A process for cascaded utilization of sludge

Abstract

The present invention belongs to the technical field of sludge treatment, and specifically relates to a process for cascaded fractionation and utilization of sludge. The process for cascaded fractionation and utilization of sludge of the present invention comprises the following steps: (1) drying, crushing and floating the sludge to obtain carbon-rich sludge and sludge residue; (2) treating the sludge residue with an acid solution to obtain a metal salt solution and an acid-insoluble residue; (3) treating the carbon-rich sludge to prepare sludge charcoal; treating the metal salt solution to prepare magnesium-aluminum hydrotalcite; treating the acid-insoluble residue to prepare ceramsite. The process for cascaded fractionation and utilization of sludge of the present invention fractionates the sludge into high-quality cascades, and can prepare sludge charcoal, magnesium-aluminum hydrotalcite and ceramsite, thereby achieving the harmlessness, resource utilization and high-quality utilization of sludge.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge treatment, and in particular relates to a process for cascade quality-based utilization of sludge. Background Art

[0002] In the current trend of urbanization, urban water pollution has received more and more attention. With the continuous increase in the scale of urban sewage treatment plants and the application of new treatment processes and technologies, the sewage treatment capacity of sewage treatment plants has increased significantly, and the treatment effect is very ideal. However, due to the large population base in my country, the demand for water resources by urban populations has continued to increase, resulting in serious water shortages in some areas. In order to alleviate this situation, a variety of measures need to be taken to purify urban sewage. However, a large amount of sludge will be generated in the process of sewage purification. These sludges contain toxic and harmful substances such as a variety of heavy metals and pathogenic microorganisms, which have caused serious pollution to the environment and animals and plants, and brought a series of hazards, such as water, heat and organic nutrients in the sludge, which are difficult to be effectively recovered or recycled, resulting in waste of resources and environmental damage, which is not conducive to the reuse of resources. Therefore, in the process of treating sewage in urban sewage treatment plants, attention should also be paid to the resource utilization of sludge.

[0003] Treatment and disposal are two stages of sludge treatment and disposal. Treatment mainly refers to the process of sludge reduction, stabilization and harmlessness; disposal is the process of further absorbing, resource-based and energy-based sludge after treatment. Currently, the commonly used technical methods are sanitary landfill, incineration, land utilization, etc. Sanitary landfill is a traditional sludge disposal technology from the perspective of environmental protection in the early days. This technology is simple and easy to operate. Generally, the pre-treated sludge is landfilled together with domestic garbage, compacted and covered with soil by tools. When landfilling, the lower layer of the land needs to be paved to prevent leakage and pollution. Landfill occupies a large area and has high transportation costs. It cannot fundamentally eliminate pollution to the environment, and its application is greatly restricted or even eliminated. Incineration is considered to be the most effective method for sludge volume reduction. It transforms and decomposes organic matter and pathogens in sludge through high-temperature oxidation combustion. This method occupies a small area and has complete treatment, but the incineration process requires a series of specific system devices, including storage and transportation, drying, incineration, waste heat utilization, flue gas purification and other equipment, which are expensive and difficult to operate. Composting is a harmless resource utilization technology that utilizes organic matter, nitrogen, phosphorus, potassium and various trace elements that are beneficial to plant growth in sludge. Under aerobic conditions, microbial metabolism converts organic matter into stable humus for use in agricultural and forestry land. Composting requires a certain amount of land, a long cycle, aeration equipment, and technical problems such as unstable and difficult to control microbial domestication and stacking processes, as well as the generation of harmful gases such as hydrogen sulfide. Therefore, people are in urgent need of a simple, efficient, and zero-pollution sludge disposal method to achieve industrialized treatment and utilization of sludge.

[0004] The treatment of domestic sludge should abandon the old concept of "focusing on water and neglecting mud", prescribe the right medicine for the right disease, and find a sludge treatment method suitable for different mud qualities. Fresh dehydrated sludge must be treated and disposed of in a timely and effective manner, and cannot be piled up for a long time, otherwise the dehydration performance and sanitary conditions will seriously deteriorate and affect subsequent treatment. In this way, the sludge can be reduced, harmless and resourced to the greatest extent, secondary pollution can be prevented and controlled, and resource waste can be eliminated. At present, facing the increasingly severe environmental situation, countries around the world are facing the problem of sludge treatment and disposal. On the basis of sludge reduction and stabilization treatment and disposal, we must also focus on developing sludge resource and energy technologies.

[0005] Therefore, it is necessary to provide an improved technical solution to address the above-mentioned deficiencies in the prior art. Summary of the invention

[0006] The object of the present invention is to provide a process for cascade quality-based utilization of sludge, so as to help solve or improve at least one of the problems of the prior art in sludge treatment process being complex, long cycle, high cost and unstable process.

[0007] In order to achieve the above-mentioned object, the present invention provides the following technical scheme: a process for cascade fractionation and utilization of sludge, comprising the following steps: (1) drying, crushing and floating the sludge to obtain carbon-rich sludge and sludge residue; (2) treating the sludge residue with an acid solution to obtain a metal salt solution and an acid-insoluble residue; (3) treating the carbon-rich sludge to prepare sludge charcoal; treating the metal salt solution to prepare magnesium-aluminum hydrotalcite; and treating the acid-insoluble residue to prepare ceramsite.

[0008] Preferably, the preparation of the sludge charcoal comprises the following steps: A1. mixing the carbon-rich sludge with agricultural and forestry wastes and immersing them in a solution containing an activator; A2. filtering and drying after the immersion treatment; A3. activating the product obtained by the treatment in step A2 to obtain the sludge charcoal.

[0009] Preferably, the mass ratio of the carbon-rich sludge to the agricultural and forestry waste is 1:1-3:7; and the agricultural and forestry waste includes at least one of sawdust, wheat straw and corn straw.

[0010] Preferably, the activator is at least one of zinc chloride, sodium hydroxide and potassium hydroxide; the mass ratio of the carbon-rich sludge to the activator is 1:1-1:3; in step A1, the immersion treatment time is 8-24h, and the immersion treatment is carried out under stirring.

