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Production Process and Equipment of Crystal/Silica Gel Cat Litter
1. Core Principle
Crystal cat litter is essentially silica gel, a highly active adsorbent material.
Its production is based on the following chemical reaction:
Sodium Silicate + Sulfuric Acid → Silicic Acid (Gel) + Sodium Sulfate
The resulting silicic acid forms porous silica gel particles with a three-dimensional network structure (filled with micro-pores) after aging, water washing, and drying. These micro-pores strongly lock in moisture and ammonia through physical adsorption and capillary condensation, achieving moisture absorption and deodorization.
2. Detailed Production Process and Equipment
Production is typically carried out in dedicated workshops of large chemical plants, featuring a highly continuous and automated process.
2.1 Phase 1: Reaction and Gelation
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2.1.1 Raw Material Preparation and Conveyance
Process: Dilute sodium silicate (water glass) solution to a specified concentration (usually with a modulus of 3.0-3.4) in a mixing tank. Sulfuric acid is also diluted to the required concentration in another storage tank.
Equipment: Raw material storage tanks, mixing tanks, metering pumps (for high-precision flow control), filters (to remove impurities).
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2.1.2 Mixing Reaction and Gelation (Core Step)
Process: The diluted sodium silicate solution and dilute sulfuric acid are rapidly and thoroughly mixed in a static mixer or reactor to undergo a neutralization reaction, producing silicic acid sol. The sol condenses into hydrous gel (like "jelly") within a very short time (seconds to minutes).
Equipment: Static mixer (commonly used for continuous production), stirred reactor (for batch production), online pH monitor.
2.2 Phase 2: Gel Treatment and Molding
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2.2.1 Aging
Process: Allow the formed gel to stand in an aging tank for several hours to dozens of hours. This process stabilizes the gel network structure, enhances strength, and optimizes pore size distribution.
Equipment: Aging tanks/vessels (usually jacketed for temperature control).
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2.2.2 Cutting and Crushing
Process: Mechanically cut or crush large gel blocks into small pieces suitable for subsequent processing.
Equipment: Gel cutting machine, crusher.
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2.2.3 Water Washing and Ion Exchange
Process: This is a critical step to remove sodium sulfate, a byproduct of the reaction. Wash the gel blocks with hot water in a washing tank through multiple countercurrent washes. Occasionally, ion exchange equipment is used to further remove sodium ions for producing higher-purity silica gel for cat litter.
Equipment: Multi-stage countercurrent washing tanks, plate and frame filter press or belt filter, ion exchange column, sewage treatment system (to handle salt-containing wastewater).
2.3 Phase 3: Drying and Sieving
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2.3.1 Drying (Core Energy-Consuming Step)
Process: The washed gel still has high moisture content (approximately 60-70%) and requires thorough drying to form hard, porous particles. Temperature and drying rate must be precisely controlled to preserve the porous structure.
Equipment:
• Fluidized bed dryer (most commonly used): Hot air fluidizes wet particles, enabling uniform and efficient drying.
• Rotary dryer: Suitable for large-scale production.
• Microwave drying or combined drying: Used for high-end or special products, better preserving particle integrity.
• Rotary dryer: Suitable for large-scale production.
• Microwave drying or combined drying: Used for high-end or special products, better preserving particle integrity.
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2.3.2 Sieving and Classification
Process: Dried particles vary in size. Use multi-layer vibrating sieves to separate particles within the particle size range required by the pet market (usually irregular particles of 1-4mm). Overly fine powder can be recycled, while oversized particles can be slightly crushed and re-sieved.
Equipment: Multi-layer linear vibrating sieve, rotary vibrating sieve.
2.4 Phase 4: Post-Processing and Packaging
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2.4.1 Colorant/Indicator Addition (Optional)
Process: Some crystal cat litters add cobalt chloride as a moisture indicator, which is blue when dry and gradually turns pink when absorbing water. This step is usually completed by light spraying or mixing after drying.
Equipment: Small mixer, micro-spraying equipment.
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2.4.2 Dust Removal and Packaging
Process: The sieved product passes through a dust removal sieve or air classifier to remove surface fine dust, ensuring product cleanliness. Finally, use an automatic packaging machine to fill the product into moisture-proof packaging bags (often aluminum film composite bags) and seal them.
Equipment: Dust removal sieve, automatic quantitative packaging machine (preferably with nitrogen filling function for moisture proofing), sealing machine.
3. Summary Table of Key Equipment
| Production Stage | Core Equipment | Function and Importance |
| Reaction Phase | Static mixer/reactor, metering pump | Enable precise raw material mixing and rapid gelation; form the basis of the product's chemical structure |
| Treatment Phase | Multi-stage countercurrent washing system, filter press | Remove impurities and byproducts; determine product purity and pH value (must be neutral) |
| Drying Phase | Fluidized bed dryer | Core energy-consuming step; drying process directly affects product porosity, strength, and moisture absorption performance |
| Finished Product Phase | Multi-layer vibrating sieve, automatic packaging machine | Control the particle size, appearance, and packaging tightness of the final product; impact user experience |
4. Production Characteristics of Crystal Cat Litter
| Characteristic | Details |
| Capital and technology-intensive | Investment is much higher than that of bentonite and plant-based cat litter production lines, involving chemical reactions, sewage treatment, etc. |
| High energy consumption | Especially the drying step, which consumes a large amount of thermal energy |
| Strict environmental requirements | Salt-containing (sodium sulfate) wastewater generated during production must be properly treated and cannot be directly discharged |
| Raw material costs affected by chemical market | Price fluctuations of sodium silicate and sulfuric acid directly impact production costs |
| Product performance determined by "pore structure" | Reaction conditions, aging time, drying curve, and other parameters during production collectively determine the pore size and distribution inside the silica gel, which in turn affect its moisture absorption capacity, absorption rate, and hardness |
5. General and Auxiliary Equipment
Regardless of the type of cat litter, the production line usually includes:
| Equipment Type | Function |
| Automatic control system | PLC control to coordinate the linkage of various equipment |
| Dust removal system | Dust collector, fan, used to collect dust during production and keep the workshop clean |
| Conveying system | Belt conveyor, bucket elevator, screw conveyor, connecting various production links |
| Quality inspection equipment | Moisture meter, particle strength tester, electronic scale, etc. |