What's the difference between traditional hydrazine method and slurry method?

Diammonium phosphate is produced by slurry method and traditional method.

The difference between the two:

1. whether phosphoric acid is concentrated before neutralization with ammonia: the production of diammonium phosphate with concentrated phosphoric acid is called "traditional process"; The production of diammonium phosphate from dilute phosphoric acid without concentration is called "slurry method"

2. The requirements for phosphate rock quality are different: the traditional method requires high grade phosphate rock, while the pulp method requires low grade phosphate rock.

3. The purity of diammonium phosphate is different: the traditional method has higher purity than the slurry method.

4. Different impurities: The traditional method has less impurities than the slurry method.

5. Different costs: traditional methods need to be centralized, so they have high requirements for equipment and technology and high costs; Slurry ammonium phosphate can be used to produce low-concentration phosphoric acid from low-grade phosphate rock, with mature technology, low equipment material requirements and low cost.

Extended data:

The core process of producing ammonium phosphate by neutralization slurry concentration in China has gone through three stages: developing and perfecting industrial equipment to building high-level large-scale domestic equipment.

The first stage is before 1988. Based on the previous research, the theoretical basis of the core part of slurry ammonium phosphate process was established, and the pilot test of the process was initially started according to this theory. The pilot-scale process flow is: wet phosphoric acid dihydrate-ammoniation in dilute acid tank-double-effect open-circuit circulating concentration of dilute slurry-centrifugal spraying and cocurrent drying of concentrated slurry-powdery monoammonium phosphate product.

1988 ~ 1999 is the second stage. At this stage, the research and development focuses on the re-optimization, engineering, industrialization and large-scale promotion of the pilot results, forming a real industry, and developing, enriching and deepening the basic theory of slurry concentration and related unit processes, the core link of slurry method, in the process of industrialization.

The third stage means that in recent years after 1999, the slurry ammonium phosphate process has realized the large-scale and domestic production of batch devices. By integrating the above technical achievements, the production capacity of the factory has been doubled with only a small amount of funds, and the investment per unit production capacity has been greatly reduced. The average investment per ton of capacity expansion device is less than that of 250 yuan, which is only 1/3 of the original 30,000-ton device.

References:

Preparation of phosphoric acid by slurry method