WO1998031970A1

WO1998031970A1 - Method for treating air for passenger space air-conditioning

Info

Publication number: WO1998031970A1
Application number: PCT/FR1998/000076
Authority: WO
Inventors: Marc Trancart
Original assignee: Marc Trancart
Priority date: 1997-01-21
Filing date: 1998-01-16
Publication date: 1998-07-23
Also published as: FR2758612B1; FR2758612A1; AU5992698A

Abstract

The invention concerns a method for treating polluted air in a single operation, using a compact appliance, with low energy consumption and limited maintenance, for supplying clean and breathable air. The invention uses a system for sucking the stale air by means of a pump with liquid jet, said jet producing liquid being itself the purifying reagent operating in close circuit. The system comprises an air intake (1), means for recycling, for operating in close circuit (6, 9) a water jet pump (2), sucking the liquid and producing the reactive air-liquid contact, a reactor (3), in which the reactive air-liquid contact is continued, the degassing (4) and the recuperating of the overflow (5). The air outlet (17) is sucked by the air conditioning system. The recommended base reagent is an aqueous medium, preferably alkaline, which fixes sulphur, nitrogen and carbon oxides, captures aerosols, dissolves hydrocarbons. Activated carbon in powder form is added so as to absorb the hydrocarbons, aldehydes and other odorous compounds which may be salted out by the reactive liquid.

Description

AIR TREATMENT SYSTEM FOR AIR CONDITIONING

The present invention is a compact air purification system, designed more particularly to provide healthy and deodorized ambient air from air contaminated by exhaust gases, cigarettes, etc.

STATE OF THE ART

In general, compact interior air treatment systems use filters with a porous structure, in order to retain dust and aerosols or activated carbon in the dry process. These systems have reduced efficiencies and are limited to certain types of pollutants. They present a risk of clogging. Filters with a porous structure are effective only on particles and from a given diameter. Activated carbon filters are only effective on certain vapors and odors. Semi-humid systems have been envisaged, the principle being to pass the stale air over a filtering or fibrous medium humidified by an absorbent liquid solution. In the system described in patent WO 96/20097, a tank filled with fibers of hollow structure and large contact surface, moistened by an absorption reagent is used. This invention applies rather to the deodorization of an internal, confined atmosphere.

Processes which can also be described as semi-humid in which a filter is impregnated with a reagent have been envisaged for extractor hoods in kitchens or laboratories.

In the treatment of industrial gaseous effluents, wet processes using washing towers in which the reagents are sprayed against the current are versatile and effective. They are widely used for treating atmospheric emissions in the chemical industry, combustion plants and incinerators. These systems which spray reagents in washing towers, against the flow of stale air, are however not very suitable for miniaturization. To treat a contaminated gas wet, the gas can also be passed through the liquid; this principle is used in industry, for the treatment of air loaded with solid or liquid suspended matter. The principles of bringing air into contact with water are the suction of air through a vortex, a venturi effect, or any means of crossing the flow of liquids and gases. The principle is notably widely used for the purification of air from paint booths. The water jet pump, which is a use of the venturi effect, has been envisaged as a means of dedusting, in various settings, in particular for vacuum cleaners. The present invention belongs to the latter range of methods.

TECHNICAL PROBLEM TO BE SOLVED

The object of the invention is more particularly to treat polluted air in a single operation, with a compact device, with low energy consumption and limited maintenance, in order to provide healthy and breathable air.

More specifically, the specifications of the invention are: • Aspirating air which can be polluted by a wide spectrum of polluting compounds,

• Provide healthy make-up or recycling air for the comfort and health of the people occupying the passenger compartment.

• Design a compact system to be accommodated, for example, under a car hood, each tank occupying no more space, for example, than a windshield washer container.

• Have a low power consumption, for example, compatible with the power supply of an automobile.

• Do not ask for excessive maintenance, do not clog up.

The system described below is intended more specifically to treat conditioned interior air, whether to purify outside make-up air, polluted by exhaust gases or indoor air in recycling, contaminated by fumes and smells of cigarettes. It meets the specifications described above, However, from the means described in the invention, It is possible to produce systems which can be used for any type of treatment of stale air to be breathed. For example, without limitation: purify the compressed air from scuba or any breathing apparatus, before the compressor, treat the air in a "smoking" area in an air-conditioned room, treat the make-up air in an air-conditioned room during peaks of pollution, for people with fragile conditions respiratory system. Finally, this invention can also be adapted to purify any type of polluted air, even heavily loaded, but at low flow and when a compact system, not requiring significant maintenance is desired,

STATEMENT OF THE INVENTION

List of attached figures relating to the description:

Fig. 1: Single line diagram of the entire system.

Fig. 2: Schematic axial section of the reactor, in which the water jet pump is fully submerged,

Fig. 3: System for lining the reactor body, with a perforated plate.

The invention provides a solution to the above problem by using a system for extracting stale air by means of a liquid jet pump. The liquid producing the jet itself being the purification reagent used in a closed circuit.

