Chemistry of inorganic compounds – Halogen or compound thereof – Binary compound containing metal
Reexamination Certificate
2001-11-02
2003-02-25
Silverman, Stanley S. (Department: 1754)
Chemistry of inorganic compounds
Halogen or compound thereof
Binary compound containing metal
C423S103000, C423S147000, C423S163000, C423S197000, C423S489000, C423S490000, C423S493000, C423S498000, C423S499400
Reexamination Certificate
active
06524546
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a continuous process for the reaction of solid metal carbonates, bicarbonates and oxides with a hydrogen halide gas in a true fluidized state with the production of a solid having a composition composed of the metal and the halide ion. The invention relates more particularly to the manufacture of calcium chloride, magnesium chloride, zinc chloride and chlorides of iron in an energy efficient non-aqueous medium using conventional or true fluidized bed technology and counter current flow generally but not exclusively between the solid flowing downward by gravity and the upward moving gas. The process is unique in that it is basically self-controlling, that is, the feed rate of the solids and gas and the design of the vessel control the production rate and degree of conversion of the solids. No elaborate controls are required, little or no recycling of reaction gas or product are necessary since the counter current aspect of the process is such that complete conversion of the solid is achieved, the exiting gas is essentially free of the hydrogen halide component of the feed gas, and the particle size of the product remains essentially the same as the original solid feed, although some finer particles are produced.
BACKGROUND OF THE INVENTION
Halogens, with some exceptions, chemically behave generally in the same manner. The reactions of hydrochloric acid therefore are similar in many respects to those of the acids of the other halogens. Anhydrous hydrogen chloride is relatively inert because of the high kinetic barrier to fission of the H—Cl bond. Anhydrous hydrogen chloride however has an extremely high affinity for water, even if the water is in the vapor or gaseous state, which was demonstrated as early as 1860 by William Odling and reported in Vol. 1 of “The Chemical News”. This is very important when the reactions in this teaching are considered. It is contemplated that the industrial gases employed in the teaching will not be anhydrous and will contain some water vapor and therefore will be significantly more reactive because of the effect of this moisture on assisting the fission of the H-Cl bond. In addition when these acid reactions proceed, water, whether gas or vapor, will be liberated and increase the reaction rate.
CaCO
3
+2HCL
(g)
→CaCl
2
+CO
2
↑+H
2
O
(g)
&Dgr;H=−8.82 kcal/mol
The reaction of the metal compounds in the instant invention all produce water in the gaseous or vapor phase and because the reactions are exothermic and the heat exchange between solid and gas in a true or conventional fluidized bed is very efficient, condensation of this water is substantially unlikely in the process to be described.
RELATED ART
For many years calcium chloride was primarily produced as a by-product of soda ash manufacture by the Solvay Process. In this process the recovery of (NH
3
) Ammonia from the process liquors containing ammonium chloride is economically essential. This is accomplished by adding milk of lime Ca(OH
2
) to the process liquors thereby producing calcium chloride.
2NH
4
Cl+Ca(OH)
2
→CaCl
2
+2NH
3
(g)+2H
2
O(g)
The calcium chloride liquors were then clarified, concentrated by evaporation, crystallized and melted to produce flake calcium chloride. With the demise of soda ash production by the Solvay Process in the USA, due to the mining of the Trona in Wyoming, significant production of calcium chloride was lost. The last remaining Solvay Process plant in North America at Amherstburg, Ontario in Canada has now been shut down for the same reason. Large tonnage is also produced through recovery from saline solutions by the Dow Chemical Companies in Michigan.
A significant percentage of USA production has now been replaced by the reaction of hydrochloric acid with calcium carbonate to produce a calcium chloride solution. The solutions produced require concentration by evaporation and crystallization processes to produce crystals of calcium chloride and melting (782° C.) of the crystals to produce flake calcium chloride. Both of these operations are energy and capital intensive which in a rising energy-cost environment significantly increases the cost of production. The hydrochloric acid is produced in large quantities as a byproduct from chlorinated hydrocarbon production and off gases from chlorine production and other operations.
Loots and Van Goftberg teach in Canadian patent CA 2,038,021 three methods for producing calcium chloride, two of which are identical in almost all respects, from anhydrous gases containing hydrogen chloride, chlorine, and mixtures of these gases. The first method consists of a number of fixed beds of CaCO
3
, or Ca(OH)
2
or CaO in series and through which the anhydrous gas or mixture of anhydrous gases are passed for a period of time until the conversion to calcium chloride is complete in the first bed in the series. This bed is then removed from the series to be unloaded and recharged, while the next bed in the series becomes the first in the series. While the discussion of the process indicates that it is possible in principle for reaction (page 1, line 10) CaO+HCl→CaCl
2
+H
2
O to proceed at gas and bed ambient temperature, the inventors then state that (page 2, line 20) it will not be possible to achieve the desired bed temperatures under these conditions, which leads one to the conclusion that the reaction will not proceed without heat input to the bed and gas. Since reaction (1) outlined in the teaching has thermodynamically the highest &Dgr;H it is also presumed that none of the other reactions involving anhydrous hydrogen chloride (HCl)
g
or chlorine (Cl
2
)
g
with calcium hydroxide (Ca(OH)
2
) or calcium carbonate CaCO
3
will proceed at ambient temperature. Some of the major disadvantages of this process are that significant labor would be required to load and unload the reactors with raw materials and finished product. It was disclosed on page 7, lines 27-28 that for the calcium carbonate hydrogen chloride test that the finished product was a hard plug which required crushing. This is a major disadvantage since removal from a commercial vessel would require significant labor and crushing would produce large amounts of undesirable fines.
Another disadvantage is that the higher-pressure drop across the bed requires more energy to increase the gas pressures. In addition, more expensive, heavier walled vessels are required because of the higher pressure, increasing the capital investment.
A further disadvantage is determining when full conversion to calcium chloride is attained since the product is contained in a closed pressurized vessel. Still another disadvantage is that a large number of vessels are required to insure continuous operation while one or more vessels are being loaded and unloaded, adding considerably to capital cost.
Two additional embodiments of the Loots and Van Gottberg invention both somewhat alike and described as a “fluidized bed”, teach a process in which either calcium carbonate, oxide, or hydroxide are contained in a reaction vessel or riser and reacted with hydrochloric acid and or chlorine from which the spent gas and the finished calcium chloride (entrained in the gas stream) is withdrawn. A cyclone or other separating devise is employed to remove the finished product from the gas. Part of the gas stream is recycled to provide reheat to the feed gas. Particle size is in the rage of 50 to 300 microns. This is a very fine product that has little or no commercial value and requires melting (782° C.) and flaking or prilling if it is to be sold as a solid. Significant capital investment and energy use is required to accomplish this by way of high-pressure steam generation and flakers or prill towers.
Both processes are described as a “fluidized process”, a term which is often used to describe spouting beds similar to those produced in a “Wurster” type apparatus or a fast moving gas stream containing or conveying entrained solids, or to describe a dense phase gas agitated bed in
Cochran Keith D.
Holt Timothy G.
Rigby William J.
Nave Eileen E.
Rigbv Willaim J.
Silverman Stanley S.
LandOfFree
Process for making calcium chlorides does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for making calcium chlorides, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for making calcium chlorides will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3173005