A continuous supply system for large-particle urea-formaldehyde solution

Abstract

The utility model provides a large-particle urea-formaldehyde solution continuous supply system, including an aldehyde stock solution metering pump, a urea-formaldehyde stock solution mixer, multiple parallel urea-formaldehyde reactors, a granulation stock solution metering pump and a granulation stock solution mixer; the aldehyde stock solution metering pump is provided with a formaldehyde solution delivery pump head, a dilute ammonia delivery pump head and a urea solution delivery pump head, and the outlets of the three delivery pump heads are connected to the inlet of the urea-formaldehyde stock solution mixer; the outlet of the urea-formaldehyde stock solution mixer is connected to the inlet of multiple parallel urea-formaldehyde reactors after passing through a pH meter and a urea-formaldehyde stock solution inlet valve in sequence; the granulation stock solution metering pump is provided with a urea solution pump head and a urea-formaldehyde solution pump head; the outlets of multiple parallel urea-formaldehyde reactors are connected to the inlet of the urea-formaldehyde solution delivery pump head, the inlet of the urea solution pump head is connected to a urea solution source, and the outlets of the urea solution pump head and the urea-formaldehyde solution delivery pump head are connected to the inlet of the granulation stock solution mixer. The system ensures that the urea solution will not flow back into the formaldehyde pipeline, causing crystallization to block the formaldehyde pipeline.

Description

Technical Field

[0001] The utility model relates to the field of large-particle urea production, in particular to a large-particle urea urea-formaldehyde solution continuous supply system. Background Art

[0002] At present, the industry generally adopts fluidized bed granulation technology and drum granulation technology to produce large granular urea. In the production process, 37% formaldehyde solution is usually added as an additive before the molten urea enters the granulator. The purpose of adding formaldehyde solution is to react formaldehyde and urea to form urea-formaldehyde resin in an alkaline environment. Urea-formaldehyde resin is a water-soluble adhesive that can effectively improve the strength of urea granules, make urea granules less likely to agglomerate and break, improve product quality, and facilitate transportation and storage. However, the reaction of urea and formaldehyde to form urea-formaldehyde resin is a multi-stage, slow exothermic reaction. It is necessary to strictly control the amount of formaldehyde added and react for a long enough time at a suitable temperature and pH value. If the reaction conditions are insufficient, a large amount of intermediate product urea-based methanol will be generated. This intermediate product cannot achieve the purpose of strengthening the strength and anti-breakage ability of urea products, and will also quickly release formaldehyde gas during urea storage, causing urea to agglomerate.

[0003] The conventional large-particle urea plant generally adopts the formaldehyde addition method of using a delivery pump to directly inject the formaldehyde solution into the molten urea pipeline, perform preliminary mixing through a static mixer, and then directly send it to the granulator for granulation. This method has the following disadvantages: (1) The formaldehyde solution and molten urea are delivered by their own delivery pumps. When the pump pressure fluctuates or fails, the molten urea will flow back into the formaldehyde delivery pipeline. The temperature drop will cause the urea to crystallize, thereby blocking the formaldehyde pipeline; (2) The amount of formaldehyde added cannot be accurately controlled, resulting in excessive or insufficient formaldehyde content; (3) The mixing time of formaldehyde and urea is too short, and the granules enter the granulation section without sufficient reaction, resulting in minimal effect of the added formaldehyde. The urea granules are of poor quality, low strength, and easy to break and agglomerate.

