JP3529104B2 - Method and apparatus for generating reduced pressure - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a reduced pressure, a pumping device for use in this method (especially a diffusion pump), a fluid used as a pump fluid in this method, and an application of this method (especially thermosensitive). Purification of materials).

[0002]

BACKGROUND OF THE INVENTION Many industrial operations rely on the creation and maintenance of reduced pressure within the equipment for their effectiveness. Examples of this type of process include vacuum distillation, which is necessary for the purification of heat-sensitive materials, and freeze-drying, for example used in the food industry. The method and apparatus used to generate the reduced pressure depends on the degree of reduced pressure required, which is determined by the particular operation involved. For example, reduced pressures in the range of about 10 ² to about 10 ⁵ Pa absolute pressure, and about 10 ^-1 to about 10 ² Pa.
Within the pressure range of 1, the vacuum can be conveniently generated using displacement pumps such as liquid and gas ring vacuum pumps, rotary vanes, rotary pistons and rotary lobe vacuum pumps. Achieving high pressures in the range of 10 ⁻⁵ to 10 ⁻¹ Pa and low pressures, typically ultra-high pressures with pressures below 10 ⁻⁵ Pa, is achieved, for example, by jet pumps
Kinetic vacuum pumps such as diffusion pumps and drag vacuum pumps or gas storage vacuum pumps such as sorption pumps and condensation pumps are used.

Vacuum distillation is used to purify many heat-sensitive materials. Typical equipment for performing this vacuum distillation includes falling film and wiped liquid film evaporators. This type of method is typically 10 ^-1 to 10 ²
Operated under reduced pressure of Pa, the generation of which is conveniently accomplished using a diffusion vacuum pump. In operating a diffusion vacuum pump, a pump fluid reservoir is heated to vaporize the fluid,
The steam then exits through the openings in the nozzle to form a high velocity steam jet. The gas being pumped diffuses into and is entrained in the steam jet,
It is transferred to the area separated from the nozzle by the jet,
Here, the pump fluid vapor condenses, separates from the gas being pumped and is circulated to a reservoir. The gas being pumped is removed from the region by a pump after it has been separated from the pump fluid, commonly referred to as the "auxiliary pump" or "fore pump". Reference is made to Ullmann Encyclopedia of Industrial Chemistry, Volume B3, Unit Operation II, paragraph 21 for a description of many features of vacuum technology in general, and diffusion vacuum pumps in particular. US Pat. Nos. 2,028,340, 2,338,583, 2,358,067 and 2,560,913, and West German Patent 88 describe specific examples of diffusion vacuum pumps.
Reference is made to Japanese Patent No. 3,185.

Fluids for use as pump fluids in the diffusion decompression pump disclosed in the above patent publications include mercury, mineral oil,
Includes halogenated polyethers and polyphenyl ethers. Its wide availability and its relatively low price have made mineral oil widely recognized as the preferred pump fluid. Typical mineral oils for use as pump fluids include paraffinic, aromatic and naphthenic hydrocarbons. Particularly surprising, it has now been determined that paraffin wax, when used as a pump fluid in diffusion vacuum pumps, provides a significant improvement in overall pump performance and efficiency.

[0005]

Therefore, according to the first aspect of the present invention, when a reduced pressure is generated in a container, steam is generated by heating a paraffin wax storage tank, and the steam is introduced into a gas entrainment zone connected to the container. To generate a vapor jet in the entrainment zone, causing gas to flow from the vessel into the vapor jet, moving the vapor jet containing gas to the condensation zone, and condensing the vapor from the vapor jet.
Provided is a method of generating reduced pressure , which comprises condensing in a zone and recovering condensed wax and uncondensed material separately. The paraffin wax used in the process of the present invention preferably comprises more than 70% by weight paraffins, more preferably more than 80% by weight and even more preferably more than 90% by weight paraffins. A particularly suitable wax contains more than 95% by weight paraffin. The most preferred waxes consist essentially of paraffinic materials. The wax may comprise both straight chain and branched chain paraffins, preferably waxes containing substantial amounts of straight chain paraffins, in particular greater than 75% by weight, in particular greater than 90% by weight. To be The most preferred wax consists essentially of normal paraffin.

