CN107814365B - Cyclic concentration method for treating dilute nitric acid generated by nitrotoluene waste sulfuric acid - Google Patents
Cyclic concentration method for treating dilute nitric acid generated by nitrotoluene waste sulfuric acid Download PDFInfo
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- CN107814365B CN107814365B CN201711044153.6A CN201711044153A CN107814365B CN 107814365 B CN107814365 B CN 107814365B CN 201711044153 A CN201711044153 A CN 201711044153A CN 107814365 B CN107814365 B CN 107814365B
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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
- C01—INORGANIC CHEMISTRY
- 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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- C01P2006/80—Compositional purity
Abstract
The invention discloses a cyclic concentration method for treating dilute nitric acid generated 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 is controlled to be mixed with concentrated nitric acid with the mass fraction of more than 50% and adjusted to the density of more than nitrotoluene; 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 density adjustment, the other part 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 the waste sulfuric acid treatment.
Description
Technical Field
The invention relates to a waste acid concentration chemical process, in particular to a cyclic concentration method for treating dilute nitric acid generated 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; 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 obtain 40 percent dilute nitric acid serving as a finished productNitric acid is used.
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, a cyclic concentration method for treating dilute nitric acid generated by nitrotoluene waste sulfuric acid, which can successfully separate free nitro compounds and concentrate the dilute nitric acid to 50%, needs to be developed.
Disclosure of Invention
The invention aims to solve the defects of the background technology and provide a cyclic concentration method for treating dilute nitric acid generated by nitrotoluene waste sulfuric acid.
The technical scheme of the invention is as follows: a cyclic concentration method for treating dilute nitric acid generated by nitrotoluene waste sulfuric acid comprises the following steps:
a driving stage:
cooling and cooling the low-concentration dilute nitric acid with the mass fraction of 15-40% from the waste sulfuric acid treatment denitration condenser, separating free nitrotoluene by gravity settling, and controlling the flow of the nitric acid with the concentration of 50% as starting acid to ensure that the concentration of the starting acid and the low-concentration dilute nitric acid with the mass fraction of 15-40% are mixed and enter a nitrogen oxide compressor unit and then reaches more than 50%;
the production stage comprises:
a. cooling the low-concentration dilute nitric acid with the mass fraction of 15-40% from the waste sulfuric acid treatment denitration condenser, and controlling the flow of the nitric acid with the mass fraction of more than 50% from a nitrogen oxide compressor unit to enable the nitric acid to be mixed with the low-concentration dilute nitric acid with the mass fraction of 15-40% and enable the density to be larger than that of nitrotoluene;
b. separating free nitrotoluene in the mixed nitric acid by gravity settling, and increasing the concentration of the mixed nitric acid with the separated nitrotoluene to more than 50% by using the nitrogen oxide compressor unit;
c. carrying out step abc formation on part of the obtained nitric acid with the concentration of more than 50% and low-concentration dilute nitric acid with the mass fraction of 15% -40% from a waste sulfuric acid treatment denitration condenser to form a cyclic process; the other part is discharged to enter a finished product tank area;
d. 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, and then absorbing and discharging the nitrogen oxide gas by a nitrogen oxide absorption tower;
e. and c, combining the absorption liquid at the bottom of the absorption tower with the mixed nitric acid in the step b, and feeding the combined nitric acid into a nitrogen oxide compressor unit to increase the concentration to more than 50%. The concentration of the dilute nitric acid in the invention is mass percent.
Preferably, the mixed nitric acid with nitrotoluene separated in the step b enters the nitrogen oxide compressor unit through the hand turning groove, and the flow of the mixed nitric acid entering the nitrogen oxide compressor unit is controlled through the liquid level in the hand turning groove.
Preferably, in the step d, the nitrogen oxide gas obtained in the cooling process in the step a and the separation process in the step b 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, in the step d, the water inflow at the upper end of the absorption tower is controlled by the density of the concentrated nitric acid at the outlet of the nitrogen oxide compressor unit.
