A glass fiber tank furnace and combustion control method

Abstract

The application provides a glass fiber tank furnace and a combustion control method. The glass fiber tank furnace comprises a tank furnace and a controller. The tank furnace and the controller are electrically connected. The tank furnace is provided with a calorific value analysis device, an adjusting device, a first temperature measuring device, a second temperature measuring device, an operator and a combustion nozzle. The calorific value analysis device is used for monitoring the calorific value of natural gas. The adjusting device is used for adjusting the flow of natural gas and oxygen. The first temperature measuring device is used for monitoring the space temperature of the tank furnace. The second temperature measuring device is used for monitoring the glass liquid temperature in the tank furnace. The operator is used for inputting the electricity price, the oxygen price and the natural gas price. The combustion nozzle is used for controlling the output of oxygen and natural gas. The tank furnace is provided with a gas detection device at the passage, which is used for monitoring the carbon monoxide and oxygen concentration. The technical scheme can realize the automatic control of the power distribution of the glass fiber tank furnace combustion system, the oxygen atmosphere, the combustion system and the electric melting system.

Description

Technical Field

[0001] This invention relates to the field of glass fiber tank kiln combustion technology, specifically to a glass fiber tank kiln and a combustion control method. Background Technology

[0002] Currently, fiberglass furnaces are equipped with distributed control systems (DCS) to control key process parameters such as temperature, liquid level, and kiln pressure. However, the following problems exist:

[0003] 1) The temperature control for the combustion system is all open-loop. Thermocouples are installed inside the furnace to monitor temperature parameters in real time for operator observation. Operators make judgments based on parameter fluctuations and manually adjust the combustion system. Because multiple spray guns are arranged in the furnace and are interconnected, adjusting any one of them will affect the temperature control. Therefore, the adjustment process requires a high level of operator skill and is prone to overshoot.

[0004] 2) The heat source for the fiberglass furnace is primarily natural gas / oxygen. To monitor the combustion status of natural gas and oxygen inside the furnace, a zirconia sensor is installed to detect the residual oxygen concentration. To ensure complete combustion, the residual oxygen concentration is generally controlled above 4%—that is, when personnel observe a residual oxygen concentration below 4%, the oxygen-fuel ratio is manually fine-tuned, failing to achieve closed-loop regulation of the residual oxygen concentration and the oxygen-fuel ratio.

[0005] 3) The zirconia sensor is placed inside the furnace and operates in a high-temperature environment (>1000℃) for a long time, making it prone to damage. In addition, carbon monoxide is generally not provided inside the furnace, making it impossible to accurately determine whether the furnace is in a state of incomplete combustion.

[0006] 4) The electric melting system is manually adjusted according to the temperature of the molten glass. The power distribution between the combustion system and the electric melting system cannot be achieved automatically. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a fiberglass tank kiln and a combustion control method that can achieve automatic control of the power distribution among the fiberglass tank kiln's combustion system, oxygen atmosphere, combustion system, and electric fluxing system.

[0008] The present invention provides a fiberglass tank furnace, comprising a tank furnace and a controller; the tank furnace and the controller are electrically connected;

[0009] The furnace is equipped with a calorific value analysis device, a regulating device, a first temperature measuring device, a second temperature measuring device, an operator, and a combustion nozzle. The calorific value analysis device is used to monitor the calorific value of natural gas. The regulating device is used to regulate the flow rates of natural gas and oxygen. The first temperature measuring device is used to monitor the ambient temperature of the furnace. The second temperature measuring device is used to monitor the temperature of the molten glass inside the furnace. The operator is used to input the electricity price, oxygen price, and natural gas price. The combustion nozzle is used to control the output of oxygen and natural gas.

[0010] A gas detection device is installed at the passage of the furnace to monitor the concentration of carbon monoxide and oxygen.

[0011] The calorific value analysis device, the regulating device, the first temperature measuring device, the second temperature measuring device, the operator, the combustion nozzle, and the gas detection device are all electrically connected to the controller.

[0012] Furthermore, an electric melting system is provided at the bottom of the furnace, and the electric melting system is electrically connected to the controller.

