Solvent recovery process method for printing composite coating

Abstract

The invention relates to a solvent recovery process method for printing composite coating. The solvent recovery process method comprises the following steps that S1, workshop organic waste gas is filtered and cooled; s2, in a first closed nitrogen circulation environment, concentrating and thickening the organic waste gas filtered and cooled in the step S1 to 15-30 g / m < 3 >, and performing deep drying at a low dew point through a drying module; further adsorbing through an adsorption tower; s3, in a second closed nitrogen circulation environment, desorbing the adsorption tower subjected to adsorption saturation in the step S2, and respectively carrying out primary condensation and secondary condensation with the temperature lower than that of the primary condensation; and S4, carrying out workshop recovery on the solvent finished product formed in the step S3. The method has the advantages that the solvent does not deteriorate and can be directly recycled, follow-up devices are reduced, the occupied area is small, and investment is low; the safety of the process is improved; the adsorption air volume and the desorption air volume can be different, meanwhile, the desorption process of the concentration rotating wheel and the adsorption process of the adsorption tower are continuous, and the desorption process of the adsorption tower and the condensation recovery process are discontinuous.

Description

Technical Field

[0001] The invention relates to the technical field of waste gas treatment, and more specifically to a solvent recovery process method for printing composite coating. Background Art

[0002] VOCs (volatile organic compounds) is a general term for volatile organic compounds with a melting point below room temperature and a boiling point between 50-260°C, and sometimes refers to all gaseous organic matter. VOCs can generate photochemical smog and secondary pollutants under the action of ultraviolet light, causing environmental problems such as acid rain, photochemical pollution, and urban haze, which seriously threaten the ecological environment and directly affect human health and safety. However, it also has a certain economic recovery value. Therefore, finding an efficient and reliable method to control and recycle VOCs has become an urgent problem that needs to be solved.

[0003] A large amount of ink is used in the printing industry. The volatile organic compounds (VOCs) in the ink are discharged into the air, which will cause air pollution and endanger human health. Therefore, it is necessary to effectively control this type of organic matter. The exhaust in the printing industry is mainly divided into cartridge exhaust, floor exhaust, environmental exhaust and oven exhaust. The exhaust points are scattered, the exhaust volume is large, the emission concentration is low, and the VOCs composition is complex and flammable and explosive, which brings certain difficulties to its control.

[0004] At present, in most companies' VOCs treatment processes on printing lines, the desorption gas drying dew point temperature is relatively high, and further distillation, deacidification and dehydration treatment are required, and the process is cumbersome and complicated; it is impossible to achieve a higher concentration, resulting in a large equipment footprint and high investment costs; on the other hand, the existing processes are all in an aerobic environment, which is prone to explosion hazards and has low safety.

[0005] The preceding description is intended to provide general background information and does not necessarily constitute prior art. Summary of the invention

[0006] The object of the present invention is to provide a solvent recovery process method for printing composite coating, which reduces the operating steps and improves the process safety compared with the traditional process.

[0007] The present invention provides a solvent recovery process for printing composite coating, the process comprising the following steps:

[0008] S1: Filter and cool the organic waste gas in the workshop;

[0009] S2: In the first closed nitrogen circulation environment, the organic waste gas filtered and cooled in step S1 is concentrated to 15-30g / m 3 , deep drying is performed at a low dew point through a drying module; and further adsorption is performed through an adsorption tower;

[0010] S3: Under a second closed nitrogen circulation environment, desorb the adsorption tower saturated with adsorption in step S2 and perform primary condensation and secondary condensation at a temperature lower than the primary condensation temperature;

[0011] S4: Recycling the finished solvent product formed in step S3 in the workshop.

[0012] Furthermore, in step S2, concentration and enrichment are performed by a zeolite wheel.

[0013] Furthermore, the step S2 further includes:

[0014] S21: Part of the exhaust gas that meets the emission standards after being purified by the zeolite wheel is discharged through the chimney.

[0015] Furthermore, the step S2 further includes:

[0016] S22: In the first closed nitrogen circulation environment, the exhaust gas after adsorption in the adsorption tower returns to the zeolite wheel for cooling under the drive of the circulating nitrogen, enters the heating device for heating under the drive of the circulating nitrogen, and then continues to enter the zeolite wheel for desorption. The gas after desorption is once again deeply dried at a low dew point through the drying module, and then adsorbed by the adsorption tower again.

[0017] Furthermore, the step S3 further includes:

[0018] S31: In a second closed nitrogen circulation environment, the adsorption tower saturated with adsorption in step S2 is desorbed and a primary condensation and a secondary condensation below the primary condensation temperature are performed respectively. After the gas enters the heating device driven by the circulating nitrogen and is heated, the desorption is continued.

[0019] Furthermore, both the first closed nitrogen circulation environment and the second closed nitrogen circulation environment are replenished with nitrogen in real time.

[0020] Furthermore, the step S2 comprises two or more adsorption towers, and the two or more adsorption towers are used alternately.

