CN114620958A - Process and system for activating coal gangue by utilizing hot air of cement kiln in cooperation - Google Patents

Process and system for activating coal gangue by utilizing hot air of cement kiln in cooperation Download PDF

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CN114620958A
CN114620958A CN202210339601.XA CN202210339601A CN114620958A CN 114620958 A CN114620958 A CN 114620958A CN 202210339601 A CN202210339601 A CN 202210339601A CN 114620958 A CN114620958 A CN 114620958A
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coal gangue
cyclone separator
hot air
cement
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CN114620958B (en
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陈延信
酒少武
赵博
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Xian University of Architecture and Technology
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    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B7/00Hydraulic cements
    • C04B7/36Manufacture of hydraulic cements in general
    • C04B7/43Heat treatment, e.g. precalcining, burning, melting; Cooling
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B7/00Hydraulic cements
    • C04B7/36Manufacture of hydraulic cements in general
    • C04B7/38Preparing or treating the raw materials individually or as batches, e.g. mixing with fuel

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Abstract

The process for activating the coal gangue by utilizing the cooperation of the hot air of the cement kiln comprises the steps of taking high-temperature hot air of the cement kiln as a heat source, taking coal gangue powder as a raw material, after preheating the coal gangue powder, decomposing kaolinite in the coal gangue powder into metakaolin through suspension state calcination, further improving the activity of the metakaolin through accumulation state uniform activation, and finally cooling to form a product. The invention also provides a system for activating coal gangue by utilizing the cooperation of hot air of the cement kiln, which comprises the following components: the device comprises a preheating unit, a conveying bed calcining unit, a moving bed calcining unit and a cooling unit. The invention organically couples the high-efficiency activation of the coal gangue with the cement production process, takes the high-temperature hot air of the cement kiln as a heat source, decomposes the coal gangue by using the conveying bed reactor, and excites the activity of the product by using the moving bed reactor, thereby being capable of continuously, stably and efficiently producing the high-activity coal gangue activation product in a large scale under the condition of not obviously influencing the cement production.

Description

Process and system for activating coal gangue by utilizing hot air of cement kiln in cooperation
Technical Field
The invention belongs to the technical field of dry-method cement production, relates to a preparation process of activated coal gangue, and particularly relates to a process and a system for cooperatively activating coal gangue by utilizing hot air of a cement kiln.
Background
Energy saving and carbon reduction in the cement industry are mainly worked around two aspects: one is to improve the energy efficiency of the cement process. By optimizing the cement production process flow and operation parameters, the utilization rate of substances and energy in the cement production process is improved, and the material consumption and energy consumption of unit cement products are reduced, so that the carbon emission is reduced; the second is to develop alternative technologies for raw materials, fuels and products. The low-carbon cement is prepared by replacing limestone with low-emission raw materials and replacing pulverized coal with low-carbon-emission fuels, or replacing part of cement clinker with active solid wastes and the like. The auxiliary cementing material prepared from various solid wastes replaces part of cement clinker, so that the energy consumption and carbon emission of the cement-based material in the production process can be effectively reduced. At present, the application of solid wastes such as blast furnace slag, fly ash, desulfurized gypsum and the like in cement is popularized and forms a larger utilization scale.
As a main waste generated in the coal mining process, coal gangue is one of solid waste varieties with large storage capacity. At present, the utilization of coal gangue is not scaled, and the traditional disposal mode of stacking and landfill not only occupies the land, but also easily causes multiple pollution of soil, water, atmosphere and the like. Most of coal gangue in the area contains minerals such as kaolinite, montmorillonite and illite, and the metakaolin with an indefinite structure can be formed after calcination. Metakaolin is a material with potential gelling activity, and after being mixed into cement, the later strength of the cement can be remarkably improved, and the durability of the cement can be improved. Therefore, the coal gangue is calcined and then used as an auxiliary cementing material to be doped into cement, the proportion of cement clinker is reduced, the purposes of energy conservation and carbon reduction of the cement can be achieved, and the comprehensive utilization of the coal gangue is realized.
