Flameless combustion system and method of controlling the same

Abstract

The invention discloses a flameless combustion system and its control method. The system comprises a furnace body, a top cover, an accelerating combustor and a main fuel nozzle. The accelerating combustor comprises an accelerating chamber and a combustor. The combustor comprises a fuel inlet pipe, an oxidant inlet pipe, a core pipe, a conical bluff body and an igniter. The special design of the accelerating combustor can preheat the oxidant and accelerate the oxidant by thermal expansion, effectively avoid the phenomenon that the temperature of the central jet area is low due to the entry of cold oxidant, greatly improve the temperature uniformity in the furnace, and also improve the jet speed of the oxidant after entering the furnace to meet the requirements of flameless combustion, effectively reduce the pressure and load of the oxidant delivery system. The system also has the characteristics of simple structure, convenient operation, stable oxygen-free combustion state and uniform temperature distribution in the furnace. The matching control method has the advantages of short control process and high control precision.

Description

Technical Field

[0001] This invention relates to a combustion device, specifically to a flameless combustion system and its control method, belonging to the field of flameless combustion device and control technology. Background Technology

[0002] Gaseous fuels, such as natural gas and coke oven gas, are important industrial energy sources. However, while burning these fuels for heating, they also generate large amounts of pollutants such as NOx, causing serious environmental pollution. Therefore, reducing the amount of NOx and other pollutants generated during combustion and achieving clean combustion has become a crucial problem that researchers in this field urgently need to solve.

[0003] Existing research indicates that NOx emissions from gaseous fuel combustion are primarily thermal NOx, accounting for over 90%. Thermal NOx is formed when atoms in the system combine with oxygen atoms at high temperatures, rapidly oxidizing to form NO, NO2, and other compounds. Thermal NOx is highly temperature-sensitive, increasing exponentially with rising temperature. The typical temperature threshold for thermal NOx is 1500℃; below 1500℃, NOx formation is minimal, while above 1500℃, NOx production increases rapidly. Therefore, reducing the peak temperature of the combustion system is crucial for controlling NOx emissions during combustion.

[0004] MILD (Mild Oxygen-Free Combustion), also known as flameless combustion, is an advanced low-NOx combustion technology. It involves injecting fuel and oxidizer into the furnace at extremely high velocities (over 100 m / s). The high momentum of the reactants "extinguishes" localized flames, allowing the combustion reaction to occur throughout the furnace in a mild, low-oxygen-concentration manner. This significantly reduces the peak flame temperature, achieving low-NOx combustion. Because the reaction occurs throughout the entire furnace, a distinct flame shape is not visually apparent, hence the name "flameless combustion."

[0005] Existing flameless burners primarily employ a direct-injection pipe design, coupled with a high injection velocity and appropriate fuel-oxidizer spacing, to achieve flameless combustion. While this design achieves lower NOx emission concentrations, it creates a significant low-temperature zone in the high-speed jet region, making it unsuitable for many applications requiring high temperature uniformity (such as steel rolling furnaces). Furthermore, the ultra-high flow velocity (approximately 100 m / s) required by existing technologies results in very high pipeline resistance, significantly increasing the load on the fuel or oxidizer delivery system compared to conventional combustion. Both of these factors severely limit the widespread adoption and application of flameless combustion in industrial sectors. Summary of the Invention

[0006] To address the problems of low temperature and poor temperature uniformity in the central jet region of existing flameless burners, as well as the requirement for high fuel and oxidant flow rates at ultra-high flow velocities (approximately 100 m / s), which leads to high pipeline resistance and a significantly increased load on the delivery system compared to conventional combustion, this invention provides a novel flameless combustion system and its corresponding flameless combustion control method. This system can effectively improve the problem of excessively high NOx concentration caused by uneven flame temperature in traditional burners, while also overcoming the problems of low temperature near the injection port and high pipeline resistance in existing flameless burners. This achieves uniform temperature distribution and ultra-low NOx emissions throughout the furnace.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is specifically described as follows:

[0008] According to a first embodiment of the present invention, a flameless combustion system is provided:

[0009] A flameless combustion system includes a furnace body, a top cover, an accelerator burner, and main fuel injection pipes. The furnace body is a cabinet-type or cylindrical structure. The top cover is located at the center of one end face of the furnace body. The front end of the accelerator burner penetrates the top cover and communicates with the inner cavity of the furnace body, with the extension line of the central axis of the accelerator burner coinciding with the central axis of the furnace body. At least two main fuel injection pipes are symmetrically arranged on the top cover on both sides of the accelerator burner, and the front ends of each main fuel injection pipe penetrate the top cover and communicate with the inner cavity of the furnace body. The extension lines of the central axes of all main fuel injection pipes intersect the central axis of the furnace body. Each main fuel injection pipe's inlet is independently connected to a first fuel delivery pipe, and a first flow regulating valve is installed on the first fuel delivery pipe. Preferably, the angle between the main fuel injection pipe and the horizontal plane is 30-85°, more preferably 40-80°, and even more preferably 50-75°.

[0010] Generally, the exhaust port of the flameless burner is located on the side wall of the furnace body adjacent to the accelerating burner or on the side wall of the furnace body directly opposite the accelerating burner.

[0011] Preferably, the accelerating burner includes an accelerating chamber and a burner. The accelerating chamber is embedded in the top cover, and its front and rear end faces are flush with the front and rear end faces of the top cover, respectively. The front inlet of the accelerating chamber is connected to the burner, and the rear outlet of the accelerating chamber is connected to the inner cavity of the furnace body. The central axis of the accelerating chamber in the longitudinal direction, the extended line of the central axis of the burner in the longitudinal direction, and the central axis of the top cover in the longitudinal direction coincide, and the inner diameter of the accelerating chamber gradually decreases in the longitudinal direction.

[0012] Preferably, the burner includes a fuel inlet pipe, an oxidizer inlet pipe, a core tube, and an igniter. The outlet of the fuel inlet pipe is connected to the acceleration chamber from the center of the front end face of the acceleration chamber. The oxidizer inlet pipe is arranged parallel to the fuel inlet pipe, and its outlet is also connected to the acceleration chamber. The tail end of the core tube extends into the acceleration chamber along the lumen of the fuel inlet pipe, and the igniter is located at the tail end of the core tube within the acceleration chamber.

[0013] Preferably, the burner further includes a conical blunt body, the outer diameter of which gradually increases along its length. The conical blunt body is located within the acceleration chamber, and its narrow end is connected to the tail end of the burner tube. The igniter is located on the wide end side of the conical blunt body. The outer diameter of the narrow end of the conical blunt body is smaller than the inner diameter of the fuel inlet pipe, and the outer diameter of the wide end of the conical blunt body is larger than the inner diameter of the fuel inlet pipe. The burner tube can move back and forth within the cavity of the fuel inlet pipe, thereby moving the conical blunt body and the igniter back and forth as well.

[0014] Preferably, multiple oxidant inlet pipes are evenly arranged on the outer circumference of the fuel inlet pipe, and each oxidant inlet pipe is provided with a swirl vane at its discharge end.

[0015] Preferably, a second fuel delivery pipe is connected to the inlet of the fuel inlet pipe, and a second flow regulating valve is provided on the second fuel delivery pipe.

[0016] Preferably, an oxidant conveying pipe is connected to the inlet of the oxidant inlet pipe, and an oxidant flow regulating valve is provided on the oxidant conveying pipe.

[0017] Preferably, the system also includes a fuel delivery main, on which a fuel flow regulating valve is installed, and at the end of the fuel delivery main, a first fuel delivery pipe and a second fuel delivery pipe extend out from each other.

[0018] Preferably, the system also includes several combustion temperature detectors. These combustion temperature detectors are evenly distributed along the central axis of the furnace body along its length.

[0019] As a preferred option, a preheating smoke temperature detector is also installed in the acceleration chamber.

[0020] According to a second embodiment of the present invention, a control method for a flameless combustion system is provided:

[0021] A control method for a flameless combustion system, or a control method for a flameless combustion system according to a first embodiment, the method comprising the following steps:

[0022] S1: Based on the required thermal power and calorific value under the target operating conditions, calculate the total fuel demand and total oxidant demand per unit time. Adjust the actual total delivery rate of fuel and oxidant per unit time based on the calculated total fuel demand and total oxidant demand per unit time.

[0023] S2: Based on the actual total oxidant delivery rate per unit time and the threshold flow rate required for flameless combustion of the oxidant after preheating, calculate the oxidant preheating temperature and the preheating fuel demand per unit time. Adjust the actual preheating fuel delivery rate per unit time according to the calculated preheating fuel demand per unit time.

[0024] S3: Based on the actual total amount of oxidant delivered per unit time and the actual amount of preheating fuel delivered per unit time, the combustion ratio of oxidant and preheating fuel in the acceleration chamber is controlled by adjusting the real-time injection flow rate of the preheating fuel, so that the combustion of the preheating fuel can sustainably and stably heat the oxidant to the oxidant preheating temperature.

[0025] S4: Adjust the oxidant preheating temperature in real time according to the changes in the combustion temperature field inside the furnace body 1, so that the inside of the furnace body is always kept in a flameless combustion state.

