WO1997004854A1

WO1997004854A1 - Gas treatment apparatus

Info

Publication number: WO1997004854A1
Application number: PCT/GB1996/001791
Authority: WO
Inventors: Maurice Edward George Maton
Original assignee: Maurice Edward George Maton
Priority date: 1995-07-27
Filing date: 1996-07-25
Publication date: 1997-02-13
Also published as: AU6620996A; GB9515388D0; GB2303693A

Abstract

The hot gas treatment apparatus comprises a generally cylindrical chamber (1) of elongate form through which the gas is caused to flow. The chamber (1) has a gas inlet pipe (2) projecting into the chamber from which the gas flows towards a gas outlet (3). A pair of water pipes (4) conduct water coolant to opposite sides of the chamber (1) where it is sprayed into the gas flow by way of nozzles (5) directed at least partially towards the gas outlet (3). The water sprays (53) not only cool the gas, but also condense hydrocarbon impurities such as tars and oils, and collect solid particles from the gas. A mixture of the water, hydrocarbon condensate and solid particles therefore falls to the bottom side of the chamber (1) and then, due to the longitudinal axis (7) of the chamber being inclined to the horizontal at about 10°, the mixture flows down to a drain (6) at the outlet end (31) of the chamber, from which it leaves the chamber. Each spray (53) is in the form of a thin, curtain-like water film which extends to the opposite side of the chamber (1). The films are not directed perpendicularly to the cylinder axis (7), but are angled slightly towards the outlet end (31) of the chamber, so as to intersect the axis (7) at about 80°.

Description

GAS TREATMENT APPARATUS

BACKOROIΓND TO THE INVENTION

This invention relates to gas treatment apparatus. One application of the invention is for cooling gas and for removing solid particles and other impurities therefrom.

An example of another application of the invention uses a stream of hot gas for heating water.

In many cases the gas under treatment will be air.

SUMMARIES OF THE INVENTION

According to a first aspect of the invention, gas treatment apparatus comprises an elongate chamber having a longitudinal axis, an inlet at one end of the chamber, and an outlet at the other end thereof, whereby gas flows axially between said inlet and said outlet, and nozzle means for introducing liquid into the chamber for treating the gas, the nozzle means being adapted to produce a plurality of sprays in the form of sheets of the liquid, said sprays being disposed one behind the other so as to direct said liquid in the path of the gas flow.

Preferably each sheet comprises a thin, curtain-like film forming an obstacle in the path of the gas. The films may be distorted by the gas flow when this is introduced into the chamber.

The nozzle means conveniently comprises a plurality of spray nozzles, each nozzle producing a said spray. The nozzle means may comprise spray nozzles disposed in arrays on opposite sides of the chamber, and most preferably, on passing along the chamber from the inlet to the outlet the gas encounters a series of sprays coming alternately from opposite sides of the chamber.

An outlet from the chamber for the gas is conveniently provided in an upper side wall portion of one end of the chamber, an outlet from the chamber for liquid from the nozzles being conveniently provided in a lower side wall portion, preferably at the same end ofthe chamber.

Forms of gas treatment apparatus are known in which a stream of gas is introduced into one end of a chamber, and water for treating the gas is sprayed downwardly into the stream of gas from spray nozzles mounted near the upper wall of the chamber, the treated gas then being taken off from the other end of the chamber, and the water from the nozzles being collected from the bottom of the chamber.

However, the form of the sprays disclosed in connection with the first aspect ofthe invention, as well as the preferred arrangements of the sprays, conveniently provides a high level of exposure of the gas to the liquid being used for treating the gas, enabling a compact and efficient form of gas treatment apparatus to be constructed.

The invention may be used purely for removing impurities from a gas including, for example, solid particles and condensible substances which are trapped by the liquid sprays. Additionally, or alternatively, the invention may use the liquid to change the temperature of the gas. Where the invention is applied for heating water, the water is the liquid introduced into the chamber, and this is heated by the gas being hot gas. A convenient supply of hot gas is exhaust gas from suitable fuel burning apparatus.

