System and method for softening water for use in a scrubber

Abstract

The present invention relates generally to the field of emission control equipment for boilers, heaters, kilns, or other flue gas-, or combustion gas-, generating devices (e.g., those located at power plants, processing plants) and, in particular to a new and useful method and apparatus designed to improve the water supplied to non-calcium-based, aqueous wet SO.sub.x scrubbers. In another embodiment, the present invention relates to a system and method for softening water for use in non-calcium-based, aqueous wet SO.sub.x scrubbers.

Claims

1. A system designed to treat and/or soften raw water supplied to a calcium-based, aqueous wet SO.sub.x scrubber, the system comprising: (a) at least one floc supply means; (b) at least one raw water supply means, wherein the raw water contains at least calcium ions and magnesium ions; (c) at least one sodium carbonate supply means; (d) at least one lime slurry supply means; (e) at least one first precipitator/crystallizer tank, wherein the at least one floc supply means, the at least one raw water supply means, the at least one sodium carbonate supply means and the at least one lime slurry supply means all supply their respective compounds to the at least one first precipitator/crystallizer tank, and wherein the at least one first precipitator/crystallizer tank permits and facilitates a reaction between the raw water, the sodium carbonate and the waste liquor supply and has at least one outlet; (f) at least one first settler/thickener tank that is in fluid communication with the at least one outlet of the at least one first precipitator/crystallizer tank, the at least one first settler/thickener tank having at least one outlet; (g) at least one second precipitator/crystallizer tank that is in fluid communication with the at least one outlet of the at least one first settler/thickener tank, wherein the at least one second precipitator/crystallizer tank has at least one outlet; (h) at least one waste liquor supply means, wherein the at least one waste liquor supply means is in fluid communication with the at least one second precipitator/crystallizer tank, wherein the waste liquor is supplied from a portion of the waste liquor generated by at least one calcium-based, aqueous wet SO.sub.x scrubber, wherein the at least one waste liquor supply means supplies waste liquor to the at least one second precipitator/crystallizer tank to precipitate excess calcium and wherein the waste liquor contains solubilized sulfate ions; and (i) at least one second settler/thickener tank that is in fluid communication with the at least one outlet of the at least one second precipitator/crystallizer tank, the at least one second settler/thickener tank having at least one outlet designed to supply treated water to a calcium-based, aqueous wet SO.sub.x scrubber.

2. The system of claim 1, further comprising: (j) at least one treated water tank that is in fluid communication with the at least one outlet of the at least one second settler/thickener tank, the at least one treated water tank designed to receive and hold treated water and having at least one outlet designed to supply treated water to a calcium-based, aqueous wet SO.sub.x scrubber.

3. The system of claim 1, wherein less than about 7 percent by volume of the waste liquor produced by a calcium-based, aqueous wet SO.sub.x scrubber is utilized to treat and/or soften raw water for a calcium-based, aqueous wet SO.sub.x scrubber.

4. The system of claim 1, wherein less than about 5 percent by volume of the waste liquor produced by a calcium-based, aqueous wet SO.sub.x scrubber is utilized to treat and/or soften raw water for a calcium-based, aqueous wet SO.sub.x scrubber.

5. The system of claim 1, wherein less than about 3 percent by volume of the waste liquor produced by a calcium-based, aqueous wet SO.sub.x scrubber is utilized to treat and/or soften raw water for a calcium-based, aqueous wet SO.sub.x scrubber.

6. The system of claim 1, wherein less than about 2 percent by volume of the waste liquor produced by a calcium-based, aqueous wet SO.sub.x scrubber is utilized to treat and/or soften raw water for a calcium-based, aqueous wet SO.sub.x scrubber.

7. The system of claim 1, wherein the reaction that takes place in the at least one first precipitator/crystallizer tank of element (e) is represented by the following chemical reaction: Ca(OH).sub.2+Ca.sup.+2+Mg.sup.+2+CO.sub.3.sup.2+Na.sup.+.fwdarw.CaCO.sub.3(s)+Mg(OH).sub.2(s)+Ca.sup.+2+OH.sup.+Na.sup.+.

