Method capable of reducing moisture content of slag
By combining a three-stage temperature path and mechanical activation with tiered waste heat utilization, the problem of slag moisture reduction and activation protection was solved, achieving efficient and low-energy-consumption deep dehydration and activation repair, adapting to initial moisture content fluctuations, and reducing transportation and energy costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HOUYING GRP HAICHENG BUILDING MATERIALS CO LTD
- Filing Date
- 2026-01-19
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies struggle to reduce slag moisture while preserving its activity, and they are energy-intensive and difficult to adapt to fluctuations in initial moisture content, resulting in high transportation costs, low grinding efficiency, and reduced hydration activity.
The system employs a three-stage temperature path: low-temperature pre-drying, medium-temperature main dehydration, and low-temperature activation and stabilization. Combined with mechanical activation and cascaded waste heat utilization, the system loosens moisture in the low-temperature pre-drying stage, efficiently removes bound water in the medium-temperature main dehydration stage, and deeply dehydrates and restores activity in the low-temperature activation and stabilization stage. Energy consumption is reduced by utilizing negative pressure and cascaded waste heat utilization.
It achieves a balance between deep dehydration (final moisture content ≤2%) and activity protection, reduces energy consumption by 20%-30%, improves product activity index, adapts to fluctuations in initial moisture content, and reduces transportation and energy costs.
Abstract
Description
Technical Field
[0001] This invention relates to the field of slag technology, specifically to a method for reducing the moisture content of slag. Background Technology
[0002] The large amount of slag produced in iron and steel and non-ferrous metal smelting, after wet treatment (such as water quenching and wet stockpiling), typically has an initial moisture content as high as 15%-35%. When such high-moisture slag is used as cement admixture or building material raw material, the high moisture content not only increases transportation costs and affects grinding efficiency, but also significantly reduces its hydration activity, restricting its high-value-added utilization. Existing dewatering technologies face a contradiction between "deep dewatering" and "activity protection": Traditional thermal drying (such as rotary kiln and drum dryer) often uses a single high temperature (>300℃) for rapid dehydration. Although it can reduce moisture, the high temperature will cause the active components in the slag (such as amorphous glass and active calcium aluminum phase) to deactivate and crystallize, which will seriously damage its gelling activity and consume extremely high energy.
[0003] Low-temperature drying technology: To avoid damage to activity, low-temperature (<150℃) drying is used for a long time. However, the dehydration rate is slow, it is difficult to remove moisture to a depth of less than 2%, and the processing cycle is long and the energy consumption is poor.
[0004] Poor adaptability to initial moisture content: When the moisture content of the incoming material fluctuates greatly (15%-35%), the drying process with fixed parameters is difficult to stably control the final moisture content and product activity, and is prone to insufficient drying or over-drying. Summary of the Invention
[0005] The purpose of this invention is to provide a method for reducing the moisture content of slag, so as to solve the problems mentioned in the background art.
[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for reducing the moisture content of slag, comprising the following steps: A. Low-temperature pre-drying section (material temperature 120℃-150℃): The goal is to remove most of the free water. Wet slag with an initial moisture content of 15%-35% is fed into the pre-drying section. After exiting this section, the moisture content of the slag is reduced to 8%-15%. B. Medium-temperature main dewatering section (material temperature 350℃-400℃): The goal is to efficiently remove bound water. The pre-dried slag enters the main dewatering section, which is the main battlefield for dewatering. The output moisture content drops rapidly to 3%-5%. C. Low-temperature activation stabilization section (material temperature ≤200℃): The goal is deep dehydration and activation repair. The slag that has completed the main dehydration enters the activation stabilization section. During this stage, a moderate negative pressure is maintained (-100Pa to -200Pa), and the final discharge moisture content is ≤2%. D. Waste heat utilization and negative pressure control: The exhaust gas discharged from the active stabilization section is used to preheat the cold air or wet materials entering the pre-drying section. The high-temperature exhaust gas discharged from the main dehydration section first passes through a cyclone dust collector to recover fine powder, and then enters a spray condenser tower or a heat pump waste heat recovery system. The cooled exhaust gas is then partially recycled to the inlet of the main dehydration section and partially used in the active stabilization section or the pre-drying section.
