US2110377A - Continuous-vertical retort oven - Google Patents

Description

March s, 1938. Fm 2,110,377

CONTINUOUS VERTICAL RETORT OVEN 4 Filed Feb." 15, 1954 Patented Mar. 8, 1938 PATENT OFFEQE CONTINUOUS-VERTICAL RETORT OVEN Wilhelm Fitz, Essen,

Germany, assignor, by

mesne assignments, to Koppers Company, a corporation of Delaware Application February 13, 1934, Serial No. 710,990 In Germany February 13, 1933 4 Claims.

The invention relates to chamber or retort ovens for the production of gas and coke and particularly to ovens of the type which are operated continuously, that is to say wherein the coal is charged in a slow stream or at comparatively short intervals into the upper end of the chamber.

In such ovens for the production of gas and coke it is frequently observedpractically in all cases that offer a shorter or longer period of operation, that the refractory masonry of the coking chamber or retort is considerably damaged. The damage mostly occurs'on those zones of the chamber in which the main portion of the distillation gases are generated from the coal, that is to say at the point at which the heavy hydrocarbons mainly escape. The damage to the masonry as a rule takes place in the form that layers crack away parallel to the inner surface of the masonry. This cracking away may proceed to such an extent that the wall of the coking chamber is broken through and direct communication is formed between the heating passages provided in the wall and the coking chamber. Conse quently the distillation gases can flow into the heating passages with which are associated very considerable losses.

Such passage of gases into the heating passages of the chamber walls may also result in the formation of cutting flames in the heating passages which give rise to overheating of the refractory masonry and damage to the latter.

The object of my present invention is to so construct the walls consisting of refractory masonry, of the chamber or retorts, in which the coal is coked, that the above mentioned actions on the masonry can no longer occur.

It was hitherto not possible to ascertain with certainty the reason to which this peculiar cracking away of the refractory masonry on continuously operated chamber and retort ovens was due, although in the construction of these continuously operated ovens there have been. used refractory materials of the same qualities as those which have also been used in the usual horizontal chamber coking ovens for many years without any scruples and have there shown excellent durability.

I have now made thorough investigations as to the causes of the said cracking away of the refractory masonry of continuously operated. chamber ovens. As a result of these investigations I have ascertained that particularly in the main gasifying zone graphite, formed by the pyrogenic decomposition of the hydrocarbons, is deposited in a very hard form on the chamber walls. This graphite deposit takes place over the entire surface of the masonry, that is to say also in the pores of the masonry, open towards the chamber, which in the types of masonry at the present time usually employed in coke oven construction most- 5 1y extend very deeply into the masonry. From the separate graphite molecules, which in this manner are deposited over the entire surface of the masonry there is now built up an extremely solid coherent mass of which the breaking strength and adhesion to the surface of the masonry are greater than that of the masonry. In

addition on the separation of the graphite there mostly occurs in a peculiar manner a certain increase in volume of the graphite mass.

The said graphite deposits on the walls of coking chambers of continuously operated chamber or retort ovens for the production of gas and coke are unavoidable. In order to prevent a deleterious reduction of the coking chamber it is there i fore generally usual, to knock the graphite off the Walls of the coking chambers from time to time. For this purpose the chamber is wholly or partly emptied temporarily and the graphite scales are knocked off the walls by means of long rods passed through openings in the chamber cover.

As these graphite scales, as has been ascertained by me, do not only adhere superficially to the masonry but extend to a considerable depth into the same and as the strength of the graphite scales, as a rule, is also considerably greater than that of the refractory materials hitherto used, the outer layers of the masonry which have been grown over with the graphite scales and whose structure has also been loosened by the increase in volume of the graphite mass referred to above, are also broken away when knocking off the graphite scales. This occurs each time the graphite mass is removed. It will be readily understood that this may lead to the complete destruction of the chamber wall masonry.

According to my present invention which is based on the above investigations, I employ fer the manufacture of the walls of the coking chambers of continuously operated vertical chamber or retort ovens for the production of gas and coke a refractory brick material having a porosity of less than. 15%, preferably from 8 to 16% and which has such a structure that the volume of the closed pores is greater than the volume of the outwardly open pores. Preferably only the parts of the coking chamber are constructed with this brick material in which the main gasification of the coal takes place, that is to say at the point at which the decomposition of the hydrocarbons In a continuously operated chamber or retort.

oven, which is constructed with the above defined stone material practically no attack of the masonry of the chamber walls has been observed in operation. This is due on the one hand to the fact that the graphite separated on the wallcannot penetrate into the interior of the brick and loosen the structure, and on the other hand because the strength of the compact bricks, which I use according to my invention, is many times greater than that of those generally used considerably more porous bricks. Further, it is possible to knock ofi any graphite deposits from chamber walls constructed according to my invention without damaging the masonry when the operation is carried out efficiently. It is also possible to cause the graphite scales to peel off, as is done in many localities by blowing steam into the empty chamber by which the graphite is subjected to rapid cooling so that the graphite mass contracts and is thus released from the surface of the brick.

A brick material which satisfies the above requirements is for example produced in the following manner:

A mixture of limed kaolin and fine quartz with a total content of alumina of about 36% and as small a content as possible of .fiuxes, of which the proportion of iron must not be above 1% is moulded and burnt to fragments. The fragments are then comminuted to a suitable size of grain and again mixed with a suitable proportion of the initialmass, moulded and the moulded product burnt at a very high temperature (preferably above 1500 C.) until there is a clear formation of mullet crystals in the fragments. Such a brick, when the pressing of the molded product has been efiected in a suitable manner, only has a pore Volume of 8 to 10%, is very refractory and has a very high resistance to sudden temperature changes. The proportion of closed pores predominates in these bricks. The, very high resistance of these bricks to temperature changes in spite of their great density, therefore depends on the fact'that by reason of the mullet crystals finely distributed throughout the. entire body they possess a surprisingly great toughness.

