2026/11/03
The choice between rotary drum steam granulation and semi-slurry ammoniation depends on the company's scale, liquid ammonia supply conditions, and tail gas treatment capacity. Compared to steam granulation, semi-slurry ammoniation can reduce raw material costs by approximately 118.2 yuan/ton, fuel consumption by approximately 0.018 t/t, and pelletizing rate by 84.6%–91.8%. Steam granulation is simpler to operate and more flexible in formula switching, but energy consumption and raw material costs are higher. There is no absolute superiority or inferiority between the two methods; it depends on whether they match the company's specific conditions.
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Steam granulation is a traditional agglomeration method that relies on external steam to provide heat and moisture, causing the material to agglomerate into pellets within a rotary drum. Its core advantages are mature technology, intuitive operation, and flexible formula switching. The raw materials are mainly solid-based fertilizers, making it less dependent on raw materials. This method is mostly used by small and medium-sized compound fertilizer plants. The trade-off is high steam consumption, high subsequent drying load, and a pelletizing rate typically only 40%-60% (conventional process), with particle strength between 10-20N.
The semi-slurry ammoniation method follows a different logic: a portion of monoammonium phosphate is prepared into a slurry, which is then reacted with ammonia and sulfuric acid in a tubular reactor to produce diammonium phosphate slurry, which is then sprayed into the granulator bed. The heat of reaction is directly used to heat the material and evaporate moisture, and the bed temperature can reach 80-100℃, 20-40℃ higher than the approximately 60℃ of steam granulation. This increases the solubility of chemical salts, and under the same liquid phase ratio, the granulation moisture content can be reduced by 2-3%, thus lowering the drying load. The pelletizing rate increases to 84.6%-91.8%, and the particle strength can reach over 25N. The return material ratio is reduced, and the production capacity of a similar-scale plant can be increased by 30%-50%. However, the semi-slurry method has specific requirements for liquid ammonia storage capacity, and slurry viscosity control is a process bottleneck, making the operation more complex than steam granulation.
The semi-slurry ammoniation process uses liquid ammonia and sulfuric acid, inevitably resulting in ammonia entrainment in the granulation tail gas. Ammonia recovery is not optional but mandatory. The industry standard practice is a two-stage washing process: the granulation tail gas first passes through a washing system, where dilute sulfuric acid is added to absorb the ammonia. The washing liquid circulates within the system, and the recovered ammonium sulfate solution is returned to the granulation process as liquid phase replenishment. This design controls ammonia loss within the allowable range of the process while avoiding direct emission of ammonia-containing tail gas. Steam granulation does not use liquid ammonia; the source of ammonia in the tail gas is mainly from the raw materials themselves, resulting in a much lower load and complexity for the ammonia recovery system. This means that the semi-slurry route requires higher initial investment and daily operation and maintenance in environmental protection facilities, and the stability of the ammonia recovery system directly determines whether the process can operate continuously.
Industry data shows that the semi-slurry ammoniation process is more suitable for large enterprises with liquid ammonia storage capabilities. Small and medium-sized enterprises (SMEs) face higher barriers in terms of liquid ammonia qualifications, safety management, and tail gas treatment. Research literature also clearly indicates that "low-temperature eutectic granulation can enhance the competitiveness of SMEs," rather than the semi-slurry route. For small plants with limited annual production capacity, unstable liquid ammonia supply, and a lack of professional tail gas scrubbing and maintenance teams, steam granulation's low barriers to entry and high flexibility remain a pragmatic choice. However, if a small plant already has liquid ammonia usage qualifications, complete tail gas treatment facilities, and its product positioning is high-concentration, high-strength granular fertilizer, the savings in raw material costs and fuel consumption from the semi-slurry route can be amortized over a reasonable period. The judgment criterion is not "which process is more advanced," but whether the three conditions of "liquid ammonia qualifications, tail gas treatment capabilities, and maintenance teams" are met.
Q: Can the strength of granules produced by the semi-slurry ammoniation method meet the requirements for transportation and mechanized fertilization?
Yes. Conventional steam granulation typically produces particles with a strength of 10-20 N, while semi-slurry ammoniation granulation can achieve strengths exceeding 25 N. Under optimized conditions, the particles exhibit even higher density and stronger resistance to breakage. This increased strength stems from a more abundant and uniformly distributed liquid phase in the slurry formed by the heat of reaction, resulting in a continuous internal binder phase within the particles, rather than relying on external binders. In practical transportation and mechanized application scenarios, a strength exceeding 25 N is sufficient to withstand the impacts of conventional packaging, stacking, and transshipment. It's important to note that the strength advantage of the semi-slurry method is contingent upon controllable slurry viscosity and appropriate moisture content during granulation. If viscosity becomes uncontrolled or moisture levels deviate from the target range, the strength advantage will be weakened. Therefore, the strength level depends not on the process name but on the stable operation of the slurry preparation and granulation parameters.
The comparison above should be applied at the level of the whole rotary drum granulation production line, not only at the granulator itself. In an npk production process, formula flexibility, liquid ammonia availability, tail gas scrubbing, and drying load all influence whether rotary drum steam granulation or semi-slurry ammoniation is the better fit. For small and medium-sized plants with multiple formulas and limited liquid ammonia infrastructure, rotary drum steam granulation remains a practical choice; for large plants with liquid ammonia qualifications and ammonia recovery capacity, semi-slurry ammoniation can improve pelletizing rate and particle strength. The selection of the npk fertilizer granulator should therefore be matched to steam supply, slurry preparation, tail gas treatment, and downstream drying, rather than judged by equipment name alone. This is how the process choice becomes a line-level decision rather than a single-machine comparison.
The choice between rotary drum steam granulation and semi-slurry ammoniation is essentially a trade-off between low-threshold flexibility and high-investment, high-return processes. Steam granulation offers simplicity and flexibility, making it suitable for small and medium-sized plants lacking liquid ammonia facilities. Semi-slurry ammoniation, leveraging liquid ammonia qualifications and tail gas recovery capabilities, offers a triple advantage in cost, energy consumption, and intensity, making it suitable for large enterprises with the necessary resources. Taking stock of your liquid ammonia, tail gas, and maintenance capabilities, and then comparing them to cost figures, will yield a more reliable answer than simply consulting process brochures.