Patent Grant
12097537
The present invention pertains to the field of ventilation and exhaust management and safety during solvent and volatile fluid chemical handling. More particularly the present invention relates to a ventilated solvent containment system or containment skid and cabinet for providing a ventilation and spill management system for solvent and volatile chemical containers and solvent lines in open work areas or areas that have not been classified or equipped as hazardous work areas.
Ventilation and spill management systems are used in the safe handling of solvents, spillable liquids, volatile chemicals, flammable and combustible materials, and other toxic chemicals. Various building and fire protection codes provide restrictions and guidelines on the transport, use, and storage of volatile chemicals to mitigate fire, contamination, corrosion, and explosion hazards, and to generally control the inadvertent or excessive release of volatile chemicals into the environment. Containment regulations for volatile chemicals generally involve both spill containment and ventilation requirements to provide adequate protection to people, property, and the environment in the location of the chemical. Properly designed, constructed, and ventilated containment areas are important for confining and controlling volatile and combustible leaks, spills, residues, or deposits and to discharge any vapours to a safe location, reducing the likelihood of fire, contamination, or explosion.
Liquid solvents are used in a variety of industrial applications including for coatings, paints, lubricants, adhesives, cleaning, extraction and chromatography processes, hydrocarbon extraction and processing, and chemical synthesis. In the pharmaceutical industry in particular, solvents are to dissolve poorly soluble molecules for use in, for example, synthesis, extraction, screening, purification, and formulation. Solvents have also found applications in environmental chemistry and are known as effective countermeasures against pollutant non-aqueous phase liquids, as well as in the production of functional energy materials and synthesis of biodiesel.
While using solvent in an industrial process, each room, section, or area of the facility needs to be considered individually in determining its ventilation requirements. Adherence to, for example, National Fire Protection Association (NFPA), International Building Code (IBC), and International Mechanical Code (IMC) guidelines, as well as local and regional Occupational Health and Safety guidelines, is required to safely operate the system. In industry, venting and containment systems, such as fume hoods and industrial scale air flow and evacuation systems have been traditionally used to maintain air flow requirements of hazardous cosolvents. In an example of a ventilation system, U.S. Pat. No. 10,337,751 to Lieberman describes an extraction room and ventilation system with opposing supply and exhaust systems that provide a laminar type air flow configured to transmit fresh air flow to said extraction room. In an example of a gas containment system, U.S. Pat. No. 9,383,064 to Olander et al. describes a ventilation gas management system having an enclosure adapted to contain fluid supply vessels and through which ventilation gas is flowed to provide safe operation in the event of leakage of fluid from a vessel.
A hazardous location is generally defined as an area where fire or explosion hazard may exist due to flammable gases or vapors, flammable liquids, combustible dust, or ignitable fibers or flyings. Hazardous locations are classified for the purpose of ensuring the safe and proper specification and safe installation and operation of electrical and electronic equipment and for the regulation of ventilation standards to protect people, property, and the environment. An ordinary location is understood to be a location that is other than a hazardous location. In industrial applications where it is desirable to use a solvent or hazardous chemical in a space not deemed to be a hazardous location, there remains a need for a safe solvent containment, ventilation, and spill management system to enable volatile and hazardous chemicals to be stored and used safely.
This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.
An object of the present invention is to provide a solvent containment, ventilation and spill management in a process interlocking system to enable volatile and hazardous chemicals to be stored safely in an ordinary location. Another object of the present invention is to provide a vented containment skid for solvent containment and ventilation in an ordinary location.
In an aspect there is provided a solvent containment system comprising: a vented cabinet comprising cabinet sidewalls and a cabinet top wall; a liquid containment tray positioned below the vented cabinet comprising a tray base and tray sidewalls for enclosing a maximum liquid containment volume, at least part of the liquid containment tray fluidly connected to the vented cabinet; at least one aperture above the maximum liquid containment volume of the containment tray for receiving ambient air into the vented cabinet; a ventilation duct at or near the top of the vented cabinet connected to an air flow regulator to draw the ambient air through the at least one aperture into the vented cabinet and out the ventilation duct to an exhaust system; at least one solvent handling component inside the vented cabinet; a solvent control system connected to the at least one solvent handling component, the solvent control system capable of controlling solvent flow in the solvent handling component; and a safety sensor interlocked with the solvent control system such that a signal from the safety sensor indicating a potentially hazardous condition in the solvent containment system is sent to the solvent control system to mitigate the potentially hazardous condition.
