Safe, efficient and energy-saving ammonium nitrate solution production system

Abstract

The utility model discloses a safe, efficient and energy-saving ammonium nitrate solution production system which comprises an efficient tubular reactor, a reactor flash tank and a reflux mixer, the efficient tubular reactor is communicated with the reactor flash tank and the reflux mixer, and an ammonia gas pipe and a nitric acid pipe are connected to the efficient tubular reactor. An adjusting loop is connected among the ammonia gas pipe, the nitric acid pipe and the efficient tubular reactor, the reflux mixer comprises a neutralization washing tower, and the reactor flash tank is further connected with a falling film primary evaporator. Compared with the prior art, the system provided by the utility model has the advantage that the ammonium nitrate solution can be prepared safely, efficiently and in an energy-saving manner by utilizing the pressurized tubular reactor and the MVR evaporator.

Description

Technical Field

[0001] This utility model relates to the field of ammonium nitrate solution preparation technology, specifically to a safe, efficient and energy-saving ammonium nitrate solution production system. Background Technology

[0002] With the increasing demands for safe production in ammonium nitrate production enterprises, the State Administration for Market Regulation and the Standardization Administration of China jointly issued the "Safety Technical Specifications for Ammonium Nitrate Enterprises" (Draft for Comments), which requires that the production should be shut down immediately when the pH value of the solution (10% ammonium nitrate solution) in the flash tank is less than 1.0. The main reason is that ammonium nitrate solution is prone to decomposition or even explosion when free acid is present in high-temperature, high-concentration ammonium nitrate solutions. Furthermore, the emission dust content detection, according to the national standards "Determination of Particulate Matter and Sampling Methods for Gaseous Pollutants in Exhaust Gas from Stationary Sources" (GB / T16157-1996) and "Technical Specifications for Monitoring Exhaust Gas from Stationary Sources" (HJ / T397-2007), requires an ammonium nitrate dust content of ≤30 mg / m³, placing higher technical requirements on ammonium nitrate production enterprises.

[0003] In traditional processes, the liquid phase in the flash tank of the reactor is weakly acidic for a long time. When ammonia is added in the subsequent concentration process to raise the pH value, there is a certain risk of explosion.

[0004] Traditional processes using pressurized tubular reactors are not only simple in structure and easy to operate and adjust, allowing for the production of high-concentration ammonium nitrate solutions in a single step, but also solve the safety issues of atmospheric pressure volumetric neutralization reactors and improve the utilization rate of process steam. However, because the reaction takes place under neutral or acidic conditions, the reactor suffers from severe corrosion and a short service life. Furthermore, the reaction operates at the boiling pressure required to produce ammonium nitrate, generating large amounts of highly polluting process steam. Although these systems are equipped with dedicated process steam scrubbing systems, the process steam is superheated at high temperatures (195–200°C). In the long-term high-temperature acidic environment, the packing layer, made of corrugated metal structured packing (material: S30403 or ceramic structured packing), experiences severe corrosion and even complete collapse of the lower packing layer after a period of normal operation. Moreover, completing the neutralization of ammonia entrained in the process steam and the scrubbing of ammonium nitrate within a single scrubbing tower causes fluctuations in operating conditions, leading to significant exceedances and fluctuations in contaminants in the process steam condensate. This is extremely detrimental to the safe production of the plant and the quality of the products, ultimately affecting the production and stability of the ammonium nitrate solution.

[0005] Especially when the nitric acid concentration is below 58%, the evaporation condensate (unwashed steam condensate) in the system is excessive. If this excess evaporation condensate is sent to the electrodialysis unit for treatment, the membrane stack will become severely clogged, the cleaning frequency will increase, and the filter cartridges before entering the membrane stack will also need to be replaced frequently, resulting in a significant waste of manpower and material costs. Not only does electricity consumption increase, but operating costs also increase accordingly and the membrane stack's lifespan is reduced. Utility Model Content

[0006] The present invention aims to provide a system for the safe, efficient, and energy-saving preparation of ammonium nitrate solution using a pressurized tubular reactor and an MVR evaporator.

