CA2165633C - Method of reagent and oxidation air delivery - Google Patents
Method of reagent and oxidation air deliveryInfo
- Publication number
- CA2165633C CA2165633C CA 2165633 CA2165633A CA2165633C CA 2165633 C CA2165633 C CA 2165633C CA 2165633 CA2165633 CA 2165633 CA 2165633 A CA2165633 A CA 2165633A CA 2165633 C CA2165633 C CA 2165633C
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- dry
- absorber vessel
- oxidation
- reagent
- oxidation air
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Abstract
A method of forced oxidation flue gas desulfurization uses an oxidation air system air stream to not only provide oxidation air into an absorber vessel, but also to pneumatically convey and inject dry reagent into the absorber vessel to satisfy reagent addition requirements. If necessary, other dry additives can be added to the dry reagent so that the oxidation air stream injects both the dry reagent and the dry additives into the absorber vessel. The dry additives can be added in this method even if the reagent is introduced by other known methods.
Description
..
METHOD OF REAGENT AND OXIDATION AIR DELIVERY
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates in general to wet flue gas desulfurization (FGD) processes and, in particular, to wet lim.os~on~ forced o~i-li7~ flue gas desulfurization 5 ~roc~es (LSFO-FGD) pr~sses and other cn.,-pAIihle procesæs. Wet LSFO-FGD systems have s~ ox~ tion air and l;...~(o~e slurry streams. Theæ systems, in general, utilize a wet ~ g circuit by ~ coarse 1;...~ f to prepare a limeston~ solids-liquid slurry as the fresh reagent supplied to the absorber system. Typically, wet ball mills have been used for ~is ~u.~ose. The wet CO~ m process has the advaD~age of ~ot~ ially lower 0 hOlY~ l~Ui~ than dry ~ ;. N1;. ~ ploce~xs, and the fact that the end product after is a slurry also fits in well with the wet LSFO-FGD system design. This slurry is commonly stored in a holding tank to provide surge c~a~i~y for :~ubse(lu.,.l~ controlled supply to the absorber vessel based on l~m~n(3, In wet FGD ~,.~ lls, the sulfur dioxide (SO2) absol~io~ ~locess l~u~s a nearly lS contimloll~ supply of fresh l~e~ to ~ s~ti~f~-tory oper~tion and SO2 removal CASE ~80 2 1 6 5 6 3 3 efficiencies. Often it is desirable to incorporate air addition to the wet FGD absorber to provide in situ forced oxidation of the absorber reaction product.
Providing se~ e o~da~ll air and ;i....o~1...~ slurry streams increases the complexity and expense of these- wet LSFO~G-l}systerns. -lt is thus apparent that an approach to S providing these se~ala~ functions in a simple and cost-effective manner would be welcomed by the industry.
SUMMARY OF THE INVENTION
The filn~m~n~l nature of the present invention is the use of the oxidation air system air stream to not only provide oxidation air to an absorber vessel, but also to both l0 pneumatically convey and inject dry reagent into the absorber vessel to satisfy reagent addition requirements.
Accordingly, one aspect of the present invention is drawn to a method of forced oxidation flue gas desulrul~lion wherein dry reagent and dry additive are supplied to an absorber vessel cont~ining a liquid slurry through an oxidation air addition system. The 15 method colllylises the steps of: providing a rate controlled feed supply of ~r~ared dry reagent and dry additive to a ~.~r.. AIic collv~ying pick-up point located within air supply piping used to provide an oxidation air stream from the oxidation air addition system into the absorber vessel; and using the oxidation air addition system air stream to provide ox~ tion air into the abso~ vessel, and to ~ lly convey and inject the dry reagent 20 and dry addilive into the absoll~r vessel sufficient to partially desulfurize flue gas provided to the al)so~ vessel.
The dry reagent is a ~ ~L ~1P~d from the group cO.~icli..g of solid alkali colll~oullds used in flue gas desulruli~lion ~r(xesses inrl~lAing lillles~o~e, e~1cillm, ~o1~ c--.. ", ~1.. ;.. , so linm, and/or ~mmonillm colll~ullds. Other dry additives besides 25 reagent can be added sepz. ~ ly or added to the dry reagent so that the oxi-l~tion air stream inje ts both the dry reagent and the dry additives into the absoll,cl vessel. These additives could be added to promote oxi~ti~)n ~,vithin the absorber vessel; to ~ A.~-e cl~ ;r~l al)sol~liol~ of the SO2 within the al)sollJcr vessel or to provide a desired degree of b~rL~ g to the ~ lrl.. ;,,.~ion ~locess ~ ih; to inhibit scale growth vithin the al)soll~r vessel; or to promote or specify the type of or degree of cryst~lli7~tion7 etc., in the desulfuri_ation process occurring within the absorber vessel.
Acco,dil,~,ly, another aspect of the present invention is drawn to a method of forced oxidation flue gas desulfurization, wherein.~dry~-r~litive i~ r.~ tir~lly supplied to an absorber vessel cont~ining a liquid slurry through an oxidation air addition system. The steps of this method conl~lise: providing a rate controlled feed supply of prepared dry additive to a pn~nm~tic conveying pick-up point located within air supply piping used to provide an oxidation air stream from the oxidation air addition system into the absorber vessel; and using the oxidation air addition system air stream to provide oxidation air into the abso,l,ci vessel, and to ~ ir~lly convey and inject the dry additive into the absorber vessel.
