EXHAUST GAS HEAT RECOVERY METHOD, EXHAUST GAS HEAT RECOVERY DEVICE, AND EXHAUST GAS HEAT RECOVERY SYSTEM

To enable further recovery of heat energy from an exhaust gas which is exhausted from a boiler and from which heat energy is recovered by an economizer and enable desulfurization and denitration that do not need additive agents.SOLUTION: An exhaust gas heat recovery device 3 includes: a shell 31 serving as an exhaust gas passage formed by a tube body made of a corrosion resistant material; a tube 39 disposed within the shell 31 and serving as a cooling medium passage formed by a tube body made of a corrosion resistant material; and an outlet 38 of sulfuric acid generated by reaction between steam, which is contained in an exhaust gas flowing in the shell 31 and cooled by a cooling medium in heat exchange between the cooling medium flowing in the tube 39 and the exhaust gas flowing in the shell 31 to be condensed, and an SOx component.SELECTED DRAWING: Figure 2 【課題】ボイラから排出され、エコノマイザで熱エネルギーが回収された排ガスに対する更なる熱エネルギーの回収及び添加剤の不要な脱硫・脱硝を可能にする。【解決手段】排ガス熱回収装置３は、耐腐食性を有する素材の管体からなる排ガス流路としてのシェル３１と、シェル３１の内部に配置された、耐腐食性を有する素材の管体からなる冷却媒体流路としてのチューブ３９と、チューブ３９内を流れる冷却媒体とシェル３１内を流れる排ガスとの間の熱交換で冷却媒体により冷却されて結露したシェル３１内を流れる排ガスに含まれている水蒸気とＳＯｘ成分との反応で生成された硫酸の出口３８と、を有する。【選択図】図２