Exhaust cylinder tail gas recovery device

Abstract

This utility model relates to the field of urea production technology and is a tail gas recovery device for exhaust stacks. It includes an exhaust stack, a tail gas collector, a purification tower, and an absorbent collection tank and an ammonia tank. A stripping tail gas pipeline is fixedly connected to the lower inlet of the exhaust stack, a demineralized water pipeline is fixedly connected to the upper inlet of the exhaust stack, a first tail gas pipeline is fixedly connected to the top outlet of the exhaust stack and the top inlet of the tail gas collector, a second tail gas pipeline is fixedly connected to the outlet of the tail gas collector and the middle inlet of the purification tower, a third tail gas pipeline is fixedly connected to the upper outlet of the purification tower, and a desorption wastewater pipeline is fixedly connected to the top inlet of the purification tower. This utility model has a reasonable and compact structure and is easy to use. It utilizes desorption wastewater to wash and absorb NH3, CO2, etc., in the tail gas. The washed non-condensable gases are extracted by a fan and discharged into the atmosphere, featuring safety, labor saving, simplicity, and high efficiency.

Description

Technical Field

[0001] This utility model relates to the field of urea production technology and is a tail gas recovery device for exhaust stacks. Background Technology

[0002] Urea, also known as urea or carbamide, is a white crystalline powder used as a fertilizer, animal feed, explosive, glue stabilizer, and chemical raw material. As a neutral fertilizer, urea is suitable for various soils and plants. It is easy to store and use, and has minimal impact on soil, making it a widely used chemical nitrogen fertilizer. Urea contains 46% nitrogen (N), the highest nitrogen content among solid nitrogen fertilizers. Industrially, urea is synthesized from ammonia and carbon dioxide under specific conditions. After separation and recovery of the molten urea and unreacted substances, it is further evaporated and granulated to obtain the finished urea product.

[0003] The separation and recovery of molten urea from unreacted substances employs a carbon dioxide stripping process. The stripped exhaust gas is discharged through an exhaust stack. The exhaust stack operates at atmospheric pressure, and the main media in the discharged exhaust gas are NH3, CO2, H2O, and small amounts of O2 and N2. The ammonia and carbon dioxide emissions in the exhaust gas cause serious environmental pollution and also endanger the physical and mental health of on-site operators.

[0004] The main function of the exhaust stack is to collect the tail gas and non-condensable gases from various systems within the urea plant and vent them at a high point. The application of tail gas recovery technology can effectively reduce ammonia and carbon dioxide emissions, improve resource recycling rates, and lower production costs. However, because the gas emitted from the exhaust stack contains a certain amount of ammonia, it cannot meet the Class A enterprise standard of NH3 emission concentration not exceeding 40 mg / Nm³ for coal-to-nitrogen fertilizer production, as stipulated in the "Implementation Rules for Performance Grading of Key Industries in Heavy Pollution Weather." 3 The requirement is 52.7 ppm.

[0005] Therefore, research on the recycling and utilization of exhaust gas from urea plants is essential. Summary of the Invention

[0006] This utility model provides an exhaust gas recovery device that overcomes the shortcomings of the prior art and can effectively solve the problem of NH3 emission concentration not meeting the standards in the exhaust gas emissions of existing urea production.

[0007] The technical solution of this utility model is achieved through the following measures: an exhaust stack tail gas recovery device includes an exhaust stack, a tail gas collector, and a purification tower. The lower inlet of the exhaust stack is fixedly connected to a stripping tail gas pipeline, the upper inlet of the exhaust stack is fixedly connected to a demineralized water pipeline, the top outlet of the exhaust stack is fixedly connected to the top inlet of the tail gas collector, the outlet of the tail gas collector is fixedly connected to the middle inlet of the purification tower, the upper outlet of the purification tower is fixedly connected to a third tail gas pipeline, and the top inlet of the purification tower is fixedly connected to a desorption wastewater pipeline.

[0008] The following are further optimizations and / or improvements to the above-mentioned utility model technical solution:

[0009] The above also includes an absorbent collection tank. A first absorbent pipeline is fixedly connected between the bottom outlet of the purification tower and the upper inlet of the absorbent collection tank; a second absorbent pipeline is fixedly connected between the lower outlet of the absorbent collection tank and the upper inlet of the ammonia tank; a third absorbent pipeline is fixedly connected between the bottom outlet of the exhaust stack and the top inlet of the ammonia tank; and an ammonia pipeline is fixedly connected to the lower outlet of the ammonia tank.