[0006] paraffins present in the wax may range from C ₁₅ paraffins -C ₇₀ paraffin.
For use in the method of the present invention, mention may be made of waxes which preferably consist of paraffins in the defined molecular weight fraction. The first preferred wax is at least 60% by weight relative to the total paraffin content, more preferably C ₁₅ -C ₂₀ paraffins at least 75 wt% of the amount. A second suitable wax is at least 60% by weight, based on the total paraffin content, more preferably at least 75%.
Containing C ₂₀ -C ₃₀ paraffins% by weight. A third preferred wax is at least 60 based on total paraffin content.
It contains C _{30 to} C ₄₀ paraffins in an amount of wt.%, More preferably 75 wt.%. A fourth suitable wax comprises C ₄₀ + paraffins in an amount of at least 60% by weight, more preferably at least 75% by weight, based on total paraffin content. As used herein, the term "paraffin" means a hydrocarbon or mixture of hydrocarbons whose constituent molecules are substantially aliphatic and which are substantially or fully saturated. Preference is given to hydrocarbons or hydrocarbon mixtures which are substantially free of unsaturation.

The wax may have any suitable freezing point, especially in the range 10 to 120 ° C, more preferably in the range 25 to 110 ° C. The wax can have any viscosity suitable for effectively operating the method. In particular, the viscosity of wax measured at 120 ° C is 1-2.
The range may be 0 mm ² / s, and more preferably ² to 15 mm ² / s. From the description of the preferred characteristics of the waxes used in the method of the present invention, it can be seen that many waxes exist as solids or substantially as solid phases under ambient temperature and pressure conditions. However, it will be appreciated that for effective depressurization to occur, the conditions maintained during this process must prevent substantial amounts of wax from solidifying. Waxes of the type mentioned and having the above-mentioned properties can be prepared by conventional techniques, for example conventional crude oil, refining. However, the preferred waxes for use in the method of the present invention are synthetic materials, especially waxes made by the Fischer-Tropsch synthesis method.

The Fischer-Tropsch synthesis is generally given the name given to the process by which a hydrocarbon is produced from a mixture of carbon monoxide and hydrogen by contacting the mixture with a suitable catalyst at elevated temperature and pressure. is there. The catalyst used in the Fischer-Tropsch synthesis often consists of a metal of Group VIII of the Periodic Table of the Elements as the catalytically active component. Specific catalytically active metals include ruthenium, iron, cobalt and nickel. Particularly suitable waxes for use in the process of the invention are those prepared by the Fischer-Tropsch synthesis process using a catalyst containing cobalt as the catalytically active component. The catalytically active metal is preferably supported on a porous carrier. The porous carrier can be selected from any suitable refractory metal oxide or silicate or combinations thereof known in the art. Specific examples of suitable porous carriers include silica, alumina, titania and mixtures thereof. Regarding the catalyst used in producing the wax used in the method of the present invention,
Silica is a particularly suitable carrier material.

The amount of catalytically active metal relative to the carrier is preferably from 3 to 100 pbw per 100 pbw of carrier material.
Range, more preferably 10 to 80 pbw, especially 20 to
It is in the range of 60 pbw. If desired, the catalyst can also include one or more metals or metal oxides as promoters. Suitable metal oxide promoters can be selected from Groups IIA, IIIB, IVB, VB and VIB of the Periodic Table of the Elements or the actinide and lanthanide groups. Especially magnesium, calcium, strontium,
Barium, scandium, yttrium, lanthanum , cerium, titanium, zirconium, hafnium, thorium, uranium, vanadium and chromium oxides are the most suitable promoters. A particularly suitable metal oxide promoter for the catalyst used to prepare the wax used in the present invention is zirconium oxide. Suitable metal promoters can be selected from Groups VIIB and VIII of the Periodic Table.
Rhenium and Group VIII noble metals are particularly suitable, with platinum and palladium being particularly preferred. The amount of promoter present in the catalyst is preferably 0.1 per 100 pbw of carrier.
Is in the range of up to 150 pbw.

A particularly suitable catalyst for use in making the wax used in the process of the present invention is a cobalt / zirconium / silica catalyst. Examples of suitable catalysts which can be used for the production of waxes are European patent application EP010
4672, EP0110449, EP012722
No. 0, EP 0167215, EP 0180269 and EP 0221598. As mentioned above, the wax for use in the method of the present invention can be prepared by the Fischer-Tropsch synthesis in which a mixture of carbon monoxide and hydrogen is contacted with the catalyst.
This synthesis is typically carried out at temperatures of about 125 to about 350 ° C, preferably about 175 to 250 ° C. Typical operating pressures for synthesis range from about 5 to 100 bar, more preferably about 10 to 50 bar. During the synthesis process, the catalyst is typically contacted with a gas mixture of hydrogen and carbon monoxide in a ratio of less than 2.5, preferably less than 1.75. More preferably, the ratio of hydrogen to carbon monoxide in the mixture is in the range 0.4 to 1.5, especially 0.9 to 1.3.

