CN107814367B - Concentration method for treating low-concentration dilute nitric acid by nitrotoluene waste sulfuric acid - Google Patents
Concentration method for treating low-concentration dilute nitric acid by nitrotoluene waste sulfuric acid Download PDFInfo
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- CN107814367B CN107814367B CN201711049419.6A CN201711049419A CN107814367B CN 107814367 B CN107814367 B CN 107814367B CN 201711049419 A CN201711049419 A CN 201711049419A CN 107814367 B CN107814367 B CN 107814367B
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- C01B21/00—Nitrogen; Compounds thereof
- C01B21/20—Nitrogen oxides; Oxyacids of nitrogen; Salts thereof
- C01B21/38—Nitric acid
- C01B21/44—Concentration
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- C—CHEMISTRY; METALLURGY
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/20—Nitrogen oxides; Oxyacids of nitrogen; Salts thereof
- C01B21/38—Nitric acid
- C01B21/40—Preparation by absorption of oxides of nitrogen
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- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Abstract
The invention discloses a concentration method for treating low-concentration dilute nitric acid by nitrotoluene waste sulfuric acid, which comprises the following steps: a driving stage; in the production stage, the low-concentration dilute nitric acid with the mass fraction of 15-40% from the waste sulfuric acid treatment denitration condenser is cooled and cooled, and then is mixed with concentrated nitric acid with the mass fraction of more than 50% to adjust the concentration to 37-40%; separating out free nitrotoluene liquid, and concentrating by a nitrogen oxide compressor unit to more than 50%; after part of the obtained concentrated nitric acid with the concentration of more than 50 percent is used for subsequent concentration adjustment, the other part of the obtained concentrated nitric acid is discharged and enters a finished product tank area; the nitrogen oxide gas is compressed and absorbed by a nitrogen oxide compressor, and then is discharged after reaching the standard after being absorbed by a nitrogen oxide absorption tower. The method is suitable for separating nitrotoluene and improving the concentration of low-concentration dilute nitric acid in the waste sulfuric acid treatment, improves the use value of low-value dilute nitric acid, better solves the production balance problem of dilute nitric acid, and improves the economy of a waste sulfuric acid treatment device.
Description
Technical Field
The invention relates to a waste acid concentration chemical process, in particular to a concentration method for treating low-concentration dilute nitric acid by nitrotoluene waste sulfuric acid.
Background
The current, more advanced treatment process of waste sulfuric acid in the world is vacuum concentration of waste sulfuric acid and pressurized absorption of nitrogen oxide; in the denitration process of waste sulfuric acid vacuum concentration, condensed dilute nitric acid with the concentration of 15-40% is generally generated, and if the waste sulfuric acid is nitrotoluene waste acid, the dilute nitric acid contains a large amount of free nitrotoluene; nitrogen oxide generated in the waste sulfuric acid denitration process is condensed and then sent to a nitrogen oxide pressurized nitrogen oxide absorption tower for absorption, the pressurized nitrogen oxide absorption tower generally adopts 0.65mPa working pressure, and the emission concentration of the nitrogen oxide in the absorbed tail gas is less than or equal to 240mg/m3(ii) a Nitric acid with the concentration of 50% is obtained by a nitric oxide absorption tower; the condensed dilute nitric acid is sent into a dilute nitric acid tank to be mixed with 50 percent nitric acid obtained from a nitric acid smoke nitrogen oxide absorption tower to form 40 percent dilute nitric acid which is used as a finished product dilute nitric acid.
Dilute nitric acid contains a large amount of free nitro compounds; the density range of the dilute nitric acid is 1.1kg/L-1.25kg/L, the density of the nitro compound is about 1.19kg/L, the densities of the two materials are very similar, and the continuous separation of the free nitro compound from the dilute nitric acid is difficult to realize; in the subsequent nitration production, a large amount of nitro compounds are wasted, and side reactions are combined.
Therefore, it is necessary to develop a method for successfully separating free nitro compounds and slightly increasing the concentration of the dilute nitric acid by treating the low-concentration dilute nitric acid with the waste sulfuric acid of nitrotoluene, which is used for concentrating the dilute nitric acid to 50%.
