GB2068756A

GB2068756A - Spray drier

Info

Publication number: GB2068756A
Application number: GB8100278A
Authority: GB
Original assignee: GAVIOLI G
Current assignee: GAVIOLI G
Priority date: 1980-01-08
Filing date: 1981-01-06
Publication date: 1981-08-19
Also published as: FR2473165A3; FR2473165B3; IT8004704V0

Abstract

A suspension or solution spray drier is provided wherein to the outlet of the drying air from the drying chamber (9) there is connected a conduit (13) communicating with a pre-drying chamber (2) in the inside whereof there is arranged a spray nozzle (7) fed by a pump (5). Between the pump (5) and spray nozzle (7) there is provided a heat exchanger (6) effective to raise the suspension or solution temperature to a higher temperature than the suspension or solution boiling temperature at the supply pressure, the suspension or solution, by flowing through the spray nozzle (7) passing from the supply pressure to the pre-drying chamber pressure and self-evaporating with a reduced heat consumption. <IMAGE>

Description

SPECIFICATION Spray drier This invention relates to a spray drier having a device for reducing, for each unit weight of dried product, the amount of heat required to evaporate the liquid which holds in solution or suspension the product in the conduits leading to the spraying or nebulizing apparatus.

Known are spray driers, in which the solution or suspension (generally an aqueous one) to be dried out is sprayed into a drying chamber, whereinto hot air is also admitted, said hot air causing the rapid heating of said solution or finely divided suspension, and accordingly the evaporation of the suspension liquid or solution to a desired percentage, while achieving a granulation of the dried product to the required particle size.

Also known is that suspensions too, as obtained for example by wet milling raw materials, often contain more solvent than is strictly required for atomizing to the desired particle size; however, said excess solvent cannot be conveniently separated mechanically, and is currently also separated in the drying chamber, thus limiting its potential and increasing the heat consumption per unit of dried product.

This invention sets out to obviate such drawbacks by providing a spray drier in which the final drying chamber of the product is only engaged by a suspension or solution with a minimum of solvent required for nebulization, and the excess solvent is removed with the least specific consumption possible.

Within that general aim, it is possible to arrange that the spray drier of this invention has a simple construction, is comparatively easy to manufacture, reliable and effective in operation, and of relatively low cost.

According to one aspect of the present invention, there is provided a spray drier with economizer device, comprising a homogenizing tankforthe product in the form of suspension or solution to be dried, a product pump and product spraying means serially connected together, said spraying means being operative inside a drying chamber, and characterized in that said drying chamber has an outlet of the drying air from said chamber, to which there is connected a conduit communicating with a pre-drying chamber which has a first outlet discharging the spent air to the outside and in the inside whereof there is arranged at least one spray nozzle fed by said pump, between the pump and spray nozzle here being arranged heating means, said predrying chamber having one outlet for the pre-dried product connected to a second inlet of said tank, said heating means being adapted for raising said suspension or solution temperature to a higher tem perature than the boiling temperature thereof at the pressure prevailing in said pre-drying chamber but lower than the boiling temperature at the supply pressure, the liquid forming the suspension or solution, by flowing through said nozzle, passing from the supply pressure to the pressure of the pre-drying chamber and self-evaporating in a consistent proportion with a reduced heat consumption.

Further features will become more clearly apparent from the detailed description of a preferred, but not limitative, embodiment of a drier according to the invention, as illustrated in the accompanying drawing by way of example only, the one figure of said drawing showing a block diagram of a drier according to the invention.

In the drawing figure, there is generally indicated at 1 a drier according to this invention, the reference numeral 2 designating the pre-drying chamber thereof.

The aqueous suspension is delivered to the tank 3 from upstream storage tanks and, through the conduit 4, reaches the pump 5 which, through the conduit 4a, transfers it into the exchanger 6 which functions as a heating means; thence, as heated to a higher temperature than the water boiling temperature at the pressure in the predrying chamber, the suspension is delivered by the pump to the spray nozzle 7 over the conduit 4b.

Inside the spray nozzle, the aqueous suspension passes from the supply pressure to the pressure prevailing in the pre-drying chamber, with a substantially adiabatic variation. Said suspension, owing to its temperature at the spray nozzle inlet, during that variation releases vapor without involving of necessity the acquisition of heat from the environment, and consequently without involving additional heat losses through the exhausted air.

The partially dehumidified aqueous suspension is returned, through the conduit 8, to the homogenizing tank 3, is taken up by the pump 5 through the conduit 4, and is delivered, through the conduit 4c, to the spraying system provided in the drying chamber 9. The dried product then leaves through 10. The drying air, as drawn in at 11, is heated in the hot air generator 12 and delivered, through the conduit 1 lea, to the drying chamber 9 from which it flows out at 13, being cooled and enhanced in its moisture content, to pass into the pre-drying chamber 2. In said chamber 2, the air is brought to saturation and then, through the conduit 14, delivered to a chimney or a purifying system.

It will be apparent how, for a given evaporative capacity, the drying chamber 9 will produce a larger amount of dried product, since the moisture content of the suspension drawn in at 4 is substantially lower than that from the upstream tanks through the conduit 16.

Advantageously, the heat delivered to the aqueous suspension in the exchanger 6, the temperature to which the aqueous suspension is brought being fairly low, may be recovery heat, e.g. from the cooling system and exhaust gas of thermal engines.

Thus, it may be seen that the invention achieves its objects, and in particular affords substantial power and construction economies.

The invention as described is susceptible to many modifications and variations without departing from the scope of the instant inventive concept.

Moreover, all of the details may be replaced with other technically equivalent elements. In practicing the invention, the materials employed, and the shapes and dimensions, may be any ones, according to individual requirements, without departing from the scope of the appended claim.

Claims

CLAIM

1. A spray drier with an economizer device comprising a homogenizing tank for the product in the form of suspension or solution to be dried, a product pump and product spraying means serially connected together, said spraying means being operative inside a drying chamber and characterized in that said drying chamber has an outlet of the drying air from said chamber to which there is connected a conduit communicating with a pre-drying chamber which has a first outlet discharging the spent air to the outside and in the inside whereof there is arranged at least one spray nozzle fed by said pump, between the pump and spray nozzle there being arranged heating means, said pre-drying chamber having one outletforthe product connectedto a second inlet of said tank, said heating means being adapted for raising said suspension or solution temperature to a highertemperaturethan the boiling temperature thereof at the pressure prevailing in said pre-drying chamber, but lower than the boiling temperature at the supply pressure, the liquid forming the suspension or solution, by flowing through said nozzle, passing from the supply pressure to the pressure of the pre-drying chamber and selfevaporating in a consistent proportion with a reduced heat consumption.