[0004] Chinese patent CN204981663U discloses a large-particle urea granulation device for adding formaldehyde and mixing urine, which includes a formaldehyde storage tank, a section of evaporation diverter, a formaldehyde metering tank and a granulation device. The formaldehyde storage tank is connected to the formaldehyde metering tank through a formaldehyde pump, the section of evaporation diverter is connected to the liquid inlet of the melting pump through a urea input pipeline, a large-particle urea granulation device is connected to the liquid outlet of the melting pump, a formaldehyde metering tank is arranged above the melting pump, the formaldehyde metering tank is connected to the liquid inlet of the melting pump through a formaldehyde solution delivery pipeline arranged in the vertical direction, a valve is arranged at the lower end of the formaldehyde solution delivery pipeline, and a formaldehyde metering tank lower liquid regulating valve and a flow meter are respectively arranged on the formaldehyde solution delivery pipeline. This device simplifies the mixing process, and since the urine pipeline at the place where formaldehyde is added is slightly negative pressure, urine is not easy to flow back into the formaldehyde pipeline, ensuring that the formaldehyde pipeline will not be blocked during the start-up process and normal production process. However, the structure of this device is too compact, the mixing degree of formaldehyde and urea is average, the reaction time is short, and the urea-formaldehyde resin components produced are few, resulting in low strength and poor resistance to crushing of urea products. At the same time, the granulator generates more dust.

[0005] Chinese patent CN219441545U discloses a large-particle urea liquid supply system, which includes a granulator, a static mixer, a metering pump, a flow meter, an electric control valve and other equipment. The feed port of the granulator is connected to the discharge port of the static mixer through a pipeline. The two feed ports of the static mixer are respectively connected to the urea pipeline and the formaldehyde pipeline. The urea pipeline is equipped with an electric control valve, and the pipeline between the electric control valve and the metering pump is equipped with a pressure sensor. The flow meter and the pressure signal control the metering pump and the electric control valve. A flushing pipe is connected to the urea pipeline, and the other end is connected to the formaldehyde pipeline between the electric control valve and the static mixer. This liquid supply system detects the urine flow rate in real time through the flow meter, and controls the operation of the metering pump through the detected data to ensure the mixing ratio of urine and formaldehyde solution, and monitors the formaldehyde pipeline pressure in real time through the pressure sensor, controls the electric control valve to close, and prevents urine from pouring into the formaldehyde pipeline. However, this system uses the flow signal of the urea solution to adjust the solenoid valve, thereby controlling the amount of formaldehyde solution added. This process has a certain lag and its stability and accuracy are average. More importantly, this system still does not solve the problem of the low degree of reaction between the formaldehyde solution and the urea solution, and the effect of improving the urea product is average.

[0006] In view of this, the present utility model is proposed. Utility Model Content

[0007] In order to solve the above technical problems, the utility model provides a large-particle urea urea-formaldehyde solution continuous supply system, which will not cause the urea solution to flow back into the formaldehyde pipeline and cause crystallization to block the formaldehyde pipeline, and improves the quality of urea products.

[0008] The technical concept of the utility model is as follows:

[0009] A large-particle urea urea-formaldehyde solution continuous supply system comprises a urea-formaldehyde stock solution metering pump, a urea-formaldehyde stock solution mixer, a plurality of parallel urea-formaldehyde reactors, a granulation stock solution metering pump and a granulation stock solution mixer;

[0010] The urea-formaldehyde stock solution metering pump comprises a first motor, a first bearing, and a formaldehyde solution delivery pump head, a dilute ammonia delivery pump head, and a urea solution delivery pump head which share the first bearing; the inlets of the formaldehyde solution delivery pump head, the dilute ammonia delivery pump head, and the urea solution delivery pump head are respectively connected to a formaldehyde solution source, a dilute ammonia source, and a urea solution source, and the outlets are connected to the inlet of the urea-formaldehyde stock solution mixer; the outlet of the urea-formaldehyde stock solution mixer is connected to the inlet of a plurality of parallel urea-formaldehyde reactors after passing through a pH meter and a urea-formaldehyde stock solution inlet valve in sequence;

[0011] The granulation stock solution metering pump comprises a second motor, a second bearing, and a urea solution pump head and a urea-formaldehyde solution pump head which share the second bearing; the outlets of the multiple parallel urea-formaldehyde reactors are connected to the inlet of the urea-formaldehyde solution delivery pump head after passing through a urea-formaldehyde solution outlet valve, the inlet of the urea solution pump head is connected to a urea solution source, and the outlets of the urea solution pump head and the urea-formaldehyde solution delivery pump head are connected to the inlet of the granulation stock solution mixer.

