What is claimed is:
1. A device for producing electrical discharges in an aqueous medium, said device comprising:
a first electrode and a second electrode, each of said electrodes comprised of a superalloy having a cobalt content of greater than 8% by weight; said device producing a voltage discharge into the medium when a high electrical voltage is applied to said electrodes, the voltage discharge creating a pressure wave in the medium.
2. The device according to claim 1 wherein said superalloy has a cobalt and a nickel content of ogreater than 12% by weight.
3. The device according to claims 1 or 2 wherein said superalloy has a tungsten content of 0.1-15% by weight.
4. The device according to claims 1, 2 or 3 wherein said superalloy has a titanium content of 0.1-5% by weight.
5. A device for producing electrical discharges in an aqueous medium, said device comprising:
a first electrode and a second electrode, each of said electrodes comprised of a superalloy having a nickel content of greater than 8% by weight, said device producing a voltage discharge into the medium when a high electrical voltage is applied to said electrodes, the voltage discharge creating a pressure wave in the medium.
6. The device according to claim 5 wherein said superalloy has a tungsten content of 0.1-15% by weight.
7. The device according to claims 5 or 6 wherein said superalloy has a titanium content of 0.1-5% by weight.
8. A device for producing electrical discharges in an aqueous medium, said device comprising:
a first electrode and a second electrode, each of said electrodes comprised of a thermal-worked steel having a vanadium content of greater than 0.05% by weight and a chromium content of greater than 1% by weight, said device producing a voltage discharge into the medium when a high electrical voltage is applied to said electrodes, the voltage discharge creating a pressure wave in the medium.
9. The device according to claim 10 wherein said thermal-worked steel has a vanadium content of 0.07-3.5% by weight.
10. The device according to claim 10 wherein said thermal-worked steel has a chromium content of 1-15% by weight.
11. The device according to claims 8, 9 or 10 wherein said thermal-worked steel has a tungsten content of 1-10% by weight.
12. A device for producing electrical discharges in an aqueous medium, said device comprising:
a first electrode and a second electrode, each of said electrodes comprised of a stainless steel having a chromium content of greater than 12.5% by weight, said device producing a voltage discharge into the medium when a high electrical voltage is applied to said electrodes, the voltage discharge creating a pressure wave in the medium.
13. The device according to claim 12 wherein said stainless steel has a chromium content of less than 30% by weight.
14. The device according to claims 12 or 13 wherein said stainless steel has nickel component of 2-25% by weight.
15. An electrode for use in a device that produces electrical discharges in an aqueous medium, said electrode comprising:
a superalloy having a cobalt content greater than 8%.
16. The electrode according to claim 15 wherein said superalloy has a cobalt and a nickel content of greater than 12% by weight.
17. The electrode according to claims 15 or 16 wherein said superalloy has a tungsten content of 0.1-15% by weight.
18. The electrode according to claims 15, 16 or 17 wherein said superalloy has a titanium content of 0.1-5% by weight.
19. An electrode for use in a device that produces electrical discharges in an aqueous medium, said electrode comprising:
a superalloy having a nickel content of greater than 8% by weight.
20. The electrode according to claim 19 wherein said superalloy has a tungsten content of 0.1-15% by weight.
21. The electrode according to claims 19 or 20 wherein said superalloy has a titanium content of 0.1-5% by weight.
22. An electrode for use in a device that produces electrical discharges in an aqueous medium. said electrode comprising:
a thermal-worked steel having a vanadium content of greater than 0.05% by weight and a chromium content of greater than 1% by weight.
23. The electrode according to claim 22 wherein said thermal-worked steel has a vanadium content of 0.07-3.5% by weight.
24. The electrode according to claim 22 wherein said thermal-worked steel has a chromium content of 1-15% by weight.
25. The electrode according to claims 22. 23 or 24 wherein said thermal-worked steel has a tungsten content of 1-10% by weight.
26. An electrode for use in a device that produces electrical discharges in an aqueous medium, said electrode comprising:
stainless steel with a chromium content of greater than 12.5% by weight.
27. The electrode according to claim 26 wherein said stainless steel has a chromium content of less than 30% by weight.
28. The electrode according to claims 26 or 27 wherein said stainless steel has nickel component of 2-25% by weight.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A process for the production of soda ash which comprises:
(i) withdrawing an aqueous mining solution containing dissolved sodium carbonate and at least about 1 wt % sodium bicarbonate from an underground alkali source;
(ii) stripping CO2 gas from the withdrawn aqueous mining solution, to convert sodium bicarbonate dissolved therein to sodium carbonate;
(iii) co-crystallizing sodium carbonate monohydrate and sodium sesquicarbonate from the CO2-stripped aqueous mining solution, without co-crystallization of anhydrous sodium carbonate, by evaporation of water at a temperature of at least about 50 C. to form a slurry of crystalline solids in an aqueous liquor;
(iv) recovering crystalline solids from the slurry; and
(v) calcining recovered crystalline solids to produce soda ash.
2. The process of claim 1 which further comprises separating the calcined crystalline solids into at least two different crystal size fractions.
