Wastewater stripping recovery system and application

Abstract

The invention provides a wastewater stripping recovery system. The system comprises a wastewater stripping tower, a reactor regeneration unit and a feeding heating furnace, a wastewater stripping tower is adopted, regenerated flue gas in a reactor regeneration unit is used as a heat source for wastewater stripping, organic pollutants in wastewater are recycled and separated through gas-liquid mass transfer and heat transfer effects in a rectifying tower, and wastewater reaching the standard at the bottom of the tower is discharged to the outside. Flue gas of a reaction gas regeneration system of a propane dehydrogenation device is used as a heat source of a waste water stripping system, and gas rich in organic matter after stripping is used as combustion-supporting air fed into a heating furnace; the system adopts regenerated air flue gas as a heat source, so that steam consumption and wastewater discharge in an original wastewater steam stripping system are reduced, and the total waste gas discharge amount of the device is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and in particular relates to a wastewater stripping recovery system and application. Background Art

[0002] Propylene is an important organic chemical raw material with the characteristics of wide application and large market demand. In recent years, with the rapid development of various industries such as chemical industry and manufacturing industry, the demand for propylene has continued to rise. In recent years, with the development of propylene production technology and the commissioning of production equipment, propylene production capacity has grown rapidly. Compared with the propylene production technology of traditional petrochemical and coal chemical industries, the propane dehydrogenation process has the advantages of low project investment, high product yield, low production cost, wide source of raw materials, and environmental friendliness. It has become a popular propylene synthesis process.

[0003] In a propane dehydrogenation process unit with a relatively high market share, the operation scheme for the wastewater stripping process is to use low-pressure steam as a heat source, remove organic matter from the wastewater through steam stripping, and send the gas phase at the top of the tower to the flare system after passing through a separator tank, and the qualified wastewater at the bottom of the tower is sent to the outside. The disadvantage of this process technology is that it consumes additional low-pressure steam as a heat source, and part of the steam is condensed and discharged as wastewater. At the same time, the fuel components obtained from the top of the stripping tower are directly sent to the flare system. In the reaction regeneration system of the propane dehydrogenation unit, the regenerated air flue gas after reactor regeneration is directly sent to the chimney for discharge. Therefore, the original process technology has the disadvantages of low energy utilization efficiency, large wastewater / waste gas emissions, and high operating costs. Summary of the invention

[0004] In order to solve the above problems in the prior art, the present invention proposes a wastewater stripping recovery system and application, which is an energy-saving and emission-reduction process technology that efficiently couples the reactor regeneration system, wastewater stripping system and feed heating furnace air system in the propane dehydrogenation device.

[0005] In a first aspect, the present invention provides a wastewater stripping recovery system, which includes a wastewater stripping tower, a reactor regeneration unit, and a feed heating furnace;

[0006] A wastewater stripping tower is used, and the regenerated flue gas in the reactor regeneration unit is used as a heat source to strip the wastewater. Through the gas-liquid mass transfer and heat transfer in the distillation tower, the organic pollutants in the wastewater are recovered and separated, and the wastewater that meets the standards at the bottom of the tower is discharged outside the boundary.

[0007] As a specific embodiment of the present invention, the operating pressure of the wastewater stripping tower is 0.0 MPaG-0.8 MPaG.

[0008] As a specific embodiment of the present invention, the gas-liquid ratio of the amount of stripping gas introduced into the wastewater stripping tower to the amount of wastewater treated is ≥0.0225.

[0009] As a specific embodiment of the present invention, the reactor regeneration unit includes a filter, a waste heat boiler, and a heat exchanger.

[0010] As a specific embodiment of the present invention, the heat exchanger includes one or more sections of heat exchangers, preferably, includes a one-stage heat exchanger and a two-stage heat exchanger.

[0011] As a specific implementation of the present invention, the feed heating furnace includes a fresh air preheater and a feed heating furnace.

[0012] As a specific embodiment of the present invention, the organic pollutants in the wastewater include low-carbon alkanes and olefins, and the low-carbon alkanes and olefins include propane, propylene, C4, and C5, which are blown off by air and then sent to a feed heating furnace for combustion to recover heat value.