The various feat~lrcs of novelty which characteri_e the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better underst~n-~in~ of the invention, its opela~ing advantages and specific results ~tt~in~A by its uses, refc,c,lce is made to the ~ ol--p~.-yhlg drawings and descfl~live matter in which a ~ref~.,ed embodiment of the invention is illustrated.
BRIEF DESCRIPIION OF THE DRAWINGS
In the drawings:
Fig. 1 is a s~ P-~ ;c illllstr~tion of a system according to a first emb~im~nt of the present invention; and Fig. 2 is a sc-~ s~tion of a system acco~ing to a second embodiment of the present invention.
DESCRIPTION OF THE PREFFRRFn EMBODIMENT
In the d~s, l~e mlm~o.r~lc ~ ". ~ the same or similar elem~o-nt~ throughout the two drawings. ~.f~ to Fig. 1 in particular, one aspect of the present invention is drawn to a system 10 using a m.o.th~1 of forced o~i~3ati~n flue gas ~e~llr~ lion~ wllc~ehl dry reagent is ~u~pli~d to an absollc~ vessel, s~ lly shovn at 11, through an o~ tion air ~l-lition system. A p~ly p~ ,d reagent 12 in a dry form is IL~s~lL~d to a reagent surge bin 14, either by m~h_nir~l conveyance, or by dilute or dense phase conveyance, through a supply line 16. The dry reagent 12 is withdrawn from the surge bin 14 at a controlled rate by feeder means 18, such as a volumetric or gravimetric feeder. The controlled feed rate of dry reagent 12 corresponds to an absorber.-reagent ~m~n(1 required S by the absorber vessel 11. The feeder means 18 discl~ges to a gravity flow chute 20 which directs the dry reagent 12 to an airlock 22. The airlock 22 provides the required level of isolation between the gravity flow chute 20 and an oxidation air stream 24 provided from oxidation air supply means 25, such as a blower or COlllpl~,SSOi station, at a higher pressure via o~ tion air line supply piping 26. Oxidation air 24 which leaks across the airlock 22 can be vented through a vent filter 28 and into the atmosphere 30. Dry reagent 12 which passes through the airlock 22 is introduced to the oxidation air line 26 at a solid pn~nm~tic conveying pick-up point 32, incorporated within the air line supply piping 26 used to provide the oxidation air stream 24 into the absorber vessel 11. The oxidation air stream 24 sl~bs~~ ntly provides oxidation air to the absorber vessel 11, and pn~llm~tir~lly conveys and lS injects the dry reagent 12 to the absol~r vessel 11 through line 34 to partially or completely satisfy the reagent addition requir~-m~nt~.
The dry reagent 12 is a m.omher selected from the group con~i~ting of solid alkali col~ds used in flue gas le~llr~ ;on plocesses such as limestone, calcium, pot~inm, ~lnmimlm, sodiurn, and/or ammonium. Dry additives 36 can be added to the dry reagent 20 12 into the surge bin 14 by "~ a.,;~al con~ ~, or by dilute or dense phase collvey~ce~
through dry additive supply line 37, so that the oxidation air stream 24 injects both the dry reagent 12 and the dry addilivcs 36 into absorber vessel 11. The dry additives 36 could also be added s~ t~_ly into the o~ i~1al i~ air stream 24 at the same p ~ "~ COll~ illg pick-up point 32, or at uy~ll~ or dow~ll~ dry addidves y..~ convt;ying pick-up points 38, 39 l~sye~ y. Various dry additives 36 could be added to promote oxidation within the absoll,c~ vessel 11; to c~ A.~e cl~...i~al absorption of the SO2 within the absoll~. vessel 11 or to provide a desired degree of b..rr~ to the ~les~lr~ ;on process therein; to inhibit scale growth within the absol1~ vessel 11; or to promote or specify the type of or degree of cryst-lli7-tion, etc., in the ~ lr,.. ;,~ ,. process o~ , within the absorber CASE 5580 2 ~ 6 5 6 3 3 vesæl 11. The dry additives can be added in this method even if the reagent is introduced by other known methods.
F.Y~mples of dry additives 36 which could be added to promote oxidation within the ~ abso~ vessel 11 include compounds of iron, m~n~n~se; v~n~ lm an~other~metals that 5 promote or catalyze oxidation.
Examples of dry additives 36 which could be used to e~h~nre chemical absorption of the S2 within the absorber vessel 11 include m~nesium oxide, ammonium hydroxide, sodium carbonate, sodium sulfite, sodium hydroxide, m~n~sil-m sulfite, and other soluble aLkali compounds of m~n~sillm~ ammonium, pot~ssillm~ calcium, and sodium, used to 10 enh~nr~ absorption in a calcium (limestone or lime) based FGD system.
