CA1076320A - Prevention of calcium deposition from trona-derived sodium carbonate liquors - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method of producing a concentrated sodium carbonate solution low in calcium from calcined natural trona to minimize the deposition of pirssonite on the surfaces of processing equip-ment exposed to the solution from which the insoluble impurities, normally present in natural trona, have been separated. The method comprises dissolving the calcined trona in a hot aqueous medium to form a concentrated solution containing insoluble impurities and soluble calcium salts and adding an amount of pirssonite effective to insolubilize the major portion of the soluble calcium in the sodium carbonate solution. The pirssonite may be added to the calcined trona either before,during or after its dissolution. The pirssonite may also be added by recycling excess muds back to the sodium carbonate solution from which the insoluble impurities have not been separated. In addition, the sodium carbonate solution may be aged in the presence of the contained insoluble impurities prior to their separation from the sodium carbonate solution to reduce the amount of soluble calcium salts.

Description

~)76~32~) PREVENTION OF CALCIUM DEPOSITION FROM TRONA-DERIVED
SODIUM CARBONATE LIQUORS
BACKGROUND OF THE INVENTION
Although by far the greatest tonnage of soda ash (anhydrous sodium carbonate) is produced by the well-known Solvay Process, an increasing amount is obtained from natural trona, large deposits of which are found in the vicinity o~ Green River, Wyoming at depths varying from 800 to 1800 feet. The trona beds are generally sandwiched between and sometimes in combination with stratifications of shale. The trona consists mainly of sodium sesquicarbonate (Na2CO3 NaHCO3 2H2O), and typically contains rom 4 to 20 percent insoluble matter. The latter consists largely of ~hale, but also contains calcareous minerals and other impuritiesO
A typical natural trona composition is given below:

2 3 41.8%
NaHCO3 33.1 H2O 14.1%
89.

Insolubles:
Dolomite CaCO3 MgCO3 50 5%
Quartz SiO2 1.1 Feldspar (K, Na) O xA12O3 ySio2-zH2O 3.3%

Clay 2K2O 3MgO 8Fe2O3 24SiO2 12H2O 0.6 Shortite Na2CO3~2CaC03 0O1%

Organic Matter as Elemental Carbon 0.2%
Other (by Difference) 0.2~
In the production of sodium carbonate from natural trona, the usual procedure is to calcine the mineral to obtain a crude sodium carbonate 2(Na2CO3 NaHCO3 2H2O) ~ 2 3 5H2O CO~

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The sodium carbonate thus obtained is dissolved in an aqueous medium and/or recycled process liquors. The calcium salts present also dissolve to a slight extent, so that the final solution may contain up to about 50 parts per million (ppm), as calcium.
Unfortunately, these solubilized calcium salts later deposit from the slurry or solution on the surface of processing equipment, such as those of heat exchangers, pumps and lines, particularly in zones of high turbulence and high temperature.
The deposit is predominantly in the form of pirssonite (Na2CO3 CaCO3 2H~O). This pirssonite scale is a compact, adherent crystalline mass which may vary in thickness from a thin film to a 1/4 inch coating or more depending upon the time elapsed between treatments ~or removal of this scaleO
Not only does this scale retard fluid flow and heat transfer, but it causes pitting, corrosion and the breakdown of moving parts. Because of its hardness and adherence this scale cannot easily be removed by mechanical means. The method used commercially to meet the problem of calcium deposition has involved e~uipment shut down, followed by thorough cleaning of the fouled lines and units with inhibited acid. This approach means costly down time and contributes to the corrosion and pitting initiated by the calcareous deposits.
It has now been found that calcium in solution is the net result of two simultaneous processes:
tl) the decomposition of Ca-bearing trona minerals, and (2) the crystallization of pirssonite, the stable equilibr um calcium phase under the conditions of dissolving.
Surprisingly, the addition of small amounts of synthetic pirssonite to the dissolving system does not increase the amount of ~(3763;~

pirssonite deposition, ~ut instead, rapidly reduces calcium supersaturation even in the presence of Ca-bearing muds, to a very low level. Also, surprisingly, the addition of phases structurally adjacent to pirssonite (gaylussite and se~eral modifications of CaC03) have been ~ound relatively ineffectual in reducing calcium supersaturation.
The pirssonite scale formation may be essentially prevented if the calcium level in the trona liquor can be reduced to about 15 ppm or less. Such reduction of the calcium ion in the sodium carbonate solution would, by essentially preventing the formation of pirssonite deposits in the processing equipment, introduce ver~ significant savings in labor and equipmen~ costs, and increase the productive output of the processing equipment.

