Sludge-based biochar for strengthening ozonized sludge dehydration as well as preparation method and application of sludge-based biochar

Abstract

The invention discloses sludge-based biochar for strengthening ozonized sludge dehydration as well as a preparation method and application of the sludge-based biochar. The preparation method comprises the following steps: uniformly mixing calcium hydroxide and aluminum oxide according to a ratio, calcining to obtain mayenite, namely Ca12Al14O33, grinding into powder, and passing through a 100-mesh mesh sieve; sludge, mayenite powder and an activating agent are uniformly mixed in proportion, and the mixture is treated by a hydrothermal carbonization method to prepare the sludge-based biochar. The method for conditioning sludge by using the sludge-based biochar comprises the following steps: adding the sludge-based biochar into a sewage treatment plant (with the water content of 95%), and uniformly stirring; and introducing ozone into the product under stirring. When the prepared sludge-based biochar is added into an ozone oxidation sludge treatment system, the ozone utilization rate and the sludge dewatering effect can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of sludge treatment and environmental engineering, and in particular to a sludge-based biochar for strengthening ozonation sludge dehydration, and a preparation method and application thereof. Background Art

[0002] Sludge is the main solid waste in the sewage treatment process. It has high water content and high organic matter content. Direct landfilling will cause secondary pollution and difficult disposal. At present, the water content of dehydrated sludge is still high, usually around 70%-80%, and the organic matter content is high. There are toxic and harmful substances and foul odors, which seriously affect the urban environment and the daily life of surrounding residents. Therefore, it is of great significance to reduce, recycle and harmlessly treat dehydrated sludge to improve sewage treatment efficiency and improve environmental quality.

[0003] Existing methods for treating dewatered sludge mainly include landfill, composting, incineration, etc. These methods all have certain limitations. For example, landfill requires a lot of land resources and is prone to secondary pollution; composting requires a lot of land resources and time, and is prone to produce foul odors; incineration requires a lot of energy and causes secondary pollution. In contrast, ozone oxidation treatment is a green, environmentally friendly, and cost-effective treatment method, but it currently has problems such as low ozone utilization and poor dewatering performance of ozonated sludge. In recent years, in order to improve the utilization rate of ozone, people have added functional materials to the process of ozone treatment of sludge to enhance ozone decomposition and produce hydroxyl radicals to break the sludge gel structure and degrade hydrophilic organic matter. However, existing functional materials still have problems such as large addition amount, low efficiency, and secondary pollution. Summary of the invention

[0004] One of the purposes of the present invention is to provide a method for preparing sludge-based biochar for enhanced ozonation sludge dehydration, which uses residual sludge from urban sewage treatment plants as the main component to prepare sludge-based biochar, which can not only improve the efficiency of catalytic ozone oxidation degradation of organic matter in sludge, but also promote the resource reuse of sludge.

[0005] The second object of the present invention is to provide an application of sludge-based biochar for enhancing ozonation sludge dehydration prepared by the above-mentioned preparation method, which can greatly improve the sludge dehydration performance.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing sludge-based biochar for enhanced ozonation sludge dehydration, comprising the following steps:

[0008] Step 1: Mix calcium hydroxide and aluminum oxide in proportion and calcine to obtain calcium aluminum oxide, i.e. Ca 12 Al 14 O33 , grind into powder and pass through a 100-mesh sieve;

[0009] Step 2: The sludge, calcium aluminum powder and activator are uniformly mixed in proportion, and treated by hydrothermal carbonization method to prepare sludge-based biochar.

[0010] In one embodiment of the first aspect, in step 2, the mass ratio of the sludge, mayenite powder and activator is 65%-80%: 15%-30%: 1%-5% by weight.

[0011] In one embodiment of the first aspect, in step 1, the molar ratio of Ca:Al in the calcium hydroxide and alumina is 1-1.3:1, in molar percentage.

[0012] In one embodiment of the first aspect, in step 2, the activator is selected from any one or more of solid potassium hydroxide, sodium hydroxide, hydrochloric acid, zinc chloride or potassium hydroxide aqueous solution or a combination thereof.

