US2163762A - Heating plant - Google Patents

Description

I @11627, 1.939- w'. G. NoAcK Erm. A *2,1635762 4 HEATING LANT v Filed Deo. 2J l19:57 2 sheets-sheet 1 IVO/bf' v ATTORNEY June 27, l W. NOACK El' AL *l HEATING PLANT Filed Dec. 2,' 19:57 2 sheets-snee; 2

Patented June 27, 19.39

A UNITED STATES PATENT ol-FicE HEATING rLaN'r Walter Gustav Noack, Baden, and Claude Seip'- pel, Ennetbaden, Switzerland; assignors to Aktiengesellschaft Brown,

Switzerland Boveri & Cie.,A Baden,

Application December 2, 1937, Serial No. 177,792

In Germany December 2, 1936 14 claims. (cl. 263-19) The hitherto used hot blast plants, the so called Cowpers, which operate according to the regenerative principle are large, and expensive in first cost and upkeep. Since suitable high heat resisting material is available it has been proposed to operate the hot blast producers according to the recuperative principle, i. e., instead of the intermittent operation, to continuously transferv heat in customary heat exchangers which are 5 made of highly heat resisting material, for example, special highly heat resisting steel.

Such plants are of advantage as long. as the temperature of the heated gas or air remains below 1300" F. There are many cases where temperatures above 1300 f'F. are required and, there,

heat exchangers operated according to the recuperative principle cannot be used because at such temperatures the strength of tube and housing material is not suilicient to carry the weight of the apparatus and resist the internal pressures. In such cases the regenerative principle must be employed in which the heat exchange apparatus is not subjected to internal or external pressures and a reduction of the strength of the construction materials caused by the increased temperatures is negligible. In order to overcome the great disadvantages connected with the regenerative principle, for example, large bulky and expensive equipment, heat losses, etc.,

with the method and apparatus according t0 the present invention therate of heat /transfer is considerably increased by increasing pressure and velocity particularly of the heating gases and by making provisions for reducing the heating periods for the gases or air to be heated and accommodate these periods as much as -possible to the heating up or loading periods.

It is an object ofv thepresent invention to provide an air or gas heating plant for blast furnaces' A or similar equipment which serves heating or reduction purposes in which plant the air or gas heater operates according te the regenerative principle and is heated by a heating medium o f high pressure and high velocity. The pressure 5g oi the heating medium according to the present 'invention is at least 3.56 lbs. per sq. inch and its velocity more than 130 feet per sec.; pressures of several atmospheres and velocities of 300 feet per sec. and over may be used. Due to these high pressuresand temperatures a very high rate of heat transfer is obtainedso that heating up is accomplished very quickly and the dimensions of the apparatus can be s mall because particularly the heating gas passages can be held very small.

The size of the plant is only'a fraction ofthe 5 size of vcustomary, plants of .same capacity.

According tothe present invention a compressor is provided which is driven by means of a gas turbine which is operated bythe heating gases used in the heating plant. No foreign power is lo used for operating the compressor and no losses of heat or power are incurred by the arrangement according to the present invention. The operating efliciency of the plant according to the present invention is high because the compression 15 takes place practically without any loss and heat losses arereduced because of the much smaller dimensions of the plant.

According to the present invention also pressure and velocity of the gas or air to be heated 20 is greatly increased, whereby heat transfer and heat absorbing conditions are greatly increased.

Further and other objects of the present invention will be hereinafter set forth in the accompanying specificationand claims and shown 5 in the drawings which, by way of illustration, show what we'now consider to be a preferred embodiment of our invention.

In the drawings:

Figure l is a diagrammatic lay-out of a. plant 39 according to the present invention Figure 2 is a part sectional side elevational view of a plant according to the present invention showing parts of the plant in larger scale.

Figure 3 is a top view of a diagrammatic lay- 5 out of a plant according to the present invention. In the drawings (designates a consumer of heated gas or air, for. example, a blast furnace, 2 and 2 are gas or air heaters, 3 is the compressor for the gas or air to be heated and l is the machine for driving the compressor 3. At the moment illustrated air or gas heater 2 is just being heated up, whereas heater 2' is discharging heat' to the air or gas passing through it. Heater 2 is heated by the combustion of gas in air. The 45' air land gas' are compressed in the compressors 5 and 6 respectively. 'Ihe heat produced by the combustion is transferred to the conventionall heat absorbing bodies within the heater 2, whereby the high pressure at which combustion takes place and the high gas velocity resulting therefrom considerably reduce the time required for heating up and also the size of the heater. Not all heat produced by the combustion of the gases is absorbed in .the heater; heating is interrupted so that the high pressure gases retain enough heat for operating the gas turbine 'l .which drives the gas and air compressors 5 and t. The gases.

