GB2236748A - Process for brightening flue gas gypsum - Google Patents
Process for brightening flue gas gypsum Download PDFInfo
- Publication number
- GB2236748A GB2236748A GB9022180A GB9022180A GB2236748A GB 2236748 A GB2236748 A GB 2236748A GB 9022180 A GB9022180 A GB 9022180A GB 9022180 A GB9022180 A GB 9022180A GB 2236748 A GB2236748 A GB 2236748A
- Authority
- GB
- United Kingdom
- Prior art keywords
- flue gas
- hydrocyclone
- washing
- overflow
- recycled
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000003546 flue gas Substances 0.000 title claims abstract description 39
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 37
- 239000010440 gypsum Substances 0.000 title claims abstract description 33
- 229910052602 gypsum Inorganic materials 0.000 title claims abstract description 33
- 238000000034 method Methods 0.000 title claims abstract description 20
- 238000005282 brightening Methods 0.000 title claims abstract description 6
- 238000005406 washing Methods 0.000 claims abstract description 28
- 239000010802 sludge Substances 0.000 claims abstract description 8
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 7
- 238000004064 recycling Methods 0.000 claims abstract description 3
- 238000000926 separation method Methods 0.000 claims abstract description 3
- 241000282326 Felis catus Species 0.000 claims 1
- ZZUFCTLCJUWOSV-UHFFFAOYSA-N furosemide Chemical compound C1=C(Cl)C(S(=O)(=O)N)=CC(C(O)=O)=C1NCC1=CC=CO1 ZZUFCTLCJUWOSV-UHFFFAOYSA-N 0.000 claims 1
- 239000007787 solid Substances 0.000 description 8
- 239000006227 byproduct Substances 0.000 description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- 238000002845 discoloration Methods 0.000 description 5
- 239000002562 thickening agent Substances 0.000 description 5
- 238000011109 contamination Methods 0.000 description 4
- 239000000945 filler Substances 0.000 description 4
- 239000010881 fly ash Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 230000023556 desulfurization Effects 0.000 description 3
- 239000000725 suspension Substances 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 235000019738 Limestone Nutrition 0.000 description 2
- 239000004566 building material Substances 0.000 description 2
- 239000003086 colorant Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 239000003077 lignite Substances 0.000 description 2
- 239000006028 limestone Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 235000012054 meals Nutrition 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 235000002918 Fraxinus excelsior Nutrition 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 101100436435 Mus musculus Atp5me gene Proteins 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000002956 ash Substances 0.000 description 1
- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 239000011236 particulate material Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/46—Sulfates
- C01F11/464—Sulfates of Ca from gases containing sulfur oxides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/48—Sulfur compounds
- B01D53/50—Sulfur oxides
- B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/46—Sulfates
- C01F11/468—Purification of calcium sulfates
Abstract
The process for brightening flue gas gypsum from flue gas wet-desulfurization plants wherein the washing liquor is thickened via a hydrocyclone and the hydrocyclone overflow is recycled to the washing circulation system and the thickened hydrocyclone underflow is separated into flue gas gypsum and washing liquor, is carried out by that the hydrocyclone overflow, prior to recycling same, is subjected to a further separation by means of a hydrocyclone, the underflow of which is directly recycled into the washing circulation system and the overflow of which is separated into thick sludge and washing liquor to be recycled into the washing circulation system is disclosed. <IMAGE>
Description
PROCESS FOR BRIGHTENING FLUE GAS GYPSUM
The present invention relates to a process for brightening flue gas gypsum from flue gas wet-desulfurization plants wherein the washing liquor is thickened via a hydrocyclone and the hydrocyclone overflow is recycled to the washing circulation system and the thickened hydrocyclone underflow is separated into flue gas gypsum and washing liquor.
Frequently- the flue gas gypsum produced in these flue gas desulfurization plants still contains minor amounts of fly ashes and other polluting components (by-products). More particularly, when washing the flue gas obtained from low-chloride lignite, the washing liquor is circulated for a relatively log time until the chloride content will have accumulated to a preferred value of from 5,000 to 50,000 ppm. It is only if this range will be exceeded that part of the washing liquor will be withdrawn and be replaced with fresh process water, while attention is paid to that the process is operated within said preferred range. The content of most-finely divided by-products in the washing liquor will of course also increase together with the chloride content.These accumulated contaminating materials surprisingly will be incorporated in the flue gas gypsum and then will of course also cause some discoloration of the flue gas gypsum obtained. Said discoloration is acceptable in the case that the flue gas gypsum will be supplied to the cement industry or be used as a mortar in mining. However, if the flue gas gypsum is to be processed into building materials or even fillers, then said discoloration is very undesirable. Also, it is not possible to subsequently remove said discoloration from the flue gas gypsum without recrystallization.
Hence, it is the object of the invention to brighten a flue gas gypsum which has been contaminated and discolored by finely divided by-products and thereby to render said flue gas gypsum suitable for building purposes or as starting material for fillers.