[0012] As an example, the outlet of the granulation stock solution mixer is connected to a granulator.

[0013] As an example, the multiple parallel urea-formaldehyde reactors are jacketed kettle reactors with an inverted cone-shaped bottom structure, using a hot water jacket or a low-pressure steam jacket.

[0014] As an example, a stirrer and a liquid level meter are respectively provided in the multiple parallel urea-formaldehyde reactors.

[0015] As an example, the agitator is a paddle agitator or an anchor agitator with adjustable speed.

[0016] As an example, a first urea-formaldehyde reactor and a second urea-formaldehyde reactor are connected in parallel.

[0017] As an example, the urea-formaldehyde stock solution inlet valve is a three-way switch valve with one inlet and two outlets; the large-particle urea urea-formaldehyde solution continuous supply system automatically adjusts the opening and closing of the one inlet and the two outlets according to the liquid level signal control of the first urea-formaldehyde reactor and the second urea-formaldehyde reactor, and sends the urea-formaldehyde stock solution to the first urea-formaldehyde reactor or the second urea-formaldehyde reactor.

[0018] As an example, the urea-formaldehyde solution outlet valve is a three-way switch valve with two inlets and one outlet, and the large-particle urea-formaldehyde solution continuous supply system automatically adjusts the opening and closing of the two inlets and one outlet according to the liquid level signal control of the first urea-formaldehyde reactor and the second urea-formaldehyde reactor, and sends the urea-formaldehyde solution after the reaction in the first urea-formaldehyde reactor or the second urea-formaldehyde reactor to the granulation stock solution metering pump.

[0019] Compared with the prior art, the utility model has the following beneficial effects:

[0020] 1. The large-particle urea-formaldehyde solution continuous supply system of the utility model adopts a urea-formaldehyde stock solution metering pump to achieve stable and accurate proportion control of urea, formaldehyde and dilute ammonia water in the urea-formaldehyde reaction liquid preparation section, and the adjustment is convenient and fast; and the urea-formaldehyde stock solution metering pump can be started and stopped at the same time, ensuring that the urea solution will not flow back into the formaldehyde pipeline and cause crystallization to block the formaldehyde pipeline.

[0021] 2. The large-particle urea urea-formaldehyde solution continuous supply system of the utility model adopts two sets of parallel urea-formaldehyde reactors to achieve continuous feeding, reaction and supply of urea, formaldehyde and dilute ammonia water, ensuring the stable operation of the production device.

[0022] 3. The large-particle urea-formaldehyde solution continuous supply system of the utility model adds a urea-formaldehyde resin reaction section to allow urea and formaldehyde to react fully. The urea-formaldehyde solution after the reaction is added to the urea solution in a certain proportion as a urea granulation additive, making the urea product harder, more resistant to breakage, and less prone to agglomeration.

[0023] 4. The large-particle urea urea-formaldehyde solution continuous supply system of the utility model adopts a granulation stock solution metering pump to achieve stable and accurate ratio control of urea solution and urea-formaldehyde solution before the granulation stage, and the adjustment is convenient and fast.

[0024] Other features and advantages of the utility model will be described in the following description, and partly become apparent from the description, or understood by practicing the utility model. The purpose and other advantages of the utility model can be realized and obtained by the structures specifically pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the technical solution of the utility model and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the utility model and do not constitute a limitation on the technical solution of the utility model.

[0026] Figure 1 The utility model discloses a process flow diagram of a continuous supply system of large-particle urea-formaldehyde solution.

