EP1534414A2

EP1534414A2 - Method and device for injecting two-phase co sb 2 /sb in a transfer gaseous medium

Info

Publication number: EP1534414A2
Application number: EP03763931A
Authority: EP
Inventors: Dominique Bras; José Buil
Original assignee: LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 2002-07-11
Filing date: 2003-07-07
Publication date: 2005-06-01
Anticipated expiration: 2023-07-07
Also published as: CA2490662A1; ATE441472T1; US7648569B2; AU2003263267A1; FR2842123B1; EP1534414B1; WO2004007061A2; BR0312329A; CA2490662C; BR0312329B1; DE60329111D1; WO2004007061A3; US20050268786A1; FR2842123A1; JP2005532161A

Abstract

A method and an apparatus for injecting two-phase (gas+solid) carbon dioxide into a gas stream. Liquid carbon dioxide is cryogenically expanded into two-phase carbon dioxide, which is then injected into the center of the stream. An inerting gas is also injected into the stream along with the two-phase carbon dioxide.

Description

Method and device for injecting _two- phase CO ₂ into a gaseous transfer medium.

The invention relates to a method and a device for injecting two-phase CO, "gas + solid" in a gaseous transfer medium.

CO ₂ is used in many industrial applications; carbonation, pH regulation, neutralization of basic agents are examples among others. Carbon dioxide can be injected into a liquid medium or a gaseous medium. In a liquid medium, CO ₂ is injected in gaseous form, or liquid depending on the case.

When it comes to injecting carbon dioxide into a gaseous medium, the usual solution is to inject it in gaseous monophasic form. Most often delivered in liquefied form and stored in this form in a tank, at a pressure of the order of 14 to 20 bars and at a temperature of the order of -35 to -20 ° C, it is therefore necessary to spray it. This vaporization requires the presence on site of a vaporizer; which implies a significant cost, both in terms of operation, but also of investment, whether the energy is of electrical origin or supplied by steam available on site. Furthermore, the gaseous carbon dioxide supply line, as well as the associated accessories (valves, valves, etc.) are bulky and expensive. Thus, the conventional devices for injecting carbon dioxide into a gaseous medium are not optimized; these devices are in particular not suitable in the case of the injection of large quantities of CO ₂ .

We also know the use of CO ₂ in solid form, or carbon dioxide snow for cleaning surfaces. US 4,747,421 describes the use of solid CO ₂ in the field of the semiconductor industry for the removal of a photoresist film on the surface of a substrate.

EP 0 631 846 describes an apparatus intended to produce an aerosol for cleaning the interior surfaces of a tool chamber.

EP 0 288 263 describes an apparatus for removing small particles from the surface of a substrate using a mixture of solid and gaseous carbon dioxide.

US 4,389,820 describes a machine intended to generate a flow of accelerated sublimable particles for surface stripping. The use of CO ₂ prevents surface contamination as well as atmospheric contamination.

Furthermore, FR 2 198 778 describes a process and an apparatus for the preparation of foundry molds, a process in which carbon dioxide gas is used for the delivery of gaseous components in catalytic quantity, both during the gasification of the mixture of liquid chemical components and when adjusting the quantities of components to be added.

However, none of the documents cited relates to the enrichment in C0 ₂ of a gaseous medium in transfer.

An object of the present invention is to provide a solution to the problem of injecting carbon dioxide, especially in large quantities, into chambers containing a reactive or non-reactive gaseous medium, in transit under pressure.

Another object is to propose an injection device capable of implementing this process.

The characteristics and advantages of the invention will appear on reading the description which follows. The invention relates first of all to a method of injecting carbon dioxide into a gaseous medium under transfer under pressure to be treated, present inside an enclosure, from liquid carbon dioxide; the process comprising the steps of: - transformation of the liquid carbon dioxide into two-phase "gas + solid" carbon dioxide by a direct expansion device,

injection of the two-phase carbon dioxide thus formed into the gaseous medium to be treated using an injector inserted into the wall of the enclosure containing said gaseous medium under transfer under pressure to be treated, as well as a step of injection of an inerting gas into carbon dioxide, between the direct expansion device and the injector.

