Melamine is a versatile chemical intermediate critical to global industries—from wood adhesives and decorative panels to coatings, flame retardants, and plastics. As the world’s largest producer and exporter of melamine, China has driven significant advancements in production technology, shifting from outdated dual cyanamide methods to efficient urea-based processes. Today, the market offers a range of mature technologies, including high-pressure (e.g., Nissan, Montedison) and low-pressure (e.g., DSM, BASF, Edgein) processes, each with unique advantages for different enterprise scales and resources.
This article summary and comparison of melamine production processes, compares their technical and economic indicators, and highlights industry trends like “co-production” for tail gas recycling.
Historically, melamine was produced via the dual cyanamide method, but this process has largely been phased out due to high costs, low efficiency, and environmental drawbacks. Modern melamine production relies almost exclusively on urea as the raw material—thanks to its abundant supply, low cost, and superior technical-economic performance.
All urea-based melamine processes consist of three key stages:
Urea-based processes are primarily categorized by reaction pressure:
High-pressure processes are ideal for large-scale operations with access to urea co-production facilities. They offer fast reaction rates but require specialized equipment due to extreme operating conditions.
Operating conditions: 380–400℃, 10.0 MPa (liquid-phase reaction).
Key features:
Molten urea and high-pressure ammonia (10.0 MPa, 400℃) react in a reactor; tail gas is absorbed into concentrated ammonium carbamate and sent to urea plants.
The reaction product is quenched to 180℃, yielding a 20–30% melamine solution. After ammonia stripping, filtration, and crystallization, the final product is obtained.
It combines the advantages of low-pressure processes with improved wet-process drawbacks, but the technology is exclusive to Nissan.
Performance metrics: Melamine yield = 91%, annual operating days = 330, urea consumption = 3,100 kg/ton.
Operating conditions: 380℃, 8.0 MPa (liquid-phase reaction).
Key features:
Molten urea and ammonia (8.5 MPa, 420℃) react to form melamine; the product is quenched to 160℃ with ammonium carbamate solution.
Tail gas is recovered as ammonium carbamate; melamine solution is purified via activated carbon, filtered, and crystallized.
Requires recrystallization with NaOH to remove byproducts (e.g., melam, melem), which lengthens workflows.
Performance metrics: Melamine yield = 85–90%, annual operating days = 330, urea consumption = 3,100 kg/ton, ammonia consumption = 350 kg/ton.
Low-pressure processes are favored for their moderate operating conditions, lower equipment costs, and suitability for small- to medium-sized enterprises. Most use Al₂O₃-based catalysts.
Operating conditions: 390℃, 0.7 MPa (gas-phase catalytic reaction).
Key features:
Molten urea is sprayed into a reactor, and recycled ammonia (from the tail gas) serves as the carrier gas.
Reaction gas is quenched to 126℃, and melamine is concentrated via cyclones. The solution is stripped of residual NH₃/CO₂, mixed with recycled mother liquor, and crystallized.
Mature and stable, but requires complex purification and stainless steel equipment.
Performance metrics: Melamine yield = 85–92%, annual operating days = 300–310, urea consumption = 3,100 kg/ton.
Operating conditions: 380–400℃, 0.1 MPa (atmospheric pressure catalytic reaction).
Key features:
Molten urea is split: part reacts in a fluidized-bed reactor (with Al₂O₃ catalyst), and the rest washes tail gas in a scrubber.
Reaction gas is cooled to 330℃, filtered to remove catalyst dust, and quenched to 190–210℃ for crystallization. Dry collection eliminates the need for reprocessing.
Short workflow, high product quality, but high electricity consumption.
Performance metrics: Melamine yield = 94%, annual operating days = 300–310, urea consumption = 3,040 kg/ton, electricity consumption = 1,400 kW·h/ton.
| Indicator | High-Pressure Processes | Low-Pressure Processes | |||
|---|---|---|---|---|---|
| Nissan Process | Montedison Process | DSM Process | BASF Process | Edgein Process | |
| Investment | High | High | High | High | Low (1/3 of foreign) |
| Melamine Yield (%) | 91 | 85–90 | 85–92 | 94 | 94 |
| Annual Operating Days (d) | 330 | 330 | 300–310 | 300–310 | 300–310 |
| Equipment Corrosion | Mild | Severe | Mild | Mild | Mild |
| Key Material | Partial titanium | Partial Hastalloy | Partial stainless steel | Partial stainless steel | Partial stainless steel |
| Reaction Temp (℃) | 380–400 | 380 | 390 | 380–400 | 390 |
| Reaction Pressure (MPa) | 10.0 | 8.0 | 0.7 | 0.1 | 0.5 |
| Urea Consumption (kg/ton) | 3,100 | 3,100 | 3,100 | 3,040 | 3,100 |
| Electricity Consumption (kW·h/ton) | 450 | 700 | 500–550 | 1,400 | 1,400 |
| Ammonia Consumption (kg/ton) | 200 | 350 | 500 | 250 | 200 |
| Tail Gas Type | High-pressure dry gas | Ammonium carbamate liquid | Ammonium carbamate liquid | Low-pressure dry gas | Low-pressure dry gas |
| Product Treatment | High-pressure ammonia quenching | NaOH recrystallization | Liquid-phase treatment (no refining) | Dry collection (no refining) | Dry collection (no refining) |
| Reaction Type | Liquid-phase (no catalyst) | Liquid-phase (no catalyst) | Gas-phase (catalyzed) | Gas-phase (catalyzed) | Gas-phase (catalyzed) |
Q1: What are the main challenges of high-pressure vs. low-pressure processes?
A1: High-pressure processes face challenges such as complex operations (temperature/pressure control), corrosion, and high equipment costs. Low-pressure processes require catalyst replacement, have larger equipment footprints, and may experience reactor clogging (needing periodic shutdowns).
Q2: Can low-pressure processes produce high-purity melamine?
A2: Yes. BASF and Edgein processes use dry collection, which avoids hydrolysis and byproduct formation, resulting in high-purity melamine (≥99.8%) without additional refining—meeting global quality standards for adhesives, coatings, and flame retardants.
Q3: How does tail gas recycling impact production costs?
A3: Tail gas recycling reduces urea/ammonia consumption by 5–10% and eliminates waste treatment costs. For a 10 kt/a plant, this translates to $1–2 million in annual savings, shortening the investment payback period by 1–2 years.
Q4: Is the Chinese Edgein process competitive with foreign technologies?
A4: Yes. The Edgein process matches foreign processes in yield (94%) and product quality, while offering 60–70% lower investment (due to domestic equipment) and simpler maintenance. It has become the mainstream low-pressure technology in China, with over 20 operating plants.
Melamine production technology has evolved toward efficiency, sustainability, and cost-effectiveness, with urea-based high-pressure and low-pressure processes dominating the market. High-pressure processes excel for large-scale, urea-integrated operations, while low-pressure processes (especially China’s Edgein) offer flexibility for small-to-medium enterprises.
By selecting the right technology based on enterprise scale, capital, and infrastructure, manufacturers can enhance competitiveness in the global melamine market.
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