Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B57/00—Other carbonising or coking processes; Features of destructive distillation processes in general
  • C10B57/04—Other carbonising or coking processes; Features of destructive distillation processes in general using charges of special composition
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B47/00—Destructive distillation of solid carbonaceous materials with indirect heating, e.g. by external combustion
  • C10B47/02—Destructive distillation of solid carbonaceous materials with indirect heating, e.g. by external combustion with stationary charge
  • C10B47/10—Destructive distillation of solid carbonaceous materials with indirect heating, e.g. by external combustion with stationary charge in coke ovens of the chamber type

Definitions

• the invention relates to a method for controlling the coke quality of coking coal from feed mixtures.
• Mixtures are usually used for coking. I.e.
• the coking coals are first ground in order to achieve certain different grain sizes.
• the different grain sizes give a grain spectrum that significantly influences the bulk density of the coking coals in the coke oven. It has been shown that optimal grain spectra can usually only be achieved by mixing different ground grain sizes.
• Baking capacity is also of major importance. Baking ability is understood to mean the ability of the coal to change to a plastic state when heated in a vessel which allows the coal to expand freely, and to form a baked, lumpy coke when heated further. Coal with good baking power not only provides baked, but even melted coke.
• the baking capacity defined in this way is measured either by the swelling index or by the Roga baking number.
• a coal with a good baking capacity can still produce a less high-quality coke under the operational coking conditions than a poorly baking coal. Therefore, the coking capacity has to be considered in a special way.
• the coking capacity of a coal is assessed either by the dilatometer test or by determining the gray king coke type. To determine the course of dilatation, the change in length of a conical carbon compact is measured at a heating rate of 0.05 ° C / sec.
• the plastic behavior is understood as the ability of the coal to change into a plastic state within the temperature range between about 350 and 550 ° C.
• Modified rotary viscometers are used in the usual methods for measuring plasticity.
• the result of the measurement is not viscosities of the softened coal mass in the physical sense, but rather apparatus-influenced variables which are composed of the internal friction of the solid, liquid and gaseous phases and the elasticity values of these three phases.
• Such measurements are usually laboratory measurements. This also applies to measurements of the degassing behavior, the driving pressure and the shrinkage, which are also used to determine the quality of the coal used.
• the large number of test methods commonly used here, which are commonly used in practice, for determining the amount of coal used and for determining the quality of coke shows that until now targeted control of the quality of coking coal as the basis for high-quality coke was only possible with multiple measurements and particular difficulties.
• the object of the invention is therefore to simplify the control of the required quality of the input material.
• the invention is based on the consideration that essential parameters for the coke quality develop a common effect in a partial area of the coking process. This is the plastic area in further knowledge, which becomes clear when considering the coking process of hard coal in indirectly heated horizontal chamber furnaces.
• Coking produces heating gases that are burned in the heating trains adjacent to the ovens.
• the heat is transferred from the neighboring heating trains through the furnace walls to the furnace lining, ie the coal mixture.
• the temperature fields are usually symmetrical to the center of the furnace, where the lowest temperature prevails.
• the temperature front progresses from the walls to the center of the oven, accompanied by a steep temperature gradient during the transition from the already coked to the unchanged charcoal.
• This transition area in which all temperatures of 100 - 1000 ° C are passed, is locally limited and at the beginning of the coking process (pyrolysis) extends only a few mm in the mainly 450 mm wide oven chamber.
• the gradual coking of the hard coal takes place in the critical transition area, whereby two essential temperature ranges can be distinguished.
• One temperature range extends from about 320 - 480 ° C. In the temperature range, the coal softens and forms a quasi-plastic state. When the temperature range is exceeded, a large number of decomposition and polymerization reactions take place, the prerequisites for the incorporation of inert components being created and the coke quality being pre-embossed.
• the other area lies above the reconsolidation of the furnace stock with a contraction maximum of around 600 o C. In this area the coke structure is formed with further flavoring of the stock.
