Process for operating a cement or lime plant comprising a cement or lime kiln and a calciner, wherein heat is generated by combustion of a fuel in the kiln and/or calciner, wherein a gas fed to the kiln and the calciner or to the calciner for combustion of the fuel contains an oxygen rich exhaust gas from a bioreactor containing photoautotrophic organisms and wherein the plant is preferably operated in the oxyfuel mode by using exhaust gas from the kiln and/or calciner together with the oxygen from the bioreactor as the gas fed to the kiln and/or calciner for combustion of the fuel.

A method of utilizing lignin-containing material separated from spent kraft pulping liquor including: acidifying the liquor to a pH not less than seven thereby precipitating solid particles, separating precipitated solid particles from the accompanying liquid, and subjecting the separated precipitated solid particles to a washing process in which: the separated precipitated solid particles are washed with an aqueous medium or aqueous media in one or more washing steps, in each one of the washing steps, the aqueous washing medium contains, in a dissolved form, significant amounts of one or more added sodium salts, and a combined concentration of the added sodium salts in the washing medium in each of the washing step exceeds three percent by weight; and utilizing as fuel in a lime kiln at least part of the washed lignin-containing material is utilized as fuel in a lime kiln of a pulp mill.

The present invention provides compositions and methods relative to controlling hydration onset of an alkaline earth metal oxide such as calcium oxide, comprising heating an inorganic alkaline earth metal oxide to sub-calcination temperatures in the presence of organic material comprising a carbohydrate, an amino-carboxylic acid, a hydroxycarboxylic acid, or a mixture thereof. Preferred treated particles comprise at least 40% and more preferably at least 80% by dry weight calcium oxide which is heated in the presence of ascorbic acid and a starch. Treated particles of the present invention manifest an unexpected, surprising hydration induction postponement behavior as demonstrated through calorimetric testing.

This invention discloses a calcination process to produce high purity CO.sub.2 from solids containing CaCO.sub.3 which operates cyclically and continuously on the solids, arranged in a packed or a moving bed, and wherein each cycle comprises a first step where the combustion at atmospheric pressure of a fuel in the bed of solids containing CaCO.sub.3 heats them up to 800-900? C. and a second step wherein a vacuum pressure between 0.05 and 0.5 atm is applied to extract pure CO.sub.2 from the solids containing CaCO.sub.3 while cooling them by 30-200? C. Said combustion can be carried out directly with air, oxygen enriched air or O.sub.2/CO.sub.2 mixtures when the process is applied to the calcination of a continuous flow of limestone in a moving bed shaft kiln. The process is also applied to calcine CaCO.sub.3 formed in reversible calcium looping processes comprising a carbonation reaction step to form CaCO.sub.3 from CaO.

A process for producing caustic calcined magnesia (CCM) includes calcining a magnesium containing material, such as magnesite, in a primary calciner to produce a primary calcined material and a primary exhaust comprising dust; subjecting the primary exhaust to separation to recover a dust material includes incompletely calcined dust particles; calcining the dust material in the secondary calciner to produce calcined dust, wherein the dust material is not co-calcined with the magnesium containing material or the primary calcined material. The primary calcined material and the calcined dues thus form two CCM products, which can be kept separate or combined. The primary calciner can be a multiple hearth furnace (MHF) while the secondary calciner can be a gas suspension calciner (GSC). Using a secondary calciner in such a manner can increase throughput of the primary calciner and provide other advantages for the calcination process.

A process for producing caustic calcined magnesia (CCM) includes calcining a magnesium containing material, such as magnesite, in a primary calciner to produce a primary calcined material and a primary exhaust comprising dust; subjecting the primary exhaust to separation to recover a dust material includes incompletely calcined dust particles; calcining the dust material in the secondary calciner to produce calcined dust, wherein the dust material is not co-calcined with the magnesium containing material or the primary calcined material. The primary calcined material and the calcined dues thus form two CCM products, which can be kept separate or combined. The primary calciner can be a multiple hearth furnace (MHF) while the secondary calciner can be a gas suspension calciner (GSC). Using a secondary calciner in such a manner can increase throughput of the primary calciner and provide other advantages for the calcination process.

Air pollution includes emissions from two sources: fixed sources and moving sources. A fixed source could be an electric power generation facility or a lime kiln. A moving source can be a tail pipe such as one on an automobile. The fixed source's emissions are redirected downward into a depleted hydrocarbon reserve through an injection well. The moving source is attached to a Carbonator which takes calcium oxide from the lime kiln and carbon dioxide from the moving source to produce calcium carbonate. This removes two sources of air pollution, first the use of the Carbonator system to remove Carbon Dioxide Emissions into the Atmosphere as described in the Application and secondly the total injection of all smokestack effluents into depleted reservoirs, removing the smokestack and in an electrical generating station HVDC transmission lines are run to the displaced smokestack, and is thus a solution to air pollution.

A method for producing a cement material wherein 1) a first acid is reacted with a first cement precursor to form a second cement precursor, and 2) the second cement precursor is converted to a cement material. The first cement precursor includes one or more of Ca, Si, or Al, and the reaction with the first acid produces a second cement precursor that includes one or more of Ca, Si, or Al, and the conjugate base of the first acid. The second step can be performed by thermally converting the second cement precursor to a cement material by sintering or thermally decomposing the second cement precursor at a temperature in the range of 500 to 2000? C. The first step can be performed in the presence of water as a wet slurry. The concentration of the first acid can be greater than 20% by weight.

A method for producing a cement material wherein 1) a first acid is reacted with a first cement precursor to form a second cement precursor, and 2) the second cement precursor is converted to a cement material. The first cement precursor includes one or more of Ca, Si, or Al, and the reaction with the first acid produces a second cement precursor that includes one or more of Ca, Si, or Al, and the conjugate base of the first acid. The second step can be performed by thermally converting the second cement precursor to a cement material by sintering or thermally decomposing the second cement precursor at a temperature in the range of 500 to 2000? C. The first step can be performed in the presence of water as a wet slurry. The concentration of the first acid can be greater than 20% by weight.

Solid fuel in the form of particles is supplied to a pyrolyzer, and pyrolysis conditions are maintained in the pyrolyzer for separating condensable gaseous substances from the fuel. Heat required by the pyrolysis conditions is supplied at least partly with solid fluidized bed material which passes through the pyrolyzer simultaneously as it is fluidized by fluidizing gas in the pyrolyzer. Condensable gaseous substances separated from the fuel are conveyed from the pyrolyzer to a condenser, in which they are separated as so-called pyrolysis oil in liquid form, and solid fluidized bed material taken from the pyrolyzer and containing combustible pyrolysis residue originating from the fuel is circulated through a gasifier, in which product gas, which is burnt in a boiler or a kiln, is formed from the pyrolysis residue.