The carbon dioxide injected is in the "gas + solid" form, the injection takes place directly into the gaseous medium to be treated, through a wall of the enclosure which contains the medium to be treated. The enclosure may for example be a pipe or pipe present in a circuit. The transformation of liquid carbon dioxide into two-phase carbon dioxide involves a direct expansion device called cryogenic expansion. The device, of the variable flow valve type, first causes a restriction in the flow of the fluid, then an increase in the flow diameter has the effect of relaxing the gas causing a loss of pressure so that the pressure in output of the device corresponds to that of the triple point of CO ₂ . Liquid CO ₂ is transformed into a mixture of CO ₂ gas and solid CO ₂ (dry ice). Thus, during injection, the process of the invention uses a cryogenic fluid with a density at least twenty times greater than its gas phase. The injection of carbon dioxide involves an injector which is inserted into the wall of the enclosure and transfers the "gas + solid" mixture to the center of the transfer channel for the gaseous medium. In addition, the injection of a gas inerting in carbon dioxide, at the outlet of the cryogenic valve prevents blockages at the outlet of said valve and at the outlet of injector, in the gaseous medium. The inerting gas, ensuring a gas sweep at the level of the various elements of the device where the _two- phase CO ₂ circulates, prevents pollution by foreign bodies, in particular humidity, and prevents the accumulation of carbon dioxide snow at points where the geometry its circulation would be difficult without entrainment by the inerting gas.

Liquid CO ₂ is made available at a pressure generally between 10.10 ⁵ and 22.10 ⁵ Pa (i.e. between 10 and 22 bars) and at a temperature generally between -35 ° C and -20 ° C.

According to a particular mode, the two-phase carbon dioxide is injected in such a way that it is injected into the heart of the gaseous medium and distributed partly in co-current and partly in counter-current to the gas flow. In this way injecting carbon dioxide into the heart of the gas, that is to say into the gas stream far from the walls, ensures the best possible mixing and entrainment of CO ₂ , thus preventing its accumulation. However, the risk of formation of plugs is very great given the temperature of this CO ₂ (-80 ° C), it is therefore essential to immediately disperse it in the gaseous medium to be treated. In addition to the geometry of the injector, the presence of the inerting gas injected into the _two- phase CO ₂ according to the invention also makes it possible to limit the risk of blockages.

This inerting gas must be inert vis-à-vis the chemical species present as well as regulatory bodies (flow control valves, injector specific to the invention, etc.). It is particularly advantageous to use as inerting gas carbon dioxide originating from the vaporization of a fraction of the liquid carbon dioxide made available, and taken upstream of the cryogenic expansion. It should be noted that C0 _{2 which} does not introduce a new chemical species can by extension also be considered as an inert gas.

The quantity of carbon dioxide injected is preferably regulated as a function of a set point of a physical or chemical parameter to be reached, the measurement of this parameter is carried out in the gaseous medium, downstream of the injection point.

Thus, the cryogenic valve with variable flow of the invention is controlled as a function of this instruction.

Furthermore, an all-or-nothing cryogenic safety valve can also be placed upstream of the variable-flow cryogenic valve to cut off the supply of liquid CO ₂ in the event of a malfunction, for example if the pressure is too high. high in the gaseous medium to be treated, if the temperature is too low or if another parameter, considered to be major, has exceeded an alert threshold. The operator of the installation can also order this valve. When the power supply to the cryogenic valve with variable flow is cut, the protection of the sensitive elements of the device by a low flow of the inerting gas is maintained.

According to another aspect, the invention relates to a process for enriching a gas stream with carbon dioxide from liquid carbon dioxide.

According to a particular mode, it comprises the following stages:

- transformation of liquid carbon dioxide into two-phase "gas + solid" carbon dioxide by a direct expansion device,

injection of the two-phase carbon dioxide thus formed into the gas flow to be enriched using an injector inserted into the wall of the enclosure containing said gas flow to be enriched, and in that it comprises an injection step an inerting gas in carbon dioxide between the direct expansion device and the injector. The invention also relates to a device for injecting carbon dioxide for implementing one of the methods as defined above, characterized in that it comprises:

- a variable-flow expansion valve (intended to be supplied with liquid carbon dioxide) and a corresponding injector inserted into a wall of the enclosure and penetrating into the heart of the gaseous medium, ₍

- a tee connected in the upper part to the ejector of the expansion valve (it is understood by expansion valve, the variable flow valve), on the side to a gas supply and connected in the lower part to the injector stuck in said wall, - means for supplying the expansion valve with liquid CO ₂ ,

means for supplying the tee with inerting gas.

In a judicious manner, the end of the injector consists of:

- a deflector with two slopes distributing the _two- phase CO ₂ partly against the current of the gas flow and partly co-current, - two exhaust ports ensuring the ejection of the _two- phase CO ₂ and arranged so as to distribute it along the axis of the gas flow transfer.