Disclosure of Invention
The invention aims to solve the defects of the background technology and provide a concentration method for treating low-concentration dilute nitric acid by nitrotoluene waste sulfuric acid.
The technical scheme of the invention is as follows: a concentration method for treating low-concentration dilute nitric acid by nitrotoluene waste sulfuric acid is characterized by comprising the following steps:
a driving stage:
a. cooling and cooling low-concentration dilute nitric acid with the mass fraction of 15-40% from a waste sulfuric acid treatment denitration condenser, separating free nitrotoluene by gravity settling, mixing the free nitrotoluene with nitric acid with the concentration of 50% serving as starting acid, and then feeding the mixture into a nitrogen oxide compressor unit until the concentration of the nitric acid reaches more than 50%;
the production stage comprises:
b. cooling and cooling the low-concentration dilute nitric acid with the mass fraction of 15-40% from the waste sulfuric acid treatment denitration condenser, and then combining the low-concentration dilute nitric acid with the mass fraction of more than 50% from a nitrogen oxide compressor unit to adjust the concentration to 37-40%;
c. separating free nitrotoluene in dilute nitric acid with the concentration of 37-40% by gravity settling, and increasing the concentration of the dilute nitric acid with the concentration of 37-40% after the nitrotoluene is separated to more than 50% by the nitrogen oxide compressor unit;
d. part of the obtained nitric acid with the concentration of more than 50 percent is combined with the low-concentration dilute nitric acid with the mass fraction of 15 to 40 percent, which is obtained from a waste sulfuric acid treatment denitration condenser and is cooled to adjust the concentration to 37 to 40 percent, so as to form a concentrated nitric acid cycle; the other part is discharged to enter a finished product tank area;
e. and combining the nitrogen oxide gas generated in the system with the nitrogen oxide gas generated in the waste sulfuric acid denitration process, absorbing the nitrogen oxide gas by the nitrogen oxide compressor unit, and then absorbing and discharging the nitrogen oxide gas by the nitrogen oxide absorption tower. The concentration of the dilute nitric acid in the invention is mass percent.
Preferably, when the mixed nitric acid in the step a enters a nitrogen oxide compressor unit, the nitrogen oxide gas generated in the waste sulfuric acid denitration process is introduced at the same time.
Preferably, the nitrogen oxide gas obtained in the cooling process in the step b and the separation process in the step c is combined, and then is combined with the nitrogen oxide gas generated in the waste sulfuric acid denitration process, and the nitrogen oxide gas is absorbed by the nitrogen oxide compressor and then is absorbed and discharged by the nitrogen oxide absorption tower.
Preferably, the dilute nitric acid generated during opening and stopping of the nitrogen oxide absorption tower is combined with the 37% -40% dilute nitric acid separated from the nitrotoluene in the step c, and the concentration of the dilute nitric acid is increased to more than 50% by the nitrogen oxide compressor unit.
Preferably, the steps are as follows:
a driving stage:
a. cooling and cooling low-concentration dilute nitric acid with the mass fraction of 15% -40% from a waste sulfuric acid treatment denitration condenser, separating free nitrotoluene by gravity settling, mixing the free nitrotoluene with nitric acid with the concentration of 50% from a rotary tank as starting acid, then feeding the mixture into a nitrogen oxide compressor unit, and simultaneously introducing nitrogen oxide gas generated in a waste sulfuric acid denitration process until the concentration of the nitric acid reaches more than 50% after the nitrogen oxide compressor unit absorbs the nitric acid;
the production stage comprises:
b. cooling low-concentration dilute nitric acid with the mass fraction of 15% -40% from a waste sulfuric acid treatment denitration condenser by using a cooler, and adjusting the concentration of the low-concentration dilute nitric acid and concentrated nitric acid with the mass fraction of more than 50% from a nitrogen oxide compressor unit to 37% -40%;
c. separating free nitrotoluene from the dilute nitric acid with the concentration of 37-40% by an automatic separator and a manual separator, introducing the dilute nitric acid with the concentration of 37-40% after the nitrotoluene separation into the nitrogen oxide compressor unit, and increasing the concentration to more than 50%;
d. part of nitric acid with the concentration of more than 50 percent obtained by a nitrogen oxide compressor unit is combined with low-concentration dilute nitric acid with the mass fraction of 15-40 percent, which is subsequently from a waste sulfuric acid treatment denitration condenser and is cooled to adjust the concentration to 37-40 percent, so as to form concentrated nitric acid circulation; the other part is discharged to enter a finished product tank area;
e. and the nitrogen oxide gas generated by the cooler in the system is combined with the nitrogen oxide gas generated by the automatic separator and the manual separator, and then is combined with the nitrogen oxide gas generated by the waste sulfuric acid denitration process, and the nitrogen oxide gas is absorbed by the nitrogen oxide compressor unit and then is absorbed by the nitrogen oxide absorption tower and discharged.
