Process and system to produce multiple distributable products from source, or imported LNG

Abstract

The process that includes providing the following elements for treating source refrigerated LNG, a heat exchanger/condenser through which refrigerated LNG passes, a vaporizer receiving LNG from the heat exchanger/condenser to produce heating grade LNG product, a distillation column producing distillate condensed in the heat exchanger/condenser to produce vehicle grade LNG, some of which is returned to the distillation column, the distillation column having input of refrigerated LNG, the distillation column having a lower outlet through which produced C2+is delivered.

Description

DRAWING DESCRIPTION

FIG. 1 is a diagram showing a preferred form of the invention.

DETAILED DESCRIPTION

In FIG. 1, the preferred form of the invention, heating grade source LNG, supplied at 10 as from a ship or transport vessel, is stored at 11, as imported LNG. It is desired that vehicle engine grade LNG be derived from the LNG stored at 11, and supplied for commercial purposes as at 12, as for example from storage at 13. A commercial transport vehicle is shown at 14 receiving the vehicle grade LNG.

The refrigerated heating grade LNG supplied at 20 as from storage 11 is pumped by main send out pump at 15 for delivery at 16 to heat exchanger/condenser apparatus 17, from which it flows at 18 to a vaporizer 19. The pump elevates the LNG to pipeline pressure, typically 50 to 100 atmospheres; and the vaporizer operates to heat the cold LNG to warm temperature, typically 10 to 20 degrees Centigrade, for conversion to gas. The gasified LNG is then delivered at 21 to a commercial pipeline 41, as HGLNG (heating grade LNG).

The process utilizes the “cold” containing in the LNG stream 20 to provide refrigeration to a distillation column 26 operating to purify the LNG to vehicle grade (typically 99% methane). A secondary pump 40 receives cold LNG stream 20a, and delivers it to a mid-point 41′ of column, as for example at about 7 bara. The column pressure may vary over a broad range, from about 4 bara to the critical point of methane.

The liquid LNG flowing through one side of the exchanger 17 is heated slightly (typically from 115 degK to 120 degK). The other side involves condensing a near pure methane gas stream 21 from column 26 at a higher than atmospheric pressure (typically 7 to 14 atm). Most of the condensed methane is delivered at 28 (for flow by gravity or pumping) to the top of the distillation column 26 as reflux.

The remainder of the condensed methane is delivered at 23 to VGLNG (vehicle grade LNG) storage 24, from which that product is controllably delivered at 25 to transport vehicles 26 for distribution to fuel stations for vehicles.

The distillation column 26 has a lower outlet 44, through which bottoms product such as C2+ is delivered at 45 to C2+ storage 46, and transport at 58 where C2+ constitutes a liquid hydrocarbon stream containing ethane and heavier hydrocarbon components.

The C2+ product may be refined into nearly pure ethane and a C3+ bottoms hydrocarbon. As an alternative arrangement, the C2+ stream can be delivered at 50 for combination with the HGLNG stream at point 51, for processing in vaporizer 19 and delivery to pipeline.

Also shown is a secondary heater vaporizer 56 receiving product (such as C2+) via stream 57 from a lower portion of the column 26, for returning lighter product (such as remanent methane), and bottoms, at 57 to the column at 58.

Accordingly, the invention provides a simpler, efficient method for producing three distributable products (HGLNG, VGLNG, C2+) from imported refrigerated LNG.

Claims

1. The process that includes providing the following elements for treating source refrigerated LNG: a) a heat exchanger/condenser through which refrigerated LNG passes,b) a vaporizer receiving LNG from the heat exchanger/condenser to produce heating grade LNG product,c) a distillation column producing distillate condensed in the heat exchanger/condenser to produce vehicle grade LNG, some of which is returned to the distillation column,d) the distillation column having input of refrigerated LNG,e) the distillation column having a lower outlet through which produced C2+ is delivered.

2. The process of claim 1 including a secondary heater vaporizer receiving product from a lower portion of the distillation column and returning product to a lower portion of the column.

3. The process of claim 1 wherein said C2+ product consists of ethane and heavier hydrocarbons.

4. The process of claim 1 wherein said LNG product is delivered to a pipeline gridsaid vehicle grade LNG not returned to the column is delivered to a transport facilitysaid C3+ product is delivered to another transport facility.

5. The process of claim 1 which includes pumping a first portion of said source LNG to elevated pressure level for passage to the heat exchanger/condenser for heat exchange with said distillate, condensed in the heat exchanger/condenser to produce vehicle grade LNG, some of which is returned to the distillation column,

6. The process of claim 5 which includes pumping a second portion of said source LNG to elevate pressure for passage to the distillation column, receiving input of refrigerated LNG,

7. The process of claim 1 wherein said source LNG is imported via a transport vessel, as refrigerated LNG.

8. A system for treating heating grade source LNG to form engine fuel grade LNG, comprising: a) means for distilling a stream of said source LNG to form purified distillate,b) a heat exchanger/condenser,c) means for passing said distillate in heat exchange relation with refrigerated source LNG in the heat exchanger/condenser to condense distillate thereby forming condensate which constitutes said engine fuel grade LNG,d) and returning a portion of such condensate to said means for distilling said stream of source LNG.

9. The system of claim 8 which includes a vaporizer and a pumping means operating to pump a stream of said heating grade LNG through the heat exchanger/condenser, for supply to the vaporizer.

10. The system of claim 9 wherein the vaporizer has means for receiving heating grade LNG and for producing heating grade natural gas from said LNG, for commercial distribution.

11. The system of claim 8 including pumping means for pumping said source LNG to elevated pressure level for passage to the heat exchanger/condenser heat exchange with refrigerated source LNG in the heat exchanger/condenser to condense distillate thereby forming condensate which constitutes said engine fuel grade LNG.

12. The system of claim 21 including means for passing a reflux portion of condensate, to said distillation column at an upper level therein