Device for producing 65% dilute nitric acid

Abstract

The utility model belongs to the field of nitric acid production devices, and particularly relates to a device for producing 65% dilute nitric acid. The device comprises a dilute acid separator (1), a dilute acid tank (2) and an absorption tower (3), wherein the dilute acid separator (1) is connected with the dilute acid tank (2); the dilute acid tank (2) is divided into two branch lines after passing through a dilute acid pump, a liquid level regulating valve (5-1) is arranged on a pipeline of one branch line, and the dilute acid tank (2) is connected with the absorption tower (3) after passing through the liquid level regulating valve (5-1); and the other branch line is provided with a flow meter and a regulating valve (5-2) on the pipeline, and is communicated with a delivery pipeline through the regulating valve (5-2). The device can reduce moisture brought into the absorption tower and does not change the original process flow, so that the double-pressurization dilute nitric acid device not only can produce dilute nitric acid of a common product, but also can produce dilute nitric acid with the concentration of 65% or above, and does not consume a large amount of energy when producing the dilute nitric acid with the concentration of 65%.

Description

Technical Field

[0001] The utility model belongs to the field of nitric acid production devices, in particular to a device for producing 65% dilute nitric acid. Background Art

[0002] Dilute nitric acid is a widely used inorganic acid. It is categorized into dilute nitric acid and concentrated nitric acid based on product concentration. Existing nitric acid production processes in my country only produce dilute nitric acid. However, nitric acid applications often require various concentrations of dilute nitric acid, particularly higher concentrations. Concentrated nitric acid is also derived directly from the dehydration of dilute nitric acid. Increasing the concentration of the dilute nitric acid product can directly meet certain needs requiring higher concentrations, reducing the cost of removing water in subsequent production processes. It also reduces the transportation cost of dilute nitric acid, making it highly economical.

[0003] The mainstream dual-pressure dilute nitric acid production process utilizes the oxidation and combustion of ammonia in air to generate nitric oxide. This nitric oxide is then oxidized to nitrogen dioxide, which is then absorbed with water in an absorption tower to produce dilute nitric acid. The water content of the dilute nitric acid product primarily comes from two sources: the water carried into the absorption tower by the dilute nitric acid (approximately 35% concentration) separated in the dilute acid separator, and the desalted water added to the absorber head to ensure optimal exhaust quality. The water content of the dilute nitric acid in the dilute acid separator comes from both air carryover and ammonia oxidation. This water reacts with nitrogen oxides produced by the ammonia oxidation reaction during process gas condensation to produce some dilute nitric acid. Due to the reaction pressure and temperature, the resulting acid concentration is low (approximately 35%) and must be fed to the absorption tower for further concentration. This dilute acid is approximately 75% water. Even if no desalted water is added to the absorption tower head, and all the water carried into the absorption tower by this dilute acid reacts with nitrogen oxides to produce dilute nitric acid, the theoretical concentration of the dilute nitric acid can only reach approximately 77%. Due to the nature of the nitrogen dioxide absorption reaction to produce nitric acid, a certain amount of desalted water must be added to the top of the absorption tower to control the NOx content in the exhaust gas to meet the specified standard. Therefore, the economic concentration of the dilute nitric acid product is generally between 50% and 60%. To achieve a concentration of 65% or higher, the amount of water added during the absorption process must be reduced. Common process measures include increasing the pressure of the absorption system, adding artificial refrigeration to the absorption tower to enhance the absorption process, and adding a dehumidifier at the air compressor inlet to remove some moisture from the air. All of these measures will significantly increase the cost of dilute nitric acid production: increasing the pressure of the absorption system requires increasing the power consumption of the nitrogen oxide compressor. Since the volume content of nitrogen oxide in the process gas in the absorption system is less than 8%, more than 82% of the gas is nitrogen, and nitrogen is an inert gas throughout the entire process, most of the increased compression power consumption is used to compress the inert gas; using artificial refrigeration in the absorption tower to enhance absorption will significantly increase the energy consumption required for artificial refrigeration due to the large amount of thermal effect associated with the absorption process, thereby greatly increasing power consumption; dehumidifying the air inlet to the air compressor to reduce the moisture brought into the system by the air, because the water content in the air is usually low (usually the mass content is less than 3.5% at temperature and humidity), a large amount of air that does not need to be cooled will also be cooled during the cooling and dehumidification process, thereby greatly increasing the energy consumption of the dehumidification process. The above methods are often used in combination to increase the concentration of dilute nitric acid products, so they require additional consumption of a large amount of energy. Utility Model Content

