System for treating low-concentration VOC (Volatile Organic Compounds) by turbine expansion cryogenic method

Abstract

The utility model relates to the field of treatment of volatile organic compounds, in particular to a system for treating low-concentration volatile organic compounds (VOC) by a turbine expansion cryogenic method. Comprising a cryogenic mechanism and a turbine expansion mechanism, the deep cooling mechanism comprises a multi-stage heat exchanger and a gas-liquid separator, and liquid hydrocarbon in discharged gas flow is liquefied and separated stage by stage and recovered according to carbon number components; the turbine expansion mechanism provides cold energy lower than-100 DEG C for the deep cooling mechanism through expansion refrigeration. Through coordination and cooperation of the deep cooling mechanism and the turbine expansion mechanism, hydrocarbon substances in the exhaust gas can be efficiently recycled, the VOC component in the exhaust gas can be reduced to the emission concentration allowed by the environment or below, and therefore the treated exhaust gas can be exhausted to the atmosphere; independent recovery of C6 + high-carbon hydrocarbon, C4 + high-carbon hydrocarbon and C2 low-carbon hydrocarbon can be realized through turbine expansion of expansion gas which is wide in source and low in cost, and up-to-standard emission or cyclic utilization of exhaust gas is realized.

Description

TECHNICAL FIELD

[0001] The utility model relates to volatile organic compound processing field especially, relates to a turbine expansion cryogenic method handles low concentration VOC system. BACKGROUND

[0002] Low concentration VOC gas (such as C2-C6 hydrocarbon) is often produced in petrochemical production process, and its direct emission can cause environmental pollution, and the existing technology mostly adopts incinerator or adsorption method to handle, and there are problems such as high energy consumption, large operation cost, easy to produce secondary pollution etc. Part of cryogenic method can recover hydrocarbon, but needs to rely on high-purity refrigerant (such as liquid nitrogen) or complex compression refrigeration system, and the cost is higher, difficult to promote. In addition, the existing cryogenic technology has low liquefaction separation efficiency to low carbon hydrocarbon below C2, so that the treated gas can still exceed the standard.

[0003] The utility model provides a kind of system based on turbine expansion refrigeration and multistage cryogenic separation cooperation, utilize pressure energy conversion into cold energy, combine stepwise cooling liquefaction technology, realize the efficient separation of low concentration VOC and standard discharge. UTILITY MODEL CONTENT

[0004] The application provides a kind of turbine expansion cryogenic method handles low concentration VOC system, using the following technical scheme:

[0005] A kind of turbine expansion cryogenic method handles low concentration VOC system, including cryogenic mechanism and turbine expansion mechanism;Cryogenic mechanism includes multistage heat exchanger and gas-liquid separator, liquid hydrocarbon in discharge gas stream is recovered according to carbon number by stepwise liquefaction separation;Turbine expansion mechanism provides less than-100 ℃ cold for cryogenic mechanism by expansion refrigeration.

[0006] Optionally, the expansion gas of turbine expansion mechanism is nitrogen, air or methane.

[0007] Optionally, the expansion gas pressure is greater than or equal to 0.2 MPaG.

[0008] Optionally, multistage heat exchanger uses plate-fin type or coiled tube type structure.

[0009] Optionally, multistage heat exchanger includes one-stage heat exchanger, two-stage heat exchanger and three-stage heat exchanger.

[0010] Optionally, gas-liquid separator includes one-stage separator, two-stage separator and three-stage separator.

[0011] Optionally, expansion gas enters multistage heat exchanger precooling treatment.

[0012] Optionally, the VOC concentration in treated discharge gas stream is less than or equal to 50 mg / m.

[0013] Compared with prior art, the utility model has the beneficial effects that:

[0014] 1. By the coordination of turbo-expansion refrigeration and multi-stage separation, using nitrogen, air or methane as the cold source, C6+, C4+ and C2 hydrocarbons are separated and liquefied step by step, the VOC concentration in the exhaust gas is reduced to below the environmental standard, and the hydrocarbon resources are recycled.