8. The system of claim 1, wherein the reaction that takes place in the at least one second precipitator/crystallizer tank of element (g) is represented by the following chemical reaction: Na.sub.2SO.sub.3+Ca.sup.+2+2OH.sup..fwdarw.CaSO.sub.3.H.sub.2O(s)+2Na.sup.++2OH.sup..

9. A system designed to treat and/or soften raw water supplied to a calcium-based, aqueous wet SO.sub.x scrubber, the system comprising: (a) at least one floc supply means; (b) at least one raw water supply means, wherein the raw water contains at least calcium ions and magnesium ions; (c) at least one sodium carbonate supply means; (d) at least one lime slurry supply means; (e) at least one first precipitator/crystallizer tank, wherein the at least one floc supply means, the at least one raw water supply means, the at least one sodium carbonate supply means and the at least one lime slurry supply means all supply their respective compounds to the at least one first precipitator/crystallizer tank, and wherein the at least one first precipitator/crystallizer tank permits and facilitates a reaction between the raw water, the sodium carbonate and the waste liquor supply and has at least one outlet; (f) at least one first settler/thickener tank that is in fluid communication with the at least one outlet of the at least one first precipitator/crystallizer tank, the at least one first settler/thickener tank having at least one outlet; (g) at least one second precipitator/crystallizer tank that is in fluid communication with the at least one outlet of the at least one first settler/thickener tank, wherein the at least one second precipitator/crystallizer tank has at least one outlet; (h) at least one waste liquor supply means, wherein the at least one waste liquor supply means is in fluid communication with the at least one second precipitator/crystallizer tank, wherein the waste liquor is supplied from a portion of the waste liquor generated by at least one calcium-based, aqueous wet SO.sub.x scrubber, wherein the at least one waste liquor supply means supplies waste liquor to the at least one second precipitator/crystallizer tank to precipitate excess calcium and wherein the waste liquor contains solubilized sulfate ions; (i) at least one second settler/thickener tank that is in fluid communication with the at least one outlet of the at least one second precipitator/crystallizer tank, the at least one second settler/thickener tank having at least one outlet designed to supply treated water to a calcium-based, aqueous wet SO.sub.x scrubber; and (j) at least one treated water tank that is in fluid communication with the at least one outlet of the at least one second settler/thickener tank, the at least one treated water tank designed to receive and hold treated water and having at least one outlet designed to supply treated water to a calcium-based, aqueous wet SO.sub.x scrubber, wherein less than about 7 percent by volume of the waste liquor produced by a calcium-based, aqueous wet SO.sub.x scrubber is utilized to treat and/or soften raw water for a calcium-based, aqueous wet SO.sub.x scrubber.

10. The system of claim 9, wherein less than about 5 percent by volume of the waste liquor produced by a calcium-based, aqueous wet SO.sub.x scrubber is utilized to treat and/or soften raw water for a calcium-based, aqueous wet SO.sub.x scrubber.

11. The system of claim 9, wherein less than about 3 percent by volume of the waste liquor produced by a calcium-based, aqueous wet SO.sub.x scrubber is utilized to treat and/or soften raw water for a calcium-based, aqueous wet SO.sub.x scrubber.

12. The system of claim 9, wherein less than about 2 percent by volume of the waste liquor produced by a calcium-based, aqueous wet SO.sub.x scrubber is utilized to treat and/or soften raw water for a calcium-based, aqueous wet SO.sub.x scrubber.

13. The system of claim 9, wherein the reaction that takes place in the at least one first precipitator/crystallizer tank of element (e) is represented by the following chemical reaction: Ca(OH).sub.2+Ca.sup.+2+Mg.sup.+2+CO.sub.3.sup.2+Na.sup.+.fwdarw.CaCO.sub.3(s)+Mg(OH).sub.2(s)+Ca.sup.+2+OH.sup.+Na.sup.+.

