Method and apparatus for direct drying of mineral sediment by cylinder drawing process

Abstract

Method and apparatus for direct drying of mineral sediment by cylinder drawing process

Description

Method and apparatus for direct drying of mineral sediment by cylinder drawing process Technical background The present disclosure relates to technology for processing solid waste / drying sludge, in particular, a process and an apparatus for directly drying inorganic sludge by a cylindrical process. Fan background With the rapid development of the economy and population growth of cities, as well as the increase in the processing rate of industrial and municipal wastewater, the amount of sludge produced in sewage treatment plants is increasing day by day. Due to the relatively old sludge processing technology, the phenomenon that is becoming more and more serious is that cities are almost surrounded by sludge. Sludge drying is a necessary matter to realize the harmlessness, reduction and recycling of sludge. After the sludge is mechanically dewatered from the sewage treatment plant, its water content is generally between 75 and 85%. If the water content of the sludge is reduced to 20% or less, the conventional sludge drying technology usually uses electric or steam heating, which consumes a lot of energy and leads to increased sludge drying costs. Among the existing sludge drying technologies, CN200510048978.6 uses the waste heat of a boiler; CN200510049554.1 and CN200510049556.0 use the waste heat of a power plant flue gas; and CN200410052759.0 discloses a reverse flow type temperature-controlled sludge drying apparatus and method, in which dry sludge with a particle size of more than 4 mm moves backward and is mixed with wet sludge, and the sludge is cut into smaller pieces by a steel wire mesh and then enters a rotary kiln, thereby increasing the drying efficiency by hot air. However, if the water content of the sludge is too high, this process cannot be carried out. CN03155966.2 uses a negative pressure aeration process. While the channels for the diffusion and spread of various viruses produced in the sludge processing process are cut off, the leakage and spread of contaminated air and the viruses carried in it in the system space can be prevented during the movement of the system.However, since all the devices in this process are portable equipment, its processing capacity must be relatively small and continuous operation cannot be realized. On the other hand, as a major country in terms of steel production, our country's annual steel production is nearly 1 billion tons. At the same time, more than 200 million tons of steel slag are produced annually. The thermal energy contained in each ton of slag is equivalent to 60 kilograms of standard coal. Since slag is a poor thermal conductor, the slag waste heat recovery technology has a slow process and a large amount of heat is wasted. In order to address the challenge that traditional sludge drying is costly, which affects sludge processing, while the waste heat of steel slag cannot be effectively utilized, the present disclosure proposes a process route and an implementation method for sludge drying using waste heat of metallurgical slag. Summary The purpose of the present disclosure is to provide a method and apparatus for direct drying of inorganic sludge by a cylindrical process in which a processing technology that includes a hot slag cylindrical process is used to mix slag and sludge in a specific ratio, thus addressing the two challenges of cooling and granulating slag and drying inorganic sludge in one step. To achieve the above goal, the technical solution of the present disclosure is as follows: A method for drying inorganic sludge with slag, comprising the following steps: mixing slag and sludge; and separating steel slag and dry sludge after reducing the water content of the sludge to 3% - 15%. Preferably, the mass ratio of slag to sludge is 3 - 1.5. Preferably, mixing and drying are carried out in batch, by flow addition or by half-flow addition. Preferably, the separation of steel slag and dry sludge is carried out by a combination of screening and spinning. Further preferably, the steel slag and dry sludge are separated by screening, where the number of screen meshes is not less than 60 meshes. Preferably, the method further comprises a tail gas processing step and a tail sludge processing step. Further preferably, the tail gas processing comprises: processing the dust and sulfides in the tail gas generated during sludge drying using wet alkaline scrubbing and / or activated carbon adsorption, and then discharging the tail gas; and the tail sludge processing comprises wet scrubbing or spraying the resulting dust, collecting the dust, mixing the dust with the dried sludge, stirring and mixing with slag for drying processing. Preferably, the mixing of slag and sludge is carried out in a cylinder containing steel balls. Preferably, the method includes: transferring the slag and sludge to