Methods and compositions for delivering carbon dioxide

Abstract

Provided herein are methods, devices and systems for delivering carbon dioxide to a destination as a mixture of solid and gaseous carbon dioxide.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 62 / 779,020, filed December 13, 2018, which is incorporated herein by reference in its entirety. This application is related to U.S. Patent Application No. 15 / 650,524, filed July 14, 2017, and U.S. Patent Application No. 15 / 659,334, filed July 25, 2017, both of which are incorporated herein by reference. [Background technology]

[0002] The use of snowhorns to produce a mixture of gas and solid carbon dioxide from liquid carbon dioxide is well known. Snowhorns are typically used to deliver relatively large doses of carbon dioxide as solid carbon dioxide, and it is not usually necessary or possible to achieve precise or reproducible doses of carbon dioxide from a snowhorn, in the desired ratio of solid carbon dioxide to gaseous carbon dioxide, especially under low dose and / or intermittent conditions. Summary of the Invention

[0003] In one aspect, provided herein is a method.

[0004] In certain embodiments, provided herein is a method for intermittently delivering boluses of carbon dioxide in solid and gaseous form to a destination, the method including (i) conveying liquid carbon dioxide from a source of liquid carbon dioxide through a first conduit to an orifice, where (a) the first conduit comprises a material capable of withstanding the temperature and pressure of the liquid carbon dioxide, and (b) the pressure drop through the orifice and the configuration of the orifice are such that solid and gaseous carbon dioxide are produced as the carbon dioxide exits the orifice, (ii) conveying the solid and gaseous carbon dioxide through a second conduit, where the ratio of the length of the second conduit to the length of the first conduit is at least 1:1, and (iii) directing the carbon dioxide exiting the second conduit to a destination. In certain embodiments, the length, diameter, and material of the first conduit are such that after a transition period, the liquid carbon dioxide entering the first conduit reaches the orifice as at least 90% liquid carbon dioxide when the ambient temperature is less than 30° C. In certain embodiments, the second conduit has a smooth lumen. In certain embodiments, the first conduit is uninsulated. In certain embodiments, the method further includes directing the solid and gaseous carbon dioxide from an end of the second conduit into a third conduit, the third conduit including a portion configured to slow the flow of carbon dioxide through that portion of the third conduit sufficiently to cause the solid carbon dioxide to condense before the solid carbon dioxide exits the third conduit through the opening. In certain embodiments, the portion of the third conduit configured to slow the flow of carbon dioxide is an expanded portion compared to the second conduit. In certain embodiments, the ratio of the length of the third conduit to the length of the second conduit is less than 0.1:1. In certain embodiments, the third conduit has a length between 1 and 10 feet. In certain embodiments, the third conduit has an inner diameter between 1 inch and 3 inches. In certain embodiments, the ratio of the length of the second conduit to the length of the first conduit is at least 2:1. In certain embodiments, the first conduit has a length less than 15 feet. In certain embodiments, the first conduit has an inner diameter of between 0.25 and 0.75 inches. In certain embodiments, the first conduit comprises a braided stainless steel inner material. In certain embodiments, the second conduit has a length of at least 30 feet.In certain embodiments, the second conduit has an inner diameter between 0.5 and 0.75 inches. In certain embodiments, the second conduit includes an inner material of PTFE. In certain embodiments, the third conduit includes a rigid material and is operably connected to a fourth conduit including a flexible material. In certain embodiments, the combined length of the third and fourth conduits is between 2 and 10 feet. In certain embodiments, the first conduit includes a valve for regulating the flow of carbon dioxide, and the method further includes determining a pressure and a temperature between the valve and the orifice and determining a flow rate of the carbon dioxide based on the temperature and pressure. In certain embodiments, the flow rate is determined by comparing the pressure and temperature to a set of calibration curves of flow rates at multiple temperatures and pressures. In certain embodiments, the destination to which the carbon dioxide is directed is within the mixer. In certain embodiments, the mixer is a concrete mixer. In certain embodiments, the carbon dioxide is directed to a location within the mixer where waves of concrete fold over the mixed concrete as the mixer is mixing the concrete mix. In certain embodiments, the concrete mixer is a static mixer. In certain embodiments, the mixer is a mobile mixer. In certain embodiments, the mixer is a drum of a ready-mix truck. In certain embodiments, the total heat capacity of the first and / or second conduit is equal to or less than the heat capacity that allows liquid carbon dioxide to cool to ambient temperature in less than 30 seconds as it flows through the conduit. In certain embodiments, the orifice is such that the solid and gaseous carbon dioxide exits the orifice in a mixture that includes at least 40% solid carbon dioxide.In a particular embodiment, the conduit is directed to add carbon dioxide to the concrete mixer, and cement is added to the mixer through a cement conduit, the cement conduit including a first portion including a rigid chute connected to a second portion including a flexible boot configured to allow a ready mix truck to dig a hopper over the ready mix into the boot so that the boot is dumped into the hopper, thereby allowing the cement and other ingredients to fall through the boot into the drum of the ready mix truck, where a third conduit is positioned along the first portion of the cement conduit, and a fourth conduit is positioned to move with and direct itself along the second portion of the cement conduit. In a particular embodiment, aggregate is added to the mixer through an aggregate chute adjacent to the cement chute, where a first portion of the third conduit is positioned to reduce contact with the aggregate as it exits the aggregate chute. In certain embodiments, a first portion of the third conduit extends to the bottom of the first portion of the cement chute and a fourth conduit is attached to an end of the third conduit and extends from the end of the third conduit to or near the bottom of the rubber boot when the rubber boot is positioned in the hopper of the ready-mix truck. In certain embodiments, the fourth conduit is positioned on average within x cm of the center of the rubber boot, where x=1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, or 90 cm when the rubber boot is positioned to load concrete material into the drum of the ready-mix truck.

[0005] In another aspect, provided herein is an apparatus.

