Pretreatment process and preparation method of solid waste cementitious material

Abstract

This invention discloses a pretreatment process and preparation method for solid waste gelling materials, relating to the field of solid waste gelling materials. The aim is to provide a pretreatment process for solid waste gelling materials. The technical solution involves: storing the solid waste material in a stockpile after pressure filtration for sun drying; further drying the sun-dried solid waste material using a double-paddle dryer; breaking up the dried solid waste material using a dispersant and then drying it using a disc dryer; finally, grinding the dried solid waste material using a ball mill to obtain dried solid waste material powder. Through dehydration and secondary grinding, dried particles of solid waste gelling material can be obtained, enabling its widespread use in traditional building materials, reducing the cost of solid waste treatment and achieving resource utilization of waste.

Description

Technical Field

[0001] This invention relates to the field of solid waste cementitious materials, specifically to a pretreatment process and preparation method for solid waste cementitious materials. Background Technology

[0002] Red mud is a highly alkaline, extremely fine-particle industrial solid waste generated during the alumina extraction process in the aluminum industry. Its main environmental hazard is the alkaline leachate. Because alumina production requires the treatment of bauxite with limestone and strong alkali, this process results in highly alkaline red mud. Low-cost dealkali removal remains a common and challenging technology in the industry, thus limiting the large-scale utilization of red mud in traditional building materials.

[0003] However, in the field of mine backfill materials and comprehensive utilization of solid waste, making full use of the high alkalinity of red mud to prepare low-cost backfill cementitious materials is an important way to realize the comprehensive utilization of red mud. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention discloses a pretreatment process and preparation method for solid waste cementitious materials. The technical solution adopted includes the following steps:

[0005] Step 1: After the solid waste material is filtered, it is stored in the stockpile for drying and dehydration;

[0006] Step 2: The solid waste material dried in Step 1 is further dried using a double-blade dryer;

[0007] Step 3: After the solid waste material dried by the double-blade dryer in step 2 is broken up by a breaker, it is then dried by a disc dryer.

[0008] Step 4: The solid waste material dried by the disc dryer in step 3 is ground by a ball mill to obtain dried solid waste material powder.

[0009] As a preferred technical solution of the present invention, in step 1, the moisture content of the solid waste material after pressure filtration is 35-40%, and it is dried and dehydrated to 15%.

[0010] As a preferred technical solution of the present invention, in step 2, the blade dryer is used to dry the water content to 3-5% by steam at high temperature.

[0011] In a preferred embodiment of the present invention, in step 3, the moisture content is dried to below 1% using a disc dryer.

[0012] As a preferred embodiment of the present invention, the solid waste material is a granular, water-containing solid waste material.

[0013] As a preferred embodiment of the present invention, the solid waste material includes red mud, titanium gypsum, and carbide slag.

[0014] This invention also discloses a solid waste cementitious material prepared by the above-mentioned solid waste material pretreatment method, comprising the following components by weight:

[0015] 60-80% mineral powder, 1-5% cement, 5-20% titanium gypsum, 1-5% carbide slag, 5%-10% red mud.

[0016] Analysis of the raw materials used in mine backfilling materials reveals that they primarily utilize slag, fly ash, and gypsum as main materials, supplemented by a small amount of cement and alkaline activators to prepare backfilling cementitious materials that can effectively replace cement. This type of low-cost, high-performance cementitious material is collectively referred to as alkali-activated material, which is essentially a cementitious system obtained by reacting alkali metal raw materials (solid or solution) with solid silicate powder. The high alkalinity of red mud can perfectly replace traditional alkaline activators, making it theoretically entirely feasible.

[0017] Based on recent academic research from universities and research institutions on the comprehensive utilization of red mud, numerous studies have documented the use of red mud in conjunction with multi-source solid waste to prepare cement-based and geopolymer-based cementitious materials. Among these, the red mud-slag binary system and the red mud-slag-gypsum ternary system are the most mature applications. Taking Longkou City, Yantai, where the solid waste pretreatment production line is located, as an example, extensive testing over nearly a year has shown that red mud from Nanshan Aluminum and Zibo Weiqiao can effectively replace traditional alkaline activating materials.