[0015] 2. The inexpensive expansion gas such as nitrogen and air is used, and liquid nitrogen or a complex refrigeration unit is not needed, so that the operation cost is reduced by more than 40%.

[0016] 3. The turbo-expansion is coordinated with the multi-stage deep cooling, the deep cooling mechanism can adopt a multi-flow channel plate-fin heat exchanger or a spiral pipe heat exchanger, the heat transfer efficiency is high, the volume is small, the C2+ recovery rate is greater than or equal to 95%, and the VOC concentration in the exhaust gas meets the standard. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will describe the drawings needed to be used in the embodiments or the prior art description. Obviously, the technical solutions described in the description in combination with the drawings are only some embodiments of the present application, and for those skilled in the art, other embodiments and drawings can be obtained without creative labor on the basis of these embodiments shown in the drawings.

[0018] Figure 1 is the overall structure of the present application.

[0019] In the figure: 1, a first separator; 2, a second separator; 3, a third separator; 4, a turbo-expander; 5, a multi-stage heat exchanger. DETAILED DESCRIPTION

[0020] The technical solutions of the embodiments of the present application will be described in detail below in combination with the drawings. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0021] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0022] In the description of the utility model, it needs to explain, unless another explicit provision and limitation, the term "installation", "set with", "connection" and so on, should do broad sense understanding, for example "connection", can be fixed connection, also can be detachable connection, or integrally connected;Can be mechanical connection, also can be electrical connection;Can be directly connected, also can be indirectly connected through the intermediate medium, can be two elements inside the communication. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0023] The embodiment of the utility model provides a kind of low concentration VOC system handled by turbine expansion cryogenic method.

[0024] Embodiment: as Figure 1 Indicated, a kind of low concentration VOC system handled by turbine expansion cryogenic method, including cryogenic mechanism, cryogenic mechanism is by multistage heat exchanger 5 and gas-liquid separator series connection, multistage heat exchanger 5 is by one-stage heat exchanger, two-stage heat exchanger and three-stage heat exchanger composition, gas-liquid separator includes one-stage separator 1, two-stage separator 2 and three-stage separator 3. The exhaust gas flow needing to be handled is passed through multistage heat exchanger 5 and is gradually cooled to C6+ high carbon hydrocarbon (-30 ℃ to-50 ℃), C4+ high carbon hydrocarbon (-60 ℃ to-80 ℃), C2 low carbon hydrocarbon (-100 ℃ below) liquefied temperature, gas after cooling is passed through one-stage separator 1, two-stage separator 2 and three-stage separator 3 and realizes hydrocarbon gradually recovery.

[0025] Cryogenic mechanism is also communicated with turbine expansion mechanism arrangement, turbine expansion mechanism includes turbine expander 4 and expansion gas pretreatment unit, turbine expander 4 can be expanded after the expansion gas (such as nitrogen, air or methane) with pressure ≥0.2MPaG is gradually precooled by cryogenic mechanism multistage heat exchanger, produces lower-100 ℃ low-temperature cold energy, provides cold source for C2 separation in cryogenic mechanism. Low-temperature gas after expansion is indirectly exchanged with exhaust gas stream by multistage heat exchanger 5, forms cold energy circulation;Low-pressure gas after expansion can be discharged or returned to process system and reused. Non-condensable steam after separating hydrocarbon substance will be discharged after recovering cold energy in cryogenic mechanism. Liquefied separated hydrocarbon substance will also be sent out device after recovering cold energy in cryogenic mechanism and recycled. Expansion gas stream is sent into turbine expander 4 after being precooled by multistage heat exchanger by expansion gas pretreatment unit.

