Waste acid purification mud cake resourceful treatment system and technology

Abstract

The invention discloses a waste acid purification mud cake resourceful treatment system and process, and the waste acid purification mud cake resourceful treatment system comprises a material crushing system used for crushing waste acid purification mud cakes; the pulping system is used for mixing the crushed waste acid purification mud cake with liquid to prepare uniform slurry; the slurry adjusting system is connected with an outlet of the slurry making system and is used for receiving slurry and adding an adjusting agent to improve the physical and chemical properties of the slurry; the loose filtering system is connected with an outlet of the slurry adjusting system and is used for performing low-pressure filtering on the adjusted slurry to form loose accumulated sludge particles; the purifying and washing system is connected with an outlet of the loosening and filtering system and is used for washing the loosely accumulated sludge particles to remove chloride ions; the sludge solidifying and dewatering system is connected with an outlet of the purifying and washing system and is used for extruding, dewatering and forming the purified sludge to prepare iron-making raw material blocks; by means of the technological process, harmless treatment and resource recycling are achieved.

Description

Technical Field

[0001] This invention relates to the field of hydrochloric acid waste liquid regeneration and treatment technology, specifically to a waste acid purification sludge cake resource utilization system and process. Background Technology

[0002] In the pickling and wastewater treatment processes of industries such as steel and chemicals, a large amount of waste acid purification sludge cake is generated. This type of sludge cake has a complex composition and a high chloride ion content, and is classified as hazardous waste. If not properly disposed of, the pollutants in it can easily migrate, posing a serious threat to the soil and groundwater environment.

[0003] Currently, the main methods for disposing of waste acid purification sludge cake include secure landfill, solidification and stabilization, thermal treatment, and washing and dechlorination. While secure landfill can isolate hazardous waste, it occupies land resources for a long time and carries the risk of pollutant leakage. Solidification and stabilization can reduce the leaching toxicity of pollutants, but the treated product has low utilization value and fails to achieve true resource recovery. Thermal treatment (such as incineration and melting) can achieve complete detoxification, but it consumes extremely high amounts of energy, resulting in huge equipment investment and operating costs. Washing and dechlorination is a crucial pretreatment step for resource recovery, but existing technologies generally suffer from low washing efficiency, large water consumption, difficulty in treating washing wastewater, and high energy consumption, hindering their large-scale industrial application.

[0004] Based on this, this application provides a waste acid purification sludge cake resource utilization system and process. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a waste acid purification sludge cake resource utilization system and process, which solves the problems of low washing efficiency, large water consumption, difficulty in treating washing wastewater, and high energy consumption in existing technologies.

[0006] The waste acid purification sludge cake resource utilization system of the present invention includes the following components arranged sequentially along the material processing flow direction: The material crushing system is used to crush the waste acid purification sludge cake; The pulping system is used to mix the crushed waste acid purification sludge cake with liquid to form a uniform sludge. A mud conditioning system, connected to the outlet of the pulping system, is used to receive mud and add conditioning agents to improve the physicochemical properties of the mud; A loose filtration system, connected to the outlet of the sludge conditioning system, is used to perform low-pressure filtration on the conditioned sludge to form loosely accumulated sludge particles. A purification and washing system is connected to the outlet of the loose filtration system and is used to wash away chloride ions from loosely accumulated sludge particles. The sludge solidification and dewatering system is connected to the outlet of the purification and washing system and is used to extrude and dewater the purified sludge to form ironmaking raw material blocks. The loose filtration system is provided with a filtrate return pipeline connected to the mud conditioning system, and the purification and washing system is provided with a washing water return pipeline connected to the mud conditioning system.

[0007] As a further improvement of the present invention, the material crushing process crushes the waste acid purification sludge cake to a particle size range of 5mm to 30mm, and the pulping system mixes the crushed sludge cake with liquid at a solid-liquid ratio of 1:1 to 1:8 for a mixing time of 1 h to 3 h.

[0008] As a further improvement of the present invention, the mud conditioning system includes a conditioner dosing device and a mixing reaction device. The conditioner dosing device is configured to add at least one of an organic polymer flocculant or an inorganic cementitious material, and the mixing reaction time is 30s to 5min.

[0009] As a further improvement of the present invention, the loose filtration system is configured to operate at a filtration pressure of 0.05MPa to 0.30MPa, and the filter medium used has an air permeability of 150 / m³·s to 300L / m³·s.

[0010] As a further improvement of the present invention, the purification and washing system is configured to operate at a rinsing pressure of 0.10MPa to 0.60MPa, with a rinsing time of 5 min to 30 min, and the chloride ion content of the purified sludge is 0.5% to 5%.

[0011] As a further improvement of the present invention, the sludge solidification and dewatering system is configured to operate under a squeezing pressure of 0.60 MPa to 1.60 MPa, with a dewatering rate of 40% to 65%. The sludge solidification and dewatering system is at least one of a plate and frame filter press, a belt filter press, a chamber filter press, or a diaphragm filter press.