SUM~IARY OF THE INVENTION
When a small amount of the sodium calcium carbonate "pirssonite" (Na2C03 CaC03 2H20) is admixed with an a~ueous solution of calcined trona containing insoluble matter, and the insoluble matter is separated from the sodium carbonate solution, the major portion of the solubilized calcium wh.ich normally ~ould subsequently deposit on the surface of processing equipment, is insolubilized and removed from the solution along with the insoluble matter. The procedure provides a low calcium liquor inexpensively, by the addition of a small amount of pirssonite and requires no additional processing since the separation of the insoluble matter is a necessary step in conventional processes for preparing soda ash from calcined trona solutions.
More specifically, a method of the present invention for producing a concentrated solution of sodium carbonate from trona containing insoluble impurities and soluble calcium salts, to minimi~e deposition of pirssonite from the sodium carbonate solution from which the insoluble impurities have been separated, comprises calcining the trona, dissolving the calcined trona in ~7G3'2C~
In aqueous medium at a temperature between about 80 and 110C., admixing an amount of pirssonite effective to insolubilize a major portion of the soluble calcium in the sodium carbonate solution and separating the insoluble solids from the concentrated solution. The amount of pirssonite which may be introduced or admixed before, during or after dissolution of the calcined trona is between about 0.1 and 5~ by weight based on the weight of the dissolved calcined trona in solution. The term "aqueous medium"
is intended to include water.
In another embodiment of our invention, the pirssonite is added to the sodium carbonate solution containing insoluble impurities by recycling an excess of the insoluble impurities (muds) containing pirssonite wherein the amount recycled comprises generally between 25 and 200 percent of the weight of insoluble impurities in the calcined trona feed to the dissolving ~one~
In still another emobidment of our invention, the production of a low calcium, concentrated, sodium carbonate solution from trona which will deposit substantially no pirssonite on the liquid-contacting surfaces of the processing equipment, is accomplished by aging, that is, by retaining the solution in con-tact with the insoluble impurities for a sufficient time to effect reduction of the soluble calcium ions in the solution to less than about 15 parts per million. The practicality of this approach is rather surprising in light of the fact that in the past it was supposed that deposition of insoluble calcium salts from the concentrated sodium carbonate on the liquid-containing surfaces of processing equipment could be lessened by removing the insoluble impurities or muds from the concentrated sodium carbonate solution as rapidly as possible.

In the preparation of soda ash from natural trona, the trona is generally crushed to afford pieces predominantly larger than 1/2 inch in average diameter, but which will pass through a screen having 3 inch openings. The trona may be calcined at ,~

~7~i3~

temperatures ranging from 125 to 800C., but temperatures between about 125 and ~00C. are preferred. At temperatures in excess of 800C. the impure sodium carbonate may begin to sinter. As may be expected, the crushed material will inevit-ably contain a considerable quantity of material having particle sizes less than 1/2 inch. A coarse, particulate calcined trona is preferred.
The calcined trona is dissolved in an aqueous medium such as water, or preferably, at least in part of an aqueous sodium carbonate solution comprising solutions, rinses and washes recovered from the soda ash process. The amount of aqueous medium used will be approximately that required to produce a suhstantially saturated solution of sodium carbonate at a temperature of about 80 to 110C., preferably 85 to 100C. The sodium carbonate content of the solution will be at least 20 percent or more, preferably between about 27 and 32 percent sodium carbonate. The residual heat of the calcined trona, added to the heat of solution of the anhydrous sodium carbonate, may heat the slurry above its boiling point, hence additional make-up dilute sodium carbonate solution, or water, may be required to replace that lost through vaporiza-tion.
A small quantity of pirssonite in an amount between about 0.1 and 5 percent of the weight of the dissolved calcined trona, preferably in an amount ranging from about 0.2 to 2 percent, is admixed with the solution containing solid impuritiesO An amount of pirssonite less than 0.1 percent is at least partially effective, and an amount greater than 5 percent is effective but ~rovides no additional benefit. The solution is maintained at a temperature ranging from about 80 to 110C., preferably from 85 to 100C. The period of mixing may vary from a few minutes up to 1~76~2t~

