PROCESS TO ELIMINATE AIR POLLUTANTS WHICH RESULT FROM THE COMBUSTION OF FUELS CONTAINING SULPHUR

Abstract: Process to eliminate air pollutants which result from the combustion (1) of fuels containing sulphur, permitting the transformation of substantially all the existing SO2 and SO3 produced by the combustion of fuels, to Ammonium Sulphate. In accordance with an accomplishment of this invention, a quantity (1<o>) of gaseous Ammonia, sufficient to react with all the SO2 and SO3, is injected into the combustion gases when these are at a temperature range of 250<o>C to 600<o>C, these gases being subsequently cooled down to temperatures below 65<o>C, and then subjected to separation means to extract the submicron and micra sized particles (6, 7, 8), before being released to the atmosphere. In another accomplishment, a first injection (1<o>) of Ammonia is made into the 250<o>C to 600<o>C combustion gases in a quantity sufficient to fully react with the existing SO3, and a second Ammonia injection (2<o>) is made with the combustion gases at a 65<o>C to 250<o>C range, and in a quantity sufficient to react with all the existing SO2 or, if desired, with part of it.

Description: 1 - . . . . . - , - "PROCESS TO ELIMINATE AIR POLLUTANTS WHICH RESULT FROM THE COMBUSTION OF FUELS CONTAINING SULPHUR". TECHNICAL FIELD The present invention refers to a process aimed at ' the 5 elimination of air pollution caused by the burning of Sulphur containing fuels in all kinds of industry and equipment of all sizes. The process requires less investment than other alternative processes and produces a commercial end-product. 0 BACKGROUND ART One of today's main concerns has been to eliminate air polluting agents resulting from the burning of Sulphur containing fuels, without generating inadequate by-products. Many of the processes presently used require large 5 investments in equipments and installations, normally u/ithout return or uiith high added operational costs. DISCLOSURE OF INVENTION Aiming at solving or minimizing these problems, this process • has been developped. θasicaly simple, easily retrofitted G into the polluting equipments, with leu; investment costs, this process produces a high value end-product. Specifically, the aim of this invention is to transform all Sulphur Dioxide (SC-) and Suiohur Trioxide (5C,) existing in the combustion gases, to Ammonium Sulphate. This is obtained 5 through the reaction of SO, and Sn 2 '-ith Ammonia, preferably in gaseous state, which is injected directly into the combustion gases. The cαllecteα stable erd-product is Ammonium Sulphatε (NH^^ SP ^hich is separated from the flue gases. 0 These and other objectives of this invention are obtained by this process which comprises the following steps: undertake at least one injection of Ammonia (NH,) in the combustion gases at temperatures between 250 C and 600 C, in quantity sufficient to react with all the SO, which is present and with part of the existing S0 2 ; cool the gases to a temperature lower than about 65 C; separate the submicron and micron size particles from the combustion gases; collect the (NH.) 2 SO. from the separating equipment, and send the desulphurized combustion gases to the flue. Considering the possibility of providing more then one injection point of Ammonia (NH,), this process has foreseer the division of the injection into: a first injection of gaseous NH, (Ammonia) into the 250 C to 600 C combustion gases and in a quantity sufficient to react with all the present SO,, and a second injection of gaseous NH, at a region where the combustion gases are at a 65 C to 250 C temperature range and in a quantity sufficient to react with at least a part of the existing S0 2 . In this case, the first injection is directed mainLy the neutralization of the SC,. In case of injection αf all the Ammonia (NH,) in the 25C C to 600 C combustion gases temperature range, the . H, u-'ill react with all present SC, and the rest o r " NH-, will intermix with the combustion gases stream, up to the point where t H e temperature permits the occurence of an irreversible reaction between the 5G 2 and NH,. As already established technically, the SO, is a gas formed curing the combustion of Sulphur containing fuels, by the reaction αf gaseous SG with molecular Oxygen (C 2 ), by the reaction of SC 2 in the flame with atomic Gxygeπ and by catalytic oxidation of SO.