[0006] In certain embodiments, provided herein is an apparatus for delivering solid and gaseous carbon dioxide, the apparatus comprising: (i) a source of liquid carbon dioxide, (ii) a first conduit, the first conduit including a proximal end operatively connected to the source of liquid carbon dioxide and a distal end operatively connected to an orifice, configured to convey liquid carbon dioxide under pressure to the orifice, the orifice being open to atmospheric or near atmospheric pressure, and configured to convert the liquid carbon dioxide to a mixture of solid and gaseous carbon dioxide as the liquid carbon dioxide passes through the orifice, and (iii) a second conduit operatively connected to the orifice for directing the mixture of gaseous and solid carbon dioxide to a desired destination, wherein the second conduit has a smooth lumen, and wherein the ratio of the length of the first conduit to the length of the second conduit is less than 1:1. In certain embodiments, the ratio of the length of the first conduit to the length of the second conduit is less than 1:2. In certain embodiments, the ratio of the length of the first conduit to the length of the second conduit is less than 1:5. In certain embodiments, the first conduit is less than 20 feet long. In certain embodiments, the first conduit is less than 15 feet long. In certain embodiments, the first conduit is less than 12 feet long. In certain embodiments, the first conduit is less than 5 feet long. In certain embodiments, the first conduit includes a valve before the orifice to regulate the flow of liquid carbon dioxide. In certain embodiments, the device further includes a first pressure sensor between the valve and the orifice. In certain embodiments, the device further includes a second pressure sensor between the source of liquid carbon dioxide and the valve. In certain embodiments, the device further includes a third pressure sensor after the orifice. In certain embodiments, the device further includes a temperature sensor between the valve and the orifice. In certain embodiments, the device further includes a control system operably connected to the first pressure sensor and the temperature sensor. In certain embodiments, the controller receives the pressure from the first pressure sensor and the temperature from the temperature sensor and calculates the flow rate of carbon dioxide in the system from the pressure and temperature. In certain embodiments, the controller calculates the flow rate based on a set of calibration curves for the device.In certain embodiments, the set of calibration curves is created using a calibration setup including a source of liquid carbon dioxide, a first conduit, an orifice, a valve in the first conduit before the orifice, a pressure sensor between the valve and the orifice, and a temperature sensor between the valve and the orifice, where the material of the first conduit, the length and diameter of the first conduit, and the material and configuration of the orifice are the same or similar to that of the device. In certain embodiments, the set of calibration curves is created by determining the flow of carbon dioxide at a plurality of temperatures measured by the temperature sensor and a plurality of pressures measured by the pressure sensor. In certain embodiments, the device further includes a third conduit operably attached to the second conduit, the third conduit having a larger inner diameter than the second conduit, and the diameter and length of the third conduit configured to slow the flow of gaseous and solid carbon dioxide and to cause condensation of the solid carbon dioxide. In certain embodiments, the first conduit is not insulated.

[0007] In certain embodiments, provided herein is an apparatus for delivering low doses of solid and gaseous carbon dioxide in an intermittent manner of repetitive doses of solid and gaseous carbon dioxide, the apparatus including: (i) a source of liquid carbon dioxide; (ii) a first conduit, the first conduit including a proximal end operably connected to the source of liquid carbon dioxide and a distal end operably connected to an orifice, the first conduit configured to convey liquid carbon dioxide under pressure to the orifice, the orifice being open to atmospheric pressure and configured to convert the liquid carbon dioxide to a mixture of solid and gaseous carbon dioxide as the liquid carbon dioxide passes through the orifice; (iii) a valve in the conduit between the carbon dioxide source and the orifice for regulating the flow of liquid carbon dioxide; (iv) a section of the conduit between the valve and the orifice, and a heat source operably connected to the orifice, the heat source configured to warm the conduit and the orifice between applications to convert the liquid or solid carbon dioxide to a gas that is discharged from the orifice. In certain embodiments, the apparatus further includes a heat sink operably connected to the heat source. In certain embodiments, the apparatus further includes (v) a second conduit operably connected to the orifice for directing the mixture of gas and solid carbon dioxide to a desired destination. In certain embodiments, the second conduit has a smooth lumen. In certain embodiments, the ratio of the length of the first conduit to the length of the second conduit is less than 1:1.

[0008] In another aspect, provided herein is a system.

[0009] In certain embodiments, provided herein is a system for intermittently delivering solid and gaseous carbon dioxide in boluses of less than 60 pounds of carbon dioxide with an application interval of at least 5 minutes, the system configured to deliver repetitive boluses at an ambient temperature of 35° C. or less in less than 60 seconds per boluse, with an average ratio of solid carbon dioxide to gaseous carbon dioxide of at least 1:1.5 in each boluse. In certain embodiments, the system is configured to deliver repetitive boluses of carbon dioxide with a coefficient of variation of less than 10%. In certain embodiments, the system is configured to deliver repetitive boluses of carbon dioxide with a coefficient of variation of less than 5%. In certain embodiments, the system includes a source of liquid carbon dioxide and a conduit from the source to a device configured to convert the liquid carbon dioxide to solid and gaseous carbon dioxide, the conduit need not be insulated. In certain embodiments, the conduit is not insulated. In certain embodiments, the system further includes a second conduit connected to the device to convert the liquid carbon dioxide to solid and gaseous carbon dioxide, the second conduit delivering the solid and gaseous carbon dioxide to a desired location. In certain embodiments, the ratio of the length of the first conduit to the length of the second conduit is less than 1:1.

[0010] Incorporation by Reference All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.

[0011] The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which: [Brief description of the drawings]

[0012] [Figure 1] A direct carbon dioxide injection assembly is shown that does not require a gas line to keep the assembly free of dry ice between runs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The methods and compositions of the present invention provide reproducible application of solid and gaseous carbon dioxide under intermittent conditions and at low dosages and short delivery times without using equipment and methods that result in significant loss of carbon dioxide during the process. The methods and devices provided herein can allow for highly accurate application, e.g., application with a coefficient of variation (CV) of less than 10%, less than 8%, less than 6%, less than 5%, less than 4%, less than 3%, less than 2%, or less than 1% over repeated dosages, e.g., when applying repeated batches of less than 200, 150, 100, 90, 80, 70, 60, 50, 40, 30, 20, or 10 pounds of carbon dioxide per batch, where the carbon dioxide is delivered as a liquid in a first conduit of the system and passes through an orifice into a second conduit of the system where it flows to a destination as a mixture of solid and gaseous carbon dioxide. In particular, the methods and compositions of the invention are useful where the dosage of carbon dioxide is low and the injection time is short, but where it is desired to deliver a mixture of solid and gaseous carbon dioxide at a high solid / gas ratio, even with significant pauses between runs and at relatively high ambient temperatures. For example, the methods and compositions of the invention can be used to deliver a mixture of solid and gaseous carbon dioxide at a high solid / gas ratio, even with significant pauses between runs and at relatively high ambient temperatures. For example, the methods and compositions of the invention can be used to deliver a mixture of solid and gaseous carbon dioxide at a high solid / gas ratio, even with significant pauses between runs and at relatively high ambient temperatures, even with significant pauses between runs and at relatively high ambient temperatures. or 10 to 60 pounds, or 10 to 40 pounds of carbon dioxide, where the average time between applications is at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 40, 50, 60, 80, 100, or 120 minutes, and the delivery time for applications is less than 180, 150, 120, 100, 90, 80, 70, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, or 10 seconds.The ratio of solid carbon dioxide to gaseous carbon dioxide delivered to the target can be at least 0.3, 0.32, 0.34, 0.36, 0.38, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, or 0.49. The reproducibility of the dose between runs can be such that the coefficient of variation (CV) is less than 20, 15, 12, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1%. These values ​​can be maintained even at relatively high ambient temperatures, such as average temperatures of more than 10, 15, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40° C.