14. The system of claim 9, wherein the reaction that takes place in the at least one second precipitator/crystallizer tank of element (g) is represented by the following chemical reaction: Na.sub.2SO.sub.3+Ca.sup.+2+2OH.sup..fwdarw.CaSO.sub.3.H.sub.2O(s)+2Na.sup.++2OH.sup..

15. A system designed to treat and/or soften raw water supplied to a calcium-based, aqueous wet SO.sub.x scrubber, the system comprising: (a) at least one floc supply means; (b) at least one raw water supply means, wherein the raw water contains at least calcium ions and magnesium ions; (c) at least one sodium carbonate supply means; (d) at least one lime slurry supply means; (e) at least one first precipitator/crystallizer tank, wherein the at least one floc supply means, the at least one raw water supply means, the at least one sodium carbonate supply means and the at least one lime slurry supply means all supply their respective compounds to the at least one first precipitator/crystallizer tank, and wherein the at least one first precipitator/crystallizer tank permits and facilitates a reaction between the raw water, the sodium carbonate and the waste liquor supply and has at least one outlet; (f) at least one first settler/thickener tank that is in fluid communication with the at least one outlet of the at least one first precipitator/crystallizer tank, the at least one first settler/thickener tank having at least one outlet; (g) at least one second precipitator/crystallizer tank that is in fluid communication with the at least one outlet of the at least one first settler/thickener tank, wherein the at least one second precipitator/crystallizer tank has at least one outlet; (h) at least one waste liquor supply means, wherein the at least one waste liquor supply means is in fluid communication with the at least one second precipitator/crystallizer tank, wherein the waste liquor is supplied from a portion of the waste liquor generated by at least one calcium-based, aqueous wet SO.sub.x scrubber, wherein the at least one waste liquor supply means supplies waste liquor to the at least one second precipitator/crystallizer tank to precipitate excess calcium and wherein the waste liquor contains solubilized sulfate ions; and (i) at least one second settler/thickener tank that is in fluid communication with the at least one outlet of the at least one second precipitator/crystallizer tank, the at least one second settler/thickener tank having at least one outlet designed to supply treated water to a calcium-based, aqueous wet SO.sub.x scrubber, wherein all of the solubilized calcium ions and/or magnesium ions necessary for the reaction in element (e) are contained in the raw water and/or the lime slurry, and wherein all of any additional solubilized calcium ions necessary for the reaction in element (g) are contained in the waste liquor generated by the at least one calcium-based, aqueous wet SO.sub.x scrubber.

16. The system of claim 15, further comprising: (j) at least one treated water tank that is in fluid communication with the at least one outlet of the at least one second settler/thickener tank, the at least one treated water tank designed to receive and hold treated water and having at least one outlet designed to supply treated water to a calcium-based, aqueous wet SO.sub.x scrubber.

17. The system of claim 15, wherein less than about 7 percent by volume of the waste liquor produced by a calcium-based, aqueous wet SO.sub.x scrubber is utilized to treat and/or soften raw water for a calcium-based, aqueous wet SO.sub.x scrubber.

18. The system of claim 15, wherein less than about 5 percent by volume of the waste liquor produced by a calcium-based, aqueous wet SO.sub.x scrubber is utilized to treat and/or soften raw water for a calcium-based, aqueous wet SO.sub.x scrubber.

19. The system of claim 15, wherein less than about 3 percent by volume of the waste liquor produced by a calcium-based, aqueous wet SO.sub.x scrubber is utilized to treat and/or soften raw water for a calcium-based, aqueous wet SO.sub.x scrubber.

20. The system of claim 15, wherein less than about 2 percent by volume of the waste liquor produced by a calcium-based, aqueous wet SO.sub.x scrubber is utilized to treat and/or soften raw water for a calcium-based, aqueous wet SO.sub.x scrubber.