[0013] Furthermore, the controller includes a combustion controller and an electric melting controller; the combustion controller is electrically connected to the calorific value analysis device, the regulating device, the first temperature measuring device, the second temperature measuring device, the operator, and the combustion nozzle, respectively; the electric melting controller is electrically connected to the second temperature measuring device and the electric melting system, respectively.

[0014] Furthermore, the electric melting system is equipped with a voltage and current detection device and a voltage and current regulation device, and the electric melting controller is electrically connected to the voltage and current detection device and the voltage and current regulation device respectively.

[0015] Furthermore, the combustion nozzle opening degree = (real-time natural gas calorific value / average natural gas calorific value within a preset time period) × regulating valve opening degree signal;

[0016] The opening signal of the regulating valve is from 0 to 100% and is output by the combustion controller.

[0017] The present invention also provides a method for controlling combustion in a fiberglass tank kiln, comprising:

[0018] Obtain the measured values ​​of the controlled variables, which include the calorific value of natural gas, oxygen content in the passage, oxygen and natural gas flow rates, the space temperature of the furnace, the temperature of the molten glass, and the voltage and current values ​​of the electric melting flux.

[0019] Calculate the error between the measured value and the preliminary prediction value to obtain the prediction error value;

[0020] The preliminary prediction value is corrected based on the prediction error value to obtain the corrected prediction value;

[0021] Based on electricity prices, oxygen prices, and natural gas prices, optimize the objective function and calculate the target values ​​of process variables;

[0022] Based on the corrected predicted values, calculate the output values ​​of the operational variables;

[0023] If the output value meets the preset conditions, the corrected prediction value is updated to obtain the updated prediction value.

[0024] Furthermore, the method also includes:

[0025] If the output value does not meet the preset conditions, adjust the voltage and current of the electric flux controller.

[0026] Furthermore, the method also includes:

[0027] The formula for calculating the prediction error value is as follows:

[0028] The formula for calculating the corrected prediction value is as follows:

[0029] The formula for calculating the target value is as follows:

[0030] The formula for calculating the output value is as follows:

[0031] The formula for updating the corrected predicted value is as follows:

[0032] Among them, y i , and e i c represents the measured value, predicted value, and prediction error of the controlled variable, respectively. o c g and c e The unit prices for oxygen, natural gas, and industrial electricity are respectively, δ o δ g and δ e These represent the changes in oxygen, natural gas, and industrial electricity consumption, respectively, λ. i α i and β i As a weighting factor, and These represent the reference value, open-loop steady-state value, and setpoint of the controlled variable, respectively, and Δy. i and Δu j The changes in the controlled variable and the manipulated variable are respectively represented by the function f(Δu). j (1) represents the influence of the manipulated variable on the controlled variable.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The fiberglass tank furnace and combustion control method provided by this invention realize the automatic control of power distribution among the fiberglass tank furnace combustion system, oxygen atmosphere, combustion system and electric melting system. It also realizes the decoupling of multivariable parameters, parameter prediction and dynamic parameter correction of the tank furnace combustion system. Furthermore, it considers the overall economic efficiency of natural gas / oxygen and electricity prices, and realizes the economical distribution of heat and work generated by the combustion system and electric melting system. Attached Figure Description

[0035] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0036] Figure 1 This is a schematic diagram of the fiberglass furnace passage provided in an embodiment of the present invention;

[0037] Figure 2 This is a block diagram for controlling the constant value of residual oxygen content provided in an embodiment of the present invention;

[0038] Figure 3 A hardware structure diagram of the control system provided in an embodiment of the present invention;

[0039] Figure 4 A controller block diagram provided in an embodiment of the present invention;

[0040] Figure 5 The algorithm flowchart provided for the embodiments of the present invention. Detailed Implementation

[0041] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0042] This invention provides a fiberglass tank furnace, including a tank furnace and a controller;

[0043] The tank furnace is equipped with a calorific value analysis device, a regulating device, a first temperature measuring device, a second temperature measuring device, an operator, and a combustion nozzle. The calorific value analysis device is used to monitor the calorific value of natural gas; the regulating device is used to regulate the flow rate of natural gas and oxygen; the first temperature measuring device is used to monitor the space temperature of the tank furnace; the second temperature measuring device is used to monitor the temperature of the molten glass inside the tank furnace; the operator is used to input the electricity price, oxygen price, and natural gas price; and the combustion nozzle is used to control the output of oxygen and natural gas.