Preferably, the flow rate of the absorption liquid entering the nitrogen oxide compressor unit is controlled by the liquid level at the bottom of the absorption tower in the step e.
Preferably, the steps are as follows:
a driving stage:
cooling and cooling the low-concentration dilute nitric acid with the mass fraction of 15-40% from the waste sulfuric acid treatment denitration condenser, separating free nitrotoluene by gravity settling, controlling the flow of the nitric acid with the concentration of 50% serving as starting acid in a self-rotating hand tank, and enabling the starting acid and the low-concentration dilute nitric acid with the mass fraction of 15-40% to be mixed and enter a nitrogen oxide compressor unit, wherein the concentration of the nitric acid reaches more than 50%;
the production stage comprises:
a. cooling the low-concentration dilute nitric acid with the mass fraction of 15-40% from the waste sulfuric acid treatment denitration condenser, and controlling the flow of the concentrated nitric acid with the mass fraction of more than 50% from a nitrogen oxide compressor unit to enable the concentrated nitric acid to be mixed with the low-concentration dilute nitric acid with the mass fraction of 15-40% and enable the density to be larger than that of nitrotoluene;
b. separating free nitrotoluene from the mixed nitric acid by an automatic separator and a manual separator in sequence, introducing the mixed nitric acid after the nitrotoluene is separated into the nitric oxide compressor unit through a hand-turning tank, and increasing the concentration to more than 50%, wherein the flow of the mixed nitric acid entering the nitric oxide compressor unit is controlled by the liquid level in the hand-turning tank;
c. carrying out step abc formation circulation process on part of the obtained nitric acid with the concentration of more than 50% and low-concentration dilute nitric acid with the mass fraction of 15% -40% from a waste sulfuric acid treatment denitration condenser; the other part is discharged to enter a finished product tank area;
d. combining the nitrogen oxide gas generated by the cooler in the system with the nitrogen oxide gas generated by the automatic separator, the manual separator and the hand-turning tank, combining the combined nitrogen oxide gas with the nitrogen oxide gas generated by the waste sulfuric acid denitration process, absorbing the combined nitrogen oxide gas by the nitrogen oxide compressor unit, and absorbing the combined nitrogen oxide gas by the nitrogen oxide absorption tower to be discharged; controlling the water inflow at the upper end in the absorption tower through the density of the concentrated nitric acid at the outlet of the nitric oxide compressor unit;
e. and b, controlling the flow of the absorption liquid through the liquid level of the absorption liquid at the bottom of the absorption tower, and combining the absorption liquid with the mixed nitric acid in the step b to enter a nitrogen oxide compressor unit to increase the concentration to more than 50%.
The device used in the method for circularly concentrating the dilute nitric acid generated by treating the nitrotoluene waste sulfuric acid comprises a cooler, an automatic separator, a manual separator, a hand turning 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 incoming pipe is connected to an inlet pipeline of a cooler, the upper ends of the cooler, the automatic separator, the manual separator and the rotary hand tank 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 which is communicated with a nitrogen oxide compressor unit; a first nitrotoluene discharge pipe and a second nitrotoluene discharge pipe are respectively arranged above the automatic separator and the manual separator;
the bottom of the nitrogen oxide absorption tower is communicated to a liquid pipeline between the handle tank and the nitrogen oxide compressor unit through an absorption liquid discharge pipe.
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 discharge port of the rotary hand tank is connected with the feed port of the nitrogen oxide compressor unit through liquid pipelines.
Preferably, the device also comprises a control unit, a first densimeter 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 densimeter is connected with the first regulating valve through a DCS control system.
Further, a first 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 first liquid level meter is connected with the first conveying pump through a DCS (distributed control system);
further, be equipped with the second densimeter on the finished product discharge pipe, be equipped with the third governing valve on the nitrogen oxide absorption water pipe of nitrogen oxide absorption tower, the second densimeter passes through DCS control system with the third governing valve and is connected.
Furthermore, a second regulating valve is arranged on the absorption liquid discharge pipe, a second liquid level meter is arranged at the bottom of the nitric oxide absorption tower, and the second regulating valve is connected with the second liquid level meter through a DCS control system.
