The thermo-mechanical pulping (TMP) method is a pulping process in which the wood fibers are separated by means of mechanical forces. As a result of the frictional forces, part of the mechanical energy is converted into heat, which aids in softening the lignin binding the wood fibers together. The finished thermo-mechanical pulp contains the lignin of the wood, so that the pulp yield is double that of the pulp yield obtained from a chemical pulping process. Sometimes chemicals, in addition to temperature control, are used to improve the yield in the mechanical pulping process, which is called the CTMP process.
Metso valves and actuators have performed successfully in TMP systems since their inception. The R-series control valve with its rugged seat design has quickly proved itself to be the answer. The availability of the Neldisc metal-seated butterfly valve is the right choice for contaminated steam control. In TMP discharge, the specially designed MC segment valve provides an optimized flow path for medium-consistency pulp. The body may be cobalt-based alloy coated, and the flow path in the valve is continuously increased to eliminate restrictions where material may build up.
The seat is designed in such a way that its sealing surface is not located directly in the flow stream. This gives the seat an extended service life. The seat is located inside the valve body, which prevents forces in the pipe system from influencing the sealing effect.
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