A process for energy saving and consumption reduction in the cement industry

Abstract

The application discloses a process for energy saving and consumption reduction in the cement industry, and relates to the fields of hazardous waste collaborative treatment and flue gas denitration environmental protection technology, and comprises the following steps: step one, selecting liquid hazardous waste with a heat value in a certain range, and fully atomizing the liquid hazardous waste through compressed air and a special spray gun; step two, high-speed spraying the atomized liquid hazardous waste into a denitration furnace at a heat value liquid hazardous waste adding point in a denitration furnace system; step three, according to the temperature working condition and NO X concentration in the denitration furnace system, reducing the coal powder spraying amount of a coal spraying point of the denitration furnace, and adjusting the ammonia water consumption of an SNCR denitration system; step four, real-time monitoring the gas component concentration and temperature and pressure parameters of NO X , CO and other gases in flue gas through multiple detection points, significantly reducing coal consumption by replacing coal powder with the heat value of the liquid hazardous waste, and reducing ammonia water consumption by using hazardous waste combustion to supplement reducing gases such as CO and H2, and enhancing the self-denitration effect of the denitration furnace.

Description

Technical Field

[0001] This invention relates to the field of hazardous waste co-processing and flue gas denitrification environmental protection technology, specifically to a process for energy saving and consumption reduction in the cement industry. Background Technology

[0002] In the clinker production process of the cement industry, the high-temperature calcination (1350℃~1700℃) in the rotary kiln and the pre-decomposition of raw materials in the decomposition furnace (800℃~980℃) generate a large amount of thermal and fuel-type NO. x Not only does it harm human health, but it also causes photochemical smog pollution. With increasingly stringent environmental standards, the China Cement Association's group standard, "Ultra-Low Emission Standard for Air Pollutants in the Cement Industry," requires existing cement enterprises to meet NOx emission standards. x Emission concentrations of ≤100mg / m³ place higher demands on denitrification technology.

[0003] Currently, mainstream denitrification technologies for cement kilns include self-denitrification in denitrification furnaces, SNCR denitrification systems, and staged combustion. Among these, the denitrification furnace reduces NO₂ produced by the incomplete combustion of pulverized coal using CO. x The SNCR system further reduces the remaining NO by injecting ammonia. x Meanwhile, the co-processing of hazardous waste in cement kilns has become an important method for the harmless treatment of hazardous waste. However, existing technologies for utilizing calorific value liquid hazardous waste are limited to the "disposal" level, failing to fully explore its energy-saving and denitrification potential: the high calorific value of liquid hazardous waste has not been used to replace pulverized coal, resulting in high fuel consumption; the promoting effect of hazardous waste combustion on denitrification reactions has not been developed, leading to persistently high ammonia consumption in SNCR systems; and the dosing location is not well matched with the process, making it impossible to effectively supplement reducing gases to enhance the denitrification effect.

[0004] Therefore, there is an urgent need for a process technology that can deeply integrate the treatment of calorific value liquid hazardous waste with energy-saving denitrification, so as to achieve multiple goals such as high-value utilization of hazardous waste, reduction of coal consumption and improvement of denitrification efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a process for energy saving and consumption reduction in the cement industry, in order to solve the problems of high fuel consumption in existing denitrification furnaces; undeveloped promotion effect of hazardous waste combustion on denitrification reaction; high ammonia water consumption in SNCR system; and insufficient matching between the injection location and process, which makes it impossible to effectively supplement reducing gas to enhance the denitrification effect.

[0006] A process for energy conservation and emission reduction in the cement industry includes the following steps:

[0007] Step 1: Preparation for adding liquid hazardous waste with calorific value: Select liquid hazardous waste with a calorific value in the range of 4500-6000 kcal / kg or 10000-12000 kcal / kg, and fully atomize it using compressed air and a special spray gun;

[0008] Step 2, Selection and control of the addition location: At the addition point of calorific value liquid hazardous waste in the denitrification furnace system, the atomized liquid hazardous waste is sprayed into the denitrification furnace at a high speed of 0.5-1.2 m³ / h.

