Method for automatic adjustment of ammonia temperature tracking pressure in SCR denitration

Abstract

The application discloses a kind of SCR denitration gas ammonia temperature tracking pressure automatic adjustment method, the denitration ammonia area of SCR denitration system uses steam heat tracing, remote temperature point is set at the inlet of denitration flue, remote pressure point is set at the near end of gas ammonia buffer tank, remote temperature point, remote pressure point and steam heat tracing place are connected DCS control system, DCS control system controls steam heat tracing according to the pressure of remote pressure point, and then controls the temperature of remote temperature point.The SCR denitration gas ammonia temperature tracking pressure automatic adjustment method of the application realizes gas ammonia steam temperature automatic adjustment, reduces the labor intensity of operator, also avoids the waste of steam energy caused by gas ammonia temperature control being too high, realizes temperature fine adjustment with pressure, and forms an independent protection layer, ensures that gas ammonia temperature is higher than saturation temperature, achieves the effect of energy saving and can improve denitration operation safety factor.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermal power plant denitration system, and particularly relates to a method for automatically adjusting pressure of SCR denitration gas ammonia temperature tracking. BACKGROUND

[0002] Thermal power plants are mainly composed of steam systems, pulverizing systems and air and smoke systems, and the denitration system is an important part of the air and smoke system and mainly functions to remove the generated NOx in the exhaust gas. X Ammonia is reduced to N2 under the action of a catalyst, thereby removing NOx in the flue gas. X The main reaction is as follows:

[0003] ;

[0004] The reaction principle is as follows:

[0005]

[0006] In thermal power plants, the denitration system is an important part of plant operation and an important basis for achieving ultra-low emission of environmental data, and in actual production operation, the denitration gas ammonia temperature often has no independent protection layer and relies on artificial remote adjustment of the opening degree of the heating steam to realize temperature adjustment.

[0007] If the gas ammonia temperature is not adjusted in time due to operation reasons, the controlled gas ammonia temperature is lower than the saturation temperature corresponding to the gas ammonia pressure, which can cause gas ammonia liquefaction, and in severe cases, can cause an explosion in the explosion space between 15.8% and 28% of the explosion limit of the denitration ammonia air ratio (under the condition that the ammonia air ratio interlock is not put into operation), thereby causing a serious production accident. Therefore, it is important for safe and stable production to control the gas ammonia temperature to be higher than the saturation temperature corresponding to the pressure by automatic adjustment. SUMMARY

[0008] In view of the problems of gas ammonia liquefaction and easy safety accidents in the existing thermal power plant denitration system, the application provides a method for automatically adjusting the pressure of SCR denitration gas ammonia temperature tracking, the denitration gas ammonia temperature is automatically adjusted and controlled according to the pressure, the gas ammonia temperature is ensured to be higher than the saturation temperature corresponding to the pressure, the problem of gas ammonia liquefaction can be effectively solved, the ammonia air ratio interlock action caused by gas ammonia liquefaction can be eliminated, and the large production accidents of ammonia air ratio explosion caused by the uninstalled interlock and exceeding environmental data can be eliminated.

[0009] The application is implemented by the following technical solutions:

[0010] The application discloses a method for automatically adjusting the pressure of ammonia in an SCR denitration system, and the method is characterized in that: a steam heat tracing is arranged in an ammonia denitration area of the SCR denitration system, a remote temperature point is arranged at the inlet of a denitration flue, and a remote pressure point is arranged at the proximal end of a gas ammonia buffer tank; the remote temperature point, the remote pressure point and the steam heat tracing are connected with a DCS control system; the DCS control system controls the steam heat tracing according to the pressure of the remote pressure point, and then controls the temperature of the remote temperature point.

[0011] The control logic of the DCS control system is as follows:

[0012] (1) when the ammonia pressure of the remote pressure point is less than or equal to 0.33 Mpa, the DCS control system controls the steam quantity of the steam heat tracing, and keeps the temperature of the remote temperature point at 15 DEG C;

[0013] (2) when the ammonia pressure of the remote pressure point is greater than 0.33 Mpa, the DCS control system controls the steam quantity of the steam heat tracing, and keeps the temperature of the remote temperature point at T=P (Mpa)*25.2*Ln (3.1)+15 DEG C;

[0014] Wherein, P is the ammonia pressure (Mpa) of the remote pressure point.

[0015] Further, the steam heat tracing is provided with a steam heat tracing adjusting valve, and the steam quantity is controlled according to the valve opening degree of the steam heat tracing adjusting valve.

[0016] Further, the steam heat tracing valve is a high-precision electric regulating valve.

[0017] Further, the ammonia pressure adjusting valve is arranged between the gas ammonia buffer tank and the remote pressure point.

[0018] Further, the ammonia pressure of the remote pressure point is-0.03-1.41 MPa.

[0019] Further, the temperature of the remote temperature point is fed back to the steam heat tracing.

[0020] The application formulates the automatic control logic in stages according to the exponential relationship between the ammonia saturation pressure (zero-meter ammonia supply pressure in the ammonia area) of the remote pressure point and the saturation temperature at the inlet of the denitration flue, so that the actual ammonia temperature is strictly controlled to be higher than the saturation temperature corresponding to the pressure by 15 DEG C, that is, the steam energy waste caused by blindly increasing the ammonia temperature is avoided, and the ammonia temperature is ensured to be much higher than the saturation temperature, so that the effects of saving energy and improving the denitration operation safety factor are achieved.