It was now found that this object can be attained in a surprisingly simple manner by that the hydrocyclone overflow, prior to recycling same, is subjected to a further separation by means of a hydrocyclone, the underflow of which is directly recycled into the washing circulation system and the overflow of which is separated, preferably in a high-performance thickener or a settling basin or a similar unit, into thick sludge and and washing liquor to be recycled into the washing circulation system.
By this measure it is accomplished that the mostfinely divided by-products are removed to a significant extent from the washing liquor before they can be incorporated in the flue gas gypsum as a discoloring contamination. Unexpectedly, the amounts of these mostfinely divided by-products causative for the discoloration are very low so that the analytical composition of the flue gas gypsum is hardly changed, while nevertheless a flue gas gypsum is obtained which is substantially brighter and substantially less colored when viewed at with the naked eye. However, the differences also can be detected by an objective measurement. With a flue gas gypsum from a lignite power plant (KW Frimmersdorf, W.Germany) the brightness level of the flue gas gypsum was increased from 26.0 to 59.2 (measured by means of a Lange Photometer LFM-1 as a so-called standard color value).Thus, the measure according to the invention above all causes the highly colorant portions of the finely divided by-products to be removed from the flue gas gypsum, but in addition thereto other contaminations which particularly originate from the limestone meal and process water used are also removed.
The process measure according to the invention is somewhat similar to the process measures according to the German Offenlegungsschrift [DE-OS; Published Unexamined Patent Application] 36 07 191. According to said DE-OS, in order to reduce the chloride load of the upper absorber circulation system of two-stage flue gas wet-desulfurization plants, the diluted gypsum suspension of the hydrocyclone overflow is continuously or intermittently separated in a further hydrocyclone into a concentrated suspension which contains the lower grain-size solids and is recycled to the oxidation cycle and a hydrocyclone overflow which contains most-finely divided solids and dissolved salts and is withdrawn from the system. Thereby a considerable proportion of the chloride was removed from the washing liquor without discharging higher proportions of the suspension.In the process according to the invention, said hydrocyclone overflow is once more separated, namely, for example, in a high-performance thickener, into a thick sludge to be discharged and a washing liquor to be recycled to the washing circulation system and, hence, the overall water balance is not deteriorated; that is, the amount of waste water is not increased. Thus, in the process according to the invention the total amount of chloride is recycled into the washing circulation system. It is only if the chloride content in the flue gas desulfurization plant will have become too high that said washing liquor portionwise or in intervals will not be recycled.It is of crucial importance that according to the invention the most-finely divided particles are withdrawn from the process as fast as possible and in an amount as high as possible, before said particles can be incorporated in the flue gas gypsum. Thus, the process according to the invention will be used, more particularly, if low-chloride flue gases of flue gases having higher fly ashes contents (e.g. with older electrofilters) are to be desulfurized and nevertheless a flue gas gypsum is to be produced which is as bright and pure as possible and is also usable for building purposes or as a filler.
The thick sludge as also obtained in the process according to the invention quite predominantly consists of most-finely divided fly ashes and some most-finely divided contaminations of the initial limestone meal.
Thus, said thick sludge can be- disposed or utilized, respectively, together with the other fly ashes or grate ashes.
Moreover, the process measure according to the invention exhibits some parallel features to those of the DE-OS 38 03 631. In said DE-OS, for controlling the crystal growth, the filterability and the dehydratability of flue gas gypsum, solids are withdrawn from the overflow of the hydrocyclone by means of a second hydrocyclone, a thickener or a filter. In the first variant, use of a hydrocyclone or of a thickener, a fraction of medium-sized particles is mainly withdrawn from the system, whereas the finest particles are recycled into the system. On the other hand, in the second variant, the use of a filter, almost all of the solids are removed from the hydrocyclone overflow.In contrast thereto, it is the goal of the process according to the invention to only remove the most-finely divided particles from the system and to recycle the medium-sized fraction mainly consisting of gypsum as crystal nuclei.
Accordingly, both of the above-mentioned variants according to the DE-OS 38 03 631 do not meet the requirement of brightening the flue gas gypsum and nevertheless providing a sufficient amount of crystallization nuclei.
The process according to the invention is further illustrated by the following Example.
EXAMPLE
In a commercial two-stage flue gas desulfurization plant (KRC) the cyclone overflow was separated in a further hydrocyclone such as to form a hydrocyclone overflow containing a reduced amount of solids and a hydrocyclone underflow richer in solids and comprising a relatively high portion of gypsum which underflow was directly recycled into the oxidation cycle. In the course of the test period the gypsum content of the underflow still showed a significant increase. The hydrocyclone overflow above all contained most-finely divided solids and was supplied to a high-performance thickener and was separated therein to produce an aqueous portion which was nearly solid-free and was usable as process water, and a sludge predominantly consisting of most-finely divided solid particles.The analysis of said sludges revealed that they only from 14.4 to 16.8% thereof consisted of calcium sulfate dihydrate, but that they contained from 8.1 to 9.7% of Fe2O3, from 5.1 to 7.6% of A12O3, from 0.16 to 0.21% of
MnO, from 1;5.8 to 24.0% of loss on ignition and from 39.8 to 45.6% of HCl-insolubles. These values clearly show that many colorant and interfering contaminations have been accumulated in this most-finely particulate sludge.