a cylinder containing steel balls by respective transfer devices; and after the water content of the sludge is reduced to 15%-3%, transferring a mixture of the steel slag and the dry sludge to a slag sludge separation device by a slag sludge transfer device located at the outlet end of the cylinder to separate the steel slag from the dry sludge, where the dust and sulfides in the tail gas generated during the sludge drying are fed into a tail gas processing device from an outlet of the cylinder, and the gas is discharged after processing; where the dust separated in the tail gas processing is fed into a tail gas mixing device from the mud and dust outlet of the tail gas processing device, mixed with the sludge to be dried, and then conveyed to the cylinder through a mud transfer pipeline. Preferably, the inorganic sludge has an initial water content of 99%-70%; the slag and inorganic sludge are added by flow addition or half-flow addition; the inorganic sludge is processed at a rate of 10t / h-80t / h; and the slag is processed at a rate of 30t / h-120t / h. Preferably, after mixing and drying, the slag sludge has a temperature of 100 - 130 °C. Preferably, the difference between the water content of the tailings sludge and the water content of the inorganic sludge to be dried does not exceed ±5%. Another method for direct drying of inorganic sludge is presented by a cylindrical process, in which, the method includes the following steps: 1) Mixing sludge with slag in the cylinder for drying In which the slag and sludge are conveyed to a cylinder with their respective conveying device at a specific mass ratio, in which the slag and sludge are mixed, heat exchanged, dewatered, cooled and broken by the rotation of the cylinder and the rolling of steel balls, resulting in the slag and sludge being cooled and dried, followed by direct discharge; wherein the inorganic sludge has an initial water content of 99%-70%, and a target water content of 15%-3% after drying; wherein the slag / sludge flow ratio (by mass) of slag to inorganic sludge is 3.0-1.5, wherein the dryable inorganic sludge has a capacity of 10t / h-80t / h; 2) Separating slag from sludge In which steel slag and dry sludge are separated by a combination of screening and spinning. 3) Tail gas processing In which wet alkaline washing and activated carbon adsorption are performed to process the dust and sulfides in the tail gas produced during sludge drying by the cylinder process, and then the gas is discharged. 4) Tailings sludge processing Wherein steam and dust are generated after the slag and sludge are processed in the cylinder, where the dust is transported by steam to the tail gas processing device, where the dust is wet washed or sprayed, collected, and then conveyed by a conveying device to a tail sludge mixing device, where the dust is mixed with the initial sludge, stirred, and then continuously conveyed to the cylinder by a conveying device such as a sludge pump for drying, thereby achieving zero discharge of undried sludge; wherein the water content of the tail sludge after mixing and stirring should not have a large difference from the initial water content of the inorganic sludge, where the difference in water content should not exceed ±5%. Preferably, in step 2), a screening process is used to separate the slag from the sludge, where the number of screen meshes is not less than 60 meshes. An apparatus for directly drying inorganic sludge by a cylindrical process according to the present disclosure includes: a cylinder containing a plurality of steel balls; a slag sludge conveying device having an inlet end corresponding to the outlet of the cylinder; a slag sludge separating device having an inlet end corresponding to the outlet of the slag sludge conveying device and outlets corresponding to various storage boxes; a tail gas processing device having a gas inlet connected to the outlet of the cylinder through a conveying pipeline; a tail sludge mixing device having an inlet connected to the mud and dust outlet of the tail gas processing device through the conveying pipeline; a mud conveying pipeline configured to connect the outlet of the tail sludge mixing device to the inlet of the cylinder; and a mud pump disposed on the mud conveying pipeline for pumping mud into the cylinder. Preferably, the slag sludge separation device uses a screening process, in which the number of screen meshes is not less than 60 meshes. The present disclosure uses a hot slag cylinder process. Slag and inorganic sludge are synchronously transferred to the cylinder at a specific ratio by the slag conveying device and the sludge conveying system, respectively. The slag and sludge are thoroughly mixed by the rotation of the cylinder. After the mass and heat transfer process of the slag and sludge, cold granulated slag and dry sludge with the required water content are obtained. The present disclosure device can carry out the rapid, stable and continuous processing of slag granulation and sludge drying. In