Method for preparing sludge conditioner by using modified polyaluminum chloride production waste residues

Abstract

The invention relates to the field of sludge conditioning, and discloses a method for preparing a sludge conditioner by using modified polyaluminum chloride production waste residues, which comprises the following steps: step 1, mixing bauxite, calcium aluminate powder and hydrochloric acid step by step to prepare polyaluminum chloride, and further producing polyaluminum slag; and 2, carrying out acid-base modification on the polyaluminum slag, adjusting the pH value to about 6-7, not filtering to obtain a liquid product, and filtering with a plate frame to obtain a solid product for later use. According to the research, the poly-aluminum slag is used for sludge conditioning after being modified, so that the dewatering performance of the sludge is improved, the sludge filtration aiding effect is achieved, the purposes of sludge reduction and poly-aluminum slag resource utilization are achieved, and the method is relatively practical and suitable for wide popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge conditioning, and in particular relates to a method for preparing a sludge conditioner by utilizing waste residue from the production of modified polyaluminium chloride. Background Art

[0002] Polyaluminium chloride (PAC) is a widely used inorganic flocculant. The main production process of polyaluminium chloride in China uses aluminium hydroxide and calcium aluminate as raw materials. The production process of calcium aluminate powder will produce at least 15% (on an absolute dry basis) of filter press residue, with an annual output of about 60,000 t2).

[0003] At present, aluminum-containing waste slag is mainly disposed of by landfill, which has high treatment costs, great environmental risks and occupation of land resources. Therefore, its resource utilization has attracted much attention.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] In order to solve the above technical problems of high treatment cost, great environmental risk and occupation of land resources, the basic concept of the technical solution adopted by the present invention is:

[0006] A method for preparing a sludge conditioner using waste residue from the production of modified polyaluminium chloride comprises the following steps:

[0007] Step S1: Produce polyaluminum slag, mix bauxite and hydrochloric acid step by step, then add calcium aluminate powder to prepare polyaluminum chloride, and then produce polyaluminum slag.

[0008] Step S2: Modify the polyaluminium slag by adding about 1 / 1000 of calcium oxide to adjust its pH value to about 6 to 7.

[0009] Step S3: Condition the original sludge, put the modified polyaluminum slag and the original sludge into a beaker, and quickly stir and mix them to facilitate the subsequent physical and chemical analysis.

[0010] Step S4: The sludge mixed with the modified aluminum-containing waste slag is subjected to physical and chemical analysis such as calculation of sludge settling ratio (SV), determination of capillary suction time (CST), vacuum filtration, etc., and the morphological characteristics of the modified aluminum-containing waste slag are observed using a scanning electron microscope (SEM).

[0011] As a preferred embodiment of the present invention, the method for preparing a sludge conditioner using waste residue from the production of modified polyaluminium chloride as described in step 1 is characterized in that the sludge with a high water content is taken from the residual sludge in the second sedimentation tank of a sewage treatment plant, transported back to the laboratory within 2 hours and settled for 30 minutes before taking the bottom sludge, the water content of which is 98% to 99%, and the pH is 6.5 to 7.2. In order to prevent the physical and chemical properties of the sludge from changing over time, the sample is packaged and refrigerated at 4°C and used within 7 days.

[0012] As a preferred embodiment of the present invention, the method for preparing a sludge conditioner using modified polyaluminium chloride production waste residue as described in step 2 is characterized in that the polyaluminium chloride waste residue can be either a solid type or a slurry type.

[0013] As a preferred embodiment of the present invention, the method for preparing a sludge conditioner by using waste residue from the production of modified polyaluminium chloride as described in step three is characterized in that the waste residue is mixed with a certain concentration of alkali Ca(OH) in a certain proportion (one thousandth), stirred evenly for sufficient reaction and modification for later use.

[0014] As a preferred embodiment of the present invention, the method for preparing a sludge conditioner by using waste residue from the production of modified polyaluminium chloride as described in step 4 is characterized in that 200 mL of uniformly mixed sludge is placed in a 250 mL beaker, a certain amount of sludge conditioner is added respectively, the sludge with the added waste residue and the sludge to be treated are placed together on a B4-1A type six-link magnetic stirrer for stirring, and the mixture is rapidly stirred at a speed of 200 r / min for 1 min, and then slowly stirred at a speed of 50 r / min for 5 min, and physical and chemical index analysis is performed after completion.

[0015] As a preferred embodiment of the present invention, the method for preparing a sludge conditioner using modified polyaluminium chloride production waste residue as described in step 5 is characterized in that 100 mL of conditioned sludge is placed in a 100 mL measuring cylinder and the sludge settling ratio (SV) is calculated after standing for 30 minutes. The capillary absorption time (CST) is measured using a DP96097 capillary absorption time measuring instrument. The sludge is placed in a vacuum filtration device for filtration until cracks appear in the mud cake or no liquid drips within 30 seconds, and the mud cake is scraped and placed on the tray of the SH10A halogen moisture meter to measure the moisture content of the mud cake. The morphological characteristics of various types of aluminum-containing waste residues are characterized using a Hitachi S4800 scanning electron microscope (SEM).

