The production process of gypsum board primarily consists of six core steps: raw material preparation, calcination, slurry preparation, molding, drying, cutting, and packaging. It extensively utilizes natural gypsum or industrial by-product gypsum (such as desulfurization gypsum) as raw materials. The process is highly automated and aligns with the green and low-carbon development trend of China's building materials industry.
1. Preparation of raw materials
Raw material source: Mainly natural gypsum (CaSO₄·2H₂O, purity ≥95%) or desulfurization gypsum from power plants, the latter being a solid waste resource utilization, in line with national environmental protection policies.
Preprocessing:
Large chunks of gypsum are crushed to ≤50mm by a jaw crusher, and then further refined to ≤10mm by an impact crusher;
Through vibration screening, the oversize material is returned for re-crushing;
In humid areas, it is necessary to store materials in a rain-proof manner, and raw materials should be placed in sealed silos to prevent caking.
Process parameters:
Temperature control: The optimal range is 160–170℃. Above 190℃, an anhydrous phase is easily formed, leading to a decrease in strength;
Equipment type: Mainly rotary kiln (indirect heating) and fluidized bed furnace (fluidized calcination), with desulfurized gypsum mostly adopting the two-step method of "drying + calcination";
Product requirements: Semi-hydrated gypsum content ≥75%, specific surface area 350–400m²/kg, sieve residue ≤5% (120 mesh).
3. Slurry preparation
Addition of auxiliary materials:
Retarder: Sodium Citrate (0.1–0.3%), delays setting;
Foaming agent: prepared by a dynamic foaming device to enhance thermal insulation;
Pulp/modified starch: Enhance fiber structure;
Water reducing agent: reduces the water-binder ratio and enhances strength;
Waterproof/fireproof additives: added according to product type (water-resistant, fire-resistant board).
Mixed process:
Pre-mixing liquid components in a hydraulic pulper;
Fully automatic belt weigher accurately dispenses gypsum powder and coagulant;
The blender achieves homogeneous mixing of multiple components, and the system automatically adjusts the proportion according to the production line speed.
4. Forming
Process flow:
The upper and lower protective papers are fed into the forming machine via an automatic alignment device;
The gypsum slurry is evenly poured onto the surface of the lower paper;
The vibrating platform compacts the slurry, eliminating air bubbles and ensuring a tight bond with the paper surface;
Initial solidification forms a continuous slab, with its thickness controlled by the mold (typically ranging from 9.5mm to 15mm).
Technical Features: The mainstream production line in China achieves fully automated continuous molding, with a daily production capacity of over 500,000 square meters per single line.
5. Drying
Core objective: Evaporate 40–55% of the moisture content by weight of the finished product, reducing the moisture content from approximately 60% to ≤0.5%.
Process parameters:
Drying time: 8–12 hours;
Temperature gradient: inlet 60–80℃, outlet 100–120℃;
The hot air circulation system prevents the edges from being too dry and the middle from being wet and soft;
Energy consumption accounts for approximately 30% of the total production cost, and some factories adopt waste heat recovery to reduce energy consumption.
Risk control: Prevent staining (starch migration), overburning, or bonding damage on the board surface.
6. Cutting and packaging
Cutting: Utilize high-precision vertical and horizontal cutting machines to perform cutting according to standard dimensions (such as 2400×1200mm), with edge and corner trimming;
Inspection: Inspect the thickness, flatness, strength, and paper adhesion of each board;
Packaging: Automatically stack, wrap with film, bundle, and label with product type (ordinary/water-resistant/fire-resistant) and batch number.
The characteristics of China's localized craftsmanship
Raw material preference: Regions rich in gypsum resources such as Shandong, Jiangsu, and Hubei widely use desulfurized gypsum to achieve "waste treatment with waste";
Environmental protection treatment:
Exhaust gas: After undergoing cyclone and bag dust removal processes, particulate matter emissions are ≤20mg/m³;
Wastewater: closed-loop circulation, with a reuse rate exceeding 90%;
Equipment upgrade: Imported hydraulic forming system and intelligent temperature-controlled drying line are adopted, with a failure rate of less than 1%.