constant scraping

Non-PRO English to Spanish Tech/Engineering Chemistry; Chem Sci/Eng craqueo término

The classical processes of melting organic solid matter consist of tossing and mixing it. However, polyolefin wastes are poor conductors of heat and direct heating by the heated wall leads to overheating
that generates coke and char. It is only through vigorous mixing, together with constant scraping that this can be avoided.

¿raspado constante?