[0009] Step 3: Adjustment of operating parameters: Based on the temperature and NOx concentration in the denitrification furnace system, reduce the amount of pulverized coal injected at the pulverized coal injection point of the denitrification furnace to keep the temperature of the denitrification furnace system stable; at the same time, based on the NOx concentration data at the detection point, adjust the ammonia water usage of the SNCR denitrification system to ensure that the NOx concentration of flue gas at the chimney outlet is controlled within the range of 90-100 mg / m³.

[0010] Step 4: Effect Monitoring: By setting up detection points at the kiln tail flue, the middle of the denitrification furnace, the outlet of the denitrification furnace, the outlet of the decomposition furnace, the outlet of the preheater, and the outlet of the chimney, the concentration, temperature, and pressure parameters of NOx and CO gas components in the flue gas are monitored in real time to verify the energy-saving denitrification effect.

[0011] Preferably, in step one, the droplet size of the liquid hazardous waste after atomization is controlled at 50-150 μm to ensure complete combustion in the denitrification furnace.

[0012] Preferably, in step two, the point for adding the calorific value liquid hazardous waste is located in the downstream area of ​​the denitrification furnace system, near the coal injection point of the denitrification furnace, and the spraying direction of the spray gun forms an angle of 30°-60° with the flue gas flow direction in the denitrification furnace.

[0013] Preferably, in step three, the reduction in the amount of pulverized coal injected is matched with the calorific value and dosage of the liquid hazardous waste. When the calorific value of the liquid hazardous waste is 10,000-12,000 kcal / kg and the dosage is 0.8-1.2 m³ / h, the reduction in the amount of pulverized coal is 6.84-10.68 kg / tcl.

[0014] Preferably, in step three, the ammonia water usage of the SNCR denitrification system is adjusted based on online monitoring data at the chimney outlet. When the NOx concentration is below 90 mg / m³, the ammonia water usage is reduced; when it is above 100 mg / m³, the ammonia water usage is increased, thereby reducing the ammonia water consumption per ton of clinker by 0.11-0.47 kg / tcl.

[0015] Preferably, in step four, the monitoring frequency of each detection point is not less than once per hour, and the detection data is transmitted to the central control system in real time to guide the adjustment of operating parameters.

[0016] Preferably, this technology is suitable for cement kiln co-processing hazardous waste production lines with denitrification furnaces and SNCR denitrification systems, or for industrial kiln systems in power plants, smelters, and other facilities that require reduced NOx emissions from flue gas.

[0017] The advantages of this invention are as follows: The energy-saving and consumption-reducing process for the cement industry utilizes the calorific value of liquid hazardous waste to replace pulverized coal, significantly reducing coal consumption by 5.28-10.68 kg / tcl for actual clinker and 4.53-9.15 kgce / tcl for standard coal consumption; the combustion of hazardous waste supplements reducing gases such as CO and H2, enhancing the self-denitrification effect of the denitrification furnace, reducing ammonia water consumption by 0.11-0.47 kg / tcl for ammonia water consumption; and transforming calorific value liquid hazardous waste from "waste" into energy and denitrification auxiliary resources, achieving the dual goals of harmlessness and resource utilization, and maximizing the value of hazardous waste. Attached Figure Description

[0018] Figure 1 This is a process diagram for adding calorific value liquid hazardous waste in this invention.

[0019] The points are as follows: 1. Detection point 1; 2. Coal injection point of denitrification furnace; 3. Slurry and slag addition point; 4. Addition point of calorific value liquid hazardous waste; 5. Detection point 2; 6. Denitrification furnace system; 7. Detection point 3; 8. Tertiary air; 9. Coal injection point of decomposition furnace; 10. Decomposition furnace system; 11. Detection point 4; 12. SNCR denitrification system; 13. Detection point 5; 14. Detection point 6. Detailed Implementation

[0020] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0021] like Figure 1 As shown, a process for energy conservation and consumption reduction in the cement industry includes the following steps:

[0022] Step 1: Preparation for adding liquid hazardous waste with calorific value: Select liquid hazardous waste with a calorific value of 4500-6000 kcal / kg or 10000-12000 kcal / kg, and atomize it into droplets with a particle size of 50-150 μm using compressed air and a special spray gun to ensure complete combustion;

[0023] Step 2, Precise Dosing Control: Set up a dosing point in the area downstream of the coal injection point of the denitrification furnace system. The spraying direction of the spray gun is at an angle of 30°-60° with the flue gas flow direction. The atomized liquid hazardous waste is sprayed into the denitrification furnace at a high speed of 0.5-1.2 m³ / h.

