Thermal insulation of an adsorbent

Abstract

Adsorber (1) for the treatment of a gaseous mixture, the adsorber (1) comprising a casing (2) delimiting an internal volume of the adsorber (1), the adsorber comprising thermally insulating panels (14) arranged within said internal volume, said panels (14) being made of closed-cell cellular glass. Abbreviated figure: Fig. 1

Description

Title of the invention: Thermal insulation of an adsorber

[0001] The invention relates to an adsorber for the pre-purification of a gas mixture before separation in a downstream unit. It finds a particular application in an adsorber of a TSA unit upstream of a cryogenic air separation unit.

[0002] It is known that atmospheric air contains compounds that must be removed before being introduced into the heat exchangers of the cold box of an air separation unit, in particular water vapor (H2O), carbon dioxide (CO2), nitrogen oxides, and hydrocarbons. Indeed, in the absence of such air treatment to remove its H2O and CO2 impurities, these impurities solidify when the air is cooled to a cryogenic temperature typically below -150°C, which can result in clogging problems in equipment, particularly heat exchangers and distillation columns.In addition, it is also common practice to at least partially remove hydrocarbon and nitrogen oxide impurities that may be present in the air in order to prevent their excessive concentration at the bottom of the distillation column(s), and thus mitigate any risk of equipment degradation.

[0003] In order to improve the efficiency of adsorbers and limit the impact on their operation of temperature variations due to the adsorption cycle or environmental disturbances, it may be necessary to use thermal insulating materials.

[0004] Ceramic wool is known to be used in adsorbers, but it has the disadvantage of being very sensitive to humidity. This is particularly problematic in dryers, which by definition deal with humid gases.

[0005] A known alternative is to install insulating air gaps trapped between metal sheets (for example, a double air gap between three sheets). This solution is insensitive to humidity, but has the disadvantage of being complex and expensive to implement, with lower thermal insulation efficiency.

[0006] In the context of a pre-purification of an air separation unit, it is necessary to have an inorganic material as thermal insulation, to avoid the sending of volatile organic compounds towards the cryogenic air separation unit.

[0007] The invention therefore relates to an adsorber for the treatment of a gaseous mixture, the adsorber comprising an envelope delimiting an internal volume of the adsorber, the adsorber comprising thermal insulating panels arranged in said internal volume, said panels being made of closed-cell cellular glass.

[0008] The closed-cell cellular glass comprises a majority of closed cells or pores, so that no moisture penetration, even by capillarity, is possible into its internal structure.

[0009] In one embodiment, the adsorber comprises at least one adsorbent bed, and the insulating panels are arranged so as to thermally insulate said at least one adsorbent bed from the casing. In particular, the insulating panels are arranged without being in contact with the at least one adsorbent bed. This prevents the gas mixture from partially bypassing the at least one adsorbent bed due to any potential assembly defects in the insulating panels.

[0010] In one embodiment, said envelope comprises a top wall and said insulating panels are arranged so as to thermally insulate said at least one bed of adsorbent from the top wall.

[0011] In one embodiment, the insulating panels are fixed within the internal volume of the adsorber with nails and / or washers, for example, self-adhesive washers. In particular, the insulating panels are fixed within the internal volume without the use of glue or sealant.

[0012] [Fig. 1] Fig. 1 shows a cross-section of a parallelepiped-shaped adsorber; and

[0013] [Fig.2] Fig.2 represents the same adsorber in longitudinal section.

[0014] In the described embodiment, the adsorber 1 has a substantially parallelepiped shape delimited by an envelope 2. An internal part 3 of the adsorber comprises two volumes of adsorbent 4, each trapped between two gas-permeable grids 5 and a central space 6 free of adsorbent between the two volumes of adsorbent 4. Each volume 4 comprises two beds of adsorbent, for example a first bed of adsorbent intended to remove the vast majority of the water and possibly some of the CO2 (activated alumina, silica gel, doped alumina...) and a second bed of adsorbent intended to remove the remaining CO2, nitrogen oxides and certain hydrocarbons (zeolites X, preferentially exchanged particularly with calcium and / or barium). One can just as easily use a single layer (doped alumina, zeolite X) or three successive layers (for example alumina, zeolite X, exchanged zeolite).The different beds are separated by an intermediate grid 7, which is also gas-permeable. Grids 5 and 7 are fixed to an upper wall 8 of the casing 2. A gas-impermeable base 9 delimits the lower part of the adsorbent volumes 4, as well as the central space 6 between the two adsorbent volumes 4. Similarly, lateral partitions 10 delimit the adsorbent volumes 4 on their sides and delimit the central space 6 on its sides. A peripheral space 11 extends around the adsorbent volumes 4, between the casing 2 of the adsorber 1, the outermost grids 5, the lateral partitions 10, and the base 9.

[0015] During the adsorption phase, the gas mixture to be treated can enter the adsorber through a feed tube 13 from the peripheral space 11. The distributed gas mixture passes through the adsorbent volumes 4 on either side of a central space 6, and impurities, particularly H2O and CO2, are trapped by the adsorbent beds. The treated gas mixture is collected in the central space 6 and then discharged through a central discharge channel 12 extending between the aforementioned adsorbent volumes 4. However, the gas mixture can flow in the opposite direction, first entering the central space 6, to be collected by the peripheral space 11. A substantial amount of moisture therefore circulates within the adsorber 1.

[0016] In the configuration shown, where one face of the internal part 3 is abutted against the upper wall 8 of the envelope 2, it may be advantageous to use an insulating means to limit heat transfer. This could be the case if the internal part 3 were very close to the upper wall 8. The insulating means may be on the side of the internal part 3, and / or on the side of the envelope 2, and / or possibly (not shown) between the internal part 3 and the envelope 2. Thermally insulating panels 14 made of closed-cell cellular glass are arranged inside the adsorber 1, on the bottom 9, on the side walls 10, and on the upper wall 8 (also called the roof) of the adsorber 1, more precisely in the peripheral space 11 and in the upper part of the central space 6.The thermal insulation panels 14, comprising closed-cell cellular glass, effectively insulate the adsorber 1 and the adsorbent volumes 4 in the relevant areas. Moisture does not penetrate the closed cells of the glass, significantly reducing the insulation's sensitivity to moisture. Glass wool 15 is conventionally placed on the adsorber's outer casing 2, on the side facing the adsorber 1, to thermally insulate it from the environment. A cellular elastomer material could also replace the glass / rock wool. Insulating the roof of the adsorber 1 from the inside with the insulation according to the invention eliminates the need for external roof insulation, allowing an operator to walk directly on the roof of the adsorber 1 without risk of damaging external insulation and compromising its thermal performance.

Claims

Demands

1. Adsorber (1) for the treatment of a gaseous mixture, the adsorber (1) comprising a casing (2) delimiting an internal volume of the adsorber (1), the adsorber comprising thermal insulating panels (14) arranged in said internal volume, said panels (14) being made of closed-cell cellular glass.