At present, the industrialization of the activation calcination of coal gangue is not popularized yet, and the main reasons are as follows:
(1) in cement plants, part of the coal gangue is usually used as a silicoaluminous correction raw material, and the activation and calcination of the coal gangue requires a special calcination process, so that the investment and the production cost are high, and therefore, sufficient attention is not paid. Coal gangue is a complex component, and generally contains minerals such as quartz, kaolinite (montmorillonite and illite), calcite, hematite, and rutile, and also contains coal and elements such as sulfur, phosphorus, magnesium, potassium, sodium, and chlorine. Because of the limitation of cement raw meal to the proportion of oxide components and the content of harmful elements, the coal gangue used as the raw material of ordinary portland cement can only be blended by less than 6%. In cement factories, coal gangue is also used as a mixed material, however, the coal gangue which is not activated and calcined has no gelling activity, so the mixing amount of the coal gangue in cement is very small. Under the technical conditions of the existing cement production, the directly utilized coal gangue has small quantity and is difficult to meet the requirement of large-scale application.
(2) The performance of the coal gangue activation product is greatly influenced by raw material components, a calcining process and a production system, and is closely related to factors such as cement varieties, batching methods, application scenes and the like in the use process. Due to the technical difficulty of processing and application, the market is difficult to open for selling a single product, and the industrial application of the activation and calcination of the coal gangue is limited. The gangue which can meet the requirement of preparing active material must use the rich aluminum mineral such as kaolinite, illite, montmorillonite or bauxite as the main component. The principle of preparing active material from coal gangue is to convert kaolinite (montmorillonite and illite) into metakaolin by calcining, and to remove impurities such as coal, organic matter, sulfide mineral and carbonate as far as possible. Although the coal gangue is widely distributed in most coal mine areas of Shanxi, Nemeng, Anhui, Liaoning, Shaanxi and the like in China, most coal gangue is mainly quartz and cannot meet the requirement of preparing active materials. In addition, the requirements of coal gangue with different mineral components on calcining process, conditions (temperature, time and atmosphere), impurity disposal and the like are greatly different. According to the current coal mine production conditions, the output of coal gangue is not strictly screened and sorted and stockpiled, the property difference of the coal gangue in different coal mining layers is huge, and the component fluctuation of the coal gangue is determined by a disordered discharge mode. The coal gangue activation calcining process needs to adapt to production conditions with large fluctuation of raw materials and prepare products with stable quality, which has extremely high requirements on the process and the technology, and the simple flow calcining process can not be met. In addition, in cement or concrete applications, the gangue activating materials can participate in hydration and ultimately affect the performance properties (strength, durability, etc.) of the hardened body. The chemical components of the coal gangue raw material and the calcining process conditions greatly influence the activity of the activated product, and the matching of products with different activities and the properties (variety, label and mixed material type) and the mixing amount of cement is very important in the use process. The reasonable collocation can not only obviously improve the substitution level of the coal gangue active material to the cement, but also improve the service performance (mechanical property and durability) of the cement, but improper collocation can cause the problems of reduced early strength, inverted shrinkage of strength, cracking of a cement hardened body and the like of the cement. Therefore, the activation and calcination process of the coal gangue not only relates to the calcination technology, but also needs to consider the matching problem with the upstream and downstream links.
(3) At present, a batch of small shaft furnace (earth kiln) processes based on a 'moving bed' calcination technology exist around the periphery of a coal mine, and the calcined coal gangue is sold to a cement plant as an active admixture. The process has the disadvantages of bad production conditions, ineffective treatment of dust and waste gas, unstable product quality and elimination in recent years. However, the rotary kiln is a device for heat exchange in a stacking state, so that the calcining time is long, the efficiency is low, the heat consumption is high, and the phenomenon of 'under-burning' or 'over-burning' inevitably exists, so that the product quality is unstable, and the rotary kiln is not popularized at present due to the technical limitation. In recent years, the application of the suspension-state-based high-efficiency calcination technology in the aspect of coal gangue activation draws wide attention. The suspension state technology adopts a conveying bed reactor, and the technical principle is that the powder is reacted in a suspension state, and the characteristics of large transmission power and high reaction efficiency in the suspension state are fully utilized, so that the calcination reaction can be completed in a very short time. The suspension state technology has the advantages of high thermal efficiency, low energy consumption, mature process, advanced technology and high automation degree, and is applied to various fields including cement industry. A large number of researches prove that the application of the suspension state technology to the calcination of the coal gangue is not only technically feasible, but also the mainstream direction of the future process development. Related patent efforts have been made with respect to the suspension calcination of coal refuse, such as CN200910076126.6 and CN 201410114859.5. Among them, patent CN201410114859.5 is one of the results of research and development in which the applicant participates early, and the patent does not consider the coupling problem with cement production process and cement application, and has great difficulty in popularization and application in the current socioeconomic environment. Patent CN200910076126.6 proposes a scheme of performing suspension calcination on coal gangue by using heat energy of a cement plant, but limestone needs to be added in the process, the limestone decomposes and consumes a large amount of heat energy, and the discharged carbon dioxide weakens the energy saving and carbon reducing benefits of the process to a certain extent.
