Provided is a simple and low-cost method for efficiently fixing a sufficient amount of carbon dioxide contained in a carbon dioxide-containing gas (e.g. a plant exhaust gas). The method of fixing carbon dioxide comprises a contact step of bringing a carbon dioxide-containing gas having a temperature of 350° C. or more into contact with a cementitious hardened body to fix carbon dioxide in the carbon dioxide-containing gas to the cementitious hardened body. The carbon dioxide-containing gas may be a gas that is free from being supplied with moisture before the contact step and during the contact step. One of examples of the carbon dioxide-containing gas is a plant exhaust gas.

An apparatus for reducing mercury content of cement kiln exhaust gas 11 comprising: a mixing and heating device 19 for mixing cement kiln dusts D2, D4 included in a cement kiln combustion exhaust gas G1 into a cement raw material R2 withdrawn from a cyclone 4C (or 4B) other than the highest stage cyclone 4D and the lowest stage cyclone 4A of a preheater 4 for preheating cement raw material R1 while heating the cement kiln dusts D2, D4 through sensible heat of the cement raw material R2; a mercury recovery device 21 for recovering mercury Hg vaporized from the cement kiln dusts D2, D4 by the mixing and heating; and a feeder for feeding mercury-removed dusts D5, D6 discharged from the mixing and heating device 19 to a cyclone 4B (or 4A) positioning at a lower stage from the cyclone 4C (or 4B) from which the cement raw material R2 is withdrawn.

Described herein are membrane processes for separating CO.sub.2 from flue gas. An exemplary process involves passing a fluid stream including the flue gas across a membrane permeable to CO.sub.2 and H.sub.2O, removing treated gas from a feed side of the membrane that has less CO.sub.2 than the flue gas, and removing permeate from a permeate side of the membrane comprising CO.sub.2 and H.sub.2O. Suitably, the permeate is removed at a sub-atmospheric vacuum pressure. The permeate is then cooled to remove at least some of the H.sub.2O from the permeate and form a smaller volume of H.sub.2O-depleted, CO.sub.2 enriched permeate.

Shippable modular units configured for use in sequestering CO.sub.2 are provided. Aspects of the units include a support having one or more of: a CO.sub.2 gas/liquid contactor subunit, a carbonate production subunit and an alkali enrichment subunit; associated therewith. Also provided are systems made up of one or more such modular units, and methods for using the units/systems in CO.sub.2 sequestration protocols.

The invention relates to a method for reduction of HCl emission from a cement plant based on a treatment of a preheater (1) and/or bypass gas stream, characterized in that a cement raw meal, as a HCl absorber, is dispersed in the gas stream(s) from which HCl is to be removed; the cement raw meal is introduced from a raw mill (6) and/or a silo (8) into a pipe with a up going gas flow; the pipe being arranged in fluid communication at a point after a gas conditioning tower (7) and/or before a particle filter unit (5) and/or in a by-pass line before particle filter (4).

The invention provides for the optimal utilization of gas by a fermentation process, whereby the various components within the gas stream are separated to increase the efficiency of the microorganisms. The invention is capable of tailoring the composition of the gas being used by the fermentation process so as to enhance the production of various products. The invention is capable of applying such controlled separation and utilization of gas to produce different products in two parallel fermentation processes. The invention is also capable of applying such controlled separation and utilization of gas to produce one product in a first fermentation process, which may be converted to a different product in a second fermentation process. The invention is additionally capable of mitigating culture inhibition.

Gaseous CO.sub.2 capture systems are provided. Systems of interest include a plurality of gaseous CO.sub.2 sources and at least one common CO.sub.2 capture constraining element shared by the plurality of CO.sub.2 sources. The subject systems are configured to improve at least one gaseous CO.sub.2 capture performance metric relative to a suitable control. Gaseous CO.sub.2 capture systems involving power plants, industrial plants, common mineralization capture system feed sources, common electrical grids, and common building material producers are also provided.

Provided herein are methods of removing carbon dioxide from an aqueous stream or gaseous stream by: contacting the gaseous stream comprising carbon dioxide, when present, with an aqueous solution comprising ions capable of forming an insoluble carbonate salt; contacting the aqueous solution comprising carbon dioxide with an electroactive mesh that induces its alkalinization thereby forcing the precipitation of a carbonate solid from the solution and thereby the removal of dissolved inorganic carbon by electrolysis; and removing the precipitated carbonate solids from the solution, or the surface of the mesh where they may deposit. Also provided herein are flow-through electrolytic reactors comprising an intake device in fluid connection with a rotating cylinder comprising an electroactive mesh, and a scraping device and/or liquid-spray based device for separating a solid from the mesh surface.

The present invention relates to a process for removing acid compounds contained in a gaseous effluent which consists in bringing a gaseous effluent into contact, in the absorption column, with an absorbent solution comprising water, between 20% and 28% by weight of pentamethyldipropylenetriamine and between 5% and 35% by weight of N-methyldiethanolamine.

To provide a carbon dioxide separation composition which is excellent in carbon dioxide desorption efficiency (desorption amount/absorption amount) and durability to nitrogen oxides, and a method for separating carbon dioxide.

A carbon dioxide separation composition, containing at least one amine compound selected from the group consisting of an amine compound represented by the following formula (1):

##STR00001## wherein R.sup.1 to R.sup.3 each independently represent a hydrogen atom or a C.sub.1-4 alkyl group, and an amine compound represented by the following formula (2):

##STR00002## wherein R.sup.10, R.sup.11, R.sup.12, R.sup.13 and R.sup.14 each independently represent a hydrogen atom, a C.sub.1-4 alkyl group, a hydroxy group, a hydroxymethyl group, a 2-hydroxyethyl group or a C.sub.1-4 alkoxy group, a and b are each independently 0 or 1 and satisfy the relation a+b=1, and R.sup.15 is a hydrogen atom, a C.sub.1-4 alkyl group, a methoxymethyl group, a methoxyethoxymethyl group or a 2-hydroxyethyl group.