[0026] Preferably, step S1 specifically involves: setting the required thermal power as P, kW under the target operating conditions, and the calorific value of the fuel used as H, kJ / m³. 3 Then we have:

[0027] Total fuel demand Q per unit time ft for:

[0028] Q ft =P / H (1).

[0029] The total demand for oxidant per unit time, Q a for:

[0030] Q a =α·Q ft =α·P / H (2).

[0031] Wherein, α is the ratio of oxidant consumption to fuel consumption per unit time under the target operating condition (the value range of α is related to the type of fuel; for natural gas, α is 8-15, preferably 10-12).

[0032] Within a unit of time: Adjust the fuel flow control valve so that the actual amount of fuel delivered through the fuel delivery manifold is Q calculated by equation (1). ft m 3 Adjust the oxidant flow regulating valve so that the actual amount of oxidant delivered through the oxidant delivery pipe is Q, calculated using equation (2).a m 3 .

[0033] Preferably, step S2 specifically involves: setting the target operating condition as follows: the rear outlet opening area of ​​the acceleration chamber is A, m 2 The threshold flow rate for flameless combustion of the oxidant after preheating is V. c , m / s. Then we have:

[0034] The flow rate V0 of the oxidant (without preheating) discharged from the rear outlet of the acceleration chamber is:

[0035] V0=Q a / A (3).

[0036] To ensure that the oxidant discharge velocity from the rear end of the acceleration chamber reaches the threshold flow rate Vc, the acceleration ratio C of the preheated oxidant is:

[0037] C=V c / V0=V c ·A / Q a (4).

[0038] Based on the ideal gas expansion properties, the preheating temperature T of the oxidant... p1 for:

[0039] T p1 =C·(T0+273)-273 (5).

[0040] Furthermore, based on the principle of heat balance, the amount of preheated fuel required per unit time, Q fp for:

[0041] Q fp =Q a ·C p ·(T p1 -T0) / H (6).

[0042] Among them, C p The specific heat capacity of the oxidant. Within a unit time: Adjust the second flow control valve so that the amount of fuel delivered to the acceleration chamber via the second fuel delivery pipe is Q calculated using equation (6). fp m 3 The temperature at which the indoor oxidant accelerates is T, calculated using equation (5). p1 , ℃.

[0043] Preferably, step S3 specifically involves: controlling the relative position between the conical blunt body and the fuel inlet outlet by adjusting the upward movement of the core tube along the horizontal axis within a unit time, thereby adjusting and controlling the opening of the fuel inlet outlet. This means maintaining a stable real-time ejection velocity of the preheated fuel entering the acceleration chamber by controlling the real-time opening of the fuel inlet outlet (to ensure complete combustion of the fuel within the acceleration chamber). The specific process is as follows:

[0044] 1) When the actual amount of preheated fuel delivered per unit time is Q fp The actual amount of oxidant delivered per unit time is Q. a At that time, the preheating fuel combustion can sustainably and stably heat the oxidant to the oxidant preheating temperature T. p1 If the real-time ejection velocity of the preheated fuel required is U, m / s, then:

[0045] U=Q fp / {π·[R 2 -(X·tanβ) 2 ]} (7).

[0046] That is:

[0047] X={Sqr[R 2 -Q fp / (U·π)]} / tanβ (8).

[0048] Where β is the angle between the line connecting the narrow end of the conical blunt body to the edge of its wide end and the horizontal direction, R is the radius of the fuel inlet pipe cavity, and X is the depth of the narrow end of the conical blunt body extending into the fuel inlet pipe. The depth of the narrow end of the conical blunt body extending into the fuel inlet pipe is adjusted by adjusting the core tube to obtain X,m calculated by equation (8).

[0049] And / or, 2) when the actual amount of preheated fuel delivered per unit time is Q fp The actual amount of oxidant delivered per unit time is Q. a Initially, the depth of the narrow end of the conical blunt body extending into the fuel inlet pipe is set to X0, m. The real-time temperature of the oxidant in the acceleration chamber is detected by a preheating flue gas temperature sensor as T. pc , ℃. Then:

[0050] Adjust X = X0 + ΔX. After adjustment, check the real-time temperature of the oxidant in the acceleration chamber compared to before adjustment. If the temperature increases, use method ① for adjustment; if the temperature decreases, use method ② for adjustment.

[0051] Method ①: Adjust X = X0 + 2△X, compare the real-time temperature of the oxidant in the accelerating room after the adjustment with the temperature before the adjustment. If the temperature increases, continue to adjust X = X0 + 3△X, and compare the real-time temperature of the oxidant in the accelerating room after the adjustment with the temperature before the adjustment. Continue in this manner until X = X0 + n△X, and the real-time temperature of the oxidant in the accelerating room after the adjustment decreases compared with the temperature before the adjustment. Then adjust X = X0 + (n-1)△X and end the adjustment.

[0052] Method ②: Adjust X = X0 - ΔX, and compare the real-time temperature of the oxidant in the accelerating room after the adjustment with the temperature before the adjustment. If the temperature increases, adjust X = X0 - 2ΔX, and continue to compare the real-time temperature of the oxidant in the accelerating room after the adjustment with the temperature before the adjustment. If the temperature increases, continue to adjust X = X0 - 3ΔX, and compare the real-time temperature of the oxidant in the accelerating room after the adjustment with the temperature before the adjustment. Continue in this manner until X = X0 - nΔX, and the real-time temperature of the oxidant in the accelerating room after the adjustment decreases compared with the temperature before the adjustment. Then adjust X = X0 - (n-1)ΔX and end the adjustment.

[0053] Preferably, the value of △X is 0.01-0.5 times the length of the conical blunt body, more preferably 0.03-0.3 times, and even more preferably 0.05-0.15 times.

[0054] Preferably, step S4 specifically involves: numbering several combustion temperature detectors inside the furnace body sequentially along the fuel flow direction as 1, 2, 3, ..., i, i+1, ..., m-1, m, and continuously monitoring the temperature at each point on the central axis inside the furnace body as T1, T2, T3, ..., T... i T i+1 、···、T m-1 T m And calculate T max and △T max Then we have:

[0055] When T max <T max-c And △T max <△T max-c If the temperature is high, then the current operating conditions remain unchanged. Otherwise, calculate the distance L (m) between the detection point corresponding to the highest temperature and the rear exit of the acceleration chamber. Then we have:

[0056] When L > Lc, the fuel delivery rate in the fuel inlet pipe is increased until T... max <T max-c And △T max <△T max-c The adjustment is then terminated. Lc is the theoretical threshold distance.

[0057] When L ≤ Lc, reduce the fuel delivery rate of the fuel inlet pipe until T max <T max-c and ΔT max <ΔT max-c then end the adjustment.

[0058] Generally, when L > Lc, it indicates that the mixing position is too far back, and it is necessary to increase the central jet velocity → increase the oxidant preheating temperature Tp → increase the fuel amount entering the accelerating burner. When L < Lc, it indicates that the mixing position is too far forward, and it is necessary to decrease the central jet velocity → decrease the oxidant preheating temperature Tp → decrease the fuel amount entering the accelerating burner.

[0059] In the prior art, gaseous fuel (generally CH4) and oxidant (generally air) are respectively sprayed into the furnace at high speed from the fuel and oxidant nozzles. The oxidant flow rate generally exceeds 80 m / s. By using the high momentum of the oxidant, a strong central axis jet is formed in the center of the furnace, and the flue gas near the central axis flow region is entrained towards the axis flow region, thus forming a strong flue gas entrainment, enabling the flue gas to be fully mixed with the reactants (one of the flameless combustion conditions). On the other hand, the high-speed jet can instantly "blow out" the flame at the center, making it impossible to form a stable visible flame in the furnace (the second flameless combustion condition). At the same time, an appropriate interval is set between the fuel and oxidant inlets, so that the fuel sprayed into the furnace will not mix with the oxidant too early and burn violently. Instead, after leaving the nozzle for a certain distance, the fuel diluted by the flue gas meets the oxidant, and the local oxygen concentration is less than 10% (the third flameless combustion condition). Although the existing structure (as Figure 2 shown) can achieve flameless combustion with low NOx emissions by using a relatively simple structure and process, there are at least the following two obvious defects, making it impossible to be widely promoted and applied on a large scale. First: Due to the use of a high-momentum normal-temperature central jet, the temperature in the central jet region is significantly lower than that in other regions of the furnace, and the temperature uniformity near the central axis of the burner is poor; Figure 3 is the temperature field contour map obtained by simulating the above typical flameless burner. It can be seen from the figure that there is an obvious low-temperature region near the central jet. The temperature of the low-temperature region is affected by the initial temperature of the central jet, which makes it impossible to achieve good heating quality when industrial furnaces with high requirements for furnace temperature uniformity use such burners. Second: The fuel and oxidant flow rates are large, the pipeline resistance is large, and the load of the conveying system increases significantly compared with conventional combustion; generally, the fluid flow resistance is proportional to the square of the flow rate. Under the existing burner structure, the ejection flow rate required for flameless combustion is 5 to 10 times that of conventional combustion, and the flow resistance correspondingly increases by 25 to 100 times, making the pressure and load of the fuel and oxidant conveying systems of existing flameless burners very large.

