ZA200810371B - Scrubbing of fumes - Google Patents
Scrubbing of fumes Download PDFInfo
- Publication number
- ZA200810371B ZA200810371B ZA2008/10371A ZA200810371A ZA200810371B ZA 200810371 B ZA200810371 B ZA 200810371B ZA 2008/10371 A ZA2008/10371 A ZA 2008/10371A ZA 200810371 A ZA200810371 A ZA 200810371A ZA 200810371 B ZA200810371 B ZA 200810371B
- Authority
- ZA
- South Africa
- Prior art keywords
- fume
- scrubbing
- particulate matter
- solid particulate
- matter entrained
- Prior art date
Links
- 239000003517 fume Substances 0.000 title claims description 57
- 238000005201 scrubbing Methods 0.000 title claims description 26
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 40
- 239000007787 solid Substances 0.000 claims description 38
- 238000000034 method Methods 0.000 claims description 20
- 235000019270 ammonium chloride Nutrition 0.000 claims description 17
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims description 17
- 239000002245 particle Substances 0.000 claims description 16
- 239000000376 reactant Substances 0.000 claims description 16
- 239000000920 calcium hydroxide Substances 0.000 claims description 15
- 235000011116 calcium hydroxide Nutrition 0.000 claims description 15
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims description 15
- 239000013618 particulate matter Substances 0.000 claims description 15
- 239000007789 gas Substances 0.000 claims description 10
- 239000003463 adsorbent Substances 0.000 claims description 8
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 4
- 238000005203 dry scrubbing Methods 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 238000000859 sublimation Methods 0.000 claims description 4
- 230000008022 sublimation Effects 0.000 claims description 4
- 229910021529 ammonia Inorganic materials 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 3
- 235000019738 Limestone Nutrition 0.000 claims description 2
- 239000002250 absorbent Substances 0.000 claims description 2
- 230000002745 absorbent Effects 0.000 claims description 2
- 239000000292 calcium oxide Substances 0.000 claims description 2
- 235000012255 calcium oxide Nutrition 0.000 claims description 2
- 239000006028 limestone Substances 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- 239000002737 fuel gas Substances 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 3
- 239000001110 calcium chloride Substances 0.000 description 3
- 229910001628 calcium chloride Inorganic materials 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- JTJMJGYZQZDUJJ-UHFFFAOYSA-N phencyclidine Chemical class C1CCCCN1C1(C=2C=CC=CC=2)CCCCC1 JTJMJGYZQZDUJJ-UHFFFAOYSA-N 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000005686 electrostatic field Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000005243 fluidization Methods 0.000 description 1
- 238000011044 inertial separation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- -1 platinum group metals Chemical class 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working
Description
oo" R _ 2 _
SCRUBBING OF FUMES
:
This invention relates to a method of and an apparatus for scrubbing of particular fumes and the consequent separation or removal of those fumes from an industrial process.
The scrubbing efficiency of conventional wet scrubber systems is sometimes reduced when used to remove very small solid particles from a gaseous stream.
A typical example is found in the refining process of platinum group metals where ammonium chloride is used as a complexing agent. Furnace trays contain a mixture consisting of platinum group metal complexed by ammonium chloride and possibly other agents in the form of a solution or partial slurry which is then subjected to heating to recover metal ultimately. The furnace temperature may reach 900°C. A number of furnaces are usually arranged in parallel and a draught stream of air is passed over the trays. During the heating process water and other volatile components are evaporated or sublimed and enter the vapour phase at temperatures varying between ambient and maximum temperature.
The ammonium chloride forms a suspension of small particles in the vapour oo N 23- : phase on desublimation by cooling or mixing with cool air which conventionally pass through through a series of wet scrubbers which facilitate the removal of ammonia in the stream by scrubbing with a sulphuric acid solution and possibly other scrubbing agents, but are not found to be effective in the removal of ammonium chloride particles. The treated stream may finally be vented to atmosphere through a stack.
It has been found that ammonium chloride particles are able to and do bypass conventional scrubbing methods and, while certain scrubbers such as electrostatic scrubbers are more effective than conventional scrubbers they tend to be expensive to purchase, install and operate. Consequently they are rarely used.