[0012] This invention also provides a process for the resource utilization of waste acid purification sludge cake, comprising the following steps: Crushing step: The waste acid purification sludge cake is crushed. The particle size of the crushed sludge is 5 mm to 30 mm. Sludge particles larger than this size will be screened and removed. The pulping step involves homogenizing the pulverized waste acid purification sludge cake with the liquid. Mud conditioning step: Add a conditioning agent to the mud to adjust its physicochemical properties; Loose filtration step: The conditioned sludge is subjected to low-pressure filtration to form loosely accumulated sludge particles; Purification and washing steps: Water flows through multiple directional inlets on the filter, penetrating and washing away loosely accumulated sludge particles to remove chlorine ions, thus purifying the filter. Sludge solidification and dewatering steps: The purified sludge is extruded, dewatered, and shaped into ironmaking raw material blocks; The filtrate produced in the loose filtration step and the wash water produced in the purification and washing step are reused in the mud conditioning step.

[0013] As a further improvement of the present invention, in the pulping step, the solid-liquid ratio is 1:1 to 1:8, and the mixing time is 1 h to 3 h. In the mud conditioning step, the added regulator is at least one of organic polymer flocculant or inorganic cementitious material, and the reaction time of the regulator is 30s to 5min.

[0014] As a further improvement of the present invention, the loose filtration step is carried out at a filtration pressure of 0.05MPa to 0.30MPa, and the filter medium used has an air permeability of 150 / m³·s to 300L / m³·s. The purification and washing steps are carried out under a rinsing pressure of 0.10MPa to 0.60MPa, and the rinsing time is 5 min to 30 min. The chloride ion content of the purified sludge is 0.5% to 5%.

[0015] As a further improvement of the present invention, the sludge re-solidification step is carried out under an extrusion pressure of 0.60MPa to 1.60MPa, with a dewatering rate of 40% to 65%, and is extruded and molded using a filter press.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves not only harmless treatment but also resource recycling through a complete process chain of "pulverization and pulping - slurry conditioning - loose filtration - purification and washing - solidification and dehydration". This meets the raw material requirements of subsequent ironmaking processes, transforming hazardous waste into valuable industrial raw materials and completely changing the situation of low resource utilization rates in traditional disposal methods such as landfill and solidification. Meanwhile, the entire process is carried out at room temperature without the need for external heating, which greatly reduces the huge energy consumption caused by traditional heat treatment (such as incineration and melting). Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the system flow structure of the present invention. Detailed Implementation

[0018] The following illustrations disclose several embodiments of the present invention. For clarity, many physical details will be described in the following description. However, it should be understood that these physical details are not intended to limit the invention. That is, in some embodiments of the invention, these physical details are not essential. Furthermore, for the sake of simplicity, some conventional structures and components will be shown in the illustrations in a simple schematic manner.

[0019] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0020] Example 1 Please see Figure 1 This invention provides a waste acid purification sludge cake resource utilization system, comprising the following components arranged sequentially along the material processing flow direction: The material crushing system is used to crush the waste acid purification sludge cake; The pulping system is used to mix the crushed waste acid purification sludge cake with liquid to form a uniform sludge. The mud conditioning system, connected to the outlet of the pulping system, is used to receive mud and add conditioning agents to improve the physicochemical properties of the mud; The loose filtration system is connected to the outlet of the sludge conditioning system and is used to perform low-pressure filtration on the conditioned sludge to form loosely packed sludge particles. The purification and washing system is connected to the outlet of the loose filtration system and is used to wash away chloride ions from loosely accumulated sludge particles. The sludge solidification and dewatering system is connected to the outlet of the purification and washing system. It is used to extrude and dewater the purified sludge to form ironmaking raw material blocks. The loose filtration system is equipped with a filtrate return pipeline connected to the mud conditioning system, and the purification and washing system is equipped with a washing water return pipeline connected to the mud conditioning system.

[0021] In one specific embodiment of the present invention, the waste acid purification sludge cake resource utilization system breaks down lumpy or clumpy waste acid purification sludge cakes from industrial production lines. The system is typically equipped with a jaw crusher, hammer crusher, or other suitable pulverizing machinery to ensure that the input sludge cakes are effectively dispersed, creating the necessary conditions for subsequent homogeneous pulping.

[0022] Adjacent to the material crushing system is the slurry preparation system, which receives the pre-crushed mud cake material via a conveyor. In this system, the crushed solid material and a specified amount of liquid (usually industrial water or recycled process water) are fed together into a mixing container equipped with a powerful agitator. The agitator operates continuously, ensuring thorough contact, wetting, and dispersion of the solid particles and liquid, aiming to form a uniformly distributed, highly fluid suspended slurry system. This homogenized slurry is a crucial prerequisite for subsequent stable treatment.