In an embodiment, the safety sensor is one or more of an air flow sensor, fluid level sensor, moisture sensor, temperature sensor, ultrasonic sensor, door sensor, and chemical sensor.
In another embodiment, the solvent containment further comprises one or more of a asphyxiate gas dispenser and a neutralizer dispenser.
In another embodiment, the air flow regulator is capable of negative air flow velocities above the containment tray at least about 100 cubic feet per minute.
In another embodiment, the safety sensor detects one or more of electrostatic discharge, moisture, containment tray fluid level, presence of solvent, temperature, an open door in the vented cabinet, light, and air flow velocity.
In another embodiment, the solvent containment further comprises a support structure inside the vented cabinet capable of supporting the at least one solvent handling component.
In another embodiment, the solvent containment further comprises a support surface extending between the sidewalls of the containment tray, the support surface comprising a plurality of apertures.
In another embodiment, the support surface is outside of the vented cabinet and ambient air is directed through the plurality of apertures into the containment tray. In another embodiment, the support surface is capable of supporting a solvent container.
In another embodiment, the apertures of the support surface comprise one or more perforation apertures, gap apertures, and mesh surfaces.
In another embodiment, the solvent containment further comprises an air flow control system to control the air flow regulator.
In another embodiment, the maximum liquid containment volume of the containment tray is greater or equal to the solvent handling component total solvent volume capacity.
In another aspect there is provided a method of solvent containment comprising: containing a solvent handling component inside a vented cabinet; monitoring an environmental factor inside the vented cabinet with at least one safety sensor; controlling solvent flow in the solvent handling component with a solvent control system interlocked with the at least one safety sensor; and when the safety sensor detects a potentially hazardous condition, electronically sending a signal to the solvent control system to mitigate the potentially hazardous condition.
In an embodiment, the safety sensor detects one or more of electrostatic discharge, moisture, spill tray fluid level, presence of solvent, temperature, light, an open door in the vented cabinet, and air flow velocity.
In another embodiment, the safety sensor is monitoring continuously when solvent is flowing in the solvent handling component.
In another embodiment, the solvent handling component is a solvent pump, solvent tank, solvent conduit, valve, valve manifold, extraction column, or chromatography column.
In another embodiment, mitigating the potentially hazardous condition comprises increasing air flow velocity to the vented cabinet.
In another embodiment, mitigating the potentially hazardous condition comprises slowing or stopping solvent flow in the solvent handling component. In another embodiment, the method further comprises waiting until the safety sensor no longer detects the potentially hazardous condition, resetting the solvent control system, and reenabling solvent flow in the solvent handling component.
In another aspect there is provided a vented containment skid comprising: a containment tray comprising a base and sidewalls enclosing a volume and an open top; a support surface extending between the sidewalls of the containment tray, the support surface comprising a plurality of apertures; a ventilation duct in fluid connection with the containment tray; and an air flow regulator fluidly connected to the ventilation duct to create a negative air flow through the support surface, into the containment tray, and through the ventilation duct to an exhaust system.
In an embodiment of the vented containment skid, the support surface is capable of supporting a solvent container.
In another embodiment of the vented containment skid, the support surface comprises at least one plate.
In another embodiment of the vented containment skid, the air flow regulator is connected to a control system to adjust the air flow.
In another embodiment of the vented containment skid, the apertures of the support surface comprise one or more perforation apertures, gap apertures, or mesh surfaces.
In another embodiment of the vented containment skid, the air flow regulator comprises one or more fan, turbine, vacuum pump, and blower.
In another embodiment, the vented containment skid further comprises base supports attached to the containment tray.
In another embodiment of the vented containment skid, the base supports enable sliding relocation of the vented containment skid.
