Abstract: Apparatus for cleaning high temperature, high pressure gases includes a pressure vessel, and a filtration unit within the pressure vessel. The filtration unit is adapted to communicate with a fluidized bed reactor gas outlet, and includes at least one dirty gas chamber housing a plurality of porous, ceramic filter tubes, and at least one clean gas chamber for receiving clean gas from the ceramic filter tubes. The dirty gas chamber includes a particle outlet for removing particles separated from the gas by the filter tubes. The porous ceramic filter tubes are horizontally oriented within the filtration unit or housing and mounted within water cooled walls of the housing. The fluidized bed reactor and associated cyclone separator may be located within the pressure vessel with the filtration unit, or located outside the pressure vessel and in communication with the filtration unit inside the pressure vessel.

Abstract: Either atmospheric or superatmospheric pressure high temperature gases, e.g. from a fluidized bed reactor, are filtered in an upright outer vessel having at least one upright inner vessel within it. The inner vessel has gas-impervious peripheral walls and divides the gas volume in the outer vessel into clean and dirty gas volumes. A number of monolithic ceramic filter elements are mounted in openings disposed in the peripheral walls of the inner vessel and allow clean gas to flow through the filter elements from the dirty gas volume to the clean gas volume. The peripheral wall includes cooling panels formed of cooling tubes, which can lower the temperature of the filter mounting structure significantly. The cooling tubes are normally protected by refractory material from direct contact with the gases so that only the mounting structures are cooled (i.e.

Abstract: To decrease the sulfur emissions of a sulfate pulp mill, and achieve other advantages, black liquor is heated at a temperature higher than the cooking temperature of the sulfate cook (e.g. between 190.degree. C.-350.degree. C.) and the sulfidity of white liquor produced from the black liquor is adjusted by adjusting the temperature and/or retention time of the heat treatment so that a predetermined amount of sulfur compounds are separated from the black liquor. Pressure heat treatment may occur prior to or after evaporation of the black liquor, or between evaporation stages. Preferably, the sulfur containing gas is thereafter divided into different fractions which are separately cornbusted.

Abstract: Waste gases are purified by adding reagent and/or absorbent which reacts with pollutants in the gases to the gases, and then introducing the gases into a wetting reactor for activating the reagent or absorbent contained in the gases. The gases are introduced into a drying zone of the reactor and then passed upwardly into a wetting zone. The reagent or absorbent which has reacted partly or completely with the pollutants is separated from the gas by a filter in the upper section of the reactor and particles are intermittently detached from the filter and fall downwardly into an ash layer in the bottom of the reactor. The ash layer is capable of homogenizing wet particles and water droplets which fall downwardly from the wetting zone, and typically is at least about 25 cm thick. A mechanical mixer/grinder may be provided in the ash layer for mixing the particles and droplets and grinding lumps in the ash layer into particles.

Abstract: The present invention relates to a method of treating various chlorine-containing materials such as wastes, biological sludges and even metal concentrates in a circulating fluidized bed reactor (1) or a grate furnace at a high temperature of over 830.degree. C. and of cooling the resultant process gases for minimizing the amount of polyhalogenated aromatic compounds in the process gases. The process gases are cooled to a temperature below 250.degree. C. at a cooling velocity exceeding 1000.degree. C. per second. Cooling is preferably effected in a circulating fluidized bed reactor (2).

Abstract: The invention relates to a method and apparatus for use in the pulp industry for improving the safety of a spent liquor recovery boiler, such as a soda recovery boiler. The boiler comprises, for recovering chemical and energy, a furnace cooled by water tubes and connected to the water/steam circulation system of the boiler, the cooling of the bottom of the furnace being provided by a separate cooling circulation. The separately cooled lower section of the furnace is provided by separating the bottom or the bottom and part of the furnace walls from the boiler water circulation system. This separated section is supplied with a cooling fluid of its own which may be a gas (e.g. air or inert gas) or a liquid (e.g. molten zinc) which does not cause an explosion of it contacts the melt of the furnace.

Abstract: A fluidized bed reactor system, including a reactor chamber defined by a wall structure formed by a plurality of tubes through which a heat transfer medium circulates, is constructed so as to provide numerous advantages over conventional constructions. A fast fluidized bed of solid material is established in the reactor chamber. A solid material processing chamber is disposed adjacent the reactor chamber on the outer side of a wall structure defining the reactor chamber, e.g. for recovering heat from the solid material. The processing chamber shares a common wall portion with the reactor chamber and a slow fluidized bed of solid material is provided in the processing chamber. Particle passage openings are provided in the common wall. Particles from the processing chamber are recirculated to the reactor chamber after treatment (typically cooling).