[0023] The prepared mud is then pumped or gravity-fed into a connected mud conditioning system, whose inlet is connected to the outlet of the upstream mud preparation system. The mud conditioning system contains a precisely metered regulator dosing unit and a highly efficient mixing and reaction unit. As the mud flows in, a measured amount of regulator, such as a specific type of polyacrylamide-based organic polymer flocculant or a silicate-based inorganic cementitious material of a certain fineness, is added. Under continuous, gentle agitation, the regulator undergoes a physicochemical reaction with the fine particles in the mud. This process can alter the colloidal properties of the mud, the surface charge of the particles, and the flocculation structure within tens of seconds to several minutes, thereby significantly optimizing its overall physicochemical properties, particularly enhancing the solid-liquid separation tendency and filtration permeability in subsequent steps.

[0024] The modified sludge then enters a loose filtration system, the main component of which is a pressure filtration device, such as a filter press equipped with filter cloth of specific porosity and permeability. The sludge is pushed through the filter media under relatively low applied pressure. During this process, most of the free water (filtrate) is quickly separated and discharged, while solid matter gradually accumulates on the surface of the filter media. This results in a relatively loose, porous accumulation of wet sludge cake, rather than a dense, hard mass. This loose microstructure creates favorable hydraulic channels for subsequent deep washing.

[0025] The loosely structured wet sludge particles discharged from the loose filtration system are conveyed to the purification and washing system. This system is designed with targeted flushing and water distribution devices, such as multiple directional water inlets arranged above or to the sides of the filter units. When the sludge particles are at their designated positions, a pressurized stream of washing water is ejected from these inlets, allowing it to penetrate the entire sludge particle accumulation layer relatively evenly. During this penetration process, the water flow dissolves and carries away water-soluble chloride components (mainly chloride ions) adhering to the interior and surface of the sludge particles, thereby achieving effective chloride ion removal. The wastewater after washing (wash water), rich in dissolved chlorides, is collected centrally.

[0026] After thorough washing and a significant reduction in chloride ion content, the purified sludge is finally sent to a sludge solidification and dewatering system. This system typically employs mechanical pressure dewatering equipment, such as various types of filter presses. The purified sludge is subjected to higher mechanical pressure within the sealed chamber of the equipment. Under this intense pressure, the interstitial water remaining between the sludge particles is further squeezed out, the sludge volume is compressed, and the solid content is significantly increased. Finally, the sludge is compacted and formed into solid blocks with specific shapes (such as plates or cakes) and a certain mechanical strength. Because these blocks are mainly composed of compounds such as iron and calcium, and the content of harmful impurities has met standards, they can be used as alternative raw materials in the steelmaking process, realizing the resource utilization of waste.

[0027] Furthermore, to achieve resource conservation and process optimization, this system features a specially designed internal material circulation loop. Specifically, the filtrate separated from the loose filtration system and the wash water from the purification and washing system are not directly discharged as wastewater. They are guided back to the sludge conditioning system through dedicated filtrate return pipelines and wash water return pipelines, respectively. These returned liquids may contain underutilized conditioning agents or have a certain alkalinity, and their re-participation in the sludge conditioning process not only reduces the consumption of fresh process water but also allows for the recovery and utilization of residual agents to a certain extent, reflecting the system's circular economy design concept. The various systems are interconnected through pipelines, pumps, valves, and conveying machinery to achieve directional material flow and flow control, thus forming a continuous, integrated processing line.

[0028] The material crushing system crushes the waste acid purification sludge cake to a particle size range of 5mm to 30mm. The pulping system mixes the crushed sludge cake with liquid at a solid-liquid ratio of 1:1 to 1:8 for 1 to 3 hours.

[0029] The mud conditioning system includes a conditioner dosing device and a mixing reaction device. The conditioner dosing device is configured to add at least one of organic polymer flocculant or inorganic cementitious material, and the mixing reaction time is 30s to 5min.

[0030] The loose filtration system is configured to operate at a filtration pressure of 0.05MPa to 0.30MPa, and the filter medium used has an air permeability of 150 L / m³·s to 300 L / m³·s.

[0031] The purification and washing system is configured to operate at a rinsing pressure of 0.10MPa to 0.60MPa, with a rinsing time of 5 min to 30 min, and the chloride ion content of the purified sludge is 0.5% to 5%.

[0032] The sludge solidification and dewatering system is configured to operate under a squeezing pressure of 0.60MPa to 1.60MPa, with a dewatering rate of 40% to 65%. The sludge solidification and dewatering system is at least one of plate and frame filter press, belt filter press, chamber filter press, or diaphragm filter press.

[0033] When the system starts running, the material crushing system receives the waste acid purification sludge cake to be processed. The purpose of the crushing operation is to obtain a suitable particle size for subsequent processes. To this end, the crushing equipment of the system, such as an adjustable gap double-roll crusher, is set to crush the feed sludge cake until the size of most of its particles falls within the range of 5mm to 30mm. This ensures crushing efficiency and provides a suitable solid surface area for subsequent pulping steps, which is beneficial for solid-liquid mixing.

