Process for treating gaseous effluents developed in coffee roasting installation

Abstract

A process for treating gaseous effluents developed in a coffee roasting installation making it possible to treat gaseous effluents developed in a coffee roasting installation, in which the effluents are passed through an oxidative catalytic converter. Within the catalytic converter use is made of a catalyst selected from the group including: a) a catalyst including a porous faujasite support containing copper oxide nanoparticles in a quantity of between 2% and 7% of the total weight of the catalyst; b) a catalyst including a porous -alumina support containing copper oxide nanoparticles in a quantity of between 2% and 7% of the total weight of the catalyst; and c) a catalyst including a mesoporous zeolite or silica support containing iron nanoparticles in a quantity of between 2% and 7% of the total weight of the catalyst.

Claims

1. A method for processing the gaseous effluents developed in a coffee roasting installation (1), wherein said effluents are conveyed through an oxidising catalytic converter (5), and wherein in said catalytic converter use is made of a catalyst comprising a mesoporous silica support, consisting of iron nanoparticles in an amount comprised between 2% and 7% of the total weight of the catalyst.

2. The method according to claim 1, wherein said mesoporous silica is an SBA-15 silica.

3. The method according to claim 1, wherein before being admitted to the catalytic converter said gaseous effluents are heated to a temperature comprised between 350 C. and 500 C.

4. The method according to claim 1, wherein said iron nanoparticles are provided in an amount equal to 5% of the total weight of the catalyst.

5. The method according to claim 1, wherein before being admitted to the catalytic converter said gaseous effluents are heated to a temperature comprised between 400 C. and 450 C.

6. The method according to claim 1, wherein said iron nanoparticles are deposited on said supports with the Incipient Wetting Impregnation (IWI) technique.

7. A method for processing the gaseous effluents developed in a coffee roasting installation (1), wherein said effluents are conveyed through an oxidising catalytic converter (5) and wherein in said catalytic converter (5) use is made of a catalyst comprising a porous -alumina support consisting of nanoparticles of copper in an amount comprised between 2% and 7% of the total weight of the catalyst.

8. The method according to claim 7, wherein before being admitted to the catalytic converter (5) said gaseous effluents are heated to a temperature comprised between 350 C. and 500 C.

9. The method according to claim 7, wherein said nanoparticles of copper are provided in an amount equal to 5% of the total weight of the catalyst.

10. The method according to claim 7, wherein before being admitted to the catalytic converter said gaseous effluents are heated to a temperature comprised between 400 C. and 450 C.

11. The method according to claim 7, wherein said nanoparticles of copper are deposited on said supports with the Incipient Wetting Impregnation (IWI) technique.

Description

BRIEF DESCRIPTION OF THE INVENTION

(1) Further features and advantages of the invention will be apparent from the following detailed description with reference to the appended drawings provided purely by way of a non-limiting example, in which:

(2) FIG. 1 is a block diagram of a coffee roasting installation associated with a gaseous effluent treatment system operating according to the process according to this invention; and

(3) FIGS. 2 to 4 are comparative diagrams relating to the output or yield of CO.sub.2 and NO.sub.x which can indicatively be achieved using a process according to this invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) In FIG. 1, 1 indicates as a whole a roasting or torrefaction apparatus, of a type which is in itself known. In this apparatus there is a roasting chamber which receives a quantity of raw coffee that is to be roasted.

(5) A flow of hot air at a temperature of the order of 500 C., generated for example by means of a burner 2, also of a type which is in itself known, fed with a mixture of air and methane, is also fed to the roasting chamber in apparatus 1.

(6) When in operation gaseous effluents are produced in roasting apparatus 1 and in the embodiment illustrated in FIG. 1 they pass to a cyclone 3, at a temperature of for example between 150 C. and 250 C.

(7) Cyclone 3 carries out preliminary processing of the gaseous effluents, separating particles of greater inertia from the flow.

(8) On leaving cyclone 3 the gaseous effluents are passed to an oxidative catalytic converter 5 by means of a blower device 4.

(9) On leaving blower 4 the gaseous effluents have a temperature of for example between 100 C. and 200 C.

(10) Conveniently, although not necessarily, before reaching catalytic converter 5 the said gaseous effluents pass into an after-burner 6, advantageously fed with the same combustible mixture as used for burner 2.

(11) When they enter oxidative catalyser 5 the gaseous effluents are therefore at a higher temperature, of for example between 350 C. and 500 C., and preferably between 400 C. and 450 C.

(12) In accordance with this invention one of the following catalysts is advantageously used in catalytic converter 5:

(13) a) a catalyst comprising a porous faujasite support, containing copper nanoparticles in a quantity of substantially between 2% and 7%, and preferably approximately 5% of the total weight of the catalyst;

(14) b) a catalyst comprising a porous -alumina support, containing copper nanoparticles in a quantity of substantially between 2% and 7%, and preferably approximately 5% of the total weight of the catalyst; and

(15) c) a catalyst comprising a mesoporous zeolite or silica support, containing iron nanoparticles in a quantity of substantially between 2% and 7%, and preferably approximately 5% of the total weight of the catalyst.

(16) Conveniently the said mesoporous zeolite or silica is a SBA 15 (Santa Barbara Amorphous) zeolite.

(17) The copper or iron nanoparticles are conveniently deposited on corresponding supports using the IWI (Incipient Wetting Impregnation) technique.

(18) Simulations and tests performed have demonstrated that the catalysts listed above make it possible to achieve quite high selective oxidation of CO, nitrogen-containing molecules and organic compounds, while at the same time preventing or reducing the oxidation of nitrogen atoms. These catalysts have demonstrated that they produce few nitrogen oxides and virtually no emissions of carbon monoxide, providing almost complete conversion of all the molecules present in the system into CO.sub.2, N.sub.2 and H.sub.2O.

(19) FIGS. 2 to 4 show comparative diagrams illustrating yield of CO.sub.2, yield of NO.sub.x and NO.sub.x concentration in relation to the temperature shown on the abscissa for the three catalysts described above, determined in simulation tests carried out by oxidising a test mixture of molecules typically developed in the roasting of coffee, and in particular a test mixture having the composition shown in the table below:

(20) TABLE-US-00001 Compound Concentration Carbon monoxide 450 ppm Pyridine 280 ppm Methanol 250 ppm Oxygen 10% Helium Remainder

(21) The graph in FIG. 2 shows how the three catalysts described above provide a high yield in terms of carbon dioxide, more than 70%, over an extended temperature range. The catalyst having the highest performance is the catalyst comprising 5% by weight on a -alumina substrate, the yield from it throughout the temperature range from 375 C. to 500 C. being over 60%, reaching 100% above 435 C.

(22) From FIG. 4 it can be seen how the concentration of NO.sub.x forming during the test with the copper-based catalyst on the faujasite support is always below 25 g/Nm.sup.3, with a NO.sub.x yield of below 5% (FIG. 3).

(23) The iron-based catalyst on SBA-15 zeolite or silica tends asymptotically to a yield of 25% as temperature increases (FIG. 3).

(24) With regard to the copper-based catalyst on a -alumina substrate, it will instead be seen that nitrogen oxides increase with increasing temperature.

(25) Of course, without altering the principle of the invention, embodiments and details of embodiments may be varied extensively in relation to what has been described and illustrated purely by way of a non-limiting example without thereby going beyond the scope of the invention as defined in the appended claims.