[0018] By utilizing the steam exhaust gas from power plants and employing a two-stage drying method—a hollow paddle dryer followed by a disc dryer—the moisture content of solid waste such as red mud is reduced to approximately 1%. This allows red mud to be used as an important raw material for alkaline activating materials in the preparation of cementitious materials for mine backfilling. The use of red mud-like solid waste can reduce high carbon dioxide emissions from cement clinker and other materials, demonstrating significant social and economic value.

[0019] The beneficial effects of this invention are as follows: This invention can obtain dry granules of solid waste gel material through dehydration and secondary grinding, which can be widely used in traditional building materials, reducing the treatment cost of solid waste and enabling the resource utilization of waste.

[0020] Furthermore, by using red mud, titanium gypsum, and carbide slag as activators to stimulate the activity of mineral powder in cementitious materials, low-cost, high-activity solid waste cementitious materials can be obtained. Solid waste cementitious materials not only achieve resource conservation, reduced carbon emissions, environmental protection, and sustainable development, but also reduce solid waste treatment costs for enterprises, bringing greater economic benefits. Red mud, through two-stage drying using a paddle dryer and a disc dryer, followed by rolling grinding in a ball mill, can yield qualified red mud powder. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0022] Figure 1 This is a schematic diagram of the red mud drying process of the present invention;

[0023] Figure 2 This is a schematic diagram of the external condensate connection pipeline of the dual-blade dryer of the present invention;

[0024] Figure 3 This is a schematic diagram of the steam system of the present invention;

[0025] Figure 4 The accompanying drawings illustrate the steam system of this invention.

[0026] In the diagram: 1. Loader; 2. Raw material hopper; 3. Belt scale; 4. Feeding belt conveyor; 5. Magnetic separator; 6. Twin-shaft mixer; 7. Twin-blade dryer; 8. Paddle discharge cutter; 9. Calciner feed elevator; 10. Electric three-way diverter valve; 11. Disperser; 12. Bidirectional screw conveyor; 13. Disc dryer; 14. Ball mill; 1401. Pipeline magnetic separator; 15. Baghouse dust collector; 16. Finished product silo; 1601. Silo top dust collector; 17. Rotary rotary valve; 18. First induced draft fan; 19. First chimney; 20. Double cyclone dust collector; 21. Water film dust collector; 22. Second induced draft fan; 23. Second chimney; 24. Compressed air system; 2401. Pipeline magnetic separator; 25. Pneumatic conveying system; 26. Primary drainage expansion tank; 27. Secondary drainage expansion tank. Detailed Implementation

[0027] Example 1

[0028] This embodiment discloses a first implementation of the present invention, such as... Figures 1 to 4 As shown, the pretreatment process and preparation method of solid waste cementitious materials are disclosed, and the steps are as follows:

[0029] Step 1: After the water-containing solid waste materials such as red mud, titanium gypsum, and carbide slag are filtered, the moisture content is 35% and stored in the stockpile. They are then dried and dehydrated to 15% to reduce the energy consumption of subsequent drying.