[0007] Preferably, the pre-drying stage in step A is carried out in a high-energy ball mill or a high-speed mechanical shear activation machine, and the main heat source is the low-temperature waste heat of the system (such as the exhaust gas of the subsequent cooling stage, with a temperature of 90-120°C). The mechanical activation treatment is carried out for 10-60 minutes with a medium to high energy intensity (ball-to-material ratio 5:1-15:1, rotation speed 200-500 rpm). During this process, the role of mechanical energy is not only to break the particles and increase the specific surface area, but also to "loosen" the binding of moisture with slag particles, especially to weaken the binding force of bound water, so as to create favorable conditions for subsequent deep dehydration. Then the slag is heated to 120-150°C. At this relatively mild temperature, the free water and some capillary water between the slag particles are slowly and evenly evaporated, thereby avoiding the surface from drying and crusting too quickly, leaving a channel for internal moisture migration. The pre-drying stage is operated under a slight negative pressure (-50Pa to -100Pa), which can remove water vapor in time.
[0008] Preferably, the mechanochemical effect induced by the mechanical activation treatment is as follows: a) destroying the original hydroxyl (-OH) structure on the surface of slag particles, weakening its hydrogen bonding force with water molecules; b) causing lattice defects and dislocations on the surface of slag particles, increasing the degree of surface amorphization, and changing its surface energy; c) partially opening closed pores.
[0009] Preferably, in step B, the main dehydration section uses a mixture of high-temperature hot air (from high-temperature flue gas or a gas-fired hot air furnace, at a temperature of 600-700℃) and medium-temperature waste gas from the pre-drying section as a heat source. Through precise control, the material bed is rapidly heated and stabilized in the medium-temperature range of 350-400℃. This medium-temperature range is the optimal window for removing adsorbed water and some interlayer water that are bound to the surface of slag particles by physical and chemical forces. The dehydration efficiency is high. The main dehydration section is operated under a significant negative pressure (-300Pa to -500Pa), which forms a strong driving force for water escape, significantly accelerates the dehydration rate, and prevents local overheating at high temperatures.
[0010] Preferably, the activity stabilization stage in step C is carried out in a belt dryer or paddle dryer, under low temperature (70-120℃) and negative pressure conditions with a vacuum degree of -0.06MPa to -0.095MPa. The low temperature avoids the damage to the activity of the slag caused by high temperature, while the negative pressure environment significantly lowers the boiling point of water, allowing the water to quickly vaporize and be removed at a lower temperature. The material's own sensible heat and the high-temperature exhaust gas from the main dehydration stage are used to heat exchange the medium-low temperature hot air (about 200-250℃), and through precise airflow control, the material temperature is slowly reduced to ≤200℃. Under this low-temperature long residence time (relatively), on the one hand, the residual strongly bound water is further removed, and on the other hand, this mild "annealing" effect helps to repair the micro-stress that may be caused by rapid dehydration and stabilize the active surface, which is beneficial to the maintenance or even slight improvement of the gelling activity.
[0011] Preferably, in step D, the temperature of the exhaust gas discharged from the active stabilization section is 120-150℃, and the temperature of the high-temperature exhaust gas discharged from the main dehydration section is 450-550℃. The negative pressure of the entire system is uniformly established at the tail end by the induced draft fan and is precisely distributed and controlled by the opening of the air valves between each section to ensure that the pre-drying section, the main dehydration section, and the active stabilization section form the required gradient negative pressure environment.
[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves the best balance between deep dehydration and activity protection: through a three-stage temperature path of "low temperature pre-drying (anti-crusting) → medium temperature main dehydration (efficient debinding) → low temperature stabilization (deep dehydration and activity repair)," it ensures that the final moisture content is ≤2% while avoiding the damage of high temperature to the activity of slag. The product activity index (such as 7d and 28d strength ratio) is better than that of traditional high temperature dried products.
[0013] It is highly adaptable to fluctuations in initial moisture content: by adjusting the hot air volume, air velocity (negative pressure) and material residence time in each section, it can flexibly cope with initial moisture content fluctuations in the range of 15%-35%, and can always stably produce qualified products, with great operational flexibility.