-pose a conduit i2 may be provided which con ducts gas from turbine l to heater 9. i

For starting up, supplementary control and for .supplying supplemental power when there is not suiilcient power available from the turbine 'l' to operate the compressors 5 and 6, an auxiliary motor ld is provided which'may be an electric motor, a steam engine or turbine, or an internal combustion motor.v

The pressure, at which combustion takes place in the combustion chamber oi the heaters 2 and 2' according to the present invention, consider- X ably exceeds atmospheric pressure and is in' between 3.'1 lbs. per sq. inch .and e4 lbs. per sq. inch. The gas and\air velocities are also much higher than the usual velocities in the neighborhood of 6 feet' per second and may, in plants according to the present invention, reach the value of 330 feet per sec. The power which is required for materializing these conditions is considerable but it is produced practically without additional /fore be increased.

expense by means of the gas turbine 1; all ofthe energy transformed in said turbine goes back to the combustion chambers of the heat exchanger 2, 2' in the form of heat.

The temperature of the gases entering turbine 1 is approximately 900 to 1100" F. The heat still in the gases exhausting from the gas turbine is partially used for preheating the fuel gas andcombustion air and/or is used for preheating the ga or air to be heated in the heat exchangers 2,

` Because of the density and 'increased velocity of the fuel gases the rate of heat transfer is much increased, whereby the heat transmitting surfaces of the heat exchanging 'bodies can be reduced and the time for heating upsaid bodies, i. e., for charging the heat exchanger is much reduced. According to the present invention the unloadln'g periods, i. e., the periods during which the gas or air is heated in the heat exchangers 2 and 2' correspond to the"v loading periods and must thereforebe considerably shorter than in conventional plants. The heat absorbing capacity of the gas or air to be heated must therevelocity of the gas or air passing through the heat exchangers 2, 2'. For producing the increased velocity an additional pressure drop must be available which is usually not available in conventional plants and an additional blower il supplementing blower 3 is provided. This blower may be driven.I by aseparat'e motor or it may be interconnected with the charging unit 5,

5, 1 lll and receive power from gas turbine 1 and motor i0. An installation of the latter type isv shown in the drawings. In order to save in the size of blower li andheater 9, if such heater is provided, not all, but only part of the gas or air is passed through blower il and heater 9. e other part hows directly from blower 3 ough conduit it into the manifold i4 and sheaves 'Ihis Yis done by increasing the therefrom alternately through valves l5 or it into the heat exchanger 2 or 2'. Blower Il and heater by means of conduits l1, IB and I9 are arranged inparallel to conduit i3. The gas or air heated in heatexchangers 2 or 2 is conducted through valves 2|! and 2l respectively into conduit 22 and therefrom into the manifold 23 of the consumer of heated gas or -air i.

It is essential that the flow resistancevof the heating gases and the gas or air to be heated is operating period illustrated the combustion air which is compressed in compressor `5 passes through conduit 24 into preheater 8 and therefrom through conduit 25, valve 26 which, at the operating period illustrated, is open into heat exchanger 2. Conduit 28 which leads from conduit 25 into heat exchanger 2' is closed at this time by means of the closed valve 2'1. The fuel gas coming from compressor 6 is passed through conduit 29 into preheater 8 and therefrom through conduit 30 and valve 3| into heat exchanger 2 where it is burnt with the combustion air. Heat exchanger 2' is shut oif from conduit 30 at the period illustrated by means of valve 32 in conduit 38. The hot gases, after having heated up the heat accumulating bodies in heat exchanger 2 leave said exchanger( through valve 34 Iandare conducted through conduit 35 into the gas turbine 1. At the moment illustrated valve 36 which controls the passage of the heating gases from heater 2' into conduit 35 is closed.

In order to properly mix the gas or air` of lncreased Ypressure and/or temperature in conduit I9 with that in conduit I3, conduit' I3 is connected to the throat of the Venturi tube 38; there the pressure built up in vsupplementary blower vIl -is'converted into velocity and reduced to the pressure of the gas or air in conduit i3.V

Figures 2 and 3 of the drawings show further details of the plant illustrated in Fig. 1. They valves which have been omitted from the plan shown in Fig. 2 in order not to complicatethis figure unnecessarily. One of the heat exchangers (2) is shawn with its upper part in section. This sectional view shows a combustion chamber 42 in which the gas supplied by the compressor 5 and the air supplied by theI compressor 6 are subjected to combustionunderpressure. The gas enters for example at 43 and the air at 44. I'he air and gas are mixed by the distributor 45 and ignited in the burner 46. Due to combustion taking place under pressure the combustion chamber is very small and can be arranged in the upper part of the heat exchanger, whereby a very favourable construction is possible. The products -of comhigh velocity and density their path of flow must be comparatively long whilst the cross-section of iiow is small and therefore these gases are dl-I rected upwards at least once more and again '.bustion rst ow downwards because due to their nular space is filled with inert gases and the Y change-over valve 2l to the blast furnace is` to the furnace.

