A control method for low-oxygen safe and environmentally-friendly operation of a common pressure reduction heating furnace

Abstract

A kind of control method of low-oxygen safe and environmentally-friendly operation of atmospheric and vacuum heating furnace, comprising: obtaining CO value in flue gas by online CO analyzer installed on flue; obtaining NOx value and SO2 value in flue gas by online flue gas analyzer installed on flue; obtaining O2 value in flue gas by online oxygen analyzer installed on flue; taking CO value and O2 value as input values, determining blast fan outlet damper control amount according to preset override control strategy; controlling blast fan outlet damper valve opening degree according to blast fan outlet damper control amount; taking NOx value and SO2 value as input values, determining blast fan outlet damper valve position limit value according to preset alarm control.The present application can achieve rapid and accurate optimization control of blast fan outlet damper, to realize safe operation of heating furnace under low-oxygen environment.

Description

Technical Field

[0001] This invention relates to a control method for an atmospheric and vacuum distillation furnace. In particular, it relates to a control method for the safe and environmentally friendly operation of an atmospheric and vacuum distillation furnace under low oxygen conditions. Background Technology

[0002] With the goal of promoting low-carbon and environmentally friendly practices, saving energy and reducing harmful gas emissions have become the most important tasks in the production and management of heating furnaces in the petrochemical industry. How to improve the thermal efficiency of heating furnaces while ensuring safe and environmentally friendly operation is a research topic for many refineries. Reducing the oxygen content in flue gas is one way to directly improve the thermal efficiency of heating furnaces; however, reducing the oxygen content in flue gas also leads to increased CO and SO2 levels, which can bring considerable safety and environmental risks.

[0003] The DCS (Distributed Control System) automatic control system of petrochemical plants is generally designed to include automatic control loops for the outlet dampers of the heater blowers and the flue dampers. However, due to various reasons, its performance is not ideal, and most systems still rely entirely on manual adjustment of air distribution. The heater thermal efficiency obtained through periodic testing and evaluation generally reflects the meticulous operation of personnel at each position and cannot truly represent the average thermal efficiency of the heater over the entire operating cycle. In other words, relying solely on manual labor, it is impossible for the heater to maintain a consistently high level of meticulous operation throughout a continuous 24-hour production cycle. Therefore, there is still potential to improve the average thermal efficiency of the heater over the entire operating cycle.

[0004] Existing technologies mainly use a single loop of O2 or CO to control the opening of the blower outlet damper. The inventors have found that the existing technology has at least the following drawbacks:

[0005] In practical applications, when O2 is used as the control point, the oxygen content in the flue gas of the heating furnace will be controlled to be relatively high, resulting in low thermal efficiency and NOx exceeding the standard in some heating furnaces.

[0006] When CO is used as the control point, the oxygen content will be relatively low, the overall control stability will be low, and it will be easily affected by fuel fluctuations. When the fluctuations are too large, some heating furnaces will have SO2 levels in the flue gas exceeding the required values. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a control method for safe and environmentally friendly operation of atmospheric and vacuum furnaces in a low-oxygen environment.

[0008] The technical solution adopted in this invention is: a control method for the safe and environmentally friendly operation of an atmospheric and vacuum distillation furnace under low oxygen conditions, comprising the following steps:

[0009] 1) Obtain the CO value in the flue gas using an online CO analyzer installed on the flue; obtain the NOx and SO2 values ​​in the flue gas using an online flue gas analyzer installed on the flue; obtain the O2 value in the flue gas using an online oxygen analyzer installed on the flue.

[0010] 2) Input the CO and O2 values ​​and determine the control amount of the blower outlet damper according to the preset override control strategy;

[0011] 3) Control the opening degree of the blower outlet damper valve according to the blower outlet damper control quantity;

[0012] 4) Input the NOx and SO2 values ​​and determine the limit value of the blower outlet damper valve according to the preset alarm control.

[0013] The resolution of both the CO analyzer and the flue gas analyzer mentioned in step 1) is ppm.

[0014] The sampling frequency of the online CO analyzer described in step 1) is less than or equal to 0.14 seconds / time.

[0015] The sampling output frequency of the online oxygen analyzer described in step 1) is less than or equal to 2 seconds / time.

[0016] The sampling output frequency of the online flue gas analyzer described in step 1) is less than or equal to 10 seconds / time.