[0013] In one embodiment of the first aspect, in step 1, the calcination temperature is 1000-1500° C., and the calcination time is 0.5-4 h.

[0014] In one embodiment of the first aspect, in step 2, the hydrothermal carbonization method is carried out in a closed reactor, the reaction time is 1-4 hours, and the reaction temperature is 150-250°C.

[0015] In a second aspect, the present invention provides an application of sludge-based biochar for enhancing ozonation sludge dehydration prepared by the preparation method described in the first aspect, to remove organic matter in the sludge and improve the dehydration effect, the method comprising:

[0016] Step a: adding the sludge-based biochar to the sludge (water content 95%) of a municipal sewage treatment plant and stirring evenly;

[0017] Step b: Under stirring, ozone is introduced into the product of step a.

[0018] In one embodiment of the second aspect, the amount of the sludge-based biochar is 100-500 mg / g TS, preferably 200-500 mg / g TS, more preferably 300-500 mg / g TS, based on the weight of the sludge, wherein TS represents the dry mass of the sludge.

[0019] In one embodiment of the second aspect, 5-30 mg / L of ozone is introduced into the sludge, the gas flow rate is 1 L / min, the ventilation time is 20 min, and the dosage is 10-60 mg / gTS.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) This application uses sludge as the main raw material to prepare sludge-based biochar, which is a solid waste resource utilization that meets the national energy conservation, environmental protection, and carbon emission reduction requirements. The surface of the burned sludge-based biochar is enriched with a large number of active groups such as hydroxyl and carbonyl, which can effectively catalyze ozone to produce a large number of active oxygen free radicals, greatly improving the ozone utilization efficiency and sludge dehydration effect.

[0022] (2) The sludge-based biochar loaded with calcium aluminum prepared in this application can adsorb sludge liquid phase anions, such as CO3 2 -、Cl - 、NO3 - 、H2PO4 - and HCO3 - At the same time, the prepared biochar particles are small, the surface is loose and porous, and it is rich in components such as calcium aluminum and Fred salt (3CaO·Al2O3·CaCl2·10H2O) generated by the reaction, which can effectively serve as a sludge skeleton structure to construct drainage channels and promote the release of sludge water.

[0023] (3) As a strong oxidant, ozone will not produce any harmful residues or secondary pollution during the sludge treatment process. Compared with traditional chemical treatment methods, ozone sludge conditioning is more environmentally friendly and pollution-free. In addition, ozone will decompose into oxygen after the reaction and will not cause harm to environmental safety and human health. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the process of preparing and applying sludge-based biochar according to an embodiment of the present application.

[0025] Figure 2 It is the XRD diagram of the sludge bio-based carbon prepared in the examples of the present application.

[0026] Figure 3 It is a SEM image of the sludge bio-based charcoal prepared in the examples of the present application.

[0027] Figure 4 Graph showing the elemental content of the sludge bio-based charcoal prepared in the examples of the present application. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] "Scope" disclosed herein is expressed in the form of lower limit and upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundary of a particular range. All ranges that can be defined in this way include end values ​​and can be combined with each other, i.e. any lower limit can be combined with any upper limit to form a range. For example, for a specific parameter, a range of 60-120 and 80-110 is listed, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​listed are 1 and 2, and the maximum range values ​​3, 4 and 5 are listed at the same time, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0030] In this application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations.

[0031] In the present application, "above" or "below" following a number includes the number itself. For example, "below 5" means less than or equal to 5, and "above 7" means greater than or equal to 7.

[0032] In this application, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution.

[0033] In this application, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0034] In the present application, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0035] In this application, unless otherwise specified, the term "comprising" as used herein may be open-ended or closed-ended. For example, the term "comprising" may mean that other components not listed may also be included, or may only include the listed components.

[0036] The above expressions are also commonly used in the art. It should be emphasized that what is shown in the drawings and described below are only some specific embodiments of the present invention, and the protection scope of the present invention is not limited to these specific embodiments. The protection scope of the present invention is defined by the claims of the present invention, and may include any technical methods within the scope of the claims, including but not limited to further improvements and substitutions to these specific embodiments.

