Automatic control system for indirect ammonia distillation in coking

Abstract

The utility model discloses an automatic control system for coking indirect ammonia distillation, which comprises an ammonia distillation tower, a steam reboiler, an ammonia dephlegmator, an alkali liquor storage tank, an ammonia water heat exchanger and a gas-liquid separator, a first path of the ammonia water heat exchanger is connected with a residual ammonia water pipeline, and a second path of the ammonia water heat exchanger is connected with an ammonia distillation wastewater pipeline. The third path of the ammonia water heat exchanger and the alkali liquor pipeline are respectively connected with the first end and the second end of the pipeline mixer, the third end of the pipeline mixer is connected with the top of one side of the ammonia still, the circulating ammonia water pipeline is provided with a circulating ammonia water regulating valve, and the alkali liquor pump is interlocked with the circulating ammonia water regulating valve; an ammonia still tower top thermometer is mounted at the top of the other outer side of the ammonia still, the top of the ammonia still is connected with a first path of the ammonia dephlegmator, the side surface of the ammonia dephlegmator is respectively connected with circulating water feed water and circulating water return water, and the top and the bottom of the ammonia dephlegmator are connected with the gas-liquid separator. By means of automatic fine control, energy conservation, consumption reduction and stable wastewater discharge in the ammonia distillation process are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of environmental protection and surplus ammonia water treatment, and in particular to an automatic control system for coking indirect ammonia distillation. Background Art

[0002] The emergence of ammonia evaporation process has solved the problem of residual ammonia treatment very well. The ammonia evaporation process uses steam as a heat source and can be divided into direct ammonia evaporation, indirect ammonia evaporation by water vapor heating, and ammonia evaporation by heat pump valve. Using general heat carrier water vapor as a heating agent, the equilibrium vapor pressure of ammonia on the circulating water surface is greater than the partial pressure of ammonia in the heat carrier, and the vapor and liquid two phases are in countercurrent contact to carry out mass transfer and heat transfer, so that ammonia is gradually released from the circulating water, and a mixture of ammonia vapor and water vapor is obtained at the top of the tower, and relatively pure circulating water is obtained at the bottom of the tower. The purpose of adding an alkali source is to convert fixed ammonium salts into volatile ammonium salts. After ammonia evaporation, qualified wastewater is sent to the next process of wastewater treatment, and concentrated ammonia water is sent to the desulfurization section and added to the desulfurization liquid for continued use.

[0003] At present, the existing coking enterprises mainly have the following problems:

[0004] (1) Ammonia nitrogen content in ammonia evaporation wastewater often fluctuates greatly, resulting in wastewater indicators exceeding the standard;

[0005] (2) The alkali solution is added through the alkali solution pump. The alkali solution pump does not have a frequency conversion function and it is difficult to control the amount of alkali added. The pH value is often high, resulting in excessive alkali consumption and increased auxiliary material costs;

[0006] (3) The steam flow rate is regulated by the temperature at the top of the ammonia evaporation tower. The steam inlet is farther away from the temperature at the top of the ammonia evaporation tower, and the regulation is prone to delay, resulting in excessive steam addition to increase the temperature inside the tower, which indirectly affects the rise in the temperature of the desulfurized liquid.

[0007] (4) The ammonia separator uses circulating water for cooling, which poses a risk of scaling in the tubes, increasing circulation resistance and affecting circulation efficiency. Summary of the invention

[0008] In order to overcome the deficiencies of the prior art, the utility model provides an automated control system for coking indirect ammonia distillation, which realizes energy saving and consumption reduction in the ammonia distillation process and stabilizes wastewater discharge indicators by utilizing automated fine control.