an hour or more, but mixing periods exceeding an hour provide no additional benefit. The solution, having suspended solids, is next transferred to clarifiers where the solids are separated from the sodium carbonate solution leaving only a minimal amount of dissolved calcium salts, namely less than about 15 parts per million (ppm) as Ca (based on the weight of the sodium carbonate solution), and generally less than 10 ppm.
The downstream deposition o~ calcium, particularly pirssonite from a solution treated as above will be minimal or essentially non-existent. If desired, the pirssonite can alternately be added to the calcined trona prior to its dissolution in the aqueous solution. The pirssonite need not be pure, and may, if desired, be added in combination with other insoluble matter.
The concentrated sodium carbonate solution, substan-tially free of insolubles and containing less than about 15 ppm calcium, may be processed according to any of the commonly employed methods for the manufacture of soda ash.
Generally this is accomplished by subjecting the purified sodium carbonate solution to a crystallization or series of crystallizations wherein sodium carbonate monohydrate cr~stals are obtained and calcined to produce a refined soda ash product.
The insoluble impurities or muds which are separated ~rom the aqueous trona solution, even when pirssonite is not deliberately added to the solution, contain pirssonite, generally in an amount between about 2 to 5 percent based on the dry weight of the muds. We have now found that aging the solution with the muds alone provides a low calcium ~iltrate ~rom which pirssonite will not subsequently deposit. In one embodiment of our invention the sodium carbonate solution ~rom calcined ~9~3,~
trona with its insoluble impurities is a~ed for periods of between 2 to 5 hours or more, to effect the desired reduction of soluble calcium salts in the eventually clarified solution.
A combination of these two procedures can be employed wherein pirssonite is added either before, during or after dissolution of the calcined trona, and the insoluble impurities or muds are retained in intimate contact with the sodium carbonate solution for an extended period, before separation or clarification of said sodium carbonate solution. Less pirssonite need be employed in this combination procedure.
A process for producing a substantially saturated clarified aqueous sodium carbonate solution from calcined trona, said solution having a concentration of at least 20 percent by weight and containing less than about 15 ppm of calcium, to essentially eliminate deposition of pirssonite scale on the liquid-contacting surfaces of the processing equipment, is herein disclosed as a preferred embodiment of our invention.
The calcined trona is dissolved in an aqueous medium in a dissolving zone at a temperature preferably between about 85 and 100C. to obtain an aqueous solution of sodium carbonate containing soluble calcium salts and insoluble matter as impurities.
Preferably, the aqueous medium employed as a solvent is comprised, at least in part, of sodium carbonate solutions, rinses and washes recovered from the soda ash process.
A first stream of trona solution containing solids is continuously withdrawn from the dissolving zone and transferred to a thickening zone wherein said first stream is divided into two portions. In one portion, the concentration of the insoluble impurities is increased by separating therefrom, trona solution containing a lesser concentration of insoluble matter. This s~parated solution comprises the second portion o~ the divided ~763~2~
first stream. Preferably, the thickening zone is a SOlias thickener and the concentrated or thickened portion is predominantly solid impurities or muds, whereas the remaining portion of the first stream may consist of trona solution, either without solids, or with contained solids diluted by the liquor separated from the thickened portion. The concentrated or thic~ened por~ion contains a quantity of solids, dry basis, equivalent to about 25 to 200 percent or more; preferably about 30 to 70 percent by weight, of the amoun~ of solids in the calcined trona charged to the dissolving zone. This thickened portion is recycled to the dissolving zone. The remaining portion of the first stream which now has a lesser density because of the greater amount of sodium carbonate solution associated therewith, is directed to a clarification zone.
A second stream of sodium carbonate solution containing insoluble impurities is also transferred directly from the dissolving zone to the clarifier in an amount to maintain a material balance within the system. The term "clarification zone" is here intended to encompass the final solids separation system.
The first stream which is transferred to the clarification zone, and the second stream transferred to the clarification zone are preferably combined and clarified to provide a clear sodium carbonate solution having less than 15 ppm of calcium. This solution is essentially incapable of depositing an appreciable film of pirssonite on the liquid-contacting surfaces of the processing equipment.
A better understanding of the process of our invention may be had by reference to the descrip-tion of the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
Figure 1 graphically demonstrates the rapid reduction of calcium supersaturation when relieved by the direct addition of 0.3 percent pirssonite, and alternately by recycling clarifier muds (trona insoluble impurities) which have been shown to contain pirssonite. The muds are only slightly less effective than pure pirssonite.
Figure 2 is a highly simplified schematic flow diagram of a process for the production of soda ash from natural trona, drawn to illustrate particularly the recycling of the 1nsoluble impurities from trona, which constitutes a preferred embodiment of our invention. In the diagram, a portion of the solution or slurry from the dissolver is thickened in a solids thickener, and the densified solid impurities are returned to the dissolver `
together with a small amount of sodium carbonate solution.
Alternately, the solid impurities separated downstream during the classification, clarification or filtration steps could be recycled if desired.
With reference to the diagram, mi~ed natural trona is fed into crusher 1 then to trona calciner 2 through line 14. The calcined trona is charged continuously to dissolver 3 through line 15 and an aqueous dissolving medium containing 0 to 15 percent or more sodium carbonate is charged through line 4. A 27 to 32 percent sodium carbonate solution is produced in dissolver 3 at a temperature of between about 85 and 100C.
To illustrate the present invention, assume that over a unit of time, the charge comprises in totalO
100 lbs. Insoluble impurities from trona 700 lbs. Na2CO3 and 1,590 lbs.H2O
2,390 lbs.Total 1~7~3~

