Abstract: A heat exchanger has a cylindrical chamber (6) with a tangential peripheral gas inlet (1), an axial gas outlet (2), a material inlet (3) which introduces the material with a tangential velocity components in the same sense as that of the spiral gas flow at the point of introduction, and a material outlet (5).

Abstract: A spark-over detector for an electrostatic precipitator has a current sensor (3) which provides a signal (a) which is differentiated twice to produce a signal (c). If the level of the signal (c) is above a predetermined level then a level-detecting circuit (7) passes a signal (d) to an AND-gate (8). A second level detecting circuit (9) receives the signal (a) and if this signal is above a predetermined level passes the signal (e) to a timing circuit (10) which provides a signal (f) from a first preset time after having received the signal (e) until a second preset time after the signal (e) has ceased. Thus, if a spark over starts to occur signals (d) and (f) occur simultaneously and the AND-gate produces an output signal (g) which can be used to trigger the thyristor switch circuit of the pulse generator to conduction to prevent thyristor damage or destruction.

Abstract: A separator has a rotor (1) with radial vanes (12) between plates (8,11). Material to be sorted is supplied, entrained in a conveying gas, through an inlet duct (6) to some rotor vane interspaces through inlet openings (13). The flow is then radially outwards, around the vane ends, radially into the other vane interspaces and into an outlet duct (9) through outlet openings (14), carrying the fine fraction. The coarse fraction is flung outwards by the vanes and collected in a hopper (4).

Abstract: In the method of controlling the period length of an intermittent voltage supply to an electrostatic precipitator, a search procedure is carried out at predetermined time intervals or at time intervals determined by one or more continuously monitored/measured precipitator or operational parameters. During the search procedure either the number of system voltage half-periods during which the power supply to the precipitator is cut off (the length of the non-conduction (n.sub.p) period), or the number of system voltage half-periods during which the power supply supplies current to the precipitator (the length of the conduction period), are changed according to a predetermined scale or to a scale determined by one or more precipitator or operational parameters. The charge transmitted per system half-period is current in the precipitator divided by the total number of half-periods of conduction per second.

Abstract: A method of controlling the pulse frequency of an electrostatic precipitator energized by a pulse superimposed direct voltage, is disclosed in which, for a given direct and/or pulse voltage, the pulse repetition frequency, at intervals which are preset or determined by one or more precipitator or operational parameters, is lowered and then increased stepwise according to a predetermined scale. At each value of the pulse repetition frequency the average current being measured and the transmitted charge per pulse (defined as the average current divided by the pulse repetition frequency) calculated.

Abstract: A separator for sorting particulate material suspended in a conveying gas into coarse and fine fractions has a rotor (1) with two sets (9,10) of vanes. Dampers (13,14) in outlet ducts for the fine fraction regulate the relative flow through the two vane sets and hence control the cut between the fine fraction and the coarse fraction which is flung centrifugally outwards by the vanes and falls down inside a casing (3).

Abstract: In a method and an apparatus for burning away organic components in raw phosphate, the burning taking place in two stages carried out in two reactors each having its separate air supply. A first suspension transport reactor (3) and a second reactor (5) are coupled in series via a separator (4), to which reactors combustion air (9), (11), preheated raw material (14), (15) and, if desired, fuel (8) are supplied separately. The reaction temperature in both reactors preferably lies in the range 700.degree.-850.degree. C. The majority of the organic components are burnt in the first stage which operates with a suspension having a density of 1-50 kg/m.sup.3. The remaining part of the organic components is burnt in the second stage which operates with a suspension density of 75-1600 kg/m.sup.

Abstract: In order to enable a reduction of the percentage of liquid in a liquid/coal pumping mixture the coal is dry-ground in a first grinding stage (1) to provide a relatively coarse particle size and then a fraction of the coarse ground coal is then dry-ground in a second grinding stage (9) to a relative fine particle size. The fine ground fraction is then mixed with the remainder of the coarse-ground fraction (7) and with the liquid.

Abstract: A method of removing cadmium from raw phosphate material in an apparatus comprising a preheater section (2,13) a reactor section (3,4,5), a cooler section (7) and an exit gas cleaning section having a cadmium condenser (6,20,21), where the reactors (3,5) work in series and are formed as suspension reactors, or alternatively as a suspension reactor and a fluid-bed reactor, and where the treated raw phosphate in the first reactor having a short material retention time is suspended in a gas/fuel mixture and through a flash-process heated to a reaction temperature of 750.degree.-1050.degree. C.

