Chemistry: fischer-tropsch processes; or purification or recover – Plural zones each having a fischer-tropsch reaction
Reexamination Certificate
2002-10-08
2004-09-21
Parsa, J. (Department: 1621)
Chemistry: fischer-tropsch processes; or purification or recover
Plural zones each having a fischer-tropsch reaction
C518S702000, C518S703000, C518S704000, C518S705000
Reexamination Certificate
active
06794418
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for increasing production in an existing processing plant and to a processing plant that has been modified in order to carry out the method.
DESCRIPTION OF THE INVENTION BACKGROUND
Today, in the building of new processing plants, such as, e.g., plants for the production of methanol from natural gas or other suitable carbon sources, there is a clear trend towards building plants with an ever-increasing production capacity, such as more than 5000 tonnes of methanol each day. Thus, production costs are reduced due to economies of scale.
In areas where the price of natural gas is low, it is possible to produce methanol at a cost of as little as about USD 80 per tonne, and this is allowing methanol to obtain a foothold in a fuel market, i.e., for fuel cell cars and electricity production.
For existing processing plants that are too small in relation to current demands, there is a need to find solutions which allow an increase of total production and thus a reduction in production costs per unit without having to make major costly conversions and refits of the existing processing plant.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide a method of increasing production in an existing processing plant without necessitating major, costly conversions of the existing plant, and to provide a processing plant that has been modified in order to carry out the present method.
According to the present invention, this is achieved by means of a method for increasing production in an existing processing plant for the conversion of natural gas to a product, wherein the natural gas is first converted to a synthesis gas in a synthesis gas section, the synthesis gas is reacted in a reactor for synthesis of the product, where non-converted synthesis gas and product are separated into two streams, where a product-rich stream is taken out of the process, whilst a product-poor stream is recycled as feed to the reactor together with make-up synthesis gas, and where a portion of the recycle stream is taken out of the recycle loop as a purge gas, where the purge gas is separated into hydrogen-rich and hydrogen-poor streams, where hydrogen-rich streams are introduced into steps in the process in which it is desirable to have a supplement of hydrogen, and where the residual thermal value of the hydrogen-poor stream may, if desired, be used for heating before it is discharged.
It is preferable that the synthesis gas from the synthesis gas section should be fed with a hydrogen-rich stream from the separated purge gas, and that this hydrogen-enriched synthesis gas should be passed through a new once-through reactor for production of the product and through a unit in order to separate a product-rich stream that is taken out, and a product-poor stream that is used as feed in the original reactor.
It is also preferable that the product-poor stream which is used as feed for the original reactor should be fed with additional synthesis gas that is produced in a separate secondary synthesis gas line.
The existin, reactor will preferably be operated virtually unchanged.
It is preferable that the secondary synthesis gas line should be based on ATR or POX.
It is also preferable that the product should be methanol or dimethyl ether.
Also provided is a processing plant for the production of a product based on natural gas, where the processing plant comprises a synthesis gas section for producing synthesis gas that mainly consists of CO, CO
2
, H
2
and water, a synthesis section where the product is formed, and a purification section where the product is separated from unconverted reactants and other substances and purified, where unconverted reactants that are separated from the product are recycled to the synthesis section, and where a portion of the gas that is recycled is drawn off in a line in order to prevent build-up of inert gases, where the plant also comprises a separation unit for separating the gas that is drawn off in a line into hydrogen-rich and hydrogen-poor fractions, a line for conveying hydrogen-poor fractions to optional combustion and lines for leading hydrogen-rich fractions into the natural gas feed and for recycling to the synthesis section respectively.
It is preferable that between the synthesis gas section and the synthesis section there should be provided a once-through reactor for synthesis of the product, and a separation unit for the separation of a product-rich fraction to a line and a product-poor fraction to a line leading to the synthesis section.
Furthermore, it is preferable that the processing plant should also comprise a separate secondary synthesis gas line for producing a secondary synthesis gas, and a line for conveying the secondary synthesis gas as feed for the synthesis section.
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Bahr Linda
Olsvik Ola
Sogge Jostein
Veland Bjørn Jarle
Kirkpatrick & Lockhart LLP
Parsa J.
Statoil ASA
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