AU8538398A

AU8538398A - Device for carrying out gas reactions, use of the device and process for operating the device

Info

Publication number: AU8538398A
Application number: AU85383/98A
Authority: AU
Inventors: Werner Auel; Helmut Elkendorf; Jurgen Muller
Original assignee: Metallgesellschaft AG
Current assignee: GEA Group AG
Priority date: 1997-06-25
Filing date: 1998-06-16
Publication date: 1999-01-19
Also published as: WO1999000184A3; EP1024892A2; DE19727038C1; CA2294947A1; WO1999000184A2

Description

Translation of PCT/EP98/03618 Apparatus for Carrying Out Gas Reactions, Use of the Apparatus and Method of Operating the Apparatus Description This invention relates to an apparatus for carrying out gas reactions, comprising a reaction space which is closed at the bottom by a container filled with water and at the top by a fume hood, where a first gas stream is introduced through nozzles into the reaction space and a second gas stream is introduced through nozzles into the water, where the reaction space has a constriction in whose vicinity the nozzles dis posed in the reaction space are provided, and where the gase ous reaction products are discharged from the fume hood. Each gas stream may consist of one or several gaseous substances. This invention furthermore relates to the use of the appara tus and to a method of operating the apparatus. An apparatus as described above is known from the publication by Kimmel and Wiese, Chemie-Anlagen + Verfahren, 1977, issue 7, pages 56 to 57 and 66. The publication proposes to use the known apparatus for the combustion of exhaust gases which contain noxious substances and/or together with air form an explosive mixture. It has turned out that the operational -2 safety of the known apparatus requires improvement, as the combustion reactions performed in the known apparatus do not always take a quantitative course, and furthermore the inlet nozzles for the combustion air, which are disposed in the re action space, are attacked by corrosion. It is the object underlying the invention to improve and de fine the known apparatus as well as the conditions for oper ating the same such that the gas reactions taking place within the same take a quantitative course, and that the noz zles disposed in the reaction space are protected against corrosion. The object underlying the invention is solved in that the nozzles disposed in the reaction space are inclined towards the water surface and have an angle of inclination of 12 to 160 with respect to the horizontal, that the diameter of the reaction space in the vicinity of the constriction is reduced by 20 to 30 %, and that the constriction in the reaction space is disposed such that 20 to 30 % of the height of the reaction space lie between water surface and constriction, and 80 to 70 % of the height of the reaction space lie be tween constriction and fume hood. By means of this combination of features it is advantageously achieved that the gas streams are mixed thoroughly, so that the reactions taking place between them take a quantitative course. Since the nozzles of the reaction space are inclined in the direction of the water surface, the reactions between the individual gaseous substances start directly above the water surface. The constriction of the reaction space effects a very good vortexing of the gaseous reactants, where the re duction of the diameter of the reaction space by 20 to 30 %, which is caused by the constriction, on the one hand effects a good vortexing of the reactants and on the other hand only a comparatively small increase of the flow rate of the gase- -3 ous reactants, so that the reaction space on the whole has optimum flow and mixing conditions. Due to the fact that be tween the constriction and the fume hood the major part of the volume of the reaction space is disposed, the quantita tive course of the gas reactions is ensured, as the part of the reaction space disposed above the constriction ensures a dwell time of the reactants which is necessary and sufficient for the quantitative course of the reaction. Even in the fume hood disposed above the reaction space there still takes place a secondary, although minor, reaction of the gaseous reactants. In particular when using the apparatus for the combustion of exhaust gases containing noxious substances, which exhaust gases have a comparatively low calorific value and a variable content of noxious substances, it has turned out to be advan tageous in accordance with the invention that in the reaction space and/or in the container filled with water fuel nozzles are provided, through which a gaseous auxiliary fuel is blown into the reaction space and/or into the water. Hence it is possible to always maintain a high enough combustion tempera ture in the apparatus and to prevent the combustion reaction from coming to an end. As gaseous auxiliary fuel natural gas is preferably used. By blowing the auxiliary fuel into the water, a high enough combustion temperature is adjusted di rectly above the water surface, which promotes the quantita tive course of the reaction. Although the nozzles disposed in the reaction space consist of the usual heat- and corrosion-resistant materials, corro sion problems are nevertheless frequently observed. The cor rosion problems occurring at the nozzles disposed in the re action space for introducing the first gas stream and at the fuel nozzles can, however, advantageously be avoided in ac cordance with the invention in that the nozzles disposed in -4 the reaction space consist of titanium or an alloy having a high titanium content. In accordance with the invention it is provided that the ap paratus is used for the combustion of gases and exhaust gases which contain gaseous as well as dust-like noxious substances and/or together with air form an explosive mixture. The com bustion air or the combustion air enriched with oxygen is in troduced as first gas stream through nozzles into the reac tion space, and the gas or exhaust gas is introduced as sec ond gas stream through nozzles into the water. When the gases and exhaust gases have a low calorific value, an auxiliary fuel, preferably natural gas, is blown into the reaction space and/or into the water through fuel nozzles. It was sur prisingly found out that dust contained in the gases and ex haust gases does not impede the combustion process, as it is washed out by the water. To prevent the dust from being en riched in the water, it must be separated from the water con tinuously or discontinuously by means of filtration. The gases and exhaust gases burnt in the apparatus may contain CO, hydrocarbons, halogenated hydrocarbons,

