CH645666A5 - NON - POLLUTANT PROCESS FOR THE MANUFACTURE OF CHARCOAL. - Google Patents

Description

The present invention essentially consists in arranging a continuous carbonization oven with an auxiliary oven, so that the pyroligneous vapors are completely burnt, even when treating very humid woods without pre-drying, so as to thus eliminate any atmospheric pollution.

For this purpose, the fumes from the annex hearth are used to bring the air used in this hearth to high temperature for the complete final combustion of the pyroligneous vapors coming from the oven and for heating the latter by partial combustion of these vapors on the coal.

We describe this set below, referring to the attached diagram:

The carbonization furnace is a vertical cylindrical device with metal walls, comprising:

1. At the head, a loading chimney H, of reduced section, where the level of wood is periodically checked with the ball B. The wood is periodically loaded into this chimney by any lifting device A, so as to maintain this chimney H constantly furnished with wood.

2. Below, a tank C, of much wider section, where the wood is gradually dried, then charred under the effect of very hot gases coming from the lower part of this tank. The pyroligneous vapors are evacuated from this tank by the pipe 10.

This entire area is preferably walled in stainless steel and externally insulated.

3. Below, the tank is made of ordinary steel and its section is reduced by an interior lining made of insulating refractory materials. It is in this zone that the charcoal is cooked, it being understood that this term corresponds to the reduction of the volatile matter content of the charcoal.

At this level, there are two chambers F and D, formed in the mass of coal, one, F, receiving by the pipe 11 the pyroligneous vapors coming from the tank C by the pipe 10 and discharged by the fan V! with adjustment by valve 1. At the same time, very hot air (400 to 500 ° C.) from the exchanger E is injected therein via the pipe 13, with adjustment by the valve 2.

The pyroligneous vapors thus burn catalytically at low temperature on the coal at the bottom of the pipe F without consumption of coal.

A sufficient flow of pyroligneous vapors is adjusted by the valve 1 so that the carbonization zone C remains hot enough (350 ° C in Ts and 200 to 250 ° C in T6) without exceeding 150 ° C in T too much.

Via the valve 2, the quantity of heating air is adjusted to obtain the desired cooking temperature of the coal (450 to 600 ° C.) observed in T4.

The gaseous products are evacuated from the chamber D situated substantially at the level of the chamber F, at a temperature close to that of the cooking of the coal. They exit through the pipe 15 with adjustment by the valve 3 to go to the annex hearth M.

The passage of all the pyroligneous vapors through the hot coal causes the cracking of the tars and, as a result, the gaseous products leaving the oven are no longer coking.

4. Below the coal cooking zone is a capacity with ordinary steel walls R where the coal is cooled by a recycling of gas taken from the pipe 18, itself cooled with water in the column L and discharged cold by the pipe 19 at the base of the cooling zone by means of the fan V2 and with the adjustment by the valve 5.

5. Finally, at the base of the oven, there is an airlock S for the evacuation of the coal; this airlock, comprised between the valve O and the valve K, is periodically supplied with a capacity I comprised between the valve O and retaining claws N. This device is not in particular; it is generally adopted for the evacuation of coal in continuous ovens.

As indicated above, the cracked and high-temperature pyroligneous vapors are sent through the pipe 15 into the annex hearth M. This is a capacity with an ordinary steel casing internally lined with insulating refractory materials. This hearth communicates directly with the heat exchanger E where the air necessary for the combustion of all the pyroligneous vapors circulates against the current, both in the furnace (at F) and in the adjoining hearth.

This appliance is made so as to bring the combustion air to a temperature of 400 to 500 ° C, or slightly higher if the wood is very humid.

This air is blown by the fan V3 and admitted to the heat exchanger by the pipe 16.

The hot air leaving E is distributed by pipes 13 and 14 with

5

10

15

20

25

30

35

40

45

50

55

60

65

3

645,666

adjustment by valves 2 and 4 between the heating of the oven and the complete final combustion, in the hearth M, of the pyroligneous vapors.

Under these conditions, the temperature of the hearth M is high enough for combustion to be complete there, and the partially cooled burnt gases are evacuated, after passage through E, through the pipe 17 s into the atmosphere.

