System and method for supplying backup production in air separation device

Abstract

A system and method for supplying a backup product in an air separation device, as well as a system and method for supplying a lower-pressure product to a user by means of pressurization of a cryogenic liquid pump during normal operation of an air separation device, i.e., when the cryogenic liquid pump is in the cold standby state. By means of the system and method, a cryogenic liquid product taken from a storage tank is pressurized by the cryogenic liquid pump to produce a lower-pressure product by taking full advantage of the low-speed operation of the cryogenic liquid pump in the cold standby state, and the lower-pressure product is transmitted to product supply lines of a user, to achieve the function of supplying the lower-pressure product to the user. The system and method not only reduce the energy loss of the cryogenic liquid pump in the cold standby state for a long time, but also avoid the bleeding rate of the cryogenic liquid product generated by sending a part of the cryogenic liquid product back to the storage tank, so that the advantage of quickly starting the cryogenic liquid pump from the cold standby state is ensured, and the requirements of the user to the higher-pressure product and the lower-pressure product can be satisfied.

Claims

1. A method for supplying a backup product using a backup system, the method comprising the steps of: a. providing the backup system, wherein the backup system comprises: i. a storage tank configured to store a cryogenic liquid product, the storage tank having a lower region, a middle region, and an upper region; ii. a cryogenic liquid pump in fluid communication with an outlet of the storage tank that is in the lower region of the storage tank, wherein the cryogenic liquid pump is speed adjustable and is also configured to pressurize the cryogenic liquid product sent out from the storage tank to form a pressurized product fluid; iii. a delivery pipeline in fluid communication with an outlet of the cryogenic liquid pump, the delivery pipeline having a liquid pump outlet control valve disposed thereon that is configured to control a flow of the pressurized product fluid; iv. a first product supply line disposed downstream of the liquid pump outlet control valve and in fluid communication with the delivery pipeline, wherein the first product supply line is configured to have an operating pressure at a first pressure; and V. a second product supply line disposed downstream of the liquid pump outlet control valve and in fluid communication with the delivery pipeline, wherein the second product supply line is configured to have an operating pressure at a second pressure, wherein the first pressure is lower than the second pressure; b. sending the cryogenic liquid product to the storage tank; c. during normal operation of the air separation apparatus, the method further comprises the steps of: i. extracting the cryogenic liquid product from the storage tank and then pressurizing the cryogenic liquid product using the cryogenic liquid pump running at a first speed, ii. delivering at least a portion of the pressurized product fluid to the first product supply line at the first pressure; and iii. an absence of sending any of the pressurized product fluid to the second product supply line; and d. during temporary operation when the air separation apparatus shuts down or the operation thereof slows down, the method further comprises the steps of: i. extracting the cryogenic liquid product from the storage tank and then pressurizing the cryogenic liquid product using the cryogenic liquid pump running at a second speed that is higher than the first speed, and ii. delivering at least a portion of the pressurized product fluid to the second product supply line at the second pressure.

2. The method as claimed in claim 1, wherein the cryogenic liquid pump is driven by a variable speed motor, and when a rotation speed of the variable speed motor is adjusted according to the operating pressure of the first product supply line, the cryogenic liquid pump is caused to run at the first speed, pressurizing the cryogenic liquid product to a pressure approximately equal to the operating pressure of the first product supply line; when the rotation speed of the variable speed motor is adjusted according to the operating pressure of the second product supply line, the cryogenic liquid pump is caused to run at the second speed, thereby pressurizing the cryogenic liquid product to the operating pressure of the second product supply line.

3. The method as claimed in claim 1, further comprising the step of vaporizing, in a vaporizer, the pressurized product fluid to provide a pressurized gas product, wherein the vaporizer is disposed on the delivery pipeline between the liquid pump outlet control valve and the first product supply line and the second product supply line.

4. The method as claimed in claim 3, wherein the vaporizer is an air bath vaporizer or a water bath vaporizer.

5. The method as claimed in claim 1, wherein the first product supply line comprises at least one depressurization device that is configured to depressurize the pressurized product fluid, which is received from the delivery pipeline, to the operating pressure of the first product supply line.

6. The method as claimed in claim 1, wherein the cryogenic liquid product is liquid oxygen, liquid nitrogen or liquid argon.