Examples of dry additives 36 which could be used to provide a desired degree of burr~.hlg to the desu!furization process occurring within the absorber vessel 11 include sodium fo~ , dibasic acid (DBA), sodium citrate, adipic acid, succinic acid, and other organic acids and/or their solid colL~poullds including formic, acetic, hydroxypropionic, 15 sulfosuGr-inic, adipic, phthalic, benzoic, fumaric, hydroxyacetic, succinic, and lactic.
F~ s of dry additives 36 which could be used to inhibit oxidation to reduce scale growth within the absorber vessel 11 include coul~oullds of formate and thiosnlf~ and el~m~nt~l sulfur.
An ~Y~.IIplr- of a dry additive 36 which could be used to promote or specify the type 20 of or degree of cryst~lli7~tion, etc. in the desulfuri_ation pl~cess occurring within the absGll~r vessel 11 is polysulfonate.
As the examples Listed above in(~ir~t.q., some of the various dry additives 36 can ~)lOLU<~k: more than one kind of desired activity within the absorber vessel 11. For eY~n rle, sod~m formate has been shown to inhibit oyi~tion and provide l UlLlldlS; ions to buffer and 25 ~l~LuO~ SO2 removal in r~lrillm based FGD ~ms. Also, additives such as iron EDTA
can be used to plOLuo~ removal of nitrous oxides in a flue gas desulrll. ;~ion system. It wiU also be a~l~id~ that more than one dry additive 36 could be employed at the same time, i.e., two or more dry additives 36 could be ~ lly injected into the absoll3el vessel 11 via the q~ air ar1<liti~n system, so long as the two or more dry additives do 30 not ploduce an adverse .~ l reaction th~wæL~, or upon the ~esnl r~ ;on ~r~cess ` - 216S~33 CAS~ 5580 occurring within the absorber vessel 11. By way of example and not limitation, the dry additives sodiurn formate and sodiurn thiosnlf~t~, or calcium carbonate and DBA, could be pn~ lly injected simlllt~nfously without adverse effect. However, combinations of u~.iron and thiosulfate, or sodium formate and DBA for example, would not be;desirable S because the first combination ,e~resellls opposing goals of promoting and inhibiting oxidation while the second is not desirable because the two additives are used to accomplish the same goal of l~urr~ g.
While the solids pick-up point 32 can be located at virtually any point in the line 26 dc,w~l~ll of the oxidation air supply means 25, it is preferable to locate it as close to the absorber vessel as practical. This will minimi7~ the length of line 34 and the associated additional ~res~ulc: drop and abrasive wear due to the solids conveying function. Sirnilar location considerations would apply to any sep~ate dry additives 36 pneumatic conveying pick-up points 38, 39. l\~finimi7.ing the number of bends and line direction changes in line 34 will also serve this end.
Multiple system design configurations and arrangements are also possible. Through the use of the present invention, each individual overall FGD system design may be adapted for use with the present invention, even uniquely designf~l and e-nginf~ered arrangements, equipment selections, and configurations. An exarnple of one such variation is illustrated in Fig. 2.
Rf f~ g to Fig. 2, the system 40 l~ceivt;s dry reagent 12 through line 16, either by ~llfY`~ conveyallce, or by dilute or dense phase pl~f~..l.~ti- conveyance, in order to be stored in surge bin 14. A rotary airlocl~/Ç~der 42 provides both the airlock and feed rate control function to supply the dry reagent 12 through chute 44 to oxidation air line 26 at pick-up point 32. I~e solids and air mix~re is then collv~d di~ly through a straight run 25 of pipe 46 to an injection point or points 48 located within an absorber reaction tank or vessel 50. n~ f s or mllltiple alla~g~ can be configured in order to ~cr~ase theu~~ y of injection points 48 as l~uh~d by the FGD process. If desired, injection point or points 48 can ~ e in a ~/i,i~ily of a pln,~ flow discllarge from a m~.l-~
agitator 52, for lli~ .~;on of both o~iA~tinn air stream 24 and reagent 12 into the absofl~l30 reaction tank or vessel 50. To f~rilitslt~ other possible arrangements, t~he reagent flow control function could be provided remotely, wllel~y the dry reagent 12 is either dilute or dense phase ~ lly conveyed, from a remote location, directly to the oxidation air line 26 solids pick-up point 32 at the desired rate. This would allow the feed rate of the dry reagent addition into the absorber vessel 50 and the feed rate of the oxidation air stream into !i.
5 the absorber vessel 50 to be independently controlled. In either case, the oxidation air line 26 solids pick-up point 32 should be provided at an elevation above a slurry liquid level 56 in absorber reaction tank 50, so that if the air supply means 25 fails, the slurry 54 will not back-up into the e~ "~ piping 26, 44 located at or above the elevation corresponding to the liquid level 56. Additionally, a lllillill""" feed rate of the oxidation air stream 24 would 10 usually be supplied whenever the feed rate of the dry reagent 12 is greater than zero, to prevent solids dropout in the piping 26, 46.
Variations in the dis~ ing means 52 used to disperse the solids-air mixture into the slurry 54, such as by the use of modified sparge headers, injection lances, jet mixers/aerators, etc., can also be applied as deemed applicable to the overall process.