In another embodiment, the vented containment skid further comprises a cabinet in fluid connection with the contamination tray and the ventilation duct.
In another embodiment of the vented containment skid, the air flow above the support surface is at least 50 cubic feet per minute.
In another embodiment, the vented containment skid further comprises an air flow control system to control the air flow regulator.
In another embodiment of the vented containment skid, the air flow control system is electrically coupled with a solvent supply control system.
For a better understanding of the present invention, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
As used in the specification and claims, the singular forms “a”, “an” and “the” include plural references unless the context clearly dictates otherwise.
The term “comprise” and any of its derivatives (e.g. comprises, comprising) as used in this specification is to be taken to be inclusive of features to which it refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied. The term “comprising” as used herein will also be understood to mean that the list following is non-exhaustive and may or may not include any other additional suitable items, for example one or more further feature(s), component(s) and/or element(s) as appropriate. The terms “having”, “including” and “containing”, and grammatical variations thereof, are inclusive or open-ended and do not exclude additional, unrecited elements and/or method steps. The term “consisting essentially of” when used herein in connection with a composition, device, article, system, use, or method, denotes that additional elements and/or method steps may be present, but that these additions do not materially affect the manner in which the recited composition, device, article, system, method, or use functions. A composition, device, article, system, use, or method described herein as comprising certain elements and/or steps may also, in certain embodiments, consist essentially of those elements and/or steps, and in other embodiments consist of those elements and/or steps, whether or not these embodiments are specifically referred to.
As used herein, the term “about” refers to an approximately +/−10% variation from a given value. It is to be understood that such a variation is always included in any given value provided herein, whether or not it is specifically referred to. The recitation of ranges herein is intended to convey both the ranges and individual values falling within the ranges, to the same place value as the numerals used to denote the range, unless otherwise indicated herein.
The use of any examples or exemplary language, e.g. “such as”, “exemplary embodiment”, “illustrative embodiment” and “for example” is intended to illustrate or denote aspects, embodiments, variations, elements or features relating to the invention and not intended to limit the scope of the invention.
As used herein, the terms “connect” and “connected” refer to any direct or indirect physical association between elements or features of the present disclosure. Accordingly, these terms may be understood to denote elements or features that are partly or completely contained within one another, attached, coupled, disposed on, joined together, in communication with, in fluid communication with, electrically joined to, operatively associated with, etc., even if there are other elements or features intervening between the elements or features described as being connected.
As used herein the term “supercritical fluid” refers to a fluid wherein the fluid can exist in a supercritical condition with no clear distinction between vapour and liquid states, or combination of both vapour and liquid states. In a supercritical state, the fluid is at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist, but below the pressure required to compress it into a solid. Generally supercritical conditions for carbon dioxide, for example, exist above 7.38 MPa (1070 psi) and above 31.1 degrees centigrade (88° F.). The term “superfluid” encompasses both supercritical fluids and subcritical fluids.
As used herein, the term “hazardous location” is a term of art defined and classified by safety and regulatory authorities as a location where flammable liquids, gases or vapors or combustible materials exist in sufficient quantities to produce an explosion or fire and where ventilation, electrical, and safety systems have been designed and installed to accommodate the presence of these materials. In hazardous locations, specifically designed equipment and special installation techniques must be used to protect against the explosive and flammable potential of these substances. The designation of hazardous location can vary between jurisdictions, however each jurisdiction will have a variety of fire, safety, electrical, and other regulations which are required to be satisfied for building, maintenance, and use of hazardous materials in these locations.
As used herein, the term “ordinary location” refers to a room, building, or location that is not classified as a hazardous location and is not equipped with the specifically designed equipment or ventilation systems required under safety guidelines and regulations for the use and storage of hazardous, volatile, and flammable chemicals.