[0014] For example, using the methods and compositions of the present invention, it is possible to deliver intermittent doses of 5 to 60 pounds of carbon dioxide with an average solid / gas ratio of at least 0.4, delivery times of less than 60 seconds, and at least 2, 4, 5, 7, or 10 minutes between runs, where the ambient temperature is at least 25° C. and the CV is less than 10%, or even CV is less than 5%, 4%, 3%, 2%, or 1%. Such short delivery times, high solid / gas ratios, and high repeatability achieved during intermittent low doses are only possible with current equipment due to significant waste of carbon dioxide, for example, by continuously venting the gaseous carbon dioxide formed between runs from the lines. The methods and systems provided herein can enable precise, accurate, and repeatable application of low doses of carbon dioxide, for example, as described above, where liquid carbon dioxide is converted to a mixture of solid and gaseous carbon dioxide without venting the gaseous carbon dioxide in the lines carrying the liquid carbon dioxide.

[0015] In a current conventional setup where carbon dioxide is converted to a solid and gas, a source of liquid carbon dioxide is connected to an orifice via a conduit, which is open to the atmosphere. Generally, beyond the orifice, the conduit extends for a relatively short distance, such as 1-4 feet, to direct the combination of solid and gaseous carbon dioxide to the desired destination. In a typical current operation, the conduit leading from the source of liquid carbon dioxide to the orifice is well insulated. Nevertheless, in intermittent operation, the conduit warms up to some degree depending on the ambient temperature and the interval between uses. If the interval between uses is long enough, when a new burst of liquid carbon dioxide is released into the conduit, the carbon dioxide in the conduit has been converted to gas between runs, and the conduit may warm up enough for some of the carbon dioxide released into the conduit to be converted to gaseous carbon dioxide, and the initial carbon dioxide leaving the orifice is often only gaseous carbon dioxide. This continues until the liquid carbon dioxide cools the conduit to a temperature low enough that the desired mixture of solid and gaseous carbon dioxide is delivered at this point, while the carbon dioxide in the conduit has been converted to gas between runs. However, the initial portion of the carbon dioxide is entirely or nearly entirely gaseous carbon dioxide, and is a relatively large amount, since the length of the conduit extends from the source of carbon dioxide to the point of use. For use in, for example, food production and other such processes, this initial burst of gaseous carbon dioxide is not a problem, since precise dosage amounts of the solid / gas mixture are not required, and dosages are carried out at intervals that allow little time for the conduit to equilibrate with the ambient temperature.

[0016] However, there are applications where a precise dose of carbon dioxide is desired, delivered intermittently in low doses, with a desired ratio of solid to gaseous carbon dioxide. This requires that the carbon dioxide reaching the orifice from the source be maintained in liquid form with a small enough amount of gas formed that it does not significantly affect the application. This can be done with cumbersome equipment such as an in-line liquid-gas separator, or through a counter-current mechanism in the snowhorn itself that maintains the carbon dioxide in a liquid state before it reaches the orifice (e.g., U.S. Pat. No. 3,667,242). However, such methods require the exhaust or re-liquefaction of the gas, both of which are wasteful, inefficient, and expensive to implement. This is especially wasteful when the distance from the source of carbon dioxide to the orifice, which is generally located near the desired target of the snow produced by the snowhorn, is long, as this provides ample opportunity for the liquid carbon dioxide to transform into a gas. There are many applications where the configuration of the various equipment on-site does not allow for a short distance between the source of liquid carbon dioxide (e.g., a tank of liquid carbon dioxide) and the final destination of the carbon dioxide. For example, in concrete operations such as ready-mix concrete operations or precast operations, where it is necessary to deliver a dose of carbon dioxide to the concrete mix in a mixer, the liquid carbon dioxide tank must be located a distance from the delivery point, for example, often more than 50 feet from the delivery point.

[0017] Provided herein are methods and compositions that 1) allow for the transport of liquid carbon dioxide from a source, such as a tank, to an orifice where it is converted to solid and gaseous carbon dioxide, while maximizing the percentage of carbon dioxide that is liquid that reaches the orifice without the need to vent the carbon dioxide or use insulated lines, 2) maximize the amount of carbon dioxide that remains solid as it travels from the orifice to its point of use, and 3) allow for repeatable and reproducible application under a variety of ambient conditions and at low dosages of carbon dioxide.

[0018] In the methods and compositions provided herein, a first conduit, also referred to herein as a transfer conduit or transfer line, conveys liquid carbon dioxide from a holding tank to an orifice that is open to atmospheric or near atmospheric pressure and configured to convert the liquid carbon dioxide to solid and gaseous carbon dioxide. The first conduit is configured to minimize the amount of gaseous carbon dioxide initially produced during and over the course of a run. Thus, the length of the first conduit from the source of liquid carbon dioxide to the orifice that produces the mixture of solid and gaseous carbon dioxide is kept short, preferably as short as possible, and / or at a set calibrated length, and the diameter is maintained at a value that allows for a small total volume in the first conduit without narrowing so much as to cause a pressure drop sufficient to convert the liquid carbon dioxide to gaseous carbon dioxide within the conduit. The first conduit is generally not insulated and is made of a material, such as braided stainless steel, that can withstand the temperature and pressure of liquid carbon dioxide. Due to its short length, the total heat capacity of the first conduit is low, and the conduit quickly equilibrates with the temperature of the liquid carbon dioxide when the liquid carbon dioxide first enters the conduit. It should be appreciated that at very low ambient temperatures, i.e., below the temperature of the carbon dioxide in the storage tank (which may vary depending on the pressure in the tank), the conduit is at a temperature low enough that the liquid carbon dioxide is not substantially converted to gas at the beginning of a run, but at ambient temperatures above the temperature at which the carbon dioxide remains liquid in the conduit, gas will inevitably evolve, with the amount of gas formed depending on the temperature the conduit reaches between runs and the heat capacity of the conduit. However, even when the ambient temperature is relatively high (e.g., above 30° C.) and the run interval is sufficient for the conduit to come into equilibrium with the ambient temperature, the time required to cool the conduit to the temperature of the liquid carbon dioxide flowing through it is negligible, e.g., less than 10, 8, 7, 6, 5, 4, 3, 2, or 1 second. As the liquid carbon dioxide flows through the conduit, additional heat is lost through the walls of the conduit to the outside air during the time of flow (assuming an ambient temperature above the temperature of the liquid carbon dioxide), but because the diameter and length of the conduit are kept low, the flow is fast and relatively little heat is lost as the carbon dioxide flows to the orifice.Thus, within a few seconds, e.g., within 10 seconds, or within 8 seconds, or within 5 seconds, the majority of the carbon dioxide remains liquid when it reaches the orifice, such as at least 80, 90, 92, 95, 96, 97, 98, or 99%. Because the ratio of solid to gaseous carbon dioxide exiting the orifice is related, at least in part, to the ratio of carbon dioxide that is liquid when it reaches the orifice, a ratio approaching 1:1 solid:gas (by weight) can be reached within seconds.

