Heat exchange method for efficient heat energy recovery of maleic anhydride device

Abstract

The invention provides a heat exchange method for efficient heat energy recovery of a maleic anhydride device, and relates to the technical field of chemical production. Comprising the following steps: S1, performing oxidation reaction in a maleic anhydride reactor to produce maleic anhydride process gas, and releasing a large amount of heat at the same time; S2, enabling the process gas to enter a cooling system from a lower end socket of the maleic anhydride reactor for heat recovery and product separation; process gas enters from an inlet in the bottom of the combined cooler and sequentially washes S-shaped heat exchange pipes of the first-stage cooler and the second-stage cooler, the cooled process gas is led out to the upper portion of the third-stage cooler from an outlet in the top of the combined cooler, and the process gas washes a tube nest in the third-stage cooler to be cooled to 170 DEG C and is led out of a cooling system. And S3, absorbing the cooled maleic anhydride process gas by a solvent, and refining to obtain a finished product. The two shell-and-tube heat exchangers are optimized into the coil pipe and steam drum combined heat exchanger, the heat exchanger and the steam drum are combined, the leakage risk can be effectively reduced, steam can be generated through heat exchange, and heat waste is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production, and in particular to a heat exchange method for efficient heat energy recovery of a maleic anhydride device. Background Art

[0002] Maleic anhydride, also known as maleic anhydride, maleic anhydride, 2,5-furandione, etc., is an orthorhombic colorless needle-shaped or flaky crystal with a strong pungent odor. It is soluble in ethanol, ether and acetone, and is difficult to dissolve in petroleum ether and carbon tetrachloride. It reacts with hot water to generate maleic acid. It is mainly used as a raw material for the production of unsaturated polyester resins, alkyd resins, pesticide malathion, high-efficiency and low-toxic pesticides, and long-acting iodine amines; it is also a comonomer of coatings, maleic rosin, polymaleic anhydride, and maleic anhydride-styrene copolymers; it is also an organic chemical raw material for the production of ink additives, papermaking additives, plasticizers, tartaric acid, fumaric acid, tetrahydrofuran, etc.

[0003] Maleic anhydride reaction is an oxidative exothermic reaction in which 199KPa air provided by a compressor is mixed with 130℃ butane gas in a mixer (pressure drop 6KPa) and then enters a reactor (pressure drop 100KPa) for reaction. The reaction temperature is 400℃ and the pressure is 88KPa.

[0004] The main reaction is:

[0005] C4H 10 +3.5O2→C4H2O3+4H2O+21453KJ;

[0006] Side effects include:

[0007] C4H 10 +4.5O2→4CO+5H2O+26322KJ;

[0008] C4H 10 +6.5O2→4CO2+5H2O+45820KJ;

[0009] The rear section of the reaction device needs to absorb the maleic anhydride gas generated by the reaction with a solvent, and then produce the finished product through a series of refining steps. However, the solvent is easy to crack at high temperature to produce by-products, so the high-temperature maleic anhydride gas after the reaction must be cooled to about 170°C before absorption. At present, two shell and tube heat exchangers are used to cool the maleic anhydride gas generated by the reaction with deoxygenated water. The deoxygenated water after heat exchange is returned to the deaerator for reuse after cooling. In this process, there is heat loss and leakage risk.

[0010] Therefore, the present invention proposes a new cooling system to solve the problem of heat loss. Summary of the invention

[0011] According to the above technical problem that there is heat loss and leakage risk when two shell and tube heat exchangers are used to cool maleic anhydride gas, a heat exchange method for efficient heat energy recovery from maleic anhydride device is provided. The present invention mainly utilizes a combined heat exchanger to reduce the pressure drop of maleic anhydride gas generated by the reaction passing through the equipment, while reducing the load of the compressor.