Abstract: A vertical roller mill has a grinding table (1), rollers (3) and a separator (6) for separating ground material, which is conveyed to the separator in an air stream supplied through an inlet (7), into a fine fraction, which passes out through an outlet (8), and a coarse fraction which is returned for further grinding through an outlet (10). A part of the ground material is conveyed through an outlet (11) to a second separator (13), where it is separated from the air and returned for further grinding via an outlet (14) and an inlet (9) for fresh material to the mill. This provides a flatter grain size distribution curve in the finish ground material.

Abstract: An apparatus for burning pulverulent raw material, in particular cement raw meal to cement clinker, has a kiln (1), a cooler (2), a suspension calciner (4-12) and a multi-stage preheater (14-27). The preheater is provided with two material outlet ducts (22 and 22') directing a first stream of preheated material to a suspension burning chamber (4) with a hot air inlet (7) and a fuel inlet (5) and a second stream of preheated material to a kiln gas duct (28), respectively. Rapid quenching of kiln gas and accelerated rate of combustion in suspension calciner are provided by suspending and calcining the material in the streams in the burning chamber and the kiln gas duct, respectively, and uniting the two suspensions downstream of the suspension burning chamber (4). The calcined material is precipitated in and passed to the kiln from a precipitator (9), to which the united suspensions are directed.

Abstract: A method of removing acid gases from hot flue gases wherein the flue gas is fed through a pipe (3) and up through a tubular reaction chamber (1) having a diverging bottom wall (2) which causes a rapid reduction in axial velocity. Further flue gas is introduced tangentially through a pipe (5) to produce a rising swirling stream of flue gas, in which a powdery absorption agent, that has been introduced through an inlet (4), is entrained. The agent reacts with the acid gas to produce powdery reaction products which are subsequently removed in separators (7,7').

Abstract: A method and an apparatus for calcining pulverulent raw material, in particular cement raw meal, wherein the material is calcined suspended in a stream of hot gas in a calcining zone (4) in an overheated atmosphere by burning fuel in a stream of oxygen-containing gas in the zone, and precipitated in a precipitation zone (9). The rate of combustion of the fuel is accelerated by maintaining a temperature within the range 900.degree.-1250.degree. C. in the calcining zone by dividing the raw material into two streams (22',22) introducing and calcining only the first stream of material (22') in the calcination chamber (4). The temperature of the hot suspension withdrawn from the calcining zone is reduced by 100.degree.-300.degree. C. to a level within the range 800.degree.-1000.degree. C. by suspending the second stream of material (22) in the hot suspension during withdrawal thereof from the calcination chamber (4) and before the calcined material is precipitated in the precipitator (9).

Abstract: Raw phosphate material is calcined to remove pollutants, such as organic compounds and sulphides, by heat treatment in two suspension calciners (3,5) arranged in series. Fuel supplied at burners (8) is burnt in the calciners with air, supplied in parallel through pipes (9) from a cooler (7) for the treated material. The material is preheated in a preheater, for instance a pipe (13) and cyclone (2) by exit gases from the calciner before entering the calciners and, after leaving the calciners, is separated from the gas streams in separators (4,6).

Abstract: Sulfur oxides and other acid gases are removed from hot flue gases by dispersing and suspending an absorption agent and water, preferably Ca(OH).sub.2 suspended in water, in a rising stream of hot gas at the lower part of a reaction chamber, where the hot gases are subjected to a rapid reduction in velocity. Sulfur oxides and other acid gases are absorbed on and reacted with the absorption agent in the presence of evaporating water producing a dry powder which is separated from the flue gas in a particle precipitator and partially recirculated to the reaction chamber.

Abstract: The invention relates to a bridge scraper for raking material from a storage heap onto a belt conveyor by means of a scraper chain mounted on a bridge which also carries a carriage which feeds material from the heap to the scraper chain. The speed of the conveyor and that of the bridge, the scraper chain and the carriage is controlled by means of a bolt weigher at the outlet end of the belt conveyor which controls the speed of the belt and consequently that of the other elements of the bridge scraper so as to discharge a constant amount of material per unit time.

Abstract: A vertical roller mill has a rotary grinding table (1), grinding rollers (3) and a nozzle ring (13) surrounding the table for providing an air stream to entrain ground material. Downstream of each roller is a scraper (20) with a nozzle for directing a blast of air onto the crushed material leaving the roller to break up the material so that finer fractions pass into the conveying air stream and coarser fractions are carried on the table to the next roller.