System for controlling co2 temperature in steam outlet

Abstract

The invention proposes a liquid cryogenic fluid vaporization equipment, comprising a heat exchanger (4), suitable for enabling heat exchange between the liquid cryogenic fluid (1, 2) and water (or any other exchange fluid such as oil, glycol water, etc.), in order to carry out said vaporization, characterized in that it comprises a means for injecting (5) a liquid gas into the gas produced at the outlet of the vaporization exchanger, in order to lower the temperature of this produced gas into a given range.

Description

[0001] The present invention relates to the field of liquid CO2 vaporization equipment, and is more particularly concerned with the possibilities of controlling its temperature after its vaporization and transformation into a gaseous state.

[0002] Documents US2007 / 095077, DE-10 2011 109824, US2019 / 137041, and US2006 / 086100 illustrate the state of the art in the field of cryogenic liquid vaporization.

[0003] We know that gaseous CO2 is used for a large number of industrial applications, including food applications and in particular the enrichment of greenhouses with CO2, the anesthesia of poultry and pigs with CO2, the carbonation of drinks, water treatment etc... etc....

[0004] Typically, beverage manufacturers cannot use CO2 that is too "hot"; CO2 is generally injected into the water at a temperature close to 2°C. And it is known that if the CO2 is too "hot," the carbonation quality will not be optimal, or even unacceptable.

[0005] It is known that various technical solutions are used to achieve such vaporization of liquid CO2, and in particular, equipment is known that implements heat exchange between liquid CO2 and hot water (or any other hot fluid such as oil, steam, etc.). For the sake of simplicity, we will consider CO2 / water heat exchangers in the following discussion.

[0006] Such equipment requires a continuous energy supply during gas vaporization.

[0007] However, such equipment presents the following problems when an exchange is carried out between liquid CO2 and a hot fluid, at a temperature generally above 30°C: The heat exchanger used is sized to prevent the water from freezing inside it, thus establishing a lower sizing limit. In such equipment, heat exchangers facilitate the exchange between liquid CO2 at -20°C and water at a temperature above 10°C. Therefore, the exchanger will be sized for the maximum CO2 flow rate and a minimum water temperature of 10-15°C (or lower). Subsequently, for the same maximum CO2 flow rate, if the water temperature is above 15°C, there will be no risk of the exchanger becoming blocked by freezing water during the exchange process. However, the CO2 at the outlet becomes warmer as the water temperature increases.Depending on the CO2 production rate and the downstream user site's consumption, for water temperatures exceeding certain limits (30°C in some cases), the CO2 temperature can match the incoming water temperature, which can reach up to 90°C (or even higher if it's steam). This is because the water is traditionally supplied by the user site itself; this is what is most often referred to as "process water," the water the site uses in its production process at a specific temperature. The site expends energy to cool the water so it can be used in its process (cooling machines, compressors, etc.). The vaporization equipment cools this water by vaporizing the CO2, which is then consumed by the site for a specific application, such as carbonation (resulting in a double energy saving).Overheating of the produced CO2 can then be observed, and its temperature can then pose application problems at user sites, as soon as it exceeds 15°C in some cases. All current CO2 vaporization systems (notably the one mentioned above, involving heat exchange with water) do not allow for adjusting, and in particular regulating, the temperature of the gas, for example, the CO2, obtained at the equipment outlet.

[0008] One of the objectives of the present invention is therefore to offer a solution to the problems mentioned above.

[0009] As will be seen in more detail below, the present invention proposes to inject a liquid gas into the gas obtained at the outlet of the vaporization equipment, equipment of the type implementing a liquid / water cryogenic heat exchanger.

[0010] Preferably, the same liquid gas that is to be vaporized will be added to the gas obtained at the outlet of the vaporizer (therefore, here, liquid CO2 in the gaseous CO2 outlet for a liquid CO2 vaporizer°).

[0011] This injection can be done by an automatic regulation to finely adjust the gas outlet temperature, it can also be done by adopting a fixed setting.

[0012] This involves the dosing of gaseous CO2, after vaporization, with liquid CO2. This could be done automatically, for example, by a progressive valve on the liquid CO2 supply, to ensure proper dosing and control the final CO2 temperature.

[0013] It can also be done manually, for example through a calibrated orifice on the liquid CO2 inlet, if one wants to limit only the temperature of the gaseous CO2.

[0014] The regulation is all the more precise because there is a natural self-adaptation: the greater the flow rate in the exchanger, the greater the quantity of liquid that can be injected at the outlet.

[0015] It is possible to regulate the CO2 temperature, including at the point of use, to take into account the effects of expansion, ambient temperature, with a measurement of the temperature at the point of use.

[0016] And as will become clear to the person skilled in the art, CO2, due to its very particular properties (due to its liquid-gas-solid phases), poses very specific technical problems, and the present invention focuses on an implementation that guarantees better homogenization between liquid CO2 and gaseous CO2 after the injection of liquid CO2 into gaseous CO2.