[0060] In this invention, the flameless combustion system includes a furnace body, a top cover, an accelerator burner, and a main fuel nozzle. The front end of the accelerator burner penetrates the top cover and connects to the inner cavity of the furnace body. The extended line of the central axis of the accelerator burner in the length direction coincides with the central axis of the furnace body in the length direction. The main fuel nozzle is located on the top cover outside the accelerator burner. The accelerator burner delivers all the oxidant and a portion of the fuel simultaneously. This portion of the fuel preheats the oxidant to the required temperature before it enters the furnace (the inner cavity of the furnace body), ensuring that the oxidant has a certain temperature after entering the furnace. This effectively avoids the phenomenon that the temperature in the central jet region is lower than the temperature in other areas of the furnace due to the entry of cold oxidant, improving the temperature uniformity near the central axis of the burner. In addition, the heated oxidant can expand and be accelerated, thereby increasing its jet velocity after entering the furnace to meet the requirements of flameless combustion. That is, it effectively reduces the flow rate of the oxidant during the delivery process before preheating, greatly reducing the pressure and load on the oxidant delivery pipeline.

[0061] In this invention, the accelerated burner includes an acceleration chamber and a burner. The acceleration chamber is installed through the top cover, and the burner is connected to the furnace through the acceleration chamber. The burner includes a fuel inlet pipe, an oxidizer inlet pipe, a core tube, and an igniter. The acceleration chamber has a variable diameter design, wider at the front and narrower at the rear. During operation, a portion of the fuel and all the oxidizer (generally air) are ejected from the fuel inlet pipe and oxidizer inlet pipe respectively at a speed of 10-20 m / s, mix and burn in the acceleration chamber, producing high-temperature flue gas (generally 300-1100°C), which expands in volume to 2-5 times its original size. The expanded high-temperature flue gas is further accelerated to a certain speed (meeting the flameless combustion injection speed requirements) after passing through the tapered channel at the rear of the acceleration chamber, and then injected into the furnace, forming a high-temperature central jet. The remaining fuel is injected into the furnace through the main fuel nozzles on both sides of the accelerated burner at a conventional speed (10-30 m / s), and merges with the high-temperature central jet to complete flameless combustion in the furnace. By adjusting the fuel ratio in the accelerator burner and the main fuel nozzle, the heating temperature of the mixture in the acceleration chamber is controlled, thereby flexibly adjusting the velocity of the central jet ejected from the acceleration chamber. By adjusting the appropriate central jet velocity, flameless combustion of the fuel in the furnace is achieved. Furthermore, in the oxidant delivery system, only a low flow rate is required before the oxidant enters the acceleration chamber, placing minimal pressure load on the delivery system. After being accelerated by heating and expansion in the acceleration chamber, it can be directly injected into the furnace, thus meeting the requirements for flameless combustion within the furnace.

[0062] Furthermore, a conical blunt body (e.g., a cone-shaped blunt body with a narrow front and a wide rear) is also provided at the tail end of the core tube. The core tube, the conical blunt body, and the igniter as a whole can move back and forth along the central axis. By moving the core tube back and forth, the depth of the narrow front end of the conical blunt body extending into the fuel inlet pipe can be adjusted, thereby adjusting the opening of the fuel inlet outlet and thus adjusting the fuel injection velocity in the acceleration chamber to ensure combustion stability under different fuel flow rates. A swirl vane is provided at the tail end of the oxidizer inlet pipe to achieve full mixing of the gas in the accelerator. The conical blunt body at the tail end of the core tube creates turbulence around the conical blunt body to stabilize combustion in the accelerator. During operation, all the oxidizer and a portion of the fuel are fed into the acceleration chamber from the oxidizer inlet pipe and the fuel inlet pipe, respectively. After being ignited by the igniter, combustion occurs, the temperature rises, the volume expands, and it is accelerated and ejected from the tapered nozzle of the acceleration chamber. Since the fuel fed through the fuel inlet pipe accounts for only a small portion of the total fuel volume, the high-temperature flue gas after combustion contains a large amount of unreacted oxidant. After this high-temperature flue gas is accelerated and ejected from the nozzle of the acceleration chamber, it forms a high-temperature and high-speed oxidant central jet, thereby inducing flameless combustion in the furnace.

[0063] In actual industrial production processes, a very wide adjustable range of heating power for a single burner is generally required to adapt to different operating conditions. The adjustment ratio is generally used to represent the burner's heat power adjustment capability; it is the ratio of the maximum to the minimum allowable combustion capacity of the burner unit. Flameless combustion is highly sensitive to initial physical parameters such as velocity, temperature, and concentration, generally requiring burner parameters designed for specific power levels. Under a given burner structure, deviations from the design power can easily disrupt the flameless combustion mode, causing combustion to change from flameless to flaming. Specifically, if the operating power is higher than the design power, the increased flow of oxidizer and fuel leads to an increase in the central jet flow rate, causing the oxidizer-fuel interface to shift forward. The fuel encounters the oxidizer prematurely before it has had sufficient time to be fully mixed with the flue gas, thus preventing flameless combustion. Conversely, if the operating power is lower than the design power, the central jet flow rate decreases, resulting in insufficient flue gas entrainment in the furnace, also hindering flameless combustion. Therefore, the adjustment ratio for flameless combustion is generally small, limiting its application under certain operating conditions. Therefore, this invention also provides a corresponding control method for the aforementioned flameless combustion system (see appendix). Figure 6 This ensures a stable flameless combustion effect within a certain power adjustment range.

[0064] In this invention, the second flow regulating valve for the gas is used to regulate the amount of gas entering the acceleration chamber (requiring the preheating of the oxidant to the preheating temperature), and the movement of the core tube is used to regulate the combustion state in the acceleration chamber (regulating the gas flow rate of the preheated oxidant entering the furnace chamber). The specific control logic is as follows: Assuming flameless combustion has a speed threshold Vc (this speed refers to the ejection speed of the main fluid (combustion air, i.e., oxidant), because in typical gaseous fuel combustion (natural gas, coke oven gas), the amount of combustion air is much greater than the amount of fuel)), deviations from this speed (too high or too low) will cause the combustion mode to change from flameless combustion to flaming combustion. Therefore, for a specific burner, the fuel quantity and combustion air quantity at its rated power are generally calculated in advance, and then the size of the air duct is deduced from the speed threshold Vc and the combustion air quantity. Once the burner design is finalized, the dimensions of the fuel duct and air duct become fixed values. At this time, if the actual power of the burner deviates from the rated power, for example, the rated power of a sintering furnace burner is 3MW, but in actual production, due to the sintering machine output dropping to 50% of the design value, the actual power of the burner will be adjusted to 1.5MW, and the corresponding combustion air injection speed will also become 50% of the design value. This is a serious deviation from the speed threshold Vc required to achieve flameless combustion, and the combustion mode will change from flameless combustion to flame combustion.

[0065] Furthermore, addressing the aforementioned problem (changes in burner power leading to variations in the velocity and momentum of the combustion air ejection, resulting in unstable flameless combustion), this invention proposes adding an accelerating burner (burner + acceleration chamber). By adjusting the temperature of the combustion air (oxidizer) entering the furnace, the combustion air injection velocity is maintained stable (the velocity threshold Vc required for flameless combustion) even when the burner power changes. Specifically: when the actual burner power is higher than the rated power, and the combustion air volume increases, the preheating temperature of the combustion air entering the furnace is reduced to increase the combustion air density, thereby maintaining the ejection velocity of the combustion air entering the furnace. For example: assuming the burner rated power is 1MW and the combustion air volume is 1000Nm³ / h. 3 / h, the preheating temperature is set to 819℃, and under flameless combustion conditions, the velocity of the combustion air ejected from the acceleration chamber is 80m / s (i.e., the velocity threshold Vc); while when the actual burner power increases to 2MW, the combustion air volume increases to 2000Nm 3 If the preheating temperature of the combustion air remains unchanged, the ejection velocity of the combustion air from the acceleration chamber will increase to 160 m / s, thus deviating significantly from the velocity threshold Vc required to achieve flameless combustion. At this point, simply reducing the preheating temperature of the combustion air to 273°C will double its density ((819+273) / (273+273)=2), thus maintaining the ejection velocity of the combustion air from the acceleration chamber at 80 m / s.

[0066] Furthermore, the preheating temperature of the combustion air is adjusted by regulating the amount of fuel entering the acceleration chamber.

[0067] Furthermore, for the small burner within the acceleration chamber, changes in the amount of fuel entering the chamber due to adjustments in the preheating temperature of the combustion air can cause the burner's operating conditions to deviate from their optimal state. The most direct reason is that changes in fuel quantity lead to significant variations in the fuel injection velocity into the acceleration chamber, thus affecting the combustion performance of the small burner. To address this, a blunt body structure is designed on the small burner. This serves two purposes: firstly, it stabilizes the flame; secondly, by adjusting the position of the blunt body relative to the fuel nozzle, the outlet area is altered, thereby regulating the fuel injection velocity.