the present disclosure method: (1) Sludge drying process by mixing with slag The slag and sludge may be conveyed by respective conveying devices to a suitable chamber at a specific mass ratio. A suitable stirring device may be provided in the chamber to achieve complete mixing and contact of the slag and sludge. Preferably, the chamber itself can rotate under an external force. Preferably, the desired chamber is a cylinder in which there are a certain number of steel balls of a certain size. The slag and sludge under the action of the rotating cylinder and the rolling steel balls undergo physical processes such as mixing, heat exchange, dehydration, cooling and crushing, so that the cooling and granulation processes of the slag are carried out, and the direct drying of the sludge is carried out until the desired water content in the sludge is reached. In all drying processes, the slag and sludge are rapidly cooled and dried within minutes, and then directly discharged. Generally, the mass ratio of slag to sludge in the chamber is 3 – 1.5. If the mass ratio of slag / sludge in the chamber is less than 1.5, a drying process should be provided before the mechanical process on site to reduce the OG of the sludge water to below 40%. This seriously affects the efficiency of sludge drying, makes continuous production impossible, and greatly increases the investment of equipment. As a result, the advantages of the drum sludge drying process cannot be achieved. If the mass ratio of slag / sludge exceeds 3, the temperature of the slag and sludge will be too high. If the temperature exceeds 250 °C, water must be added to control the temperature. This seriously affects the output of the dried sludge. For mixing and drying, the slag and sludge may be added in batches, by adding a stream, or by adding a half-stream. If mixing and drying is done in batches, the slag and sludge are added to the chamber in a mass ratio specified by the present disclosure. After the drying process, the slag and sludge mixture is poured out, and the next batch of slag and sludge is subjected to mixing and drying. Adding a stream means that the slag and sludge are added to the chamber continuously at a given flow rate, and the mixed and dried slag and sludge are continuously discharged from the chamber. Adding a half-stream means that the addition of slag and / or sludge is not continuous. Instead, a certain amount of slag and / or sludge is added at intervals according to the mixing and drying mode in the chamber. Generally, when mixing and drying is carried out in the flow addition mode, the flow rate of slag entering the cylinder is 30t / h-120t / h, the flow rate of dryable inorganic sludge is 10t / h-80t / h, and the flow rate of slag / sludge to inorganic sludge is 3.0-1.5. Generally, the initial water content of inorganic sludge (not dried in any way) is 99% - 70%, and the target water content after drying is 15% - 3%. (2) Slag separation process from sludge After cooling and drying, the slag and sludge are completely mixed together, and in order to facilitate the use of subsequent resources, they must be separated. In general, steel slag and dry sludge have significant differences in physical properties. The main differences are in density, particle size, and so on. Therefore, in the present disclosure, a combination of screening and spinning is adopted to separate steel slag from dry sludge. Since the particle sizes of steel slag and dry sludge are at least slightly different, in the present disclosure, a screening process in which the number of screen meshes is not less than 60 meshes, generally 80-100 meshes, is preferably used. (3) Tail gas processing process The tail gas produced during sludge drying by cylindrical process contains dust, sulfides and other environmentally harmful substances. Therefore, the tail gas needs green processing before discharge. The tail gas processing process includes wet alkaline washing and activated carbon adsorption to achieve green emission. (4) Tailings sludge processing process After the slag and sludge are processed in the cylinder, a large amount of steam and dust are generated, and the dust is transported by the steam into a tail gas processing device. The dust is collected after wet washing or spraying in the tail gas processing device, and then transported to the tail sludge mixer by a conveying device such as a sludge pump, where it is mixed and stirred with the primary sludge. It is regularly transported by a conveying device such as a sludge pump to the cylinder where it will be dried, resulting in zero discharge of undried sludge. The water content of the tail sludge after mixing and stirring should not be much different from that of the primary sludge, so as not to affect the subsequent conveying efficiency and sludge drying. In general, this water content difference should not exceed ± 5%. The beneficial effects of current disclosure include: Compared with the existing technology for drying sludge with a tail gas heat