[0034] The crushed material is fed into the pulping system via a closed screw conveyor. Process water is then added to mix the solid material with the liquid medium. The liquid is typically industrial clean water or qualified recycled water. The solid-to-liquid mass ratio in the mixture is maintained between 1:1 and 1:8. This ratio range is set to balance the fluidity of the slurry and its solid content, ensuring smooth pumping while minimizing the load on subsequent dewatering. The mixing process takes place in a mixing tank with double-layered impellers. The impellers operate at a set speed to ensure that solid particles and liquid are fully wetted and dispersed, forming a homogeneous suspension. To ensure consistent mixing results, the entire mixing operation, from the initial contact between the material and liquid to the formation of a qualified slurry, is controlled to last between 1 and 3 hours.

[0035] The prepared homogeneous slurry then enters the slurry conditioning system. This system is equipped with a separate conditioner storage tank and a precision metering feeder, such as a screw feeder. Based on online monitoring of slurry flow rate and properties, the control system instructs the feeder to quantitatively add conditioner to the flowing slurry. The conditioner used can be anionic polyacrylamide (an organic polymeric flocculant) with a molecular weight within a certain range, or metakaolin or silica fume (inorganic cementitious materials) with a fineness of several hundred meshes, or a composite formulation of both. The addition of these substances aims to change the surface electrical properties of the slurry particles or improve its overall structure through the filling and cementing effect of microparticles. The slurry and conditioner enter a static mixer or a slow-moving mixing tank together, where rapid physicochemical reactions occur. From the time the conditioner comes into contact with the slurry until the mixture leaves the reaction zone and enters the next unit, this effective contact and reaction time is controlled within 30 seconds to 5 minutes. This period of time is sufficient for the regulator to fully exert its effect, significantly improving the settling or filtration characteristics of the slurry, without causing a decrease in processing capacity or unnecessary energy consumption due to excessive retention.

[0036] The sludge, after being regulated and optimized, is pumped to a loose filtration system. The core of this system is a pressure filtration device, such as the initial low-pressure feed section of a chamber filter press. During operation, the feed pump pushes the sludge into the chambers between the filter plates at a certain pressure. The key here is that the inlet pressure, or the outlet pressure of the feed pump, is stably maintained at a relatively low level of 0.05 MPa to 0.03 MPa. Simultaneously, the selected filter medium, typically a synthetic fiber filter cloth with a specific weave, possesses specific fluid permeability characteristics, with an air permeability index in the range of 150 L / m³·s to 300 L / m³·s. The lower applied pressure, combined with the appropriately permeable filter cloth, aims to achieve rapid filtration of a large amount of free water from the sludge while avoiding excessive compaction of solid particles. This gradually forms a loosely structured, relatively porous, wet sludge cake on the surface of the filter cloth, rather than a dense, impermeable block.

[0037] The loosely packed wet sludge cakes, unloaded from the filtration equipment, are sent to a purification and washing system. This system is typically integrated into the filtration equipment or used as a standalone unit. During washing, pressurized washing water is sprayed onto the wet sludge layer piled on the filter cloth through multiple nozzles distributed above or on the sides of the filter plates. The pressure provided by the washing water pump is maintained between 0.01 MPa and 0.06 MPa. The water flow penetrates the relatively loose sludge layer from multiple directions, dissolving and carrying away soluble salts, especially chloride ions, from the interior and surface of the particles. To ensure sufficient leaching of chloride ions to meet the requirements for resource recovery, this high-pressure penetration washing process continues for 5 to 30 minutes. The washing process ends when the chloride ion content in the sludge cake has been reduced to the target range of 0.5% to 5% by timed sampling and testing. The wastewater after washing contains a high concentration of chloride salts and is collected and treated separately.

[0038] After washing and meeting chlorine content standards, the purified sludge enters a sludge solidification and dewatering system for final shaping and dewatering. This system is typically a shaping and dewatering device capable of applying higher mechanical pressure, such as a plate and frame filter press, belt filter press, chamber filter press, or diaphragm filter press. In these devices, the purified sludge is subjected to strong mechanical extrusion pressure. The extrusion pressure at this stage is significantly higher than the previous loose filtration stage, typically between 0.06 MPa and 1.6 MPa. Under high pressure, the voids between sludge particles are further compressed, and a large amount of residual water is squeezed out. After this step, the moisture content of the sludge is significantly reduced, and its dewatering rate can reach 40% to 65%. Finally, the sludge is compacted into a solid block with a certain thickness, strength, and regular shape (such as a square plate or a round cake). At this point, its physical form and chemical composition meet the requirements for use as a raw material in ironmaking production (such as sintering feedstock or pelletizing additive), thus completing the transformation from hazardous waste to usable resource.

[0039] Example 2 This embodiment describes a process for the resource utilization of waste acid purification sludge cake, including the following steps: Crushing step: The waste acid purification sludge cake is crushed. The particle size of the crushed sludge is 5 mm to 30 mm. Sludge particles larger than this size will be screened and removed. The pulping step involves homogenizing the pulverized waste acid purification sludge cake with the liquid. Mud conditioning steps: Add conditioning agents to the mud to adjust its physicochemical properties; Loose filtration step: The conditioned sludge is subjected to low-pressure filtration to form loosely accumulated sludge particles; Purification and washing steps: Water flows through multiple directional inlets on the filter, penetrating and washing away loosely accumulated sludge particles to remove chlorine ions, thus purifying the filter. Sludge solidification and dewatering steps: The purified sludge is extruded, dewatered, and shaped into ironmaking raw material blocks; The filtrate from the loose filtration step and the wash water from the purification and washing step are reused in the mud conditioning step.