In the accompanying drawing, with reference to which my present invention will now be described in detail, Fig. 1 is a vertical longitudinal section of a continuously operated vertical chamber oven according to my invention. Fig. 2 shows a vertical cross section on the line A--A of Fig. 1.

In the arrangement illustrated the coking of the coal is effected in the vertical chambers indicated by I. The raw coal is charged into the chamber from a bunker 2, only partly shown, through a pipe 3, preferably of cast iron, which projects into the interior of the chamber I. In the chamber l the coal is converted into coke which is continuously withdrawn from the lower end of the chamber by the usual discharge device 4. Consequently fresh raw coal passes continuously from the bunker 2 into the chamber, which is thus constantly filled with coal and/or coke during normal operation. In Fig. 2 the portion of the chamber charge practically still consisting of coal is indicated by 5 and that consisting of coke by 6.

The coking chamber I is formed of walls, consisting of refractory masonry in which vertical heating ducts l are provided. At the upper and lower ends these heating ducts communicate with horizontal communicating ducts 8, 9 each connected to one of the regenerators I0, I I. The regenerators which serve to pre-heat the combustion air, or in cases when the oven is to be heated by generator gas or the like, for preheating gas and air, are fitted as usual, with a chequer work I2, consisting of refractory stones. The regenerators H], .II are connected by pipes l3, 14 with elbows IE to which there are connected the generator gas pipe 16 and the waste gas pipe IT. The elbows l5 are so constructed that during one operating period heating gas and air are supplied to one of the regenerators, for example the regenerators ll, whilst the waste gases pass through the other regenerators l0 and then pass out through the outflow pipe IT.

The gas and air are thus pre-heated in the regenerators H and the chequer work in the regenerators I0 is heated by the waste gases. As soon as the required temperature of the preheated air and gas, which is necessary for obtaining the desired flame temperature, is no longer reached, the path of the gases is reversed i. e. gas and air are conducted into the regenerators l0, heated during the previous operating period and hot waste gases are withdrawn through the cooled regenerators.

The gases which escape during the dry heating of the coal, whilst excluding air in the chamber Lare withdrawn at the upper end of the chamber I through a stand pipe l8 into the hydraulic main IS. The hydraulic main also communicates with a gas outflow pipe 20 terminating substantially at the middle of the chamber. Through this outflow pipe '20 water gas is withdrawn from the chamber, this water gas being formed by the introduction of steam at the lower end of the chamber into the incandescent coke mass.

The walls of the coking chamber l consist of a brick material 2| having a high resistance to temperature changes, having a porosity of less than 15% preferably from 8 to 10% and in which i the proportion of closed pores predominates over the open pores. This refractory material is enclosed in a masonry block 22, consisting of usual refractory material, for example chamotte, which on the outside is insulated by a poor heat conducting material and held together by rim girders 23.

Under certain circumstances only the upper portion of the chamber walls, for example down to the line 24 may be constructed of the said very dense refractory brick material, and the lower part of the chamber walls formed of the usual material, for example silica stones.

The entire oven or the coke oven battery consisting of a number of ovens rests on a substructure 25, underneath which are located in the usual manner the discharging and conveying devices which have not been illustrated for the sake of clearness.

' My present invention, which has been described above with reference to a single example of construction is not limited to the form of construction shown, but is capable of modification within the scope of the following claims.

I claim:

1. Oven for the production of gas and coke comprising a vertical coking chamber adapted to be supplied continuously at its top with coal to be coked and adapted to continuously discharge coke at its lower end, said coking chamber being formed of Walls consisting of refractory brick masonry consisting of refractory brick having been previously burnt at a temperature above 1500 C. and having a clear formation of mullet crystals in its fragments so as to be resistant to temperature changes, and having a porosity of less than whilst the closed pore volume in the masonry brick predominates over the volume of outwardly open pores.

2. Oven for the production of gas and coke comprising a vertical coking chamber adapted to be supplied continuously at its top with coal to be coked and adapted to continuously discharge coke at its lower end, said coking chamber being formed of walls consisting of refractory brick masonry consisting of refractory brick having been previously burnt at a temperature above 1500 C. and having a clear formation of mullet crystals in its fragments so as to be resistant to temperature changes, and having a porosity within the limits of 8 to 10%, whilst the closed pore volume in the masonry brick predominates over the volume of outwardly open pores.

3. Oven for the production of gasand coke comprising a vertical coking chamber adapted to be continuously charged with raw coal at its top, and adapted to continuously discharge coke at its lower end, said coking chamber being formed of walls consisting of refractory masonry, the masonry of the upper parts of the coking chamber for the main gasification of coal consisting of refractory brick masonry having been previously burnt at a temperature above 1500 C. and having a clear formation of mullet crystals in its fragments so as to be resistant to temperature changes, and having a porosity of less than 15%, whilst the closed pore volume in the masonry brick predominates over the volume of outwardly open pores.

4. Oven for the production of gas and coke comprising a coking chamber adapted to be supplied continuously at its top with coal to be coked and adapted to continuously discharge the coke at its lower end, said coking chamber being formed by walls consisting of refractory brick masonry of kaolin and fine quartz with not more than 36% alumina and having a content of iron below 1% and having previously been burnt at a temperature of 1500 C. until the brick shows a clear formation of mullet crystals in the brick body with a porosity of less than 15%, whilst the closed pore volume in masonry brick predominates over the volume of outwardly open pores.

WILHELM FITZ.

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