source from a power plant, etc., the present disclosure can effectively utilize the high heat of the slag according to different needs (target water content), and achieve rapid, stable and continuous direct drying of inorganic sludge and separation of slag sludge. This leads to the subsequent utilization of granular slag and sludge powder resources, so that the added value of the dried sludge is increased. Considering the availability of process equipment, the present disclosure adopts the cylindrical technology used in the processing of hot steel slag. The device has a simple structure and is easy to operate. Description of shapes Figure 1 is a flow chart of a process for drying inorganic sludge with a cylinder according to the present disclosure. Figure 2 is a schematic view showing the structure of an inorganic sludge drying apparatus with a cylinder according to the present disclosure. Detailed description Referring to Figure 1, the method of direct drying of inorganic sludge by a cylindrical process includes the following steps: 1) Mixing sludge with slag in the cylinder for drying The slag and sludge are conveyed to a cylinder with their respective conveying devices at a certain ratio, where the slag and sludge are mixed, heat exchanged, dewatered, cooled and broken by the rotation of the cylinder and the rolling of the steel balls, and the slag and sludge are cooled and dried, followed by direct discharge. The initial content of the inorganic sludge is 99%-70% and the target water content is 15%-3% after drying. The flow ratio of slag / sludge to inorganic sludge is 0.3-1.5. The mass of the inorganic sludge that can be dried is 10t / h-80t / h. 2) Separating slag from sludge Steel slag and dry sludge are separated by a combination of screening and spinning. 3) Tail gas processing Wet alkaline washing and activated carbon adsorption are used to process dust, sulfides, and organic compounds in the tail gas produced during sludge drying by the cylindrical process, and then the gas is discharged. 4) Tailings sludge processing Steam and dust are generated during the processing of slag and sludge in the cylinder. The dust is introduced into the tail gas processing device by steam, where the dust is subjected to wet washing or spraying, and then collected. Then, the dust is conveyed by a conveying device to the tail sludge mixing device, where the dust is mixed with the primary sludge, stirred, and then regularly, by a conveying device such as a sludge pump, in a quantitative manner, to the cylinder device for drying operation, thereby achieving zero discharge of undried sludge. The water content of the tail sludge after mixing and stirring should not have a large difference from the water content of the primary sludge, while the difference in water content should not exceed ± 5%. Preferably, in step 2), a screening process is used to separate the slag from the sludge, in which the number of screen meshes is not less than 60 meshes. Referring to Figure 2, the apparatus for directly drying inorganic sludge by a cylindrical process according to the present disclosure includes: a cylinder 1 containing a plurality of steel balls; a slag sludge conveying device 2 with an inlet end corresponding to the outlet of the cylinder 1; a slag sludge separating device 3 having an inlet end corresponding to the outlet of the slag sludge conveying device 2 and outlets corresponding to various storage boxes; a tail gas processing device 4 having a gas inlet connected to the outlet of the cylinder 1 through a conveying pipeline; a tail sludge mixing device 5 having an inlet connected to a mud and dust outlet of the tail gas processing device 4 through a conveying pipeline, wherein an outlet of the tail sludge mixing device 5 is connected to an inlet of the cylinder 1 through a mud conveying pipeline and a sludge pump. Preferably, the slag sludge separation device uses a screening process, in which the number of screen meshes is not less than 60 meshes. The present disclosure uses a hot slag cylinder process. Molten slag and inorganic sludge are respectively synchronously transferred to the cylinder at a specific ratio by a slag conveying device and a sludge conveying system. The slag and sludge are thoroughly mixed by the rotation of the cylinder. After the mass and heat transfer process of the slag and sludge, cold granulated slag and dry sludge with required water content are obtained. The present disclosure can realize rapid, continuous and low-cost processing of slag granulation and sludge drying. The process is as follows: Metallurgical slag 100 is first continuously transferred from a slag boiler to a rotating cylinder 1. At the same time, inorganic sludge is transferred to the cylinder 1 at a certain flow rate by a sludge transfer device from the place where it is produced. Under the combined action of the cylinder body and the steel balls in the cylinder 1, the slag and the sludge containing water are thoroughly mixed. After the heat and mass transfer process, the