Artificial stone production line waste gas treatment system based on styrene concentration incineration energy supply

Abstract

The utility model discloses an artificial stone production line waste gas treatment system based on styrene concentration incineration energy supply, which comprises a rotating wheel unit, an absorption tower and a flash evaporation analysis unit which are sequentially connected, a waste gas pipeline is connected with a tail gas inlet of the rotating wheel unit, and a concentrated gas outlet of the rotating wheel unit is connected with a gas phase inlet at the bottom of the absorption tower. A gas phase outlet of the absorption tower is connected with the adsorption tower group; a rich liquor outlet of the absorption tower is connected with the flash evaporation analysis unit, and a barren liquor outlet of the flash evaporation analysis unit is connected with an absorbent inlet in the top of the absorption tower. The system disclosed by the utility model is simple, low in investment and operation cost, good in tail gas purification effect, capable of effectively coupling absorption and adsorption, energy-saving, consumption-reducing and high in styrene recovery rate.

Description

Technical Field

[0001] The utility model belongs to the field of air pollution control, and relates to a resource recovery of polluting components in VOC tail gas, specifically an artificial stone production line waste gas treatment system based on styrene concentrated incineration energy supply. Background Art

[0002] Volatile organic compounds (VOCs) are organic compounds with a boiling point below 260°C at normal pressure. Most VOCs are toxic, irritating and toxic to the human body, and pose risks of teratogenicity, carcinogenesis, and mutagenesis. VOCs are important precursors of PM2.5 and O3, reacting chemically with atmospheric substances such as SO2 and NOx to cause secondary pollution. Coordinated control of atmospheric fine particulate matter and ozone pollution should be the primary focus of my country's current air pollution prevention and control efforts. VOCs, as common precursors of both, pose a significant threat when their waste gases enter the atmosphere.

[0003] The main VOCs waste gas treatment processes include adsorption, combustion, absorption, and condensation. These treatment technologies are relatively mature [Lin Yu. Study on the Treatment of Styrene Waste Gas by Condensation and Its Influencing Laws. Modern Chemical Industry, 2018, 38(10):192-195] and have many successful application cases. Traditional treatment methods each have their own advantages, but also have certain limitations.

[0004] The condensation method can realize the resource recovery of polluting components in exhaust gas, but the operating cost is high, the power consumption is large, and the exhaust gas after purification is difficult to meet the standards.

[0005] The absorption method can recycle pollutants in tail gas as resources. However, since the absorption process mainly uses organic solvents, the absorption driving force is small, the purification effect is poor, and the purified tail gas is difficult to meet the standards. The absorbent has a small absorption capacity and the absorbent regeneration cost is high.

[0006] Adsorption is a common treatment method for VOC tail gas, achieving standard emissions. However, for high-concentration, high-volume tail gas, adsorption suffers from short adsorption cycles, frequent adsorption and desorption, high energy consumption, and the saturated adsorbent is classified as hazardous waste. This leads to high adsorbent consumption and disposal costs.

[0007] The combustion method has relatively low operating costs and more thorough treatment, but it requires the provision of auxiliary heat enthalpy, especially for low-concentration tail gas. The carbon auxiliary heat enthalpy consumption is large, the carbon emissions are large, and it also leads to a large amount of styrene resource waste.

[0008] From a theoretical analysis, traditional VOC tail gas treatment technology can be used for styrene tail gas treatment. However, since the styrene component is prone to polymerization and heat generation under certain temperature conditions, there are problems such as polymerization-induced blockage and heat safety when traditional treatment technology is used to treat styrene tail gas. Summary of the Invention

[0009] The purpose of the utility model is to solve the above-mentioned technical problems and to provide an artificial stone production line waste gas treatment system based on styrene concentrated incineration power supply, which has a simple system, low investment and operating costs, good tail gas purification effect, effective coupling of absorption and adsorption, energy saving and consumption reduction, and high styrene recovery rate.

[0010] The system of the utility model includes a rotor unit, an absorption tower and a flash evaporation analysis unit connected in sequence, wherein the exhaust gas pipeline is connected to the tail gas inlet of the rotor unit, the concentrated gas outlet of the rotor unit is connected to the gas phase inlet at the bottom of the absorption tower, and the gas phase outlet of the absorption tower is connected to the adsorption tower group; the rich liquid outlet of the absorption tower is connected to the flash evaporation analysis unit, and the lean liquid outlet of the flash evaporation analysis unit is connected to the absorbent inlet at the top of the absorption tower.

[0011] The rotor unit includes two stages of rotors connected in series and corresponding desorption gas heat exchangers, wherein the purified gas outlet of the first-stage rotor is connected to the external exhaust pipe via the second-stage rotor; the concentrated gas outlet of the first-stage rotor is connected to the gas phase inlet of the absorption tower via the first-stage desorption fan and the tower inlet cooler; and the concentrated gas outlet of the second-stage rotor is connected to the incinerator.

[0012] The outlet of the first-stage desorption fan is divided into two routes, one route is connected to the tower cooler, and the other route is connected to the incinerator.

[0013] The adsorption tower group includes at least two parallel adsorption towers, the tail gas inlet of each adsorption tower is connected in parallel, the purified tail gas outlet is connected in parallel, the absorbent inlet is connected in parallel, and the absorbent outlet is connected in parallel; each adsorption tower is provided with a cooling gas inlet and outlet, the cooling gas inlet is connected to the purified tail gas outlet at the top of the adsorption tower, and the cooling gas outlet is connected to the exhaust gas pipe.

[0014] The flash evaporation and parsing unit comprises a flash evaporation kettle, which has at least two stages of flash evaporation chambers and a bottom liquid storage tank from top to bottom.