[0019] The first conduit may be of any suitable length, but should be short enough that a significant amount of gas does not accumulate in the conduit (and does not need to be removed before the liquid carbon dioxide can reach the orifice). Thus, the length of the first conduit may be less than 30, 25, 20, 17, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5 or 0.25 feet, and / or 25, 20, 17, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, 0.25, 0.1, or 0.01 feet or less, e.g., 0.1 to 25 feet, 0.1 to 15 feet, or 0.1 to 10 feet, or 1 to 15 feet. Different systems, e.g., systems provided to different customers, may all include the same length, diameter, and / or material of the first conduit, e.g., a 10 foot length or any other suitable length of conduit, so that a calibration curve developed using the same length and type of conduit can be applied to the different systems.

[0020] The inner diameter (ID) of the first conduit may be any suitable diameter, generally a smaller diameter is preferred to reduce mass and transit time to the orifice, but the diameter cannot be so small that it causes a sufficient pressure drop over the length of the conduit to convert the liquid carbon dioxide to a gas. Thus, the ID of the first conduit may be at least 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 inches, and no greater than 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, or 2 inches, e.g., 0.1-0.8, or 0.1-0.6, or 0.2-0.7, or 0.2-0.6, or 0.2-0.5 inches, e.g., about 0.25 inches, or 0.30 inches, or 0.375 inches, or 0.5 inches. The first conduit that delivers the carbon dioxide to the orifice does not need to be highly insulated and can in fact be made of a material with high thermal conductivity, for example a thin-walled metal conduit. For example, a braided stainless steel line such as that found inside a vacuum jacketed line (but without the vacuum jacket) can be used. The conduit can be rigid or flexible. The conduit is short and has a small diameter, so it has a low heat capacity, and therefore when the liquid carbon dioxide is released into the conduit, it cools rapidly to the temperature of the liquid carbon dioxide, and the liquid carbon dioxide also passes through its length quickly, so that there is a short lag time from the start of carbon dioxide delivery until the carbon dioxide delivered to the orifice is substantially all liquid carbon dioxide, or at least 80, 85, 90, 95, 96, 97, 98, or 99% liquid carbon dioxide. The lag time can be less than 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 second. The lag time depends on the ambient temperature and the run interval, and at low ambient temperatures and / or short run intervals, little or no time is needed to bring the first conduit to the temperature of liquid carbon dioxide. At sufficiently low ambient temperatures, i.e., at or below the temperature of liquid carbon dioxide at the pressure being used, substantially no time is needed to equilibrate the first conduit, since when the liquid carbon dioxide passes through it, it is already at a temperature that will not produce gaseous carbon dioxide.An exemplary conduit is 3 / 8 inch X120 with OA 321SS braided hose C / W stainless steel MnPt Attd on each end.

[0021] Typically, the first conduit includes a valve for starting and stopping the flow of carbon dioxide to the orifice, the valve being located near the orifice. The section of the conduit between the valve and the orifice, and / or the conduit located after the orifice, may freeze between runs. In certain embodiments, a separate gas conduit extends from the carbon dioxide source to the section of the first conduit between the valve and the orifice, and carbon dioxide gas is routed through this section and the orifice to remove residual liquid carbon dioxide between runs.

[0022] In alternative embodiments, no gas conduit is required. In these embodiments, a heat source is arranged so that the section of the conduit between the valve and the orifice, the orifice itself, and / or the section of the conduit after the orifice can be heated sufficiently to convert any liquids or solids in these sections and / or the orifice to gas between runs (this may usually only be necessary when the solenoid is closed and pressure is reduced, which causes the carbon dioxide to drop to the gas / solid phase part of the phase diagram, resulting in some gas and some solid snow that needs to be converted to gas by introducing heat before the next cycle). Additionally, enough suitable material can be included in the heat source, so that a heat sink of sufficient capacity is formed to sublimate the dry ice that forms between the valve and the orifice between cycles. As the liquid carbon dioxide passes through the valve, the valve temperature approaches the equilibrium temperature of the liquid, and closing the valve causes the liquid trapped between the solenoid and the orifice to change to gas and dry ice in a ratio of about 1:1, for example with dry ice at -78.5°C. This provides some additional cooling to the valve, but to function, the heat sink needs to have enough mass to utilize this cooling and still have the ability to sublimate the dry ice, which has an enthalpy of sublimation of 571 kJ / kg (25.2 kJ / mol) before reaching -78.5°C. An exemplary heat sink may be constructed with a finned design and may include any suitable material, such as aluminum. The fins help the heat sink quickly gain heat from the surroundings, and aluminum may be used due to its rapid heat transfer properties, allowing the heat to be transferred quickly to the valve to sublimate the dry ice. In certain embodiments, induction heating may be used. This design allows for cycles at short intervals, such as minimum intervals of 10, 8, 7, 6, 5, 4, 3, 2, or 1 minute, such as a minimum interval time of about 5 minutes. Heating bands can be used to provide redundancy in cooler areas, such as a band claim heater, with a first band claim heater wrapped around a heat sink under the liquid valve and a second band claim heater wrapped around the orifice.In certain embodiments, one or more induction heaters may be used. In certain embodiments, for example, one or more (e.g., two) redundant pressure sensors may be included, for example, so that if one fails, the other can begin taking readings.

[0023] In these embodiments, the need for gas lines is eliminated, reducing materials in the system. Furthermore, because no source of gaseous carbon dioxide is required in addition to a source of liquid carbon dioxide, the system can be run with smaller tanks that are not configured to output gaseous carbon dioxide, such as mizer tanks or portable dewars that are not designed to output very high gas flow rates, e.g., soda fountain tanks. These are readily available for ready installation in such facilities, thus eliminating the need to install custom tanks that are small enough for the operation, and thus eliminating the need to install gas lines.

[0024] An example of a system that does not require a separate gas line is shown in FIG. The CO2 piping assembly 100 includes fittings 102 (e.g., ½ inch MNPT to ¼ inch FNPT), valves 104 (e.g., ½ inch FNPT stainless steel solenoid valves, cryogenic liquid rated), fittings 106 (e.g., ½ inch MNPT x ½ inch 2FNPT tees), nozzles 108 (e.g., stainless steel orifices), heaters 110, fittings 112 (e.g., ½ inch MNPT thermowells), probes 114 (e.g., ½ inch MNPT temperature probes), transmitters 116 (e.g., ¼ inch MNPT pressure sensors and transmitters), fittings 118 (e.g., ½ inch MNPT x 4 inch nipples), fittings 120 (e.g., ½ inch FNPT x ¾ inch FNPT), transmitters 122 (e.g., a temperature transmitter that allows the probe to read temperatures below 0° C.), and heat sinks 124.