[0009] The technical solution adopted by the utility model to achieve the above-mentioned purpose is:

[0010] An automatic control system for indirect ammonia distillation in coking, comprising an ammonia distillation tower, a steam reboiler, an ammonia fractionator, an alkali liquid storage tank, an ammonia water heat exchanger and a gas-liquid separator, wherein the first path of the ammonia water heat exchanger is connected to a residual ammonia water pipeline, the second path of the ammonia water heat exchanger is connected to an ammonia distillation wastewater pipeline, the third path of the ammonia water heat exchanger and an alkali liquid pipeline extracted from an alkali liquid storage tank by a variable frequency alkali liquid pump are respectively connected to a first end and a second end of a pipeline mixer, the third end of the pipeline mixer is connected to the top of one side of the ammonia distillation tower, a circulating ammonia water regulating valve is installed on the residual ammonia water pipeline, and the alkali liquid pump is interlocked with the circulating ammonia water regulating valve; an ammonia distillation tower top thermometer is installed on the other outer top of the ammonia distillation tower, the top of the ammonia distillation tower is connected to the first path of the ammonia fractionator, the second path and the third path of the ammonia fractionator are respectively connected to circulating water supply and circulating water return, and the top and bottom of the ammonia gas fractionator are connected to the gas-liquid separator.

[0011] Furthermore, a alkali liquid check valve is provided on the alkali liquid pipeline, and a circulating ammonia water pressure-stabilizing valve is provided on the pipeline connecting the pipeline mixer and the ammonia distillation tower.

[0012] Preferably, the solution in the alkali solution pipeline is 32% NaOH solution.

[0013] Preferably, the circulating ammonia water regulating valve, the ammonia evaporation tower top thermometer, the ammonia evaporation tower bottom thermometer, and the steam flow regulating valve are all solenoid valves, and the circulating ammonia water regulating valve, the ammonia evaporation tower top thermometer, the ammonia evaporation tower bottom thermometer, the steam flow regulating valve and the variable frequency alkali solution pump are respectively connected to the controller.

[0014] The utility model extracts alkali liquid from the alkali liquid storage tank and adds it to the ammonia distillation tower. The alkali adding position is located between the residual ammonia water pipeline and the ammonia distillation tower. The adding point is not easy to be too close to the ammonia distillation tower, which is not conducive to the full mixing of ammonia water and alkali source. NaOH with a concentration of 32% is added to the pipeline, the original alkali liquid pump is changed, the alkali adding amount is adjusted by frequency conversion, and the ammonia water flow valve is interlocked. Accurate alkali addition can be achieved according to the real-time data of the residual ammonia water amount, so as to achieve automatic adjustment of the alkali adding amount. The temperature in the ammonia tower is mainly controlled according to the steam flow rate. The waste water and steam at the bottom of the ammonia distillation tower can be used for heat exchange by using a steam reboiler to form a steam-water mixture. Provide heat source for ammonia evaporation; the internal temperature is mainly controlled by the tower top temperature and the tower bottom temperature. The original steam flow control valve and the tower top temperature form a cascade control setting, but the tower bottom pressure increases with the tower bottom temperature, and it is not easy to observe the change of tower bottom pressure when the processing capacity is increased; the tower bottom temperature and the steam flow regulating valve are added to form a cascade control, and the tower top temperature and the tower bottom temperature can proportionally control the ammonia evaporation steam intake at the same time, thereby playing a role in controlling the pressure and temperature in the tower; the ammonia separator replaces the heat exchange medium, and uses a heating water pipe to connect the original circulating water pipe. Because the temperature is similar, the water quality is better and it is not easy to scale, so the heat exchange effect is better.

[0015] The utility model has the advantages of simple structure, high automation effect, small investment and simple operation. Through automatic alkali addition and automatic temperature control operation in the tower, the utility model effectively solves the problem of excessive ammonia nitrogen in ammonia evaporation, saves energy and reduces consumption, and reduces operation risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the utility model process;

[0017] Explanation of the reference numerals: ammonia distillation tower 1, steam reboiler 2, ammonia fractionator 3, alkali solution storage tank 4, alkali solution pump 5, circulating ammonia water regulating valve 6, circulating ammonia water pressure-stabilizing valve 7, alkali solution check valve 8, steam flow regulating valve 9, ammonia distillation tower top thermometer 10, ammonia distillation tower bottom thermometer 11, wastewater cooler 12, ammonia water heat exchanger 13, gas-liquid separator 14, pipeline mixer 15. DETAILED DESCRIPTION