[0037] The method of the present application will now be described in detail.

[0038] In a first aspect, a method for preparing sludge-based biochar with enhanced ozone oxidation efficiency is provided, the route being as follows: Figure 1 As shown, the method may include the following steps 1-3.

[0039] Step 1: Calcium hydroxide and aluminum oxide are uniformly mixed in proportion, calcined to obtain mayenite, ground into powder, and passed through a 100-mesh sieve;

[0040] In a specific embodiment, the mixture is mixed in a ratio of, for example, 1:1, 2:1, or 3:1.

[0041] In a specific embodiment, the calcination is performed at a high temperature, for example, at 1000°C, 1100°C, 1200°C, 1300°C, 1400°C or 1500°C.

[0042] Step 2: The sludge, calcium aluminum powder and activator are uniformly mixed in proportion, and treated by hydrothermal carbonization method to prepare sludge-based biochar.

[0043] In a specific embodiment, the sludge accounts for 65%-80% of the total amount of the sludge, calcium aluminum powder, and the activator. For example, the sludge accounts for 65%, 70%, 75% or 80% of the total amount of the sludge, calcium aluminum powder, and the activator, or any range consisting of any numerical value therebetween. The application does not limit the source of the sludge, for example, the sludge can be derived from industrial wastewater or domestic sewage treatment.

[0044] In a specific embodiment, the calcium aluminum powder accounts for 15%-30% of the total of the sludge, calcium aluminum powder, and activator by weight. For example, the calcium aluminum powder accounts for 15%, 20%, 25% or 30% of the total of the sludge, calcium aluminum powder, and activator by weight.

[0045] In a specific embodiment, the molar ratio of Ca to Al in mayenite is Ca:Al=1-1.3:1.

[0046] In a specific embodiment, the activator accounts for 1%-5% of the total of the sludge, calcium aluminum powder and the activator by weight. For example, the activator accounts for 1%, 2%, 3%, 4% or 5% of the total of the sludge, calcium aluminum powder and the activator by weight.

[0047] In a specific embodiment, the activator is selected from any one or more or combinations of solid potassium hydroxide, sodium hydroxide, hydrochloric acid, zinc chloride or potassium hydroxide aqueous solution. In a specific embodiment, the activator is solid potassium hydroxide. In another specific embodiment, the activator is sodium hydroxide. In another specific embodiment, the activator is hydrochloric acid. In another specific embodiment, the activator is zinc chloride. In another specific embodiment, the activator is potassium hydroxide aqueous solution.

[0048] In a specific embodiment, the hydrothermal process temperature is 150-250° C., for example, 150° C., 160° C., 170° C., 180° C., 190° C., 200° C., 210° C., 220° C., 230° C., 240° C. or 250° C. The heating in step 3 forms the mixture into porous sludge-based biochar.

[0049] In a second aspect of the present application, a method for removing organic matter from sludge and improving dehydration effect using the sludge-based biochar as described in the first aspect of the present application is provided, the method comprising:

[0050] Step a: adding the sludge-based biochar to the sludge (water content 95%) of a municipal sewage treatment plant and stirring the sludge evenly.

[0051] In a specific embodiment, the amount of the sludge-based biochar is 100-500 mg / g TS, preferably 200-500 mg / g TS, more preferably 300-500 mg / g TS, based on the weight of the sludge. For example, 300 mg / g TS, 350 mg / g TS, 400 mg / g TS, 450 mg / g TS and 500 mg / g TS of sludge-based biochar are added.

[0052] Step b: Under stirring, ozone is introduced into the product of step a.

[0053] In a specific embodiment, the introduction of ozone refers to the introduction of ozone at a concentration of 5-30 mg / L, a gas flow rate of 1 L / min, and a ventilation time of 20 min. For example, 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, and 30 mg / L of ozone are introduced.

