MXPA00007569A - Treatment of iron chloride from chlorination dust - Google Patents

Abstract

A process for producing chlorine and iron oxide from iron chloride (which may be generated as a by-product of the direct chlorination of titaniferous ores) comprises the steps of converting ferrous chloride to ferric chloride by reaction with chlorine, separating the solids from the gaseous products, reacting the gaseous ferric chloride with oxygen, condensing unreacted ferric chloride onto iron oxide particles, separating the gaseous products from the iron oxide particles and recycling the iron oxide particles to the oxidation or condensation step.

Description

TREATMENT OF IRON CHLORIDE FROM CHLORIDE DUST DESCRIPTION OF THE INVENTION This invention relates to a process for the production of chlorine and metal oxides from metal chlorides. While the process applies to any metal chloride that is oxidizable to chlorine and to the corresponding metal oxide, it is particularly applicable to iron chloride. Several industrial processes, such as the production of titanium dioxide from titanium tetachloride that result from the direct chlorination of titaniferous minerals, generate large amounts of iron chloride byproduct. The disposal of this iron chloride imposes potential environmental problems and represents an economic loss of chlorine. Depending on the chlorination process, the iron chloride may be present as ferrous chloride, ferric chloride or a mixture of the two. There have been many attempts to produce an economic process to overcome this problem, and these are well summarized in U.S. Patent Specification No. 4994255. A common step in these processes is the reaction of ferric chloride in the vapor phase. with oxygen, for example 2FeCl3 + 1,502? Fe203 + 3 Cl2 At low temperature (600 ° C) where the thermodynamics of this reaction are favorable, the speed is slow and a catalyst is needed, and at higher temperatures (800 ° C-900 ° C) where speed is practical, thermodynamics are unfavorable and the reaction is far from complete. As a result, particularly when operating at such higher temperatures, the gaseous reaction products contain a relatively high proportion of ferric chloride which needs to be separated from the chlorine. British Patent GB-A-2019376 describes a way to achieve this separation by cooling the gaseous product by causing the ferric product to condense on the iron oxide particles. However, in the arrangement shown, there will be a tendency for the ferric chloride to settle on the cooling coils in the condenser vessel. A further problem of the reaction is that there is a tendency for the iron oxide to build up on the walls of the reactor and associated equipment. According to one aspect of the invention, there is provided a process for the production of chlorine and iron oxide comprising the treatment of ferric chloride in the vapor phase with oxygen, at a temperature of 700 to 900 ° C in a reactor of fluidized bed, by continuously recirculating a portion of the bed material from the reactor to the reactor, condensing unreacted ferric chloride in the gas stream, by cooling the iron oxide particles below the condensation point of the ferric chloride and injecting the particles in the gas stream, whereby the ferric chloride condenses on the surface of the iron oxide particles and the particles are carried by the gas stream to a separator, the separated, iron oxide particles coated are recycled to the condensation step or to the reaction step.

The problem of unwanted deposition of ferric chloride is avoided because the ferric chloride does not come into contact with the cooling coils as it does in British Patent 2019376. In this way, a greater amount of ferric chloride can be tolerated without react (and therefore a lower conversion rate). The process can, therefore, be operated at a higher temperature where the kinetics are more favorable and a catalyst is not necessary. The condensation step is preferably carried out in a fluidized bed condenser as described in European Patent EP-A-467441 (US-A-5205350). According to a preferred feature of this invention, the ratio between the recirculation rate of the solid material and the feed rate of the ferric chloride is at least 10: 1.

This high proportion provides a purifying action that prevents the formation of rust on the equipment. The aforementioned chlorination processes are conveniently carried out in a fluidized bed constituted of mineral and coal in the form of coke.