21. The system of claim 15, wherein the reaction that takes place in the at least one first precipitator/crystallizer tank of element (e) is represented by the following chemical reaction: Ca(OH).sub.2+Ca.sup.+2+Mg.sup.+2+CO.sub.3.sup.2+Na.sup.+.fwdarw.CaCO.sub.3(s)+Mg(OH).sub.2(s)+Ca.sup.+2+OH.sup.+Na.sup.+.

22. The system of claim 15, wherein the reaction that takes place in the at least one second precipitator/crystallizer tank of element (g) is represented by the following chemical reaction: Na.sub.2SO.sub.3+Ca.sup.+2+2OH.sup..fwdarw.CaSO.sub.3.H.sub.2O(s)+2Na.sup.++2OH.sup..

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an illustration of a conventional system that is designed to treat raw makeup water for use in a wet flue gas desulfurization (WFGD) system;

(2) FIG. 2 is a plot that illustrates the effect of lime softening on a raw water whose hardness comes from only calcium and magnesium carbonates (no sulfates were present);

(3) FIG. 3 is a plot illustrating the effect of lime softening on a raw water whose hardness comes from only calcium and magnesium sulfates (no carbonates were present);

(4) FIG. 4 is a plot showing the ability of a softening system in accordance with one embodiment of the present invention to remove calcium from raw water;

(5) FIG. 5 is a schematic of a raw water softening system in accordance with one embodiment of the present invention where waste liquor from a soda scrubber is used to treat and/or soften raw water; and

(6) FIG. 6 is a schematic of a raw water softening system in accordance with another embodiment of the present invention where waste liquor from a soda scrubber is used in place of the sulfuric acid in a conventional lime slaking system to treat and/or soften raw water to precipitate the excess calcium that is generated when the pH is raised high enough to precipitate magnesium from the system.

DESCRIPTION OF THE INVENTION

(7) The present invention relates generally to the field of emission control equipment for boilers, heaters, kilns, or other flue gas-, or combustion gas-, generating devices (e.g., those located at power plants, processing plants) and, in particular to a new and useful method and apparatus designed to improve the water supplied to non-calcium-based, aqueous wet SO.sub.x scrubbers. In another embodiment, the present invention relates to a system and method for softening water for use in non-calcium-based, aqueous wet SO.sub.x scrubbers.

(8) Lime softening relies on the relatively low solubility of calcium carbonate. Solubility expressed in complex ionic systems such as water treatments systems express the solubility of the various inorganic constituents by their solubility products. The solubility product of calcium carbonate at 25 C. is 2.810.sup.9. The solubility product for magnesium carbonate is a little less at 3.510.sup.8. But, the solubility product for Mg(OH).sub.2 is 1.310.sup.11. So, slaked lime, Ca(OH).sub.2 precipitates calcium carbonate by converting HCO.sub.3.sup. to CO.sub.3.sup.2 and precipitates magnesium by increasing the OH.sup. concentration. But, the soda scrubber generates sulfite and bisulfite ions in the process of absorbing SO.sub.2 from the flue gas. Additionally, calcium sulfite has a solubility product of 6.810.sup.8. This means that in one instance one could precipitate calcium from raw water as calcium sulfite directly without raising the pH of the raw water at all.

(9) Given this, one embodiment of the present invention involves diverting some of the waste liquor from a non-calcium-based, aqueous wet SO.sub.x scrubber that would be disposed of anyway to a precipitator/crystallizer that is used to treat and/or soften the raw water feed stream for such a wet scrubber. The typical composition of the waste liquor from such a scrubber is: about 70% of the sulfur is in the form of sodium sulfite (Na.sub.2SO.sub.3), while about 30% is in the form of sodium sulfate (Na.sub.2SO.sub.4); about 7 or 8% (depending on pH) is sodium carbonate (Na.sub.2CO.sub.3); and the balance is impurities. Thus, a small portion of waste liquor can be diverted to the water softener, precipitate the calcium as calcium sulfite and deliver the waste liquor and sludge, so produced, to the waste pond for disposal. A plot showing the ability of this system to remove calcium, as an example, is presented in FIG. 4.

