Gas phase passageway nitro compound treatment device and method for poly-nitrotoluene spent sulfuric acid vacuum concentration device

Abstract

The application discloses a device and method for treating nitro compounds in a gas phase channel of a vacuum concentration device for waste sulfuric acid of polynitrotoluene, wherein the device is supplemented with o-nitrotoluene in the three-stage and four-stage condensers to reduce the freezing point of the acid vapor feed; and the heavy phase containing o-nitrotoluene separated by the three-stage and four-stage condensers is supplemented to the two-stage condenser to reduce the freezing point of the acid vapor feed of the two-stage condenser, thereby solving the problem of nitro compound accumulation in the existing treatment system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical technology, in particular to a gas phase channel nitro compound treatment device and method for a multi-nitrotoluene waste sulfuric acid vacuum concentration device. BACKGROUND

[0002] The vacuum concentration device is used for waste acid sulfuric acid treatment. In the gas phase pipeline of the multi-nitrotoluene waste sulfuric acid treatment vacuum concentration device, nitro compounds are accumulated and accumulated. In the existing vacuum concentration technical route, the mainstream technology is as follows:

[0003] 1) MNT is sprayed into the condenser to reduce the freezing point of the nitro compound and prevent the accumulation and accumulation of the nitro compound in the second, third and fourth stages of the condenser;

[0004] 2) The stripping technology is used to strip DNT in the second stage, and the second stage condenser is cooled by about 53 DEG C warm water to prevent the accumulation and accumulation of the nitro compound in the second stage condenser. This technology believes that the nitro compound does not appear in the third and fourth stages of the condenser.

[0005] The above two technologies can only prevent the accumulation and accumulation of the nitro compound in the condenser equipment, but cannot eliminate the accumulated and accumulated nitro compound in the gas phase channel.

[0006] The existing multi-nitrotoluene vacuum concentration device: the company uses a set of two-stage stripping DNT, and the second stage condenser is cooled by about 53 DEG C warm water to accumulate and accumulate the waste sulfuric acid vacuum concentration device for processing special multi-nitrotoluene waste acid. The special multi-nitrotoluene waste acid contains mononitrotoluene (MNT), dinitrotoluene (DNT) and multi-nitrotoluene.

[0007] Problems:

[0008] (1) The stripping effect of the stripping tower on the multi-nitro compound with high freezing point is poor. The high freezing point nitro compound continues to be stripped under the condition of high vacuum in the third and fourth stages, resulting in the blocking of the third and fourth stages of the condenser and the accumulation of the nitro compound in the related gas phase pipeline;

[0009] (2) The vacuum pump system providing stripping vacuum has nitro compound accumulation;

[0010] (3) The second stage gas phase pipeline, i.e. the condenser, also has nitro compound accumulation.

[0011] Therefore, it is necessary to design a gas phase channel nitro compound treatment device and method for a vacuum concentration device to solve the problem of nitro compound accumulation in the existing treatment system. SUMMARY

[0012] The application provides a device and method for treating nitro compounds in a gas phase channel of a vacuum concentration device of a waste sulfuric acid of a multi-nitrotoluene, which is used for solving the problem of nitro compound accumulation in the existing treatment system.

[0013] To achieve the above-mentioned object, the application has the following solutions:

[0014] In one aspect of the application, a device for treating nitro compounds in a gas phase channel of a vacuum concentration device is provided, which comprises a first treatment unit, a second treatment unit and a third treatment unit connected in series, wherein:

[0015] The first treatment unit comprises a condenser one, and an acid vapor pipe one and an acid liquid pipe one are respectively arranged at the inlet end and the outlet end of the condenser one; the acid vapor pipe one is connected to a second section of a gas phase channel of the vacuum concentration device, and the acid liquid pipe one is connected to a liquid phase separation unit one and a gas phase recovery unit one; the liquid phase separation unit one is used for separating water and nitro compounds, and the gas phase recovery unit one is used for recovering non-condensable gases and condensing them into the liquid phase separation unit one.

