Sludge treatment method

Abstract

The invention provides a sludge treatment method. The treatment method comprises the following steps: preliminarily concentrating biochemical sludge produced from a secondary sedimentation tank, and feeding the concentrated biochemical sludge into a sludge conditioning tank; physico-chemical sludge produced from a primary sedimentation tank is introduced into the sludge conditioning tank, and the sludge in the primary sedimentation tank contains fibers; chemical sludge produced from the tertiary sedimentation tank is introduced into the sludge conditioning tank and stirred, and the three kinds of sludge are mixed. According to the sludge treatment method provided by the embodiment of the invention, the dryness of the final discharged sludge can be improved to 40% or above under the principle of saving medicines, and the influence on the boiler combustion enthalpy when the dry sludge is conveyed to a self-provided power plant for incineration is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of sludge treatment, and in particular to a sludge treatment method. Background Art

[0002] In current pulp and paper mill wastewater treatment processes, aerobic biochemical sludge produced in secondary sedimentation tanks primarily consists of activated sludge microorganisms (primarily bacteria, fungi, and protozoa), activated sludge metabolites, recalcitrant organic matter adsorbed by the activated sludge, and inorganic matter adsorbed by the activated sludge. Its intercellular moisture content exceeds 99%, making it difficult to mechanically compress and dehydrate. Effective dehydration of biochemical sludge and its subsequent disposal are currently a major challenge for wastewater treatment plants across various industries.

[0003] After standing and concentrating, the moisture content of biochemical sludge remains above 98.5%. Traditional screw presses, centrifuges, and belt presses are difficult to effectively press the sludge to a dryness of more than 26%, and the processing capacity is extremely low. However, without adding lime (lime will greatly shorten the service life of the filter cloth and is not conducive to filter cloth washing) or without adding large amounts of iron salts and polyacrylamide, the single-frame sludge treatment cycle is long, the processing capacity is low, and the sludge dryness is less than 30%, which is not conducive to the subsequent delivery of the sludge to the power plant for incineration. Summary of the Invention

[0004] The present invention provides a method for treating sludge, which includes:

[0005] The biochemical sludge produced from the secondary sedimentation tank is initially concentrated and then enters the sludge conditioning tank;

[0006] Passing the physicochemical sludge produced from the primary sedimentation tank into the sludge conditioning tank, wherein the sludge in the primary sedimentation tank contains fiber;

[0007] The chemical sludge produced from the three sedimentation tanks is introduced into the sludge conditioning tank and stirred to mix the three sludges.

[0008] In some optional embodiments, the step of entering the sludge conditioning tank after preliminary concentration of the biochemical sludge produced from the secondary sedimentation tank includes: using the first sludge thickening tank to concentrate the biochemical sludge for the first time, and then using a belt thickener to concentrate it for the second time, while adding polyacrylamide, storing the sludge after the second concentration in a sludge buffer tank, adding polyaluminum chloride and polyacrylamide to the sludge buffer tank and storing the sludge in a sludge conditioning tank.

[0009] In some optional embodiments, the step of using the first sludge thickening tank to perform the first concentration on the biochemical sludge is to concentrate the sludge to 1.2±0.2%; the step of using the belt thickener to perform the second concentration and adding polyacrylamide at the same time, and storing the sludge after the second concentration in the sludge buffer tank is to concentrate the sludge to 2.5±0.2% after the second concentration.

[0010] In some optional embodiments, in the step of performing secondary concentration using a belt concentrator and adding polyacrylamide at the same time, the amount of polyacrylamide added is 40,000 to 50,000 ppm.

[0011] In some optional embodiments, the biochemical sludge in the secondary sedimentation tank accounts for 70-75%; the physicochemical sludge in the primary sedimentation tank accounts for 20-25%; and the chemical sludge in the tertiary sedimentation tank accounts for 5-10%.

[0012] In some optional embodiments, in the step of passing the physicochemical sludge produced from the primary sedimentation tank into the sludge conditioning tank, when the fiber content of the physicochemical sludge in the primary sedimentation tank is ≥15%, the feed ratio to the sludge conditioning tank is 20±2%; when the fiber content is <15%, the feed ratio to the sludge conditioning tank is 25±2%.

[0013] In some optional embodiments, the step of introducing the chemical sludge produced from the three sedimentation tanks into the sludge conditioning tank further includes using a second sludge thickening tank to preliminarily concentrate the chemical sludge to a concentration of more than 1.5%.

[0014] In some optional embodiments, the treatment method further comprises adding polyaluminum chloride to the sludge conditioning tank after mixing the three sludges.