[0015] The upper section of the flash kettle is a primary flash chamber, and the lower section is a secondary flash chamber. The bottom liquid storage tank is divided into a lean liquid tank and a semi-lean liquid tank by at least one overflow plate. The upper part of the primary flash chamber is provided with a primary flash atomizer, and the bottom is provided with a primary flash guide plate; the upper part of the secondary flash chamber is provided with a secondary flash atomizer, and a part of the lower part of the secondary flash chamber is provided with a secondary flash guide plate above the semi-lean liquid tank, and the remaining area is connected to the lean liquid tank; the front end of the secondary flash guide plate is inserted into the lean liquid tank; the secondary flash guide plate and the overflow plate separate the semi-lean liquid tank from the secondary flash chamber; the gas phase space above the semi-lean liquid tank is connected to the primary flash chamber via a gas stripping gas guide pipe, and the primary flash chamber is connected to the semi-lean liquid tank via the primary flash guide pipe;

[0016] The rich liquid outlet of the absorption tower is connected to the first-stage flash atomizer via a rich liquid intermediate tank, a lean-rich liquid heat exchanger, a rich liquid-flue gas heat exchanger, and a rich liquid electric auxiliary heater; the semi-lean liquid tank of the flash kettle is connected to the second-stage flash atomizer via a semi-lean liquid-flue gas heat exchanger and a semi-lean liquid electric auxiliary heater; the lean liquid tank is connected to a liquid holding column.

[0017] The lean liquid outlet at the bottom of the liquid holding column is divided into two paths, one of which is connected to the absorption liquid inlet of the absorption tower through the lean-rich liquid heat exchanger, and the other is connected to the absorbent inlet of the absorption tower group; the overflow port at the top is connected to the lean liquid tank in the flash kettle through the lean liquid overflow pipe.

[0018] The lean liquid tank and the semi-lean liquid tank in the flash kettle are both provided with aeration heads.

[0019] The gas phase outlets of the first-stage flash chamber and the second-stage flash chamber are connected to the flash steam condenser through corresponding demisters; the condensate outlet of the flash steam condenser is connected to the oil-water separator in front of the pump, and the condensate outlet of the oil-water separator in front of the pump is connected to the aeration head in the lean liquid tank and the semi-lean liquid tank in the flash kettle through the condensate tank in front of the vacuum pump, the condensate pump, and the condensate-flue gas vaporizer.

[0020] In response to the problems existing in the background technology, the inventors set up a rotor unit, coupled absorption and adsorption, and combined it with an evaporation flash analysis unit to achieve exhaust gas purification to meet emission standards and recovery of styrene components in the tail gas. The specific improvements are as follows:

[0021] (1) A two-stage rotor unit is set up to adapt to the purification of VOC (styrene) tail gas in different environments. According to the different concentrations of styrene in the exhaust gas, you can choose to open all or individually, which is very flexible. In winter, the temperature is low and the concentration of VOC (styrene) in the VOC (styrene) tail gas is low, so only the first-stage rotor needs to be started. In summer, the temperature is high and the concentration of VOC (styrene) in the VOC (styrene) tail gas is high, so it is necessary to start the two-stage rotor. On the other hand, in summer, the first-stage rotor adsorbs and concentrates to produce a high concentration of the first-stage concentrated gas that enters the absorption tower, which is beneficial to increase the absorption capacity of the unit absorbent for styrene, save the power consumption of the absorption unit, reduce the amount of rich liquid analysis, and reduce the energy consumption of the analysis process. The second-stage rotor adsorption ensures that the exhaust gas meets the standards.

[0022] (2) One absorption tower is set up to correspond to at least two parallel adsorption towers, and the parallel adsorption towers alternately perform adsorption, desorption, and cooling processes. Specifically, the concentrated gas from the absorption tower is sent to the adsorption tower in the adsorption stage for adsorption and then discharged as purified exhaust gas; when the adsorption tower is saturated, it enters the desorption and cooling stage, and at the same time, the concentrated gas is switched to the adsorption tower that has completed desorption and cooling. In this alternating manner, continuous and efficient purification of exhaust gas from the artificial stone production line is achieved.

[0023] (3) Desorption of hot lean liquid. Hot lean liquid is used to wash and desorb the adsorption tower to be desorbed and cooled. The hot lean liquid is sprayed from the top of the tower to wash and desorb the adsorption filler layer. After desorption is completed, purified tail gas is used to enter the purified tail gas outlet at the top of the tower to cool the filler layer. The cooling gas is discharged from the gas phase inlet at the bottom of the adsorption tower and introduced into the absorption tower for further absorption. During the cooling process of the purified tail gas, it also has a deep desorption effect on the filler layer. After the purified tail gas is cooled, the adsorption tower enters the waiting desorption stage. This alternation achieves efficient recovery of styrene components in the exhaust gas of the artificial stone production line.

[0024] The absorbent lean liquid for washing and desorbing the packing layer of the adsorption tower stage used for desorption and cooling and the gas used for cooling come from the system itself. Except for replenishing the adsorbent, no new adsorbent needs to be introduced from outside, thus realizing the recycling of the adsorbent.

[0025] (4) A multi-layer structure is set up in the flash evaporator to perform multi-stage flash evaporation, and the equipment structure is compact and safe. A multi-stage flash evaporation chamber is set up in the flash evaporator, and a gas stripping section is set up at the bottom of the evaporator. The multi-stage flash evaporation and gas stripping are organically combined to improve the rich liquid distillation effect, save space, improve the vacuum pump's vacuum effect, and save the operating cost of the gas pump.

[0026] The flash desorption unit's flash evaporation kettle has at least two flash chambers, each connected to a lean liquid tank and a semi-lean liquid tank. The rich liquid is first introduced into the upper, primary flash chamber, where it is flash-evaporated by the primary flash atomizer. The flashed semi-lean liquid then flows through the primary flash guide pipe into the semi-lean liquid tank. The semi-lean liquid is then drawn out, heated by the semi-lean heater, and sent to the lower, secondary flash chamber, where it is sprayed out by the secondary flash atomizer for secondary flash evaporation. The lean liquid then flows through the secondary flash guide plate into the lean liquid tank. The front end of the secondary flash guide plate is inserted below the liquid level in the lean liquid tank, forming a liquid seal that separates the secondary flash chamber from the gas stripping area above the semi-lean liquid tank. This two-stage flash evaporation within a single flash evaporation kettle enhances the desorption process. Furthermore, the primary and secondary flash chambers are isolated from each other, ensuring a consistent flash evaporation effect.