[0016] The second treatment unit comprises a condenser two, and an acid vapor pipe two, an MNT feeding pipe one and an acid liquid pipe two are respectively arranged at the inlet end and the outlet end of the condenser two; the acid vapor pipe two is connected to a third section of a gas phase channel of the vacuum concentration device, and the acid liquid pipe two is connected to a liquid phase separation unit two and a gas phase recovery unit two; the liquid phase separation unit two is connected to the acid vapor pipe one and used for separating and recovering nitro compounds; and the outlet end of the gas phase recovery unit two is connected to the acid vapor pipe one.

[0017] The third treatment unit comprises a condenser three, and an acid vapor pipe three, an MNT feeding pipe two and an acid liquid pipe three are respectively arranged at the inlet end and the outlet end of the condenser three; the acid vapor pipe three is connected to a fourth section of a gas phase channel of the vacuum concentration device, and the acid liquid pipe three is connected to a liquid phase separation unit three and a gas phase recovery unit three; the liquid phase separation unit three is connected to the acid vapor pipe one and used for separating and recovering nitro compounds; and the outlet end of the gas phase recovery unit three is connected to the acid vapor pipe two.

[0018] Further, the gas phase recovery unit one, the gas phase recovery unit two and the gas phase recovery unit three are respectively provided with a hot water pipe at the gas phase inlet end and / or the gas phase outlet end.

[0019] Preferably, the gas phase recovery unit one comprises a liquid ring vacuum pump and a vacuum pump separator connected in series, and the vacuum pump separator is used for separating gas phase and liquid phase; the inlet end of the liquid ring vacuum pump is connected to the acid liquid pipe one, and the liquid phase outlet end of the vacuum pump separator is connected to the liquid phase separation unit one; and the inlet end and the outlet end of the liquid ring vacuum pump are respectively provided with a hot water pipe.

[0020] Preferably, the gas phase recovery unit two comprises a steam jet pump one; and / or, the gas phase recovery unit three comprises a steam jet pump two.

[0021] Further, the liquid phase separation unit one includes a communicating liquid-liquid separator one, the upper part of the liquid-liquid separator one is provided with a drain pipe one, and the lower part is communicated with a collection tank.

[0022] Further, the acid liquid pipe two and the acid liquid pipe three are respectively communicated with the liquid-liquid separator two, and the heavy phase outlet end of the liquid-liquid separator two is communicated with the acid vapor pipe one.

[0023] Further, the medium output end of the condenser one is provided with a temperature transmitter; and / or, the acid vapor pipe one is provided with a pressure transmitter.

[0024] In another aspect of the present application, a treatment method for nitro compounds in a gas phase channel of a vacuum concentration device is provided, and the steps include:

[0025] The second section acid vapor of the vacuum concentration device is condensed by the acid vapor pipe one through the condenser one, and then the condensed liquid phase one and the non-condensed gas phase one are collected, the non-condensed gas phase one is condensed again to separate the acid condensate and the condensed liquid phase one, and then the acid condensate and the condensed liquid phase one are combined for liquid-liquid separation; the pressure value in the acid vapor pipe one is controlled to be 37-38 KPa, and the outlet temperature of the condenser one is controlled to be 53-55℃;

[0026] The third section acid vapor of the vacuum concentration device is condensed by the acid vapor pipe two through the condenser two, and then the condensed liquid phase two and the non-condensed gas phase two are collected, and the non-condensed gas phase two is recycled into the acid vapor pipe one for further treatment;

[0027] The fourth section acid vapor of the vacuum concentration device is condensed by the acid vapor pipe three through the condenser three, and then the condensed liquid phase three and the non-condensed gas phase three are collected, and the non-condensed gas phase three is recycled into the acid vapor pipe two for further treatment;

[0028] The acid vapor pipe two and the acid vapor pipe three are respectively communicated with o-nitrotoluene; the condensed liquid phase two and / or the condensed liquid phase three are recycled to the acid vapor pipe one after being separated by liquid-liquid separation.

[0029] Further, the condensed liquid phase one and the non-condensed gas phase one are separated by a pipeline; the non-condensed gas phase one is condensed and separated by a liquid ring vacuum pump and a vacuum pump separator in series to obtain a non-condensed gas liquid phase; the pressure in the acid vapor pipe one is adjusted by the liquid ring vacuum pump; the non-condensed gas phase two and the non-condensed gas phase three are respectively recycled by a steam jet pump one and a steam jet pump two.