[0015] In some optional embodiments, in the step of adding polyaluminum chloride in the sludge conditioning tank, the amount of polyaluminum chloride added is 10,000 to 20,000 ppm.

[0016] In some optional embodiments, the treatment method further comprises using a plate and frame mill to form mud blocks with a solid content of 38-45%, and crushing the mud blocks with a crusher.

[0017] The sludge treatment method provided in the embodiment of the present application can increase the final sludge dryness to 40% or above while saving chemicals, and reduce the impact of dry sludge on boiler combustion enthalpy when it is sent to a self-contained power plant for incineration. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 It is a node block diagram of the sludge treatment process that improves the previous embodiment;

[0020] Figure 2 This is a flow chart of an improved embodiment of the present application;

[0021] Figure 3 This is a node block diagram of the sludge treatment process of an improved embodiment of the present application;

[0022] Figure 4 It is a flow chart of another improved embodiment of the present application. DETAILED DESCRIPTION

[0023] The present application will be further described in detail below in conjunction with the accompanying drawings and examples. It is particularly noted that the following examples are only intended to illustrate the present application and are not intended to limit the scope of the present application. Similarly, the following examples are only some examples of the present application and not all examples. All other examples obtained by those of ordinary skill in the art without creative work are intended to fall within the scope of protection of this application.

[0024] The terms "first", "second" and "third" in the embodiments of the present application are used only for descriptive purposes and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second" and "third" may explicitly or implicitly include at least one of such features. In the description of the present application, "multiple" means at least two, for example, two, three, etc., unless otherwise clearly and specifically defined. All directional indications in the embodiments of the present application (such as up, down, left, right, front, back...) are only used to explain the relative positional relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. The terms "including" and "having" in the embodiments of the present application and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or components inherent to these processes, methods, products or devices.

[0025] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0026] The main purpose of the present invention is to allow the biochemical sludge to enter the sludge buffer tank through the belt thickener under the premise of utilizing the existing process section, and at the same time introduce an appropriate proportion of primary sedimentation tank physicochemical sludge (the fiber content of primary sedimentation sludge from the pulp and paper mill is more than 15%) and a small amount of tertiary sedimentation chemical sludge (the two are directly introduced into the sludge buffer tank for mixing and stirring), and add a small amount of PAC (polyaluminum chloride) and PAM (polyacrylamide) to aid coagulant.

[0027] Pure biochemical sludge cannot be effectively squeezed and dehydrated due to its single composition. After the primary sludge is introduced, because its components are mostly mud, sand, inorganic matter, colloids, coatings, etc., and it contains a sufficient proportion of papermaking fiber, under the action of the coagulant aid PAM, the primary sedimentation tank and the biochemical sludge can be effectively aggregated into agglomerates. Combined with the effect of the poly-iron chemical sludge in the tertiary sedimentation tank, the feed concentration of the mixed sludge is increased to more than 4% before entering the plate and frame dehydrator for dehydration, greatly shortening the plate and frame feeding time; at the same time, the mud and water are effectively separated, shortening the single-frame pressing time, and the mud biscuit degree reaches 42% or even higher. The crushed sludge particles are sent to the self-provided power plant for incineration, which will convert the combustion enthalpy required to create combustion calorific value, while improving the quality of the primary sludge and creating external sales value.

[0028] In summary, the application of the present invention will increase the processing capacity of the plate and frame filter press (compared with pure biochemical sludge treatment) by more than 20%; provide sludge calorific value for power plant incineration; and reduce the cost of sludge treatment chemicals.

[0029] See also Figure 1 , Figure 1 This is an improved sludge treatment process node block diagram of the previous embodiment. The biochemical sludge produced from the secondary sedimentation tank (solid content approximately 0.6%) is concentrated by a thickening scraper, then pumped from the bottom and pumped to a belt thickener to further increase the concentration (PAM is added for further concentration). The sludge is then stored in a sludge buffer tank for future use. Because pure biochemical sludge is difficult to dewater directly due to its characteristics, 5%-10% lime is added. A submersible mixer in the buffer tank continuously stirs the sludge and ensures uniform mixing of the lime and material. The mixed material (concentration approximately 2.8%-3%) is then added with appropriate amounts of PAC and PAM before being pumped to a sludge conditioning tank for future use. After processing the single plate in the plate and frame press, the conditioned material is pumped to the main body of the press via high- and low-pressure pumps.

