Device and method for cyclic regeneration of catalyst in melamine production

Abstract

The invention belongs to the technical field of melamine production equipment, and particularly relates to a device and a method for cyclic regeneration of a catalyst in melamine production. The device comprises a fluidized bed reactor and a molten salt furnace, an output port of the fluidized bed reactor is connected with an input port of the molten salt furnace, and an output port of the molten salt furnace is connected with an input port of the fluidized bed reactor; a catalyst regenerator is arranged in the molten salt furnace, and the internal temperature of the catalyst regenerator is 440 DEG C or above. The method comprises the steps that S1, the molten salt furnace provides a gasification decomposition environment with the temperature interval being 440 DEG C or above for a catalyst; s2, feeding the catalyst in the fluidized bed reactor into a spiral coil pipe in a catalyst regenerator through a screw pump, and performing heat exchange with the spiral coil pipe to absorb heat; and S3, gasifying, decomposing and regenerating the catalyst after heat absorption, and enabling the regenerated catalyst to flow into the fluidized bed reactor for cyclic utilization. The catalyst is recycled, the activity of the catalyst is not reduced, and the production is stable.

Description

Technical Field

[0001] The invention belongs to the technical field of melamine production equipment, and in particular relates to a device and method for recycling and regenerating a catalyst in melamine production. Background Art

[0002] In the one-step melamine production, the raw material is urea, and the fluidized bed reactor converts urea (urea is liquid urea) into melamine (melamine is in gaseous state) and obtains a higher melamine yield.

[0003] The fluidized bed reactor is filled with about 200 tons of catalyst, the main components of which are SiO2 and Al2O3, of which SiO2 accounts for 91% and Al2O3 accounts for 8%. The reaction of urea to melamine takes place on the surface of the catalyst particles. The catalyst has an important influence on the reaction. When the catalyst activity drops to a certain level (the bulk density rises to 1.2 g / ml, and the ignition loss rate at 800 degrees reaches more than 29%), it is necessary to stop feeding. That is, the activity of the catalyst directly determines the quality of the reaction, the level of production capacity, and the cost of raw material consumption.

[0004] However, after a period of use, the catalyst will adsorb a certain amount of by-products produced by the reaction. When the adsorption reaches a certain level, the activity of the catalyst will decrease. In severe cases, it will affect the generation of the reaction, thereby affecting the reaction output, increasing the consumption of raw materials, and further causing an increase in by-products, which will lead to increased resistance in the subsequent work sections and seriously restrict production stability.

[0005] Therefore, there is an urgent need for a method to solve the problem of reduced catalyst activity in the reaction of converting urea into melamine. Summary of the invention

[0006] In order to solve the above technical problem, that is, in the one-step melamine production, the catalyst will adsorb a certain amount of by-products produced by the reaction after a period of use. When the adsorption reaches a certain degree, the activity of the catalyst will decrease. In severe cases, it will affect the generation of the reaction, thereby affecting the reaction yield, increasing the consumption of raw materials, and then causing an increase in by-products, which will lead to an increase in resistance in the subsequent process sections, seriously restricting production stability.

[0007] The present invention provides the following technical solutions:

[0008] First,

[0009] The present invention provides a device for recycling and regenerating catalysts in melamine production, comprising a fluidized bed reactor and a molten salt furnace, wherein the output port of the fluidized bed reactor is connected to the input port of the molten salt furnace, and the output port of the molten salt furnace is connected to the input port of the fluidized bed reactor; a catalyst regenerator is arranged inside the molten salt furnace, the input port of the catalyst regenerator is connected to the input port of the molten salt furnace, and the output port of the catalyst regenerator is connected to the output port of the molten salt furnace, the internal temperature of the catalyst regenerator is above 440°C, and the catalyst in the fluidized bed reactor flows to the catalyst regenerator, and flows into the fluidized bed reactor after being catalytically regenerated.

[0010] Furthermore, the output port of the fluidized bed reactor is located at the bottom of the fluidized bed reactor, and the input port of the fluidized bed reactor is located at the top of the fluidized bed reactor; the output port of the molten salt furnace is located at the top of the molten salt furnace, and the input port of the molten salt furnace is located at the bottom of the molten salt furnace; a screw pump is arranged on the pipeline connecting the output port of the fluidized bed reactor and the input port of the molten salt furnace, the temperature range of the screw pump is 400℃-550℃, and the flow rate of the screw pump is 1m 3 / h-5m 3 / h.

[0011] Furthermore, the catalyst regenerator is arranged at the lower center of the molten salt furnace, and the temperature at the lower center of the molten salt furnace is 900°C-1200°C.