[0030] Preferably, when the vacuum concentration device is stopped, the pressure value in the acid vapor pipe one is controlled to be 38-40 KPa, and hot water at 80-85℃ is supplemented to the inlet end and / or the outlet end of the following elements: the liquid ring vacuum pump, the steam jet pump one, and the steam jet pump two.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] The nitro compound treatment device provided by the present application can reduce the freezing point of the acid steam feed by supplementing o-nitrotoluene into the three-stage and four-stage condensers; and can reduce the freezing point of the second-stage acid steam feed by supplementing the heavy phase containing o-nitrotoluene obtained through the three-stage and four-stage separation to the second-stage condenser, thereby ensuring safety; and can improve the recovery rate and separation purity of the nitro compound by recycling the non-condensable gas phase obtained through the three-stage and four-stage condensation to the front-stage condenser and recycling the heavy phase obtained through the three-stage and four-stage separation to the second-stage condenser.

[0033] The o-nitrotoluene used in the treatment method is a commonly used chemical raw material and is easy to obtain. After being mixed with polynitrotoluene, the o-nitrotoluene can still be used as a raw material for producing polynitrotoluene. The process does not waste and can be reused. In addition, during the shutdown stage, the equipment and pipelines can be flushed with simple and readily available hot water at 80-85°C to avoid the accumulation of nitro compounds, which is simple, easy to implement and low in cost. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The nitro compound treatment device for the gas phase channel of the polynitrotoluene waste sulfuric acid vacuum concentration device according to the present application is shown in the figure.

[0035] In the figure: C1, condenser one; C2, condenser two; C3, condenser three; LP1, liquid ring vacuum pump; M1, pressure transmitter; P1, delivery pump one; P2, delivery pump two; P3, delivery pump three; S1, liquid-liquid separator one; S2, liquid-liquid separator two; T1, temperature transmitter; V1, collection tank; VP1, steam jet pump one; VP2, steam jet pump two; VS1, vacuum pump separator; 11, acid steam pipe one; 12, acid liquid pipe one; 13, gas phase pipe one; 14, acid liquid return pipe; 15, drain pipe one; 21, acid steam pipe two; 22, acid liquid pipe two; 23, MNT feed pipe one; 24, gas phase pipe two; 25, gas phase circulation pipe one; 26, nitro compound delivery pipe; 27, drain pipe two; 31, acid steam pipe three; 32, acid liquid pipe three; 33, MNT feed pipe two; 34, gas phase pipe three; 35, gas phase circulation pipe two. 101, hot water pipe one; 102, hot water pipe two; 201, hot water pipe three; 202, hot water pipe four; 301, hot water pipe five; 302, hot water pipe six. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0037] It should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", "left", "right", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0038] It should also be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing", "setting" and the like should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two components or the interaction relationship between two components. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0039] Related physical and chemical properties: the freezing point of o-nitrotoluene is -9℃, the freezing point of dinitrotoluene (DNT) is 65.5-70.5℃, and the freezing point of polynitrotoluene such as trinitrotoluene (TNT) is 80.9℃. The freezing point of the mixture of o-nitrotoluene and mixed nitro compounds can be reduced to below 5℃, so it is in a liquid state at room temperature.

[0040] In one embodiment, as shown in Figure 1 A gas phase channel nitro compound treatment device for a polynitrotoluene waste sulfuric acid vacuum concentration device is proposed, which comprises a condenser C1, a condenser C2, and a condenser C3; wherein:

[0041] The acid vapor pipe one 11 is arranged at the inlet end of the condenser C1, which is used for feeding the acid vapor of the second section of the polynitrotoluene waste sulfuric acid vacuum concentration device, and the acid liquid pipe one 12 is arranged at the outlet end of the condenser C1, which is connected with the liquid-liquid separator S1. The acid liquid pipe one 12 is connected with the liquid ring vacuum pump LP1 through the branch gas phase pipe one 13, and the liquid ring vacuum pump LP1 is further connected with the vacuum pump separator VS1. The liquid phase outlet end of the vacuum pump separator VS1 is provided with the acid liquid reflux pipe 14, which is further connected with the liquid-liquid separator S1. The upper part of the liquid-liquid separator S1 is provided with the drain pipe one 15 for separating the upper layer of acid wastewater, and the lower part is further connected with the collection tank V1, which is connected with the delivery pump P1. The temperature transmitter T1 is arranged at the cooling medium outlet end of the condenser C1, which is used for monitoring the outlet temperature to control the condensation temperature. The acid vapor pipe one 11 is provided with the pressure transmitter M1, which is used for monitoring the pressure provided by the liquid ring vacuum pump LP1 to the vacuum concentration device;