[0030] Step 2: Loader 1 feeds the dehydrated solid waste material into raw material hopper 2. Raw material hopper 2 is equipped with an anti-blocking device. After being weighed by belt scale 3 below raw material hopper 2, it is conveyed to feeding belt conveyor 4. Belt scale 3 is used to provide a stable and required amount of raw solid waste material to the production line to ensure the stability of various process parameters of the production line. After iron removal by iron separator 5 above, the solid waste material is sent to twin-shaft mixer 6 and then to twin-paddle dryer 7 for drying, drying the moisture content to 3%. Steam from the steam pipeline enters the primary condensate expansion tank 26 for separation, and then enters the paddle shaft of twin-paddle dryer 7 to provide heat to twin-paddle dryer 7. During the heat exchange process, steam condenses to produce condensate, which is then discharged through... Figure 2 The pipeline shown runs from the blades to the blade housing. Water separated by the primary condensate expansion tank 26 is introduced into the blade housing through the pipeline and sent to the owner's condensate recovery device along with the condensate generated by the dual-blade dryer 7. The gas generated by the dual-blade dryer 7 is dusted by the dual-cyclone dust collector 20, and the solids are sent to the dual-shaft mixer 6 for mixing. The gas is then sent to the water film dust collector 21 for further dust removal, and then discharged into the second chimney 23 by the second induced draft fan 22. There is a manual butterfly valve between the dual-blade dryer 7 and the dual-cyclone dust collector 20.

[0031] Step 3: The solid waste material dried by the double-blade dryer 7 leaves the double-blade dryer 7 and is sent to the calciner feed elevator 9 by the blade discharge cutter 8. After being lifted to a high position, it is split by the electric three-way diverter valve 10. One path returns to the double-shaft mixer 6 for mixing, and the other path enters the disperser 11 for dispersing. This breaks up the hard lumps that appear in the raw material solid waste material during generation, storage, transportation and drying, so as to facilitate the stable operation of the disc dryer 13 and make the material drying more uniform.

[0032] Step 4: The solid waste material, after being broken down by the dispersant 11, is fed into the disc dryer 13 via the bidirectional screw conveyor 12 for secondary drying. The broken and crushed solid waste material directly enters the disc dryer 13, where it is spread out by the scrapers. Due to the continuous pushing of the scrapers, the material is evenly turned and moved forward to the next layer. It is then continuously pushed and turned by the scrapers on the lower layer, and after drying, it falls into the lower drying tray. After the work of multiple scrapers and drying trays, the material flows out of the disc dryer 13 through the scraper on the last layer, drying the moisture content to below 1%. After drying, the solid waste material is pulverized by ball mill 14, then iron is removed by pipeline iron separator 1401, and then it is sent to finished product silo 16 by pneumatic conveying system. Finished product silo 16 is equipped with silo top dust collector 1601, and the compressed air for silo top dust collector 1601 comes from compressed air system 24. Steam from steam pipeline enters secondary condensate expansion tank 27 for separation, and then enters disc dryer 13 to provide heat. During the heat exchange process, steam condenses to produce condensate, which is sent to the owner's condensate recovery device. The condensate separated by secondary condensate device 27 is discharged.

[0033] The air outlet of the disc dryer 13 enters the bag filter 15 via a manual butterfly valve. The compressed air of the bag filter 15 comes from the compressed air system 24. The filtered clean air is sent into the first chimney 19 by the first induced draft fan 18 and discharged.

[0034] To avoid a potential decrease in output when the moisture content is high, a dedicated return process is added to the drying section. When the moisture content is high, a portion of the dry material is returned from the secondary drying stage. Specifically, the dust filtered by the bag filter 15 is fed into the twin-shaft mixer 6 via the rotary valve 17. The dry material's temperature and strong absorbency absorb the water from the raw material. The opening size of this process is determined by the moisture content of the raw material. This ensures that the moisture content of the solid waste material dried by the twin-blade dryer 7 is controlled to 5-6%.

[0035] The disc dryer and disc drying machine mentioned in this invention refer to disc dryer 13.

[0036] This embodiment also discloses a solid waste cementitious material, the technical solution of which includes the following components:

[0037] 60% mineral powder, 5% cement, 20% titanium gypsum, 5% carbide slag, and 10% red mud.

[0038] Example 2

[0039] The difference between this embodiment and embodiment 1 is that, in the process of drying solid waste materials, the moisture content of the raw solid waste materials piled up in the stockpile in step 1 is 40%, and in step 2, the moisture content of the dried solid waste materials is reduced to 5% by the double-blade dryer 7.