Described herein is a solvent containment and process interlocking system that provides safe liquid solvent handling, storage, and containment in an ordinary location. The presently described solvent containment and process interlocking system provides a safe solvent containment, ventilation, and spill management system enable volatile and hazardous chemicals to be stored and used safely in a non-hazardous location. Also described herein is a vented solvent containment skid that can be used as a ventilation and spill management system for the storage and use of hazardous and volatile chemicals and solvents in an ordinary or non-hazardous location. The present vented containment skid provides adequate fluid containment as well as ventilation to satisfy safe chemical and solvent storage and use regulations to enable volatile and hazardous chemicals to be stored and used safely in an ordinary location. The vented solvent containment skid can be mobile and comprise wheels or a palette based that can be easily moved with a palette truck or jack, or can be substantially immobile such as a stationary cabinet.
By providing an exhaust system, spill containment system, and process interlocking system in a single installation, the present solvent containment system and vented containment skid provides adequate air capture velocity to satisfy ventilation safety and workplace regulations for hazardous chemicals and solvents to ensure safe handling of flammable solvents in an indoor space that has not been equipped with the specifically designed equipment or ventilation systems required under safety guidelines and regulations for the use and storage of hazardous, volatile, and flammable chemicals. The present solvent containment system and vent skid also provides sufficient local exhaust ventilation to prevent dispersion into the air of dusts, fumes, mists, vapors, and gases in concentrations causing harmful exposure. Managing exhaust air flow operations of solvent allows industrial solvent processes to be carried out under the location category of ‘ordinary location’ (i.e. hazardous classification not required). Further, effective exhaust air and containment management protects laboratory and technical personnel from solvent exposure and lowers the risk of fire and explosion.
In accordance with hazardous materials handling, buildings or portions of buildings using flammable solvents used in processing are be required to install a flammable gas/vapour detection system in the area where such gases may be present that is suitable for detecting the types of gases used in the process. By encasing the solvent containers inside a vented containment system equipped with a solvent detection system this materials handling requirement can be met without retrofitting the entire room with hazardous materials ventilation equipment. Air flow regulation is accomplished in the solvent containment system by electrically connecting or coupling, also referred to as interlocking, the power for the ventilation system and the power for the control panel with the solvent control system. With adequate ventilation, spill containment capacity, and mechanical-electrical interlocking with solvent handling equipment and components, the present ventilation system can offer a regulatory compliance solution for ordinary locations. In particular, the vented exhaust system in the solvent containment system draws air from the solvent storage area directly to the outside of the building. Combined with adequate secondary fluid containment in the form of a solvent containment tray, air flow requirements and safety standards are met. With adequate make up air supplied to the room the present solvent containment and process interlocking system provides an alternative safe solvent handling device for solvent use and storage in an ordinary location.
The term “interlocking” is used in Engineering processes to refer to a feature that makes the state of two mechanisms or functions mutually dependent. An interlock can also be thought of as a hardware that stalls or stops a process pipeline when a hazard is detected until the hazard is cleared. In the present process, an interlock of solvent detection inside the solvent containment system using a solvent detector is interlocked with the solvent supply and control process such that the solvent supply and handling devices can be managed or shut off if an unsafe level of solvent is detected inside or outside the solvent cabinet. In this way solvent leaks can be detected early to avoid solvent buildup events that may pose a safety hazard.
The solvent containment system of the present invention can be used to control and regulate air flow around equipment where hazardous solvents vapours are generated or used, such as around solvent flow lines and high pressure solvent flow systems. In particular, encapsulation of solvent in secondary containment systems with ventilation as well as encapsulation of solvent transport lines in connected vent encapsulation can ensure adherence to safety regulations for the use and transport of hazardous fluids. To comply with IMC regulations, specifically Chapter 5 (Exhaust Systems): Section 503 (Motors and Fans), the power for a solvent supply system must be interlocked with the ventilation system so that the solvent supply system can only be operated if the ventilation system is running. This can be accomplished by electrically coupling the power for the ventilation system and the power for an associated solvent supply system. Ensuring that proper ventilation is present while solvent or hazardous chemicals are in the room enables safe operation of a solvent system without the need for a hazardous room classification. In high pressure systems, the present vent skid can be used to capture any released solvent fluid or vapor at the point of generation and discharge it to a remote or outdoor location to maintain a hazard-free environment in and around the equipment and indoor area. Due to the high velocity air flow generated above the vent skid through the support surface 20 and through the vented cabinet 26, the vent skid is capable of being used for storing and transporting solvent and flammable fluids in areas generally not approved for solvent containment.