(10) In this example, if the waste liquor flow to the softener is established at a rate of 1% by volume of the raw water flow, the calcium concentration can be lowered to the same extent as is achievable with the lime softening system. The softening system overall flow sheet is thus greatly simplified compared to the conventional lime slaking system. Thus, one set-up according to the present invention is schematically illustrated in FIG. 5.

(11) As is illustrated in FIG. 5, one system 200 in accordance with the present invention includes floc supply line 202, sodium carbonate solution supply line 203 (optionalif the waste liquor does not have enough Na.sub.2CO.sub.3), raw water supply line 204 and waste liquor supply line 205. The waste liquor that is supplied via waste liquor supply line 205 comes from the waste liquor from a non-calcium-based, aqueous wet SO.sub.x scrubber. Given this, floc supply line 202, sodium carbonate solution supply line 203, raw water supply line 204 and waste liquor supply line 205 respectively supply floc, sodium carbonate solution, raw water and waste liquor to precipitator/crystallizer 212. Precipitator/crystallizer 212 also includes at least one agitating device (e.g., a mixer) to facilitate the mixing of the floc, sodium carbonate solution, raw water and waste liquor. Once any undesirable solids are permitted to settle out and/or precipitate to the bottom of precipitator/crystallizer 212, this treated solution of floc, sodium carbonate solution, raw water and waste liquor is supplied via supply line 214 to a settler/thickener 216. In settler/thickener 216 the once-treated mixture of floc, sodium carbonate solution, raw water and waste liquor is further treated to remove additional unwanted solid particles via the use of one or more agitating devices (e.g., a mixer). The solids generated by this process are then supplied, with an appropriate amount of solution, to a sludge pond 222, via supply line 218, to permit further settling and reclamation of the solids contained in such a waste solution. Additionally, or in some cases optionally, a portion of the solids generated by settle/thickener 216 are re-supplied, with an appropriate amount of solution, to precipitator/crystallizer 212 via supply line 220 to supply seed crystals for the precipitation stage.

(12) Once any undesirable solids are permitted to settle out and/or precipitate to the bottom of settler/thickener 216 the twice-treated solution of floc, raw water and waste liquor is supplied via supply line 224 to treated water tank 226. From this treated water tank 226, the suitably treated solution is supplied to a non-calcium-based, aqueous wet SO.sub.x scrubber via supply line 234.

(13) In one embodiment, less than about 7% by volume, less than about 5% by volume, less than about 3% by volume, or even less than about 2% by volume of the waste soda liquor produced by a non-calcium-based, aqueous wet SO.sub.x scrubber is required to treat the raw water going to such a non-calcium-based, aqueous wet SO.sub.x scrubber. In another embodiment, the amount of waste soda liquor used and/or recycled into the system and/or process of the present invention varies depending upon various factors, each taken alone or in any combination thereof. Such factors include, but are not limited to, the amount of raw water to be treated and/or softened, the appropriate pH for the operation of the scrubber, the amount of calcium and/or calcium ions in the raw water feed, and/or the amount/level of alkalinity in the raw water feed. Given this, the present invention is, in some instances, not limited to any capped amount of waste soda liquor that is used and/or recycled.

(14) In still another embodiment, any amount of waste soda liquor from a non-calcium-based, aqueous wet SO.sub.x scrubber can be used in the systems and/or processes disclosed herein so long as a desired stoichiometric ratio between the calcium ions in the raw water and the sulfite ions contained in the waste soda liquor is achieved. In one instance, a suitable stoichiometric ratio of calcium ions to sulfite ions in the treatment and/or softening process of the present invention is in the range of about 1:4 to about 4:1, or from about 1:3 to about 3:1, or from about 1:2 to about 2:1, or even about 1:1. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form additional non-disclosed ranges.