The process accoldillg to the present invention can reduce overall plant capital costs by incorporating portions of the fresh reagent feed functions and the oxidation air addition filnrfion~ into a single piping system. If a dry grinding system is required on site, it might draw more power then a colllpalable wet grinding system. However, this could be off-set by the lack of recycle water piping from a dewatering system to a reagent ~,~al~lion system, reduced recycle water pump sizes, increased slurry solids den~itilo-s throughout the plant and by the lo~ ing of hydraulic loadings throughout the plant.
The ~ invention allows increased FGD ~Irol~ce in the absorber reaction tank 50 due to a higher slurry solids density. The present il~ ioll also eli.~ t~ the need for fresh slurry feed pumps and associated slurry supply loops.
2S Additionally, the present invention provides for a r~llrtion in the size of the fresh reagent surge storage vesæl; it also ~ tes the ~otelllial for reagent powder carryover from the absoll,c. ~ ion tank 50 since the reagent is introduced below the liquid level 56 therein, rather than clæwll~, within the absorber reaction tank 50.
The ill~t;~i~ll can be used to ~rr~ively introduce a wide varie~ of reagents into the absorber, such as the ~ lk~lin~ reagent, as well as various dry additives such as CAS~: 5580 oxidation promoters, b~fr~ g agents, etc. Accordingly, while a specific embodiment of the invention has been shown and d~-il,ed in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied oth~L ~ise without departing from such principles.- Such embodiments have been omitted herein for the sake 5 of conciselless and readability but properly fall within the scope of the following claims.
METHOD OF REAGENT AND OXIDATION AIR DELIVERY
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates in general to wet flue gas desulfurization (FGD) processes and, in particular, to wet lim.os~on~ forced o~i-li7~ flue gas desulfurization 5 ~roc~es (LSFO-FGD) pr~sses and other cn.,-pAIihle procesæs. Wet LSFO-FGD systems have s~ ox~ tion air and l;...~(o~e slurry streams. Theæ systems, in general, utilize a wet ~ g circuit by ~ coarse 1;...~ f to prepare a limeston~ solids-liquid slurry as the fresh reagent supplied to the absorber system. Typically, wet ball mills have been used for ~is ~u.~ose. The wet CO~ m process has the advaD~age of ~ot~ ially lower 0 hOlY~ l~Ui~ than dry ~ ;. N1;. ~ ploce~xs, and the fact that the end product after is a slurry also fits in well with the wet LSFO-FGD system design. This slurry is commonly stored in a holding tank to provide surge c~a~i~y for :~ubse(lu.,.l~ controlled supply to the absorber vessel based on l~m~n(3, In wet FGD ~,.~ lls, the sulfur dioxide (SO2) absol~io~ ~locess l~u~s a nearly lS contimloll~ supply of fresh l~e~ to ~ s~ti~f~-tory oper~tion and SO2 removal CASE ~80 2 1 6 5 6 3 3 efficiencies. Often it is desirable to incorporate air addition to the wet FGD absorber to provide in situ forced oxidation of the absorber reaction product.
Providing se~ e o~da~ll air and ;i....o~1...~ slurry streams increases the complexity and expense of these- wet LSFO~G-l}systerns. -lt is thus apparent that an approach to S providing these se~ala~ functions in a simple and cost-effective manner would be welcomed by the industry.
SUMMARY OF THE INVENTION
The filn~m~n~l nature of the present invention is the use of the oxidation air system air stream to not only provide oxidation air to an absorber vessel, but also to both l0 pneumatically convey and inject dry reagent into the absorber vessel to satisfy reagent addition requirements.
Accordingly, one aspect of the present invention is drawn to a method of forced oxidation flue gas desulrul~lion wherein dry reagent and dry additive are supplied to an absorber vessel cont~ining a liquid slurry through an oxidation air addition system. The 15 method colllylises the steps of: providing a rate controlled feed supply of ~r~ared dry reagent and dry additive to a ~.~r.. AIic collv~ying pick-up point located within air supply piping used to provide an oxidation air stream from the oxidation air addition system into the absorber vessel; and using the oxidation air addition system air stream to provide ox~ tion air into the abso~ vessel, and to ~ lly convey and inject the dry reagent 20 and dry addilive into the absoll~r vessel sufficient to partially desulfurize flue gas provided to the al)so~ vessel.
The dry reagent is a ~ ~L ~1P~d from the group cO.~icli..g of solid alkali colll~oullds used in flue gas desulruli~lion ~r(xesses inrl~lAing lillles~o~e, e~1cillm, ~o1~ c--.. ", ~1.. ;.. , so linm, and/or ~mmonillm colll~ullds. Other dry additives besides 25 reagent can be added sepz. ~ ly or added to the dry reagent so that the oxi-l~tion air stream inje ts both the dry reagent and the dry additives into the absoll,cl vessel. These additives could be added to promote oxi~ti~)n ~,vithin the absorber vessel; to ~ A.~-e cl~ ;r~l al)sol~liol~ of the SO2 within the al)sollJcr vessel or to provide a desired degree of b~rL~ g to the ~ lrl.. ;,,.~ion ~locess ~ ih; to inhibit scale growth vithin the al)soll~r vessel; or to promote or specify the type of or degree of cryst~lli7~tion7 etc., in the desulfuri_ation process occurring within the absorber vessel.