[0024] The area through which the flue gas flows is designated as Serial Number 6 - Denitrification Furnace System. The denitrification mechanism of this system is as follows: pulverized coal is injected from the coal distribution point at Serial Number 2 - Denitrification Furnace. A large number of pulverized coal particles undergo incomplete combustion in an oxygen-deficient environment, producing a large amount of CO reducing gas. This reducing gas then reacts with NOx in the flue gas in an oxidation-reduction reaction, reducing it to non-polluting gases such as N2, thus achieving the denitrification purpose of this area. Serial Number 3 in the diagram represents the slurry / slag addition point during normal co-processing. In both the blank test and the industrial test, the slurry / slag at this addition point was in normal operating condition. A high-calorific-value liquid hazardous waste addition point (No. 4 - calorific-value waste liquid addition point) is added at a suitable location within the denitrification furnace pipeline. At this point, the high-calorific-value liquid hazardous waste is fully atomized by compressed air and a special spray gun and then sprayed at high speed into the denitrification furnace. The fully atomized calorific-value hazardous waste droplets undergo incomplete combustion within the denitrification furnace, generating a large amount of heat and reducing gases. To maintain the temperature within the denitrification furnace system at its previous operating conditions, the amount of pulverized coal injected at (No. 2 - denitrification furnace coal distribution point) needs to be reduced. This reduces the amount of pulverized coal used in the denitrification furnace system, thereby reducing fuel consumption. The effect of consumption: After the high-calorific-value waste liquid is atomized and sprayed into a suitable location, although the amount of pulverized coal used is reduced due to its high calorific value, resulting in a decrease in the amount of CO reducing gas generated by pulverized coal in the flue gas, the waste liquid contains a certain amount of water. This water rapidly vaporizes in the high-temperature environment of the denitrification furnace and reacts with the pulverized coal particles: C + H₂O → CO + H₂. This replenishes the CO in the flue gas to a certain extent while also generating new reducing gas H₂, increasing the types and amount of reducing gases in the flue gas of the denitrification furnace, thereby enhancing the denitrification effect. The combined effect of these two aspects means that adding high-calorific-value liquid hazardous waste achieves the dual benefits of reducing pulverized coal usage and promoting flue gas denitrification while saving ammonia water usage in the subsequent 12-SNCR denitrification system.

[0025] Step 3: Coordinated Adjustment of Operating Parameters

[0026] Fuel substitution: Based on the calorific value and dosage of the liquid hazardous waste, reduce the amount of pulverized coal used at the pulverized coal injection point of the denitrification furnace to keep the temperature of the denitrification furnace system stable (800℃~980℃).

[0027] Denitrification optimization: Real-time monitoring of NO at detection points x Adjust the ammonia water dosage in the SNCR denitrification system to ensure adequate NO concentration at the chimney outlet. x The concentration should be controlled at 90-100 mg / m³;