Abstract: A method and apparatus for the treatment of fiber suspensions of the pulp and paper industry, in particular, the so-called postscreening of pulp in the bleaching stage. The method includes that the pulp discharged from a bleaching stage is diluted to the screening consistency, that the pulp is screened in a pressure screen and that the accept fraction is supplied to the subsequent treatment stage at the supply consistency of the stage without a separate thickening stage. The screening is preferably carried out in a narrow-slot screen.

Abstract: A method of reducing the nitrogen oxide level in the flue gases issuing from combustion units by introduction of reducing agents into contact with gases containing nitrogen oxides in first and second reducing stages, is provided. The first reducing stage is a non-catalytic stage (e.g. at temperatures over 800.degree. C.), while the second stage is a catalytic stage (e.g. at temperatures of about 300.degree.-400.degree. C.). A steam generation boiler with improved nitrogen reduction facilities is also provided. The amount of nitrogen oxides in the hot gases is reduced in the combination of the first and second reducing stages while producing steam in a steam generation boiler system, thus resulting in gases essentially free from nitrogen oxides while eliminating the possibility of NH.sub.3 (or other reducing agent) slip in the exhausted flue gases. Heat transfers in a convection section as used to establish stabilized temperature conditions for catalytic reduction.

Abstract: Gas is separated from fluent material, particularly a liquid or a cellulose fiber suspension having a consistency of about 8-18%, utilizing a closed separation apparatus having a spiral housing with a central axis, a fluent material inlet channel, a fluent material outlet, and a gas outlet. A pressure differential is maintained between the inlet channel and the spiral housing, and the pressure differential is converted to kinetic energy of the fluent material by causing the fluent material to flow through one or more spiral flow paths through the inlet channel toward the spiral housing. In the spiral housing a rotor is rotated to impart a strong centrifugal force to the fluent material to cause gas to separate and collect adjacent the central axis of the spiral housing, from which the gas is removed. The strong centrifugal force caused by the rotating rotor discharges the fluent material through the outlet. The spiral flow paths may be stationary or may rotate with the rotor in the spiral housing.

Abstract: A pressurized fluidized bed reactor is provided utilizing a centrifugal separator having a gas space that is distinctly non-circular, preferably having a circularity of greater than or equal to 1.15. Most desirably the cyclone has a quadrate (e.g. square) cross-section, and is disposed inside of the pressure vessel along with the reactor chamber containing the fluidized bed. A number of ceramic candle or honeycomb filters may be provided connected to the gas outlet from the cyclone separator, within the pressure vessel, to filter the gas. This construction provides a minimized diameter of the pressure vessel because the reactor chamber with square cyclones is more compact than if conventional circular cross-section cyclones are employed. Also a second pressure vessel is not needed for the candle or honeycomb filters since there is sufficient room within the pressure vessel to accommodate them.

Abstract: Gas with entrained particles, such as high temperature and pressure gas from a pressurized circulating fluidized bed reactor, is filtered using a vessel having a gas inlet, cleaned gas outlet, and filtered particles outlet. A pulse of cleaning gas is periodically or intermittently directed to the filters to dislodge particles which have been filtered and collected on the filters. Shrouds, having tubular, parallelepiped, zig-zag, or honeycomb configurations, are provided surrounding relevant portions of the filters to prevent dislodged particles from being entrained in gas passing to other filters, and instead directing the dislodged particles toward the vessel particles outlet. The shroud walls may have openings in them which allow gas to be filtered to pass through them, but prevent dislodged particles from passing through the openings.

Abstract: Filtering apparatus for filtering particles from high temperature (e.g. greater than 500 degrees C., and at a pressure of about 2-40 bar) gases includes a hollow upright vessel with at least one generally torodial shaped hollow clean gas chamber mounted within it. The gas chamber has a gas impervious peripheral wall with at least one ceramic or sintered metal filter mounted in an opening in the wall. Dirty gas flows through the filter(s) into the clean gas chamber, and then passes through a conduit to be ultimately discharged from the vessel. The torodial shaped chamber may be circular or polygonal (e.g. square) in plan, and circular or polygonal in cross-section; for example it can be constructed solely of flat plates.