In attempting to use existing forms of commercial apparatus for cooling gas rapidly from temperatures above about 500°-800°C to near room temperature using water sprays, it has been found that the rapid cooling can result in shock waves which cause an undesirable, pulsating flow of gas.

The applicants have realised that a steady suction effect can be obtained by angling the spray nozzles slightly towards the gas outlet from the chamber, so reducing any tendency to produce shock waves.

According to a second aspect of the invention, gas treatment apparatus comprises a chamber through which gas is caused to flow between an inlet and outlet thereof, and nozzle means for introducing liquid into the chamber for treating the gas, the nozzle means being directed at least partially towards said outlet so as to be angled at less than 90° to the general direction of gas flow between said inlet and said outlet.

In a preferred form of gas treatment apparatus according to the second aspect of the invention, the nozzle means is also adapted to produce a plurality of sprays in the form of sheets of the liquid, in accordance with the first aspect of the invention.

Preferably said sprays in the form of sheets of the liquid are directed by the nozzles at an angle of substantially 45° to 85° to the longitudinal axis of the chamber. The angle is most preferably substantially 80°. The spray nozzles are desirably disposed in arrays on opposite sides of the chamber such that, on passing along the chamber from the inlet to the outlet, the gas encounters a series of sprays coming alternately from opposite sides of the chamber. Conveniently the angling and spacing of each of the nozzles is such that each spray in the series is directed at the base of the next spray in the series so that, at least prior to introduction of the gas flow into the chamber, the sprays do not intersect.

Where the invention is used with pyrolysis apparatus for cooling the gas produced by the pyrolysis apparatus and for removing condensate and solid particles from the gas, hydrocarbon condensate is desirably returned to the pyrolysis apparatus for further pyrolysis treatment.

Where the gas carries solid or condensible material, as in the case of use with pyrolysis apparatus, the inlet to the gas treatment apparatus may desirably be provided with scraping means for removing any material deposited in the inlet.

However, the inlet most preferably comprises a pipe projecting into at least the first spray of a series of the liquid sprays, since this has been found to reduce any tendency for the inlet to foul with the material carried by the gas.

The chamber of the apparatus of the invention is preferably of cylindrical form, and the inlet end of the chamber is preferably higher than the outlet end thereof. For this reason, the longitudinal axis of the chamber is typically inclined, the angle of inclination preferably being substantially 5° to 15° to the horizontal, but most preferably substantially 10° to the horizontal.

The apparatus may comprise first and second elongate chambers, whereby gas leaving the first chamber is then caused to flow through the second chamber, so that the gas is treated in first and second stages.

Liquid used to treat gas in the first chamber is preferably collected for re- use in said first chamber.

The liquid used to treat gas in the first chamber may be water which is passed through a water/non-water separator before re-use in said first chamber.

Gas flow between the first and second chambers is preferably non-linear, whereby it undergoes an angular change of direction which is substantially obtuse. For example, substantially 80°.

BRIEF DESCRIPTION OF THE DRAWINΠS

By way of example only, specific embodiments of apparatus, each according to the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic side view of one embodiment of the apparatus;

Figure 2 is a diagrammatic section view along on section line 2-2 of Figure 1; Figure 3 is a diagrammatic end view of the apparatus, viewed from the lower end ofthe chamber;

Figure 4 is a diagrammatic cross-section view on section line 4-4 of Figure 1, showing the spray configuration;

Figure 5 is a side view, in section, of another embodiment of apparatus according to thε invention;

Figure 6 is a view in perspective thereof; and

Figure 7 is a fragmentary side view, in section, which illustrates a detail.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS International Patent Application No. PCT/GB93/01213 (WO 93/25848) discloses apparatus for pyrolysis of waste materials such as domestic rubbish. The apparatus produces a stream of hot, combustible gas bearing solid particles such as particles of carbon, and oils, tars and other impurities.

The embodiments disclosed herein comprise gas treatment apparatus using water sprays for cooling gas produced from such pyrolysis apparatus from around 500°-800°C to about 25°C and for condensing and removing liquid substances from the gas together with solid particles and various other impurities.

