US3020715A - Method of improving the thermal efficiency of a gas producer-gas turbine assembly - Google Patents

Description

Feb- 13, 1962 A. M. THoMsEN METHOD 0E IMPRovING THE THERMAL EFFICIENCY 0E A GAS PRODUCER-GAS TURBINE ASSEMBLY Filed May 8, 195'? far/must margin;

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,I 3,020,715 Ice Patented Feb. 13, 1962- METHOD OF IMPROING THE THERMAL EFFI- CIENCY OF A GAS PRODUCER-GAS TURBINE ASSEMBLY Alfred M. Thomsen, 265 Buckingham, Apt. 402, San Francisco, Calif. Filed May 8, 1957, Ser. No. 657,871 2 Claims. (Cl. Gil-39.12)

As of today the gas turbine, so-called, relies upon either a gaseous or a liquid fuel. In spite of much hope expressed for powdered coal as a future fuel, the fact remains that all large scale trials have ultimately ended in failure. For this reason it is not remarkable that much attention has been given to the gas producer as the means of converting solid fuel to gaseous fuel and thus automatically solving the difficulty but the inherent fault of low over-all conversion of heat content of the fuel into mechanical energy presents diiculties which require something besides conventional practice. The gas turbine, by itself, is somewhat below the conventional steam turbine and boiler in over-all efficiency and if the losses and costs of gas producer be superimposed upon this deciency then the conventional steam unit easily wins. It is the aim and object of my invention to so combine gas producer practice and the gas turbine into an economic whole that it will have an efficiency well over that of the conventional steam unit.

l, therefore, wish to make it quite clear that I do not claim any originality for the concept of rst gasifying a solid fuel and then using the resultant gas in a turbine. That concept is quite old. But I do claim that a combination of certain steps which I shall now describe are new and novel and that the eiiiciency of the combination warrants its use upon a wide variety of fuels.

In the attached drawing I have illustrated all these steps and combined them into a composite whole, it being at once apparent that it would be impossible to separate the producer from the gas turbine and consider each one by itself. Without the innovations that I have introduced both in the turbine circuit and in the producer circuit, the entire concept becomes inoperative in so far as the claimed efliciency is concerned. Contrariwise, as a single process for converting the heat value of the fuel into mechanical energy, it has specilic merit and simultaneously does serve to obtain some byproducts that also have commercial value.

For the purpose of such explanation I will take as a specificexample a lignite having a heat value of 7600 B.t.u., and the following composition. Moisture, 32.69%; volatile matter, 29.25%; xed carbon, 28.76%; ash, 7.6%; sulphur, 1.12% and nitrogen, 0.8%, as specified subsequently. The washed gas has a heat value of 149 B.t.u. per cu. ft., and the temperature of the gas leaving the producer was 840 F., due to the large amount of moisture in the fuel. Further details will be given later on as pertinent to the specific items elucidated. 'Ihe inlet temperature to the turbine is held at alittle below 1450 F. by a corresponding large excess of combustion air. Turbine exhaust will not vary much from l000 F. and will obviously consist chieliy of nitrogen and unconsumed oxygen. Lower temperatures after passing heat accumulators and reactor are given in the drawing.

I will commence my description with the exhaust from said turbine indicated by the number 7. It will be seen that I have divided this into four parts in the following manner. Owing to the large oxygen content, a large fraction can be used in place of air for the producer indicated by the number 8 but the actual amount cannot be accurately determined as it depends on the amount of water vapor and carbon dioxide simultaneously present and the ability of the producer to convert such material into combustible gases. Any deficiency is readily made up by heating the balance of the needed air to about F. less than the exhaust, by heat exchange, with said turbine exhaust. This is plainly indicated as supplementary air entering into the gas producer, after passing through the discharging phase of heat exchanger indicated by the number 4.

The remainder of the unused exhaust from the turbine is indicated as used to heat the air for combustion supplied to the combustion chamber of the gas turbine by passing through the discharging phase of heat exchanger indicated by the number 5, after initial compression in compressor number 1, and to heat the Washed gas from the producer by passage through the compressor, indicated by the number 2, and the discharging phase of the heat exchanger, indicated by the number 3, just before its entrance into the same combustion chamber, indicated by the number 10. All such heat exchange is illustrated as accomplished by means of heat accumulators rather than the conventional tube assemblies. These are far more eti'icient and permit of an approach to a regenerator of infinite surface. In practice this simply means that the technique is borrowed from the open hearth of the steel maker instead of from the heat exchangers of the power station. It is, of course, subject to the disadvantages of said system but it is gaining a steadily greater importance in the chemical industries because of its far lower cost per unit of transferred heat. In the calculations herein it is assumed that a differential of 100 F. is an adequate allowance for said accumulator when receiving and discharging heat. Inasmuch as this device is entirely conventional no more adequate description appears necessary. Personally, I have used a cylindrical vessel filled with iron rods of 1A in. dia. or less, the flow of gas being, obviously, along the rods.