H

2 S, CS 2 , COS, hydrogen and/or minor amounts of chlorine as gaseous noxious substances. It was observed that the combustion of the gases and exhaust gases takes a quantitative course, which means that the combustion gases leaving the fume hood do no longer contain the gaseous noxious substances contained in the gases and exhaust gases, and that the auxiliary fuel has been con verted into water and CO 2 for 100 %. The amount of the com bustion air is chosen such that with respect to all oxidizing compounds there is a surplus of oxygen of 0.2 to 0.4. The lower part of the inventive apparatus designed as water bed reliably protects the nozzles disposed below the water sur face against a flashback, which in the known combustion plants must be prevented by means of additional measures (flame guard) in particular when small amounts of gas and/or highly explosive gasoues substances are burnt in the plants.

-5 For the case that the gases and exhaust gases supplied to the combustion contain noxious substances that react with water, such as HCl, S03 or NH 3 , it is possible that these noxious substances adsorbed in water are continuously or discontinu ously separated from the water; for instance, so 3 may be pre cipitated as calcium sulfate, HCl may be neutralized, and NH 3 may be removed by distillation. In accordance with the invention it is furthermore provided that the apparatus is used for carrying out chemical gas re actions. It was surprisingly found out that due to the inven tive combination of features the apparatus can also be used as chemical reactor; for instance, hydrogen sulfide can be reacted with air to form sulfur dioxide. In the apparatus, there can also be effected the addition of chlorine or bro mine to lower olefins in the gas phase with a very good yield. In particular when the apparatus in accordance with the invention is used for carrying out chemical reactions, the materials of the inner walls and the inlet nozzles must be adapted to the conditions of the chemical process taking place in the apparatus. In so far, corrosion problems should be observed, which are caused by the used gaseous substances or the reaction products. The object underlying the invention is finally solved by a method of operating the apparatus, where the mean dwell time of the gaseous substances in the reaction space as well as in the fume hood is 1 to 5 s, and the mean gas velocity in the reaction space is 2 to 6 m/s, where the nozzles disposed in the reaction space are operated with an excess pressure of 35 to 45 mbar, and the nozzles disposed below the water surface are operated with an excess pressure of 45 to 55 mbar. It was found out that the reactions carried out in the apparatus take a quantitative and trouble-free course under the inven tive operating conditions. Even possibly occurring deflagra tions do not jeopardize the operational safety of the appara- -6 tus when the inventive operating conditions are maintained. The excess pressure to be maintained during the operation of the nozzles refers to the gas pressure in the reaction space and to the pressure exerted by the water column, and in the case of possible deflagrations it also prevents the flashback of gases, reaction products and water into the nozzles and the supply systems for the individual gas streams connected with the nozzles. The subject-matter of the invention will subsequently be ex plained in detail with reference to the drawing, which shows the longitudinal section of the apparatus in accordance with the invention. The apparatus in accordance with the invention consists of the reaction space 1 with the diameter dR and the height hR. The reaction space 1 has a heat-resistant and corrosion resistant inner wall, whose material is selected according to the conditions existing in the reaction space 1. For in stance, the temperature in the reaction space 1 during the combustion of gases and exhaust gases is 800 to 1000 *C with a surplus of oxygen in the gaseous reaction mixture. The re action space 1 is closed at the top by the fume hood 3 from which the hot, gaseous reaction products 16 are discharged through the exhaust gas line 4. The inner wall of the fume hood 3 and the exhaust gas line 4 is designed corresponding to the inner wall of the reaction space 1. The heat content of the hot, gaseous reaction products 16 is utilized in an expedient way, which may be effected in a recuperator or in a waste heat boiler and is not represented in the drawing. The reaction space 1 is closed at the bottom by the container 2, which is filled with water. The reaction space 1 has a constriction 8, which reduces the diameter dR of the reaction space 1 by 20 to 30 %. In the vi cinity of the constriction 8 the diameter dE thus