Preferably, the injector enters the enclosure over a length equivalent to half the width of said enclosure and according to a preferred variant, the device comprises for supplying inerting gas to the injection device, upstream cryogenic expansion device, means for sampling and vaporizing a fraction of the liquid carbon dioxide made available. The device can therefore operate by being connected to a single carbon dioxide supply source. It is also possible to use an inert gas present at the place of application or compressed air, it being understood that the inerting gas must not modify the behavior of the mixture obtained, and must not be contraindicated for the material. . An embodiment of the invention is given by way of nonlimiting example, illustrated by Figure 1 which is a schematic view of a device according to the invention and by Figures 2 and 2A which show an example of an injector according to the invention, the

Figure 2A being a sectional view along the axis AA of the end of the injector of Figure 2.

The injection device 1 is intended to supply two-phase carbon dioxide "gas + liquid" in a gaseous medium 2, under transfer under pressure in an enclosure 3, and this from a storage tank 4 of carbon dioxide liquid in which the liquid carbon dioxide is stored at a pressure between 14.10 ⁵ and 20.10 ⁵ Pa (i.e. between 14 and 20 bars) and at a temperature between -35 ° C and -20 ° C

The device 1 comprises a liquid CO ₂ supply line formed by a liquid line 5 extending from the reservoir 4 to a cryogenic valve with variable flow rate 6 which regulates a parameter "A" measured in the medium gas 2 downstream of the injection point. A filter 7 fitted with a stainless steel filter cartridge is placed upstream of the valve 6, it filters the liquid carbon dioxide in order to protect the valve seat from solid impurities which may be present in the pipes. Interposed on the line 5, upstream of the filter 7, there is an all-or-nothing type cryogenic safety valve 8 which cuts off the cryogenic CO ₂ supply to the valve 6 when the control member 9 detects a overshoot of a safety parameter under control. A cryogenic expansion valve, not shown in the Figure, protects the line downstream of the safety valve 8 after the latter has closed.

The device 1 further comprises a line for supplying inerting gas, which in this case is gaseous CO ₂ ; the line is formed in the order of a vaporizer 10, a pressure reducer 11, a manually adjusted flow valve 12, a flow meter with transmitter 13 and a non-return valve, 14.

A tee 15, supplied in the upper part with _two- phase CO ₂ coming from the ejector situated at the outlet of the valve 6, on the side in inerting gas (gaseous CO ₂ ) is connected in the lower part to an injector 16 ensuring the injection of the _two- phase CO ₂ mixture into the gaseous medium 2 by transfer under pressure into the enclosure 3.

The injector 16 transfers the CO ₂ to the center of the gaseous medium transfer pipe. When there is no injection of CO ₂ , the interior of the tee 15 and of the injector 16 are protected from the medium to be treated by means of a low but permanent flow rate of the inerting gas.

A control and regulation unit for the "A" parameter measures the value of the "A" parameter in the transfer line, processes - via the control device 9 - the signal received from "A" as well as the signals which come from the various safety parameters monitored (temperature and pressure of the gaseous medium to be treated, etc.). As a function of "A", it controls the opening level of the cryogenic valve with variable flow rate 6 to ensure that the parameter "A" is maintained at its set value; it also controls the closing of the cryogenic safety valve 8 in the event of a major fault affecting a safety parameter, or in the event of refusal of processing authorization on the part of the operator, as well as the opening or closing of the vent valve depending on the operating mode, generally synchronous with the other valves. This control of the control unit is ensured from information communicated by the transmitters AIT (measurement of the "A" parameter), PIT (measurement of the pressure in the gaseous medium 2), TT (measurement of the temperature middle 2) not referenced. Other elements, not described, can be incorporated into this control unit, in particular binary information, of the authorization type or other specific parameters of the process. Figure 2 shows in more detail an example of an injector according to the invention.

The injector 16 is supplied with _two- phase CO ₂ coming from the ejector 17 at the outlet of the valve 6 and with inerting gas consisting of gaseous C0 ₂ . This supply is made via the tee 15 which receives the inerting C0 ₂ at the side inlet 18 and the _two- phase CO ₂ from 17 in the upper part. The injector 16 made of a heat-insulating material, for example made of polysulfone, conducts the "gas + solid" mixture towards the center of the pipe 3 for transferring the gaseous medium 2.

The injector 16 is provided: - at its end with a deflector 19 with two slopes, forming an angle of 60 ° to orient part of the _two- phase CO ₂ against the current of the gaseous medium 2 in circulation, and the other part co-current

- in its lower part of two exhaust lights 20 which ensure the ejection of _two- phase CO ₂ , even at low flow and its distribution in the axis of the transfer of the gaseous medium, without hampering the exit thanks to their arrangement in the axis of the transfer.