[0042] The condenser two C2 is provided with an acid vapor pipe two 21 at the feeding end for feeding the third-stage acid vapor of the multi-nitro-toluene waste sulfuric acid vacuum concentration device; the acid vapor pipe two 21 is connected with an MNT feeding pipe one 23 for supplementing the ortho-nitrotoluene to reduce the freezing point of the mixed material. The condenser two C2 is provided with an acid liquid pipe two 22 at the discharging end for connecting a liquid-liquid separator two S2. The acid liquid pipe two 22 is provided with a branch gas phase pipe two 24 for collecting the non-condensed gas phase; the gas phase pipe two 24 is further connected to the acid vapor pipe one 11 through a vapor jet pump one VP1 to form a gas phase circulation pipe one 25 for recycling the non-condensed gas phase. The acid liquid pipe two 22 is connected to the left end of the liquid-liquid separator two S2; the liquid-liquid separator two S2 is provided with a vertical partition plate at the right end for intercepting the heavy phase nitro compound to separate the upper layer acid wastewater to the right side; the left side of the liquid-liquid separator two S2 is provided with a conveying pump two P2 connected to the acid vapor pipe one 11 through a nitro compound conveying pipe 26; the right side of the liquid-liquid separator two S2 is provided with a conveying pump three P3 connected to the outside through a drainage pipe two 27 to discharge the acid wastewater.

[0043] The condenser three C3 is provided with an acid vapor pipe three 31 at the feeding end for feeding the fourth-stage acid vapor of the multi-nitro-toluene waste sulfuric acid vacuum concentration device; the acid vapor pipe three 31 is connected with an MNT feeding pipe two 33 for supplementing the ortho-nitrotoluene to reduce the freezing point of the mixed material. The condenser three C3 is provided with an acid liquid pipe three 32 at the discharging end for connecting the left side of the liquid-liquid separator two S2. The acid liquid pipe three 32 is provided with a branch gas phase pipe three 34 for collecting the non-condensed gas phase; the gas phase pipe three 34 is further connected to the acid vapor pipe one 11 through a vapor jet pump two VP2 to form a gas phase circulation pipe two 35.

[0044] In the above embodiment, the above nitro compound treatment device can reduce the freezing point of the acid vapor feeding by supplementing the ortho-nitrotoluene to the condenser two C2 and the condenser three C3; the freezing point of the second-stage acid vapor feeding can be reduced by supplementing the heavy components containing the ortho-nitrotoluene separated by the third-stage and the fourth-stage to the condenser two C2, thereby ensuring the safety; the recycling rate of the nitro compound and the separation purity can be improved by recycling the non-condensed gas phase obtained by the third-stage and the fourth-stage condensation to the former-stage condenser and recycling the heavy phase obtained by the third-stage and the fourth-stage separation to the second-stage.

[0045] In the above embodiment, the vacuum concentration device in the field includes a concentration unit for recycling sulfuric acid and four stripping units for the acid separation containing multi-nitro compounds. The second-stage acid vapor comes from the gas phase produced by the second-stage stripping unit; the third-stage acid vapor comes from the gas phase produced by the third-stage stripping unit; and the fourth-stage acid vapor comes from the gas phase produced by the fourth-stage stripping unit.

[0046] In the preferred embodiment, in order to avoid the accumulation of non-condensed gas phase in the gas phase treatment process in the equipment and pipelines, hot water pipe one 101 is arranged at the position of gas phase pipe one 13 near the liquid ring vacuum pump LP1, and hot water pipe two 102 is arranged between the liquid ring vacuum pump LP1 and the vacuum pump separator VS1; hot water pipe three 201 is arranged at the position of gas phase pipe two 24 near the steam jet pump one VP1, and hot water pipe four 202 is arranged at the discharge end of the steam jet pump one VP1; hot water pipe five 301 is arranged at the position of gas phase pipe three 34 near the steam jet pump two VP2, and hot water pipe six 302 is arranged at the discharge end of the steam jet pump two VP2.