The invention also provides a device used in the method for concentrating the low-concentration dilute nitric acid treated by the nitrotoluene waste sulfuric acid, which is characterized in that:
comprises a cooler, an automatic separator, a manual separator, a rotary hand tank, a nitrogen oxide compressor unit and a nitrogen oxide absorption tower;
the cooler, the automatic separator, the manual separator, the turning groove and the nitrogen oxide compressor unit are sequentially connected through liquid pipelines, an outlet pipeline of the nitrogen oxide compressor unit is divided into two paths, one path of the outlet pipeline is led to the nitrogen oxide absorption tower through a gas pipeline, the other path of the outlet pipeline is continuously divided into two paths which are connected in parallel through the liquid pipeline, one path of the outlet pipeline is led to the automatic separator, the other path of the outlet pipeline is provided with a finished product discharge pipe, and a standby pipeline is arranged between the liquid pipeline at the outlet of the cooler and the liquid pipeline at the outlet of the automatic;
the low-concentration dilute nitric acid feeding pipe is connected to an inlet pipeline of the cooler, the upper ends of the cooler, the automatic separator and the manual separator are connected and combined through a gas pipeline, and then combined with a nitrogen oxide gas discharge pipe of an upstream process to form an inlet gas phase pipe communicated to the nitrogen oxide compressor unit.
Preferably, the discharge port of the cooler is connected with the feed port of the automatic separator, the discharge port of the automatic separator is connected with the feed port of the manual separator, the discharge port of the manual separator is connected with the feed port of the rotary hand tank, and the rotary hand tank is connected with the feed port of the nitrogen oxide compressor unit through liquid pipelines.
Preferably, the system further comprises a DCS control system, a first density meter is arranged in the automatic separator, a first regulating valve is arranged on one path of liquid pipeline from the discharge port of the nitrogen oxide compressor unit to the automatic separator, and the first density meter is connected with the first regulating valve through the DCS control system.
Further, a liquid level meter is arranged in the handle turning groove, a first conveying pump is arranged between the handle turning groove and the nitrogen oxide compressor unit, and the liquid level meter is connected with the first conveying pump through a DCS (distributed control system);
and furthermore, a second densimeter is arranged on the finished product discharge pipe and is connected with a nitrogen oxide absorption water pipe of the nitrogen oxide absorption tower through a DCS control system.
Preferably, the bottom of the nitrogen oxide absorption tower is connected with an inlet pipeline of the nitrogen oxide compressor unit through an absorption liquid drain pipe.
Preferably, the outer wall of the tower plate of the nitrogen oxide absorption tower is provided with a tower plate working solution discharge pipe, and the tower plate working solution discharge pipe is communicated with a liquid pipeline from the manual separator to the rotating hand tank.
Preferably, the low-concentration dilute nitric acid feeding pipe is connected with a steam-discharging condensate pipe leading to an acid water pool.
The invention has the beneficial effects that:
1. the method mixes the low-concentration dilute nitric acid with the concentration of 15-40% and the concentrated nitric acid with the concentration of 50% into the dilute nitric acid with the concentration of 37-40%, ensures that the density of the dilute nitric acid is always higher than that of the nitrotoluene, and solves the problem of difficult separation of the free nitrotoluene in the dilute nitric acid with the concentration of 15-40% through gravity settling separation.
