Optimization of Ammonium Sulfate Crystallization Under Ammonium Nitrate Based on Response Surface Method

Abstract

The response surface method is used to study the influence mechanism of three factors (seed crystal concentration, pH value, and stirring rate) on ammonium sulfate crystallization (average particle size and coefficient of variation [C.V.] value) under ammonium nitrate to prove the effect of ammonium nitrate doping on ammonium sulfate crystallization. Regression equations between each response value and the influencing factors are established. Results show that the interaction between the seed crystal concentration and the stirring rate is stronger than that between the seed crystal concentration and the pH and that between the pH and the stirring rate. The error between the verified model values and the experimental values is minimized when the seed crystal concentration is 1.5%, the pH is 4.5, and the stirring rate is 250 r min−1, at which the average particle size is 1.238 mm, and the C.V. value is 73.53. After optimization, the crystal morphology changes from needle‐ and flake‐like crystals to cubes, resulting in crystals with large average particle size, uniform distribution, regular morphology, and diffraction peak intensity that is close to that in the analysis of pure ammonium sulfate.

Optimization of Ammonium Sulfate Crystallization under the Action of Ammonium Chloride Using the Response Surface Method

“…In the implementation of the response surface method, the Design-Expert software was used to design the experimental scheme, the regression models in the software were used to establish the functional relationships between the influencing factors and the response variables, and the optimal process parameters were identified by analyzing the regression equations. − …”

“…Based on the evaporative crystallization device shown in Figure , the crystallization yield and average particle size were set as the response variables. The three influencing factors, namely, seed crystal concentration, pH value, and stirring rate, were set as the investigation variables, and their experimental levels were determined . The experimental group was designed by using the Design-Expert software, as shown in Table .…”

“…20−22 Analysis of variance is used to test the significance and adequacy of a model; the total error of the experimental results was subdivided into model error and experimental error to show whether the model change was significant compared with the change caused by the residual error. 22 The F test was conducted by calculating the ratio of the model mean square (MRR) to the residual error (MRe) (F = MRR/MRe). The smaller the F value, the more important its corresponding coefficient is.…”

“…The three influencing factors, namely, seed crystal concentration, pH value, and stirring rate, were set as the investigation variables, and their experimental levels were determined. 22 The experimental group was designed by using the Design-Expert software, as shown in Table 1. The influence of the above-mentioned factors on the crystallization of ammonium sulfate under the action of ammonium chloride was studied according to the experimental group designed in Table 1.…”

Evaporating crystallization effect of ammonium sulfate at atmospheric pressure under the action of ultrasound

“…At present, the methods used to crystallize ammonium sulfate include the addition of seed crystals, vacuum crystallization, antisolvent crystallization, and atmospheric pressure crystallization. By adding large particles of ammonium sulfate, other metal salts, fly ash, and urea [7] , [8] , ammonium sulfate grows on these large particles, which plays a role in inhibiting the spontaneous formation of small grains [9] , [10] , [11] , [12] . Although the addition of seed crystals can produce ammonium sulfate products with uniform particles and large particle sizes, there are strict requirements on the addition time and amount and the process operation is cumbersome [13] .…”