(15) In still another embodiment, the stoichiometric ratios of the present invention may be varied to include all increments of one quarter that fall within the ranges disclosed above. In one instance, a suitable stoichiometric ratio of calcium ions to sulfite ions in the treatment and/or softening process of the present invention is in the range of about 1:3.75 to about 3.75:1, 1:3.50 to about 3.50:1, or even down to about 1:1.25 to about 1.25:1.

(16) In light of the above, one embodiment of the present invention eliminates the need to purchase lime and/or sulfuric acid, as well as the purchase of all of the related equipment needed to store, handle and process such compounds. Additionally, the present invention reduces the amount of waste material that must be discarded, i.e. the lime and sulfuric acid that would be consumed in the softening process. The present invention reduces the effluent flow to the waste pond, and prevents any chance that the pond might be shocked with low pH spikes caused by inadvertent sulfuric acid excursions that might otherwise cause SO.sub.2 off-gassing from the pond. Furthermore, the control system of the system of the present invention is simplified as well. The lime softening system of the prior art requires careful control of pH compared to the waste liquor control that generally requires proportionate control of the waste liquor flow to the softener in proportion to the raw water flow. Given this, the present invention thus provides for cost savings in reagent costs, equipment costs, disposal costs, and control equipment costs.

(17) In another embodiment, illustrated in FIG. 6, waste liquor could be used in place of the sulfuric acid in a conventional lime slaking system to precipitate the excess calcium (see FIGS. 2 and 3) that is generated when the pH is raised high enough to precipitate magnesium from the system. This method would precipitate the calcium as calcium sulfite but it would not lower the pH. Once the water treatment has reduced the calcium and magnesium, a high pH treated water can be used in the scrubber to advantage. There is no reason to lower the pH of the treated water prior to its use in the scrubber. As illustrated in FIG. 6, system 300 includes floc supply line 302, sodium carbonate solution supply line 303, raw water supply line 304 and lime supply 306. Lime supply 306 supplies lime to detention slaker 308. Detention slaker 308 includes therein at least one agitating device (e.g., a mixer) and is provided with a water supply line to permit the mixing of the lime from lime supply 306 with water to yield a lime slurry that is supplied, via line 310, to precipitator/crystallizer 312. Also supplied to precipitator/crystallizer 312 are floc via floc supply line 302, sodium carbonate solution via sodium carbonate supply line 303 (optionalif the waste liquor does not have enough Na.sub.2CO.sub.3), and raw water via raw water supply line 304. Precipitator/crystallizer 312 also includes at least one agitating device (e.g., a mixer) to facilitate the mixing of the sodium carbonate solution, floc, raw water and lime slurry. Once any undesirable solids are permitted to settle out and/or precipitate to the bottom of precipitator/crystallizer 312, this treated solution of sodium carbonate solution, lime, raw water and floc is supplied via supply line 314 to a settler/thickener 316. In settler/thickener 316 the once-treated mixture of sodium carbonate solution, lime, raw water and floc is further treated to remove additional unwanted solid particles via the use of one or more agitating devices (e.g., a mixer). The solids generated by this process (predominantly Mg(OH).sub.2, but may include CaCO.sub.3 depending upon the source of the raw water) are then supplied, with an appropriate amount of solution, to a sludge pond 322, via supply line 318, to permit further settling and reclamation of the solids contained in such a waste solution. Additionally, or in some cases optionally, a portion of the solids generated by settler/thickener 316 are re-supplied, with an appropriate amount of solution, to precipitator/crystallizer 312 via supply line 320 to supply seed crystals for the precipitation stage.