2. The concentration of 15-40% dilute nitric acid is increased to more than 50%, the use value is improved, and the problems that a large amount of 30% low-concentration dilute nitric acid is required to be generated when the nitrogen oxide absorption tower is started and stopped, and long working time is required for acid filling preparation and the like are solved; the economical efficiency of the waste sulfuric acid treatment device is increased.
3. After the nitrogen oxide is absorbed by the nitrogen oxide compressor unit and the nitrogen oxide absorption tower, the tail gas reaches the European emission standard and is discharged, and the method has the advantage of environmental friendliness.
4. The automation degree is high, and the water absorption quantity at the top of the nitrogen oxide absorption tower is adjusted through the acid density detection signal of 50% dilute nitric acid finished products of the nitrogen oxide compressor unit, so that the nitrogen oxide compressor unit separator obtains stable dilute nitric acid of more than 50%.
Drawings
FIG. 1 is a schematic diagram of a device for treating dilute nitric acid and concentrating waste nitrotoluene sulfuric acid according to the present invention
Wherein: 1-cooler 2-automatic separator 3-manual separator 4-spare pipeline 5-rotary handle groove 6-nitrogen oxide compressor unit 7-nitrogen oxide absorption tower 8-low concentration dilute nitric acid feed pipe 9-nitrogen oxide gas discharge pipe 10-inlet gas phase pipe 11-finished product discharge pipe 12-first densimeter 13-first regulating valve 14-liquidometer 15-first delivery pump 16-second densimeter 17-steam discharge condensate pipe 18-first gas pipeline 19-second gas pipeline 20-third gas pipeline 21-spare valve 22-gas pipeline merging section 6.1-nitrogen oxide compressor 6.2-separator 7.1-nitrogen oxide absorption water pipe 7.2-tray working solution discharge pipe 7.3-gas-liquid balance pipe 7.4-absorption liquid discharge pipe 7.5-tail gas discharge pipe.
Detailed Description
The invention is described in further detail below with reference to the figures and the specific embodiments.
As shown in figure 1, the device used in the method for treating low-concentration dilute nitric acid by nitrotoluene waste sulfuric acid provided by the invention comprises a cooler 1, an automatic separator 2, a manual separator 3, a rotary tank 5, a nitrogen oxide compressor unit 6, a nitrogen oxide absorption tower 7, a liquid pipeline and a gas pipeline; the nitrogen oxide compressor unit 6 comprises a nitrogen oxide compressor 6.1 and a separator 6.2 connected in series.
The cooler 1, the automatic separator 2, the manual separator 3, the rotating tank 5 and the nitrogen oxide compressor unit 6 are sequentially connected through liquid pipelines, an outlet pipeline of the nitrogen oxide compressor unit 6 is divided into two parallel-connected pipelines, one pipeline leads to the nitrogen oxide absorption tower 7 through a gas pipeline, the other pipeline is continuously divided into two parallel-connected pipelines through a liquid pipeline, one pipeline leads to the automatic separator 2, the other pipeline is provided with a finished product discharge pipe 11, and a spare pipeline 4 is arranged between the liquid pipeline at the outlet of the cooler 1 and the liquid pipeline at the outlet of the automatic separator 2; the low-concentration dilute nitric acid feeding pipe 8 is connected to an inlet pipeline of the cooler 1, the upper ends of the cooler 1, the automatic separator 2 and the manual separator 3 are connected and combined through a gas pipeline, and then combined with a nitrogen oxide gas discharge pipe 9 of an upstream process to form an inlet gas phase pipe 10 which leads to the nitrogen oxide compressor unit 6.