The gaseous products from the process (at 700-1100 ° C), in the case of a titanium mineral such as ilmenite, consist mainly of titanium tetrachloride and iron chloride. The iron chloride can be in the ferrous and / or ferric form, the amount of each one present, is dependent on the conditions in the chlorination reaction. In addition, the finely divided solids, mainly carbon and unreacted titanium dioxide, are elutriated from the fluidized bed and carried in the gas stream. Thus, after proper separation of the titanium tetrachloride, a residue, hereinafter referred to as a chlorination powder, is typically left to consist of approximately 70% iron chloride, 20% carbon, and 5% dioxide of titanium, the rest being small amounts of various chlorides and oxides of other metals such as aluminum, magnesium, manganese, etc. Great difficulties are associated with oxidative chlorination dust. To oxidize the ferrous chloride in the vapor phase, high temperatures have to be used because of their low volatility, and therefore large amounts of energy have to be added.

^^^^ ^ ¡¡¡Problems are intensified by the elutriated material. The separation of these impurities from the iron chloride is impracticable before the oxidation step, and the resulting iron oxide is contaminated. In addition, the carbon will react with the added oxygen in preference to the oxidation of the iron chloride by producing an excessive amount of carbon dioxide which dilutes the recovered chlorine to a degree that is unsuitable for later use without an expensive separation step. In addition, the released energy provides difficulties in the downstream process and is costly to eliminate. Problems due to the presence of carbon and other impurities will be relevant even if the iron chloride is present in the ferric form. The carbon problem is ignored in many of the processes of the prior art. In European Patent EP-A-165543, the content of carbon in the powder is controlled in relation to the amount of iron chloride and in U.S. Patent No. 4,994,255, the coal is removed in a separate step .

An attempt to solve this problem is, however, realized in the JBP Patent CB-A-1517264. In the process described, the ferrous chloride is reacted with oxygen to form ferric oxide and ferric chloride, but insufficient to liberate any substantial amount of chlorine, the gaseous products being treated, after separation of the solid material, to the process of conventional oxidation. Although this reference mentions the problem of excess carbon dioxide, it does not solve this problem because u -the product < Ja-seoso final contains almost equal amounts of chlorine and carbon dioxide. According to a further aspect of the present invention, there is provided a process for the treatment of chlorination powder comprising reacting the powder with chlorine in a recirculating fluidized bed to convert the ferrous chloride to ferric chloride, separating the solids from the gaseous products, and passing the gaseous product to an oxidation reactor to oxidize the ferric chloride to chlorine and iron oxide. When operating it is: The final, final gaseous product that contains only about 22% carbon dioxide can be obtained. The residual solids containing the largest amounts of carbon and unreacted titanium dioxide can be returned for further treatment in the chlorination process. According to a preferred feature, the temperature necessary for the reaction is achieved, by burning a smaller proportion of the carbon in the powder. According to a third aspect of the invention, there is provided a process for the production of chlorine and iron oxide from ferrous chloride-containing material comprising the reaction of the material with chlorine in a recirculating fluidized bed to convert the ferrous chloride to ferric chloride, separating the gaseous ferric chloride from any solid residues, by reacting the gaseous ferric chloride with oxygen at a temperature of about 700 to 900 ° C in a fluidized bed reactor, by continuously recirculating a portion - from the material of the reactor bed back to the reactor, condensing the unreacted ferric chloride in the gaseous stream, by cooling the iron oxide particles below the condensation point of the ferric chloride and injecting the particles into the stream gaseous, with which the ferric chloride condenses on the surface of the oxide particles When the iron particles and the particles are carried by the gas stream to a separator, the separated particles of coated iron oxide are recirculated to the condensation step or to the reaction step. According to a fourth aspect of the invention, there is provided a process for the production of chlorine and iron oxide from ferrous chloride-containing material, which comprises reacting the material with chlorine in a recirculating fluidizing bed to convert the ferrous chloride to ferric chloride, separating the gaseous ferric chloride from any residual solids, condensing the ferric chloride by injecting the iron oxide particles at a temperature below the dew point of the ferric chloride in the gas stream, whereby the Ferric chloride is condensed on the surface of the iron oxide particles, by reacting the condensed ferric chloride with oxygen at a temperature of 700 to 900 ° C in a fluidized bed reactor, by continuously recirculating a portion of the fluidized bed material including a portion of the iron oxide particles from the reactor back to the reactor, and passing the remaining iron oxide particles to a separator, the separated iron dioxide particles being recycled to the condensation step or to the reaction passage. The processes of the invention can be carried out satisfactorily at atmospheric pressure. However, there are advantages to carrying out the processes at higher pressures, for example 2-5 bars above atmospheric pressure. For example, the volume of gaseous products produced will be reduced and therefore the reaction vessels may be smaller. An additional advantage is that less pumping effort will be required to transport the final chlorine product either to store or to recycle the process, particularly where the chlorine is recycled to the ore chlorination process, which normally operates under pressure.