[0010] A fourth absorbent pipeline is fixedly connected between the first absorbent pipeline and the analytical wastewater pipeline.

[0011] A steam condensate pipeline is fixedly connected to the wastewater pipeline between the inlet of the above-mentioned wastewater pipeline and the fourth absorbent pipeline.

[0012] The first absorbent liquid transfer pump, the second absorbent liquid transfer pump, and the fan are respectively fixedly installed on the first absorbent liquid pipeline, the second absorbent liquid pipeline, and the third tail gas pipeline between the fourth absorbent liquid pipeline and the purification tower.

[0013] A first concentration meter and a remote level gauge are fixedly installed on the above-mentioned absorption liquid collection tank, and a second concentration meter is fixedly installed on the first absorption liquid pipeline between the first absorption liquid delivery pump and the purification tower.

[0014] A first control valve is fixedly installed on the first absorbent pipeline between the fourth absorbent pipeline and the absorbent collection tank, a second control valve is fixedly installed on the fourth absorbent pipeline, and a third control valve is fixedly installed on the analytical wastewater pipeline between the inlet of the analytical wastewater pipeline and the steam condensate pipeline.

[0015] The above also includes a DCS controller, a first absorbent transfer pump, a second absorbent transfer pump, a fan, a first concentration meter, a remote level gauge, a second concentration meter, a first control valve, a second control valve, and a third control valve, all of which are electrically connected to the DCS controller.

[0016] This utility model has a reasonable and compact structure and is easy to use. It uses the desorption wastewater to wash and absorb NH3, CO2 and other substances in the tail gas. The washed non-condensable gas is extracted by the fan and discharged into the atmosphere. It has the characteristics of safety, labor saving, simplicity and high efficiency. Attached Figure Description

[0017] Appendix Figure 1 This is a schematic diagram of the process flow of this utility model.

[0018] Appendix Figure 1 The codes in the diagram are as follows: 1 for exhaust stack, 2 for tail gas collector, 3 for purification tower, 4 for stripping tail gas pipeline, 5 for demineralized water pipeline, 6 for first tail gas pipeline, 7 for second tail gas pipeline, 8 for third tail gas pipeline, 9 for analytical wastewater pipeline, 10 for absorbent collection tank, 11 for ammonia tank, 12 for first absorbent pipeline, 13 for second absorbent pipeline, 14 for third absorbent pipeline, 15 for ammonia pipeline, 16 for fourth absorbent pipeline, 17 for first absorbent transfer pump, 18 for second absorbent transfer pump, 19 for blower, 20 for first concentration meter, 21 for remote level gauge, 22 for second concentration meter, 23 for first control valve, 24 for second control valve, 25 for third control valve, and 26 for steam condensate pipeline. Detailed Implementation

[0019] This utility model is not limited to the following embodiments, and the specific implementation method can be determined according to the technical solution of this utility model and the actual situation.

[0020] Unless otherwise specified, all equipment and devices used in this invention are existing, publicly known, and commonly used equipment and devices in the field.

[0021] In this utility model, for ease of description, the description of the relative positions of the components is based on the appendix to the specification. Figure 1 The layout is described using a diagrammatic method, such as the positional relationships of front, back, top, bottom, left, and right, which are based on the instructions attached. Figure 1 The orientation of the layout is determined by the direction of the map.

[0022] The present invention will be further described below with reference to the embodiments and accompanying drawings:

[0023] Example 1: As shown in the attached document Figure 1As shown, the exhaust gas recovery device includes an exhaust stack 1, an exhaust gas collector 2, and a purification tower 3. The lower inlet of the exhaust stack 1 is fixedly connected to a stripping exhaust gas pipeline 4, the upper inlet of the exhaust stack 1 is fixedly connected to a demineralized water pipeline 5, the top outlet of the exhaust stack 1 is fixedly connected to a first exhaust gas pipeline 6, the outlet of the exhaust gas collector 2 is fixedly connected to a second exhaust gas pipeline 7, the upper outlet of the purification tower 3 is fixedly connected to a third exhaust gas pipeline 8, and the top inlet of the purification tower 3 is fixedly connected to a desorption wastewater pipeline 9.