[0040] In this embodiment, the entire process begins with the crushing step. The operator feeds the lumps of waste acid purification sludge into the crusher. The crusher's operating parameters are pre-set to ensure that the output sludge particles are primarily concentrated in the range of 5mm to 30mm. After the crusher's discharge port, a simple vibrating screen or grid is typically installed. This screen intercepts any occasionally larger sludge lumps exceeding 30mm in size. The intercepted coarse material is not discarded but returned to the crusher's feed port via a bypass conveyor belt, where it is crushed again along with the newly fed material. This cycle continues until all materials meet the required particle size requirements, providing the physical basis for sufficient contact between the material and water or chemicals in subsequent steps.

[0041] After screening and ensuring the particle size meets specifications, the crushed mud blocks proceed to the pulping step. In this step, the crushed mud blocks and a certain amount of liquid are simultaneously fed into a mixing tank equipped with a powerful agitator. The amount of liquid added is not arbitrary but is determined based on the weight of the weighed mud blocks, added according to a pre-calculated ratio. This solid-to-liquid mass ratio is controlled within a selected value between 1:1 and 1:8. The agitator in the mixing tank is activated, operating at a speed with sufficient shear force. Under continuous mechanical agitation, the solid mud blocks gradually break down and disperse, integrating with the liquid to form a non-stratified, homogeneous suspension system—the mud slurry. To ensure the overall homogeneity of the mud slurry, the time from initial feeding to homogenization and pumpability is typically maintained between 1 and 3 hours.

[0042] The homogenized mud is then pumped to the next stage, the mud conditioning step. In this step, one or more substances called conditioners are added to the flowing mud. These conditioners may be pre-prepared organic polymer flocculant solutions or powdered inorganic cementitious materials, such as specific types of silicate mineral powder. The addition point is usually located at a mixing tee on the mud delivery pipeline or at the inlet of a dedicated conditioning tank with slow stirring. The amount of conditioner added is calculated online or batch-wise based on the mud flow rate and properties. Once the conditioner and mud are combined, they mix rapidly in flow or agitation. The effective time from contact to complete mixing is very short, generally controlled within 30 seconds to 5 minutes. During this time, the conditioner exerts its effect, either by flocculating fine particles through charge neutralization or by improving the mud's gradation through microparticle filling, thereby altering the overall properties of the mud, such as increasing its settling velocity or improving its permeability during filtration.

[0043] The improved sludge then enters the loose filtration stage. The main task of this step is to perform preliminary solid-liquid separation and intentionally create a sludge structure conducive to subsequent treatment. The sludge is fed into a filtration device, such as a filter press. During operation, the sludge is pumped into the filter chamber, but special care is taken to control the pumping pressure. The feed pressure here is deliberately maintained at a low level, between 0.05 MPa and 0.3 MPa. Simultaneously, the filter cloth used in the filtration device is a selected model, whose material and weave method give it high air permeability, with an air permeability value in the range of 150 L / m³·s to 300 L / m³·s. With this combination of low pressure and high air permeability filter cloth, the water in the sludge (now called filtrate) can be easily discharged through the filter cloth, while solid particles are retained on the surface of the filter cloth. The key is that, due to the low pressure, these solid particles are not immediately compressed into a dense layer. Instead, they gradually accumulate on the filter cloth, forming a relatively loose, wet sludge cake layer that still retains many internal pores. The filtrate discharged from the filtration equipment is collected in a temporary storage tank.

[0044] The subsequent purification and washing step aims to remove chloride ions from the sludge. Once a wet sludge cake forms in the filtration equipment (or is transferred to a dedicated washing device), the washing program begins. Multiple nozzles mounted on the filter plates or washing unit activate, spraying pressurized water streams onto the wet sludge cake from different angles. The pressure of the washing water is higher than the feed pressure of the previous stage, typically between 0.1 MPa and 0.6 MPa. This powerful water stream penetrates the relatively loosely structured sludge cake layer, dissolving and flushing out the soluble chloride salts. This process needs to continue for a period to ensure washing effectiveness, usually lasting 5 to 30 minutes. Washing is stopped when the chloride ion content in the sludge has decreased to the predetermined target range of 5‰ to 5% (mass fraction) through periodic sampling and testing. The large amount of chloride-rich wastewater generated during washing, i.e., the washing water, is also collected separately.