[0011] Preferably, in step A3, the temperature of the activation treatment is 500-800° C., and the time of the activation treatment is 30-90 min.

[0012] Preferably, in step (2), the pH of the acid solution is 2-5; the temperature of the acid solution is 50-80°C; the dissolution time of the acid solution is 8-24h; and the mass ratio of the sludge residue to the acid solution is 1:1-1:5.

[0013] Preferably, before step (2), the step of mixing the magnesium compound with the sludge residue is also included; the preparation of magnesium aluminum hydrotalcite comprises the following steps: mixing the metal salt solution with alkali solution for co-precipitation to obtain the magnesium aluminum hydrotalcite; the alkali solution is a mixed solution of sodium carbonate and sodium hydroxide or a mixed solution of sodium carbonate and potassium hydroxide; the magnesium compound is at least one of magnesium oxide, magnesium chloride, magnesium nitrate and magnesium sulfate.

[0014] Preferably, the preparation of the ceramsite comprises the following steps: B1. mixing the acid-insoluble residue with auxiliary materials and granulating; B2. drying the particles obtained by the treatment in step B1; B3. sintering the particles obtained by the treatment in step B2 to obtain the ceramsite.

[0015] Preferably, in step B1, the auxiliary material is at least one of fly ash, kaolin, glass powder, bentonite, starch, coal gangue and coal powder; and before step B3, the process further includes preheating the particles obtained by the treatment in step B2.

[0016] Preferably, in step B3, the sintering temperature is 1000-1200° C., and the sintering time is 10-30 min.

[0017] Beneficial effects:

[0018] The process for cascaded quality-based utilization of sludge of the present invention can utilize sludge in a cascaded manner with high quality, and can prepare sludge charcoal, magnesium-aluminum hydrotalcite and ceramsite, thus achieving harmless, resourceful and high-quality utilization of sludge.

[0019] The sludge charcoal and magnesium-aluminum hydrotalcite prepared by the process for cascade quality-separated utilization of sludge of the present invention can be used as adsorbents for wastewater treatment, and the ceramsite can be used as building materials and industrial filtering materials.

[0020] The process for cascaded fractionation and utilization of sludge of the present invention can "turn waste into treasure" after fractionation of sludge, and has great industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. Among them:

[0022] Figure 1 A flow chart of a process for cascaded sludge quality-separation utilization according to an embodiment of the present invention;

[0023] Figure 2 This is a SEM image of the sludge carbon, magnesium aluminum hydrotalcite and ceramsite prepared in one embodiment of the present invention;

[0024] Figure 3 This is the XRD diagram of the magnesium aluminum hydrotalcite prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0026] The present invention will be described in detail below in conjunction with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0027] The present invention aims at at least one of the problems existing in the current sludge treatment process, namely, the sludge treatment process is complex, the cycle is long, the cost is high, and the process is unstable. The present invention provides a process for cascade quality-based utilization of sludge, comprising the following steps: (1) drying, crushing and floating the sludge to obtain carbon-rich sludge and sludge residue; (2) treating the sludge residue with an acid solution to obtain a metal salt solution and an acid-insoluble residue; treating the carbon-rich sludge to obtain sludge charcoal; treating the metal salt solution to obtain magnesium-aluminum hydrotalcite; and treating the acid-insoluble residue to obtain ceramsite.

[0028] During the operation of urban sewage treatment plants, sludge is a very effective resource. Through the resource utilization of sludge, significant economic benefits, environmental benefits and social benefits can be reflected. The present invention creatively applies the flotation process to sludge treatment, separates the sludge into carbon-rich sludge and sludge residue, and performs acid dissolution treatment on the sludge residue obtained after flotation (so that the magnesium ions and aluminum ions in the sludge residue are fully dissolved) to obtain a metal salt solution and an acid-insoluble residue; and further treats the three components (carbon-rich sludge, metal salt solution and acid-insoluble residue) respectively, and three high value-added products, namely, sludge charcoal, magnesium-aluminum hydrotalcite and ceramsite, can be prepared, thereby realizing the graded utilization of sludge.

[0029] In a preferred embodiment of the present invention, in step (1), the particle size of the sludge obtained after crushing is 0.074 mm; flotation is carried out in the presence of pine oil and kerosene. Among them, the particle size of the sludge will affect the effect of flotation. Within a certain range, the smaller the sludge particle size, the better the flotation effect, and the more carbon-rich sludge that floats out (the density of carbon-rich sludge is smaller than that of sludge residue, and it is easier to float out); but if the particle size of the sludge is too small, it will also have an adverse effect on flotation. Pine oil, as a foaming agent, has a strong foaming ability, fast speed, and good foam stability during the flotation process, and can effectively improve the flotation operating conditions. Kerosene, as a collector, can selectively adhere to the surface of sludge particles, enhance its sulfur water property, and make the sludge particles easily adhere to bubbles. The ratio of pine oil and kerosene is determined according to the amount of minerals to be floated.

[0030] In a preferred embodiment of the present invention, the volume ratio of pine oil to kerosene is 3:4; the mass volume ratio of sludge to kerosene is 20:1; wherein the mass of sludge is measured in g and the volume of kerosene is measured in mL. If the relative amount of kerosene is too small (relative to pine oil), the hydrophobicity of the sludge is low and it cannot be attached to the bulging bubbles in large quantities, affecting the yield of carbon-rich sludge; if the relative amount of pine oil is too small (relative to kerosene), the foaming ability is weakened, the foaming speed is slow, and the foam stability is poor, which will affect the yield of carbon-rich sludge.

[0031] In a preferred embodiment of the present invention, the preparation of sludge carbon includes the following steps: A1. Mixing carbon-rich sludge with agricultural and forestry wastes and placing them in a solution containing an activator for immersion treatment; A2. After the immersion treatment is completed, filtering and drying; A3. Activating the product obtained by the treatment in step A2 to obtain sludge carbon. Among them, agricultural and forestry wastes can play a role in increasing the carbon content; the activator helps to increase the specific surface area of ​​the prepared sludge carbon.

