, H2O is 6.356%, NO is 0.529%, CO2 is 2.488%, NO2 is 0.009%), and the alkali absorption process is generally composed of 4-8 alkali absorption towers. 5222.7kg / h of dilute nitric acid with a mass fraction of 44.91% produced in the acid production section enters the conversion tower 30, reacts with the sodium nitrite crystal mother liquor, and converts the sodium nitrite in the mother liquor into sodium nitrate.

[0065] Another part of the mixed gas after ammonia oxidation directly enters the alkali absorption process at a flow rate of 47735kg / h for reaction absorption. The mixed gas enters the bottom of absorption towers 6, 7, 8, and 9 in turn, and is forced to circulate sodium carbonate solution by pumps 10, 11, 12, and 13 respectively. The top temperature of the tower is controlled by heat exchangers 14, 15, 16, and 17 to be 85°C, 80°C, 75°C, and 70°C respectively. After spraying and absorbing at the top of each tower, sodium nitrate and sodium nitrite products are generated. In order to make NO, the unreacted mixed gas is discharged from the top of tower 17 together with the absorption reaction product CO2. The discharge flow rate is 47605kg / h, and its composition is 3.673% O2, 71.276% N2, 16.44% H2O, 1.796% NO, 0.132% NO2, and 6.681% CO2.

[0066] After the gas from the top of the alkali absorption tower 17, the tail gas discharged from the top of the tail gas absorption tower 3 and the tail gas from the neutralizer are mixed, the total flow rate is 56768kg / h, and its composition is 4.597% O2, 73.022% N2, 14.713% H2O, 1.584% NO, 5.96% CO2, and 0.114% NO2. The mixed gas continues to enter the bottom of the absorption towers 18, 19, 20, and 21 of the alkali absorption process in sequence, and the sodium carbonate solution is forced to circulate by pumps 22, 23, 24, and 25 respectively, and the temperature of each tower top is controlled in the range of 60-65°C through heat exchangers 26, 27, 28, and 29, wherein the gas phase feed of the absorption towers 19, 20, and 21 also contains part of the conversion gas from the conversion tower. After the feed mixed gas is sprayed and absorbed at the top of each tower, sodium nitrate and sodium nitrite products are generated. The unreacted mixed gas is discharged from the top of tower 29 together with the reaction product CO2 in the absorption process. The flow rate is 51964kg / h, and the composition is 4.65% O2, 80.327% N2, 7.06% H2O, 0.0005% NO, 7.91% CO2, and 0.0002% NO2.

[0067] After the alkali solution in each tower of the alkali absorption section reaches the specified concentration, it is discharged from the bottom of the tower to the sodium nitrate evaporation process. In the sodium nitrate evaporation process, most of the sodium nitrate is precipitated from the solution through evaporation and crystallization. The crystallization mother liquor is pumped into the middle of the conversion tower 30. The conversion section is set in the lower part of the conversion tower 30, and the absorption section is set in the upper part. The temperature at the top of the conversion tower is controlled at 35-40°C and the pressure is controlled at 220kPa. The crystallization mother liquor reacts with dilute nitric acid in the conversion section of the lower part of the tower 30 to generate sodium nitrate. After the gas after the reaction is further absorbed by the sprayed dilute nitric acid in the absorption section of the upper part of the conversion tower 30, its flow rate is 1105kg / h, and the composition is 13.7% of H2O, 65.23% of NO, 3.52% of CO2, and 17.46% of NO2. After being pressurized by the supercharger 34, it is mixed with part of the mixed gas from the ammonia oxidation process through the mixer 40, and then adjusted to 35°C by the heat exchanger 2. Then it enters the acid production process to recover nitrogen oxides such as NO and NO2 in the tail gas of the conversion tower. The sodium nitrate solution at the bottom of the conversion tower enters the neutralizer, where an appropriate amount of alkali solution is added to neutralize the excess nitric acid in the sodium nitrate solution, and appropriate air is added to make the reaction complete. The tail gas flow rate of the neutralizer is 2383.7kg / h, and the composition is 22.21% O2, 73.19% N2, 3.13% H2O, 0.23% NO, 1.19% CO2, and 0.05% NO2.

[0068] Since nitric acid and sodium nitrite react to generate NO gas in the conversion section of the conversion tower, part of the conversion gas is taken out from the side line in the middle of the conversion tower. After the gas taken out from the side line is cooled by the heat exchanger 31, it enters the separator 32 for gas-liquid separation, and the liquid phase returns to the conversion tower. The gas phase flow rate is 114.54 kg / h, and the composition is 1.19% H2O, 74.76% NO, 4.03% CO2, and 20.0% NO2. After being pressurized by the supercharger 33, it is divided into mixers 37, 38, and 39. At the same time, after the air is pressurized by the supercharger 36 at 383.56 kg / h, the temperature is adjusted to less than 60°C by the heat exchanger, and then it is divided into corresponding mixers 37, 38, and 39 to mix with the conversion gas from the supercharger 33. In the mixers 37, 38, and 39, the NO in the conversion gas reacts with the O2 in the air, so that most of the NO is converted into NO2, and then enters the corresponding alkali absorption towers 19, 20, and 21 for re-reaction and absorption. After multiple levels of absorption in the alkali absorption process, the gas is finally discharged from the top of the alkali absorption tower 29 in compliance with the standards, with a flow rate of 51964 kg / h and a composition of 4.65% O2, 80.327% N2, 7.06% H2O, 0.005% NO, 7.91% CO2, 0.0002% NO2, and a total content of nitrogen oxides NO and NO2 of 90.9 mg / m 3 .