The flue gas gypsum obtained was analyzed over a period of several days; the results were as follows:
Time (days) 0 2 4
Measured Quantity
Brightness level 26.2 29.0 33.2
Fines 100 80 45
Iron content 0.09 0.08 0.05
Manganese content 0.004 0.002 0.001
Long-term tests have shown that the brightness level may be increased to values above 60% upon the complete removal of the finest particulate material.
It goes without saying that the distinct reduction in the amount of by-products clearly enlarges the field of possible uses of the flue gas gypsum, irrespectively of its color, for example in building materials or as a filler in plastics, dyes or adhesive. Since the latter usually are multi-material systems, undesirable side reactions are prevented by the improvement achieved of the purity of the flue gas gypsum.
Claims (2)
1. A process for brightening flue gas gypsum from flue
gas wet-desulfurization plants wherein the washing
liquor is thickened via a hydrocyclone and the hydro
cyclone overflow is recycled to the washing circulation
system and the thickened hydrocyclone underflow is
separated into flue gas gypsum and washing liquor,
characterized in that the hydrocyclone overflow, prior
to recycling same, is subjected to a further separation
by means of a hydrocyclone, the underflow of which is
directly recycled into the washing circulation system
and the overflow of which is separated into thick sludge
and washing liquor to be recycled into the washing
circulation system.
2. A process as claimed in claim 1 substantially as herein
described with particular reference to the exempi i fi cat i on.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3934352 | 1989-10-14 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9022180D0 GB9022180D0 (en) | 1990-11-28 |
| GB2236748A true GB2236748A (en) | 1991-04-17 |
| GB2236748B GB2236748B (en) | 1993-03-24 |
Family
ID=6391483
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9022180A Expired - Fee Related GB2236748B (en) | 1989-10-14 | 1990-10-12 | Process for brightening flue gas gypsum |
Country Status (3)
| Country | Link |
|---|---|
| DE (1) | DE4032249C2 (en) |
| GB (1) | GB2236748B (en) |
| IT (1) | IT1243740B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT403015B (en) * | 1996-06-14 | 1997-10-27 | Austrian Energy & Environment | Process for desulphurization of flue gases |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4123258A1 (en) * | 1991-07-13 | 1993-01-14 | Steinmueller Gmbh L & C | METHOD FOR CLEANING A SULFUR DIOXIDE AND Possibly. OTHER EXHAUST GASES CONTAINING POLLUTANTS |
| DE19636243C2 (en) * | 1996-08-28 | 2003-06-18 | Vattenfall Europe Generation | Process for improving the operation of wet desulphurization of fossil-fired power plants using quicklime or limestone |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3607191A1 (en) * | 1986-03-05 | 1987-09-10 | Knauf Res Cottrell | METHOD FOR REDUCING CHLORIDE EXPOSURE IN WET FLUE GAS DESULFURATION PLANTS |
| DE3803631A1 (en) * | 1988-02-06 | 1989-08-17 | Krc Umwelttechnik Gmbh | Method for controlling the crystal growth, the filterability and the dewaterability of flue gas gypsum |
-
1990
- 1990-10-11 DE DE4032249A patent/DE4032249C2/en not_active Expired - Fee Related
- 1990-10-12 IT IT02173290A patent/IT1243740B/en active IP Right Grant
- 1990-10-12 GB GB9022180A patent/GB2236748B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3607191A1 (en) * | 1986-03-05 | 1987-09-10 | Knauf Res Cottrell | METHOD FOR REDUCING CHLORIDE EXPOSURE IN WET FLUE GAS DESULFURATION PLANTS |
| DE3803631A1 (en) * | 1988-02-06 | 1989-08-17 | Krc Umwelttechnik Gmbh | Method for controlling the crystal growth, the filterability and the dewaterability of flue gas gypsum |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT403015B (en) * | 1996-06-14 | 1997-10-27 | Austrian Energy & Environment | Process for desulphurization of flue gases |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9022180D0 (en) | 1990-11-28 |
| DE4032249A1 (en) | 1991-04-18 |
| GB2236748B (en) | 1993-03-24 |
| DE4032249C2 (en) | 1998-09-24 |
| IT1243740B (en) | 1994-06-21 |
| IT9021732A0 (en) | 1990-10-12 |
| IT9021732A1 (en) | 1992-04-12 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19991012 |