Dust urea on-line hot melting recovery process

Abstract

The invention belongs to the field of urea hot-melt recovery, and particularly relates to a dust urea online hot-melt recovery process which comprises the following steps: dust collection: collecting dust screened by a rotary screen into a urea dust hot-melt recovery device through a shuttle pipe; and adding hot melting water: adding 90-100 DEG C steam condensate, desorption waste liquid or 140-145 DEG C liquid discharged from the second desorption tower into the middle lower part of the hot melting tank. The hot melting recovery device is used for carrying out centralized treatment on dust urea in the production process, and a dust packaging link is not needed, so that the problem that dust escapes in the packaging process is avoided from the source, and the production efficiency is improved. And the working environment of a packaging station is effectively improved, and the influence of dust on the health of operators is reduced. The urea which is originally treated as low-value dust is fully recycled and granulated again through links such as hot melting, stirring and circulating dissolving, so that the dust urea is converted into a qualified granular urea product, byproducts generated in the production process are utilized to the maximum extent, and resource waste is reduced.

Description

Technical Field

[0001] This invention belongs to the field of urea thermal melting recovery, specifically a process for online thermal melting recovery of dust urea. Background Technology

[0002] During urea production, the granulation stage generates a large amount of urea dust. Currently, the urea dust, which accounts for 8-9% of the total urea product, is usually separated by sieving and then packaged using a packaging machine.

[0003] However, this approach has obvious drawbacks:

[0004] On the one hand, the price of powdered urea products is 150-210 yuan lower per ton than that of genuine urea, which has led to certain economic losses;

[0005] On the other hand, during the packaging process of powdered urea, dust may escape, which can have an adverse impact on the working environment.

[0006] Therefore, the present invention provides an online hot-melt recovery process for urea dust. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0008] The technical solution adopted by this invention to solve its technical problem is: an online hot-melt recovery process for urea dust, which includes the following steps:

[0009] S1. Dust collection: The dust separated by the rotary screen is collected in the urea dust hot melt recovery device through the shuttle tube.

[0010] S2. Add hot water: Add 90~100℃ steam condensate, desorption waste liquid or 140~145℃ second desorption tower effluent to the lower part of the hot water tank, and control the liquid level of the hot water tank through the liquid level regulating valve installed in the hot water pipeline.

[0011] S3. Stirring and circulating dissolution: Start the stirrer in the hot dissolution tank to stir the dust and hot dissolution water. At the same time, start the circulation pump to extract the urea solution that is not completely dissolved at the bottom of the hot dissolution tank and send it into the hot dissolution tank from the middle and upper part to promote the full dissolution of dust.

[0012] S4. Maintain negative pressure: The hot melt tank is kept under negative pressure by the negative pressure dust suction pipe in the upper space of the hot melt tank to prevent steam in the hot melt tank from backflowing into the dust discharge pipe.

[0013] S5. Solution delivery: When the concentration of urea solution in the hot melting tank is increased to 50-60%, start the transfer pump to send the completely dissolved urea solution from the lower part of the hot melting tank to the urea tank for regranulation. The concentration in the hot melting tank is controlled by the flow regulating valve and flow meter set at the outlet of the transfer pump.

[0014] S6. Process control: Hot water directly enters the lower part of the hot melting tank, reducing water vapor in the upper part of the hot melting tank and reducing the load on the negative pressure dust removal pipe.

[0015] Preferably, in step S1, the urea dust hot melting recovery device includes a hot melting tank, a stirrer, a circulating pump, a transfer pump, and related process pipelines.

[0016] Preferably, in step S2, a heating steam coil is installed inside the hot melt tank.

[0017] Preferably, in step S3, the drive motor of the stirrer has a power of 11kW and a speed of 100 rpm.

[0018] Preferably, in step S3, the motor power of the circulating pump is 5.5kW, the flow rate is 60m³ / h, and the dust emission is 12m.

[0019] Preferably, in step S5, the motor power of the transfer pump is 15kW, the flow rate is 50m³ / h, and the head is 50m.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. The online hot-melt recovery process for urea dust described in this invention centrally processes urea dust through a hot-melt recovery device, eliminating the need for a separate dust packaging step. This avoids secondary dust escape during the packaging process from the source, effectively improving the working environment of the packaging station and reducing the impact of dust on the health of operators.