It should be noted that while considerable emphasis has been placed on removing ammonium chloride particulates from an effluent stream the invention is not limited to this application and it is envisaged that it can be used to remove a variety of small solid particles suspended in a draught stream provide they can be sublimed or volatilized to a homogeneous vapour. In addition, the particles themselves may be pollutants such as ammonium chloride or they may be desired chemicals or the like which are concentrated by extracting them from a gaseous stream.
OBJECT
It is an object of this invention to provide a method for scrubbing of particular fumes. :
In accordance with this invention there is provided a method of scrubbing a fume to remove solid particulate matter entrained therein comprising heating the fume to sublime the particles if the particles are unsublimed, directing the heated fume so as to make intimate contact with a suitable solid adsorbent or reactant such that the sublimed vapour is substantially removed from the fume, and removing the cleaned fume from the system.
» hs 4.
In accordance with a second aspect of the invention, a source vapour is prevented from cooling and forming a fume by desublimation, directing the heated vapour so as to make intimate contact with a suitable solid adsorbent or reactant such that desired species are substantially removed from the vapour, and removing the cleaned vapour from the system.
There is also provided for the heated fume or source vapour to make intimate contact with a suitable solid adsorbent or reactant in a dry scrubbing vessel containing a solid bed. Alternatively, the suitable solid adsorbent or reactant is in a powdered form and intimate contact between it and the heated fume or source vapour occurs in a fluidised bed scrubber, preferably the powdered absorbent or reactant bed is fluidised by a gas.
There is further provided for the fume to be an ammonium chloride containing fume, for the fume to be heated to a temperature above the sublimation temperature of ammonium chloride (known to be 340°C at atmospheric pressure) and contacting the fumes with a solid reactant which reacts with and removes the ammonium chloride component either partially or completely.
There is also provided for the solid reactant to be commercial slaked lime and for the gaseous residuals after scrubbing to be water air, ammonia and water vapour. The solid reactants may also be commercial quicklime or commercial limestone in appropriate particle sizes and at appropriate temperatures. The related chemical reactions are the following:
Ca(OH)z(s)+2NH Clg) 2CaClysy+2NHzg)+2H20
CaOys+2NH Clg ?CaClzsy+2NH3g+H20
CaCOs3(5)+2NH Clg) ?CaClos)+ CO) + 2NH31g+H20g)
Preferably, the reaction between the slaked lime and ammonium chloride fume takes place in a fixed bed reactor, in which the slaked lime forms a bed.
Alternatively there is provided for the reaction between the slaked lime and ammonium chloride fume to take place in a fluidised bed reactor which is fluidised by the fumes passing through the reactor.
oe RN -5-
The above and additional features of the invention will be described below by way of example only and with reference to the accompanying drawings in which:
Figure 1 is a schematic diagram of a general dry scrubbing circuit;
Figure 2 is a schematic diagram of a fixed bed scrubber;
Figure 3 is a schematic diagram of a transported fluidised bed system; and
Figure 4 is a schematic diagram of a fixed fluidised bed system.
The scrubbing systems illustrated can be used in the embodiment of the invention which is described below by way of example only. In this embodiment a process for removing solid ammonium chloride fume from a stream of carrier gas is described.
: Referring to Figure 1, a general dry scrubbing circuit (1) is used to remove particles from a raw fume stream (2) from at least one platinum group metal recovery circuit (not shown) although in practice a number of platinum group metal circuits in parallel contribute to the fume stream (2). The platinum group metal circuits are, typically, cyclic and variable in operation and this results in the fume stream (2) being variable in quantity, temperature and pressure.
The raw fume stream (2) is fed into a heat exchanger (3) and from the heat exchanger (3) to a fuel gas burner (4) which increases the temperature of the fume where the temperature is below the 340°C volatilization temperature of ammonium chloride to about 400°C. A temperature controller (5) regulates the flow of fuel gas (6) to the fuel gas burner (4) and, consequently, regulates the temperature of fume passing through the fuel gas burner (4) to a dry scrubber (7) which accepts the hot gas stream (8) as well as a calcium hydroxide stream (9).
