GAS SUPPLY

Press, Volume LXXXIX, Issue 27040, 15 May 1953, Page 10

GAS SUPPLY

calorific value REDUCED TECHNICAL REASONS FOR CHANGE

Gas of a lower calorific value than previously has been supplied by the Christchurch Gas Company for the last five months. This is revealed in the statutory annual report of the gas examiner (Mr N. P. Alcorn) for the year ended March 31, 1953. The report says that the company gave notice to the Minister of Industries and Commerce of its intention to supply gas of a calorific value of 450 British thermal units a cubic foot as from December 18, 1952. From that date until the end of March this year the average calorific value of the gas supplied was 459 British thermal units. When the Board of Trade (Gas) Regulations came into effect in 1925 the company undertook to supply gas of a calorific value of 470 British thermal units, and did not alter this undertaking until last. year. At that time the Christchurch gas supply was of higher calorific value.than that of any other main centre in New Zealand. The 4-per cent, drop in calorific value since December brings Christchurch into line with most other gas companies in New Zealand. A British thermal unit is defined as “the amount of heat required to raise the temperature of a pound of water at its maximum density through one degree Fahrenheit.” Engineer’s Explanation The alternation in calorific value was induced by the necessity to provide new gas manufacturing plant of a different type from that used in the past, said Mr E.- F. Gorman, engineer to the company, when asked the reason for the change. "The company is planning to lay down a new coal carbonisation plant, incorporating the cost modern developments in gas technology, said Mr Gorman. “This plant will work in conjunction with the new water gas plant now under construction, and production factors induced by this change make it desirable to qse a high proportion of water gas in order to achieve this. The optimum calorific value of 450 British thermal units per cubit foot, has been decided upon. Asked what, effect the change, in calorific value would have on the efficiency of Consumers’ appliances, Mr Gorman said their efficiency would not be adversely affected. Would the change be reflected in the Amount of gas consumed? Mr. Gortqan was asked. “The shift in' calorific value is small compared with the' other changes which have occurred'to bring about this shift,” he replied; Composition of Gas Changed “The analysis or composition of the gas is radically changed by the\ increase in water gas content, and this has a material effect upon the combustion or flame characteristics,, and upon the volume of air required to ensure complete combustion. “It is anticipated that under the more stable conditions that’ will prevail when the new plant is commissioned, appliances will be adjustable to more rigid limits than heretofore, and that the consumer will gain more ‘useful’ heat from the gas purchased than has been possible heretofore. ■ “Christchurch now distributes gas of the same calorific value as Auckland and Wellington have been manufacturing for some years; past, and the Christchurch gas consumer pays considerably less per 1000 cu. ft used than in either of the other centres,” Mr Gorman concluded.