[0047] In the above embodiment, the liquid-liquid separator one S1 and the liquid-liquid separator two S2 are common phase separation equipment in the art for separating light components and heavy components, including but not limited to the type shown in the specific liquid-liquid separator two S2. The steam jet pump one VP1 and the steam jet pump two VP2 are common steam jet pumps in the art for recovering non-condensed gas phase by negative pressure suction. The vacuum pump separator VS1 is a common separator in the art for separating liquid components such as oil and water.

[0048] In the above embodiment, the equipment material is a corrosion-resistant material that can be selected in the art, such as the common steel glass / carbonized silicon material selected for heat exchangers. The treatment device further includes control valves arranged on each pipeline, which are not described herein.

[0049] In another embodiment, a method for treating nitro compounds in the gas phase channel of a vacuum concentration device for waste sulfuric acid of polynitrotoluene is provided, which is specifically as follows:

[0050] a) When the vacuum concentration device for waste sulfuric acid of polynitrotoluene is running:

[0051] The second-stage acidic steam of the vacuum concentration device is condensed by the condenser one C1 through the acidic steam pipe one 11, and the condensed liquid phase one and the non-condensed gas phase one are collected, respectively. The non-condensed gas phase one enters the liquid ring vacuum pump LP1 and is separated by the vacuum pump separator VS1 to obtain acidic condensate and condensed liquid phase one, which are combined and subjected to liquid-liquid separation in the liquid-liquid separator one S1. The heavy phase nitro compound enters the collection tank V1 and is sent to the next process by the delivery pump one P1. The pressure value in the acidic steam pipe one 11 is controlled to be 37-38 KPa, and the outlet temperature of the condenser one C1 is controlled to be 53-55°C.

[0052] The third-stage acidic steam of the vacuum concentration device is mixed with o-nitrotoluene supplied by the acidic steam pipe two 21 and the MNT feed pipe one 23, and is condensed by the condenser two C2. The condensed liquid phase two and the non-condensed gas phase two are collected, respectively. The non-condensed gas phase two is recovered by the steam jet pump one VP1 and then enters the acidic steam pipe one 11 for further treatment.

[0053] The acidic steam in the vacuum concentration device is mixed with the o-nitrotoluene supplemented by the acidic steam pipe three 31 and the MNT feed pipe two 33, condensed by the condenser three C3, and then collected as the condensed liquid phase three and the non-condensed gas phase three. The non-condensed gas phase three is recovered by the steam jet pump two VP2 and then enters the acidic steam pipe two 21 for further treatment.

[0054] The condensed liquid phase two and the condensed liquid phase three are combined into the liquid-liquid separator two S2, recovered by liquid-liquid separation, and then transported to the acidic steam pipe one 11 by the nitro compound delivery pipe 26. The upper layer of acidic wastewater is transported to the next process by the drain pipe two 27.

[0055] b) When the vacuum concentration device for waste sulfuric acid of polynitrotoluene is stopped:

[0056] The acidic hot steam at about 76-80°C enters the condenser one C1 through the acidic steam pipe one 11. The liquid ring vacuum pump LP1 is running, the value of the pressure transmitter M1 is maintained at 38-40 KPa, and the value of the temperature transmitter T1 is maintained at 53-55°C to ensure that the nitro compounds in the condenser one C1 do not solidify.

[0057] Start the hot water pipe four 202 and the hot water pipe six 302. Hot water at 80-85°C enters the gas phase circulation pipe one 25 and the gas phase circulation pipe two 35, respectively. The delivery pump two P2 is working normally to transport the heavy components containing o-nitrotoluene collected by the liquid-liquid separator two S2 to the acidic steam pipe one 11 and then to the condenser one C1.

