A bisphenol A reactor capable of reducing heat load and avoiding catalyst bed clogging

Abstract

The present invention relates to the technical field of general chemical or physical methods performed in the presence of fluids and solid particles. Disclosed is a bisphenol A reactor capable of reducing heat load and preventing catalyst bed clogging. The reactor is used to synthesize bisphenol A using phenol and acetone as raw materials through a heterogeneous catalytic reaction. The reactor is an adiabatic fixed-bed reactor with two upper and lower separated catalyst beds. In the present invention, acetone is separated from the feed and heat exchanged with hot reaction liquid drawn from the middle section of the reactor in a heat exchanger. The vaporized acetone carries a large amount of reaction heat and is then transferred to the feed, significantly raising the temperature of the reaction liquid entering the catalyst bed. This prevents crystallization clogging in the cooler upper bed and significantly reduces the heat load of preheating the reactor feed. Furthermore, the hot reaction liquid in the middle section of the reactor is cooled and then returned to the lower bed, preventing the lower bed from overheating and causing a large number of side reactions, as would be the case when the feed temperature is directly raised.

Description

Technical Field

[0001] The present invention relates to the technical field of general chemical or physical methods carried out in the presence of fluids and solid particles, and in particular to a bisphenol A reactor capable of reducing heat load and avoiding catalyst bed blockage. Background Art

[0002] Bisphenol A is a raw material for a variety of synthetic resins, including epoxy resins, polycarbonate, polyphenylene ether resins, polysulfone resins, and unsaturated polyester resins. It is also used in plasticizers, flame retardants, rubber antioxidants, heat stabilizers, coatings, and pesticides. With the rapid development of the national economy, the application of bisphenol A is becoming increasingly widespread.

[0003] The bisphenol A reactor is a key piece of equipment in a bisphenol A production plant, and its operating conditions directly impact the yield of bisphenol A. The bisphenol A synthesis reaction is exothermic (-90 kJ / mol [Applied Catalysis, 1988, 37:129-138]) and involves parallel side reactions. To ensure conversion and selectivity, the feed temperature must be kept within a certain range, with the optimal feed temperature being near the crystallization temperature of bisphenol A [Journal of Chemical Engineering of Universities, 2004, 18 (3): 367-370].

[0004] Bisphenol A precipitation and catalyst bed clogging are a major problem plaguing BPA production. Blockages disrupt normal production, leading to frequent production starts and stops that not only reduce output but also produce large quantities of substandard product. These starts and stops also release significant amounts of pollutants into the environment. Nantong Xingchen (Bluestar)'s BPA unit suffered from catalyst bed blockage, resulting in multiple shutdowns and the premature scrapping of fresh catalyst (five reactors, each loaded with over 100 tons of catalyst), resulting in significant losses. Tianjin Shuangfu's BPA unit even shut down due to losses. However, research in this area has languished in recent years, and satisfactory solutions have eluded the market. The various makeshift solutions currently employed by manufacturers have proven inadequate.

[0005] A common solution is to increase the feed temperature (based on the optimal feed temperature). This not only consumes more heating steam but also causes the lower half of the reactor to overheat, producing more byproducts (generally speaking, temperatures above 80°C should be avoided in the reactor). Another common solution is to increase the molar ratio of solvent phenol in the feed, but this not only reduces production capacity but also places a greater burden on the subsequent dephenolization step, increasing the failure rate of equipment such as thin-film evaporators, which are already prone to failure. (For example, in Yanshan Petrochemical's bisphenol A unit, the thin-film evaporator suffers from repeated seal failures or stalls, and the elevator frequently becomes stuck.)

[0006] Existing solutions for impurity accumulation and bed blockage are relatively mature. For example, patent CN1829787A (Fischer-Tropsch synthesis system) mentions acid pretreatment of the feed. This approach is not suitable for bisphenol A precipitation clogging the catalyst bed, because in this system, the clogging is not caused by impurities but by the bisphenol A product. A similar situation (i.e., blockage caused by crystallization in the solution) is the crystallization of urea solution added to the exhaust gas treatment system of large diesel engines due to water loss. The solution is to add more solvent. This method has been tried by some manufacturers (see above), but the results are not ideal.