[0044] Gas detection devices are installed at the passageway of the tank furnace to monitor the concentration of carbon monoxide and oxygen.

[0045] An electric melting system is installed at the bottom of the tank furnace; the electric melting system is equipped with a voltage and current detection device and a voltage and current regulation device;

[0046] The controller includes a combustion controller and an electric melting controller; the combustion controller is electrically connected to the calorific value analysis device, the regulating device, the first temperature measuring device, the second temperature measuring device, the operator, and the combustion nozzle, respectively; the electric melting controller is electrically connected to the second temperature measuring device, the voltage and current detection device, and the voltage and current regulating device, respectively.

[0047] Specifically,

[0048] 1) Online monitoring of natural gas calorific value: The calorific value of natural gas is monitored in real time through a calorific value analysis device. The average calorific value of natural gas within a preset time period is taken as a benchmark. The real-time calorific value is compared with the average value to obtain a calorific value proportionality coefficient. This coefficient is multiplied by the actual output of each combustion controller to obtain the fine-tuned opening degree of the combustion nozzle, thereby fine-tuning the overall heat output of the combustion system. That is, combustion nozzle opening degree = (real-time natural gas calorific value / average natural gas calorific value within the preset time period) × regulating valve opening signal; wherein, the regulating valve opening signal is from 0 to 100% and is output by the combustion controller. The calorific value analysis device can be an infrared calorific value analyzer.

[0049] 2) Online monitoring of oxygen and carbon monoxide concentrations at the furnace passageway to monitor the furnace combustion status in real time. Please refer to [link / reference]. Figure 1 The gas detection device is installed at the furnace passageway; it consists of two sets of laser measuring instruments—one for oxygen and one for carbon monoxide. The transmitter generates two laser beams of different wavelengths. The 650nm wavelength laser is used to measure oxygen (the internal controller monitors the laser absorption spectrum of oxygen, calculates laser energy loss, and further calculates the oxygen concentration); the 2310nm wavelength laser is used to measure carbon monoxide. The laser transmitter and receiver are installed outside the furnace, transmitting light through glass windows on both sides of the furnace; the measured carbon monoxide and oxygen are inside the furnace.

[0050] 3) Please refer to Figure 2 When natural gas and oxygen are fully combusted, the chemical reaction is as follows:

[0051] 2O2 + CH4 = CO2 + 2H2O

[0052] When natural gas and oxygen burn completely, the oxygen-fuel ratio is an integer of 2. However, in practical applications, to ensure complete combustion, the oxygen-fuel ratio is typically higher than 2. A higher oxygen-fuel ratio results in higher residual oxygen content, leading to decreased fuel consumption and combustion efficiency in the furnace, thus reducing overall economic efficiency. To balance complete combustion with ensuring the furnace operates at a low residual oxygen level (approximately 2%), residual oxygen content control is implemented based on a setpoint. The controller output, after being converted by a formula, becomes the oxygen-fuel ratio setpoint for each burner. To prevent the furnace from entering an incomplete combustion state, upper and lower limits are imposed on the controller output. During actual commissioning, the carbon monoxide concentration is monitored in real time. When a sharp increase in carbon monoxide concentration is detected, the oxygen-fuel ratio is at its lower limit (less than or equal to 2). The upper limit of the oxygen-fuel ratio is determined by the allowable upper limit of residual oxygen content, which in practical applications is 4%.