[0068] In this invention, the control process is as follows:

[0069] Step 1: Calculate the total fuel demand per unit time (denoted as Q) based on the required thermal power and calorific value under the target operating conditions. ft m 3 ) and the total demand for oxidant per unit time (denoted as Q) a m 3 );

[0070] Step 2: Given an accelerator burner, calculate the acceleration ratio of the preheated oxidant (denoted as C) and the preheating temperature of the oxidant (denoted as T). p1 (℃), based on theoretical temperature (T) p1 ), calculate the preheating fuel demand per unit time (denoted as Q). fp m 3 );

[0071] Step 3: Adjust the oxidant flow control valve to ensure that the oxidant delivery rate per unit time reaches Q. a Adjust the total fuel flow control valve to make the total fuel delivery per unit time reach Q. ft Adjust the second flow control valve (i.e., the fuel branch pipe flow condition valve) to ensure that the amount of fuel delivered into the fuel pipe per unit time (i.e., the amount of fuel required for preheating) reaches Q. fp ;

[0072] Step 4: Adjust the front and rear positions of the core tube (horizontally along the central axis) to maximize the temperature of the flue gas at the acceleration chamber outlet (the temperature of the preheated oxidant);

[0073] Step 5: Real-time monitoring of the measured temperature of the oxidant after accelerated indoor preheating (denoted as T). pc ), compared with the measured T pc and the calculated theoretical temperature T p1 If T pc >T p1 Then proceed to step 6; if T pc <Tp1 Then proceed to step 7; if T pc =T p1 Then proceed to step 8.

[0074] Step 6: Reduce the gas branch valve (i.e., the second flow regulating valve), then proceed to step 4;

[0075] Step 7: Increase the gas branch valve (i.e., the second flow regulating valve), then proceed to step 4;

[0076] Step 8: Measure the temperature values ​​at each temperature detection point on the central axis of the furnace inner wall and record them as Ti. Calculate the highest temperature T. max and maximum temperature difference ΔT max ;

[0077] Step 9: Compare T max and ΔT max With typical critical T max-c and ΔT max-c The size of T, if T max <T max-c And ΔT max <ΔT max-c If yes, proceed to step 5; otherwise, proceed to step 10.

[0078] Step 10: Calculate the distance between the temperature detection point corresponding to the highest temperature and the acceleration chamber nozzle, and record it as L, m;

[0079] Step 11: If L > Lc (theoretical threshold distance), proceed to step 12; otherwise, proceed to step 13.

[0080] Step 12: Increase the gas branch valve (i.e., the second flow regulating valve), then proceed to step 14;

[0081] Step 13: Reduce the gas branch valve (i.e., the second flow regulating valve), then proceed to step 14;

[0082] Step 14: Adjust the front and rear positions of the core tube to maximize the temperature of the flue gas at the outlet of the acceleration chamber, then proceed to step 9;

[0083] Step 15: End adjustment.

[0084] In this invention, the calculation process for the operating parameters of the accelerated burner is as follows: Based on the required thermal power P and fuel calorific value H under the actual target operating conditions, the total fuel demand Q per unit time can be calculated using the following formula. ft :

[0085] Q ft =P / H (1).

[0086] Based on the total fuel demand per unit time and the oxidizer / fuel ratio α (the ratio of oxidizer usage to fuel usage per unit time under the target operating condition), the total oxidizer demand Q per unit time can be calculated using the following formula. a for:

[0087] Q a =α·Q ft =α·P / H (2).

[0088] In the accelerator chamber, the velocity V0 of the oxidant flowing out of the accelerator chamber outlet with cross-sectional area A at room temperature (T0) can be calculated by the following formula:

[0089] V0=Q a / A (3).

[0090] Since the oxidant participating in combustion within the accelerator accounts for only a small portion of the total oxidant quantity, the change in the amount of oxidant caused by combustion within the accelerator is negligible and can be ignored. Therefore, to ensure that the preheated oxidant injection velocity reaches the preset flameless combustion threshold velocity V... c Then, the acceleration ratio C of the oxidant after preheating can be calculated by the following formula:

[0091] C=V c / V0=V c ·A / Q a (4).

[0092] Based on the ideal gas expansion properties, to obtain the required acceleration ratio C, the preheating temperature T of the oxidant after preheating is... pl It can be calculated using the following formula:

[0093] T p1 =C·(T0+273)-273 (5).

[0094] Based on the preheating temperature T of the oxidant after preheating pl The amount of preheated fuel required per unit time, Q, can be calculated using the following formula based on the principle of heat balance. fp That is, the amount of fuel supplied from the fuel inlet pipe for heating the oxidizer:

[0095] Q fp =Q a ·C p ·(T p1 -T0) / H (6). Wherein, C p is the specific heat capacity of the oxidant.

[0096] In this invention, the combustion of fuel in the acceleration chamber is characterized by a severe excess of oxidant, meaning the combustion deviates significantly from the stoichiometric ratio, resulting in harsh combustion conditions. Therefore, it is necessary to rationally manage and match the oxidant and fuel velocities. During the adjustment process, the real-time flow rate of fuel injected into the acceleration chamber from the fuel branch pipe (fuel inlet pipe) varies greatly. If a fixed fuel injection nozzle cross-sectional area is used, the fuel velocity exiting the nozzle will fluctuate significantly, leading to incomplete combustion. Therefore, this invention employs a structural design that adjusts the core tube position and changes the fuel injection outlet cross-sectional area (i.e., the fuel inlet pipe outlet opening) using a conical blunt body. This ensures stable fuel velocity at the fuel injection outlet (ensuring stable and complete combustion of fuel in the acceleration chamber) even with significant adjustments to the flow rate in the fuel branch pipe per unit time. Furthermore, this invention provides three methods for adjusting the core tube position:

[0097] Adjustment Method 1: Formula Derivation and Calculation Method: In this system, the depth X of the conical blunt body extending into the fuel inlet pipe, controlled by the core tube, has a definite functional relationship with the cross-sectional area A of the fuel inlet pipe outlet: A = A(X); the specific form of A(X) is related to the shape of the conical blunt body. In this system, when the conical blunt body is conical, A(X) = π·(R 2 -r 2 ), where R is the radius of the inner cavity of the fuel inlet pipe, and r is the radius of the maximum cross-section of the conical blunt body extending into the fuel inlet pipe. Let β be the angle between the hypotenuse of the conical blunt body and the central axis (i.e., half the cone angle at the narrow end of the conical blunt body's cross-section), then r = X · tanβ, that is, A(X) = π · [R 2 -(X·tanβ) 2 ].

[0098] In this invention, the inner diameter of the fuel pipe in industrial burners is generally above 100mm, and the ratio of the core tube cross-sectional area to the fuel inlet pipe cross-sectional area is small (generally no more than 5%, for example, 1:100, 1:80, 1:60, 1:50, 1:40, 1:30, 1:20, etc.). Therefore, the influence of the core tube on the flow cross-section is generally ignored in the derivation process. If necessary, the influence of the core tube on the flow cross-section can be incorporated into the actual calculation, and adjustments can be made according to actual needs.

[0099] Furthermore, according to the continuity equation, the fuel velocity U ejected from the fuel inlet outlet has a definite single-valued functional relationship with the cross-sectional area A: U = Q fp / A, that is, U=Q fp / {π·[R 2 -(X·tanβ) 2 ]}, then X={Sqr[R 2 -Q fp / (U·π)]} / tanβ. From this formula, we can derive the required amount of preheated fuel Q within a given unit time. fp At the same time, by controlling the depth X of the narrow end of the conical blunt body extending into the fuel inlet pipe through the core tube, the fuel flow rate U ejected from the fuel inlet pipe outlet can be precisely adjusted to match the actual oxidant delivery rate Q per unit time. a Accelerated indoor preheating of fuel combustion sustainably and stably heats the oxidant to the oxidant preheating temperature T. p1 .

[0100] Adjustment Method Two: Feedback Adjustment Method (e.g.) Figure 7 As shown): The degree of matching between the real-time fuel injection velocity and the degree of combustion completion in the acceleration chamber can be directly characterized by the combustion temperature under a given fuel flow rate. The real-time flue gas temperature in the acceleration chamber is recorded as T. pc T pc The larger the value, the more complete the combustion. Therefore, T can be used to determine the combustion process. pc As feedback, the wick position is adjusted. The wick position is gradually adjusted in one direction; if the temperature increases, adjustment continues; if the temperature decreases, adjustment is reversed until the maximum temperature is reached. The specific adjustment method is as follows: Adjust X = X0 + ΔX. After adjustment, the real-time temperature (T) of the oxidant in the accelerating chamber is measured. pc Compared to the value before adjustment, if the temperature (T) pc If the temperature (T) increases, then method ① should be used for adjustment. pc If the value decreases, then adjustment method ② is used (where method ① and method ② are adjustment mechanisms in opposite directions):

[0101] Method ①: Adjust X = X0 + 2△X, and compare the real-time temperature of the oxidant in the acceleration chamber 31 after the adjustment with the temperature before the adjustment. If the temperature increases, continue to adjust X = X0 + 3△X, and compare the real-time temperature of the oxidant in the acceleration chamber 31 after the adjustment with the temperature before the adjustment. Continue in this manner until X = X0 + n△X, and the real-time temperature of the oxidant in the acceleration chamber 31 after the adjustment decreases compared with the temperature before the adjustment. Then adjust X = X0 + (n-1)△X and end the adjustment.

