Urea pyrolysis-to-ammonia structure and method capable of reducing sulfur dioxide/sulfur trioxide conversion rate of SCR denitration system

Abstract

The invention provides a urea pyrolysis-to-ammonia structure and method capable of reducing sulfur dioxide / sulfur trioxide conversion rate of an SCR denitration system. An atomizing spray gun is mounted in a pyrolysis chamber; a gas outlet of the pyrolysis chamber communicates with an ammonia spraying grid; a smoke heat exchanger is arranged between a first layer catalyst and a second layer catalyst, the smoke inlet of the smoke heat exchanger communicates with a smoke outlet of the first layer catalyst, and the smoke outlet communicates with the smoke inlet of the second layer catalyst; the heat exchange medium outlet of the smoke heat exchanger communicated with the gas inlet of the pyrolysis chamber, and the heat exchange medium inlet communicates with the outlet of a diluting fan; an electric heater is arranged between the heat exchange medium outlet of the smoke heat exchanger and the gas inlet of the pyrolysis chamber. By using waste heat of smoke, the conventional urea pyrolysis cost is lowered; meanwhile, the temperature of smoke entering the second layer catalyst is reduced, the SO2 / SO3 conversion rate of the second layer catalyst and the behind catalytic device is reduced, the generating amount of SO3 is reduced, and the depositing problem of ammonium sulfate and ammonium hydrogen sulfate of downstream equipment is effectively alleviated.

Description

technical field [0001] The invention relates to a structure and method for producing ammonia by urea pyrolysis that can reduce the conversion rate of sulfur dioxide / sulfur trioxide in an SCR denitrification system, and belongs to the field of SCR flue gas denitrification in coal-fired power stations. Background technique [0002] Selective Catalytic Reduction (SCR) flue gas denitrification technology has become the preferred technology for denitrification of large thermal power units due to its high denitrification efficiency and mature technology. The technical principle is to inject the reducing agent NH into the flue gas 3 , react with NOx in the flue gas under the action of catalyst to generate harmless N 2 and H 2 O. One of the keys to the engineering application of SCR flue gas denitrification technology is the preparation of reducing agents, such as the Chinese patent application number 201310542654.2, the reducing agents used at home and abroad mainly include liqu...

AI Technical Summary

Problems solved by technology

With the increase in the operation time of the SCR flue gas denitrification device of the coal-fired unit and the implementation of the ultra-low emission transformation, the deposition problem of ABS has gradually become prominent, mainly manifested in the substantial increase in the resistance of the air preheater, which seriously affects the safe and stable operation of the unit

[0004] At the same time, the catalyst in the SCR denitration system of the coal-fired unit also has a certain range and requirements for the operating temperature. The flue gas temperature lower than the minimum continuous operating temperature (MOT) will cause NH4HSO 4 Generate and block the reaction micropores inside the catalyst, resulting in catalyst deactivation

Therefore, in the actual denitrification operation, in order to ensure the activity of the catalyst, the denitrification device should be operated stably for a long time above the minimum continuous operation flue gas temperature; The problem of putting denitrification devices into operation under working conditions is also more prominent

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