[0053] 4) A regulating device is installed inside the furnace to dynamically adjust the flow rate of natural gas / oxygen. In practical applications, the number of burners is related to the furnace's melting capacity. The higher the daily melting capacity, the more burners are required. Simultaneously, orifice plate flow meters are installed on the natural gas / oxygen branch pipes of the burners to monitor the real-time consumption of natural gas and oxygen. Specifically, the regulating device may consist of combustion nozzles arranged on the left and right sides and the arch of the furnace, each nozzle comprising an oxygen lance and a natural gas lance. Regulating valves are installed on the oxygen and natural gas lance pipelines; adjusting the valve opening achieves flow rate regulation. Flow meters are also installed on the pipelines to measure the gas flow rate in real time. Dynamic adjustment based on the flow meters on the oxygen / natural gas branch pipes achieves constant flow control.

[0054] 5) Temperature measuring instruments are installed inside the furnace to monitor the space temperature, glass melt temperature, and refractory material temperature in each process section, such as feeding, melting, and passage.

[0055] 6) Please refer to Figure 3 This advanced control system is based on a conventional DCS control system, adding an advanced control algorithm server to the DCS. The server communicates with the DCS system in real time via OPC (Open Platform Communication) to obtain the required process data (including furnace space temperature, molten glass temperature, refractory brick temperature, furnace pressure, furnace liquid level, feeder frequency, molten glass / space temperature in the passage, glass / space temperature in the forming section, stencil temperature, stencil SCR (Silicon Controlled Rectifier) ​​current value, etc.).

[0056] Please see Figure 4 The system inputs and outputs of the controller are shown in the figure. In practical applications, the calorific value of natural gas is measured by an infrared calorific value analyzer, the oxygen content is measured by a laser analyzer, the temperature is measured by a thermocouple, the voltage and current are measured by a current transformer, the oxygen and natural gas flow rates are measured by an orifice plate flow meter, and the electricity price, oxygen price, and natural gas price are manually input through a human-machine interface.

[0057] Please see Figure 5 The present invention also provides a method for controlling combustion in a fiberglass tank kiln, comprising:

[0058] Obtain the measured values ​​of the controlled variables, which include the calorific value of natural gas, oxygen content in the passage, oxygen and natural gas flow rates, the space temperature of the furnace, the temperature of the molten glass, and the voltage and current values ​​of the electric melting flux.

[0059] Calculate the error between the measured value and the preliminary prediction value to obtain the prediction error value;

[0060] The preliminary prediction value is corrected based on the prediction error value to obtain the corrected prediction value;

[0061] Based on electricity prices, oxygen prices, and natural gas prices, optimize the objective function and calculate the target values ​​of process variables;

[0062] Based on the corrected predicted values, calculate the output values ​​of the operational variables;

[0063] If the output value meets the preset conditions, the corrected prediction value is updated to obtain the updated prediction value.

[0064] In an optional implementation, the method further includes:

[0065] If the output value does not meet the preset conditions, adjust the voltage and current of the electric flux controller.

[0066] The electro-fusing system mainly consists of a transformer system and a molybdenum electrode. The system is regulated by the deviation between the actual temperature of the molten glass and the set temperature. If the molten glass temperature is lower than the set value, the output voltage of the transformer system is increased, thereby increasing the output power of the molybdenum electrode. Conversely, the voltage is decreased. P = V² / R, where P is the power, V is the electrode voltage, and R is the electrode resistance.

[0067] In an optional implementation, the method further includes:

[0068] The formula for calculating the prediction error value is as follows:

[0069] The formula for calculating the corrected prediction value is as follows:

[0070] The formula for calculating the target value is as follows:

[0071] The formula for calculating the output value is as follows:

[0072] The formula for updating the corrected predicted value is as follows:

[0073] Where k, k1, and k2 represent the subscript indices of the sampling time, k = 1, 2, ..., N, k1 = 1, 2, ..., N, k2 = 1, 2, ..., M, N is the user-defined prediction time domain, and M is the user-defined control time domain. i , and e i Let be the measured value, predicted value, and prediction error of the i-th controlled variable, respectively. The predicted value is the open-loop step response, obtained through open-loop testing. When calculating the prediction error... Take the previous calculation period The calculation results. o c g and c e The unit prices for oxygen, natural gas, and industrial electricity are respectively, δ o δ g and δ e The consumption of oxygen, natural gas, and industrial electricity, respectively, can be calculated using the corresponding testing instruments. λ i α i and β i This is the weighting factor. and These are the reference value, open-loop steady-state value, and setpoint of the controlled variable, respectively. The program automatically updates the value during each calculation cycle. K ij It is the gain coefficient from the j-th operated variable to the i-th controlled variable, which can be obtained by open-loop testing or specified by the user based on experience; Provided by the user; y i r (k1) represents N numerical points set by the user, serving as reference values ​​for the controlled variable, also known as the reference trajectory, which represents how the controlled variable changes from the measured value to the setpoint. Δy i and Δu j These represent the changes in the controlled variable and the manipulated variable, respectively. The manipulated variables include oxygen, natural gas, and electricity consumption. The function is f(Δu). j (1) represents the dynamic change process from the j-th manipulated variable to the i-th controlled variable. This process is generally represented by a step response function, i.e. g ij (k) is the step response sequence from the j-th operated variable to the i-th controlled variable, which can be obtained by open-loop testing or specified by the user based on experience.

[0074] Specifically, the combustion controller employs model predictive control. The controlled variables are the furnace space temperature and the molten glass temperature; the manipulated variables are the burner opening setpoint and the power setpoint of the electric melting controller. The model predictive algorithm for the combustion controller consists of two parts: steady-state optimization and dynamic control. Steady-state optimization considers the process variable constraints and economic benefits, simultaneously optimizing the steady-state objectives of both the manipulated and controlled variables. The dynamic control layer calculates the control output of the combustion controller, i.e., the burner opening setpoint. The electric melting controller receives the power setpoint calculated by the combustion controller in real time and, in conjunction with its own regulation system, tracks the power setpoint to achieve the control objective together with the combustion controller.

[0075] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A fiberglass tank furnace, characterized in that, Includes a tank furnace and a controller; the tank furnace and the controller are electrically connected; The furnace is equipped with a calorific value analysis device, an adjustment device, a first temperature measuring device, a second temperature measuring device, an operator, and a combustion nozzle; the calorific value analysis device is used to monitor the calorific value of natural gas. The regulating device is used to regulate the flow rate of natural gas and oxygen; The first temperature measuring device is used to monitor the space temperature of the furnace; the second temperature measuring device is used to monitor the temperature of the molten glass inside the furnace; the operator is used to input the electricity price, oxygen price, and natural gas price; the combustion nozzle is used to control the output of oxygen and natural gas. A gas detection device is installed at the passage of the furnace to monitor the concentration of carbon monoxide and oxygen. The calorific value analysis device, the regulating device, the first temperature measuring device, the second temperature measuring device, the operator, the combustion nozzle, and the gas detection device are all electrically connected to the controller. An electric melting system is installed at the bottom of the tank furnace, and the electric melting system is electrically connected to the controller; The controller includes a combustion controller and an electric melting controller; the combustion controller is electrically connected to the calorific value analysis device, the regulating device, the first temperature measuring device, the second temperature measuring device, the operator, and the combustion nozzle; the electric melting controller is electrically connected to the second temperature measuring device and the electric melting system. Combustion nozzle opening = (real-time natural gas calorific value / average natural gas calorific value within a preset time period) × regulating valve opening signal; The opening signal of the regulating valve is from 0 to 100% and is output by the combustion controller; The combustion controller employs model predictive control; the controlled variables are the furnace space temperature and the glass melt temperature; the operated variables are the burner opening setpoint and the power setpoint of the electric melting controller; the electric melting controller receives the power setpoint calculated by the combustion controller in real time, and tracks the power setpoint in conjunction with its own adjustment system, working together with the combustion controller to achieve the control objective.

2. The fiberglass tank furnace according to claim 1, characterized in that, The electric melting system is equipped with a voltage and current detection device and a voltage and current regulation device, and the electric melting controller is electrically connected to the voltage and current detection device and the voltage and current regulation device respectively.

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