[0007] To solve the above-mentioned technical problems, the technical solution provided by this utility model is as follows: a safe, efficient and energy-saving ammonium nitrate solution production system, including an ammonia pipeline, a nitric acid pipeline, a high-efficiency tubular reactor, a reactor flash evaporation tank, a neutralization and washing tower, and an ammonium nitrate solution tank, characterized in that: the neutralization and washing tower is an atomizing washing tower, the acid inlet of the neutralization and washing tower is located at its top, a reflux mixer is provided between the high-efficiency tubular reactor, the reactor flash evaporation tank and the neutralization and washing tower, an indicating and regulating valve is provided between the neutralization and washing tower and the reflux mixer, a flow control valve is also provided between the ammonia pipeline and the reflux mixer, a Venturi scrubber is also connected between the reactor flash evaporation tank, the nitric acid pipeline and the neutralization and washing tower, and a solution concentration and evaporation assembly is connected between the ammonium nitrate solution tank and the reactor flash evaporation tank.

[0008] As an improvement, the solution concentration evaporation assembly includes a falling film primary evaporator and an evaporative steam compressor. The falling film primary evaporator includes an upper evaporation receiving tank, a first-stage falling film primary evaporator, a second-stage falling film primary evaporator, and a second flash evaporator. The upper evaporation receiving tank, the first-stage falling film primary evaporator, the second-stage falling film primary evaporator, and the second flash evaporator are sequentially connected to the ammonium nitrate solution tank. The inlet of the evaporative steam compressor is connected to the upper evaporation receiving tank and the second flash evaporator, and the output of the evaporative steam compressor is connected to the second-stage falling film primary evaporator. The outlet of the neutralization and washing tower is connected to the first-stage falling film primary evaporator.

[0009] As an improvement, the output ends of both the primary falling film evaporator and the secondary falling film evaporator are connected to the process steam condensate tank, which is connected to the acid inlet of the neutralization and washing tower.

[0010] As an improvement, the neutralization washing tower includes a spray washing section, a bubble cap tray section, and a fiber demisting section. A washing circulation reflux pump is provided at the bottom of the neutralization washing tower. The washing circulation reflux pump is connected to a reflux mixer, and an indicator regulating valve is connected between the washing circulation reflux pump and the reflux mixer.

[0011] As an improvement, the ammonia pipeline is provided with two branch pipes connected to the pipeline reactor. A flow indicator valve one is connected to the ammonia pipeline away from the two branch pipes, and a flow indicator valve two is connected to the ammonia pipeline between the two branch pipes. The second branch pipe is connected to the reflux mixer, and a flow control valve is located between the second branch pipe and the reflux mixer.

[0012] The advantages of this invention compared to existing technologies are as follows: This ammonium nitrate solution production system not only solves the problem of unstable pH control in the ammonium nitrate production process, but also completely eliminates the problem of iron ions in the ammonium nitrate solution caused by acid corrosion during the neutralization and washing process by eliminating the packing layer of the neutralization and washing tower; the addition of ammonia to the flash tank coolant allows for precise control of the pH value of the flash tank; and the use of MVR technology (evaporative steam heating and pressurization) in the ammonium nitrate concentration process to fully upgrade and pressurize the evaporative steam in the system, using it as a heat source for the second-stage falling film evaporator instead of fresh steam, greatly saves on the amount of externally supplied steam, and significantly reduces the pollutants in the generated process steam condensate (30 ppm), allowing it to be directly discharged to the process steam condensate treatment system, making the system's exhaust emissions almost zero, thus greatly saving on environmental protection investment. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a safe, efficient, and energy-saving ammonium nitrate solution production system.

[0014] Figure 2 This is a schematic diagram of the pH adjustment system.

[0015] Figure 3 This is a schematic diagram of pH adjustment in a neutralization scrubbing tower. Detailed Implementation

[0016] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings. Identical components are indicated by the same reference numerals.