[0018] like Figure 1 As shown, the automatic control system of the indirect ammonia distillation of coking in this embodiment includes an ammonia distillation tower 1, a steam reboiler 2, an ammonia fractionator 3, an alkali liquid storage tank 4, an ammonia water heat exchanger 13 and a gas-liquid separator 14, wherein the first path of the ammonia water heat exchanger 13 is connected to the residual ammonia water pipeline, the second path of the ammonia water heat exchanger 13 is connected to the ammonia distillation wastewater pipeline, the third path of the ammonia water heat exchanger 13 and the alkali liquid pipeline extracted from the alkali liquid storage tank 4 by the variable frequency alkali liquid pump are respectively connected to the first end and the second end of the pipeline mixer 15 The third end of the pipeline mixer 15 is connected to the top of one side of the ammonia still 1, a circulating ammonia water regulating valve 6 is installed on the residual ammonia water pipeline, and the alkali solution pump 5 is interlocked with the circulating ammonia water regulating valve 6; an ammonia still top thermometer 10 is installed on the other outer top of the ammonia still 1, the top of the ammonia still 1 is connected to the first path of the ammonia fractionator 3, the second path and the third path of the ammonia fractionator 3 are respectively connected to the circulating water supply and the circulating water return, and the top and bottom of the ammonia fractionator 3 are connected to the gas-liquid separator 14.

[0019] Furthermore, a alkali liquid check valve 8 is provided on the alkali liquid pipeline, and a circulating ammonia water pressure-stabilizing valve 7 is provided on the pipeline connecting the pipeline mixer 15 and the ammonia distillation tower 1 .

[0020] Preferably, the solution in the alkali solution pipeline is 32% NaOH solution.

[0021] Preferably, the circulating ammonia water regulating valve 6, the ammonia evaporation tower top thermometer 10, the ammonia evaporation tower bottom thermometer 11, and the steam flow regulating valve 9 are all solenoid valves, and the circulating ammonia water regulating valve 6, the ammonia evaporation tower top thermometer 10, the ammonia evaporation tower bottom thermometer 11, the steam flow regulating valve 9 and the variable frequency alkali solution pump 5 are respectively connected to the controller.

[0022] The residual ammonia water passes through the ceramic filter of the coke ammonia treatment section and is sent to the ammonia distillation system for ammonia distillation. Before entering the ammonia distillation tower, the residual ammonia water (about 70°C) is heated in the ammonia water heat exchanger 13 using the residual heat of the ammonia distillation wastewater (90-105°C), and the temperature of the residual ammonia water is raised to about 85°C. At the same time, the temperature of the ammonia distillation wastewater is lowered, the load of the ammonia distillation wastewater cooler is reduced, and the temperature of the ammonia distillation wastewater is stabilized.

[0023] Alkali is added to the residual ammonia water after heating before entering the ammonia distillation tower 1. The alkali liquid extracted from the alkali liquid storage tank 4 by the alkali liquid pump 5 is added to the circulating ammonia water pipeline in proportion. An alkali liquid check valve 8 is added before the alkali liquid pipeline enters the circulating ammonia water pipeline to ensure that the alkali liquid is effectively added to the pipeline. However, the adding position is moved forward compared to before, so that the alkali liquid and the residual ammonia water can be fully integrated, thereby increasing the efficiency of removing fixed ammonia. In order to stabilize the pressure of the circulating ammonia water, a pressure regulating valve 7 is set on the pipeline to ensure that the ammonia water flow stabilizes the pressure. The original alkali liquid pump 5 is changed, and the amount of alkali added is adjusted by frequency conversion, and it is interlocked with the circulating ammonia water regulating valve 6, and NaOH with a concentration of 32% is added to the pipeline. Accurate alkali addition is achieved based on the real-time data of the amount of residual ammonia water added, thereby achieving automatic adjustment of the amount of alkali added.

