Note that, in the above-described embodiment, the evaluation apparatus 120 is provided with the temperature sensor 125 and the CO2 sensor 126, and the controller 130 makes judgments again on the oxygen concentration Oc and the temperature Tc of the treatment gas 103, according to the carbon dioxide concentration Ce in the air 102 on the basis of the information from the CO2 sensor 126 (step S6 above), when the temperature Te of the air 102 is higher than the lower limit value Tel but lower than the higher limit value Teh based on the information from the temperature sensor 125. Nevertheless, as another embodiment, for example, the CO2 sensor 126 is omitted, and when the temperature Te of the air 102 is higher than the lower limit value Tel but lower than the higher limit value Teh based on the information from the temperature sensor 125, the blowers 113,115 and the heater 114 are controlled in such a manner as to maintain the oxygen concentration Oc and the temperature Tc of the treatment gas 103 as they are, regardless of the carbon dioxide concentration Ce in the air 102. To put it differently, step S6 above may be omitted. Moreover, in the above-described embodiment, the description has been given for the case where the controller performs control in such a manner that a portion of the reformed coal 2 discharged from the treatment apparatus body 111 is fractionated as the sample 3 by the movable fractionation device 117 for each predetermined period or continuously and is supplied to the evaluation apparatus body 121 for each predetermined period or continuously. Nevertheless, as another embodiment, for example, a portion of the reformed coal 2 discharged from the treatment apparatus body 111 may be fractionated as the sample 3 by a stationary type (fixed type) of fractionation means such as a fixed gate or a fixed scraper without being controlled by the control means and supplied to the evaluation apparatus body 121. Further, in the above-described embodiment, the treatment gas 103 having a desired oxygen concentration Oc is generated by mixing the nitrogen gas 101 with the air 102. Nevertheless, as another embodiment, for example, by mixing the nitrogen gas 101 with an oxygen gas, the treatment gas 103 having a desired oxygen concentration may be generated. Nonetheless, as in the above-described embodiment, it is particularly preferable to generate the treatment gas 103 having a desired oxygen concentration by mixing the nitrogen gas 101 with the air 102 because this eliminates the need to prepare the oxygen gas only for the purpose. Furthermore, it is needless to say that the nitrogen gas cylinder and so forth prepared just to generate the treatment gas 103 are usable as the nitrogen gas supply source 112; besides, it is also possible, for example, to use a pyrolysis gas (main component: nitrogen gas) which is a nitrogen gas supplied to a pyrolyzer to pyrolyze low grade coal and discharged from the pyrolyzer, and from which a volatile component, dust, and the like are separated thereafter. In this case, thermal energy newly applied to the treatment gas 103 can be saved for an inactivation treatment. Furthermore, in the above-described embodiment, the air 102 is utilized as the test gas. Nevertheless, as another embodiment, it is possible, for example, to utilize a test gas having an oxygen concentration Oc higher than the higher limit value Oh (for example, 16%) by mixing the nitrogen gas 101 with the air 102 as in the case of the treatment gas 103. As the nitrogen gas source in this case, the above-described pyrolysis gas is also usable in addition to, although needlessly to say, a nitrogen gas from the nitrogen gas cylinder, as in the case of the treatment gas 103. Furthermore, in the above-described embodiment, the description has been given of the case where the pyrolyzed coal 1 is inactivated. Nevertheless, the present invention is not limited thereto, and is applicable to any inactivation treatment on coals as in the case of the above-described embodiment. Industrial Applicability Even when the composition of coal supplied to the treatment apparatus body varies from time to time, the coal inactivation system according to the present invention is capable of readily inactivating coals of such compositions under necessary and sufficient conditions. Therefore, the present invention is applicable to the industry very usefully. Reference Signs List 1 PYROLYZED COAL 2 REFORMED COAL 3 SAMPLE 100 COAL INACTIVATION SYSTEM 101 NITROGEN GAS 102 AIR 103 TREATMENT GAS 111 TREATMENT APPARATUS BODY 112 NITROGEN GAS SUPPLY SOURCE 113 BLOWER 114 HEATER 115 BLOWER 116 FILTER 117 FRACTIONATION DEVICE 120 EVALUATION APPARATUS 121 EVALUATION APPARATUS BODY 122 BLOWER 123 HEATER 124 FILTER 125 TEMPERATURE SENSOR 126 C02 SENSOR 130 CONTROLLER 131 CONTROL BOARD WE CLAIM: 1. A coal inactivation system configured to inactivate coal by heating the coal with a treatment gas containing oxygen, characterized in that the coal inactivation system comprises: a treatment apparatus body, to inside of which the coal is supplied; treatment gas-supply means configured to supply the treatment gas to the inside of the treatment apparatus body; treatment gas-oxygen concentration-adjustment means configured to adjust an oxygen concentration Oc in the treatment gas; treatment gas-temperature-adjustment means