(18) Once any undesirable Mg(OH).sub.2 solids are permitted to settle out and/or precipitate to the bottom of settler/thickener 316 the twice-treated solution of sodium carbonate solution, lime, raw water and floc is supplied via supply line 324 to a second precipitator/crystallizer 327 which also includes at least one agitating device (e.g., a mixer) to facilitate the mixing. In precipitator/crystallizer 327, the thrice-treated mixture of sodium carbonate solution, lime, raw water and floc is combined with waste liquor from a non-calcium-based, aqueous wet SO.sub.x scrubber via waste liquor supply line 328 to precipitate excess calcium. Once any undesirable solids are permitted to settle out and/or precipitate to the bottom of precipitator/crystallizer 327, this treated solution of sodium carbonate solution, lime, raw water and floc is supplied via supply line 330 to a second settler/thickener 332. In settler/thickener 332, the thrice-treated mixture of sodium carbonate solution, lime, raw water and floc is further treated to remove additional unwanted solid particles via the use of one or more agitating devices (e.g., a mixer). The solids generated by this process (CaSO.sub.3) are then supplied, with an appropriate amount of solution, to a sludge pond 340, via supply line 334, to permit further settling and reclamation of the solids contained in such a waste solution. Additionally, or in some cases optionally, a portion of the solids generated by settler/thickener 332 are re-supplied, with an appropriate amount of solution, to precipitator/crystallizer 327 via supply line 336 to supply seed crystals for the precipitation stage. The treated water is then supplied via supply line 338 to a treated water tank 326. From this treated water tank 326, the suitably treated solution is supplied to a non-calcium-based, aqueous wet SO.sub.x scrubber via supply line 342.

(19) Given the above, in one embodiment the present invention relates to a system designed to treat and/or soften raw water supplied to a non-calcium-based, aqueous wet SO.sub.x scrubber, the system comprising: (a) at least one floc supply means; (b) at least one raw water supply means; (c) at least one sodium carbonate supply means; (d) at least one waste liquor supply means, wherein the waste liquor is supplied from a portion of the waste liquor generated by at least one non-calcium-based, aqueous wet SO.sub.x scrubber; (e) at least one precipitator/crystallizer tank, wherein the at least one floc supply means, the at least one raw water supply means, the at least one sodium carbonate supply means and the at least one waste liquor supply means all supply their respective compounds to the at least one precipitator/crystallizer tank, and wherein the at least one precipitator/crystallizer tank has at least one outlet; and (f) at least one settler/thickener tank that is in fluid communication with the at least one outlet of the at least one precipitator/crystallizer tank, the at least one settler/thickener tank having at least one outlet designed to supply treated water to a non-calcium-based, aqueous wet SO.sub.x scrubber.

(20) In another embodiment, the present invention relates to a system designed to treat and/or soften raw water supplied to a non-calcium-based, aqueous wet SO.sub.x scrubber, the system comprising: (a) at least one floc supply means; (b) at least one raw water supply means; (c) at least one sodium carbonate supply means; (d) at least one lime slurry supply means; (e) at least one first precipitator/crystallizer tank, wherein the at least one floc supply means, the at least one raw water supply means, the at least one sodium carbonate supply means and the at least one lime slurry supply means all supply their respective compounds to the at least one first precipitator/crystallizer tank, and wherein the at least one first precipitator/crystallizer tank has at least one outlet; (f) at least one first settler/thickener tank that is in fluid communication with the at least one outlet of the at least one first precipitator/crystallizer tank, the at least one first settler/thickener tank having at least one outlet; (g) at least one second precipitator/crystallizer tank that is in fluid communication with the at least one outlet of the at least one first settler/thickener tank, wherein the at least one second precipitator/crystallizer tank has at least one outlet; (h) at least one waste liquor supply means, wherein the at least one waste liquor supply means is in fluid communication with the at least one second precipitator/crystallizer tank, wherein the waste liquor is supplied from a portion of the waste liquor generated by at least one non-calcium-based, aqueous wet SO.sub.x scrubber, and wherein the at least one waste liquor supply means supplies waste liquor to the at least one second precipitator/crystallizer tank to precipitate excess calcium; and (i) at least one second settler/thickener tank that is in fluid communication with the at least one outlet of the at least one second precipitator/crystallizer tank, the at least one second settler/thickener tank having at least one outlet designed to supply treated water to a non-calcium-based, aqueous wet SO.sub.x scrubber.