[0032] In a preferred embodiment of the present invention, the mass ratio of the carbon-rich sludge to the agricultural and forestry waste is 1:1-3:7 (for example, 1:1, 1:1.5, 1:2 or 3:7); the agricultural and forestry waste includes at least one of sawdust, wheat straw and corn straw.

[0033] In a preferred embodiment of the present invention, the activator is at least one of zinc chloride, sodium hydroxide and potassium hydroxide; the mass ratio of the carbon-rich sludge to the activator is 1:1-1:3 (for example, 1:1, 1:2 or 1:3); in step A1, the immersion treatment time is 8-24h (for example, 8h, 11h, 13h, 15h, 18h, 20h, 23h or 24h), and the immersion treatment is carried out under stirring.

[0034] In a preferred embodiment of the present invention, in step A3, the activation temperature is 500-800°C (for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C), and the activation treatment time is 30-90min (for example, 30min, 40min, 50min, 60min, 70min, 80min or 90min). If the activation temperature is too high, the micropores are reduced and the adsorption capacity of the sludge carbon is reduced; if the activation temperature is too low, the activation pore-forming effect is not ideal, thereby affecting the adsorption effect.

[0035] In a preferred embodiment of the present invention, the pH of the acid solution is 2-5 (for example, pH=2, pH=3, pH=4 or pH=5); the temperature of the acid solution is 50-80°C (for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C); the time for the acid solution to dissolve is 8-24h (for example, 8h, 11h, 13h, 15h, 18h, 20h, 23h or 24h); the mass ratio of the sludge residue to the acid solution is 1:1-1:5 (for example, 1:1, 1:2, 1:3, 1:4 or 1:5). Among them, the pH of the acid solution, the temperature of the acid solution, the time for the acid solution to dissolve and the amount of the acid solution will all affect the dissolution of aluminum ions and magnesium ions in the sludge residue. The reasonable setting of the above parameters helps to fully dissolve the metal ions in the sludge residue, thereby helping to increase the yield of magnesium-aluminum hydrotalcite.

[0036] In a preferred embodiment of the present invention, the step of mixing the magnesium compound with the sludge residue is included before step (2); the preparation of the magnesium aluminum hydrotalcite includes the following steps: mixing the metal salt solution with the alkali solution for co-precipitation to obtain the magnesium aluminum hydrotalcite; the alkali solution is a mixed solution of sodium carbonate and sodium hydroxide or a mixed solution of sodium carbonate and potassium hydroxide; the magnesium compound is at least one of magnesium oxide, magnesium chloride, magnesium nitrate and magnesium sulfate. Since aluminum salt flocculants are added during flocculation and precipitation during sewage treatment, the sludge contains aluminum. The present invention allows aluminum ions to enter the metal salt solution by acid dissolving the sludge residue, and then the preparation of the magnesium aluminum hydrotalcite can be achieved by adding magnesium ions and performing alkali solution precipitation. Mixing the magnesium compound with the sludge residue before step (2) and then mixing with the acid solution helps to evenly mix the magnesium ions and aluminum ions in the acid solution; in addition, it also helps to expand the selection range of the magnesium compound. Among them, the main components of the metal salt solution are magnesium ions and aluminum ions, in addition, it also contains a small amount of other impurity metal ions (for example, iron, chromium, zinc, etc.), but magnesium and aluminum have higher metallic activity, so when co-precipitated with alkali solution, highly active magnesium-aluminum hydrotalcite will be synthesized preferentially; sodium carbonate is mainly used to provide carbonate ions for the formation of magnesium-aluminum hydrotalcite, and sodium hydroxide or potassium hydroxide is mainly used to provide hydroxide ions for the formation of magnesium-aluminum hydrotalcite.

[0037] In a preferred embodiment of the present invention, the mass ratio of the sludge residue to the magnesium compound is 1:1-1:3 (eg, 1:1, 1:2 or 1:3).

[0038] In a preferred embodiment of the present invention, the preparation of magnesium-aluminum hydrotalcite includes the following steps: C1. mixing a metal salt solution and an alkali solution in a deionized water at 60-80°C (for example, 60°C, 65°C, 70°C, 75°C or 80°C), and stirring for 30-60min (for example, 30min, 35min, 40min, 45min, 50min, 55min or 60min) to obtain a complex; C2. transferring the complex obtained by the treatment in step C1 to a reactor for crystallization; C3. filtering the reaction solution obtained by the treatment in step C2, washing and drying the obtained solid to obtain the magnesium-aluminum hydrotalcite of this embodiment.

[0039] In a preferred embodiment of the present invention, in the alkali solution of step C1, the concentration of sodium hydroxide or potassium hydroxide is 1-3 mol / L (for example, 1 mol / L, 2 mol / L or 3 mol / L), the concentration of sodium carbonate is 1-3 mol / L (for example, 1 mol / L, 2 mol / L or 3 mol / L), and the molar ratio of sodium hydroxide or potassium hydroxide to sodium carbonate is (1-4):1 (for example, 1:1, 2:1, 3:1 or 4:1).

[0040] In a preferred embodiment of the present invention, in step C2, the crystallization temperature is 80-160°C (for example, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or 160°C), and the crystallization time is 12-48h (for example, 12h, 16h, 24h, 30h, 35h, 39h, 44h or 48h).

[0041] In a preferred embodiment of the present invention, the preparation of ceramsite comprises the following steps: B1. mixing the acid-insoluble residue with auxiliary materials and granulating; B2. drying the particles obtained by the treatment in step B1; B3. sintering the particles obtained by the treatment in step B2 to obtain ceramsite.