[0027] Marking description: 1-urea-formaldehyde stock solution metering pump, 11-formaldehyde solution delivery pump head, 12-dilute ammonia delivery pump head, 13-urea solution delivery pump head, 2-urea-formaldehyde stock solution mixer, 3- pH meter, 4-urea-formaldehyde stock solution inlet valve, 5-first urea-formaldehyde reactor, 6-second urea-formaldehyde reactor, 51-first urea-formaldehyde stock solution inlet, 61-second urea-formaldehyde stock solution inlet, 52-first agitator, 62-second agitator, 53-first liquid level meter, 63-second liquid level meter, 54-first urea-formaldehyde solution outlet, 64-second urea-formaldehyde solution outlet, 7-urea-formaldehyde solution outlet valve, 8-granulation stock solution metering pump, 81-urea solution delivery pump head, 82-urea-formaldehyde solution delivery pump head, 9-granulation stock solution mixer. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution of the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings of the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all of the embodiments. Based on the described embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0029] Example 1

[0030] A continuous supply system for large-particle urea-formaldehyde solution, such as Figure 1 As shown, it includes a urea-formaldehyde stock solution metering pump 1, a urea-formaldehyde stock solution mixer 2, a pH meter 3, a urea-formaldehyde stock solution inlet valve 4, a first urea-formaldehyde reactor 5 and a second urea-formaldehyde reactor 6, a urea-formaldehyde solution outlet valve 7, a granulation stock solution metering pump 8 and a granulation stock solution mixer 9.

[0031] The urea-formaldehyde solution metering pump 1 is a special device, including a first motor, a first bearing and three pump heads. The three pump heads are formaldehyde solution delivery pump head 11, dilute ammonia delivery pump head 12 and urea solution delivery pump head 13. When working normally, the three pump heads share the first bearing to ensure that all pump heads have the same rotation speed, and the flow control of formaldehyde solution, dilute ammonia solution and urea solution is achieved by adjusting the stroke of the corresponding pump heads.

[0032] The inlets of the formaldehyde solution delivery pump head 11, the dilute ammonia water delivery pump head 12 and the urea solution delivery pump head 13 of the urea-formaldehyde stock solution metering pump 1 are connected to the formaldehyde solution source, the dilute ammonia water source and the urea solution source respectively, and the outlets of the formaldehyde solution delivery pump head 11, the dilute ammonia water delivery pump head 12 and the urea solution delivery pump head 13 are connected to the inlet of the urea-formaldehyde stock solution mixer 2, and the outlet of the urea-formaldehyde stock solution mixer 2 is connected to the inlet of the first urea-formaldehyde reactor 5 and the second urea-formaldehyde reactor 6 after passing through the pH meter 3 and the urea-formaldehyde stock solution inlet valve 4 in sequence. The first urea-formaldehyde reactor 5 and the second urea-formaldehyde reactor 6 are arranged in parallel.

[0033] The granulation stock solution metering pump 8 is similar to the urea-formaldehyde stock solution metering pump 1, and is a special device, including a second motor, a second bearing, and two pump heads, namely, a urea solution pump head 81 and a urea-formaldehyde solution pump head 82. When the two pump heads are working normally, the second bearing is shared by the two pump heads to ensure the same rotation speed, and the flow of the urea solution and the urea-formaldehyde solution is controlled by adjusting the stroke of the corresponding urea solution pump head 81 and the urea-formaldehyde solution pump head 82. The two pump heads are started and stopped at the same time, so as to avoid the situation in which the urea solution flows back into the formaldehyde pipeline and causes crystallization and blockage due to pressure fluctuation or pump stop of the formaldehyde metering pump in the traditional process.

[0034] The outlets of the first urea-formaldehyde reactor 5 and the second urea-formaldehyde reactor 6 are connected to the inlet of the urea-formaldehyde solution delivery pump head 82 of the granulation stock solution metering pump 8 after passing through the urea-formaldehyde solution outlet valve 7. The inlet of the urea solution pump head 81 is connected to the urea solution source, and the outlets of the urea solution pump head 81 and the urea-formaldehyde solution delivery pump head 82 are connected to the inlet of the granulation stock solution mixer 9, and the outlet of the granulation stock solution mixer 9 is connected to the granulator.