[0021] Furthermore, the first closed nitrogen circulation environment of step S2 and the second closed nitrogen circulation environment of step S3 coexist.

[0022] Furthermore, in step S2, the low dew point is minus 55 degrees Celsius.

[0023] Furthermore, in step S3, the temperatures of the primary condensation and the secondary condensation are 0-4 degrees Celsius and minus 35 degrees Celsius respectively.

[0024] The solvent recovery process for printing composite coating of the present invention is to dry the desorbed gas at a low dew point of minus 55 degrees Celsius, so that the adsorption tower is in an oxygen-free and water-free state, the solvent does not deteriorate, and can be directly recycled and used. Compared with the traditional process, the distillation and deacidification and dehydration treatment processes are reduced; the concentration is increased to 15-30g / m 3 The high concentration reduces the size of subsequent equipment, occupies a small area and requires less investment; in the first closed nitrogen circulation environment and the second closed nitrogen circulation environment, a closed nitrogen adsorption cycle and a closed nitrogen desorption cycle are formed respectively, and the oxygen-free environment improves the safety of the process; adsorption and desorption have their own independent nitrogen circulation systems, and the adsorption air volume and desorption air volume can be different. At the same time, the desorption process of the concentration wheel and the adsorption tower are continuous, and the desorption process of the adsorption tower and the condensation recovery process are intermittent; in the traditional process, the distillation equipment belongs to the chemical equipment, and the general printing and coating factory does not have a license, and this process does not require a license. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic flow chart of a solvent recovery process for printing composite coating provided in an embodiment of the present invention.

[0026] Figure 2 for Figure 1 Schematic diagram of the process for solvent recovery process used in printing composite coating. DETAILED DESCRIPTION

[0027] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0028] The terms "first", "second", "third", "fourth" and the like in the description and claims of the present invention are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence.

[0029] Example 1

[0030] Figure 1 A schematic diagram of a process flow of a solvent recovery process for printing composite coating provided by an embodiment of the present invention, Figure 2 for Figure 1 Schematic diagram of the solvent recovery process for printing composite coating. Figure 1 , Figure 2 The solvent recovery process for printing composite coating provided by the embodiment of the present invention comprises the following steps:

[0031] S1: Filter and cool the organic waste gas in the workshop;

[0032] S2: In the first closed nitrogen circulation environment, the organic waste gas filtered and cooled in step S1 is concentrated to 15-30g / m 3 , deep drying is performed at a low dew point through a drying module; and further adsorption is performed through an adsorption tower;

[0033] Specifically, the low dew point in step S2 is a dew point of minus 55 degrees Celsius;

[0034] It should be noted that the concentration is increased to 15-30g / m 3 , which increases the concentration and reduces the size of the equipment; at minus 55 degrees Celsius, there is almost no moisture (water content below 0.1%), so no moisture is generated during the recovery process and it can be directly turned into a finished product for use.

[0035] S3: Under a second closed nitrogen circulation environment, desorb the adsorption tower saturated with adsorption in step S2 and perform primary condensation and secondary condensation at a temperature lower than the primary condensation temperature;

[0036] Specifically, the temperatures of the primary condensation and the secondary condensation in step S3 are 0-4 degrees Celsius and minus 35 degrees Celsius respectively;

[0037] S4: Recycling the finished solvent product formed in step S3 in the workshop.

[0038] It should be noted that the first closed nitrogen circulation environment of step S2 and the second closed nitrogen circulation environment of step S3 coexist.

[0039] The solvent recovery process for printing composite coating of the present invention is to dry the desorbed gas at a low dew point of minus 55 degrees Celsius, so that the adsorption tower is in an oxygen-free and water-free state, the solvent does not deteriorate, and can be directly recycled and used. Compared with the traditional process, the distillation and deacidification and dehydration treatment processes are reduced; the concentration is increased to 15-30g / m 3 The high concentration reduces the size of subsequent equipment, occupies a small area and requires less investment; in the first closed nitrogen circulation environment and the second closed nitrogen circulation environment, a closed nitrogen adsorption cycle and a closed nitrogen desorption cycle are formed respectively, and the oxygen-free environment improves the safety of the process; adsorption and desorption have their own independent nitrogen circulation systems, and the adsorption air volume and desorption air volume can be different. At the same time, the desorption process of the concentration wheel and the adsorption tower are continuous, and the desorption process of the adsorption tower and the condensation recovery process are intermittent; in the traditional process, the distillation equipment belongs to the chemical equipment, and the general printing and coating factory does not have a license, and this process does not require a license.

[0040] Further references Figure 2 In step S2 of the present invention, concentration and enrichment are carried out by a zeolite wheel.

[0041] Step S2 of the present invention also includes:

[0042] S21: Part of the exhaust gas that meets the emission standards after being purified by the zeolite wheel is discharged through the chimney.

