摘要:
A process and an apparatus enhance urea utilization for selective catalytic reduction (SCR) of NOx, by controlled preparation and feed of gasified urea during combustor load variation. The concentration of NOx in the combustion gases and a required total gas flow necessary to supply an SCR reactor with NOx reducing and carrier gases are determined. Urea is gasified by gasification gases in a thermal gasification reactor. The resulting urea gasification products are mixed with carrier gases to provide an injection grid supply stream. Heating is reduced and flue gas enthalpy is efficiently used by controls utilizing monitoring the temperatures of gases fed to the thermal gasification reactor and of the stream of carrier gases.
摘要:
Disclosed are a process and apparatus for selective catalytic reduction of NOx. The process is enabled by bypassing a heat exchanger section, such as an economizer, of the boiler in advance of an SCR unit at low load conditions to enable NOx reduction even at low loads using urea instead of ammonia. In a preferred form, under high load conditions, the bypass can be almost fully closed and the economizer can be operated normally without excessively cooling the combustion gases, using only a portion of bypassed gases which are hot enough to decompose the urea into its active components including ammonia.
摘要:
Disclosed are a process and apparatus for selective catalytic reduction of NOx. The process is enabled by passing a heat exchanger section, such as an economizer, of the boiler in advance of an SCR unit at low load conditions to enable NOx reduction even at low loads using urea instead of ammonia. In a preferred form, under high load conditions, the bypass can be almost fully closed and the economizer can be operated normally without excessively cooling the combustion gases, using only a portion of bypassed gases which are hot enough to decompose the urea into its active components including ammonia.
摘要:
A process for reducing nitrogen oxides in a combustion effluent is presented. The process involves introducing a nitrogenous treatment agent other than ammonia into the effluent to create a treated effluent having reduced nitrogen oxides concentration such that ammonia is present in the treated effluent; introducing a source of ammonia into the effluent; and contacting the treated effluent with a nitrogen oxides reducing catalyst.
摘要:
A system for the reduction of nitrogen oxides in the effluent from the combustion of a carbonaceous fuel is presented. This system utilizes means for determining the lowest achievable nitrogen oxides concentration with respect to a treatment agent to be introduced into the effluent; means for determining whether the baseline nitrogen oxides concentration at the point of introduction is above the lowest achievable nitrogen oxides concentration; and means for introducing the treatment agent into the effluent under conditions effective to reduce the effluent nitrogen oxides concentration.
摘要:
A process for reducing nitrogen oxides in a combusiton effluent is presented. The process involves introducing a nitrogenous treatment agent into the effluent under conditions effective to create a treated effluent having reduced nitrogen oxides concentration such that ammonia is present in the treated effluent; and then contacting the treated effluent under conditions effective to reduce the nitrogen oxides in the effluent with a nitrogen oxides reducing catalyst.
摘要:
A process is presented for the reduction of nitrogen oxides in the effluent from the combustion of a carbonaceous fuel while reducing the generation of nitrous oxide. The process comprises introducing a treatment agent comprising ammonium carbamate into the effluent in an amount effective to substantially avoid the presence of nitrous oxide.