[0024] The control of the amount of steam added is to use indirect steam to evaporate ammonia. The steam enters the steam reboiler 2, and after heat exchange with a part of the wastewater at the bottom of the ammonia evaporation tower, it enters the ammonia evaporation tower 1 to evaporate ammonia. Another part of the ammonia evaporation wastewater coming out of the bottom of the tower exchanges heat with steam in the steam reboiler 2 to form a steam mixture that enters the ammonia evaporation tower 1 as a heat source to evaporate ammonia. The water vapor mixture formed by the condensation of the steam after the heat exchange is collected and processed, which is not within the scope of this transformation. The original steam flow control method is to perform cascade control with the steam flow control valve 9 and the tower top thermometer 10, and the tower top temperature control range is 90-105°C. However, when the residual ammonia water treatment amount is increased during actual operation, the steam flow will also increase accordingly. After the steam flow rate increases, the tower bottom temperature increases accordingly, and the tower bottom pressure increases at the same time. An additional cascade control is set up to allow the tower bottom thermometer 11 to form a series adjustment with the steam flow control valve 9, and the tower bottom pressure is then controlled by the tower bottom temperature, so as to control the steam addition amount to the greatest extent, thereby playing a role in energy saving and consumption reduction.

[0025] The ammonia decompressor 3 is located at the top of the ammonia evaporation tower, and a circulating water inlet is provided inside the shell and a circulating water outlet is provided on the other side. The ammonia gas is cooled in the internal heat dissipation sleeve by circulating water. However, the original design used circulating water for cooling. There is a risk of scaling if circulating water is used for a long time, which increases the circulation resistance and reduces the heat exchange efficiency. The circulating water is changed to heating water. After the heating water is electro-desalted, all indicators are better than those of circulating water. The liquid ammonia gas after the ammonia decompressor 3 leaves the ammonia evaporation section through the gas-liquid separator 14. The ammonia evaporation wastewater is discharged from the bottom of the ammonia evaporation tower 1, and after the ammonia water heat exchanger 13 and the wastewater cooler 12 are cooled and treated to reach the qualified range, it is discharged into the wastewater treatment section. This transformation achieves material balance by accurately controlling the substances entering the internal part of the ammonia evaporation tower, ensuring that the wastewater indicators are controllable, reliable and stable, and achieving the goal of energy saving and consumption reduction for the enterprise with the least resources to achieve the maximum precision control.

[0026] The above is a preferred embodiment of the present invention, and the description of the specific embodiment is only used to better understand the concept of the present invention. For ordinary technicians in this technical field, several improvements or equivalent substitutions can be made according to the principle of the present invention, and these improvements or equivalent substitutions are also considered to fall within the protection scope of the present invention.

Claims

1. An automatic control system for indirect ammonia distillation in coking, characterized in that: It includes an ammonia still, a steam reboiler, an ammonia fractionator, an alkali liquid storage tank, an ammonia heat exchanger and a gas-liquid separator. The first path of the ammonia heat exchanger is connected to a residual ammonia pipeline, the second path of the ammonia heat exchanger is connected to an ammonia still wastewater pipeline, the third path of the ammonia heat exchanger and an alkali pipeline drawn from an alkali liquid storage tank by a variable frequency alkali pump are respectively connected to a first end and a second end of a pipeline mixer, the third end of the pipeline mixer is connected to the top of one side of the ammonia still, the residual ammonia pipeline is provided with a circulating ammonia regulating valve, and the alkali liquid pump is interlocked with the circulating ammonia regulating valve; an ammonia still top thermometer is provided on the other outer top of the ammonia still, the top of the ammonia still is connected to the first path of the ammonia fractionator, the second path and the third path of the ammonia fractionator are respectively connected to circulating water supply and circulating water return, and the top and bottom of the ammonia fractionator are connected to a gas-liquid separator.

2. The automatic control system for indirect ammonia distillation from coking according to claim 1, characterized in that: The alkali solution pipeline is provided with an alkali solution check valve, and the pipeline connecting the pipeline mixer and the ammonia distillation tower is provided with a circulating ammonia water pressure-stabilizing valve.

3. The automatic control system for indirect ammonia distillation by coking according to claim 1 or 2, characterized in that: The solution in the alkali solution pipeline is 32% NaOH solution.

4. The automatic control system for indirect ammonia distillation from coking according to claim 2, characterized in that: The circulating ammonia water regulating valve, the ammonia evaporation tower top thermometer, the ammonia evaporation tower bottom thermometer, and the steam flow regulating valve are all solenoid valves, and the circulating ammonia water regulating valve, the ammonia evaporation tower top thermometer, the ammonia evaporation tower bottom thermometer, the steam flow regulating valve and the variable frequency alkali solution pump are respectively connected to the controller.

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