A CO.sub.2 recovery unit includes an absorber that reduces CO.sub.2 in flue gas (101) discharged from a combustion facility (50) by absorbing CO.sub.2 by an absorbent, a regenerator that heats the absorbent having absorbed CO.sub.2 to emit CO.sub.2, and regenerates and supplies the absorbent to the absorber, and a regenerating heater that uses steam (106) supplied from the combustion facility (50) for heating the absorbent in the regenerator and returns heated condensed water (106a) to the combustion facility (50). The CO.sub.2 recovery unit further includes a condensed water/flue gas heat exchanger (57) that heats the condensed water (106a) to be returned from the regenerating heater to the combustion facility (50) by heat-exchanging the condensed water (106a) with the flue gas (101) in a flue gas duct (51) in the combustion facility (50).

An offgas treatment apparatus having a reduction catalyst and an oxidation catalyst downstream of the reduction catalyst may also include a temperature-affecting apparatus for the offgas positioned between the reduction catalyst and the oxidation catalyst. In some examples, the apparatus may include a second temperature-affecting apparatus for the offgas positioned upstream of the reduction catalyst. At least one of the first or second temperature affecting apparatuses may comprise a heat exchanger, a preheating apparatus, an auxiliary heater, or a mixing-in device for a fluid, for instance. In some examples, the apparatus may involve a dust filter positioned upstream of the reduction catalyst.

A method for producing steam while concurrently reducing emissions. The method includes combusting fuel and an oxidant stream having a high concentration of oxygen in a combustion zone having multiple combustion chambers and heat exchangers to produce a flue gas. The flue gas is subsequently cleaned in a dry flue gas cleaning chamber by contacting it with a dry adsorbent. In one embodiment, the method advantageously regenerates the dry adsorbent so that the dry adsorbent can be subsequently recycled back into the dry gas flue chamber.

A combustion system for operational connection to an energy conversion system and a method of providing thermal energy to the energy conversion system. The system comprises a combustor to be oxy-fired at above atmospheric pressure, using solid, liquid or gaseous fuels, with a supply of oxygen and supercritical carbon dioxide. The combustion gases from the combustor are delivered to a heat exchanger which interfaces with the energy conversion system. Temperatures in the combustor, and the delivery temperature to the heat exchanger, are controlled by selective recirculation of at least part of the combustion gases to the combustor, and by modulating the supply of oxygen and fuel to the combustor. Any combustion gases which are not recirculated are processed to separate carbon dioxide for use or sequestration. The system and method substantially eliminate emissions of carbon dioxide, while providing a highly efficient supply of thermal energy to the energy conversion system.

A thermally efficiency regenerative air preheater 250 extracts more thermal energy from the flue gas exiting a solid fuel fired furnace 26 by employing an alkaline injection system 276. This mitigates acid fouling by selectively injecting different sized alkaline particles 275 into the air preheater 250. Small particles provide nucleation sites for condensation and neutralization of acid vapors. Large particles are injected to contact and selectively adhere to the heat exchange elements 542 and neutralize liquid acid that condenses there. When the deposit accumulation exceeds a threshold, the apparatus generates and utilizes a higher relative percentage of large particles. Similarly, a larger relative percentage of small particles are used in other cases. Mitigation of the fouling conditions permits the redesign of the air preheater 250 to achieve the transfer of more heat from the flue resulting in a lower flue gas outlet temperature without excessive fouling.

Proposed is a carbon dioxide and sulfur oxide capture and carbon resource conversion system for coal-fired power generation, the system being capable of capturing and converting carbon dioxide in an exhaust gas into a carbon resource by using a basic alkaline mixture solution, thereby being capable of reducing carbon dioxide and also capable of manufacturing sodium carbonate or sodium bicarbonate. In the system, sodium carbonate or sodium bicarbonate manufactured from the captured carbon dioxide is used as a desulfurization agent capturing sulfur oxide in an exhaust gas discharged from a coal-fired power generation plant, and carbon dioxide and sulfur oxide are simultaneously captured, so that an additional flue gas desulfurization equipment is not required to be mounted. Accordingly, the installation space of the desulfurization equipment for removing pollutants contained in gas introduced into carbon dioxide capture equipment may be minimized, and the process cost may be reduced.

An air pollution control system includes: a desulfurization device which removes sulfur oxides in a flue gas generated from a boiler; a cooler which is provided at the downstream side of the desulfurization device, decreases a flue gas temperature and enlarges a particle diameter of SO.sub.3 mist contained in the flue gas through cooling or heating the flue gas by a temperature adjustment means for adjusting a gas dew point temperature of the flue gas; and a CO.sub.2 recovery device which includes a CO.sub.2 absorber bringing CO.sub.2 in the flue gas into contact with the CO.sub.2 absorbent so as to remove CO.sub.2 therefrom and a regenerator recovering CO.sub.2 by dissociating CO.sub.2 from the CO.sub.2 absorbent and regenerating the CO.sub.2 absorbent, wherein the flue gas is cooled by a cooling unit so as to enlarge the SO.sub.3 mist in the flue gas.

A method and system for cost effectively converting a feedstock using thermal plasma, or other styles of gassifiers, into to a feedwater energy transfer system. The feedstock can be any organic material, or fossil fuel. The energy transferred in the feedwater is converted into steam which is then injected into the low turbine of a combined cycle power plant. Heat is extracted from gas product issued by a gassifier and delivered to a power plant via its feedwater system. The gassifier is a plasma gassifier and the gas product is syngas. In a further embodiment, prior to performing the step of extracting heat energy, there is provided the further step of combusting the syngas in an afterburner. An air flow, and/or EGR flow is provided to the afterburner at a rate that is varied in response to an operating characteristic of the afterburner. The air flow to the afterburner is heated.

A gas separation process for treating exhaust gases from multiple combustion sources. The invention involves directing an exhaust gas stream from one combustion step to a carbon capture step. An off-gas stream depleted in carbon dioxide from the carbon capture step is mixed with a second exhaust stream from a second combustion step to form a mixed gas stream. The mixed gas stream is passed as a feed stream across the feed side of a membrane that is selectively permeable to carbon dioxide over nitrogen and carbon dioxide over oxygen. A sweep gas stream, usually air, flows across the permeate side, and picks up the preferentially permeating carbon dioxide. The permeate stream withdrawn from the permeate side of the membrane is then recycled back to the combustor.

Embodiments of the present disclosure are directed to systems and methods of removing carbon dioxide from a gaseous stream using magnesium hydroxide and then regenerating the magnesium hydroxide. In some embodiments, the systems and methods can further comprise using the waste heat from one or more gas streams to provide some or all of the heat needed to drive the reactions. In some embodiments, magnesium chloride is primarily in the form of magnesium chloride dihydrate and is fed to a decomposition reactor to generate magnesium hydroxychloride, which is in turn fed to a second decomposition reactor to generate magnesium hydroxide.