[0017] It should be noted that the terms “front,” “back,” “left,” “right,” “up,” and “down” used in the following description refer to the directions shown in the attached diagram, while the terms “inside” and “outside” refer to the directions toward or away from the geometric center of a specific component, respectively.

[0018] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly associated with those skilled in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] To make the content of this utility model easier to understand, the technical solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings.

[0021] Please refer to the appendix carefully. Figure 1-3

[0022] Gaseous ammonia and nitric acid are mixed and reacted in a tubular reactor R101, releasing heat to generate steam. In a flash tank F101, the process steam is separated from the ammonium nitrate solution, which remains at the bottom with a concentration of at least 87%.

[0023] To improve the conversion rate of ammonia and nitric acid, the calculated ratio of acid / ammonia ratio using FIC-101 and FIC-102 in a single closed-loop control is a molar ratio. FIC-101 is the main flow control loop, and FIC-102, the secondary flow control loop, tracks the gaseous ammonia flow rate at a molar ratio of 1:1. FIC-101 acts as the secondary loop tracking in the cascade control mode of LIC-101, achieving the main load control of the ammonium nitrate solution production process.

[0024] Since a small amount of ammonium nitrate will decompose in this process, the gaseous ammonia in tubular reactor R101 is supplemented according to the pH value of the process steam AIC-101 to ensure the pH value in the ammonium nitrate solution and steam.

[0025] The ammonium nitrate solution flash evaporation tank AIC-102 (pH control loop) serves as the control variable of the controller, controlling the gaseous ammonia in the reflux mixer M101 to fully mix with the washing liquid from the neutralization washing tower F102, so that the pH value of the reflux solution entering the flash evaporation tank F101 of the reactor can be controlled in a timely manner. Its function is to effectively and fully regulate the free nitric acid escaping from the tubular reactor in the flash evaporation tank F101 of the reactor, thereby improving reaction efficiency and increasing safety performance.

[0026] Before use, the process steam is first washed in the neutralization and scrubbing tower F102. This process consists of four parts:

[0027] Feature 1: The spray washing section uses a direct atomized spray washing method, which fundamentally eliminates the corrosion problem of the packing layer in the neutralization washing tower.

[0028] Feature 2: Acid is introduced at the top of the scrubbing tower, which prolongs the contact time of neutralization and washing and increases the vapor-liquid contact area, significantly reducing the amount of ammonia escaping. This lowers the pH of the process steam while raising the pH of the scrubbing liquid (in the AIC104 control loop at the bottom of the neutralization scrubbing tower (F102), the pH of the scrubbing solution in the F102 neutralization scrubbing tower is controlled in stages according to its rate of change, significantly reducing the amount of ammonia escaping. This lowers the pH of the process steam while raising the pH of the scrubbing liquid).

[0029] Venturi scrubber J101: Circulates the washing solution via neutralization and washing pump P101. Nitric acid is added to the washing solution to supplement the reaction; calculations are referenced. Figure 3 Ammonia is absorbed and neutralized in the acidic washing solution. Simultaneously, the superheated process steam is gradually cooled and saturated through the washing process, serving a pre-washing function.

[0030] The direct atomized spray washing method in the spray washing section fundamentally eliminates the corrosion problem of the packing layer in the neutralization washing tower (changing the situation where the lower packing layer of the neutralization washing tower would suffer severe corrosion or even collapse after a period of normal operation; the neutralization washing tower eliminates the original system's packing layer, fundamentally eliminating the corrosion problem). Acid is introduced at the top of the washing tower, prolonging the neutralization washing contact time and increasing the vapor-liquid contact area, significantly reducing the amount of ammonia escaping. This lowers the pH value of the process steam while raising the pH value of the washing liquid.

[0031] The spray system is located at the lower part of F102: the washing liquid circulation is maintained by the neutralization and washing pump P101. Makeup water overflows from the tray. The washing liquid is maintained at a slightly alkaline pH, with a small amount of ammonia further absorbed and neutralized in the acidic washing liquid. Excess washing liquid is returned to the flash evaporator F101 of the reactor to cool the ammonium nitrate solution. Simultaneously, since the washing liquid is a slightly acidic solution, the AIC-102 module replenishes ammonia in the reflux liquid before it returns to the flash evaporator F101 to further ensure the pH value of the ammonium nitrate solution.