[0021] The application has the following beneficial effects:

[0022] The method for automatically adjusting the ammonia temperature tracking pressure of the SCR denitration gas realizes automatic adjustment of the ammonia steam temperature, reduces the labor intensity of the operator, avoids waste of steam energy caused by excessively high ammonia temperature control, realizes fine adjustment of the temperature with the pressure, forms an independent protection layer, ensures that the ammonia temperature is higher than the saturation temperature, and achieves the effects of energy saving and improvement of the denitration operation safety factor. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The figure is a schematic diagram of the SCR denitration ammonia temperature tracking pressure automatic adjustment system of the present application. DETAILED DESCRIPTION

[0024] The above content of the present application is further described in detail through the following examples, but this should not be understood as limiting the scope of the above subject matter of the present application to only the following examples. Any technology realized based on the above content of the present application belongs to the scope of the present application.

[0025] The schematic diagram of the SCR denitration ammonia temperature tracking pressure automatic adjustment system in the present application is shown in Figure 1 As Figure 1 can be seen, the SCR denitration ammonia temperature tracking pressure automatic adjustment system adopts steam tracing, a steam tracing regulating valve is installed at the steam tracing position, the steam amount is controlled according to the opening degree of the valve, a remote temperature point is arranged at the inlet of the denitration flue, a remote pressure point is arranged at the proximal end of the ammonia buffer tank, and an ammonia pressure regulating valve is arranged between the ammonia buffer tank and the remote pressure point. The remote temperature point, the remote pressure point and the steam tracing position (steam tracing regulating valve) are connected to a DCS control system, the DCS control system controls the opening degree of the valve of the steam tracing according to the pressure of the remote pressure point, and then controls the temperature of the remote temperature point.

[0026] The control logic of the DCS control system is as follows:

[0027] (1) When the ammonia pressure of the remote pressure point is ≤0.33 Mpa, the DCS control system controls the opening degree of the steam tracing regulating valve of the steam tracing to control the steam amount, keeps the temperature T of the remote temperature point =15℃, and keeps the ammonia temperature at least 15℃ higher than the ammonia temperature corresponding to the pressure.

[0028] (2) When the ammonia pressure of the remote pressure point is >0.33 Mpa, the DCS control system controls the steam amount at the steam tracing position, keeps the temperature T of the remote temperature point =P (Mpa)*25.2*Ln(3.1)+15℃, and keeps the ammonia temperature at least 15℃ higher than the ammonia temperature corresponding to the pressure.

[0029] Wherein: P is the ammonia pressure (Mpa) of the remote pressure point.

[0030] Example 1

[0031] like Figure 1 The SCR denitrification ammonia gas temperature tracking pressure automatic adjustment system shown in the figure, when the remote pressure point displays 0.21 MPa, it feeds back to the DCS control system. The control system calculates that the ammonia gas temperature should be maintained at 15℃ and feeds the signal back to the ammonia vapor regulating valve. By controlling the opening degree, the ammonia gas temperature is maintained at 15℃.

[0032] Example 2

[0033] like Figure 1 The SCR denitrification ammonia temperature tracking pressure automatic adjustment system shown in the figure, when the remote pressure display of ammonia gas is 0.7 MPa, feeds back to the DCS control system. The control system calculates the ammonia temperature T = 0.7 * 25.2 * Ln (3.1) + 15 = 34.96 (°C), which is 16.96°C higher than the corresponding saturation temperature of 18°C.

Claims

1. A method for SCR denitration gas ammonia temperature tracking pressure automatic adjustment, characterized in that, The denitration ammonia area of the SCR denitration system is steam traced, a remote temperature point is arranged at the inlet of the denitration flue, a remote pressure point is arranged at the proximal end of the gaseous ammonia buffer tank, the remote temperature point, the remote pressure point and the steam tracing place are connected with a DCS control system, the DCS control system controls the steam tracing according to the pressure of the remote pressure point, and then controls the temperature of the remote temperature point; The control logic of the DCS control system is: (1) when the gaseous ammonia pressure of the remote pressure point is ≤0.33 Mpa, the DCS control system controls the steam amount of the steam tracing place, and keeps the temperature T of the remote temperature point =15℃; (2) when the gaseous ammonia pressure of the remote pressure point is >0.33 Mpa, the DCS control system controls the steam amount of the steam tracing place, and keeps the temperature T of the remote temperature point = P (Mpa)*25.2*Ln(3.1)+15℃; Wherein: P is the gaseous ammonia pressure (Mpa) of the remote pressure point.

2. The method for SCR De-NOx ammonia temperature tracking pressure automatic adjustment according to claim 1, characterized in that, The steam tracing place is provided with a steam tracing adjusting valve, and the steam amount is controlled according to the valve opening of the steam tracing adjusting valve.

3. The method for SCR De-NOx ammonia temperature tracking pressure automatic adjustment according to claim 1, wherein, The steam tracing valve is a high-precision electric regulating valve.

4. The method for SCR de-NOx ammonia temperature tracking pressure automatic adjustment according to claim 1, characterized in that, A gaseous ammonia pressure adjusting valve is arranged between the gaseous ammonia buffer tank and the remote pressure point.

5. The method for SCR de-NOx ammonia temperature tracking pressure automatic adjustment of claim 1, wherein, The gaseous ammonia pressure of the remote pressure point is-0.03~1.41 MPa.

6. The method for SCR De-NOx ammonia temperature tracking pressure automatic adjustment of claim 1, wherein, The temperature of the remote temperature point is fed back to the steam tracing place.

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