Mixed gas generating device

Abstract

Disclosed is a mixed gas generating device and has an object to provide a mixed gas generating device capable of generating CO and H 2 with favorable energy efficiency. An energy efficiency characteristic line 10 of electrolysis with respect to a generation ratio between CO and H 2 (CO/H 2 ) becomes a curve projecting downward. Thus, electrolysis is executed not at an operation point A where CO/H 2 =1/2 is given but in a divided manner at an operation point B and an operation point C. However, the electrolysis time is divided into electrolysis time periods such that the generation ratio of a mixed gas becomes CO/H 2 =1/2 after the electrolysis is executed with the respective generation ratios. As a result, energy efficiency in the vicinity of an operation point D higher than the operation point A can be obtained.

1 . A mixed gas generating device for generating a mixed gas composed of hydrogen and carbon monoxide with a predetermined mixing ratio by electrolyzing water and carbon dioxide, comprising:
 at least one electrolytic tank provided with water and carbon dioxide therein;   a pair of electrodes provided in said electrolytic tank; and   potential control means for applying, instead of a predetermined potential difference which achieves said predetermined mixing ratio, a plurality of potential differences including a potential difference larger than said predetermined potential difference and a potential difference smaller than said predetermined potential difference between said electrodes.   
     
     
         2 . The mixed gas generating device according to  claim 1 , wherein
 said plurality of potential differences are determined so that an energy efficiency (a calorific value of a generated product to input energy) obtained in the case where each of said plurality of potential difference is applied between said electrodes is higher than that obtained in the case where said predetermined potential difference is applied between said electrodes.   
     
     
         3 . The mixed gas generating device according to  claim 2 , wherein
 the order of applying said plurality of potential differences between said electrodes is determined in accordance with a degree of temporal change of an energy efficiency obtained in the case where each of said potential differences is applied between said electrodes.   
     
     
         4 . The mixed gas generating device according to any one of  claims 1  to  3 , wherein
 said electrolytic tank is provided with an electrolytic solution having carbon dioxide absorbing characteristics therein; and 
 the order of applying said plurality of potential differences between said electrodes is determined to be an order from the larger potential difference. 
 
     
     
         5 . The mixed gas generating device according to  claim 4 , further comprising:
 pH changing means for changing pH of said electrolytic solution from the alkali side to the acid side, when said plurality of potential differences are to be applied between said electrodes.   
     
     
         6 . The mixed gas generating device according to any one of  claims 1  to  5 , wherein
 each potential difference on the side smaller than said predetermined potential difference is set to a potential difference larger than a predetermined potential difference at which a generation speed of hydrogen to be generated becomes the lowest speed determined in advance.