The Fischer-Tropsch synthesis process, as described above, produces high yields of waxes suitable for use in the process of the present invention. The wax exists substantially as a liquid phase under the conditions predominantly present in the process. However, in addition to the desired wax, the effluent from this process consists of unconverted feed gas and light gases and liquid hydrocarbons produced during the synthesis reaction. The wax can be separated from the unconverted feed gas and light products by conventional separation techniques well known in the art (eg, distillation). The wax may be further purified, if desired, after separation from the light product to produce, for example, one or more of the various wax fractions mentioned above. Again, separation techniques for purifying this type of wax are known in the art. Due to the low thermal stability of the wax, high temperatures should be avoided in the purification of the wax if thermal decomposition of the heavy wax molecules is to be prevented. Therefore, separation techniques such as vacuum distillation should be carried out using, for example, micro vacuum or short path evaporators well known in the art. Typical evaporators used in this type of purification process include high vacuum falling liquid film evaporators and high vacuum wiped liquid film evaporators. Typical operating pressures for the evaporator are in the range of 10 ^-1 to 10 ² Pa.

In a second aspect, the invention relates to the use of paraffin wax of the above character as a pump fluid in a diffusion vacuum pump. In a third aspect, the invention comprises a paraffin wax reservoir, a heating means for generating steam from the paraffin wax, a steam conduit forming a path for the steam and a pump container, the container comprising a gas entrainment zone. A steam inlet connected to the steam conduit and configured to form steam flowing into the pump vessel into a steam jet extending into the gas entrainment zone; and a gas inlet for contacting the gas flowing into the pump vessel with the steam jet, A vapor condensing zone arranged to receive the gas and vapor jet exiting the entrainment zone, cooling means for condensing the vapor in the vapor condensing zone, and means for separately recovering the condensed vapor and gas from the condensing zone. A characteristic decompression generator is provided.

The paraffin wax which forms part of the device according to the invention can be any wax or wax fraction described above. Hereinafter, the apparatus of the present invention will be further described by way of specific examples with reference to the accompanying drawings, although not limited thereto. Referring to the drawings, a pump container 1 comprises a body 2 having a general shape of an inverted cone and having a dome-shaped upper end 3. The gas inlet 4 is shown in the upper region of the side of the body 2. A container (not shown) for generating and maintaining a reduced pressure is connected to the gas inlet 4 via the path 5. The gas outlet 6 is shown in the lower region of the side of the body 2. A vacuum fore pump (not shown) is connected to the gas outlet 6 by way of the path 7. A steam inlet 8 is shown centrally located at the upper end 3 of the body 2, which comprises a small aperture through which steam passes and flows into the upper region of the pump container 1. The lower end of the main body 2 is
It is formed to provide an outlet 9 for the condensation wax. The pump container further comprises a cooling means, which in the drawing is a spiral tube 1 extending around the conical outer surface of the body 2.
Shown as 0. The path 11 extends from the condensation wax outlet 9 to the wax circulation pump 12. The path 13 extends from the wax circulation pump 12 to the wax vaporizer 14. The heating-mediated supply to the wax vaporizer 14 is indicated in the drawing by path 15. The line 16 connects the vapor outlet of the wax vaporizer 14 to the vapor inlet 8 of the pump container 1.

In operating the apparatus shown in the drawings, the paraffin wax reservoir is located under the pump container in the region of the condensation wax outlet, the passage 11, the wax circulation pump 1.
2, included in the body of path 13 and wax vaporizer 14. For example, if a larger volume of wax is needed in the reservoir, the second container should be the condensing wax outlet 9 of the pump container 1.
And the wax circulation pump 12 may be provided. The wax in the wax vaporizer 14 is heated by a heating medium to generate wax vapor. The heating medium may conveniently be the hot water or steam contained within conventional shell tubes and tube heat exchangers. The steam generated in the vaporizer 14 moves along the path 16 to the steam inlet 8 of the pump container 1. The steam passes through a small opening in the steam inlet 8 and forms a steam jet 17 in the upper region of the pump container 1. The steam inlet has a plurality of openings to generate a plurality of steam jets. Furthermore, one or more baffles or deflectors can be provided in the entrainment zone to form and guide the vapor jet.