[0014] Significantly reduced energy consumption: The waste heat cascade utilization mode greatly reduces external energy consumption, the gradient negative pressure setting enhances the mass transfer process and improves heat utilization rate, the mechanical activation energy consumption is relatively fixed, while the low temperature negative pressure drying has high dehydration efficiency and the latent heat demand for water vaporization is reduced due to the lower boiling point, so the total energy consumption of the system is reduced by 20%-30% compared with single high temperature drying. Detailed Implementation
[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0016] A method for reducing the moisture content of slag includes the following steps: A. Low-temperature pre-drying section (material temperature 120℃-150℃): The goal is to remove most of the free water. Wet slag with an initial moisture content of 15%-35% is fed into the pre-drying section. After exiting this section, the moisture content of the slag is reduced to 8%-15%. B. Medium-temperature main dewatering section (material temperature 350℃-400℃): The goal is to efficiently remove bound water. The pre-dried slag enters the main dewatering section, which is the main battlefield for dewatering. The output moisture content drops rapidly to 3%-5%. C. Low-temperature activation stabilization section (material temperature ≤200℃): The goal is deep dehydration and activation repair. The slag that has completed the main dehydration enters the activation stabilization section. During this stage, a moderate negative pressure is maintained (-100Pa to -200Pa), and the final discharge moisture content is ≤2%. D. Waste heat utilization and negative pressure control: The exhaust gas discharged from the active stabilization section is used to preheat the cold air or wet materials entering the pre-drying section. The high-temperature exhaust gas discharged from the main dehydration section first passes through a cyclone dust collector to recover fine powder, and then enters a spray condenser tower or a heat pump waste heat recovery system. The cooled exhaust gas is then partially recycled to the inlet of the main dehydration section and partially used in the active stabilization section or the pre-drying section.
[0017] The pre-drying stage in step A is carried out in a high-energy ball mill or a high-speed mechanical shear activation machine. The main heat source is the low-temperature waste heat of the system (such as the exhaust gas from the subsequent cooling stage, at a temperature of 90-120℃). The mechanical activation treatment is carried out for 10-60 minutes at a medium to high energy intensity (ball-to-material ratio 5:1-15:1, rotation speed 200-500 rpm). During this process, the role of mechanical energy is not only to break up particles and increase specific surface area, but also to "loosen" the binding of moisture with slag particles, especially to weaken the binding force of bound water, creating favorable conditions for subsequent deep dehydration. Then, the slag is heated to 120-150℃. At this relatively mild temperature, the free water and some capillary water between slag particles are slowly and evenly evaporated, thereby avoiding the surface from drying and forming a crust too quickly, leaving a channel for internal moisture migration. In addition, the pre-drying stage is operated under a slight negative pressure (-50Pa to -100Pa), which can remove water vapor in time.
[0018] The mechanochemical effects induced by mechanical activation treatment are: a) destroying the original hydroxyl (-OH) structure on the surface of slag particles, weakening their hydrogen bonding force with water molecules; b) causing lattice defects and dislocations on the surface of slag particles, increasing the degree of surface amorphization, and changing their surface energy; c) partially opening closed pores.
[0019] In step B, the main dehydration section uses a mixture of high-temperature hot air (from high-temperature flue gas or a gas-fired hot air furnace, at a temperature of 600-700℃) and medium-temperature waste gas from the pre-drying section as a heat source. Through precise control, the material bed is rapidly heated and stabilized in the medium-temperature range of 350-400℃. This medium-temperature range is the optimal window for removing adsorbed water and some interlayer water that are bound to the surface of slag particles by physical and chemical forces. The dehydration efficiency is high. The main dehydration section is operated under a significant negative pressure (-300Pa to -500Pa), which forms a strong driving force for water escape, significantly accelerates the dehydration rate, and prevents local overheating at high temperatures.
[0020] The activity stabilization stage in step C is carried out in a belt dryer or paddle dryer, under low temperature (70-120℃) and negative pressure conditions with a vacuum degree of -0.06MPa to -0.095MPa. The low temperature avoids the damage to the activity of the slag caused by high temperature, while the negative pressure environment significantly lowers the boiling point of water, allowing the water to quickly vaporize and be removed at a lower temperature. The material's own sensible heat and the high temperature exhaust gas from the main dehydration stage are used to heat exchange the medium-low temperature hot air (about 200-250℃). Through precise air volume control, the material temperature is slowly reduced to ≤200℃. Under this low temperature and long residence time (relatively), on the one hand, the residual strongly bound water is further removed in depth, and on the other hand, this mild "annealing" effect helps to repair the micro-stress that may be caused by rapid dehydration and stabilize the active surface, which is conducive to the maintenance or even slight improvement of the gelling activity.
