Solvent recovery tail gas re-concentration recovery system and method

Abstract

The application discloses a solvent recovery tail gas re-concentration recovery system and method, which comprises the following steps: adsorbing VOCs in gas through a plurality of parallelly arranged active carbon adsorbers, and then adsorbing the remaining VOCs in the gas through a zeolite rotary device; when one active carbon adsorber meets the regeneration condition, the regeneration process is implemented on the one active carbon adsorber, and at least one of the plurality of active carbon adsorbers is in the regeneration process; compared with a single-system nitrogen regeneration system, the application can save heating and cooling energy consumption, has a higher cooling temperature and higher system efficiency; compared with a single-system vacuum regeneration system, the application can be applied to solvent recovery of the printing industry.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of recovery systems, in particular to a solvent recovery tail gas re-concentration recovery system and a solvent recovery tail gas re-concentration recovery method. BACKGROUND

[0002] China is a large country of packaging printing, with numerous enterprises. According to statistics, there are more than 40,000 packaging printing enterprises in China, with a total output value of more than 400 billion yuan. These enterprises use a large amount of volatile organic solvents as diluents, including toluene, ethyl acetate, butanone, isopropyl alcohol, etc. They are all volatilized into organic waste gas during the drying process of finished products. Therefore, the packaging printing industry has become one of the key monitoring industries of VOCs (volatile organic compounds) emission, and how to control packaging printing VOCs has become a key problem for many soft packaging printing enterprises.

[0003] At present, the technologies for VOCs recovery in the domestic soft packaging market mainly include catalytic combustion method and adsorption recovery technology. The former is to concentrate and catalytically combust organic waste gas, so that the organic matter in the waste gas is changed into carbon dioxide and water before being discharged. The heat energy after combustion can be utilized. However, the catalytic combustion method has certain disadvantages. A large amount of carbon dioxide produced after combustion will aggravate the "greenhouse effect", and high-temperature nitrogen oxides and other dangerous gases are also easy to cause secondary pollution to the environment.

[0004] The adsorption recovery technology can solve the problem of organic waste gas emission polluting the environment, and can also recycle the recovered organic solvents, thereby saving a large amount of organic solvent procurement funds for soft packaging enterprises and truly realizing the win-win of social and economic benefits.

[0005] However, the waste gas emission of some soft package printing VOCs recovery equipment cannot meet the emission requirements of the relevant standards, that is, the VOCs of some soft package printing cannot meet the emission requirements after being treated by a single adsorption recovery technology. In this way, the soft package printing enterprises need a composite technology to treat VOCs, which can not only recycle organic solvents for recycling, but also make the waste gas emission meet the emission requirements of the relevant standards. SUMMARY

[0006] Therefore, the present application provides a composite treatment technology and a treatment device thereof, which has high organic solvent recovery efficiency, low running cost and waste gas emission up to standard. The composite treatment technology can well solve the problems encountered by soft package printing enterprises, ensure a safe and reliable production environment for soft package printing enterprises, reduce the consumption of raw materials of enterprises, improve the production efficiency of enterprises, and reduce the running cost of environmental protection.

[0007] The technical solutions adopted by the present application are as follows:

[0008] A solvent recovery tail gas re-concentration recovery system is used for treating waste gas, wherein the system comprises:

[0009] A solvent recovery device comprises a plurality of activated carbon adsorbers arranged in parallel, and the solvent recovery device is provided with a solvent recovery device air inlet pipe and a solvent recovery device common air outlet pipe;

[0010] A zeolite runner device;

[0011] An adsorption treatment system pipeline is connected to the solvent recovery device common air outlet pipe, sequentially passes through the zeolite runner device, an adsorption treatment fan, and is connected to an exhaust cylinder;

[0012] A concentration treatment system pipeline is connected to the solvent recovery device common air outlet pipe, sequentially passes through the zeolite runner device, a heat exchanger, the zeolite runner device, a concentration fan, and is connected to the solvent recovery device air inlet pipe.

