Integrated air preheating and dehumidification system and method for reducing coke burning loss and nitrogen consumption

Abstract

The application discloses an integrated air preheating and dehumidification system and method for reducing coke burning loss and nitrogen consumption, and belongs to the technical field of dry quenching. 3 The system of the application is connected with the dry quenching furnace through the air preheater and the air introduction pipe instead of being directly connected with the dry quenching furnace, the introduced air is preheated to reduce the relative humidity of the air, the driving force of the water-gas reaction is weakened from the source, and thus the coke burning loss and the nitrogen consumption are reduced.

Description

Technical Field

[0001] This invention relates to the field of dry quenching technology, and more specifically, to a system and method for reducing coke burn-off and nitrogen consumption by utilizing the low-temperature waste heat of the dry quenching system itself to preheat the introduced air, thereby reducing the humidity of the circulating gas and inhibiting the water-gas reaction. Background Technology

[0002] Dry quenching technology is one of the key technologies for energy conservation, emission reduction, and green low-carbon production in the iron and steel metallurgical industry. Its principle involves using inert circulating gas to exchange heat with red-hot coke to achieve efficient cooling and high-temperature sensible heat recovery of the coke. This is significant for improving coke quality, reducing energy consumption, and decreasing pollutant emissions. The dry quenching furnace loss rate refers to the ratio of the amount of coke lost due to the reaction between red-hot coke and circulating gas during the quenching process to the total amount of red-hot coke entering the dry quenching furnace. This loss is unavoidable in the operation of the dry quenching system and is a key indicator characterizing the loss caused by the reaction between red-hot coke and circulating gas during quenching. It directly affects the production efficiency and system stability of enterprises and is a common technical problem that has long existed in the industry and is difficult to completely solve.

[0003] To control the concentration of combustible components such as H2 and CO in the circulating gas and prevent system explosion risks, current industrial production commonly employs methods such as introducing air into the dry quenching furnace flue to react with the combustible components or introducing nitrogen for dilution. The air introduction method utilizes oxygen from the air to oxidize and remove combustible components, thus ensuring the safe and stable operation of the system. However, in actual operation, water vapor in the introduced air is the primary source of moisture in the circulating gas system, significantly affected by seasons, regions, and meteorological conditions. Summer air humidity can reach more than eight times that of winter, resulting in extremely drastic seasonal fluctuations in operating conditions. After entering the high-temperature circulating system, water vapor undergoes a significant water-gas reaction with red-hot coke (C + H2O → CO + H2), continuously generating additional combustible gases (CO, H2), further increasing the concentration of combustible components in the circulating gas. This not only significantly exacerbates unnecessary coke burn-out and increases the dry quenching furnace burn-out rate but also causes significant fluctuations in system operating conditions with humidity, severely weakening the control effect of air introduction. When the system runs for a long time and the air intake regulation capacity is insufficient, it is necessary to add a large amount of high-purity nitrogen for dilution, resulting in high nitrogen consumption and a significant increase in operating costs.

[0004] To address the aforementioned issues, existing technologies primarily focus on passive regulation or end-of-pipe treatment improvements. One approach optimizes nitrogen introduction and flow control strategies, which only passively mitigates fluctuations in combustible component concentrations but cannot suppress moisture introduction and water-gas reactions at the source, resulting in limited loss reduction and energy-saving effects. Another approach involves deep dehumidification of the circulating gas, removing moisture through adsorption and condensation devices. For example, Chinese Patent Publication No. CN219567861U, published on August 22, 2023, entitled "A Dehumidification Device for Reducing the Burn-off Rate of Dry-Quenched Coke," uses a dehumidification cylinder with an adsorption cylinder containing multiple activated carbon discs coaxially mounted within it for moisture adsorption. Another example is Chinese Patent Publication No. CN116162474A, published on May 26, 2023, entitled "A Device for Reducing the Burn-off Rate of Dry-Quenched Coke through Circulating Gas Dehumidification." This patent adds a dehydration device to evaporate the medium in the dehydration heat exchange tube into gas, which absorbs heat from the tube wall and lowers the tube wall temperature. This causes the moisture in the circulating gas entering the dry quenching furnace to condense into liquid on the outer surface of the dehydration heat exchange tube, thereby reducing the water-gas reaction in the dry quenching furnace and achieving the goal of reducing the burn-off of dry quenched coke.

[0005] However, the two patented technologies mentioned above suffer from drawbacks such as complex device structures, easy adsorbent failure, and high regeneration energy consumption, resulting in poor economic viability for engineering applications and making large-scale promotion on existing production lines difficult. Therefore, there is an urgent need for a simple process that does not require additional complex devices or increased energy consumption, can stably control the introduced air humidity from the source, simultaneously reduce dry quenching burn-off rate and nitrogen consumption, and is adaptable to all seasons and operating conditions—a highly efficient and low-cost method. Summary of the Invention

[0006] To address the problem that moisture in the air introduced into the existing dry quenching process reacts with water at high temperatures, leading to increased coke burn-off and abnormal increases in combustible components, thus necessitating large-scale nitrogen replenishment, this invention provides an integrated air preheating and dehumidification system and method to reduce coke burn-off and nitrogen consumption in dry quenching. By utilizing the low-temperature waste heat of the dry quenching system itself, the air to be introduced into the dry quenching furnace is preheated, thereby reducing its relative humidity (rather than absolute humidity), fundamentally weakening the driving force of the water-gas reaction, thus achieving the dual goals of reducing burn-off and nitrogen consumption.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides an integrated air preheating and dehumidification method for reducing dry quenching scorch loss and nitrogen consumption, comprising the following steps: Step S1: Extract a low-temperature waste heat medium from the dry quenching process system. The low-temperature waste heat medium is taken from at least one of the tail flue gas of the dry quenching boiler, boiler feedwater or low-pressure steam. Its temperature range is 60℃~200℃. It is a low-grade heat energy that the system itself cannot efficiently utilize and is conventionally directly discharged. Step S2: Pass the low-temperature waste heat working fluid obtained in step S1 into an air preheater; Step S3: Introduce ambient air into the air preheater for non-contact heat exchange with the low-temperature waste heat medium, heating the air to a target temperature T, where 50℃≤T≤80℃, and T≥ambient air dew point temperature+20℃. After heating, the absolute moisture content of the air remains unchanged, but the relative humidity is significantly reduced. This temperature range ensures that the relative humidity of the air drops below 30%, while avoiding adverse effects on subsequent equipment and reactions caused by excessively high preheating temperatures. For example, excessively high temperatures place higher demands on heat exchange equipment, increase costs, and are not conducive to suppressing the dissolution reaction of coke.