[0025] The device may include various sensors, which may include pressure and / or temperature sensors. For example, there may be a first pressure sensor before the valve, a second pressure sensor after the valve and before the orifice, and / or a third pressure sensor immediately after the orifice, indicating tank pressure. One or more temperature sensors may be used, for example, after the valve but before the orifice, and / or after the orifice. Feedback from one or more of these sensors may be used, for example, to determine the flow rate of carbon dioxide. The flow rate may be determined by calculation using one or more of the pressure or temperature values. See, for example, U.S. Pat. No. 9,758,437.

[0026] Additionally or alternatively, the flow rate can be determined by comparison to a calibration curve, which can be obtained, for example, by measuring the flow, for example, by measuring the change in weight of the liquid carbon dioxide tank, or by any other suitable method, using conduits and orifices similar or identical to those used in the operation, at various ambient temperatures and tank pressures. In either case, measurements of suitable pressure and / or temperature in the system can be taken at intervals such as at least every 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 3, 4, or 5 seconds, and / or no more than every 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 3, 4, 5, or 6 seconds. The control system can also calculate the amount of carbon dioxide delivered based on the flow rate and time. In certain embodiments, such as a concrete operation, the control system can be configured to send a signal to a central controller for the concrete operation each time a certain amount of carbon dioxide flows through the system, and the central controller can be configured, for example, to count the signals and stop the flow of carbon dioxide after a predetermined number of signals corresponding to a desired dose of carbon dioxide are received. This is similar to how such a controller can regulate the amount of admixture added to a concrete mix. In some systems, the admixture is pore weighted, in which case the system simulates batching up to a predetermined weight by mimicking the output of a load cell, and then when notified to drop carbon dioxide into the mixer, the system counts back from the target dose with the actual discharged carbon dioxide. This involves receiving a signal and providing a feedback voltage based on the weight of the simulated (ghost) scale.

[0027] Alternatively, the temperature and pressure of the system may be fitted to one or more suitable calibration curves, or a series of curves interpolated to create an infusion equation, and for a given dose, the time to deliver that dose is based on the appropriate infusion equation. The control system may shut off the flow of carbon dioxide after an appropriate time has elapsed. The calibration curve being used at any given time may change depending on the temperature and / or pressure readings at that time.

[0028] In certain embodiments, a temperature sensor is used that provides instantaneous or near instantaneous feedback of the liquid carbon dioxide temperature, allowing for improved accuracy when metering. It can also quickly detect when only gas is flowing in the system or when the tank is near empty. Without being bound by theory, it is believed that after orifice snow formation occurs at temperatures below -70°C, the area of ​​solid formation begins to affect the temperature of the liquid in front of the orifice, thus increasing the flow rate. This temperature sensor flow model can also indicate when the storage tank is out of equilibrium (e.g., after tank filling, when the ambient temperature is lower than the liquid temperature, when the tank pressure builder is turned off, etc.). This model may allow for very low CVs, e.g., less than 5%, or less than 3%, or less than 2%, or less than 1%. This model can remove the assumption of a carbon dioxide tank and equilibrium between the pressure and temperature of the liquid carbon dioxide. The model reads the tank pressure at the start of injection and calculates the expected temperature of the liquid carbon dioxide based on the boiling curve equation derived from the carbon dioxide phase diagram. The system also takes an initial temperature reading and calculates the transition time, which is the time from when the liquid valve opens to when liquid flows. During the transition time, a mixture of gas and liquid carbon dioxide and the gas / liquid flow equations are expected to be used, and then the liquid flow equation is used to calculate the carbon dioxide flow. The model uses a linear equation derived from multiple injections (e.g., 10, 100, over 500, or over 1000 injections) across the range of tank pressures, and is dependent on the upstream pressure. The model also has a pressure multiplier, which calculates the drop-in pressure from the inlet liquid pressure sensor to the upstream pressure sensor, and modifies the flow as the difference between these two sensors deviates. If there is an obstruction in the system piping, the multiplier adjusts the flow accordingly. The temperature multiplier reads the temperature sensor and compares it to the calculated liquid carbon dioxide temperature. If the sensor reads a temperature lower or higher than the calculated value, the temperature multiplier modifies the flow accordingly.Existing systems may have a new pressure sensor, a taller valve enclosure for quick and easy repairs, and also have a new check and hydraulic fitting stand on the downstream pressure sensor for increased durability, removing the sensor from the cold area of ​​snow formation after the orifice. The hydraulic stand has been proven to significantly reduce the failure rate of the downstream pressure sensor.

[0029] The carbon dioxide is converted to a mixture of gaseous and solid carbon dioxide at the orifice, with the ratio of solids to gas produced at the orifice depending on the percentage of carbon dioxide reaching the orifice that is liquid. If the carbon dioxide reaching the orifice is 100% liquid, the ratio of solids to gases in the mixture of solids and gases leaving the orifice may approach 50%. The orifice may be any suitable diameter, such as at least 1 / 64, 2 / 64, 3 / 64, 4 / 64, 5 / 64, 6 / 64, or 7 / 64 inches, and / or 2 / 64, 3 / 64, 4 / 64, 5 / 64, 6 / 64, 7 / 64, 8 / 64, 9 / 64, 10 / 64, 11 / 64, or 12 / 64 inches or less, for example, about 5 / 64 inches or about 7 / 64 inches. The length of the orifice must be sufficient to prevent the liquid carbon dioxide passing through from freezing, and in addition, the orifice may be flared to prevent clogging. In certain systems, a dual orifice manifold block is used which allows one valve to feed two orifices and two exhaust lines.

[0030] A dual orifice system can deliver a given carbon dioxide flow to a destination in a shorter time, and / or can deliver the flow to two different destinations, and / or can deliver the flow to a single destination at two different points of the destination (e.g., two different points in a mixer, such as a concrete mixer), which can allow for more efficient capture of carbon dioxide at the destination. This can avoid reliability and accuracy issues with certain systems, e.g., twin shaft or roller mixers for concrete, or other systems that have very short cycle times. Thus, a dual orifice system can allow both a larger delivery in a given time (e.g., up to 1.8 times that of a single orifice system; the theoretical 2x is not reached due to thermodynamic changes in the system) and a more targeted delivery (e.g., to two different points in a mixer), which can, for example, allow for improved capture efficiency. Dual orifice systems can be manufactured and used in any suitable manner. For example, a steel manifold, such as a rolled steel or stainless steel manifold, can be fully machined and can include one inlet and two outlets with appropriate orifices, e.g., 7 / 64 inch orifices, sized as described herein. The manifold may have connections for two downstream pressure sensors and T-connections for a temperature sensor and an upstream pressure sensor to reduce the mass of the system and the liquid-to-metal contact time. The dual injection system calculates the flow rate through both orifices. The dual injection system may also have an additional smooth bore discharge hose (second conduit as described herein), an additional injection nozzle, an additional downstream pressure sensor with a stand, and / or two discharge points to the mixer.