[0027] An aeration head is set in the lean liquid tank and the semi-lean liquid tank. The condensate from which the non-condensable gas and styrene components are separated after flash evaporation is heated and vaporized by a heater, and then introduced into the aeration head in the form of water vapor. The lean liquid tank and the semi-lean liquid tank can be gas-lifted, thus truly realizing the reuse of the condensate. At the same time, the non-condensable gas separated by the flash steam condenser is also divided into two streams, which are respectively returned to the absorption tower and the aeration head, thus also realizing the reuse of the non-condensable gas, saving energy and reducing consumption, and being environmentally friendly.

[0028] (5) Setting up a liquid holding column to eliminate "cavitation". Taking into account the problem of "cavitation" when the lean liquid is drawn out from the bottom of the flash kettle, a liquid holding column is set up to increase the pressure before the pump to extract the lean liquid. Since the working pressure of the flash kettle is maintained below 4kPa (absolute pressure), which is much lower than the atmospheric pressure, when the lean liquid is directly drawn out from the bottom of the flash kettle through the pump into the absorption-adsorption unit at normal pressure, the pressure difference before and after the pump is large, and the residual styrene components and dissolved water in the lean liquid will produce "cavitation", which not only affects the stability of the pump operation, but also causes the pump blades to be impacted and corroded. Setting up a liquid holding column to draw the lean liquid from the bottom of the liquid holding column into the absorption tower increases the liquid phase pressure at the pump inlet, effectively overcoming the "cavitation" phenomenon.

[0029] (6) Set up a pre-pump oil-water separator. Control the amount of condensed water discharged from the pre-pump oil-water separator to the condensate tank, increase the oil-water interface level in the pre-pump oil-water separator, and discharge excess water from the condensate. Since part of the water vapor brought in by the tail gas during the absorption process is absorbed by the absorbent, during flash evaporation, the boiling point of water is lower than that of styrene, and the water vaporizes first and enters the flash steam together with the water vapor introduced. After condensation, it enters the condensate, disrupting the water balance of the system, and excess water needs to be discharged. Keeping the amount of condensed water discharged from the pre-pump oil-water separator to the condensate tank constant and raising the oil-water interface to a higher position is conducive to discharging the water absorbed by the absorbent from the tail gas together with the oil phase, thereby reducing the styrene concentration in the water phase and improving the styrene recovery rate. Because the higher the level of the oil-water interface, the more thorough the oil phase separation at the water phase outlet, thereby reducing the styrene concentration in the water vapor circulating into the flash evaporator.

[0030] (7) The condensate tank is connected to the aeration head through the condensate-flue gas vaporizer. The condensate is vaporized and returned to the flash kettle as the stripping gas. Experiments show that when the rich liquid contains a certain amount of water, the styrene desorption rate increases significantly. Since the water vapor partial pressure in the flash steam is much higher than the styrene partial pressure, and the saturated vapor pressure of water is greatly affected by temperature within the operating temperature range (7.381 kPa at 40°C and 19.932 kPa at 60°C), the rotary evaporation experiment shows that the maximum desorption rate is achieved when all the water in the rich liquid is evaporated (that is, when the water phase disappears). Water vapor can be aerated into the lean liquid and semi-lean liquid for a long time (about 75 kg / h, 3000 m3), with a high gas-liquid ratio of 200-300:1, which is conducive to further reducing the residual styrene concentration in the lean liquid.

[0031] Beneficial effects:

[0032] This utility model achieves ultra-purified exhaust gas discharge from artificial stone production lines while simultaneously recovering VOC components from the exhaust gas. This approach offers low investment and operating costs, excellent exhaust gas purification, effective coupling of absorption and adsorption, energy savings and consumption reduction, high styrene recovery rates, and environmental friendliness. The utility model achieves a pollutant removal rate of over 99.9% from artificial stone production line exhaust gas, recovers over 98% of the styrene component from styrene exhaust gas, and purifies the exhaust gas for ultra-clean emissions. Absorbent consumption is less than 0.1kg / t-styrene. Compared to distillation processes, this method saves over 50% energy consumption and reduces operating costs by over 50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a system diagram of an embodiment of the present utility model.

[0034] Figure 2 This is a Henry constant curve fitted with experimental data from the process of the embodiment of the present invention.

[0035] Among them, 1a: main fan; 1b: first-stage desorption fan; 1c: second-stage desorption fan; 1d: incinerator fan; 1e: high-temperature flue gas exhaust fan; 1f: low-temperature flue gas exhaust fan; 1g-purified tail gas fan; 2: adsorption tower group; 2a: adsorption tower A; 2b: adsorption tower B; 3a: first-stage rotor; 3b: second-stage rotor; 4a: first-stage desorption gas heat exchanger; 4b: second-stage desorption gas heat exchanger; 4c: inlet and outlet gas heat exchanger; 4d: inlet gas cooler; 4e: rich liquid-flue gas heat exchanger; 4f: lean-rich liquid heat exchanger; 4g: inlet lean liquid cooler; 4h: flash steam condenser; 4j: condensate-flue gas vaporizer; 4k: semi-lean liquid-flue gas heat exchanger 6: Demisting tower; 7: Absorption tower; 8: Absorption liquid intermediate tank; 9a: Primary spray pump; 9b: Secondary spray pump; 9c: Third-stage spray pump; 9d: Primary flash pump; 9e: Secondary flash pump; 9f: Lean liquid discharge pump; 9g: Auxiliary discharge pump; 9j: Condensate pump; 9k: Rich liquid circulation washing pump; 9p: Washing rich liquid into the tower pump; 10a: Rich liquid electric auxiliary heater; 10b: Semi-lean liquid electric auxiliary heater; 11a: Rich liquid intermediate tank; 11b: Condensate tank; 11c: Rich liquid tank; 12a: Primary flash demister; 12b: Secondary flash demister; 12c: Stripping demister; 13: Flash kettle; 13-2: Primary flash atomizer; 13- 3: Secondary flash atomizer; 13-4: Primary flash guide plate; 13-5: Primary flash guide pipe; 13-6: Secondary flash guide plate; 13-7: Stripping air guide pipe; 13-8: Secondary flash guide pipe; 13-9: Primary flash guide pipe; 13-10: Lean liquid tank; 13-11: Semi-lean liquid tank; 13-12: Semi-lean liquid aeration head; 13-13: Lean liquid aeration head; 14: Liquid holding column; 14-1: Lean liquid overflow pipe; 15: Pre-pump oil-water separator; 16: Intermediate oil tank; 17: Vacuum discharge valve; 18: Vacuum pump; 19: Incinerator; 20a: Flue gas exhaust emergency valve; 20b: Rich liquid heating flue gas valve; 20c: Flue gas recirculation Valve; 20d: Semi-lean liquid heating flue gas valve; 20e: Condensate vaporization flue gas valve; 20f: Purge gas regulating valve; 20g: First-stage high-temperature flue gas valve; 20h: Second-stage high-temperature flue gas valve; 20j: Condensate gas inlet valve; 20k: Condensate gas inlet valve; 20m: External flue gas valve; 20n: Rich liquid heating emergency valve; 20p: First-stage rotor air inlet valve; 20q: Second-stage rotor air inlet valve; 20r: First-stage desorption air valve; 20s: Second-stage desorption air valve; 20t: Tail gas check valve; 20u: Second-stage tower inlet flue gas valve; 20v: Second-stage turbine inlet flue gas valve; 20w: Furnace fresh air valve; 20x: Furnace inlet flue gas main valve; 21: Lower explosion limit detector; 22: Filter; DETAILED DESCRIPTION