[0021] In step D, the exhaust gas temperature of the active stabilization section is 120-150℃, and the high-temperature exhaust gas temperature of the main dehydration section is 450-550℃. The negative pressure of the entire system is uniformly established at the tail by the induced draft fan and is precisely distributed and controlled by the opening of the air valves between each section to ensure that the pre-drying section, the main dehydration section and the active stabilization section form the required gradient negative pressure environment.
[0022] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for reducing the moisture content of slag, characterized in that: Includes the following steps: A. The goal of the low-temperature pre-drying section is to remove most of the free water: wet slag with an initial moisture content of 15%-35% is sent into the pre-drying section, and after exiting this section, the moisture content of the slag is reduced to 8%-15%; B. The goal of the medium-temperature main dewatering section is to efficiently remove bound water: the pre-dried slag enters the main dewatering section, which is the main battlefield for dewatering, and the output moisture content drops rapidly to 3%-5%; C. The goal of the low-temperature activation and stabilization section is deep dehydration and activation repair: The slag that has completed the main dehydration enters the activation and stabilization section. During this stage, a moderate negative pressure is maintained, and the final discharge moisture content is ≤2%. D. Waste heat utilization and negative pressure control: The exhaust gas discharged from the active stabilization section is used to preheat the cold air or wet materials entering the pre-drying section. The high-temperature exhaust gas discharged from the main dehydration section first passes through a cyclone dust collector to recover fine powder, and then enters a spray condenser tower or a heat pump waste heat recovery system. The cooled exhaust gas is then partially recycled to the inlet of the main dehydration section and partially used in the active stabilization section or the pre-drying section.
2. The method for reducing the moisture content of slag according to claim 1, characterized in that: The pre-drying section in step A is carried out in a high-energy ball mill or a high-speed mechanical shear activation machine. The system's low-temperature waste heat is introduced as the main heat source, and mechanical activation is performed for 10-60 minutes at a medium to high energy intensity. Then, the slag is heated to 120-150°C. At this relatively mild temperature, the free water and some capillary water between the slag particles are slowly and evenly evaporated, thereby avoiding the surface from drying and forming a crust too quickly and leaving a channel for internal moisture migration. The pre-drying section is operated under a slight negative pressure.
3. The method for reducing the moisture content of slag according to claim 2, characterized in that: The mechanochemical effects induced by the mechanical activation treatment are as follows: a) It destroys the original hydroxyl (-OH) structure on the surface of slag particles, weakening their hydrogen bonding force with water molecules; b) It causes lattice defects and dislocations on the surface of slag particles, increases the degree of surface amorphization, and changes their surface energy; c) Some closed pores are opened.
4. The method for reducing the moisture content of slag according to claim 1, characterized in that: In step B, the main dehydration section uses a mixture of high-temperature hot air and medium-temperature exhaust gas from the pre-drying section as a heat source. Through precise control, the material bed is rapidly heated and stabilized in the medium-temperature range of 350-400℃. The main dehydration section operates under significant negative pressure, forming a strong driving force for moisture escape.
5. The method for reducing the moisture content of slag according to claim 1, characterized in that: The active stabilization stage in step C is carried out in a belt dryer or paddle dryer, and is dried at a relatively low temperature (70-120℃) and a vacuum degree of -0.06MPa to -0.095MPa. The material's own sensible heat and the medium-low temperature hot air from the high-temperature exhaust gas from the main dehydration stage are used for heat exchange, and the material temperature is slowly reduced to ≤200℃ through precise air volume control.
6. The method for reducing the moisture content of slag according to claim 1, characterized in that: In step D, the exhaust gas temperature of the active stabilization section is 120-150℃, and the high-temperature exhaust gas temperature of the main dehydration section is 450-550℃. The negative pressure of the entire system is uniformly established at the tail by the induced draft fan and is precisely distributed and controlled by the opening of the air valves between each section to ensure that the pre-drying section, the main dehydration section and the active stabilization section form the required gradient negative pressure environment.