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 low-concentration dilute nitric acid with the concentration of 15-40% and the concentrated nitric acid with the concentration of 50% are mixed into the dilute nitric acid with the concentration of 37-40%, the density of the dilute nitric acid is ensured to be always higher than that of the nitrotoluene, and the problem that the free nitrotoluene in the dilute nitric acid with the concentration of 15-40% is difficult to separate is solved 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 used in the cyclic concentration method for treating dilute nitric acid generated from nitrotoluene waste sulfuric acid
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-first 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 5.1-fourth gas pipeline 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 A liquid balance pipe 7.4, an absorption liquid discharge pipe 7.5, a tail gas discharge pipe 7.6, a second regulating valve 7.7, a second liquid level meter 7.8 and a third regulating valve.
Detailed Description
The invention is described in further detail below with reference to the figures and the specific embodiments.
As shown in fig. 1, the device used in the cyclic concentration method for treating dilute nitric acid generated from 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. A first nitrotoluene discharge pipe 2.1 and a second nitrotoluene discharge pipe 3.1 are respectively arranged above the automatic separator 2 and the manual separator 3. The bottom of the nitrogen oxide absorption tower 7 is connected to a liquid pipeline between the rotary arm tank 5 and the nitrogen oxide compressor unit 6 through an absorption liquid drain pipe 7.4.
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 first 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 first 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, a third regulating valve 7.8 is arranged on a nitrogen oxide absorption water pipe 7.1 of the nitrogen oxide absorption tower 7, and the second densimeter 16 is connected with the third regulating valve 7.8 through a DCS control system. And a second regulating valve 7.6 is arranged on the absorption liquid drain pipe 7.4, a second liquid level meter 7.7 is arranged at the bottom of the nitrogen oxide absorption tower 7, and the second regulating valve 7.6 is connected with the second liquid level meter 7.7 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, a third gas pipeline 20 arranged at the top end of the manual separator 3, a fourth gas pipeline 5.1 arranged at the top end of the rotary trough 5, the first gas pipeline 18, the second gas pipeline 19, the third gas pipeline 20 and the fourth gas pipeline 5.1 are connected and combined to form a gas pipeline combining section 22, and the gas pipeline combining section 22 and the nitrogen oxide gas discharge pipe 9 are combined to form an inlet gas phase pipe 10 which leads to the nitrogen 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 pipeline merging section 22 is large, the liquid to be fed into the nitrogen oxide compressor unit 6 can be directly fed into the gas pipeline merging section 22, and then fed into the nitrogen oxide compressor unit 6 together with the nitrogen oxide gas through the inlet gas phase pipe 10, so that the absorption liquid discharge pipe 7.4 can also be directly fed into the gas pipeline merging section 22; 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 circulating concentration method for treating the dilute nitric acid generated by the nitrotoluene waste sulfuric acid comprises the following specific steps:
a driving stage:
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 DCS control system uses the density of 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, controls the flow of starting acid in the rotary hand tank 5 by controlling the opening of the first delivery pump 15, and enables the concentration of the starting acid to reach more than 50% after the starting acid and 15% -40% of low-concentration dilute nitric acid are mixed and enter the nitric oxide compressor unit.
The production stage comprises:
a. 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 that the DCS control system takes the density measured by the first densimeter 12 as a signal, the opening of the first adjusting valve 13 is controlled, the flow of the concentrated nitric acid with the mass fraction of more than 50% from the nitric oxide compressor unit 6 is adjusted, the density of the adjusted dilute nitric acid is always larger than that of nitrotoluene, and the dilute nitric acid is a heavy phase.
b. The mixed nitric acid passes through an automatic separator 2 and a manual separator 3 to separate free nitrotoluene, and then automatically flows into a hand transferring tank 5. The nitrotoluene is continuously separated by 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 special discharge pipelines (a first nitrotoluene discharge pipe 2.1 and a second nitrotoluene discharge pipe 3.1) at the tops 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 first liquid level meter 14 as a signal, the opening degree of the first delivery pump 15 is automatically controlled, the delivery flow is adjusted, redundant 37% -40% dilute nitric acid is delivered into the inlet gas phase pipe 10 at the inlet of the nitric oxide compressor 6.1 through the flow meter 15.1, and the concentration is improved to be more than 50% through the nitric oxide compressor unit 6.
