Industry Applications
Coal washing wastewater treatment plan:
Coal preparation plants typically use a "cyclone-thickener-plate filter (coal slurry sedimentation pond)" process to treat coal slurry water. In most cases, high-molecular-weight flocculants (polyacrylamide) are purchased for this purpose. The polyacrylamide interacts with coal slurry particles or colloids, neutralizing the surface charge of the slurry and reducing surface energy, thereby promoting particle aggregation and sedimentation. The molecular weight of polyacrylamide generally ranges in the millions, and different molecular weights should be selected according to the particle size distribution of the coal slurry water. Polyacrylamide can be classified into three types: anionic, cationic, and non-ionic. When using polyacrylamide for water treatment, it is essential to match the type with the pH value of the coal slurry water— anionic polyacrylamide is suitable for slightly alkaline slurry water, while cationic polyacrylamide works best for slightly acidic conditions. A combination of anionic and cationic polyacrylamides often yields better flocculation and sedimentation results.
Features:
1. Highly water-soluble, dissolves completely even in cold water.
2. Adding a small amount of this anionic polyacrylamide product yields excellent flocculation results. Typically, only 0.01 to 10 ppm (0.01 to 10 g/m³) is required to achieve optimal performance.
3. Using anionic polyacrylamide products together with inorganic coagulants (such as polyferric sulfate, polyaluminum chloride, and iron salts) can achieve significantly better results.
Scope of Application
1. Used in the textile and dyeing industries, polyacrylamide serves as a sizing agent and finishing agent for fabric treatment, forming a protective layer that provides softness, wrinkle resistance, and anti-mold properties. Due to its strong moisture absorption capacity, it helps reduce yarn breakage during fine spinning. As a post-treatment agent, polyacrylamide prevents static electricity and enhances flame retardancy in fabrics. When used as a dyeing auxiliary, it improves color fastness and brightness of the final product, and can also act as a non-silicone high-molecular stabilizer in bleaching processes.
2. Primarily used as a flocculant: For wastewater containing suspended particles that are relatively coarse, highly concentrated, and carry a positive charge, with water pH being neutral or alkaline, anionic polyacrylamide is effective because its molecular chains contain polar groups capable of adsorbing suspended solid particles in water, thereby bridging the particles to form larger flocs. This significantly accelerates particle settling in suspensions, greatly enhances solution clarification, and improves filtration efficiency. The product is widely applied in the treatment of chemical industry wastewater and waste liquids, municipal sewage treatment, drinking water purification, high-turbidity water clarification and sedimentation, coal washing, mineral processing, metallurgy, steel production, zinc and aluminum processing, electronics manufacturing, and other water treatment processes.
3. Widely used in the petroleum industry for oil production, drilling muds, waste mud treatment, preventing water channeling, reducing friction resistance, enhancing recovery rate, and tertiary oil recovery.
4. Used in the papermaking industry, it serves two main purposes: first, to increase retention of fillers and pigments, thereby reducing raw material loss and environmental pollution; second, to enhance paper strength (including dry and wet strength). Additionally, PAM can improve paper tear resistance and porosity, enhancing visual appearance and printability. It is also used in food packaging and tea packaging papers.
5. Other industries: In the food industry, it is used for juice clarification in sugarcane and beet sugar production, as well as for phosphoric flotation extraction of syrup. It is also applied in industrial flocculation and clarification of enzyme preparation fermentation liquids, recovery of feed protein with stable quality and excellent performance; the recovered protein powder has no adverse effects on chicken survival rate, weight gain, or egg production. Additionally, it is used in synthetic resin coatings, civil construction grouting materials for water sealing, building materials industry to improve cement quality, construction adhesives, crack filling and repair agents, soil improvement, electroplating industry, and dyeing and printing industries.