[0102] Method ②: Adjust X = X0 - ΔX, and compare the real-time temperature of the oxidant in the acceleration chamber 31 after the adjustment with the temperature before the adjustment. If the temperature increases, adjust X = X0 - 2ΔX, and continue to compare the real-time temperature of the oxidant in the acceleration chamber 31 after the adjustment with the temperature before the adjustment. If the temperature increases, continue to adjust X = X0 - 3ΔX, and compare the real-time temperature of the oxidant in the acceleration chamber 31 after the adjustment with the temperature before the adjustment. Continue in this manner until X = X0 - nΔX, and the real-time temperature of the oxidant in the acceleration chamber after the adjustment decreases compared with the temperature before the adjustment. Then adjust X = X0 - (n-1)ΔX and end the adjustment.

[0103] Adjustment Method 3: Coarse adjustment using formula derivation and calculation + fine adjustment using feedback adjustment (e.g.) Figure 8 As shown): First, the formula derivation calculation method of adjustment method one is used to calculate an initial core tube position, and then the feedback adjustment method of adjustment method two is used to obtain the maximum temperature, thereby quickly achieving the adjustment purpose.

[0104] In this invention, the accelerated burner has two levels of adjustment logic: ① adjusting the preheating temperature; ② adjusting the combustion state of the accelerated burner.

[0105] ① Regarding the adjustment of preheating temperature: First step: Calculate the theoretical amount of gas to be introduced into the acceleration chamber using heat balance theory, and adjust the flow rate to the theoretical calculated amount using a regulating valve. This step is called initial adjustment (because the theoretical calculated value usually deviates from the actual value); Second step: Measure the actual temperature of the flue gas (preheated oxidant) flowing out of the acceleration chamber, compare the difference between the actual temperature of the flue gas and the target preheating temperature, and adjust the flow valve accordingly to ultimately achieve the same actual preheating temperature as the target preheating temperature.

[0106] ② Adjusting the combustion state of the accelerator burner: The purpose of adjusting the combustion state of the accelerator burner is to obtain the maximum preheating temperature under a given fuel flow rate (that is, to ensure that the amount of fuel gas and oxidant in the accelerator chamber reaches the optimal ratio for complete combustion in real time, because generally, the more complete the fuel combustion in the accelerator chamber, the higher the temperature at which the oxidant is preheated).

[0107] In this invention, two methods are provided for adjusting the combustion state of the accelerated burner: one is adjusting the real-time injection velocity when fuel is given, and the other is feedback regulation. Adjusting the injection velocity when fuel is given: It is assumed that the fuel injection velocity required for complete combustion is a constant value, V. f-best When the fuel quantity in the accelerated burner changes, theoretical calculations are used to obtain the value that maintains the injection velocity V. f-bestThe position of the core tube (i.e., the position of the conical blunt body). Feedback adjustment: Move the core tube back and forth, observe the change in flue gas temperature, and obtain the maximum flue gas temperature. This invention achieves precise adjustment of the oxidant preheating temperature by coupling the adjustment of the oxidant preheating temperature with the adjustment of the combustion state of the accelerated burner. The complete process is as follows: coarse adjustment of preheating temperature → adjustment of accelerated burner state → fine adjustment of preheating temperature.

[0108] In this invention, under flameless combustion conditions, there is no clearly visible flame in the furnace; combustion occurs uniformly and gently throughout the furnace space. Therefore, the maximum temperature of flameless combustion is much lower than that of ordinary combustion, and the furnace temperature uniformity is very high. Thus, the presence of flameless combustion can be determined by the maximum temperature of the combustion zone and the uniformity of the furnace temperature distribution. The maximum temperature of the combustion zone is generally distributed on the central plane (or the maximum temperature on the central plane can reflect the maximum furnace temperature; generally, the higher the maximum temperature on the central plane, the higher the maximum furnace temperature). Therefore, this invention uses the maximum temperature on the central plane and temperature uniformity to determine whether flameless combustion is occurring in the furnace. The specific process is as follows: Several combustion temperature detectors are installed on the central plane of the furnace, numbered sequentially along the fuel flow direction as 1, 2, 3, ..., i, i+1, ..., m-1, m, and the temperatures at various points on the central axis within the furnace body 1 are monitored in real time as T1, T2, T3, ..., T... i T i+1 、···、T m-1 T m The highest temperature T in the central plane max It can be approximated as T max =max(T i The temperature non-uniformity of the central plane can be determined by the maximum temperature difference ΔT. max =max(T i )-min(T i Therefore, the criterion for determining flameless combustion is:

[0109] When T max <T max-c And △T max <△T max-c If the temperature is high, then the current operating conditions remain unchanged. Otherwise, calculate the distance L (m) between the detection point corresponding to the highest temperature and the rear exit of the acceleration chamber. Then we have:

[0110] When L > Lc, the depth of the narrow end of the conical blunt body extending into the fuel inlet pipe is reduced by adjusting the core tube until T. max <T max-c And △T max <△T max-c The adjustment was then terminated.

[0111] When L≤Lc, the depth of the narrow end of the conical blunt body extending into the fuel inlet pipe is increased by adjusting the core tube until T. max <T max-c And △T max <△T max-c The adjustment is then terminated. Here, Lc is the theoretical threshold distance.

[0112] In this invention, the velocity (momentum) of the central jet within the furnace is crucial for achieving flameless combustion. If the central jet is too small, it is difficult to form a sufficiently strong high-temperature flue gas recirculation and mixing within the furnace; if the central jet is too large, fuel is prematurely entrained into the central jet, mixing with the oxidizer prematurely and igniting. Both situations disrupt the gentle combustion of fuel within the furnace, causing combustion to degenerate into a flaming combustion mode. Therefore, this invention employs a central jet momentum control strategy based on the fuel-oxidizer mixing position. Specifically, the highest temperature T is first obtained... max For the corresponding temperature measurement point i, the distance L between temperature measurement point i and the accelerator exit can be obtained. This distance can be approximated as the location of the highest temperature corresponding to the mixing point of fuel and oxidizer, thus obtaining the mixing position L. Then, the actual mixing position L is compared with the threshold Lc. If L < Lc, it indicates that the mixing position is too far forward, and the central jet velocity needs to be reduced (by lowering the oxidizer preheating temperature T). p1 Conversely, increasing the central jet velocity (increasing the oxidant preheating temperature T) will increase the oxidant preheating temperature T. p1 ).

[0113] In this invention application, the unit of time is a second (S).

[0114] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0115] 1. The flameless combustion system of the present invention, through the design of the accelerated burner, preheats all the oxidant in advance through the acceleration chamber, thereby increasing the temperature of the oxidant after entering the furnace. This effectively avoids the phenomenon that the temperature of the central jet area is lower than that of other areas of the furnace due to the entry of cold oxidant, and greatly improves the temperature uniformity near the central axis of the burner.

[0116] 2: This invention uses the buffer of the acceleration chamber to accelerate the thermal expansion of the oxidant after heating, thereby increasing its jet velocity after entering the furnace to meet the requirements of flameless combustion. It effectively reduces the flow rate of the oxidant during the preheating process and greatly reduces the pressure and load on the oxidant delivery pipeline.

[0117] 3: The present invention adopts a center jet flow control strategy based on the fuel mixing position as the adjustment basis, which realizes precise control of the oxidant and fuel ratio in the flameless combustion system described in the present invention, while ensuring that the furnace is always in a stable and uniform flameless combustion state, thereby improving the adaptability of the flameless combustion system to different working conditions and expanding the application range of the flameless combustion system.

[0118] 4. The flameless combustion system provided by this invention also features simple structure, convenient operation, stable oxygen-free combustion state, and uniform temperature distribution in the furnace. Its matching control method has the advantages of short control process and high control accuracy. Attached Figure Description

[0119] Figure 1 This is a schematic diagram of the overall structure of the flameless combustion system of the present invention.

[0120] Figure 2 This is a structure for existing flameless burners.

[0121] Figure 3 This is a temperature cloud map inside the furnace of a flameless burner using existing technology.

[0122] Figure 4 This is a schematic diagram of the structure of the accelerated burner of the present invention.

[0123] Figure 5 This is a plan view of the front end of the flameless combustion system of the present invention.

[0124] Figure 6 This is a control flowchart of the flameless combustion system of the present invention.

[0125] Figure 7 This is a flowchart of the feedback regulation method of the present invention.

[0126] Figure 8 This is a flowchart illustrating the adjustment process of the coarse adjustment using the formula derivation and calculation method combined with the fine adjustment using the feedback adjustment method of this invention.

[0127] Figure 9 This invention accelerates the burner regulation and control logic. Figure 1 .

[0128] Figure 10 This invention accelerates the burner regulation and control logic. Figure 2 .

[0129] Figure 11 This invention accelerates the burner regulation and control logic. Figure 3 .