includes an annular space lll separated by a partition 49 which has narrow communicating openings in it. During the charging period this anclosed. During the discharging period this annular space in both heat exchangers serves as a Y receiver for the air or gas which passes through opening 48 (or 48') and the open valve 20 (or 2l) The-air or gas supply comes through conduit Il and the change-over valves l5 or I6. Previously the air or gas passes through the heater (recuperator) 8 which on account of the comparatively low temperature of the heating gas (below 750 F.) can be made of metal whilst the heat transferring and heat accumulating elements in the heat exchangers (2, 2'), at least those parts which are subjected `to the high gas temperatures, must be )made of stone (ceramic material).

In order to obtaima highV heat transfer during discharge and to be able to finish the discharging inabout the same time as the charging, the air or gas is given a higher velocity of ow. A special blower I I is provided for this purpose in case this additional pressure drop cannot be provided by the compressor 3.

The exhaust gases which serve to heat: the

i heater (recuperator) 9 leave the heater through the flue 41.

loading of the combustion chamber (free heat inv .A its former value.

The charging set is started by a special engine l0 which is generally a steam turbine but can also be'an electric motor or a gas engine. This engine also assists the gas turbine 1 in case the` powerof the latter is inadequate to drive the compressor which is coupled with it.`

The great'advantage vof this pressure boosting or increase in pressure and velocity of the heating gases in the Cowpers is that all the dimensions of the plant can be considerably reduced. Not only is there a saving in space but above all material and capital costs are smaller. The compactness of the plant enables air or gas producers and heaters to be installed in the immediate vicinity of the blast vfurnace so that conduits are saved 'and heating losses reduced.

The reduction in size achieved is obvious when one considers that when the' combustion pressure inthe combustion chamber of the heat exchanger is increased to 2 to 3 atmospheres absolute the the combustion chamber), according to results obtain/ed with pressure tired plants, can be ten to twenty times higher than with atmospheric combustion. Since the increased pressure also enables the velocity of the heating gases to be considerably increased (from ten to twenty `times)v the'A sectional area'of the heating gas channels can be reduced to a fraction (about lyo to 1/,0) of The most important result of the pressure charging is, however, the, reduction in the quantity of heatLaccumulating material required. Due to the mu h increased heat transfer heating-up and discharging is greatly-accelerated on condition that the usual brickwork is used, and the charging and discharging periods can therefore be considerably shortened so that th) change-over operations follow each other f more rapidly. The heat accumulating elements can be correspondingly reduced. It is, however, advisable to use good heat conducting brickwork, such as carborundum of which the conductivity is 15 times higher than that of chamotte. Forall parts exposed to lower temperatures (below l850 F.) metal, for example molybdenum cast-iron can be used. The change-over valves are ofthe usual construction. Sincev the velocities and densities are much higher the dimensions of the lvalves will, however, also be smaller so that their described, for obvious modifications will occur to a person skilled in the art.

We claim:

l. The method of producing large quantities of highly heated gas or air comprising the step of alternately burning combustion materials at high pressure yin a heat accumulator and driving the gas or air to be heated at high pressure and velocity through said accumulator, and producing power with the products of combustion and using said power for producing the high combustion pressure in said heat accumulator.

2. 'Ihe method of producing large quantities of highly heated gas or air comprising the step of alternately burning combustion materials at high pressure in a heat accumulator and driving the gas or air to be heated at high pressure and velocity through said accumulator, and producing power with the products of combustion and using said power for producing the high combustion' pressure in said heat accumulator and for producing the high pressure and velocity of the gases to be heated.

3. The method of producing large quantities of highly heated gas or air comprising the step of alternately burning ,combustion materials at high pressure in a heat accumulator and driving the gas or air to be heated at high pressure and velocity through said accumulator, and producing power with. the products 'of combustion and using said power for producing the high combustion pressure, in said heat accumulator and preheating the combustion materials with the heat left in the products of combustion after having ing power witl:\the products of combustion and using said powenfor producing the high combustion pressure in aid heat accumulator and preheating the gas or. ir to be heated with the heat 'left in the produ ts of combustion after having produced power.