• the reactions taking place in both areas are dependent on the type of coal used and the grain size of the feed components, but the invention is based on the fact that the type of coal and grain size are largely predetermined in normal coking plant operation and rather the dependence of the coking on the operating conditions and for the respective coke quality
• the focus is on the pretreatment of the feed or the use of coking agents. I.e. According to the invention, the extent and the uniformity of the reactions taking place in these critical transition areas are of decisive importance.
• the temperature gradient is decisive for the course of these reactions.
• a high temperature gradient means a high local heating rate at which the reactions taking place can only develop inadequately or, depending on their kinetics, are even overflowed. This leads to great inhomogeneity in the reaction process and results in an inhomogeneous coke structure.
• the duration of the plasticity which correlates clearly with the heating rate i.e. decreasing with increasing heating rate is too short.
• the diffusion paths for the released gases increase with increasing width of the plastic zone.
• the gas pressure is maintained over a longer period of time, which can lead to greater homogeneity in the gas bubble distribution as in the previous generation and further reactions of gaseous decomposition products.
• the quality of the feed according to the invention is controlled by measuring the plastic area during coking and when the width of the plastic zone falls below the following depending on the cooking time:
• the minimum distance from the chamber wall or ⁇ 1 pl.min. (Minimum of the width of the plastic zone) is the lower limit, below which further measures must be initiated.
• preheated coal and / or carbo- and / or petro-derived coal binder can be added.
• the width of the plastic zone is the decisive factor influencing the coke quality.
• Their measurement enables a precise prediction of the coke quality that is established and is therefore to be used as a central control variable for the provision of the insert components, the course of the coking process and for the resulting coke quality as a target variable.
• carbo- and / or petro-derived binders reduces the softening temperature of the furnace stock, but hardly changes its reconsolidation temperature. A larger temperature range is created for the plastic zone. This results in a spatial expansion of the plastic zone, so that the above-mentioned essential effects take effect in the duration of the plasticity, in the course of the reactions, in the gas bubble size and in the homogeneity of the gas bubble distribution.
• preheated coal according to the invention also results in a reduction in the temperature gradient. As already explained, this causes the plastic area to widen as a function of the distance from the chamber wall, this effect becoming more important and larger as the cooking time increases.
• the lower heating rate is of great importance.
• the mechanical stresses are reduced. This reduces the tendency to crack.
• the output on blast furnace coke increases as a success.
• the abrasion resistance M 10 ) and the piece strength (M40) increase.
• the average pore diameter of the coke is significantly reduced.
• the average wall thickness of the cell walls of the coke structure increases, which increases the structural strength of the coke.
• the width of the plastic area is measured on the basis of the temperature distribution in the furnace bed. This means that temperature measurements are carried out at closely spaced intervals from the chamber wall to the center of the chamber. The resulting temperature values are compared with the temperature setpoints that determine the minimum width of the plastic area. If the temperature falls below the specified target temperature, coal binders and / or preheated coal are added to the feed mixture in subsequent furnace batches until the desired target temperatures (minimum temperatures) are reached in the furnace. Corresponding to the plastic area that changes during the coking process, the target temperatures corresponding to the limit values of the plastic area must be observed at other points in the cross-section of the furnace in each coking phase. The target temperature can remain constant and assume one of the values between 320 and 480 ° C. A value at the lower temperature limit is preferably selected.
• the quality of the coke can be controlled more precisely the more often the plastic area is measured during the coking process.
• a special accuracy can already be achieved with at least two measurements at intervals of at least 1 hour.
• the temperature measurements are therefore not only carried out at spatial intervals over the width of the furnace chamber, but also at time intervals.
• the spatial distances can be taken into account by a number of temperature measuring devices distributed over the width of the furnace chamber or by a single temperature measuring device which can be moved back and forth across the width of the furnace chamber.
• Thermocouples can be used as temperature measuring devices, which are preferably provided with protective tubes and inserted into the furnace stock before the coking begins. With a suitable choice of material for the protective tubes (e.g. Incoly), longer service lives can be achieved.
• thermocouples can be placed in an electrical comparison circuit with setpoint devices, e.g. Potentiometer, bring.
• setpoint devices e.g. Potentiometer
• the differential voltage can then be taken as a measure of the necessary addition of preheated coal and / or advantageous coal binder.