Flocculation and sedimentation refer to the process by which particles in water form flocs and settle. After adding coagulants to water, colloidal substances and dispersed particles suspended in it aggregate into flocs through intermolecular forces. During settling, these flocs collide and consolidate with each other, continuously increasing in size and mass, thereby accelerating their settling velocity. The removal efficiency of suspended solids depends not only on settling velocity but also on the depth of sedimentation. Flocs formed after coagulant addition in surface water, organic suspended matter in domestic wastewater, and activated sludge all exhibit flocculation and sedimentation during the settling process.
Disadvantages
Disadvantages of wastewater treatment agents
1. It will increase the COD and ammonia nitrogen content in water.
2. Salinity will increase; acrylamide is toxic, while polyacrylamide has relatively low toxicity.
3. When the dosage is increased, the viscosity of the effluent will rise. However, reducing the dosage leads to poor results, so it's essential to carefully control the amount used.
Polyacrylamide is primarily used for flocculation and sedimentation in wastewater treatment. Adding only a small amount of polyacrylamide to wastewater can significantly reduce suspended solids, resulting in clearer effluent. However, excessive dosage may cause the wastewater to become viscous, reducing its flowability and potentially leading to clogging of drainage pipes. This is the most common issue encountered during application.
The molecular weight, molecular structure and shape, as well as the functional groups carried by the flocculant, all influence its activity.
Generally, the higher the molecular weight, the greater the flocculating activity; linear molecules exhibit high flocculating activity, whereas branched or cross-linked molecules show lower flocculating ability. When flocculant-producing bacteria are in the later stages of cultivation, their cell surface hydrophobicity increases, resulting in higher flocculant activity.
Although polyacrylamide has many drawbacks as a flocculant, it remains one of the most widely used and largest-volume flocculant products. With its ultra-high molecular weight structure, low dosage requirements, and relatively low cost per unit volume of wastewater treated, polyacrylamide is undoubtedly a highly promising flocculant product until more cost-effective and efficient alternatives are developed.
Dosage method
Dosage methods of chemicals
Chemical dosing is carried out using either gravity or pressure feeding. Regardless of the dosing method, chemical lifting equipment should be installed from the dissolution tank to the solution tank and then to the chemical injection point. Commonly used chemical lifting devices include metering pumps and ejectors.
1. Gravity dosing
Add the chemical into the pump suction pipe or at the suction bell mouth of the sump using gravity, and mix it with the pump impeller.
2. Pressure Injection
Use a pump or ejector to add chemicals into the raw water pipeline, suitable for dosing chemicals into pressurized water pipes or into water treatment structures located at higher elevations or over long distances.
3. Pump dosing
Pump dosing involves lifting the chemical solution from the solution tank into the pressure line, either directly using a metering pump or employing acid-resistant pumps to enhance performance.
Polyacrylamide is generally prepared as a 0.1% to 0.5% diluted solution before use. The prepared solution should not be stored for too long before application. This concentration range typically requires further dilution to 0.01% to 0.05% prior to use, as this helps improve the dispersion of the flocculant in the suspension system, reduces dosage requirements, and achieves better flocculation results.
Ingredients
Anionic Polyacrylamide
Anionic Polyacrylamide (APAM) Product Description: Anionic polyacrylamide (APAM) appears as white powder or granules, with a molecular weight ranging from 6 to 25 million. It is highly water-soluble, dissolving in water at any concentration ratio and insoluble in organic solvents. Its effective pH range is 7 to 14, exhibiting characteristics of a high-polymer electrolyte in neutral to alkaline media. It is sensitive to salt electrolytes and can cross-link with divalent metal ions to form insoluble gel structures.
Industrial wastewater treatment: This product performs best in treating wastewater containing suspended particles, high concentrations, positively charged particles, and neutral or alkaline pH levels—such as steel plant effluent, electroplating wastewater, metallurgical wastewater, and coal washing wastewater. Drinking water treatment: Many municipal waterworks in China source their water from rivers with high sediment and mineral content, resulting in turbid water. Even after sedimentation and filtration, the water often fails to meet required standards. Adding this coagulant at a dosage of only 1/50 that of inorganic coagulants achieves several times better results. For river water heavily contaminated with organics, combining inorganic coagulants with cationic polyacrylamide yields even better performance. By adding anionic polyacrylamide, starch particles can be flocculated and settled; the resulting sludge is then pressed into cakes using filter presses, which can be used as animal feed. Anionic polyacrylamide can also be used for dewatering and recovery of alcohol in distilleries through filtration. It is also effective for settling river slurry and serves as a dry-strength agent in papermaking.
