US1301960A - Use of solid fuel for power production. - Google Patents

Description

A. C. IVIICHIE I E, G. WEEKS.

USE OF SOLID FUEL FOR POWER PRODUCTION. APPLICATION FILED MAR. 2| I9I8.

LLQQU Patented Apr. 29, IJIQ.

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USE OF SOLlD FUEL F035, RODUTION; 'i

Specification of letters Patent.

Patented Apr., 29, 191W.,

Application led March 2, 1913. Serial No. 219,998. Y

To ZZ whom t may concern.'

Be it known that we, ARTHUR CUMMING MICHIE and EDMUND GEORGE VVEEKs, subjects ofthe King of England, and residents, respectively, of Newcastle-upon-Tyne, Eng-- land, and Northumberland, England, have invented certain new and useful Improvements in the Use of Solid Fuel for Large- Scale Power Production, of which the following is a specification.

This invention relates to the economic use of solid fuel for large-scale power-produ-ction by means of low-temperature distillation of the 'fuel with the consequent separation of valuable distillation products and of `combustible gaseous and solid residues. The solid residues are hereinafter and in the claims referred to as the coke or alternatively as the` coke-product, the distillation products and combustible gaseous products jointly as the retort gases, and the combustible gases therein which remain gaseous as the power-gases.

It has heretofore been proposed' to eect the low-temperature distillation, for example, of coal, by subjecting it to the action of superheated steam at lowvpressu're, without any external heating.

ln carrying out this. process it is customary to charge the retorts'with coal and periodically'to discharge the coke when it has been sufficiently exposed to the action of the superheated steam. In order that the process may be usefully employed in the manner provided by this invention the discharge of coke-product must be continuous, or substantially so, that is to say, it must take place sufficiently regularly to enable it to be discharged by automatic means so as to dispense as far as possible with manual labor or attention and in suflicient quantity to constitute the fuel-feed vfor an industrial furnace of some kind. It is the object of the present invention to provide means for lrecovering the volatile products of the fuel-many of which are of great industrial importance-in coperationwith means for utilizing, on the spot, as far as practicable the heat of combustion of the coke-product and power gases, and the recoverable heat contained in the retort gases by suitable heat-utilization devices, and applying the whole of the heat so obtained'to the production of steam power. This is only commercially feasible if the construction of the apparatus can be made simple and in sufficiently large sizes to prevent the capital outlay from overburdeningthe undertaking. `We have vfound that by combining apparatus for low-temperature distillation of fuel by superheated steam with utilization apparatus for the power-gases and the cokeproduct therefrom and with heat-utilization apparatus for the recoverable heat contained in the retort gases, power can be generated and sold ata lower cost than by methods heretofore in use.

By the present invention, a combination of parts is provided to constitute means for producing power from solid fuel and to recover by-products from the fuel, which parts comprise- (a) a continuous (or substantially continuous) steam-heatedlow-temperature distillation plant for solid fuel;

a hot-coke utilization plant consisting of a furnace and steam-boiler with or without auxiliary gas-producers;

I (c) means for utilizing for power production the power gases obtained from the said distillation plant;

(ci) a steam turbine power-unit or units (with or without auxiliary internal-com-l bustion power-units) with provision for the supply of bleed-steam from the turbineunit or units to the said distillation plant;

(e) a low-pressure superheater for heating the said bleed-steam to the temperature required for distilling the fuel in the said distillation plant;

means for heating the boiler feedwater for the said steam-boiler by means of the recoverable heat (other than their heat of combustion) in the retort gases from the distillation plant.

The development of the energy by the means of the hot coke utilization plant and the transformations to which it is subsequently subjected, constitute a cycle of changes which 'are hereinafter collectively referred to as the main power cycle.

Preferably the low-pressure superhea-ter indicated in the item (c) is so combined with f a high-pressure superheater for the turbineunit or units of item (d) as to constitute therewith a single apparatus built in as a unit into the boiler supplying the said turbine or turbines.

The power derived from the combustion of the power-gases may be used, if desired to supplement the main power cycle or in any vother way that is convenient and economical. 1 'Ihe term bleed-steam is hereinafter clearly defined.' i

This invention is now further described by reference to one embodiment thereof illustrated diagrammatically in the accompanying drawing.