The scrubber (7) has an outlet (10) for scrubbed gas which feeds into the heat exchanger (3) where it heats up the raw fume stream (2) and, in turn, is cooled
J ) o -6- before it passes through the heat exchanger and is vented to atmosphere as a clean gas.
The scrubber (7) also has an outlet (11) for a reject stream of calcium chloride - and a fan (12) provides a pressure differential in the fume extraction system "which is necessary to maintain flow through the system.
Figures 2, 3, and 4 represent possible detailed execution of item 7 in Figure 1.
There are many other possibilities which will be known to engineers experienced in the field of gas-solid contact.
Referring the Figure 2, a fixed bed scrubber (13) comprises a bed (14) of calcium hydroxide pellets which are placed on a porous support plate (15) in a vertically orientated vessel (16). Fresh pelleted calcium hydroxide is added as required through an operatively upper manhole (17) and manually extracted from an operatively lower manhole (18) although it can also be extracted from the vessel (16) by pneumatic vacuum extraction or other means. Fume (19) enters the : vessel towards its lower end and cleaned gas (20) is extracted from its 3 operatively upper end.
Referring to Figure 3, a transported fluidised bed scrubber system (21) has a solids hopper (22) containing calcium hydroxide (23) introduced through a calcium hydroxide feed chute (24). Spent calcium hydroxide in the form of calcium chloride is removed from the hopper (22) via a waste pipe (25).
Powdered calcium hydroxide is fed into a vertical riser duct (26) at a flow rate suitable to form a vertically transported dilute phase fluidised bed within which it is envisaged most of the ammonium chloride in a fume (27) will be eliminated leaving scrubbed gas (28) to be vented to atmosphere. Any remaining powder is removed from the system by at least one cyclone separator (29).
Referring specifically to Figure 4, a fluidised fixed bed system (30) comprises a fume inflow duct (31) and a cleaned gas outflow duct (32). The scrubber (33) incorporates a pair of cyclones (34) which eliminate powder from a fixed bed entrained in cleaned gas. In this system fluidisation occurs in a dense phase
A N -7. : fluidised bed (35) which is supported on a suitable gas distributor (19). Calcium hydroxide is fed into the system through an inflow conduit (36) and spent calcium hydroxide containing calcium chloride is removed by any one of a number of appropriate techniques (37) which are well known in the art.
Ammonium chloride is difficult to remove from a fume because, when deposited in a stream of air below the sublimation temperature, it forms a white cloud in form of solid particles very small in size (about | ym in diameter or less). The small particle size tends to prevent inertial separation, or alternatively encourages the formation of electrostatic fields that inhibit separation. According to one embodiment of the invention, the ammonium chloride particles are heated to sublime them thus eliminating the cloud and enhancing the action of any one of the above-described scrubbers which can be used in the invention.
It is envisaged that the invention can be adapted to separate other initially solid components which behave in a similar fashion to ammonium chloride by altering the temperature to which a fume containing these components such that the temperature is above the sublimation or vaporisation temperature of the component.
Claims (14)
1. A method of scrubbing a fume to remove solid particulate matter entrained . therein comprising heating the fume to sublime the particles if the particles are unsublimed, directing the heated fume so as to make intimate contact with a suitable solid adsorbent or reactant such that the sublimed vapour is substantially removed from the fume, and removing the cleaned fume from the system.
2. A method of scrubbing a fume to remove solid particulate matter entrained therein comprising preventing a source vapour from cooling and forming a fume by desublimation, directing the heated vapour so as to make intimate contact with a suitable solid adsorbent or reactant such that desired species are substantially removed from the vapour, and removing the cleaned vapour from the system.
3. A method of scrubbing a fume to remove solid particulate matter entrained therein as claimed in claim 1 or in claim 2 in which the heated fume or source vapour makes intimate contact with a suitable solid adsorbent or reactant in a dry scrubbing vessel containing a solid bed.
4. A method of scrubbing a fume to remove solid particulate matter entrained therein as claimed in claim 1 or in claim 2 in which the suitable solid adsorbent or reactant is in a powdered form and intimate contact between it and the heated fume or source vapour occurs in a fluidised bed scrubber.
5. A method of scrubbing a fume to remove solid particulate matter entrained therein as claimed in claim 4 in which the powdered absorbent or reactant bed is fluidised by a gas.