Used as a papermaking additive and retention aid. Adding a small amount of PAM-LB-3 anionic polyacrylamide to the pump inlet storage tank before papermaking can increase the retention of fillers and fine fibers on the wire by 20–30%. This saves 20–30 kg of pulp per ton of production. For example, large volumes of wastewater are generated during coal washing. Direct discharge pollutes the environment, so the water must be clarified and recycled. Recovering coal sludge from the water is also valuable, but natural sedimentation is time-consuming, labor-intensive, and often fails to achieve sufficient clarity.
In addition, anionic polyacrylamide is becoming increasingly popular in the incense manufacturing industry. This product features excellent solubility, high viscosity, strong toughness, and non-toxicity with low or no smoke emission and no unpleasant odor when burned. Its stable performance eliminates the need for repeated formula adjustments during production, which are often required with other plant-based gel powders or common starches due to variations in origin and batch quality that result in inconsistent bonding performance. Incense products made with this material exhibit smooth, even surfaces, good molding quality, and enhanced resistance to breakage. Notably, its ability to gelatinize in cold water means there's no need for cooking; materials can be directly mixed uniformly and stirred with water to begin production. Moreover, the mixture remains workable for extended periods without drying out or hardening, effectively saving energy and simplifying production operations.
Usage Effect: The incense blanks (finished products) made with this product are smooth in appearance, free from cracks or mold spots, and exhibit strong resistance to bending. The finished products have excellent color retention and do not fade after drying or sunning. They offer sufficient burning duration, good combustibility, and do not extinguish when passing through the iron comb, ensuring effective release of active ingredients and reducing losses during the drying process. Additionally, it significantly reduces labor intensity and improves work efficiency. Moreover, the product is environmentally friendly and meets green requirements.
Economic Benefits: Using this product can reduce raw material costs by 5–12% and save energy consumption by 20–30%.
Packaging and Storage
Anionic Polyacrylamide Packaging, Storage, Transportation, and Precautions:
Packed in 25 kg plastic-lined woven bags or paper-plastic composite bags, or customized according to customer requirements. During storage and transportation, protect against heat and moisture, prevent package damage, as dry powder products may absorb moisture and clump when exposed for extended periods. Stacking should not exceed 20 layers. Shelf life is 2 years. The product particle size ranges from 20 to 80 mesh, but can also be produced according to specific customer specifications.
Production Principle
The polymerization reaction of acrylamide monomers under the influence of a catalyst. In this specific process, the polymerization involves two steps:
Step one: the redox system catalyst releases free radicals;
The second step involves the release of free radicals from azo catalysts upon thermal activation.
Production Steps
1. Dissolution tank temperature
The dissolution tank temperature is maintained at approximately 18°C. Above 18°C, the solution tends to polymerize; below 17°C, sodium carbonate may precipitate on the coil. Adjustment method: Keep the temperature above 18°C by cooling the dissolution tank with circulating chilled water (5–10°C) from the refrigeration system to a fixed polymerization temperature of 18°C. If the actual cooling temperature falls below the setpoint, reheat the tank using the same coil. Hot water for heating is supplied via an electric water heater.
2. pH value of the dissolution tank
The pH of the dissolution tank should be controlled around 12.3 in the process, as a higher pH helps stabilize Na₂CO₃ and promotes the hydrolysis reaction. Adjustment method: After mixing AM with Na₂CO₃ solution, the pH typically ranges from 10.9 to 11.8; gradually adjust it to 12.3 using NaOH (30%). If the pH exceeds 12.3, it can be adjusted back using H₂SO₄ (95.1%).