[0030] Summary: Pure biochemical sludge treated by adding lime, PAC (polyaluminium chloride) and PAM (polyacrylamide) has a single plate filter press treatment cycle of about 5 hours and a solid content of about 30% in the sludge. 2+ The sludge after crushing is sent to the power plant and mixed with coal for combustion, which affects the combustion efficiency of the coal (incomplete combustion) and thermal enthalpy (water evaporation loss); the pH of the plate and frame filtered liquid after adding lime increases, and the return to the sewage system causes an increase in the amount of hydrochloric acid used for neutralization; a single 600m 2 The processing capacity of the plate and frame machine is only 11 (ADT / roof. platform).

[0031] In view of this, this application proposes an improved embodiment, please refer to Figure 2 , Figure 2 1 is a flow chart of an improved embodiment of the present application, wherein the sludge treatment method in this embodiment includes but is not limited to the following steps.

[0032] In step S100, the biochemical sludge produced from the secondary sedimentation tank is initially concentrated and then enters the sludge conditioning tank.

[0033] Please also refer to Figure 3 , Figure 3 This is a node block diagram of the sludge treatment process of an improved embodiment of the present application. The biochemical sludge (solid content of about 0.6%) produced from the secondary sedimentation tank, the step specifically includes using the first sludge thickening tank to concentrate the biochemical sludge for the first time, wherein the first concentration concentrates the sludge to 1.2±0.2%; then using a belt thickener for secondary concentration, while adding polyacrylamide (PAM), in this step, specifically after the secondary concentration, the sludge can be concentrated to 2.5±0.2%; the amount of polyacrylamide added is 40,000 to 50,000 ppm, specifically the amount of polyacrylamide added can be 42,000 ppm, 43,000 ppm, 45,000 ppm, 48,000 ppm, 48,500 ppm, 49,000 ppm, 50,000 ppm and the like.

[0034] The secondary concentrated sludge is stored in a sludge buffer tank, polyaluminium chloride and polyacrylamide are added to the sludge buffer tank, and the sludge is stored in a sludge conditioning tank. In this step, the amount of polyaluminium chloride and polyacrylamide added can be about 20,000 ppm.

[0035] Please continue reading Figure 2 The sludge treatment method in this embodiment further includes step S200, introducing the physicochemical sludge produced from the primary sedimentation tank into the sludge conditioning tank, wherein the sludge in the primary sedimentation tank contains fiber.

[0036] In step S300, the chemical sludge produced from the three sedimentation tanks is introduced into the sludge conditioning tank and stirred to mix the three types of sludge.

[0037] It should be noted here that the premise of the method in the embodiment of the present application is: through simple technical modification, the primary sludge pipe and the tertiary concentrated sludge pipe are connected to the sludge conditioning tank.

[0038] Optionally, the biochemical sludge in the secondary sedimentation tank accounts for 70-75%; the physicochemical sludge in the primary sedimentation tank accounts for 20-25%; and the chemical sludge in the tertiary sedimentation tank accounts for 5-10%. The sludge inflow to the sludge conditioning tank is calculated using a flow meter.

[0039] The fiber content of the primary sedimentation tank sludge determines the feed rate. Physicochemical sludge (solids content 4% or higher) from the primary sedimentation tank is pumped directly into the sludge conditioning tank for mixing with the biochemical sludge. In this embodiment, when the fiber content of the primary sedimentation tank sludge is ≥15%, the feed rate to the sludge conditioning tank is 20±2%. When the fiber content is <15%, the feed rate to the sludge conditioning tank is 25±2%.

[0040] In step S300, the chemical sludge is initially concentrated to a concentration of more than 1.5% in a second sludge thickening tank, and then directly pumped into a sludge conditioning tank for mixing with sludge.

[0041] The three types of sludge, namely biochemical sludge, primary sedimentation sludge and tertiary chemical sludge, are slowly stirred and mixed in the conditioning tank by a paddle mixer. Due to the high fiber content of primary sedimentation sludge, it is necessary to add an appropriate amount of PAC (polyaluminium chloride) to the sludge conditioning tank for conditioning materials ( Figure 3 The amount of polyaluminium chloride added is 10,000 to 20,000 ppm, specifically 10,000 ppm, 12,000 ppm, 13,000 ppm, 15,000 ppm, 18,000 ppm, 20,000 ppm, etc. Because PAM coagulant aid is added to the primary and tertiary sedimentation tanks, residual PAM (polyacrylamide) carried over from the sludge conditioning tank will continue to play a role. Actual operation has proven that additional PAM addition is unnecessary.

[0042] See also Figure 4 , Figure 4 2 is a flow chart of another improved embodiment of the present application. The sludge treatment method in this embodiment includes but is not limited to the following steps.

[0043] In step S100, the biochemical sludge produced from the secondary sedimentation tank is initially concentrated and then enters the sludge conditioning tank.

