Energy-saving operation method of preheating and pre-decomposing system for cement production

Abstract

The invention relates to the technical field of preheating and predecomposition in cement production, and discloses an energy-saving operation method of a preheating and predecomposition system for cement production. Energy saving is achieved through cooperative control of raw material components and the temperature of the preheater. According to the raw material component control, 2.02.5% by mass of specific coal gangue is added into the raw material, the initial decomposition temperature of calcium carbonate is reduced by utilizing the chemical characteristics of the specific coal gangue, and advanced decomposition of the raw material in a C1C4-level preheater is promoted. According to the preheater temperature control, the outlet temperatures of C1C4-grade preheaters are actively increased to about 340 DEG C, 520 DEG C, 640 DEG C and 800 DEG C respectively, so that the total decomposition rate of raw materials before the raw materials enter a C5-grade preheater is greatly increased. On the basis, the C5 outlet temperature can be reduced to about 840 DEG C on the premise that the kiln-entering decomposition rate is not changed, and the energy input of the decomposing furnace is reduced. The system heat distribution is effectively optimized, the problem of high energy consumption caused by excessive dependence on a decomposing furnace in the prior art is solved, and the fuel consumption of a unit product is remarkably reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of preheating and pre-decomposition in cement production, and particularly relates to an energy-saving operation method for a preheating and pre-decomposition system in cement production. BACKGROUND

[0002] The cement industry is an energy-intensive industry, and the sintering process of raw meal in a rotary kiln has the highest energy consumption. In order to reduce energy consumption, modern cement production generally uses a rotary kiln with a preheating and pre-decomposition system. In this system, the raw meal first passes through multiple stages of cyclone preheaters (usually four or five stages) in sequence, and is gradually preheated through countercurrent heat exchange with high-temperature exhaust gas discharged from the rotary kiln. Subsequently, the preheated raw meal enters a decomposition furnace, where it meets the coal powder injected into the furnace and undergoes intense combustion and calcium carbonate decomposition reactions, with most of the calcium carbonate being decomposed into calcium oxide and carbon dioxide at this point. Finally, the pre-decomposed raw meal enters the rotary kiln to complete the clinker sintering process.

[0003] The in-kiln decomposition rate refers to the percentage of calcium carbonate (CaCO3) in the raw meal that has been decomposed into calcium oxide (CaO) and carbon dioxide (CO2) before entering the rotary kiln. The in-kiln decomposition rate is an important parameter (usually targeting 92%-95%). To achieve this target, the decomposition furnace usually needs to operate at a relatively high temperature (e.g., above 880°C), which requires a continuous supply of a large amount of fuel to the decomposition furnace and the last-stage cyclone preheater C5 to maintain the temperature of the decomposition furnace and the last-stage cyclone preheater C5 above 880 degrees, directly leading to high unit coal consumption in the raw meal curing process. SUMMARY

[0004] In view of the above problems, the embodiments of the present application provide an energy-saving operation method for a preheating and pre-decomposition system in cement production, which cooperatively uses raw meal component control and preheater temperature control to effectively reduce unit coal consumption.

[0005] According to an aspect of the embodiments of the present application, an energy-saving operation method for a preheating and pre-decomposition system in cement production is provided. The energy-saving operation method for the preheating and pre-decomposition system in cement production cooperatively uses raw meal component control and preheater temperature control. The raw meal component control includes that the raw meal contains coal gangue, and the mixing amount of the coal gangue is configured to be able to reduce the calcium carbonate decomposition starting temperature of the raw meal and promote the early decomposition of the raw meal in the C1-C4 stage preheater. The preheater temperature control includes that the operating temperature of at least one upper preheater except the last stage in the pre-decomposition system is actively raised, so that the overall decomposition rate of the raw meal before entering the last-stage preheater is improved. Based on the improved decomposition rate, the energy input of the decomposition furnace associated with the last-stage preheater is reduced, thereby achieving the reduction of unit product fuel consumption of the entire system.

[0006] In some embodiments, the pre-decomposition system is a five-stage preheating pre-decomposition system, the upper preheaters are first to fourth stage cyclone preheaters (C1-C4), and the last stage preheater is a fifth stage cyclone preheater (C5).