The present solvent containment system is further designed to meet all regulatory solvent handling safety requirements such that solvents can be handled inside the solvent containment system placed in an ordinary location. All sources of potential ignition, such as electrostatic charge and thermal buildup, can be eliminated or adequately controlled inside the vented cabinet 26 and safety sensors to detect hazardous situations are connected by interlock to the solvent control system. Metallic or conductive containers used to transfer or move flammable liquids can be electrically bonded to each other or electrically grounded while their contents are being transferred from one container to the other in accordance with solvent handling regulations. This grounding can be accomplished, by example, through a support structure inside the vented cabinet or on the support surface that is used to support the solvent containing components. The solvent containment system can also be fitted with one or more asphyxiate gas dispenser or non-flammable gas sources, such as a carbon dioxide or nitrogen source, that can be injected into the solvent cabinet in the rare case of fire. Additionally, the solvent containment system can also be fitted with one or more integrated neutralizer dispenser. For example, if the vented cabinet contains a strong base or strong acid, the neutralizer dispensing system can discharge neutralizing agent into the cabinet in the event of a solvent leak.
The ventilation duct 16 is connected with an outflow ventilation duct system, which may also comprise one or more ventilation devices for creating air flow from the support surface 20 of the containment tray 22 through apertures 12, through the vented cabinet 26. The two arrows shown depict the direction of flow of solvent exhaust. The solvent exhaust enters the containment tray 22 via solvent apertures 12a, 12B present on top of support surface 20. The solvent exhaust then flows through the solvent containment tray 22 and vented cabinet 26 and to the ventilation duct 16 to be safely carried off to a remote location. The example shown comprises only one ventilation duct 16, however multiple ducts can also be envisaged. The diameter, design, and shape of the ventilation duct 16 can also be modified as desired provided the desired and/or required air flow volume above the support surface can be maintained. The vented cabinet 26 can also be fitted with one or more air flow conduits to create a negative pressure in one or more peripheral cabinets or secondary containment devices. The containment tray 22 can further be provided with one or more fluid outlet or drain to remove any collected solvent.
Strict air flow requirements exist for the control of flammable solvents in open areas. In an example of occupational work and safety regulations in British Columbia, Canada, (British Columbia Occupational Health & Safety Regulations OHS5.30) if a flammable liquid is dispensed or transferred inside a flammable liquids storage room the storage room must be mechanically ventilated at a rate of at least 18 m3/hr per square metre (1 cfm/sq ft) of floor area but not more than 250 m3/hr (150 cfm). Additionally, exhaust air must be discharged to the outdoors, and makeup air provided, and any makeup air duct passing through a fire separation must be equipped with an approved fire damper, and doors must be self-closing. By enclosing all solvent handling equipment within, above, or inside the present solvent containment system all solvent handling requirements can be easily met. Additionally, any door on the vented cabinet 26 which houses the solvent-handling components of the solvent containment system can also be interlocked with the solvent control system such that the door cannot be opened if the air flow requirements and solvent level requirements are not met. Stricter interlock rules can also be put in place such that any door in the vented cabinet 26 cannot be opened unless the solvent control system has limited or stopped solvent flow in the system. Additionally, the solvent containment system 10 may be designed such that all solvent handling components including the solvent tanks 24a, 24b, and other solvent handling components 46 are contained within the solvent cabinet.
The solvent containment system comprises an electronic control system comprising at least one microprocessor connected to an air flow sensor for monitoring the airflow inside the vented containment system to ensure that the system has adequate air flow to meet regulatory guidelines and for controlling the air flow regulator. Various air flow sensors can be used in the ventilation skid to ensure proper air flow and interlock with the solvent containment system and solvent flow process control. Some examples of air flow sensors include but are not limited to velometers, anemometers, vane sensor, hot wire sensors, cold wire sensors, and laminar flow sensors. Optional additional safety sensors can include chemical sensors and temperature sensors to detect leaked solvent and ensure that there is no safety hazard from increased temperature. The air flow control system of the solvent containment system can also be connected to the solvent control system to ensure that use of solvent in the solvent supply is restricted or shut off when air flow requirements are not met. The air flow control system and one or more associated microprocessor can be housed in a control box 50 above the vented cabinet 26.