c. Carrying out step abc formation on a part of the obtained nitric acid with the concentration of more than 50% and low-concentration dilute nitric acid with the mass fraction of 15% -40% from a waste sulfuric acid treatment denitration condenser to form a cyclic process; the other part is discharged into the finished product tank area.
d. The nitric oxide gas generated by the cooler 1 in the system, the nitric oxide gas generated by the automatic separator 2, the manual separator 3 and the rotary hand tank 5 are combined in a gas pipeline combining section 22, and then combined with the nitric oxide gas generated by the waste sulfuric acid denitration process discharged by the nitric oxide gas discharge pipe 9, and then enter the nitric oxide compressor unit 6 through an inlet gas phase pipe 10 for absorption, the nitric oxide gas which is not absorbed 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, so that 30% low-concentration dilute nitric acid is generated, and the 37% -40% dilute nitric acid with the concentration of 30% in the absorption liquid discharge pipe 7.4, which is conveyed by the first conveying pump 15.1, is mixed with the 30% low-concentration dilute nitric acid in the absorption liquid discharge pipe 7.4 through the flow meter to form; the tail gas reaches the European emission standard and is discharged from a tail gas discharge pipe 7.5 at the top. 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 opening of the third regulating valve 7.8, that is, the water inflow of the nitric oxide absorption water pipe 7.1 (the amount of water absorbed at the top of the nitric oxide absorption tower 7), so that the nitric oxide compressor unit separator 6.2 obtains the stable dilute nitric acid with the concentration of 50% or more.
And e, controlling the flow of the absorption liquid entering the nitrogen oxide compressor unit 6 by using the measured liquid level of a second liquid level meter 7.7 at the bottom of the nitrogen oxide absorption tower 7 as a signal through controlling the opening of a second regulating valve 7.6 by the DCS control system, combining the absorption liquid with the mixed nitric acid in the step b, entering the nitrogen oxide compressor unit, increasing the concentration to be more than 50%, and avoiding flooding the tower.
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 (6)
1. A cyclic concentration method for treating dilute nitric acid generated by nitrotoluene waste sulfuric acid is characterized by comprising the following steps:
a driving stage:
cooling and cooling the low-concentration dilute nitric acid with the mass fraction of 15-40% from the waste sulfuric acid treatment denitration condenser, separating free nitrotoluene by gravity settling, and controlling the flow of the nitric acid with the concentration of 50% as starting acid to ensure that the concentration of the starting acid and the low-concentration dilute nitric acid with the mass fraction of 15-40% are mixed and enter a nitrogen oxide compressor unit and then reaches more than 50%;
the production stage comprises:
a. cooling the low-concentration dilute nitric acid with the mass fraction of 15-40% from the waste sulfuric acid treatment denitration condenser, and controlling the flow of the nitric acid with the mass fraction of more than 50% from a nitrogen oxide compressor unit to enable the nitric acid to be mixed with the low-concentration dilute nitric acid with the mass fraction of 15-40% and enable the density to be larger than that of nitrotoluene;
b. separating free nitrotoluene in the mixed nitric acid by gravity settling, and increasing the concentration of the mixed nitric acid with the separated nitrotoluene to more than 50% by using the nitrogen oxide compressor unit;
c. carrying out step abc formation on part of the obtained nitric acid with the concentration of more than 50% and low-concentration dilute nitric acid with the mass fraction of 15% -40% from a waste sulfuric acid treatment denitration condenser to form a cyclic process; the other part is discharged to enter a finished product tank area;
d. 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, and then absorbing and discharging the nitrogen oxide gas by a nitrogen oxide absorption tower;
e. and c, combining the absorption liquid at the bottom of the absorption tower with the mixed nitric acid in the step b, and feeding the combined nitric acid into a nitrogen oxide compressor unit to increase the concentration to more than 50%.