With reference to Figures 1 to 4, gas treatment apparatus 50 comprises a generally cylindrical chamber 1 of elongate form through which the hot gas is caused to flow. The chamber 1 has a longitudinal axis 7 and an inlet for the gas, which inlet comprises an inlet pipe 2 projecting into the chamber 1 (Figures 1 and 2) and from which the gas flows towards an outlet 3 for the gas at outlet end 3' of the chamber 1. A partition 20 forms one end wall of chamber 1, whilst the opposite end wall is indicated by reference 30. The chamber 1 is supported by a leg 11.

The chamber 1 is inclined, with its inlet end 2 higher than its outlet end 3. The angle of inclination is 5° to 15° from the horizontal; preferably at 10° to the horizontal.

A pair of internal water pipes 4 conduct water coolant to opposite sides of the chamber 1 where it is sprayed into the path 52 of gas flow by way of water nozzles 5 directed at least partially towards the gas outlet 3. The sprayed water not only cools the hot gas, but also condenses hydrocarbon impurities such as tars and oils, and collects solid particles from the gas. A mixture of the water, hydrocarbon condensate and solid particles therefore falls to the bottom side of the chamber 1 and then, due to the longitudinal axis 7 of the chamber being inclined to the horizontal at about 10°, the mixture flows down to a drain 6 at the outlet end 3', of the chamber, from which it leaves the chamber.

The water spray nozzles 5 are disposed in two opposite rows, one behind the other in each.

The hydrocarbon condensate may then be separated from the mixture and returned to the pyrolysis apparatus, for further pyrolysis treatment.

Due to the nozzle shape, each nozzle 5 produces a spray in the form of a thin, curtain-like water film 53 which extends to the opposite side of the chamber 1. The water films are not directed perpendicularly to the cylinder axis, but are angled slightly towards the outlet end 3' of the chamber, so as to intersect the longitudinal axis 7 at about 80°.

As viewed in Figure 4, dotted line 8 delimits the rear of a water film 53 coming from a nozzle 5 on the left hand side of the chamber 1, whereas dotted line 9 delimits the rear of a water film coming from an oppositely- disposed nozzle 5 on the right hand side ofthe chamber 1.

The angle and spacing of the nozzles 5 are such that the water film 53 produced by each nozzle impinges near the base of the next nozzle in the series on the opposite side, at least prior to introduction of the gas flow into the chamber. The chamber 1 is thus partitioned by a series of water films 53 passing in a zigzag formation from the gas inlet 2 to the gas outlet 3.

Although the water films are disrupted by the flow of gas, the angled configuration of the films gives a steady suction effect as the gas is cooled and promotes flow of the gas from inlet pipe 2 to outlet 3 without pulsating.

The inlet is in the form of a pipe 2, the exit end of which projects into the first of the series of sprays, since this arrangement has been found to reduce any tendency for the inlet to foul with impurities carried by the gas, An automatic scraping device (not shown) can also be provided to remove any impurities deposited at the inlet.

The hot gas 52 enters the pipe 2 by way of a gas flow control valve 51. A demister in the form of a mesh may cover the gas outlet 3 to remove spray and other remaining particles from the gas.

In a preferred embodiment, there is a series of twelve nozzles 5 on each side of the chamber 1, although in the drawings only six are shown on each side. Suitable nozzles have been found to be gas burner fan nozzles produced by Bray Burners of Education Road, Leeds. The nozzles have part number 23A1906 and part reference CAT 4277.

Figures 5 and 6 illustrate a modified gas treatment apparatus 100 comprising first 101 and second chambers 102, each of elongate form, with longitudinal axes 103, 104. The chambers 101, 102 are interconnected so that gas flow between them is non-linear. Hot gas flowing from the first

101 to the second 102 chamber undergoes an angular change of direction, indicated by arrow 137, which is substantially obtuse, more particularly substantially 80°.

Chamber 101 has a gas inlet end 121 and a gas outlet end 122. Chamber

102 has a gas inlet end 123 and a gas outlet end 124.

Apparatus 100 treats the hot gas in first and second stages. Gas enters chamber 101 by way of interconnected ducts 105, 106, as indicated by arrows 107, 108.