[0058] Stop the acidic steam pipe one 11 from entering hot steam, and stop the liquid ring vacuum pump LP1. Start the hot water pipe three 201 and the hot water pipe five 301. Hot water at 80-85°C enters the gas phase pipe two 24 and the gas phase pipe three 34, respectively, to flush the steam jet pump one VP1 and the steam jet pump two VP2. Start the hot water pipe one 101 and the hot water pipe two 102. Hot water at 80-85°C enters the liquid ring vacuum pump LP1 and the vacuum pump separator VS1, respectively, to clean the pipeline and the vacuum pump separator VS1, the liquid ring vacuum pump LP1, and then enters the liquid-liquid separator one S1.

[0059] In the above embodiment, the treatment method supplements o-nitrotoluene to the condenser two C2 and the condenser three C3 to reduce the freezing point and eliminate accumulated nitrotoluene. The condenser one C1 can use hot water or mixed liquid containing o-nitrotoluene from the liquid-liquid separator two S2 to eliminate accumulated nitro compounds. When the vacuum concentration device is stopped, first, keep the liquid ring vacuum pump LP1 running, and use hot water at 80-85°C to eliminate the accumulation of nitro compounds in the gas phase circulation pipe one 25 and the gas phase circulation pipe two 35. Then, stop the liquid ring vacuum pump, and use hot water at 80-85°C to eliminate the accumulation of nitro compounds in the liquid ring vacuum pump LP1, the vacuum pump separator VS1, and the related gas phase channels.

[0060] In the above-mentioned embodiments, o-nitrotoluene is a commonly used chemical raw material and is easy to obtain. After o-nitrotoluene is mixed with polynitrotoluene, it can still be used as a raw material for producing polynitrotoluene. The process does not waste and can be reused.

[0061] In the preferred embodiments, the content of o-nitrotoluene in the heavy phase in the liquid-liquid separator two S2 can be controlled to be not less than 20% by controlling the o-nitrotoluene feed amount of the MNT feed pipe one 23 and the MNT feed pipe two 33, thereby ensuring that the mixture of the recovered and the two-stage acidic steam is in a liquid state at the condensation temperature.

[0062] Based on the above-mentioned treatment method, the device can be continuously operated by setting an automatic control, which is easy to operate and can effectively remove the accumulated nitrotoluene in the gas phase channel of the vacuum concentration device; eliminate the blockage problem of the pipeline and equipment of the vacuum concentration device, make the production process more continuous and reliable, reduce the number of start-up and shutdown, reduce the production cost, and greatly reduce the inventory of nitro compounds in the vacuum concentration device, thereby reducing the safety risk.

[0063] Although embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A nitro compound treatment apparatus for treating a gaseous phase passage nitro compound of a multi-nitro toluene waste sulfuric acid vacuum concentration apparatus; characterized by, The first processing unit, the second processing unit and the third processing unit are connected; wherein: The first processing unit comprises a condenser one (C1), and the feeding end and the discharging end of the condenser one (C1) are respectively provided with an acid vapor pipe one (11) and an acid liquid pipe one (12); the acid vapor pipe one (11) is connected with a gas phase channel of a second vacuum concentration device, and the acid liquid pipe one (12) is connected with a liquid phase separation unit one and a gas phase recovery unit one; the liquid phase separation unit one is used for separating water and nitro compounds, and the gas phase recovery unit one is used for recovering non-condensable gases and condensing to the liquid phase separation unit one; The second processing unit comprises a condenser two (C2), and the feeding end of the condenser two (C2) is provided with an acid vapor pipe two (21) for feeding acid vapor of a third vacuum concentration device; the acid vapor pipe two (21) is connected with an MNT feeding pipe one (23) for supplementing ortho-nitrotoluene to reduce the freezing point of the mixture; the discharging end of the condenser two (C2) is provided with an acid liquid pipe two (22); the acid vapor pipe two (21) is connected with a gas phase channel of the third vacuum concentration device, and the acid liquid pipe two (22) is connected with a liquid phase separation unit two and a gas phase recovery unit two; the liquid phase separation unit two is connected with the acid vapor pipe one (11) and is used for separating and recovering nitro compounds; the discharging end of the gas phase recovery unit two is connected with the acid vapor pipe one (11); The third processing unit comprises a condenser three (C3), and the feeding end of the condenser three (C3) is provided with an acid vapor pipe three (31) for feeding acid vapor of a fourth vacuum concentration device; the acid vapor pipe three (31) is connected with an MNT feeding pipe two (33) for supplementing ortho-nitrotoluene to reduce the freezing point of the mixture, and the discharging end of the condenser three (C3) is provided with an acid liquid pipe three (32); the acid vapor pipe three (31) is connected with a gas phase channel of the fourth vacuum concentration device, and the acid liquid pipe three (32) is connected with a liquid phase separation unit three and a gas phase recovery unit three; the liquid phase separation unit three is connected with the acid vapor pipe one (11) and is used for separating and recovering nitro compounds; the discharging end of the gas phase recovery unit three is connected with the acid vapor pipe two (21).