[0035] The above-mentioned urea-formaldehyde stock solution mixer 2 is used for fully mixing the urea-formaldehyde stock solution. A pH meter 3 is installed on its outlet pipeline, so that the pH value of the urea-formaldehyde stock solution can be monitored in real time, and the stroke of the dilute ammonia water delivery pump head 12 of the urea-formaldehyde stock solution metering pump 1 can be adjusted according to the monitoring results, so as to achieve rapid and accurate control of the dilute ammonia water flow rate, and then adjust the pH value of the urea-formaldehyde stock solution to remain within a stable range.

[0036] As a specific example, the urea-formaldehyde stock solution inlet valve 4 is a three-way switch valve having one inlet and two outlets, which is controlled by the liquid level signals of the first urea-formaldehyde reactor 5 and the second urea-formaldehyde reactor 6, and can be automatically switched according to the program to send the urea-formaldehyde stock solution to one of the first urea-formaldehyde reactor 5 and the second urea-formaldehyde reactor 6.

[0037] As a specific example, the urea-formaldehyde solution outlet valve 7 is a three-way switch valve having two inlets and one outlet. It is controlled by the liquid level signals of the first urea-formaldehyde reactor 5 and the second urea-formaldehyde reactor 6 and can automatically adjust according to the program to send the urea-formaldehyde solution after the reaction in one of the first urea-formaldehyde reactor 5 and the second urea-formaldehyde reactor 6 to the granulation stock solution metering pump 8.

[0038] As a specific example, the first urea-formaldehyde reactor 5 and the second urea-formaldehyde reactor 6 are two identical jacketed kettle reactors, which adopt a hot water jacket or a low-pressure steam jacket and have an inverted cone design at the bottom. The first urea-formaldehyde reactor 5 and the second urea-formaldehyde reactor 6 are respectively equipped with a first agitator 52, a second agitator 62 and a first liquid level gauge 53, and a second liquid level gauge 63. The first agitator 52 and the second agitator 62 are paddle agitators or anchor agitators with adjustable speeds. The function of the agitator is to ensure that the urea-formaldehyde stock solution entering the urea-formaldehyde reactor is fully and evenly mixed, so that the reaction liquid can efficiently transfer mass and heat and keep the temperature of the system consistent.

[0039] The first liquid level gauge 53 and the second liquid level gauge 63 monitor the changes of the liquid levels in the two first urea-formaldehyde reactors 5 and the second urea-formaldehyde reactors 6 in real time. The liquid level signals are connected to the urea-formaldehyde stock solution inlet valve 4 and the urea-formaldehyde solution outlet valve 7. The switching of the urea-formaldehyde stock solution inlet valve 4 and the urea-formaldehyde solution outlet valve 7 can be controlled according to the liquid level signals of the two first urea-formaldehyde reactors 5 and the second urea-formaldehyde reactors 6 to realize the continuous feeding of unreacted urea-formaldehyde stock solution and the continuous discharging of the completely reacted urea-formaldehyde solution.

[0040] Its control logic is: during normal operation, one of the first urea-formaldehyde reactor 5 and the second urea-formaldehyde reactor 6 opens the feed and closes the discharge, which is a reaction condition, and the other closes the feed and opens the discharge, which is a liquid supply condition; when the first urea-formaldehyde reactor 5 and the second urea-formaldehyde reactor 6 are in the reaction condition and the liquid supply condition respectively, the first urea-formaldehyde reactor 5 continuously feeds and the second urea-formaldehyde reactor 6 continuously discharges. When the first liquid level gauge 53 of the first urea-formaldehyde reactor 5 monitors that the liquid level in the kettle reaches the set upper limit, the following actions are performed: a. Switch the urea-formaldehyde stock solution inlet valve 4, close the feed of the first urea-formaldehyde reactor 5, and open the feed of the second urea-formaldehyde reactor 6; b. Switch the urea-formaldehyde solution outlet valve 7, close the discharge of the second urea-formaldehyde reactor 6, and open the discharge of the first urea-formaldehyde reactor 5.