[0044] Please continue reading Figure 3, the biochemical sludge (solid content of about 0.6%) produced from the secondary sedimentation tank, this step specifically includes using a first sludge thickening tank to concentrate the biochemical sludge for the first time, wherein the first concentration concentrates the sludge to 1.2±0.2%; then using a belt concentrator to perform a secondary concentration, and adding polyacrylamide (PAM) at the same time. In this step, specifically, the sludge can also be concentrated to 2.5±0.2% after the secondary concentration; the amount of polyacrylamide added is 40,000 to 50,000 ppm, specifically, the amount of polyacrylamide added can be 42,000 ppm, 43,000 ppm, 45,000 ppm, 48,000 ppm, 48,500 ppm, 49,000 ppm, 50,000 ppm and the like.

[0045] The secondary concentrated sludge is stored in a sludge buffer tank, polyaluminium chloride and polyacrylamide are added to the sludge buffer tank, and the sludge is stored in a sludge conditioning tank. In this step, the amount of polyaluminium chloride and polyacrylamide added can be about 20,000 ppm.

[0046] Please continue reading Figure 4 The sludge treatment method in this embodiment further includes step S200, introducing the physicochemical sludge produced from the primary sedimentation tank into the sludge conditioning tank, wherein the sludge in the primary sedimentation tank contains fiber.

[0047] In step S300, the chemical sludge produced from the three sedimentation tanks is introduced into the sludge conditioning tank and stirred to mix the three types of sludge.

[0048] It should be noted here that the premise of the method in the embodiment of the present application is: through simple technical modification, the primary sludge pipe and the tertiary concentrated sludge pipe are connected to the sludge conditioning tank.

[0049] Optionally, the biochemical sludge in the secondary sedimentation tank accounts for 70-75%; the physicochemical sludge in the primary sedimentation tank accounts for 20-25%; and the chemical sludge in the tertiary sedimentation tank accounts for 5-10%. The amount of sludge fed into the sludge conditioning tank is counted by a flow meter. Among them, the fiber content of the sludge in the primary sedimentation tank determines the feed amount, and the physicochemical sludge in the primary sedimentation tank (with a solid content of more than 4%) is pumped directly into the sludge conditioning tank to be mixed with the biochemical sludge. In this embodiment, when the fiber content of the physicochemical sludge in the primary sedimentation tank is ≥15%, the feed ratio to the sludge conditioning tank is 20±2%, and when the fiber content is <15%, the feed ratio to the sludge conditioning tank is 25±2%.

[0050] In step S300, the chemical sludge is initially concentrated to a concentration of more than 1.5% by using a second sludge thickening tank. The sludge is directly pumped into the sludge conditioning tank for mixing with the sludge. The three types of sludge, namely, biochemical sludge, primary chemical sludge and tertiary chemical sludge, are slowly stirred and mixed in the conditioning tank by a paddle mixer. Due to the high fiber content of the primary sludge, an appropriate amount of PAC (polyaluminium chloride) is added to the sludge conditioning tank for standby use. Figure 3 The amount of polyaluminium chloride added is 10,000 to 20,000 ppm, specifically 10,000 ppm, 12,000 ppm, 13,000 ppm, 15,000 ppm, 18,000 ppm, 20,000 ppm, etc. Because PAM coagulant aid is added to the primary and tertiary sedimentation tanks, residual PAM (polyacrylamide) carried over from the sludge conditioning tank will continue to play a role. Actual operation has proven that additional PAM addition is unnecessary.

[0051] Different from the above-mentioned embodiment, this embodiment further includes step S400, using a plate-and-frame mill to form mud blocks with a solid content of 38-45%, and using a crusher to crush the mud blocks.

[0052] After the single plate of the plate and frame press is processed, the material is pumped to the machine body for pressing through high and low pressure pumps, and then directly sent to the power plant for mixing with coal after crushing.

[0053] In the wastewater workshop of a wood pulp and paper mill, the primary sludge contains a high amount of paper fibers. The flocculant traps the sludge particles, microorganisms, colloids, and coatings, forming larger sludge agglomerates, which greatly improves the processing performance of the plate and frame filter press. The plate and frame filter press has a single plate processing cycle of about 4 hours, and the solid content of the sludge output is increased to 38%-45%. After crushing, the sludge has a low moisture content. The calorific value of the sludge (including fiber components) deducts the evaporation enthalpy of its own water and also provides a certain amount of heat energy. A single 600m 2 The processing capacity of the board and frame machine is up to 15 (ADT / table).