[0130] Reference numerals in the attached drawings: 1: Furnace body; 2: Top cover; 3: Accelerator burner; 31: Acceleration chamber; 32: Burner; 321: Fuel inlet pipe; 322: Oxidant inlet pipe; 323: Core tube; 324: Ignition device; 325: Conical blunt body; 326: Swirl vane; 4: Main fuel injection pipe; 5: Combustion temperature detector; 6: Preheating flue gas temperature detector; L0: Fuel delivery main pipe; L1: First fuel delivery pipe; L2: Second fuel delivery pipe; L3: Oxidant delivery pipe; M0: Fuel flow control valve; M1: First flow control valve; M2: Second flow control valve; M3: Oxidant flow control valve. Detailed Implementation

[0131] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments.

[0132] A flameless combustion system includes a furnace body 1, a top cover 2, an accelerator burner 3, and main fuel injection pipes 4. The furnace body 1 is a cabinet-type or cylindrical structure. The top cover 2 is located at the center of one end face of the furnace body 1. The front end of the accelerator burner 3 penetrates the top cover 2 and communicates with the inner cavity of the furnace body 1, with the extended line of the central axis of the accelerator burner 3 coinciding with the central axis of the furnace body 1. At least two main fuel injection pipes 4 are symmetrically arranged on the top cover 2 on both sides of the accelerator burner 3, and the front ends of each main fuel injection pipe 4 penetrate the top cover 2 and communicate with the inner cavity of the furnace body 1. The extended lines of the central axes of all main fuel injection pipes 4 intersect the central axis of the furnace body 1. The feed inlet of each main fuel injection pipe 4 is independently connected to a first fuel delivery pipe L1, and a first flow regulating valve M1 is installed on the first fuel delivery pipe L1. Preferably, the angle between the main fuel nozzle 4 and the horizontal plane is 30-85°, more preferably 40-80°, and even more preferably 50-75°.

[0133] Preferably, the accelerating burner 3 includes an accelerating chamber 31 and a burner 32. The accelerating chamber 31 is embedded in the top cover 2, and the front and rear end faces of the accelerating chamber 31 are flush with the front and rear end faces of the top cover 2, respectively. The front inlet of the accelerating chamber 31 is connected to the burner 32, and the rear outlet of the accelerating chamber 31 is connected to the inner cavity of the furnace body 1. The central axis of the accelerating chamber 31 in the longitudinal direction, the extension line of the central axis of the burner 32 in the longitudinal direction, and the central axis of the top cover 2 in the longitudinal direction coincide, and the inner diameter of the accelerating chamber 31 gradually decreases in the longitudinal direction.

[0134] Preferably, the burner 32 includes a fuel inlet pipe 321, an oxidizer inlet pipe 322, a core tube 323, and an igniter 324. The outlet of the fuel inlet pipe 321 is connected to the acceleration chamber 31 from the center of the front end face of the acceleration chamber 31. The oxidizer inlet pipe 322 is arranged parallel to the fuel inlet pipe 321, and the outlet of the oxidizer inlet pipe 322 is also connected to the acceleration chamber 31. The tail end of the core tube 323 extends into the acceleration chamber 31 along the lumen of the fuel inlet pipe 321, and the igniter 324 is located at the tail end of the core tube 323 and inside the acceleration chamber 31.

[0135] Preferably, the burner 32 further includes a conical blunt body 325, the outer diameter of which gradually increases along its length. The conical blunt body 325 is located within the acceleration chamber 31, and its narrow end is connected to the tail end of the core tube 323. The igniter 324 is located on the wide end side of the conical blunt body 325. The outer diameter of the narrow end of the conical blunt body 325 is smaller than the inner diameter of the fuel inlet pipe 321, and the outer diameter of the wide end of the conical blunt body 325 is larger than the inner diameter of the fuel inlet pipe 321. The core tube 323 can move back and forth within the cavity of the fuel inlet pipe 321, thereby moving the conical blunt body 325 and the igniter 324 back and forth.

[0136] Preferably, the fuel inlet pipe 321 is provided with a plurality of oxidant inlet pipes 322 evenly arranged on the outer circumference, and each oxidant inlet pipe 322 is provided with a swirl vane 326 at its discharge end.

[0137] Preferably, a second fuel delivery pipe L2 is connected to the inlet of the fuel inlet pipe 321, and a second flow regulating valve M2 is provided on the second fuel delivery pipe L2.

[0138] Preferably, an oxidant conveying pipe L3 is connected to the inlet of the oxidant inlet pipe 322, and an oxidant flow regulating valve M3 is provided on the oxidant conveying pipe L3.

[0139] Preferably, the system also includes a fuel delivery main pipe L0, on which a fuel flow regulating valve M0 is installed, and at the end of the fuel delivery main pipe L0, a first fuel delivery pipe L1 and a second fuel delivery pipe L2 extend out independently.

[0140] Preferably, the system also includes a plurality of combustion temperature detectors 5. The plurality of combustion temperature detectors 5 are evenly distributed along the central axis of the furnace body 1 along its length.

[0141] As a preferred option, a preheating smoke temperature detector 6 is also installed in the acceleration chamber 31. Example 1

[0142] like Figure 1 , 3As shown in Figure -5, a flameless combustion system includes a furnace body 1, a top cover 2, an accelerator burner 3, and main fuel injection pipes 4. The furnace body 1 is a cabinet-type or cylindrical structure. The top cover 2 is located at the center of one end face of the furnace body 1. The front end of the accelerator burner 3 penetrates the top cover 2 and connects to the inner cavity of the furnace body 1, with the extended line of the central axis of the accelerator burner 3 coinciding with the central axis of the furnace body 1. At least two main fuel injection pipes 4 are symmetrically arranged on the top cover 2 on both sides of the accelerator burner 3, and the front ends of each main fuel injection pipe 4 penetrate the top cover 2 and connect to the inner cavity of the furnace body 1. The extended lines of the central axes of all main fuel injection pipes 4 intersect the central axis of the furnace body 1. Each main fuel injection pipe 4 has its inlet independently connected to a first fuel delivery pipe L1, and a first flow regulating valve M1 is installed on the first fuel delivery pipe L1. The angle between the main fuel injection pipe 4 and the horizontal plane is 45°. Example 2

[0143] The embodiment 1 is repeated, except that the accelerating burner 3 includes an accelerating chamber 31 and a burner 32. The accelerating chamber 31 is embedded in the top cover 2, and the front and rear end faces of the accelerating chamber 31 are flush with the front and rear end faces of the top cover 2, respectively. The front inlet of the accelerating chamber 31 is connected to the burner 32, and the rear outlet of the accelerating chamber 31 is connected to the inner cavity of the furnace body 1. The central axis of the accelerating chamber 31 in the longitudinal direction, the extended line of the central axis of the burner 32 in the longitudinal direction, and the central axis of the top cover 2 in the longitudinal direction coincide, and the inner diameter of the accelerating chamber 31 gradually decreases in the longitudinal direction. Example 3

[0144] The embodiment 2 is repeated, except that the burner 32 includes a fuel inlet pipe 321, an oxidant inlet pipe 322, a core tube 323, and an igniter 324. The outlet of the fuel inlet pipe 321 is connected to the acceleration chamber 31 from the center of the front end face of the acceleration chamber 31. The oxidant inlet pipe 322 is arranged parallel to the fuel inlet pipe 321, and the outlet of the oxidant inlet pipe 322 is also connected to the acceleration chamber 31. The tail end of the core tube 323 extends into the acceleration chamber 31 along the lumen of the fuel inlet pipe 321, and the igniter 324 is located at the tail end of the core tube 323 and is located inside the acceleration chamber 31. Example 4

[0145] The embodiment 3 is repeated, except that the burner 32 further includes a conical blunt body 325, the outer diameter of which gradually increases along its length. The conical blunt body 325 is located within the acceleration chamber 31, and its narrow end is connected to the tail end of the core tube 323. The igniter 324 is located on the wide end side of the conical blunt body 325. The outer diameter of the narrow end of the conical blunt body 325 is smaller than the inner diameter of the fuel inlet pipe 321, and the outer diameter of the wide end of the conical blunt body 325 is larger than the inner diameter of the fuel inlet pipe 321. The core tube 323 can move back and forth within the cavity of the fuel inlet pipe 321, thereby moving the conical blunt body 325 and the igniter 324 back and forth. Example 5

[0146] Example 4 is repeated, except that multiple oxidant inlet pipes 322 are uniformly arranged on the outer circumference of the fuel inlet pipe 321, and each oxidant inlet pipe 322 is provided with a swirl vane 326 at its discharge end. Example 6

[0147] Repeat Example 5, except that a second fuel delivery pipe L2 is connected to the inlet of the fuel inlet pipe 321, and a second flow regulating valve M2 is provided on the second fuel delivery pipe L2. Example 7

[0148] Example 6 is repeated, except that an oxidant conveying pipe L3 is connected to the inlet of the oxidant inlet pipe 322, and an oxidant flow regulating valve M3 is provided on the oxidant conveying pipe L3. Example 8

[0149] Repeat Example 7, except that the system also includes a fuel delivery main pipe L0, on which a fuel flow regulating valve M0 is provided, and at the end of the fuel delivery main pipe L0, a first fuel delivery pipe L1 and a second fuel delivery pipe L2 extend out independently. Example 9

[0150] The same method as Embodiment 8 is used, except that the system also includes a plurality of combustion temperature detectors 5. The plurality of combustion temperature detectors 5 are evenly distributed along the central axis of the furnace body 1 along its length. Example 10

[0151] The same method as Example 1 is used, except that a preheating smoke temperature detector 6 is also installed in the acceleration chamber 31. Example 11

[0152] Repeat Example 1, except that the angle between the main fuel nozzle 4 and the horizontal plane is 55°. Example 12

[0153] Repeat Example 1, except that the angle between the main fuel nozzle 4 and the horizontal plane is 65°.