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] In this study, aluminum-containing waste slag was modified and used for sludge conditioning, aiming to improve the sludge dewatering performance and play a role in sludge filtration, thereby achieving the purpose of sludge reduction and resource utilization of aluminum-containing waste slag.

[0018] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In the attached picture:

[0020] Figure 1 A schematic diagram of the original sludge treatment process of a method for preparing a sludge conditioner using waste residue from the production of modified polyaluminium chloride;

[0021] Figure 2 A schematic diagram of the original sludge conditioning process of a method for preparing a sludge conditioner using waste residue from the production of modified polyaluminium chloride;

[0022] Figure 3 The present invention is a schematic diagram of the physical and chemical analysis process of a method for preparing a sludge conditioner by utilizing waste residue from the production of modified polyaluminium chloride. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention.

[0024] like Figures 1 to 3 As shown, a method for preparing a sludge conditioner using waste residue from the production of modified polyaluminium chloride comprises the following steps:

[0025] Step S1: preparing aluminum-containing waste slag, mixing bauxite and hydrochloric acid in steps, and then adding calcium aluminate powder to prepare polyaluminum chloride, thereby generating polyaluminum waste slag.

[0026] Step S2: The aluminum-containing waste slag is subjected to acid-base modification, and its pH value is adjusted to about 6 to 7, and mixed with the original sludge, and then dried, ground and sieved to make it into powder for use.

[0027] Step S3: Condition the original sludge, put the modified aluminum-containing waste slag and the original sludge into a beaker, and quickly stir and mix them to facilitate subsequent physical and chemical analysis.

[0028] Step S4: The sludge mixed with the modified aluminum-containing waste slag is subjected to physical and chemical analysis such as calculation of sludge settling ratio (SV), determination of capillary suction time (CST), vacuum filtration, etc., and the morphological characteristics of the modified aluminum-containing waste slag are observed using a scanning electron microscope (SEM).

[0029] like Figures 1 to 3 As shown, in a specific embodiment, a method for preparing a sludge conditioner using waste residue from the production of modified polyaluminium chloride in step 1 is characterized in that the sludge with a high water content is taken from the residual sludge in the second sedimentation tank of a sewage treatment plant, transported back to the laboratory within 2 hours and the bottom sludge is taken after settling for 30 minutes, and the water content is 98% to 99%, and the pH is 6.5 to 7.2. In order to prevent the physical and chemical properties of the sludge from changing over time, the sample is packaged and refrigerated at 4°C and used within 7 days.

[0030] like Figures 1 to 3 As shown, in a specific embodiment, step 2 is a method for preparing a sludge conditioner using modified polyaluminum chloride production waste residue, characterized in that the polyaluminum waste residue can be any one of a drying type, a filter press type and a mud type.

[0031] like Figures 1 to 3 As shown, in a specific embodiment, a method for preparing a sludge conditioner by using waste residue from the production of modified polyaluminium chloride in step three is characterized in that the waste residue is mixed with a certain concentration of alkali Ca(OH): in proportion (add 2 mL of alkali to 1 g of waste residue), and after mixing evenly, a plastic film is covered to prevent the water from evaporating too quickly, and the mixture is placed at 85°C for 2 to 3 hours to dry, grind, and sieve for use.

[0032] like Figures 1 to 3 As shown, in a specific embodiment, a method for preparing a sludge conditioner using modified polyaluminium chloride production waste residue in step four is characterized in that 200 mL of uniformly mixed sludge is placed in a 250 mL beaker, and a certain amount of alkali-modified aluminum-containing waste residue is added respectively, and the sludge with added waste residue is placed together with the original sludge on a B4-1A type six-link magnetic stirrer for stirring, and then stirred rapidly at a speed of 200 r / min for 1 min, and then stirred slowly at a speed of 50 r / min for 5 min, and physical and chemical index analysis is performed after completion.

[0033] like Figures 1 to 3 As shown, in a specific embodiment, a method for preparing a sludge conditioner using modified polyaluminium chloride production waste residue in step 5 is characterized in that 100 mL of conditioned sludge is placed in a 100 mL measuring cylinder, and the sludge settling ratio (SV) is calculated after standing for 30 minutes. The capillary absorption time (CST) is measured using a DP96097 capillary absorption time measuring instrument. The sludge is placed in a vacuum filtration device for filtration until cracks appear in the mud cake or no liquid drips within 30 seconds, and the mud cake is scraped and placed on the tray of the SH10A halogen moisture meter to measure the moisture content of the mud cake. The morphological characteristics of various types of aluminum-containing waste residues are characterized using a Hitachi S4800 scanning electron microscope (SEM).

[0034] The implementation principle of the method for preparing a sludge conditioner using modified polyaluminium chloride production waste residue in this embodiment is as follows:

[0035] Sludge: The residual sludge from the secondary sedimentation tank of a sewage treatment plant was transported back to the laboratory within 2 hours and the bottom sludge was collected after settling for 30 minutes. The water content was 98% to 99% and the pH was 6.5 to 7.2. To prevent the physical and chemical properties of the sludge from changing over time, the samples were packaged and refrigerated at 4°C and used within 7 days.