[0028] The changes in parameters such as NOx and CO concentrations in the flue gas inside the denitrification furnace after the addition of high-calorific-value liquid hazardous waste can be detected by flue gas detection instruments at points 5-2 (middle of the denitrification furnace) and 7-3 (outlet of the denitrification furnace). After exiting the denitrification furnace system, the flue gas enters the second main reaction unit of the kiln tail preheating and pre-decomposition system—the decomposition furnace system. The decomposition furnace system is responsible for decomposing approximately 95% of the CaCO3 in the raw materials, resulting in about 60% of the fuel (pulverized coal) being consumed there. As shown in the diagram, five pulverized coal injection points are set at different locations (9) of the decomposition furnace, indicating staged combustion. The oxygen required for combustion is provided by the tertiary air (8). Consequently, a large amount of NOx is generated in the decomposition furnace system (10). The NOx concentration in the flue gas can be detected at detection point 4 (11) (decomposition furnace outlet). The flue gas and entrained raw material powder from the decomposition furnace outlet are divided into two streams, entering the C5A and C5B cyclone separator units respectively. Multiple ammonia water injection points are set at different locations in these two cyclone separator units, leading to the flow into the kiln tail preheating and pre-decomposition furnace system (1). The 2-SNCR denitrification system unit, also known as selective non-catalytic reduction technology, mainly uses atomized ammonia water reducing agent to reduce the large amount of NOx generated in the decomposition furnace and the remaining NOx after removal in the denitrification furnace into non-polluting gases such as N2, ensuring that the NOx concentration emitted into the atmosphere meets environmental emission requirements. As shown in the figure, there are two detection points: Detection Point 5 (preheater outlet) at number 13 and Detection Point 6 (chimney outlet) at number 14. Since there are no new NOx generation links in the subsequent C4A~C1A and C4B~C1B production processes after denitrification by the SNCR system at number 12, the NOx detection data at detection points 5 and 6 are generally similar. Detection point 6 is equipped with online monitoring instruments in accordance with environmental management requirements, which can monitor the composition of flue gas emitted into the atmosphere in real time around the clock. The SNCR denitrification system (number 12 in the diagram) is the final denitrification stage of this project. The reduction and control of NOx in the flue gas exiting the decomposition furnace can be achieved by adjusting the amount of ammonia used as a reducing agent. This ensures that the NOx concentration at detection point 6 (chimney outlet, number 14) is controlled within the limit (this project requires NOx to be controlled at 90~100 mg / m³). 3 Within the specified range, that is: the change in the amount of ammonia water used as the reducing agent in the SNCR denitrification system (serial number 12) is actually adjusted in real time by the operators in the central control room based on the fluctuations in the online monitoring data at monitoring point 6 (chimney outlet) (serial number 14). When the NOx concentration in the flue gas online monitoring data is below 90 mg / m³, the adjustment is made accordingly. 3 When the NOx concentration in the flue gas exceeds 100 mg / m³, the operator should immediately reduce the ammonia dosage appropriately. 3At the same time, the operator would appropriately increase the amount of ammonia water. Through repeated observation and operation, the NOx concentration in the online monitoring data was dynamically controlled between 90 and 100 mg / m³. 3 Within the range.

[0029] Step 4: Full-process effect monitoring: Monitor flue gas temperature, pressure, and NO at least once per hour through monitoring points at the kiln tail flue, the middle of the denitrification furnace, the denitrification furnace outlet, the decomposition furnace outlet, the preheater outlet, and the chimney outlet. x The system monitors CO and O2 concentrations, providing real-time feedback and optimizing operating conditions.

[0030] When the high-temperature flue gas from the cement kiln flows through detection point 1 (kiln tail flue chamber), it enters the first reaction unit of the kiln tail preheating and pre-decomposition system—the denitrification furnace system. At detection point 1, flue gas monitoring instruments can detect the temperature, pressure parameters, and concentrations of gaseous components such as NOx, CO, and O2 in real time. The NOx concentration can be used as the initial concentration for this study. The NOx concentrations at the subsequent five detection points will be compared with this initial NOx concentration to measure the denitrification effect at each detection location of the denitrification system. In the denitrification furnace reaction unit, some raw meal powder, separated into the C4B cyclone separator unit, can achieve partial pre-decomposition of the raw meal within the denitrification furnace system.