slag is granulated, and the sludge water is drawn out. Then the sludge 200 is transferred to the slag and sludge separation device 3 for processing by the sealed slag and sludge transfer device 2. The separated materials are stored in different boxes according to the composition and classification. The waste gas generated during the drying of the sludge cylinder is purified by the tail gas processing device 4 and discharged if the discharge standard is met.The tail sludge produced in the tail gas processing device 4 is pumped into the inlet of the tail sludge mixing device 5 by a sludge transfer pump, mixed with the mud produced from the sludge source, stirred uniformly by a stirrer, and pumped by a sludge pump with a certain concentration into a mud transfer pipeline through which it is sent to the cylinder 1. Example 1 According to a comprehensive steel slag granulation processing process and OG sludge drying with a cylinder in a steelmaking plant, a single-cylinder machine processes 180,000 tons of high-temperature steel slag annually. In the steel slag processing process, OG sludge with a water content of 80% was pumped into the cylinder machine. The water in the OG sludge was used to cool the steel slag at high temperature, while the sensible heat of the steel slag was used to dry the sludge. The desired water content in the sludge was set to 3%. The slag / sludge flow ratio fed into the cylinder was 1.0:1.9. 95,000 tons of OG sludge could be dried each year. After rapid processing such as cylinder cooling and water extraction, the slag sludge (100 - 130 °C) was directly transferred to the slag sludge separator by a conveying device. The sludge was dried to a water content of about 3%. The whole process took only 5 minutes. After complete heat exchange in the cylinder, the steel slag and dried sludge were continuously discharged from the bottom of the slag and sludge separation device.After screening and even spinning, the granular slag and sludge powder were sent to various storage boxes and waited for trucks to deliver to users. Example 2: In the steel slag processing process, the OG sludge with a water content of 70% was pumped into the cylinder device. The water in the OG sludge was used to cool the steel slag at high temperature, while the sensible heat of the steel slag was used to dry the sludge. The desired water content in the sludge was set to 15%. The flow ratio of slag / sludge fed into the cylinder was 1.0:1.5. After rapid processing such as cylinder cooling and water drawing, the slag sludge (130-100°C) was directly transferred to the slag sludge separator by a conveying device. The sludge was dried to a water content of about 3%. The whole process took only 5 minutes. After complete heat exchange in the cylinder, the steel slag and dried sludge were continuously discharged from the bottom of the slag and sludge separator. After screening and even turning, the granular slag and sludge powder were sent to different storage boxes and waited for trucks to deliver to users. Example 3: In the steel slag processing process, the OG sludge with a water content of 95% was pumped into the cylinder device. The water in the OG sludge was used to cool the steel slag at high temperature, while the sensible heat of the steel slag was used to dry the sludge. The desired water content in the sludge was set to 3%. The flow ratio of slag / sludge fed into the cylinder was 3.0:1.0. After rapid processing such as cylinder cooling and water drawing, the slag sludge (130-100°C) was directly transferred to the slag sludge separator by a conveying device. The sludge was dried to a water content of about 3%. The whole process took only 5 minutes. After complete heat exchange in the cylinder, the steel slag and dried sludge were continuously discharged from the bottom of the slag and sludge separator. After screening and even turning, the granular slag and sludge powder were sent to different storage boxes and waited for trucks to deliver to users. Example 4: In the steel slag processing process, a batch mode was adopted for feeding, in which the OG sludge with a water content of 80% was pumped into a cylinder device. The water in the OG sludge was used to cool the steel slag at high temperature, while the sensible heat of the steel slag was used to dry the sludge. The desired water content in the sludge was set to 3%. The mass ratio of slag / sludge fed into the cylinder was 1.9:1.0. After rapid processing such as cylinder cooling and water extraction, the slag sludge (130-100°C) was directly transferred to the slag sludge separator by a conveying device. The sludge was dried to a water content of about 3%. The whole process took only 5 minutes. After complete heat exchange in the cylinder, the steel slag and dried sludge were continuously discharged from the bottom of the slag and sludge separator. After screening and even spinning, the granular slag and sludge powder were sent to various storage boxes and waited for trucks to deliver to users.

