Structural design of the digester cylinder based on thermokinetics

Abstract

This work focuses on key high-temperature and high-pressure digestion equipment in the chemical and pulp & paper industries. Based on thermodynamic principles, a systematic structural design and strength verification were conducted for the core pressure-bearing component—the cylinder. The design conditions include a calculation pressure of 1.20 MPa, a design temperature of 240.00°C, and an inner diameter of 2000.00 mm. Q345R was selected as the primary material. Through theoretical calculations, the nominal thickness of the shell was determined to be 12 mm, and corrosion allowance, along with plate thickness negative deviation, were incorporated to ensure long-term service safety. The study details the derivation of the stress verification process at the hydraulic test pressure and the reverse-calculation verification of the maximum allowable working pressure. The results indicate that all indicators of the proposed design meet the standard specifications, with a high safety margin. This provides reliable data support and a theoretical basis for the optimized design of similar process equipment.