A method for transfer of heat between a first and a second fluid, wherein the first and the second fluid circulate respectively on both sides of a thermally conductive wall of a monobloc assembly formed in a single piece. The monobloc assembly, which is arranged in the interior of a device, includes: a first, three-dimensional, cellular, thermally conductive structure through which the first fluid can pass; at least the thermally conductive wall; and a second, three-dimensional, cellular, thermally conductive structure through which the second fluid can pass. The first and second three-dimensional, cellular structures are situated on both sides of and integral with the wall such that heat transfer is carried out from the first to the second fluid through the wall, and both first and second fluids are under liquid phases and under gaseous phases, with the liquid phases circulating in a direction opposite that of the gaseous phases.

A matrix, configured to form at least part of a material-transfer separation unit, the matrix having a stack of several plates arranged parallel to one another in a direction known as the direction of stacking, thereby defining passages, the matrix having a length, a width and a thickness, the length of a matrix being the greatest dimension of the parallel plates, the width of the matrix being measured perpendicular to the length, and the thickness of the matrix being measured in the direction of stacking of the plates.

A direct heat exchange and material transfer apparatus having a plurality of columns, a single stack of at least two solid metal plates of rectangular section, the plates being substantially all of the same shape and dimensions and parallel to a determined direction, each plate being separated from the adjacent plate, at least in a first direct heat exchange and material transfer zone of the apparatus, by a group of hollow metal columns that are aligned and have a section which is polygonal and has at least two parallel surfaces, the channels being parallel to the determined direction and contiguous with one another, the columns of each group each being in contact with the two metal plates on either side of the group, at least some of the columns of a group containing a material and heat exchange means.

A method for manufacturing a heat and material exchange apparatus having a plurality of columns and by a series of at least three metal plates of rectangular section, the plates being substantially all of the same shape and dimensions, each plate being separated from the adjacent plate by a group of hollow metal columns that are aligned and have a section which is polygonal, the columns of each group being parallel to one another, at least some of the columns of a group containing a material and heat exchange means, at least the parts of the plates which are in contact with the columns being coated with a brazing material wherein the plates are secured to the columns by placing the exchange apparatus in a furnace and by heating the furnace in order to braze the apparatus to form a parallelepipedal block.

In a method for separating air by cryogenic distillation, cooled air purified to remove water is sent to a first column operating at a first pressure, where it is separated into a nitrogen-enriched gas as an oxygen-enriched liquid; a gas enriched in argon relative to the air is withdrawn from the second column; at least a portion of the oxygen-enriched liquid is vaporized by heat exchange with the argon-enriched gas; and the vaporized, oxygen-enriched liquid is sent to an intermediate level of the second column.