EXAMPLE

The process of the invention is implemented for enriching CO ₂ with natural gas combustion fumes. The parameter "A" to be regulated is the CO ₂ content of these fumes. Initially at approximately 8% CO ₂ , the fumes are enriched by the process of the invention up to contents of between 12 and 18%, for their subsequent use in a papermaking process. The smoke flow is around 12,000 m ³ / h. The amount of CO ₂ used is around 1,200 m ³ / h CO ₂ (gas equivalent) to reach 16% CO ₂ in the flue gases. The fumes thus enriched are intended in particular for the manufacture of calcium carbonate. The presence of water vapor in these fumes creates, due to the interface between the hot fumes and the cryogenic source, problems linked to the risk of ice formation, in particular at the level of the lights of the injector. This risk is avoided thanks to the permanent inerting of the injector by a neutral and dry gas. The method of the invention is particularly applicable in many fields using CO ₂ as a raw material. The enrichment implemented according to the invention not using gaseous CO ₂ emerges from the dimensional constraints and the drawbacks which are linked to it.

The invention is thus particularly suitable for industrial installations having fumes containing CO ₂ , a polluting agent in the state, and moreover using CO ₂ as a raw material.

The method of the invention can also be used in cases where it is desired to treat CO _{2 with} a gaseous transfer medium.

It is also able to provide pH regulation using fumes doped with CO ₂ .

The process of the invention can thus be applied advantageously to the CO ₂ enrichment of fumes for the manufacture of calcium carbonate for the paper industry.

Claims

1. A method of injecting carbon dioxide into a gaseous medium under pressure transfer to be treated present inside an enclosure from liquid carbon dioxide, characterized in that it comprises the following steps: - transformation liquid carbon dioxide into two-phase "gas + solid" carbon dioxide by a direct expansion device,

injection of the two-phase carbon dioxide thus formed into the gaseous medium to be treated using an injector inserted into the wall of the enclosure containing said gaseous medium under transfer under pressure to be treated, and in that it comprises a step of injecting an inerting gas into carbon dioxide, between the direct expansion device and the injector.

2. Method according to claim 1, characterized in that the two-phase carbon dioxide is injected so that it is injected into the heart of the gaseous medium and distributed partly in co-current and partly in counter-current to the flow gaseous.

3. Method according to one of claims 1 or 2, characterized in that the inerting gas is carbon dioxide originating from the vaporization of a fraction of the liquid carbon dioxide provided, and taken upstream of the device of relaxation.

4. Method according to one of claims 1 to 3, characterized in that the quantity of carbon dioxide injected into the gaseous medium to be treated is regulated according to a set point of a physical or chemical parameter to be reached, measured in the gaseous medium, downstream of the injection point.

5. Method for enriching a gas stream with carbon dioxide from liquid carbon dioxide.

6. Method according to claim 5, characterized in that it comprises the following steps: - transformation of liquid carbon dioxide into two-phase "gas + solid" carbon dioxide by a direct expansion device,

injection of the two-phase carbon dioxide thus formed into the gas flow to be enriched using an injector inserted into the wall of the enclosure containing said gas flow to be enriched, and in that it comprises an injection step an inerting gas in carbon dioxide, between the direct expansion device and the injector.

7. A carbon dioxide injection device for implementing the method of one of claims 1 to 6, characterized in that it comprises: - a pressure-reducing expansion valve and a corresponding injector inserted in a wall of the enclosure and penetrating into the heart of the gaseous medium,

- a tee connected at the top to the ejector of the expansion valve, on the side to a gas supply and connected at the bottom to the injector inserted into said wall,

- means for supplying the expansion valve with liquid carbon dioxide, - means for supplying the tee with inerting gas.

8. Device according to claim 7, characterized in that the end of the injector consists of:

- a deflector with two slopes distributing the _two- phase CO ₂ partly against the current of the gas flow and for the other part co-current, - two exhaust ports ensuring the ejection of the _two- phase CO ₂ and arranged so as to distribute the mixture along the axis of the transfer of the gas flow.

9. Device according to one of claims 7 or 8, characterized in that the injector enters the enclosure over a length equivalent to half the width of said enclosure.

10. Device according to one of claims 7 to 9, characterized in that it comprises for the supply of inerting gas to the injection device, upstream of the device cryogenic expansion, means for sampling and vaporizing a fraction of the liquid carbon dioxide provided.

11. Application of the method according to one of claims 5 or 6 for the manufacture of calcium carbonate.