The gas flows out of the container in which the reduced pressure is maintained and flows into the upper region of the pump container 1 via the path 5 and the gas inlet 4. The gas flowing into the pump container 1 comes into contact with the vapor jet 17 and is entrained in the jet by being diffused in the jet. The steam jet 17 moves with the entrained gas to the outer region of the pump container 1 and comes into contact with the container body 2. Under the cooling action of the cooling tube 10, the vapor in the region of the container body 2 condenses on the inner surface of the body 2. The cooling medium flowing in the cooling tube 10 is conveniently water. The condensed wax flows down on the inner surface of the main body 2, collects in the lower part of the pump container 1, and finally flows out of the container by the condensed wax outlet 9. The condensed wax is circulated to the wax vaporizer 14 via the path 11, the wax circulation pump 12, and the path 13.

The gas exits the pump container 1 via the gas outlet 6 together with the uncondensed wax vapor. The removal of gas and uncondensed vapor is performed by a fore pump connected via line 7 to the gas outlet. The fore pump may be any suitable pump, such as a rotary oil sealed pump device. The above-described method and apparatus according to the present invention can be used to generate and maintain vacuum at any step known in the art that requires operation at vacuum. Examples include freeze-drying used in the food industry, as well as vacuum distillation used to purify the heat sensitive materials.

However, the method and apparatus of the present invention, which relies on paraffin wax as the pump fluid, when used for vacuum distillation of paraffin wax has the efficiency and efficiency of a diffusion vacuum pump compared to similar pumps that rely on conventional pump fluids. It has been found that the operation gives a particularly significant improvement. This is particularly surprising given the current knowledge of operating diffusion vacuum pumps. In this regard, reference is made to Ullmann Encyclopedia of Industrial Chemistry. Ullmann Encyclopedia Part 21 (Vol. B3) generally describes various aspects of decompression techniques. Subsection 2.3.2.3 of subsection 21. Provides a summary of the properties required of pump fluids for efficient operation of diffusion vacuum pumps. In particular, it has been shown that the pumped gas must have a low solubility in the pump fluid. Therefore, it is particularly surprising that paraffin wax is an excellent pump fluid for use in pumping wax vapors.

Accordingly, in another aspect, the present invention produces steam by heating a paraffin wax reservoir and discharges the steam through an inlet into the gas entrainment zone to generate a vapor jet within the entrainment zone, thereby producing a wax. Vaporize and distill in the distillation zone, contact at least a portion of the vaporized wax from the distillation zone with a vapor jet in the entrainment zone, move the vapor jet containing vaporized wax to the condensation zone and contain vaporized wax. A method for distilling paraffin wax is characterized in that the vapor from the vapor jet is condensed in a condensation zone and the condensed wax and uncondensed material are recovered separately. The paraffin wax used in the method of this aspect according to the invention can be any wax or wax fraction described above. The paraffin wax distillation method is particularly advantageous when used for refining the above-mentioned paraffin wax produced using the Fischer-Tropsch synthesis method.

According to another aspect of the present invention, there is provided a diffusion decompression pump including a paraffin wax storage tank, heating means for generating steam from the paraffin wax, a steam conduit forming a steam passage, and a pump container. This vessel comprises a gas entrainment zone, a vapor inlet connected to the vapor conduit to form vapor entering the pump vessel into a vapor jet extending into the gas entrainment zone, and a gas entering the pump vessel for the vapor jet. A gas inlet for contact with
It consists of a vapor condensing zone arranged to receive the gas and vapor jet exiting the entrainment zone, cooling means for condensing the vapor in the vapor condensing zone, and means for separately recovering condensed vapor and uncondensed material from the condensing zone. , Further comprising an evaporator, which comprises a distillation zone, heating means for evaporating the paraffin wax to be distilled in the distillation zone, and an outlet for the evaporation wax, which is used as a gas inlet of the diffusion pressure reducing pump. Provided is a paraffin wax distillation apparatus characterized by being connected.