[0008] Step S4: The preheated and dehumidified air obtained in step S3 is delivered to the air inlet pipeline of the dry quenching circulating gas system, and the flow rate is controlled at 4000~12000 m³ / h. 3 The gas is introduced into the dry quenching furnace at a rate of / h to suppress the water-gas reaction at the source, reduce coke burn-off, and decrease the amount of nitrogen added.

[0009] It should be noted that the following reactions mainly occur during the entire dry quenching process:

[0010] Although the main component of the circulating gas in dry quenching coke is N2, it also contains reducing gases such as CO and H2, gasification media such as CO2 and H2O, and a very small amount of O2. Therefore, the circulating gas is a complex system with both reducing and weak oxidizing properties.

[0011] Oxygen is the dominant factor causing coke burn-off, directly oxidizing the coke into CO and CO2, making it the most direct and significant source of burn-off. CO and H2 in the circulating gas, as reducing gases, preferentially react with oxygen, inhibiting direct contact between oxygen and coke to some extent, thus buffering and protecting against burn-off. However, this protective effect is significantly weakened when oxygen supply is excessive or gas distribution is uneven.

[0012] Meanwhile, CO2 and H2O continuously consume coke through gasification reactions, representing a significant, albeit hidden, source of burn-off in dry quenching furnaces. CO2 reacts with coke at high temperatures, while H2O reacts with water gas to produce CO and H2. Both contribute to coke mass loss and form a cyclical reaction system, further intensifying the burn-off process. Furthermore, H2 consumes oxygen while simultaneously generating H2O, exhibiting a dual effect on burn-off. Therefore, to reduce the burn-off rate in dry quenching, the composition of the circulating gas should be carefully controlled to maintain a low oxygen content, a high proportion of reducing gases, and a low water vapor content, thereby weakening the oxidation reaction intensity and inhibiting the gasification reaction.

[0013] In recent years, there have been numerous reports on the impact of the reaction between coke and H2O on the coke burn-off (solution) rate. Studies have shown that the initial reaction temperature of coke with H2O is relatively low at high temperatures, and its reaction rate is higher than that of coke with CO2. The activation energies of internal diffusion and interfacial reactions in the coke-H2O reaction are lower than those in the coke-CO2 reaction. Therefore, high relative humidity in the air increases the amount of moisture entering the dry quenching coke oven per unit time, which leads to an increased probability of water-gas reaction. At the same time, the CO and H2 generated in the reaction further enter the circulating reaction system, resulting in an increase in the coke burn-off (solution) rate.

[0014] In existing technologies, the common approach to addressing moisture in the air introduced into a dry quenching furnace is to remove moisture from the air, such as through common adsorption and condensation methods. However, this approach involves significant system modifications, relies on independent dehumidification equipment, has a complex structure, high energy consumption, and poor economic efficiency. Especially considering seasonal fluctuations in burn-off and excessive nitrogen consumption, existing methods are costly and difficult to apply industrially. Therefore, the solution proposed in this invention only requires adding an air preheater and corresponding piping and temperature feedback control equipment to the existing system. It avoids the complex setup of adsorption / desorption cycles, solid material conveying, and regeneration heat sources. The overall system complexity, investment cost, and maintenance workload are significantly lower than existing adsorption dehumidification solutions.

[0015] Furthermore, another innovation of this invention lies in utilizing a large amount of low-temperature waste heat (60°C to 200°C) present in the tail-end flue gas, boiler feedwater, and low-pressure steam of the dry quenching system, which is not recognized in existing technologies. This portion of heat is of low grade and difficult to use for conventional power generation or process heating, and is generally directly discharged. The applicant discovered that this low-grade waste heat is not a useless energy source, but rather the most suitable energy source to solve the three major problems of high humidity of the introduced air, high coke burn-off, and high nitrogen consumption in the dry quenching system of this invention. Therefore, the low-grade waste heat directly discharged from the tail-end flue gas, boiler feedwater, and low-pressure steam of the dry quenching system is creatively used to preheat the air introduced into the dry quenching furnace, and the flow rate and temperature of the introduced air are controlled according to specific operating conditions to suppress water-gas reaction from the source, reduce coke burn-off, and reduce nitrogen replenishment.

[0016] To fully demonstrate the effectiveness of this invention in reducing coke burn-off by lowering the relative humidity of the introduced air through preheating, thereby inhibiting the water-gas reaction at its source, the applicant further simulated a dry quenching circulation atmosphere (gas composition of 15% CO2 + 5% CO + 80% N2 by volume fraction) and measured coke reactivity by introducing air with different moisture contents. This proved that by lowering the relative humidity of the introduced air through preheating, the invention can inhibit coke dissolution reactions to a certain extent. The basic properties of the coke used are shown in the table below: Table 1. Industrial Analysis of Experimental Coke

[0017] In Table 1, M ad For air-dried basis moisture, A ad Ash content on an air-dried basis, V ad FC is an air-dried volatile component. ad Carbon is fixed on an air-dried basis.

[0018] The experiment was conducted on the reactivity of self-made granular coke, with two control groups, group A and group B. The specific experimental steps are as follows: (1) Lay high-alumina balls at a set height at the bottom of the reaction tube as support, place a sieve plate on it, and then load 20±0.5 g of coke sample with a particle size of (3-6 mm). (2) When loading the sample, adjust the height of the high-alumina sphere layer to ensure that the coke layer is completely within the constant temperature zone of the heating furnace. Suspend the entire reaction tube below the electronic balance and adjust the nuts to allow it to hang vertically in the furnace. Set the temperature control program to make the furnace temperature rise uniformly from 180℃ to the reaction temperature within 2 hours. When the material layer temperature reaches 180℃, introduce N2 gas at a flow rate of 0.5L / min.