-, in the heat transfer Surfaces under high temperatures. The co responding reactions are the following: S + 0 2 5C 2 SQ 2 + -— 2 SC, 3 (O- ςn. Without the presence of catalysers, the burning of Sulphur containing fuels results in up to 5% SO, in the total of SO compounds. In spite αf the fact that gaseous Ammonia reacts with SO, in the temperature range of 250°C to about 600 α C, it has been verified that the ideal temperature " range is 300°C tα 4Q0 α C In this range, the reatioπ of " SU 3 with NH 3 - : - is instantaneous resulting in (NH.) 2 SO- (Ammonia Sulphate) and eliminating the possibility of corrosion in the- surfaces which would have been contacted by the SO,. This corrosion occurs due to the formation αf liquid Sulphuric Acid (H 2 SG.) when SO-- and water of combustion (H 2 0) combine at temperatures bellow the Sulphuric Acid dew point. The quantity of injected NH, is sufficient to insure the formation of (NH,) 2 SO, (Ammonium Sulphate). Smaller quantities of NH, would result in the formation of Hydrogen Ammonium Sulphate (NH, H SO,), which is a corrosive compound. The corresponding reactions are the following: 2 H 3 + H 2 C + SQ 3 -( NH 4 ) 2 S0 Δ NH 3 + H 2 0 + S0 3 — — H 4 H S0 The minimum calculated quantity of NH, to avoid formation of NH. H SO. in 3 Sulphur bearing fuel oils, for example, is G,08^ of the oil weight. For higher levels of Sulphur, the percentage will correspondingly higher (up to 9%) . The reaction product (NH.) 2 SC. is stable and is carried together with the combustion gases' stream. As previously meπtionπed, this process is directed towards a complete and reliable elimination of the S0 resulting from the combustion cf liquid, solid or gaseous fuels. To neutralize the S0 2 , the gaseous NH, is injected in one or more locations of the equipment, where the combustion gases are at a range of 65°C to 6G0°C. If the gaseous NH-- is totaly injected in a 20Q C tα 6GC C region, the excess portion which does not participate in the reaction with SC,, is carried in the combustion gases' stream, forming an intimate mixture which will react when the right temperature O PΓ range is reached. At 120°C the quantities of SQ 2 which react with NH-. increases, and as the temperature of the gases decreases tα about 108°C, an equilibrium situation is reached with 35% to 40 / O αf the existing S0 2 having reacted with NH- j according tα the following reversible reations: NH- H 2 0 SO. - (NH A ) H S0 3 Ammonium Hydrogen Sulphite (NH.) H SO, + NH. (NH l,i,)' 2 SO- Ammonium Sulphite ( H ) 2 S0 3 :2 NH 3 + H 2 0 + S0 2 It has been experimentaly verified that this equilibrium situation is maintained until temperatures in the range of 65 C are attained. θetween 65°C and 48°C it has been exoerimentaly proven that this reaction is stable with the simultaneous oxidation of Ammonium Sulphite tα Ammonium Sulphate according to the following reactions: 2 H 3 + H 2 G + 50 2 -(NH 4 )2 so 3 2 (NH 4 ) 2 SG 3 + 0 2 -2(,MH^) 2 S0 This oxidation is processed by existing combustion air in excess or by an extra air antra nmert nto the gases, just before the senaratiαn system. The ( H^ SC^ (Aπ-momum Sulphate)is astable, solid, subr.icror, tc a low value micra sized, product. The above mentionned facts Lead to verified results, if the combustion gases are released at higher e<-;_eratures then 65°C, part of the S0 2 (even if aireacy re-cteσ^ might be released to the at osohere, due to the reversic Le nature of the reations at that higher ra^ge. The separation of the stable βrc- r Cjct • ' •'•H^^ S0 ( mmonium Sulphate)fro the combustion gases' stream, ca oe accomplished by dry methods such as Electrostatic Precipitators or other kinds of filters, or more economically by wet processessuch as water absorbers. The absorption of (NH 4 ) 2 SO^ (Ammonium Sulphate) in water is possible due to the highly soluble nature of this product. DESCRIPTION OF THE DRAWINGS The process will now be briefly outlined so as to show an 5 example of a feasible and tested lay-out of the " Oasulphurizatioπ of Combustion Gases with Ammonia. Figure n s 1 represents a flaw diagram of the main components - αf an installation comprising the equipment where the Sulphur bearing fuel is burned, two distinct Ammonia injection 10 points, the (NH.) 2 SO. wet