In fact, the activity of the coal gangue activation product determines the mixing amount of the coal gangue activation product in cement to a great extent. The activity of the coal gangue activation product is not only related to the content of metakaolin, but also influenced by the development degree of the amorphous structure of metakaolin. During the calcination process, the kaolinite (or illite and montmorillonite) in the coal gangue is decomposed to form metakaolin, and the reaction can be completed in a suspension state at 700-980 ℃ within only ten seconds. However, metakaolin also requires proper excitation to exert optimal activity. The common excitation means include both physical excitation and chemical excitation. The physical excitation belongs to early stage excitation, and usually adopts a heat treatment method to continuously calcine metakaolin at a high temperature of 700-980 ℃ for a period of time, so as to promote the original layered structure of kaolinite to be further adjusted to disorder, simultaneously promote quartz to be gradually changed from crystal to partial amorphous state at the high temperature, and enable the carbon in the coal gangue structure to be deeply removed, thereby improving the activity of the product. According to a great deal of research, the heat treatment time of metakaolin varies from tens of minutes to several hours, which is also the root cause of the long-time calcination usually adopted by coal gangue, but cannot be realized on the common suspension state calcination process. Chemical excitation belongs to later-stage excitation, and needs to be implemented in an application link of a coal gangue activation product, for example, a proper chemical excitation agent is added to promote active aluminum and active silicon to be effectively dissolved out to participate in a hydration reaction, so that the gelling activity of the coal gangue is improved. The existing suspended state activated coal gangue process has certain defects in the aspects of subsequent activation of metakaolin and associativity with cement production and application, so technical innovation is still needed.
The analysis shows that the preparation of the auxiliary cementing material by activating and calcining the coal gangue is beneficial to energy conservation and carbon reduction in the cement industry and realization of large-scale utilization of the coal gangue, but has the limitations in various aspects such as technology, process, application linkage and the like under the existing production technology conditions. Therefore, technical innovation must be carried out by combining comprehensive utilization of the coal gangue and production conditions of the cement industry, a series of limitations in the aspects of requirements, production and application are broken through, and a coal gangue activation calcination process and a high-performance product with large-scale popularization and application values are developed, so that contribution is made to coal gangue utilization and sustainable development of the cement industry.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a process and a system for cooperatively activating coal gangue by utilizing hot air of a cement kiln, wherein the efficient activation of the coal gangue is organically coupled with a cement production process, the high-temperature hot air of the cement kiln is used as a heat source, a transport bed reactor is used for decomposing the coal gangue, and a moving bed reactor is used for exciting the activity of a product, so that a high-activity coal gangue activated product can be continuously, stably and efficiently produced in a large scale under the condition of not obviously influencing cement production.
In order to achieve the purpose, the invention adopts the technical scheme that:
the process for activating the coal gangue by utilizing the cooperation of the hot air of the cement kiln comprises the steps of taking high-temperature hot air of the cement kiln as a heat source, taking coal gangue powder as a raw material, after preheating the coal gangue powder, decomposing kaolinite in the coal gangue powder into metakaolin through suspension state calcination, further improving the activity of the metakaolin through accumulation state uniform activation, and finally cooling to form a product.
In one embodiment, the preheating is accomplished using a multi-stage suspension preheater that preheats the coal gangue powder above 500 ℃.
In one embodiment, the reaction temperature of the suspension state calcination is 700-980 ℃, and the coal gangue powder is carried by the high-temperature hot air of the cement kiln to move upwards in a concurrent manner in the process.