[0017] The overdrive control strategy described in step 2) is specifically as follows:

[0018] (1) Taking the O2 value collected by the oxygen analyzer as input, the first PID control output is generated according to the PID control logic in the DCS control system of the atmospheric and vacuum furnace.

[0019] (2) Taking the CO content value collected by the CO online analyzer as input, a second PID control output is generated according to the PID control logic in the DCS control system of the atmospheric and vacuum furnace.

[0020] (3) Using the high-selection module in the DCS control system of the atmospheric and vacuum furnace, determine one of the first PID control output and the second PID control output as the control quantity of the blower outlet baffle.

[0021] (4) Adjust the control amount of the blower outlet baffle to control the CO content, O2 content, and NOx and SO2 content alarm values ​​within the preset range.

[0022] In step (4): the CO content is controlled between 0 and 100 ppm; the O2 content is controlled between 1% and 2.5%.

[0023] In step (4): the NOx content alarm value is controlled at 65-90 mg / m³. 3 The SO2 content alarm value is controlled at 30-45 mg / m³. 3 .

[0024] The alarm control mentioned in step 4) is as follows:

[0025] The SO2 value collected by the flue gas analyzer is used as the first interlock point to determine the upper limit value of the control quantity of the blower outlet damper;

[0026] The NOx value collected by the flue gas analyzer is used as the second interlock point to determine the lower limit of the control quantity of the blower outlet damper.

[0027] This invention discloses a control method for the safe and environmentally friendly operation of an atmospheric and vacuum distillation furnace under low oxygen conditions. To improve the control accuracy and stability of the actuators, an online CO analyzer is installed in the area from the convection chamber outlet to the induced draft fan in the flue to collect CO content values. These values ​​are then combined with the O2 content values ​​detected by an oxygen analyzer located at the top of the furnace. An override control strategy is used to generate the control value for the blower outlet damper valve position. Simultaneously, SO2 and NOx content values ​​collected by an online flue gas analyzer located on the chimney are interlocked to generate the upper and lower limits of the blower outlet damper valve position. This achieves rapid and accurate optimized control of the blower outlet damper, thereby ensuring safe operation of the furnace under low oxygen conditions.

[0028] The CO online analyzer in this invention measures the CO content and O2 override control in a well-mixed flue gas. Therefore, unlike the prior art that detects only the oxygen content, it does not suffer from poor accuracy and high oxygen content in the flue gas due to leaks in the heating furnace. It also avoids the problems of poor stability and low safety associated with detecting only the CO content. Therefore, this invention can effectively improve control accuracy, stability and safety.

[0029] In this invention, interlocking control can also be used to set interlocking points for SO2 and NOx, ensuring that the entire control process is carried out within the scope of existing environmental protection requirements.

[0030] In this invention, through override control and interlock control, the heating furnace can achieve the goal of maximizing thermal efficiency and minimizing pollutant emissions by dynamically monitoring the CO, SO2 and NOx content while gradually reducing the total air volume. Attached Figure Description

[0031] Figure 1 This is a flowchart of a control method for low-oxygen, safe, and environmentally friendly operation of an atmospheric and vacuum distillation furnace according to the present invention;

[0032] Figure 2 This is a schematic diagram of the theoretical fuel combustion curve described in this invention. Detailed Implementation

[0033] The following describes in detail a control method for low-oxygen, safe, and environmentally friendly operation of an atmospheric and vacuum distillation furnace according to the present invention, with reference to embodiments and accompanying drawings.

[0034] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] like Figure 1 As shown, the present invention provides a control method for the safe and environmentally friendly operation of an atmospheric and vacuum distillation furnace under low oxygen conditions, comprising the following steps:

[0036] 1) Obtain the CO value in the flue gas using an online CO analyzer installed on the flue; obtain the NOx and SO2 values ​​in the flue gas using an online flue gas analyzer installed on the flue; obtain the O2 value in the flue gas using an online oxygen analyzer installed on the flue.

[0037] The resolution of both the CO analyzer and the flue gas analyzer is ppm.

[0038] The sampling frequency of the online CO analyzer is less than or equal to 0.14 seconds / time; the sampling output frequency of the online oxygen analyzer is less than or equal to 2 seconds / time; and the sampling output frequency of the online flue gas analyzer is less than or equal to 10 seconds / time.

