In the hot desulfurization of coal gas with lime-based absorbens CaS will be formed. This must be regenerated or transfered in other usable products, because a deposition seems not to possible. Previous studies have shown that the reactivity of regenerated lime decreases. The conversion to CaSO4 could be probably seen as an alternative. The addition of doping agents should accelerated the conversion rate at low temperature. In this connection the influence of the doping agent to the desulfurization behavior of lime was investigated. The investigation of the desulfurization and conversion characteristics were carried out with a thermogravimetric balance and in a fixed bed reactor of laboratory- and semi-technicalscale. The experiments have shown, that the removal of H2S at high temperature could be realized without difficulties. The doping agent can enhance the reactivity thoroughly. The thermogravimetric and laboratory-scale experiments let recognize, that the doping agents cause a positive effect, too. In comparison to the untreated CaO-pellets the content of CaS was clearly lower. Certainly the turnover rates were generally too low. In the semi-technical-scale experiment could be obtained a rate to 95%. But in this case a definite influence of the doping agent could not observed. The primary SO2 emission in the conversion reaction could not be prevented. A subsequently SO2 removal with excessive lime could be confirmed. A two-step process without using doping agent might be promising.