In one embodiment, the temperature of the heat treatment for the stacking state uniform activation is 700-950 ℃, and the retention time is 10 min-2 h.
In one embodiment, the high-temperature hot air is 800-1200 ℃ hot air from the kiln head of a cement rotary kiln, which is used as a heat source for suspension state calcination, and the temperature of high-temperature tail gas after suspension state calcination is 750-900 ℃, and the high-temperature tail gas enters a cement preheater; the cooling takes air as a cold source, the heated air is used for preheating the coal gangue powder, the temperature of the air after heat exchange is 200-300 ℃, and the air enters a kiln tail waste gas disposal system.
The invention also provides a system for utilizing the hot air of the cement kiln to cooperatively activate the coal gangue, which comprises the following components:
the preheating unit is used for preheating the coal gangue powder;
the conveying bed calcining unit is connected with the material outlet of the preheating unit, and the preheated coal gangue powder is subjected to suspension state calcination by taking high-temperature hot air of the cement kiln as a heat source;
the moving bed calcining unit is connected with a material outlet of the conveying bed calcining unit and is used for uniformly activating the coal gangue powder subjected to suspension state calcination in a stacking state;
and the cooling unit is connected with the material outlet of the moving bed calcining unit and is used for cooling the coal gangue powder which is subjected to the stacking state uniform activation.
In one embodiment, the preheating unit is a multi-stage suspension preheater which consists of a plurality of stages of cyclone separators, a connecting pipeline, a feeding device and a centrifugal fan, the multi-stage cyclone separators consist of a plurality of cyclone separators and a connecting pipeline, the airflow inlet of the previous stage of cyclone separator is connected with the airflow outlet of the next stage of cyclone separator by a pipeline, and the material outlet of the previous stage is connected with the airflow inlet pipeline of the next stage; the feeding device is connected with an airflow inlet pipeline of the first-stage cyclone separator, powder materials move from top to bottom in the preheating unit, the powder materials enter the conveying bed calcining unit after being separated and collected in the last-stage cyclone separator, the airflow moves from bottom to top in the preheating unit, is discharged from an airflow outlet of the first-stage cyclone separator and is conveyed to a kiln tail waste gas disposal system of a cement production line through a centrifugal fan.
In one embodiment, the conveying bed calcining unit consists of a conveying bed reactor, a cyclone separator and a high-temperature centrifugal fan, wherein the conveying bed reactor is in vertical arrangement for pipeline structure, the lower part of the conveying bed reactor is connected with a high-temperature hot air pipeline from a kiln head of a cement production line, the upper part of the conveying bed reactor is connected with an air inlet pipeline of the cyclone separator through a bent pipe, an air outlet of the cyclone separator is connected with the high-temperature centrifugal fan through a pipeline, a feeding pipe is arranged at the position, above a hot air inlet, of the lower part of the conveying bed reactor and is connected with a material outlet pipeline of the last stage of cyclone separator of the preheating unit, and an outlet of the high-temperature centrifugal fan is connected with a decomposing furnace of the cement preheater.
In one embodiment, the moving bed calcination unit consists of a moving bed reactor and connecting piping.
In one embodiment, the cooling unit consists of a multi-stage cyclone separator and a connecting pipeline, the multi-stage cyclone separator consists of a plurality of cyclone separators and a connecting pipeline, an airflow inlet of the previous stage cyclone separator is connected with an airflow outlet of the next stage cyclone separator through a pipeline, and a material outlet of the previous stage is connected with an airflow inlet pipeline of the next stage; the material discharged from the moving bed calcining unit enters from a material inlet of the first-stage cyclone separator, sequentially passes through the cyclone separators at all stages, is cooled and is discharged from an outlet of the cyclone separator at the last stage, air enters from an airflow inlet of the cyclone separator at the last stage, sequentially passes through the cyclone separators at all stages to exchange heat with the high-temperature material, and finally enters the preheating unit from an airflow outlet pipeline of the cyclone separator at the first stage.