[0154] Application Example 1

[0155] When using the system described in Example 10 for flameless combustion, the required thermal power in this operating condition is: P = 2000 kW, and the calorific value of the fuel combustion is approximately H = 34000 KJ / m³. 3 The ratio α of oxidant (air) to fuel is taken as 10.

[0156] Therefore, the total fuel demand Q per unit time (in 1 hour) is... ft for:

[0157] Q ft =P / H=2000÷34000×3600≈211.76m 3

[0158] The total demand for oxidant per unit time (1 hour) is Qa:

[0159] Qa=α×Q ft =211.76×10=2117.6m 3

[0160] Adjusting the first flow regulating valve M1 ensures that the actual total amount of fuel delivered per unit time via the first fuel delivery pipe L1 is 212m³. 3 Adjusting the oxidant flow regulating valve M3 ensures that the actual total amount of oxidant transported per unit time via the oxidant delivery pipe L3 is 2120 m³. 3 .

[0161] In this operating condition, the outlet opening area at the rear end of accelerator chamber 31 is A = 0.02 m². 2 The threshold flow rate V for flameless combustion of the oxidant after preheating c =80m / s

[0162] The flow rate V0 of the oxidant discharged from the rear outlet of the acceleration chamber 31 at room temperature is:

[0163] V0=Qa / A=2117.6÷3600÷0.02≈29.41m / s

[0164] The acceleration ratio C of the oxidant is:

[0165] C=V c / V0=80÷29.41≈2.72

[0166] Under this operating condition, the initial temperature of the oxidant is T0 = 20℃, then the preheating temperature of the oxidant after preheating is T. p1 for:

[0167] T p1=C·(T0+273)-273=2.72×(20+273)-273≈523.96℃

[0168] The specific heat capacity of the oxidant is 1.4 kJ / m³. 3 If the temperature is ℃, then the preheating fuel demand Q per unit time (in 1 hour) is... fp for:

[0169] Q fp =Q a ·C p ·(T p1 -T0) / H=2117.6×1.4×(523.96-20)÷34000≈44.81m 3

[0170] Then, by adjusting the second flow regulating valve M2, the amount of fuel delivered to the acceleration chamber 31 via the second fuel delivery pipe L2 per unit time is 44m³. 3 .

[0171] Under this operating condition, the fuel injection velocity U required for accelerated stable combustion in the chamber is 15 m / s, the radius R of the fuel inlet pipe is 20 mm, and the angle β between the line connecting the narrow end of the conical blunt body to the edge of its wide end and the horizontal direction is 45°. Therefore, the depth to which the narrow end of the conical blunt body extends into the fuel inlet pipe is:

[0172] X={Sqr[R 2 -Q fp / (U·π)]} / tanβ=Sqr[20×20-44.81×1000000000 / (3600×3.14×15÷1000)]≈11.65mm

[0173] Then, by adjusting the core tube, the depth to which the narrow end of the conical blunt body extends into the fuel inlet pipe is 11.65mm.

[0174] Under this operating condition, a total of 5 temperature sensors are installed on the central axis of the furnace chamber of furnace body 1. The detection results are shown in the table below. The set temperature difference threshold is ΔT. max =30℃, temperature threshold T max-c =1250℃, Lc=1m.

[0175] Temperature number T1 T2 T3 T4 T5 <![CDATA[△T max ]]> Temperature value ℃ 1150 1173 1241 1274 1205 124

[0176] Obviously T max =T4=1274>T max-c , △T max =124>△T max-c .

[0177] Therefore, the current combustion state is a flaming combustion state.

[0178] Further analysis revealed that the highest temperature distance L=1.2m>Lc, indicating that the mixing location is further back and the central jet flow rate is too small.

[0179] The amount of preheated fuel should be increased by adjusting the corresponding valves to maintain a total fuel quantity of Qft = 212m³. 3 In the case of / h, increase the amount of preheated fuel Q fp up to 50m 3 / h, then calculate the appropriate core position (the depth at which the narrow end of the conical blunt body extends into the fuel inlet pipe), and adjust it to stabilize combustion in the accelerated combustion chamber.

[0180] The suitable core position is:

[0181] X={Sqr[R 2 -Q fp / (U·π)]} / tanβ=Sqr[20×20-50×1000000 / (3600×3.14×15)]≈10.25mm

[0182] The depth to which the narrow end of the conical blunt body extends into the fuel inlet pipe is adjusted to 10.25 mm by adjusting the core tube.

[0183] Continue monitoring the furnace temperature and assess the combustion status: The furnace temperature was measured again, and the results are shown in the table below:

[0184] Temperature number T1 T2 T3 T4 T5 <![CDATA[△T max ]]> Temperature value ℃ 1188 1205 1211 1217 1209 29

[0185] Obviously T max =T4=1217<T max-c , △T max =29<△ Tmax-c If the adjusted combustion state is flameless combustion, then the adjustment can be stopped.

Claims

1. A flameless combustion system, characterized in that: The system includes a furnace body (1), a top cover (2), an accelerator burner (3), and main fuel nozzles (4); the furnace body (1) is a cabinet-type or cylindrical structure, the top cover (2) is located in the middle of the end face of one end of the furnace body (1), the front end of the accelerator burner (3) passes through the top cover (2) and is connected to the inner cavity of the furnace body (1), and the extension line of the central axis of the accelerator burner (3) in the length direction coincides with the central axis of the furnace body (1) in the length direction; at least two main fuel nozzles (4) are symmetrically arranged on the top cover (2) on both sides of the accelerator burner (3), and the front end of each main fuel nozzle (4) passes through the top cover (2) and is connected to the inner cavity of the furnace body (1), and the extension lines of the central axis of each main fuel nozzle (4) in the length direction intersect on the central axis of the furnace body (1) in the length direction; Each main fuel injection pipe (4) has its feed inlet independently connected to a first fuel delivery pipe (L1), and a first flow regulating valve (M1) is provided on the first fuel delivery pipe (L1); the accelerating burner (3) includes an accelerating chamber (31) and a burner (32); the accelerating chamber (31) is embedded in the top cover (2), and the front and rear end faces of the accelerating chamber (31) are flush with the front and rear end faces of the top cover (2); the front inlet of the accelerating chamber (31) is connected to the burner (32), and the rear outlet of the accelerating chamber (31) is connected to the inner cavity of the furnace body (1); the central axis of the accelerating chamber (31) in the length direction, the extension line of the central axis of the burner (32) in the length direction, and the central axis of the top cover (2) in the length direction coincide, and the inner diameter of the accelerating chamber (31) gradually decreases in the length direction; The burner (32) includes a fuel inlet pipe (321), an oxidant inlet pipe (322), a core tube (323), and an igniter (324); the outlet of the fuel inlet pipe (321) is connected to the acceleration chamber (31) from the center of the front end face of the acceleration chamber (31); the oxidant inlet pipe (322) is arranged parallel to the fuel inlet pipe (321), and the outlet of the oxidant inlet pipe (322) is also connected to the acceleration chamber (31); the tail end of the core tube (323) extends into the acceleration chamber (31) along the lumen of the fuel inlet pipe (321), and the igniter (324) is located at the tail end of the core tube (323) and inside the acceleration chamber (31); The burner (32) also includes a conical blunt body (325), the outer diameter of which gradually increases along its length; the conical blunt body (325) is located in the acceleration chamber (31), and the narrow end of the conical blunt body (325) is connected to the tail end of the core tube (323), and the igniter (324) is located on the wide end side of the conical blunt body (325); the outer diameter of the narrow end of the conical blunt body (325) is smaller than the inner diameter of the fuel inlet pipe (321), and the outer diameter of the wide end of the conical blunt body (325) is larger than the inner diameter of the fuel inlet pipe (321); the core tube (323) can move back and forth in the cavity of the fuel inlet pipe (321), and drive the conical blunt body (325) and the igniter (324) to move back and forth.

2. The system according to claim 1, characterized in that: The angle between the main fuel nozzle (4) and the horizontal plane is 30-85°.

3. The system according to claim 2, characterized in that: The angle between the main fuel nozzle (4) and the horizontal plane is 40-80°.

4. The system according to claim 3, characterized in that: The angle between the main fuel nozzle (4) and the horizontal plane is 50-75°.

5. The system according to any one of claims 1-4, characterized in that: The fuel inlet pipe (321) has multiple oxidant inlet pipes (322) evenly arranged circumferentially on its outer side, and each oxidant inlet pipe (322) has a swirl vane (326) at its discharge end; and / or A second fuel delivery pipe (L2) is connected to the inlet of the fuel inlet pipe (321), and a second flow regulating valve (M2) is provided on the second fuel delivery pipe (L2); and / or The oxidant inlet pipe (322) is connected to an oxidant delivery pipe (L3), and an oxidant flow regulating valve (M3) is installed on the oxidant delivery pipe (L3).