3. Reactor Feed Rate
The reactor feed rate is controlled at approximately 12,100 kg in the process. Feeding more than 12,100 kg will cause volume expansion during polymerization, leading to overflow from the reactor.
4. Nitrogen Purging Time: The process controls the nitrogen purging time between 40 and 60 minutes, typically 40 minutes. If the purging time is less than 40 minutes, the oxygen content will not fall below 0.3 mg/L, which may lead to polymerization inhibition. Five minutes after feeding begins, the azo catalyst AZDN—premixed with 30 ml of deionized water and some Span 20—is injected from the storage tank into the reactor using compressed air, at a dosage of approximately 12 kg. Thirty minutes after nitrogen purging starts, 1.8 kg of sodium formate (a chain transfer agent) is added from the sodium formate storage tank into the reactor. The solution supply line loop maintains constant pressure via a reflux pressure-stabilizing valve, and the addition rate is controlled by the ICS system (with electromagnetic flow meters used for more accurate dosing).
5. Initiator, chain transfer agent dosage and addition sequence
Five minutes before stopping the nitrogen purge, add 0.18 kg of oxidizing agent ammonium persulfate into the reactor. Two minutes later, add 0.18 kg of sodium formaldehyde sulfoxylate, following the same procedure as for sodium formate. Ammonium persulfate is metered by a flowmeter and pumped from the storage tank into the reactor, while sodium bisulfite is also metered by a flowmeter and then pumped from the storage tank into the reactor. Two minutes after adding NaFS, stop the nitrogen purge—this marks the beginning of the reaction, during which temperature gradually increases. As the hydrolysis reaction accelerates, large amounts of NH₃ and CO₂ are generated, causing the colloid volume to expand to 2.5 times its original size. The polymerization reaction completes in approximately 30 minutes, at which point the temperature reaches around 90°C. However, hydrolysis continues. To increase the product's degree of hydrolysis, the colloid must be matured in the reactor for 3 hours before entering the pre-grinding stage. Whether the polymerization process proceeds normally can be determined by comparing temperature changes across different stages using the recorded temperature curve.
6. Reaction temperature
Temperature is also a critical parameter in the polymerization process. The polymerization temperature is set at approximately 18°C (this temperature can be adjusted according to the raw material formulation and the desired molecular weight of the product). After mixing, the temperature of the components ranges from 18 to 25°C. This cooling process is carried out by a refrigeration system, with cooling water maintained at 2–10°C, pumped into the jacket coil of the dissolving tank and controlled via a temperature controller regulating the cooling water valve. If, due to equipment shutdown or operational error, the cooling temperature falls below the set point, the dissolving tank can alternatively be heated using the jacket coil. Hot water is supplied from a hot water storage tank and pumped into the system.
7. Pre-grinding and granulation
The process of pouring the colloid from the reactor into the pre-grinder is controlled by the DCS system. After opening the cover, the reactor is slowly tilted by a hydraulic system, allowing the colloid to slide down along the lubricated polypropylene wall and be cut into three pieces by a crossbeam knife under gravity. At this stage, the colloid temperature is approximately 90°C. The procedure is as follows: the reactor lid is lifted by a lifting device, and the hydraulic pump is activated to gradually tilt the reactor from the hydraulic tank, thereby pouring the colloid into the pre-grinder. Inside the pre-grinder, six parallel cutting screws shred the colloid and press it into the feed screw (which is perpendicular to the cutting screws). The feed screw then transports the colloid into a screw metering pump for dosing before feeding it into the pelletizer. The metering speed and colloid flow rate in the cutter are manually adjusted. To facilitate cutting—especially for polymers with low to medium relative molecular weight—a certain amount of surfactant must be sprayed onto the colloid to maintain free-flowing viscous particles. This solution is manually pumped from a storage tank into the pre-grinder, with the addition volume controlled by a timer connected to the DCS system, set at 5 L. To ensure smooth feeding into the pelletizer, the material requires lubrication using 2% Span20 in Exxsol oil (approximately 20 L per hour), with the dosage per pelletizer depending on product specifications.