MXPA98006558A

MXPA98006558A - Procedure for the conversion of a current, which contains hydrocarbons, by parc oxidation

Info

Publication number: MXPA98006558A
Application number: MXPA/A/1998/006558A
Authority: MX
Inventors: Zhijie Chen
Original assignee: L'air Liquide Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude
Priority date: 1997-08-14
Filing date: 1998-08-13
Publication date: 1999-09-20

Abstract

The air is distilled in a single column (8), installed on a boat, and from there, a liquid enriched with oxygen is extracted. This flow is pressurized by a pump (9), and vaporized by a heat exchanger with air or nitrogen. Oxygen (105) is used for the partial oxidation of a stream (101) containing hydrocarbons, for example from natural gas.

Description

PROCEDURE FOR THE CONVERSION OF A CURRENT, WHICH CONTAINS HYDROCARBONS. FOR PARTIAL OXIDATION The present invention relates to a process and a plant for the conversion of a stream, which contains hydrocarbons, by partial oxidation. • In this type of procedure, a stream, which relies on hydrocarbons, typically natural gas, becomes a synthesis gas, after partial oxidation with oxygen or air enriched with oxygen. This conversion can be carried out by a reforming procedure, for example of the ATR type (Autothermal Reforming), which makes it possible to produce a synthesis gas. Following the catalytic conversion, the synthesis gas is converted into liquid hydrocarbons (kerosene, diesel, naphtha). This type of process is described in patents US 5 628 931, WO 93 15999, GB 2249555, GB 2183672, EP 214 432 A. The present invention also relates to a process and a plant for air separation by cryogenic distillation and, in particular, to those processes and plants that make it possible to produce oxygen. According to an object of the invention, a method is provided for the conversion of a stream containing hydrocarbons, by partial oxidation with oxygen, characterized in that the oxygen necessary for the conversion is separated by cryogenic distillation from the air into a single column, installed on a boat. According to other aspects of the invention, the current containing hydrocarbons is methane, natural gas or LPG, oxygen is withdrawn from the single column in liquid, pressurized and vaporized form, the conversion is carried out by a reforming process, which produces a synthesis gas, whose reformation is followed by the catalytic conversion of this synthesis gas into liquid hydrocarbons, the nitrogen necessary for the process is produced by adsorption or permeation. According to another object of the invention, a plant is provided for the conversion of a hydrocarbon-containing stream, comprising a partial oxidation unit fed with oxygen, characterized in that it includes an air separation apparatus, which includes a single column (8), installed on a boat. Oxygen is generally produced by the distillation of air in a double column. When this column is placed on an unstable support, such as the deck of a vessel, the quality of the distillation is degraded, because the plates or packages, contained in the column, can not function properly. The articles "Nitrogen for Inserting", Tank and Bulk Carrier, November 1973 and "Distillation Problems on a Floating Plant" CEP, November 1982, describe solutions to improve distillation on a vessel. The object of this invention is to provide an air separation process which is compatible with the working conditions on a boat. According to another object of the invention, a method is provided for the separation of air by cryogenic distillation in a single column, in which: i) the air, which is to be distilled, is sent inside a single column, where it is separated in a steam enriched with nitrogen and a liquid enriched with oxygen; ii) the base of the column is heated by means of a cauldron; characterized in that at least some of the liquid enriched with oxygen is extracted, pressurized and vaporized by the exchange of heat with a pressurized flow. According to other aspects of the invention, the fluid used to heat the cauldron is nitrogen or some of the air to be distilled; the air sent to the cauldron comes from a turbine, optionally coupled to a booster or boost device; - the pressurized flow is the air at a driven pressure or the compressed nitrogen; -the steam is removed from the head of the column and at least some of it is compressed, at least some of the compressed nitrogen is recycled to the column; - a liquid enriched with oxygen is produced; - at least some of the air attempted for the column, is cooled to an intermediate temperature in a heat exchanger, before being expanded, optionally to the pressure of the column, in a turbine. According to another aspect of the invention, a plant for air separation by cryogenic distillation is provided, which comprises: a single column, an element for feeding the single column with air; - a cauldron at the base of the single column; an element for sending a heating fluid to the cauldron; characterized in that it comprises: - an element for extracting a liquid enriched with oxygen from the base of the single column; - an element for pressurizing at least some of the liquid; - an element for vaporizing at least some of the pressurized liquid by exchanging heat with a pressurized flow. According to other aspects of the invention, the cauldron is heated with nitrogen or at least some of the air to be distilled; - this cauldron is connected to a turbine; - the pressurized flow is the air at a driving pressure, or the compressed nitrogen; - elements are supplied to compress a flow enriched with nitrogen, extracted from the head of the column; the only column contains plates or structured packing. Other aspects of the invention will now be described with reference to Figures 1 to 3, which are process diagrams according to the invention. In Figure 1, an air flow is compressed by compressor 1 at a pressure of 4.5 bar and purified in unit 2 to remove water and CO2.