[0032] The tower trays are divided into two parts: the upper tray is a bubble-covered tray structure, fed with evaporated condensate, equipped with level control, and overflows layer by layer. Each tray has a bubble cover plate for further washing of the process steam. Due to the presence of an acid addition control loop AIC-104 at this washing location, the process steam at the top of the washing tower is slightly acidic.

[0033] High-efficiency demister: The process steam after the tray washing still contains a small amount of ammonium nitrate droplets. The demister removes the droplets, the separated liquid is returned to the tower, and the washed process steam enters the system steam pipeline network.

[0034] The dilute ammonium nitrate solution is concentrated in a falling film primary evaporator. The evaporation system is divided into five parts. The high-temperature ammonium nitrate solution first enters the upper evaporation tank F103 for depressurization. The ammonium nitrate solution flashes, and the water vapor rises to the upper part while the solution falls by gravity. It first enters the lower primary falling film primary evaporator E101 for heating and evaporation. The heating medium is 0.35 MPa washing process steam. Then it enters the secondary falling film primary evaporator E102 for heating and evaporation. The heating medium is 0.8 MPa steam upgraded by the evaporation steam compressor. At the same time, most of the ammonium nitrate vapor-liquid mixture flows into F104 through the balance pipe for further flash separation. After secondary evaporation and secondary flash separation, the solution is concentrated to 96% and flows into the ammonium nitrate solution tank F105.

[0035] The saturated steam from the process enters the primary evaporator F103 and the secondary flash evaporator F104, respectively, and is heated and pressurized to 0.8 MPa by the evaporative steam compressor J101. This process steam then enters the falling film evaporator E102 for evaporation and is finally separated at the bottom of the primary evaporator E102 and the primary evaporator separator F104. This allows for the full utilization of the waste heat of the saturated steam from the process.

[0036] The heating steam condensate is collected in the atmospheric pressure washing evaporation condensate tank F107 and sent to the process steam condensate treatment system: electrodialysis system.

[0037] Please refer to the attached document carefully. Figure 2 The AIC-104 is an indicating control valve. For the pH control system in production, due to the large volume of the flash tank in the reactor, it takes a considerable amount of time for the ammonia mixing effect to become apparent after the reflux liquid from the mixer is mixed with ammonia. In actual production, it takes approximately 6-12 minutes to show the effect. Because the pH measurement at this location has a long lag time, and the concentration relationship expressed by pH is a logarithmic relationship of pH = [H+]10-n, exhibiting a significant non-linearity, a multi-parameter pH control loop was specifically designed to address this characteristic. The specific control method is as follows:

[0038] This module is a pH adjustment module; the optional functions of this module include: whether to use rate of change adjustment K (optional input or output).

[0039] When MA=1, it is in automatic mode; when MA=0, it is in manual mode.

[0040] The first absolute value refers to the change in the first time difference; the second absolute value refers to the change in the second time difference. The third absolute value refers to the rate of change. When the rate of change is ≥0, it indicates that the pH fluctuates significantly, and adjustments should be made according to the two parameters thereafter; when the rate of change is <0, it indicates that the pH is stabilizing and the regulator should not be adjusted for the time being.

[0041] A dual-parameter setting scheme is used to achieve control by employing different parameters based on the magnitude of the deviation between the measured value and the set value.

[0042] Specific PID parameter settings:

[0043] P1 = 0.5I1 = 1.2D1 = 0

[0044] P² = 0.8I² = 1.2D² = 0

[0045] P3 = 1.5I3 = 1.8D3 = 1.0

[0046] The control capabilities of the above three sets of parameters are progressively enhanced, enabling effective control of the pH value of the ammonium nitrate solution.