Compared with the prior art and method for activating and calcining the coal gangue in a suspended state, the invention has the beneficial effects that:
firstly, a two-step calcination method is adopted according to the characteristics of coal gangue activation reaction, firstly, a conveying bed reactor is adopted to quickly finish decomposition of kaolinite and combustion of carbon in a suspension state to form metakaolin and remove most of organic carbon, and then a moving bed reactor is adopted to finish further activation of metakaolin at a high temperature by using the heat of materials per se in a stacking state and deeply remove impurities such as organic carbon and the like. The method combines the technical advantages of high efficiency of the conveying bed reactor and long calcination time of the moving bed reactor, and has good adaptability to the calcination of coal gangue of different types and qualities.
Secondly, the conditions of the cement production process and the characteristics of the coal gangue activation calcination are combined, and the rich hot air at the kiln head of the rotary kiln is used as a heat source to complete the activation calcination of the coal gangue without supplementing fuel. Because the coal gangue has a certain calorific value and has the property of self-heating, the energy consumption of the activation and calcination of the coal gangue is low, and the temperature of 800-1200 ℃ high-temperature hot air from the kiln head of the rotary kiln is reduced by about 200 ℃ after passing through the conveying bed reactor. On one hand, the waste gas at 750-900 ℃ is introduced into the cement preheater, and the air quantity balance of the cement production system is not obviously influenced; on the other hand, coal (carbon) in the coal gangue is partially combusted in the preheating unit, and the content of the coal (carbon) is low and does not consume a large amount of oxygen in hot air, so that the combustion condition of the coal in the decomposing furnace cannot be obviously influenced by introducing waste gas into the cement preheater. The other path of cooling air firstly realizes the cooling and heat recovery of the product, and then uses the heat for preheating the raw material, thereby realizing the full utilization of the heat. The cooling air does not enter the cement production system, but directly enters the waste gas treatment system at the tail of the kiln, so that the cement production process is not influenced. In conclusion, the process and the method of the invention fully utilize the conditions of the cement process, and have no significant adverse effect on the cement production, which is of great importance to the popularization of the process.
The method has the advantages of simple flow, clear function, high reaction efficiency, high energy utilization rate, large-range adjustable calcining time and good adaptability of the process to raw materials, is convenient to implement under the existing cement process conditions, not only meets the technical conditions of activating and calcining the coal gangue, but also meets the technical requirements of energy saving and carbon reduction of the cement industry, and provides a new technical approach for energy saving and carbon reduction of the cement industry and comprehensive utilization of the coal gangue.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to the drawings and examples.
The invention relates to a process for activating coal gangue by utilizing cooperation of hot air of a cement kiln and hot air, which takes high-temperature hot air of the cement kiln as a heat source, takes coal gangue powder as a raw material, decomposes kaolinite in the coal gangue powder to form metakaolin through suspension state calcination after the coal gangue powder is preheated, further improves the activity of the metakaolin through accumulation state uniform activation, and finally cools to form a product.
As shown in figure 1, the process system for co-activating coal gangue by using hot air of a cement kiln adopted by the embodiment comprises a preheating unit 1, a conveying bed calcining unit 2, a moving bed calcining unit 3 and a cooling unit 4. The material flow is that the material sequentially passes through a preheating unit 1, a conveying bed calcining unit 2, a moving bed calcining unit 3 and a cooling unit 4 to form a product. The airflow is divided into two paths: one path is high temperature hot wind at 800-1200 ℃ from the kiln head of the cement rotary kiln, and enters the cement preheater with waste gas at 750-900 ℃ after passing through the moving bed calcining unit 3. The other path of air is air, and the air is heated after heat exchange with high-temperature materials sequentially through a cooling unit 4, then enters a preheating unit 1 to preheat coal gangue powder, and finally enters a kiln tail waste gas disposal system of a cement production line through waste gas at 200-300 ℃.