2. The apparatus of claim 1, wherein, The gas phase recovery unit one, the gas phase recovery unit two and the gas phase recovery unit three are respectively independently provided with a hot water pipe at the gas phase feeding end and / or the gas phase discharging end.

3. The apparatus of claim 2, wherein, The gas phase recovery unit one comprises a liquid ring vacuum pump (LP1) and a vacuum pump separator (VS1) connected with each other, and the vacuum pump separator (VS1) is used for separating gas phase and liquid phase; the feeding end of the liquid ring vacuum pump (LP1) is connected with the acid liquid pipe one (12), and the liquid phase discharging end of the vacuum pump separator (VS1) is connected with the liquid phase separation unit one; the feeding end and the discharging end of the liquid ring vacuum pump (LP1) are respectively provided with a hot water pipe.

4. The apparatus of claim 2, wherein, The gas phase recovery unit two comprises a steam jet pump one (VP1), and / or the gas phase recovery unit three comprises a steam jet pump two (VP2).

5. The apparatus of claim 1, wherein, The liquid phase separation unit one comprises a liquid-liquid separator one (S1) connected with a collecting tank (V1); and the upper part of the liquid-liquid separator one (S1) is provided with a water drainage pipe one (15).

6. The apparatus of claim 1, wherein, The acid liquid pipe two (22) and the acid liquid pipe three (32) are communicated with the liquid-liquid separator two (S2) respectively, and the heavy phase outlet end of the liquid-liquid separator two (S2) is communicated with the acid vapor pipe one (11).

7. The apparatus of claim 1, wherein, The medium output end of the condenser one (C1) is provided with a temperature transmitter (T1); and / or, the acid vapor pipe one (11) is provided with a pressure transmitter (M1).

8. A method of treating gaseous phase nitro compounds from a gas phase passageway of a poly-nitrotoluene spent sulfuric acid vacuum concentration apparatus, characterized by the steps of The method comprises the following steps: The acid vapor in the third section of the vacuum concentration device is condensed by the acid vapor pipe three (31) and the condenser three (C3), and condensed liquid phase three and non-condensable gas phase three are collected respectively, and the non-condensable gas phase three is recycled and further treated in the acid vapor pipe two (21); The acid vapor in the third section of the vacuum concentration device is condensed by the acid vapor pipe three (31) and the condenser three (C3), and condensed liquid phase three and non-condensable gas phase three are collected respectively, and the non-condensable gas phase three is recycled and further treated in the acid vapor pipe two (21); The acid vapor pipe two (21) and the acid vapor pipe three (31) are respectively connected with o-nitrotoluene; The condensed liquid phase two and / or the condensed liquid phase three are recycled to the acid vapor pipe one (11) after being separated by liquid-liquid separation. The condensed liquid phase one and the non-condensable gas phase one are separated by a pipeline; the non-condensable gas phase one is condensed and separated by a liquid ring vacuum pump (LP1) and a vacuum pump separator (VS1) in series to obtain a non-condensable gas liquid phase; the pressure in the acid vapor pipe one (11) is adjusted by the liquid ring vacuum pump (LP1); the non-condensable gas phase two and the non-condensable gas phase three are recycled by a steam jet pump one (VP1) and a steam jet pump two (VP2) respectively.

9. The treatment method according to claim 8, characterized in that, When the vacuum concentration device is shut down, the pressure in the acid vapor pipe one (11) is controlled to be 38-40 KPa, and hot water at 80-85 ℃ is supplied to the inlet end and / or the outlet end of the following elements: the liquid ring vacuum pump (LP1), the steam jet pump one (VP1), and the steam jet pump two (VP2).

10. The processing method according to claim 9, wherein, ​

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