[0036] The following is an explanation of the system of the utility model in conjunction with the accompanying drawings:

[0037] See also Figure 1 , the system of the utility model is connected in sequence to the rotor unit, the absorption tower 7 and the flash evaporation analysis unit;

[0038] Wherein, the rotor unit includes two stages of rotors connected in series and corresponding desorption gas heat exchangers. The purified gas outlet of the first-stage rotor 3a is connected to the external exhaust pipe via the second-stage rotor 3b; the cooled gas outlet of the first-stage rotor 3a is connected back to the first-stage rotor 3a via the first-stage desorption gas heat exchanger 4a. Similarly, the cooled gas outlet of the first-stage rotor 3b is connected back to the first-stage rotor 3a via the first-stage desorption gas heat exchanger 4b. The specific connection relationship and working principle of each component of the rotary unit are prior art and will not be described in detail here. The concentrated gas outlet of the first-stage rotor 3a is divided into two routes through the first-stage desorption fan 1b. One route is connected to the gas phase inlet of the absorption tower 7 via the tower inlet cooler 4d, and the other route is connected to the incinerator 19 (preferably an RTO incinerator). The concentrated gas outlet of the second-stage rotor 3b is connected to the incinerator 19.

[0039] The exhaust gas pipeline is divided into three routes after passing through the main fan 1a. The first and second routes are connected to the desorption gas inlet and exhaust gas inlet of the rotor unit through the first-level desorption air valve 20r and the first-level rotor air inlet valve 20p respectively. The third route is connected to the air inlet of the second-level rotor 3b through the second-level rotor air inlet valve 20q.

[0040] The absorption tower can be a conventional absorption tower, or a conventional absorption tower such as Figure 1 The absorption tower 7 shown is provided with an absorption liquid intermediate tank 8, wherein at least three spray layers are provided from top to bottom in the middle of the absorption tower 7, and each spray layer corresponds to an independent absorption liquid intermediate tank 8; the upper absorption liquid intermediate tank is connected to the lower absorption liquid intermediate tank through a full flow pipe.

[0041] The gas phase outlet of the absorption tower 7 is connected to the adsorption tower group 2; in this embodiment, the adsorption tower group 2 includes two parallel adsorption towers A 2a and B 2b, and the tail gas inlet of each adsorption tower is connected in parallel, the purified tail gas outlet is connected in parallel, the absorbent inlet is connected in parallel, and the absorbent outlet is connected in parallel; each of the adsorption towers is provided with a cooling gas inlet and outlet, the cooling gas inlet is connected to the purified tail gas outlet at the top of the adsorption tower, and the cooling gas outlet is connected to the exhaust gas pipe, and the two parallel adsorption towers A 2a and B towers 2b take turns to perform adsorption, desorption and cooling processes.

[0042] The flash evaporation analysis unit includes a flash evaporation kettle 13 and a liquid holding column 14. The flash evaporation kettle 13 has at least two flash evaporation chambers and a lower storage tank from top to bottom. In this embodiment, the upper section of the flash evaporation kettle 13 is a primary flash evaporation chamber, the lower section is a secondary flash evaporation chamber, and the bottom storage tank is divided into a lean liquid tank 13-10 and a semi-lean liquid tank 13-11 by an overflow plate. The upper part of the primary flash evaporation chamber is provided with a primary flash evaporation atomizer 13-2, and the bottom is provided with a primary flash evaporation guide plate 13-4; the upper part of the secondary flash evaporation chamber is provided with a secondary flash evaporation atomizer 13-3, and a part of the lower part of the secondary flash chamber located above the semi-lean liquid tank is provided with a secondary flash evaporation guide plate 13- 6, the remaining area is connected to the lean liquid tank 13-10; the front end of the secondary flash guide plate 13-6 is inserted into the lean liquid tank 13-10; the secondary flash guide plate 13-6 and the overflow plate separate the semi-lean liquid tank 13-11 from the secondary flash chamber; the gas phase space above the semi-lean liquid tank 13-11 is connected to the primary flash chamber through the gas stripping gas guide pipe 13-7, and the primary flash chamber is connected to the semi-lean liquid tank 13-11 through the primary flash guide pipe 13-5;

[0043] The rich liquid outlet of the absorption tower 7 is connected to the first-level flash atomizer 13-2 via the rich liquid intermediate tank 11a, the first-level flash pump 9d, the lean-rich liquid heat exchanger 4f, the rich liquid-flue gas heat exchanger 4e, and the rich liquid electric auxiliary heater 10a; the semi-lean liquid tank 13-11 is connected to the second-level flash atomizer 13-3 via the second-level flash pump 9e, the semi-lean liquid-flue gas heat exchanger 4k, and the semi-lean liquid electric auxiliary heater 10b; the lean liquid tank 13-10 is connected to the liquid holding column 14; the gas phase outlets of the first-level flash chamber and the second-level flash chamber are connected to the flash steam condenser 4h via the corresponding first-level flash demister 12a and the second-level flash demister 12b.