[0045] The final step is sludge solidification and dewatering. After thorough washing and achieving the required chloride ion content, the wet sludge undergoes final dewatering and shaping to transform it into a usable product. This portion of sludge is fed into another dewatering and shaping device capable of applying higher pressure, such as different types of filter presses. Once the device is closed, a strong mechanical pressure is applied to the sludge within the chamber, typically between 0.6 MPa and 1.6 MPa. Under this high pressure, the residual water between the sludge particles is forcibly squeezed out, the sludge mass is significantly compressed, its volume is significantly reduced, and its solid content is greatly increased. After this treatment, the sludge dewatering rate, i.e., the percentage of water removed relative to the total water content in the untreated wet sludge, can reach 40%–65%. Finally, the device is opened, yielding solid blocks with a certain strength, regular shape (depending on the mold shape), and low moisture content. These blocks, due to their main components and physicochemical properties meeting the requirements, can be used as a raw material in ironmaking processes, for example, as an admixture in sintering materials or as part of a slagging agent.

[0046] Throughout the entire process flow, particular emphasis is placed on the internal recycling of resources. Specifically, the large amounts of filtrate generated in the loose filtration step, and the large amounts of wash water generated in the purification and washing step, are not simply discharged directly as wastewater. Both streams are directed to a collection system and then pumped back to the front end of the production line via pipelines. They are then reintroduced into the system's sludge conditioning step in a controlled manner. On the one hand, this recycled water may contain trace amounts of unreacted conditioning agents that can continue to function; on the other hand, this significantly reduces the overall process's demand for fresh industrial water from external sources, while also alleviating the load on subsequent wastewater treatment, reflecting the closed-loop and energy-saving principles of the process design.

[0047] Furthermore, in the pulping step, the solid-liquid ratio is 1:1 to 1:8, and the mixing time is 1 h to 3 h. In the mud conditioning step, the added conditioning agent is at least one of organic polymer flocculant or inorganic cementitious material, and the reaction time of the conditioning agent is 30s to 5min.

[0048] Furthermore, the loose filtration step is carried out at a filtration pressure of 0.05MPa to 0.30MPa, and the filter medium used has an air permeability of 150L / m³·s to 300L / m³·s. The purification and washing steps are carried out under a rinsing pressure of 0.10MPa to 0.60MPa, and the rinsing time is 5 min to 30 min. The chloride ion content of the purified sludge is 0.5% to 5%.

[0049] Furthermore, the sludge re-solidification step is carried out under an extrusion pressure of 0.60 MPa to 1.60 MPa, with a dewatering rate of 40% to 65%, and is extruded and molded using a filter press.

[0050] In the pulping step, the crushed and sieved mud lumps are fed into the mixing equipment. A suitable solid-liquid mixing ratio is typically determined, ranging from 1:1 to 1:8. For example, for drier, more absorbent mud cakes, a lower ratio close to 1:1 might be chosen to form a pumpable, thick slurry; while for mud cakes with a high water content, a higher ratio of 1:8 might be used to facilitate thorough washing later. The liquid is usually industrial water or treated recycled water. After the two are combined in the mixing tank, the agitator begins operation. The purpose of agitation is to completely wet and disperse the solid particles in the liquid, forming a uniform suspension system without significant particle sedimentation. To achieve this ideal homogeneous state, agitation needs to continue for a sufficient time. Depending on the amount of material and the efficiency of the equipment, this mixing process usually needs to be maintained for 1 to 3 hours. During this period, the homogeneity requirements can be determined by observing the fluidity of the slurry or by sampling and testing its solid content.

[0051] After entering the mud conditioning stage, a conditioning agent is introduced into the homogenized mud during its flow. The choice of conditioning agent depends on the specific situation; sometimes a single agent is used, and sometimes two are used in combination. One commonly used type of conditioning agent is an organic polymeric flocculant, such as a polyacrylamide solution with a certain degree of ionization, which can aggregate and enlarge small particles through the bridging effect of long molecular chains. Another type is inorganic cementitious material powders such as bentonite and silica fume, which change the internal structure of the mud through particle filling and surface physicochemical effects. Regardless of the type chosen, it is added to the mud stream continuously or in batches according to a certain percentage relative to the dry solids of the mud, using a metering device. After the conditioning agent and mud are mixed, they need time to interact. This time, from the moment they come into contact until the mixture is ready to enter the next process, is controlled within a relatively short window of 30 seconds to 5 minutes. During this period, the mixture is gently stirred in a static mixing tube or conditioning tank to ensure sufficient reaction without destroying the already formed flocs.

[0052] The subsequent loose filtration step is performed on a filtration device equipped with specially selected filter cloth. The type of filter cloth is important; its permeability, or air permeability, must reach 1m. 3The standard is that 150L to 300L of air can pass through per second per unit area. Such filter cloth can provide good liquid permeability while ensuring sufficient interception accuracy. During operation, the slurry is fed into the filtration chamber under the drive of pressure. The pressure applied here is a carefully controlled low pressure, with its value within the range of 0.05MPa to 0.3MPa. Under such low-pressure conditions, the water in the slurry can pass through the filter cloth smoothly and become clear filtrate discharged, while the solid substances are slowly deposited on the surface of the filter cloth. Due to the low pressure, the deposited solid layer will not be immediately pressed very tightly, but gradually accumulates into a wet sludge cake with relatively more internal pores and a relatively fluffy structure. This "loose" state is the origin of its name and is also the key to achieving efficient washing in the next stage.