[0024] In this invention, the stripping tail gas entering the exhaust stack 1 comes from the stripping separation and recovery process of urea melt and unreacted products in the upstream process. The tail gas discharged from the exhaust stack 1 is collected in the tail gas collector 2, and the collected tail gas enters the purification tower 3 for washing. The washing liquid is the deamination wastewater from the existing ammonia water desorption process in the urea plant. The non-condensable gas after washing is discharged through the first tail gas pipeline 6.

[0025] The exhaust gas recovery device described above can be further optimized and / or improved according to actual needs:

[0026] Example 2: Its difference from Example 1 is as follows: (See attached) Figure 1 As shown, it also includes an absorbent collection tank 10, an ammonia tank 11, a first absorbent pipeline 12 that is fixedly connected between the bottom outlet of the purification tower 3 and the upper inlet of the absorbent collection tank 10, a second absorbent pipeline 13 that is fixedly connected between the lower outlet of the absorbent collection tank 10 and the upper inlet of the ammonia tank 11, a third absorbent pipeline 14 that is fixedly connected between the bottom outlet of the exhaust stack 1 and the top inlet of the ammonia tank 11, and an ammonia pipeline 15 that is fixedly connected to the lower outlet of the ammonia tank 11.

[0027] Example 3: Its difference from Examples 1 to 2 is as follows: (See attached) Figure 1 As shown, a fourth absorbent pipeline 16 is fixedly connected between the first absorbent pipeline 12 and the analytical wastewater pipeline 9.

[0028] As needed, when the concentration of absorbent in the absorbent collection tank 10 reaches 5% to 10%, it is transported to the ammonia tank 11 for recycling. When the concentration of absorbent is less than 5%, it is transported to the purification tower 3 through the fourth absorbent pipeline 16 for continued circulation and absorption.

[0029] Example 4: Its difference from Examples 1 to 3 is as follows: (See attached) Figure 1 As shown, a steam condensate pipeline 26 is fixedly connected to the analytical wastewater pipeline 9 between the inlet of the analytical wastewater pipeline 9 and the fourth absorbent pipeline 16.

[0030] If necessary, when an abnormality occurs in the upstream ammonia water analysis system, the supply of washing liquid will be switched to the steam condensate from the urea evaporation process.

[0031] Example 5: It differs from Examples 1 to 4 in that, as shown in the appendix... Figure 1 As shown, a first absorbent transfer pump 17, a second absorbent transfer pump 18, and a fan 19 are respectively fixedly installed on the first absorbent pipeline 12, the second absorbent pipeline 13, and the third tail gas pipeline 8 between the fourth absorbent pipeline 16 and the purification tower 3.

[0032] Depending on the requirements, the fan 19 can be a centrifugal fan, which provides a slight negative pressure space inside the equipment, allowing the exhaust gas to be effectively collected into the purification tower. The collected exhaust gas first enters the packing layer of the purification tower 3, where it comes into full contact with and mixes with the washing liquid medium inside the packed tower 3. The mass transfer between the gas and liquid phases takes place at the interface between the liquid and gas on the surface of the packing. Through the first absorbent transfer pump 17, the ammonia molecules in the air or water are fully mixed with the water medium.

[0033] Example 6: Its difference from Examples 1 to 5 is as follows: (See attached) Figure 1 As shown, a first concentration meter 20 and a remote level gauge 21 are fixedly installed on the absorption liquid collection tank 10, and a second concentration meter 22 is fixedly installed on the first absorption liquid pipeline 12 between the first absorption liquid delivery pump 17 and the purification tower 3.

[0034] Example 7: Its difference from Examples 1 to 6 is as follows: (See attached) Figure 1 As shown, a first control valve 23 is fixedly installed on the first absorbent pipeline 12 between the fourth absorbent pipeline 16 and the absorbent collection tank 10, a second control valve 24 is fixedly installed on the fourth absorbent pipeline 16, and a third control valve 25 is fixedly installed on the analytical wastewater pipeline 9 between the inlet of the analytical wastewater pipeline 9 and the steam condensate pipeline 26.