2. The cyclic concentration method for treating dilute nitric acid generated from nitrotoluene waste sulfuric acid as claimed in claim 1, wherein: and c, the mixed nitric acid with the nitrotoluene separated in the step b enters the nitric oxide compressor unit through the hand turning groove, and the flow of the mixed nitric acid entering the nitric oxide compressor unit is controlled through the liquid level in the hand turning groove.
3. The cyclic concentration method for treating dilute nitric acid generated from nitrotoluene waste sulfuric acid as claimed in claim 1, wherein: and d, combining the nitrogen oxide gas obtained in the cooling process in the step a and the separation process in the step b, 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 cyclic concentration method for treating dilute nitric acid generated from nitrotoluene waste sulfuric acid as claimed in claim 1, wherein: and d, controlling the water inflow at the upper end in the absorption tower through the density of the concentrated nitric acid at the outlet of the nitrogen oxide compressor unit.
5. The cyclic concentration method for treating dilute nitric acid generated from nitrotoluene waste sulfuric acid as claimed in claim 1, wherein: and d, controlling the flow of the absorption liquid entering the nitrogen oxide compressor unit through the liquid level at the bottom of the absorption tower.
6. The cyclic concentration method for treating dilute nitric acid generated from nitrotoluene waste sulfuric acid as claimed in claim 1, which comprises the following steps:
a driving stage:
cooling and cooling the low-concentration dilute nitric acid with the mass fraction of 15-40% from the waste sulfuric acid treatment denitration condenser, separating free nitrotoluene by gravity settling, controlling the flow of the nitric acid with the concentration of 50% serving as starting acid in a self-rotating hand tank, and enabling the starting acid and the low-concentration dilute nitric acid with the mass fraction of 15-40% to be mixed and enter a nitrogen oxide compressor unit, wherein the concentration of the nitric acid reaches more than 50%;
the production stage comprises:
a. cooling the low-concentration dilute nitric acid with the mass fraction of 15-40% from the waste sulfuric acid treatment denitration condenser, and controlling the flow of the concentrated nitric acid with the mass fraction of more than 50% from a nitrogen oxide compressor unit to enable the concentrated nitric acid to be mixed with the low-concentration dilute nitric acid with the mass fraction of 15-40% and enable the density to be larger than that of nitrotoluene;
b. separating free nitrotoluene from the mixed nitric acid by an automatic separator and a manual separator in sequence, introducing the mixed nitric acid after the nitrotoluene is separated into the nitric oxide compressor unit through a hand-turning tank, and increasing the concentration to more than 50%, wherein the flow of the mixed nitric acid entering the nitric oxide compressor unit is controlled by the liquid level in the hand-turning tank;
c. carrying out step abc formation circulation process on part of the obtained nitric acid with the concentration of more than 50% and low-concentration dilute nitric acid with the mass fraction of 15% -40% from a waste sulfuric acid treatment denitration condenser; the other part is discharged to enter a finished product tank area;
d. combining the nitrogen oxide gas generated by the cooler in the system with the nitrogen oxide gas generated by the automatic separator, the manual separator and the hand-turning tank, combining the combined nitrogen oxide gas with the nitrogen oxide gas generated by the waste sulfuric acid denitration process, absorbing the combined nitrogen oxide gas by the nitrogen oxide compressor unit, and absorbing the combined nitrogen oxide gas by the nitrogen oxide absorption tower to be discharged; controlling the water inflow at the upper end in the absorption tower through the density of the concentrated nitric acid at the outlet of the nitric oxide compressor unit;
e. and b, controlling the flow of the absorption liquid through the liquid level of the absorption liquid at the bottom of the absorption tower, and combining the absorption liquid with the mixed nitric acid in the step b to enter a nitrogen oxide compressor unit to increase the concentration to more than 50%.
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| 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 |
| CN105366653A (en) * | 2014-08-25 | 2016-03-02 | 蒋小华 | Nitric acid production technology with double-pressurized method |
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| 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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