Showing papers on "Spray tower published in 1990"

Spray-drying detergent compositions

Abstract: A method is provided for spray-drying large volumes of a detergent slurry in a spray-drying tower which comprises spraying at least a portion of the slurry, cocurrently with air having a specified temperature and velocity range, through uniformly spaced atomizing nozzles into a cylindrically shaped drying zone. Any remaining balance of the slurry is sprayed countercurrently into the drying zone at higher levels in the spray tower. Apparatus is provided for practicing this process. Granular detergent compositions having improved physical properties are also disclosed.

Spray drier simulation and air flow pattern studies

Abstract: The literature pertaining to the key stages of spray drying has been reviewed in the context of the mathematical modelling of drier performance. A critical review is also presented of previous spray drying models. A new mathematical model has been developed for prediction of spray drier performance. This is applicable to slurries of rigid, porous crust-forming materials to predict trajectories and drying profiles for droplets with a distribution of sizes sprayed from a centrifugal pressure nozzle. The model has been validated by comparing model predictions to experimental data from a pilot-scale counter-current drier and from a full-scale co-current drier. For the latter, the computed product moisture content was within 2%, and the computed air exit temperature within 10oC of experimental data. Air flow patterns have been investigated in a 1.2m diameter transparent countercurrent spray tower by flow visualisation. Smoke was introduced into various zones within the tower to trace the direction, and gauge the intensity, of the air flow. By means of a set of variable-angle air inlet nozzles, a variety of air entry configurations was investigated. The existence of a core of high rotational and axial velocity channelling up the axis of the tower was confirmed. The stability of flow within the core was found to be strongly dependent upon the air entry arrangement. A probe was developed for the measurement of air temperature and humidity profiles. This was employed for studying evaporation of pure water drops in a 1.2m diameter pilot-scale counter-current drier. A rapid approach to the exit air properties was detected within a 1m distance from the air entry ports. Measured radial profiles were found to be virtually flat but, from the axial profiles, the existence of plug-flow, well-mixed-flow and some degree of air short-circuiting can be inferred. The model and conclusions should assist in the improved design and optimum operation of industrial spray driers.

Production of detergent compositions by spray drying

Abstract: A method is provided for spray-drying large volumes of a detergent slurry in a spray-drying tower which comprises spraying at least a portion of the slurry, cocurrently with air having a specified temperature and velocity range, through uniformly spaced atomizing nozzles into a cylindrically shaped drying zone. Any remaining balance of the slurry is sprayed countercurrently into the drying zone at higher levels in the spray tower. Apparatus is provided for practicing this process. Granular detergent compositions having improved physical properties are also disclosed.

Process and installation for the preparation of calcium hydrogen phosphate

Abstract: In order to prepare dicalcium phosphate dihydrate which has been stabilised by means of dimagnesium phosphate trihydrate and sodium pyrophosphate, an aqueous suspension of calcium carbonate is introduced into a reactor and pumped in a circuit by a high-speed mixer which is connected by flow to the lower and upper parts of the reactor, at a speed of 3500 to 8000 rpm. An amount of phosphoric acid at least sufficient for quantitative formation of dicalcium phosphate dihydrate is introduced into the mixer, and an oxygen-containing magnesium compound is subsequently introduced into the reactor. Finally, milk of lime is metered into the reactor to a maximum pH of 6.9, before sodium pyrophosphate is introduced into the reactor. The resultant suspension, containing from 20 to 33% by weight of stabilised dicalcium phosphate dihydrate, is spray-dried. … An installation for carrying out the process comprises, in addition to a stirred reactor 1, two slurry tanks (6, 7) provided with stirrers and an intermediate tank 16, from which a line 17 leads to a spray tower 18 and terminates within the spray tower 18 above an atomiser wheel 19. Hot-air lines 20 run into the spray tower 18. The spray tower 18 is connected with respect to flow to a filter 22. A product line 24, via which highly adsorptive dicalcium phosphate dihydrate can be removed, leaves the base of the filter 22.

Process for the preparation of sodium of tripolyphosphate

Abstract: To prepare sodium tripolyphosphate, a sodium orthophosphate solution, which has been obtained by neutralising raw phosphoric acid produced at least partially by precipitation purification after digestion of raw phosphates with strong mineral acids and has been concentrated with the aid of the waste gases from the spray tower and contains 66.6 % by weight of diphosphate and 33.4 % by weight of monophosphate, is introduced into the upper part of a spray tower. In the spray tower, the sodium orthophosphate solution is sprayed by means of at least one nozzle through a flame zone generated by a plurality of burners in a circular arrangement. The pulverulent sodium tripolyphosphate is collected in the lower part of the spray tower. A silica-containing compound is added to the sodium orthophosphate solution while it is being concentrated.