[0053] After the wet sludge cake is formed, it is transferred to the purification washing step. The power for washing comes from water flow with a certain pressure, and its pressure is set between 0.1MPa and 0.6MPa. The pressurized water is sprayed onto the wet sludge cake simultaneously from multiple directions such as above and side through several to dozens of nozzles pre-distributed in the equipment chamber. Thanks to the previously formed loose structure, these water flows can effectively penetrate the entire thickness of the sludge cake instead of just washing the surface. During the penetration process, a large amount of soluble chlorides attached to the inside and surface of the sludge particles are dissolved and carried away. To ensure that the vast majority of chloride ions are leached out, this high-pressure penetration flushing process needs to last for a period of time, usually between 5min and 30min. The operator will regularly drill small samples from the sludge cake being washed and quickly detect its chloride ion content. Only when the test result shows that the mass percentage of chloride ions has steadily dropped to the preset target range of five thousandths to five percent will it be determined that the washing is qualified and the flushing will be stopped.

[0054] The final sludge solidification step is the finishing touch in the shaping process. After washing and meeting standards, the wet sludge remains loose and cake-like with a high moisture content, making it unsuitable for direct use as a product. Therefore, it requires final pressure dewatering and shaping. This step is typically performed on a filter press capable of applying higher mechanical pressure, such as a chamber filter press or a diaphragm filter press. The sludge is loaded between the filter plates, the press is closed, and the hydraulic system activates, applying strong pressure to the sludge. This pressure ranges from 0.6 MPa to 1.6 MPa, significantly higher than the previous filtration pressure. Under continuous high pressure, a large amount of water is squeezed out from between the sludge particles, and the sludge volume is significantly compressed. Once the pressure reaches the set value and is maintained for a period of time, the dewatering process ends. At this point, the percentage of water removed relative to the total water content of the original wet sludge, i.e., the dewatering rate, can reach 40% to 65%. After opening the equipment, a hard block with uniform thickness, a certain mechanical strength, and a regular shape is obtained. This block is the final resource product—the ironmaking raw material block, which can be directly packaged and shipped out for use in blast furnaces or sintering processes, thus completing the entire process.

[0055] Example 3 This embodiment describes in detail the specific implementation process of treating the waste acid purification sludge cake generated during the pickling wastewater treatment process of a steel plant using the process described in this invention. The initial state of this batch of sludge cake is black and lumpy, with a chloride ion content as high as 21% (on a dry basis).

[0056] The processing procedure is carried out according to the following specific steps and parameters: Step 1: Crushing and Pulping Take 1 ton of the above-mentioned waste acid purification sludge cake and crush it using a jaw crusher. After crushing, it is screened through a vibrating screen with a 30 mm aperture. Sludge lumps with a particle size larger than 30 mm are returned to the crusher for further crushing until all material passes through the screen. All the obtained crushed sludge lumps (about 1 ton) are added together with 4 tons of industrial water into a neutralization tank equipped with a stirrer, controlling the solid-liquid mass ratio to be 1:4. Start the stirrer and continuously stir at a speed of 45 rpm for 2 hours until a uniform, grayish-black sludge without visible large particles is formed.

[0057] Step 2: Mud Conditioning While continuously stirring, an anionic polyacrylamide aqueous solution (1.5% by dry solids) was added to the prepared mud as a conditioning agent. The addition of the conditioning agent was completed within 2 minutes, followed by stirring for another 3 minutes to ensure thorough mixing and reaction between the agent and the mud. The total reaction time for the entire mud conditioning stage was controlled within 5 minutes.

[0058] Step 3: Loose filtration The adjusted sludge was pumped to a chamber filter press for filtration using a screw pump. The pressure during loose filtration was controlled at 0.1 MPa, and the filter cloth used was made of polypropylene with an air permeability of 220 L / m³ / s. Under these conditions, a large amount of water was separated to form the filtrate, while a loosely structured, porous, wet sludge cake was formed in the filter chamber. After filtration, approximately 3.2 tons of filtrate were collected and temporarily stored in a filtrate tank.

[0059] Step 4: Purification and Washing The loosely filtered, wet sludge cake is retained in the filter chamber of the filter press for washing. The filter press's washing water pump is started, and clean water (reclaimed water can also be used) is used to rinse the sludge cake layer at an output pressure of 0.16 MPa for 15 minutes to fully dissolve and remove chloride salts from the sludge cake. After washing, approximately 1.8 tons of chloride-rich washing water is collected and temporarily stored in a washing water tank.

[0060] Step 5: Sludge solidification and dewatering After washing, the washing water valve is closed, and the high-pressure extrusion system of the filter press is started. A mechanical extrusion pressure of 0.6 MPa is applied to the sludge in the filter chamber and held for 10 minutes to further squeeze out the residual water between the sludge particles. After unloading, a smooth, dark gray, regular sludge cake with a certain strength is obtained. After weighing and testing, the final solidified sludge cake has a moisture content of 45%, and the chloride ion content in the solidified sludge cake has decreased from 21% in the waste acid purification sludge cake to 3%.