A display panel 48 can provide data from the control system to a system operator to report on the ventilation system status and sensor readings. An output for the solvent control system can be displayed on display panel 48, and some or all of the control hardware for the solvent control system can be housed and protected in the control box 50. Control hardware comprises one or more processor, microprocessor, computer, or other computer hardware device containing operating instructions to execute the air regulation, solvent control, and sensor devices which are part of the solvent containment system 10. The display panel 48 can provide a human-machine interaction site on the solvent containment system to provide an indication of the set preferences, system status, and optional input control of the solvent control system and air flow control system. The system display screen or display panel 48 can also provide an interactive port for access and reporting from the control system to a human technician, and the same data can also potentially be sent to one or more peripheral or external computers, computing devices, or electronic components. The display panel 48 can further provide process information on the process progress, time to completion, and equipment operation parameters such as lower flammability limit (LFL) levels of any solvent(s) being used and air flow measurements through the containment tray 22 and/or vented cabinet 26. Actions can also be initiated by a technician from the control screen, such as draining specific equipment, valve control, drain sequences, solvent recovery protocols, interlock resetting, and drain protocols. Alarms and reminders can also be displayed and the system can confirm that certain technician checks have been done through the human machine interface. The control system, via the display panel on the solvent control system, can also provide information on the rates of solvent flow and supply, process run information, and solvent and process pressures. Data from the control system can also be collected and sent to one or more computing device for additional analysis, recording, or storage. The control system for the solvent containment system 10 can also comprise one or more communication ports, communication hubs, transceivers, or wired or wireless connections for sending data to interlock with the solvent control system. Additionally, data from the solvent control system and air flow control system can be sent to one or more computer, cloud, or other data processing or reporting system.
Vented cabinet 26 contains and protects one or more solvent handling components. Solvent handling components can include but are not limited to solvent containers, solvent tanks, valves, valve manifolds, solvent pumps, extractors, solvent mixing devices, chromatography columns, fluid lines, and conduit fittings, all of which can have mechanical, electrical, and electronic components for controlling the flow of solvent. The solvent handling components can be fluidly connected to one or more solvent supply tanks and to external systems, such as solvent extraction systems, via one or more valve manifolds. Vented cabinet 26 is ventilated to the exterior to exhaust any hazardous vapors, such as from the solvent, through a ventilation duct and ventilation conduits.
The power for the solvent control system, powered solvent handling components, and other mechanical components in the vented cabinet 26 can also be interlocked with the ventilation system such that the solvent control system can only be powered on if the air flow control system and other solvent detection and safety interlocks are running adequately. One or more air flow detectors in the vented cabinet 26 can provide feedback to ensure that the ventilation levels inside the vented cabinet are at or above required speed and/or air change volume. Regulations require minimum volumes of air flow in areas where solvent is used, and coupling or interlocking the air flow control in the vented cabinet 26 with the solvent control system ensures that when solvent is flowing an appropriate and safe level of ventilation is provided in the vented cabinet around the solvent-handling components. This can be accomplished, in one example, by electrically coupling the power for the air flow control system and the power for the solvent control system. Alternatively, other algorithmic methods of coupling one or more of the solvent sensors, air flow sensors, to the solvent control system can be done to adjust the air flow inside the vented cabinet in the case of detection of higher than expected solvent levels in the cabinet. Fires and explosions can happen when the solvent is at a high enough level in the presence of sufficient oxygen such that it will burn. Mechanical devices and systems can provide a source of ignition that can trigger a fire, such as an electrical spark, friction, static discharge, air stream, or thermal source. The most reliable way to prevent fire or explosion in an industrial setting when using flammable solvents is to continuously measure environmental factors and limit the amount of solvent liquid and vapor to a safe level.