[0042] In a preferred embodiment of the present invention, in step B1, the auxiliary material is at least one of fly ash, kaolin, glass powder, bentonite, starch, coal gangue and coal powder. Among them, fly ash or coal gangue is mainly used as a ceramic component in the preparation process of ceramsite, and its main components are SiO2, Al2O3, etc., forming the skeleton structure of ceramsite, improving chemical stability and sintering strength, so that sludge ceramsite ceramics have a certain compressive strength and prevent ceramsite deformation. Kaolin, bentonite or glass powder mainly plays a role of flux in the preparation process of ceramsite, and its main components are neutral oxides such as SiO2 and Al2O3. Due to the high melting point of the ceramic component, the sintering temperature increases, and components such as glass powder help to reduce the liquid phase temperature produced by ceramsite and reduce the sintering temperature. Starch or coal powder mainly plays a role of gas production in the preparation process of ceramsite, and its main components are carbon, organic matter, iron oxide, etc. Ceramsite will produce gases such as H2 and CO2 at high temperature during the sintering process. Part of the gas components escape, and the other part of the gas components are wrapped by the liquid phase material, forming a large number of microporous structures on the surface and inside of the expanded clay. On the one hand, it is beneficial to improve the adsorption capacity of the expanded clay; on the other hand, it can reduce the density of the expanded clay.

[0043] In a preferred embodiment of the present invention, in step B2, the drying temperature is 105° C. and the drying time is 24 hours.

[0044] In a preferred embodiment of the present invention, before step B3, a step of preheating the particles obtained by the treatment in step B2 is also included. Preferably, the preheating temperature is 400° C. and the preheating time is 60 minutes.

[0045] In a preferred embodiment of the present invention, in step B3, the sintering temperature is 1000-1200°C (for example, 1000°C, 1050°C, 1100°C, 1150°C or 1200°C), and the sintering time is 10-30min (for example, 10min, 15min, 20min, 25min or 30min). During the sintering process, if the temperature is too high, the glass phase of the ceramsite will be destroyed, resulting in the ceramicization of the ceramsite and the formation of many interconnected pores. If the temperature continues to rise, the ceramsite particles will adhere to each other; if the temperature is too low, the ceramic cannot obtain good expansion, the glass phase cannot seal the gas, and the mechanical strength is low. As for the sintering time, if the time is too long, a lot of energy will be wasted. If the time is too short, the baking expansion effect is not good, the mechanical strength of the ceramsite is low, and the physical properties of the ceramsite are affected.

[0046] The following is a detailed description of a process for cascade quality-based utilization of sludge according to the present invention through specific embodiments.

[0047] Example 1

[0048] Reference Figure 1 The process of cascaded sludge quality-based utilization in this embodiment includes the following steps:

[0049] (1) Dry and crush the sludge to 0.074 mm, place 80 g of sludge, 3 mL of pine oil and 4 mL of kerosene in a 1 L flotation machine (water is added to the flotation machine) for flotation to obtain carbon-rich sludge and sludge residue;

[0050] (2) Mixing the sludge residue and magnesium oxide in a ratio of 1:1, adding the mixture to a hydrochloric acid solution with a pH of 2 (the mass ratio of the sludge residue to the hydrochloric acid solution is 1:5), and dissolving the mixture at 70°C for 12 hours to form a metal salt solution and an acid-insoluble residue; (3)

[0052] A. Treating the carbon-rich sludge to prepare sludge charcoal comprises the following steps:

[0053] A1. Mix 10g of carbon-rich mud with pine sawdust in a ratio of 1:1, add to 150mL of an aqueous solution containing 20g of zinc chloride, and stir to activate for 24h;

[0054] A2. After the activation treatment, filter and dry;

[0055] A3. The product obtained by step A2 was heated at 700°C for 60 min and cooled to room temperature to prepare the sludge charcoal of this embodiment;

[0056] B. treating the acid-insoluble residue obtained by the treatment in step (2) to prepare ceramsite, comprising the following steps:

[0057] B1. The acid-insoluble residue is mixed with fly ash, kaolin, glass powder and coal powder in a ratio of 6:1:1:1:1 and granulated into balls;

[0058] B2. The particles obtained by step B1 were dried in a constant temperature drying oven at 105°C for 24h;

[0059] B3. The particles obtained by drying in step B2 are preheated at 400 ° C for 60 min;

[0060] B4. The particles obtained after preheating in step B3 are sintered at 1200° C. for 20 min to obtain the ceramsite of this embodiment.

[0061] C. treating the metal salt solution obtained by the treatment in step (2) to prepare magnesium aluminum hydrotalcite, comprising the following steps:

[0062] C1. Mix the metal salt solution with sodium hydroxide (2 mol / L) and sodium carbonate (2 mol / L) in deionized water at 60°C and stir for 40 min to obtain a complex (the molar ratio of sodium hydroxide to sodium carbonate is 1:1;

[0063] C2. The complex obtained by step C1 was transferred to a reactor for crystallization (crystallization temperature was 150° C. and time was 12 h);

[0064] C3. The reaction solution obtained by the treatment in step C2 is filtered, and the obtained solid is washed and dried to obtain the magnesium aluminum hydrotalcite of this embodiment.

[0065] The SEM image of the sludge carbon prepared in this example is as follows: Figure 2 a; The SEM image of the magnesium aluminum hydrotalcite prepared in this embodiment is shown in Figure 2 As shown in b, the XRD pattern is Figure 3 The SEM image of the ceramsite prepared in this embodiment is shown in Figure 2 cd shown ( Figure 2 d is Figure 2 c).

