Descaling method and descaling system of cooler for melamine production

Abstract

The invention relates to the technical field of melamine cooling devices, in particular to a descaling method and a descaling system of a cooler for melamine production. The descaling method comprises the steps that when the cooler needs to be descaled, an ultrasonic generating device is arranged at an inlet of a heat exchange pipe of the cooler; a silica-alumina gel storage tank filled with silica-alumina gel is connected with an inlet of the cooling pipe; the silica-alumina gel storage tank is stamped, when the silica-alumina gel storage tank is stamped to the set pressure P, an ultrasonic wave generating device is started, after the set time T1, an outlet valve of the silica-alumina gel storage tank is opened, and silica-alumina gel in the silica-alumina gel storage tank is pressed into a heat exchange pipe of a cooler through gas; and feeding the descaled mixture into a cyclone separator through an outlet of the cooler for separation, heating the separated mixture for a set time T2 to obtain silica-alumina gel, and feeding the silica-alumina gel into a silica-alumina gel storage tank. The silica-alumina gel is repeatedly utilized, and the descaling cost is reduced. And the descaling frequency is effectively reduced, the service life of the cooler is prolonged, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of melamine cooling devices, and in particular to a descaling method and a descaling system for a cooler used in melamine production. Background Art

[0002] Melamine is a white monoclinic crystal, almost odorless, harmful to human body, and cannot be used in food processing or food additives. Melamine is mainly used as the main raw material for the manufacture of melamine formaldehyde resin, organic element analysis reagent, organic and resin synthesis as tanning agent and filler for leather processing. The main melamine production processes include European high pressure method, DSM low pressure method, and BASF atmospheric pressure gas phase cold extraction method.

[0003] At present, the production of melamine in China mainly adopts the BASF atmospheric pressure gas phase extraction and cooling process. The reaction gas coming out from the top of the fluidized bed mainly contains ammonia and carbon dioxide, melamine, isocyanic acid, melamine deamination products and other gases and catalyst particles. Since the deamination products of melamine will affect the quality of melamine-formaldehyde resin, they must be removed. For this reason, the generated gas from the fluidized bed must first enter the cooler for cooling. The generated gas passes through the tubes inside the cooler and exchanges heat with the coolant in the cooler shell, thereby achieving cooling of the generated gas.

[0004] After the cooler is used for a long time, by-products will be produced in the tubes and scale will be formed on the inner wall of the tubes, which will increase the resistance of the cooler, reduce the flux of the cooler tubes, or even make it unusable. Therefore, the cooler needs to be descaled every once in a while. Common descaling methods include backwashing, descaling with descaling agents, and high-pressure flushing. The backwashing method usually uses water for descaling, but the backwashing method is not effective for harder scale layers. The descaling with descaling agents can remove most of the scale layers, but some descaling agents may cause certain damage to the tube walls. The high-pressure flushing method uses the principle of high-pressure friction to remove scale, but the products after removal are usually directly poured out and cannot be recycled, resulting in a waste of descaling materials. Summary of the invention

[0005] In order to solve the above technical problems existing in the prior art, the present invention provides a descaling method and a descaling system for a cooler for melamine production.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] On the one hand, the present invention provides a descaling method for a cooler for melamine production, comprising: when the cooler needs to be descaled, an ultrasonic generator is arranged at the inlet of a heat exchange tube of the cooler; a silica-alumina gel storage tank filled with silica-alumina gel is connected to the inlet of the cooling tube; the silica-alumina gel storage tank is punched, and when the punching reaches a set pressure P, the ultrasonic generator is turned on, and after a set time T1, an outlet valve of the silica-alumina gel storage tank is opened, and the silica-alumina gel in the silica-alumina gel storage tank is pressed into the heat exchange tube of the cooler using gas;

[0008] The descaling mixture is sent to a cyclone separator for separation through the cooler outlet. The separated mixture is heated for a set time T2 to obtain silica-alumina gel, which is then sent to a silica-alumina gel storage tank.