[0012] The technical means adopted by the present invention are as follows:

[0013] A heat exchange method for efficient heat recovery of a maleic anhydride device comprises the following steps:

[0014] S1. Oxidation reaction occurs in the maleic anhydride reactor to produce maleic anhydride process gas, while releasing a large amount of heat:

[0015] S2, the process gas enters the cooling system from the lower head of the maleic anhydride reactor for heat recovery and product separation;

[0016] The cooling system includes a primary cooler, a secondary cooler and a tertiary cooler, wherein the primary cooler and the secondary cooler are combined coolers;

[0017] The process gas enters from the bottom inlet of the combined cooler, flushes the serpentine heat exchange tubes of the first and second coolers in turn, and the cooled process gas is led out from the top outlet of the combined cooler to the upper part of the third cooler. The process gas flushes the tubes in the third cooler until it is cooled to 170℃ and then leads out of the cooling system;

[0018] S3. The cooled maleic anhydride process gas is absorbed by the solvent and then refined to produce the finished product.

[0019] Furthermore, the process flow of the maleic anhydride oxidation reaction in S1 is as follows: 199KPa air provided by the compressor passes through a preheater with a pressure drop of 3.44KPa, and a raw material gas of 130°C n-butane is input through a gas distributor, the air and n-butane gas are fully mixed in a static mixer with a pressure drop of 6kPa, and then enter from the maleic anhydride reactor head, and the n-butane content of the mixed gas is 1.85mol%, and the gas temperature is 178°C;

[0020] The mixed gas enters the reaction tube from the upper head. The reaction tube is filled with vanadyl pyrophosphate vanadium (VO)2P2O7 catalyst. The mixed gas undergoes oxidation reaction in the reaction tube to produce maleic anhydride.

[0021] Further, the oxidation reaction is as follows:

[0022] C4H 10 +3.5O2→C4H2O3+4H2O+21453KJ;

[0023] C4H 10 +4.5O2→4CO+5H2O+26322KJ;

[0024] C4H 10 +6.5O2→4CO2+5H2O+45820KJ.

[0025] Furthermore, the primary cooler distributes cooling water to the heated pipes of the heated pipe group in the primary cooler through the water supply inlet container. After the cooling water is heated, it is led to the salt cooler through the water supply outlet header and the connecting pipe to continue to be heated and evaporated.

[0026] Furthermore, the feed water of the secondary cooler is introduced into the steam drum and mixed with the secondary cooling circulating water, and then enters the lower header through the downcomer and is distributed to the heated tubes of the heated tube group. After being heated, the circulating water becomes a steam-water mixture and is led to the steam drum through the upper header and the riser for steam-water separation. The separated water continues to participate in the circulation, and the saturated steam is led out of the boundary area.

[0027] Furthermore, the feed water of the tertiary cooler is introduced into the shell side of the heat exchanger and swept upward through a special baffle, and the heat exchange tube of the tertiary cooler is heated into a steam-water mixture, which evaporates in the evaporation space reserved at the top of the tertiary cooler, and the saturated steam is led out of the boundary area.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. The present invention optimizes two shell and tube heat exchangers into a coil + drum combined heat exchanger. The combination of the heat exchanger and the drum can effectively reduce the risk of leakage, and can use heat exchange to generate steam, thereby avoiding heat waste.

[0030] 2. The present invention changes two heat exchangers into one combined heat exchanger, which greatly reduces the pressure drop caused by the reaction of maleic anhydride gas passing through the equipment. Now the pressure only needs to pass through one heat exchanger to drop to 83KPa, and the equipment pressure drop is 5KPa. Therefore, the compressor load can be reduced while meeting the process conditions, bringing considerable benefits to the company. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 It is a flow chart of maleic anhydride reaction and cooling system in the present invention.

[0033] Figure 2 It is the working flow chart of the combined cooler in the present invention.

[0034] Figure 3It is a schematic diagram of the combined cooler in the present invention.