Acco,dil,~,ly, another aspect of the present invention is drawn to a method of forced oxidation flue gas desulfurization, wherein.~dry~-r~litive i~ r.~ tir~lly supplied to an absorber vessel cont~ining a liquid slurry through an oxidation air addition system. The steps of this method conl~lise: providing a rate controlled feed supply of prepared dry additive to a pn~nm~tic conveying pick-up point located within air supply piping used to provide an oxidation air stream from the oxidation air addition system into the absorber vessel; and using the oxidation air addition system air stream to provide oxidation air into the abso,l,ci vessel, and to ~ ir~lly convey and inject the dry additive into the absorber vessel.
The various feat~lrcs of novelty which characteri_e the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better underst~n-~in~ of the invention, its opela~ing advantages and specific results ~tt~in~A by its uses, refc,c,lce is made to the ~ ol--p~.-yhlg drawings and descfl~live matter in which a ~ref~.,ed embodiment of the invention is illustrated.
BRIEF DESCRIPIION OF THE DRAWINGS
In the drawings:
Fig. 1 is a s~ P-~ ;c illllstr~tion of a system according to a first emb~im~nt of the present invention; and Fig. 2 is a sc-~ s~tion of a system acco~ing to a second embodiment of the present invention.
DESCRIPTION OF THE PREFFRRFn EMBODIMENT
In the d~s, l~e mlm~o.r~lc ~ ". ~ the same or similar elem~o-nt~ throughout the two drawings. ~.f~ to Fig. 1 in particular, one aspect of the present invention is drawn to a system 10 using a m.o.th~1 of forced o~i~3ati~n flue gas ~e~llr~ lion~ wllc~ehl dry reagent is ~u~pli~d to an absollc~ vessel, s~ lly shovn at 11, through an o~ tion air ~l-lition system. A p~ly p~ ,d reagent 12 in a dry form is IL~s~lL~d to a reagent surge bin 14, either by m~h_nir~l conveyance, or by dilute or dense phase conveyance, through a supply line 16. The dry reagent 12 is withdrawn from the surge bin 14 at a controlled rate by feeder means 18, such as a volumetric or gravimetric feeder. The controlled feed rate of dry reagent 12 corresponds to an absorber.-reagent ~m~n(1 required S by the absorber vessel 11. The feeder means 18 discl~ges to a gravity flow chute 20 which directs the dry reagent 12 to an airlock 22. The airlock 22 provides the required level of isolation between the gravity flow chute 20 and an oxidation air stream 24 provided from oxidation air supply means 25, such as a blower or COlllpl~,SSOi station, at a higher pressure via o~ tion air line supply piping 26. Oxidation air 24 which leaks across the airlock 22 can be vented through a vent filter 28 and into the atmosphere 30. Dry reagent 12 which passes through the airlock 22 is introduced to the oxidation air line 26 at a solid pn~nm~tic conveying pick-up point 32, incorporated within the air line supply piping 26 used to provide the oxidation air stream 24 into the absorber vessel 11. The oxidation air stream 24 sl~bs~~ ntly provides oxidation air to the absorber vessel 11, and pn~llm~tir~lly conveys and lS injects the dry reagent 12 to the absol~r vessel 11 through line 34 to partially or completely satisfy the reagent addition requir~-m~nt~.
The dry reagent 12 is a m.omher selected from the group con~i~ting of solid alkali col~ds used in flue gas le~llr~ ;on plocesses such as limestone, calcium, pot~inm, ~lnmimlm, sodiurn, and/or ammonium. Dry additives 36 can be added to the dry reagent 20 12 into the surge bin 14 by "~ a.,;~al con~ ~, or by dilute or dense phase collvey~ce~
through dry additive supply line 37, so that the oxidation air stream 24 injects both the dry reagent 12 and the dry addilivcs 36 into absorber vessel 11. The dry additives 36 could also be added s~ t~_ly into the o~ i~1al i~ air stream 24 at the same p ~ "~ COll~ illg pick-up point 32, or at uy~ll~ or dow~ll~ dry addidves y..~ convt;ying pick-up points 38, 39 l~sye~ y. Various dry additives 36 could be added to promote oxidation within the absoll,c~ vessel 11; to c~ A.~e cl~...i~al absorption of the SO2 within the absoll~. vessel 11 or to provide a desired degree of b..rr~ to the ~les~lr~ ;on process therein; to inhibit scale growth within the absol1~ vessel 11; or to promote or specify the type of or degree of cryst-lli7-tion, etc., in the ~ lr,.. ;,~ ,. process o~ , within the absorber CASE 5580 2 ~ 6 5 6 3 3 vesæl 11. The dry additives can be added in this method even if the reagent is introduced by other known methods.
F.Y~mples of dry additives 36 which could be added to promote oxidation within the ~ abso~ vessel 11 include compounds of iron, m~n~n~se; v~n~ lm an~other~metals that 5 promote or catalyze oxidation.
