Title of Invention	"METHOD AND EQUIPMENT FOR PRODUCING AND MAINTAINING A GAS MIXTURE"
Abstract	A method of producing and maintaining a gas mixture comprising: providing a gas, mixture including carbon dioxide, oxygen, and air, wherein a concentration of oxygen in the gas mixture is" in a range of 10% to 22%; adding carbon dioxide to the gas mixture based on a measured carbon dioxide concentration level in the gas mixture; and adding oxygen to the gas mixture based on one of the amount of carbon dioxide added to the gas mixture and a measured oxygen concentration level in the gas mixture.

Title of Invention

"METHOD AND EQUIPMENT FOR PRODUCING AND MAINTAINING A GAS MIXTURE"

Abstract

A method of producing and maintaining a gas mixture comprising: providing a gas, mixture including carbon dioxide, oxygen, and air, wherein a concentration of oxygen in the gas mixture is" in a range of 10% to 22%; adding carbon dioxide to the gas mixture based on a measured carbon dioxide concentration level in the gas mixture; and adding oxygen to the gas mixture based on one of the amount of carbon dioxide added to the gas mixture and a measured oxygen concentration level in the gas mixture.

Full Text	FORM 2 THE PATENTS ACT 1970 [39 OF 1970] COMPLETE SPECIFICATION [See Section 10] ' "METHOD AND EQUIPMENT FOR PRODICING AND MAINTAINING A GAS MIXTURE" NORSK HYDRO ASA, a Norwegian Company, OF N-0240, Oslo, Norway The following specification particularly describes the nature of the invention and the manner in which it is to be performed :- The present invation relates to a method and equipment for procducing and maintaining a gas mixture. The present invention concerns a method and equipment for the production and maintenance of a gas mixture in one or more chambers for use in relation to poultry stunning or killing. More specifically, the present invention may expediently be used in connection with the applicant's previous, patent application PCT/NO97700331, which describes the use of gas mixtures containing mainly a constant, natural level of 02 concentration, whereby the concentration of C02 may be varied in accordance with a further speci¬fied process during treatment. Such treatment may take place by the C02 concentration being varied continuously or in stages. Treatment in stages may preferably take place in three phases, which is, moreover, stated using examples in the above patent application. In the following, a brief description will be given of how the gas treatment of poultry in three phases may take place: Phase 1 This is an introductory phase in which the animals are made accustomed to an at¬mosphere which is different to a normal atmosphere. The purpose is to expose the animals to a low concentration of C02 which causes no discomfort but which never¬theless appears to have a certain calming effect. It has been observed in many tests that this phase is decisive for how the animals react to the next phase. They behave very calmly in phase 2 if they have received the correct pretreatment, which is the purpose of phase 1. The dwell time in phase 1 is 30-40 seconds. Phase 1 may have the following atmosphere: 18-20% CO2 18-22% O2 58-64% Air Phase2 The actual stunning starts in this phase and the animals become completely relaxed and fall asleep. The atmosphere is changed further by the addition of more CO2. In this phase, the oxygen plays a very important role. If the oxygen concentration is too low, the animals become agitated with a lot of spasms, while, if the concentration is too high, it is more difficult to stun the animals. Our experience shows that the oxy¬gen concentration should be close to that of a normal atmosphere. Dwell time 40-50 seconds. Phase 2 may have the following atmosphere: 33-35% C02 18-22% 02 43-49% Air In this phase, .the required C02 concentration may vary beyond the recommended levels, depending on the type of animal and the size of the animals. The conditions must be regulated to meet individual requirements. Phase 3 After phase 2, the animals are slightly stunned but will wake up again after a very short time. Phase 3 must therefore stun the animals more deeply so that it takes longer for them to wake up. The atmosphere is changed further by the addition of more C02. The dwell time in phase 3 must be 30-40 seconds. Phase 3 may have the following atmosphere: 54-60% CO2 18-22% O2 18-28% Air The required CO2 concentration may vary in this phase as well, depending on the type of animal and depending on whether the animals are to be stunned deeply or killed. Recently, we have found out that the requirements for the quantity of 02 in this phase may be reduced down towards 10%, depending on the type of animal (for ex¬ample, chicken) which is to be treated. US 5,653,629 relates to the slaughter of poultry in an oxygen-depleted atmosphere, where the poultry is held in the atmosphere for a sufficient period of time to lose con¬sciousness and then to die. The method is a one chamber method based upon stun¬ning in an atmosphere with an extremely low oxygen concentration, less than 2% oxygen. In the examples there is given different compositions of atmospheres for batchwise treatment of the poultry. In example 4, there is stated that an oxygen con¬centration of 5% is too high to achieve satisfactory stunning results. Further, no indications are given in the disclosure how the desired atmosphere should be main¬tained during an industrial, continuous stunning process. In fact, this disclosure do not relate to the basic principles of the present application, where the poultry are ex¬posed to a mainly normal level of oxygen consentration during the stunning process, which in addition may involve plural atmospheres of treatment. US 5,152,714 is another example of anoxic poultry stunning where the gas mixture contains less than 2% oxygen. The present invention