[0019] (3) When the temperature at the center of the material layer rises to 400 ℃, switch to the flow rate of the reaction gas (gas volume concentration composition = 15%CO2 + 5%CO + 80%N2) and the flow rate of the humid air (0.05 L / min) for 60 min.

[0020] It should be noted that the humidified air introduced into Group A was at 25℃ with a humidity (moisture content) of 10%, while the humidified air introduced into Group B was preheated to 60℃, and the relative humidity of the humidified air was measured to be 5%. During the experiment, data on the reaction tube temperature and coke mass were continuously collected. Samples were taken at 950℃, 1050℃, and 1150℃ for gas composition analysis using an infrared gas analyzer to analyze the effect of humidity changes on the concentrations of CO, CO2, and H2 during the reaction process, until the heating program ended.

[0021] (4) After the experimental requirements are met, cut off the reaction gas, increase the N2 flow rate to 0.5 L / min and turn off the heating power. Continue to introduce N2 for 2 hours to cool, then close the valve. After the furnace has cooled to room temperature naturally, remove the reaction tube, collect the coke after the reaction, and seal it for storage.

[0022] Record and calculate the reactivity index PRI of coke in groups A and B: PRI = (mass of coke before reaction - mass of coke after reaction) / mass of coke before reaction × 100%. See Table 2 for the specific results. Table 2. Reactivity of coke under different relative humidity levels

[0023] The analysis and comparison in the table above show that the PRI value of coke is directly proportional to the reaction temperature under the same humidity. As the relative humidity increases, the PRI value of coke at different reaction temperatures all show an increasing trend, indicating that reducing the relative humidity is beneficial to inhibiting the reactivity of coke.

[0024] Coke loss in the dry quenching process is a typical gas-solid reaction. Many kinetic models exist for this reaction. Since the experiment requires gas switching and involves changes in gas composition, the Coats-Redfern integral method was chosen for kinetic analysis. The rate equation for thermogravimetric loss with reaction order is:

[0025] In the formula: α is the percentage of thermal weight loss at a certain moment; n The reaction order is [number]. k The rate constant is for n First-order reaction mechanism function.

[0026] k With reaction temperatureT It conforms to the Arrhenius equation:

[0027] In the formula: The apparent activation energy is expressed in kJ / mol. For frequency factor, min -1 ; Let be the gas constant, taken as 8.314 × 10⁻⁶. - 3 kJ / mol·k.

[0028] Equipment heating rate during the test C Constant, that is: reaction temperature , T 0 represents the ambient temperature. Combining the above formulas, we can obtain:

[0029] Combining the above two equations and integrating them, we get:

[0030] In the coke dissolution reaction, it can be considered a 0th-order reaction, and We can consider it as 0, and further simplifying, we get:

[0031] Will right Plotting a curve and fitting it yields a regression equation. The activation energy can then be calculated using the slope and intercept. and frequency factor .

[0032] The results obtained from the above kinetic analysis are shown in Tables 3 and 4. Table 3. Rate constants of coke dissolution reaction after air introduction at different temperatures and humidity levels. k

[0033] Table 3 shows the coke dissolution reaction rate constant under the same humidity. k The rate constant of coke dissolution reaction is directly proportional to temperature; as relative humidity decreases, the rate constant of coke dissolution reaction at different reaction temperatures also changes. k The decrease in both values ​​indicates that the reduction in relative humidity will, to some extent, inhibit the rate of dissolution reaction of coke.

[0034] Table 4. Activation energy and frequency factor of coke dissolution reaction after introduction of air with different humidity levels.

[0035] In Table 4, Ea is the activation energy of the coke dissolution reaction, and A is the frequency factor.

[0036] As shown in Table 4, reducing the relative humidity of the introduced air through preheating leads to a decrease in the apparent activation energy and frequency factor of the coke dissolution reaction. In particular, the frequency factor decreases by 43.2%, indicating that the reduction in relative humidity after preheating does not increase the chemical reaction energy barrier. Instead, it reduces the water content introduced per unit time, thereby lowering the H2O partial pressure and the coke surface adsorption coverage. This causes the reaction control step to gradually shift from chemical reaction control to diffusion-adsorption synergistic control. Due to the significant decrease in effective collision frequency, the overall coke gasification rate is suppressed, ultimately resulting in reduced coke reactivity. This effectively reduces the coke burning (dissolution) reaction in dry quenching coke ovens.

[0037] Furthermore, to intuitively understand the mechanism by which the reduced relative humidity of the air after preheating leads to a decrease in the coke burn-off (dissolution) rate, this invention will provide a detailed explanation through the following specific examples.

[0038] With a temperature of 25℃, a relative humidity of φ1 of 80%, and a volumetric flow rate of V = 10000 m³, 3 The following example illustrates the process: heating air to 70°C per hour (with no change in outlet volumetric flow rate). At standard atmospheric pressure, the saturated water vapor partial pressure at 25°C is 3.17 kPa, and the inlet water vapor partial pressure P v1 for: P v1 =Relative humidity φ1×3.17=80%×3.17kPa =2.536kPa; Air humidity d1 (kg) 水 / kg 干空气 = (Molar mass of water vapor / Molar mass of air) × P v1 / (PP v1 ) = 0.622 × P v1 / (PP v1 ), where P=101.325kPa, then d1=0.0159kg / kg is calculated; since the heating is an isohumid heating process, the saturated water vapor partial pressure of water at 70℃ is 31.2kPa, and its air moisture content d2=d1, the outlet relative humidity φ2=φ1×3.17 / 31.2=2.536 / 31.2=8.13%, then the relative humidity decreases by about 71.87%.