[0054] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0055] In the following examples, sludge was taken from the Shenshui Chengbei Sewage Treatment Plant in Changzhou; calcium hydroxide, aluminum oxide, and potassium hydroxide were all commercially available products.

[0056] Example 1: Preparation of sludge-based biochar

[0057] (1) Calcium hydroxide and aluminum oxide are uniformly mixed in proportion to prepare calcium aluminum sulfate

[0058] At room temperature, weigh 7.4g of calcium hydroxide and 5.1g of aluminum oxide. Mix the two powders evenly and add them into a tube furnace, and heat them at 1200℃ for 3h. After heating and cooling to room temperature, weigh 8.743g. Grind the coarse calcium aluminum oxide into fine particles and pass them through a 100-mesh sieve.

[0059] (2) Preparation of sludge-based biochar loaded with calcium aluminum

[0060] At room temperature, 30g of sludge, 8.7g of calcium aluminum stone and 1.3g of sodium hydroxide were weighed respectively. After being fully mixed, the above substances were added into a hydrothermal reactor, and heated for 3h under a closed condition at 200℃. After the heating was completed, the reactor was cooled to room temperature, the product was taken out and vacuum filtered, dried in an oven at 80℃, and the dried product was ground to 100 mesh to obtain a final product of 20.48g.

[0061] Example 2: Preparation of sludge-based biochar

[0062] (1) Calcium hydroxide and aluminum oxide are uniformly mixed in proportion to prepare calcium aluminum sulfate

[0063] At room temperature, weigh 9.62g of calcium hydroxide and 5.1g of aluminum oxide. Mix the two powders evenly and add them into a tube furnace, and heat them at 1500℃ for 2h. After heating and cooling to room temperature, weigh 9.7184g. Grind the coarse calcium aluminum oxide into fine particles and pass them through a 100-mesh sieve.

[0064] (2) Preparation of sludge-based biochar loaded with calcium aluminum

[0065] At room temperature, 20g of sludge, 9.7g of calcium aluminum stone and 1.2g of potassium hydroxide were weighed respectively. After being fully mixed, the above substances were added into a hydrothermal reactor, and heated for 4h under a closed condition at a temperature of 250°C. After the heating was completed, the reactor was cooled to room temperature, the product was taken out and vacuum filtered, dried in an oven at 80°C, and the dried product was ground to 100 mesh to obtain a final product of 14.81g.

[0066] Example 3: Preparation of sludge-based biochar

[0067] (1) Calcium hydroxide and aluminum oxide are uniformly mixed in proportion to prepare calcium aluminum sulfate

[0068] At room temperature, weigh 8.88g of calcium hydroxide and 5.1g of aluminum oxide. Mix the two powders evenly and add them into a tube furnace, and heat them at 1000℃ for 1h. After heating and cooling to room temperature, weigh 8.6428g. Grind the coarse particles of calcium aluminum into fine particles and pass them through a 100-mesh sieve.

[0069] (2) Preparation of sludge-based biochar loaded with calcium aluminum

[0070] At room temperature, 20g of sludge, 8.6g of calcium aluminum stone, and 1.1g of zinc chloride were weighed respectively. After being fully mixed, the above substances were added into a hydrothermal reactor, and heated for 3h at 150℃ under closed conditions. After the heating was completed, the reactor was cooled to room temperature, the product was taken out and vacuum filtered, dried in an oven at 80℃, and the dried product was ground to 100 mesh to obtain a final product of 13.96g.

[0071] Depend on Figure 2 The XRD patterns and Figure 4 The element content diagram shown in the figure shows that the biochar prepared by the present invention contains a large amount of metal oxides (such as Al2O3, CaO and Ca 12 Al 14 O 33 This will enrich the surface of biochar with a large number of active groups such as hydroxyl and carbonyl groups. After the introduction of ozone, it can effectively catalyze ozone to produce a large number of active oxygen free radicals, efficiently oxidize and degrade hydrophilic organic matter, and greatly improve the sludge dehydration effect. The calcium aluminum oxide in biochar can adsorb anions in sludge, such as CO3 2 -, Cl-, NO3-, H2PO4- and HCO3-, etc., which can reduce the free radical quencher components in the system and improve the oxidation efficiency of the system.