The system includes:

• an air intake (1),

The recirculation means, for the operation of the closed circuit,

• a water jet pump (2), sucking up the liquid and making the air-reactive contact,

• a reactor (3), in which the air-liquid contact, the degassing (4) and the recovery of the overflow (5) continue,

The overflow is either pumped directly by the recirculation pump (6), or directed by gravity flow (7) into a reagent tank (8), where a submerged pump (9) is installed, which replenishes the recirculation pump (6 ).

The air to be treated is drawn in directly by the liquid jet pump. It is taken up, after degassing, in the upper part of the reactor, directly by the cabin air conditioning system.

The flow rate of the purification system can be increased and regulated by means of an air booster upstream of the suction. The basic reagent recommended is an aqueous medium, preferably an alkaline medium, which fixes the oxides of sulfur, nitrogen and carbon, captures the aerosols, dissolves the hydrocarbons,

Powdered activated carbon is added to adsorb hydrocarbons, aldehydes and other odorous compounds which may be released by the reagent.

These two reagents can be used at very high concentrations, in order to increase the efficiency of the process, but above all to fix, in a small volume, a large quantity of polluting compounds, before saturation of the reagent,

Optimal efficiency is obtained by using a pump provided with a jet breaker in its lower part (10) and by directing the jet towards the base of a reactor of cylindrical shape (1 1), thus uniformly distributing the bubbles of air in the reactor and avoiding increasing the size of the air bubbles by melting them.

The efficiency is also increased by increasing the contact time in the reactor, before degassing in the upper part, A filling with perforated plates or inclined strips allows this effect to be obtained,

DETAILED DESCRIPTION OF THE INVENTION

The detailed description presented below relates more particularly to the production of a make-up air treatment system for a passenger compartment. It can be housed in a hood and provide purified make-up air for passenger breathing, even from air heavily polluted by exhaust gases or cigarette smoke. It includes a reagent tank separate from the reactor, The stale air is sucked in by the air inlet (1) from the water jet pump (2), which is immersed in the reactor (3). Its axis is superimposed on the vertical axis (13) of the cylindrical reactor. The suction of the water jet pump (14) is connected by a pipe to an orifice located on the external wall of the reactor (15). The jet is directed vertically, downwards, on the lower horizontal wall of the cylinder (1 1). An overflow (5) is located in the upper part of the reactor.

On the upper horizontal wall (16) there is an orifice (1 7) which collects the degassed air at the surface of the reagent (4) and the upper orifice for connection of the liquid inlet to the water jet pump (18). An orifice and a drain valve are provided in the lower part of the tank (19). The reactor has in its middle part a macroporous packing hermetically applied against the walls of the cylinder. This lining (12) is intended to slow the upward movement of the air bubbles by interposing on their trajectory a series of baffles, before arriving at the surface of the liquid, It is located between the lower part of the jet pump d water (12) and the overflow (13), An example of lining with perforated cellular etching plates is given on p 8, and fig 4. NB The lining is not essential for the operation of the device, however, it improves the efficiency, without significantly increasing the pressure drop.

The reactor overflow (5) flows by gravity into a reagent tank (8), located in the lower position relative to the reactor. A submerged pump (9) is located in the tank. This pump ensures both the mixing of the reagent and the raising of the liquid to the reactor. A hole in the upper part of the reservoir (21) allows the filling of reagent (water, soda, activated carbon, or others, ...). A drain valve is provided in the lower part (22). The discharge pipe (23) of the submerged pump supplies the water jet pump, either directly or through a so-called "jockey" pump (6 ) whose function is to restore sufficient pressure to the inlet of the water jet pump (18). The reactive liquid has several functions:

• Air entrainment when passing through the liquid jet pump.

• Contact with polluting compounds. • Neutralization, dissolution, fixation of pollutants;

• storage of these compounds in the reactive liquid, until the latter is saturated;

• The modification of the surface tension, which will cause the reduction of the size of the bubbles and therefore will increase the contact surface and the efficiency of the system.

For the example of use taken into account, and to fulfill the functions indicated above, the following mixture is recommended:

A concentrated solution of sodium hydroxide in an aqueous medium, or any other alkaline solution, to which powdered activated carbon is added,

• Water produces the capture and fixing effect by dissolving vapors and gases such as carbon nitrogen oxides, sulfur, ozone, etc.,)

• The use of an alkaline aqueous solution increases the efficiency, and the fixing capacity of the compounds described above, by neutralization reaction. It also makes it possible to fix hydrocarbons in the form of aerosols or vapors, tars, oils and tars, by increasing their solubility.

It is important to specify that the device is effective without soda, that it is more effective with soda and that the fixing capacity of the products mentioned above is proportional to the amount of soda dissolved. The only drawback of a high sodium hydroxide concentration is the need to handle a corrosive liquid for filling.

• Powdered activated carbon is added to the solution, in order to capture residual odors and increase the capacity to fix unburnt volatile hydrocarbons, aldehydes and other volatile odorous products weakly fixed by the alkaline solution.