is in particular suited for performance in relation to the princi¬ples given in the Applicants own patent application'PCT/NO97/00331, which is an non oxygen depleted process for the treatment of poultry, i.e. the oxygen level is mainly at the natural level in the stunning gas mixtures. The treatment of animals with a gas mixture having a rather natural content of oxygen is believed to be more human than the prior art gas mixtures, because it is not a low level of oxygen that gives the stunning effect. It is rather the level of the carbondioxide concentration that is-the effective parameter in this sense. WO 94/15469 relates to two-chamber stunning of poultry where a stunning gas or gas mixture via a shut-off valve can be portioned to a mixing chamber. In addition, oxygen from a reservoir can be led to the same mixing chamber via an other shut-off valve. Further, a portion of gas can be taken from one chamber to the other. This publication does neither teach the man skilled in the art to add oxygen as a function of the carbon dioxide concentration measured in the gas from the zone(s), nor does it teach that the control of the oxygen addition can be of volumetric type. Further, it is not disclosed what the oxygen concentration should be in the second chamber. The present invention describes a method and equipment for supplying and regulat¬ing the gas composition in the different phases of treatment. The present invention also ensures that it is easy to maintain the desired concentration in different zones of the stunning equipment in connection with treatment in stages and, on the other hand, to maintain the desired gas concentration during treatment by continuously changing the C02 concentration. Moreover, the present invention contributes to the gas mixture/concentration being uniform throughout the zone (chamber/section) in which the animals are located during treatment. The above conditions are important parameters for achieving uniform quality of treatment of the animals so that all the animals are in the same state after treatment (stunned or killed). The treatment method has been specially developed with a view to reversible stunning, which means that there are strict requirements for good control in connection with the gas mixtures in question if the animals are to be returned to their original state. The present invention will be described in the following by means of examples and figures where: Figure 1A shows a stunning tunnel with three treatment zones, Figure 1B ' shows a cross-section of the tunnel and details of a transport system, Figure 2A shows a longitudinal section of details of the tunnel shown in figure 1 A, Figure 2B shows a cross-section of the tunnel shown in figure 1A, Figure 2C shows details of a nozzle device, Figure 3A shows a longitudinal section of part of the tunnel shown in figure 1 A, Figure 3B shows a top section of part of the tunnel shown in figure 1 A, Figure 3C shows a cross-section of part of the tunnel shown in figure 1A, Figure 4A shows a section of a system for the creation of up to three different gas mixtures in one chamber, Figure 4B shows a section of a shaft with means for the production of gas mixtures at different vertical levels, Figure 5 shows a diagram of equipment with means of regulation for the production of one or more gas mixtures. The stunning tunnel 1 in figure 1A is as described in the applicant's previous patent application. The present application concerns a solution involving equipment and a method for creating and regulating the gas level in each individual zone 2, 3, 4. The equipment is designed to ensure that it is easier to maintain the desired concentra¬tion in each zone and that the concentration is uniform throughout the zone. The cir¬culation which is described for the three zones 2, 3, 4 is also designed, together with means of separation or lamellar curtains 6, 6' between the zones, to ensure minimal leakage of gas between the zones. In the first zone 2, there will seldom be a need to add C02 and 02 because the con¬centration must be low and there is a certain back-flow from the second zone 3. How¬ever, means for producing and regulating the gas level must be arranged. This can be done simply using the following equipment: A nozzle device 7 placed in the roof of the tunnel (figure 2A) is parallel to the longitu¬dinal direction of the tunnel. The nozzle device is designed so that it spreads the gas over the belt or the cages in which the animals are located. The nozzle device 7 is shown in cross-section in figure 2B. As an alternative option (not shown) the nozzle device can be arranged in the transverse direction of the tunnel. The nozzle device 7 itself, see figure 2C, is simply made from a pipe which is sealed at both ends. Holes 10 are drilled and arranged parallel to the longitudinal direction of the nozzle device and the gas can flow out of these holes. The nozzle device 7 is connected lo a gas supply 11 for CO2 and a gas supply 12 for 02, which are supplied via the regulation unit. The regulation unit for the control and supply of gas will be de¬scribed later. Nozzle 13 for return/control gas (figure 2B) to the regulation unit is located in the cen¬tre of the section at the animals' head height so that gas can be sucked back for analysis. The analysis results control the addition of more gas. C02 and 02 are added at the same time through the same nozzle device because there must be a given ratio between these gases at all times. In the second zone 3 (figure 1A), the actual stunning begins and it is important to keep an accurate, uniform gas concentration throughout the zone. It is also important to have as little gas leakage as possible from zone 3 to zones 2 and 4. Optimal concentration and distribution of gas and minimal gas spread to the other chambers are achieved as follows: A nozzle device 14, 15 (figures 3A, 3B, 3C) is placed on each of the side walls of the zone 3 in the longitudinal direction of the tunnel. The nozzle device 14, 15 are designed in the same way as in the first zone 2 and can be raised and lowered independently of one another so that the gas flow conditions can be changed (figure 3C). The nozzle device 14, 15 are connected to one another via a pipe system 18 (figure 3C) and a circulation pump 19 so that the gas can be circulated. The gas is sucked into one nozzle device 14 and blown out via the other nozzle device 15. The purpose of such circulation is to obtain more uniform gas distribution in the zone 3. The circu¬lation will also contribute to less leakage of gas to the other, adjacent zones 2 and 4. It should be understood however, as an alternative arrangement (not shown), the gas circulation can be forced in the longitudinal or in the vertical direction of the tunnel zones by appropriate means. The outlet 20 for the return/control gas to the regulation unit is located in the circula¬tion system on the suction side right opposite the nozzle device (figure 3C). This con¬trol gas constitutes a very small quantity of the circulation gas and is sucked into the regulation unit (to be mentioned later) for analysis, the results of which control the ad¬dition of gas to the system. Supply pipes 21, 22 for C02 and 02 are connected to the circulation system on the blowing side just before the nozzle device 15 (figure 3C). The addition of gas is con¬trolled by the regulation unit, which will be described later. C02 is added as a function of the C02 concentration measured in the gas from the zone 3, while the 02 is added as a function of the quantity of C02 which is added. Al¬ternatively, 02 can be added as a function of the 02 concentration measured in the gas from the zone 3. The third zone 4 is shown in figure 1A. This zone can be equipped in the same way as the first zone 2, but with the difference that the nozzle device are adapted to the curvature of the tunnel 1 (not shown). The tunnel, which is described in the applicant's previous application, has a belt con¬veyor 9 which conveys the animals either freely or in transport boxes 8. The tunnel can easily be modified with a simpler transport arrangement which in¬volves the transport boxes 8 being pulled through the tunnel 1 on two fixed rails 5 (figure 1B). A single chain with dogs 6 pulls the box or cage along with it through the three zones of the tunnef. The tunnel can be equipped with a powerful extractor fan which starts automatically if someone opens inspection or washing doors (not shown). Moreover, this may be controlled by the regulation unit. The present invention will also be described in connection with another version of stunning equipment, see figure 4A. The equipment comprises a shaft 22 in which a cage 8 containing animals to be treated is lowered. The gas is added to the shaft in three phases as follows: The shaft 22 is connected to three separate gas tanks 23, 23', 23", each of which' contains a gas mixture equivalent to the gas prescribed for each of the three treat¬ment phases. Gas is circulated between the tank 23 and the shaft for the prescribed time in order to perform phase 1 of the stunning. The circulation is created by a fan 24 sucking gas from the shaft and blowing it into the tank 23. Gas from the tank 23 is then pressed back to the shaft via the nozzle device 25. Gas is then circulated between the tank 23' and the shaft 22 according to the same principle. Finally, gas is circulated between the tank 23" and the shaft 22, also according to the same principle. Each tank is equipped with valves 50, 50', 50" and 51, 51', 51" which can be opened/closed in accordance with the type of gas mixture which is to be conducted into the shaft. The concentration in each container 23, 23', 23" is controlled via a regulation unit which will be described later. C02 and 02 are added to each tank when the regulation unit indicates that there is a need for more gas. When the circulation in phase 3 has been completed, some extra gas is sucked back to the tank 23 so that the start concentration is not too high when the treatment of a new cage begins. Another alternative is to build a deep shaft 26, see figure 4B. The cage 8 can be low¬ered and kept at various vertical levels in accordance with a predefined pattern. The upper part of the shaft corresponds to phase 1, the central part to phase 2 and the lower part to phase 3. In a first gas circulation unit, a nozzle device 27 is connected to an opposite nozzle device 28 in a circulation system with a pump 29. The gas supply 30, 30' for C02 and 02 comes from the regulation unit, which will be described later, and is connected to the circulation's blowing side close to the nozzle device 28. The outlet 34 for the return/control gas is located in the suction side of the circulation. The central gas circulation unit 32 and lower gas circulation unit 33 work according to the same principle but the gas concentrations will correspond to phases 2 and 3 re¬spectively in the stunning process. The stunning takes place by the cage 8 being lowered to the first gas circulation unit 31. After the described dwell time, the cage is lowered to the second gas circulation unit 32 and finally to the bottom, the third gas circulation unit 33. Finally, the cage is quickly lifted out and the shaft is ready for the treatment of a new cage. In the following, the regulation equipment will be described with reference to figure 5. Regardless of the type of technical arrangement (tunnel, shaft, etc.) used in connec¬tion with the method, it is necessary to have a suitable system/suitable equipment for gas regulation. The purpose of this equipment is continuously to analyse the gas con¬centration in the different sections and to regulate