[0039] From the ideal gas law, we know that: m da(质量流量） =PV / R a T R a=287 J / (kg·K) is the universal gas constant, V = 10000 m 3 / h, then Inlet (25 ℃ = 298.15 K) dry air flow rate (m³) da1 =(101325×10000) / (287×298.15)=11840kg / h, inlet water vapor mass flow rate (m³) v =m da ×d,m v1= 11840 × 0.0159 = 188.3 kg / h; Dry air flow rate at the outlet (70 ℃ = 343.15 K) in m³ / s da2 =(101325×10000) / (287×343.15)=10290kg / h, outlet water vapor mass flow rate (m³) v2= 10290 × 0.0159 = 163.6 kg / h; The water content entering the dry quenching coke oven per unit time decreases by Δm = 24.7 kg / h.

[0040] The above analysis shows that preheating the air can effectively reduce the relative humidity of the air introduced into the dry quenching system. After being introduced into the dry quenching oven, it can inhibit the reaction of water and gas from the source. Moreover, this method is cost-effective, requires minimal equipment modification, and yields significant benefits to enterprises.

[0041] It is worth emphasizing that, since the coke burning (melting) loss in dry quenching coke is affected by various operating conditions such as circulating air volume and CO concentration, air introduction volume, coke discharge volume and coke discharge temperature, the flow rate and temperature of preheating air must be correlated and controlled with other operating conditions, and the temperature of preheating air in particular needs to be strictly monitored.

[0042] Coke dissolution reaction ( ) and water-gas reaction ( All of these reactions are endothermic, and increasing the temperature is beneficial for their progress. Furthermore, as the temperature rises, the surface activity of the coke increases and the reaction interface is renewed, leading to continuous CO generation while CO2 and H2O are consumed. Therefore, excessively high preheating air temperatures will also increase coke loss. Conversely, excessively low preheating air temperatures will fail to effectively reduce humidity, making it difficult to suppress coke burn-off.

[0043] Meanwhile, the significant inhibitory effect of CO generated in the reaction on the coke dissolution reaction has been confirmed by numerous studies. In the 850℃-1050℃ range, the reaction system between coke and circulating gas is in a transitional stage from chemical reaction control to internal diffusion control. On the one hand, an increase in CO concentration (it should be noted that, unless otherwise specified, all concentrations mentioned in this invention refer to gas volume fractions) can shift the reaction equilibrium towards the reverse reaction direction; on the other hand, CO competitively adsorbs on the coke surface and occupies active sites, thereby weakening the reaction driving force. Through extensive experimental research, the applicant found that, under the condition of constant coke particle size and CO2 concentration, with the increase of CO concentration, the onset temperature of the coke dissolution reaction significantly increased from 987℃ to 1006℃, indicating that CO has a significant inhibitory effect on the coke dissolution reaction. However, when the CO concentration increases from 3.5% to 7.5%, the increase in the coke onset reaction temperature gradually narrows, indicating that the inhibitory effect of high-concentration CO on this reaction has limitations. The applicant studied the coke onset reaction temperature under different CO concentrations, such as... Figure 2 As shown.

[0044] Furthermore, excessively high preheating air temperatures increase the CO and H2 content generated by the system reaction, necessitating an increase in the amount of air introduced to reduce system safety risks, thereby increasing the coke burn-off rate. Therefore, in the actual operation and burn-off rate control of the dry quenching furnace, the CO concentration must be controlled within a reasonable range. This requires effectively increasing the initial temperature of the coke melting reaction within the furnace while ensuring safety. This necessitates reasonable control of the preheating air flow rate and strict temperature regulation, linking the preheating air flow rate and temperature to the composition of the dry quenching circulating gas and actual operating conditions. The core control system uses circulating air volume, CO concentration, coke discharge rate, and material level as parameters. It adjusts the preheating air flow valve based on the detected air-to-material ratio (circulating air volume / coke discharge rate), adjusts the set preheating temperature based on the material level and CO concentration, and uses the set gas preheating temperature as feedback to control the flow valve of the heating pipeline.

[0045] Specifically, based on the above analysis, taking a coking plant with a dry quenching capacity of 140 t / h as an example, the applicant further studied and found that: The material level in the dry quenching furnace is pre-divided into a first material level interval, a second material level interval, and a third material level interval, and the CO concentration in the furnace is divided into a first concentration interval and a second concentration interval. The first material level range is not less than 14m and not less than 16m, the second material level range is not less than 16m and not less than 18m, and the third material level range is not less than 18m and not more than 19m; The first concentration range is where the CO volume fraction is not less than 2% and not less than 4%, and the second concentration range is where the CO volume fraction is not less than 4% and not more than 7%. Based on the current material level range and the current CO concentration range, the flow rate and temperature of the introduced air are controlled accordingly, wherein: When the material is in the first material level range and the first concentration range, the airflow rate should be controlled to be 6000~12000 m³ / h. 3 / h, air temperature is 50~65℃; When the material is in the first material level range and the second concentration range, the airflow rate should be controlled to be 6000~10000 m³ / h. 3 / h, air temperature is 55~80℃; When the material is in the second material level range and the first concentration range, the airflow rate should be controlled to be 4000~10000 m³ / h. 3 / h, air temperature is 50~60℃; When the material is in the second material level range and the second concentration range, the airflow rate should be controlled to be 4000~9000 m³ / h. 3 / h, air temperature is 50~65℃; When the material is in the third material level range and the first concentration range, the airflow rate should be controlled to be 5000~10000 m³ / h. 3 / h, air temperature is 50~60℃; When the material is in the third material level range and the second concentration range, the airflow rate should be controlled to be 5000~9000 m³ / h. 3 / h, air temperature is 50~65℃.

[0046] A second aspect of the present invention also provides an integrated air preheating and dehumidification system for reducing burn-off and nitrogen consumption in dry quenching coke, comprising a low-temperature waste heat preheating unit and a control system disposed in the dry quenching coke system. The low-temperature waste heat preheating unit includes a low-temperature waste heat extraction pipeline, an air preheater, and a temperature regulating valve. One end of the low-temperature waste heat extraction pipeline is connected to the low-temperature waste heat supply unit of the dry quenching coke system via a blower, and the other end is connected to the air preheater. A temperature regulating valve is provided on the low-temperature waste heat extraction pipeline.