The apparatus 100 also comprises a weir-type water/carbon separator 109, a cooled gas outlet stack 110, a water pump 111, a filter 112, a wire mesh spray demister 113 disposed at the gas outlet end 124 of chamber 102, and a carbon removal chamber 114. The lower end of the gas duct 105 is disposed centrally within the chamber 114. The water pump 111 draws separated-out water from the bottom of the water separator 109 by way of a line 115 in which the filter 112 is fitted. The pump 111 discharges the water to the chamber 101 by way of a line 116.

The line 116 is connected to a water manifold 117 which extends through the chamber 101, spaced from and substantially parallel to the longitudinal axis 103 thereof, in close proximity to the chamber wall bottom.

Four longitudinally-spaced branch pipes 118 extend laterally from the manifold 117 to terminate at the longitudinal axis 103 where water spray nozzles 119 are fitted. The nozzles 119 create water sprays 120 of hollow, conical form, disposed one behind the other, so as to direct cooling treatment water into the path of gas flow through the chamber 101. The water curtain forming each conical spray 120 leaves the associated nozzle 119 at substantially 90°.

Although in the embodiment of Figure 5, four nozzles 119 are provided, more, or less, than four may be employed, if required.

The exit end of the manifold 117 is connected to a ring 125 carrying four (or more) nozzles 126 operable to spray water in fan-shaped converging jets 127 which cross the mouth of the hot gas stream 108 as it enters the chamber 101 by way of the duct 106.

Thus the hot gas entering the first chamber 101 encounters the non-conical sprays 127 before encountering the conical sprays 120. This results in a substantial cooling of the gas as it enters the first chamber 101. Typically from 600°C to 30°C. Water, after forming the water sprays 120, 127, plus water sprays 142 referred to below, flows by gravity, (chamber 101 being inclined downwardly about 10° from the horizontal), into the separator 109, by way of a duct 135, which forms a downward, axial extension of the secondary chamber 102.

Any excess water may be removed from the separator 109 by way of an overflow line, flow through the line being controlled by a float-operated switches 162.

After separation out of carbon and other impurities, the water, now raised in temperature to say 30°C by contact with the hot gas, is eventually returned to the primary chamber 101, by way ofthe pump 111 and line 116.

The gas leaving the primary chamber 101 is non-linear, as it undergoes an angular change of direction which is substantially obtuse, namely substantially 80°, see arrow 137, as it enters the secondary chamber 102 to flow axially towards the demister 113 and the gas outlet stack 110.

Fresh, cold, water is fed to the mid-upper end of the secondary chamber 102 by way of a pair of vertically-spaced manifold pipes 140 which terminate on the longitudinal axis 104 of the chamber. Nozzles 141 are fitted to the exit ends of the manifold pipes 140. The cold water is discharged from the nozzles 141 as conical sprays 142. The conical sprays 142, as do conical sprays 120, actually contact the walls of chamber 102 or chamber 101 respectively.

The manifold pipes 140 (more than two may be employed if desirable), are supplied with fresh water by way of a line 145 connected to the outlet of a pump 143 drawing from the separator 109, by way of a line 144. The fresh water line 145 has a ROTOMETER^® 146 fitted therein, whereby the amount of water sprayed into the secondary chamber 102 may be measured. Thus the amount of heat withdrawn from the hot gas flowing through the system may be calculated.

The carbon removal chamber 114 has a hot gas inlet 150 which enters the top of the chamber, and an outlet 151 at the chamber bottom for carbon and other deposits removed from the gas flow. A screw conveyor 152 is disposed at the outlet 152, and is operable to remove carbon etc from the chamber 114.

The chamber 114 and associated ducts 105, 106 are enclosed in thermal insulation 153.

The chamber 114 defines a space 154 through which hot, combustible gas passes at about 700°C, by way of the inlet 150, to leave by way of the lower end of the duct 105, as indicated by arrow 107. The hot gas originates from apparatus 149 (Figure 6) for pyrolysis of waste materials, of the form disclosed by the above-mentioned International Patent Application No. PCT/GB93/01213 (WO 93/25848).

