NOVELTY - Preventing reactor from scaling and purifying biogas comprises removing high concentration carbon ions in material storing tank, reducing carbon ion concentration by calcium carbonate deposition method so as to reduce hardness of wastewater, thus preventing scaling in reactor; and feeding biogas converted from organism in anaerobic expanded grain sludge bed biological reactor into material storing tank, reacting carbon dioxide (CO2) of biogas with organic wastewater with high concentration carbon ions, and generating calcium carbonate deposition.    USE - Method for preventing reactor from scaling and purifying biogas.    ADVANTAGE - The method solves the problem that an anaerobic reactor scales due to calcium carbonate deposition in the process of treating organic wastewater with high concentration carbon ions. CO2 is consumed during the decalcification process so as to improve methane content in the biogas and improve purity of the biogas. The reactor is environmentally friendly.    DETAILED DESCRIPTION - Preventing reactor from scaling and purifying biogas comprises before feeding organic wastewater with high concentration carbon ions into anaerobic expanded grain sludge bed biological reactor, firstly removing high concentration carbon ions in material storing tank, reducing carbon ion concentration by calcium carbonate deposition method so as to reduce hardness of wastewater to be treated, thus preventing scaling in reactor; and feeding the biogas converted from organism due to metabolism process of anaerobic microorganism in the anaerobic expanded grain sludge bed biological reactor into the material storing tank, reacting CO2 of the biogas with organic wastewater with high concentration carbon ions, and generating calcium carbonate deposition, thus obtaining purified biogas with methane from material storing tank. An INDEPENDENT CLAIM is included for a device used for preventing reactor from scaling and purifying biogas, comprising a wastewater storing tank (1), a buffer tank (2), an anaerobic reactor (3), a feeding pump (4), a cycling pump (5), and a channel (6).    DESCRIPTION OF DRAWING(S) - The drawing is a schematic flow diagram of a method for preventing reactor from scaling and purifying biogas (Drawing includes non-English language text).    Wastewater storing tank (1)    Buffer tank (2)    Anaerobic reactor (3)    Feeding pump (4)    Cycling pump (5)    Channel (6)