[0007] In addition to the above, CN108774113B, a bisphenol A production apparatus and method, discloses a method that uses heat pipes to transfer some of the reaction heat from the hotter bottom of the reactor to the cooler top, thereby preventing reactor clogging. However, in actual use, this method requires the use of more than 2,000 copper heat pipes that penetrate the entire catalyst bed (6 meters thick), significantly increasing reactor costs and making loading and unloading of the catalyst within the reactor difficult. Furthermore, these heat pipes, due to their large number and elongated length, are very susceptible to damage.

[0008] The inventors discovered during their research that in the existing bisphenol A synthesis reactor, the temperature of the lower section of the catalyst bed is higher than the boiling point of acetone at normal pressure, and that a large amount of heat is released when acetone dissolves in phenol. Summary of the Invention

[0009] The invention provides a bisphenol A reactor which can reduce heat load and avoid catalyst bed blockage.

[0010] The technical problem to be solved is that the optimal feed temperature of the bisphenol A reactor is at the edge of the crystallization temperature of bisphenol A, which makes the reactor prone to clogging; but directly increasing the feed temperature will lead to increased energy consumption and overheating of the lower half of the reactor (overheating will cause a large amount of by-products to be produced).

[0011] To solve the above technical problems, the present invention adopts the following technical solution: a bisphenol A reactor capable of reducing heat load and preventing catalyst bed clogging, for synthesizing bisphenol A using phenol and acetone as raw materials through a heterogeneous catalytic reaction, wherein the reactor is an adiabatic fixed-bed reactor having two catalyst beds separated from each other, the upper catalyst bed being referred to as the upper bed and the lower catalyst bed being referred to as the lower bed;

[0012] The feed to the reactor is divided into two parts: fresh acetone and components other than fresh acetone. The components other than fresh acetone are recorded as acetone components. The fresh acetone and the acetone components are mixed in a gas-liquid mixer to form a reaction liquid. The reaction liquid flows from top to bottom through two catalyst beds. The reaction liquid flowing through the upper bed is recorded as the middle hot liquid.

[0013] The reactor also includes an acetone vaporizing heat exchanger, wherein the hot fluid inlet of the acetone vaporizing heat exchanger is connected to the bottom of the upper bed through a pipeline, the hot fluid outlet is connected to the upper part of the lower bed through a pipeline, the cold fluid inlet is connected to the feed pipeline of fresh acetone, and the cold fluid outlet is connected to the gas phase inlet of the gas-liquid mixer through a pipeline, the feed pipeline of the external component of acetone is connected to the liquid phase inlet of the gas-liquid mixer, and the outlet of the gas-liquid mixer is connected to the upper part of the upper bed through a pipeline.

[0014] Furthermore, the acetone vaporization heat exchanger is a shell-and-tube heat exchanger, and the fresh acetone flows through the shell-and-tube heat exchanger via the tube path.

[0015] Furthermore, the acetone vaporization heat exchanger is a double-pass shell-and-tube heat exchanger, and the tube passes in the shell-and-tube heat exchanger are arranged vertically.

[0016] Furthermore, the static pressure of the fluid at the cold fluid outlet of the acetone vaporizing heat exchanger is recorded as P, the boiling point of acetone at P is recorded as H, and the temperature of the bottom of the upper bed layer is not less than H.

[0017] Furthermore, the static pressure of the fluid at the cold fluid outlet of the acetone vaporizing heat exchanger is normal pressure, the gas-liquid mixer is a venturi tube, the feed pipe of the acetone component is connected to one end of the venturi tube, and the cold fluid outlet pipe of the acetone vaporizing heat exchanger is connected to the throat of the venturi tube.

[0018] Furthermore, a spray-type liquid distributor is provided at the end of the outlet pipe of the gas-liquid mixer, and a liquid redistributor is provided at the end of the hot fluid outlet pipe of the acetone vaporization heat exchanger.