The required capture velocity of a ventilation system for a particular chemical can be used to describe the air flow requirements for an exhaust to capture the specific hazardous, flammable, or volatile chemical. Each chemical has its own required capture velocity or minimum flow rate based on its volatility, which can be measured as the lower flammability limit (LFL) also referred to as the lower explosive limit (LEL) of a solvent, which is the lowest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in the presence of an ignition source (arc, flame, heat). The safety limit of the chemical in air is generally determined to be the volume of air in cubic feet necessary to dilute the vapor from 1 gallon of solvent to 25 percent of the lower explosive limit. At a concentration in air lower than the LFL, gas mixtures are considered to be “too lean” to burn. To determine the volume of air in cubic feet necessary to dilute any solvent vapor to 25 percent of the lower explosive limit (LEL), also referred to as the lower flammable limit (LFL) the capture velocity of the surrounding area is calculated as the dilution volume required per gallon of solvent which is:
4(100−LEL)(cubic feet of vapor per gallon)+LEL
A table of LELs for common solvents and air flow volume requirements in cubic feet per gallon at 21° C. is shown in Table 1. A more comprehensive list of common solvents and their LELs and required capture velocities can be found in the United States Occupational Health and Environmental Controls Standard Number: 1926.57.
In accordance with occupational health and safety regulations, the concentration of flammable gas or vapor must not exceed 20% of the lower explosive limit (LEL). In the present solvent containment system, accurate and regular monitoring and air flow control can ensure that the amount of solvent released into the solvent cabinet or present above the containment tray does not exceed the regulatory maximum. The interlocked solvent control system can also stop solvent flow if safe levels cannot be achieved by normal means, indicating a leak in one or more of the solvent-handling components. In the solvent containment system as described, the concentration of flammable gas or vapor can be maintained, for example, below 20% in the solvent cabinet using sufficient air flow velocities from the ambient air in the room, through the cabinet, and out of the cabinet via a ventilation duct. An air flow regulator in the ventilation duct or ventilation system draws air from the room through the cabinet and an air flow control system preferably fitted with an air velocity sensor can ensure that the ventilation in the vented cabinet is adequate to prevent the accumulation of vapors at the required air flow velocity for the LEL of the particular solvent(s) contained in the cabinet to be below the required level. Further the air flow control system is preferably interlocked with the solvent control system operation such that if the air flow is less than required for a particular solvent as measured by the air flow sensor the solvent control system will reduce or stop the flow of solvent in the solvent containment system. Additionally, in the case of an abnormally high vapor percentage of solvent or failure of ventilation in the solvent cabinet, the solvent containment system can be flushed with an asphyxiate gas such as carbon dioxide, which is a fire extinguishing agent, to dilute the solvent and oxygen amounts in the solvent cabinet and prevent combustion. Any solvent and gas could then be safely vented to the exterior.
The present vented containment system can preferably achieve negative air flow velocities above the support surface and containment tray of at least 1 cfm and up to at least about 50 cfm and preferably 100 cubic feet per minute over the capture area (support surface) and the flow rate of the air flow regulator can be adjusted as desired to achieve the required air flow volume to direct flow of solvent exhaust from the capture support surface 20 to the ventilation and exhaust system. The air flow regulator can further be connected to a control system and one or more air flow sensors to monitor and adjust the flow rate of solvent exhaust through the support surface. Each air flow regulator in the system can also have a programmable set point and an acceptable range for the solvent exhaust flow above the solvent apertures 20. In one embodiment, depending on the detected air flow rate, the sensor output can induce a signal to be sent to the air flow regulator through the control system to raise or lower the air flow rate. In another embodiment the type and/or volume of solvent supported on the support surface can be input to the control system and the control system can regulate the air flow based on the LEL or LFL requirements of the solvent. Alternatively, the flow rate of the air flow regulator can be adjusted manually.