[0047] Please refer to the attached document carefully. Figure 3 In actual production, situations often arise where the adjustment speed is slightly slow or the regulating valve operates slowly. This can easily lead to short-term imbalances in the ortho-amino acid ratio. The addition of the AIC101 regulating loop in the ortho-amino acid ratio circuit results in a situation where there is more ammonia and less acid in the process steam. Furthermore, the inherent fluctuations in the ammonia flow rate cause slight fluctuations in the nitric acid tracking amount. pH fluctuations in the washing liquid are unavoidable. To ensure that the excess ammonia content FY108 of the top outlet steam of the flash evaporator F101 in the reactor is calculated in advance, and the same molar amount of nitric acid is added to the Venturi scrubber J101 at the inlet of the washing tower, a neutralization reaction is carried out in the Venturi scrubber, thus maintaining a stable pH value in the neutralization washing tower.

[0048] Where FY-108=(FI101)+(FI-103)-(FI102)

[0049] The above formula is for mol calculations.

[0050] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0051] All standard parts used in this utility model can be purchased from the market, and irregular parts can be customized according to the description and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts and equipment adopt conventional models in the prior art. In addition, the circuit connection adopts conventional connection methods in the prior art, which will not be described in detail here. The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0052] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the inventive spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A safe, efficient and energy-saving production system of ammonium nitrate solution, comprising an ammonia gas pipeline, a nitric acid pipeline, a high-efficiency tubular reactor, a reactor flash tank, a neutralization washing tower and an ammonium nitrate solution tank, characterized in that: The neutralization washing tower is an atomization washing tower, an acid inlet of the neutralization washing tower is arranged at the top of the neutralization washing tower, a reflux mixer is arranged between the high-efficiency tubular reactor, the reactor flash tank and the neutralization washing tower, an indicating adjusting valve is arranged between the neutralization washing tower and the reflux mixer, a flow control valve is further arranged between the ammonia gas pipeline and the reflux mixer, a Venturi scrubber is further connected between the reactor flash tank, the nitric acid pipeline and the neutralization washing tower, and a solution concentration evaporation assembly is further connected between the ammonium nitrate solution tank and the reactor flash tank. ​ 2. The system for producing safe, efficient and energy-saving ammonium nitrate solution according to claim 1, characterized in that: The solution concentration evaporation assembly comprises a falling film primary evaporator and an evaporation vapor compressor, the falling film primary evaporator comprises an upper evaporation receiving tank, a first-stage falling film primary evaporator, a second-stage falling film primary evaporator and a secondary flash evaporator, the upper evaporation receiving tank, the first-stage falling film primary evaporator, the second-stage falling film primary evaporator and the secondary flash evaporator are sequentially connected with the ammonium nitrate solution tank, an air inlet end of the evaporation vapor compressor is connected with the upper evaporation receiving tank and the secondary flash evaporator, an output end of the evaporation vapor compressor is connected with the second-stage falling film primary evaporator, and an air outlet end of the neutralization washing tower is connected with the first-stage falling film primary evaporator.

3. The system for producing safe, efficient and energy-saving ammonium nitrate solution according to claim 2, characterized in that: The output ends of the first-stage falling film primary evaporator and the second-stage falling film primary evaporator are both connected with a process steam condensate tank, and the process steam condensate tank is connected with the acid inlet of the neutralization washing tower.

4. The system for producing safe, highly efficient and energy-saving ammonium nitrate solution according to claim 1, characterized in that: The neutralization washing tower comprises a spray washing section, a bubble cap tray section and a fiber demisting section, a washing circulating reflux pump is arranged at the bottom of the neutralization washing tower, the washing circulating reflux pump is connected with the reflux mixer, and the indicating adjusting valve is arranged between the washing circulating reflux pump and the reflux mixer.

5. The system for producing safe, efficient and energy-saving ammonium nitrate solution of claim 1, wherein: The ammonia gas pipeline is provided with two branch pipes connected with the pipeline reactor, a flow indicating valve one is arranged on the ammonia gas pipeline away from the two branch pipes, a flow indicating valve two is arranged on the ammonia gas pipeline between the two branch pipes, the second branch pipe is connected with the reflux mixer, and the flow control valve is arranged between the second branch pipe and the reflux mixer.

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