[0007] In some embodiments, in the five-stage preheating pre-decomposition system, the temperature of each stage preheater is controlled as follows: the outlet temperature of preheater C1 is 340℃±10℃; the outlet temperature of preheater C2 is 520℃±10℃; the outlet temperature of preheater C3 is 640℃±10℃; the outlet temperature of preheater C4 is 800℃±10℃; and the outlet temperature of preheater C5 is 840℃±10℃.

[0008] In some embodiments, in the raw material, the components of each component are as follows: limestone 80-85 components, silica debris 7-8 components, low-alkali sulfur slag 2.5-3 components, coal ash powder 4 components, and coal gangue 2.5 components.

[0009] In some embodiments, the chemical composition of the coal gangue satisfies: the SiO2 content is 40%-55%, the Al2O3 content is 20%-30%, and the fixed carbon content is 5%-10%; and the mass ratio of the coal gangue in the raw material is controlled between 2-2.5%.

[0010] In some embodiments, before actively increasing the operating temperature of the upper preheater, it is necessary to confirm that the material scattering box function of the C3 and C4 stage cyclone preheater downpipe is normal, so as to ensure that the raw material can form a uniform material curtain in the rising pipe and fully exchange heat with the hot flue gas.

[0011] In some embodiments, the reduction of energy input to the decomposition furnace is specifically manifested as: reducing the outlet temperature set value of the decomposition furnace by 20-40℃.

[0012] The beneficial effects in the present application are: 1. The present application promotes the temperature of C1-C4 stage preheaters and uses coal gangue to promote the early decomposition of raw materials, which directly reduces the heat load of the decomposition furnace, so that the coal feeding amount of the decomposition furnace can be significantly reduced under the premise of maintaining the same kiln decomposition rate, and the kiln head coal consumption can also be reduced simultaneously due to the improvement of system thermal efficiency, thereby realizing a decrease of more than 3% in the comprehensive coal consumption per unit product of the system.

[0013] 2. The application breaks the inherent idea of traditional technology that excessively relies on the decomposition furnace. By active regulation, part of the reaction heat and heat is distributed to the C1-C4 stage preheater, so that the system thermal distribution is more reasonable. This not only greatly reduces the outlet temperature of the last stage cyclone (C5), reduces the heat loss caused by the direct discharge of high-temperature exhaust gas to the upper preheater, but also improves the heat exchange efficiency of the preheater system as a whole, breaking through the energy efficiency bottleneck of the existing technology.

[0014] 3. In the application, coal gangue is added as a functional raw material. Not only does it play a catalytic and combustion-supporting role, but it also realizes the resource utilization of industrial solid waste. This conforms to the development direction of green circular economy, reduces production costs, and brings good environmental benefits.

[0015] The above description is only a summary of the technical solutions of the application. In order to more clearly understand the technical means of the application, the specific embodiments of the application can be implemented in accordance with the content of the specification, and in order to make the above and other purposes, features and advantages of the application more obvious and easy to understand, the following specific embodiments of the application are described. DETAILED DESCRIPTION

[0016] The embodiments of the technical solutions of the application will be described in detail below. The following examples are only used to more clearly illustrate the technical solutions of the application, and therefore only serve as examples, and cannot limit the protection scope of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as understood by those skilled in the art to which the application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the application; the terms "include" and "have" and any variations thereof in the specification and claims of the application are intended to cover non-exclusive inclusion.

[0017] An energy-saving operation method for a preheating and pre-decomposition system for cement production, which cooperatively uses raw material component control and preheater temperature control; the raw material component control includes that the coal gangue is contained in the raw material, and the mixing amount of the coal gangue is configured to be able to reduce the calcium carbonate decomposition starting temperature of the raw material, and promote the early decomposition of the raw material in the C1-C4 stage preheater; the preheater temperature control includes that the operating temperature of at least one upper preheater except the last stage in the pre-decomposition system is actively raised, so that the overall decomposition rate of the raw material before entering the last stage preheater is improved; based on the improved decomposition rate, the energy input of the decomposition furnace associated with the last stage preheater is reduced, thereby realizing the reduction of unit product fuel consumption of the whole system.

[0018] In some embodiments, the pre-decomposition system is a five-stage preheating pre-decomposition system, the upper preheaters are first to fourth stage cyclone preheaters (C1-C4), and the last stage preheater is a fifth stage cyclone preheater (C5).