The preheating unit 1 is a multistage suspension state preheater which consists of a first multistage cyclone separator 11, a connecting pipeline, a feeding device and a centrifugal fan 12 and has the functions of drying and preheating coal gangue powder and realizing the heat recovery of hot air of the cooling unit 4. In this embodiment, a two-stage cyclone separator is used. Wherein, feeding device mainly comprises powder conveyor, feeder, metering device and filling tube. The feeder includes, but is not limited to, a vibration type, a screw type, a belt type and other devices suitable for feeding powder. This embodiment adopts spiral double helix structure's conveyer, can guarantee the continuous stable transport of material, can play the effect of lock wind again, avoids the air admission cooling unit 4. The feed pipe is connected with an airflow inlet pipeline of the first-stage cyclone separator. The airflow inlet of the previous stage cyclone separator (i.e. the first stage cyclone separator in the embodiment) is connected with the airflow outlet of the next stage cyclone separator (i.e. the second stage cyclone separator in the embodiment) through a pipeline, the material outlet of the previous stage is connected with the airflow inlet pipeline of the next stage, and the like. The powder material moves from top to bottom in the preheating unit 1, enters the first-stage cyclone separator through the feed inlet, enters the second-stage cyclone separator after being separated and collected, and enters the conveying bed calcining unit 2 through the material outlet pipeline of the second-stage cyclone separator. The air flow moves from bottom to top in the preheating unit 1, hot air at 500-600 ℃ from the cooling unit 4 firstly enters an air flow inlet of a second-stage cyclone separator of the preheating unit 1, passes through the cyclone separator, then enters a first-stage cyclone separator from an air flow outlet, and finally is discharged from an air flow outlet of the first-stage cyclone separator, and waste gas at 200-300 ℃ is conveyed to a kiln tail waste gas disposal system of a cement production line through a centrifugal fan 12. The cyclone separator and the connecting pipeline of the preheating unit 1 are subjected to heat preservation treatment, so that the heat dissipation is reduced as much as possible.
The conveying bed calcining unit 2 consists of a conveying bed reactor 21, a cyclone separator 22 and a high-temperature centrifugal fan 23, and has the function of decomposing kaolinite in coal gangue to form metakaolin. The conveying bed reactor 21 is of a pipeline structure and is arranged vertically, the shell of the pipeline is a stainless steel pipeline, and a refractory material is poured inside the pipeline. The lower part of the conveying bed reactor 21 is connected with a high-temperature hot air pipeline from a kiln head of a cement production line, and the upper part of the conveying bed reactor is connected with an air inlet pipeline of the cyclone separator 22 through a bent pipe. The airflow outlet of the cyclone 22 is connected with a high-temperature centrifugal fan 23 by a pipeline. A feed pipe is provided at a position above the hot air inlet in the lower part of the transport bed reactor 21, and is connected to a material outlet pipe of the last stage cyclone (i.e., the second stage cyclone in this embodiment) of the preheating unit 1. After entering the conveying bed reactor 21, the materials are carried upwards to move in a same flow mode by hot air at 800-1200 ℃ from the kiln head of the rotary kiln, the materials react in the conveying bed reactor 21 at 750-900 ℃, the materials enter a cyclone separator after the reaction is finished, the materials are separated and collected and then enter the moving bed calcining unit 3, airflow at 750-850 ℃ is discharged from an airflow outlet of the cyclone separator, the airflow enters a decomposing furnace of a cement preheater through a high-temperature centrifugal fan 23, and heat is recycled. The cyclone separator 22 and the pipeline are made of stainless steel materials, and heat insulation treatment is performed inside the cyclone separator in a refractory material pouring mode, so that heat dissipation is reduced as much as possible.
The moving bed calcining unit 3 consists of a moving bed reactor 31 and a connecting pipeline and has the function of further activating the metakaolin to improve the activity of the product. The moving bed reactor 31 includes, but is not limited to, a hollow device of a rotary, spiral stirring or gravity type principle, and may be arranged in a vertical, horizontal or inclined manner, and is provided with a heat insulating material, and the working temperature range is 700-1000 ℃, preferably 700-950 ℃, and more preferably 750-850 ℃. Has the function of adjusting the retention time of the materials. The embodiment adopts a vertical structure, the upper part is a cylindrical barrel, the lower part is a conical barrel, and the upper part and the lower part are welded. The moving bed reactor 31 is internally poured with refractory materials, and the inner surface is paved with heat-resistant steel. The material discharging pipe is arranged below the moving bed reactor 31, the rotary material valve is arranged on the moving bed reactor, the material flows downwards under the action of gravity, and the material flow can be adjusted by changing the rotating speed. In order to avoid the blockage of the moving bed reactor 31, an air cannon is arranged on the lower conical part of the moving bed reactor, and the material blockage is avoided by regularly back flushing. The working temperature of the moving bed reactor 31 is 700-950 ℃, metakaolin which is reacted by the conveying bed calcining unit 2 enters the moving bed reactor 31 and is subjected to further heat treatment at the temperature of 750-850 ℃, the property retention time of different materials can be adjusted within the range of 10 min-2 h, and in the embodiment, the average retention time of the materials in the reactor is 20 min. The material out of the moving bed reactor 31 enters the cooling unit 4 for cooling treatment, and the heat of the material is recovered.