[0047] The air duct of the dry quenching system is no longer directly connected to the dry quenching furnace. Instead, it is connected to the air preheater and then to the dry quenching furnace through the air inlet pipe. This allows for the preheating and dehumidification of the introduced air. The air duct is equipped with a flow control valve to control the air flow rate, and the air inlet pipe is equipped with a temperature regulating valve to measure the temperature of the preheated air. The air is then introduced into the dry quenching furnace only after the set requirements are met.

[0048] The control system is electrically connected to all flow control valves and temperature regulating valves. The control system automatically controls the temperature regulating valve to detect the temperature of the medium in the pipeline in real time, and adjusts the valve opening according to the detected temperature, so as to heat the introduced air to the preset target temperature T.

[0049] The aforementioned low-temperature waste heat supply unit includes the tail flue of a dry quenching coke boiler, a boiler feedwater system, or a low-pressure steam network, used to supply low-temperature waste heat working fluid for preheating air.

[0050] The air preheater is a shell-and-tube heat exchanger or a plate heat exchanger, which has a hot side channel and a cold side channel. The inlet and outlet of the hot side channel are connected to the low-temperature waste heat extraction pipeline to form a waste heat circulation loop. The inlet of the cold side channel is connected to the outlet of the air pipeline, and the outlet of the cold side channel is connected to the air inlet pipe to introduce the preheated air into the dry quenching furnace.

[0051] Figure 1 The diagram illustrates the structure of a dehumidification system according to the present invention. The dehumidification system includes an existing dry quenching system, a low-temperature waste heat preheating unit located within the dry quenching system, and a controller (not shown in the diagram). The existing dry quenching system includes a dry quenching furnace 5, an air duct 4, a primary dust collector 7, a secondary dust collector 8, a circulating fan 6, and a waste heat boiler system 9. The top of the dry quenching furnace 5 is connected to the waste heat boiler system 9 via a duct and the primary dust collector 7. The waste heat boiler system 9, in turn, is connected to the dry quenching furnace 5 via a duct and the circulating fan 6, and transports the heat-exchanged flue gas back into the dry quenching furnace 5.

[0052] The low-temperature waste heat preheating unit includes a low-temperature waste heat extraction pipeline 1, an air preheater 2, and a temperature regulating valve. One end of the low-temperature waste heat extraction pipeline 1 is connected to the waste heat boiler system 9 of the dry quenching system via a blower 10, and the other end is connected to the air preheater 2. A first temperature regulating valve 11 is installed on the low-temperature waste heat extraction pipeline 1 for flow control and temperature detection of the extracted low-temperature working fluid. The air duct 4 is no longer directly connected to the dry quenching furnace 5, but is first connected to the cold side inlet of the air preheater 2 to preheat the introduced air, and then connected to the dry quenching furnace 5 via an air inlet pipe 3. A regulating valve 41 is installed on the air duct 4 to control the flow rate of the introduced air, and a second temperature regulating valve 31 is installed on the air inlet pipe 3 to stabilize the flow rate and temperature of the preheated air entering the dry quenching furnace 5.

[0053] The first temperature regulating valve 11, the second temperature regulating valve 31, and the regulating valve 41 are all connected to the control system. The control system can be a PLC, which can automatically measure the temperature of the regulating valves and adjust the valve opening through programming. At the same time, the air preheater 2 and the blower 10 are also connected to the control system, and the control system performs automatic control, thereby improving the level of automation of the system.

[0054] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The method of this invention differs from the traditional design approach of removing moisture from introduced air through adsorption and condensation. It creatively preheats the introduced air, significantly reducing its relative humidity without changing the absolute moisture content, but by increasing the temperature. Relative humidity, the ratio of water vapor partial pressure to saturated vapor pressure, is crucial in determining the migration of water molecules to the coke surface and the driving force of the reaction. Heating saturated air at room temperature (e.g., 30°C, RH 100%) to 70°C (RH drops to approximately 15%) does not change its water vapor partial pressure, but greatly suppresses the thermodynamic tendency for water-gas reaction. This solves the problem at the source of chemical equilibrium and reaction kinetics, with a direct logic and significant effect.

[0055] (2) The method of the present invention, by matching the temperature and flow rate of the preheating air for different working conditions, not only effectively suppresses the coke burning (dissolving) loss reaction, but also controls the flow rate of the preheating air introduced into the dry quenching furnace according to the material height, thereby controlling (increasing) the CO concentration in the furnace, so as to increase the initial reaction temperature of coke and further reduce the coke burning (dissolving) loss.

[0056] (3) The method and system of the present invention do not consume any high-quality energy (such as electricity, fuel, or fresh steam), but cleverly utilize the low-temperature waste heat that is difficult to utilize in the dry quenching system itself. The boiler tail flue gas (~120-150℃) and low-temperature steam have low heat grade and poor economic efficiency in conventional recovery and utilization, but they are just right for heating air to 50-80℃. This realizes the "targeted cascade utilization of waste heat", turning the original "burden" into a "resource", and the energy consumption (fan resistance) added to the system operation is extremely low, with huge economic advantages.

[0057] (4) The method of this invention suppresses the water-gas reaction at the source at extremely low cost, directly reducing carbon loss and increasing coke yield. Because the amount of H2 and CO produced by the water-gas reaction is reduced, the amount of nitrogen required to control their concentration can be reduced accordingly, saving the expensive cost of nitrogen production or purchasing. It eliminates the impact of seasonal and diurnal fluctuations in ambient air humidity on the composition of the circulating gas, making the system operate more smoothly and improving the level of automation control. While reducing burn-off and nitrogen consumption, it also indirectly reduces energy consumption and carbon emissions in the nitrogen production process.

[0058] (5) The dehumidification system of the present invention only requires the addition of a gas-to-gas or gas-to-liquid heat exchanger (air preheater) and corresponding pipelines and temperature control units to the existing system. It does not involve complex adsorption / desorption cycles, solid material conveying, regeneration heat sources and other equipment. The system complexity, investment cost and maintenance workload are far lower than existing adsorption dehumidification schemes. It has excellent compatibility with existing dry quenching systems, is simple to modify, and is relatively reliable in operation. Attached Figure Description

[0059] Figure 1This is a schematic diagram of an integrated air preheating and dehumidification system for reducing dry quenching burn-off and nitrogen consumption according to Embodiment 1 of the present invention. Figure 2 The values ​​represent the initial reaction temperatures of coke under different CO concentration atmospheres in this invention; where (a) is 1.5% CO, (b) is 3.5% CO, (c) is 5.5% CO, and (d) is 7.5% CO.