[0019] Furthermore, a pump for extracting the middle section of hot liquid is provided on the hot fluid inlet pipe of the acetone vaporization heat exchanger.

[0020] Furthermore, the bottom of the upper bed layer and the bottom of the lower bed layer are provided with catalyst support plates fixedly connected to the reactor shell. The catalyst support plate at the bottom of the upper bed layer is a sealing plate, and the catalyst support plate at the bottom of the lower bed layer is a sieve plate.

[0021] Compared with the prior art, the bisphenol A reactor of the present invention, which can reduce heat load and avoid catalyst bed clogging, has the following beneficial effects:

[0022] In the present invention, fresh acetone is separated from the feed (without mixing with phenol and recycled materials before being vaporized) and heat-exchanged with the hot reaction liquid in the middle section of the reactor in a heat exchanger. The vaporized fresh acetone carries a large amount of reaction heat and is then transferred to the feed, thereby significantly raising the temperature of the reaction liquid entering the catalyst bed and preventing crystallization and blockage in the cooler upper bed. Simultaneously, the hot reaction liquid in the middle section of the reactor is cooled and returned to the lower bed, preventing the lower bed from overheating and causing a large number of side reactions, as would be the case if the feed temperature were directly increased.

[0023] In the present invention, since the reaction heat can be used to heat the feed, the feed temperature of the reactor can be much lower than that of a conventional reactor (from 55°C mixed feed to 50.6°C propylene component plus 25°C acetone), thereby significantly reducing the heat load of preheating the reactor feed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic structural diagram of a bisphenol A reactor of the present invention that can reduce heat load and avoid catalyst bed clogging;

[0025] Figure 2 Figure 2 is a temperature distribution diagram of the catalyst bed of various different reactors. For the convenience of comparison, the upper bed and the lower bed of the reactor in the present invention are regarded as a continuous whole (that is, the depth of the bottom end of the upper bed is the same as the depth of the top end of the lower bed);

[0026] Among them, 1-upper bed layer, 2-lower bed layer, 3-acetone vaporization heat exchanger, 4-gas-liquid mixer. DETAILED DESCRIPTION

[0027] like Figure 1 As shown, a bisphenol A reactor that can reduce heat load and avoid catalyst bed clogging is used to synthesize bisphenol A using phenol and acetone as raw materials through a heterogeneous catalytic reaction. The reactor is an adiabatic fixed-bed reactor with two catalyst beds separated above and below. The upper catalyst bed is denoted as upper bed 1, and the lower catalyst bed is denoted as lower bed 2.

[0028] The feed to the reactor is divided into two parts: fresh acetone and components other than fresh acetone. The components other than fresh acetone are recorded as acetone components.

[0029] Note that although the raw materials used in the synthesis of bisphenol A are phenol and acetone, since phenol and acetone cannot react completely in the reactor, the feed to the reactor also includes recycled materials, that is, the reaction liquid after the reaction is returned to the reactor after separating some bisphenol A. The feed to the reactor is a mixture of fresh phenol, fresh acetone and recycled materials. The acetone component here refers to the mixture of fresh acetone and recycled materials. The recycled materials have complex components, including unreacted phenol and acetone, and unseparated bisphenol A, as well as many by-products. These by-products are collectively referred to as impurities in this article.

[0030] Fresh acetone and the acetone components are mixed in the gas-liquid mixer 4 to form a reaction liquid, which flows through the two catalyst beds from top to bottom. The reaction liquid flowing through the upper bed 1 is recorded as the middle hot liquid;

[0031] The reactor also includes an acetone vaporizing heat exchanger 3, the hot fluid inlet of the acetone vaporizing heat exchanger 3 is connected to the bottom of the upper bed layer 1 through a pipeline, the hot fluid outlet is connected to the upper part of the lower bed layer 2 through a pipeline, the cold fluid inlet is connected to the feed pipeline of fresh acetone, and the cold fluid outlet is connected to the gas phase inlet of the gas-liquid mixer 4 through a pipeline, the feed pipeline of the external component of acetone is connected to the liquid phase inlet of the gas-liquid mixer 4, and the outlet of the gas-liquid mixer 4 is connected to the upper part of the upper bed layer 1 through a pipeline.

