Refrigeration – Cryogenic treatment of gas or gas mixture – Separation of gas mixture
Reexamination Certificate
2002-01-15
2003-12-23
Bennett, Henry (Department: 3744)
Refrigeration
Cryogenic treatment of gas or gas mixture
Separation of gas mixture
Reexamination Certificate
active
06666048
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a process for increasing the capacity of a separation apparatus and an air separation process and apparatus.
BACKGROUND OF THE INVENTION
Industrial plants frequently treat at least one gaseous mixture by distillation and/or liquefaction and/or adsorption and/or permeation to produce at least one product which may include energy in the form of electricity or steam or a gaseous or liquid product having a composition or state different from that of one of the gaseous mixtures treated.
Generally when the product requirement increases, in a first phase, the capacity of the plant is pushed to the limit by increasing the amount of mixture treated and, if necessary, changing the plant equipment to permit this increase. Once the maximum capacity of the existing plant is not sufficient, a second phase is initiated and a further similar plant is constructed to supply the additional requirements, by itself producing part of the required product.
For example, in many cases, an air separation plant must supply variable amounts of gas and liquid over its lifetime. If the amount of product required increases, in the first phase, the air separation plant can be operated at maximum capacity as disclosed in EP-A-0678317 to increase the amount of air sent to the column.
Additionally different products may be required during the lifetime of the plant. For example, the purity required for a supplied gas may change or a gas not initially needed may subsequently be requested. Thus as described in U.S. Pat. No. 4,869,742 and EP-A-0699884 (S3901), additional trays may be placed within the column of an existing plant or a new column may be added to an existing plant as a retrofit so as to provide a new product. In the examples of
EP-A-0081472 and U.S. Pat. Nos. 4,433,990 and 4,715,874 a plant which produces only oxygen is modified to produce argon also.
GB-A-1416163 and J-A-11325718 disclose modifying an existing plant by increasing the oxygen content of the air fed to the separation unit, using a membrane or a PSA.
Research Disclosure 39361 (January 1997) describes the integration of a mixing column into an existing air separation plant.
U.S. Pat. No. 5,170,630 discloses improving the purity of nitrogen produced by a plant by modifying the condenser and column and adding a phase separation tank and associated piping.
EP-A-0628778 describes an air separation plant in which liquid oxygen from a column of the plant and liquid oxygen from an external source are mixed and vaporized in the heat exchanger of the air separation plant.
In particular, the apparatus and process of the invention allows the capacity of an existing air separation unit to be increased beyond the limits of previously known systems.
It is known for an air separation apparatus to comprise a double column and a further column fed by air. In such cases the further column is commonly a mixing column fed by an oxygen rich liquid at the top of the column as disclosed in U.S. Pat. Nos. 4,022,030, 4,883,517, 5,244,489, 5,291,737 and EP732556.
Nitrogen stripping columns are also known from EP387872, EP532155 and EP542559. In none of these cases is an air stream fed to the column.
It is an object of the present invention to minimize the cost of the second phase by using an additional plant which may or may not directly produce any of the additional product required but which is linked to the existing plant by exchanges of matter and /or energy so that the existing plant can produce the additional quantity of product required as well as new products, in some cases.
Thus the aim of the invention is to increase the amount of a first product of an installation comprising a first existing unit only from A mol. /h before modification to Cmol/h following modification, the production of the first unit being boosted to A+B mol./h, A+B being less than or equal to C and of course greater than A.
The modification consists in incorporating in the installation a second unit and sending energy and/or matter either from the first unit to the second unit or from the second unit to the first unit such that the production of the first unit is boosted to A+B.
In certain cases, where A+B is smaller than C, the difference B′ mol./h may be produced directly by the second unit and mixed with A+B from the first unit to produce C om the whole installation.
The pressure of the first product in amount A and amount C may vary by up to 5 bars.
The temperature of the first product in amount A and amount C may vary by up to 25° C., or preferably 5° C.
It will generally be the case that the total amount of feed in mol./h sent to the existing first unit before modification will be less than the total amount of feed sent to the first unit (or to the first and second units if feed is sent to both).
SUMMARY OF THE INVENTION
According to a first embodiment of the invention, there is provided a process for increasing the amount of at least one product produced by a first unit for treating at least one fluid mixture by at least one of the group of processes comprising pressurization, expansion, distillation, mixing in a mixing column, liquefaction, adsorption and permeation wherein at least one fluid mixture is sent to the first unit and at least one product is removed from the first unit, said product having a different composition from said at least one fluid mixture and optionally a different state and/or a different pressure from said at least one fluid mixture, wherein the first unit alone before integrating a second unit to the first unit produces an amount A moles/h of a first product and said amount of first product withdrawn from the first unit and optionally from the second unit is increased to C moles/h, C being greater than A, and the amount C comprising at least one fluid stream withdrawn from the first unit and optionally from the second unit, by integrating the second unit with the first unit, said integration comprising sending energy and/or at least one fluid from the first unit to a second unit and/or from the second unit to the first unit, wherein said second unit treats at least one fluid mixture by at least one of the group of processes comprising pressurization, expansion, warming, cooling, distillation, mixing in a mixing column, liquefaction, adsorption and permeation such that the first unit produces an amount of first product A+B moles/h.
The first unit comprises means for carrying out at least one of the group of processes comprising pressurization, expansion, distillation, mixing in a mixing column, liquefaction, adsorption and permeation. It may also include other means such as pretreatment means for cooling and/or purifying and/or compressing, storage means or insulation means, for example a cold box.
The second unit comprises means for carrying out at least one of the group of processes comprising pressurization, expansion, warming, cooling, distillation, mixing in a mixing column, liquefaction, adsorption and permeation. It may also include other means such as pretreatment means for cooling and/or purifying and/or compressing, storage means or insulation means, for example a cold box.
The amount of first product may be increased such that A+B is less than or equal to C.
Where A+B is less than C, the difference between C and A+B is an amount of product B′ moles/h produced by the second unit.
The compositions of the first product before and after integration need not be strictly identical: for example the percentage of principal component in the first product in amount A and amount C may differ by up to 5 mol. %, up to 1 mol. % or up to 0.2 mol. %.
Similarly the composition of the first product produced by the first and second units, before or after integration need not be strictly identical: for example the percentage of principal component in the first product in amount A and amount B′ may differ by up to 10 mol. % or up to 5 mol. % or up to 2 mol. %
In some cases, the second unit treats a mixture having substantially the sam
Bretesche Jean-Luc
Brugerolle Jean-Renaud
Darredeau Bernard
Fossier Alain
Guillard Alain
Bennett Henry
Drake Malik N.
L'Air Liquide - Societe Anonyme a Directoire et Conseil de
Young & Thompson
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