[0013] A solvent recovery tail gas re-concentration recovery method, wherein the above-mentioned solvent recovery tail gas re-concentration recovery system is used, and the method comprises:

[0014] VOCs in the gas are adsorbed by a plurality of activated carbon adsorbers arranged in parallel, and the remaining VOCs in the gas are adsorbed by the zeolite runner device;

[0015] When one of the activated carbon adsorbers meets the regeneration condition, a regeneration process is performed on the one activated carbon adsorber, and at least one of the plurality of activated carbon adsorbers is performing a regeneration process;

[0016] The regeneration process comprises:

[0017] Oxygen is removed from the activated carbon adsorber by nitrogen, and a nitrogen heated gas stream is used for desorption recovery at a set temperature, the nitrogen heated gas stream causes the activated carbon bed of the activated carbon adsorber to have a solvent concentration gradient with higher concentration at the bottom and lower concentration at the top, and a temperature gradient with higher temperature at the top and lower temperature at the bottom;

[0018] When the peeling is about to start, the nitrogen heated gas stream is stopped, and the solvent is extracted from the bottom layer with higher concentration of the activated carbon bed by a vacuum pump and an ejector of a vacuum group, the solvent is used as a power fluid of the vacuum group, and the power fluid continues until the activated carbon bed is completely regenerated;

[0019] The mixed fluid is cooled after leaving the vacuum group so as to liquefy the solvent;

[0020] The activated carbon bed is cooled.

[0021] The solvent recovery tail gas re-concentration recovery method, wherein each of the plurality of parallelly arranged activated carbon adsorbers is provided with an activated carbon adsorber exhaust pipe, and each of the activated carbon adsorber exhaust pipes is connected with the solvent recovery device common exhaust pipe.

[0022] The regeneration conditions include one or more of the following:

[0023] The activated carbon adsorber exhaust pipe of the activated carbon adsorber in the adsorption stage reaches a predetermined process value;

[0024] The solvent recovery device common exhaust pipe reaches a predetermined process value;

[0025] And / or, the adsorption stage of the activated carbon adsorber reaches a predetermined time.

[0026] The solvent recovery tail gas re-concentration recovery method, wherein when the particulate matter content in the exhaust gas exceeds 1 mg / m 3 , pretreatment is performed by filtration or washing;

[0027] When the exhaust gas contains components that are difficult to desorb or cause adsorbent poisoning after adsorption, pretreatment is performed by washing or pre-adsorption.

[0028] The solvent recovery tail gas re-concentration recovery method, wherein the non-condensable gas generated by condensation of the mixed fluid enters the solvent recovery device for re-adsorption.

[0029] The solvent recovery tail gas re-concentration recovery method, wherein the zeolite rotary device includes a shell and a zeolite rotor located in the shell, and the zeolite rotary device includes at least an adsorption zone and a desorption zone sealed by a sealing material, and the zeolite rotor and the shell are also sealed by a sealing material.

[0030] The solvent recovery tail gas re-concentration recovery method, wherein the concentration ratio of the zeolite rotary device is 5-30 times.

[0031] The solvent recovery tail gas re-concentration recovery method, wherein the superficial gas velocity of the adsorption zone of the zeolite rotary device is less than 4.5 m / s.

[0032] The solvent recovery tail gas re-concentration recovery method, wherein the concentration of the gas after concentration of the zeolite rotary device does not exceed 25% of the lower explosive limit.

[0033] The solvent recovery tail gas re-concentration recovery method, wherein the zeolite rotary device uses hydrophobic zeolite or zeolite material modified by hydrophobic modification; and the zeolite rotary device has high temperature resistance and non-combustible characteristics.

[0034] The present invention, by employing the above-mentioned technology, has the following positive effects compared with the prior art:

[0035] (1) Compared with a single-system nitrogen regeneration system, the present invention can save heating and cooling energy consumption, achieve higher cooling temperature, and have higher system efficiency. Compared with a single-system vacuum regeneration system, the present invention can be applied to solvent recovery in the printing industry.

[0036] (2) The operating cost of this invention is 40% lower than that of the traditional system; compared with the combustion system, it does not require spending money to buy natural gas to maintain combustion.

[0037] (2) The present invention has low maintenance costs. All valves are the same size and are installed at ground height. No cranes or scaffolding are needed to replace gaskets; no need to enter the carbon canister to replace carbon.

[0038] (3) The recycled solvent of the present invention can be recycled, reducing the raw material consumption of printing companies and improving economic benefits. It is applicable to various printing companies of different sizes (300 tons / year and above of solvent) and is applicable to mixed solvents. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the solvent recovery tail gas reconcentration and recovery system of the present invention.