the addition of gas on the basis of the analysis results. rhe regulation unit is designed to modify the stunning atmosphere on the basis of de-sired parameters. C02 is the active gas in the process and its addition is controlled by the measured concentration in each individual zone. 02 is a secondary gas and it is necessary to strive to maintain a normal level for this gas component. The need to add 02 depends on the quantity of C02 added and can thus be controlled volumetri-cally on the basis of this quantity. As an alternative, 02 is controlled by the measured concentration in each individual zone, and can be added automatically. "he regulation equipment is contained in a cabinet 34. The cabinet is located as dose to the zones as possible in order to limit the distance over which the eturn/control gas is conveyed. he cabinet 34 consists of the following parts which have the following functions: C02 meters 35, 35', 35", one for each zone. The meters are each connected to heir stunning zone via a hose 36, 36', 36" and they are equipped with a pump 37, 7', 37" which sucks gas from the section into the measuring unit. The gas may, for example, be sucked from outlet 13 in figure 2B, outlet 20 in figure 3C or outlet 34 in gure 4B. C02 flows through the meters 35, 35', 35" continuously and is continuously analysed or each zone. The analysis results are transferred directly to a regulator 38, 38', 38". each meter 35, 35', 35" with a regulator 38, 38', 38" controls its own phase in the tunning process. Is shown, the three regulators 38, 38', 38" are located in the cabinet and each is onnected on one side to its own C02 meter. In turn, each regulator 38, 38', 38" is onnected to its own set of (2) solenoid valves 39, 139, 39', 139', 39", 139". ach regulator can be set to the desired level of C02 concentration. If the C02 con-entration indicated by the meter 35 is lower than the set level, a signal is sent to the solenoid valves 39, 139 that they are to open. If the concentration of C02 is higher lan or equal to the set level, the solenoid valves are kept closed. Each set of solenoid valves 39, 139 (2) controls the supply of CO2 and O2 to its own zone. CO2 is supplied via a pressure regulator 40 to the solenoid valve 39 and is conducted from the solenoid valve via a pipe 41 to the stunning zone, for example to inlet 11 in figure 2C, inlet 21 in figure 3C or inlet 30 in figure 4B. O2 is supplied via a volume regulator 42 to the solenoid valve 139 and is conducted from the solenoid valve to the stunning zone via a pipe 43 which can be connected to inlet 12 in figure 2C, inlet 22 in figure 3C or inlet 30' in figure 4B. If the solenoid valves 39, 139 are open, both CO2 and O2 are supplied. The quantity of O2 can be regulated according to the desired mixture ratio in relation to CO2. This can be done by changing the O2 supply via the volume regulator. The regulation cabinet 34 must also have room for supplementary and safety equip¬ment 44 which may comprise: - Cut-out functions for emergency stop and door openers (washing/inspection doors). - Start of emergency fans. - Control of extractor fans for free gas. - Emergency warnings of high CO2 content in the room. It should be understood that if 02 is added in the alternative manner i.e. as a function of the measured O2 concentration, the control system for supplying this gas compo nent will be similar to that of CO2 in the above described embodiment, comprising O2 meters connected with corresponding regulators controlling the solenoid valves (not shown). Further, the gas analysing and mixing system can be run automatically to ensure that the desired concentrations of both gases are kept within certain limits by means of a computerbased system analysing and controlling the gas addition. WE CLAIM; - 1. A method of producing and maintaining a gas mixture comprising: providing a gas, mixture including carbon dioxide, oxygen, and air, wherein a concentration of oxygen in the gas mixture is" in a range of 10% to 22%; adding carbon dioxide to the gas mixture based on a measured carbon dioxide concentration level in the gas mixture; and adding oxygen to the gas mixture based on one of the amount of carbon dioxide added to the gas mixture and a measured oxygen concentration level in the gas mixture. 2. The method as claimed in Claim 1, wherein the gas mixture is added at one side of the zone and the gas is sucked through the other side of the zone, thus causing the gas mixture to flow through the zone or along the zone. 3. The method as claimed in Claim 1, wherein the carbon dioxide concentration is determined on the basis of the gas which is sucked out of the Chamber through an outlet. 4. Equipment for carrying out the process as claimed in claim 1, characterised in that the carbon dioxide is measured in the gas from the zone (s) by a meter (35) which gives a signal to the regulator (38) which opens and closes a valve (39) for the supply of carbon dioxide from a store (42) to the zone and that the regulation is designed in such a way that oxygen is added as a. function of the quantity of carbon dioxide added to the zone or added as a function, of the oxygen concentration measured in the gas from the zone (s), where the concentration of oxygen in the gas mixture is at a level equivalent to the concentration of oxygen in naturally occurring air or lower and within the range 22-10%. 5. Equipment as claimed in claim 4, wherein fitted to two opposite side of the zones are nozzle devices (14,15). 6. Equipment as claimed in claim 4, wherein a stunning tunnel (1) is provided having three zones. 7. Equipment as claimed in claim 1, wherein a stunning shaft (26) is provided having three txeatment zones arranged at different vertical levels. Dated this the 29th day of November, 2000 [RITUSHKA NEGI] OF REMFRY & SAGAR ATTORNEY FOR THE APPLICANTS]