Abstract: White water from a paper machine is treated in an improved fiber recovery process, i.e., the "save-all" process. Prior to the mixing of sweetener stock into the white water the sweetener stock is fractionated (undiluted) into fine and coarse fiber fractions, of which only the coarse fraction is fed as sweetener stock into the white water. The inlet line for the sweetener stock is provided with a fractionation apparatus for removing the fine fraction from the sweetener stock. Treatment apparatus may also be utilized to separate the white water into fine and coarse fractions before passing the fine fraction to a mixer for mixing with the sweetener stock coarse fraction.

Abstract: A method of reducing material containing metal oxide in a circulating fluidized bed, in which coal in excess and air is introduced into the fluidization chamber so as to maintain a temperature of >850.degree. C. in the chamber. Bed material which has been separated from the flue gases is conveyed through a carbidization chamber in a recirculation system at a temperature of <850.degree. C. to the lower part of the fluidization chamber. Conditions favorable for formation of carbide are maintained in the carbidization chamber.

Abstract: Hot gases from a pressurized fluidized bed reactor system are purified. Under superatmospheric pressure conditions hot exhaust gases are passed through a particle separator, forming a flitrate cake on the surface of the separator, and a reducing agent--such as an NO.sub.x reducing agent (like ammonia), is introduced into the exhaust gases just prior to or just after particle separation. The retention time of the introduced reducing agent is enhanced by providing a low gas velocity (e.g. about 1-20 cm/s) during passage of the gas through the filtrate cake while at superatmospheric pressure. Separation takes place within a distinct pressure vessel the interior of which is at a pressure of about 2-100 bar, and-introduction of reducing agent can take place at multiple locations (one associated with each filter element in the pressure vessel), or at one or more locations just prior to passage of clean gas out of the pressure vessel (typically passed to a turbine).

Abstract: A fluidized bed gas cooler assembly includes a fluidized bed gas cooler with a metal inlet duct for directing hot process or flue gases into the cooler as fluidizing gas. In order to remove deposits which form on the duct inner surface a cooling fluid is passed into and then out of contact with the outer surface of the inlet duct so that the cooling fluid increases in temperature (but does not change phase) and so that deposits which form on the inlet duct interior surface become brittle and readily disengageable. The deposits are disengaged at different times by pulsation of the cooling fluid (especially where the inlet duct is a metal spiral tube), effecting pulsation of the temperature of the cooling fluid, or subjecting an enclosure surrounding the duct or the exterior surface of the duct itself to a sudden mechanical force.

Abstract: The amount of N.sub.2 O emission from a fluidized bed reactor is reduced by adding a hydrogen radical providing additive (e.g. a hydrogen containing fuel such as natural gas or alcohol) to the flue gases discharged from the fluidized bed. Sufficient oxygen is present in the flue gases--either by addition with the additive, or by addition of an excess to the combustion chamber--so that the additive reacts with the oxygen, typically raising the temperature of the flue gases (e.g. from about 700.degree.-900.degree. C. to about 950.degree.-1100.degree. C.) that is from about 1292.degree.-1652.degree. F. to about 1742.degree.-2012.degree. F. so that N.sub.2 O production is reduced about 10-90%. The additive may be injected in or just prior to a cyclone for separating particles from the flue gases, in a gas discharge immediately after the cyclone (e.g.

Abstract: A circulating fluidized bed (CFB) system, and a method of operation thereof, provide a heat transfer zone containing primarily clean fluidizing gas providing advantageous conditions for superheating, while providing a large enough flow of solid material in the heat exchange chamber during both high and low load conditions to achieve the desired heat transfer capacity. The heat exchange chamber is provided near the bottom of a return duct connected between the particle separator and combustion chamber of the CFB, with a common wall separating the combustion and heat exchange chambers. Particles are reintroduced into the combustion chamber through a solid particle inlet (plurality of narrow, substantially horizontal, elongated, vertically stacked slots) in the common wall, and particles may pass directly from the combustion chamber into the heat exchange chamber through a passage in the common wall above the solid particle inlet.

Abstract: A simplified method and apparatus for handling black liquor (or other spent liquor from the pulp industry) includes utilization of a mixing tank directly with a black liquor storage tank. The mixing tank has a side wall defined by a part of the side wall of the black liquor storage tank, and the mixing tank may either be disposed within the volume of the storage tank, or immediately exterior of it. Fly ash from a recovery boiler and make-up chemical are introduced into the mixing tank along with black liquor from evaporators, and the mixed liquid from mixing tank overflows into the interior volume of the black liquor storage tank. From the storage tank the black liquor is sent to a recovery boiler where it is burned. Also, some black liquor from the recovery boiler is recirculated to the storage tank, and introduced into the storage tank remote from the mixing tank.