[0004] The purpose of this utility model is to address the problems existing in the current technology and provide a device for producing 65% dilute nitric acid. The device can reduce the amount of water carried into the absorption tower while maintaining the original process flow. Thus, the dual-pressure dilute nitric acid device can produce both conventional dilute nitric acid and dilute nitric acid with a concentration of 65% or higher, while also not consuming a large amount of energy when producing 65% dilute nitric acid.

[0005] In order to achieve the above purpose of the utility model, the specific technical solution of the utility model is:

[0006] A device for producing 65% dilute nitric acid comprises a dilute acid separator, a dilute acid tank and an absorption tower; wherein the dilute acid separator is connected to the dilute acid tank; the dilute acid tank is divided into two branches after passing through a dilute acid pump; a liquid level regulating valve is provided on the pipeline of one of the branches, and the branch is connected to the absorption tower through the liquid level regulating valve; and a flow meter and a regulating valve are provided on the pipeline of the other branch, and the branch is connected to an external delivery pipeline through the regulating valve.

[0007] Preferably, the external delivery pipeline includes a dilute acid storage tank pipeline and a dilute acid tank pipeline to an adjacent nitric acid production device.

[0008] Furthermore, a nitrogen oxide gas inlet and a nitrogen oxide gas outlet are respectively provided on the dilute acid separator; wherein the nitrogen oxide gas outlet is connected to a nitrogen oxide gas compressor.

[0009] Preferably, the dilute acid pumps (for boosting the dilute nitric acid in the dilute acid tank) are two, namely, dilute acid pump 1 and dilute acid pump 2; dilute acid pump 1 and dilute acid pump 2 are connected in parallel; that is, the dilute acid coming out of the dilute acid tank is divided into two, one of which enters the absorption tower through dilute acid pump 1 and a liquid level regulating valve on one of the branches (the liquid level regulating valve is set to adjust the dilute acid tank liquid level and control the amount of dilute nitric acid going to the absorption tower according to the dilute acid tank liquid level measurement signal); the other dilute acid enters the external delivery pipeline through dilute acid pump 2, a flow meter and a regulating valve. The flow meter and regulating valve are set to control the flow rate of the external delivery dilute nitric acid according to the analysis result of the dilute nitric acid concentration of the absorption tower product.

[0010] Furthermore, the external delivery pipeline includes a dilute acid tank (used to collect dilute nitric acid separated by a temporary dilute acid separator) or a dilute acid storage tank of an adjacent nitric acid production device.

[0011] Furthermore, the dilute acid storage tank is connected to the absorption tower. More preferably, a booster pump is installed in the pipeline connecting the dilute acid storage tank and the absorption tower, so that the dilute acid entering the dilute acid storage tank can be pressurized by the booster pump before entering the absorption tower. The dilute acid storage tank is used to store the dilute nitric acid delivered. After the production of the 65% dilute nitric acid batch is completed, the booster pump boosts the pressure of the dilute nitric acid in the storage tank and returns it to the dilute acid tank within the device, where it is then re-delivered to the absorption tower for concentration through the original process.

[0012] Furthermore, the dilute acid tank of the adjacent dilute nitric acid production unit is connected to the absorption tower via a pump (dilute acid pump) and corresponding pipelines. The dilute acid tank in the adjacent dilute nitric acid production unit can be pumped to the absorption tower in this device through the dilute acid pump for concentration to a normal product concentration.

[0013] Furthermore, the pipeline between the dilute acid separator and the dilute acid tank is also connected to a liquid level regulating valve.

[0014] Compared with the prior art, the positive effects of the present invention are embodied in:

[0015] (1) The dilute acid separator produces a large amount of dilute acid (approximately 35 wt% for a 150,000 ton / year dual-pressure process) and carries a significant amount of water into the absorption tower (approximately 9.2 t / h for a 150,000 ton / year dual-pressure process). While maintaining the exhaust gas output at the absorption tower, the amount of desalted water added to the top of the absorption tower cannot be significantly reduced. With the present invention, the 35 wt% dilute nitric acid can be diverted to reduce the amount of water entering the absorption tower.