The embodiment specifically includes: the upper right end discharge port of the cooler 1 and the lower left end feed inlet of the automatic separator 2, the lower right side discharge port of the automatic separator 2 and the lower right end feed inlet of the manual separator 3, the upper right end discharge port of the manual separator 3 and the upper end feed inlet of the turning groove 5, the lower right side of the turning groove 5 and the left side of the first conveying pump 15, the top of the first conveying pump 15 and the left side feed inlet of the nitrogen oxide compressor unit 6 are connected through liquid pipelines, the pipeline at the discharge port of the nitrogen oxide compressor unit 6.2 is divided into two gas-liquid paths in parallel, one path is led to the feed inlet at the bottom of the nitrogen oxide absorption tower 7 through a gas pipeline, the other path is divided into two paths in parallel through the liquid pipeline, one path is communicated with the liquid pipeline at the discharge port of. The top parts of the automatic separator 2 and the manual separator 3 are also provided with special discharge pipelines for discharging the separated nitrotoluene out of the system. A standby valve 21 is arranged on a standby pipeline 4 between a discharge port at the upper right end of the cooler 1 and a liquid pipeline at a feed port at the lower left end of the automatic separator 2, and is connected with a liquid pipeline between a discharge port at the lower right end of the automatic separator 2 and a feed port at the lower right end of the manual separator 3.
The device system also comprises a DCS control system, wherein a first densimeter 12 is arranged in the automatic separator 2, a first regulating valve 13 is arranged on one path of liquid pipeline from a discharge port of the nitrogen oxide compressor unit 6 to the automatic separator 2, and the first densimeter 12 is connected with the first regulating valve 13 through the DCS control system; a liquid level meter is arranged in the handle turning groove 5, a first conveying pump 15 is arranged between the handle turning groove 5 and the nitrogen oxide compressor unit 10, the liquid level meter is connected with the first conveying pump 15 through a DCS control system, and a flow meter 15.1 is arranged on a liquid pipeline at the top of the first conveying pump 15; and a second densimeter 16 is arranged on the finished product discharge pipe 11, and the second densimeter 16 is connected with the nitrogen oxide absorption water pipe 7.1 of the nitrogen oxide absorption tower 7 through a DCS control system.
The gas pipeline comprises a first gas pipeline 18 arranged at the top end of the cooler 1, a second gas pipeline 19 arranged at the top end of the automatic separator 2 and a third gas pipeline 20 arranged at the top end of the manual separator 3, the first gas pipeline 18, the second gas pipeline 19 and the third gas pipeline 20 are connected and combined to form a gas pipeline combining section 22, and the gas pipeline combining section 22 and the nitric oxide gas discharge pipe 9 are combined to form an inlet gas phase pipe 10 which leads to the nitric oxide compressor unit 6. The bottom of the nitrogen oxide absorption tower 7 is connected to the gas pipeline merging section 22 through an absorption liquid drain pipe 7.4. In this embodiment, because the diameter of the gas pipe merging section 22 is large, the liquid to be introduced into the nitrogen oxide compressor unit 6 can be directly introduced into the gas pipe merging section 22, and then enters the nitrogen oxide compressor unit 6 together with the nitrogen oxide gas through the inlet gas phase pipe 10; the liquid to be fed to the nitrogen oxide compressor unit 6 can also be fed directly to the nitrogen oxide compressor unit 6 via a liquid line.
The outer wall of the tower plate of the nitrogen oxide absorption tower 7 is provided with a tower plate working liquid discharge pipe 7.2, and the tower plate working liquid discharge pipe 7.2 is communicated with a liquid pipeline between the manual separator 3 and the rotating hand tank 5. The low-concentration dilute nitric acid feeding pipe 8 is connected with a steam-discharging condensate pipe 17 leading to an acid water pool. The bubble cap tower plate of the nitrogen oxide absorption tower is provided with a tower plate discharge hole, so that the tower plate can be kept at a full liquid level under the condition of any water addition amount; the gas-liquid balance pipe 7.3 at the top of the nitrogen oxide absorption tower 7 ensures that the nitrogen oxide absorption tower does not flood under the condition that a certain layer of tower plate is accidentally leaked, and ensures the continuous and stable work of the nitrogen oxide absorption tower. And a tail gas discharge pipe 7.5 is arranged at the top of the nitrogen oxide absorption tower.
Through the device system, the method for treating low-concentration dilute nitric acid by nitrotoluene waste sulfuric acid comprises the following specific steps:
a driving stage:
a. steam condensate water generated in the starting stage flows out from the low-concentration dilute nitric acid feeding pipe 8 and is discharged into an acid wastewater system, namely an acid water pool, through the steam condensate water discharge pipe 17, and a valve on the steam condensate water discharge pipe 17 is closed under the normal operation condition of the system.
