Petcoke is applied to reception of various kinds of carbon production, such as anode weight and graphites electrodes. Also from petcoke receive fillers for release of special marks of constructional graphites. The pitch represents the dehydrated coal pitch received at cooling gas of coke. Petcoke receive by coking of a pitch without air access.
One of the basic units pitchs shops is the battery of petcoke which form petcoke stoves. The structure petcoke stoves includes heating system and actually chamber of coking where there is a formation petcoke. Both the heating system, and the coking chamber are carried out from fire-resistant products. Quality of a received pitch and quantity of by-products of coking (petcoke gas) directly depend on a condition petcoke stoves, and, hence, from a condition of a fire-resistant laying.
The fire-resistant laying of thermal units works under trying conditions. In petcoke stoves a laying long time stays under the influence of high temperatures (1250° C) – to a full exit flying (the coking period). During coking the fire-resistant laying of heating piers is exposed to simultaneous influence of two excited environments: a torch of burning and products of its combustion – in heating channels; a pitch passing in petcoke and allocated thus petcoke gas – from the coking chamber. Besides a laying negatively influence: mechanical efforts from serving cars, thermal blows, infringements of hydraulic and temperature modes of heating.
Thus, working out of actions for decrease in destruction of a fire-resistant laying of thermal units remains an actual problem.
Working out of actions for decrease in destruction of a fire-resistant laying of thermal units includes studying of an urgency of the given problem and the review of existing methods of the decision of the given problem. It is for this purpose developed 3D – model of a fire-resistant laying of the thermal unit (a heating pier of petcoke stove).
Working out 3D – model includes calculation of technological indicators (material, thermal and hydraulic balances), drawing up and calculation of indicators of reliability (drawing up of the Tree of refusals and calculation of factors of the importance), representation in a system kind (to present the unit in the form of elements with all external and internal communications), working out of mathematical model of accumulation and development of defects (classification of defects and the reasons causing them, and also consequences of these defects).
As a result of work actions for decrease in destruction of a fire-resistant laying of thermal units are developed.
As coal pitch is called the rest received at fraction of coal pitch. It is the product of black color homogeneous for appearance. The pitch stiffens in a certain temperature interval in firm fragile weight. It has no certain temperature of fusion and hardening: melts in a temperature interval. Fusion and pitch hardening isn't accompanied by thermal effect, it has no latent warmth of fusion. By the chemical nature the coal pitch represents a multicomponent mix of multinuclear hydrocarbons and the heterocycles formed not only in the course of reception of coal pitch at coking of coals, but also at its processing as a result of thermal polycondensation.
The connections which are a part of a pitch can be broken into three groups:
1) maltens, or 
-substances, soluble in a neutral ether (the mixed solution of the crystallizing substances forming a phase of viscous oil form);
2) asfaltens, or 
-substances, soluble in toluene, but insoluble in a neutral ether (fusible substance of black color), this part can be extended in a thread;
3) the insoluble rest, or 
-substances, insoluble in toluene (not fusible and nonplastic powder of black color).
At temperature of a softening of a pitch 63 – 70° С an exit -a making part about 25%; -a component of 41% and -a component of 34%.
By the physical nature the coal pitch represents the overcooled system of true and colloidal solutions therefore on the properties it sharply differs from usual firm crystal substances. For a pitch the temperature interval of plasticity is characteristic. It is defined by a difference of two conditional temperature points: temperatures of a softening and temperature of occurrence of fragility. This interval is the important technical indicator characterizing suitability of a pitch for those or other processes.
Depending on temperature of a softening pitches are divided on soft, average and firm. Soft pitches have temperature of a softening 40 – 55° С (density of 1286 kg/m3), average 65 – 90° С (density of 1290 kg/m3) and firm 135 – 150° С (density of 1320 kg/m3).
Separate stages of process cokeforming arise in a consecutive order simultaneously at both walls of petcoke chambers and in process of penetration of heat into depth of loading move ahead to the central axial plane of the furnace where intermediate layers (plastic, semicoke), moving from walls of petcoke chambers, approach. Thus the intermediate zones with the same name converge (and in a plastic condition merge), then disappear, passing in the subsequent condition.
At influence of temperature and time for the loading which is in the chamber of coking, viscous plastic renders bigger or smaller resistance of evacuation of products of decomposition which aspire to increase loading volume; certain pressure which depends also on gas permeability of layers of semicoke – coke and density of a network of the cracks formed in them thus can develop [4, 7].
In petcoke stoves heat transfer occurs simultaneously by means of heat conductivity, a convection and thermal radiation. All kinds of transfer of heat are possible only in the presence of a difference of temperatures.
In petcoke stoves heat transfer is carried out as follows. In channels of a heating pier burns down heating gas. Warm products of burning by emission and a convection it is transferred to a surface of the wall turned to a flame. Then warmly, apprehended by this surface, thanks to heat conductivity it is transferred through a chamber wall. The thermal stream between the party of the wall turned to the heating channel, and the party of the wall turned in coke the chamber is thus created.
From a chamber wall to coal loading heat transfer occurs at first as a result of heat conductivity while coked loading is driven into the corner, and then – emission. External surfaces of furnaces transfer heat in surrounding space also emission and a convection.
In regenerators on a descending stream there is heat return by warm products of burning to a regenerator nozzle, and on an ascending stream heat is given by a nozzle to air or poor (domain) gas. This exchange too occurs by emission and a convection.
Maintenance of the set temperature mode of heating and stable distribution of temperatures (curve) on length of heating piers rather important for preservation of a laying of furnaces.