[0017] To achieve this, we propose installing what can be called a "hairpin" at the outlet of the heat exchanger. Liquid CO2 is injected at the beginning of the hairpin. The first section of this hairpin has a slight upward slope, just a few degrees (typically 10 degrees or less), which forces any unvaporized liquid CO2 droplets at the exchanger outlet to flow back into the exchanger. This ensures that the liquid CO2 is completely vaporized, providing better temperature control of the gaseous CO2.

[0018] As will be seen in more detail below, the present invention also offers the possibility of detecting the presence of liquid at the outlet, thus guaranteeing the absence of unvaporized liquid CO2 droplets.

[0019] There Figure 1 The attached diagram provides a partial schematic view of a traditional vaporization equipment employing a liquid / water CO2 exchanger.

[0020] We recognize on the figure 1 the following installation elements: 5. Liquid CO2 storage 6. Liquid CO2 7. Gaseous CO2 8. CO2 / water heat exchanger

[0021] There Figure 2 The attached diagram provides a partial schematic view of a vaporization equipment employing a liquid / water CO2 exchanger, with an injection into the gaseous CO2 produced by the equipment of a liquid cryogen (here liquid CO2), where reference 5 represents the metered injection of liquid CO2 into the outlet gas.

[0022] According to one embodiment of the invention, the user site has a source of water vapor that it wishes to utilize, and this vapor source is then used to vaporize CO2, according to one of the following embodiments: by direct injection into exchanger 4 of the figure 1 attached; or with the help of an additional heat exchanger, by adding a water / steam exchange loop as illustrated in the figure 3 attached. The water circulates in a closed loop, it is heated by steam, then cooled by CO2. For this purpose, an adjacent water reservoir is available, typically of a few tens of liters, or even a hundred liters (somewhat similar to the coolant reservoir of a car).

[0023] We recognize on the figure 3 the following installation elements: 8. Liquid CO2 storage 9. Liquid CO2 10. Gaseous CO2 11. CO2 / water heat exchanger 12. Closed-loop water system 13. Steam inlet 14. Water / steam heat exchanger

[0024] The advantages of this technical proposal can be summarized as follows: The cooling of the gas and the adjustment of its temperature at the outlet of the vaporization equipment; improved gas utilization by the user site (since typically some user sites and processes would be severely disrupted by the arrival of excessively hot CO2, thus rendering production impossible); and improved process stabilization at the user site, particularly for beverage carbonation applications.

[0025] The invention relates to a solution for controlling the temperature of gaseous CO2 produced at the outlet of liquid CO2 vaporization equipment, equipment comprising a heat exchanger, capable of allowing heat exchange between the liquid cryogenic fluid and hot water (or any other exchange fluid such as oil, steam, etc.), in order to control the temperature of the gas, in accordance with claim 1 below.

[0026] The invention may also implement one or more of the following embodiments: The heat exchanger is a source of water vapor, which is injected directly into the main heat exchanger to perform vaporization. The heat exchanger is water vapor, and the following measures are implemented: an additional heat exchanger is provided; a water reservoir is provided; and a closed-loop system is provided, comprising the additional heat exchanger and the main heat exchanger, in which the water circulates and is heated by exchanging heat with the vapor before being injected into the main heat exchanger to perform vaporization. The liquid gas injected into the gas produced at the outlet of the vaporization exchanger is the same liquid gas that is to be vaporized.

[0027] According to the invention, the outlet pipe of the exchanger, into which the cryogenic liquid is injected, has the shape of a hairpin, the injection of cryogenic liquid being carried out at the beginning of the hairpin, which is mounted with a slope, forcing the few drops of liquid CO2 that would be unvaporized at the outlet of the exchanger to return to the exchanger, thus ensuring that the liquid CO2 is totally vaporized, thereby offering better regulation of the temperature of the gaseous CO2.

[0028] There Figure 4 The attached illustration shows an example of the implementation of such a pin structure. We can see on the figure 4 the following elements and functionalities: At the outlet of heat exchanger 10, the gas enters the hairpin bend, which has an initial slightly sloping section, a few degrees upwards. Liquid CO2 12 is injected at the beginning of the hairpin bend. After a bend and a section of vertical or nearly vertical piping, the gas enters a second section of piping in the hairpin bend.

[0029] also sloping, to then head (11) towards the user station of this gas thus cooled. We note the presence at the end of the first sloping section of an accumulation point 13 equipped with a temperature probe.