[0032] The reason for removing the hot liquid from the middle section, rather than the hotter reaction liquid at the bottom of the reactor's catalyst bed, is that using the reaction heat to heat the feed, raising its temperature, could overheat the lower section of the reactor, leading to the production of large amounts of byproducts. Therefore, removing the hot liquid from the middle section, cooling it with fresh acetone, and then returning it to the reactor prevents overheating in the lower section. Using acetone to carry the reaction heat, rather than directly exchanging heat with the feed, allows the high heat transfer coefficient of phase change heat transfer to be utilized, thereby reducing the required heat exchange area and taking advantage of the acetone's heat of solution. This is crucial for reducing equipment costs, as the heat exchanger requires expensive stainless steel to resist phenol corrosion.

[0033] The acetone vaporizing heat exchanger 3 is a double-pass shell-and-tube heat exchanger, through which fresh acetone flows. This shell-and-tube heat exchanger was chosen because it is readily available in chemical plants, the required heat exchange area is small, and the temperature difference between the hot and cold fluids is significant, eliminating the need for specialized heat exchangers such as plate heat exchangers. The reason for placing fresh acetone in the tube side is that, in actual use, we have found that placing fresh acetone in the shell side causes severe vibration throughout the reactor due to the intense vaporization process. The double-pass heat exchanger is chosen to further reduce the heat exchanger volume and stainless steel consumption. A U-tube heat exchanger is preferably used for this double-pass heat exchanger to minimize the effects of thermal stress.

[0034] The tubes in the shell-and-tube heat exchanger are set vertically. The reason why the heat exchanger is placed vertically here is that the heat exchange tubes of the heat exchanger contain a gas-liquid mixture. If the heat exchanger is placed horizontally, the upper part of the tube will not be in good contact with the acetone liquid.

[0035] The hydrostatic pressure at the cold fluid outlet of acetone vaporizing heat exchanger 3 is denoted as P, the boiling point of acetone at P is denoted as H, and the temperature at the bottom of upper bed 1 is not less than H. In other words, the temperature at the bottom of upper bed 1 must be higher than the boiling point of acetone to enable acetone vaporization. Temperature control is achieved by controlling the thickness of upper bed 1 and lower bed 2. Specifically, the temperature distribution within a conventional reactor under identical conditions (no mid-stage hot liquid is drawn out, the reaction liquid flows continuously from top to bottom throughout the reactor, and all other conditions remain the same) is simulated and calculated to derive the functional relationship between catalyst bed depth and temperature. The portion above the boiling point of acetone and meeting the required temperature difference for heat exchange is then designated as lower bed 2.

[0036] The static pressure of the fluid at the cold fluid outlet of the acetone vaporizing heat exchanger 3 is normal pressure. The gas-liquid mixer 4 is a venturi tube. The feed pipe of the acetone component is connected to one end of the venturi tube, and the cold fluid outlet pipe of the acetone vaporizing heat exchanger 3 is connected to the throat of the venturi tube.

[0037] To ensure that the reaction solution flows smoothly through the catalyst bed in the reactor, the reactor feed pressure is significantly higher than normal pressure, generally at an absolute pressure of three atmospheres. However, at three atmospheres, the boiling point of acetone will be higher than the temperature of the mid-section hydrothermal solution, resulting in the acetone being unable to vaporize. Therefore, here we choose to reduce the static pressure of fresh acetone to make it easy to vaporize. But this has brought a new problem, that is, the acetone vapor cannot be merged into the acetone outer component, so we choose to use a venturi tube with negative pressure at the throat as the gas-liquid mixer 4 here. After the acetone vapor merges into the low-temperature acetone outer component, it immediately liquefies.