The hydraulic mode or the regulated distribution of pressure in the chamber of coking and heating system of petcoke stoves, is a major factor defining necessary term of their service. From the beginning of operation the volume of the chamber of coking is completely separated from a heating pier by a wall of a small thickness and theoretically they shouldn't be informed. However in practice even the most perfect stone laying what the laying petcoke stoves is, can't be absolutely dense. In it there can be empty seams, cracks in due course are formed and at even to very small difference of pressure in the chamber of coking and heating piers, the overflow of gas and air streams through thinnesses of a laying of the chamber of coking can be observed.
In the beginning of process of coking when from a pitch there is a rough allocation of gaseous products, superfluous pressure in the chamber can reach 6 – 8 kPа. Thus gases products pass through cracks in a laying, or thinnesses of doors of petcoke stoves, decay, filling with their graphite, and, thus, the coking chamber completely separates from heating system and atmosphere.
In the end of the period of coking the quantity of allocated gaseous products sharply decreases. As a result such position when pressure of gases in the coking chamber becomes less atmospheric and less pressure in heating system can be created. In this case air oxygen in heating piers and regenerators on an ascending stream can promote graphite burning out in empty seams, cracks and other thinnesses of the heated laying of piers. The same process will occur to the carbonaceous adjournment which have condensed doors of furnaces. After carbon will burn out, air oxygen, passing in the chamber of coking and adjoining to the heated coke, will cause its intensive burning. In burning places high temperature to 1600° С develops. The basic connections of ashes of coke, reacting with a sour laying, will give fusible connection. Thus, at delivery the pie of coke the laying surface will collapse.
At new loading of the chamber process will repeat. In the beginning through thinnesses of a laying a significant amount gases products will arrive in heating system, to burn, especially in the regenerators of an ascending stream filled with air, in heating piers where gas is burned a lot of air.
Then, after reduction of quantity of allocated gases process will go upside-down. At repeated repetition of these phenomena in a laying of chambers of coking can be formed defects, the nozzle of regenerators can be melted off [2, 3].
Representation the petcoke stove in a system kind consists in its decomposition on elements (assembly units and details), the description of properties and communications of these elements; allocation in elements of components (a surface, an edge), the description of their properties and parameters, and also the description of the working environments directly contacting to components.
Let's enter designations:
1 – Assembly unit (
).
2 – the Detail (
).
3 – the Component (
).
Let's result structure petcoke stove (drawing 2) [8].
By means of the program the COMPAS 3D V11 it is developed 3D – model of a heating pier of the petcoke stove. The model consists of 2877 details, from them unique 112.
Deterioration of a laying of oven chambers begins with a loosening of superficial structure of a brick ("shirt"), occurrence of cracks on bricks of walls against extreme verticals. Dynamics and character of the crack forming on walls of chambers against extreme verticals and laying destructions between cracks are shown on draw. 4.
In the beginning cracks appear on bricks in separate numbers of a laying, and further their quantity continuously increases before formation of a continuous crack in all numbers of a laying. At first there is one, and then the second parallel crack. On the edges of cracks leaving on a surface of walls of chambers, appear chopped of bricks. Chopped edges gradually increase and go deep. As soon as depth chopped along the edges of a crack becomes more sizes cross-section shrinkage a pitch, coke remains in an edge and at delivery creates the efforts leading to displacement of "columns" between parallel cracks. In this connection it is very important to start repair of cracks before depth having chopped off on edges of cracks won't exceed critical greatness (10 – 15 mm).
Factors which influencing on the deterioration of layings of the petcoke stove can be subdivided:
1) mechanical efforts;
2) thermal blows;
3) infringements of hydraulic and temperature modes of heating [1, 2, 5].
The most widespread kinds of deterioration of chambers of coking concern:
1) vertical cracks on extreme verticals and displacement – laying deformation between them;
2) deformation of walls of chambers at level of the top numbers of a laying extreme verticals;
3) deformation of walls – cambers or concavities against various verticals;
4) cracks and promotion of bricks in the central part of chambers, mainly, under loading hatches;
5) "undercuts" – furrows in walls on first two numbers of a laying;
6) bowls – corrosion in a zone of the maximum temperatures;
7) chopped of edges from reinforcing the reservation;
8) cracks;
9) destructions extreme bricks.
At drawing up of likelihood mathematical model following assumptions and restrictions are accepted:
– Operation process consists of repeating cycles of efforts, possessing in constant parameters;
– Time t is discrete (t = 0, 1, 2, …);
– Conditions of defects are discrete and designated through 1, 2, …, j, …, b. At condition achievement b there is a refusal of a pier and a conclusion of the stove to repair or achievement of the sizes of defect of inadmissible values and its indispensable elimination;
– Change of a condition of object for a cycle of effort depends only on parameters of this cycle of effort and from an object condition in its beginning.
For n cycles the object can remain in a current condition, or to pass in a condition with higher number.
The matrix of transitive probabilities is made:
where pjj – probability of that the object remains in a condition j for one step;
qjk – probability of transition of damage for one step from a condition j in one of the subsequent conditions {j+1, …, b}.
Distribution of probability of achievement by object of a certain condition by the time of time t:
where p0 – distribution of probability of a finding of object in a certain condition during the initial moment of time of operation of object [5, 6, 9, 10].
At the moment of delivery of a site work hasn't been finished yet, therefore results of work not presentation. It is possible to judge prospective result only on the structure of work resulted above. Results of work can be seen at the author or at the scientific adviser after December, 2011.