NOx Reduction – [SNCR] Selective Non-Catalytic Reduction Process
SNCR is a post-combustion NOx reduction method that reduces NOx through a controlled injection of an aqueous urea solution into the combustion gas of industrial fired sources including: coal-fired boilers; waste-fired boilers; incinerators or heaters. The most commonly used reagent consists of a 50 % Urea solution. SBS provides the most efficient Continuous Steady State Process for handling Urea prills and rapidly and continuously converting them into Urea Solution.
Semi-Bulk Systems provides a totally automated and modular turn-key design for receiving and handling Urea prills and delivering a Urea solution to storage or directly to the furnace.
Systems can be designed for total bulk delivery of Urea Prill from bulk rail cars, bulk trucks, bulk silo, bulk bags or paper bags. If the delivery silo cannot be installed adjacent to the mix skid, a pneumatic receiver will be located to supply continuous Urea prill feed to the mix station. A pneumatic receiver can be supplied directly from a remote silo, a rail car, or a bulk truck. Paper bags can be unloaded into a surge hopper for continuous delivery to the mix station.
Urea Prill is typically dissolved into a 50% Urea solution. The reaction of Urea prill into water produces a highly endothermic reaction requiring the addition of heat to dissolve the prill at a temperature to achieve stability for a given concentration.
Continuous Steady-State Processing of Urea Prill into Urea Solution
The VACUCAM® Ejector Mixer unit is designed into a modular skidded process. The VACUCAM® Dynamic Continuous Steady State (DCSS) Slurry Skid inhales the prill from the pick-up funnel below the feeder. Heated water (170-175°F) is supplied continuously to the slurry skid. The rate of water addition is controlled by the feedback from a density meter to control the concentration at set-point [typically 40-50%].
The water pumped through the Ejector Mixer generates a vacuum to convey the prill into the high velocity liquid flow through the mixer for rapid reaction and dissolving. The second pump circulates the mix and returns solution back to the mix tank until the mix reaches solution set point. When the mix reaches its set point [50% solution], the valves divert the recycled liquid to Urea solution storage. Fresh heated water addition is slaved to the rate of prill addition to maintain 50% solids. The solution is recirculated through a mass flow/density meter to confirm and control the concentration level before it is continuously pumped forward to the storage tank.
The process maintains the temperature of the solution at a set-point temperature to overcome the endothermic heat of reaction of the Urea and achieve rapid dissolution. The final solution temperature will be approximately 92°F with an endothermic temperature loss of approximately 78°F, which is approximately 30°F above the salt out temperature of 50% Urea solution.
The process achieves total reaction and solubility with initial hot water only. No additional heat needs to be added to the process before solution is pumped to solution storage tank.
Process Flow Schematic – Continuous Steady State Processing of Urea Prill into Urea Solution: Paper bags; Bulk bags; and Bulk Truck.