[0061] In this embodiment, the filtrate produced in the third step and the washing water produced in the fourth step are both pumped to the mud conditioning tank through pipelines and reused as part of the process water for mud preparation in the second step, which significantly reduces the consumption of fresh water and the amount of wastewater discharged.

[0062] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A waste acid purification sludge cake resource utilization system, characterized in that, Including those arranged sequentially along the material handling flow direction: The material crushing system is used to crush the waste acid purification sludge cake; The pulping system is used to mix the crushed waste acid purification sludge cake with liquid to form a uniform sludge. A mud conditioning system, connected to the outlet of the pulping system, is used to receive mud and add conditioning agents to improve the physicochemical properties of the mud; A loose filtration system, connected to the outlet of the sludge conditioning system, is used to perform low-pressure filtration on the conditioned sludge to form loosely accumulated sludge particles. A purification and washing system is connected to the outlet of the loose filtration system and is used to wash away chloride ions from loosely accumulated sludge particles. The sludge solidification and dewatering system is connected to the outlet of the purification and washing system and is used to extrude and dewater the purified sludge to form ironmaking raw material blocks. The loose filtration system is provided with a filtrate return pipeline connected to the mud conditioning system, and the purification and washing system is provided with a washing water return pipeline connected to the mud conditioning system.

2. The waste acid purification sludge cake resource utilization system according to claim 1, characterized in that: The material crushing process involves crushing the waste acid purification sludge cake to a particle size range of 5mm to 30mm. The pulping system mixes the crushed sludge cake with liquid at a solid-liquid ratio of 1:1 to 1:8 for a mixing time of 1 h to 3 h.

3. The waste acid purification sludge cake resource utilization system according to claim 1, characterized in that: The mud conditioning system includes a conditioner dosing device and a mixing reaction device. The conditioner dosing device is configured to add at least one of organic polymer flocculant or inorganic cementitious material, and the mixing reaction time is 30s to 5min.

4. The waste acid purification sludge cake resource utilization system according to claim 1, characterized in that: The loose filtration system is configured to operate at a filtration pressure of 0.05 MPa to 0.30 MPa, and the filter medium has an air permeability of 150 L / m³·s to 300 L / m³·s.

5. The waste acid purification sludge cake resource utilization system according to claim 1, characterized in that: The purification and washing system is configured to operate at a rinsing pressure of 0.10MPa to 0.60MPa, with a rinsing time of 5 min to 30 min, and the chloride ion content of the purified sludge is 0.5% to 5%.

6. The waste acid purification sludge cake resource utilization system according to claim 1, characterized in that: The sludge solidification and dewatering system is configured to operate under a compression pressure of 0.60 MPa to 1.60 MPa, with a dewatering rate of 40% to 65%. The sludge solidification and dewatering system is at least one of a plate and frame filter press, a belt filter press, a chamber filter press, or a diaphragm filter press.

7. A process for the resource utilization of waste acid purification sludge cake, comprising the following steps: S1, Crushing Step: The waste acid purification sludge cake is crushed. The particle size of the crushed sludge is 5 mm to 30 mm. Sludge particles larger than this size will be screened and removed. S2, Pulping step; Homogenize the crushed waste acid purification mud cake with the liquid; S3, mud conditioning step: Add a conditioning agent to the mud to adjust its physicochemical properties; S4, Loose Filtration Step: The adjusted sludge is subjected to low-pressure filtration to form loosely packed sludge particles. S5, Purification and Washing Step: Water flows through multiple directional inlets on the filter, penetrating and washing away loosely accumulated sludge particles to remove chlorine ions, thus purifying the filter. S6, Sludge solidification and dewatering step: The purified sludge is extruded, dewatered and shaped into ironmaking raw material blocks; The filtrate produced in the loose filtration step and the wash water produced in the purification and washing step are reused in the mud conditioning step.

8. The waste acid purification sludge cake resource utilization process according to claim 7, characterized in that, It also includes mixing in the pulping step at a solid-liquid ratio of 1:1 to 1:8 for a mixing time of 1 h to 3 h; In the mud conditioning step, the added regulator is at least one of organic polymer flocculant or inorganic cementitious material, and the reaction time of the regulator is 30s to 5min.

9. The waste acid purification sludge cake resource utilization process according to claim 7, characterized in that, The loose filtration step is carried out at a filtration pressure of 0.05MPa to 0.30MPa, and the filter medium used has an air permeability of 150L / m³·s to 300L / m³·s. The purification and washing steps are carried out under a rinsing pressure of 0.10MPa to 0.60MPa, and the rinsing time is 5 min to 30 min. The chloride ion content of the purified sludge is 0.5% to 5%.

10. The waste acid purification sludge cake resource utilization process according to claim 7, characterized in that, The sludge re-solidification step is carried out under an extrusion pressure of 0.60MPa to 1.60MPa, with a dewatering rate of 40% to 65%, and is performed by extrusion molding using a filter press.

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