[0016] (2) The amount of water added to the absorption tower is reduced by reducing the amount of low-concentration dilute acid entering the absorption tower from the dilute acid separator in the device; it is suitable for occasions where 65% dilute nitric acid product is required for batch production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic structural diagram of a device for producing 65% dilute nitric acid in Example 1 of the present utility model;

[0018] Figure 2 This is a schematic structural diagram of a device for producing 65% dilute nitric acid in Example 2 of the present utility model;

[0019] Among them, 1 is the dilute acid separator, 2 is the dilute acid tank, 3 is the absorption tower, 4-1 is the dilute acid pump 1, 4-2 is the dilute acid pump 2, 5-1 is the liquid level regulating valve, 5-2 is the regulating valve, 6-1 is the dilute acid tank of the adjacent nitric acid production unit, 6-2 is the dilute acid storage tank, 7 is the booster pump, 8 is the nitrogen oxide gas inlet, and 9 is the nitrogen oxide gas outlet. DETAILED DESCRIPTION

[0020] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0021] Any feature disclosed in this specification (including claims and abstract), unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0022] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0023] Example 1:

[0024] A device for producing 65% dilute nitric acid, the structural flow diagram of which is shown in Figure 1 The device includes a dilute acid separator 1, a dilute acid tank 2, and an absorption tower 3; wherein the dilute acid separator 1 is connected to the dilute acid tank 2; the dilute acid tank 2 is divided into two branches after passing through the dilute acid pump, and a liquid level regulating valve 5-1 is provided on the pipeline of one branch, and the branch is connected to the absorption tower 3 after passing through the liquid level regulating valve 5-1; the other branch is provided with a flow meter and a regulating valve 5-2 on the pipeline, and is connected to the external delivery pipeline through the regulating valve 5-2.

[0025] Furthermore, a pipeline connected to the liquid level regulating valve 5 - 1 is connected to the pipeline between the dilute acid separator 1 and the dilute acid tank 2 .

[0026] Furthermore, a nitrogen oxide inlet 8 and a nitrogen oxide outlet 9 are respectively provided on the dilute acid separator 1; wherein the nitrogen oxide outlet 8 is connected to a nitrogen oxide compressor.

[0027] Preferably, two dilute acid pumps (for boosting the dilute nitric acid in the dilute acid tank) are provided, namely, dilute acid pump 1 4-1 and dilute acid pump 2 4-2. These pumps are connected in parallel, so that the dilute acid from dilute acid tank 2 is split into two. One portion of the dilute acid enters absorption tower 3 via dilute acid pump 1 4-1 and a liquid level regulating valve 5-1 on one branch line (the liquid level regulating valve is configured to maintain the dilute acid tank liquid level and control the amount of dilute nitric acid delivered to the absorption tower based on the dilute acid tank liquid level measurement signal); the other portion of the dilute acid enters the external delivery pipeline via dilute acid pump 2 4-2, a flow meter, and a regulating valve 5-2. The flow meter and regulating valve 5-2 are configured to control the flow rate of the external delivery dilute nitric acid based on the analysis of the dilute nitric acid concentration in the absorption tower product.

[0028] Furthermore, the external delivery pipeline is a pipeline going to the dilute acid tank 6-1 of the adjacent nitric acid production device.

[0029] Furthermore, the dilute acid tank 6-1 of the adjacent dilute nitric acid production unit is connected to the absorption tower 3 via a pump (dilute acid pump) and corresponding pipelines. The dilute acid tank 6-1 in the adjacent dilute nitric acid production unit can be pumped to the absorption tower 3 in this device through the dilute acid pump to be concentrated to the normal product concentration.

[0030] Example 2:

[0031] A device for producing 65% dilute nitric acid, the structural flow diagram of which is shown in Figure 2The device includes a dilute acid separator 1, a dilute acid tank 2, and an absorption tower 3; wherein the dilute acid separator 1 is connected to the dilute acid tank 2; the dilute acid tank 2 is divided into two branches after passing through the dilute acid pump, and a liquid level regulating valve 5-1 is provided on the pipeline of one branch, and the branch is connected to the absorption tower 3 after passing through the liquid level regulating valve 5-1; the other branch is provided with a flow meter and a regulating valve 5-2 on the pipeline, and is connected to the external delivery pipeline through the regulating valve 5-2.