The equipment suitable for carrying out the process of this invention is shown in the attached drawing. As shown, the equipment is constituted by a first stage consisting of the reactor vessel 1, a cyclone separator 2, and the storage vessel 3 for solids, a second stage consisting of a reactor vessel 10, a cyclone separator. 11 and a container 12 for storage of solids, and a third stage consisting of a condenser vessel 20, a cyclone separator 21 and a storage vessel 22 for solids. The chlorine through line 4 and the powder through line 5 enter the vessel 1 where they mix to form a fluidized bed. The temperature inside the container is maintained close to 600 ° C either through external heating or by admission of an adequate amount of oxygen through lines 6 and 7, to cause partial burning of the coke in the powder. The main reactions that take place in vessel 1 are 2FeCl2 + Cl2? 2FeCl3 [Some of the other oxides in the powder are also chlorinated by a similar reaction] 2C + 1.502? CO + C02 CO + H0Z? C02 The solid and vapor products pass into the cyclone 2. The solid products pass into the storage container 3 from which they are recirculated to the fluidized bed of the container 1 or are removed. The steam products pass to the second reactor vessel 10 which is charged at the start with iron dioxide particles, where these are mixed with the oxygen admitted through the line 13 to form a fluidized bed at a temperature close to 800 ° C. The main reaction that takes place in the container 10 is 2FeCl3 + 1,502? Fe203 + 3C12 The solid and gaseous products pass into the cyclone 11. The solid products pass into the storage container 12 from which they are recirculated to the fluidized bed in the container 10, go to the container 20 or are eliminated. The vapor products pass to the condenser vessel 20 (described in more detail below) containing iron oxide particles where they are cooled to a temperature in the range of 100-250 ° C, such that the residual ferric chloride is deposited on the iron oxide particles. The solid and gaseous products pass into the cyclone 21. The solid particles pass into the storage container 22, from which they are recirculated to the fluidized beds in the containers 10 and 20 or are removed. The gaseous product consisting of chlorine, carbon dioxide and oxygen is recirculated again with the containers 1 and 20 and / or recirculated back to the ore gner. As mentioned above, the condenser vessel 20 contains iron oxide particles. The chlorine is passed into the base of the vessel at a rate suitable for fluidizing the particles, sufficiently for them to flood a gas inlet 25 through which the vapor products from the cyclone 11 enter the vessel 20. The products steam and iron oxide form a recirculating fluidized bed at about 150 ° C, this temperature being maintained by means of cooling coils 26 in the base of vessel 20, so that the ferric chloride is condensed on the oxide particles of iron. By placing the cooling coils 26 below the gas inlet 25, the condensation of the ferric chloride on the cooling coils is prevented. The condenser is described in more detail in European Patent EP-A-467441. In an alternative arrangement, the condenser vessel 20 can be inserted between the first and second reactor vessels 1 and 10, such that the ferric chloride is deposited on the iron oxide particle and then oxidized to iron oxide and chlorine. The result is a build-up of iron oxide layers that lead to larger amounts that are more easily handled. The invention is illustrated by the following example.

