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DISCUSSION WITH MESSRS. GUMMERT, TRAENKNER,
WUNSCH, JUST, GROOTE, NISTLER, AND GRATKOWSKI
OF RUHRGAS

            Ruhrgas is a gas distributing company that owns and operates a gas distribution grid containing about 2000 Km of pipelines.  The stock of Ruhrgas is owned by the coal mining companies.  Under normal conditions, Ruhrgas was active in the development of increased markets for gas, particularly in the industrial field.  The growth of the demand is indicated by an increase in gas sold from 3 x 10⁹m³ in 1920 to 9 x 10⁹ m³ in 1938.  At present the gas distributed amounts to 6 x 10⁹ m³ per year.

            All of the gas distributed by Ruhrgas comes from modern central coke ovens.  With the steel output limited as it is at present, it is not possible to meet increased demands for gas by increasing the amount of coal coked.  Coke cannot be used for domestic fuel because of the price (32 marks per ton for coal, 45 marks per ton for coke).  To obtain more coke-oven gas, it is necessary to substitute producer gas for coke-oven gas used in underfiring.  At present, approximately 30% of the gas distributed has been made available by the use of producer gas for underfiring.  Ruhrgas is, therefore, interested at the present time in the development of processes for the production of cheap producer gas.  From the long range standpoint, Ruhrgas is interested in any process which will produce approximately 500 Btu gas economically.  At present the average selling price of gas is 4.9 pf per m³ of gas having a heating value of 4600 cal./m.3 (32.8¢ per M cu. ft. of 520 Btu gas).  We were requested to keep this selling price confidential.

            Ruhrgas is currently developing a vortex producer.  The first unit had an internal diameter of 50 cm. And a height of 100 cm.  The present unit has a diameter of 100 cm. And a height of 100 cm.  Coal is carried into the unit tangentially with preheated air in a single stream.  The flow of gases and residue is up and slag is tapped from the bottom.  The gases pass through a dust separator and in full scale unit through a waste heat boiler.  The overhead residue contains some ash but has the approximately composition of fresh coal.  Most of the ash is removed by slag tapping at the bottom.  The Ruhrgas producer will use coal having a top size of 1 mm. containing up to 25% ash and 10% water.  Air is preheated in two stages by gas.  In the first stage the temperature is 450°C. and in the second stage 760°C.  The capacity of the present unit is 150 to 200 Kg coal/hour.  The next unit built will have a capacity of 500 Kg coal/hour.  The heat balance on the unit is shown in figure 6.  The following results were obtained with brown coal:

            We observed the unit operating on high ash bituminous coal.  Operation on this type of coal had not been studied extensively, however, the unit was performing satisfactorily and no difficulty was experienced in slag tapping.  The carbon conversion in the run that we observed was not as high as desired.

            Ruhrgas is in the orienting phases of a study of the application of unsteady state or pulsating flow on gasification processes.  This principle was used in the V-1 rocket or “buzz-bomb”.  It is an attractive principle because it offers a means for speeding up reactions between solids and gases that are controlled by diffusion processes.  In a system in which the gas pulsates there is rapid relative flow between the solid particle and the gas because of the greater inertia of the solid particles.  In a vortex relative motion is achieved by the radial flow of gas across a particle, whereas in conventional coal burning equipment there is very little relative motion between the air and coal.  These points are illustrated by the relative heat release rates in the three systems.

*This figure does not agree with results to tests at Battelle, which showed heat release rates up to 4 x 10⁶ Btu/cu.ft./hr. in a vortex.  However, under non-slagging conditions, Hurley’s heat release rates are of this order of magnitude.

            The Ruhrgas pulsating flow unit is shown diagrammatically in figure 7.  The system as shown has a natural frequency of 80 to 100 cycles per second.  This may be altered by changing the relative proportions between the length og the tail pipe and the volume of the reaction vessel.  The unit has a capacity of 15 Kg of brown coal (heating value 5000 Kcal./Kg)/hour, uses 25-30 m.³ of air per hour, and produces a gas having a heating value of 1000-1200 cal./m.³ and utilizes 80% of the carbon in the coal.  The tail gas temperature was 900°C.  It is interesting to note that this corresponds to a gasification rate of 420#/cu.ft. of reaction space per hour.  The highest rate we have obtained in the vortex is 200#/cu.ft./hour with about 60% carbon conversion.  The foregoing figure of 420#/cu.ft./hour was calculated from the data given for the pilot unit but does not check the value given verbally which was 1 ton of normal brown coal per cubic meter per hour (63#/cu.ft./hour).  Present work in the vortex at Pittsburgh is at a rate of 16#/cu.ft./hour.

            The Ruhrgas pulsating unit is started up on gasoline and can be operated to produce gas having a heating value of 800 Kcal/m.³.  It has been found that coal preheat is essential otherwise ignition is lost.  In the opinion of Nistler of Ruhrgas, preheating coal generates sufficient gas and hydrocarbon vapors to maintain ignition.  No difficulties haebeen experienced in preheating coal to 300 to 500°C. in an indirect gas fired preheater.

            The fluid dynamics of the unit have been followed by means of a cathode ray oscillograph which has shown pulsating frequencies ranging from 80 to 100 cycles per second and peek pressures in the pressure wave of 0.7 atmosphere.

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