To elucidate another portion of my process I now turn to the top center of the drawing and the item called a compressor indicated by the number 1. Assuming a 5 to 1 ratio of compression of the needed combustion air and allowing for the turbulence feature of the axial compressor we have in actual performance a rise in temperature to 540 F. from a normal of 60 F. To combat this I introduce Water as an atomized mist before the air enters said compressor, and, as needed, at any intermediate point. Inasmuch as a pound of dry air at 180 F. will absorb over 0.6 pound of moisture, allowing for the reduction in volume and the specific heat of air, it will be seen that said temperature of 540 can be reduced to 180 by the volatilization of approximately 0.1 pound of injected water. Furthermore, that said air can be so reduced in temperature without reaching actual saturation. It follows that while I cannot reach a truly iso-thermal compression in this manner I can approach it, and as all work performed by the compressor is negative all such gain in power input is direct gain in output.

But there is a further gain involved. The relatively humid air has larger mass and larger volume which gain is likewise directly obtained at no expense for consumed power and thus results in another net gain. Finally, the moisture laden air ultimately arrives in large part as a direct contribution to the eiiiciency of the gas producer. All this, and the added heat supplied to combustion zone of the gas producer, represents a transfer of energy from the exhaust of the turbine into potential chemical work in the producer. So far I have been considering only the air and water vapor supplied to the combustion chamber of the turbine but it is obvious that the same technique applies to the fuel gas entering the combustion chamber and I have illustrated that at the right hand of said combustion chamber by showing water injection vinto the compressor indicated by the number 2.

below the gas producer which is indicated by the number 8. This device receives fuel and produces ashes and gas respectively. The gas is represented as entering a washer indicated by the number 9, a conventional device, where by condensation and scrubbing it is cleaned and cooled, the separated product being ammoniacal liquor in which tar is disseminated. The cooled, purified gas, as already referred to previously, goes to a compressor indicated by the number 2, an accumulator heater indicated by the number 3, and then to the combustion chamber indicated by the number 10. The ammoniacal liquor passes through a tar separator indicated by the number 11 and then to the reactor, a non-conventional phase indicated by the number 12. Here intimate contact is achieved between the partially cooled Vexhaust gases from the turbine, vafter passage through the various heat accumulators, and said ammoniacal liquor. It is in effect a scrubber. The ammonia in the liquor is present in part as carbonate and in part as sulphide. The sulphur dioxide and trioxide present in the exhaust react with the ammonia compounds to produce ammonium sulphate and separated sulphur. Simultaneously, as said gases leave at a lower temperature than they enter they are able to produce much evaperation.

Now Vall lignite contains some nitrogen, and in the instant case said nitrogen i's present to the extent of 0.8%. In gasification, as the temperature is kept low by the presence of so much Water vapor and carbon dioxide, about half of this nitrogen appears as ammonia. However, as there is also so much moisture in the fuel the ammoniacal water -becom'es very dilute. `'It is, therefore, of prime importance that, 'simultaneously with the chemical etfect present in the reactor, 'there is 'also this advantageous feature of attendant concentration. It is also desirable -to keep as low a `concentration of fthe volatile ammonia salts as possible in the scrubbing liquor so, by the double-dotted lines connecting washer and reactor, I have indicated a commingling, at will, of the liquors used in both devices, thus reducing volatile ammonia 'salts to `a minimum.

The products leaving the reactor are indicated 'on the drawing as va concentrated solution of ammonium vsulphate and gas at approximately 212 F., leaving the total water content in said gas in the form of vapor. The actual temperature is optional but it is obvious that to obtain maximum concentration in the liquid scrubbing medium in the reactor the gas in contact with said liquid must be at the proper temperature to cause evaporation in place ofcondensation.

The nal 'step inthe drawing is devoted to the reclamation of such water as may be desiredfrom the gases leaving the reactor. -In many places where adequate fuel is available, water 'is quite scarce, Ahence vfuel is generally brought to the source of more abundant water. Whenever enough water is present to permit the use of a conventional condenser, said recovery 'of water becomes unnecessary, but in isolated localities it may become quite important. If such moisture laden gas is passed through the charging phase of asimple heat'accumulator, indicated by the vnumber 6, consisting of a bed of pebbles, then much water 'will be condensed for a while until the 'pebbles become unduly warm. The current is then cut off and sent to another accumulator. `Meanwhile cold air enters the heated accumulator and effectively removesthe storedlheat to suchan extent that it may once more be used as a condenser, after which the cycle is repeated.

Although such use of a heat accumulatoris truly conventional-in many industries and hence needs no specific description, nevertheless because of the importance of this 4device to my `process a few words, and Aa further 'explanation of the legend I have used on the drawing, may

Abe useful. Throughout, I lhave represented `such use of a heat accumulator in Iheat exchange by placing two rectangles 'side lby side connected by an X-bridge to show that they form a part o'f one system. I have used an unbroken line in the rectangles denoted as receiving heat.