In the initial start-up or after overhaul, the concentration of the dilute nitric acid from the separator 6.2 is low, the function of adjusting the concentration of the dilute nitric acid is not realized, the valve 21 on the standby pipeline 4 is opened, and the nitric acid flowing out from the low-concentration dilute nitric acid inlet pipe 8 directly enters the manual separator 3 to manually separate the nitrotoluene. Before starting, dilute nitric acid with the concentration of 50% is injected into the handle-turning groove 5 and is used as the concentration adjusting starting acid in the starting stage.
The mass fraction of 15% -40% of low-concentration dilute nitric acid from a low-concentration dilute nitric acid feed pipe 8 is cooled to 20 ℃ through heat conduction of a cooler 1, nitrotoluene is intermittently separated by a manual separator 3, free nitrotoluene is separated out, the nitrotoluene is mixed with nitric acid with the concentration of 50% from a hand-turning tank 5 and then enters a nitrogen oxide compressor unit 6, nitrogen oxide gas is generated in a waste sulfuric acid denitration process discharged from a nitrogen oxide gas discharge pipe 9 and is simultaneously introduced into the nitrogen oxide compressor unit 6 until the concentration of the nitric acid reaches more than 50%, and the nitrogen oxide gas discharged from the nitrogen oxide compressor unit 6 enters an absorption tower 7 for absorption;
the production stage comprises:
b. the mass fraction of the low-concentration dilute nitric acid from the low-concentration dilute nitric acid feeding pipe 8 is 15-40%, and the temperature is reduced to 20 ℃ through heat conduction of the cooler 1, so that the solubility of the dilute nitric acid p-nitrotoluene is reduced. The concentration of the cooled low-concentration dilute nitric acid with the mass fraction of 15% -40% and concentrated nitric acid with the mass fraction of more than 50% from the nitric oxide compressor unit 6 is adjusted to 37% -40%, the concentration is adjusted to be a signal measured by a DCS control system by using a first densimeter 12, the concentrated nitric acid with the mass fraction of more than 50% from the nitric oxide compressor unit 6 is automatically adjusted and added through a first adjusting valve 13, the density of the adjusted dilute nitric acid is always higher than that of nitrotoluene, and the dilute nitric acid is a heavy phase.
c. Dilute nitric acid with the concentration of 37-40% passes through the automatic separator 2 and the manual separator 3 to separate free nitrotoluene, and then automatically flows into the hand transferring tank 5. The nitrotoluene is continuously separated by the gravity settling of the automatic separator 2, the nitrotoluene is intermittently separated by the manual separator 3, and the nitrotoluene is discharged out of the system from a special discharge pipeline at the top of the automatic separator 2 and the manual separator 3. The hand-turning tank 5 always keeps a liquid level which is not more than 50% of the highest liquid level, the DCS control system takes the liquid level measured by the liquid level meter 14 as a signal, automatically controls the first delivery pump 15 to send redundant 37% -40% dilute nitric acid into the inlet gas phase pipe 10 at the inlet of the nitric oxide compressor 6.1 through the flowmeter 15.1, and the concentration is improved to be more than 50% through the nitric oxide compressor unit 6. The DCS control system uses the density of the nitric acid flowing out of the nitric oxide compressor unit 6 detected by the second densimeter 16 on the finished product discharge pipe 11 as a signal, and controls the absorption water quantity at the top of the nitric oxide absorption tower 7, namely the water inflow quantity of the nitric oxide absorption water pipe 7.1, so that the nitric oxide compressor unit separator 6.2 can obtain the stable dilute nitric acid with the concentration of more than 50%.
d. Part of the concentrated nitric acid with the concentration of more than 50 percent obtained by the nitric oxide compressor unit 6 enters a liquid pipeline between a discharge hole of the cooler 1 and a feed hole of the automatic separator 2; continuously mixing the concentrated nitric acid with the low-concentration dilute nitric acid with the mass fraction of 15% -40% which is obtained from a waste sulfuric acid treatment denitration condenser and is cooled by the cooler 1, and adjusting the concentration to 37% -40% to form concentrated nitric acid circulation; another part of the nitric acid with the concentration of more than 50 percent is discharged into a finished product tank area through a finished product discharge pipe 11 by a second densimeter 16.