[0035] In the figure: 1. Maleic anhydride reactor; 2. Primary cooler; 3. Secondary cooler; 4. Tertiary cooler; 5. Salt cooler; 6. Steam drum. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0039] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0040] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0041] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0042] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0043] like Figure 1-3 As shown, the present invention provides a heat exchange method for efficient heat energy recovery of a maleic anhydride device, comprising the following steps:

[0044] S1, maleic anhydride reactor 1 undergoes oxidation reaction to produce maleic anhydride process gas, while releasing a large amount of heat:

[0045] The process flow of maleic anhydride oxidation reaction is as follows: 199KPa air provided by the compressor passes through the preheater with a pressure drop of 3.44KPa, and the raw material gas 130℃ n-butane is input through the gas distributor. The air and n-butane gas are fully mixed in the static mixer with a pressure drop of 6kPa, and then enter from the maleic anhydride reactor head. The n-butane content of the mixed gas is 1.85mol%, and the gas temperature is 178℃.

[0046] The mixed gas enters the reaction tube from the upper head. The reaction tube is filled with a vanadyl pyrophosphate vanadium (VO)2P2O7 catalyst. The mixed gas undergoes an oxidation reaction in the reaction tube to produce maleic anhydride.

[0047] The oxidation reaction is as follows:

[0048] C4H 10 +3.5O2→C4H2O3+4H2O+5.124kcal / kg;

[0049] C4H 10 +4.5O2→4CO+5H2O+6.287kcal / kg;

[0050] C4H 10 +6.5O2→4CO2+5H2O+10.944kcal / kg.

[0051] The oxidation reaction process releases a large amount of heat, part of which is used to increase the temperature of the raw gas n-butane and the air itself to 410°C, and the other part is released to the shell side through the reaction tube wall.

[0052] S2, the process gas enters the cooling system from the lower head of the maleic anhydride reactor 1 for heat recovery and product separation;

[0053] The cooling system includes a primary cooler 2, a secondary cooler 3 and a tertiary cooler 4, wherein the primary cooler 2 and the secondary cooler 3 are combined coolers;

[0054] The process gas enters from the bottom inlet of the combined cooler, flushes the serpentine heat exchange tubes of the primary cooler 2 and the secondary cooler 3 in turn, and the cooled process gas is led out from the top outlet of the combined cooler to the upper part of the tertiary cooler 4. The process gas flushes the tubes in the tertiary cooler 4 until it is cooled to 170°C and then leads out of the cooling system;

[0055] The primary cooler 2 distributes cooling water to the heated pipes of the heated pipe group in the primary cooler 2 through the water supply inlet container. After the cooling water is heated, it is led to the salt cooler 5 through the water supply outlet header and the connecting pipe to continue to be heated and evaporated.

[0056] The feed water of the secondary cooler 3 is introduced into the steam drum 6 and mixed with the secondary cooling circulating water, then enters the lower header through the downcomer and is distributed to the heated tubes of the heated tube group. After being heated, the circulating water becomes a steam-water mixture and is led to the steam drum 6 through the upper header and the riser for steam-water separation. The separated water continues to participate in the circulation, and the saturated steam is led out of the boundary area.

[0057] The feed water of the tertiary cooler 4 is introduced into the shell side of the cooler and swept upward through a special baffle. The heat exchange tube of the tertiary cooler 4 is heated into a steam-water mixture, which evaporates in the evaporation space reserved at the upper part of the tertiary cooler 4, and the saturated steam is led out of the boundary area.

[0058] S3. The cooled maleic anhydride process gas is absorbed by the solvent and then refined to produce the finished product.

[0059] According to the current 2.3MPa steam price of 155 yuan / ton, the three coolers of the maleic anhydride unit can increase the steam generation by 2 tons / h, and the annual operation time of the unit is 8000h:

[0060] 2.3MPa steam annual revenue: 155*2*8000÷10000=2.48 million yuan / year;

[0061] Deoxygenated water 4 yuan / ton: 4*2*8000÷10000=64,000 yuan / year;

[0062] Minimum operating power of compressor: 11410kw; Maximum operating power: 31487kw;

[0063] The minimum compressor outlet pressure is 78kpa; the maximum is 202kpa;