7. The method as claimed in claim 1, wherein the cryogenic liquid product is produced by the air separation apparatus.

8. A method for supplying a backup product from a backup system of an air separation apparatus, the method comprising the steps of: providing the backup system, wherein the backup system comprises: i. a storage tank configured to store a cryogenic liquid product, the storage tank having a lower region, a middle region, and an upper region; ii. a cryogenic liquid pump in fluid communication with an outlet of the storage tank that is in the lower region of the storage tank, wherein the cryogenic liquid pump is speed adjustable and is also configured to pressurize the cryogenic liquid product sent out from the storage tank to form a pressurized product fluid; iii. a delivery pipeline in fluid communication with an outlet of the cryogenic liquid pump, the delivery pipeline having a liquid pump outlet control valve disposed thereon that is configured to control a flow of a pressurized product fluid; iv. a first product supply line disposed downstream of the liquid pump outlet control valve and in fluid communication with the delivery pipeline, wherein the first product supply line is configured to have an operating pressure at a first pressure; and v. a second product supply line disposed downstream of the liquid pump outlet control valve and in fluid communication with the delivery pipeline, wherein the second product supply line is configured to have an operating pressure at a second pressure, wherein the first pressure is lower than the second pressure; extracting the cryogenic liquid product from the storage tank; vaporizing at least a portion of the cryogenic liquid product in a vaporizer to form a gaseous product; determining whether to operate in a normal operating state or a temporary operating state, wherein the normal operating state comprises the steps of: operating the cryogenic liquid pump in a cold standby state, wherein the cold standby state includes a cold standby flow rate and a cold standby operating pressure; and sending the gaseous product to only the first product supply line at the first pressure such that no gaseous product is sent to the second product supply line during the cold standby state; wherein the temporary operating state comprises the steps of: operating the cryogenic liquid pump in a backup state, wherein the backup state includes a backup flow rate and a backup operating pressure, wherein the backup operating pressure is higher than the cold standby operating pressure; and sending the gaseous product to the second product supply line at the second pressure.

9. The method as claimed in claim 8, wherein the cold standby operating pressure is based on the operating pressure at the first pressure and the backup operating pressure is based on the operating pressure at the second pressure.

10. The method as claimed in claim 8, wherein the speed-adjustable cryogenic liquid pump is driven by a variable speed motor.

11. The method as claimed in claim 8, wherein the liquid pump outlet control valve is configured to adjust a flow rate of the pressurized product fluid passing through the delivery pipeline.

12. The method as claimed in claim 8, wherein a liquid pump back-flow control valve can adjust a flow rate of the pressurized product fluid passing through a recycle fluid circuit.

13. The method as claimed in claim 8, further comprising a recycle fluid circuit in fluid communication with the outlet of the cryogenic liquid pump and an inlet of the storage tank, wherein the inlet is the upper region of the storage tank, wherein the recycle fluid circuit is configured to transfer at least a recycled portion of the pressurized product fluid from the outlet of the cryogenic liquid pump into the storage tank, wherein the recycle fluid circuit further comprises a liquid pump back-flow control valve disposed thereon that is configured to control a flow of the recycled portion of the pressurized product fluid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features, advantages and possible applications of the invention are apparent from the following description of working and numerical examples and from the drawings. All described and/or depicted features on their own or in any desired combination form the subject matter of the invention, irrespective of the way in which they are combined in the claims or the way in which said claims refer back to one another.

(2) Embodiments of the present invention are described further below with reference to the drawings, wherein:

(3) The Figure is a schematic diagram of the connection of the constituent parts of a system for supplying a backup product in an air separation apparatus according to at least one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) The storage tank herein is a storage tank which is thermally isolated or installed in a suitable cold box and used for storing a cryogenic liquid product of an air separation apparatus, and may be a liquid oxygen storage tank, a liquid nitrogen storage tank or a liquid argon storage tank. During normal operation of the air separation apparatus, a portion of the cryogenic liquid product produced is accumulated and stored in the storage tank as a backup.

(5) The cryogenic liquid pump, as a constituent part of the air separation apparatus, is used to circulate the cryogenic liquid product of the air separation apparatus, or extract the cryogenic liquid product from the storage tank and pressurize same for entry into a heat exchanger, and a pressurized gas product resulting from vaporization is delivered to the user. The speed-adjustable cryogenic liquid pump herein is driven by a variable speed motor, wherein a rotation speed of the variable speed motor is changed using the method of changing the number of poles of the motor, the voltage, current or frequency thereof, etc.; the variable speed motor operates continuously within the range of 10%-100% of a nominal rotation speed, in order to adapt to changes in demand of a cryogenic liquid pump load, and drives the cryogenic liquid pump to operate continuously within a nominal rotation speed range. The faster the rotation speed of the motor, the higher the cryogenic liquid product pressure obtained by conversion of mechanical energy of the motor by the cryogenic liquid pump.

(6) The fluid circuit herein is a pipeline for extracting the cryogenic liquid product from the storage tank, and sending same back to the storage tank via the speed-adjustable cryogenic liquid pump and a liquid pump back-flow control valve. In the prior art, in a cold standby state, a small amount of the portion of the cryogenic liquid product that is extracted from the storage tank and circulated back to the storage tank will be vaporized and released into the air, resulting in a loss of liquid and energy.