[0038] A spray-type liquid distributor is installed at the end of the outlet pipe of the gas-liquid mixer 4, and a liquid redistributor is installed at the end of the hot fluid outlet pipe of the acetone vaporization heat exchanger 3. This also provides an additional benefit: it redistributes the reaction liquid, preventing abnormal flows such as short-circuiting, channeling, and wall flow in the lower bed 2. The liquid redistributor is generally a tubular type to reduce the volume occupied by the existing reactor. If the internal volume of the reactor allows, a spray-type liquid redistributor can also be used.

[0039] The hot fluid inlet pipe of the acetone vaporization heat exchanger 3 is provided with a pump for extracting the hot liquid in the middle section, and this pump also supplies pressure to the liquid redistributor below.

[0040] The bottoms of both upper and lower beds 1 and 2 are equipped with catalyst support plates fixed to the reactor shell. The catalyst support plate at the bottom of upper bed 1 is a sealing plate, while the catalyst support plate at the bottom of lower bed 2 is a sieve plate. The catalyst support plate at the bottom of lower bed 2 remains unchanged and can be directly reused, while the sealing plate is used to intercept the mid-stage hot liquid.

[0041] like Figure 2 As shown: We also compared the temperature distribution in three reactors, which are respectively denoted as the original reactor, the reactor using heat pipes, and the present invention. The specifications of the three reactors are as follows:

[0042] Original reactor:

[0043] In the fixed bed reactor, the reaction liquid flows from top to bottom through the catalyst bed. The catalyst bed has a diameter of 5.1 meters and a height of 6.42 meters. The feed temperature is 55°C and the pressure is three atmospheres absolute pressure. It contains 1.175 kg / s of bisphenol A, 9.7625 kg / s of phenol, 0.4375 kg / s of acetone, and 1.125 kg / s of impurities.

[0044] Using heat pipes:

[0045] Based on the original reactor, heat pipes were inserted vertically into the catalyst bed. The heat pipes were arranged in an equilateral triangle, with a center-to-center distance of 100 mm. The heat pipes had an outer diameter of 20 mm and a wall thickness of 1 mm. Their length matched the catalyst bed. The exterior of the heat pipes was threaded with a 45° included thread angle and a rib count of 8. The heat pipe wall was made of T2-m copper. The working fluid inside the heat pipes was acetone, and no wick was provided.

[0046] The present invention:

[0047] On the basis of the original reactor, the original reactor structure was transformed into the style of the present invention, wherein the upper bed layer 1 is 1.5 meters high and the lower bed layer 2 is 4.92 meters high;

[0048] Specifications for the acetone vaporizing heat exchanger 3 are as follows: 64 double-pass heat exchange tubes arranged in a square pattern with a center-to-center distance of 23.812 mm; tube length of 2 meters, outer diameter of 19.05 mm, wall thickness of 1.65 mm, made of 304 stainless steel, with a tube-side pressure drop of 0.1 atmosphere; the heat exchanger shell has an inner diameter of 257.4 mm and an outer diameter of 273 mm, and is equipped with seven staggered baffles;

[0049] It can be seen that the acetone vaporization heat exchanger 3 is very small;

[0050] The external component: temperature 50.6 ° C, pressure of three atmospheres absolute pressure, containing 1.175 kg / s of bisphenol A, 9.7625 kg / s of phenol, 0.0875 kg / s of acetone, 1.125 kg / s of impurities

[0051] Fresh acetone: temperature 25°C, pressure 1 atmosphere absolute pressure, containing 0.35 kg / s of acetone.

[0052] Depend on Figure 2 It can be seen that the temperature of the upper bed layer 1 of the reactor of the present invention is higher than that of the other two reactors, so that crystallization blockage is less likely to occur, while the maximum temperature is equivalent to that of the original reactor.

[0053] According to the production data of Nantong Xingchen (the original reactor belongs to Nantong Xingchen), the location where crystallization blockage occurs in the reactor is the top of the catalyst bed. Crystallization blockage can be avoided by increasing the temperature of the reaction liquid entering the catalyst bed from 55°C to 57°C. In the present invention, the temperature of the reaction liquid entering the reactor is 59.23°C, and the composition is consistent with the original reactor, so crystallization blockage will not occur.