' In the said diagram a low-temperature distillation retort for treating coal is indicated at A, the retort being of gradually incsreas ing diameter from the top downward to permit the fuel to swell freely'as it undergoes distillation and so avoid choking of the fuel .and the steam in their passage through the retort. A continuous-feed hoppper A1 is 'provided for coal for the retort and a continuous discharge device A2 for the cokeproduct. The device at A2 may take the form .of a feed-grate of the known type coinpri'sing toothed rollers geared .together in airs. y

The lowest and hottest portion of the retort is preferably lagged` with kieselguhr A3 and a greater proportion of the upper part with magnesiaAi.

The coke-product is discharged by the device A2 into a closed and lagged feed trunk A, leading to the grate B1 of a boiler B, any convenient form of mechanical stolzer being employed to receive the coke-product and feed it into the boiler-furnace. High-pressure steam from the boiler B is fed through a high-pressure superheater B2 to the highpressure end of a steam turbine C from which bleed-steam is taken at the point Cf and fed through a low-pressure superheater D in the .boiler B, the discharge from the v superheater D serving to supply, through the pipe D2, the steam required by the retort A for distillation of the coal. The termo bleedsteam is employed throughout this specification and claims to denote steam taken from the casing of a turbine at a point intermediate between the ends of the turbine, at which point the'steam. has been partially expanded. It is well-known that by thus incleasing the. weight of high-pressure steam to be taken in by the turbine without increasing the total weight of steam discharged at the low-pressure end, the high-pressure blades may be made of longer radius and the percentages of leakage, eddy losses,

etc., reduced, with a consequent increase of economy.

denser as cooling medium therefor, and

main power cycle.

moroso thence through auxiliary feed-water heating devices such as are ordinarily employed, for example, through an economizer or a feedwater heater G4, back to the boiler B by way of the piping G2.

Beverting now to the retort A, the retortgases are taken by a discharge main J and passed through thedevice G which serves not only as a condenser and cooler for the retortgases but also as a heat exchanger in the The distillates from the retort which are here condensed to liquid form are collected at G2 for further treatment or sale, and the distillation products which still remain gaseous pass by a pipe K1 to a cooler K where they are finally cooled, and then passed to a gas-stripping plant L for the recovery of the light oils and other by-products.

v After this treatment the power-gases are fed to any utilization devices and are used for the production of steam and power, either, as indicated in the diagram, by being passed to the furnac'eof the boiler B through a pipe L1 and there burned to assist in raising steam, or thus used and in part also, if desired, by means of a pipe such as L2 passed to internal-combustion engines or other heatutilizing devices. By such means the gas is immediately utilized, that is to say is not held in store nor transmitted a great distance before use. i

Instead of feeding the whole of the cokeproduct to the boiler B, as shown in the diagram, it may be fed, in part at least, to the furnace of a gas-producer, the gas frm which may be burnt under the boilers or employed in internal-combustion vengines for power-production.

Owing to the continuous operatio of the retort A, which result is in fact o tained sav by constructing it of sufficient size to insure the fuel being properly and fully treated in its passage from top to bottom of the retort,

'and in sutlicient quantity to be immediately ldown the retort meets the hot gases rising from the coking Zone, the coal is preheated and the hot gases are cooled. In this way, the lowest portion of the retort is the hottest and forms the coking zone, while the upper regions are relatively cool. This state of things is favorable to economy in working and the reduction to a minimum of the heat lost by radiation. The latter can be reduced to a permissible amount by suitably laggingv the retort. 4 y

The construction `of the retort as a whole operating costs are reduced to a minimum' by lthe. provision for its continuous operation in the mannen described. Owing to the 'adoption of van inclosed direct feed of the coke-product fromthe'retort to the furnace,

` the plantjnay be kept clean and free from manner described dust withf a minimumof labor.

It willffbe observed that the bleed-steam is not recovered as feed-water for the boiler, but is lost in the. .form of water, although the heat contained in it is usefully employed. This bleed-steam passes with theretort-gases into the combined feed-water heater and condenser and is then condensed to water with a portion-"of the distillation products from which it is subsequently separated. At the same time thearrangement of apparatus to take bleed-steam from the turbine in the permits a greater quantity of bleed-steam to be taken than is `ordinarily the case where the practice is adopted of passing it ythrough plain feed-water heaters, the cost of which-withA engineering considerations-prohibits employment of a sufiicient number of heaters for the utilization of a large quantity of bleed-steam by such means. An increase in the amount of bleedsteam, tends to increase the mechanical efficiency. of the turbine, as is known, because vit permits the'length of the highf pressure blades to be increased relatively to. that -which would be employed if bleeding were not adopted and so reduces the percentage of the leakage, eddy losses, etc., incidental to the high-pressure blading. At the same time,-the thermal eiiiciency of the power cycle as a whole is enhanced. The facility afforded by the above described arrangements for increasing the relative amount of bleed-steam 1s thus advantageous.