[0031] The gaseous and solid carbon dioxide mixture is then conducted from the orifice to a location for delivery to its point of use, e.g., in the case of a concrete operation such as a ready mix operation or a precast operation, a second conduit, also referred to herein as a delivery conduit or delivery line, delivers the mixture to a mixer containing a cement mixture including hydraulic cement and water, such as the drum of a ready mix truck or a central mixer. The second conduit is configured to deliver the solid and gaseous carbon dioxide mixture to its point of use, where there is little conversion of the solid carbon dioxide to gaseous carbon dioxide, so that the solid and gaseous carbon dioxide mixture delivered to the point of use is still in a high solid to gas ratio, e.g., the percentage of solid carbon dioxide in the mixture may be at least 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, or 49% of the total.

[0032] The second conduit is typically constructed to minimize friction along its length, to minimize heat exchange with the surrounding atmosphere, and to have a small total volume to maximize flow rate. For example, the second conduit may be a relatively small diameter smooth bore conduit. Any suitable means may be used to provide the second conduit with a smooth bore, such as ensuring that the inner surface of the conduit is free of irregularities and that the conduit is free of spiral grooves. Materials with coatings such as polytetrafluoroethylene (PTFE) may be used, which helps keep the conduit bore smooth as long as there are no substantial irregularities or spiral grooves. With a thin PTFE and a small amount of stainless steel braid, the hose has a low thermal mass. It may be insulated, for example, with conventional pipe insulation. The conduit typically needs to be smooth (not spiral grooved) to allow for smooth flow, and it must also be able to withstand low temperatures, i.e., dry ice (snow) passing through a hose can be at a temperature of -78°C. An exemplary second conduit is the SmoothFlex series manufactured by PureFlex (Kentwood, MI). The materials and weight used in the SmoothFlex series make them good candidates to ensure minimal temperature rise during the transition from the orifice to the destination. This maximizes the percentage of solid carbon dioxide due to low sublimation rates. The second conduit may be flexible or rigid or a combination thereof, and in certain embodiments, at least a portion may be flexible for easy positioning or repositioning. The second conduit may conduct the solid and gaseous carbon dioxide mixture over long distances with little solid-to-gas conversion because the transport time through the conduit is relatively short due to the forces resulting from the rapid conversion of liquid carbon dioxide to gas, followed by a 500-fold or greater expansion, which forces the gas and solid mixture through the conduit.The inner diameter of the second conduit can be any suitable inner diameter that allows for the rapid passage of carbon dioxide, for example, at least 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 inch, and / or 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, or 2 inches or less, for example, 0.5 inch, or 0.625 inch, or 0.750 inch. The second conduit can be, for example, at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, or 100 feet long to reach the final point where the carbon dioxide is used; the length of the second conduit generally depends on the particular operating setting in which the carbon dioxide is being used. Typically, the first conduit is kept as short as possible, and the second conduit should be of a suitable length to reach the point of use (often remote from the injection orifice), and the ratio of the length of the second conduit to the first conduit can be at least 0.5, 0.7, 1.0, 1.2, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 6, 7, 8, 9, or 10, or even greater than 10. For example, the length of the first conduit can be 10 feet or less, while the length of the second conduit can be at least 20, 30, 40, or 50 feet. The second conduit may be placed inside another conduit, such as a loosely attached plastic hose, for example, to prevent kinking during installation. The second conduit may be further insulated, for example with pipe insulation, to further minimize heat gain between injections from an external source.

[0033] In certain embodiments, the admixture may be added to the carbon dioxide stream as it is delivered. The admixture may be, for example, a liquid. A small amount of the liquid admixture may flow into the discharge line behind the orifice. The liquid may be rapidly frozen to a solid and conveyed into the mixer with the carbon dioxide. The frozen admixture is conveyed into the concrete mix with the carbon dioxide and melts or sublimes in the concrete mix. This method is particularly useful when adding admixtures that are synergistic with the carbon dioxide and / or that may affect the mineralization reaction of the carbon dioxide. For example, the admixture TIPA is effective at very low dosages, but is usually added in the form of a liquid cocktail, so that low dosage is entrained by a large amount of carrier fluid. If only the active ingredient is added, a small amount may be distributed throughout the dosage of the carbon dioxide. If chemicals do not need to be added to a dilute solution, the admixture system may be smaller.

[0034] The second (delivery) conduit can be attached to a third conduit, also referred to herein as a targeting conduit. The third conduit can be of a larger diameter than the second conduit, allowing the solid / gaseous carbon dioxide to slow down and mix, so that the solid carbon dioxide agglomerates into larger pellets. This is useful, for example, in concrete operations where carbon dioxide is added to a mixed cement mix, so that the pellets are large enough to be incorporated into the mixed cement before sublimating to any significant extent. The third conduit may be of any suitable inner diameter so long as it allows sufficient deceleration and coalescence for the desired use, for example, at least 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.2, 3.4, 3.8, or 4 inches. and / or may be 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.2, 3.4, 3.8, 4, or 4.5 inches or less, such as 0.5 to 4 inches, or 0.5 to 3 inches, or 0.5 to 2.5 inches, or about 2 inches. The third conduit may be of any suitable length that slows down the carbon dioxide significantly or for a very long period of time to allow for the desired condensation without the material sticking to the walls or sublimating to any significant extent, for example at least 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 28, 32, 36, 40, 44, or 48 inches, and / or 8, 10, 12, 14, 16, 18, 20, 22, 24, 28, 32, 36, 40, 44, 48, 54, 60, 72, 84 inches or less, for example, 2-8 feet, or 2-6 feet, or 3-6 feet, or 3-5 feet. The third conduit is typically made of a rigid material and is durable enough to withstand the conditions in which it will be used.For example, in concrete mixing operations, the third conduit is often located in the chute where aggregate-containing material is poured into the mixer, and is in repeated contact with the moving aggregate, so it should be strong and durable enough to withstand repeated contact with the aggregate daily. This could be as much as 20 tons of material per truck, and as many as 400-500 trucks per month. Traditional snow horn materials would not withstand such an environment. A suitable material is stainless steel of a suitable diameter, such as 1 / 8 to 1 / 4 inch. In some cases, it may be desirable to increase the thickness, for example to 1 / 2 inch or more, for example by installing armor in high wear locations. The third conduit is typically a high wear item and may be inspected periodically, for example every 3-6 months depending on production. In certain operations, for example, where the third conduit is never or rarely moved, or is moved slightly between runs, the third conduit may be the last conduit in the system. This is the case, for example, for stationary mixers, such as central mixers used in ready mix operations.

[0035] In some operations, such as concrete mixing operations where the mixed material is dropped into the drum of a ready-mix truck, the material is dropped through a chute that terminates in a flexible section, allowing the chute to be placed into the hopper of the drum and then removed. In such situations, a fourth conduit of flexible material, also referred to herein as an end conduit, may be attached to the third conduit to travel with the flexible chute used to drop the concrete material. The inner diameter of the flexible conduit is such that it fits snugly against the outer diameter of the third conduit. Any suitable flexible and durable material may be used in the fourth conduit, such as silicone.