[0072] from Figure 3The SEM image shown shows that the prepared biochar particles are small, the surface is loose and porous, and it is rich in components such as calcium aluminum stone and Fred salt (3CaO·Al2O3·CaCl2·10H2O) generated by the reaction. It can effectively serve as a sludge skeleton constructor, construct drainage channels and promote the release of sludge water.

[0073] Example 4: Sludge-based biochar enhanced ozone oxidation dehydration effect

[0074] At room temperature, 200 mL of sludge with a moisture content of 95% was weighed, and the dosage was as shown in Table 1 below. Ozone with a concentration shown in Table 1 below was introduced while stirring, and the gas flow rate was 1 L / min, and the ventilation time was 20 minutes. The sludge was then filtered through a plate and frame filter press at a pressure of 1 MPa and a filtration time of 30 minutes. The moisture content of the mud cake was measured as shown in Table 1 below.

[0075] Table 1

[0076]

[0077] From the above examples, it can be seen that adding 10 mg of the product of Example 1 to 200 mL of sludge with a moisture content of 95%, and passing 25 mg / L of ozone, the gas flow rate is 1 L / min, and the ventilation time is 20 minutes, the best effect is achieved. The sludge is filtered by a plate and frame filter press at a pressure of 1 MPa and a filtration time of 30 minutes. The moisture content of the mud cake is measured to be 58.13%.

[0078] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing sludge-based biochar for enhanced ozonation sludge dehydration, characterized in that: The following steps are involved: Step 1: Mix calcium hydroxide and aluminum oxide in proportion and calcine to obtain calcium aluminum oxide, i.e. Ca 12 Al 14 O 33 , grind into powder and pass through a 100-mesh sieve; Step 2: The sludge, calcium aluminum powder and activator are uniformly mixed in proportion, and treated by hydrothermal carbonization method to prepare sludge-based biochar.

2. The method for preparing sludge-based biochar for enhanced ozonation sludge dehydration according to claim 1, characterized in that: In step 2, the mass ratio of the sludge, the calcium aluminum powder and the activator is 65%-80%: 15%-30%: 1%-5% by weight.

3. The method for preparing sludge-based biochar for enhanced ozonation sludge dehydration according to claim 1, characterized in that: In step 1, the molar ratio of Ca:Al in the calcium hydroxide and alumina is 1-1.3:1 in molar percentage.

4. The method for preparing sludge-based biochar for enhanced ozonation sludge dehydration according to claim 1, characterized in that: In step 2, the activator is selected from any one or more of solid potassium hydroxide, sodium hydroxide, hydrochloric acid, zinc chloride or potassium hydroxide aqueous solution or a combination thereof.

5. The method for preparing sludge-based biochar for enhanced ozonation sludge dehydration according to claim 1, characterized in that: In step 1, the calcination temperature is 1000-1500° C. and the calcination time is 0.5-4 h.

6. The method for preparing sludge-based biochar for enhanced ozonation sludge dehydration according to claim 1, characterized in that: The hydrothermal carbonization method is carried out in a closed reactor, with a reaction time of 1-4 hours and a reaction temperature of 150-250°C.

7. Application of the sludge-based biochar for enhanced ozonation sludge dehydration prepared by the preparation method of claim 1 in sludge dehydration.

8. The use according to claim 7, characterized in that: The specific steps include: Step a: adding the sludge-based biochar to the sludge of a municipal sewage treatment plant with a water content of 95% and stirring evenly; Step b: Under stirring, ozone is introduced into the product of step a.

9. The use according to claim 8, characterized in that: Based on the weight of the sludge, the amount of the sludge-based biochar is 100-500 mg / g TS, wherein TS represents the dry mass of the sludge.

10. The use according to claim 8, characterized in that: 5-30 mg / L ozone was introduced into the sludge, the gas flow rate was 1 L / min, the aeration time was 20 min, and the dosage was 10-60 mg / g TS.

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