[0031] Example 1: Experiment on the addition of high-calorific-value liquid hazardous waste

[0032] Hazardous waste preparation: Select liquid hazardous waste with a calorific value of 10,000-12,000 kcal / kg, and atomize it with a special spray gun (nozzle diameter 1.5 mm) and 0.6 MPa compressed air, with the droplet size controlled at 80-120 μm;

[0033] Dosing control: At dosing point 4 of the denitrification furnace system (1.5m downstream of coal injection point 2 of the denitrification furnace), inject at a flow rate of 0.8-1.2m³ / h, with the spray gun at a 45° angle to the flue gas flow direction;

[0034] Parameter adjustment:

[0035] Coal powder substitution: The amount of coal powder used at point 2 of the denitrification furnace was reduced by 10.68 kg / tcl (actual coal consumption), and the temperature of the denitrification furnace was maintained at 850℃-950℃;

[0036] Ammonia water adjustment: Based on detection point 14 (chimney outlet) NO x With a concentration of 94.50 mg / m³, the average hourly ammonia water consumption of the SNCR denitrification system decreased by 106.79 kg / h, and the ammonia water consumption per ton of clinker decreased by 0.47 kg / tcl.

[0037] Monitoring results: The CO concentration at the denitrification furnace outlet (detection point 7) increased by 120 ppm compared to the blank test; the NO concentration at the decomposition furnace outlet (detection point 11) increased... x A 15% reduction in concentration at the chimney outlet NO x It remained stable at 94.50 mg / m³.

[0038] Example 2: Experiment on the addition of medium-calorific-value liquid hazardous waste

[0039] Hazardous waste preparation: Select liquid hazardous waste with a calorific value of 4500-6000 kcal / kg, and atomize it with 0.5 MPa compressed air through a spray gun, with the droplet size controlled at 50-100 μm;

[0040] Dosing control: Inject at a flow rate of 1.0 m³ / h at dosing point 4 of the denitrification furnace, with the spray gun at an angle of 30° to the flue gas flow direction;

[0041] Parameter adjustment:

[0042] Coal powder substitution: The amount of coal powder used at point 2 of the denitrification furnace was reduced by 5.28 kg / tcl (actual coal consumption), and the temperature of the denitrification furnace was maintained at 800℃-900℃;

[0043] Ammonia adjustment: According to the detection point 14NO x With a concentration of 95.76 mg / m³, the average hourly ammonia consumption decreased by 66.02 kg / h, and the ammonia consumption per ton of clinker decreased by 0.29 kg / tcl.

[0044] Monitoring results: The H2 concentration in the middle of the denitrification furnace (detection point 5) increased by 80 ppm compared with the blank test, and the NO at the chimney outlet... x It remained stable at 95.76 mg / m³.

[0045] Example 3: Blank Control Experiment

[0046] Without the addition of liquid hazardous waste, the pulverized coal consumption at point 2 of the denitrification furnace is 157.97 kg / tcl (actual coal consumption), the hourly average ammonia water consumption of the SNCR system is 560.38 kg / h, the ammonia water consumption per ton of clinker is 2.45 kg / tcl, and the NO at the chimney outlet is... x Concentration 94.49 mg / m³.

[0047] Results analysis:

[0048] During the treatment of two types of liquid hazardous waste with calorific values ​​ranging from 4500-6000 kcal / kg and 10000-12000 kcal / kg respectively at appropriate locations in a denitrification furnace, the flow rate was controlled at 0.5-1.2 m³ / kg. 3Within the range of / h, compared with the operating condition without the addition of liquid hazardous waste, when the NOx concentration in the flue gas emitted into the atmosphere is controlled within the same range of 90-100 mg / m³, compared with Examples 1 and 2 and the blank test, using the above-mentioned liquid hazardous waste with a certain calorific value can reduce the actual coal consumption of clinker combustion by 5.28-10.68 kg / tcl, which is equivalent to 4.53-9.15 kgce / tcl in standard coal consumption. The amount of reduction in actual coal consumption per ton of clinker depends on the calorific value of the liquid hazardous waste and the time of addition. The higher the calorific value of the liquid hazardous waste and the higher the dosage, the more significant the reduction in actual coal consumption. The reduction in coal consumption per ton of clinker is significant. The experimental data are shown in Table 1. Before and after the addition of liquid hazardous waste with calorific value, when the NOx content in the flue gas emitted into the atmosphere is controlled within the same range of 90-100 mg / m³, 3 When the calorific value of the liquid hazardous waste within the above-mentioned range is specified, adding it can reduce the average hourly ammonia consumption by 24.69 kg / h to 106.79 kg / h. Converted to ammonia consumption per ton of clinker, this translates to a reduction of 0.11 to 0.47 kg / tcl. The reduction in ammonia consumption per ton of clinker is significant, as shown in Table 2. This invention, by adding liquid hazardous waste with a specific calorific value, ensures that NO... x Under the premise of meeting emission standards, the coal consumption and ammonia water consumption were significantly reduced, verifying the effectiveness of the technical solution.