[0019] In some embodiments, in the five-stage preheating pre-decomposition system, the temperature of each stage preheater is controlled as follows: the outlet temperature of preheater C1 is 340℃±10℃; the outlet temperature of preheater C2 is 520℃±10℃; the outlet temperature of preheater C3 is 640℃±10℃; the outlet temperature of preheater C4 is 800℃±10℃; and the outlet temperature of preheater C5 is 840℃±10℃.

[0020] In some embodiments, in the raw material, the components are as follows: limestone 80-85 components, silicon stone debris 7-8 components, low-alkali sulfuric acid slag 2.5-3 components, coal ash powder 4 components, and coal gangue 2.5 components.

[0021] In some embodiments, the chemical composition of the coal gangue satisfies: SiO2 content is 40%-55%, Al2O3 content is 20%-30%, and fixed carbon content is 5%-10%; and the mass ratio of the coal gangue in the raw material is controlled between 2-2.5%.

[0022] In some embodiments, before actively increasing the operating temperature of the upper preheater, it is necessary to confirm that the material scattering box function of the C3 and C4 stage cyclone preheater downpipe is normal, so as to ensure that the raw material can form a uniform material curtain in the rising pipe and fully exchange heat with the hot flue gas.

[0023] In some embodiments, the reduction of energy input to the decomposition furnace is specifically manifested as: reducing the outlet temperature set value of the decomposition furnace by 20-40℃.

[0024] The following are actual production data: Control group: Normal batching, the duration of this batch is 4d, the rotary kiln feeding amount is controlled at 170±1t / h, the limestone proportion is 83.7±2%, the siliceous raw material ratio is 7.0±0.5%, the low-alkali sulfuric acid residue ratio is 2.8±0.2%, the dry fly ash ratio is 6.5±0.2%, the raw material composition is controlled within the normal range according to the batching scheme, the decomposition furnace calcination temperature is normally controlled at 855-865℃, and the production system runs normally. The raw material batching is according to KH: 0.960±0.02, the qualified rate is ≥85%, N: 2.75±0.10, the qualified rate is ≥85%, P: 1.35±0.10, the qualified rate is ≥85%, 80μm: 20±2.0%, the qualified rate is ≥85%, 0.2%μm, the qualified rate is ≤3.0%; the clinker is according to KH: 0.910±0.02, the qualified rate is ≥90%, N: 2.70±0.10, the qualified rate is ≥90%, P: 1.30±0.10, the qualified rate is ≥90%. The preheater C1 outlet temperature is controlled at 310℃±10℃; the preheater C2 outlet temperature is 495℃±10℃; the preheater C3 outlet temperature is 610℃±10℃; the preheater C4 outlet temperature is 760℃±10℃; the preheater C5 outlet temperature is 870℃±10℃.

[0025] A total of 3680.27 tons of clinker were produced, 5557.21 tons of raw meal were consumed, a total of 389.0 tons of silica chips were consumed, a total of 155.60 tons of low-alkali sulfuric acid residue were consumed, a total of 361.22 tons of dry fly ash were consumed, and a total of 478.51 tons of raw coal were consumed. Through the physical coal consumption accounting during the experiment period, the physical coal consumption is 130.02kg / t, the standard coal consumption is 102.32kg / t, the subsequent detection of the composition of the clinker out of the kiln is in line with the requirements, the strength detection is carried out, the average 1d strength is 16.3MPa, and the average 3d strength is 31.3MPa.

[0026] Experimental group; The above-mentioned embodiment method is used for control and production is completed, the experiment batch duration is 4d, the rotary kiln feeding amount is controlled at 170±1t / h, the coal gangue addition ratio is 2.5%, the limestone ratio is 83.7±2%, the siliceous raw material ratio is 7.0±0.5%, the low-alkali sulfuric acid residue ratio is 2.8±0.2%, the dry fly ash ratio is 4.0±0.2%, the raw meal composition control is still executed according to the batching scheme, the raw meal batching is according to KH: 0.960±0.02, the qualified rate is ≥85%, N: 2.75±0.10, the qualified rate is ≥85%, P: 1.35±0.10, the qualified rate is ≥85%, 80μm: 20±2.0%, the qualified rate is ≥85%, 0.2%μm, the qualified rate is ≤3.0%; the clinker is according to KH: 0.910±0.02, the qualified rate is ≥90%, N: 2.70±0.10, the qualified rate is ≥90%, P: 1.30±0.10, the qualified rate is ≥90%. The preheater C1 outlet temperature is controlled at 340℃±10℃; the preheater C2 outlet temperature is 520℃±10℃; the preheater C3 outlet temperature is 640℃±10℃; the preheater C4 outlet temperature is 800℃±10℃; the preheater C5 outlet temperature is 840℃±10℃.