[0040] Figure 2 This is a structural block diagram of the solvent recovery tail gas reconcentration and recovery system of the present invention.

[0041] Figure 3 This is a schematic diagram of the solvent recovery tail gas reconcentration and recovery system of the present invention.

[0042] Figure 4 This is a schematic diagram of the solvent recovery tail gas reconcentration and recovery system of the present invention.

[0043] In the attached diagram: 1. Zeolite rotor equipment; 21. Adsorption treatment system pipeline; 22. Concentration treatment system pipeline; 3. Adsorption treatment fan; 4. Exhaust stack; 5. Heat exchanger; 6. Concentration fan. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0045] Figure 1 This is a schematic diagram of the solvent recovery tail gas reconcentration and recovery system of the present invention. Figure 2 This is a structural block diagram of the solvent recovery tail gas reconcentration and recovery system of the present invention. Figure 3 This is a schematic diagram of the solvent recovery tail gas reconcentration and recovery system of the present invention. Figure 4is a schematic diagram of the solvent recovery tail gas re-concentration recovery system of the present application, please see Figures 1 to 4 As shown in the figure, the solvent recovery tail gas re-concentration recovery system of a preferred embodiment is shown for processing waste gas, comprising: a solvent recovery device, the solvent recovery device comprising a plurality of activated carbon adsorbers arranged in parallel, the solvent recovery device having a solvent recovery device air inlet pipe and a solvent recovery device common exhaust pipe; further comprising: a zeolite rotary device 1; and an adsorption treatment system pipeline 21 connected to the solvent recovery device common exhaust pipe, sequentially passing through the zeolite rotary device 1, an adsorption treatment fan 3, and connected to an exhaust cylinder 4; and a concentration treatment system pipeline 22 connected to the solvent recovery device common exhaust pipe, sequentially passing through the zeolite rotary device 1, a heat exchanger 5, the zeolite rotary device 1, a concentration fan 6, and connected to the solvent recovery device air inlet pipe.

[0046] The present application further provides a solvent recovery tail gas re-concentration recovery method, comprising:

[0047] The VOCs in the gas are adsorbed by a plurality of activated carbon adsorbers arranged in parallel, and the remaining VOCs in the gas are adsorbed by the zeolite rotary device 1.

[0048] Specifically, when the emission value of the solvent recovery device common exhaust pipe does not meet the required value, the gas in the solvent recovery device common exhaust pipe is introduced into the zeolite rotary device, and the remaining VOCs are adsorbed by the zeolite; the standard-compliant gas after zeolite adsorption is finally discharged into the atmosphere by the exhaust cylinder.

[0049] More specifically, the gas after desorption of the zeolite rotary device is high-concentration low-flow VOCs gas, achieving the effect of waste gas concentration, and the concentrated waste gas is introduced into the inlet of the solvent recovery device for further recovery treatment.

[0050] When one activated carbon adsorber meets the regeneration condition, the regeneration process is performed on the one activated carbon adsorber, and at least one of the plurality of activated carbon adsorbers is in the regeneration process; specifically, when the adsorbent capacity reaches the maximum working capacity, the regeneration process is performed. More specifically, when another activated carbon adsorber enters the regeneration stage, the activated carbon adsorber that has undergone the regeneration process is ready to enter the adsorption stage. Before that, the regeneration device can be on standby at all times.

[0051] The regeneration process comprises:

[0052] Oxygen is removed from the activated carbon adsorber by nitrogen, specifically, the purification device is purged by injecting nitrogen to eliminate residual oxygen in the regeneration circuit.

[0053] The desorption recovery is performed using a nitrogen stream heated to a set temperature, which creates a solvent concentration gradient in the activated carbon bed of the activated carbon adsorber, with higher concentrations at the bottom and lower concentrations at the top, and a temperature gradient, with higher temperatures at the top and lower temperatures at the bottom;

[0054] Preferably, the desorption recovery is performed using nitrogen heated to 150°C.

[0055] Specifically, the nitrogen heating of the activated carbon and the condensation of the solvent released by the activated carbon in the closed loop is performed when the oxygen concentration is below a pre-set value. The activated carbon is heated by the nitrogen, which is made to flow through the adsorption phase by means of a dedicated fan, so as to desorb as much solvent as possible from it. The solvent desorbed from the activated carbon is cooled and condensed by means of a multi-stage heat exchanger.