[0009] Furthermore, the set pressure P of the stamping is 0.3 MPa.

[0010] Furthermore, after the ultrasonic generating device is turned on, the waiting setting time T1 is 8-11 minutes.

[0011] Furthermore, after the ultrasonic generating device is turned on, the waiting setting time T1 is 10 minutes.

[0012] Furthermore, after the set time T1, the opening degree of the outlet valve of the silica-alumina gel storage tank is 100%.

[0013] Furthermore, the gas is carbon dioxide or nitrogen.

[0014] Furthermore, the separated mixture is heated in a molten salt furnace.

[0015] Furthermore, the heating temperature is 600°C.

[0016] Furthermore, the heating setting time T2 is 8 hours.

[0017] Furthermore, after obtaining the silica-alumina gel, a blower is used to deliver the silica-alumina gel into a silica-alumina gel storage tank.

[0018] On the other hand, the present invention also provides a descaling system for a cooler for melamine production, which is used to perform the above-mentioned descaling method for a cooler for melamine production, and the descaling system includes: a silica-alumina gel storage tank connected to the inlet of the cooler, a cyclone separator connected to the outlet of the cooler, a molten salt furnace connected to the cyclone separator, and a blower connected to the molten salt furnace, wherein the outlet of the blower is connected to the inlet of the silica-alumina gel storage tank; an ultrasonic generating device is arranged at the inlet of the cooler.

[0019] Furthermore, a valve is provided at the outlet of the silica-alumina gel storage tank.

[0020] Furthermore, the cooler includes a shell and a heat exchange tube arranged inside the shell, one end of the shell is provided with an inlet for process gas to enter, and the other end of the shell is provided with an outlet for process gas to be discharged; the inlet is connected to one end of the heat exchange tube, and the outlet is connected to the other end of the heat exchange tube; the side wall of the shell is provided with a water inlet and a steam outlet.

[0021] Furthermore, a pressure relief valve is also provided on the side wall of the shell.

[0022] Furthermore, a sewage outlet is provided at the bottom of the shell.

[0023] Furthermore, there are two water inlets, namely a first water replenishment inlet and a second water replenishment inlet.

[0024] Furthermore, the heat exchange tube is spiral.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The descaling method and descaling system for a cooler for melamine production provided by the present invention are provided with an ultrasonic generator at the inlet of the cooler, the ultrasonic generator is first started for a certain period of time, the internal scale layer is subjected to ultrasonic vibration treatment for a certain period of time, and then the silicon-aluminum glue is pressed into the heat exchange tube by high-pressure gas, and the silicon-aluminum glue and the scale layer rub against each other to achieve the purpose of removing the scale layer. The silicon-aluminum glue used for descaling can be reused after separation and heating, thereby reducing the waste of silicon-aluminum glue and reducing the descaling cost. According to actual use verification, the descaling time of the cooler for melamine production is extended from 35 days to 50 days, which effectively reduces the number of descaling times, extends the use cycle of the cooler, and reduces production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a block diagram of the descaling system of the present invention.

[0028] Figure 2 This is a schematic diagram of the cooler structure used in the present invention.

[0029] Description of reference numerals:

[0030] 1. Inlet; 2. First water supply inlet; 3. Second water supply inlet; 4. Shell; 5. Drain outlet; 6. Outlet; 7. Heat exchange tube; 8. Steam outlet; 9. Pressure relief valve. DETAILED DESCRIPTION

[0031] 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.

[0032] It should be noted that, unless otherwise specifically stated, the relative arrangements of components and steps, and numerical expressions set forth in these embodiments should not be construed as limiting the scope of the present invention.

[0033] The following description of the exemplary embodiments is merely illustrative and is not intended to limit the present invention and its application or use in any sense. Techniques, methods and devices known to ordinary technicians in the relevant field may not be discussed in detail here, but where applicable, these techniques, methods and devices should be considered as part of this specification.