EXAMPLE The reactor system was preheated by feeding oxygen at approximately 500 ° C into the container 1. Dust from a mineral greaser comprising 75% ferrous chloride, 13% carbon, 5% titanium dioxide and 7% other chlorides (mainly aluminum and magnesium) and oxides, was admitted with chlorine into the vessel 1 to form a fluidized bed. The flow of unheated oxygen was adjusted to provide sufficient burn of the coal, to give a reaction temperature in the state of rest in the container 1 close to 600 ° C. The steam product produced comprised 81% ferric chloride, 11% carbon dioxide, 3% carbon monoxide, 3% aluminum chloride and 2% other chlorides. The solid product comprised 55% carbon, 26% titanium dioxide, 10% magnesium chloride and 9% other chlorides and oxides. The temperature at rest in the container 10 was close to 800 ° C due to the exothermic nature of the reaction that takes place. The vapor product from the container 10 comprised 59% chlorine, 19% ferric chloride, 17% carbon dioxide, 4% zirconium chloride and 1% oxygen. The solid product comprised 96% iron oxide, 3% aluminum oxide, and 1-% niobium, phosphorus and magnesium oxides. The temperature in the resting state of the condenser vessel 20 was 153 ° C. The vapor product from the container 21 comprised 76% chlorine, 22% carbon dioxide, 2% oxygen and a minor amount of hydrogen chloride. The solid product of the container 22 comprised 48% iron oxide, 41% ferric chloride, 8% zirconium chloride and 3% of other minor compounds.

Claims (9)

1. A process for producing chlorine and iron oxide, which comprises the treatment of ferric chloride in the vapor phase, with oxygen at a temperature of 700 to 900 ° C in a fluidized bed reactor, which continuously recirculates a portion of the material of the bed from the reactor back to the reactor, condensing unreacted ferric chloride in the gas stream, by cooling the iron oxide particles below the dew point of the ferric chloride and injecting said particles into the gas stream, with As the ferric chloride condenses on the surface of the iron oxide particles and the particles are carried by the gas stream to a separator, the separated iron oxide particles coated are recycled to the condensation step or to the passage of reaction.

2. A process for the treatment of chlorination powder, which comprises reacting the powder with chlorine in a recirculating fluidized bed, to convert the ferrous chloride to ferric chloride, • sana-C separating the solids from the gaseous products, and passing the gaseous product to an oxidation reactor, to oxidize the ferric chloride to chlorine and iron oxide.

3. A process for producing chlorine and iron oxide from ferrous chloride-containing material, which comprises reacting the material with chlorine in a recirculating fluidized bed, to convert the ferrous chloride to ferric chloride, preparing the gaseous ferric chloride of any solids by reacting the gaseous ferric chloride with oxygen at a temperature close to 800 ° C in a fluidized bed reactor, by continuously recirculating a portion of the bed material from the reactor back to the reactor, condensing the unreacted ferric chloride in the reactor. gas stream, by cooling the iron oxide particles below the dew point of the ferric chloride and injecting the particles into the gas stream, whereby the ferric chloride condenses on the surface of the oxide particles of iron, and the particles are carried by the gas stream towards a separated or, the separated coated iron oxide particles are recycled to the condensation step or to the reaction step.

4. A process for producing chlorine and iron oxide from the material containing ferrous chloride, which comprises reacting the material with chlorine in a recirculating fluidizing bed to convert the ferrous chloride to ferric chloride, separating the gaseous ferric chloride from any solids The ferric chloride is condensed by injecting iron oxide particles at a temperature below the dew point of the ferric chloride within the gas stream, with which the ferric chloride condenses on the surface of the oxide particles. iron, by reacting the ferric chloride condensed with oxide at a temperature of 700 to 900 ° C in a fluidized bed reactor, by continuously recirculating a portion of the bed material including a portion of the iron oxide particles from the reactor back to the "reactor, and passing the remaining particles of iron oxide towards a separ The separated particles of iron oxide are recycled to the condensation step or to the reaction step.

5. A process according to claim 1 or 3 wherein the ratio between the recirculation rate of the solid material and the feed ratio of the ferric chloride to the oxidation reactor is 1: 1: 1 Trienos.

6. A process according to claim 1 or 3 in which the condensation step is carried out in a fluidized bed condenser.

7. A process according to claim 2, 3 or 4 wherein the conversion step is carried out at a temperature of 550 to 700 ° C.

8. A process according to claim 2, 3, 4 or 7 in which the temperature necessary for the conversion step is reached by burning a proportion of the carbon in the powder.

9. A process according to any preceding claim that is carried out above atmospheric pressure.