T 0269/92 07-06-1994

Reasons for the Decision

The appeal is admissible.

1. Main request:

1.1. Claim 1 differs in substance from the original Claim 1 in that the feature concerning the utilisation of a structured packing in at least those regions of the distillation column system of an argon concentration and a densimetric superficial gas velocity as specified has been replaced by the feature concerning the utilisation of a structured packing in at least one region of the distillation column system of an argon concentration and a densimetric superficial gas velocity as specified.

Thus, it is the substitution of the feature "...in at least one region..." for the feature "...in at least those regions..." which was considered by the first instance to contravene Article 123(2) EPC because it allegedly extends the subject-matter of the European patent application beyond the content as filed.

1.2. When investigating the question of an infringement of Article 123(2)EPC it has to be first determined what is the content of the application as filed in respect of the subject in question.

According to the jurisprudence of the Boards of Appeal, cf. e.g. decision T 169/83 dated 25 March 1985 (published in OJ EPO 1985, 193); in particular section 3.4, it is the application as a whole which serves the purpose under Article 83 EPC of providing the information needed to carry out the invention. This information includes the statements concerning particular effects to be obtained and the problem to be solved.

1.3. In the present case, the critical question to be answered is, therefore, whether the skilled person reading the application as a whole is taught that the underlying problem can still be solved with the structured packing being utilized in at least one region of the distillation column of the argon concentration and gas velocity as specified or whether the application teaches that to obtain the desired aim the structured packing has to be utilized in all these regions.

1.4. In a number of passages, the original description of the application emphasises the relevance of attaining a reduced pressure drop per theoretical stage within the different components of the distillation system such as the high pressure column, the low pressure column and the argon column of the usual three column distillation system, cf. e.g. page 6, line 13 to 14, page 13, lines 27 to 34, page 16, lines 9 to 31 and page 17, lines 18 to 26.

The inherent technical problem to be solved by the application as illustrated in the original description has therefore to be seen in obtaining savings in the energy to be raised in the separation process by means of arriving at a pressure drop per theoretical stage in the separation components of the distillation system.

1.5. On page 16, line 9 to page 17, line 26 of the original description an analysis is presented in which the improvement in the total power consumption of a cryogenic air separation plant having a high pressure column and a low pressure column-argon column combined system is calculated as the pressure drop per theoretical stage in the column system is reduced. It arises from this analysis that in each of the two system components a certain percentage of power in dependence of a given reduction in the pressure drop within the respective component can be saved. It is substantiated that a reduction of pressure drop in the high pressure column can lead to substantial but not overwhelming power saving up to about 2.6% in the example given whereas a reduction in the pressure drop within the low pressure column-argon column system can result in power savings of substantially greater extent (in the order of 6% depending on the cycle used). It is further stated that for a 800 TPD high purity oxygen plant, for distillation trays the pressure drop per theoretical stage would be 0.5 KPa/stage and that experiments indicate that the use of ordered (structured) packing would lead to a pressure drop of 0.06 KPa/stage, i.e. a substantially smaller pressure drop as compared with the use of distillation trays.

In the view of the Board, the skilled person reading the application including the detailed description is provided with the information that he can arrive at a pressure drop already by providing structured packing only in one of the components of the distillation system where argon concentration and the densimetric superficial gas velocity are within the range as specified and following therefrom attain a power saving which would achieve the object as defined above in section 1.4.

This interpretation of the disclosure of the application is consistent with the general knowledge of the skilled person relating to the laws of flow technology. In a flow system comprising a number of flow resistance elements, the removal or reduction of only part of the flow resistance elements leads already to a reduction of the overall pressure loss of the fluid while it is clear that the maximum benefit is obtained by removing or affecting all the flow resistance elements.

1.6. The Appellant has drawn the attention of the Board to the decision T 331/87 dated 6 July 1989 (published in OJ EPO 1991, 22) pointing out that the claims according to the main request of the application in suit comply with the principle set up in the cited decision.

According to this decision, the replacement or removal of a feature from a claim may not violate Article 123(2) EPC provided the skilled person would directly and unambiguously recognise that (1) the feature was not explained as essential in the disclosure, (2) it is not, as such, indispensable for the function of the invention in the light of the technical problem it serves to solve, and (3) the replacement or removal requires no real modification of other features to compensate for the change.

The examination of the question whether these criteria are fulfilled in the present case leads to the following result:

(1) No passage can be found in the application from which it has to be concluded that it is essential to provide structured packing in all those regions where argon concentration and densimetric superficial gas velocity is in the range as specified in order to solve the inherent problem.

(2) Notwithstanding the circumstance that the greatest energy saving may be obtained in a process in which all the regions of the specified conditions utilise a structured packing, the skilled person derives from the application that a reduction in pressure drop and thus a benefit due to energy saving is effected in the case that only a part of the regions of the specified conditions is provided with the structured packing which due to its characteristic properties under the conditions as specified shows the effect of a reduced pressure drop in the range of use.

(3) The removal of the feature "...in at least those regions..." and the replacement thereof by the feature "...in at least one region..." does not require any modification of the other features of the invention. With exception of this feature, Claim 1, indeed, has not been changed in substance as compared with the original Claim 1.

1.7. It follows from the foregoing that the test for essentiality as suggested in the above-mentioned decision confirms the finding according to the above sections 1.3 to 1.5 which results from interpreting the disclosure of the application taking account of the general knowledge of the skilled person.

Summing up, the Board takes the view that the subject- matter of Claim 1 is consistent with the original disclosure of the application taken as a whole and interpreted in the light of the general knowledge of the skilled person.

Claim 1 is therefore in compliance with Article 123(2) EPC.

1.8. Having regard to the independent Claim 10, the opinion expressed in the decision under appeal (cf. page 3, paragraph 3) that Claim 10 filed with the letter of 25. April 1991 does not comply with Article 84 EPC because contrary to the requirement of clarity of the claims under Article 84 EPC, it does not contain the information compared to which arrangement the "HETP" is reduced, is shared by the Board. The Representative of the Appellant, when asked by the Chairman of the Board during the oral proceeding whether he was prepared to substitute Claims 10A for Claim 10 due to the objection of lack of clarity of Claim 10, agreed with the proposed substitution amending his request correspondingly.

Claim 10A is supported essentially by the original Claim 1 in combination with the original description page 14, lines 7 to 10. The wording of Claim 10A "said reduction of HETP being in comparison with the calculated value assuming no enhancement of mass transfer performance" explains the reference value of the reduced HETP and is based on page 7, line 4, to page 9, line 9 of the original description.

Having regard to the feature relating to the use of structured packing in a region of a distillation column system, the considerations presented in above sections 1.1 to 1.7 apply correspondingly.

Claim 10A is, therefore, in compliance with Article 123(2) EPC.

2. Auxiliary request:

Since Claims 1 and 10A are found to comply with the requirements of Article 123(2) and 84 EPC, respectively, consideration of the auxiliary requests is not necessary.

3. The examination of the issue of patentability by the first instance has only been initiated by expressing an opinion, but not been concluded. Since the ground of refusal of the application is not confirmed by the Board, the decision under appeal has to be set aside and the case, in conformity with the request of the Appellant, has to be remitted to the first instance for further prosecution (Article 111(1)) EPC.

In the substantive examination to be carried out by the first instance, the subject-matter of the observation by a third party filed with the letter dated 18 May 1993 will also have to be taken into consideration.