[0044] The condensate outlet of the flash steam condenser 4h is connected to the pre-pump oil-water separator 15. The condensate outlet of the pre-pump oil-water separator 15 is connected to the lean liquid aeration head 13-13 in the lean liquid tank 13-10 and the semi-lean liquid aeration head 13-12 in the semi-lean liquid tank 13-11 in the flash kettle 13 via the pre-exhaust pump condensate tank 11b, the condensate pump 9j, and the condensate-flue gas vaporizer 4j. The non-condensable gas outlet of the flash steam condenser 4h is connected to the exhaust pipe via the exhaust pump 18.

[0045] The lean liquid outlet at the bottom of the liquid holding column 14 is divided into two routes. One route is connected to the absorption liquid inlet of the upper section of the absorption tower 7 through the lean-rich liquid heat exchanger 4e and the lean liquid inlet cooler 4g, and the other route is connected to the absorbent inlet of each tower in the adsorption tower group 2; the overflow port at the top of the liquid holding column 14 is connected to the lean liquid tank 13-10 in the flash kettle 13 through the lean liquid overflow pipe 14-1.

[0046] The high-temperature flue gas outlet of the incinerator 19 is divided into two paths, which are respectively merged into one path after passing through the desorption gas heat exchangers corresponding to the two-stage wheels (the first-stage desorption gas heat exchanger 4a and the second-stage desorption gas heat exchanger 4b), and then divided into three paths after passing through the high-temperature flue gas exhaust fan 1e. The first path is connected to the external exhaust pipe through the semi-lean liquid-flue gas heat exchanger 4k, the second path is connected to the external exhaust pipe through the condensed water-flue gas vaporizer 4j, and the third path is divided into two paths after passing through the rich liquid-flue gas heat exchanger 4e, one path is connected to the incinerator 19 through the flue gas circulation valve 20c, and the other path is connected to the external exhaust pipe through the external flue gas valve 20m.

[0047] The low-temperature flue gas outlet of the incinerator 19 is divided into two paths through 1f, one path is connected to the rich liquid-flue gas heat exchanger 4e, and the other path is connected to the external discharge pipeline through the flue gas external discharge emergency valve 20a.

[0048] Process:

[0049] For example, a local artificial stone production plant has three artificial stone production lines. The VOC production units mainly come from mixing, feeding, unloading, spreading, vacuuming, pressing, film removal, and drying. The main pollutants include styrene and non-methane hydrocarbons. During the collection process, the amount of styrene-rich tail gas is 95,000-105,000 Nm 3 / h, the concentration of styrene in exhaust gas is 1500-2000mg / Nm3 in summer 3 , 300-500mg / Nm in winter 3 The heat enthalpy required by the exhaust gas purification system is provided by the system itself.

[0050] refer to Figure 1 The implementation process is divided into two different working conditions: summer and winter. The specific operations are as follows:

[0051] Summer: The temperature is high in summer, and the concentration of styrene in the exhaust gas from the production line is high, 1500-2000mg / Nm 3 .

[0052] 1) Wheel adsorption

[0053] Close the secondary rotor air inlet valve 20q, and the styrene tail gas on the production line is collected and blown into the first-stage rotor 3a through the exhaust pipe under the suction action of the main fan 1a, and enters the second-stage rotor 3b after adsorption, and is further adsorbed and purified before being discharged.

[0054] 2) Desorption

[0055] While the first-stage rotor 3a and the second-stage rotor 3b are adsorbing, the first-stage desorption gas valve 20r and the second-stage desorption gas valve 20s are opened. Under the suction action of the first-stage desorption fan 1b and the second-stage desorption fan c, the desorption gas first cools the rotor. The cooled gas enters the first-stage desorption gas heat exchanger 4a and the second-stage desorption gas heat exchanger 4b respectively for indirect heat exchange with the flue gas of about 850°C drawn out from the RTO incinerator 19. The desorption gas temperature rises to about 210°C and then enters the rotor for desorption.

[0056] 3) Concentrated gas absorption tower absorption

[0057] Under the suction action of the first-stage desorption fan 1b, the first-stage concentrated gas (styrene concentration 11000-12000 mg / Nm3) after desorption of the first-stage impeller 3a is divided into two parts. One part is introduced into the absorption tower 7, and the styrene component in the concentrated gas is absorbed by the absorption liquid; according to the system heat balance requirements, a part of the first-stage concentrated gas is separated and mixed with the second concentrated attached gas to be incinerated in the RTO incinerator 19 as a balancing measure for the system heat enthalpy requirements.

[0058] The concentrated gas enters the tower from the lower air inlet of the absorption tower 7 and contacts the absorption liquid (diethyl phthalate absorbent) sprayed from the upper part of the tower in countercurrent, and most of the styrene components in the concentrated gas are absorbed.

[0059] The concentrated gas exiting absorption tower 7 enters adsorption tower 2. Styrene is adsorbed from the adsorption packing layer within adsorption tower 2, and the resulting purified gas is discharged directly from the chimney. One absorption tower corresponds to at least two parallel adsorption towers, which alternately perform the adsorption and desorption processes.

[0060] The adsorption process is as follows:

[0061] The concentrated gas leaving the absorption tower 7 enters the adsorption tower A 2a, and the styrene component remaining in the concentrated gas leaving the tower is adsorbed. Before reaching the adsorption breakthrough line, the concentrated gas leaving the tower is switched to enter the adsorption tower B 2b, and the adsorption tower A 2a enters the desorption and cooling stage, and the adsorption tower B 2b starts adsorption.

[0062] Adsorption Tower A 2a is spray-washed and desorbed using the hot lean liquid exiting the flash evaporator 13. The hot lean liquid flow rate from the flash evaporator 13 is controlled at 4-5 t / h and is sprayed into the adsorption packing layer of Adsorption Tower A 2a via the rich liquid circulation wash pump 9k. The rich liquid circulation wash flow rate from the rich liquid circulation wash pump 9k is controlled at 20-25 t / h.