The sodium carbonate included above is composed of the Na2CO3 in the trona plus that contained in the 0 - 15 percent Na2CO3 solvent solution.
These mat~rials are continuously charged into dissolver

3 together with recycled thickened insoluble materials continuously received from the thickening device (solids thickener) 5 through line 16. These recycled materials comprise:
60 lbs. Insoluble impuYities 27 lbs, Na2CO3 63 lbs. H O
150 lbs. ~otal The mixture which now contains about 30 percent Na2CO3 is agitated at a temperature of about 85 to 100C. with a re~ention time (solution in contact with solids) of at least 20 minutes.
A first stream is continuously withdrawn from dissolver 3 per unit of time by pump 6 containing:
120 lbs. Solid impurities 5~6 lbs. Na2CO3 - 1,238 lbs. H O
1,904 lbs. T~tal This first stream is pumped through line 17 into solids thickener S which returns about half of the solids to the dissolver. This half constitutes the recycled material listed above as leaving the solids thickener.
The other half of the above solids with its associated liquor is continuously directed to the final solids separation means 7 through line 18. This portion comprises:
60 lbs. Solids 519 lbs. Na2CO3 1,175 lbs. H2O
1,754 lb~. Total ~ ~ 7 ~ 3 ~

Simultaneously, a second stream is withdrawn from the dissolver by pump 8 and delivered through line 19 directly to the final solids separation system 7. This stream serves to maintain the material balance and comprises:
40 lbs. Solids 181 lbs. Na2CO3 415 lbs. H2O
636 lbs. Total The streams of sodium carbonate solution directed to the final solids separation system are combined and separated from the associated insoluble impurities or muds. The increased magma den-sity in the dissolver results in an increased residence time for the insolubles and increases the relative concentration of pirssonite. Calcium supersaturation is therefore rapidly relieved, and the liquor attains non-scaling calcium levels.
In the schematic diagram, clear sodium carbonate solution leaves the final solids separation system 7 with a càlcium content of less than about 15 ppm and passes to the crystallizer through line 21. The insoluble muds are discharged at 13. Water washes of these muds may be included in the aqueous medium used as a solvent for the incoming calcined trona.
The crystallization process is represented by block 9.
The sodium carbonate monohydrate crystals from crystallizer 9 enter calciner 11 through line 22 where they are calcined at temperatures between about 125 and 200C. to produce a purified soda ash product at 12.
EXAMPLES

