SE427550B - SET TO MAKE HYDROCHLIC ACID - Google Patents

Description

7810526-9 10 10 25 25 25 35 35 2 This silica waste, although normally considered inert, is far more reactive to high temperature alkaline materials than the ground quartz used in the failed method already mentioned, and furthermore, this waste material is substantially non-crystalline and the particles have a very low mass, so that they exert a much less abrasive effect if they are carried in the air stream used to advance the water vapor in the pyrohydrolysis of calcium chloride. Furthermore, the silica waste has a large inner surface (porosity), while the quartz crystals are active only on the outer surface.

The ground quartz (less than 0.074 mm) according to the 2 to 1.0 m2 / g. The silica residues from acid processes, which originate from known processes, had a specific surface area of about 0.5 m from acid treatment of anorthosite (ground to less than 0.074 mm) or clay, on the other hand, have a specific surface area of at least 20 m2 / g and usually of 30 to 60 m2 / g depending on the origin of the silicon-containing materials treated and the conditions used in the acid attack.

Specific surface area / g and particle size are of course parameters, which are in a certain relation to each other.

Normally, silica residues from acid processes are difficult to wash and they must be carefully neutralized for risk-free disposal. The present process eliminates the need for complete washing and neutralization.

It has been found that CaCl 2 can be pyrohydrolyzed to a very high degree, eg 90% or more, very rapidly or at a lower temperature than when pyrohydrolyzing in the presence of ground quartz. According to the present invention, the process for producing HCl involves heating calcium chloride with a molar excess of SiO 2 having a specific surface area of at least 15 m 2 / g at a temperature above 600 ° C in the presence of water vapor. The process temperature should suitably not be much above 100 ° C, as this increases the equipment and energy requirements. Depending on the temperature, the specific surface area of the silica and on the excess water vapor used, it is usually possible to provide a version of CaCl 2 to HCl in a process time of 20 to 100 minutes in a static bed and faster in a fluidized bed.

In a suitable commercial process, a mixture of calcium chloride and active silicon-containing waste of the specified type is briquetted and reacted with a stream of water vapor in a fluidized bed reactor or the material is passed through a tunnel, a rotary kiln or other type of kiln. The molar ratio of CaCl2: SiO2 in the mixture is usually in the range 0.25- 0.90, and 0.90 is preferred for thermal economy reasons. A normal residence time of the material at the reaction temperature is 30 minutes and the temperature can be adjusted to achieve at least 90%, preferably 95% conversion of calcium chloride to HCl. Alternatively, the residence time of the CaCl 2 / active SiO 2 mixture at the reaction temperature can be controlled relative to a predetermined reaction temperature to achieve a predetermined percentage conversion or a predetermined HCl / H 2 O ratio in the product gas.

It has been found that the product in the reaction between CaCl 2 and SiO 2 is alpha-CaSiO 3, which is formed in a very porous form and can be used as thermal insulation at temperatures up to its melting point (about 150,000). Its usefulness for these and other purposes depends on the amount of free SiO2 present, which in turn depends on the molar excess of SiO2 used in the process.

In a series of tests, the following results were obtained, when waste of CaCl2 / active SiO2 in briquetted form was heated in a furnace with glow sticks in an atmosphere saturated with water vapor. 7810526-9 N o.m @ N H.Nm | . | 1 uooom = mq ow.o = <HH «~> <N ~. @ Mm, @ N wH.o m.NH uoooo fl = n« m ~ .o = N HH «u> <+ N @. ~ @ M . ~ m @@. H o.mH uooow = mq mN.o = = N ~. «m o. @ m« mH @. ~ H o ° oom_ = NN mN.o = = N H.wm o. « m «« .o @. ~ H uoooo fl = m «m ~ .o = = _ Qmmw N w. @ m o.« m «oo NN ~ uooo fi ñ: Ne nq m ~ .o .w. <w «~ @ w> ~ 0 ~ u> fl uwø fi umw Nm N No N wo N» ewa UNU ^ »HWH ° avmmw mo _ Nm | ouhm N | ux«> wouwuwum> mw> Hm: <wc fi: Eum> ma = omo Hm fl umuwâ fi Qåümëß 1o_ 15 20 25 30 35 7810526-'9 5 Waste A is active silica waste, from digestion of anorthosite with hydrochloric acid in the presence of calcium and fluoride ions, as described in SE PA 7810527-7.

Waste B is active silica waste, which results from the digestion of kaolin with sulfuric acid for the extraction of alumina material.