[0054] In addition, the final acetone conversion rate of the reactor in the present invention is slightly improved (less than 1%, but at least not reduced) compared with the other two.

[0055] Of course, the equipment and process parameters in this article are designed to ensure minimal changes to the original reactor. The discharge temperature remains consistent with the original reactor, and subsequent process flow remains unchanged. This design is not necessarily optimal. For example, if a new reactor were to be designed, the catalyst bed could be modified into two 1.5-meter-high sections.

[0056] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A bisphenol A reactor capable of reducing heat load and avoiding catalyst bed clogging, for synthesizing bisphenol A from phenol and acetone via a heterogeneous catalytic reaction, characterized in that: The reactor is an adiabatic fixed bed reactor having two catalyst beds separated from each other, the upper catalyst bed being designated as the upper bed (1) and the lower catalyst bed being designated as the lower bed (2); The feed of the reactor is divided into two parts: fresh acetone and components other than fresh acetone. The components other than fresh acetone are recorded as acetone components. The fresh acetone and the acetone components are mixed in the gas-liquid mixer (4) to form a reaction liquid. The reaction liquid flows from top to bottom through the two catalyst beds. The reaction liquid flowing through the upper bed (1) is recorded as the middle hot liquid. The reactor further comprises an acetone vaporizing heat exchanger (3), wherein the hot fluid inlet of the acetone vaporizing heat exchanger (3) is connected to the bottom of the upper bed (1) through a pipeline, the hot fluid outlet is connected to the upper part of the lower bed (2) through a pipeline, the cold fluid inlet is connected to the feed pipeline of fresh acetone, and the cold fluid outlet is connected to the gas phase inlet of the gas-liquid mixer (4) through a pipeline, the feed pipeline of the acetone component is connected to the liquid phase inlet of the gas-liquid mixer (4), and the outlet of the gas-liquid mixer (4) is connected to the upper part of the upper bed (1) through a pipeline; The static pressure of the fluid at the outlet of the cold fluid of the acetone vaporizing heat exchanger (3) is recorded as P, the boiling point of acetone at P is recorded as H, and the temperature of the bottom of the upper bed layer (1) is not less than H; The static pressure of the fluid at the cold fluid outlet of the acetone vaporizing heat exchanger (3) is normal pressure, the gas-liquid mixer (4) is a venturi tube, the feed pipe of the acetone component is connected to one end of the venturi tube, and the cold fluid outlet pipe of the acetone vaporizing heat exchanger (3) is connected to the throat of the venturi tube.

2. A bisphenol A reactor capable of reducing heat load and avoiding catalyst bed clogging according to claim 1, characterized in that: The acetone vaporizing heat exchanger (3) is a shell-and-tube heat exchanger, and fresh acetone flows through the shell-and-tube heat exchanger via the tube path.

3. A bisphenol A reactor capable of reducing heat load and avoiding catalyst bed clogging according to claim 2, characterized in that: The acetone vaporizing heat exchanger (3) is a double-pass shell-and-tube heat exchanger, and the tube passes in the shell-and-tube heat exchanger are arranged vertically.

4. The bisphenol A reactor according to claim 1, which can reduce heat load and avoid catalyst bed clogging, is characterized in that: A spray-type liquid distributor is provided at the end of the outlet pipe of the gas-liquid mixer (4), and a liquid redistributor is provided at the end of the hot fluid outlet pipe of the acetone vaporizing heat exchanger (3).

5. The bisphenol A reactor capable of reducing heat load and avoiding catalyst bed clogging according to claim 1, characterized in that: The hot fluid inlet pipe of the acetone vaporizing heat exchanger (3) is provided with a pump for extracting the middle section hot fluid.

6. The bisphenol A reactor according to claim 1, which can reduce heat load and avoid catalyst bed clogging, is characterized in that: The bottoms of the upper bed layer (1) and the lower bed layer (2) are both provided with catalyst support plates fixedly connected to the reactor shell. The catalyst support plate at the bottom of the upper bed layer (1) is a sealing plate, and the catalyst support plate at the bottom of the lower bed layer (2) is a sieve plate.

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