[0041] Although the implementation methods disclosed in the utility model are as above, the above contents are only implementation methods adopted to facilitate the understanding of the utility model, and are not used to limit the utility model. Any technician in the field to which the utility model belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in the utility model, but the scope of patent protection of the utility model shall still be based on the scope defined in the attached claims.

Claims

1. A continuous supply system for large-particle urea-formaldehyde solution, characterized in that: It includes an aldehyde stock solution metering pump, a urea-formaldehyde stock solution mixer, a plurality of parallel urea-formaldehyde reactors, a granulation stock solution metering pump and a granulation stock solution mixer; The urea-formaldehyde stock solution metering pump comprises a first motor, a first bearing, and a formaldehyde solution delivery pump head, a dilute ammonia delivery pump head, and a urea solution delivery pump head which share the first bearing; the inlets of the formaldehyde solution delivery pump head, the dilute ammonia delivery pump head, and the urea solution delivery pump head are respectively connected to a formaldehyde solution source, a dilute ammonia source, and a urea solution source, and the outlets are connected to the inlet of the urea-formaldehyde stock solution mixer; the outlet of the urea-formaldehyde stock solution mixer is connected to the inlet of a plurality of parallel urea-formaldehyde reactors after passing through a pH meter and a urea-formaldehyde stock solution inlet valve in sequence; The granulation stock solution metering pump comprises a second motor, a second bearing, and a urea solution pump head and a urea-formaldehyde solution pump head which share the second bearing; the outlets of the multiple parallel urea-formaldehyde reactors are connected to the inlet of the urea-formaldehyde solution pump head after passing through a urea-formaldehyde solution outlet valve, the inlet of the urea solution pump head is connected to a urea solution source, and the outlets of the urea solution pump head and the urea-formaldehyde solution pump head are connected to the inlet of the granulation stock solution mixer.

2. The large-particle urea-formaldehyde solution continuous supply system according to claim 1, characterized in that: The outlet of the granulation stock solution mixer is connected to a granulator.

3. The large-particle urea-formaldehyde solution continuous supply system according to claim 1, characterized in that: The multiple parallel urea-formaldehyde reactors are jacketed kettle reactors with an inverted cone-shaped bottom structure, and are jacketed with hot water or low-pressure steam.

4. The large-particle urea-formaldehyde solution continuous supply system according to claim 1, characterized in that: Agitators and liquid level meters are respectively arranged in the plurality of parallel urea-formaldehyde reactors.

5. The large-particle urea-formaldehyde solution continuous supply system according to claim 4, characterized in that: The stirrer is a paddle stirrer or an anchor stirrer with adjustable speed.

6. The large-particle urea-formaldehyde solution continuous supply system according to claim 1, characterized in that: It comprises a first urea-formaldehyde reactor and a second urea-formaldehyde reactor connected in parallel.

7. The large-particle urea-formaldehyde solution continuous supply system according to claim 6, characterized in that: The urea-formaldehyde stock solution inlet valve is a three-way switch valve with one inlet and two outlets; the large-particle urea urea-formaldehyde solution continuous supply system automatically adjusts the opening and closing of the one inlet and the two outlets according to the liquid level signal control of the first urea-formaldehyde reactor and the second urea-formaldehyde reactor, and sends the urea-formaldehyde stock solution to the first urea-formaldehyde reactor or the second urea-formaldehyde reactor.

8. The large-particle urea-formaldehyde solution continuous supply system according to claim 6, characterized in that: The urea-formaldehyde solution outlet valve is a three-way switch valve with two inlets and one outlet. The large-particle urea-formaldehyde solution continuous supply system automatically adjusts the opening and closing of the two inlets and one outlet according to the liquid level signal control of the first urea-formaldehyde reactor and the second urea-formaldehyde reactor, and sends the urea-formaldehyde solution after the reaction in the first urea-formaldehyde reactor or the second urea-formaldehyde reactor to the granulation stock solution metering pump.

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