A method for on-line removal of molecular sieve residue from an atomizing disc of a centrifugal spray dryer

Abstract

The application relates to a method for removing the residual molecular sieve of a centrifugal atomizing disc of a centrifugal spray dryer in line, belonging to the technical field of centrifugal spray drying. During the spray forming process of the molecular sieve slurry by the centrifugal spray dryer, a large amount of material is easily condensed in the hole channel of the centrifugal dryer atomizing disc, causing the equipment to be unable to continuously operate. By setting the rotating speed of the centrifugal spray dryer atomizing disc, different temperature water and hot sodium hydroxide solution are sent into the spray dryer atomizing disc by a peristaltic pump, based on the principle of thermal expansion and cold contraction of the material, the principle that the material is easily dissolved in the lye and the centrifugal effect of the atomizing disc, the caked material in the atomizing disc and the residual lye in the pipeline can be completely removed. The application avoids repeated disassembly, washing and installation of the atomizing disc, realizes rapid removal of the caked material, the process is simple and easy to operate, meanwhile, the centrifugal spray device is not damaged, the continuous use of the centrifugal spray device is realized, and the utilization efficiency of the device is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of centrifugal spray drying, and particularly relates to a method for removing molecular sieve residues from an atomizing disc of a centrifugal spray dryer. BACKGROUND

[0002] In the chemical industry, a centrifugal spray dryer is often used to prepare microspherical molecular sieve catalysts suitable for fluidized bed reactors. The centrifugal spray dryer mainly comprises an electrical control cabinet, an electrical heating system, an atomizer, a drying tower, a peristaltic pump, an air blower and the like. The atomizing disc in the atomizer is the core component of the entire device. When the centrifugal spray dryer is fed, the heating system and the air blower and the like are first turned on, then the material (mainly molecular sieve slurry) is fed into the atomizer through the peristaltic pump, and then the atomizing disc (a stainless steel disc with a uniform pore structure) in the atomizer is rotated to form a liquid film under the action of separation, the liquid film is broken and dried by hot air to form powder or particles. Since the molecular sieve slurry is prone to dehydration and caking at high temperatures, thereby blocking the pore channels of the atomizing disc in the atomizer, the caked material in the atomizing disc cannot be removed by simple water flushing, therefore, according to the traditional process, the atomizing disc needs to be removed after each use, soaked in hot water for a period of time, and then the caked material is removed with a brush or the like. The process is complicated and time-consuming, and the centrifugal spray dryer cannot be used continuously, which is a great problem for the continuity of the production process. Therefore, how to quickly remove the caked material in the atomizing disc without removing the atomizing disc has become a technical problem to be solved. SUMMARY

[0003] The present application aims to provide a method for removing molecular sieve residues from an atomizing disc of a centrifugal spray dryer.

[0004] The normal feeding process of the centrifugal spray dryer is as follows: the process parameters such as the temperature of the feeding port of the centrifugal spray device, the feeding rate and the rotating speed of the atomizing disc are set, and after the process parameters reach the target values and are stable, the molecular sieve slurry is fed into the atomizing disc of the spray drying device through the peristaltic pump, the molecular sieve slurry is separated into a liquid film under the action of the high-speed rotating atomizing disc in the atomizer, and the liquid film is broken and dried by hot air to form microspherical molecular sieve particles; after the spray operation is completed, a large amount of caked material is left in the atomizing disc of the spray dryer due to the drying of part of the slurry, which blocks the pore channels of the atomizing disc and affects the next spray operation.

[0005] The molecular sieve slurry is mixed from molecular sieve and silica sol, and the mass ratio of the molecular sieve to the silica sol is 1:7-12; the molecular sieve is one or two of ZSM-5, TS-1 and TS-2, and the silica sol is a water dispersion of nano-sized silicon dioxide particles; in the molecular sieve slurry, the total solid content of the molecular sieve and the nano-sized silicon dioxide particles is 20-30wt%.

