This article was originally published in Electrochemical and Metallurgical Industry Publication of November 1907. Information within this article is therefore correct as of 1907. The publication of this material aims to provide historical insight on the subject and its place in industry.
One of the first uses to which gas analysis was put in the chemical industries was in the manufacture of sulphur dioxide by burning sulphur. It was early recognized that if the supply of air to the sulphur burners was not exactly regulated the operation did not proceed to the best advantage and for this reason it became general practice to analyze the gases coming from the burners and regulate the air supply to the burners accordingly.
Although this method of regulating the air supply represented a great advance over the old-style sulphur burners, to which air was admitted from the end in unrestricted quantity and ungoverned proportion to the sulphur vapor, yet a perfectly uniformed gas could not be obtained, since the conditions in the apparatus fluctuated during operation, and especially since they were not perfectly uniform in all parts of the apparatus.
The fundamental feature of a new agitating sulphur burner, invented by Mr. J. C. Wise and built by the Raquette Foundry & Supply Co. of Massena, NY as shown in the accompanying illustration, is such a construction that those obnoxious fluctuations are avoided and perfect uniformity of conditions within the combustion chamber of the apparatus is assured.
In the" old-style burners the feeding of the oven was the cause of fluctuating conditions. The cold charge smothered for an appreciable period the surface flames upon which it was thrown, thereby lowering the temperature and reducing the capacity. Being fed through the door, the operation allowed an excess of oxygen to rush through the system during the feeding. These troubles are done away with in the Wise sulphur burner by means of the use of automatic hoppers in which the sulphur is melted by radiated heat and flows in a continuous stream into the bowl of the oven, being at the same temperatures as the contents so that any chilling effect is avoided. The sulphur supply may be regulated to equal the consumption, so that the quantity of sulphur in the bowl remains constant.
With respect to the possibility of maintaining perfectly uniform conditions within the apparatus itself, great emphasis is laid upon the fact that the general form of the pot is circular, and that the draft slots are, therefore, arranged in the form of a circle and are equidistant from the center of the pot. By this arrangement the several distinct volumes of air passing inward radially through the different slots toward the center of the burner, must travel equal distances, and are, therefore, exposed to like conditions. The tendency is to produce uniformity in the conditions existing throughout the pot and to promote the uniform combustion of the sulphur vapor.
Actual trials have shown that the circular form of the pot increased the general efficiency of the apparatus to an astonishing degree. This is undoubtedly due to the fact that because of the several drafts being produced in different directions but converging towards the center of the pot, a uniform mixture of air and sulphur vapor is produced. Moreover, the combustion chamber is provided with a horizontal baffle-plate or partition with four equal slots at each end. The gas passing from the chamber is therefore split up into ten streams which unite in the upper compartment. This again promotes a thorough mixture of air and sulphur vapor.
In some instances it is desirable to admit some air through the dampers or draft slots, located at the tank of different slots in the baffle-plate. The shutters at the ends of the combustion box may be opened to any desired extent, admitting a corresponding amount of air. This auxiliary admission of air is desirable when, for any reason, difficulty is encountered in causing thorough combustion within the oven, and, consequently, there is a tendency for unburned sulphur vapors to pass off in elementary form. Air, when admitted through the ends of the box, as above described, will cause any unburned sulphur vapors to burn and form SO2, provided the aeriform portions just mentioned have sufficient heat. It should be borne in mind that it may sometimes happen, especially in a rapidly working apparatus, that some portion of sulphur vapor is not brought into contact with a proportionate quantity of air, and while possessing sufficient heat to support combustion, is prevented from being consumed upon this account. In such an instance, the auxiliary air outlets are also useful. The dampers and baffle-plates are essential to thorough combustion.
The first machine of this type was installed in July, 1905, in the Deferiet mill of the St. Regis Paper Co. and has given continually perfect satisfaction. When tested recently no material wear or deterioration could be detected.
During a week's test this machine burned 14,000 pounds of American sulphur in 24 hours, producing a gas testing 18 to 19% S02. It occupies only 38 square feet of floor space, is 10 feet 6 inches high, and weighs approximately 10,000 pounds.
The experience of the Fort Edward mill of the International Paper Co. where two machines of this type were installed in August, 1906, is also interesting. Formerly fifteen flat burners of a total burning area of 460 square feet were employed, in connection with four Partington systems of three tanks each. Each system was equipped with an 18 x 20 duplex vacuum pump. Full capacity was seldom obtained. After the installation of the two new Wise machines the use of the old burners was discontinued and two entire acid systems with the exhausters were cut off. The capacity was greatly increased and an immense saving of sulphur and lime per ton of sulphate pulp was shown. A gas of 18 per cent SO2 is commonly obtained, and the two machines make about 80 tons sulphite pulp daily.
The very high efficiency obtained is evident from the fact that if the operation was ideal, the sulphur being burnt with atmospheric air of standard composition according to theoretical proportions, the proportion of SO2 in the gas would be about 21%.
Image credit: The Internet Archive Book Images