General Experimental Procedure Ground calcined trona ore assaying 87 percent Na2CO3 was used in all the examples. The solutions were prepared by adding 64.4 grams of the calcined ore to 144 milliliters (ml.) ~7~;32C9 of deionized, millipore-filtered water contained in a 250 ml.
volumetric flask to obtain a 28 percent Na2CO3 solution. The solution was stirred with a Teflon-coated magnetic stirrer and maintained at 90C. by immersion in a thermostatically controlled oil bath. 10 ml. samples of the solution were withdrawn (after allowing the insolubles to settle for a few minutes) at definite time intervals, ~iltered through a 0.22 ~ millipore filter and immediately diluted with 10 ml. deionized millipore-filtered water.
The solutions were analyzed for calcium by atomic absorption spectroscopy using a Perkin Elmer 303 Spectrophotometer employing a calcium hollow cathode lamp and air-acetylene fuel.
The test solution was acidified to the methyl orange end-point and the absorption measured at 4227 angstroms after adding lanthanum chloride to suppress anionic chemical interferences.
Standard prepared calcium samples were submitted periodically as a check on internal consistency. Calcium levels are reported at an accuracy of + 1 ppm.

Slow Calcium Supersaturation Relief In Trona-Solution The slow decrease in calcium level in untreated trona liquor (28 percent Na2CO3) is shown in Table 1.

CALCIUM SUPERSATURATION RELIEF IN
28% ASH-FROM-TRONA SOLUTION -90C.

TIME CA, PPM

10 minutes 38.2 20 minutes 35.7 30 minutes 32.6 1 hour 27.0 302 hours 20.0

4 hours 11~8 24 hours 9.7 ~ [D7632~3 It is seen that the calcium level in the solution is reduced to the non-scaling value after about 4 hours.

Rapid Calcium Supersaturation Relief In Trona Solutions By The Addition of Pirssonite ____ _ When small quantities of pirssonite are added to calcined trona during dissolution, there is a rapid reduction of calcium levels in the solution as shown in Table 2. The pirssonite samples consisted of scale from process lines, ground to -100 mesh. This pirssonite assayed better than 99 percent as det~rmined by x-ray and chemical analysis.

EFFECT OF ADDED PIRSSONITE ON CALCIUM
SOLUBILITY IN 28% TRONA SOLUTIONS-90C.
TIME
PIRSSONITE
(BASIS Na2~3) 10 min. 20 min. 30 min. 4 hrs.
~ - - - - - Ca, ppm - - - - - - - - -0.0 38.2 35.7 32.6 11.8 0.1 24.6 22.1 -- 12.3 0.3 15.5 13.4 11.7 9.6 0.9 17.7 12.3 -- 9.6 It is seen that 0. 3 percent pirssonite (basis Na2CO3) is quite effective in relieving calcium supersaturation in less than 20 minutes.

Rapid Calcium Supersaturation Relief In Trona Solutions By The Addition Of Trona Insoluble ImPurities Or Muds --. .
The pirssonite found in the trona insolubles was estimated by optical microscopy. The trona muds were found to contain approximately 2 - 5 percent pirssonite.
Dried muds were added to calcined trona during dissolu-tion. The amount of muds added was equivalent to about 50 percent of the insolubles obtained when the calcined trona i9 dissolved in ~7~i~2~
water to obtain 28 percent Na2CO3 solution, i.e., a 50 percent muds excess.
TAsLE 3 EFFECT OF ~DDED MUDS (S0% EXOE SS) ON
CALCIUM SOLUBILITY IN TRONA SOLUTIONS
(28% Na2 ~ ~ 90C~) ... . .. .
TIME
10 min. 20 min. 30 min. 4 hrs. 5 hrs.
. A
------------------- Ca, ppm ---------------~-No addition 38.2 35.7 32.6 11.8 --10Clarifier Feed Insolubles 20.0 16.9 15.1 9.6 8.5 Clarifier Muds 22.3 16.8 16.3 12.0 10.6 It is seen that clarifier feed insolubles and clarifier muds added to calcined trona, as above, give calcium levels in the clarif ied liquors only slightly higher than those obtained on the addition of pirssonite (Example 2).

.
Effect Of High Concentrations Of Trona Muds On Calcium Su~rsaturation Relief The effect of the addition of larger amounts (up to 200 percent excess)of trona muds are shown in Table 4.