5. The method of produc ng large u'antities o1 highly heated gas or air comprising the step of alternately burning comb tion materials at high pressure in a heat accu /ulator and driving the gas or air to be heated/r t high pressure and ve-` locity through said acci/nnulatonprodcing power with the products of combustion and usingsaid power for producing the high combustion pressure in said heat accumulator, and preheating the heated with theV heat lef-t in the products of combustion after having produced power. A

6. The method of producing large-quantities of highly heated gas or air comprising the step of periodically burning combustion materials at a pressure of at least 3.7 lbs. per sq. inc h in a heat accumulator and driving the products of combustion through said accumulator at a speed of at least 130 feet per second and producing power with the products of combustion after they have left said accumulator and using said power for producing said high combustion pressure.

'7. A heating plant for producing highly heated ,gas or air comprising a plurality of heat exchangers of the fuel burning and heat accumulating type. combustion material supply means periodically supplying combustion materials at high pressure t0 one and then to another of said heat exchangers, a gas turbine periodically connected for gas ow to' that one of said heatexchangers which is supplied with heating materials and being adapted to be operated by the gaseous products of combustion emerging froml said heat exchangers and being connected to and driving said combustion material supply means.

8. A heating plant for producing highly heated gas or air comprising a plurality-of heat exchangers of the fuel burning and heat accumulating type,combustion material supply means periodically supplying combustion materials at high pressure to one and then to another of said heat exchangers, a gas turbine periodically connected for gas ilow to that one of said heat exchangers which isA supplied with heating materials and being adapted to be-operated byl the gaseous products of combustion emerging from said heat exchangers and being connected'to and driving said combustion material supply means, a preheater interposed in the path of said combustion materials in between said supply means and said heat exchangers and being connected for gas flow with said gas turbine and adapted to be heated by gases exhausting from said turbine. I

9. A heating plant for producing 'highly heated gas or air comprising a plurality of heat exheat exchangers, a gas turbine periodically connected for gas ow to that one of said heat exchangers which is supplied with heating materials and being adapted 'to be operated by the gaseous products of combustion emerging from said heat exchangers and being conn ted to and driving said combustion material supp means, air or gas supply means connectedwi h said heat exchangers for periodically supplying air or gas to be heated to said heat exchangers and being also connected with and driven by said gas turbine.

10. A. heating plant for producing highly heated gas or air comprising a plurality of heat exchangers of the fuel burning and heat ac rials at high pressure to one and then to another oi' said heat exchangers, a gas consumer periodically connected for gasiiow to that one of said heat exchangers which is supplied with heating materials, a preheater interposed in the flow of the combustion materials to. said heat exchanger and being connected for'gas ow with 7c said gas consumer and being heated with gaseous arcanos products of. combustion after they have passed through said consumer.

11. A heating plant for producing highly heated gas or air comprising a pluralityl of heat exchangers of the fuel burning and heat accumulating type, combustion material supply means periodically Vsupplying combustion materials at high pressure to one and then to another of said heat exchangers, a gas turbine periodically connected for gas iiow to that one of said heat exchangers which is supplied with heating materials and being adapted to be operated by the gaseous products of combustion emerging from said heat exchangers and` being connected t0 and driving said combustion material supply means, and an auxiliary motor also connected with and driving said combustion material supply means during the starting up period and when not sumcient products of combustion are available for operating said gas machine.

12. A heating plant for producing highly heated gas or air comprising in combination; a heat exchanger, a gaseous heating medium passed at high pressure and high velocity through said heat exchanger, a gas turbine connected for gas ow with, said heat exchanger and being operated by gaseous heating medium. coming from saidv heat exchanger, gas or air supply means connected with said heat exchanger and suppassed at high pressure and high velocity through said heat exchanger, a gas turbine connected for gas flow with said heat exchanger and be, lng operated by a gaseous heating medium c0m' ing from said heat exchanger, gas or air supply means including a gas or air conduit connected with said heat exchanger and supplying gas or air to be heated to said exchanger, booster means arranged in parallel with respect to the gas or air flow to'said exchanger and through said conduit for increasing the pressure of said gas or air, said booster means bein'g connected with and driven by said gas-turbine.

14. A heating plant for producing highly heated gas or air comprising in combination, a heat exchanger, a gaseous heating medium passed at high pressure and high velocity through said heat exchanger, a gas turbine connected for gas flow with said heat, exchanger and being operated by a gaseous heating medium coming from said heat exchanger, gas or air supply air ilow to said exchanger and through said con-l duit for increasing the pressure of said gasl or air, said booster means being connected with and driven by said gas turbine, and a preheater arranged also in parallel with said conduit and in series with respect to said booster means.

with respect to the flow of gas or air and being connected for gas ow with said gas turbine and heated by gaseous medium exhausted by said turbine.

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