Contrariwise, the discharging phase of the accumulator is represented by the rectangle consisting of dotted lines. In each and every case I have presented said accumulator as consisting of a single pair, that being the minimum number to constitute an operative unit and to illustrate the principle. However, in practice, such devices will always be used in multiple so as to smooth the transition on reversal of ilow. Thus, there should always be present as a minimum two accumulators receiving, and simultaneously two discharging heat. Obviously, in any design the greater the number of devices employed the less will the inevitable fluctuation induced when any accumulator 'is taken from the charging line and put on stream in the discharging line.

While in this specific description of my process I have used lignite as fuel and submitted the over-all picture of inter-relations, temperatures, and gas compositions, it is obvious that my process will be equally applicable to any type of carbonaceous fuel from anthracite dust to bituminous coal. Similarly, to take even lower grades of fuel, we may employ peat or any type of forest-waste in the manner herein described. It is even possible to use the urban waste of our great cities, as a means `of disposal of such objectionable material, as gas producer fuel. lThe great objection to incineration has always been the objectionable products sent into the atmosphere and of which we are now so conscious as originators of smog It is obvious that in my process perfect combustion is attained and `hence little if any contamination of the atmosphere becomes possible. All such uses of my process to a great variety of Vfuels I consider as within the scope-of this disclosure as long as the theme involved contains the simultaneous use of a gas producer and a gas turbine `inter-connected into a composite whole in the manner `herein described for lignite.

Inasmuch `as I have used lignite as my fuel in the specific illustration represented on the drawing and thus used it to point out clearly the operation of my process, I wish it 'specifically understood 'that I do not attribute any special importance to lignite over and above extended use of other fuels. Having thus fully described my process.

I claim:

1. The method of improving the thermal eiciency of a gas producer-'gas turbine assembly operating upon a fuel, selected from the group consisting of anthracite, bituminous coal, and lignite, containing both sulphur and nitrogen, which comprises; dividing the hot gas of the turbine exhaust, lwhich Yconsists of a mixture of nitrogen, oxygen,c'arbon dioxide, oxides ofsulphur, and Water vapor, into two portions; utilizing one portion as the air of 'combustion required by the gas lproducer thus converting the sensible heat contained therein into additional chemicalenergy as it passes through said fuel, and by its water content improving the conversion of the nitrogen of said ffu'el `into ammonia; passingthe second portion of the 'exhaust through heat accumulators, thus storing the sensible heatresident therein, and subsequently imparting said 'stored heat to traversing, relatively cool, gas and air, respectively, required inthe operation vof turbine and producer, by reversal of ow throughsaid heat accumulators; injecting water into air and gas before said traverse through said heat accumulators thus enriching said gases in `water vapor and improving the over-all eiciency of turbine and producer with increased yield of ammonia; washing the producer gas `with water to remove, in part, said ammonia with attendant removal of tar and sulphur; 'separating the tar Vfrom vthe resulting ammoniated water and commingling said ammoniated water with the exhaust 'gas from the turbine after partialcooling of same by pas- 'sage throughthe heat accumulators, thus converting said ammonia together with attendant sulphur into ammonium sulphate with simultaneous 'evaporation of water thus increasing the concentration ofammonium sulphate in said water; and further increasing said concentration by the 5 6 re-use of said water solution of ammonium sulphate in at ambient temperatures, the condensed water simultanethe removal of ammonia and sulphur from producer gas. ously formed being suitable for re-use wherever required 2. The method of improving the thermal efficiency of in the process. a .gs grode'gas turline lssembly setlfirth in claim 1 References Cited in the file of this patent wit t e a e step t at t e moisture a en gases, con- 5 stituting the nal gaseous reject from the operation, then UNITED STATES PATENTS pass through a relatively cold heat accumulator with at- 2,223,572 Noack etal Dec. 3, 1940 tendant condensation of a part of said moisture, the heat 2,305,785 Jendrassik Dec. 22, 1942 thus stored in said accumulator being subsequently dis- 2,549,819 Kane Apr. 24, 1951 charged and the accumulator cooled by the passage of air, 10 2,675,296 Gollmar Apr. 13, 1954

Claims (1)

1. THE METHOD OF IMPROVING THE THERMAL EFFICIENCY OF A GAS PRODUCER-GAS TURBINE ASSEMBLE OPERATING UPON A FUEL, SELECTED FROM THE GROUP CONSISTING OF ANTHRACITE, BITUMINOUS COAL, AND LIGNITE, CONTAINING BOTH SULPHUR AND NITROGEN, WHICH COMPRISES; DIVIDING THE HOT GAS OF THE TURBINE EXHAUST, WHICH CONSISTS OF A MIXTURE OF NITROGEN, OXYGEN, CARBON DIOXIDE, OXIDES OF SULPHUR, AND WATER

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