A first fraction of the air has its pressure raised to 6 bars by the booster 4, is partially cooled in the exchanger 6 and expands in the turbine 5 to 1.4 bar. The fraction is then supercooled in exchanger 10, before being sent to column 8, installed on a vessel 31. A second air fraction has its pressure raised to 70 bars in booster 3 and condenses, at least partially , in the exchanger 6. The rest of the air passes completely through the exchanger 6, is condensed, at least partially, in the cauldron 7 of the base and is sent to the head of the column 8, after having been overcooled and expanded in a valve. A flow containing oxygen, with a purity of at least 95%, in liquid form, is extracted from the base of column 8, pumped at a pressure of 36 bar (in 9) and vaporized in exchanger 6 by the exchanger of heat with the air at a reinforced pressure of 70 bar. The steam enriched with nitrogen is extracted from the head of the column 8 and heated in the exchangers 10 and 6. Figure 2 shows the turbine driven 4, 5, but the booster 3 is replaced by a nitrogen cycle.

The steam enriched with nitrogen is heated to room temperature and compressed at 70 bar by a compressor 30. At least some of the compressed nitrogen is recycled to the column, after having been cooled in exchangers 6 and 10. The procedure can be simplified (Figure 3) to use a single air compressor. All the air is compressed by the compressor 4 at approximately 28 bars and then cooled in the exchanger 6 to an intermediate temperature, at which some of the air is extracted, expanded and sent into the cauldron 7, where it is condensed, at least partially , before being expanded in a valve and sent to the head of the column 8. The rest of the air continues to cool and liquefies in the exchanger 6, is overcooled in the exchanger 10 and is sent to the column, after has mixed with the other part of the air. Figure 4 shows a process diagram, according to the invention, in which air 103 is distilled in an air separation unit 104, such as that illustrated in Figures 1 to 3. Vaporized liquid oxygen 105 is sent to a partial oxidation unit 102, also supplied with natural gas 101. The synthesis gas 107, produced in this manner, is subjected to a catalytic conversion stage 109 (of the FISCHER-TROPSCH type), in order to produce hydrocarbons liquids (kerosene, diesel and / or naphtha).

Claims

CLAIMS 1. Procedure for the separation of air by cryogenic distillation in a single column (8), in which: i) the air, which is to be distilled, is sent inside a single column, where it is separated in a steam enriched with nitrogen and a liquid enriched with oxygen; ii) the base of the column is heated by means of a cauldron (7); e (iii) at least some of the liquid, enriched with oxygen, is extracted, pressurized and vaporized by the exchange of heat with a pressurized flow; characterized in that the cauldron (7) is heated with an air flow.
2. Process, according to claim 1, in which the air sent to the cauldron, coming from a turbine (5), is optionally coupled to a pulse device (4):
3. Process, according to one of claims 1 and 2, in which the pressurized flow is the air at a boosted pressure, or the compressed nitrogen.
4. Process according to one of claims 1 to 3, in which the steam is extracted from the head of the column (8) and at least some of it is compressed.
5. Process, according to claim 4, in which at least some of the compressed steam is recycled to the column (8).
6. Process, according to one of the preceding claims, in which a liquid enriched with oxygen is produced.
7. Process, according to one of claims 1 to 6, in which at least some of the air, attempted for the column (8), is cooled to an intermediate temperature in a heat exchanger (6), before being expanded, optionally at the pressure of the column, in a turbine (5).
8. A plant for air separation by cryogenic distillation, this plant comprises: a single column (8); an element for feeding the single column with air (103); a cauldron (7) at the base of the single column; an element for sending a heating fluid to the cauldron; an element for extracting the liquid enriched with oxygen from the base of the single column; an element (9) for pressurizing at least some of the liquid; an element (6) to vaporize at least some of the pressurized liquid by the heat exchange with a pressurized flow; characterized in that the heating fluid is air.
9. The plant, according to claim 8, wherein the cauldron (7) is connected to a turbine (5).
10. The plant, according to one of claims 8 and 9, in which the pressurized flow is air at a boosted pressure, or compressed nitrogen.
11. The plant, according to one of claims 8 to 10, comprising an element (30) for compressing a flow enriched with nitrogen, extracted from the head of the column (8).
12. The plant according to one of claims 8 to 11, wherein the single column contains plates or structured packages.
13. The use of a plant, according to one of claims 8 to 12, on a vessel.
14. Process for the conversion of a stream (101) containing hydrocarbons, by partial oxidation with oxygen; characterized in that the oxygen necessary for the conversion is separated by cryogenic distillation of air in a single column (8), installed on a boat.
15. The process, according to claim 14, wherein the stream containing hydrocarbons is methane, natural gas or LPS.
16. The process, according to claims 14 or 15, in which the oxygen is extracted from the single column in liquid form, is pressurized and vaporized.
17. The process according to claims 14 to 16, wherein the conversion is carried out by a reforming process that produces a synthesis gas, whose reformation is followed by the catalytic conversion of the synthesis gas into the liquid hydrocarbons.
18. The process, according to claims 14 to 17, wherein the nitrogen necessary for the process is produced by adsorption or permeation.
19. Plant for the conversion of a current (101) which contains hydrocarbons, comprising one unit (102) partial oxidation, fed with oxygen; characterized in that it comprises an air separation apparatus (104), which includes a single column (8), installed on a boat (31).