Claims

Claims 1. A method of drying inorganic sludge with molten slag, comprising the following steps: mixing slag and sludge; and separating steel slag and dry sludge after a water content of the sludge is reduced to 3%-15%;the slag and the sludge are mixed in a drum containing steel balls.

2. The method of drying inorganic sludge with molten slag according to claim 1, wherein a mixing mass ratio of the slag to the sludge is 1.5-3.

3. The method of drying inorganic sludge with molten slag according to claim 1, wherein the steel slag and the dry sludge are separated by a combination of screening and spinning.

4. The method of drying inorganic sludge with molten slag according to claim 1, wherein the method further comprises a tail gas treatment step and a tail sludge treatment step.

5. The method of drying inorganic sludge with molten slag according to claim 4, wherein the tail gas treatment comprises: treating dust, sulfides and organic compounds existing in a tail gas generated during the drying of the sludge by means of wet alkaline washing and / or activated carbon adsorption, and then discharging the tail gas; the tail sludge treatment comprises wet washing or sprinkling the resulting dust, collecting the dust, mixing the dust with sludge to be dried, agitating, and mixing with slag for drying treatment.

6. The method of drying inorganic sludge with molten slag according to claim 1, wherein the method comprises: conveying the slag and the sludge to the drum containing the steel balls with respective conveying devices; and after the water content of the sludge is reduced to 3%-15%, conveying a mixture of the steel slag and the dry sludge to a slag-sludge separation device with a slag-sludge conveying device positioned at an outlet end of the drum to separate the steel slag from the dry sludge, wherein dust, sulfides and organic compounds existing in a tail gas generated during the drying of the sludge enter a tail gas treatment device from a drum outlet, and the gas is discharged when it satisfies the discharge standard after the treatment; wherein the dust separated in the tail gas treatment enters a tail sludge mixing device from a dust mud outlet of the tail gas treatment device, mixes with sludge to be dried, and is then conveyed to the drum through a mud conveying pipeline.

7. The method of drying inorganic sludge with molten slag according to claim 3, wherein the slag-sludge separation device utilizes a screening process, wherein a screen mesh number is not less than 60 meshes.

8. The method of drying inorganic sludge with molten slag according to claim 1, wherein mixing and drying are carried out in batches, by flow addition or by semi-flow addition.

9. The method of drying inorganic sludge with molten slag according to claim 1, wherein the method comprises the following steps: 1) Mixing sludge with slag in a drum for drying wherein the slag and the sludge are conveyed to the drum with their respective conveying devices at a specific flow ratio; wherein the slag and the sludge are mixed, heat exchanged, dehydrated, cooled and broken under the action of rotation of the drum and rolling of steel balls, whereby the slag and the sludge are cooled and dried, followed by direct discharge; wherein the inorganic sludge has an initial water content of 70%-99%, and a target water content of 3%-15% after drying; wherein a slag / sludge flow ratio of the slag to the inorganic sludge is 1.5-3.0; wherein the inorganic sludge has a flow rate of 10t / h-80t / h; 2) Separating the slag from the sludge wherein the steel slag and the dry sludge are separated by a combination of screening and spinning; 3) Treating tail gas wherein wet alkaline washing and activated carbon adsorption are utilized to treat dust, sulfides and organic compounds existing in the tail gas generated during the drying of the sludge by the drum process, and then the gas is discharged; 4) Treating tail sludge wherein the dust generated in the tail gas treatment is wet washed or sprinkled, collected, and then conveyed to a tail sludge mixing device with a conveying device, wherein the dust is mixed with primary sludge, agitated, and then regularly conveyed to the drum with a sludge pump for drying treatment, wherein a difference between a water content of the tail sludge after mixing and agitation and the initial water content of the inorganic sludge does not exceed ±5%.

10. The method of drying inorganic sludge with molten slag according to claim 9, wherein in step 2), a screening process is used for separating the slag from the sludge, wherein a screen mesh number is not less than 60 meshes.

11. An apparatus for directly drying inorganic sludge by a drum process, comprising: a drum containing a number of steel balls; a slag-sludge conveying device having an inlet end corresponding to an outlet of the drum; a slag-sludge separation device having an inlet end corresponding to an outlet of the slag-sludge conveying device and outlets corresponding to different stock bins; a tail gas treatment device having a gas inlet connected to the outlet of the drum through a conveying pipeline; a tail sludge mixing device having an inlet connected to a dust mud outlet of the tail gas treatment device through a conveying pipeline, where a dust from the tail gas treatment device is mixed with primary inorganic sludge; a mud conveying pipeline configured to connect an outlet of the tail sludge mixing device to an inlet of the drum; and a sludge pump arranged on the mud conveying pipeline for pumping the sludge to the drum.

12. The apparatus for directly drying inorganic sludge by a drum process according to claim 11, wherein the slag-sludge separation device utilizes a screening process, wherein a screen mesh number is not less than 60 meshes.

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