amounts to 7 80 to 70 % of the diameter dR of the reaction space 1. The constriction 8 should expediently have surfaces inclined with respect to the horizontal, as this is schematically illus trated in the drawing. The constriction 8 divides the reac tion space 1 into two parts, and it is arranged such that 20 to 30 % of the height hR of the reaction space 1 lie between the water surface 9 and the constriction 8, and 80 to 70 % of the height hR of the reaction space 1 lie between the con striction 8 and the fume hood 3. The container 2, which may have a flat or funnel-shaped bot tom 17, is filled with water. When the water takes up dust or gaseous noxious substances from the second gas stream, part of the water is discharged from the container 2 through line 15 and purified by corresponding processes, which is not rep resented in the drawing. At the height of the water level 9, fresh water or purified water is supplied to the container 2 through line 14, so that a constant water level can always be maintained in the container 2. The supply of water is regu lated according to the principle of communicating vessels, so that even variations in the water content of the container 2 are safely compensated. As the gaseous substances supplied by means of the water take up water and discharge the same from the container 2, a completion of the water content of the container 2 is necessary in any case. In the container 2, gas inlet nozzles are provided, which are preferably designed as nozzle tubes 11, and to which the sec ond gas stream is supplied through line 10. As second gas stream, gases and exhaust gases are used, which are burnt with the first gas stream or reacted. The second gas stream is distributed in the water by means of the nozzle tubes 11, rises in the water and through the water surface 9 enters into the reaction space 1. In the vicinity of the constric tion 8 nozzles 7 are provided, to which the first gas stream is supplied through line 6, and through which the first gas stream is introduced into the reaction space 1. The nozzles 7 are inclined towards the water surface 9 and have an angle of inclination of 12 to 160 with respect to the horizontal, so that the gas jet emerging from the nozzles 7 is directed onto the water surface 9. The nozzles 7 preferably consist of an alloy with a high titanium content. In particular when exhaust gases and gases of low calorific value should be burnt in the inventive apparatus, it is nec essary to supply a gaseous auxiliary fuel, preferably natural gas, to the apparatus, in order to maintain the required com bustion temperature and ensure a quantitative combustion of all noxious substances contained in the gases and exhaust gases. The gaseous auxiliary fuel may be introduced both into the reaction space 1 and into the container 2 filled with wa ter, where the introduction of the auxiliary fuel into the container 2 turned out to be particularly advantageous. In the container 2 fuel nozzles are provided, which are prefera bly designed as nozzle tubes 13, and to which the auxiliary fuel is supplied through line 12. Mixing the auxiliary fuel with the second gas stream is already effected in the water, and through the water surface 9 the gas mixture enters the reaction space 1, where close to the water surface 9 it al ready gets in contact with the first gas stream. Furthermore, the auxiliary fuel may be introduced into the reaction space 1 wholly or in part through the nozzles 18, which are dis posed above the constriction 8, and to which the auxiliary fuel is supplied through line 15. In the apparatus in accordance with the invention exhaust gases were burnt on a technical scale, which contained the hydrocarbons and chlorinated hydrocarbons in small amounts. These noxious substances could be converted into C0 2 , H 2 0 and HCl for 100 %. The combustion was effected at 800 to 900*C, where the apparatus was constantly provided with natural gas as auxiliary fuel. In the inventive apparatus there was also -9 burnt the exhaust gas obtained in the production of titanium tetrachloride from TiO 2 , C1 2 and carbon. There was utilized the Deacon equilibrium, where HCl is formed from chlorine and water. The operation of the apparatus is performed such that the mean dwell time of the gaseous substances in the reaction space 1 and the fume hood 3 is about 3 to 4 s. In addition, a mean gas velocity of 3 to 5 m/s is maintained in the reaction space 1. The first gas stream is introduced into the reaction space 1 through the nozzles 7 with an excess pressure of about 40 mbar. The second gas stream is blown into the water through the nozzles 11 with an excess pressure of about 50 mbar. The auxiliary fuel is supplied with a corresponding ex cess pressure.