[0063] The washing rich liquid after washing the packing layer enters the bottom storage tank of the adsorption tower A 2a, and the washing rich liquid flows into the rich liquid tank 11a. Then, it is sent from the rich liquid tank 11a to the middle of the absorption tower 7 through the washing rich liquid inlet pump 9p, mixed with the secondary spray liquid, and then flows into the lower storage tank of the absorption liquid intermediate tank 8, and participates in the secondary spray of the absorption tower through the secondary spray pump 9b.

[0064] The rich liquid entering rich liquid tank 11a is sampled and analyzed regularly. When the styrene concentration in the washed rich liquid falls below the set value, washing and desorption in adsorption tower 2a is stopped, and adsorption tower 2a enters the cooling phase. The gas phase pipeline valve is switched, and purified gas is used to cool adsorption tower 2a. The cooling exhaust gas mixes with the non-condensable gas from the exhaust pump 18 and enters the air inlet of the main fan 1a. It then mixes with the exhaust gas from the production line and enters the rotary adsorption purification process.

[0065] After cooling is completed, the adsorption tower A 2a enters the waiting adsorption stage, completing an adsorption-desorption-cooling cycle.

[0066] The absorption process is as follows:

[0067] ① The absorption liquid is sprayed into the tower in three layers. The absorbent from the flash evaporation unit is mixed with the absorption liquid extracted from the upper layer of the absorption liquid intermediate tank 8 by the first-level spray pump 9a and sprayed into the absorption tower 7. The absorption liquid contacts the concentrated gas in countercurrent through the upper packing layer, and part of the styrene component in the concentrated gas is absorbed; the lean liquid and the supplementary fresh absorbent / liquid (diethyl phthalate) are added through the pump head of the first-level spray pump 9a.

[0068] ② The absorption liquid flowing through the upper packing layer flows back into the upper layer of the absorption liquid intermediate tank 8 and is circulated and sprayed through the first-level spray pump 9a; an overflow pipe is set on the upper layer of the absorption liquid intermediate tank 8, and the excess absorption liquid flows to the lower layer of the absorption liquid intermediate tank 8 through the overflow pipe.

[0069] ③ The absorption liquid in the lower layer of the absorption liquid intermediate tank 8 is sprayed into the absorption tower 7 through the secondary spray pump 9b, and contacts with the concentrated gas in countercurrent through the middle packing layer, and part of the styrene component in the concentrated gas is absorbed.

[0070] ④ The absorption liquid flowing through the middle packing layer flows into the lower storage tank of the absorption tower 7 and is circulated and sprayed through the secondary spray pump 9b; an overflow pipe is set in the middle layer of the absorption liquid intermediate tank 8, and the excess absorption liquid flows to the lower storage tank of the absorption tower 7 through the overflow pipe.

[0071] ⑤ A portion of the absorption liquid in the liquid storage tank at the lower part of the absorption tower 7 is sprayed into the absorption tower 7 through the three-stage spray pump 9c, and contacts with the concentrated gas in countercurrent through the lower packing layer, and part of the styrene component in the concentrated gas is absorbed.

[0072] ⑥ The absorption liquid flowing through the lower packing layer enters the lower storage tank of the absorption tower 7 and is circulated and sprayed by the three-stage spray pump 9c; the absorption liquid is sprayed into the absorption tower 7, and contacts with the concentrated gas in countercurrent through the middle packing layer, and part of the styrene component in the concentrated gas is absorbed.

[0073] ⑦ The rich liquid sent to the flash unit is drawn out through the three-stage spray pump 9c.

[0074] 4) Concentrated gas incineration for heat generation

[0075] Under the suction of secondary desorption blower 1c, the secondary concentrated gas, with a styrene concentration of 5000-6000 mg / Nm³, enters RTO incinerator 19 for incineration. It is mixed with a portion of the primary concentrated gas before entering RTO incinerator 19. Incineration in RTO incinerator 19 produces high-temperature flue gas at 850°C and low-temperature flue gas at 110-115°C, which provide heat to the system.

[0076] 5) Rich liquid flash evaporation and styrene recovery

[0077] ① 15-20t / h of rich liquid is drawn from the lower storage tank of the absorption tower 7 into the rich liquid intermediate tank 11a, and then pumped out by the first-stage flash pump 9d and sequentially enters the rich liquid-flue gas heat exchanger 4e and the lean-rich liquid heat exchanger 4f for heat exchange and temperature increase, and then enters the flash kettle 13 for the first-stage flash evaporation.

[0078] ② Under the suction action of the vacuum pump, the pressure in the flash kettle 13 is controlled at about 4kPa.

[0079] ③ The rich liquid in the rich liquid intermediate tank 11a is pumped out by the first-stage flash pump 9d and first exchanged with the lean liquid from the flash unit, and then with the low-temperature flue gas from the RTO incinerator 19, heated to 60-65°C. It is then atomized by the first-stage flash atomizer 13-2 and enters the flash kettle 13. Under negative pressure, 30-40% of the styrene component in the rich liquid evaporates into the flash steam. The semi-lean liquid from which some styrene has evaporated flows through the first-stage flash guide plate 13-4 and the first-stage flash guide pipe 13-5 into the semi-lean liquid tank 13-11.

[0080] ④ The semi-lean liquid in the semi-lean liquid tank 13-11 is pumped out by the secondary flash pump 9e and heated to 65-70°C by the semi-lean liquid-flue gas heat exchanger 4k. It is then atomized by the secondary flash atomizer 13-3 and enters the flash kettle 13 for secondary flash evaporation. The styrene component in the semi-lean liquid further evaporates into the flash steam; the lean liquid with about 20-30% of the styrene component remaining is introduced into the lean liquid tank 13-12 through the secondary flash guide plate 13-6.

[0081] ⑤ Water vapor is introduced into the semi-lean liquid tank 13-11 and the lean liquid tank 13-10 through the semi-lean liquid aeration head 13-12 and the lean liquid aeration head 13-13 respectively, so as to further gas strip the lean liquid and the semi-lean liquid, thereby further reducing the styrene concentration in the lean liquid and the semi-lean liquid.

[0082] ⑥ The stripping gas and flash steam are respectively led out through the stripping gas duct 13-7, the secondary flash evaporation duct 13-8, and the primary flash evaporation duct 13-9, and are respectively defogged by the stripping demister 12c, the secondary flash evaporation demister 12b, and the primary flash evaporation demister 12a, and then enter the flash steam condenser for 4 hours under the suction action of the vacuum pump 18.

