Experimental and numerical simulation verification of depositional characteristics of NH₄Cl particles under variable conditions

ABSTRACT

The primary cause of U-tube heat exchanger leakage and perforation is attributed to the deposition and corrosion of NH₄Cl within the condensing pipeline located at the summit of the crude oil distillation tower. This paper aims to investigate the deposition law of NH₄Cl in U-shaped tubes under variable operating conditions and the impact of diverse factors on the deposition features of NH₄Cl. To achieve this objective, the study establishes appropriate experimental equipment, designs a 4-factor and 4-level orthogonal experimental table, and manipulates the variables of particle incidence velocity (v), relative humidity (RH), particle size (d), and temperature (T). The experimental results of each group are recorded and analyzed. The observed experimental data reveals that under the operational parameters of Group H (v: 7 m/s, RH: 50%, d: 0.7 mm, T: 140°C), particle accumulation peaks at the elbow outlet, resulting in a substantial volume ratio of 17.14%. Conversely, Group M (v: 10 m/s, RH: 1%, d: 0.1 mm, T: 140°C) demonstrated the minimal particle deposition in the angular sector between 30° − 60° of the elbow, yielding a minimal volume ratio of 0.22%. Further scrutiny suggests that environmental humidity and incident flow velocities significantly influence particle deposition, whilst ambient temperature and particle size exert less substantial effects. A multivariate linear deposition equation between NH₄Cl deposition and v, RH, d, T was derived through linear regression, yielding an Rc² of 0.913, indicating a high level of concordance. A mathematical model was constructed, incorporating computational fluid dynamics (CFD), to simulate and analyze the flow characteristics of ammonium chloride particles in U-shaped tube bundles, which was subsequently validated with the experimental results obtained, the comparison results showed a good degree of coincidence, with an error of 4.41%.

KEYWORDS:

• Heat exchanger
• ammonium salt crystallization
• flow deposition
• experimental test
• numerical simulation

Acknowledgements

This work is supported by the National Natural Science Foundation of China (Grant No.52176048， No. 51876194，No. U1909216). We are grateful for that.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China.

Notes on contributors

Guofu Ou

Guofu Ou, is a male born in 1965 and serves as a doctcoral supervisor. His primary research focus is on the flow corrosion mechanism and characterization prediction method of chemical engineering equipment.

Yiqian Zhang

Yiqian Zhang, is a male graduate student, born in 1999, whose primary research focus lies in the field of corrosion caused by ammonium salt deposition and intelligent prevention and control of chemical equipment.

Haozhe Jin

Yiqian Zhang, is a male graduate student, born in 1999, whose primary research focus lies in the field of corrosion caused by ammonium salt deposition and intelligent prevention and control of chemical equipment.

Haozhe Jin, is a male born in 1982 and serves as a doctoral supervisor. His area of expertise is in the analysis of high temperature, high pressure special equipment valve internal flow characteristics and the prevention of valve failure.

Youjie Gu

Youjie Gu, is a male graduate student born in 1997, specializes in the research of chemical equipment safety assurance technology.