[0013] Taking into account the actual operating conditions of different devices, for different regeneration air and flue gas introduction positions, in order to ensure the best thermal efficiency and economic efficiency, the wastewater stripping system's stripping gas volume, heat exchanger parameters, etc. have different optimal values.

[0014] The above raw materials in the present invention can be prepared in-house or commercially available, and the present invention is not particularly limited thereto.

[0015] In a second aspect, the present invention provides application of the wastewater stripping recovery system described in the first aspect in the field of propane dehydrogenation.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The wastewater stripping recovery system of the present invention uses the flue gas of the reaction gas regeneration system of the propane dehydrogenation device as the heat source of the wastewater stripping system, and uses the organic-rich gas after stripping as the combustion-supporting air of the feed heating furnace; the system uses the regenerated air flue gas as the heat source, reduces the steam consumption and wastewater discharge in the original wastewater stripping system, and reduces the total waste gas emission of the device.

[0018] 2. The wastewater stripping recovery system of the present invention uses the organic-rich gas after stripping as the combustion-supporting air of the feed heating furnace, which not only fully utilizes the calorific value of the organic matter in the wastewater, but also reduces the feed amount of fresh air in the feed heating furnace system, realizes the process coupling between multiple systems of the propane dehydrogenation device, improves the energy utilization efficiency of the device, reduces the exhaust gas emissions of the device, reduces the operating cost of the device, and realizes energy saving and emission reduction of the device.

[0019] 3. The wastewater stripping recovery system of the present invention improves the energy utilization efficiency of the device and reduces the operating cost of the device. While ensuring the process design requirements, this method has the advantages of reduced steam consumption, reduced fresh air consumption, reduced waste gas and wastewater emissions, high energy utilization efficiency, and reduced annual operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic flow diagram of a wastewater stripping and recovery system for a propane dehydrogenation device in Example 1 of the present invention;

[0021] Among them, 1-reactor; 2-filter; 3-waste heat boiler; 4-first stage heat exchanger; 5-second stage heat exchanger; 6-chimney; 7-waste water stripping tower; 8-waste water cooler; 9-pump; 10-fresh air preheater; 11-feed heating furnace;

[0022] Figure 2 This is a schematic flow diagram of a wastewater stripping and recovery system for a propane dehydrogenation device in Example 2 of the present invention;

[0023] Among them, 1-reactor; 2-filter; 3-waste heat boiler; 4-first stage heat exchanger; 5-second stage heat exchanger; 6-chimney; 7-wastewater stripping tower; 8-inlet and outlet heat exchanger; 9-pump; 10-fresh air preheater; 11-feed heating furnace;

[0024] Figure 3 This is a schematic flow diagram of a wastewater stripping and recovery system for a propane dehydrogenation device in Example 3 of the present invention;

[0025] Among them, 1-reactor; 2-filter; 3-waste heat boiler; 4-first stage heat exchanger; 5-second stage heat exchanger; 6-chimney; 7-wastewater stripping tower; 8-inlet and outlet heat exchanger; 9-pump; 10-fresh air preheater; 11-feed heating furnace;

[0026] Figure 4 This is a schematic flow diagram of a wastewater stripping and recovery system for a propane dehydrogenation device in Example 4 of the present invention;

[0027] Among them, 1-reactor; 2-filter; 3-waste heat boiler; 4-first stage heat exchanger; 5-second stage heat exchanger; 6-chimney; 7-wastewater stripping tower; 8-wastewater cooler; 9-pump; 10-fresh air preheater; 11-feed heating furnace. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments, but they do not constitute any limitation to the present invention.