Full Text

FORM 2
THE PATENTS ACT 1970
[39 OF 1970]
COMPLETE SPECIFICATION
[See Section 10] '
"METHOD AND EQUIPMENT FOR PRODICING AND MAINTAINING A
GAS MIXTURE"

NORSK HYDRO ASA, a Norwegian Company, OF N-0240, Oslo, Norway
The following specification particularly describes the nature of the invention and the manner in which it is to be performed :-

The present invation relates to a method and equipment for procducing and
maintaining a gas mixture.
The present invention concerns a method and equipment for the production and maintenance of a gas mixture in one or more chambers for use in relation to poultry stunning or killing.
More specifically, the present invention may expediently be used in connection with
the applicant's previous, patent application PCT/NO97700331, which describes the
use of gas mixtures containing mainly a constant, natural level of 02 concentration, whereby the concentration of C02 may be varied in accordance with a further speci¬fied process during treatment.
Such treatment may take place by the C02 concentration being varied continuously or in stages. Treatment in stages may preferably take place in three phases, which is, moreover, stated using examples in the above patent application.
In the following, a brief description will be given of how the gas treatment of poultry in three phases may take place:
Phase 1
This is an introductory phase in which the animals are made accustomed to an at¬mosphere which is different to a normal atmosphere. The purpose is to expose the animals to a low concentration of C02 which causes no discomfort but which never¬theless appears to have a certain calming effect. It has been observed in many tests that this phase is decisive for how the animals react to the next phase. They behave very calmly in phase 2 if they have received the correct pretreatment, which is the purpose of phase 1. The dwell time in phase 1 is 30-40 seconds. Phase 1 may have the following atmosphere:
18-20% CO2
18-22% O2
58-64% Air
Phase2
The actual stunning starts in this phase and the animals become completely relaxed and fall asleep. The atmosphere is changed further by the addition of more CO2. In

this phase, the oxygen plays a very important role. If the oxygen concentration is too low, the animals become agitated with a lot of spasms, while, if the concentration is too high, it is more difficult to stun the animals. Our experience shows that the oxy¬gen concentration should be close to that of a normal atmosphere. Dwell time 40-50 seconds. Phase 2 may have the following atmosphere:
33-35% C02
18-22% 02
43-49% Air
In this phase, .the required C02 concentration may vary beyond the recommended levels, depending on the type of animal and the size of the animals. The conditions must be regulated to meet individual requirements.
Phase 3
After phase 2, the animals are slightly stunned but will wake up again after a very
short time. Phase 3 must therefore stun the animals more deeply so that it takes
longer for them to wake up. The atmosphere is changed further by the addition of
more C02. The dwell time in phase 3 must be 30-40 seconds.
Phase 3 may have the following atmosphere:
54-60% CO2
18-22% O2
18-28% Air
The required CO2 concentration may vary in this phase as well, depending on the type of animal and depending on whether the animals are to be stunned deeply or killed.
Recently, we have found out that the requirements for the quantity of 02 in this phase may be reduced down towards 10%, depending on the type of animal (for ex¬ample, chicken) which is to be treated.
US 5,653,629 relates to the slaughter of poultry in an oxygen-depleted atmosphere, where the poultry is held in the atmosphere for a sufficient period of time to lose con¬sciousness and then to die. The method is a one chamber method based upon stun¬ning in an atmosphere with an extremely low oxygen concentration, less than 2% oxygen. In the examples there is given different compositions of atmospheres for

batchwise treatment of the poultry. In example 4, there is stated that an oxygen con¬centration of 5% is too high to achieve satisfactory stunning results. Further, no indications are given in the disclosure how the desired atmosphere should be main¬tained during an industrial, continuous stunning process. In fact, this disclosure do not relate to the basic principles of the present application, where the poultry are ex¬posed to a mainly normal level of oxygen consentration during the stunning process, which in addition may involve plural atmospheres of treatment.
US 5,152,714 is another example of anoxic poultry stunning where the gas mixture contains less than 2% oxygen.
The present invention is in particular suited for performance in relation to the princi¬ples given in the Applicants own patent application'PCT/NO97/00331, which is an non oxygen depleted process for the treatment of poultry, i.e. the oxygen level is mainly at the natural level in the stunning gas mixtures. The treatment of animals with a gas mixture having a rather natural content of oxygen is believed to be more human than the prior art gas mixtures, because it is not a low level of oxygen that gives the stunning effect. It is rather the level of the carbondioxide concentration that is-the effective parameter in this sense.
WO 94/15469 relates to two-chamber stunning of poultry where a stunning gas or gas mixture via a shut-off valve can be portioned to a mixing chamber. In addition, oxygen from a reservoir can be led to the same mixing chamber via an other shut-off valve. Further, a portion of gas can be taken from one chamber to the other. This publication does neither teach the man skilled in the art to add oxygen as a function of the carbon dioxide concentration measured in the gas from the zone(s), nor does it teach that the control of the oxygen addition can be of volumetric type. Further, it is not disclosed what the oxygen concentration should be in the second chamber.
The present invention describes a method and equipment for supplying and regulat¬ing the gas composition in the different phases of treatment. The present invention also ensures that it is easy to maintain the desired concentration in different zones of the stunning equipment in connection with treatment in stages and, on the other hand, to maintain the desired gas concentration during treatment by continuously