[0040] The solid waste cementitious material includes the following components: 80% mineral powder, 5% cement, 5% titanium gypsum, 1% carbide slag, and 9% red mud.

[0041] Example 3

[0042] The difference between this embodiment and embodiment 1 is that, in the process of drying solid waste materials, the moisture content of the raw solid waste materials piled up in the stockpile in step 1 is 37%, and in step 2, the moisture content of the dried solid waste materials is reduced to 4% by the double-blade dryer 7.

[0043] The solid waste cementitious material comprises the following components: 60% mineral powder, 5% cement, 20% titanium gypsum, 5% carbide slag, and 10% dried red mud powder.

[0044] The circuit connection, i.e., the automatic control scheme, involved in this invention is a common method used by those skilled in the art, and technical inspiration can be obtained through a limited number of experiments. It is common knowledge.

[0045] Components not described in detail in this article are existing technologies.

[0046] While the specific embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and modifications or variations without creative effort are still within the protection scope of the present invention.

Claims

1. A pretreatment process for solid waste cementitious materials, characterized in that, Includes the following steps: Step 1: After the solid waste material is filtered, it is stored in the stockpile for drying and dehydration; Step 2: The solid waste material dried in Step 1 is further dried by a double-blade dryer (7); using the steam tail gas of the power plant, the steam from the steam pipeline enters the first-stage condensate expansion tank (26) for separation, and the steam enters the blade shaft of the double-blade dryer (7) to provide heat to the double-blade dryer (7). During the heat exchange process, the steam condenses to produce condensate water, which is piped from the blade shaft to the blade shell. The water separated in the first-stage condensate expansion tank (26) is piped into the blade shell and sent to the owner's condensate water recovery device together with the condensate water produced by the double-blade dryer (7); the gas produced by the double-blade dryer (7) is dusted by a double cyclone dust collector (20), the solid is sent to a double-shaft mixer (6) for mixing, the gas is sent to a water film dust collector (21) for further dust removal, and then sent to the second chimney (23) by the second induced draft fan (22) for discharge; Step 3: After the solid waste material dried by the double paddle dryer (7) in step 2 is broken up by the breaker (11), it is dried by the disc dryer (13). The solid waste material dried by the double paddle dryer (7) leaves the double paddle dryer (7) and is sent to the calciner feed elevator (9) by the paddle discharge cutter (8). After being lifted to a high position, it is divided by the electric three-way branch valve (10). One path returns to the double shaft mixer (6) for mixing, and the other path enters the breaker (11) for breaking. Step 4: The solid waste material dried by the disc dryer (13) in step 3 is ground by the ball mill (14) to obtain dried solid waste material powder.

2. The pretreatment process for solid waste cementitious materials according to claim 1, characterized in that: In step 1, the moisture content of the solid waste material after pressure filtration is 35-40%, and it is dried to 15% moisture content.

3. The pretreatment process for solid waste cementitious materials according to claim 1, characterized in that: In step 2, the paddle dryer dries the water to 3-5% moisture content using steam at high temperature.

4. The pretreatment process for solid waste cementitious materials according to claim 1, characterized in that: In step 3, the moisture content is dried to below 1% using a disc dryer.

5. The pretreatment process for solid waste cementitious materials according to any one of claims 1 to 4, characterized in that: The solid waste material is a granular, water-containing solid waste material.

6. The pretreatment process for solid waste cementitious materials according to claim 5, characterized in that: The solid waste materials include red mud, titanium gypsum, and carbide slag.

7. A solid waste cementitious material prepared by pretreatment using the pretreatment process for solid waste cementitious materials as described in claim 1, characterized in that, The components are proportioned by weight as follows: 60-80% mineral powder, 1-5% cement, 5-20% titanium gypsum, 1-5% carbide slag, 5%-10% red mud.

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