Examples of dry additives 36 which could be used to e~h~nre chemical absorption of the S2 within the absorber vessel 11 include m~nesium oxide, ammonium hydroxide, sodium carbonate, sodium sulfite, sodium hydroxide, m~n~sil-m sulfite, and other soluble aLkali compounds of m~n~sillm~ ammonium, pot~ssillm~ calcium, and sodium, used to 10 enh~nr~ absorption in a calcium (limestone or lime) based FGD system.
Examples of dry additives 36 which could be used to provide a desired degree of burr~.hlg to the desu!furization process occurring within the absorber vessel 11 include sodium fo~ , dibasic acid (DBA), sodium citrate, adipic acid, succinic acid, and other organic acids and/or their solid colL~poullds including formic, acetic, hydroxypropionic, 15 sulfosuGr-inic, adipic, phthalic, benzoic, fumaric, hydroxyacetic, succinic, and lactic.
F~ s of dry additives 36 which could be used to inhibit oxidation to reduce scale growth within the absorber vessel 11 include coul~oullds of formate and thiosnlf~ and el~m~nt~l sulfur.
An ~Y~.IIplr- of a dry additive 36 which could be used to promote or specify the type 20 of or degree of cryst~lli7~tion, etc. in the desulfuri_ation pl~cess occurring within the absGll~r vessel 11 is polysulfonate.
As the examples Listed above in(~ir~t.q., some of the various dry additives 36 can ~)lOLU<~k: more than one kind of desired activity within the absorber vessel 11. For eY~n rle, sod~m formate has been shown to inhibit oyi~tion and provide l UlLlldlS; ions to buffer and 25 ~l~LuO~ SO2 removal in r~lrillm based FGD ~ms. Also, additives such as iron EDTA
can be used to plOLuo~ removal of nitrous oxides in a flue gas desulrll. ;~ion system. It wiU also be a~l~id~ that more than one dry additive 36 could be employed at the same time, i.e., two or more dry additives 36 could be ~ lly injected into the absoll3el vessel 11 via the q~ air ar1<liti~n system, so long as the two or more dry additives do 30 not ploduce an adverse .~ l reaction th~wæL~, or upon the ~esnl r~ ;on ~r~cess ` - 216S~33 CAS~ 5580 occurring within the absorber vessel 11. By way of example and not limitation, the dry additives sodiurn formate and sodiurn thiosnlf~t~, or calcium carbonate and DBA, could be pn~ lly injected simlllt~nfously without adverse effect. However, combinations of u~.iron and thiosulfate, or sodium formate and DBA for example, would not be;desirable S because the first combination ,e~resellls opposing goals of promoting and inhibiting oxidation while the second is not desirable because the two additives are used to accomplish the same goal of l~urr~ g.
While the solids pick-up point 32 can be located at virtually any point in the line 26 dc,w~l~ll of the oxidation air supply means 25, it is preferable to locate it as close to the absorber vessel as practical. This will minimi7~ the length of line 34 and the associated additional ~res~ulc: drop and abrasive wear due to the solids conveying function. Sirnilar location considerations would apply to any sep~ate dry additives 36 pneumatic conveying pick-up points 38, 39. l\~finimi7.ing the number of bends and line direction changes in line 34 will also serve this end.
Multiple system design configurations and arrangements are also possible. Through the use of the present invention, each individual overall FGD system design may be adapted for use with the present invention, even uniquely designf~l and e-nginf~ered arrangements, equipment selections, and configurations. An exarnple of one such variation is illustrated in Fig. 2.
Rf f~ g to Fig. 2, the system 40 l~ceivt;s dry reagent 12 through line 16, either by ~llfY`~ conveyallce, or by dilute or dense phase pl~f~..l.~ti- conveyance, in order to be stored in surge bin 14. A rotary airlocl~/Ç~der 42 provides both the airlock and feed rate control function to supply the dry reagent 12 through chute 44 to oxidation air line 26 at pick-up point 32. I~e solids and air mix~re is then collv~d di~ly through a straight run 25 of pipe 46 to an injection point or points 48 located within an absorber reaction tank or vessel 50. n~ f s or mllltiple alla~g~ can be configured in order to ~cr~ase theu~~ y of injection points 48 as l~uh~d by the FGD process. If desired, injection point or points 48 can ~ e in a ~/i,i~ily of a pln,~ flow discllarge from a m~.l-~
agitator 52, for lli~ .~;on of both o~iA~tinn air stream 24 and reagent 12 into the absofl~l30 reaction tank or vessel 50. To f~rilitslt~ other possible arrangements, t~he reagent flow control function could be provided remotely, wllel~y the dry reagent 12 is either dilute or dense phase ~ lly conveyed, from a remote location, directly to the oxidation air line 26 solids pick-up point 32 at the desired rate. This would allow the feed rate of the dry reagent addition into the absorber vessel 50 and the feed rate of the oxidation air stream into !i.
