Method for green recovery and energy-saving utilization of ammonium nitrate alkaline steam heat

Abstract

A method for green recovery and energy-saving utilization of ammonium nitrate alkaline steam heat comprises the following steps: step 1, in an ammonium nitrate start-up stage, the lower part of an ammonium nitrate neutralization reaction kettle is communicated with a conveying pipeline of a dilute nitric acid solution and superheated ammonia gas; 2, a vacuum ejector utilizes saturated steam to carry out vacuum, a vacuum falling film evaporator adopts saturated steam to preheat, an ammonium nitrate solution conveying pipeline and an ammonium nitrate solution tank utilize saturated steam to heat and insulate an ammonium nitrate solution to prevent crystallization, and ammonia gas is heated by utilizing saturated steam; and 3, after the ammonium nitrate is normally started and the temperature and the steam flow of high-temperature alkaline steam generated by the acid-base neutralization reaction of the dilute nitric acid solution and the ammonia gas in the ammonium nitrate neutralization reaction kettle are stable, replacing saturated steam with the high-temperature alkaline steam, so that the high-temperature alkaline steam can be fully utilized, and resources are effectively saved. High-temperature alkaline steam heat is recycled in the ammonium nitrate production process, use of saturated steam is reduced, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of ammonium nitrate production in the chemical industry, and specifically relates to a method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam. Background Art

[0002] At present, the main production processes of ammonium nitrate in China are tubular reactor method and volumetric reactor method. Compared with the tubular reactor method, the process flow of pressurized volumetric reactor is simpler, occupies a smaller area, and has a higher level of automation. The pressurized volumetric reaction method uses 58%-65% dilute nitric acid and gaseous ammonia to carry out acid-base neutralization reaction in a volumetric reactor to generate a dilute ammonium nitrate solution with a concentration of about 75-80%, while releasing heat. The dilute ammonium nitrate solution needs to be concentrated for external sale or subsequent production of nitro compound fertilizer. Most companies use vacuum falling film evaporators, using saturated steam as a heat source to prevent ammonium nitrate crystallization. At the same time, vacuum ejectors use saturated steam to bring vacuum to concentrate the ammonium nitrate solution under vacuum. The dilute ammonium nitrate solution with a concentration of about 75-80% out of the neutralizer can be concentrated to about 90-93%, and stored in the ammonium nitrate solution tank. The ammonium nitrate solution tank has a built-in heating coil, and saturated steam is used to keep the ammonium nitrate solution warm to prevent crystallization. The neutralization reaction of dilute nitric acid and ammonia alkali is an exothermic reaction. The heat of the high-temperature alkaline steam generated is not fully utilized, resulting in energy waste. At the same time, the direct use of saturated steam will increase production costs. Summary of the invention

[0003] The invention provides a method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam, which is used to solve the defects in the prior art.

[0004] The present invention is achieved through the following technical solutions:

[0005] A method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam comprises the following steps:

[0006] Step 1: During the ammonium nitrate start-up phase, the lower part of the ammonium nitrate neutralization reactor is connected to the conveying pipelines of the dilute nitric acid solution and the superheated ammonia gas, the middle part of the ammonium nitrate neutralization reactor is connected to the vacuum falling film evaporator through a pipeline, and the top of the vacuum falling film evaporator is connected to the vacuum ejector through a pipeline;

[0007] Step 2: The vacuum ejector uses saturated steam to create a vacuum, the vacuum falling film evaporator uses saturated steam for preheating, the ammonium nitrate solution delivery pipeline and the ammonium nitrate solution tank use saturated steam to heat and insulate the ammonium nitrate solution to prevent crystallization, and the ammonia gas is heated by saturated steam to prevent liquid ammonia from being entrained in the ammonia gas. The saturated steam comes from the saturated steam network;

[0008] Step 3: After the ammonium nitrate is started normally, and the temperature and steam flow of the high-temperature alkaline steam generated by the acid-base neutralization reaction of the dilute nitric acid solution and ammonia in the ammonium nitrate neutralization reactor are stable, close the vacuum ejector saturated steam regulating valve and open the alkaline steam regulating valve to bring about vacuum; close the vacuum falling film evaporator saturated steam regulating valve and open the alkaline steam regulating valve to heat and insulate the vacuum falling film evaporator, close the ammonium nitrate solution conveying pipeline and the ammonium nitrate solution tank heating steam coil saturated steam regulating valve and open the alkaline steam regulating valve to heat and insulate the ammonium nitrate solution conveying pipeline and the ammonium nitrate solution tank; close the ammonia superheater saturated steam regulating valve and open the alkaline steam regulating valve, thereby making full use of the high-temperature alkaline steam and effectively saving resources.

[0009] In the method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam as described above, a one-way valve can be provided on the conveying pipeline of the dilute nitric acid solution and the superheated ammonia gas to prevent the backflow of the dilute nitric acid solution or the superheated ammonia gas.

[0010] According to the method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam as described above, the vacuum falling film evaporator utilizes partition wall heat exchange, the ammonium nitrate solution delivery pipeline utilizes jacketed pipe, the ammonium nitrate solution tank utilizes heating coil heat exchange to insulate and heat the ammonium nitrate solution to prevent crystallization, and the ammonia is heated by an ammonia superheater.