[0069] The invention discloses a process for improving the conversion gas efficiency in a sodium production device. The conversion gas is respectively supplied to an acid production process and an alkali absorption process in two routes, and the tail gas of a neutralizer returns to the alkali absorption process. In this process, the conversion gas and the neutralizer are both reasonably distributed and accurately matched with air, which can not only reduce the nitrogen oxide content of the final tail gas to meet the emission standards, but also increase the sodium nitrate production and obtain a higher yield.

[0070] The present invention can be used for the transformation of existing sodium-sodium devices or new devices. For the transformation of old devices, the final tail gas treatment process, such as the ammonia reduction treatment load, can be effectively reduced, thereby reducing energy consumption. For new devices, the emission can be directly up to standard, the tail gas treatment process can be reduced, and the equipment cost and the operation cost can be reduced, thereby protecting the ecological environment, saving resources, making the best use of resources, reducing economic losses in production, and ultimately achieving energy conservation and emission reduction.

[0071] In addition, the present invention can be used in multiple environments, such as normal pressure, medium pressure or high pressure environment, and can achieve the above functions.

[0072] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for improving the conversion gas efficiency in a sodium and sodium production device, characterized in that: include: In the two sodium production units, the conversion gas goes to the acid production process in one way and to the alkali absorption process in the other way; The alkali absorption process includes at least two processes, the first process is to pre-treat the NO gas for reaction absorption, the second process is to mix the unreacted NO mixed gas in the first process, the tail gas discharged in the acid making process and the tail gas of the neutralization tower for reaction absorption, and after the alkali solution absorption reaches a specified concentration, it is discharged to the sodium sulfite evaporation process; In the sodium nitrate evaporation process, most of the sodium nitrate is precipitated from the solution by evaporation and crystallization, and the crystallization mother liquor is pumped into the conversion process, and the conversion process is linked with the second process of the acid production process and the alkali absorption process respectively; The conversion gas in the sodium production device is compressed air and mixed with gaseous ammonia, and then enters the ammonia oxidation process to generate a mixed gas mainly containing NO, N2, O2, CO2 and H2O; The acid production process mainly involves the oxidation of the NO-containing mixed gas to generate NO2, which is then absorbed by water to produce dilute nitric acid; The above-mentioned processes are reacted and nested in sequence, and the products or exhaust gases of the reaction process are also interconnected, so that the air can be reasonably distributed and accurately matched.

2. A process for improving conversion gas efficiency in a sodium and sodium production device according to claim 1, characterized in that: After multiple rounds of alkali absorption, acid production, sodium nitrate evaporation and crystallization, and conversion, the nitrogen oxide content of the tail gas is reduced to 100 mg / m 3 The following can be discharged.

3. A process for improving conversion gas efficiency in a sodium and sodium production device according to claim 1, characterized in that: The concentration of the dilute nitric acid is controlled by controlling the NO oxidation temperature and oxidation time. The lower the oxidation temperature and the longer the oxidation time, the higher the nitric acid concentration.

4. A process for improving conversion gas efficiency in a sodium and sodium production device according to claim 1, characterized in that: The conversion process includes a conversion tower, which includes an absorption section and a conversion section. The conversion gas generated by the conversion tower is respectively extracted from the top of the tower and the middle of the tower in two ways, one part of which returns to the acid production process and the other part goes to the alkali absorption process.

5. A process for improving conversion gas efficiency in a sodium and sodium production device according to claim 4, characterized in that: The operating pressure of the conversion tower is controlled at 150-300 kPa, the tower top temperature is 30-45°C, and the tower bottom temperature is 65-100°C.

6. A process for improving conversion gas efficiency in a sodium and sodium production device according to claim 4, characterized in that: The conversion gas extracted from the middle of the conversion tower is mixed with a certain ratio of air and then enters each level of alkali absorption tower. The temperature after mixing is controlled at 45-70°C. The ratio of air to conversion gas is adjusted according to the molar ratio of O2:NO. After adjustment, the molar ratio of O2:NO is in the range of 0.5-5.

7. A process for improving conversion gas efficiency in a sodium and sodium production device according to claim 1, characterized in that: The alkali solution in the alkali absorption process is a Na2CO3 aqueous solution with a mass percentage concentration of 10-45%.

8. A process for improving conversion gas efficiency in a sodium and sodium production device according to any one of claims 1 to 7, characterized in that: The first step of the alkali absorption step includes at least 4 alkali absorption towers, and the second step includes at least 4 alkali absorption towers.

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