5 the absorber vessel 50 to be independently controlled. In either case, the oxidation air line 26 solids pick-up point 32 should be provided at an elevation above a slurry liquid level 56 in absorber reaction tank 50, so that if the air supply means 25 fails, the slurry 54 will not back-up into the e~ "~ piping 26, 44 located at or above the elevation corresponding to the liquid level 56. Additionally, a lllillill""" feed rate of the oxidation air stream 24 would 10 usually be supplied whenever the feed rate of the dry reagent 12 is greater than zero, to prevent solids dropout in the piping 26, 46.
Variations in the dis~ ing means 52 used to disperse the solids-air mixture into the slurry 54, such as by the use of modified sparge headers, injection lances, jet mixers/aerators, etc., can also be applied as deemed applicable to the overall process.
The process accoldillg to the present invention can reduce overall plant capital costs by incorporating portions of the fresh reagent feed functions and the oxidation air addition filnrfion~ into a single piping system. If a dry grinding system is required on site, it might draw more power then a colllpalable wet grinding system. However, this could be off-set by the lack of recycle water piping from a dewatering system to a reagent ~,~al~lion system, reduced recycle water pump sizes, increased slurry solids den~itilo-s throughout the plant and by the lo~ ing of hydraulic loadings throughout the plant.
The ~ invention allows increased FGD ~Irol~ce in the absorber reaction tank 50 due to a higher slurry solids density. The present il~ ioll also eli.~ t~ the need for fresh slurry feed pumps and associated slurry supply loops.
2S Additionally, the present invention provides for a r~llrtion in the size of the fresh reagent surge storage vesæl; it also ~ tes the ~otelllial for reagent powder carryover from the absoll,c. ~ ion tank 50 since the reagent is introduced below the liquid level 56 therein, rather than clæwll~, within the absorber reaction tank 50.
The ill~t;~i~ll can be used to ~rr~ively introduce a wide varie~ of reagents into the absorber, such as the ~ lk~lin~ reagent, as well as various dry additives such as CAS~: 5580 oxidation promoters, b~fr~ g agents, etc. Accordingly, while a specific embodiment of the invention has been shown and d~-il,ed in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied oth~L ~ise without departing from such principles.- Such embodiments have been omitted herein for the sake 5 of conciselless and readability but properly fall within the scope of the following claims.
Claims (17)
1. A method of forced oxidation flue gas desulfurization, wherein dry reagent and dry additive are pneumatically supplied to an absorber vessel containing a liquid slurry through an oxidation air addition system, comprising:
providing a rate controlled feed supply of prepared dry reagent selected from the group consisting of solid alkali compounds used in flue gas desulfurization processes including calcium, potassium, aluminum, sodium and ammonium compounds and dry additive used to promote at least one of the functions selected from the group consisting of promoting oxidation, enhancing chemical absorption of SO2 from the flue gas provided to the absorber vessel, providing buffering and promoting crystallization to a pneumatic conveying pick-up point located within air supply piping used to provide an oxidation air stream from the oxidation air addition system into the absorber vessel;
controlling a feed rate of the dry reagent to the pneumatic conveying pick-up point independently of a feed rate of the oxidation air stream into the absorber vessel;
using the oxidation air addition system air stream as the sole means of providing oxidation air into the absorber vessel, and to pneumatically convey and inject the dry reagent and dry additive into the absorber vessel to at least partially desulfurize flue gas provided to the absorber vessel; and injecting the oxidation air stream, the dry reagent, and the dry additive beneath a liquid surface level of the liquid slurry within the absorber vessel.
providing a rate controlled feed supply of prepared dry reagent selected from the group consisting of solid alkali compounds used in flue gas desulfurization processes including calcium, potassium, aluminum, sodium and ammonium compounds and dry additive used to promote at least one of the functions selected from the group consisting of promoting oxidation, enhancing chemical absorption of SO2 from the flue gas provided to the absorber vessel, providing buffering and promoting crystallization to a pneumatic conveying pick-up point located within air supply piping used to provide an oxidation air stream from the oxidation air addition system into the absorber vessel;
controlling a feed rate of the dry reagent to the pneumatic conveying pick-up point independently of a feed rate of the oxidation air stream into the absorber vessel;
using the oxidation air addition system air stream as the sole means of providing oxidation air into the absorber vessel, and to pneumatically convey and inject the dry reagent and dry additive into the absorber vessel to at least partially desulfurize flue gas provided to the absorber vessel; and injecting the oxidation air stream, the dry reagent, and the dry additive beneath a liquid surface level of the liquid slurry within the absorber vessel.
2. The method according to claim 1, wherein the dry reagent injected into the absorber vessel via the oxidation air addition system is sufficient to completely desulfurize flue gas provided to the absorber vessel.
3. The method according to claim 1, further including the step of adding the dryadditive to the dry reagent so that the oxidation air stream injects both the dry reagent and the dry additive into the absorber vessel.
4. The method according to claim 1, further including the step of providing a minimum feed rate oxidation air stream whenever the feed rate of the dry reagent is greater than zero, to prevent solids dropout in the air supply piping.
5. The method according to claim 1, further including the step of pneumatically conveying the dry reagent to the pneumatic conveying pick-up point located within the air supply piping.