[0032] Furthermore, a nitrogen oxide inlet and a nitrogen oxide outlet are respectively provided on the dilute acid separator 1; wherein the nitrogen oxide outlet is connected to a nitrogen oxide compressor.

[0033] Preferably, two dilute acid pumps (for boosting the dilute nitric acid in the dilute acid tank) are provided, namely, dilute acid pump 1 4-1 and dilute acid pump 2 4-2. These pumps are connected in parallel, so that the dilute acid from dilute acid tank 2 is split into two. One portion of the dilute acid enters absorption tower 3 via dilute acid pump 1 4-1 and a liquid level regulating valve 5-1 on one branch line (the liquid level regulating valve is configured to maintain the dilute acid tank liquid level and control the amount of dilute nitric acid delivered to the absorption tower based on the dilute acid tank liquid level measurement signal); the other portion of the dilute acid enters the external delivery pipeline via dilute acid pump 2 4-2, a flow meter, and a regulating valve 5-2. The flow meter and regulating valve 5-2 are configured to control the flow rate of the external delivery dilute nitric acid based on the analysis of the dilute nitric acid concentration in the absorption tower product.

[0034] Furthermore, the external delivery pipeline is a pipeline to a newly added storage facility, that is, to the dilute acid storage 6-2.

[0035] Furthermore, the dilute acid storage tank 6-2 is connected to the absorption tower 3. More preferably, a booster pump 7 is installed in the pipeline connecting the dilute acid storage tank 6-1 and the absorption tower 3. This allows the dilute acid entering the dilute acid storage tank 6-2 to be pressurized by the booster pump 7 before entering the absorption tower 3. The dilute acid storage tank 6-2 is used to store the dilute nitric acid being delivered. Upon completion of the production of a batch of 65% dilute nitric acid, the booster pump boosts the pressure of the dilute nitric acid in the storage tank and returns it to the dilute acid tank within the apparatus. The dilute nitric acid is then re-delivered to the absorption tower through the original process for concentration.

[0036] Example 3:

[0037] Actual production was carried out using the apparatus for producing 65% dilute nitric acid described in Example 1 or Example 2.

[0038] Taking a 150,000 ton / year nitric acid plant as an example, under normal circumstances, its dilute nitric acid concentration is about 60%, and the output is 20.833 tons / h (equivalent to 100%), which means the dilute nitric acid contains 13.889 tons of water. If the concentration of the product dilute acid is increased to 65% by reducing the amount of dilute acid added to the absorption tower from the 35% concentration in the dilute acid tank, and assuming that the amount of 35% dilute nitric acid required to be delivered is X tons / h, then the output of 65% acid is Y tons / h. Assuming other operating conditions remain unchanged, the amount of water used in the absorption tower to react and generate nitric acid remains unchanged; only the amount of water used to dilute the nitric acid solution changes. Based on the amount of nitric acid produced (100%) and the change in the water volume in the system, the following equation can be listed:

[0039] 20.833-0.35X=0.65Y————————1

[0040] 20.833 / 0.6*0.4-0.35Y=0.65X——————2

[0041] Formula 1 is the acid balance formula, and formula 2 is the water balance formula

[0042] Solving the two equations yields: X = 5.81 t / h, Y = 28.928 t / h. This means the amount of 35% dilute nitric acid that needs to be delivered is 5.81 t / h, while the output of 65% nitric acid is 28.928 t / h (equivalent to 100% nitric acid, 18.8 t / h).

[0043] The specific process is as follows:

[0044] The dilute nitric acid (about 35wt% concentration) from the dilute acid separator 1 is temporarily stored in the dilute acid tank 2. After the dilute nitric acid in the dilute acid tank 2 is pressurized to 1.80MPa by the dilute acid pump, it is divided into two branches. One branch is the original pipeline and is controlled by the regulating valve 5-2 before being sent to the absorption tower 3.