In contrast to the almost complete conversion of CaCl 2 to hydrochloric acid under the conditions set forth above, it was found that when a mixture of NaCl and waste A in a molar ratio of 0.25 was heated for 60 minutes at temperatures of 900-1100 ° C in the presence of a stream of wet air, the conversion of NaCl was only 22-32%.

The process of the present invention is an inexpensive and convenient way to produce hydrochloric acid and to dispose of calcium chloride waste. It is particularly suitable for the regeneration of hydrochloric acids in processes of the kind described in SE PA 7810527-7, according to which calcium chloride and active silica waste are formed as a result of the digestion of silicon-containing mineral with hydrochloric acid. In another series of experiments, silicon-containing residues obtained by acid treatment of anorthosite as described in SE PA 7810527-7 were heated in the presence of water vapor with crude CaCl 2 obtained by heating to dryness a portion of the process liquid used ( after precipitation of AlCl3). The crude calcium chloride MgCl 2, 8% FeCl 3 and 1% The degree of conversion was compared with the results, containing approximately 10% TiCl 3. obtained when heating finely ground quartz (less than 0.074 mm) with CaCl2.

The results of these tests are summarized in Table 2, which shows that the conversion obtained by reaction of resin with CaCl2 can be achieved in the same treatment time by reaction between anorthosite residues with crude CaCl2 at a temperature which is about 100 ° C lower.

Due to the known advantages of fluidized bed reactors, this type of process was tested in the laboratory. A vertical tube with a diameter of 3.8 cm 7810526-9 10 6. was heated from the outside to 600-1000 ° C. The bed was filled with 50 g of briquettes of calcium chloride-silica residues measuring 20 x 65 mesh, the silica residues having a specific fl consisting of nitrogen containing 0.6 to 3.6% by weight of water and flowing at a rate of 25 liters per minute.

The observed equilibrium constant corresponded reasonably well to Kp, which was calculated from thermodynamic data.

The reaction at 800 ° C was completed in less than 30 minutes.

The estimated heat demand - based on solid, wet material, was estimated at 550 ~ 750 x 106 cal / ton dry calcium chloride, which is clearly favorable. 7810526-9 mm o.m ~ ~. ~ M.m ~. uoooom = mm mm.o = = mm m.m ~ m.H m.m ~ uooom = mm mm.o =. = Hm Hm ~ mm om ~ uooøm = mm mm.o = = mm mm ~ ~. ~ M mm ~ uooom = mm mm.o = = mm m.mH mm ~ o.- oooom = mm mm.o = = ONIN wUh fl m / X o «.mH ~, mw m.mm uooom ._ mm m ~ .o .mmußu = w9bQo ~ | mm om ~ mo m.- uøooom = mm mm.o = = mm mm ~ mo mm ~ uoøom = mm «mo = =« m mm ~ mm. ~ mH ~ uooom = mm «mo = = Hm mm ~ H.« m mo ~ uoooß = mm «~ .o = = mm mm ~ mm mH ~ uooom = om« mo = = mm oo ~ m. ~ m m.mm uooom = mm «mo = = mm mm ~ mH ~ m.« m uooom = mm «mo = = umwcw fi mm m.mH mm ~ m.mm uooom = mm mm.o | @ ~ ° ~ mm = ONEN ÜOUWHUQW om m.mH«, m ~ «.« ~ oooom: ma mm wæuwwh fl ouvæn ... w N HU N mo N mEmu wmu No fl m m0 ä loußm N wouwuwum> m 97234 ws fl câumšwøs m. Ûum fl o fi v mmm fl mwnmuwz N .HHWNQB

Claims (5)

? 8'šÛ526-9 lO 15 PATENTKRAV 1. A process for producing HCl, characterized in that calcium chloride is heated with a molar excess of SiO2 with a specific surface area of at least 15 m2 / 9 at a temperature above 600 ° C in the presence of water vapor. 2. A method according to claim 1, characterized in that the temperature is not higher than 100 ° C. 3. A method according to claim 1, characterized in that the molar ratio of CaCl2: SiO2 varies between 0.25 and 0.90. 4. A method according to any one of claims 1-3, characterized in that a mixture of calcium chloride and silica is briquetted and reacted with a stream of water vapor in a fluidized bed reactor. 5. A method according to any one of claims 1: 4, characterized in that the silica is obtained as a by-product from the extraction of alumina material by acid treatment of silica-alumina-containing starting material. 7810526-9 SUMMARY A method of producing HCl, which means heating calcium chloride with a molar excess of SiO fluidized bed reactor. Silica residues from acid processes and calcium chloride waste can be used to advantage. The by-product CaSiO 3 is also useful for thermal insulation.