[0011] In the method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam as described above, the neutralization reaction temperature of the ammonium nitrate neutralization reactor is controlled at 160-180°C.

[0012] According to the method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam as described above, a temperature sensor is arranged in the ammonium nitrate neutralization reactor, the upper part of the ammonium nitrate neutralization reactor is connected to the lower part of the cooling water tank through a pipeline, when the temperature in the ammonium nitrate neutralization reactor exceeds 180°C, cooling water is added to the ammonium nitrate neutralization reactor by opening the cooling water pump and cooling water valve on the pipeline connecting the ammonium nitrate neutralization reactor and the cooling water tank, and when the temperature drops to 165°C, the water pump and the water valve are closed, thereby completing the temperature control in the ammonium nitrate neutralization reactor.

[0013] According to the method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam as described above, the high-temperature alkaline steam is sent to a cooling water tank through a pipeline after heat exchange, and then a dilute nitric acid solution is added and then softened water is added. Since ammonia and dilute nitric acid do not contain metal ions, the water in the liquefied alkaline steam after heat exchange can be reused, and the ammonia contained in the alkaline steam will also undergo a neutralization reaction with the dilute nitric acid solution to achieve full utilization of resources.

[0014] The advantages of the present invention are as follows: the present invention realizes heat recovery and utilization of high-temperature alkaline steam in the ammonium nitrate production process, reduces the use of saturated steam (only used in the start-up stage), and can simultaneously recover and utilize ammonia in the alkaline steam and water resources in the steam, thereby reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0016] Figure 1 It is a schematic diagram of the structure of the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] A method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam comprises the following steps:

[0019] Step 1: During the ammonium nitrate start-up phase, the lower part of the ammonium nitrate neutralization reactor is connected to the conveying pipelines of the dilute nitric acid solution and the superheated ammonia gas, the middle part of the ammonium nitrate neutralization reactor is connected to the vacuum falling film evaporator through a pipeline, and the top of the vacuum falling film evaporator is connected to the vacuum ejector through a pipeline;

[0020] Step 2: The vacuum ejector uses saturated steam to create a vacuum, the vacuum falling film evaporator uses saturated steam for preheating, the ammonium nitrate solution delivery pipeline and the ammonium nitrate solution tank use saturated steam to heat and insulate the ammonium nitrate solution to prevent crystallization, and the ammonia gas is heated by saturated steam to prevent liquid ammonia from being entrained in the ammonia gas. The saturated steam comes from the saturated steam network;

[0021] Step 3: After the ammonium nitrate is started normally, and the temperature and steam flow of the high-temperature alkaline steam generated by the acid-base neutralization reaction of the dilute nitric acid solution and ammonia in the ammonium nitrate neutralization reactor are stable, close the vacuum ejector saturated steam regulating valve and open the alkaline steam regulating valve to bring about vacuum; close the vacuum falling film evaporator saturated steam regulating valve and open the alkaline steam regulating valve to heat and insulate the vacuum falling film evaporator, close the ammonium nitrate solution conveying pipeline and the ammonium nitrate solution tank heating steam coil saturated steam regulating valve and open the alkaline steam regulating valve to heat and insulate the ammonium nitrate solution conveying pipeline and the ammonium nitrate solution tank; close the ammonia superheater saturated steam regulating valve and open the alkaline steam regulating valve, thereby making full use of the high-temperature alkaline steam and effectively saving resources.

[0022] Specifically, a one-way valve may be provided on the delivery pipeline of the dilute nitric acid solution and the superheated ammonia gas described in this embodiment to prevent the backflow of the dilute nitric acid solution or the superheated ammonia gas.

[0023] Specifically, the vacuum falling film evaporator described in this embodiment utilizes partition heat exchange, the ammonium nitrate solution delivery pipeline utilizes a jacketed pipe, the ammonium nitrate solution tank utilizes a heating coil for heat exchange to insulate and heat the ammonium nitrate solution to prevent crystallization, and the ammonia is heated by an ammonia superheater, which is used to heat the ammonia to vaporize the liquid ammonia entrained in the ammonia to prevent the liquid ammonia from being entrained in the gaseous ammonia evaporated from the front end liquid ammonia evaporator. After the liquid ammonia is brought into the ammonium nitrate neutralization reactor, the instantaneous vaporization of the liquid ammonia will cause violent fluctuations in the neutralization reaction, thereby ensuring the safe progress of the reaction.

[0024] More specifically, the neutralization reaction temperature of the ammonium nitrate neutralization reactor described in this embodiment is controlled at 160-180°C.

[0025] Furthermore, a temperature sensor is arranged in the ammonium nitrate neutralization reactor described in this embodiment, and the upper part of the ammonium nitrate neutralization reactor is connected to the lower part of the cooling water tank through a pipeline. When the temperature in the ammonium nitrate neutralization reactor exceeds 180°C, cooling water is added into the ammonium nitrate neutralization reactor by opening the cooling water pump and cooling water valve on the pipeline connecting the ammonium nitrate neutralization reactor and the cooling water tank. When the temperature drops to 165°C, the water pump and the water valve are closed, thereby completing the temperature control in the ammonium nitrate neutralization reactor.