6. The system according to any one of claims 1-4, characterized in that: The system also includes a fuel delivery manifold (L0), on which a fuel flow regulating valve (M0) is installed. At the end of the fuel delivery manifold (L0), two independent first fuel delivery pipes (L1) and second fuel delivery pipes (L2) extend out; and / or The system also includes several combustion temperature detectors (5); the several combustion temperature detectors (5) are evenly distributed along the central axis of the furnace body (1) along its length; and / or A preheating smoke temperature detector (6) is also installed in the acceleration chamber (31).

7. The system according to claim 5, characterized in that: The system also includes a fuel delivery manifold (L0), on which a fuel flow regulating valve (M0) is installed. At the end of the fuel delivery manifold (L0), two independent first fuel delivery pipes (L1) and second fuel delivery pipes (L2) extend out; and / or The system also includes several combustion temperature detectors (5); the several combustion temperature detectors (5) are evenly distributed along the central axis of the furnace body (1) along its length; and / or A preheating smoke temperature detector (6) is also installed in the acceleration chamber (31).

8. A control method for a flameless combustion system or a control method for a flameless combustion system as described in any one of claims 1-7, characterized in that: The method includes the following steps: S1: Calculate the total fuel demand and total oxidant demand per unit time based on the required thermal power and calorific value of the target operating condition; adjust the actual total delivery of fuel and oxidant per unit time based on the calculated total fuel demand and total oxidant demand per unit time. S2: Calculate the oxidant preheating temperature and the preheating fuel demand per unit time based on the actual total oxidant delivery rate per unit time and the threshold flow rate required for flameless combustion of the preheated oxidant; adjust the actual preheating fuel delivery rate per unit time based on the calculated preheating fuel demand per unit time. S3: Based on the actual total amount of oxidant delivered per unit time and the actual amount of preheated fuel delivered per unit time, the combustion ratio of oxidant and preheated fuel in the acceleration chamber (31) is controlled by adjusting the real-time injection velocity of preheated fuel, so that the combustion of preheated fuel can sustainably and stably heat the oxidant to the oxidant preheating temperature. Step S3 specifically involves: within a unit time, controlling the relative position between the conical blunt body (325) and the fuel inlet pipe (321) outlet by adjusting the upward movement of the core tube (323) on the horizontal axis, thereby adjusting and controlling the opening size of the fuel inlet pipe (321) outlet. That is, maintaining the stability of the real-time ejection velocity when the preheated fuel enters the acceleration chamber (31) by controlling the real-time opening size of the fuel inlet pipe (321) outlet. The specific process is as follows: 1) When the actual amount of preheated fuel delivered per unit time is Q fp The actual amount of oxidant delivered per unit time is Q. a At that time, the preheating fuel combustion can sustainably and stably heat the oxidant to the oxidant preheating temperature T. p1 If the real-time ejection velocity of the preheated fuel required is U, m / s, then: U=Q fp / {π·[R 2 -(X·tanβ) 2 ]} (7); That is: X={Sqr[R 2 -Q fp / (U·π)]} / tanβ (8) Where β is the angle between the line connecting the narrow end of the conical blunt body (325) to its wide end edge and the horizontal direction, R is the radius of the lumen of the fuel inlet pipe (321), and X is the depth of the narrow end of the conical blunt body (325) into the fuel inlet pipe (321); the depth of the narrow end of the conical blunt body (325) into the fuel inlet pipe (321) is adjusted by adjusting the core tube (323) to obtain X,m calculated by equation (8); And / or, 2) when the actual amount of preheated fuel delivered per unit time is Q fp The actual amount of oxidant delivered per unit time is Q. a At that time, the initial depth of the narrow end of the conical blunt body (325) extending into the fuel inlet pipe (321) is set to X0, m; the real-time temperature of the oxidant in the acceleration chamber (31) is detected by the preheating flue gas temperature detector (6) as T. pc ℃; but: Adjust X = X0 + ΔX. After adjustment, check the real-time temperature of the oxidant in the acceleration chamber (31) compared to before adjustment. If the temperature increases, adjust using method ①; if the temperature decreases, adjust using method ②. Method ①: Adjust X = X0 + 2△X, compare the real-time temperature of the oxidant in the acceleration chamber (31) after the adjustment with the temperature before the adjustment. If the temperature increases, continue to adjust X = X0 + 3△X, and compare the real-time temperature of the oxidant in the acceleration chamber (31) after the adjustment with the temperature before the adjustment. Repeat this process until X = X0 + n△X, and the real-time temperature of the oxidant in the acceleration chamber (31) after the adjustment decreases compared with the temperature before the adjustment. Then adjust X = X0 + (n-1)△X and end the adjustment. Method 2: Adjust X = X0 - ΔX, compare the real-time temperature of the oxidant in the acceleration chamber (31) after the adjustment with the temperature before the adjustment. If the temperature increases, adjust X = X0 - 2ΔX, continue to compare the real-time temperature of the oxidant in the acceleration chamber (31) after the adjustment with the temperature before the adjustment. If the temperature increases, continue to adjust X = X0 - 3ΔX, and compare the real-time temperature of the oxidant in the acceleration chamber (31) after the adjustment with the temperature before the adjustment. Continue in this manner until X = X0 - nΔX, and the real-time temperature of the oxidant in the acceleration chamber (31) after the adjustment decreases compared with the temperature before the adjustment. Then adjust X = X0 - (n-1)ΔX and end the adjustment. S4: Adjust the oxidant preheating temperature in real time according to the change of the combustion temperature field inside the furnace body (1) so that the inside of the furnace body (1) is always in a flameless combustion state.

9. The method according to claim 8, characterized in that: Step S1 specifically involves setting the target operating conditions as follows: the required thermal power is P, kW; the calorific value of the fuel used is H, KJ / m³. 3 Then we have: Total fuel demand Q per unit time ft for: Q ft =P / H (1); The total demand for oxidant per unit time, Q a for: Q a =α·Q ft =α·P / H (2); Wherein, α is the ratio of oxidant consumption to fuel consumption per unit time under the target operating condition; Within a unit of time: Adjust the fuel flow control valve (M0) so that the actual amount of fuel delivered through the fuel delivery manifold (L0) is Q calculated by equation (1). ft m 3 Adjust the oxidant flow regulating valve (M3) so that the actual amount of oxidant delivered through the oxidant delivery pipe (L3) is Q calculated by equation (2). a m 3 .

10. The method according to claim 8 or 9, characterized in that: Step S2 specifically involves setting the target operating condition as follows: the rear outlet opening area of ​​the acceleration chamber (31) is A, m 2 The threshold flow rate for flameless combustion of the oxidant after preheating is V. c , m / s; then we have: The flow rate V0 of the oxidant discharged from the rear outlet of the acceleration chamber (31) at room temperature is: V0=Q a / A (3); To ensure that the oxidant discharge velocity from the rear end of the acceleration chamber (31) reaches the threshold flow rate Vc, the acceleration ratio C of the preheated oxidant is: C=V c / V0=V c ·A / Q a (4); Based on the ideal gas expansion properties, the preheating temperature T of the oxidant... p1 for: T p1 =C·(T0+273)-273 (5); Furthermore, based on the principle of heat balance, the amount of preheated fuel required per unit time, Q fp for: Q fp =Q a ·C p ·(T p1 -T0) / H (6); Among them, C p The specific heat capacity of the oxidant; within a unit time: adjust the second flow regulating valve (M2) so that the amount of fuel delivered to the acceleration chamber (31) via the second fuel delivery pipe (L2) is Q calculated by equation (6). fp m 3 ; so that the temperature of the oxidant in the acceleration chamber (31) is T calculated by equation (5). p1 , ℃.

11. The method according to claim 8, characterized in that: The value of △X is 0.01-0.5 times the length of the conical blunt body (325).

12. The method according to claim 11, characterized in that: The value of △X is 0.03-0.3 times the length of the conical blunt body (325).

13. The method according to claim 12, characterized in that: The value of △X is 0.05-0.15 times the length of the conical blunt body (325).

14. The method according to claim 8 or 9, characterized in that: Step S4 specifically involves numbering several combustion temperature detectors (5) inside the furnace body (1) sequentially along the fuel flow direction as 1, 2, 3, ..., i, i+1, ..., m-1, m, and detecting the temperature of each point on the central axis inside the furnace body (1) in real time as T1, T2, T3, ..., T i T i+1 、···、T m-1 T m And calculate T max and △T max Then we have: When T max <T max-c And △T max <△T max-c If the current operating conditions remain unchanged, then the distance L,m between the detection point corresponding to the highest temperature and the rear outlet of the acceleration chamber (31) is calculated; then: When L > Lc, the fuel delivery rate of the fuel inlet pipe (321) is increased until T max <T max-c And △T max <△T max-c The adjustment ends thereafter; Lc is the theoretical threshold distance. When L≤Lc, the fuel delivery rate of the fuel inlet pipe (321) is reduced until T max <T max-c And △T max <△T max-c The adjustment was then terminated.

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