e. The nitric oxide gas generated by the cooler 1 in the system is combined with the nitric oxide gas generated by the automatic separator 2 and the manual separator 3 in the gas pipeline combining section 22, then is combined with the nitric oxide gas generated by the waste sulfuric acid denitration process discharged by the nitric oxide gas discharge pipe 9, enters the nitric oxide compressor unit 6 through the inlet gas phase pipe 10 for absorption, the nitric oxide gas unabsorbed by the nitric oxide compressor unit 6 is discharged from the separator 6.2 and then is introduced to the bottom of the nitric oxide absorption tower 7 to be absorbed by water in a counter-current manner to generate 30% low-concentration dilute nitric acid, and the 37% -40% concentration dilute nitric acid conveyed by the first conveying pump 15 through the flow meter 15.1 and the 30% low-concentration dilute nitric acid in the absorption liquid discharge pipe 7.4 are mixed into working liquid to be added into the nitric oxide compressor unit 6; the tail gas reaches the European emission standard and is discharged from a tail gas discharge pipe 7.5 at the top.
The two conveying pumps 15 are provided, one is opened, the other is standby, when the production pump fails, the standby pump is immediately started, and the continuous production of the system can be fully ensured. The method has less newly added equipment, and can be arranged between the procedures of nitrogen oxide absorption and waste sulfuric acid treatment, and does not need newly added site construction.
Claims (5)
1. A concentration method for treating low-concentration dilute nitric acid by nitrotoluene waste sulfuric acid is characterized by comprising the following steps:
a driving stage:
a. cooling and cooling low-concentration dilute nitric acid with the mass fraction of 15-40% from a waste sulfuric acid treatment denitration condenser, separating free nitrotoluene by gravity settling, mixing the free nitrotoluene with nitric acid with the concentration of 50% serving as starting acid, and then feeding the mixture into a nitrogen oxide compressor unit until the concentration of the nitric acid reaches more than 50%;
the production stage comprises:
b. cooling and cooling the low-concentration dilute nitric acid with the mass fraction of 15-40% from the waste sulfuric acid treatment denitration condenser, and then combining the low-concentration dilute nitric acid with the mass fraction of more than 50% from a nitrogen oxide compressor unit to adjust the concentration to 37-40%;
c. separating free nitrotoluene in dilute nitric acid with the concentration of 37-40% by gravity settling, and increasing the concentration of the dilute nitric acid with the concentration of 37-40% after the nitrotoluene is separated to more than 50% by the nitrogen oxide compressor unit;
d. part of the obtained nitric acid with the concentration of more than 50 percent is combined with the low-concentration dilute nitric acid with the mass fraction of 15 to 40 percent, which is obtained from a waste sulfuric acid treatment denitration condenser and is cooled to adjust the concentration to 37 to 40 percent, so as to form a concentrated nitric acid cycle; the other part is discharged to enter a finished product tank area;
e. and combining the nitrogen oxide gas generated in the system with the nitrogen oxide gas generated in the waste sulfuric acid denitration process, absorbing the nitrogen oxide gas by the nitrogen oxide compressor unit, and then absorbing and discharging the nitrogen oxide gas by the nitrogen oxide absorption tower.
2. The method for concentrating the low-concentration dilute nitric acid treated by the nitrotoluene waste sulfuric acid as claimed in claim 1, wherein the concentration of the dilute nitric acid is as follows: and (b) when the mixed nitric acid in the step a enters a nitrogen oxide compressor unit, introducing nitrogen oxide gas generated in the waste sulfuric acid denitration process.