changing the C02 concentration. Moreover, the present invention contributes to the gas mixture/concentration being uniform throughout the zone (chamber/section) in which the animals are located during treatment. The above conditions are important parameters for achieving uniform quality of treatment of the animals so that all the animals are in the same state after treatment (stunned or killed). The treatment method has been specially developed with a view to reversible stunning, which means that there are strict requirements for good control in connection with the gas mixtures in question if the animals are to be returned to their original state.
The present invention will be described in the following by means of examples and figures where:
Figure 1A shows a stunning tunnel with three treatment zones,
Figure 1B ' shows a cross-section of the tunnel and details of a transport system,
Figure 2A shows a longitudinal section of details of the tunnel shown in figure 1 A,
Figure 2B shows a cross-section of the tunnel shown in figure 1A,
Figure 2C shows details of a nozzle device,
Figure 3A shows a longitudinal section of part of the tunnel shown in figure 1 A,
Figure 3B shows a top section of part of the tunnel shown in figure 1 A,
Figure 3C shows a cross-section of part of the tunnel shown in figure 1A,
Figure 4A shows a section of a system for the creation of up to three different gas mixtures in one chamber,
Figure 4B shows a section of a shaft with means for the production of gas mixtures at different vertical levels,
Figure 5 shows a diagram of equipment with means of regulation for the production of one or more gas mixtures.

The stunning tunnel 1 in figure 1A is as described in the applicant's previous patent application. The present application concerns a solution involving equipment and a method for creating and regulating the gas level in each individual zone 2, 3, 4. The equipment is designed to ensure that it is easier to maintain the desired concentra¬tion in each zone and that the concentration is uniform throughout the zone. The cir¬culation which is described for the three zones 2, 3, 4 is also designed, together with means of separation or lamellar curtains 6, 6' between the zones, to ensure minimal leakage of gas between the zones.
In the first zone 2, there will seldom be a need to add C02 and 02 because the con¬centration must be low and there is a certain back-flow from the second zone 3. How¬ever, means for producing and regulating the gas level must be arranged. This can be done simply using the following equipment:
A nozzle device 7 placed in the roof of the tunnel (figure 2A) is parallel to the longitu¬dinal direction of the tunnel. The nozzle device is designed so that it spreads the gas over the belt or the cages in which the animals are located. The nozzle device 7 is shown in cross-section in figure 2B. As an alternative option (not shown) the nozzle device can be arranged in the transverse direction of the tunnel.
The nozzle device 7 itself, see figure 2C, is simply made from a pipe which is sealed at both ends. Holes 10 are drilled and arranged parallel to the longitudinal direction of the nozzle device and the gas can flow out of these holes. The nozzle device 7 is connected lo a gas supply 11 for CO2 and a gas supply 12 for 02, which are supplied via the regulation unit. The regulation unit for the control and supply of gas will be de¬scribed later.
Nozzle 13 for return/control gas (figure 2B) to the regulation unit is located in the cen¬tre of the section at the animals' head height so that gas can be sucked back for analysis. The analysis results control the addition of more gas. C02 and 02 are added at the same time through the same nozzle device because there must be a given ratio between these gases at all times.
In the second zone 3 (figure 1A), the actual stunning begins and it is important to keep an accurate, uniform gas concentration throughout the zone. It is also important to have as little gas leakage as possible from zone 3 to zones 2 and 4.

Optimal concentration and distribution of gas and minimal gas spread to the other chambers are achieved as follows:
A nozzle device 14, 15 (figures 3A, 3B, 3C) is placed on each of the side walls of the zone 3 in the longitudinal direction of the tunnel.
The nozzle device 14, 15 are designed in the same way as in the first zone 2 and can be raised and lowered independently of one another so that the gas flow conditions can be changed (figure 3C).
The nozzle device 14, 15 are connected to one another via a pipe system 18 (figure 3C) and a circulation pump 19 so that the gas can be circulated. The gas is sucked into one nozzle device 14 and blown out via the other nozzle device 15. The purpose of such circulation is to obtain more uniform gas distribution in the zone 3. The circu¬lation will also contribute to less leakage of gas to the other, adjacent zones 2 and 4. It should be understood however, as an alternative arrangement (not shown), the gas circulation can be forced in the longitudinal or in the vertical direction of the tunnel zones by appropriate means.
The outlet 20 for the return/control gas to the regulation unit is located in the circula¬tion system on the suction side right opposite the nozzle device (figure 3C). This con¬trol gas constitutes a very small quantity of the circulation gas and is sucked into the regulation unit (to be mentioned later) for analysis, the results of which control the ad¬dition of gas to the system.
Supply pipes 21, 22 for C02 and 02 are connected to the circulation system on the blowing side just before the nozzle device 15 (figure 3C). The addition of gas is con¬trolled by the regulation unit, which will be described later.
C02 is added as a function of the C02 concentration measured in the gas from the zone 3, while the 02 is added as a function of the quantity of C02 which is added. Al¬ternatively, 02 can be added as a function of the 02 concentration measured in the gas from the zone 3.
The third zone 4 is shown in figure 1A. This zone can be equipped in the same way as the first zone 2, but with the difference that the nozzle device are adapted to the curvature of the tunnel 1 (not shown).