The cooling unit 4 consists of a second multistage cyclone separator 41 and a connecting pipeline and has the functions of cooling the coal gangue activation product and recovering heat. In this embodiment, two stages of cyclones are used, but when the production scale is large, three stages of cyclones are required, and the form and processing method of the two stages of cyclones and the connecting pipes thereof are the same as those of the preheating unit 1. The airflow inlet of the first-stage cooling cyclone separator is connected with the airflow outlet of the second-stage cooling cyclone separator through a pipeline, and the material outlet of the first-stage cooling cyclone separator is connected with the airflow inlet pipeline of the second-stage cooling cyclone separator. The 750-850 ℃ material discharged from the moving bed calcining unit 3 is cooled to below 200 ℃ after sequentially passing through the first-stage cooling cyclone separator and the second-stage cooling cyclone separator, discharged from the outlet of the second-stage cooling cyclone separator, and conveyed and transported to a product warehouse by a belt. Air enters the cooling unit 4 from the airflow inlet of the second-stage cooling cyclone separator, passes through the second-stage cooling cyclone separator and then enters the first-stage cooling cyclone separator, heat exchange with high-temperature materials is sequentially completed, and hot air at 500-600 ℃ enters the preheating unit 1 from the airflow outlet pipeline of the first-stage cooling cyclone separator. The cyclone separator and the connecting pipeline of the cooling unit 4 are insulated by pouring refractory materials, so that the heat dissipation is reduced as much as possible.
The coal gangue activation calcining system is adopted to activate and calcine the coal gangue covering a certain place. Then the product and the reference cement (42.5 label) are mixed to carry out the mechanical property test, the mixture ratio is shown in table 1, and the result of the mechanical strength test is shown in table 2.
Table 1 proportions of the tests
Group of Portland cement mixing amount/%) The blending amount of activated coal gangue/%)
A0 100 0
A1 90 10
A2 85 15
A3 80 20
A4 75 25
A5 70 30
TABLE 2 compression strength/MPa of test blocks of different ages
Figure BDA0003578503970000101
Figure BDA0003578503970000111
The test result of the coal gangue in the inner Mongolia places shows that the coal gangue active material product prepared by the process system and the calcining method of the invention has higher 28d compressive strength than pure cement in the range of 30 percent of substituted cement in the A1-A5 experimental groups. The coal gangue active material produced by the process system of the invention can not reduce the performance of cement under the condition that the substitution proportion of the cement is up to 30 percent, and the common activated calcined product can only reach the substitution proportion of more than 15 percent. According to production data, the cement production cost can be reduced by 20%, the energy can be saved by 15%, and the carbon emission can be reduced by 20% under the condition that the proportion of the substitute cement is 30%. The invention realizes the organic combination of cement production and coal gangue utilization, and has wide popularization and application prospects.

Claims (10)

1. The process for cooperatively activating the coal gangue by utilizing the hot air of the cement kiln is characterized in that high-temperature hot air of the cement kiln is used as a heat source, coal gangue powder is used as a raw material, after the coal gangue powder is preheated, kaolinite in the coal gangue powder is decomposed into metakaolin through suspension state calcination, the activity of the metakaolin is further improved through accumulation state uniform activation, and finally the product is formed through cooling.
2. The process for synergistically activating coal gangue by using hot air of a cement kiln as claimed in claim 1, wherein the preheating is performed by using a multistage suspension preheater, and the multistage suspension preheater preheats the coal gangue powder to more than 500 ℃.
3. The process for synergistically activating coal gangue by using hot air in a cement kiln as claimed in claim 1, wherein the reaction temperature of the suspension state calcination is 700 ℃ to 980 ℃, and the coal gangue powder is brought up to perform the co-current movement by the high-temperature hot air in the cement kiln in the process.
4. The process for synergistically activating the coal gangue by using the hot air of the cement kiln as claimed in claim 1, wherein the heat treatment temperature for the stacked uniform activation is 700 ℃ to 950 ℃, and the retention time is 10min to 2 h.