[0064] The pressure drop of the present invention is 10kpa less than that of the original process, so:

[0065] Annual savings for compressor: (31487-11410)÷(202-78)×10×8000÷10000=12.953 million yuan / year;

[0066] Annual savings in production costs: 2.48 million yuan / year + 12.953 million yuan / year - 64,000 yuan / year = 15.369 million yuan / year.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heat exchange method for efficient heat recovery of maleic anhydride device, characterized in that: The steps include: S1. Oxidation reaction occurs in the maleic anhydride reactor to produce maleic anhydride process gas, while releasing a large amount of heat: S2, the process gas enters the cooling system from the lower head of the maleic anhydride reactor for heat recovery and product separation; The cooling system includes a primary cooler, a secondary cooler and a tertiary cooler, wherein the primary cooler and the secondary cooler are combined coolers; The process gas enters from the bottom inlet of the combined cooler, flushes the serpentine heat exchange tubes of the first and second coolers in turn, and the cooled process gas is led out from the top outlet of the combined cooler to the upper part of the third cooler. The process gas flushes the tubes in the third cooler until it is cooled to 170℃ and then leads out of the cooling system; S3. The cooled maleic anhydride process gas is absorbed by the solvent and then refined to produce the finished product.

2. The heat exchange method for efficient heat energy recovery of maleic anhydride device according to claim 1, characterized in that: The process flow of maleic anhydride oxidation reaction in S1 is as follows: 199KPa air provided by the compressor passes through a preheater with a pressure drop of 3.44KPa, and a raw material gas of 130℃ n-butane is input through a gas distributor. The air and n-butane gas are fully mixed in a static mixer with a pressure drop of 6kPa, and then enter from the maleic anhydride reactor head. The n-butane content of the mixed gas is 1.85mol%, and the gas temperature is 178℃; The mixed gas enters the reaction tube from the upper head. The reaction tube is filled with vanadyl pyrophosphate vanadium (VO)2P2O7 catalyst. The mixed gas undergoes oxidation reaction in the reaction tube to produce maleic anhydride.

3. The heat exchange method for efficient heat energy recovery of maleic anhydride device according to claim 2, characterized in that: The oxidation reaction is as follows: C4H 10 +3.5O2→C4H2O3+4H2O+21453KJ; <h2 style=";text-align:left;direction:ltr">C4H<h2 style=";text-align:left;direction:ltr"> 10 <h2 style=";text-align:left;direction:ltr"> +4.5O2→4CO2+5H2O+26322KJ; <h2 style=";text-align:left;direction:ltr">C4H<h2 style=";text-align:left;direction:ltr"> 10 <h2 style=";text-align:left;direction:ltr"> +6.5O2→4CO2+5H2O+45820KJ.

4. The heat exchange method for efficient heat energy recovery of maleic anhydride device according to claim 1, characterized in that: The primary cooler distributes cooling water to the heated pipes of the heated pipe group in the primary cooler through the water supply inlet container. After the cooling water is heated, it is led to the salt cooler through the water supply outlet header and the connecting pipe to continue to be heated and evaporated.

5. The heat exchange method for efficient heat energy recovery of maleic anhydride device according to claim 1, characterized in that: The feed water of the secondary cooler is introduced into the steam drum and mixed with the secondary cooling circulating water, then enters the lower header through the downcomer and is distributed to the heated tubes of the heated tube group. After being heated, the circulating water becomes a steam-water mixture and is led to the steam drum through the upper header and the riser for steam-water separation. The separated water continues to participate in the circulation, and the saturated steam is led out of the boundary area.

6. The heat exchange method for efficient heat energy recovery of maleic anhydride device according to claim 1, characterized in that: The feed water of the three-stage cooler is introduced into the shell side of the cooler and swept upward through a special baffle. The heat exchange tube of the three-stage cooler is heated into a steam-water mixture, which evaporates in the evaporation space reserved at the top of the three-stage cooler, and the saturated steam is led out of the boundary area.

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