[0039] 2) Using the CO and O2 values ​​as input values, determine the control amount of the blower outlet damper according to a preset override control strategy; the override control strategy is specifically as follows:

[0040] (1) Taking the O2 value collected by the oxygen analyzer as input, the first PID control output is generated according to the PID control logic in the DCS control system of the atmospheric and vacuum furnace.

[0041] (2) Taking the CO content value collected by the CO online analyzer as input, a second PID control output is generated according to the PID control logic in the DCS control system of the atmospheric and vacuum furnace.

[0042] (3) Using the high-selection module in the DCS control system of the atmospheric and vacuum furnace, determine one of the first PID control output and the second PID control output as the control quantity of the blower outlet baffle.

[0043] (4) Adjust the blower outlet damper control value to keep the CO content, O2 content, and NOx and SO2 content alarm values ​​within the preset range; after generating the blower outlet damper control value, the blower frequency can be adjusted using the blower outlet damper control value as the control parameter to keep the O2 and CO content in the furnace flue gas within a reasonable range (i.e., the preset range). Wherein:

[0044] The CO content is controlled between 0 and 100 ppm; the O2 content is controlled between 1% and 2.5%.

[0045] The NOx content alarm value is controlled at 65-90 mg / m³. 3 The SO2 content alarm value is controlled at 30-45 mg / m³. 3 .

[0046] 3) Control the opening degree of the blower outlet damper valve according to the blower outlet damper control quantity;

[0047] 4) Input the NOx and SO2 values, and determine the limit value of the blower outlet damper valve according to the preset alarm control; the alarm control is as follows:

[0048] The SO2 value collected by the flue gas analyzer is used as the first interlock point to determine the upper limit of the control quantity of the blower outlet damper; the NOx value collected by the flue gas analyzer is used as the second interlock point to determine the lower limit of the control quantity of the blower outlet damper.

[0049] In this embodiment of the invention, by dynamically monitoring the CO, NOx, and SO2 contents during the process of gradually reducing the total air volume, it is possible to achieve the following: Figure 2 The combustion curve shown effectively reduces oxygen consumption within its control range, thereby maximizing thermal efficiency and minimizing pollutant emissions, thus enabling the heating furnace to operate safely and environmentally in a low-oxygen environment.

Claims

1. A control method for the safe and environmentally friendly operation of an atmospheric and vacuum distillation furnace under low oxygen conditions, characterized in that, Includes the following steps: 1) The CO value in the flue gas is obtained by an online CO analyzer installed on the flue; the NOx and SO2 values ​​in the flue gas are obtained by an online flue gas analyzer installed on the flue; the O2 value in the flue gas is obtained by an online oxygen analyzer installed on the flue; the resolution of the CO analyzer and the flue gas analyzer is ppm; the sampling frequency of the online CO analyzer is less than or equal to 0.14 seconds / time; the sampling output frequency of the online oxygen analyzer is less than or equal to 2 seconds / time; the sampling output frequency of the online flue gas analyzer is less than or equal to 10 seconds / time. 2) Using the CO and O2 values ​​as input values, determine the control amount of the blower outlet damper according to a preset override control strategy; the override control strategy is specifically as follows: (1) Taking the O2 value collected by the oxygen analyzer as input, the first PID control output is generated according to the PID control logic in the DCS control system of the atmospheric and vacuum furnace. (2) Taking the CO content value collected by the CO online analyzer as input, a second PID control output is generated according to the PID control logic in the DCS control system of the atmospheric and vacuum furnace. (3) The output of the first PID control and the output of the second PID control are determined by the high-selection module in the DCS control system of the atmospheric and vacuum heating furnace as the control quantity of the blower outlet baffle. (4) Adjust the control amount of the blower outlet baffle to control the CO content, O2 content, and NOx and SO2 content alarm values ​​within the preset range; 3) Control the opening degree of the blower outlet damper valve according to the blower outlet damper control quantity; 4) Input the NOx and SO2 values, and determine the limit value of the blower outlet damper valve according to the preset alarm control; the CO content is controlled between 0 and 100 ppm; the O2 content is controlled between 1% and 2.5%; the NOx alarm value is controlled between 65 and 90 mg / m³; the SO2 alarm value is controlled between 30 and 45 mg / m³; the alarm control is as follows: The SO2 value collected by the flue gas analyzer is used as the first interlock point to determine the upper limit value of the control quantity of the blower outlet damper; The NOx value collected by the flue gas analyzer is used as the second interlock point to determine the lower limit of the control quantity of the blower outlet damper.

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