[0066] Example 2

[0067] The process of cascaded sludge quality-based utilization in this embodiment includes the following steps:

[0068] (1) Dry and crush the sludge to 0.074 mm, place 80 g of sludge, 3 mL of pine oil and 4 mL of kerosene in a 1 L flotation machine (water is added to the flotation machine) for flotation to obtain carbon-rich sludge and sludge residue;

[0069] (2) Mixing the sludge residue and magnesium chloride in a ratio of 1:1, adding the mixture to a sulfuric acid solution with a pH of 2 (the mass ratio of the sludge residue to the sulfuric acid solution is 1:5), and dissolving the mixture at 70°C for 12 hours to form a metal salt solution and an acid-insoluble residue; (3)

[0071] A. Treating the carbon-rich sludge to prepare sludge charcoal comprises the following steps:

[0072] A1. Mix 10g of carbon-rich sludge with corn straw in a ratio of 1:1, add to 150mL of an aqueous solution containing 30g of zinc chloride, and stir to activate for 24h;

[0073] A2. After the activation treatment, filter and dry;

[0074] A3. The product obtained by step A2 was heated at 600°C for 90 min and cooled to room temperature to obtain the sludge charcoal of this embodiment;

[0075] B. treating the acid-insoluble residue obtained by the treatment in step (2) to prepare ceramsite, comprising the following steps:

[0076] B1. The acid-insoluble residue is mixed with coal gangue, kaolin, glass powder and starch in a ratio of 6:1:1:1:1 and granulated into balls;

[0077] B2. The particles obtained by step B1 were dried in a constant temperature drying oven at 105°C for 24h;

[0078] B3. The particles obtained by drying in step B2 are preheated at 400 ° C for 60 min;

[0079] B4. The particles obtained after preheating in step B3 are sintered at 1000° C. for 10 min to obtain the ceramsite of this embodiment.

[0080] C. treating the metal salt solution obtained by the treatment in step (2) to prepare magnesium aluminum hydrotalcite, comprising the following steps:

[0081] C1. The metal salt solution was mixed with sodium hydroxide (1 mol / L) and sodium carbonate (3 mol / L) in deionized water at 80°C and stirred for 60 min to obtain a complex (the molar ratio of sodium hydroxide to sodium carbonate was 4:1;

[0082] C2. The complex obtained by step C1 was transferred to a reactor for crystallization (crystallization temperature was 100° C. and time was 15 h);

[0083] C3. The reaction solution obtained by the treatment in step C2 is filtered, and the obtained solid is washed and dried to obtain the magnesium aluminum hydrotalcite of this embodiment.

[0084] Example 3

[0085] The process of cascaded sludge quality-based utilization in this embodiment includes the following steps:

[0086] (1) Dry and crush the sludge to 0.074 mm, place 80 g of sludge, 3 mL of pine oil and 4 mL of kerosene in a 1 L flotation machine (water is added to the flotation machine) for flotation to obtain carbon-rich sludge and sludge residue;

[0087] (2) Mixing the sludge residue and magnesium nitrate in a ratio of 1:1, adding the mixture to a nitric acid solution with a pH of 2 (the mass ratio of the sludge residue to the nitric acid solution is 1:5), and dissolving the mixture at 70°C for 12 hours to form a metal salt solution and an acid-insoluble residue; (3)

[0089] A. Treating the carbon-rich sludge to prepare sludge charcoal comprises the following steps:

[0090] A1. Mix 10g of carbon-rich sludge with poplar branches in a ratio of 1:1, add to 150mL of an aqueous solution containing 10g of potassium hydroxide, and stir to activate for 24h;

[0091] A2. After the activation treatment, filter and dry;

[0092] A3. The product obtained by step A2 was heated at 800°C for 40 min and cooled to room temperature to obtain the sludge charcoal of this embodiment;

[0093] B. treating the acid-insoluble residue obtained by the treatment in step (2) to prepare ceramsite, comprising the following steps:

[0094] B1. The acid-insoluble residue is mixed with coal gangue, bentonite, glass powder and starch in a ratio of 6:1:1:1:1 and granulated into balls;

[0095] B2. The particles obtained by step B1 were dried in a constant temperature drying oven at 105°C for 24h;

[0096] B3. The particles obtained by drying in step B2 are preheated at 400 ° C for 60 min;

[0097] B4. The particles obtained after preheating in step B3 are sintered at 1050° C. for 20 min to obtain the ceramsite of this embodiment.

[0098] C. treating the metal salt solution obtained by the treatment in step (2) to prepare magnesium aluminum hydrotalcite, comprising the following steps:

[0099] C1. Mix the metal salt solution with sodium hydroxide (3 mol / L) and sodium carbonate (1 mol / L) in a 70°C deionized water and stir for 50 min to obtain a complex (the molar ratio of sodium hydroxide to sodium carbonate is (1-4):1);

[0100] C2. The complex obtained by step C1 was transferred to a reactor for crystallization (crystallization temperature was 120° C. and time was 16 h);

[0101] C3. The reaction solution obtained by the treatment in step C2 is filtered, and the obtained solid is washed and dried to obtain the magnesium aluminum hydrotalcite of this embodiment.

[0102] Example 4

[0103] The process of cascaded sludge quality-based utilization in this embodiment includes the following steps:

[0104] (1) Dry and crush the sludge to 0.074 mm, place 80 g of sludge, 3 mL of pine oil and 4 mL of kerosene in a 1 L flotation machine (water is added to the flotation machine) for flotation to obtain carbon-rich sludge and sludge residue;

[0105] (2) Mix the sludge residue and magnesium sulfate in a ratio of 1:1, add them to a hydrochloric acid solution with a pH of 2 (the mass ratio of the sludge residue to the hydrochloric acid solution is 1:5), and dissolve them at 70°C for 12 hours to form a metal salt solution and an acid-insoluble residue; (3)

[0107] A. Treating the carbon-rich sludge to prepare sludge charcoal comprises the following steps:

[0108] A1. Mix 10g of carbon-rich sludge with wheat straw in a ratio of 1:1, add to 150mL of an aqueous solution containing 20g of sodium hydroxide, and stir to activate for 24h;

[0109] A2. After the activation treatment, filter and dry;

[0110] A3. The product obtained by step A2 was heated at 700°C for 30 min and cooled to room temperature to obtain the sludge charcoal of this embodiment;

[0111] B. treating the acid-insoluble residue obtained by the treatment in step (2) to prepare ceramsite, comprising the following steps:

[0112] B1. The acid-insoluble residue is mixed with fly ash, bentonite, glass powder and coal powder in a ratio of 6:1:1:1:1 and granulated;

[0113] B2. The particles obtained by step B1 were dried in a constant temperature drying oven at 105°C for 24h;

[0114] B3. The particles obtained by drying in step B2 are preheated at 400 ° C for 60 min;

[0115] B4. The particles obtained after preheating in step B3 are sintered at 1200° C. for 10 min to obtain the ceramsite of this embodiment.