(7) The delivery pipeline herein is a pipeline which extracts the cryogenic liquid product from the storage tank and is connected to a product supply pipeline of the user via the speed-adjustable cryogenic liquid pump and a liquid pump outlet control valve. A vaporizer, located between the liquid pump outlet control valve and the product supply pipeline of the user, may be installed on the delivery pipeline, and used to vaporize the pressurized cryogenic liquid product, so as to provide a pressurized gas product. The vaporizer may be an air bath vaporizer, or one of various types including a water bath vaporizer.

(8) The product supply pipeline of the user herein at least comprises a first product supply pipeline and a second product supply pipeline; the delivery pipeline is connected to the first product supply pipeline and the second product supply pipeline separately, and an operating pressure of the first product supply pipeline is lower than an operating pressure of the second product supply pipeline.

(9) In a cold standby state, when the air separation apparatus shuts down or the operation thereof slows down, the cryogenic liquid pump driven by the variable speed motor changes from low-speed running to high-speed running; the cryogenic liquid product is extracted from the storage tank and passes through the cryogenic liquid pump and the liquid pump outlet control valve; the cryogenic liquid product is pressurized to the required high pressure, and is vaporized by heat exchange to form a high-pressure gas, such as gaseous oxygen to be supplied to the user. In the prior art, there is only one user product supply pipeline for supplying a high-pressure product.

(10) Taking the prior art as a starting point, the first product supply pipeline is added in order to realize the function of supplying the cryogenic liquid product, which was originally extracted from the storage tank and sent back to the storage tank via the speed-adjustable cryogenic liquid pump and the liquid pump back-flow control valve, to the user as a low-pressure product; during normal operation of the air separation apparatus, the cryogenic liquid product extracted from the storage tank is pressurized via the speed-adjustable cryogenic liquid pump running at a low speed, and delivered to the first product supply pipeline via the delivery pipeline.

(11) At the same time, the present invention still ensures the advantage of rapid startup of the cryogenic liquid pump from the cold standby state. The supply pipeline used to supply a high-pressure product in the prior art is defined as the second product supply pipeline; during temporary operation when the air separation apparatus shuts down or the operation thereof slows down, the cryogenic liquid product extracted from the storage tank is pressurized via the speed-adjustable cryogenic liquid pump running at a high speed, and delivered to the second product supply pipeline via the delivery pipeline.

(12) The depressurization device herein is a device which, by means of adjustment, reduces an inlet pressure to a certain required outlet pressure and, relying on the energy of a fluid itself, causes the outlet pressure to automatically remain stable. From the perspective of fluid mechanics, the depressurization device is a throttle element in which local resistance can change, i.e. flow speed and fluid kinetic energy can be changed by changing a throttle area, causing different pressure losses, and thereby achieving the objective of depressurization. Then, relying on adjustment by a control and adjustment system, fluctuation of pressure after the depressurization device is balanced with a spring force, such that the pressure after the depressurization device stays constant within a certain error range. Herein, the depressurization device may be a pressure relief valve, for depressurizing the cryogenic liquid product, sent out by the speed-adjustable cryogenic liquid pump and having a pressure higher than the operating pressure of the first product supply pipeline, to the operating pressure of the first product supply pipeline.

(13) The vaporizer herein is a heat exchange apparatus in which a gas in liquid state is heated until it vaporizes and turns into a gas. Heating may be indirect (steam vaporizer, water bath vaporizer, air bath vaporizer or electrically heated vaporizer), or direct (hot gas or submerged combustion). The vaporizer used in an air separation apparatus backup system is generally an air bath vaporizer or a water bath vaporizer.

(14) FIG. 1 is a schematic diagram of the connection of the constituent parts of a system for supplying a backup product in an air separation apparatus. A system for supplying a backup product in an air separation apparatus comprises a storage tank 1 for storing a cryogenic liquid product; a speed-adjustable cryogenic liquid pump 2, which pressurizes the cryogenic liquid product sent out from the storage tank 1; a liquid pump back-flow control valve 3, and a fluid circuit 4 for extracting the cryogenic liquid product from the storage tank 1 and sending same back to the storage tank 1 via the speed-adjustable cryogenic liquid pump 2 and the liquid pump back-flow control valve 3; a liquid pump outlet control valve 5, and a delivery pipeline 6 which extracts the cryogenic liquid product from the storage tank 1 and is connected to a product supply pipeline of a user via the speed-adjustable cryogenic liquid pump 2 and the liquid pump outlet control valve 5; and the product supply pipeline of the user located downstream of the delivery pipeline 6.