It is also possible to use the invention without powdered activated carbon, as a pretreatment before a powdered activated carbon filter. The two processing steps are then complementary. The service life of the dry activated carbon filter will be increased, if the system presented is used in αmont. In addition, the range of application of the overall system constituted by the present invention, followed by an activated carbon filter is considerably extended compared to an active carbon filter alone.

The water jet pump used consists of a water inlet pipe (18), followed by a reduction in diameter creating a pressure drop, then by a conical throttle accelerating the jet (24) . This is sent into a pipe with a diameter greater than the jet and widening towards a tubular end part (25). Upstream of this pipe, in the vacuum zone (14), is the air intake. A jet breaker (10), located in the tubular part, divides the jet, creating the upstream air draw and the air-water contact.

The internal lining of the reactor is intended to prevent bubbles from rising vertically and rapidly in a straight line. This filling must create baffles which will slow down this ascent. In any case, the packing must not create a significant loss of load, nor passage through pores or orifices of small diameters which would risk clogging and block the free rise of bubbles. This lining can be produced from stacks of perforated cell plates or grids made up of strips inclined with respect to the horizontal (12). Fig. 3 describes a stack made up of plates (26), the underside of which is made up of cells of square shape (27) in plan view and of hollow triangular shape in cross section (28), the top of the triangle, facing towards top, is extended by a perforation (29). The organization of the stack, by shifting the orifices relative to the vertical, causes a movement of the bubbles, in a sawtooth fashion, the result of which is vertical. By this device, there is an increase in contact time, without significant pressure drop.

As a variant of the system, a booster can be added to the air supply (1), which allows the flow to be increased and regulated. The ventilation system of the passenger compartment air conditioning also allows, to a lesser extent, to increase and vary the flow. The purifying yield will however decrease at the same time as the increase in the air flow / purifying reagent flow ratio. The system can also be modified in that the bringing into contact between the air and the purifying liquid is carried out by means of a booster assembly - injection pipe in the reactor, and suction in the upper part. The purifying liquid being kept in circulation in a closed circuit, only to ensure mixing and homogeneity. The injection rod is provided at its end with means for distributing fine bubbles at the base of the reactor.

Claims

1 - Compact air purification system, suitable for the treatment of cabin air, characterized in that it comprises;

• The means of connection to an air intake (1),

• A liquid jet pump (2) sucking the stale air, the liquid being a reactant circulating in a closed circuit, thanks to which it is possible to trap a wide range of polluting compounds in a single operation,

• A reactor (3) into which is injected the jet having sucked the stale air, provided with an overflow (5) for the evacuation of the reactive liquid and a cavity

- upper degassing of purified air (4), • The pumping means and the pipes making it possible to create the circulation of the reactive liquid with sufficient pressure for the operation of the liquid jet pump system in closed circuit,

• The means of connection of the purified air outlet, to a ventilation system (17),

2 - Air cleaning system according to claim 1, characterized in that it sends the jet of the liquid jet pump vertically on the horizontal base (1 1) of a cylindrical reactor and thus distributes the bubbles of gas uniformly in the reactor before they begin their upward movement.

3 - Air cleaning system according to claim 1 characterized in that the reactor contains, above the point of injection of the jet, the means of increasing the time of rise of the bubbles in the tank, for a small loss load, thanks to a lining (12) forming an obstacle to the direct vertical movement of the air bubbles towards the degassing surface.

4 - Air cleaning system according to claim 1, characterized in that the closed circuit comprises the flow by gravity of the overflow (5) of the reactive liquid in a tank (8) in which there is a submerged pump ( 9) which replenishes the liquid jet pump (2). 5 - Air cleaning system according to claims 1 and 4, characterized in that a pump (6) located just upstream of the liquid jet pump restores the pressure necessary for the optimal operation thereof.

6 - Air cleaning system according to claim 1, characterized in that the reactive liquid is an aqueous solution, making it possible to capture and fix in the solution, for example nonlimiting, oxides of carbon, sulfur, d 'nitrogen, oil aerosols, tars, unburnt hydrocarbons ... by a set of phenomena involving in particular capillarity, migration by difference in concentration, solubilization.

7 - Air cleaning system according to claims 1 and 6, characterized in that the aqueous solution is alkaline and contains hydroxide ions whose higher value of concentration is not limited, allowing to improve the efficiency of the aqueous solution, in particular for the oxides of carbon, sulfur, nitrogen and to increase the capacity of retention for the compounds quoted previously by neutralization as well as the aerosols of oils, and the tars, the hydrocarbons unburnt by dissolution .

8 - Air cleaning system according to all of claims 1, 4, and 6, or 1, 4, 6 and 7 characterized in that the reactive liquid contains powdered activated carbon, allowing the treatment of volatile hydrocarbons , aldehydes and other odorous compounds and their fixation by adsorption in the reactive liquid, until saturation,

9 - Air cleaning system according to claims 1, 6 and 7, characterized in that it is used as pretreatment before the use of an activated carbon filter in the dry process.

10 - Air cleaning system according to claim 1, characterized in that a means of creating and adjusting an overpressure located upstream of the air inlet of the liquid jet pump, makes it possible to increase and regulate the air flow.