A chemical or solvent sensor inside or near the vented cabinet 26 can also be used to monitor solvent liquid levels and/or solvent vapor levels inside the cabinet. A variety of different types of sensors can be used as LEL monitors, such as catalytic sensors, infrared absorption sensors, flame ionization sensors, and flame temperature sensors. The sensor can take regular air samples inside the cabinet and determine the amount of solvent inside the air in the cabinet. Since the amount of solvent in the air outside of the cabinet where solvent is not being used is lower than the amount of solvent in the air inside the cabinet, sensor methods that use combustion are generally positioned outside of the cabinet to limit hazard that may be caused by the sensor itself. Other sensors that can be used to interlock with the solvent containment system include but are not limited to fluid level sensors, temperature sensors, and electrical buildup or discharge sensors. In a preferred embodiment an ultrasonic sensor is used as a fluid level sensor to measure change in the level of the containment tray.
The control system can also comprise visual and/or audible alarms that can indicate when the solvent containment and ventilation system is not operating within specification. This will also cause the interlock system to prevent the transfer or use of solvent until ventilation operation is restored. Further, if the ventilation capture velocity is less than the calibrated value for the specific type of solvent, the control system will trigger an alarm and cause the interlock system to prevent further operation of the unit until the correct capture velocity is restored. In another embodiment a LEL detector can be installed within the skid internal area and connected to the control system. Using predetermined LEL or LFL requirements of the selected solvent, the control system can regulate the air flow based on real time concentrations of solvent vapor within the ventilated solvent containment system.
The present solvent containment system or ventilated containment skid can be used, for example, in a cosolvent system for superfluid extraction and chromatography systems for the extraction of desirable oils from plants. Ethanol in particular is used as a cosolvent in a carbon dioxide extraction of cannabinoids and has been found to increase the efficiency of the exaction process by significantly reducing extraction cycle time and improving operational efficiencies. Ethanol is classified as a “Flammable Liquid: Category 1 or 2 depending on formulation” by the National Fire Protection Association (NFPA), thus stringent adherence to ventilation guidelines to ensure effective capturing of ethanol vapours at the point of generation and safe discharge to outdoors needs to be maintained. The maximum allowable supply container of ethanol permitted within a standard extraction room is 55 gallons and the spill containment area (max 55 gallons of solvent) should be 84 ft2 (110″×110″) or less. The spill containment area for ethanol must always maintain adequate ventilation when ethanol is present, even if the ethanol is in a closed container. The current vent skid regulates exhaust flow to ensure adequate dilution of ethanol vapors, preferably below 25% of the lower flammability limit (LFL), and confines ethanol vapors to the area in which they are generated by way of the high air flow above the containment tray 22.
In the event of a sudden rise in solvent in the solvent cabinet the process system can be further interlocked with safety processes to rapidly address a situation involving solvent leakage. These may include, for example, increasing air flow through the solvent cabinet by increasing ventilation, activating cooling systems, or injecting an asphyxiate into the solvent cabinet. In a hazardous environment with a hazardous room classification, certain regulatory requirements must be met to ensure safety, for example minimum air flow requirements. The present process interlocking in a contained space in a solvent containment system provides a higher level of monitoring and therefore safety protection such that any potentially hazardous situation is quickly detected, the situation is mitigated quickly, and any potential damage is reduced or eliminated. The present solvent containment and process interlocking system can be used in ordinary locations, as well as in hazardous workplaces where additional protection and monitoring is desired, providing an additional layer of protection to workplaces, increasing worker and property safety.
The present solvent containment and process interlocking system can also be used in combination with other solvent systems in a variety of industrial chemical and extractive processes. One example use is in combination with carbon dioxide superfluid extraction and processing activities to extract oils from plants, for example by processes including but not limited to extraction, winterization, evaporation, essential oil capture, chromatography, and distillation. Other applications may include in oil and natural gas capture and refinement.
All publications, patents and patent applications mentioned in this specification are indicative of the level of skill of those skilled in the art to which this invention pertains and are herein incorporated by reference. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such prior art forms part of the common general knowledge.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
This application claims priority to U.S. provisional patent application 63/178,695 filed on 23 Apr. 2021, which is hereby incorporated by reference herein in its entirety.
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