[0043] S22: In the first closed nitrogen circulation environment, the exhaust gas after adsorption in the adsorption tower returns to the zeolite wheel for cooling under the drive of the circulating nitrogen, enters the heating device for heating under the drive of the circulating nitrogen, and then continues to enter the zeolite wheel for desorption. The gas after desorption is once again deeply dried at a low dew point through the drying module, and then adsorbed by the adsorption tower again.

[0044] Further references Figure 2 , step S3 of the present invention further comprises:

[0045] S31: In a second closed nitrogen circulation environment, the adsorption tower saturated with adsorption in step S2 is desorbed and a primary condensation and a secondary condensation below the primary condensation temperature are performed respectively. After the gas enters the heating device driven by the circulating nitrogen and is heated, the desorption is continued.

[0046] It should be noted that, in the present invention, both the first closed nitrogen circulation environment and the second closed nitrogen circulation environment are supplemented with nitrogen in real time; step S2 comprises two or more adsorption towers, which are used alternately.

[0047] Based on the above description, it can be seen that the advantages of the present invention are:

[0048] 1. The solvent recovery process for printing composite coating of the present invention is to dry the desorbed gas at a low dew point of minus 55 degrees Celsius, so that the adsorption tower is in an oxygen-free and water-free state, the solvent does not deteriorate, and can be directly recycled and reused, which reduces the distillation and deacidification and dehydration treatment processes compared with the traditional process;

[0049] 2. The solvent recovery process for printing composite coating of the present invention is concentrated to 15-30g / m 3 The high concentration makes the subsequent equipment smaller, with small footprint and low investment;

[0050] 3. The solvent recovery process for printing composite coating of the present invention forms a nitrogen adsorption closed cycle and a nitrogen desorption closed cycle in the first closed nitrogen circulation environment and the second closed nitrogen circulation environment, respectively, and the oxygen-free environment improves the safety of the process;

[0051] 4. The solvent recovery process for printing composite coating of the present invention has independent nitrogen circulation systems for adsorption and desorption, and the adsorption air volume and desorption air volume can be different. At the same time, the desorption process of the concentration wheel and the adsorption tower are continuous, and the desorption process of the adsorption tower and the condensation recovery process are intermittent;

[0052] 5. The solvent recovery process for printing composite coating of the present invention, in the traditional process, the distillation equipment belongs to the chemical equipment, and the general printing coating factory does not have a license, and this process does not require a license.

[0053] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A solvent recovery process for printing composite coating, characterized in that: The process comprises the following steps: S1: Filter and cool the organic waste gas in the workshop; S2: In the first closed nitrogen circulation environment, the organic waste gas filtered and cooled in step S1 is concentrated to 15-30g / m 3 , deep drying is performed at a low dew point through a drying module; and further adsorption is performed through an adsorption tower; S3: Under a second closed nitrogen circulation environment, desorb the adsorption tower saturated with adsorption in step S2 and perform primary condensation and secondary condensation at a temperature lower than the primary condensation temperature; S4: Recycling the finished solvent product formed in step S3 in the workshop.

2. The solvent recovery process for printing composite coating according to claim 1, characterized in that: In the step S2, the concentration is carried out by a zeolite wheel.

3. The solvent recovery process for printing composite coating according to claim 2, characterized in that: The step S2 further comprises: S21: Part of the exhaust gas that meets the emission standards after being purified by the zeolite wheel is discharged through the chimney.

4. The solvent recovery process for printing composite coating according to claim 2, characterized in that: The step S2 further comprises: S22: In the first closed nitrogen circulation environment, the exhaust gas after adsorption in the adsorption tower returns to the zeolite wheel for cooling under the drive of the circulating nitrogen, enters the heating device for heating under the drive of the circulating nitrogen, and then continues to enter the zeolite wheel for desorption. The gas after desorption is once again deeply dried at a low dew point through the drying module, and then adsorbed by the adsorption tower again.

5. The solvent recovery process for printing composite coating according to claim 1, characterized in that: The step S3 further comprises: S31: In a second closed nitrogen circulation environment, the adsorption tower saturated with adsorption in step S2 is desorbed and a primary condensation and a secondary condensation below the primary condensation temperature are performed respectively. After the gas enters the heating device driven by the circulating nitrogen and is heated, the desorption is continued.

6. The solvent recovery process for printing composite coating according to claim 1, characterized in that: The first closed nitrogen circulation environment and the second closed nitrogen circulation environment are both replenished with nitrogen in real time.

7. The solvent recovery process for printing composite coating according to claim 1, characterized in that: The step S2 comprises two or more adsorption towers, and the two or more adsorption towers are used alternately.

8. The solvent recovery process for printing composite coating according to claim 1, characterized in that: The first closed nitrogen circulation environment of step S2 and the second closed nitrogen circulation environment of step S3 coexist.

9. The solvent recovery process for printing composite coating according to claim 1, characterized in that: The low dew point in step S2 is minus 55 degrees Celsius.

10. The solvent recovery process for printing composite coating according to claim 1, characterized in that: The temperatures of the primary condensation and the secondary condensation in step S3 are 0-4 degrees Celsius and minus 35 degrees Celsius respectively.

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