# US 10,500,535 B2 · Submicron particle removal from gas streams > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,500,535 B2 - Document ID: US10500535B2 - Status: Granted - Kind: B2 - Application number: 16/300,434 - Filed: 2017-05-09 - Published: 2019-07-25 - Granted: 2019-12-10 - Earliest claimed: 2016-05-09 - Assignees: Stamicarbon B.V. - Applicants: Stamicarbon B.V. - Inventors: Brian Sayre Higgins; John Marshall Tate, III; Robert Arthur Yates; Marcel Julien Pomerleau; Jon Michael Heon; Wilfried Marc Renaat Dirkx; Juan Coloma González - Web page: https://patentgrep.com/patent/US10500535B2 ## CPC - B01D 47/10: Venturi scrubbers - B01D 47/05: by condensation of the separating agent - B01D 47/06: Spray cleaning - B01D 47/12: Washers with plural different washing sections (B01D47/14 takes precedence) - B01D 53/40: Acidic components (B01D53/44 takes precedence) - B01D 53/58: Ammonia - B01D 53/79: Injecting reactants - B01J 2/04: in a gaseous medium {(if combined with suspending the material in a gas, e.g. fluidised beds B01J2/16)} - C05C 9/005: {Post-treatment} - C07C 273/16: Separation; Purification - B01D 2247/106: using a structured demister, e.g. tortuous channels - B01D 2251/206: Ammonium compounds - B01D 2251/2067: Urea - B01D 2251/304: of sodium - B01D 2251/402: of magnesium - B01D 2251/404: of calcium - B01D 2251/50: Inorganic acids - B01D 2251/502: Hydrochloric acid - B01D 2251/504: Nitric acid - B01D 2251/506: Sulfuric acid - B01D 2251/602: Oxides - B01D 2251/604: Hydroxides - B01D 2251/606: Carbonates - B01D 2251/70: Organic acids - B01D 2258/02: Other waste gases - Y02C 20/30: of perfluorocarbons [PFC], hydrofluorocarbons [HFC] or sulfur hexafluoride [SF6] - Y02P 20/582: Recycling of unreacted starting or intermediate materials - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS - C05C: NITROGENOUS FERTILISERS - C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS - Y02C: CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG] - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract Disclosed are methods and systems for removing submicron particles from a gas stream, in particular from urea prilling off-gas, wherein a Venturi ejector is used. A method comprises contacting a gas stream containing submicron particles in a Venturi ejector with an injected high velocity scrubbing liquid to provide a pumping action, wherein the scrubbing liquid has an initial velocity of at least 2 m/s and wherein the ratio of scrubbing liquid and gas flow is between 0.0005 and 0.0015 (m3/h)/(m3/h). The disclosure also pertains to a prilling tower having a gas stream treatment system comprising a Venturi ejector at the top of the prilling tower, and to a method of modifying an existing prilling tower. ## Claims ### Claim 1 A method for removing submicron particles from a gas stream containing submicron particles said stream being off-gas from urea finishing, the method comprising: contacting the gas stream in a Venturi ejector with an injected high velocity scrubbing liquid to provide a pumping action, wherein the scrubbing liquid has an initial velocity of at least 25 m/s and wherein the ratio of scrubbing liquid and gas flow is between 0.0005 and 0.0015 (m3/h)/(m3/h), whereby the method comprises treatment in two Venturi stages in series, wherein each of said two Venturi stages comprises a horizontally placed Venturi ejector, wherein said Venturi stages are placed above each other, and whereby the two Venturi stages are connected by a scrubbing column. ### Claim 2 (depends on 1) The method of claim 1, wherein the gas stream is the off-gas from a urea granulator. ### Claim 3 (depends on 1) The method of claim 1 wherein the gas stream is the off-gas from a urea prilling tower. ### Claim 4 (depends on 3) The method of claim 3 wherein the residence time between the first and the downstream second Venturi ejector is at least 0.4 s. ### Claim 5 (depends on 4) The method of claim 4 wherein the residence time between the first and the downstream second Venturi ejector is more than 0.8 s. ### Claim 6 (depends on 1) The method of claim 1, wherein the gas stream contains a concentration of submicron particles greater than 20 mg/Nm3. ### Claim 7 (depends on 1) The method of claim 1 wherein the Venturi ejector comprises a nozzle positioned for spraying scrubbing liquid in a direction parallel with the gas flow through the gas inlet of the Venturi ejector. ### Claim 8 (depends on 1) The method of claim 1 wherein a basic reagent is added selected from the group consisting of: caustic, lime, limestone, hydrated lime, fly ash, magnesium oxide, soda ash, sodium bicarbonate, sodium carbonate, and mixtures thereof. ### Claim 9 (depends on 1) The method of claim 1 wherein an acidic reagent is added selected from the group consisting of: acetic acid, boric acid, carbonic acid, citric acid, hydrochloric acid, hydrofluoric acid, nitric acid, oxalic acid, phosphoric acid, sulfuric acid, and mixtures thereof. ### Claim 10 (depends on 9) The method of claim 9, wherein the method comprises acid scrubbing and dust scrubbing, both