[0045] The second branch is a newly added pipeline. After dilute nitric acid from dilute acid pump 5-1 is regulated by a regulating valve, it is no longer fed into absorption tower 3. Instead, it is sent to a temporary storage location or to the adjacent dilute nitric acid unit absorption tower. The reduced dilute acid volume is adjusted by regulating valve 2 based on the nitric acid concentration at the absorption tower outlet.

[0046] The dilute nitric acid sent out through the regulating valve can be sent to the dilute acid tank of the absorption tower of the adjacent dilute nitric acid device, and then pressurized by a pump and sent into the absorption tower for concentration; it can also be sent to a storage tank for temporary storage, and after a batch of 65% dilute nitric acid is produced, it will be pressurized by a pump and then sent back to the absorption tower in the device for concentration.

[0047] Example 4:

[0048] When there are two adjacent dual-pressure dilute nitric acid units, the following process is used:

[0049] The 35% concentrated dilute nitric acid separated by the dilute acid separator is temporarily stored in the dilute acid tank. After being pressurized by the dilute acid pump, the dilute nitric acid in the tank is split into two routes. One route is regulated by regulating valve 1 and enters the absorption tower, where it is concentrated. Finally, the nitric acid outlet concentration at the absorption tower reaches 65% before exiting the absorption tower. The other route, measured by a flowmeter and regulated by regulating valve 2, is temporarily stored in the dilute acid tank of an adjacent dilute nitric acid unit. The dilute acid pump within that unit then boosts the pressure and sends it to the absorption tower within that unit for concentration. The flow rate of the 35% dilute nitric acid sent out is adjusted based on the nitric acid concentration at the absorption tower outlet. When production of 65% dilute nitric acid is not required, regulating valve 2 and its upstream and downstream shut-off valves can be closed, and the dilute acid handle level can be controlled as normal.

[0050] The above-described embodiments merely represent specific implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of protection of the present application. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the technical concept of the present application, and all such variations and improvements fall within the scope of protection of the present application.

[0051] This background technology section is provided to generally present the context of the present invention, and the work of the presently named inventors, the work to the extent described in this background technology section, and aspects of the description in this section that did not constitute prior art at the time of application are neither explicitly nor implicitly admitted to be prior art to the present invention.

Claims

1. A device for producing 65% dilute nitric acid, characterized in that: The device comprises a dilute acid separator (1), a dilute acid tank (2) and an absorption tower (3); wherein the dilute acid separator (1) is connected to the dilute acid tank (2); the dilute acid tank (2) is divided into two branches after passing through a dilute acid pump, a liquid level regulating valve (5-1) is provided on the pipeline of one of the branches, and the branch is connected to the absorption tower (3) through the liquid level regulating valve (5-1); and the other branch is provided with a flow meter and a regulating valve (5-2) on the pipeline, and is connected to an external delivery pipeline through the regulating valve (5-2).

2. A device for producing 65% dilute nitric acid according to claim 1, characterized in that: The external delivery pipeline includes a dilute acid tank (6-1) or a dilute acid storage tank (6-2) of an adjacent nitric acid production device.

3. A device for producing 65% dilute nitric acid according to claim 1 or 2, characterized in that: A nitrogen oxide inlet (8) and a nitrogen oxide outlet (9) are respectively provided on the dilute acid separator (1); the nitrogen oxide outlet (9) is connected to a nitrogen oxide compressor.

4. A device for producing 65% dilute nitric acid according to claim 3, characterized in that: There are two dilute acid pumps, namely dilute acid pump one (4-1) and dilute acid pump two (4-2); dilute acid pump one (4-1) and dilute acid pump two (4-2) are connected in parallel.

5. A device for producing 65% dilute nitric acid according to claim 2, characterized in that: The dilute acid storage tank (6-2) is connected to the absorption tower (3).

6. A device for producing 65% dilute nitric acid according to claim 2, characterized in that: The dilute acid tank (6-1) of the adjacent dilute nitric acid production device is connected to the absorption tower (3) through a pump and corresponding pipelines.

7. A device for producing 65% dilute nitric acid according to claim 5, characterized in that: A booster pump (7) is provided on the pipeline between the dilute acid storage tank (6-2) and the absorption tower (3).

8. A device for producing 65% dilute nitric acid according to claim 1, characterized in that: The pipeline between the dilute acid separator (1) and the dilute acid tank (2) is also connected to a liquid level regulating valve (5-1).

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