coke strength and fabric expansion joints Under coke strength means its ability to withstand a variety of breaking load (drums pulverize) to which it is subjected to during transportation, handling, and feeding into the furnace during smelting.This property is considered to be the most important indicator of the quality of coke.Durable coke does not form little things can save the high gas permeability of the charge and the performance of the blast furnace.coke strength is determined by artificial destruction of samples under the influence of shock and abrasive loads.A measure of the strength of a change in the sieve (particle size distribution) of the composition of coke in the process of testing and the use of fabric expansion joints.The most widely used method for determining the strength of coke by destroying it in a rotating drum.This method consists in the fact that a certain size sample coke drum is placed inside a particular size, after which it is rotated at a predetermined speed for a predetermined time.Entrained coke lumps up falling, and are poured, thus obtaining fraction abrasive and shock loads are destroyed to some extent depending on their mechanical strength.Strength is characterized by a change in size of lumps of coke as a result of the test.Our country has long been the standard method for determining the strength of coke drum proposed in Russia in the late nineteenth century E.Sundgrenom.drum diameter of 2000 mm and a width of 800 mm has a cylindrical surface in a lattice of rods of diameter 25 mm with same defined therebetween
compensators .The drum is loaded sample weighing 410 kg of coke in pieces of 25 mm.The drum is rotated for 15 minutes at 10 rev / min.The resulting destruction of small pieces of coke fall through the gaps between the bars.An indicator of the strength is the mass of coke remaining inside the drum.An additional feature is the number of fraction 10-0 mm podbarabannom product.Long experience has shown that the normal operation of the blast furnace can be coke, giving the rest of the drum at least 300 kg.The best varieties are 340-350 kg drum sample.Similar methods of testing fabric expansion joints are used in many countries, however, the size of the drums, the mass of the sample, the number of revolutions were different.This led to the incompatibility of the strength of coke and the results of them blast furnaces.Therefore, in 1963 in the USSR above method Sundgren has been replaced by an international method of determining the strength of coke in a small gated drum diameter and a length of 1000 mm (GOST 8929-65).On the inner surface of the drum 4 are welded corner height of 100 mm.To test the coke sampled larger 60 mm in an amount of 150 kg, which is divided into three parts by weight of 50 kg.The drum is charged with one of these parts (50 kg) and cause it to rotate at a speed of 25 rev / min for 4 minutes.The sample is then removed and scatter sieve with round holes with a diameter of 40 mm and 10 mm.The strength of coke is characterized by the release of 40 mm fraction (a measure of M40), and its abrasion - output fraction 10-0 mm (figure M10) in percentage by mass of the sample.Two samples shall be tested.This divergence of results in terms of more than 3% of M40 and M10 in terms of more than 1% test third sample.The final result is determined as the arithmetic mean.The higher the M40 and M10 below, the stronger coke.In recent years, many plants coke strength test in the same (small) drum (GOST 5953-72), with the same regimen for downloading and rotation, but take test coke particle size 25 mm.An indicator of the strength of the coke yield is 25 mm fraction (M25) and abrasion - M10.The average value of these indicators of the strength of coke in 1985, the factories of the South of the USSR varied within the following limits: the M25 - from 70.7 to 88.9%;M10 - from 6.3 to 11.3%, and the factories in Russia and Kazakhstan: M40 - from 57.8 to 75.1%;M25 - from 83.7 to 87.6% and M10 - from 6.5 to 10.0%.Also outlined methods for determining the strength of the coke used and others.A disadvantage of these test methods coke strength in the cold state lies in the fact that they can not estimate its strength at high temperature to which the heated coke in the blast furnace.Attempts to create a method for determining the thermal stability of coke.Coke strength strongly depends on the number and shape of cracks in its pieces.The destruction of the pieces takes place through cracks, places of internal stresses generated during the coking process.Research has shown that a change in particle size distribution of coke is not proportional to the work of destruction: first, quickly crushed coke, the amount of fines increases dramatically, and large decreases rapidly, then slows down crushing.Subsequent growth of the fracture leads mainly to coke abrasion, as on a piece of crushing difficult.This allowed to assess the strength of coke stabilized screen composition obtained after the implementation of all the cracks and internal stresses.Removing the coke from the furnace through the blast tuyere showed that its composition corresponds approximately to sieve the stabilized composition.It is known that the gas permeability of fabric expansion joints loose lump materials is improved with an increase in the homogeneity of the size of its pieces.In order to improve the homogeneity of the coke particle size to produce pieces of the optimum size for blast furnaces (25-40 mm) attempts to pre-stabilize his screen composition by exposure to a certain amount of mechanical load, followed by classifying the resulting fines.This will reduce further damage to the pieces to form coke fines in the blast furnace and improve its gas permeability of the charge in the high temperature zones. 