[0022] 2. The online hot-melt recovery process for urea dust described in this invention fully recovers and regranulates urea that was originally treated as low-value dust through hot melting, stirring, and circulating dissolution, transforming urea dust into qualified granular urea products. This maximizes the utilization of by-products generated during the production process, reduces resource waste, and achieves efficient resource utilization throughout the entire urea production process.

[0023] 3. The dust urea online hot-melt recovery process described in this invention maintains a negative pressure state in the hot-melt tank through a negative pressure dust suction pipe, avoiding blockage caused by water vapor backflow into the dust discharge pipe and abnormal moisture content in the finished urea; at the same time, through precise control of liquid level and concentration, it ensures that the recovered solution meets the granulation requirements, guarantees the stability of the final product quality, and reduces quality problems such as finished product caking caused by dust mixing. Detailed Implementation

[0024] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0025] An online thermal fusion recovery process for urea dust according to an embodiment of the present invention includes the following steps:

[0026] S1. Dust collection: The dust separated by the rotary screen is collected in the urea dust hot melt recovery device through the shuttle tube.

[0027] S2. Add hot water: Add 90~100℃ steam condensate, desorption waste liquid or 140~145℃ second desorption tower effluent to the lower part of the hot water tank, and control the liquid level of the hot water tank through the liquid level regulating valve installed in the hot water pipeline.

[0028] S3. Stirring and circulating dissolution: Start the stirrer in the hot dissolution tank to stir the dust and hot dissolution water. At the same time, start the circulation pump to extract the urea solution that is not completely dissolved at the bottom of the hot dissolution tank and send it into the hot dissolution tank from the middle and upper part to promote the full dissolution of dust.

[0029] S4. Maintain negative pressure: The hot melt tank is kept under negative pressure by the negative pressure dust suction pipe in the upper space of the hot melt tank to prevent steam in the hot melt tank from backflowing into the dust discharge pipe.

[0030] S5. Solution delivery: When the concentration of urea solution in the hot melting tank is increased to 50-60%, start the transfer pump to send the completely dissolved urea solution from the lower part of the hot melting tank to the urea tank for regranulation. The concentration in the hot melting tank is controlled by the flow regulating valve and flow meter set at the outlet of the transfer pump.

[0031] S6. Process control: Hot water directly enters the lower part of the hot melting tank to reduce water vapor in the upper part of the hot melting tank and reduce the load on the negative pressure dust removal pipe.

[0032] In step S1, the urea dust hot melting recovery device includes a hot melting tank, a stirrer, a circulating pump, a transfer pump, and related process pipelines.

[0033] In step S2, a heating steam coil is installed in the hot melting tank to increase the temperature of the urea solution and improve its solubility.

[0034] In step S3, the stirrer is model FBJ-11, the drive motor power is 11kW, and the speed is 100 rpm.

[0035] In step S3, the motor power of the circulating pump is 5.5kW, the flow rate is 60m³ / h, and the dust emission is 12m.

[0036] In step S5, the motor power of the transfer pump is 15kW, the flow rate is 50m³ / h, and the head is 50m.

[0037] Working principle:

[0038] First, the dust urea separated by each rotary screen is collected by the dust collection pipe and transported to the urea dust hot melting recovery device through the shuttle tube, so as to avoid the low efficiency caused by the dust dispersion treatment and provide a stable source of raw materials for the subsequent dissolution process.

[0039] Subsequently, 90-100℃ steam condensate, desorption waste liquid, or 140-145℃ effluent from the second desorption tower is injected into the lower part of the hot dissolving tank as hot dissolving water. The liquid level in the hot dissolving tank is controlled by a level regulating valve (LC-405). Injecting the hot dissolving water from the lower part of the tank reduces the amount of water vapor generated directly entering the upper gas phase space, lowers the load on the negative pressure dust removal pipe, and provides favorable conditions for the rapid dissolution of dust urea in the high-temperature environment.

[0040] Subsequently, the stirrer (model FBJ-11) in the hot melt tank is started to forcibly stir the dust and hot melt water at a speed of 100 rpm, increasing the contact area between the two; at the same time, the circulation pump (flow rate 60 m³ / h) is started to extract the incompletely dissolved urea solution from the bottom of the hot melt tank and return it from the middle and upper part to form an internal circulation. This, together with the heating steam coil in the hot melt tank, raises the solution temperature, further promotes the complete dissolution of dust, and ensures a highly efficient dissolution effect.