[0083] ⑦ The lean liquid after flash evaporation is pumped from the lean liquid tank 13-10 into the liquid holding column 14 by the auxiliary discharge pump 9g, and then pumped from the bottom of the liquid holding column 14 by the lean liquid discharge pump 9f. It is cooled to 20-30°C through the lean-rich liquid heat exchanger 4f and the tower lean liquid cooler 4g before entering the absorption tower 7. An overflow pipe 14-1 is provided at the top of the liquid holding column 14 to drain the excess lean liquid back to the lean liquid tank 13-10 to maintain a stable liquid level in the liquid holding column 14.

[0084] ⑧ The flash steam and stripping gas entering the flash steam condenser 4h are cooled by a low-temperature refrigerant (7°C low-temperature water), and most of the styrene and water therein are condensed and enter the pre-pump oil-water separator 15 for oil-water separation. The water phase enters the condensate tank 11b, and is then sent to the condensate-flue gas vaporizer 4j through the condensate pump 9j for heating and vaporization to form superheated steam at 60-65°C, which is bubbled into the semi-lean liquid tank 13-11 and the lean liquid tank 13-10; the oil phase, i.e., styrene, is discharged into the intermediate oil tank 16 through the vacuum unloading valve 17 to realize the recovery of the styrene component.

[0085] 6) System heating

[0086] According to the system heat balance analysis, the media that need to be heated include the primary desorbed gas, the secondary desorbed gas, the rich liquid entering the flash kettle 13, and the aeration water vapor. The primary desorbed gas and the secondary desorbed gas need to be heated from about 100°C after the cooling wheel to 220°C, the rich liquid entering the flash kettle 13 needs to be heated from 20-30°C to 60-65°C, and the aeration water vapor entering the flash kettle 13 needs to be heated from condensed water at 20-30°C to 60-65°C.

[0087] ① The secondary desorbed gas and part of the primary desorbed gas are introduced into the RTO incinerator 19 through the incinerator fan 1d for incineration, generating high-temperature flue gas of 850°C and low-temperature flue gas of 110-115°C.

[0088] ② Through the high-temperature flue gas exhaust 1e, high-temperature flue gas of 800-850℃ is drawn out from the high-temperature flue gas outlet of the RTO incinerator 19 with a speed of 5500-6000Nm 3 / h, and is divided into two parts by the first-level high-temperature flue gas valve 20g and the second-level high-temperature flue gas valve 20h, and enters the first-level desorbed gas heat exchanger 4a and the second-level desorbed gas heat exchanger 4b respectively to exchange heat with the first-level desorbed gas and the second-level desorbed gas. The temperature of the desorbed gas is increased from 100℃ to 220℃, and the temperature of the high-temperature flue gas is reduced to 210-250℃;

[0089] ③ The high-temperature flue gas cooled to 210-250℃ is extracted by the high-temperature flue gas exhaust 1e, and is divided into three parts through the semi-lean liquid heating flue gas valve 20d, the condensed water vaporization flue gas valve 20e, and the rich liquid heating emergency valve 20n. One part enters the semi-lean liquid-flue gas heat exchanger 4k to heat the semi-lean liquid, one part enters the condensed water-flue gas vaporizer 4j, and the remaining part is introduced into the RTO incinerator 19 through the incinerator fan 1d for circulation to dilute the concentrated gas entering the furnace.

[0090] ④ Through the low-temperature flue gas exhaust 1f, the low-temperature flue gas of 105-115℃ and 13000-14000Nm 3 / h, and is divided into two parts through the regulation of the rich liquid heating flue gas valve 20b and the flue gas discharge emergency valve 20a. One part enters the rich liquid-flue gas heat exchanger 4e to exchange heat with the rich liquid, and the low-temperature flue gas temperature is cooled from 105-115℃ to 60-70℃; the remaining part is discharged from the chimney through the flue gas discharge emergency valve 20a to adjust the flow rate.

[0091] ⑤ The low-temperature flue gas with a temperature of 60-70°C exiting the rich liquid-flue gas heat exchanger 4e is adjusted through the flue gas circulation valve 20c and the exhaust flue gas valve 20m to adjust the amount of circulating flue gas entering the RTO incinerator 19 and the amount of exhaust flue gas.

[0092] ⑥ The amount of flue gas discharged from the chimney is adjusted to be as small as possible through the external discharge emergency valve 20a. The amount of primary desorbed gas introduced into the RTO incinerator 19 is adjusted according to the amount of low-temperature flue gas discharged through the external discharge emergency valve 20a. When the amount of low-temperature flue gas discharged through the external discharge emergency valve 20a is large, the amount of primary desorbed gas introduced into the RTO incinerator 19 is reduced until no external discharge is adjusted through the external discharge emergency valve 20a. The amount of primary desorbed gas entering the absorption tower 7 is increased to improve the absorption amount of styrene.

[0093] 7) Non-condensable gas recovery and treatment

[0094] The pressure in the flash kettle cavity is controlled at 4kPa, and the amount of gas discharged by the vacuum pump is about 4000m3 / h, of which 10-20% is non-condensable gas (calculated at 60m3 / h). After being cooled to about 20°C in the flash steam condenser for 4h, the moisture and most of the styrene components in the flash steam are condensed, and after leaving the vacuum pump, it enters the normal pressure state. The volume of non-condensable gas is 2.11m3 / h. The concentration of styrene in the remaining non-condensable gas is high, about 29g / Nm3, and the amount of styrene carried out by the non-condensable gas is about 60g / h.

[0095] If the styrene concentration in the non-condensable gas exceeds the lower explosion limit of styrene, it will be promptly mixed with the cooling gas from the adsorption tower 2 and diluted to below the lower explosion limit, and then introduced into the air inlet of the main fan 1a and mixed with the tail gas from the production line to enter the rotor adsorption purification.

[0096] 8) Diethyl phthalate is preferably used as the styrene absorbent

[0097] The absorbent used in the method of the present invention is a high-boiling-point organic solvent having a boiling point 100° C. or higher than that of styrene, preferably diethyl phthalate.