[0116] C. treating the metal salt solution obtained by the treatment in step (2) to prepare magnesium aluminum hydrotalcite, comprising the following steps:

[0117] C1. Mix the metal salt solution with sodium hydroxide (1 mol / L) and sodium carbonate (1 mol / L) in deionized water at 80°C and stir for 60 min to obtain a complex (the molar ratio of sodium hydroxide to sodium carbonate is (1-4):1);

[0118] C2. The complex obtained by step C1 was transferred to a reactor for crystallization (crystallization temperature was 80° C. and time was 48 h);

[0119] C3. The reaction solution obtained by the treatment in step C2 is filtered, and the obtained solid is washed and dried to obtain the magnesium aluminum hydrotalcite of this embodiment.

[0120] Example 5

[0121] The process of cascaded sludge quality-based utilization in this embodiment includes the following steps:

[0122] (1) Dry and crush the sludge to 0.074 mm, place 80 g of sludge, 3 mL of pine oil and 4 mL of kerosene in a 1 L flotation machine (water is added to the flotation machine) for flotation to obtain carbon-rich sludge and sludge residue;

[0123] (2) Mixing the sludge residue and magnesium chloride in a ratio of 1:1, adding the mixture to a sulfuric acid solution with a pH of 2 (the mass ratio of the sludge residue to the sulfuric acid solution is 1:5), and dissolving the mixture at 70°C for 12 hours to form a metal salt solution and an acid-insoluble residue; (3)

[0125] A. Treating the carbon-rich sludge to prepare sludge charcoal comprises the following steps:

[0126] A1. Mix 10g of carbon-rich sludge with poplar sawdust in a ratio of 1:1, add to 150mL of an aqueous solution containing 30g of sodium carbonate, and stir to activate for 24h;

[0127] A2. After the activation treatment, filter and dry;

[0128] A3. The product obtained by step A2 is heated at 800°C for 60 min and cooled to room temperature to obtain the sludge charcoal of this embodiment;

[0129] B. treating the acid-insoluble residue obtained by the treatment in step (2) to prepare ceramsite, comprising the following steps:

[0130] B1. The acid-insoluble residue is mixed with coal gangue, kaolin, glass powder and coal powder in a ratio of 6:1:1:1:1 and granulated;

[0131] B2. The particles obtained by step B1 were dried in a constant temperature drying oven at 105°C for 24h;

[0132] B3. The particles obtained by drying in step B2 are preheated at 400 ° C for 60 min;

[0133] B4. The particles obtained after preheating in step B3 are sintered at 1000° C. for 30 min to obtain the ceramsite of this embodiment.

[0134] C. treating the metal salt solution obtained by the treatment in step (2) to prepare magnesium aluminum hydrotalcite, comprising the following steps:

[0135] C1. Mix the metal salt solution with sodium hydroxide (3 mol / L) and sodium carbonate (2 mol / L) in deionized water at 80°C and stir for 40 min to obtain a complex (the molar ratio of sodium hydroxide to sodium carbonate is (1-4):1);

[0136] C2. The complex obtained by step C1 was transferred to a reactor for crystallization (crystallization temperature was 120° C. and time was 12 h);

[0137] C3. The reaction solution obtained by the treatment in step C2 is filtered, and the obtained solid is washed and dried to obtain the magnesium aluminum hydrotalcite of this embodiment.

[0138] Example 6

[0139] The process of cascaded sludge quality-based utilization in this embodiment includes the following steps:

[0140] (1) Dry and crush the sludge to 0.074 mm, place 80 g of sludge, 3 mL of pine oil and 4 mL of kerosene in a 1 L flotation machine (water is added to the flotation machine) for flotation to obtain carbon-rich sludge and sludge residue;

[0141] (2) Mixing the sludge residue and magnesium oxide in a ratio of 1:1, adding the mixture to a hydrochloric acid solution with a pH of 2 (the mass ratio of the sludge residue to the hydrochloric acid solution is 1:5), and dissolving the mixture at 70°C for 12 hours to form a metal salt solution and an acid-insoluble residue; (3)

[0143] A. Treating the carbon-rich sludge to prepare sludge charcoal comprises the following steps:

[0144] A1. Mix 10g of carbon-rich mud with pine sawdust in a ratio of 1:1, add to 150mL of an aqueous solution containing 20g of zinc chloride, and stir to activate for 24h;

[0145] A2. After the activation treatment, filter and dry;

[0146] A3. The product obtained by step A2 was heated at 700°C for 60 min and cooled to room temperature to prepare the sludge charcoal of this embodiment;

[0147] B. treating the acid-insoluble residue obtained by the treatment in step (2) to prepare ceramsite, comprising the following steps:

[0148] B1. The acid-insoluble residue is mixed with fly ash, kaolin, glass powder and coal powder in a ratio of 6:1:1:1:1 and granulated into balls;

[0149] B2. The particles obtained by step B1 were dried in a constant temperature drying oven at 105°C for 24h;

[0150] B3. The particles obtained by drying in step B2 are preheated at 400 ° C for 60 min;

[0151] B4. The particles obtained after preheating in step B3 are sintered at 1200° C. for 20 min to obtain the ceramsite of this embodiment.

[0152] C. treating the metal salt solution obtained by the treatment in step (2) to prepare magnesium aluminum hydrotalcite, comprising the following steps:

[0153] C1. Mix the metal salt solution with sodium hydroxide (2 mol / L) and sodium carbonate (2 mol / L) in deionized water at 60°C and stir for 40 min to obtain a complex (the molar ratio of sodium hydroxide to sodium carbonate is 1:1;

[0154] C2. The complex obtained by step C1 was transferred to a reactor for crystallization (crystallization temperature was 160° C., time was 12 h);

[0155] C3. The reaction solution obtained by the treatment in step C2 is filtered, and the obtained solid is washed and dried to obtain the magnesium aluminum hydrotalcite of this embodiment.

