US 4,608,764 A · Process of drying a particulate material and apparatus for implementing the process

Abstract

The particles of the particulate material to be dried are cooled before the drying operation proper, or in the initial phase thereof, to a temperature low enough to make the liquid to be extracted solidify. At least the drying operation proper is carried out in a space bounded by a container, in which a gas, more particularly air, is passed through the particles. While in said space, the particles are subjected to motion, for example, they are whirled by the gas to form a whirling layer. The temperature of the gas is adjusted to have at least a considerable part of the drying operation take place by sublimation, the heat energy required for the sublimiation being supplied to the particles at least in part by the gas passed through them. In this way, the particulate material may be dried with care and nevertheless in relatively large batches, and with limited time expenditure.

Claims27

Dependent claims

A process for drying particulate material that includes a liquid substance to be extracted, the process comprising the steps of:

freezing the material within a container in a freezing operation and subsequently drying the material in the same container in a drying operation, wherein a cooling medium having one of the states solid and liquid and particles of the said material are subjected to movement during the said freezing operation in the said container, so that the particles of the material are cooled to a temperature at which the liquid substance is solidified and wherein the cooling medium is separated from the particulate material in the gaseous state, and wherein the particulate material, after the solidification of the liquid substance is dried during the drying operation in the same container by passing gas through the particulate material and subjecting the particulate material to motion, wherein the particulate material is held at least during a part of the drying operation at a temperature at which at least a part of the substance to be extracted from it remains in the solid state until it is extracted by sublimation, and wherein vapor generated during the drying operation is carried away from the particulate material by the gas passed through the particulate material together with said gas.

A process for drying a particulate material having a substance to be extracted during a drying operation and originally being in the liquid state and having been at least in part solidified by cooling, said process including the steps of:

(a) drying a batch of the particulate material in a container while subjecting the material to movement and to gas passing through it in such a way that the material is kept at least during a substantial part of the drying operation at a temperature low enough for maintaining at least a part of the substance to be extracted from the particulate material in the solid state until it is sublimed;
(b) subsequently introducing into the container gas with a higher temperature than the temperature of the gas passed through the container during the drying operation to perform a warming-up operation within the container and the batch of dried particulate material provided therein for warming up the inside of the container and the batch of dried particulate material to a temperature high enough to ensure that substantially no humidity condenses on the inside wall of the container and on the dried particulate material upon contact with the air from the surroundings;
and
(c) removing the dried batch of particulate material from the container after the warming-up operation.

1 more element

Apparatus for drying a particulate material comprising:

a container to receive a batch of particulate material to be dried;
gas conducting means connected with said container forming together with said container a closed loop that includes gas pumping means and drying means and cooling means for drying and cooling a gas and passing the dried and cooled gas through said container at a temperature low enough to ensure that at least a part of the substance to be extracted from the particulate material during a drying operation is at least during a part of the drying operation in the solid state, wherein the gas conducting means further comprises valve means for disconnecting said cooling means from the closed loop during a warming-up operation and a batch-removing operation, and heating means for passing gas through the container during the warming-up operation at a temperature exceeding the temperature of the gas passed through the container during the drying operation for warming up the inside of said container and the batch of particulate material provided therein to a temperature high enough to ensure that substantially no humidity condenses inside said container and on the particulate material upon contact with air from the surroundings when the container is opened and the batch of dried particulate material is removed from the container.

Dependencies are inferred from the claim text.

Process of drying a particulate material and apparatus for implementing the process

Life of this patent

Process of drying a particulate material and apparatus for implementing the process

Life of this patent

Abstract

Claims27