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 25 m/s and wherein the ratio of scrubbing liquid and gas flow is between 0.0005 and 0.0015 (m.sup.3/h)/(m.sup.3/h).

Zeolite catalysts and systems and methods for preparing and using zeolite catalysts having the CHA crystal structure are disclosed. The catalysts can be used to remove nitrogen oxides from a gaseous medium across a broad temperature range and exhibit hydrothermal stability at high-reaction temperatures. The zeolite catalysts include a zeolite carrier having a silica-to-alumina ratio from about 15:1 to about 256:1 and a copper to alumina ratio from about 0.25:1 to about 1:1.

A process, composition, and apparatus for carbon dioxide (CO.sub.2) conversion are disclosed. The CO.sub.2 conversion comprises reacting CO.sub.2 with a cyclopropenimine (CPI) to activate the CO.sub.2 and transferring the activated CO.sub.2 to generate a product of the transferring. The transferring also generates a conjugate acid of the CPI. The process further comprises regenerating the CPI from the conjugate acid.

A catalytic composition for treating a NOx-containing exhaust gas, wherein the composition comprises a copper-substituted zeolite comprising: i) Ce in a total amount of about 0.1 to about 200 g/ft.sup.3; and ii) Mn in a total amount of about 0.1 to about 200 g/ft.sup.3.

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 (m.sup.3/h)/(m.sup.3/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.

A nozzle lance for exhaust gas treatment, a combustion plant with nozzle lances for exhaust gas treatment, and a method for exhaust gas treatment in a combustion plant are proposed, whereby an added fluid can be mixed in with the active fluid in or immediately in front of the nozzle lance.

Apparatus and methods for controlling aerosol production during absorption in ammonia desulfurization, by removing sulfur dioxide in flue gas with an absorption circulation liquid containing ammonium sulfite, so as to control the aerosol production during absorption in ammonia desulfurization. Efficient desulfurization and dust removal may be achieved by staged solution composition control and reaction condition control. At the same time ammonia escape and aerosol production during absorption may be controlled. The flue gas may be subjected to preliminary temperature lowering and purification, and may be allowed to contact with an absorption circulation liquid and a fine particle washing circulation liquid sequentially. Levels of solution compositions and reaction temperatures may be controlled.

Apparatus and methods for controlling aerosol production during absorption in ammonia desulfurization, by removing sulfur dioxide in flue gas with an absorption circulation liquid containing ammonium sulfite, so as to control the aerosol production during absorption in ammonia desulfurization. Efficient desulfurization and dust removal may be achieved by staged solution composition control and reaction condition control. At the same time ammonia escape and aerosol production during absorption may be controlled. The flue gas may be subjected to preliminary temperature lowering and purification, and may be allowed to contact with an absorption circulation liquid and a fine particle washing circulation liquid sequentially. Levels of solution compositions and reaction temperatures may be controlled.

There is provided a catalyst that exhibits a high denitration efficiency at a relatively low temperature and does not cause oxidation of SO.sub.2 in a selective catalytic reduction reaction that uses ammonia as a reducing agent. A denitration catalyst molded in a block shape contains 43 wt % or more of vanadium pentoxide. The denitration catalyst has a BET specific surface area of 30 m.sup.2/g or more and is used for denitration at 200 C. or lower.

A method for treating a basaltic formation includes providing a CO.sub.2-rich fluid in the basaltic formation, generating one or more metal ions from a metal ion source in the basaltic formation with the CO.sub.2-rich fluid, providing heat from a thermogenic reaction between a first salt solution and a second salt solution in the basaltic formation, and enhancing a reaction between the one or more metal ions and the CO.sub.2-rich fluid with the heat, thereby treating the basaltic formation. A system for treating a basaltic formation including a metal ion source includes a CO.sub.2-rich fluid that includes a source of carbon dioxide dissolved in a first aqueous fluid, a first salt solution that includes a first thermogenic agent dissolved in a second aqueous fluid, and a second salt solution that includes a second thermogenic agent dissolved in a third aqueous fluid.