[0054] Compared with the biochemical sludge treatment mode of adding lime, the improved embodiment of the present application has the following advantages:

[0055] 1. Improved dryness. The treatment model adopted by this invention utilizes the characteristics of log pulp and paper mills, mixing primary sludge, biochemical sludge, and chemical sludge in an optimal ratio of 20%-25%:70%-75%:5%. Through precise controlled addition of chemicals, the materials are kept in an optimal dehydrated state, and the dryness of the sludge is increased to 40%, which is beneficial for subsequent co-combustion in power plants.

[0056] 2. Reduced chemical consumption. The present invention utilizes the high fiber content of primary sludge and adds a certain amount of PAC and PAM (wherein the amount of PAM added is also reduced compared to the pre-improved embodiment), without the need to add lime, to achieve the ideal subsequent disposal state of dry sludge.

[0057] 3. Selling physical and chemical sludge to external customers. Because primary sludge from wood pulp and paper mills contains a high fiber content, the remaining 75%-80% can be processed directly using a screw press, excluding the portion used for biochemical sludge treatment. This classified sludge improves the equipment's processing capacity, and the single sludge type benefits the sludge's selling price.

[0058] The sludge treatment method provided in this embodiment can increase the final sludge dryness to 40% or above while conserving chemicals, reducing the impact of dry sludge on boiler combustion enthalpy when incinerated at a self-contained power plant. Separately treating the biochemical sludge improves the quality of the primary sedimentation tank sludge, which, due to its high fiber content, can be sold externally to generate revenue.

[0059] The above descriptions are only some embodiments of the present application and do not limit the scope of protection of the present application. Any equivalent device or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the scope of patent protection of this application.

Claims

1. A method for treating sludge, characterized in that: The processing method comprises: The biochemical sludge produced from the secondary sedimentation tank is initially concentrated and then enters the sludge conditioning tank; Passing the physicochemical sludge produced from the primary sedimentation tank into the sludge conditioning tank, wherein the sludge in the primary sedimentation tank contains fiber; The chemical sludge produced from the three sedimentation tanks is introduced into the sludge conditioning tank and stirred to mix the three sludges.

2. The processing method according to claim 1, characterized in that The step of initially concentrating the biochemical sludge produced in the secondary sedimentation tank and then entering the sludge conditioning tank includes: using a first sludge concentrating tank to concentrate the biochemical sludge for the first time, then using a belt concentrator to concentrate it for the second time, adding polyacrylamide at the same time, storing the sludge after the second concentration in a sludge buffer tank, adding polyaluminum chloride and polyacrylamide to the sludge buffer tank and storing the sludge in a sludge conditioning tank.

3. The processing method according to claim 2, characterized in that The step of using the first sludge thickening tank to perform the first concentration on the biochemical sludge to concentrate the sludge to 1.2±0.2%; the step of using the belt thickener to perform the second concentration, adding polyacrylamide, and storing the second concentrated sludge in the sludge buffer tank to concentrate the sludge to 2.5±0.2% after the second concentration.

4. The processing method according to claim 3, characterized in that In the step of performing secondary concentration using a belt concentrator and adding polyacrylamide at the same time, the amount of polyacrylamide added is 40,000 to 50,000 ppm.

5. The processing method according to claim 1, characterized in that The biochemical sludge in the secondary sedimentation tank accounts for 70-75%; the physicochemical sludge in the primary sedimentation tank accounts for 20-25%; and the chemical sludge in the tertiary sedimentation tank accounts for 5-10%.

6. The processing method according to claim 5, characterized in that: In the step of introducing the physicochemical sludge produced from the primary sedimentation tank into the sludge conditioning tank, when the fiber content of the physicochemical sludge in the primary sedimentation tank is ≥15%, the feed ratio to the sludge conditioning tank is 20±2%; when the fiber content is <15%, the feed ratio to the sludge conditioning tank is 25±2%.

7. The processing method according to claim 5, characterized in that The step of introducing the chemical sludge produced from the three sedimentation tanks into the sludge conditioning tank further comprises utilizing a second sludge concentrating tank to preliminarily concentrate the chemical sludge to a concentration of more than 1.5%.

8. The processing method according to claim 1, characterized in that The treatment method further comprises adding polyaluminum chloride into the sludge conditioning tank after the three sludges are mixed.

9. The processing method according to claim 8, characterized in that: In the step of adding polyaluminium chloride in the sludge conditioning tank, the amount of polyaluminium chloride added is 10,000 to 20,000 ppm.

10. The processing method according to claim 8, characterized in that: The treatment method further comprises using a plate-and-frame mill to form mud blocks with a solid content of 38-45%, and using a crusher to crush the mud blocks.

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