[0056] Preferably, the oxygen concentration is determined by means of an oxygen analyzer. Preferably, the nitrogen is heated by means of a heat exchanger 5, in particular a hot oil heat exchanger.

[0057] When the stripping is about to start, the nitrogen heating stream is stopped and the solvent is extracted from the lower part of the activated carbon bed, which has a higher concentration, by means of the vacuum pumps and the ejectors of the vacuum group. The solvent is used as the motive fluid of the vacuum group, which continues until the activated carbon bed is completely regenerated.

[0058] The mixed fluid, after leaving the vacuum group, is cooled so as to liquefy the solvent. Preferably, the recovered raw solvent is purified by means of distillation or dehydration.

[0059] The activated carbon bed is cooled. Preferably, in this case, the cooling fluid moves from the bottom to the top of the bed, thus avoiding the movement of potential residual solvent to the upper part of the bed.

[0060] Further, as a preferred embodiment, each of the plurality of activated carbon adsorbers in parallel is provided with an activated carbon adsorber exhaust pipe, each of which is connected to the solvent recovery plant common exhaust pipe.

[0061] wherein the regeneration conditions comprise one or more of the following:

[0062] the activated carbon adsorber exhaust pipe of the activated carbon adsorber during the adsorption phase reaches a pre-set process value;

[0063] the solvent recovery plant common exhaust pipe reaches a pre-set process value;

[0064] and / or the adsorption phase of the activated carbon adsorber reaches a pre-set time.

[0065] Further, as a preferred embodiment, when the particulate matter content of the exhaust gas exceeds 1 mg / m 3 , a pre-treatment by filtration or washing is performed.

[0066] Further, as a preferred embodiment, when the exhaust gas contains components that are difficult to desorb or cause poisoning of the adsorbent after adsorption, washing or pre-adsorption is used for pretreatment.

[0067] Further, as a preferred embodiment, the amount of activated carbon used in the activated carbon adsorber is determined according to the amount of exhaust gas to be treated, the concentration of pollutants, and the dynamic adsorption capacity of the adsorbent.

[0068] Further, as a preferred embodiment, the gas flow rate in the carbon layer of the activated carbon adsorber is less than 0.60 m / s.

[0069] Further, as a preferred embodiment, the non-condensable gas generated by the condensation of the mixed fluid enters the solvent recovery device for re-adsorption.

[0070] Further, as a preferred embodiment, the zeolite rotary device includes a housing and a zeolite rotor located in the housing, and the zeolite rotary device includes at least an adsorption zone and a desorption zone sealed from each other by a sealing material, and the zeolite rotor is also sealed from the housing by a sealing material.

[0071] Further, as a preferred embodiment, the zeolite rotary device is generally divided into an adsorption zone, a desorption zone, and a cooling zone according to different functions. If the cooling zone is not required to meet the purification requirements, the separate cooling zone can be omitted.

[0072] Further, as a preferred embodiment, the concentration ratio of the zeolite rotary device is 5-30 times.

[0073] Further, as a preferred embodiment, the superficial gas velocity in the adsorption zone of the zeolite rotary device is less than 4.5 m / s.

[0074] Further, as a preferred embodiment, the concentration of the concentrated gas in the zeolite rotary device does not exceed 25% of the lower explosive limit.

[0075] Further, as a preferred embodiment, the zeolite rotary device uses hydrophobic zeolite or zeolite material modified by hydrophobic modification.

[0076] Further, as a preferred embodiment, the zeolite rotary device has high temperature resistance and non-combustible properties.

[0077] Compared with the single-system nitrogen regeneration system, the present application saves heating and cooling energy (the heating and cooling stages are separated, and the regenerated gas is not heated and then cooled during all the regeneration time); the cooling temperature is higher, and the system efficiency is higher (3℃ vs. -12℃).

[0078] The present invention, compared to single system vacuum regeneration systems: due to the low concentration work capacity of the nitrogen recirculation of the present invention, which heats the carbon, otherwise single system vacuum regeneration is not suitable for solvent recovery in the printing industry.

[0079] The above merely preferred embodiments of the present application and are not intended to limit the embodiments and protection scope of the present application. Those skilled in the art should be able to realize that any equivalent replacements and obvious changes made according to the present application description and drawings should be included in the protection scope of the present application.