[0006] The method comprises the following steps:

[0007] (1) The rotation speed of the atomizing disc of the centrifugal spray dryer and the parameters of the peristaltic pump are set, hot water at 40-60 DEG C is sent into the atomizing disc through the peristaltic pump after the parameters of the equipment reach the set values, the feeding rate is 5-15 mL / min, and the feeding time is 10-20 min; then the hot water is replaced by low-temperature water at 3-8 DEG C, the feeding rate is 20-60 mL / min, and the feeding time is 20-40 min, and part of the caked materials are separated from the holes of the atomizing disc under the impact of water and the centrifugal force of the atomizing disc after thermal expansion and cold contraction;

[0008] Further, the rotation speed of the atomizing disc is 300-600 r / min;

[0009] (2) The rotation speed of the atomizing disc of the centrifugal spray dryer is adjusted, the sodium hydroxide aqueous solution at 50-70 DEG C is sent into the atomizing disc of the spray dryer through the peristaltic pump after the parameters of the equipment reach the set values and are stable, the feeding rate is 6-12 mL / min, and the feeding time is 30-90 min; then the sodium hydroxide aqueous solution is replaced by low-temperature water at 5-10 DEG C, the feeding rate is 10-20 mL / min, the feeding time is adjusted to 10-20 min, and part of the caked materials are separated from the holes of the atomizing disc under the impact of water and the centrifugal force of the atomizing disc after the caked materials are dissolved by the alkali solution;

[0010] Further, the rotation speed of the atomizing disc is 100-300 r / min, and the concentration of the sodium hydroxide aqueous solution is 2-3 mol / L;

[0011] (3) The rotation speed of the atomizing disc of the centrifugal spray dryer and the parameters of the peristaltic pump are adjusted, the sodium hydroxide aqueous solution at 60-80 DEG C is sent into the atomizing disc of the spray dryer through the peristaltic pump after the parameters of the equipment reach the set values, the feeding rate is 3-6 mL / min, and the feeding time is 10-30 min; then the sodium hydroxide aqueous solution is replaced by low-temperature water at 10-15 DEG C, the feeding rate is 30-50 mL / min, and the feeding time is 30-60 min, so that the caked molecular sieve materials in the atomizing disc and the residual alkali solution in the pipeline are completely removed;

[0012] Further, the rotation speed of the atomizing disc is 200-400 r / min, and the concentration of the sodium hydroxide aqueous solution is 1-2 mol / L;

[0013] The waste water generated in the cleaning process flows into the laboratory drain through the opening at the lower part of the centrifugal spray dryer, and then flows into a sewage tank for treatment.

[0014] The maximum feeding capacity of the centrifugal spray dryer is 5 L / h, and the equipment is well known and used in the market.

[0015] The beneficial effects of the present application are: firstly, the centrifugal spray dryer can remove the caked material completely without dismounting the atomizing disc, avoiding the repeated dismounting, washing and mounting process of the atomizing disc; secondly, the atomizing disc is cleaned on line by using high and low temperature water and hot alkaline solution with a suitable concentration, and the caked material is removed quickly by using the principle that the caked material is easy to separate after thermal expansion and cold contraction, the material is easy to dissolve in the alkaline solution with a certain temperature and concentration, and the dissolved caked material is accelerated to separate under the centrifugal force of the fast rotating atomizing disc, so that the process is simple and easy to operate, the centrifugal spray device is not damaged, the continuous use of the centrifugal spray device is realized, and the utilization efficiency of the device is improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 : the photo of the atomizing disc of the centrifugal spray dryer before cleaning in Example 2;

[0017] Figure 2 : the photo of the atomizing disc of the centrifugal spray dryer after cleaning in Example 2. DETAILED DESCRIPTION

[0018] Example 1: This example is a detailed operation method of the process of spraying and shaping the molecular sieve slurry in the centrifugal spray dryer and the on-line removal of the molecular sieve residues in the atomizing disc of the centrifugal spray dryer.

[0019] Firstly, 3L of the molecular sieve slurry is configured, which is mixed by ZSM-5 molecular sieve and silica sol (the silica sol is a water dispersion of nano-sized silicon dioxide particles), and the mass ratio of the molecular sieve to the silica sol is 1:10; in the molecular sieve slurry, the total solid content of the molecular sieve and the nano-sized silicon dioxide particles is 25wt%.

[0020] The process parameters of the centrifugal spray dryer are set, and after the process parameters of the equipment reach the target value and are stable, the molecular sieve slurry is sent into the atomizer of the centrifugal spray dryer by the peristaltic pump, and then is separated into liquid film under the action of the high-speed rotating atomizing disc, the liquid film is broken and dried by hot air to form microspherical molecular sieve particles, and a large amount of caked material is found to be left in the atomizing disc after the spraying operation is completed.