6. The method according to claim 1, further including the step of injecting the dry reagent and the dry additive into the absorber vessel in the vicinity of a dispersion means to enhance dispersion of the oxidation air stream, the dry reagent, and the dry additive within the liquid slurry contained within the absorber vessel.
7. The method according to claim 1, wherein the dry additive is added in catalytic amounts to promote oxidation within the absorber vessel and is a member selected from the group consisting of compounds of iron, manganese, and vanadium.
8. The method according to claim 1, wherein the reagent is lime or limestone and the dry additive is a member selected from the group consisting of alkali compounds of magnesium, ammonium, potassium, calcium, and sodium.
9. The method according to claim 1, wherein the dry additive is a buffering agent for the desulfurization occurring within the absorber vessel and is a member selected from the group consisting of sodium formate, dibasic acid (DBA), sodium citrate, adipic acid, succinic acid, and solid compounds of formic, acetic, hydroxypropionic, sulfosuccinic, adipic, phthalic, benzoic, fumaric, hydroxyacetic, succinic, and lactic acid.
10. The method according to claim 1, wherein the dry additive is a member selected from the group consisting of compounds of formate and thiosulfate and elemental sulfur.
11. The method according to claim 1, wherein the dry additive is polysulfonate.
12. A method of forced oxidation flue gas desulfurization, wherein dry additive is pneumatically supplied through an oxidation air addition system to an absorber vessel containing a liquid slurry, comprising:
providing into the absorber vessel at least one reagent selected from the group consisting of solid alkali compounds used in flue gas desulfurization processes including calcium, potassium, aluminum, sodium and ammonium compounds;
providing a rate controlled feed supply of dry additive used to promote at least one of the functions selected from the group consisting of promoting oxidation, enhancing chemical absorption of SO2 from the flue gas provided to the absorber vessel, providing buffering and promoting crystallization to a pneumatic conveying pick-up point located within air supply piping used to provide an oxidation air stream from the oxidation air addition system into the absorber vessel;
controlling a feed rate of the dry additive to the pneumatic conveying pick-up point independently of a feed rate of the oxidation air stream into the absorber vessel;
using the oxidation air addition system air stream as the sole means of providing oxidation air oxidation air into the absorber vessel, and to pneumatically convey and inject the dry additive into the absorber vessel; and injecting the oxidation air stream, and the dry additive beneath a liquid surface level of the liquid slurry within the absorber vessel.
providing into the absorber vessel at least one reagent selected from the group consisting of solid alkali compounds used in flue gas desulfurization processes including calcium, potassium, aluminum, sodium and ammonium compounds;
providing a rate controlled feed supply of dry additive used to promote at least one of the functions selected from the group consisting of promoting oxidation, enhancing chemical absorption of SO2 from the flue gas provided to the absorber vessel, providing buffering and promoting crystallization to a pneumatic conveying pick-up point located within air supply piping used to provide an oxidation air stream from the oxidation air addition system into the absorber vessel;
controlling a feed rate of the dry additive to the pneumatic conveying pick-up point independently of a feed rate of the oxidation air stream into the absorber vessel;
using the oxidation air addition system air stream as the sole means of providing oxidation air oxidation air into the absorber vessel, and to pneumatically convey and inject the dry additive into the absorber vessel; and injecting the oxidation air stream, and the dry additive beneath a liquid surface level of the liquid slurry within the absorber vessel.
13. The method according to claim 12, wherein the dry additive is added in catalytic amounts to promote oxidation within the absorber vessel and is a member selected from the group consisting of compounds of iron, manganese, and vanadium.
14. The method according to claim 12, wherein the reagent is lime or limestone and the dry additive is a member selected from the group consisting of alkali compounds of magnesium, ammonium, potassium, calcium, and sodium.
15. The method according to claim 12, wherein the dry additive is a buffering agent for the desulfurization occurring within the absorber vessel and is a member selected from the group consisting of sodium formate, dibasic acid (DBA), sodium citrate, adipic acid, succinic acid, solid compounds of formic, acetic, hydroxypropionic, sulfosuccinic, adipic, phthalic, benzoic, fumaric, hydroxyacetic, succinic, and lactic acid.
16. The method according to claim 12, wherein the dry additive is added to inhibit oxidation to reduce scale growth within the absorber vessel and is a member selected from the group consisting of compounds of formate and thiosulfate and elemental sulfur.
17. The method according to claim 12, wherein the dry additive is polysulfonate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/359,147 | 1994-12-19 | ||
| US08/359,147 US5520897A (en) | 1993-08-16 | 1994-12-19 | Method of reagent and oxidation air delivery |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2165633A1 CA2165633A1 (en) | 1996-06-20 |
| CA2165633C true CA2165633C (en) | 1999-05-18 |
Family
ID=23412518
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2165633 Expired - Fee Related CA2165633C (en) | 1994-12-19 | 1995-12-18 | Method of reagent and oxidation air delivery |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2165633C (en) |
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1995
- 1995-12-18 CA CA 2165633 patent/CA2165633C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2165633A1 (en) | 1996-06-20 |
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