[0034] Embodiment 1

[0035] The present embodiment provides a descaling method for a cooler for melamine production, comprising: when the cooler needs to be descaled, an ultrasonic generator is arranged at the inlet of a heat exchange tube of the cooler; a silica-alumina gel storage tank filled with silica-alumina gel is connected to the inlet of the cooling tube; the silica-alumina gel storage tank is punched, and when the punching reaches a set pressure P, the ultrasonic generator is turned on, and after a set time T1, the outlet valve of the silica-alumina gel storage tank is opened, and the silica-alumina gel in the silica-alumina gel storage tank is pressed into the heat exchange tube of the cooler using gas;

[0036] The descaling mixture is sent to a cyclone separator for separation through the cooler outlet. The separated mixture is heated for a set time T2 to obtain silica-alumina gel, which is then sent to a silica-alumina gel storage tank.

[0037] Among them, the criteria for judging whether the cooler needs to be descaled can be determined by judging the resistance inside the cooler, or by judging the cooling effect of the cooler, or by using a method. When the cooler needs to be descaled, a new cooler is switched to ensure that the melamine production line does not stop production; the cooler to be descaled is descaled.

[0038] Before descaling, add 50KG of silica-alumina gel into the silica-alumina gel storage tank, and then pressurize the silica-alumina gel storage tank, usually to 0.3MPa. Then turn on the ultrasonic generator, and the waiting setting time T1 is 8-11 minutes, and the preferred waiting setting time T1 is 10 minutes. After that, open the outlet valve of the silica-alumina gel storage tank, and the opening is 100%. Use carbon dioxide or nitrogen to quickly press the silica-alumina gel into the cooler heat exchange tube. In order to better press in the silica-alumina gel, the outlet of the silica-alumina gel storage tank can be set below the silica-alumina gel, and the silica-alumina gel storage tank is set at a high position of the cooler.

[0039] The pressed silica-alumina gel has a large kinetic energy, and it rubs against the byproduct scale layer on the inner wall of the heat exchange tube to achieve the purpose of removing the scale. The byproduct scale and silica-alumina gel mixture is sent out through the outlet of the cooler, and then passes through a cyclone separator to initially separate the byproduct scale and silica-alumina gel, but the separated silica-alumina gel is still mixed with byproducts; the separated byproduct scale and silica-alumina gel mixture is then fired at a high temperature of 600°C in a molten salt furnace for 8 hours to gasify the internal byproducts, and the remaining silica-alumina gel is sent to the silica-alumina gel storage tank through a blower for recycling.

[0040] After the descaling method provided by the present invention is used to descale the cooler used for melamine production, the production cycle of the cooler is extended from the original descaling period of 35 days to the descaling period of 50 days.

[0041] Embodiment 2

[0042] This embodiment provides a descaling system for a cooler for melamine production, which is used to perform the descaling method for a cooler for melamine production provided in the first embodiment. Figure 1 As shown, the descaling system includes: a silica-alumina gel storage tank connected to the inlet of a cooler, a cyclone separator connected to the outlet of the cooler, a molten salt furnace connected to the cyclone separator, a blower connected to the molten salt furnace, and the outlet of the blower is connected to the inlet of the silica-alumina gel storage tank; an ultrasonic generator is arranged at the inlet of the cooler.

[0043] In order to better control the flow of the silica-alumina gel, a valve is provided at the outlet of the silica-alumina gel storage tank, and the valve may be a manual valve or an electric valve.

[0044] like Figure 2 As shown, the cooler includes a shell 4 and a heat exchange tube 7 arranged inside the shell 4, an inlet 1 for process gas to enter is provided at one end of the shell 4, and an outlet 6 for process gas to be sent out is provided at the other end of the shell 4; the inlet 5 is connected to one end of the heat exchange tube 7, and the outlet 6 is connected to the other end of the heat exchange tube 7; the side wall of the shell 4 is provided with a water inlet and a steam outlet 8.