The tunnel, which is described in the applicant's previous application, has a belt con¬veyor 9 which conveys the animals either freely or in transport boxes 8.
The tunnel can easily be modified with a simpler transport arrangement which in¬volves the transport boxes 8 being pulled through the tunnel 1 on two fixed rails 5 (figure 1B). A single chain with dogs 6 pulls the box or cage along with it through the three zones of the tunnef.
The tunnel can be equipped with a powerful extractor fan which starts automatically if someone opens inspection or washing doors (not shown). Moreover, this may be controlled by the regulation unit.
The present invention will also be described in connection with another version of stunning equipment, see figure 4A.
The equipment comprises a shaft 22 in which a cage 8 containing animals to be treated is lowered. The gas is added to the shaft in three phases as follows: The shaft 22 is connected to three separate gas tanks 23, 23', 23", each of which' contains a gas mixture equivalent to the gas prescribed for each of the three treat¬ment phases.
Gas is circulated between the tank 23 and the shaft for the prescribed time in order to perform phase 1 of the stunning. The circulation is created by a fan 24 sucking gas from the shaft and blowing it into the tank 23. Gas from the tank 23 is then pressed back to the shaft via the nozzle device 25.
Gas is then circulated between the tank 23' and the shaft 22 according to the same principle.
Finally, gas is circulated between the tank 23" and the shaft 22, also according to the same principle.
Each tank is equipped with valves 50, 50', 50" and 51, 51', 51" which can be opened/closed in accordance with the type of gas mixture which is to be conducted into the shaft.

The concentration in each container 23, 23', 23" is controlled via a regulation unit which will be described later. C02 and 02 are added to each tank when the regulation unit indicates that there is a need for more gas.
When the circulation in phase 3 has been completed, some extra gas is sucked back to the tank 23 so that the start concentration is not too high when the treatment of a new cage begins.
Another alternative is to build a deep shaft 26, see figure 4B. The cage 8 can be low¬ered and kept at various vertical levels in accordance with a predefined pattern. The upper part of the shaft corresponds to phase 1, the central part to phase 2 and the lower part to phase 3.
In a first gas circulation unit, a nozzle device 27 is connected to an opposite nozzle device 28 in a circulation system with a pump 29.
The gas supply 30, 30' for C02 and 02 comes from the regulation unit, which will be described later, and is connected to the circulation's blowing side close to the nozzle device 28.
The outlet 34 for the return/control gas is located in the suction side of the circulation.
The central gas circulation unit 32 and lower gas circulation unit 33 work according to the same principle but the gas concentrations will correspond to phases 2 and 3 re¬spectively in the stunning process.
The stunning takes place by the cage 8 being lowered to the first gas circulation unit 31. After the described dwell time, the cage is lowered to the second gas circulation unit 32 and finally to the bottom, the third gas circulation unit 33. Finally, the cage is quickly lifted out and the shaft is ready for the treatment of a new cage.
In the following, the regulation equipment will be described with reference to figure 5. Regardless of the type of technical arrangement (tunnel, shaft, etc.) used in connec¬tion with the method, it is necessary to have a suitable system/suitable equipment for gas regulation. The purpose of this equipment is continuously to analyse the gas con¬centration in the different sections and to regulate the addition of gas on the basis of the analysis results.

rhe regulation unit is designed to modify the stunning atmosphere on the basis of de-sired parameters. C02 is the active gas in the process and its addition is controlled by the measured concentration in each individual zone. 02 is a secondary gas and it is necessary to strive to maintain a normal level for this gas component. The need to add 02 depends on the quantity of C02 added and can thus be controlled volumetri-cally on the basis of this quantity. As an alternative, 02 is controlled by the measured concentration in each individual zone, and can be added automatically.
"he regulation equipment is contained in a cabinet 34. The cabinet is located as dose to the zones as possible in order to limit the distance over which the eturn/control gas is conveyed.
he cabinet 34 consists of the following parts which have the following functions:
C02 meters 35, 35', 35", one for each zone. The meters are each connected to heir stunning zone via a hose 36, 36', 36" and they are equipped with a pump 37, 7', 37" which sucks gas from the section into the measuring unit. The gas may, for example, be sucked from outlet 13 in figure 2B, outlet 20 in figure 3C or outlet 34 in gure 4B.
C02 flows through the meters 35, 35', 35" continuously and is continuously analysed or each zone. The analysis results are transferred directly to a regulator 38, 38', 38".
each meter 35, 35', 35" with a regulator 38, 38', 38" controls its own phase in the tunning process.
Is shown, the three regulators 38, 38', 38" are located in the cabinet and each is onnected on one side to its own C02 meter. In turn, each regulator 38, 38', 38" is onnected to its own set of (2) solenoid valves 39, 139, 39', 139', 39", 139".
ach regulator can be set to the desired level of C02 concentration. If the C02 con-entration indicated by the meter 35 is lower than the set level, a signal is sent to the solenoid valves 39, 139 that they are to open. If the concentration of C02 is higher lan or equal to the set level, the solenoid valves are kept closed.