[0012] Furthermore, the catalyst regenerator includes a shell, on which a catalyst airflow inlet, a catalyst airflow outlet and an airflow mixing component are arranged. The catalyst airflow inlet is connected to the input port of the molten salt furnace through a pipeline for transporting the catalyst airflow, and the catalyst airflow outlet is connected to the output port of the molten salt furnace through a pipeline for transporting the catalyst airflow.

[0013] Furthermore, the catalyst regenerator also includes an airflow mixing component, which includes a nitrogen pipeline. The nitrogen pipeline is arranged on the shell, and the angle between the nitrogen pipeline and the horizontal catalyst airflow conveying pipeline at the catalyst regenerator inlet is in the range of 20°-30°.

[0014] Furthermore, the nitrogen source of the airflow mixing component adopts 0.6Mpa-0.8Mpa nitrogen.

[0015] Furthermore, the catalyst regenerator also includes a spiral coil, the bottom end of which is arranged at the bottom center of the molten salt furnace and connected to the catalyst air flow inlet; the top end of the spiral coil is connected to the catalyst air flow outlet.

[0016] Furthermore, the spiral coil is spirally wound upwards parallel to the axis line in the molten salt furnace for several turns.

[0017] Furthermore, the pipeline at the outlet of the catalyst regenerator is provided with a temperature sensor and a flow meter.

[0018] Second,

[0019] The present invention provides a method for recycling and regenerating a catalyst in melamine production, using the above-mentioned device for recycling and regenerating a catalyst in melamine production, comprising the following steps:

[0020] S1. The catalyst in the fluidized bed reactor is input into the catalyst regenerator in the molten salt furnace, and the molten salt furnace provides a gasification decomposition environment with a temperature range of more than 440°C for the catalyst;

[0021] S2, sending the catalyst in the fluidized bed reactor into the spiral coil in the catalyst regenerator through a screw pump, and the catalyst absorbs heat after heat exchange with the spiral coil;

[0022] S3, the catalyst after absorbing heat is gasified and decomposed and then regenerated, and the regenerated catalyst flows into the fluidized bed reactor for recycling.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention utilizes the high temperature in the molten salt furnace and adopts a high-temperature resistant catalyst regenerator to transport the catalyst in the fluidized bed reactor into the catalyst regenerator for regeneration and return it to the upper part of the fluidized bed reactor, thereby realizing the recycling of the catalyst. Even if the feeding is not stopped, the catalyst can be activated separately, thereby realizing the online recycling regeneration of the catalyst, the activity of the catalyst will not decrease, and the production is stable.

[0025] The regenerated catalyst of the present invention does not need to be cooled down for a second time; conventional catalysts need to be cooled down after regeneration and then added to the fluidized bed reactor through a catalyst storage tank. Since the temperature in the molten salt furnace is above 900°C, most of the byproducts of the regenerated catalyst are completely decomposed and have a high temperature, so they do not need to be heated up again and directly enter the fluidized bed reactor, thereby reducing heat waste.

[0026] The present invention utilizes the high temperature in the molten salt furnace and adopts high-temperature resistant pipe materials made of alloy steel to make high-temperature heat exchange equipment - catalyst regenerator. The catalyst in the fluidized bed reactor is transported into the catalyst regenerator for regeneration through a screw pump and returned to the upper part of the fluidized bed reactor to achieve the recycling of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a schematic diagram of the structure of a catalyst recycling device for melamine production;

[0028] Reference numerals:

[0029] 1- fluidized bed reactor; 2- screw pump; 3- molten salt furnace; 4- catalyst regenerator; 41- shell; 42- air flow mixing component; 43- spiral coil; 5- flow meter; 6- thermometer. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly described below in conjunction with the accompanying drawings. Obviously, the described embodiments are not all embodiments of the present invention, and all other embodiments obtained by ordinary technicians in the field without making creative work are within the protection scope of the present invention.

[0031] It should be noted that the directions or positional relationships indicated by terms such as “center”, “up”, “down”, “horizontal”, “left”, “right”, “front”, “back”, “lateral” and “longitudinal” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0032] Example 1

[0033] like Figure 1 As shown, the present invention provides a device for recycling and regenerating catalysts in melamine production, comprising a fluidized bed reactor 1, a screw pump 2, a molten salt furnace 3, and a pipeline for transporting catalyst gas flow.

[0034] The output port of the fluidized bed reactor 1 is located at the bottom of the fluidized bed reactor 1 , and the input port of the fluidized bed reactor 1 is located at the top of the fluidized bed reactor 1 .

[0035] The output port of the molten salt furnace 3 is located at the top of the molten salt furnace 3 , and the input port of the molten salt furnace 3 is located at the bottom of the molten salt furnace 3 .