(21) The various supply means of the present invention include, but are not limited to, tubing, pipes, conduits, hoses, etc. that are designed to carry, supply and/or contain liquid material.

(22) In one instance, the above systems utilize less than about 7% by volume of the waste liquor produced by a non-calcium-based, aqueous wet SO.sub.x scrubber to treat and/or soften raw water for a non-calcium-based, aqueous wet SO.sub.x scrubber. In another instance, the above system utilize less than about 5% by volume of the waste liquor produced by a non-calcium-based, aqueous wet SO.sub.x scrubber to treat and/or soften raw water for a non-calcium-based, aqueous wet SO.sub.x scrubber. In still another instance, the above systems utilize less than about 3% by volume of the waste liquor produced by a non-calcium-based, aqueous wet SO.sub.x scrubber to treat and/or soften raw water for a non-calcium-based, aqueous wet SO.sub.x scrubber. In still another instance, the above systems utilize less than about 2% by volume of the waste liquor produced by a non-calcium-based, aqueous wet SO.sub.x scrubber to treat and/or soften raw water for a non-calcium-based, aqueous wet SO.sub.x scrubber.

(23) Given the above, the following chemical reactions are provided to offer insight into the reaction process that occurs in various raw water treatment and/or softening systems. It should be noted that while the following chemical reactions are provided, that the following chemical reactions do not necessarily represent all of the reactions taking place during the processes discussed herein. Additionally, the present invention is not bound to just the chemical reactions shown below. Conventional lime treatment, softening and/or slaking is detailed in reactions (5) and (6), while reaction (7) detail a reaction of interest in the embodiment of FIG. 5, and reactions (8) and (9) detail the reactions of interest in the embodiment of FIG. 6.
FIG. 1Stage 1
Ca(OH).sub.2+Ca.sup.+2+Mg.sup.+2+CO.sub.3.sup.2+Na.sup.+.fwdarw.CaCO.sub.3(s)+Mg(OH).sub.2(s)+Ca.sup.+2+OH.sup.+Na.sup.+(5)
FIG. 1Stage 2
H.sub.2SO.sub.4+Ca.sup.+2+2OH.sup.+CO.sub.3.sup.2+Na.sup.+.fwdarw.CaCO.sub.3(s)+2H.sub.2O+Na.sup.++SO.sub.4.sup.2(6)
FIG. 5
Ca.sup.+2+CO.sub.3.sup.2+2Na.sup.++SO.sub.3.sup.2.fwdarw.CaSO.sub.3(s)+2Na.sup.++CO.sub.3.sup.2(7)
FIG. 6Stage 1
Ca(OH).sub.2+Ca.sup.+2+Mg.sup.+2+CO.sub.3.sup.2+Na.sup.+.fwdarw.CaCO.sub.3(s)+Mg(OH).sub.2(s)+Ca.sup.+2+OH.sup.+Na.sup.+(8)
FIG. 6Stage 2
Na.sub.2SO.sub.3+Ca.sup.+2+2OH.sup..fwdarw.CaSO.sub.3.sub..H.sub.2O(s)+2Na.sup.++2OH.sup.(9)

(24) While specific embodiments of the present invention have been shown and described in detail to illustrate the application and principles of the invention, it will be understood that it is not intended that the present invention be limited thereto and that the invention may be embodied otherwise without departing from such principles. In some embodiments of the invention, certain features of the invention may sometimes be used to advantage without a corresponding use of the other features. Accordingly, all such changes and embodiments properly fall within the scope of the following claims.