[0021] The molecular sieve residues in the atomizing disc are cleaned on line as follows:

[0022] (1) the rotating speed of the atomizing disc of the centrifugal spray dryer is set to 600r / min, after the process parameters of the equipment reach the set value and are stable, hot water at 60℃ is sent into the atomizing disc by the peristaltic pump, the feeding rate is 5mL / min, the feeding time is 10min, then the hot water is replaced by low temperature water at 8℃, the feeding rate is 60mL / min, the feeding time is 20min, and part of the caked material is separated from the atomizing disc channel under the impact of the water and the centrifugal force of the atomizing disc after thermal expansion and cold contraction;

[0023] (2) Adjust the rotation speed of the atomizing disc of the centrifugal spray dryer to 200 r / min. After the equipment parameters reach the set values and are stable, send 50℃ sodium hydroxide solution (concentration of 2 mol / L) into the atomizing disc of the spray dryer through a peristaltic pump at a feeding rate of 12 mL / min for 90 min. Then replace the sodium hydroxide solution with 5℃ low-temperature water at a feeding rate of 20 mL / min for 10 min. Most of the caked materials are dissolved in the alkali solution and are separated from the atomizing disc under the impact of water and the centrifugal force of the atomizing disc.

[0024] (3) Adjust the rotation speed of the atomizing disc of the centrifugal spray dryer to 400 r / min. After the equipment parameters reach the set values and are stable, send 80℃ sodium hydroxide solution (concentration of 2 mol / L) into the atomizing disc of the spray dryer through a peristaltic pump at a feeding rate of 3 mL / min for 30 min. Then replace the sodium hydroxide solution with 15℃ low-temperature water at a feeding rate of 30 mL / min for 60 min, so as to completely remove the caked molecular sieve materials in the atomizing disc and the residual alkali solution in the pipeline.

[0025] Example 2: This example is a detailed operation method of the process of spraying and shaping of the molecular sieve slurry in the centrifugal spray dryer and the online removal of the molecular sieve residues in the atomizing disc of the centrifugal spray dryer.

[0026] First, configure 5L of molecular sieve slurry, which is mixed from TS-2 molecular sieve and silica sol (silica sol is a water dispersion of nano-sized silicon dioxide particles), and the mass ratio of the molecular sieve to the silica sol is 1:12. In the molecular sieve slurry, the total solid content of the molecular sieve and the nano-sized silicon dioxide particles is 22wt%.

[0027] Set the process parameters of the centrifugal spray dryer. After the equipment process parameters reach the target values and are stable, send the molecular sieve slurry into the atomizer of the centrifugal spray dryer through a peristaltic pump. Then, under the action of the high-speed rotating atomizing disc, the molecular sieve slurry is separated into liquid films. The liquid films are broken and dried by hot air to form microspherical molecular sieve particles. After the spraying operation is completed, it can be found that a large amount of caked materials are left in the atomizing disc.

[0028] Online cleaning of the molecular sieve residues in the atomizing disc:

[0029] (1) Set the rotation speed of the atomizing disc of the centrifugal spray dryer to 300 r / min. After the equipment process parameters reach the set values and are stable, send 40℃ hot water into the atomizing disc through a peristaltic pump at a feeding rate of 15 mL / min for 20 min. Then replace the hot water with 3℃ low-temperature water at a feeding rate of 30 mL / min for 30 min. Part of the caked materials are separated from the atomizing disc under the impact of water and the centrifugal force of the atomizing disc after thermal expansion and cold contraction.

[0030] (2) Adjust the rotation speed of the atomizing disc of the centrifugal spray dryer to 100 r / min, and after the equipment parameters reach the set values and are stable, then send the 70℃ sodium hydroxide aqueous solution (concentration of 3 mol / L) into the atomizing disc of the spray dryer through a peristaltic pump, the feeding rate of the sodium hydroxide aqueous solution is 6 mL / min, and the feeding time is 30 min; then replace the sodium hydroxide aqueous solution with 10℃ low-temperature water, the feeding rate is 10 mL / min, and the feeding time is 20 min, and most of the caked materials are separated from the atomizing disc channel under the impact of water and the centrifugal force of the atomizing disc after being dissolved by the alkali solution;

[0031] (3) Adjust the rotation speed of the atomizing disc of the centrifugal spray dryer to 200 r / min, and after the equipment parameters reach the set values and are stable, send the 60℃ sodium hydroxide aqueous solution (concentration of 2 mol / L) into the atomizing disc of the spray dryer through a peristaltic pump, the feeding rate is 6 mL / min, and the feeding time is 10 min; then replace the sodium hydroxide aqueous solution with 10℃ low-temperature water, the feeding rate is 50 mL / min, and the feeding time is 30 min, so as to completely remove the caked molecular sieve materials in the atomizing disc and the residual alkali solution in the pipeline.