With reference to Figure 7, the chamber 114 is provided with deposit removal means 157 comprising an internal scraper 155 in the form of a shell 156, which is rotated within the chamber space 154 by a worm and a wheel drive. The wheel 158 of the drive embraces and is integral with the shell 156. The worm 159 of the drive, which is external, meshes with the wheel by way of an aperture or window 160, formed in the wall of the chamber 114. The worm 159 is rotated by an electric motor 161. A gas seal (not shown) is disposed in the window 160 to prevent outleakage of gas from the chamber 114.

The outer surface of the shell 156 carries oppositely-disposed scraper tools 165 which, when the shell is rotated, contact the inner surface 166 of the chamber 114, to remove carbon and other deposits therefrom. These deposits then fall to the bottom of the chamber 114, so as to be removed therefrom, by the screw conveyor 152, which discharges to an ash hopper 167. The auger of the screw conveyor 152 is housed in a tubular casing 168 and is driven by an electric drive unit 169.

The space 154 may house baffles whereby gas passing through the space is caused to swirl, thus assisting gas/carbon particle separation.

The upper ends of the gas ducts 105, 106 are interconnected with duct 105 which is disposed substantially vertical, projecting through duct 106 which is disposed downwardly, at an angle of about 30° to the horizontal. Any deposits tending to adhere to the intersecting parts of the ducts 105, 106 are removed by deposit removal means comprising hydraulically-powered flail units 170, 171.

Flail unit 170 projects into the upper end of duct 105 and is rotatable therein, as well as movable axially by a rotary/linear actuator 172, as indicated by arrows 173, 174.

The flail unit 170 comprises a drive shaft 175, which extends, in a gas- sealing manner, into the upper end of the duct 105. A head 176 is secured to the lower end of the shaft 175 and one or more pairs of scraper blades 177 are diametrically and pivotally mounted on the head. When the head 176 is rotated, as it moves up and down within the duct 105, the scraper blades 177 are flung out, by centrifugal force, into contact with the duct, whereby deposits are removed from the duct wall.

Flail unit 171 is identical to unit 172 and operates, within duct 106, in the same way. See arrows 180, 181.

After treatment by the apparatus 100, the gas leaving the apparatus by way of the outlet stack 110 is usefully employed. For example, in driving a turbine 180 which drives in turn an electrical generating set 181.

Claims

CLΔ1MS

1. Gas treatment apparatus comprising an elongate chamber having a longitudinal axis, an inlet at one end of the chamber, and an outlet at the other end thereof, whereby gas fiows axially between said inlet and said outlet, characterised in that nozzle means (5, 119) are provided for introducing liquid into the chamber (1, 101) for treating the gas, the nozzle means (5, 119) being adapted to produce a plurality of sprays in the form of sheets (53, 120) of the liquid, said sprays being disposed one behind the other so as to direct said liquid into the path (52, 106) of the gas flow.

2. Apparatus as claimed in claim 1, in which the nozzle means (5, 119) is directed at least partially towards said outlet (3, 122, 124) so as to be angled at less than 90° to the general direction of gas flow between said inlet and said outlet.

3. Apparatus as claimed in claim 1 or claim 2, wherein the nozzle means (5, 119) compris oes a ci p f liuuriauluitiy o uf s opyriaayy n iiouziz- -lietsa,, t mhec s apyriaayy n iiouz--.z--.liets-i d uirietcttiiingg the sprays at an aaannngggllleee ooofff 444555°°° tttooo 888555°°° tttooo ttthhheee lllooonnngggiiitttuuudddiiinnnaaalll aaaxxxiiisss (((777,,, 103).

4. Apparatus as claimed in claim 3, wherein the spray nozzles (5) are disposed in arrays on opposite sides of the chamber (1).

5. Apparatus as claimed in claim 4, wherein on passing along the chamber (1) from the inlet (2) to the outlet (3) thereof, the gas encounters a series of said sprays coming alternately from opposite sides of the chamber.

6. Apparatus as claimed in claim 4 or 5, wherein the inlet comprises a pipe (2) projecting into at least the first spray (53) of the series of said sprays.