3. The method for concentrating the low-concentration dilute nitric acid treated by the nitrotoluene waste sulfuric acid as claimed in claim 1, wherein the concentration of the dilute nitric acid is as follows: and (c) combining the nitrogen oxide gas obtained in the cooling process in the step (b) and the nitrogen oxide gas obtained in the separation process in the step (c), combining the combined nitrogen oxide gas with the nitrogen oxide gas generated in the waste sulfuric acid denitration process, absorbing the combined nitrogen oxide gas by the nitrogen oxide compressor, and absorbing and discharging the combined nitrogen oxide gas by the nitrogen oxide absorption tower.
4. The method for concentrating the low-concentration dilute nitric acid treated by the nitrotoluene waste sulfuric acid as claimed in claim 1, wherein the concentration of the dilute nitric acid is as follows: and (c) mixing dilute nitric acid generated during opening and stopping of the nitrogen oxide absorption tower with the 37-40% dilute nitric acid of the nitrotoluene separated in the step c, and increasing the concentration to more than 50% by using the nitrogen oxide compressor unit.
5. The method for concentrating the low-concentration dilute nitric acid treated by the nitrotoluene waste sulfuric acid as claimed in claim 1, wherein the concentration of the dilute nitric acid is as follows:
a driving stage:
a. cooling and cooling low-concentration dilute nitric acid with the mass fraction of 15% -40% from a waste sulfuric acid treatment denitration condenser, separating free nitrotoluene by gravity settling, mixing the free nitrotoluene with nitric acid with the concentration of 50% from a rotary tank (5) as starting acid, then feeding the mixture into a nitrogen oxide compressor unit (6), and simultaneously introducing nitrogen oxide gas generated in a waste sulfuric acid denitration process until the concentration of the nitric acid reaches more than 50% after the nitrogen oxide compressor unit (6) absorbs the nitric acid;
the production stage comprises:
b. cooling low-concentration dilute nitric acid with the mass fraction of 15% -40% from a waste sulfuric acid treatment denitration condenser by using a cooler (1), and adjusting the concentration of the low-concentration dilute nitric acid and concentrated nitric acid with the mass fraction of more than 50% from a nitrogen oxide compressor unit to 37% -40%;
c. dilute nitric acid with the concentration of 37-40% is sequentially separated out from free nitrotoluene by an automatic separator (2) and a manual separator (3), and the dilute nitric acid with the concentration of 37-40% after the nitrotoluene is separated is introduced into the nitrogen oxide compressor unit to increase the concentration to more than 50%;
d. part of nitric acid with the concentration of more than 50 percent obtained by a nitrogen oxide compressor unit (6) is combined with low-concentration dilute nitric acid with the mass fraction of 15-40 percent, which is subsequently from a waste sulfuric acid treatment denitration condenser and is cooled to adjust the concentration to 37-40 percent, so as to form concentrated nitric acid circulation; the other part is discharged to enter a finished product tank area;
e. and the nitrogen oxide gas generated by the cooler (1) in the system is combined with the nitrogen oxide gas generated by the automatic separator (2) and the manual separator (3), then is combined with the nitrogen oxide gas generated by the waste sulfuric acid denitration process, is absorbed by the nitrogen oxide compressor unit (6), and then is absorbed by the nitrogen oxide absorption tower (7) and is discharged.
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| CN102838096A (en) * | 2012-09-24 | 2012-12-26 | 杭州先进富春化工有限公司 | Joint production method and production device of dilute nitric acid and concentrated nitric acid |
| CN102838489A (en) * | 2012-09-19 | 2012-12-26 | 辽宁庆阳特种化工有限公司 | Clean production method and device of dinitrotoluene |
| CN104016317A (en) * | 2014-06-18 | 2014-09-03 | 天脊煤化工集团股份有限公司 | Method and device for preparing high-concentration dilute nitric acid |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102838489A (en) * | 2012-09-19 | 2012-12-26 | 辽宁庆阳特种化工有限公司 | Clean production method and device of dinitrotoluene |
| CN102838096A (en) * | 2012-09-24 | 2012-12-26 | 杭州先进富春化工有限公司 | Joint production method and production device of dilute nitric acid and concentrated nitric acid |
| CN104016317A (en) * | 2014-06-18 | 2014-09-03 | 天脊煤化工集团股份有限公司 | Method and device for preparing high-concentration dilute nitric acid |
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