3. The process of claim 1 which further comprises separating large crystals of sodium carbonate monohydrate, by crystal size separation, from small crystals of sodium carbonate monohydrate and from small crystalline sodium sesquicarbonate in the crystalline solids mixture.
4. The process of claim 3 which further comprises calcining the recovered large sodium carbonate monohydrate crystals to produce soda ash.
5. The process of claim 1 wherein the alkali source is selected from the group consisting of trona, nahcolite and wegscheiderite.
6. The process of claim 1 wherein the aqueous mining solution contains a total alkali content, expressed as Na2CO3, of sodium carbonate and sodium bicarbonate of at least about 8 wt % Na2CO3.
7. The process of claim 6 wherein the aqueous mining solution contains at least about 6 wt % sodium carbonate and from about 2 wt % to about 8 wt % sodium bicarbonate dissolved therein.
8. The process of claim 6 wherein the aqueous mining solution further contains sodium chloride dissolved therein, in an amount of up to about 8 wt %.
9. The process of claim 1 wherein the CO2 stripping step is operated at a temperature of from about 50 C. to about 140 C.
10. The process of claim 1 wherein CO2 gas is stripped from the aqueous mining solution by countercurrent multistage contact of the aqueous mining solution with a water vapor gas stream.
11. The process of claim 10 which further comprises recovering a CO2-rich gas from the CO2 stripping step, by condensing and separating water from a CO2-containing exit gas stream from the CO2 stripping step.
12. The process of claim 1 which further comprises concentrating the withdrawn aqueous mining solution, prior to the co-crystallization step, by evaporation of water at a temperature of at least about 50 C., without crystallization of sodium carbonate or sodium bicarbonate dissolved therein.
13. The process of claim 12 wherein the concentration step and CO2 stripping step are carried out as continuous sequential operations in which the CO2 stripping step is carried out before the concentration step.
14. The process of claim 13 wherein CO2 gas is stripped from the aqueous mining solution by countercurrent multistage contact of the aqueous mining solution with a water vapor gas stream from the concentration step.
15. The process of claim 12 wherein the concentration step and CO2 stripping step are carried out as a single step.
16. The process of claim 1 wherein the CO2 stripping step and the co-crystallization step are carried out in a single vessel.
17. The process of claim 1 wherein the co-crystallization of sodium carbonate monohydrate and sodium sesquicarbonate is carried out at a temperature of about 70 C. to about 100 C.
18. The process of claim 1 wherein sufficient CO2 is stripped from the aqueous mining solution to provide, in the subsequent co-crystallization step, a mixture of crystalline sodium carbonate monohydrate and crystalline sodium sesquicarbonate having a total alkali content in which sodium carbonate monohydrate is at least about one-quarter of the total alkali content in the crystallized solids.
19. The process of claim 18 wherein the mixture of crystalline sodium carbonate monohydrate and crystalline sodium sesquicarbonate has a total alkali content in which sodium carbonate monohydrate is at least about one-half of the total alkali content in the crystallized solids.
20. The process of claim 12 wherein sufficient CO2 is removed from the aqueous mining solution during the CO2 stripping and concentration steps to provide, in the subsequent co-crystallization step, a mixture of crystalline sodium carbonate monohydrate and crystalline sodium sesquicarbonate having a total alkali content in which sodium carbonate monohydrate is at least about one-quarter of the total alkali content in the crystallized solids.
21. The process of claim 20 wherein the mixture of crystalline sodium carbonate monohydrate and crystalline sodium sesquicarbonate has a total alkali content in which sodium carbonate monohydrate is at least about one-half of the total alkali content in the crystallized solids.
22. The process of claim 1 wherein sufficient CO2 is stripped from the aqueous mining solution to convert at least about 10% of the sodium bicarbonate in the aqueous mining solution to sodium carbonate prior to co-crystallization of sodium carbonate monohydrate and sodium sesquicarbonate.
23. The process of claim 1 wherein sufficient CO2 is stripped from the aqueous mining solution to convert at least about 20% of the sodium bicarbonate in the aqueous mining solution to sodium carbonate prior to co-crystallization of sodium carbonate monohydrate and sodium sesquicarbonate.
24. The process of claim 1 which further comprises introducing the soda ash into an aqueous medium to recrystallize the soda ash as sodium carbonate monohydrate, recovering the crystalline sodium carbonate monohydrate, and calcining the recovered sodium carbonate monohydrate to produce a dense soda ash product.
25. The process of claim 1 which further comprises introducing the soda ash into an aqueous suspension containing crystalline sodium carbonate monohydrate as a sole stable solid phase in equilibrium with the aqueous liquor of the suspension, to effect solubilization and conversion of the soda ash into crystalline sodium carbonate monohydrate, recovering crystalline sodium carbonate monohydrate from the suspension, and calcining the recovered sodium carbonate monohydrate to produce a dense soda ash.
26. The process of claim 1 which further comprises converting the soda ash to sodium carbonate monohydrate in a hydrator and thereafter calcining such sodium carbonate monohydrate to produce a dense soda ash.