DE3121050C2 - Process for equalizing the feed carbon mixtures for coking furnace batteries - Google Patents

Abstract

The invention relates to a method for equalizing the feed coal mixture for coking furnace batteries, where part of the wet coal is dried and this dried coal is added to the undried portion of the coal and the portion of the dried coal is regulated depending on the desired moisture content of the entire feed coal mixture. The coal is to be dried using the thermal energy from the flue gases from the regeneratively heated coking ovens.

Description

35

The invention relates to a method according to the preamble of claim 1 and a device for Implementation of the procedure.

The purpose of the invention is to provide improvements in the coking operation of horizontal chamber coking furnace batteries to be achieved by equalizing the feed coal mixtures. During operation and especially when heating coking furnace batteries, there are always considerable problems when the moisture content of the coal feed mixture is subject to major fluctuations. before Especially in today's large coking plants, which have a large number of coal components from a wide variety of parts the earth and this in huge storage areas jo If stored in the open air, it can happen that the water content increases due to sudden rainfall Subject to fluctuations. For the heating of the coking ovens, this means that the heat supplied must be adapted to the respective moisture content of the coal feed mixture. If z. B. the battery heating is set for a coal mixture with 8% water and an operating time of 18 hours, approx consumes an amount of heat of 550 kcal / kg wet coal. If the humidity suddenly drops to 5%, the coal needs only 525 kcal / kg feed coal to be fully coked. This is about 5% less than 8% water.

Converted to the heating, the coking furnace could be about 5% earlier, i.e. H. so instead of after 18 hours can be pressed after 17 hours and 6 minutes. But this is because of compliance with the pre-determined printing plan, which does not take into account unforeseen changes, is not possible. This Oven is usually pressed even after 18 hours, although a higher amount of heat is supplied has been as effectively needed. It can therefore be seen that a constant humidity of the Charcoal is of great importance for a uniform coking plant operation and to a heat saving leads. In addition, with a very high water content of the coal used, it has been shown that a> can very easily form so-called moisture pockets in some places of the coke cake during coking. So that these areas are also completely cooked out, it is necessary to lengthen the total coking time. However, this means that large areas of the coke cake when leaving the coking chamber are already overheated.

The object on which the present invention is based is now to achieve a simple and inexpensive equalization to achieve the moisture content of the feed coal, which leads to a saving of underfiring gas. Uniformity of the furnace operation and an improvement of the coke properties leads.

According to the invention, this object is achieved in that part of the wet coal is dried and this is dried Coal is added to the non-dried portion of the coal and the portion of the dried Charcoal depending on the desired moisture content the entire feed coal mixture is regulated.

This partial drying of the coal with subsequent mixing with the remaining feed coal components According to the invention, a relatively low water content of the entire feed coal mixture is achieved and overall an average water content that is practically not subject to fluctuations. In particular In some cases it may be possible to use the entire feed coal mixture the drying system runs through it.

According to the invention, it has proven to be particularly advantageous to dry the portion of the feed coal to be dried directly or indirectly with the aid of the flue gases from the regeneratively heated coking furnace batteries. These flue gases are previously derived depending on the type of Unterfeuerungsgases at a temperature of 200-300 ⁰ C above the chimney into the atmosphere. A utilization of the sensible heat of these flue gases at these low temperatures was not previously possible. From DE-PS 28 16 476 and DE-OS 27 15 536 it is known to preheat the entire charge coal for coking furnace batteries with flue gases to a temperature of 200 ° C, but this is a much higher flue gas temperature than normal regeneratively operated Coke oven batteries required. A temperature of the flue gases of about 250 to 300 ⁰ C after leaving the regenerators would not be sufficient for preheating the entire feed coal to about 200 ° C. According to DE-OS 27 15 536, a flue gas temperature for preheating the coal is therefore also provided, which should in no case fall below 400 ° C. For the heat balance of the entire coking process, this document also provides that a considerable amount of heat is recovered from the coke cooling and used to preheat the combustion media for the coking ovens.

In the previous considerations on the utilization of the sensible heat of flue gases, the main focus was on the fluctuating O2 content of the smoke

against. During the heating period of a battery, the flue gas normally has an oxygen content, which is below about 6%. During the changeover of the heating from one side to the other, the The feed of the underfiring gas is interrupted and the system is only purged with air. This means that then the Or content of the exhaust gases increases sharply, in extreme cases up to 21% in the case of pure air Oxygen content leads to a risk of explosion in preheating systems. The invention now provides that the coal feed to the drying plant is interrupted or interrupted depending on the C> 2 content of the flue gases is started again. When using an entrained flow pipe to dry the coal, the down and The coal feed spinner can be switched on within a very short time, so that no coal is wasted quickly is more present in the entrained flow pipe and thus no more explosive mixture can arise.

According to the invention, it is also advantageous to couple the coal task with the changeover winch and then stop the coal feed during the changeover break. In this case one is of the measurement of the 02 content of the flue gases independently uno can directly receive the switch-on and switch-off signal from the converting winch.