[0026] As Figure 1The expansion gas from the expansion front gas flow port E enters the multi-stage heat exchanger in turn for temperature reduction and precooling, the precooled expansion gas enters the turbine expander 4, the turbine expander 4 utilizes the temperature reduction of the expansion gas after expansion to generate low-temperature cold energy below-100 DEG C, and provides a cold source for C2 separation in the cryogenic mechanism, the expansion gas after expansion and pressure reduction is discharged from the expansion rear gas flow port F; the treated exhaust gas flow A enters the first heat exchanger in the multi-stage heat exchanger, liquefies C6+ in the exhaust gas flow, and then is separated by the first separator 1, the liquefied C6+ is discharged from the C6+ flow port B for recovery, the remaining exhaust gas flow passes through the second heat exchanger for temperature reduction, the exhaust gas flow after temperature reduction by the second heat exchanger is separated by the second separator 2, the liquefied C4+ is discharged from the C4+ flow port G for recovery, finally, the exhaust gas flow passes through the third heat exchanger for temperature reduction, the exhaust gas flow after temperature reduction by the third heat exchanger is separated by the third separator 3, the liquefied C2 is discharged from the C2 flow port D for recovery, and finally, the remaining exhaust gas flow is discharged from the exhaust gas flow treatment port C, at this time, the VOC concentration of the treated exhaust gas flow reaches the discharge standard and is discharged.

[0027] The turbine expander mechanism is cooperated with the multi-stage cryogenic mechanism, the multi-flow channel plate fin heat exchanger or the coil pipe heat exchanger can be adopted in the cryogenic mechanism, the heat transfer efficiency is high, the volume is small, the C2+ recovery rate is greater than or equal to 95%, the VOC concentration in the final exhaust gas is less than or equal to 50 mg / m3, and the VOC concentration of the exhaust gas reaches the standard.

[0028] It is obvious for those skilled in the art that the utility model is not limited to the details of the above-mentioned exemplary embodiments, and the utility model can be realized in other specific forms without departing from the spirit or basic characteristics of the utility model. Therefore, no matter from which point, the embodiments should be regarded as exemplary and non-limiting. The scope of the utility model is defined by the appended claims, not the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the utility model. Any figure reference in the claims should not be regarded as limiting the involved claims.

[0029] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description manner of the specification is only for the sake of clarity, those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be properly combined to form other embodiments which can be understood by those skilled in the art.

Claims

1. A turbine expansion cryogenic method for treating low-concentration VOCs, characterized in that: It includes a cryogenic mechanism and a turbine expansion mechanism; the cryogenic mechanism includes a multi-stage heat exchanger and a gas-liquid separator, which liquefies and separates liquid hydrocarbons in the exhaust gas in stages and recovers them according to their carbon number; the turbine expansion mechanism provides the cryogenic mechanism with a cooling capacity below -100°C through expansion refrigeration.

2. The turbine expansion cryogenic method for treating low-concentration VOCs according to claim 1, characterized in that: The expanding gas in the turbine expansion mechanism is nitrogen, air, or methane.

3. The turbine expansion cryogenic method for treating low-concentration VOCs according to claim 2, characterized in that: The pressure of the expanding gas is ≥0.2 MPaG.

4. The turbine expansion cryogenic method for treating low-concentration VOCs according to claim 1, characterized in that: Multi-stage heat exchangers employ plate-fin or coiled tube structures.

5. The turbine expansion cryogenic method for treating low-concentration VOCs according to claim 1, characterized in that: Multistage heat exchangers include primary, secondary, and tertiary heat exchangers.

6. A turbine expansion cryogenic treatment system for low-concentration VOCs according to claim 1, characterized in that: Gas-liquid separators include primary separators, secondary separators, and tertiary separators.

7. A turbine expansion cryogenic method for treating low-concentration VOCs according to claim 2, characterized in that: The expanding gas enters a multi-stage heat exchanger for pre-cooling.

8. A turbine expansion cryogenic method for treating low-concentration VOCs according to claim 1, characterized in that: The VOC concentration in the treated exhaust gas is ≤50mg / m³.

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