[0036] The output port of the fluidized bed reactor 1 is connected to the input port of the molten salt furnace 3 through a pipeline for transporting the catalyst gas flow.

[0037] The output port of the molten salt furnace 3 is connected to the input port of the fluidized bed reactor 1 through a pipeline for transporting the catalyst gas flow.

[0038] The pipeline for transporting the catalyst gas flow connecting the output port of the fluidized bed reactor 1 and the input port of the molten salt furnace 3 is provided with a screw pump 2. The temperature range of the screw pump 2 is 400°C-550°C. The flow rate of the screw pump 2 is 1m / s. 3 / h-5m 3 / h.

[0039] A catalyst regenerator 4 is arranged inside the molten salt furnace 3 .

[0040] The catalyst regenerator 4 is arranged at the lower center position of the molten salt furnace 3. The lower center position of the molten salt furnace 3 is the position with the highest temperature in the molten salt furnace 3. The temperature of the lower center position of the molten salt furnace 3 is 900℃-1200℃. The molten salt furnace 3 provides a high-temperature catalytic regeneration environment of more than 440℃ for the catalyst regenerator 4.

[0041] The catalyst regenerator 4 includes a shell 41 , an air flow mixing component 42 , and a spiral coil 43 .

[0042] A catalyst airflow inlet is arranged on the left side of the bottom of the shell 41 , a catalyst airflow outlet is arranged on the right side of the top of the shell 41 , and an airflow mixing component 42 is also arranged on the left side of the bottom of the shell 41 .

[0043] The catalyst airflow inlet is connected to the input port of the molten salt furnace 3 through a pipeline for transporting the catalyst airflow, and the catalyst airflow outlet is connected to the output port of the molten salt furnace 3 through a pipeline for transporting the catalyst airflow.

[0044] The airflow mixing component 42 includes a nitrogen pipeline, which is installed on the housing 41 through a mounting hole, and the diameter of the mounting hole is 2 mm. The angle between the nitrogen pipeline and the pipeline for conveying the horizontal catalyst airflow at the inlet of the catalyst regenerator 4 is α, and the range of α is 20°-30°. In this embodiment, α is 25°.

[0045] Under the power of the screw pump 2, the catalyst gas flow output from the fluidized bed reactor 1 is input into the catalyst regenerator 4, first mixed by the gas flow mixing component 42, and then heated by the spiral coil 43 for regeneration. After the catalyst is regenerated in the catalyst regenerator 4, it is input into the fluidized bed reactor 1 and put into circulation again.

[0046] The function of the airflow mixing component 42 is to make the catalyst airflow be evenly mixed in the spiral coil 43. The catalyst is transported by the 25° inclined nitrogen pipeline and the screw pump 2. After adjusting the nitrogen pressure and the flow rate of the screw pump 2, the airflow mixing of nitrogen and catalyst is realized. The higher the nitrogen pressure, the faster the mixing speed. When it reaches a certain value, it will be all nitrogen and the mixing effect cannot be achieved. The test results show that the best effect is achieved when it is controlled at 0.6Mpa-0.8Mpa. Therefore, the nitrogen source of the airflow mixing component 42 adopts 0.6Mpa-0.8Mpa nitrogen.

[0047] One end of the spiral coil 43 is welded to the bottom center of the molten salt furnace 3, and spirally coils 12 times parallel to the axis line in the molten salt furnace 3. The other end of the spiral coil 43 is connected to the catalyst airflow outlet; the catalyst airflow outlet is connected to the top of the fluidized bed reactor 1, and the regenerated catalyst airflow enters the fluidized bed reactor 1 for recycling.

[0048] Catalyst regeneration mainly decomposes by-products adsorbed in the surface micropores. The by-products will be completely gasified and decomposed at 440°C. The internal temperature of the molten salt furnace 3 is as high as 900°C, which fully meets the decomposition conditions of the by-products.

[0049] The spiral coil 43 is made of alloy steel, which has high temperature resistance. The spiral design increases the heat exchange area and prolongs the residence time of the catalyst in the spiral coil 43, which is beneficial to the regeneration of the catalyst.

[0050] A thermometer 6 is provided at the outlet of the catalyst regenerator 4 as a temperature detection point of the catalyst, and a flow meter 5 is provided at the temperature detection point.

[0051] By adjusting the frequency of the inverter of screw pump 2, the catalyst delivery volume is controlled at 1m 3 / h-3m 3 / h, and control the temperature of the catalyst after regeneration to be above 440°C, such as between 450°C and 480°C. At this temperature, most of the by-products adsorbed in the catalyst can be decomposed.

[0052] Example 2

[0053] like Figure 1 As shown, the present invention provides a method for recycling and regenerating a catalyst in melamine production.