[0026] Furthermore, the high-temperature alkaline steam described in this embodiment is sent to the cooling water tank through the pipeline after heat exchange, and then a dilute nitric acid solution is added and then softened water is added. Since ammonia and dilute nitric acid do not contain metal ions, the water in the liquefied alkaline steam after heat exchange can be reused, and the ammonia contained in the alkaline steam will also react with the dilute nitric acid solution to achieve full utilization of resources.

[0027] Furthermore, the alkaline steam with vacuum in the vacuum ejector described in this embodiment flows downward from the top of the vacuum ejector to form negative pressure, thereby driving the vacuum falling film evaporator to form negative pressure, and the alkaline steam evaporated from the vacuum falling film evaporator is extracted with the negative pressure.

[0028] It can be known from actual production that the production cost per ton can be saved by 50-100 yuan compared with the previous production method directly using saturated steam after using the method of the present invention, the thermal energy of high-temperature alkaline steam is effectively utilized, and the residual ammonia and water resources in the high-temperature alkaline steam can be recovered and utilized, thereby achieving full utilization of resources.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for green recovery and energy-saving utilization of heat from ammonium nitrate alkaline steam, characterized in that: The steps include: Step 1: During the ammonium nitrate start-up phase, the lower part of the ammonium nitrate neutralization reactor is connected to the conveying pipelines of the dilute nitric acid solution and the superheated ammonia gas, the middle part of the ammonium nitrate neutralization reactor is connected to the vacuum falling film evaporator through a pipeline, and the top of the vacuum falling film evaporator is connected to the vacuum ejector through a pipeline; Step 2: The vacuum ejector uses saturated steam to create a vacuum, the vacuum falling film evaporator uses saturated steam for preheating, the ammonium nitrate solution delivery pipeline and the ammonium nitrate solution tank use saturated steam to heat and insulate the ammonium nitrate solution to prevent crystallization, and the ammonia gas is heated by saturated steam to prevent liquid ammonia from being entrained in the ammonia gas. The saturated steam comes from the saturated steam network; Step 3: After the ammonium nitrate is started normally, and the temperature and steam flow of the high-temperature alkaline steam generated by the acid-base neutralization reaction of the dilute nitric acid solution and ammonia in the ammonium nitrate neutralization reactor are stable, close the vacuum ejector saturated steam regulating valve and open the alkaline steam regulating valve to bring about vacuum; close the vacuum falling film evaporator saturated steam regulating valve and open the alkaline steam regulating valve to heat and insulate the vacuum falling film evaporator, close the ammonium nitrate solution conveying pipeline and the ammonium nitrate solution tank heating steam coil saturated steam regulating valve and open the alkaline steam regulating valve to heat and insulate the ammonium nitrate solution conveying pipeline and the ammonium nitrate solution tank; close the ammonia superheater saturated steam regulating valve and open the alkaline steam regulating valve, thereby making full use of the high-temperature alkaline steam and effectively saving resources.

2. The method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam according to claim 1, characterized in that: A one-way valve may be provided on the conveying pipeline of the dilute nitric acid solution and the superheated ammonia gas to prevent the dilute nitric acid solution or the superheated ammonia gas from flowing back.

3. The method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam according to claim 1, characterized in that: The vacuum falling film evaporator utilizes partition heat exchange, the ammonium nitrate solution delivery pipeline utilizes jacketed pipes, the ammonium nitrate solution tank utilizes heating coils for heat exchange to insulate and heat the ammonium nitrate solution to prevent crystallization, and the ammonia is heated by an ammonia superheater.

4. The method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam according to claim 1, characterized in that: The neutralization reaction temperature of the ammonium nitrate neutralization reactor is controlled at 160-180°C.

5. The method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam according to claim 4, characterized in that: A temperature sensor is arranged in the ammonium nitrate neutralization reactor, and the upper part of the ammonium nitrate neutralization reactor is connected with the lower part of the cooling water tank through a pipeline. When the temperature in the ammonium nitrate neutralization reactor exceeds 180°C, cooling water is added into the ammonium nitrate neutralization reactor by opening the cooling water pump and the cooling water valve on the pipeline connecting the ammonium nitrate neutralization reactor and the cooling water tank. When the temperature drops to 165°C, the water pump and the water valve are closed, thereby completing the temperature control in the ammonium nitrate neutralization reactor.

6. The method for green recovery and energy-saving utilization of heat of ammonium nitrate alkaline steam according to claim 1, characterized in that: The high-temperature alkaline steam is sent to the cooling water tank through the pipeline after heat exchange, and then a dilute nitric acid solution is added and then softened water is added. Since ammonia and dilute nitric acid do not contain metal ions, the water in the liquefied alkaline steam after heat exchange can be reused, and the ammonia contained in the alkaline steam will also react with the dilute nitric acid solution to achieve full utilization of resources.

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