Claims

1. A method for the recovery of a solvent from a tail gas by re-concentration, characterized in that The solvent recovery tail gas re-concentration recovery system is used for treating the waste gas, and the solvent recovery tail gas re-concentration recovery system comprises: The solvent recovery device comprises a plurality of activated carbon adsorbers arranged in parallel, and the solvent recovery device is provided with a solvent recovery device air inlet pipe and a solvent recovery device common air outlet pipe; The zeolite wheel device; The adsorption treatment system pipeline is connected with the solvent recovery device common air outlet pipe, sequentially passes through the zeolite wheel device, an adsorption treatment fan, and is connected with an exhaust cylinder; The concentration treatment system pipeline is connected with the solvent recovery device common air outlet pipe, sequentially passes through the zeolite wheel device, a heat exchanger, the zeolite wheel device, a concentration fan, and is connected with the solvent recovery device air inlet pipe; The method comprises: The VOCs in the gas are adsorbed by the plurality of activated carbon adsorbers arranged in parallel, and the remaining VOCs in the gas are adsorbed by the zeolite wheel device; When one of the activated carbon adsorbers meets the regeneration condition, the regeneration process is performed on the one activated carbon adsorber, and at least one of the plurality of activated carbon adsorbers is in the regeneration process; The regeneration process comprises: Oxygen is removed from the activated carbon adsorber by nitrogen, desorption recovery is performed by using a nitrogen heating gas flow at a set temperature, the nitrogen heating gas flow causes a solvent concentration gradient with high concentration at the bottom and low concentration at the top, and a temperature gradient with high temperature at the top and low temperature at the bottom in the activated carbon bed of the activated carbon adsorber; When the peeling is about to start, the nitrogen heating gas flow is stopped, solvent is extracted from the bottom layer with high concentration of the activated carbon bed by a vacuum pump and an ejector of a vacuum group, the solvent is used as a power fluid of the vacuum group, and the power fluid continues until the activated carbon bed is completely regenerated; The mixed fluid is cooled after leaving the vacuum group so as to liquefy the solvent; The activated carbon bed is cooled.

2. The solvent recovery off-gas reconcentration recovery method according to claim 1, characterized by, Each of the plurality of activated carbon adsorbers arranged in parallel is provided with an activated carbon adsorber air outlet pipe, and each of the activated carbon adsorber air outlet pipes is connected with the solvent recovery device common air outlet pipe; The regeneration condition comprises one or more of the following: The emission value of the activated carbon adsorber air outlet pipe in the adsorption stage of the activated carbon adsorber reaches a predetermined process value; The emission value of the solvent recovery device common air outlet pipe reaches a predetermined process value; And / or, the adsorption stage of the activated carbon adsorber reaches a predetermined time.

3. The solvent recovery off-gas reconcentration recovery method according to claim 1, characterized by, The particulate matter content in the exhaust gas exceeds 1 mg / m 3 when pre-treatment is performed using filtration or washing; When the waste gas contains components that are difficult to desorb or cause poisoning of the adsorbent after adsorption, washing or pre-adsorption is used for pretreatment.

4. The solvent recovery off-gas reconcentration recovery method according to claim 1, characterized by, The non-condensable gas generated by condensation of the mixed fluid enters the solvent recovery device for re-adsorption.

5. The solvent recovery off-gas reconcentration recovery method according to claim 1, characterized by, The zeolite wheel device comprises a shell and a zeolite wheel located in the shell, the zeolite wheel device at least comprises an adsorption zone and a desorption zone which are sealed from each other by a sealing material, and the zeolite wheel and the shell are also sealed by a sealing material.

6. The solvent recovery off-gas reconcentration recovery method according to claim 1, characterized by, The concentration ratio of the zeolite wheel device is 5-30 times.

7. The solvent recovery off-gas reconcentration recovery method according to claim 1, characterized by, The superficial gas velocity of the adsorption zone of the zeolite wheel device is less than 4.5 m / s.

8. The solvent recovery off-gas reconcentration recovery method according to claim 1, characterized by, The concentration of the condensed gas of the zeolite rotary device is not more than 25% of the lower explosive limit.

9. The solvent recovery off-gas reconcentration recovery method according to claim 1, characterized by, The zeolite rotary device adopts hydrophobic zeolite or zeolite material modified by hydrophobic modification; the zeolite rotary device has high-temperature resistance and non-combustion characteristics.

Images