The paraffin wax which forms part of the device of this aspect according to the invention can be any wax or wax fraction described above. Specific examples of the diffusion vacuum pump are as described above with reference to the accompanying drawings. The evaporator is any micro-vacuum evaporator or short-pass evaporator known in the art and applicable to the distillation of heat-sensitive materials, such as the falling film evaporator or wiped liquid film evaporator described above. be able to. The use of a wiped liquid film evaporator is particularly suitable for purifying waxes made using the Fischer-Tropsch synthesis method. As can be seen from the description of the apparatus shown in the drawings and its operation which constitutes the third aspect of the present invention, the evaporation wax flowing out of the distillation zone in the method and apparatus for distilling paraffin wax relates to the operation of a diffusion vacuum pump. Generates the gas described above. During operation of this method, vaporized wax is diffused into and entrained in the vapor jet. The wax vapor mixture then travels to the condensation zone. It will be appreciated that condensation of both part of the wax vapor forming the vapor jet and part of the vaporized wax from the distillation zone can occur. The operating conditions at any point in the distillation apparatus for the purification of paraffin wax must be maintained to avoid substantial solidification of the wax being distilled or the wax being used as the pump fluid.

The typical operating conditions of the distillation process for the purification of paraffin wax are known in the art. The method should operate at a temperature above which the wax begins to solidify. However, this method should not operate at or above the temperature at which the wax undergoes thermal decomposition. The preferred operating temperature is less than 300 ° C, more preferably less than 275 ° C. Preferably the diffusion vacuum pump is
The pressure in the distillation zone is 1 to 20 Pa, more preferably 5 to
It should be operated to maintain the range of 15 Pa. If it is necessary to produce various wax fractions (for example, the above-mentioned fractions), the purification of the wax feedstock can be carried out in multiple steps, each step comprising an apparatus and operation of the type described above. In general, the waxes used as pump fluids in vacuum pumps for the processing of waxes have properties that are similar (and more preferably substantially the same) to the wax vapor being pumped in, such as melting point, carbon number distribution and boiling range. To be selected.

[0022]

EXAMPLES The present invention will be further described below with reference to examples. Paraffin wax was made by the Fischer-Tropsch synthesis using the following method: According to the procedure described in EP-A-0428223,
A cobalt / zirconium / silica catalyst was prepared. The catalyst is charged into a reaction vessel, the catalyst is mixed with hydrogen and nitrogen at a temperature of 250 ° C., a pressure of 5 bar and 500-60.
Reduction was carried out by contacting at a gas hourly space velocity of 0 Nl / l / h. The activated catalyst is then admixed with a mixture of carbon monoxide and hydrogen having a hydrogen / carbon monoxide ratio of 1: 1 with a gas inlet pressure of 37-39 bar, a temperature of 210-220 ° C. and 1110-1130 Nl / l. The contact was performed at a gas hourly space velocity of / h. The reaction product was essentially a mixture of paraffinic hydrocarbons.

The hydrocarbon fraction was subjected to conventional distillation to remove the C ₂₀ -component, leaving a C ₂₁ + hydrocarbon mixture. The resulting mixture was subjected to vacuum distillation to further remove C ₂₁ +
The hydrocarbon mixture was purified to a range of wax fractions. The light and heavy fractions, each with a paraffin content of greater than 99%, were selected for further testing. Light wax fraction is 90
It was composed of more than wt% paraffins in the C _{18 to} C ₂₇ range. The heavy wax fraction consisted of greater than 75% by weight paraffins in the C _{28 to} C ₄₀ range. The light wax fraction and the heavy wax fraction were each tested for performance as pump fluids in a 18B4A steam booster pump commercially available from Edwards High Vacuum International. The pump had the general arrangement shown in the drawing. The operating conditions of the pump and the performance of the two fractions are summarized in the table below. In each test, the pump was operated at a power of 6.0 kW. Pump throughput is 0.05
When reducing pressures to mbar and 0.1 mbar were determined for each of the two fractions. The pumping rate was determined for each fraction when producing a vacuum of up to 0.005 mbar. For comparison purposes, a similar test was performed by using a commercially available apiezon oil (AP201) of the type shown in the above US Pat. No. 2,560,913 as the pump fluid.
The results of this test are also shown in the table below.

[0024]

[Table 1] Table Pump fluid Light wax Heavy wax Apiezon Fraction Fraction ( AP201 ) Output (kW) 6.0 6.0 6.0 6.0 Throughput (mbarl / s) 0.03 mbar 81 70 50 0.1 mbar 92 80 78 78 Pump speed (l / s) 9400 9400 4900 0.005 mbar

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the device according to the invention.