(15) The product supply pipeline of the user at least comprises a first product supply pipeline 7 and a second product supply pipeline 8; the delivery pipeline 6 is connected to the first product supply pipeline 7 and the second product supply pipeline 8 separately, and an operating pressure of the first product supply pipeline 7 is lower than an operating pressure of the second product supply pipeline 8.

(16) The first product supply pipeline 7 comprises at least one depressurization device 9, for depressurizing the cryogenic liquid product, sent out by the speed-adjustable cryogenic liquid pump 2 and having a pressure higher than the operating pressure of the first product supply pipeline 7, to the operating pressure of the first product supply pipeline 7.

(17) A vaporizer 10, located between the liquid pump outlet control valve 5 and the product supply pipeline of the user, is installed on the delivery pipeline 6.

Embodiment 1

(18) In the air separation apparatus, air is separated to produce the cryogenic liquid product, which is delivered and stored in the storage tank 1. During normal operation of the air separation apparatus, the cryogenic liquid product extracted from the storage tank 1 is pressurized via the speed-adjustable cryogenic liquid pump 2 running at a low speed, and the liquid pump back-flow control valve 3 is closed, such that all of the cryogenic liquid product at a low pressure is delivered to the product supply pipeline of the user via the delivery pipeline 6. The delivery pipeline 6 comprises the liquid pump outlet control valve 5, and a vaporizer 10 located between the liquid pump outlet control valve 5 and the product supply pipeline of the user; vaporization takes place by heat exchange in the vaporizer 10 to form a low-pressure gas, such as low-pressure gaseous oxygen to be supplied to the user. Ideally, the speed-adjustable cryogenic liquid pump is driven by a variable speed motor; the rotation speed of the variable speed motor must be adjusted according to the operating pressure of the first product supply pipeline, such that the cryogenic liquid pump runs at a low speed, pressurizing the cryogenic liquid product to a pressure approximately equal to the operating pressure of the first product supply pipeline. If the low pressure is greater than the operating pressure of the first product supply pipeline, depressurization to the pressure of the first product supply pipeline is necessary; if the low pressure is precisely equal to the operating pressure of the first product supply pipeline, delivery to the first product supply pipeline is carried out directly. Since the operating pressure of the first product supply pipeline is lower than the operating pressure of the second product supply pipeline, a gas product at a low pressure will not be delivered to the second product supply pipeline.

(19) Compared with the prior art, this embodiment makes full use of the low-speed running of the speed-adjustable cryogenic liquid pump when in the cold standby state, realizing the function of supplying a low-pressure product to the user, reducing the energy loss associated with the cryogenic liquid pump being in the cold standby state on a long-term basis, and at the same time avoiding the release of the cryogenic liquid product caused by this portion of the cryogenic liquid product being circulated back to the storage tank.

Embodiment 2

(20) In the air separation apparatus, air is separated to produce the cryogenic liquid product, which is delivered and stored in the storage tank 1. During temporary operation when the air separation apparatus shuts down or the operation thereof slows down, the cryogenic liquid product extracted from the storage tank 1 is pressurized via the speed-adjustable cryogenic liquid pump 2 running at a low speed, and the liquid pump back-flow control valve 3 is closed, such that all of the cryogenic liquid product at a high pressure is delivered to the product supply pipeline of the user via the delivery pipeline 6. The delivery pipeline 6 comprises the liquid pump outlet control valve 5, and a vaporizer 10 located between the liquid pump outlet control valve 5 and the product supply pipeline of the user; vaporization takes place by heat exchange in the vaporizer 10 to form a high-pressure gas, such as high-pressure gaseous oxygen to be supplied to the user. Ideally, the speed-adjustable cryogenic liquid pump is driven by a variable speed motor; the rotation speed of the variable speed motor must be adjusted according to the operating pressure of the second product supply pipeline, such that the cryogenic liquid pump runs at a high speed, pressurizing the cryogenic liquid product to the operating pressure of the second product supply pipeline, for direct delivery to the second product supply pipeline. Since the operating pressure of the first product supply pipeline is lower than the operating pressure of the second product supply pipeline, a gas product at a high pressure must be depressurized and delivered to the first product supply pipeline.

(21) Compared with the prior art, this embodiment ensures the advantage of rapid startup of the cryogenic liquid pump from the cold standby state while also being able to satisfy the user's demand for a high-pressure product and a low-pressure product.

(22) While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

(23) The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

(24) Comprising in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of comprising). Comprising as used herein may be replaced by the more limited transitional terms consisting essentially of and consisting of unless otherwise indicated herein.

(25) Providing in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

(26) Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

(27) Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

(28) All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.