Another measure according to the invention for avoiding an unnecessarily high O ₂ content of the flue gases can consist in mixing the flue gases from coking furnace batteries for use in the drying system, the heating breaks being staggered in time. By mixing two streams, the maximum possible (V content has only a very slight effect on the mean O 2 content of the flue gas achieved, so that a maximum Or content is obtained which is definitely below 10%

The process of the invention offers the following operational, economic and environmental concerns Advantages:

- Heat savings in the coke oven due to lower coal moisture after drying;

- Heat savings in the coke oven as a result of uniform coal moisture, so there are no losses Fluctuations in the heat demand of the feed coal;

- Uniform furnace operation and thus protection of the battery masonry;

- lowering the battery temperature due to lower heat consumption;

- Environmentally friendly, as no hungarian ovens are pressed will;

- Environmentally friendly, as the NO _x formation is reduced at a lower battery temperature.

The method according to the invention is explained using the figure, for example.

The flue gases are from the heating system of the coke oven battery via the flue gas ducts 1 wholly or partially bypassing the flue gas chimney 12 to the drying system of any type. For the necessary suction in the drying operation, as well as for the transport of the coal within the drying system A fan 2 provides for the drying of the coal. A single-stage entrained flow pipe is used here in particular with direct heat transfer from flue gas to coal. Such a system offers a good one Degree of heat utilization with the simplest design without moving parts with minimal wear. She is largely maintenance-free and inexpensive.

The coal to be dried is fed into the drying column 3 via an intermediate container 4. the Coal dried in this way is largely separated from the cooled gas stream in a material separator 6 and The exhaust gases freed from the solids flow through via the conveyor 9 to the mixing device 10 an exhaust gas cleaner 8, in which the remaining fine dust is separated. The exhaust gases cleaned in this way can either directly or via line 16 and controller 15 to battery chimney 12 into the atmosphere be directed. With the help of the control flaps 13 in the flue gas duct 1, the necessary for drying Flue gas volume can be regulated. The excess smoke gases are via the battery chimney 12 discharged

The regulation of the suction for heating the battery is also carried out by this flap 12. In normal operation, a constant amount of flue gas is passed through the drying system 3 The moisture in the coal is measured continuously before and after drying.

Depending on the desired controlled moisture content of the undried coal mixture 5, part of this coal 5b is passed through the drying system and dried to a residual moisture content of 1 to 2% water.

Then it is mixed with the undried coal 5a in a ratio so that at the end of the Process 11 the desired moisture is present. The regulation of the individual coal flows is therefore with the appropriate Specification depending on the continuously measured coal moisture values 5a / 5i> and 11 made automatically.

In the flue gas duct 1, the O2 content of the exhaust gases is continuously measured at 18. The drying company can only be added if the O2 content in the gas is below 10%. The CV measuring device 18 is with the discharge element 17 for wet coal is electrically locked in the dryer. When the O2 content is exceeded from 10% the coal feed 17 is stopped automatically. When falling below the 10% limit again a release signal occurs, which means that the drying operation can be restarted manually or automatically enables.

Accordingly, every time the battery heating is changed over, if the changeover period is 30 minutes, then twice every hour, the coal drying is interrupted for a period of 2 to 3 minutes each time.

Application example

In order to avoid condensation, it is assumed here that the heat content of the waste heat to a TFMP; is utilized raiur of 120 ⁰ C.. In the case of heating with coke oven gas (HU = 17138 kJ / Nm ³ ) there is normally a waste heat quantity of 1.6 NmVkg of moist charcoal, which reaches the outside via the chimney at a temperature of around 290 ° C. The amount of heat that can be used when this waste heat is cooled from 290 to 120 ^° C. is around 272 kJ / kg of moist coal.

In the case of heating with lean or mixed gas (HU = 4389 kJ / Nm ^J ), an amount of waste heat of around 1.65 Nm ³ / kg of moist feed coal is produced. Könren at a cooling of the resulting mixed gas in the heating of the flue gas from 250 ⁰ C to 12O ⁰ C for about 305 kj / kg of moist coal are utilized.

If the moisture on a coking plant

If the content of the coal feed mixture fluctuates from 6-10% H ₂ O, according to the invention the heating of the battery could be set to a water level of 6% and kept constant. This means that in the extreme case the entire amount of coal would have to be dried _{to 6% H 2 O.} The amount of heat required for this can be specified in the following way:

For drying the coal from 10 to 6% water content an amount of heat of 90 kJ / kg moist coal is required for water evaporation and for heating the coal would need the same amount of heat when it is dried by 60 ° C. At a A heat utilization rate of 80% would have to be supplied here so 226 kj / kg moist coal. How from these Numbers can be seen, the usable heat available from the waste heat is higher than the heat necessary for drying. With coke oven gas heating there would be a reserve of approx. 42 kJ and with mixed gas heating, a reserve of approx. 84 kJ / kg moist charge coal is available.

1 sheet of drawings

25th

30th

35

40

50

55

Claims (5)

Patent claims: 1. Process for equalizing the feed carbon mixtures for coking furnace batteries, characterized in that part of the wet coal is dried and this is dried coal is added to the non-dried portion of the coal and the portion of the dried coal regulated depending on the desired moisture content of the entire feed coal mixture will. 2. The method according to claim 1, characterized in that the portion to be dried of the feed coal directly or indirectly dried with the help of the flue gases from the regeneratively heated coking ovens will. 3. The method according to claims 1 and 2, characterized in that the coal task to Drying plant depending on the organic content the flue gases are interrupted or restarted. 4. The method according to claims 1 to 3, characterized in that the coal task to The drying system is coupled with the changeover winch of the coking furnace batteries and during the Changeover pause is switched off. 5. Process according to claims 1 to 4, characterized in that the flue gas is used for drying the coal is taken from two coking furnace batteries at the same time, during which the heating breaks be carried out staggered in time.