• Exceeding the target values specified according to the invention is harmless, since with the addition of preheated coal and advantageous coal binders only a limited enlargement of the plastic zone can be achieved.
• the limitation in the admixing of preheated coal results from the maximum preheating temperature of 250 0 C, the limitation for the coal binder from the maximum admixable amount, which should not exceed a certain ratio of carbon substance to the amount of plasticizing additives, taking into account the coke quality.
• every new feed mixture is tested in trial furnaces before it is used on an industrial scale.
• coking experiments are carried out in 350 kg test furnaces with a feed mixture consisting of 67% gas flame coal (36% FB waf) and 33% eating coal (16% FB waf) before being used in the operating ovens of the coking plants.
• the test furnace is modeled on the operational conditions. It has a total width of 340 mm.
• the temperature changes in the furnace batch run symmetrically towards the center of the coke oven. It is therefore sufficient that. Measure the area between a chamber wall and the center of the furnace.
• protective tubes are installed in the oven at intervals of 20 mm, which protrude from above into the furnace bed when the furnace is full and during the coking process allow the introduction of thermocouples and temperature measurements in the furnace stock up to half of the furnace batch.
• the temperature is measured at the prepared measuring points every hour.
• the resulting actual values are compared with the target values belonging to the hourly measurement. It is also possible to choose other time intervals for the temperature measurement.
• the target temperature is a temperature between 320 and 480 ° C. That means, depending on the progress of the coking process, after one, two, four, etc. hours there is a place in the furnace half covered by the temperature measurement, at which the temperature of the charge should be at least 320 ° C. Exceeding this temperature is harmless. On the other hand, if the temperature falls below the target temperature, there is no guarantee that high-quality blast furnace coke will be produced.
• the target temperature always denotes the target position at the boundary of the plastic zone facing the center of the chamber.
• the control variable in the exemplary embodiment is the boundary of the plastic zone facing the center of the chamber. In some cases, the other limit of the plastic zone can also be selected as the control variable. Then the target temperature is 480 ° C and the minimum distance from the
• Chamber wall equals the minimum distance for a target temperature of 320 ° C minus the minimum width specified according to the invention for the plastic zone.
• the following minimum distances from the chamber wall result after a cooking time of four, six, eight and ten hours for the target temperature 320 ° C.
• the measured distances when using moist feed mixture differ from the minimum distances in the table above as follows: instead of 84 mm after four hours only 60 mm, instead of 130 mm after six hours only 104 mm, instead of 167 mm after eight hours only 145 mm and instead of 206 mm after 10 hours only 184 mm.
• the difference between the minimum distances and the desired distances is exemplified by adding Carbopech and / or preheated. Coal decreased.
• the addition of Carbopech brings a maximum 0.5 - 0.8 mm reduction in the difference per percent Carbopech admixture.
• An upper limit of around 15% Carbopech can be assumed. Above 15%, the coke quality changes back to the negative because the amount of plastic components in relation to the remaining carbon structure becomes too large (depending on the type of coal).
• preheated coal The differences to the minimum distance required to achieve the specified target values after the carbopech was added could be eliminated by adding preheated coal to the moist feed.
• preheated coal instead of Carbopech, the only focus is on the addition of preheated coal.
• the addition of preheated coal averages about 4 mm Approximation per 10% addition of preheated coal of 220 ° C preheating temperature. This generally applies to all preheating temperatures above 200 ° C.
• the target values specified according to the invention apply not only to the insert coal selected in the exemplary embodiment but also to other insert coal or insert mixtures, since the influence of the thermal conductivity of the insert material on the course of the temperature fields is small.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Combustion & Propulsion (AREA)
• Coke Industry (AREA)

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• 1980
  • 1980-10-25 DE DE19803040331 patent/DE3040331A1/de active Granted
• 1981
  • 1981-07-29 EP EP81105965A patent/EP0048802B1/fr not_active Expired
  • 1981-10-23 JP JP56168879A patent/JPS57100182A/ja active Pending
  • 1981-10-23 US US06/314,259 patent/US4421604A/en not_active Expired - Fee Related

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