[0098] See also Figure 2 The Henry constant of the solution after diethyl phthalate absorbs styrene is: 23.04kg / (moL·kPa).

[0099] The process of the present invention can recover more than 98% of the styrene components in styrene tail gas, purify the tail gas to meet emission standards, and consume less than 0.1kg / t-styrene. Compared with the distillation process, it saves more than 50% of energy consumption and reduces the recovery cost by more than 50%.

[0100] Winter: The temperature is low in winter, and the concentration of styrene from the tail gas of the production line is low, 300-500mg / Nm 3 .

[0101] During winter operation, only the second-stage runner 3b is opened, and the first-stage runner 3a is closed, that is, the first-stage runner air inlet valve 20p is closed, and the second-stage runner air inlet valve 20q is opened. The styrene tail gas on the production line is collected and blown into the second-stage runner 3b for adsorption and purification under the suction action of the main fan 1a, and then discharged. At the same time, the absorption and flash evaporation units are shut down, and the rest of the operation process is the same as above.

Claims

1. An artificial stone production line waste gas treatment system based on styrene concentrated incineration energy supply, characterized in that: It includes a rotor unit, an absorption tower and a flash evaporation analysis unit connected in sequence, wherein the exhaust gas pipe is connected to the tail gas inlet of the rotor unit, the concentrated gas outlet of the rotor unit is connected to the gas phase inlet at the bottom of the absorption tower, and the gas phase outlet of the absorption tower is connected to the adsorption tower group; the rich liquid outlet of the absorption tower is connected to the flash evaporation analysis unit, and the lean liquid outlet of the flash evaporation analysis unit is connected to the absorbent inlet at the top of the absorption tower.

2. The artificial stone production line waste gas treatment system based on styrene concentrated incineration energy supply according to claim 1 is characterized in that: The rotor unit includes two stages of rotors connected in series and corresponding desorption gas heat exchangers, wherein the purified gas outlet of the first-stage rotor is connected to the external exhaust pipe via the second-stage rotor; the concentrated gas outlet of the first-stage rotor is connected to the gas phase inlet of the absorption tower via the first-stage desorption fan and the tower inlet cooler; and the concentrated gas outlet of the second-stage rotor is connected to the incinerator.

3. The artificial stone production line waste gas treatment system based on styrene concentrated incineration energy supply as claimed in claim 2 is characterized in that: The outlet of the first-stage desorption fan is divided into two routes, one route is connected to the tower cooler, and the other route is connected to the incinerator.

4. The artificial stone production line waste gas treatment system based on styrene concentrated incineration energy supply according to claim 1 is characterized in that: The adsorption tower group includes at least two parallel adsorption towers, the tail gas inlet of each adsorption tower is connected in parallel, the purified tail gas outlet is connected in parallel, the absorbent inlet is connected in parallel, and the absorbent outlet is connected in parallel; each adsorption tower is provided with a cooling gas inlet and outlet, the cooling gas inlet is connected to the purified tail gas outlet at the top of the adsorption tower, and the cooling gas outlet is connected to the exhaust gas pipe.

5. The artificial stone production line waste gas treatment system based on styrene concentrated incineration energy supply according to any one of claims 1 to 4, characterized in that: The flash evaporation and parsing unit comprises a flash evaporation kettle, which has at least two stages of flash evaporation chambers and a bottom liquid storage tank from top to bottom.

6. The artificial stone production line waste gas treatment system based on styrene concentrated incineration energy supply as claimed in claim 5, characterized in that: The upper section of the flash kettle is a primary flash chamber, and the lower section is a secondary flash chamber. The bottom liquid storage tank is divided into a lean liquid tank and a semi-lean liquid tank by at least one overflow plate. The upper part of the primary flash chamber is provided with a primary flash atomizer, and the bottom is provided with a primary flash guide plate; the upper part of the secondary flash chamber is provided with a secondary flash atomizer, and a portion of the lower part of the secondary flash chamber is provided with a secondary flash guide plate above the semi-lean liquid tank, and the remaining area is connected to the lean liquid tank; the front end of the secondary flash guide plate is inserted into the lean liquid tank; the secondary flash guide plate and the overflow plate separate the semi-lean liquid tank from the secondary flash chamber; the gas phase space above the semi-lean liquid tank is connected to the primary flash chamber via a gas stripping gas guide pipe, and the primary flash chamber is connected to the semi-lean liquid tank via the primary flash guide pipe; The rich liquid outlet of the absorption tower is connected to the first-stage flash atomizer via a rich liquid intermediate tank, a lean-rich liquid heat exchanger, a rich liquid-flue gas heat exchanger, and a rich liquid electric auxiliary heater; the semi-lean liquid tank of the flash kettle is connected to the second-stage flash atomizer via a semi-lean liquid-flue gas heat exchanger and a semi-lean liquid electric auxiliary heater; the lean liquid tank is connected to a liquid holding column.

7. The artificial stone production line waste gas treatment system based on styrene concentrated incineration energy supply according to claim 6 is characterized in that: The lean liquid outlet at the bottom of the liquid holding column is divided into two paths, one of which is connected to the absorption liquid inlet of the absorption tower through the lean-rich liquid heat exchanger, and the other is connected to the absorbent inlet of the absorption tower group; the overflow port at the top is connected to the lean liquid tank in the flash kettle through the lean liquid overflow pipe.

8. The artificial stone production line waste gas treatment system based on styrene concentrated incineration energy supply according to claim 5 is characterized in that: The lean liquid tank and the semi-lean liquid tank in the flash kettle are both provided with aeration heads.

9. The artificial stone production line waste gas treatment system based on styrene concentrated incineration energy supply according to claim 8, characterized in that: The gas phase outlets of the first-stage flash chamber and the second-stage flash chamber are connected to the flash steam condenser through corresponding demisters; the condensate outlet of the flash steam condenser is connected to the oil-water separator in front of the pump, and the condensate outlet of the oil-water separator in front of the pump is connected to the aeration head in the lean liquid tank and the semi-lean liquid tank in the flash kettle through the condensate tank in front of the vacuum pump, the condensate pump, and the condensate-flue gas vaporizer.

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