[0060] In the picture: 1. Low-temperature waste heat extraction pipeline; 11. First temperature regulating valve; 2. Air preheater; 3. Air inlet pipe; 31. Second temperature regulating valve; 4. Air pipeline; 41. Regulating valve; 5. Dry quenching furnace; 6. Circulating fan; 7. Primary dust collector; 8. Secondary dust collector; 9. Waste heat boiler system; 10. Blower. Detailed Implementation

[0061] It should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to facilitate the description of the present invention and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of the present invention.

[0062] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0063] It should be noted that, taking a 140t / h dry quenching coke oven in a certain coking plant as an example, the basic operating conditions of this dry quenching furnace are as follows: circulating gas CO concentration 2%~6% (i.e., CO volume fraction 2%~6%), coke discharge rate 80~120t / h, coke discharge temperature 160~180℃, and circulating air volume 100,000~180,000 m³ / h. 3 / h. Due to long-term operation, the overall burn-off rate of dry quenching coke is relatively high (greater than 2.5%). Dry quenching coke adopts air introduction method as the main control method and nitrogen supplementation dilution method as the auxiliary method. When the boiler inlet temperature T6 is >960℃ or <680℃ after air introduction, nitrogen should be quickly supplemented for dilution in the annular flue. Or when the oxygen content increases after air introduction and the volume fraction of O2 is >1% or the hydrogen content and CO content increase simultaneously and the volume fraction of H2 is >3%, nitrogen should be quickly supplemented for dilution at nitrogen charging points such as before / after the blower, annular flue, rotary sealing valve, and primary dust removal.

[0064] The present invention will be further described below with reference to specific embodiments.

[0065] Example 1 Reference Figure 1 This embodiment describes an integrated air preheating and dehumidification system and method for reducing coke burn loss and nitrogen consumption in dry quenching. The low-temperature waste heat extraction pipeline 1 is connected to the waste heat boiler system 9. Low-temperature waste heat working fluid is extracted from the waste heat boiler system 9 to preheat and dehumidify the air introduced into the dry quenching furnace 5. The specific operation is as follows: The low-temperature waste heat medium extracted from the waste heat boiler system 9 is 120℃. This temperature is monitored in real-time by the first temperature regulating valve 11 and the second temperature regulating valve 31 to ensure that the incoming ambient air at 20℃ and 70% relative humidity is stably heated to the target temperature of 60℃ in the air preheater 2. Finally, the preheated 60℃ ambient air is introduced into the dry quenching furnace 5. The material level in the furnace is 15.8m, and the CO concentration is 2.5%, therefore the air inlet flow rate is controlled at 8800m³ / h. 3 / h. After continuous control and production using the air introduction method for a period of time, when the oxygen content in the dry quenching furnace is detected to rise and the volume fraction of O2 is >1%, nitrogen dilution can be added inside the furnace until the dry quenching furnace condition returns to stability.

[0066] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured and statistically analyzed. The results are shown in Table 5.

[0067] Example 2 This embodiment describes an integrated air preheating and dehumidification system and method for reducing coke burn-off and nitrogen consumption in dry quenching. The low-temperature waste heat extraction pipeline 1 is connected to a low-pressure steam network. Low-temperature waste heat is extracted from the low-pressure steam network to preheat and dehumidify the air introduced into the dry quenching furnace 5. The dehumidification operation differs from that in Embodiment 1 in that the air is preheated to 70°C before being introduced into the dry quenching furnace 5. The material level inside the furnace is 15.6m, and the CO concentration is 4.5%. Therefore, the air flow rate is controlled at 8700 m³ / h. 3 / h.

[0068] After continuous control and production using the air introduction method for a period of time, when the oxygen content in the dry quenching furnace is detected to rise and the volume fraction of O2 is >1%, nitrogen dilution is performed until the dry quenching furnace condition returns to stability.

[0069] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured, and the results are shown in Table 5.

[0070] Example 3 This embodiment describes an integrated air preheating and dehumidification system and method for reducing coke burn-off and nitrogen consumption in dry quenching. The low-temperature waste heat extraction pipeline 1 is connected to a low-pressure steam network. Low-temperature waste heat is extracted from the low-pressure steam network to preheat and dehumidify the air introduced into the dry quenching furnace 5. The dehumidification operation differs from that in Embodiment 1 in that the air is preheated to 80°C before being introduced into the dry quenching furnace 5. The material level inside the furnace is 15.6m, and the CO concentration is 5%. Therefore, the air flow rate is controlled at 8430 m³ / h. 3 / h.

[0071] After continuous control and production using the air introduction method for a period of time, when the hydrogen content and CO content in the dry quenching furnace are detected to rise synchronously and the volume fraction of H2 is >3%, nitrogen dilution is performed until the dry quenching furnace condition returns to stability.

[0072] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured, and the results are shown in Table 5.

[0073] Example 4 This embodiment describes an integrated air preheating and dehumidification system and method for reducing coke burn-off and nitrogen consumption in dry quenching. The low-temperature waste heat extraction pipeline 1 is connected to a low-pressure steam network. Low-temperature waste heat is extracted from the low-pressure steam network to preheat and dehumidify the air introduced into the dry quenching furnace 5. The dehumidification operation differs from that in Embodiment 1 in that the air is preheated to 50°C before being introduced into the dry quenching furnace 5. The material level is 15.2m, and the CO concentration is 2%, therefore the air flow rate is controlled at 7890 m³ / h. 3 / h.

[0074] After continuous control and production using the air introduction method for a period of time, when the hydrogen content and CO content in the dry quenching furnace are detected to rise synchronously and the volume fraction of H2 is >3%, nitrogen dilution is performed until the dry quenching furnace condition returns to stability.