Each set of solenoid valves 39, 139 (2) controls the supply of CO2 and O2 to its own zone.
CO2 is supplied via a pressure regulator 40 to the solenoid valve 39 and is conducted from the solenoid valve via a pipe 41 to the stunning zone, for example to inlet 11 in figure 2C, inlet 21 in figure 3C or inlet 30 in figure 4B.
O2 is supplied via a volume regulator 42 to the solenoid valve 139 and is conducted from the solenoid valve to the stunning zone via a pipe 43 which can be connected to inlet 12 in figure 2C, inlet 22 in figure 3C or inlet 30' in figure 4B.
If the solenoid valves 39, 139 are open, both CO2 and O2 are supplied. The quantity of O2 can be regulated according to the desired mixture ratio in relation to CO2. This can be done by changing the O2 supply via the volume regulator.
The regulation cabinet 34 must also have room for supplementary and safety equip¬ment 44 which may comprise:
- Cut-out functions for emergency stop and door openers (washing/inspection doors).
- Start of emergency fans.
- Control of extractor fans for free gas.
- Emergency warnings of high CO2 content in the room.
It should be understood that if 02 is added in the alternative manner i.e. as a function of the measured O2 concentration, the control system for supplying this gas compo nent will be similar to that of CO2 in the above described embodiment, comprising O2 meters connected with corresponding regulators controlling the solenoid valves (not shown).
Further, the gas analysing and mixing system can be run automatically to ensure that the desired concentrations of both gases are kept within certain limits by means of a computerbased system analysing and controlling the gas addition.

WE CLAIM; -
1. A method of producing and maintaining a gas mixture comprising:
providing a gas, mixture including carbon dioxide, oxygen, and air, wherein a concentration of oxygen in the gas mixture is" in a range of 10% to 22%;
adding carbon dioxide to the gas mixture based on a measured carbon dioxide concentration level in the gas mixture; and
adding oxygen to the gas mixture based on one of the amount of carbon dioxide added to the gas mixture and a measured oxygen concentration level in the gas mixture.
2. The method as claimed in Claim 1, wherein the gas mixture is added at one side of the zone and the gas is sucked through the other side of the zone, thus causing the gas mixture to flow through the zone or along the zone.
3. The method as claimed in Claim 1, wherein the carbon dioxide concentration is determined on the basis of the gas which is sucked out of the Chamber through an outlet.
4. Equipment for carrying out the process as claimed in claim 1, characterised in that the carbon dioxide is measured in the gas from the zone (s) by a meter (35) which gives a signal to the regulator (38) which opens and closes a valve (39) for the supply of carbon dioxide from a store (42) to the zone and that the regulation is designed in such a way that oxygen is added as a. function of the quantity of carbon dioxide added to the zone or added as a function, of the oxygen concentration measured in the gas from the zone (s), where the concentration of oxygen in the gas mixture is at a level equivalent to the concentration of oxygen in naturally occurring air or lower and within the range 22-10%.
5. Equipment as claimed in claim 4, wherein fitted to two opposite side of the zones are nozzle devices (14,15).
6. Equipment as claimed in claim 4, wherein a stunning tunnel (1) is provided having three zones.
7. Equipment as claimed in claim 1, wherein a stunning shaft (26) is provided having three txeatment zones arranged at different vertical levels.
Dated this the 29th day of November, 2000
[RITUSHKA NEGI]
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANTS]

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Patent Number

207031

Indian Patent Application Number

IN/PCT/2000/00678/MUM

PG Journal Number

30/2007

Publication Date

27-Jul-2007

Grant Date

16-May-2007

Date of Filing

29-Nov-2000

Name of Patentee

YARA INTERNATIONAL ASA

Applicant Address

BYGDOY ALLE 2, P.O. BOX 2464 SOLLI, N-0240 OSLO, NORWAY.

Inventors:

#	Inventor's Name	Inventor's Address
1	AAGE GRIMSLAND	HVELVEN 6, N-3269 LARVIK, NORWAY.
2	BENT KLOSTER ANDREASEN	SOLBAKKEN 14, DK-7000 FREDERICIA, DENMARK.

PCT International Classification Number

A22B 3/00

PCT International Application Number

PCT/NO99/00150

PCT International Filing date

1999-05-10

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	19982402	1998-05-27	Norway