[Explanation of symbols] 1 pump container 2 body 3 upper end 4 gas inlet 6 gas outlet 8 steam inlet 9 Wax outlet 12 Circulation pump 14 Wax vaporizer

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Joachim Anzolge Netherlands 2596 H. Earl, The Hague, Karel van Bilantran 30 (72) Inventor Rippu Pyan Kuh Netherlands 2596 H. Earl, The Hague, Karel Juan Billantran 30 (56) References US Patent 2338583 (US, A) US Patent 2358067 (US, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F04F 9/00 F04B 37 / 16 C10G 7/06

Claims (16)

(57) [Claims] 1. When generating a reduced pressure in a container, steam is generated by heating a paraffin wax storage tank, and this steam is discharged through an inlet to a gas entrainment zone connected to the container to enter the entrainment zone. Generate a steam jet,
Injecting gas from a vessel into a vapor jet, moving a vapor jet containing gas to a condensation zone, condensing vapor from the vapor jet in the condensation zone, and collecting condensed wax and uncondensed material separately. A method of generating reduced pressure characterized by: 2. A process according to claim 1, characterized in that the wax consists of paraffins in the range C ₁₅ -C ₇₀ . 3. Process according to claim 1, characterized in that the wax consists of more than 70% by weight of paraffin. 4. The method according to claim 1, wherein the wax comprises a large amount of normal paraffin. 5. A wax comprising a C ₁₅ -C ₂₀ paraffin in an amount of at least 60% by weight of the total paraffin content, a wax comprising a C ₂₀ -C ₃₀ paraffin in an amount of at least 60% by weight of the total paraffin content. A wax consisting of C _{30 to} C ₄₀ paraffins in an amount of at least 60% by weight of the total paraffin content, or a wax consisting of C ₄₀ + paraffins in an amount of at least 60% by weight of the total paraffin content, Claims 1-4
The method according to any one of 1. 6. The method according to claim 1, wherein the wax has a freezing point of 10 to 120 ° C. 7. Wax is 1-20 as measured at 120.degree.
7. It has a viscosity of mm ² / s, characterized in that
The method according to any one of 1. 8. The method according to claim 1, wherein the wax is a synthetic wax. 9. The method of claim 8 wherein the wax is made by Fischer-Tropsch synthesis using a catalyst consisting of cobalt as the catalytically active metal. 10. A paraffin wax storage tank, heating means for generating steam from the paraffin wax, a steam conduit forming a passage for the steam, and a pump container, the container comprising a gas entrainment zone and a steam conduit. A steam inlet that is connected and forms steam that flows into the pump vessel into a steam jet that extends into the gas entrainment zone, a gas inlet that contacts the gas that flows into the pump vessel with the steam jet, and exits from the entrainment zone. A reduced pressure characterized in that it comprises a vapor condensing zone arranged to receive a gas and a vapor jet, cooling means for condensing the vapor in the vapor condensing zone, and means for separately recovering the condensed vapor and gas from the condensing zone. Generator. 11. A paraffin wax storage tank is heated to generate steam, which is discharged into the gas entrainment zone through an inlet to generate a vapor jet in the entrainment zone to evaporate the wax and distill the zone. Vaporizing from the vapor jet containing vaporized wax by distilling in the vapor and contacting at least a portion of the vaporized wax from the distillation zone with the vapor jet in the entrainment zone to move the vapor jet containing vaporized wax to the condensation zone A method for distilling paraffin wax, characterized in that the condensed wax and the uncondensed substance are separately recovered while being condensed in a condensation zone. 12. A process according to claim 11, characterized in that the wax to be distilled is prepared by the Fischer-Tropsch synthesis. 13. Process according to claim 11 or 12, characterized in that the distillation is carried out at a temperature below 300 ° C. 14. Process according to claim 11, characterized in that the distillation zone is maintained at a pressure in the range 1 to 20 Pa. 15. A diffusion decompression pump, which comprises a paraffin wax storage tank, heating means for generating steam from the paraffin wax, a steam conduit forming a steam passage, and a pump container. Is a gas entrainment zone, a steam inlet connected to the steam conduit to form steam entering the pump vessel into a steam jet extending into the gas entrainment zone, and a gas inlet for contacting the gas entering the pump vessel with the steam jet And a vapor condensing zone arranged to receive the gas and vapor jet exiting the entrainment zone, and cooling means for condensing the vapor within the vapor condensing zone,
It comprises means for recovering condensed vapor and uncondensed substances separately from the condensing zone, further comprising an evaporator, which comprises a distillation zone, heating means for evaporating the paraffin wax to be distilled in the distillation zone, and evaporation. A paraffin wax distillation apparatus comprising a wax outlet and the outlet connected to the gas inlet of a diffusion pressure reducing pump. 16. The apparatus according to claim 15, wherein the evaporator is a falling liquid film evaporator or a wiped liquid film evaporator.