[0045] The side wall of the shell 4 is also provided with a pressure relief valve 9, which is an emergency pressure relief valve. When the internal pressure of the cooler exceeds the set pressure of the pressure relief valve, the pressure relief valve 9 is automatically opened to ensure that the internal pressure of the cooler is within the set pressure range, thereby avoiding safety accidents caused by high pressure inside the cooler.

[0046] The bottom of the shell 4 is provided with a sewage outlet 5 to facilitate cleaning of dirt inside the cooler.

[0047] There are two water inlets, namely a first water replenishment inlet 2 and a second water replenishment inlet 3. Cooling water enters the cooler shell through the first water replenishment inlet 2 or the second water replenishment inlet 3, and exchanges heat with the process gas inside the cooler to achieve the purpose of cooling the process gas.

[0048] As a preferred embodiment, the heat exchange tube 7 is spiral.

[0049] When the cooler is working, the process gas enters the heat exchange tube 7 from the inlet 1, and the process gas exchanges heat with the water inside the shell 4. After the heat exchange, the process gas temperature drops to 320°C-340°C, and is discharged from the heat exchange tube 7 through the outlet 6. During the heat exchange process, high-pressure steam is generated inside the cooler shell 4, and the generated high-pressure steam flows from the steam outlet 8 to the high-pressure steam network, thereby realizing full recovery and utilization of the high-pressure steam.

[0050] The above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, a person skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A descaling method for a cooler for melamine production, characterized in that: include: When the cooler needs to be descaled, an ultrasonic generator is installed at the inlet of the heat exchange tube of the cooler; a silica-alumina gel storage tank filled with silica-alumina gel is connected to the inlet of the cooling tube; the silica-alumina gel storage tank is punched, and when the pressure reaches the set pressure P, the ultrasonic generator is turned on, and after the set time T1, the outlet valve of the silica-alumina gel storage tank is opened, and the silica-alumina gel in the silica-alumina gel storage tank is pressed into the heat exchange tube of the cooler with gas; The descaling mixture is sent to a cyclone separator for separation through the cooler outlet. The separated mixture is heated for a set time T2 to obtain silica-alumina gel, which is then sent to a silica-alumina gel storage tank.

2. The descaling method according to claim 1, characterized in that: The set pressure P of the punching is 0.3 MPa.

3. The descaling method according to claim 1, characterized in that: After turning on the ultrasonic generator, the waiting time T1 is set to 8-11 minutes.

4. The descaling method according to claim 3, characterized in that: After turning on the ultrasonic generator, the waiting time T1 is set to 10 minutes.

5. The descaling method according to claim 1, characterized in that: The gas is carbon dioxide or nitrogen.

6. The descaling method according to claim 1, characterized in that: The separated mixture is heated in a molten salt furnace at a heating temperature of 600°C.

7. The descaling method according to claim 6, characterized in that: The heating setting time T2 is 8 hours.

8. A descaling system for a cooler for melamine production, used for executing the descaling method for a cooler for melamine production according to any one of claims 1 to 7, characterized in that: The descaling system includes: a silica-alumina gel storage tank connected to the cooler inlet, a cyclone separator connected to the cooler outlet, a molten salt furnace connected to the cyclone separator, a blower connected to the molten salt furnace, and the outlet of the blower is connected to the inlet of the silica-alumina gel storage tank; an ultrasonic generator is arranged at the inlet of the cooler.

9. The descaling system according to claim 8, characterized in that: The cooler includes a shell and a heat exchange tube arranged inside the shell. An inlet for process gas is provided at one end of the shell, and an outlet for process gas is provided at the other end of the shell. The inlet is connected to one end of the heat exchange tube, and the outlet is connected to the other end of the heat exchange tube. A water inlet and a steam outlet are provided on the side wall of the shell.

10. The descaling system according to claim 9, characterized in that The side wall of the shell is also provided with a pressure relief valve.

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