[0036] Aluminum-containing waste slag: It is taken from a water purification agent company. It uses calcium aluminate powder as raw material and adopts a two-step acid dissolution method to prepare polyaluminium chloride.

[0037] Method for obtaining acid / base modified aluminum-containing waste slag: Take the waste slag and a certain concentration of acid (HSO) / base Ca(OH): mix them in proportion (add 2mL of acid / base to 1g of waste slag), cover them with plastic film after mixing evenly to prevent the evaporation of water too quickly, place them at 85°C for 2-3h, dry them, grind them, and sieve them for later use.

[0038] Sludge conditioning method: Take 200mL of evenly mixed sludge and place it in a 250mL beaker, add a certain amount of original aluminum-containing waste slag, acid-modified aluminum-containing waste slag and alkali-modified aluminum-containing waste slag respectively, place the sludge with waste slag and the original sludge on a B4-1A six-link magnetic mixer and stir, stir quickly at 200r / min for 1min, then stir slowly at 50r / min for 5min, and then perform physical and chemical index analysis.

[0039] Analysis method: Take 100mL of conditioned sludge and place it in a 100mL measuring cylinder. After standing for 30 minutes, calculate the sludge settling ratio (SV). Use the DP96097 capillary absorption time tester to measure the capillary absorption time (CST). Place the sludge in a vacuum filtration device for filtration until cracks appear in the mud cake or no liquid drips within 30 seconds. Scrape the mud cake and place it on the tray of the SH10A halogen moisture tester to measure the moisture content of the mud cake. Use a Hitachi S4800 scanning electron microscope (SEM) to characterize the morphological characteristics of various types of aluminum-containing waste slag.

[0040] The results show that using alkali-modified modified polyaluminium chloride waste residue to treat sludge can enhance the sludge filtration rate. The main method is that the polyaluminium chloride waste residue is acidic (about pH 2) and calcium hydroxide is added to neutralize it to neutral (pH 6 to 7), which plays a role in sludge filtration.

Claims

1. A method for preparing a sludge conditioner using waste residue from the production of modified polyaluminium chloride, characterized in that: The steps include: Step S1: generating polyaluminum slag, mixing bauxite and hydrochloric acid step by step, and then adding calcium aluminate powder to prepare polyaluminum chloride, thereby generating polyaluminum slag; Step S2: modifying the polyaluminum slag and adjusting its pH value to 6 to 7 with calcium oxide; Step S3: The sludge fused with the modified polyaluminum slag is subjected to physical and chemical analysis such as calculation of sludge settling ratio (SV), determination of capillary water absorption time (CST), vacuum filtration, etc., and the morphological characteristics of the modified aluminum-containing waste slag are observed using a scanning electron microscope (SEM).

2. The method for preparing a sludge conditioner by using waste residue from the production of modified polyaluminium chloride according to claim 1, characterized in that: The polyaluminium slag with a high water content in step S1 has a pH of about 3-4 and is acidic.

3. The method for preparing a sludge conditioner by using waste residue from the production of modified polyaluminium chloride according to claim 1, characterized in that: In the step S2, one thousandth of calcium oxide is added to modify the polyaluminum slag for sludge conditioning. The polyaluminum waste slag can be either solid or slurry.

4. The method for preparing a sludge conditioner by using waste residue from the production of modified polyaluminium chloride according to claim 1, characterized in that: In step S3, the waste residue is mixed with a certain concentration of alkali Ca(OH): in proportion (adding about one thousandth of calcium oxide), and the stirring time is sufficient for one hour, mixed evenly, and reacted fully, so that the pH value of the product reaches 6 to 7, so that the polyaluminum slag is fully modified and can be efficiently used for sludge conditioning, accelerate the sludge filtration speed and improve other indicators.

5. The method for preparing a sludge conditioner by using waste residue from the production of modified polyaluminium chloride according to claim 1, characterized in that: In the step S4, the polyaluminum waste slag is filtered and becomes solid.

6. The method for preparing a sludge conditioner by using waste residue from the production of modified polyaluminium chloride according to claim 1, characterized in that: In step S5, the polyaluminum waste slag is not filtered and becomes a slurry, which can be transported by a tank truck.

7. The method for preparing a sludge conditioner by using waste residue from the production of modified polyaluminium chloride according to claim 1, characterized in that: In step S6, 200 mL of the mixed sludge to be treated is placed in a 250 mL beaker, and a certain amount of sludge conditioner is added respectively. The added sludge and the original sludge are placed on a B4-1A six-link magnetic stirrer for stirring, and stirred rapidly at 200 r / min for 1 min, and then stirred slowly at 50 r / min for 5 min. The sludge is placed in a vacuum filtration device for filtration, and the filtration time is recorded until cracks appear in the mud cake or no liquid drips within 30 s. The mud cake is scraped and placed on the tray of the SH10A halogen moisture meter to measure the moisture content of the mud cake. The morphological characteristics of various types of aluminum-containing waste slag are characterized using a Hitachi S4800 scanning electron microscope (SEM).

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