These gases, which are still very hot, can be used for certain heaters if necessary. They are not polluting because, in addition to water vapor and nitrogen, they only contain carbon dioxide, the air admitted to the hearth by the pipe 14 being in sufficient quantity for the combustion to be complete. The regulation of this combustion can be ensured automatically by a device for measuring free oxygen in the fumes acting on the valve 4.

Returning to the settings for the flow of pyroligneous vapors through valve 1 for circulation by Vj and to the outlet of cracked gases 15 through valve 3, it is noted that it is possible to let through 3 a little more gas than one does not return 1 to the oven, which allows, taking into account the production of wood pyroligneous vapors, to cause an air inlet at the top of the oven.

This is how the gas outlet will be regulated by valve 3 so that there is always a certain proportion of air sucked in by Vi with the pyroligneous vapors. This proportion of air will however be checked by the free F 02 analyzer so that there is no risk of explosion.

This control device can advantageously be a register and regulator by acting on valve 3.

Thus, there is no smoke at the top of the furnace since it is kept in slight depression compared to the atmosphere.

The assembly described above makes it possible to carbonize without pollution of wood having up to 45% humidity without prior artificial drying, the productivity of an oven being all the greater when the wood is less humid and in pieces of smaller size.

It should be noted that the principle of the method of carbonizing wood, according to the present invention, is independent of the embodiment of the chambers F and D which are provided, according to FIG. 1, in the form of large diametrically opposite lateral tubes.

By using refractory steels, these chambers F and D can be produced by simple internal partitions in the furnace according to FIG. 2.

They can also be made with frustoconical interior crowns according to fig. 3.

Finally, it does not matter whether the cracked pyroligneous vapors are discharged below or above the chamber F. FIG. 4 shows D a little above F; these chambers need only be close enough for the temperature in D to be very little lower than that prevailing in F.

R

2 sheets of drawings

Claims (3)

645,666 1. Non-polluting process for carbonizing wood, comprising a continuous furnace supplied with moist wood, consisting of at least one central pyrolysis zone in which the usually annoying residual gases are cracked on the charcoal in formation and burnt in an additional hearth which heats its combustion air and the air needed to heat the oven. 2. Carbonization oven for implementing the method according to claim 1, comprising in its central zone two chambers allowing the admission and evacuation of the gaseous mixture before and after pyrolysis on the reaction product. 2 3. Charcoal obtained by the process according to claim 1. This memo describes a non-polluting process for carbonizing wood, essentially comprising a production furnace arranged so as to recover the recoverable content of the residual products by coal itself. It concerns the necessary equipment, the method of use and the new charcoal thus obtained. In many known techniques, it has not seemed advantageous to recover the volatile products from the carbonization of wood in order to extract chemicals therefrom; so we are happy to collect charcoal. The pyroligneous vapors which are released during carbonization are constituted by water vapor, incondensa ble gases and various organic bodies such as methanol, acetic acid and homologs, tars. The incondensable gases are rich in carbon monoxide therefore toxic, and, on the other hand, the tars make these vapors suffocating and polluting. These pyroligneous vapors have a significant overall calorific value and the best way to recover them is to burn them. However, this is only possible if the humidity of the treated wood does not exceed a limit close to 25%. However, this is only exceptionally the case for naturally dried wood: it is therefore usually necessary, for continuous charring, to treat the wood beforehand in artificial dryers. These dryers are bulky, expensive and can present fire risks. In addition, their use requires additional handling. When charred wood is very humid, the pyroligneous vapors are too rich in water vapor and they are no longer combustible in ordinary fireplaces. One can however burn part of it by catalytic combustion with air on the coal to heat the carbonization devices. This is partly what happens in discontinuous carbonization wheels, and this possibility has been used in some continuous carbonization ovens (ERIM ovens and CISR ovens). In any case, this combustion can only be partial and the rest of the pyroligneous vapors, still depleted by dilution with the nitrogen of the air used, are non-combustible and they must be released into the atmosphere, which is annoying for the 'environment.