absorption system, an entrained water separator, the dessulphurized flue gases released to atmosphere and the concentrated Ammonium Sulphate solution collection system. Figure n s 2 illustrates one of the several assemblies of the 15 Ammonia injection elements, in adequate locations of the combustion gases' stream. Figure πS 3 shows a typical configuration of the NH, injection tubes. BEST MODE OF CARRYING OUT THE INVENTION 20 As shown in Figure 1, this process is applied in industrial installations such as bailers, furnaces, ovens, dryers, etc (l), burning Sulphur bearing fuels. Heat recovery equipment (2) may αr not be present. In the present process, NH, coming from a storage tank (3) is distributed in gaseous or 25 liquid form. If as a liquid, NH, is vaporised or not and injected initialy in a region where the gases are preferably between 250 C and 60Q°C and before the heat recovery equipment. The quantity αf the first injection is, as previously explained, adequate to insure complete reaction 30 with the S0 3 , therefore eliminating corrosion problems in the heat recovery or other metallic or nan metallic components of the existing installation. This permits the use of cheaper construction materials or results in longer life of the existing ones. 35 The combustion gases which leave the heat recovery equipment (2) in the example shown, are conducted by means of a duct (5) and ventilator (4) to a point where a second injection of gaseous NH 3 is undertaken at lower temperature levels. Even if the gaseous NH, is injected at only one location, the quantity will always be such as to react iπitialy with the existing SO, and further on at lower temperatures with the S0 2 . The combustion gases, after the last NH-, injection, are sent along the duct (5) and into an apropriately dimensioned duct (6). This duct (6) has a battery of atomizing nozzles (6a)in adequate number and sizing. These nozzles spray a recirculating solution αf Ammonium Sulphate into the combustion gases. This solution is recirculated under pressure by a pump and piping (7). A water make-up system (7a) is hooked up into this r recirculating system. This pre-washing phase insures initial absorption αf the existing ( H.) 2 SO particles and a severe temperature drop cf the combustion gases. Depending on the inlet temperature αf the gases to this pre-washer/absorber, the completion of the SG 2 reaction to (NH.) 2 SO. , may also happen in this region. In the second stage of the (NH.)- 5C 4 (Ammonium Sulphate) absorption in water, the combustion gases pass through a high pressure injector ( 8a) (or aαditional nozzles) soraying (NH,) 2 SO, solution into the gaseous stream, which is assembled on top of a solution collection tank (8). At this phase the simultaneous retention of the soluble Ammonium Sulphate particles and of the insoluble particles such as carbon, inorganic materials, etc, is achieved. The concentrated solution of Ammonium Sulphate may be continuously or periodicaly taken away from the collection tank (8) into a storage tank (9). This volume is substituted by make-up water. One of the advantages αf this wet separation process is that the insoluble and undesirable particles can be easily separated from the dissolved Ammonium Sulphate solution by conventional filters or gravity settling. The system has also foreseen, for the cases where water entrained as mist should not be lost, the installation of a low pressure drop demister (10) which recovers part of the water which is returned to the solution tank (8) by piping (11). The combustion gases leave the solution tank (8) totaly desulphurized or, if desired, within the S0 2 emission levels specified by the local Environmental Control Agency. The emission level is easily adjusted by the variation of the Ammonia flow to be injected, with the use αf proportioning or manual valves and flowmeters. The complete system can also receive a pH controller of the tank (8) solution to insure continuous neutralization of the so 2 . Direct or indirect measurement systems of the Ammonium Sulphate concentration in the solution contained in the tank (8) can also be added. The duct (5) which receives the combustion gases, can also remain connected to the existing chimney (12) through a nor aly closed gate valve which functions as a by-pass to the separation system. As