[0075] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured, and the results are shown in Table 5.

[0076] Example 5 This embodiment describes an integrated air preheating and dehumidification system and method for reducing coke burn-off and nitrogen consumption in dry quenching. The low-temperature waste heat extraction pipeline 1 is connected to a low-pressure steam network. Low-temperature waste heat is extracted from the low-pressure steam network to preheat and dehumidify the air introduced into the dry quenching furnace 5. The dehumidification operation differs from that in Embodiment 1 in that the air is preheated to 60°C before being introduced into the dry quenching furnace 5. The material level is 16m, and the CO concentration is 2.1%, therefore the air flow rate is controlled at 4000m³. 3 / h.

[0077] After continuous control and production using the air introduction method for a period of time, when the hydrogen content and CO content in the dry quenching furnace are detected to rise synchronously and the volume fraction of H2 is >3%, nitrogen dilution is performed until the dry quenching furnace condition returns to stability.

[0078] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured, and the results are shown in Table 5.

[0079] Example 6 This embodiment describes an integrated air preheating and dehumidification system and method for reducing coke burn-off and nitrogen consumption in dry quenching. The low-temperature waste heat extraction pipeline 1 is connected to a low-pressure steam network. Low-temperature waste heat is extracted from the low-pressure steam network to preheat and dehumidify the air introduced into the dry quenching furnace 5. The dehumidification operation differs from that in Embodiment 1 in that the air is preheated to 65°C before being introduced into the dry quenching furnace 5. The material level is 15.2m, and the CO concentration is 2%. Therefore, the air flow rate is controlled at 12000 m³ / h. 3 / h.

[0080] After continuous control and production using the air introduction method for a period of time, when the hydrogen content and CO content in the dry quenching furnace are detected to rise synchronously and the volume fraction of H2 is >3%, nitrogen dilution is performed until the dry quenching furnace condition returns to stability.

[0081] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured, and the results are shown in Table 5.

[0082] Comparative Example 1 In this comparative example, ambient air at 20°C and 70% relative humidity was directly introduced into the dry quenching furnace 5, and the introduction flow rate was the same as in Example 1.

[0083] After continuous control and production using the air introduction method for a period of time, when the oxygen content in the dry quenching furnace is detected to rise and the volume fraction of O2 is >1%, nitrogen dilution can be added inside the furnace until the dry quenching furnace condition returns to stability.

[0084] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured, and the results are shown in Table 5.

[0085] Comparative Example 2 This comparative example uses the air preheating and dehumidification system of Example 1. The difference between this system and Example 1 is that the air is preheated to 45°C and then introduced into the dry quenching furnace 5.

[0086] After continuous control and production using the air introduction method for a period of time, when the oxygen content in the dry quenching furnace is detected to rise and the volume fraction of O2 is >1%, nitrogen dilution can be added inside the furnace until the dry quenching furnace condition returns to stability.

[0087] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured, and the results are shown in Table 5.

[0088] Comparative Example 3 This comparative example uses the air preheating and dehumidification system of Example 1. The difference between this system and Example 1 is that the air is preheated to 40°C and then introduced into the dry quenching furnace 5.

[0089] After continuous control and production using the air introduction method for a period of time, when the oxygen content in the dry quenching furnace is detected to rise and the volume fraction of O2 is >1%, nitrogen dilution can be added inside the furnace until the dry quenching furnace condition returns to stability.

[0090] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured, and the results are shown in Table 5.

[0091] Comparative Example 4 This comparative example uses the air preheating and dehumidification system of Example 1. The difference between this system and Example 1 is that the air is preheated to 30°C and then introduced into the dry quenching furnace 5.

[0092] After continuous control and production using the air introduction method for a period of time, when the oxygen content in the dry quenching furnace is detected to rise and the volume fraction of O2 is >1%, nitrogen dilution can be added inside the furnace until the dry quenching furnace condition returns to stability.

[0093] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured, and the results are shown in Table 5.

[0094] Comparative Example 5 This comparative example uses the air preheating and dehumidification system of Example 1. The difference between this system and Example 1 is that the air is preheated to 90°C and then introduced into the dry quenching furnace 5.

[0095] After continuous control and production using the air introduction method for a period of time, when the hydrogen content and CO content in the dry quenching furnace are detected to rise synchronously and the volume fraction of H2 is >3%, nitrogen dilution can be added in the furnace until the dry quenching furnace condition returns to stability.

[0096] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured, and the results are shown in Table 5.

[0097] Comparative Example 6 This comparative example uses the air preheating and dehumidification system of Example 1. The difference between this system and Example 1 is that the material level in the dry quenching furnace 5 is 15.4m, the CO concentration is 2%, and the controlled air inlet flow rate is 4300m³. 3 / h.

[0098] After continuous control and production using the air introduction method for a period of time, when the oxygen content in the dry quenching furnace is detected to rise and the volume fraction of O2 is >1%, nitrogen dilution can be added inside the furnace until the dry quenching furnace condition returns to stability.

[0099] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured, and the results are shown in Table 5.

[0100] Comparative Example 7 This comparative example uses the air preheating and dehumidification system of Example 1. The difference between this system and Example 1 is that the material level in the dry quenching furnace 5 is 15.6m, the CO concentration is 6%, and the controlled air inlet flow rate is 11000m³. 3 / h .

[0101] After continuous control and production using the air introduction method for a period of time, when the oxygen content in the dry quenching furnace is detected to rise and the volume fraction of O2 is >1%, nitrogen dilution can be added inside the furnace until the dry quenching furnace condition returns to stability.

[0102] The coke burn-off rate and nitrogen consumption in the dry quenching furnace were measured, and the results are shown in Table 5.

[0103] Table 5. Coke burn-off rate and nitrogen consumption in dry quenching furnaces of various embodiments and comparative examples of the present invention.