[0035] Example 8: It differs from Examples 1 to 7 in that: as shown in the appendix Figure 1 As shown, it also includes a DCS controller, a first absorbent transfer pump 17, a second absorbent transfer pump 18, a fan 19, a first concentration meter 20, a remote level gauge 21, a second concentration meter 22, a first control valve 23, a second control valve 24, and a third control valve 25, all of which are electrically connected to the DCS controller.

[0036] Depending on the needs, the pipelines and equipment of the exhaust gas recovery device can also be equipped with conventional valves, thermometers, and pressure gauges known in the art, according to production requirements. The DCS controller can be a CS3000 controller manufactured by Yokogawa Corporation of Japan.

[0037] Comparison before and after use: Before use, the NH3 emission concentration at the exhaust outlet was higher than 40 mg / Nm³. 3 The highest was 56.6 mg / m³.3 After use, the NH3 emission concentration at the exhaust outlet will not exceed 10 mg / m³, with a minimum of 0.94 mg / m³. 3 .

[0038] The above technical features constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

[0039] The usage process of this utility model embodiment is as follows: First, after the stripping tail gas is sprayed with demineralized water in the exhaust stack 1, most of the harmful substances are removed, and sprayed tail gas is obtained; then, the sprayed tail gas is in countercurrent contact with the desorption wastewater in the purification tower 3 for secondary impurity removal, and purified tail gas is obtained; finally, the purified tail gas is discharged through the fan 19 in compliance with standards.

Claims

1. An exhaust gas recovery device for an exhaust stack, characterized in that... It includes an exhaust stack, a tail gas collector, and a purification tower. The lower inlet of the exhaust stack is fixedly connected to a stripping tail gas pipeline, the upper inlet of the exhaust stack is fixedly connected to a demineralized water pipeline, the top outlet of the exhaust stack is fixedly connected to the top inlet of the tail gas collector, the outlet of the tail gas collector is fixedly connected to the middle inlet of the purification tower, the upper outlet of the purification tower is fixedly connected to a third tail gas pipeline, and the top inlet of the purification tower is fixedly connected to a desorption wastewater pipeline.

2. The exhaust gas recovery device according to claim 1, characterized in that... It also includes an absorbent collection tank and an ammonia tank. A first absorbent pipeline is fixedly connected between the bottom outlet of the purification tower and the upper inlet of the absorbent collection tank. A second absorbent pipeline is fixedly connected between the lower outlet of the absorbent collection tank and the upper inlet of the ammonia tank. A third absorbent pipeline is fixedly connected between the bottom outlet of the exhaust stack and the top inlet of the ammonia tank. An ammonia pipeline is fixedly connected to the lower outlet of the ammonia tank.

3. The exhaust gas recovery device according to claim 2, characterized in that... A fourth absorbent pipeline is fixedly connected between the first absorbent pipeline and the analytical wastewater pipeline.

4. The exhaust gas recovery device according to claim 3, characterized in that... A steam condensate pipeline is fixedly connected to the wastewater pipeline between the inlet of the analytical wastewater pipeline and the fourth absorbent pipeline.

5. The exhaust gas recovery device according to claim 3 or 4, characterized in that... The first absorbent liquid transfer pump, the second absorbent liquid transfer pump, and the fan are respectively fixedly installed on the first absorbent liquid pipeline, the second absorbent liquid pipeline, and the third tail gas pipeline between the fourth absorbent liquid pipeline and the purification tower.

6. The exhaust gas recovery device according to claim 2, 3, or 4, characterized in that... A first concentration meter and a remote level gauge are fixedly installed on the absorption liquid collection tank, and a second concentration meter is fixedly installed on the first absorption liquid pipeline between the first absorption liquid delivery pump and the purification tower.

7. The exhaust gas recovery device according to claim 6, characterized in that... A first control valve is fixedly installed on the first absorbent pipeline between the fourth absorbent pipeline and the absorbent collection tank, a second control valve is fixedly installed on the fourth absorbent pipeline, and a third control valve is fixedly installed on the analytical wastewater pipeline between the inlet of the analytical wastewater pipeline and the steam condensate pipeline.

8. The exhaust gas recovery device according to claim 7, characterized in that... It also includes a DCS controller, a first absorbent transfer pump, a second absorbent transfer pump, a fan, a first concentration meter, a remote level gauge, a second concentration meter, a first control valve, a second control valve, and a third control valve, all of which are electrically connected to the DCS controller.

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