shown in figures 2 and 3, the Ammonia gas injection is made in the gas ducts through pεrfurεted tubes (20), the number and disposition αf the tubes being determined by the calculated Ammonia gas flow, and by the objective of obtaining complete intermixing with the combustion gases. The tubes are preferentialy built out of mild steel and completely cross the combustion gas ducts, each tube being divided in three equal parts, with different number and sizes of holes (2l), as better detailed in figure 3. The first part has two series αf holes (21) with a diameter d and a spacing of x. The second part has two lines of d. diameter holes, where d. is larger than d and spaced in an interval x., smaller than x. Likewise the third part has d 2 diameter holes (d 2 larger than d,) spaced at x 2 intervals smaller than x .. The usual installation requires two parallel tubes (fig.2). In this case, the H 3 gas will enter one tube from the right end αf the duct while the other tube enters from the left. The NH, gas always enters the tube going through the d diameter, x spaced holes (2l). A plug (30) blocks the end αf each tube. The two series of holes of each tube (fig. 3) are located so that a hole of one series is always in between two holes of the other seri es . • •

Claims: 9 CLAIMS 1. A process to eliminate air pollutants resulting from the combustion of sulphur bearing fuels, characterized- in that it comprises the following steps: 5 . provide at least one injection αf Ammonia into 25G C to 600 C combustion gases, in sufficient quantity to transform substantialy all the existing 30-, and S0 2 (produced by the combustion of these fuels) into Ammonium Sulphate; . cool the combustion gases tc a temperature lower than 65 C; 0 . pass these gases through a separation system adequate for submicron to low value micra particulates; . collect the Ammonium Sulphate end-product from the separation system; -. release the desulphurized gases to the atmosphere. 5 2. A process as claimed in claif 1, characterized in that the Ammonia injection is made _ith the cπrbustion gases being at a temperature range of about 25'_" ' C to -• •■ ϋ"C. .3. A process as claimed in ciai~ i, charactsrized in. that the injection phase comprises: G . a first injection of Amπcn a irto the cr.~o-_-s ion gases when these are at a 25G C tc 6-...1." "" C te.-^r era; _re range and in sufficient quantity to react -ith ail -e ' -. ~ , r c.rmed during by the combustion of these fuels; . a second injection of Ammonia ι- ■* _:- r e c : - z. -m.r-,tion gases 5 when these are at a 65 C to 25.- ' C terncer t_re range, and in a. sufficient quantity tα react ,n s ■ _,csta ■ .ialy all SC~ if desired, with part of the 50-., so as to be within tne local limits for emission of SC--, as established by the Environmental Authorities. 0 4. A process as claimed in claim 3, characterized in that 1° the first injection of Ammonia is made with the combustion gases when they are at a temperature range of 300 C tα 400°C and second injection of Ammonia with the gases at 65 C to 120 C range. 5. A process as claimed in any one of the claims 1 or 2, characterized in that the separation means include " absorbers with water, with the resulting Ammonium Sulphate Solution being separated from the desulphurized combustion gases. 6. A process as claimed in claim 5, characterized in that the cooling of the combustion gases to temperatures under 65 C can also be completed in the separation system. 7. A process as claimed in any cn.e of the claims 1 tα -4, characterized by the fact that the Ammonia is preferably injected in gaseous state. 8. A process as claimed in claim 7, characterized in that the injection of Ammonia, when as gas, is made by means of perfurated tubes installed transvarsally to the combustion gases' stream.

Inventors: DE OLIVEIRA PAULO ROBERTO MEDE, KREPEL PEDRO ANDREA, LADEIRA NEWTON GONCALVES, MARANTE ADILSON PINTO, DE OLIVEIRA, PAULO, ROBERTO, MEDEIROS, KREPEL, PEDRO, ANDREA, LADEIRA, NEWTON, GONCALVES, MARANTE, ADILSON, PINTO
Applicants: KREPEL PEDRO ANDREA, LADEIRA NEWTON GONCALVES, MARANTE ADILSON PINTO, OLIVEIRA PAULO ROBERTO MEDEIRO, DE OLIVEIRA, PAULO, ROBERTO, MEDEIROS, KREPEL, PEDRO, ANDREA, LADEIRA, NEWTON, GONCALVES, MARANTE, ADILSON, PINTO
Application year: 1983
Main classification: B01D53
IPC codes: B01D53, C01C1