EFFECT OF ADDED TRONA INSOLUBLE IMPURITIES
ON CALCIUM SOLUBILITY IN TRONA SOLUTIONS
(28~ Na2 _3 - 90~C.) TIME
10 min. 20 min. 30 min. 1 hr. 2 hrs. 4 hrs.
- - - - - - - - - - - Ca, ppm - - - - - - - - ~ -No addition 38.2 35.7 32.6 27.0 20.0 11.8 100~ Excess Muds 22.4 16.8 15.5 13.4 12.0 10.4 150% Excess Muds 20.6 15.5 13.2 12.5 11.4 11.2 200% Excess Muds 18.9 15.4 14.3 13.4 12.3 12.2 It i5 seen that an increase of up to 200% ln muds concentration does not reduce the calcium levels significantly ~l3763~1 below that produced with 50% excess muds.

Effect of Calcium Compounds Other Than ~ On C~ ur Su~rsaturation_ The addition o~ the calcium compounds tabulated in Table 5 below~ whiCh are broadly representatiVe~ Were found tO
have substantially no effect on calcium supersaturation. Among those tested was gaylussite ~Na2CO3 CaCO3 5H20) which is an adjacent phase to pirssonite (Na2CO3 CaCO3 2H20~. Surprisingly, none of these compounds was appreciably effective.

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~ 7 ~ ~ ~0 since changes can be made in carrying out the above process without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

~17-

Claims (8)

We claim:

1. In a process for the production of soda ash from natural trona which comprises crushing the trona, cal-cining the crushed trona, dissolving the sodium carbonate values of the calcined trona in aqueous medium in a dissolving zone at a temperature of from about 80° to 110°C to provide a substantially saturated sodium carbonate solution containing soluble calcium ions and insoluble impurities, separating the insoluble impurities from said saturated sodium carbonate solution, crystallizing sodium carbonate monohydrate from said separated saturated sodium carbonate solution, separating the sodium carbonate monohydrate crystals and calcining the separated monohydrate crystals to produce soda ash, the im-provement which comprises introducing pirssonite into said substantially saturated sodium carbonate solution, said pirs-sonite being introduced in an amount of between about 0.1 and 5% by weight, based on the weight of the dissolved calcined trona in the solution.

2. The process according to claim 1 wherein said pirssonite is introduced into said substantially saturated sodium carbonate solution in an amount of between about 0.2 and 2% by weight, based on the weight of the dissolved cal-cined trona in the solution.

3. The process according to claim l wherein the pirssonite introduced into said substantially saturated sodium carbonate solution is obtained by recycling to said solution insoluble impurities containing pirssonite.

4. The process according to claim 3 wherein the amount of insoluble impurities recycled to said solution is between 30 and 70% of the weight of insoluble impurities in the calcined trona.

5. In a process for the production of soda ash from natural trona which comprises crushing the trona, cal-cining the crushed trona, dissolving the sodium carbonate values of the calcined trona in aqueous medium in a dissolving zone at a temperature of from about 80° to 110°C to provide a substantially saturated sodium carbonate solution containing soluble calcium ions and insoluble impurities, separating the insoluble impurities from said saturated sodium carbonate solution, crystallizing sodium carbonate monohydrate from said separated saturated sodium carbonate solution, separating the sodium carbonate monohydrate crystals and calcining the separated monohydrate crystals to produce soda ash, the improve-ment which comprises: introducing pirssonite-containing insoluble matter into said substantially saturated sodium carbonate solution and retaining said insoluble matter in contact with said substan-tially saturated sodium carbonate solution for a sufficient time to effect reduction of the soluble calcium ions in said substan-tially saturated sodium carbonate solution to less than about 15 parts per million, said pirssonite being introduced in an amount of between about 0.1 and 5% by weight, based on the weight of the dissolved calcined trona in the solution.

6. The process according to claim 5 wherein said pirssonite-containing insoluble matter comprises insoluble impurities produced in the dissolving of the calcined trona.

7. The process according to claim 5 wherein said pirssonite-containing insoluble matter is obtained by recycling to said dissolving zone insoluble impurities separated from said saturated sodium carbonate solution and, containing pirssonite in an amount between about 2 and 5% by weight, based on the dry weight of said separated insoluble impurities.

8. The process according to claim 5 wherein said sub-stantially saturated sodium carbonate solution is contacted with said pirssonite-containing insoluble matter for a period of between 2 and 5 hours.