6. A method of scrubbing a fume to remove solid particulate matter entrained therein as claimed in any one of the preceding claims in which the fume is an: ammonium chloride containing fume.
7. A method of scrubbing a fume to remove solid particulate matter entrained
= Oe } 9 i . ~~ " therein as claimed in claim 6 in which the fume is heated to a temperature above the sublimation temperature of ammonium chloride (known to be 340°C at atmospheric pressure) and contacting the fumes with a solid reactant which reacts with and removes the ammonium chloride component either partially or completely.
8. A method of scrubbing a fume to remove solid particulate matter entrained therein as claimed in claim 6 or in claim 7 in which solid reactant to be commercial slaked lime.
9. A method of scrubbing a fume to remove solid particulate matter entrained therein as claimed in claim 8 in which the gaseous residuals after scrubbing to be water air, ammonia and water vapour.
10. A method of scrubbing a fume to remove solid particulate matter entrained therein as claimed in claim 6 or in claim 7 in which the solid reactants is : commercial quicklime or commercial limestone in appropriate particle sizes and at appropriate temperatures.
11. A method of scrubbing a fume to remove solid particulate matter entrained therein as claimed in any one of claims 6 to 10 in which the related chemical reactions are: Ca(OH) y5)+2NH Clg) >CaCly) +2NH 3g 2H20(g), Ca O(s)+2NHCl(g ->Ca Clys)r2NH3) +H>0(g). and CaCOg5+2NH Cl CaCl) CO +2NH3g+H20g).
12. A method of scrubbing a fume to remove solid particulate matter entrained therein as claimed in any one of claims 6 to 9 in which the reaction between the slaked lime and ammonium chloride fume takes place in a fixed bed reactor in which the slaked lime forms a bed.
13. A method of scrubbing a fume to remove solid particulate matter entrained therein as claimed in any one of claims 6 to 9 in which the reaction between the
LR -10- ~ slaked lime and ammonium chloride fume takes place in a fluidised bed reactor which is fluidised by the fumes passing through the reactor.
14. A method of scrubbing a fume to remove solid particulate matter entrained therein substantially as herein described with reference to and as illustrated in the accompanying example. DATED THIS 8™ DAY OF DECEMBER 2008. y) BOWMAN GILFILLAN INC. (JOHN & KERNICK) FOR THE APPLICANT
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA200709117 | 2007-12-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| ZA200810371B true ZA200810371B (en) | 2009-12-30 |
Family
ID=42683064
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| ZA2008/10371A ZA200810371B (en) | 2007-12-23 | 2008-12-05 | Scrubbing of fumes |
Country Status (2)
| Country | Link |
|---|---|
| RU (1) | RU2477643C2 (en) |
| ZA (1) | ZA200810371B (en) |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2583013A (en) * | 1945-10-26 | 1952-01-22 | Standard Oil Dev Co | Condensation of sublimable material |
| DE2247229A1 (en) * | 1972-09-27 | 1974-03-28 | Interatom | DESUBLIMATOR, ESPECIALLY FOR UF TIEF 6 |
| SU1018708A1 (en) * | 1982-02-19 | 1983-05-23 | Ордена Трудового Красного Знамени Институт Физической Химии Ан Ссср | Sorbent production method |
| GB8304067D0 (en) * | 1983-02-14 | 1983-03-16 | Ici Plc | Gas treatment |
| FI82612C (en) * | 1987-05-08 | 1991-04-10 | Ahlstroem Oy | Process and apparatus for treating process gases |
| SU1725987A1 (en) * | 1990-03-30 | 1992-04-15 | Московский институт тонкой химической технологии им.М.В.Ломоносова | Method of cleaning gas from iodine vapors |
| FR2867092B1 (en) * | 2004-03-05 | 2007-09-14 | Inst Francais Du Petrole | PROCESS FOR DECARBONATION OF SMOKE WITH COOLED PARTICLES |
-
2008
- 2008-12-05 ZA ZA2008/10371A patent/ZA200810371B/en unknown
- 2008-12-18 RU RU2008149919/04A patent/RU2477643C2/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| RU2477643C2 (en) | 2013-03-20 |
| RU2008149919A (en) | 2010-06-27 |
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