Importance

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Abstract

In a continuous digester for paper pulp (comminuted cellulosic material), abrupt variations in high pressure steam flow are minimized. First and second vertically spaced annular screens are provided in a vertical vessel. Each has an annular header associated with it and first and second circumferentially spaced liquid outlets associated with each header. The first outlet for the first screen is generally vertically in line with the first outlet for the second screen, and the second outlet of the first screen is generally vertically in line with the second outlet of the second screen. Simultaneous withdrawal of liquid from the first outlet of the first screen and the second outlet of the second screen takes place, and then is terminated, and then simultaneous withdrawal of liquid from the second outlet of the first screen and the first outlet of the second screen takes place, and then is terminated. This withdrawal sequence is repeated continously. Each header is divided into two substantially equal volumes by vertical walls with an outlet provided at the circumferential center of each volume. Any material that passes through the screens flows under the force of gravity from the vertical walls to the outlet associated with that header volume due to the provision of downwardly sloping bottom portions in each volume.

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First Claim