[0156] Comparative Example 1

[0157] The difference between this comparative example and Example 1 is that the acid-insoluble residue, fly ash, kaolin and glass powder are mixed in a ratio of 6:1:1:1 and granulated to prepare ceramsite. The rest is consistent with Example 1.

[0158] Comparative Example 2

[0159] The difference between this comparative example and Example 1 is that the acid-insoluble residue, fly ash, kaolin and coal powder are mixed in a ratio of 6:1:1:1 and granulated to prepare ceramsite. The rest is consistent with Example 1.

[0160] Comparative Example 3

[0161] The difference between this comparative example and Example 1 is that the acid-insoluble residue, fly ash, glass powder and coal powder are mixed in a ratio of 6:1:1:1 and granulated to prepare ceramsite, and the rest is consistent with Example 1.

[0162] Comparative Example 4

[0163] The difference between this comparative example and Example 1 is that the acid-insoluble residue, kaolin, glass powder and coal powder are mixed in a ratio of 6:1:1:1 and granulated to prepare ceramsite, and the rest is consistent with Example 1.

[0164] Comparative Example 5

[0165] The only difference between this comparative example and Example 1 is that the acid-insoluble residue, fly ash, kaolin, glass powder and coal powder are mixed in a ratio of 6:0.9:0.9:0.9:0.9, granulated and used to prepare ceramsite, and the rest are consistent with Example 1.

[0166] Comparative Example 6

[0167] The difference between this comparative example and Example 1 is that the sintering temperature in step B3 is 1300° C., and the rest is consistent with Example 1.

[0168] Comparative Example 7

[0169] The difference between this comparative example and Example 1 is that the sintering temperature in step B3 is 900° C., and the rest is consistent with Example 1.

[0170] Comparative Example 8

[0171] The difference between this comparative example and Example 1 is that the crystallization temperature in step C2 is 60° C., and the rest is consistent with Example 1.

[0172] Experimental example

[0173] The adsorption of methyl orange by sludge carbon was tested by using a UV-visible spectrophotometer: 0.1 g of sludge carbon was weighed and poured into a prepared 400 mg / L methyl orange solution, mixed and stirred for 12 hours and then allowed to stand, the supernatant was filtered with a 0.45 μm microporous membrane, and the concentration of methyl orange after adsorption was measured with a UV-visible spectrophotometer, and the adsorption of methyl orange by sludge carbon was calculated.

[0174] Atomic absorption spectrometer was used to test the effect of magnesium aluminum hydrotalcite on Pb 2+ The adsorption capacity and stability of multiple adsorption cycles were calculated by weighing 0.1 g of the powder and pouring it into the prepared 200 mg / L lead ion solution. The mixture was stirred for 10 h and then allowed to stand. The supernatant was filtered with a 0.45 μm microporous membrane and the lead ion concentration after adsorption was measured with an atomic absorption spectrophotometer. The adsorption capacity of magnesium-aluminum hydrotalcite on Pb 2+ The adsorption amount.

[0175] The bulk density (the greater the bulk density of the ceramsite, the higher the strength), water absorption and porosity of the ceramsite are tested according to the national standard QB / T 4383-2012.

[0176] The test results are shown in Table 1 below:

[0177] Table 1

[0178]

[0179]

[0180] In summary:

[0181] The ceramsite prepared in Examples 1-6 meets the national standard requirement for ordinary lightweight aggregate of grade 700.

[0182] The main influencing factor in the preparation process of sludge charcoal is the amount of agricultural and forestry waste added. The greater the proportion of agricultural and forestry waste added, the better the adsorption performance of sludge charcoal. Sludge charcoal and agricultural and forestry waste have a synergistic effect. Agricultural and forestry waste increases the carbon content of biochar. The moisture in sludge has a certain activation effect, which increases the roughness of the surface of activated carbon. This co-pyrolysis process can reduce the energy consumption of sludge treatment and improve the adsorption capacity of the prepared biochar, and has broad application prospects.

[0183] The preparation of magnesium aluminum hydrotalcite is greatly affected by the dissolution salt solution and the synthesis temperature. When the magnesium aluminum ions in the salt solution are less, the yield of the preparation is low and there are more impurities. When the coprecipitation and crystallization synthesis reaction temperature is low, the structure of the grown hydrotalcite is affected, and the uniformity and saturation are also affected (refer to comparative example 8, after the crystallization temperature is lowered, the prepared magnesium aluminum hydrotalcite has a high yield of Pb 2+ The adsorption amount decreased).

[0184] The main factors affecting the preparation of ceramsite include the raw material ratio and sintering conditions. The higher the sintering temperature, the more fully the ceramsite surface is vitrified, the more compact the internal structure is, and the strength of the ceramsite particles is increased. As the sintering temperature of the sludge ceramsite increases, the flux is converted into liquid and glassy substances, which increases the volume shrinkage of the ceramsite, increases the density of the surface and interior of the ceramsite, and reduces the water absorption rate (refer to Example 1 and Comparative Examples 6-7).

[0185] Specifically, the influence of raw material ratio on ceramsite is:

[0186] Combining Example 1 and Comparative Example 1, it can be seen that after omitting coal powder in the preparation of ceramsite in Comparative Example 1, the density of the prepared ceramsite is relatively large, and the porosity and water absorption rate are reduced. This is because coal powder is a gas-producing component, containing carbon and organic matter, which will produce H2, CO2, etc. at high temperatures, forming a large number of microporous structures on the surface and inside of the ceramsite, which is beneficial to improving the adsorption capacity of the ceramsite on the one hand; on the other hand, it can reduce the density of the ceramsite. If coal powder is omitted, the synthetic roasted ceramsite has a large density, is very hard, and does not have a rich pore structure.