configured to adjust a temperature Tc of the treatment gas; fractionation means configured to fractionate a portion of the coal inactivated in the treatment apparatus body; an evaluation apparatus body, to inside of which a sample of the coal fractionated by the fractionation means is supplied; test gas-supply means configured to supply a test gas having an evaluation temperature Tt to the inside of the evaluation apparatus body; test gas-temperature-detection means configured to detect a temperature Te of the test gas having heated the sample in the evaluation apparatus body; and control means configured to, based on information from the test gas-temperature-detection means, when the temperature Te of the test gas is equal to or higher than a higher limit value Teh, judge whether or not the oxygen concentration Oc of the treatment gas is equal to or higher than a higher limit value Oh, if the oxygen concentration Oc of the treatment gas is lower than the higher limit value Oh, control the treatment gas-oxygen concentration-adjustment means in such a manner as to increase the oxygen concentration Oc of the treatment gas by a given value Ofu, and if the oxygen concentration Oc of the treatment gas is equal to or higher than the higher limit value Oh, further judge whether or not the temperature Tc of the treatment gas is equal to or higher than a higher limit value Th, and control the treatment gas-temperature-adjustment means in such a manner as to increase the temperature Tc of the treatment gas by a given value Tfu if the temperature Tc of the treatment gas is lower than the higher limit value Th, and when the temperature Te of the test gas is equal to or lower than a lower limit value Tel, judge whether or not the temperature Tc of the treatment gas is equal to or lower than a lower limit value Tl, if the temperature Tc of the treatment gas is higher than the lower limit value Tl, control the treatment gas-temperature-adjustment means in such a manner as to decrease the temperature Tc of the treatment gas by a given value Tfd, if the temperature Tc of the treatment gas is equal to or lower than the lower limit value TL further judge whether or not the oxygen concentration Oc of the treatment gas is equal to or lower than a lower limit value Ol, and control the treatment gas-oxygen concentration-adjustment means in such a manner as to decrease the oxygen concentration Oc of the treatment gas by a given value Ofd if the oxygen concentration Oc of the treatment gas is higher than the lower limit value Ol. 2. The coal inactivation system according to claim 1, characterized in that, when the temperature Te of the test gas is equal to or lower than the lower limit value Tel, the control means controls the treatment gas-oxygen concentration-adjustment means and the treatment gas-temperature-adjustment means in such a manner as to set the oxygen concentration Oc and the temperature Tc of the treatment gas at the lower limit values Ol and Tl, respectively, if the temperature Tc of the treatment gas is equal to or lower than the lower limit value Tl while the oxygen concentration Oc of the treatment gas is equal to or lower than the lower limit value Ol. 3.The coal inactivation system according to any one of claims 1 and 2, characterized in that, when the temperature Te of the test gas is higher than the lower limit value Tel but lower than the higher limit value Teh, the control means controls the treatment gas-oxygen concentration-adjustment means and the treatment gas-temperature-adjustment means in such a manner as to maintain the oxygen concentration Oc and the temperature Tc of the treatment gas as they are. 4.The coal inactivation system according to any one of claims 1 to 3, characterized in that the coal inactivation system further comprises test gas-carbon dioxide concentration-detection means configured to detect a carbon dioxide concentration Ce of the test gas having heated the sample in the evaluation apparatus body, and when the temperature Te of the test gas is higher than the lower limit value Tel but lower than the higher limit value Teh, the control means, based on information from the test gas-carbon dioxide concentration-detection means, if the carbon dioxide concentration Ce in the test gas is equal to or higher than a higher limit value Ceh, judges again whether or not the oxygen concentration Oc of the treatment gas is equal to or higher than the higher limit value Oh, and if the carbon dioxide concentration Ce in the test gas is equal to or lower than a lower limit value Cel, judges again whether or not the temperature Tc of the treatment gas is equal to or lower than the lower limit value Tl. 5.The coal inactivation system according to claim 4, characterized in that, when the temperature Te of the test gas is higher than the lower limit value Tel but lower than the higher limit value Teh, the control means controls the treatment gas-oxygen concentration-adjustment means and the treatment gas-temperature-adjustment means in such a manner as to maintain the oxygen concentration Oc and the temperature Tc of the treatment gas as they are if the carbon dioxide concentration Ce in the test gas is higher than the lower limit value Cel but lower than the higher limit value Ceh based on the information from the test gas-carbon dioxide concentration-detection means.