Claims

1. An apparatus for carrying out gas reactions, comprising a reaction space (1) which is closed at the bottom by a container (2) filled with water and at the top by a fume hood (3), where a first gas stream is introduced through nozzles (7) into the reaction space (1) and a second gas stream is introduced through nozzles (11) into the water, where the reaction space (1) has a constriction (8), in whose vicinity the nozzles (7) disposed in the reaction space (1) are provided, and where the gaseous reaction products (16) are discharged from the fume hood (3), characterized in that the nozzles (7) disposed in the re action space (1) are inclined towards the water surface (9) and have an angle of inclination of 12 to 160 with respect to the horizontal, that the diameter of the reac tion space (1) in the vicinity of the constriction (8) is reduced by 20 to 30 %, and that the constriction (8) in the reaction space (1) is disposed such that 20 to 30 % of the height of the reaction space (1) lie between the water surface (9) and the constriction (8), and 80 to 70 % of the height of the reaction space (1) lie between the constriction (8) and the fume hood (3).

2. The apparatus as claimed in claim 1, characterized in that in the reaction space (1) and/or in the container (2) filled with water fuel nozzles (18, 13) are provided, through which a gaseous auxiliary fuel is blown into the reaction space (1) and/or into the water.

3. The apparatus as claimed in claims 1 to 2, characterized in that the nozzles (7, 18) disposed in the reaction space (1) consist of titanium or an alloy with a high ti tanium content. - 11

4. Use of the apparatus as claimed in claims 1 to 3 for the combustion of gases and exhaust gases which contain gase ous as well as dust-like noxious substances and/or to gether with air form an explosive mixture.

5. Use of the apparatus as claimed in claims 1 to 3 for car rying out chemical gas reactions.

6. A method of operating the apparatus as claimed in claims 1 to 3, characterized in that the mean dwell time of the gaseous substances in the reaction space (1) as well as in the fume hood (3) is 1 to 5 s, and the mean gas veloc ity in the reaction space (1) is 2 to 6 m/s, where the nozzles (7) disposed in the reaction space (1) are oper ated with an excess pressure of 35 to 45 mbar, and the nozzles (11) disposed below the water surface (9) are op erated with an excess pressure of 45 to 55 mbar.