riihe use of steam in the manner provided by the present invention in the cycle of operations above described 'is advantageous,

commercially and otherwisefor various reasons, among which may be mentionedthe 'following:-The condensation and cooling i of the gases prior to their entry into Athe stripping plant reduces their volume andl 'so `thus the size of the stripping plant required; the employment of bleed-steam has the advantages above referred to, and furv'ther the employment of steam asthe distillingagent and employed in such a way as to be put into direct contact with the fuel ap- ".pears to have a favorable eect as regards 'Y thecharacter or volume vof the distillates obqtained. Further advantagesad'orded'by the resentjinvention b reason of the direct 7 v`dischargel of coke provided by it from the distillation-plant to 'the furnace comprise savin ofthe heat contained in the eolie and t e avoidance of combustion thereof byv combination with the air such as arises when' the `coke is discharged into the open air and allowed either to cool `there or to undergo some degree of. cooling before it is quenched.

What we claim as our invention and desire to secure' by Letters Patent is zl. The method of generating power from coal, comprising the steps of feeding coal to a retort, then passing at least some of the coke from the retort to a steam generating plant in which it is consumed to generate steam, passing the steam from the steam in which it is consumed, passing the steamfrom the steam generator to a motor, delivering the steam from the motor to the retort, `returning the exhaust from the motor through a heat exchanger to the steam generator-,passing the distilled products fromI the retort through the heat exchanger to partially condense said products, removing the condensed products 'to a receiver and passing the gases from said heat exchanger through a condenser, and passing the gases from said condenser to a point ofuse, substantially as described.

3. rlhe method of generating power from coal, comprising the steps of feeding coal to a retort, passing at least some of the coke from the retort to a steam generating plant in which it is consumed, passing the steam from the steam generator to a motor, delivering steam from'the motor to the retort,

- returning` the vexhaust from the motor through a heat exchanger to the steam generator, passing the distilled products from the retort through the heat exchanger to partially condense said products, removing the condensed products to a receiver and passing the gases from said heat exchanger through a condenser, and passing at least some of said' gases to the steam generator, substantially as d'e'scribec a. A power plant, comprising a still for the low temperature distillation of solid fuel, a steam generator, means for feeding some of the solid fuel in a heated condition from vthe retort to the steam' generator, means to convey the combustible gases from the retort to the furnace of the generator, a steam turbine, means for conveying bleedsteam from the turbine to the retort, means for conveying theexhaust products from the steam turbine bach, to Athe steam. genn iis erator through a` heat exchanger, said heat exchanger being in the line for transferring the combustible gases from the retort to the furnace of the steam generator, substantially as described. A y

5. A power plant, comprising a retort, means for feeding coal to the retort, a steam generator having a combustion chamber, means for feeding the hot'colre from the retort to the combustion chamber of the steam generator, a motor connected to the steam generator', means. for conveying bleed-steam from the turbine to the retort, a heat exchanger, connec'tions between said heat exchanger and the turbine for the remainder of the exhaust products, a second connection from said' heat exchanger to the steam generator, means for forcing the exhaust vproducts` from the turbine to the boiler through the heat exchanger, a connection from the retort to the heat exchanger, and a connec tion from said heat exchanger to the combustion 'chamber of the steam generator for conveying at least some of the gases from the heat exchanger to the combustion chaml ber, substantially as described.

6. A power plant, comprising a still for I the low temperature distillation of solid fuel,

a steam generator, means for feeding some of the solid fuel-in a heated condition from the retort to the steam generator, means to convey the combustible gases from the retort to a utilization device therefor, a Steam turbine, means for conveying bleed-steam from the turbine to the retort, means for conveying the exhaust products from.Y the steam turbine back to the' steam generator through a heat exchanger, said heat exchanger being in the line for transferring the combustible gases from vthe retort to the furnace yof the steam generator, substantially as described.

7. A power plant, comprising a still for the low-temperature distillation of solid fuel, a

steam-generator tted with a high-pressure and low-pressure superheater built as a unit into the generator, means for feeding some of the solid fuel in a heated condition from lthe retort to the steam generator, means-to convey the combustible gases from the retort to a utilization device, a steamy turbine and meansto feed it with steam from the said high-pressure superheater in the generator,

GOI

ARTHUR CUMMING inertie.,

EDMUND GEORGE WEEKS. i'

Witnesses:

H. Nixon, F. F. P. BISARRE.

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