[0104] As shown in Table 5, compared with Comparative Example 1, the dry quenching burn-off rate was reduced to some extent and nitrogen consumption was decreased in all examples after the introduction of preheated and dehumidified air. Specifically, under the dry quenching conditions corresponding to Example 2, the temperature of the introduced air was 70℃ and the flow rate was 8700 m³ / s. 3 At a rate of / h, the burn-off rate of dry quenching (1.72%) and nitrogen consumption (3600m³ / h) were [data missing]. 3 The lowest relative temperature ( / h) indicates that this treatment process can effectively reduce dry quenching coke burn-off and nitrogen consumption. Meanwhile, comparisons between the various examples and comparative examples show that the preheating temperature and flow rate of the introduced air need to be matched with the dry quenching coke circulating air volume, CO concentration, material level, and other operating conditions. Under the same dry quenching operating conditions, excessively high or low preheating temperatures of the introduced air will affect the burn-off rate and nitrogen consumption of the dry quenching coke. Compared with Example 1, in Comparative Examples 2, 3, and 4, after the preheating temperature of the introduced air was reduced from 60℃ to 45℃, 40℃, and 30℃ respectively, the burn-off rate of the dry quenching coke increased by 0.1%, 0.1%, and 0.11%, respectively, and the nitrogen consumption increased by 50m³ / h.3 / h、60m 3 / h and 40m 3 / h, in Comparative Example 5, increasing the air preheating temperature from 60℃ to 90℃ significantly increased the dry quenching burn-off rate by 0.17% and increased nitrogen consumption by 320m³. 3 / h. Furthermore, the airflow rate of Comparative Example 6 was too low, and the airflow rate of Comparative Example 7 was too high, both exceeding the required control range for the corresponding material level and CO concentration ranges. This resulted in an increase in dry quenching coke burn-off rate of 0.09% and 0.15%, respectively, and an increase in nitrogen consumption of 100m³. 3 / h and 400m 3 / h. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An integrated air preheating and dehumidification method for reducing coke burn loss and nitrogen consumption during dry quenching, characterized in that, Ambient air is preheated to a target temperature T (50℃~80℃) using a low-temperature waste heat medium at 60℃~200℃. The preheated ambient air is then transported to the dry quenching furnace via the air inlet pipe of the dry quenching system to replace nitrogen replenishment. The flow rate of the ambient air introduced into the dry quenching furnace is controlled to be 4000~12000 m³ / h. 3 / h.

2. The integrated air preheating and dehumidification method according to claim 1, characterized in that, The target temperature T of the preheated ambient air must satisfy: T ≥ ambient air dew point temperature + 20℃.

3. The integrated air preheating and dehumidification method according to claim 1, characterized in that, Considering the influence of material level height and CO concentration in the dry quenching furnace, the material level height in the dry quenching furnace is pre-divided into a first material level interval, a second material level interval, and a third material level interval, and the CO concentration in the furnace is divided into a first concentration interval and a second concentration interval. The first material level range is not less than 14m and not less than 16m, the second material level range is not less than 16m and not less than 18m, and the third material level range is not less than 18m and not more than 19m; The first concentration range is where the CO volume fraction is not less than 2% and not less than 4%, and the second concentration range is where the CO volume fraction is not less than 4% and not more than 7%. Based on the current material level range and the current CO concentration range, the flow rate and temperature of the introduced air are controlled accordingly, wherein: When the material is in the first material level range and the first concentration range, the airflow rate should be controlled to be 6000~12000 m³ / h. 3 / h, air temperature is 50~65℃; When the material is in the first material level range and the second concentration range, the airflow rate should be controlled to be 6000~10000 m³ / h. 3 / h, air temperature is 55~80℃; When the material is in the second material level range and the first concentration range, the airflow rate should be controlled to be 4000~10000 m³ / h. 3 / h, air temperature is 50~60℃; When the material is in the second material level range and the second concentration range, the airflow rate should be controlled to be 4000~9000 m³ / h. 3 / h, air temperature is 50~65℃; When the material is in the third material level range and the first concentration range, the airflow rate should be controlled at 5000~10000 m³ / h. 3 / h, air temperature is 50~60℃; When the material is in the third material level range and the second concentration range, the airflow rate should be controlled to be 5000~9000 m³ / h. 3 / h, air temperature is 50~65℃.

4. The integrated air preheating and dehumidification method according to claim 1, characterized in that, The low-temperature waste heat medium is a low-grade waste heat medium that is conventionally directly discharged from the dry quenching system and cannot be efficiently recovered and utilized. It is taken from at least one of the following: tail flue gas of the dry quenching boiler, boiler feedwater, or low-pressure steam.

5. An integrated air preheating and dehumidification system for performing the method as described in any one of claims 1-4, comprising a dry quenching system and an air duct (4), characterized in that, The dry quenching system is equipped with a low-temperature waste heat preheating unit and a control system, wherein: The low-temperature waste heat preheating unit includes a low-temperature waste heat extraction pipeline (1) and an air preheater (2). One end of the low-temperature waste heat extraction pipeline (1) is connected to the low-temperature waste heat supply unit of the dry quenching system through a blower (10), and the other end is connected to the air preheater (2). The air duct (4) is connected to the air preheater (2), and the air preheater (2) is connected to the dry quenching furnace (5) through the air inlet pipe (3). A second temperature regulating valve (31) is provided on the air inlet pipe (3). The second temperature regulating valve (31) is electrically connected to the control system.

6. The integrated air preheating and dehumidification system according to claim 5, characterized in that, The low-temperature waste heat extraction pipeline (1) is equipped with a first temperature regulating valve (11), which is electrically connected to the control system.

7. The integrated air preheating and dehumidification system according to claim 5, characterized in that, The air preheater (2) and the blower (10) are both electrically connected to the control system.

8. The integrated air preheating and dehumidification system according to claim 5, characterized in that, The air preheater (2) is a shell-and-tube, plate, or finned non-contact heat exchange device, with the heat medium channel and the air channel completely separated.

9. The integrated air preheating and dehumidification system according to any one of claims 5-8, characterized in that, The air duct (4) is equipped with a regulating valve (41), which is electrically connected to the control system.

10. The integrated air preheating and dehumidification system according to any one of claims 5-8, characterized in that, The low-temperature waste heat supply unit of the dry quenching system includes any one of the following: dry quenching boiler, feedwater boiler, or low-pressure steam pipeline.

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