[0029] Example 1

[0030] This embodiment provides a propane dehydrogenation device wastewater stripping recovery system, combined with Figure 1 , the details are as follows:

[0031] The regeneration air flue gas at the outlet of the reactor (1) passes through a filter (2) to remove solid impurities in the flue gas, enters a waste heat boiler (3) for energy recovery and denitration, and then passes through a first-stage heat exchanger (4) and a second-stage heat exchanger (5) for primary energy recovery and secondary energy recovery. Most of the regeneration air flue gas is sent to a chimney (6) for discharge, and a small part of the regeneration air flue gas is used as a heat source in the wastewater stripping process. It enters from the bottom of the wastewater stripping tower (7) and contacts with the wastewater of the device in countercurrent. After stripping and separation, the qualified wastewater at the bottom of the tower is cooled by a wastewater cooler (8) and then discharged to the outside. The gas phase containing organic matter at the top of the stripping tower is mixed with fresh air, heated by a fresh air preheater (10), and used as combustion air for the feed heating furnace (11).

[0032] Example 2

[0033] This embodiment provides a propane dehydrogenation device wastewater stripping recovery system, combined with Figure 2 , the details are as follows:

[0034] The regeneration air flue gas at the outlet of the reactor (1) passes through a filter (2) to remove solid impurities in the flue gas, enters a waste heat boiler (3) for energy recovery and denitration, and then passes through a first-stage heat exchanger (4) for primary energy recovery. Most of the regeneration air flue gas passes through a second-stage heat exchanger (5) for secondary energy recovery and is then sent to a chimney (6) for discharge. A small portion of the regeneration air flue gas is used as a heat source in the wastewater stripping process, enters from the bottom of the wastewater stripping tower (7), and is in countercurrent contact with the wastewater of the device. After stripping and separation, the wastewater at the bottom of the tower that meets the standards is sent to the outside after energy recovery through the inlet and outlet heat exchanger (8). The gas phase containing organic matter at the top of the stripping tower is mixed with fresh air, heated by a fresh air preheater (10), and used as combustion air for the feed heating furnace (11).

[0035] Example 3

[0036] This embodiment provides a propane dehydrogenation device wastewater stripping recovery system, combined with Figure 3 , the details are as follows:

[0037] The regeneration air flue gas at the outlet of the reactor (1) passes through a filter (2) to remove solid impurities in the flue gas, enters a waste heat boiler (3) for energy recovery and denitration, and then passes through a first-stage heat exchanger (4) for primary energy recovery. Most of the regeneration air flue gas passes through a second-stage heat exchanger (5) for secondary energy recovery and is then sent to a chimney (6) for discharge. A small portion of the regeneration air flue gas is used as a heat source in the wastewater stripping process, enters from the bottom of the wastewater stripping tower (7), and is in countercurrent contact with the wastewater of the device. After stripping and separation, the wastewater at the bottom of the tower that meets the standards is sent to the outside after energy recovery through the inlet and outlet heat exchangers (8). The gas phase containing organic matter at the top of the stripping tower is mixed with the fresh air heated by the fresh air preheater (10) as the combustion air of the feed heating furnace (11).

[0038] Example 4

[0039] Taking a 600,000 ton / year propane dehydrogenation unit as an example, the total wastewater flow of the unit is 5-20 t / h, the organic matter content in the wastewater is 60-120 ppmw, and the removal efficiency of organic matter in the wastewater is 99.5%. Taking the recovery system of the wastewater stripping tower stripping gas as an example, the process flow is as follows: Figure 4 As shown:

[0040] The regeneration air flue gas (520-580°C; 800-1100t / h) at the outlet of the reactor (1) passes through a filter (2) to remove solid impurities in the flue gas, and then enters a waste heat boiler (3) for energy recovery and denitration. After passing through a first-stage heat exchanger (4) and a second-stage heat exchanger (5) for primary energy recovery and secondary energy recovery (105-200°C), most of the regeneration air flue gas is sent to a chimney (6) for discharge, and a small part of the regeneration air flue gas (2-4t / h) is used as a heat source in the wastewater stripping process, enters from the bottom of the wastewater stripping tower (7) (tower diameter: 0.8m; operating pressure: 0.1MPaG), and is in countercurrent contact with the device wastewater (10-20t / h). After stripping and separation, the wastewater at the bottom of the tower that meets the standards is cooled by a wastewater cooler (8) and then discharged to the outside. The gas phase containing organic matter at the top of the stripping tower is mixed with fresh air, heated by a fresh air preheater (10), and then used as combustion air for the feed heating furnace (11).