[0187] Combining Example 1 and Comparative Example 2, it can be seen that after omitting the glass powder when preparing the ceramsite in Comparative Example 2, the volume density of the prepared ceramsite is reduced, and the hardness and wear resistance are also reduced.

[0188] Combining Example 1 and Comparative Example 3, it can be seen that after kaolin is omitted in the preparation of ceramsite in Comparative Example 3, the bulk density of the ceramsite prepared is reduced; kaolin is a fluxing component, which mainly plays a role in improving the cohesiveness of ceramsite. Kaolin is conducive to the formation of mullite, which helps to improve the chemical stability and sintering strength of ceramsite. After kaolin is omitted, the cohesiveness of ceramsite is poor and not hard enough.

[0189] Combining Example 1 and Comparative Example 4, it can be seen that after fly ash is omitted in the preparation of ceramsite in Comparative Example 4, the volume density of the prepared ceramsite decreases significantly; this is because not adding fly ash will lead to a decrease in the alumina content in the ceramsite, and the prepared ceramsite is not easy to be fired into shape, or the fired shape is weird and the hardness is poor.

[0190] Combining Example 1 and Comparative Example 5, it can be seen that when the amount of fly ash, kaolin, glass powder and coal powder is reduced relative to the acid-insoluble residue, the bulk density (strength) of the prepared ceramsite decreases.

[0191] The process of the invention is simple to operate, the prepared material has good performance, and can be adapted to different types of sludge for resource utilization.

[0192] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A process for cascaded utilization of sludge, characterized in that: The steps include: (1) drying, crushing and flotation the sludge to obtain carbon-rich sludge and sludge residue; (2) treating the sludge residue with an acid solution to obtain a metal salt solution and an acid-insoluble residue; (3) treating the carbon-rich sludge to prepare sludge charcoal; Treating the metal salt solution to prepare magnesium aluminum hydrotalcite; Treating the acid-insoluble residue to prepare ceramsite; In step (1), the particle size of the sludge obtained after crushing is 0.074 mm; the flotation is carried out in the presence of pine oil and kerosene; the volume ratio of the pine oil to the kerosene is 3:4; the mass-to-volume ratio of the sludge to the kerosene is 20:1, the mass of the sludge is measured in g, and the volume of the kerosene is measured in mL; In step (2), the pH of the acid solution is 2, the temperature of the acid solution is 70° C., the dissolution time of the acid solution is 12 hours, and the mass ratio of the sludge residue to the acid solution is 1:5; the preparation of the ceramsite comprises the following steps: B1. mixing the acid-insoluble residue with excipients and granulating; B2. Drying the particles obtained by step B1; B3. Sintering the particles obtained by step B2 to obtain the ceramsite; In step B1, the auxiliary material is at least one of fly ash, kaolin, glass powder, bentonite, starch, coal gangue and coal powder; Before step B3, the process further includes preheating the particles obtained by the treatment in step B2, wherein the preheating temperature is 400° C. and the preheating time is 60 minutes; In step B3, the sintering temperature is 1000-1200° C., and the sintering time is 10-30 min; In step B1, the auxiliary materials include a first auxiliary material, a second auxiliary material and a third auxiliary material, the first auxiliary material is fly ash or coal gangue, the second auxiliary material is a mixture of glass powder and kaolin or a mixture of glass powder and bentonite, the third auxiliary material is starch or coal powder, and the mass ratio of the acid-insoluble residue to the first auxiliary material, the second auxiliary material and the third auxiliary material is 6:1:2:1; in the second auxiliary material, the mass ratio of glass powder to kaolin is 1:1, or the mass ratio of glass powder to bentonite is 1:1; The step of mixing the magnesium compound with the sludge residue is included before step (2); the preparation of the magnesium aluminum hydrotalcite includes the following steps: mixing the metal salt solution with an alkali solution for co-precipitation to obtain the magnesium aluminum hydrotalcite; the alkali solution is a mixed solution of sodium carbonate and sodium hydroxide or a mixed solution of sodium carbonate and potassium hydroxide; the magnesium compound is at least one of magnesium oxide, magnesium chloride, magnesium nitrate and magnesium sulfate; The preparation of the magnesium aluminum hydrotalcite comprises the following steps: C1. Mix the metal salt solution and the alkali solution in a 60-80°C deionized water, and stir for 30-60 min to obtain a complex; in the alkali solution, the concentration of sodium hydroxide or potassium hydroxide is 1-3 mol / L, the concentration of sodium carbonate is 1-3 mol / L, and the molar ratio of sodium hydroxide or potassium hydroxide to sodium carbonate is (1-4):1; C2. The complex obtained by step C1 is transferred to a reactor for crystallization; the crystallization temperature is 80-160°C and the crystallization time is 12-48h; C3. The reaction solution obtained by the treatment in step C2 is filtered, and the obtained solid is washed and dried to obtain magnesium aluminum hydrotalcite.

2. The process for cascaded utilization of sludge according to claim 1 is characterized in that: The preparation of the sludge charcoal comprises the following steps: A1. Mixing the carbon-rich sludge with agricultural and forestry waste and immersing it in a solution containing an activator; A2. After the impregnation treatment is completed, filtering and drying; A3. Activate the product obtained by the treatment in step A2 to obtain the sludge charcoal.

3. The process for cascaded utilization of sludge according to claim 2 is characterized in that: The mass ratio of the carbon-rich sludge to the agricultural and forestry waste is 1:1-3:7; The agricultural and forestry waste includes at least one of wood chips, wheat straw and corn straw.

4. The process for cascaded utilization of sludge according to claim 2 is characterized in that: The activator is at least one of zinc chloride, sodium hydroxide and potassium hydroxide; The mass ratio of the carbon-rich sludge to the activator is 1:1-1:3; In step A1, the immersion treatment time is 8-24 hours, and the immersion treatment is carried out under stirring conditions.

5. The process for cascaded utilization of sludge according to claim 2 is characterized in that: In step A3, the temperature of the activation treatment is 500-800° C., and the time of the activation treatment is 30-90 min.

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