7. Apparatus as claimed in any one of the preceding claims for use in heating water, the water being the liquid sprayed into the chamber, whereby heating of the water results from the temperature of the gas being higher than that ofthe water.

8. Apparatus as claimed in any one of claims 1 to 7, wherein the sprays (120) are of conical form.

9. Apparatus as claimed in any one of claims 1 to 8, comprising first (101) and second (102) such chambers, whereby gas leaving the first chamber (101) is then caused to flow through the second chamber (102), so that the gas is treated in first and second stages.

10. Apparatus as claimed in claim 9, wherein liquid used to treat gas in the first chamber (101) is collected (135) for re-use in said first chamber.

11. Apparatus as claimed in claim 10, wherein the liquid used to treat gas in the first chamber (101) is water which is passed through a water/non- water separator (107) before re-use in said first chamber (101).

12. Apparatus as claimed in claim 9, 10 or 11, wherein gas flow between the first (101) and second (102) chambers is non-linear (137).

13. Apparatus as claimed in claim 12, wherein said gas (137) flowing between the first (101) and second (102) chambers undergoes an angular change of direction which is substantially obtuse.

14. Apparatus as claimed in claim 13, wherein said angular change of direction (137) is substantially 80°.

15. Apparatus as claimed in any one of claims 9 to 14, wherein some of the liquid spray in the first chamber (101) is of conical form (120) and some is of non-conical form ( 127).

16. Apparatus as claimed in claim 15, wherein the non-conical spray (127) is of fan-like form.

17. Apparatus as claimed in claim 15 or 16, wherein gas (106) entering the first chamber (101) encounters the non-conical form (127) of spray before encountering the conical form (120) of spray.

18. Apparatus as claimed in any one of claims 9 to 17, provided with means (157 and/or 171, 172) for removing carbon or other deposits from gas flowing to the first chamber (101).

19. Apparatus as claimed in claim 18 wherein the deposit removal means (157) comprise a chamber (114) through which the gas is caused to flow and means (156, 165) for scraping deposits from the inner surface of the chamber.

20. Apparatus as claimed in claim 19, wherein the scraper means (156, 165) comprise a shell (156) rotatable within the chamber and scrapers (165) carried by the shell so as to contact the inner surface of the chamber (114) as the shell (156) is rotated.

21. Apparatus as claimed in claim 20 wherein the shell (156) is rotated by a worm and wheel drive (158, 159), the wheel (158) of the drive being attached to the shell (156).

22. Apparatus as claimed in claim 19, 20 or 21, wherein the chamber (114) is provided with an outlet (151) and with screw conveyor means (152) connected thereto, whereby deposits are removed from the chamber.

23. Apparatus as claimed in claim 18, wherein the deposit removal means (171, 172) comprise a flail device (e.g. 172) having centrifugally operated scrapers (177) which, in operation, contact a surface (duct 105 or 106) to be scraped and means for moving the scrapers against the surface in linear directions (174) whilst rotating the scrapers (173).

24. Apparatus as claimed in claim 23 wherein the surface to be scraped comprises the inner surface of a gas duct (105 or 106).

25. Gas treatment apparatus comprising at least one elongate chamber having a longitudinal axis, an inlet at one end of the chamber, and an outlet at the other end thereof, whereby gas flows axially between said inlet and said outlet, characterised in that the apparatus (100) comprises first (101) and second (102) such chambers, whereby gas leaving the first chamber (101) is then caused to flow through the second chamber (102), so that the gas is treated in first and second stages, and nozzle means (119, 141) are provided for introducing liquid into the chambers (101, 102) for treating the gas, the nozzle means (119, 141) being adapted to produce a plurality of sprays in the form of sheets (126, 142) of the liquid, said sprays being disposed one behind the other so as to direct said liquid into the path (108, 137) ofthe gas flow.

26. Gas treatment apparatus substantially as hereinbefore described with reference to Figures 1 to 4 ofthe accompanying drawings.

27. Gas treatment apparatus substantially as hereinbefore described with reference to Figures 5 and 6 of the accompanying drawings