[0036] In certain embodiments, a token system is used as a security measure. For example, if the customer has no outstanding bills, at regular intervals (e.g., monthly), a unique key (or "token") is generated and distributed to the customer. In case of outstanding bills or other fraudulent activity, the token may be withheld. The customer enters the token into the system, for example, via a touch screen or a web interface display (which functions the same as a touch screen, but is displayed on a batch computer, i.e., suitable for potential installation of the system without a touch screen). At the end of the time interval (e.g., a month), the system program disables the system only if the unique key has not been entered, e.g., in the absence of a unique key, the system goes into idle mode and ignores any start injection signal sent to the system. The same can happen, for example, if the system loses network connectivity for a period of time (e.g., if the customer disables the network signal in an attempt to run the system without the unique key). Additionally or alternatively, an external connector may be used on the enclosure for input and output, allowing the provider to disable the system manually or automatically if an attempt is made to modify the enclosure. There is no reason for a customer or installer to open the enclosure, and if the unit fails, the customer can request that the external connector be disconnected and a replacement unit will be sent out to replace the faulty one. EXAMPLES

[0037] Example 1 Ready-mix concrete plants provide dry batching in their trucks; that is, dry concrete ingredients are placed in a drum in the truck along with water, and the concrete is mixed in the truck. It is desired to deliver carbon dioxide to the truck while the concrete is being mixed, where the carbon dioxide is a mixture of solid and gaseous carbon dioxide with a high percentage of solid carbon dioxide, e.g., at least 40% solid carbon dioxide. The batching facility does not have space for a tank of liquid carbon dioxide to feed the line to the truck, so the liquid carbon dioxide tank is located more than 50 feet away from the final destination. It is desired to deliver application amounts of 1% carbon dioxide by weight of cement (bwc) to successive batches of concrete in different trucks during the day. The trucks can be full loads of 10 cubic yards of concrete, or partial loads of 1 cubic yard of concrete. A typical batch of concrete uses 15% cement by weight, and a typical cubic yard of concrete weighs 4000 pounds, so a cubic yard of concrete contains 600 pounds of cement. Thus, the minimum application amount of carbon dioxide would be 6 pounds, and the maximum application amount would be 60 pounds. The time between applications is on average at least 10 minutes.

[0038] The liquid carbon dioxide is released from the tank through a 10-foot line of 3 / 8-inch ID braided stainless steel to atmospheric pressure, where it is directed to an orifice configured to convert the liquid carbon dioxide to solid and gaseous carbon dioxide. Upon release from the orifice, the mixture of solid and gaseous carbon dioxide is directed through a 5 / 8-inch ID smooth bore insulated 50-foot line to the drum of a ready-mix truck. This line terminates in a 1 / 4-inch thick and 2-foot long piece of 2-inch ID stainless steel tubing contained inside a chute that directs the concrete ingredients from their respective storage containers to the drum of the truck; the stainless steel line terminates in a flexible section mounted on the steel tubing that runs with a rubber boot on the end of the chute that is dumped into the hopper of the ready-mix truck.

[0039] The system is calibrated against a calibration system using the same length, diameter, and material as the original conduit and tested for flow rate under various temperature and pressure conditions. The appropriate pressure and temperature are obtained during operation of the system for a given batch and matched against the appropriate calibration curve or curves to determine the flow rate and length of time required to deliver the desired dosage, and when the system determines that a 1% bwc dosage has been delivered to the truck, the flow of carbon dioxide is stopped.

[0040] The daily ambient temperature ranges from 10 to 25 degrees Celsius. Each truck remains in the loading area while the material is loaded for a maximum of 90 seconds, with carbon dioxide delivery time being less than 45 seconds.

[0041] The system delivers adequate dosage to achieve 1% carbon dioxide bwc with an average of 5 loads per hour (40 loads total) over an 8 hour period with a solids / total carbon dioxide ratio of at least 0.4, with an accuracy of less than 10% coefficient of variation.

[0042] While preferred embodiments of the present invention have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will occur to those skilled in the art without departing from the present invention. It should be understood that various alternatives to the embodiments of the present invention described herein may be used in carrying out the present invention. It is intended that the following claims define the scope of the invention, and that methods and structures within the scope of these claims and their equivalents are covered thereby.

Claims

1. 1. A method for intermittently delivering doses of carbon dioxide in solid and gaseous form to mixed concrete in a concrete mixer, comprising: (i) conveying liquid carbon dioxide from a source of liquid carbon dioxide through a first conduit to an orifice open to atmospheric or near atmospheric pressure; (a) the first conduit comprises a material capable of withstanding the temperature and pressure of the liquid carbon dioxide; (b) the pressure drop through and the configuration of the orifice are such that solid and gaseous carbon dioxide are produced as the carbon dioxide exits the orifice; carrying liquid carbon dioxide; and (ii) conveying the solid and gaseous carbon dioxide through a second conduit, wherein a ratio of a length of the second conduit to a length of the first conduit is at least 1:1; (iii) directing the solid and gaseous carbon dioxide from an end of the second conduit into a third conduit, the third conduit including a portion configured to slow a flow of the carbon dioxide through that portion of the third conduit sufficiently to condense the solid carbon dioxide before the solid carbon dioxide exits the third conduit through an opening; (iv) directing the carbon dioxide exiting the third conduit to the mixed concrete; and Including, the third conduit comprises a rigid material and is operably connected to a fourth conduit comprising a flexible material; a second portion including a rigid chute connected to a second portion including a flexible boot configured to allow a ready mix truck to dig the hopper on a ready mix into the flexible boot such that the flexible boot is dumped into a hopper, thereby allowing cement and other ingredients to drop through the flexible boot into a drum of the ready mix truck, wherein the third and fourth conduits are directed to add carbon dioxide to the concrete mixer, and wherein the cement is added to the concrete mixer via a cement chute; the second portion including a rigid chute connected to a second portion including a flexible boot configured to allow a ready mix truck to dig the hopper on a ready mix into the flexible boot such that the flexible boot is dumped into a hopper, thereby allowing cement and other ingredients to drop through the flexible boot into a drum of the ready mix truck, wherein the third conduit is disposed along the first portion of the cement chute and a fourth conduit is disposed to move with and direct itself along the second portion of the cement chute.

2. 2. The method of claim 1, wherein the length, diameter, and material of the first conduit are such that the liquid carbon dioxide entering the first conduit reaches the orifice as at least 90% liquid carbon dioxide when the ambient temperature is less than 30° C.

3. The method of claim 1 , wherein the second conduit has a smooth lumen.

4. The method of claim 1 , wherein the first conduit has a length of less than 20 feet.

5. The method of claim 1 , wherein the portion of the third conduit configured to slow the flow of the carbon dioxide is an expanded portion compared to the second conduit.