[0041] When the wastewater stripping recovery system proposed in the present invention is adopted for a 600,000 t / a propane dehydrogenation unit, it is calculated that the steam consumption can be reduced by 6,400 t / a and the waste gas emission can be reduced by 14.5 million Nm 3 / year, reducing wastewater discharge by 40t / year and reducing annual operating costs by more than 1.5 million yuan, effectively improving the energy utilization efficiency of the device, reducing operating costs, and achieving energy conservation and emission reduction for the device.

[0042] In summary, the wastewater stripping system of the present invention is an energy-saving and emission-reduction technology that efficiently couples the reactor regeneration system, wastewater stripping system and feed heating furnace air system in the propane dehydrogenation device. The flue gas of the reaction gas regeneration system of the propane dehydrogenation device is used as a heat source for wastewater stripping, and the organic-rich gas after stripping is used as the combustion-supporting air of the feed heating furnace. Through the efficient coupling between the three systems, the steam consumption in the wastewater treatment process of the device is effectively reduced, the consumption of fresh air and the exhaust gas emission of the device are reduced, and at the same time, the fuel components in the gas phase at the top of the wastewater stripping tower are utilized, thereby improving the energy utilization efficiency, reducing the operating cost of the device, and realizing energy saving and emission reduction of the device.

[0043] Any numerical value mentioned in the present invention, if there is only an interval of two units between any minimum value and any maximum value, includes all values ​​from the minimum value to the maximum value each time increasing by one unit. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is declared to be 50-90, in this specification it means that 51-89, 52-88... and 69-71 and 70-71 are specifically listed. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 can be appropriately considered as a unit. These are just some specially specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0044] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A wastewater stripping recovery system, characterized in that: The system includes a wastewater stripping tower, a reactor regeneration unit, and a feed heating furnace; A wastewater stripping tower is used, and the regenerated flue gas in the reactor regeneration unit is used as a heat source to strip the wastewater. Through the gas-liquid mass transfer and heat transfer in the distillation tower, the organic pollutants in the wastewater are recovered and separated, and the wastewater that meets the standards at the bottom of the tower is discharged outside the boundary.

2. The wastewater stripping recovery system according to claim 1, characterized in that: The operating pressure of the wastewater stripping tower is 0.0MPaG-0.8MPaG.

3. The wastewater stripping recovery system according to claim 1 or 2, characterized in that: The gas-liquid ratio of the amount of stripping gas introduced into the wastewater stripping tower to the amount of wastewater treated is ≥0.0225.

4. The wastewater stripping recovery system according to any one of claims 1 to 3, characterized in that: The reactor regeneration unit includes a filter, a waste heat boiler, and a heat exchanger.

5. The wastewater stripping recovery system according to any one of claims 1 to 4, characterized in that: The heat exchanger includes one or more sections of heat exchangers, preferably, includes a first section heat exchanger and a second section heat exchanger.

6. The wastewater stripping recovery system according to any one of claims 1 to 5, characterized in that: The feed heating furnace comprises a fresh air preheater and a feed heating furnace.

7. The wastewater stripping recovery system according to any one of claims 1 to 6, characterized in that: The organic pollutants in the wastewater include low-carbon alkanes and olefins, and the low-carbon alkanes and olefins include propane, propylene, C4, and C5.

8. The wastewater stripping recovery system according to any one of claims 1 to 7, characterized in that: The tower types of the wastewater stripping tower include plate towers, packed towers, etc., and the theoretical number of plates of the wastewater stripping tower includes 8 to 25.

9. The wastewater stripping recovery system according to any one of claims 1 to 8, characterized in that: The degassing gas source position includes the outlet of the first stage heat exchanger and the outlet of the second stage heat exchanger in the reactor regeneration unit, and the operating temperature of the degassing gas includes 105°C-205°C.

10. The wastewater stripping recovery system according to any one of claims 1 to 8, characterized in that: The feeding position of the stripping gas is the bottom of the wastewater stripping tower, and the feeding position of the wastewater is the top of the wastewater stripping tower.

11. Application of the wastewater stripping recovery system according to any one of claims 1 to 10 in the field of propane dehydrogenation.

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