Case Study: 50% NaOH in Kraft Paper Production — 20% Chemical Savings
1. Background
Binh Duong is one of the largest paper production centers in the South, home to numerous kraft paper mills serving the export packaging industry. Kraft paper—a type of paper with high mechanical strength, produced from softwood pulp via the sulfate process—is the primary raw material for corrugated boxes, cement packaging, and industrial paper bags. NaOH plays a central role in this process: it dissolves lignin in wood chips at temperatures of 160–170°C and high pressure, releasing cellulose fibers to form paper pulp.
A paper mill in the Tân Uyên Industrial Park, with a capacity of 150 metric tons of paper per day, uses NaOH as the primary chemical in the pulp cooking stage—the most critical phase determining the quality and efficiency of the entire production line. Each cooking batch consumes approximately 300–350 kg of NaOH (calculated as 100% NaOH) for 5 metric tons of pulp, equivalent to a ratio of 6–7% NaOH relative to the dry weight of wood chips.
Over the past five years of operation, the mill has consistently used 99% flake NaOH (solid form, packed in 25-kg bags) for the Kraft pulping process. However, as production increased from 80 to 150 metric tons per day, the shortcomings of this method began to become apparent, directly impacting productivity and profitability.
2. Issues
The old process using flaked NaOH encountered several serious problems as the mill expanded its operations:
| Issue | Impact |
|---|---|
| Labor-intensive dissolution | Each shift required 2 workers dedicated to opening bags, weighing, and dissolving flaked NaOH — totaling 6 workers per day |
| Inconsistent concentration | Manual dissolution leads to concentration deviations of ±5–8%, directly affecting the quality of the cooking pulp |
| Significant chemical loss | NaOH flakes are highly hygroscopic and clump during storage, resulting in a loss of ~8–12% per batch |
| Occupational safety risks | Workers are in direct contact with solid NaOH, posing a high risk of chemical burns |
| Warehouse space requirements | Storing 15 metric tons of flaked NaOH requires ~60 m² of warehouse space; packaging generates significant waste |
The plant estimates total NaOH costs (including loss + labor + electricity for dissolution) to reach 3.8 billion VND/year for an annual consumption of ~350 metric tons of flake NaOH—a figure that requires urgent optimization. Additionally, inconsistent pulp quality results in a defect rate of ~3–5%, equivalent to losses of hundreds of millions of VND each month due to substandard pulp that must be recycled or discarded.
3. Solution
Loc Thien Chemicals has proposed switching to 50% liquid NaOH, transported via specialized tanker trucks, pumped directly into a 20 m³ stainless steel tank, and integrated with the plant’s automatic dosing system.
Implementation Plan:
| Phase | Description | Timeline |
|---|---|---|
| Survey & Design | Site survey, design of storage tank and feed piping | Weeks 1–2 |
| Installation | 20 m³ stainless steel tank, metering pump, flow meter, overflow prevention system | Weeks 3–4 |
| Commissioning | Test operation with 3 batches, parameter calibration | Week 5 |
| Full Operation | Complete transition to 50% liquid NaOH | Week 6 onward |
The plant is supplied with 50% NaOH by Lộc Thiên Chemicals from its warehouse in Bà Rịa–Vũng Tàu, delivered by tanker trucks carrying 10–15 metric tons per trip, at a frequency of 2 trips per week, ensuring an uninterrupted supply.
4. Results
After 6 months of operation using 50% liquid NaOH, the plant recorded significant improvements:
| Parameter | 99% flake NaOH | 50% liquid NaOH | Change |
|---|---|---|---|
| Equivalent NaOH consumption (metric tons/year) | 350 | 336 | ↓ 4% |
| Storage/usage loss | 8–12% | <1% | ↓ 90% |
| Labor (people/day) | 6 | 1 (supervision) | ↓ 83% |
| Cooking concentration uniformity | ±8% | ±1% | 8-fold improvement |
| Total costs (million VND/year) | 3,800 | 3,040 | ↓ 20% |
| Warehouse area (m²) | 60 | 15 (outdoor tanks) | ↓ 75% |
- 20% savings on total costs, equivalent to 760 million VND/year
- More consistent pulp quality, with a stable Kappa index of 22–24
- Completely eliminates manual handling of solid NaOH — no more chemical burn incidents
- No packaging waste generated, reducing packaging waste by 15 metric tons per year
5. Lessons Learned
- 50% liquid NaOH is the essential choice for medium- and large-scale paper mills — full automation, consistent quality
- Investing in storage tanks and a dosing system pays for itself quickly — in just 10 months of operation
- A reliable supplier with a multi-location warehouse system is critical — ensuring a continuous supply and preventing production disruptions
🔰 Are you currently using flake NaOH and want to switch to liquid NaOH?
Loc Thien Chemicals supplies industrial-grade 50% NaOH, with tank delivery available throughout Southern Vietnam.
📞 Hotline: 0979 891 929
🏭 Warehouses: Ho Chi Minh City, Ba Ria-Vung Tau, Dong Nai, Da Nang, Can Tho, Bac Ninh