[0030] Indeed, such a system allows the following behavior: if there are few or no droplets left in the gas approaching the slope, due to the change of direction, due to their inertia, these droplets will hit the wall, and if there are few, they will vaporize, while if there were many, they will run down the wall, accumulate at the lowest point (13) and the temperature probe, judiciously positioned, will detect the presence of liquid. as illustrated in the implementation method of the figure 2A bypass circuit for liquid CO2 is installed in parallel with the heat exchanger. In this circuit, liquid CO2 is transported from the inlet to the outlet (to be injected into the gas exiting the exchanger) solely by the pressure difference created by the flow of the fluid (LCO2 then GCO2). Therefore, no additional pumps or devices are required. This pressure difference is proportional to the fluid flowing through the exchanger. This characteristic is used to ensure system safety: in the absence of hot gas, there is no need to cool it, or even excessively cool it, thus preventing the presence of liquid after the exchanger. This situation cannot occur because, in the absence of hot gas, the pressure difference across the exchanger is zero, and therefore no liquid CO2 is injected.

[0031] This results in an "intrinsic" security system.

[0032] Let's explain this phenomenon better: in the exchanger, liquid CO2 passes through plates, which is a particular form of circulation, but the physical phenomenon is the same; circulating fluid in a pipe generates pressure losses (basically due to the friction of the liquid on the walls).

[0033] On the liquid side there is little, but as soon as the liquid vaporizes, there is expansion of CO2, therefore higher fluid velocities and therefore pressure loss.

[0034] This pressure loss on the main flow is a pressure difference: insofar as only liquid is diverted in the bypass, the pressure losses remain low, which allows a sufficient flow of liquid to be generated in the bypass with a small upstream / downstream pressure difference.

Claims

1. An equipment for vaporizing cryogenic liquid fluids, comprising a main heat exchanger (4), suitable for allowing a heat exchange between the cryogenic liquid fluid (1, 2) and water or any other exchange fluid such as oil or even glycol water, in order to perform said vaporization, which equipment comprises a means (5) for injecting a liquid gas into the gas produced at the outlet of the main heat exchanger (4), to lower the temperature of this produced gas within a given range, characterized by the implementation of the following measures: - the equipment is provided with an outlet pipe from the main heat exchanger (4), in which the injection of liquid gas is performed; - this outlet pipe has the shape of a hairpin presenting: i) a first sloped portion arranged in an ascending manner by a few degrees at the outlet of the main heat exchanger (4), ii) an elbow and a vertical portion, and iii) a second sloped portion configured to be connected to the user station (11), the injection (12) of liquid gas being carried out at the beginning of the hairpin, at the level of the first sloped portion, in order to force any droplets of liquid fluid that would not be vaporized at the outlet of the main heat exchanger (4) to return to the main heat exchanger (4), and thus to ensure that the liquid is completely vaporized.

2. The equipment according to claim 1, characterized in that the exchange fluid is water vapor, water vapor being injected directly into said main heat exchanger (4) to perform said vaporization.

3. The equipment according to claim 1, characterized in that the exchange fluid is water vapor (6), and in that the following measures are implemented: - an additional exchanger (7) is provided; - a water reserve is provided; - a loop (5) is provided comprising said additional exchanger and said main heat exchanger (4), a loop where water can circulate in a closed circuit and be reheated by exchanging heat with the vapor, before being injected into the main heat exchanger (4) to perform said vaporization.

4. The equipment according to any one of claims 1 to 3, characterized in that the liquid gas injected (12) into the gas produced at the outlet of the main heat exchanger (4) is the same liquid gas that is to be vaporized.

5. The equipment according to any one of the preceding claims, characterized in that the pipe which comprises the first sloped portion is provided at its end with an accumulation point (13), which accumulation point is itself provided with a temperature probe.

6. A method for vaporizing cryogenic liquid fluids, implementing to perform the vaporization a main heat exchanger (4) between the cryogenic liquid fluid and water or any other exchange fluid such as oil or even glycol water, in order to perform said vaporization, characterized in that a liquid gas (12) is injected into the gas produced at the outlet of the main heat exchanger (4), in order to lower the temperature of this produced gas within a given range, before directing this thus cooled gas to a user station for this gas (11), and characterized in that the possible presence of liquid in the thus cooled gas is detected, before its arrival at the user station, in the following manner: - an outlet pipe from the main heat exchanger (4) is provided, in which the injection (12) of liquid gas is performed; - this outlet pipe has the shape of a hairpin presenting: i) a first sloped portion arranged in an ascending manner by a few degrees at the outlet of the main heat exchanger (4), ii) an elbow and a substantially vertical portion, and iii) a second sloped portion configured to be connected to the user station (11), the injection of liquid gas being carried out at the beginning of the hairpin, at the level of the first sloped portion, in order to force any droplets of liquid fluid that would not be vaporized at the outlet of the main heat exchanger (4) to return to the main heat exchanger (4), and thus to ensure that the liquid is completely vaporized; - said first sloped portion is provided at its end with an accumulation point (13), which accumulation point is itself provided with a temperature probe, and the possible presence of liquid in the gas is detected according to the temperature value provided by the probe.

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