[0027] A total of 4505.09 tons of clinker are produced, 6802.69 tons of raw meal are consumed, a total of 225 tons of coal gangue are consumed, a total of 476.11 tons of silica debris are consumed, a total of 190.44 tons of low-alkali sulfuric acid residue are consumed, a total of 272.06 tons of dry fly ash are consumed, and a total of 565.56 tons of raw coal are consumed. Through the physical coal consumption accounting during the experiment, the physical coal consumption is 125.56kg / t, the standard coal consumption is 98.84kg / t, the subsequent clinker composition after the kiln is detected, and all meet the requirements. The strength is detected, the average 1d strength is 16.3MPa, and the average 3d strength is 31.3MPa.

[0028] According to the experimental group and the control group data, it can be concluded that after the operation method of the present application is used, the physical coal consumption accounting physical coal consumption is reduced from 130.02kg / t to 125.56kg / t, which is reduced by 4.46kg / t, the standard coal consumption is reduced from 102.32kg / t to 98.84kg / t, which is reduced by 3.48kg / t, according to 2.5kg CO2 emission per 1kg standard coal, the CO2 emission is reduced by 8.70kg per ton of clinker.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although the foregoing embodiments have provided a detailed description of this application, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. An energy-saving operation method for a preheating and pre-decomposition system used in cement production, characterized in that, This method combines raw material composition control with preheater temperature control. The raw meal composition control includes: the raw meal contains coal gangue, and the amount of coal gangue added is configured to reduce the initial decomposition temperature of calcium carbonate in the raw meal and promote its early decomposition in the C1-C4 stage preheaters; The preheater temperature control includes: actively increasing the operating temperature of at least one upper preheater in the pre-decomposition system, excluding the final stage, so as to improve the overall decomposition rate of raw materials before entering the final stage preheater; based on the improved decomposition rate, reducing the energy input to the decomposition furnace associated with the final stage preheater, thereby reducing the fuel consumption per unit product of the entire system.

2. The method according to claim 1, characterized in that, The pre-decomposition system is a five-stage preheating and pre-decomposition system. The upper preheater is a cyclone preheater of stages 1 to 4 (C1-C4), and the final preheater is a cyclone preheater of stage 5 (C5).

3. The method according to claim 2, characterized in that, In the five-stage preheating and predecomposition system, the temperature control of each stage of the preheater is as follows: The outlet temperature of preheater C1 is 340℃±10℃; The outlet temperature of preheater C2 is 520℃±10℃; The outlet temperature of preheater C3 is 640℃±10℃; The outlet temperature of preheater C4 is 800℃±10℃; The outlet temperature of preheater C5 is 840℃±10℃.

4. The method according to claim 1, characterized in that, The raw materials consist of the following components: limestone (80-85 parts), silica fragments (7-8 parts), low-alkali sulfuric acid slag (2.5-3 parts), fly ash (4 parts), and coal gangue (2.5 parts).

5. The method according to claim 4, characterized in that, The chemical composition of the coal gangue is as follows: SiO2 content is 40%-55%, Al2O3 content is 20%-30%, and fixed carbon content is 5%-10%; the mass ratio of the coal gangue in the raw meal is controlled between 2% and 2.5%.

6. The method according to claim 1, characterized in that, Before actively increasing the operating temperature of the upper preheater, it is necessary to confirm that the feeding box of the feed pipe of the C3 and C4 cyclone preheater is functioning normally to ensure that the raw material can form a uniform material curtain in the rising pipe and fully exchange heat with the hot flue gas.

7. The method according to claim 1 or 2, characterized in that, The reduction in energy input to the decomposition furnace is specifically manifested in lowering the outlet temperature setpoint of the decomposition furnace by 20-40℃.