5. The process for synergistically activating the coal gangue by using the hot air of the cement kiln as claimed in claim 1, wherein the high-temperature hot air is 800-1200 ℃ hot air from a kiln head of the cement rotary kiln, and is used as a heat source for suspension state calcination, and the temperature of high-temperature tail gas after the suspension state calcination is 750-900 ℃ and enters a cement preheater; the cooling takes air as a cold source, the heated air is used for preheating the coal gangue powder, the temperature of the air after heat exchange is 200-300 ℃, and the air enters a kiln tail waste gas disposal system.
6. A system for utilizing hot air in a cement kiln to co-activate coal gangue, comprising:
the preheating unit is used for preheating the coal gangue powder;
the conveying bed calcining unit is connected with the material outlet of the preheating unit, and the preheated coal gangue powder is subjected to suspension state calcination by taking high-temperature hot air of the cement kiln as a heat source;
the moving bed calcining unit is connected with a material outlet of the conveying bed calcining unit and is used for performing accumulation state uniform activation on the suspended state calcined coal gangue powder;
and the cooling unit is connected with the material outlet of the moving bed calcining unit and is used for cooling the coal gangue powder which is subjected to the stacking state uniform activation.
7. The system for co-activating coal gangue by using hot air in a cement kiln as claimed in claim 6, wherein the preheating unit is a multi-stage suspension preheater comprising a plurality of cyclone separators, a connecting pipe, a feeding device and a centrifugal fan, the cyclone separators comprise a plurality of cyclone separators and a connecting pipe, the air inlet of the cyclone separator at the upper stage is connected with the air outlet of the cyclone separator at the lower stage by a pipe, and the material outlet of the cyclone separator at the upper stage is connected with the air inlet pipe of the air inlet pipe at the lower stage; the feeding device is connected with an airflow inlet pipeline of the first-stage cyclone separator, the powder material moves from top to bottom in the preheating unit, the powder material enters the conveying bed calcining unit after being separated and collected in the last-stage cyclone separator, the airflow moves from bottom to top in the preheating unit, is discharged from an airflow outlet of the first-stage cyclone separator and is conveyed to a kiln tail waste gas treatment system of a cement production line through a centrifugal fan.
8. The system for activating coal gangue by using the hot air in cooperation with the cement kiln as claimed in claim 6, wherein the transport bed calcining unit comprises a transport bed reactor, a cyclone separator and a high temperature centrifugal fan, the transport bed reactor is arranged vertically in a pipeline structure, the lower part of the transport bed reactor is connected with a high temperature hot air pipeline from the kiln head of the cement production line, the upper part of the transport bed reactor is connected with an air inlet pipeline of the cyclone separator through a bent pipe, an air outlet of the cyclone separator is connected with the high temperature centrifugal fan through a pipeline, a feeding pipe is arranged at a position above a hot air inlet at the lower part of the transport bed reactor and is connected with a material outlet pipeline of the last stage cyclone separator of the preheating unit, and an outlet of the high temperature centrifugal fan is connected with a decomposing furnace of the cement preheater.
9. The system for the cooperative activation of coal gangue with hot wind of a cement kiln as claimed in claim 6, wherein the moving bed calcination unit consists of a moving bed reactor and a connecting pipeline.
10. The system for co-activating coal gangue by using hot wind of a cement kiln as claimed in claim 6, wherein the cooling unit is composed of a multi-stage cyclone separator and a connecting pipeline, the multi-stage cyclone separator is composed of a plurality of cyclone separators and a connecting pipeline, the gas flow inlet of the previous stage cyclone separator is connected with the gas flow outlet of the next stage cyclone separator by a pipeline, and the material outlet of the previous stage is connected with the gas flow inlet pipeline of the next stage; the material discharged from the moving bed calcining unit enters from a material inlet of the first-stage cyclone separator, sequentially passes through the cyclone separators at all stages, is cooled and is discharged from an outlet of the cyclone separator at the last stage, air enters from an airflow inlet of the cyclone separator at the last stage, sequentially passes through the cyclone separators at all stages to exchange heat with the high-temperature material, and finally enters the preheating unit from an airflow outlet pipeline of the cyclone separator at the first stage.
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