[0049]

[0050]

[0051] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

Claims

1. A process for energy conservation and consumption reduction in the cement industry, characterized in that: Includes the following steps: Step 1: Preparation for adding liquid hazardous waste with calorific value: Select liquid hazardous waste with a calorific value in the range of 4500-6000 kcal / kg or 10000-12000 kcal / kg, and fully atomize it using compressed air and a special spray gun; Step 2, Selection and Control of Dosing Location: At the dosing point for calorific value liquid hazardous waste within the denitrification furnace system, the atomized liquid hazardous waste is dispensed at a depth of 0.5-1.2m. 3 A flow rate of / h is injected at high speed into the denitrification furnace; Step 3: Adjust operating parameters: Based on the temperature and NO conditions within the denitrification furnace system... X To reduce the concentration of pulverized coal and decrease the amount of pulverized coal injected into the denitrification furnace, the temperature of the denitrification furnace system should be kept stable. Simultaneously, based on the NO concentration at the detection points... X Based on the concentration data, adjust the ammonia water dosage of the SNCR denitrification system to ensure that the NO concentration in the flue gas at the chimney outlet is within acceptable limits. X Concentration controlled at 90-100 mg / m³ 3 Within the range; Step 4: Effect Monitoring: NO in the flue gas is monitored in real time at detection points set up at the kiln tail flue, the middle of the denitrification furnace, the denitrification furnace outlet, the decomposition furnace outlet, the preheater outlet, and the chimney outlet. X The concentration of CO gas components, as well as temperature and pressure parameters, were used to verify the energy-saving denitrification effect. In step one, the droplet size of the liquid hazardous waste after atomization is controlled at 50-150μm to ensure complete combustion in the denitrification furnace; In step two, the point for adding calorific value liquid hazardous waste is located in the downstream area of ​​the denitrification furnace system, near the coal injection point of the denitrification furnace, and the spraying direction of the spray gun forms an angle of 30°-60° with the flue gas flow direction in the denitrification furnace.

2. The process for energy conservation and consumption reduction in the cement industry according to claim 1, characterized in that: In step three, the reduction in the amount of pulverized coal injected is matched to the calorific value and dosage of the liquid hazardous waste. This applies when the calorific value of the liquid hazardous waste is 10000-12000 kcal / kg and the dosage is 0.8-1.2 m³. 3 When the coal powder consumption rate is 6.84-10.68 kg / tcl, the coal powder consumption rate is reduced by 6.84-10.68 kg / tcl.

3. The process for energy conservation and consumption reduction in the cement industry according to claim 1, characterized in that: In step three, the ammonia water dosage of the SNCR denitrification system is adjusted based on online monitoring data at the chimney outlet. When NO X Concentration below 90 mg / m 3 Reduce ammonia usage when it exceeds 100 mg / m³. 3 Increasing the amount of ammonia water used can reduce the ammonia water consumption per ton of clinker by 0.11-0.47 kg / tcl.

4. The process for energy conservation and consumption reduction in the cement industry according to claim 1, characterized in that: In step four, the monitoring frequency of each detection point is no less than once per hour, and the detection data is transmitted to the central control system in real time to guide the adjustment of operating parameters.

5. The process for energy conservation and consumption reduction in the cement industry according to claim 1, characterized in that: This process is suitable for cement kiln co-processing hazardous waste production lines equipped with denitrification furnaces and SNCR denitrification systems, or for power plants and smelters requiring reduction of NO in flue gas. X Industrial kiln systems that emit pollutants.

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