[0032] As shown in Figure 1 and Figure 2 , wherein (a) is a front view of the atomizing disc, and (b) is a back view of the atomizing disc; it can be seen that there are caked materials on the surface and in the channel of the atomizing disc after the centrifugal spray dryer works; after the cleaning method described in the application is used, the caked materials on the surface and in the channel of the atomizing disc are all cleaned away, and the surface and the channel of the atomizing disc are restored to be clean and smooth.

[0033] The details not described in the application are the conventional technical means known to those skilled in the art. The above description is only the preferred embodiment of the application and is not used to limit the application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A method for online removal of molecular sieve residues from the atomizing disc of a centrifugal spray dryer, characterized in that: The steps are as follows: (1) Set the speed of the centrifugal spray drying atomizing disc and the parameters of the peristaltic pump. After the equipment parameters reach the set values, send hot water at 40~60℃ into the atomizing disc through the peristaltic pump. The feeding rate is 5~15mL / min and the feeding time is 10~20min. Then replace the hot water with low temperature water at 3~8℃. The feeding rate is 20~60mL / min and the feeding time is 20~40min. After thermal expansion and contraction, some of the agglomerated materials are separated from the atomizing disc channels under the impact of water and the centrifugal force of the atomizing disc. (2) Adjust the rotation speed of the atomizing disc of the centrifugal spray dryer. After the equipment parameters reach the set value and stabilize, feed the sodium hydroxide aqueous solution at 50~70℃ into the atomizing disc of the spray dryer through a peristaltic pump. The feeding rate is 6~12mL / min and the feeding time is 30~90min. Then replace the sodium hydroxide aqueous solution with low temperature water at 5~10℃. The feeding rate is 10~20mL / min and the feeding time is adjusted to 10~20min. After the alkaline solution dissolves the material, it is separated from the atomizing disc channel under the impact of water and the centrifugal force of the atomizing disc. (3) Adjust the speed of the centrifugal spray dryer atomizing disc and the parameters of the peristaltic pump. After the equipment parameters reach the set value, send the sodium hydroxide aqueous solution at 60~80℃ into the atomizing disc of the spray dryer through the peristaltic pump. The feeding rate is 3~6mL / min and the feeding time is 10~30min. Then replace the sodium hydroxide aqueous solution with low temperature water at 10~15℃. The feeding rate is 30~50mL / min and the feeding time is 30~60min, so as to completely remove the molecular sieve agglomerated material in the atomizing disc and the residual alkali in the pipeline.

2. The method for online removal of molecular sieve residue from the atomizing disc of a centrifugal spray dryer as described in claim 1, characterized in that: In step (1), the molecular sieve slurry is a mixture of molecular sieve and silica sol, with a mass ratio of molecular sieve to silica sol of 1:7~12; the molecular sieve is one or two of ZSM-5, TS-1, and TS-2, and the silica sol is an aqueous dispersion of silica nanoparticles; the total solid content of molecular sieve and silica nanoparticles in the molecular sieve slurry is 20~30wt%.

3. The method for online removal of molecular sieve residue from the atomizing disc of a centrifugal spray dryer as described in claim 1, characterized in that: In step (1), the rotation speed of the atomizing disc is 300~600 r / min.

4. The method for online removal of molecular sieve residue from the atomizing disc of a centrifugal spray dryer as described in claim 1, characterized in that: In step (2), the rotation speed of the atomizing disc is 100~300 r / min, and the concentration of the sodium hydroxide aqueous solution is 2~3 mol / L.

5. The method for online removal of molecular sieve residue from the atomizing disc of a centrifugal spray dryer as described in claim 1, characterized in that: In step (3), the rotation speed of the atomizing disc is 200~400 r / min, and the concentration of the sodium hydroxide aqueous solution is 1~2 mol / L.

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