carried out at the top of a natural draft urea prilling tower. ### Claim 11 (depends on 1) The method of claim 1, further comprising the step of urea prilling in a natural draft urea tower and wherein said Venturi ejector is positioned at the top of said prilling tower, and wherein the static pressure at the exit of at least one Venturi ejector is larger than at the entrance of the Venturi ejector. ### Claim 12 (depends on 1) The method of claim 1, comprising subsequently: A) providing a gas stream, B) spraying an aqueous solution into the gas stream, C) passing the gas stream through a first ejector Venturi scrubber having a throat, wherein an aqueous scrubbing liquid is sprayed into the gas stream in the direction of the throat, D) spraying an aqueous solution into the gas stream, and F) passing the gas stream through a second ejector Venturi scrubber having a throat, wherein an aqueous scrubbing liquid is sprayed into the gas stream in the direction of the throat. ### Claim 13 (depends on 12) A method for removing submicron particles from a gas stream, according to claim 12, comprising subsequently: providing a gas stream comprising off-gas from a urea prilling tower, spraying an aqueous solution comprising 20 wt. % to 55 wt. % urea into the gas stream, passing the gas stream through a first ejector Venturi scrubber having a throat, wherein an aqueous scrubbing liquid comprising 20 wt. % to 55 wt. % urea is sprayed into the gas stream in the direction of the throat, spraying an aqueous solution comprising 0 wt. % to 5 wt. % urea into and co-currently with the gas stream, passing the gas stream through a mist eliminator, passing the gas stream through a second ejector Venturi scrubber having a throat, wherein an aqueous scrubbing liquid comprising 0 wt. % to 5 wt. % urea is sprayed into the gas stream in the direction of the throat, spraying an aqueous solution comprising 0 wt. % to 5 wt. % urea into the gas stream, and passing the gas stream through a mist eliminator. ### Claim 14 A gas stream treatment system, comprising two Venturi stages in series, wherein each of said Venturi stages comprises a horizontally placed Venturi ejector comprising a converging part, a throat, and a diverging tube part, and a nozzle for spraying into said throat, wherein said Venturi stages are placed above each other, and wherein each Venturi stage comprises a scrubbing liquid recirculation loop comprising a pump for pressurizing and recirculating scrubbing liquid to said nozzle, wherein the Venturi stages have separate recirculation loops, further comprising a sprayer between a first and a downstream second Venturi stage, for spraying an aqueous solution having a higher water concentration than the scrubbing liquid of the first Venturi stage. ### Claim 15 A urea prilling tower having a gas stream treatment system at the top of the prilling tower, said gas stream treatment system comprising two Venturi stages in series, wherein each of said Venturi stages comprises a horizontally placed Venturi ejector comprising a converging part, a throat, and a diverging tube part, and a nozzle for spraying into said throat, wherein said Venturi stages are placed above each other, and wherein each Venturi stage comprises a scrubbing liquid recirculation loop comprising a pump for pressurizing and recirculating scrubbing liquid to said nozzle, wherein the Venturi stages have separate recirculation loops. ### Claim 16 A natural draft urea prilling tower, having a gas stream treatment system at the top of the prilling tower, wherein the gas stream treatment system comprises at least two Venturi ejector scrubbers in series. ### Claim 17 (depends on 16) The natural draft urea prilling tower of claim 16, wherein the gas stream treatment section comprises two Venturi stages in series, wherein each of said Venturi stages comprises a horizontally placed Venturi ejector comprising a converging part, a throat, and a diverging tube part, and a nozzle for spraying into said throat, wherein said Venturi stages are placed above each other, and wherein each Venturi stage comprises a scrubbing liquid recirculation loop comprising a pump for pressurizing and recirculating scrubbing liquid to said nozzle, wherein the Venturi stages have separate recirculation loops. ### Claim 18 A method of modifying an existing prilling tower, comprising installing a the gas stream treatment system comprising two Venturi stages in series, wherein each of said Venturi stages comprises a horizontally placed Venturi ejector comprising a converging part, a throat, and a diverging tube part, and a nozzle for spraying into said throat, wherein said Venturi stages are placed above each other, and wherein each Venturi stage comprises a scrubbing liquid recirculation loop comprising a pump for pressurizing and recirculating scrubbing liquid to said nozzle, wherein the Venturi stages have separate recirculation loops on top of the prilling tower. ### Claim 19 (depends on 18) The method of claim 18, wherein the existing prilling tower is a natural draft urea prilling tower.