[0054] S1, inputting the catalyst in the fluidized bed reactor 1 into the catalyst regenerator 4 in the molten salt furnace 3, providing a gasification decomposition environment with a temperature above 440°C, such as between 450°C and 480°C for the catalyst;

[0055] S2, the catalyst flows into the spiral coil 43 in the catalyst regenerator 4, and absorbs heat after heat exchange with the spiral coil 43;

[0056] S3, the catalyst after absorbing heat is regenerated and decomposed, and flows into the fluidized bed reactor 1 for recycling.

[0057] The above technical features constitute the best embodiment of the present invention, which has strong adaptability and best implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the needs of different situations.

[0058] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A device for recycling and regenerating a catalyst in melamine production, comprising a fluidized bed reactor, characterized in that: It also includes a molten salt furnace, the output port of the fluidized bed reactor is connected to the input port of the molten salt furnace, and the output port of the molten salt furnace is connected to the input port of the fluidized bed reactor; a catalyst regenerator is arranged inside the molten salt furnace, the input port of the catalyst regenerator is connected to the input port of the molten salt furnace, and the output port of the catalyst regenerator is connected to the output port of the molten salt furnace, the internal temperature of the catalyst regenerator is above 440°C, the catalyst of the fluidized bed reactor flows to the catalyst regenerator, and flows into the fluidized bed reactor after catalytic regeneration.

2. The device for recycling and regenerating catalyst in melamine production according to claim 1, characterized in that: The output port of the fluidized bed reactor is located at the bottom of the fluidized bed reactor, and the input port of the fluidized bed reactor is located at the top of the fluidized bed reactor; the output port of the molten salt furnace is located at the top of the molten salt furnace, and the input port of the molten salt furnace is located at the bottom of the molten salt furnace; a screw pump is arranged on the pipeline connecting the output port of the fluidized bed reactor and the input port of the molten salt furnace. The temperature range of the screw pump is 400℃-550℃, and the flow rate of the screw pump is 1m 3 / h-5m 3 / h.

3. The device for recycling and regenerating catalyst in melamine production according to claim 2, characterized in that: The catalyst regenerator is arranged at the lower center of the molten salt furnace, and the temperature at the lower center of the molten salt furnace is 900°C-1200°C.

4. The device for recycling and regenerating catalyst in melamine production according to claim 3, characterized in that: The catalyst regenerator includes a shell, on which a catalyst airflow inlet, a catalyst airflow outlet and an airflow mixing component are arranged. The catalyst airflow inlet is connected to the input port of the molten salt furnace through a pipeline for conveying catalyst airflow, and the catalyst airflow outlet is connected to the output port of the molten salt furnace through a pipeline for conveying catalyst airflow.

5. The device for recycling and regenerating catalyst in melamine production according to claim 4, characterized in that: The catalyst regenerator also includes an airflow mixing component, which includes a nitrogen pipeline. The nitrogen pipeline is arranged on the shell, and the angle between the nitrogen pipeline and the horizontal catalyst airflow conveying pipeline at the catalyst regenerator inlet is in the range of 20°-30°.

6. The device for recycling and regenerating catalyst in melamine production according to claim 5, characterized in that: The nitrogen source of the air flow mixing component adopts 0.6Mpa-0.8Mpa nitrogen.

7. The device for recycling and regenerating catalyst in melamine production according to claim 4, characterized in that: The catalyst regenerator also includes a spiral coil made of alloy steel. The bottom end of the spiral coil is arranged at the bottom center of the molten salt furnace and is connected to the catalyst airflow inlet; the top end of the spiral coil is connected to the catalyst airflow outlet.

8. The device for recycling and regenerating catalyst in melamine production according to claim 7, characterized in that: The spiral coil is spirally wound upward for several turns parallel to the axis line in the molten salt furnace.

9. The device for recycling and regenerating catalyst in melamine production according to claim 1, characterized in that: The pipeline at the outlet of the catalyst regenerator is provided with a temperature sensor and a flow meter.

10. A method for recycling and regenerating a catalyst in melamine production, using the device for recycling and regenerating a catalyst in melamine production according to claim 7, characterized in that: The steps include: S1. The catalyst in the fluidized bed reactor is input into the catalyst regenerator in the molten salt furnace, and the molten salt furnace provides a gasification decomposition environment with a temperature range of more than 440°C for the catalyst; S2, sending the catalyst in the fluidized bed reactor into the spiral coil in the catalyst regenerator through a screw pump, and the catalyst absorbs heat after heat exchange with the spiral coil; S3, the catalyst after absorbing heat is gasified and decomposed and then regenerated, and the regenerated catalyst flows into the fluidized bed reactor for recycling.

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