6. The method of claim 1 , wherein the ratio of the length of the third conduit to the length of the second conduit is less than 0.1:

1.

7. The method of claim 1 , wherein the third conduit has a length between 1 and 10 feet.

8. The method of claim 1 , wherein the third conduit has an inside diameter of between 1 inch and 3 inches.

9. The method of claim 1 , wherein the ratio of the length of the second conduit to the length of the first conduit is at least 2:

1.

10. The method of claim 1 , wherein the first conduit has a length of less than 15 feet.

11. The method of claim 1 , wherein the first conduit has an inside diameter of between 0.25 and 0.75 inches.

12. The method of claim 1 , wherein the first conduit comprises a braided stainless steel inner material.

13. The method of claim 1 , wherein the second conduit has a length of at least 30 feet.

14. The method of claim 1 , wherein the second conduit has an inside diameter of between 0.5 and 0.75 inches.

15. The method of claim 1 , wherein the second conduit comprises an inner material of PTFE.

16. 10. The method of claim 1, wherein the combined length of the third and fourth conduits is between 2 and 10 feet.

17. 2. The method of claim 1, wherein the first conduit includes a valve for regulating a flow of carbon dioxide, the method further comprising determining a pressure and a temperature between the valve and the orifice, and determining a flow rate of the carbon dioxide based on the temperature and pressure.

18. The method of claim 17 , wherein the flow rate is determined by comparing the pressure and temperature to a set of calibration curves of flow rates at multiple temperatures and pressures.

19. 10. The method of claim 1, wherein the carbon dioxide is directed to a location within the concrete mixer where waves of concrete fold onto the mixed concrete as the concrete mixer is mixing the concrete mix.

20. The method of claim 1 , wherein the concrete mixer is a static mixer.

21. The method of claim 1 , wherein the concrete mixer is a mobile mixer.

22. 22. The method of claim 21, wherein the mixer is a drum of a ready-mix truck.

23. 2. The method of claim 1, wherein aggregate is added to the concrete mixer through an aggregate chute adjacent to the cement chute, and a first portion of the third conduit is positioned to reduce contact with the aggregate as it exits the aggregate chute.

24. 2. The method of claim 1, wherein a first portion of the third conduit extends to a bottom of the first portion of the cement chute and the fourth conduit is attached to an end of the third conduit and extends from the end of the third conduit to or near the bottom of the flexible boot when the flexible boot is disposed in the hopper of the ready-mix truck.

25. 1. An apparatus for delivering solid and gaseous carbon dioxide to mixed concrete in a concrete mixer, comprising: (i) a source of liquid carbon dioxide; (ii) a first conduit comprising a proximal end operably connected to a source of liquid carbon dioxide and a distal end operably connected to an orifice, the first conduit being not thermally insulated, having a length of less than 12 feet, having an inner diameter of between 0.25 and 0.75 inches, and configured to convey liquid carbon dioxide under pressure to the orifice, the orifice being open to atmospheric pressure or near atmospheric pressure, and configured to convert the liquid carbon dioxide to a mixture of solid and gaseous carbon dioxide as the liquid carbon dioxide passes through the orifice; (iii) a second conduit operatively connected to the orifice for directing the mixture of gaseous and solid carbon dioxide to a third conduit, the second conduit having a smooth bore and a ratio of a length of the first conduit to a length of the second conduit being less than 1:1; (iv) a third conduit including a portion configured to slow the flow of the carbon dioxide through that portion of the third conduit sufficiently to condense the solid carbon dioxide before it exits the third conduit through an opening to a concrete mixer; and (v) concrete mixers; An apparatus comprising:

26. 26. The apparatus of claim 25, wherein a ratio of a length of the first conduit to a length of the second conduit is less than 1:

2.

27. 26. The apparatus of claim 25, wherein the ratio of the length of the first conduit to the length of the second conduit is less than 1:

5.

28. 26. The apparatus of claim 25, wherein the first conduit is less than 5 feet in length.

29. 26. The apparatus of claim 25, wherein the first conduit includes a valve before the orifice to regulate the flow of the liquid carbon dioxide.

30. 30. The apparatus of claim 29, further comprising a first pressure sensor between the valve and the orifice.

31. 30. The apparatus of claim 29, further comprising a second pressure sensor between the source of liquid carbon dioxide and the valve.

32. 30. The apparatus of claim 29, further comprising a third pressure sensor after the orifice.

33. 31. The apparatus of claim 30, further comprising a temperature sensor between the valve and the orifice.

34. 34. The apparatus of claim 33, further comprising a control system operably connected to the first pressure sensor and the temperature sensor.

35. 35. The apparatus of claim 34, wherein the control system receives a pressure from the first pressure sensor and a temperature from the temperature sensor, and calculates a flow rate of carbon dioxide within the apparatus from the pressure and temperature.

36. 36. The apparatus of claim 35, wherein the control system calculates the flow rate based on a set of calibration curves for the apparatus.

37. 37. The apparatus of claim 36, wherein the set of calibration curves is created using a calibration setup including a source of liquid carbon dioxide, a first conduit, an orifice, a valve in the first conduit prior to the orifice, a pressure sensor between the valve and the orifice, and a temperature sensor between the valve and the orifice, wherein the material of the first conduit, the length and diameter of the first conduit, and the material and configuration of the orifice are the same or similar to that of the apparatus.

38. 38. The apparatus of claim 37, wherein the set of calibration curves is generated by determining carbon dioxide flow at a plurality of temperatures measured by the temperature sensor and a plurality of pressures measured by the pressure sensor.

39. 1. An apparatus for delivering low doses of solid and gaseous carbon dioxide in an intermittent manner of repeated doses of solid and gaseous carbon dioxide, comprising: (i) a source of liquid carbon dioxide; (ii) a first conduit including a proximal end operably connected to a source of liquid carbon dioxide and a distal end operably connected to an orifice, the first conduit configured to convey liquid carbon dioxide under pressure to the orifice, the orifice being open to atmospheric pressure, and configured to convert the liquid carbon dioxide into a mixture of solid and gaseous carbon dioxide as the liquid carbon dioxide passes through the orifice; (iii) a valve in the conduit between the source of carbon dioxide and the orifice for regulating the flow of liquid carbon dioxide; (iv) a section of a conduit between the valve and the orifice, and a heat source operably connected to the orifice, the heat source configured to heat the conduit and the orifice between applications to convert liquid or solid carbon dioxide to a gas that is discharged from the orifice; An apparatus comprising:

40. 40. The apparatus of claim 39, further comprising a heat sink operably connected to the heat source.

41. 40. The apparatus of claim 39, further comprising: (v) a second conduit operatively connected to said orifice for directing said mixture of gaseous and solid carbon dioxide to a desired destination.

42. 42. The apparatus of claim 41, wherein the second conduit has a smooth lumen.

43. 42. The apparatus of claim 41, wherein a ratio of a length of the first conduit to a length of the second conduit is less than 1:1.

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