[0041] Then, the negative pressure suction pipe of the dust scrubber is connected to the upper space of the hot melting tank to maintain a negative pressure state in the tank, which effectively prevents water vapor in the hot melting tank from backflowing to the dust discharge pipe, avoids dust pipe blockage and abnormal moisture content of finished urea, and ensures stable operation of the recycling system.

[0042] Finally, when the urea solution concentration in the hot-melt tank reaches 50-60%, the transfer pump (50m head) is started to transport the completely dissolved urea solution from the lower part of the tank to the urea tank for regranulation. The flow regulating valve (FI-101) and flow meter at the outlet of the transfer pump control the outgoing flow rate of the solution, thereby adjusting the concentration of the solution in the hot-melt tank to ensure that the solution sent to the urea tank meets the granulation requirements, realizing the conversion of dust urea into granular urea and improving product value.

[0043] In this process, the hot melting tank (made of SUS304 stainless steel, 1800mm in diameter and 2000mm in height) provides a corrosion-resistant space for the dissolution process, and the heating steam coil enhances the solubility; the liquid level regulating valve and the flow regulating valve are linked to achieve a dynamic balance between the replenishment of hot melting water and the external delivery of solution, ensuring the stability of the liquid level and concentration in the hot melting tank, and ultimately achieving the goal of unpackaged recycling of dust urea and improving the working environment, which meets occupational health requirements.

[0044] Based on an annual urea production of 330,000 tons, and assuming a dust rate of 8% to 9%, 26,400 to 29,700 tons of dust urea can be recovered annually. This process converts dust urea into genuine granular urea, avoiding the price difference of 210 yuan per ton between dust urea and genuine urea. After deducting annual electricity costs of 79,200 yuan, the company can still achieve an annual profit increase of 5.4648 million to 6.1578 million yuan, significantly improving its economic returns.

[0045] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. An online thermal melting recovery process for urea dust, characterized in that, The process includes the following steps: S1. Dust collection: The dust separated by the rotary screen is collected in the urea dust hot melt recovery device through the shuttle tube. S2. Add hot water: Add 90~100℃ steam condensate, desorption waste liquid or 140~145℃ second desorption tower effluent to the lower part of the hot water tank, and control the liquid level of the hot water tank through the liquid level regulating valve installed in the hot water pipeline. S3. Stirring and circulating dissolution: Start the stirrer in the hot dissolution tank to stir the dust and hot dissolution water. At the same time, start the circulation pump to extract the urea solution that is not completely dissolved at the bottom of the hot dissolution tank and send it into the hot dissolution tank from the middle and upper part to promote the full dissolution of dust. S4. Maintain negative pressure: The hot melt tank is kept under negative pressure by the negative pressure dust suction pipe in the upper space of the hot melt tank to prevent steam in the hot melt tank from backflowing into the dust discharge pipe. S5. Solution delivery: When the concentration of urea solution in the hot melting tank is increased to 50-60%, start the transfer pump to send the completely dissolved urea solution from the lower part of the hot melting tank to the urea tank for regranulation. The concentration in the hot melting tank is controlled by the flow regulating valve and flow meter set at the outlet of the transfer pump. S6. Process control: Hot water directly enters the lower part of the hot melting tank, reducing water vapor in the upper part of the hot melting tank and reducing the load on the negative pressure dust removal pipe.

2. The online thermal fusion recovery process for urea dust according to claim 1, characterized in that: In step S1, the urea dust hot melting recovery device includes a hot melting tank, a stirrer, a circulating pump, a transfer pump, and related process pipelines.

3. The online thermal fusion recovery process for urea dust according to claim 1, characterized in that: In step S2, a heating steam coil is installed inside the hot melt tank.

4. The online thermal fusion recovery process for urea dust according to claim 1, characterized in that: In step S3, the drive motor of the stirrer has a power of 11kW and a speed of 100 rpm.

5. The online thermal fusion recovery process for urea dust according to claim 1, characterized in that: In step S3, the motor power of the circulating pump is 5.5kW, the flow rate is 60m³ / h, and the dust emission is 12m.

6. The online thermal fusion recovery process for urea dust according to claim 1, characterized in that: In step S5, the motor power of the transfer pump is 15kW, the flow rate is 50m³ / h, and the head is 50m.