DE2844607A1 - Heat recovery from coke-oven gas - using liq. obtained from scrubbing as coolant for the gas - Google Patents

Abstract

The following processes are claimed for recovering heat from coke-oven gas: (A) The gas is cooled by heat exchange with a coolant and then scrubbed with a solvent to remove volatile impurities (esp. H2S). A liq. derived from the scrubbing soln. is used as the coolant, and the heat transferred to it is utilised to strip the volatile impurities from the scrubbing soln. (B) The gas is scrubbed with gas condensate and then cooled by heat exchange with a coolant. A dil. NH4OH soln. recovered from the scrubbing liquor is subjected to activated sludge (AS) treatment, the AS waste water is used as the coolant, and the heat transferred to it is utilised to concentrate the AS waste water by evepn. (pref. in a cooling tower or vacuum evaporator).

Description

Process for the recovery of thermal energy

Coke oven grass The invention relates to the recovery of waste heat in coke ovens and particularly relates to a method of efficient recovery of low temperature waste heat from coke oven gas that is currently being lost, and although without the usual cooling systems for coke oven gas to be changed significantly to need.

The cooling of coke oven gas is currently carried out in the following manner. The coke oven gas with a temperature of around 1000 ° C, which is produced in a coke oven, is brought into contact with a gas liquid in a cooler in a dry way and thereby quenched to about 80 ° C.

The coke oven gas quenched in this way can continue with at least an indirect gas cooler and / or at least one direct gas cooler to one Temperature of about 35 ° C can be cooled. The coke oven gas gives the warmth to sea water or another coolant in the indirect gas cooler and also comes directly comes into contact with water and gives off heat to the water, which is then returned and is used again, as dilute ammonia water or in Form of other refrigerants used in the direct gas cooler.

The diluted ammonia water or other coolant from the direct The gas cooler is in turn cooled by sea water or in some other way.

In this way, the heat in the coke oven gas is raised the gas liquid, the sea water or another cooling medium transferred and is then released into the environment or taken out of the system by the warm Cooling water flows out.

This means wasting valuable energy without losing the huge amount of heat contained in the coke oven gas is used. In some Cases when sea water, lake water or river water is used as a coolant, the large quantities of warm water, especially seawater, give rise to that Form large amounts of dinoflagellates.

As an example of the amount of heat contained in the coke oven gas the following figures are given if e.g. 135,000 Nm3 coke oven gas / hour. be generated.

1) In the dry cooling system, the heat given off by the coke oven gas to the atmosphere is 8,000,000 kcal / h 2) In the circulating line of the gas liquid, the heat given off by the coke oven gas via the gas liquid is 15,000,000 kcal / h 3) In direct and indirect gas cooler is the heat given off by the coke oven gas Sea water-J warm sea water: 74,000,000 kcal / h diluted ammonia water Total: 97,000,000 kcal / h If sea water of 30 0C is used as a coolant, warm sea water of around 530C is released in an internal amount of 3200 m3 / h.

A wide variety of devices are used in a coke oven need large amounts of heat, such as the gas cleaning system, the systems for processing the resulting liquids with absorption columns and towers, with desorption columns or strippers and the like for the separation of impurities, contained in the coke oven gas, such as hydrogen sulfide, hydrogen cyanide, Ammonia and light oils. Because of this, there is a need for an effective one Utilization of the heat contained in the coke oven gas.

The invention is based on the object of a method for recovery to indicate the waste heat of coke oven gas, in which the contained in the coke oven gas Thermal energy is used without the need for existing systems to cool the coke oven gas significantly. This is essentially the case about the recovery of waste heat from the coke oven gas, which was previously not considered valuable has held because it is only at a low temperature, and to the evaluation the heat within the coking plant.

According to the invention the method is for the recovery of thermal energy from coke oven gas, in which the coke oven gas is cooled by heat exchange with is subjected to a cooling medium and cleaning with a solvent, so that a solution is formed which is a volatile contaminant component of the gas contains, characterized in that a liquid which comes from the solution, and which has a temperature lower than the temperature of the blast furnace gas in the heat exchange, is used as a cooling medium in the heat exchange, and that the thermal energy that is transferred to the liquid during heat exchange, is used to remove the volatile component of the liquid by evaporation remove.

In a further development of the invention, a) the cleaning mentioned above with a solvent after cooling the coke oven gas by heat exchange with a cooling medium carried out separately from the quenching by the gas liquid; b) contains the above-mentioned solution of the volatile components of the coke oven gas e.g., hydrogen sulfide; c) the liquid that comes out of the solution is the liquid obtained in cleaning; d) this solution is used as a cooling medium in the above-mentioned cooling of the coke oven gas by heat exchange with a cooling medium used; and e) the thermal energy transferred to this solution during the heat exchange is used to remove the dissolved volatile components such as hydrogen sulfide to be removed from the solution obtained during the cleaning process.

In this case, it is a method of recovering the heat energy from coke oven gas, in which the coke oven gas is cooled by heat exchange with is subjected to a cooling medium, and the cooled coke oven gas is subjected to purification subjected to a solvent to remove a volatile component of the gas resulting in a solution that contains the volatile constituent in solution, the invention characterized in that the solution is an abortion of the volatile Component is subjected to heat, resulting in a lean solution that the lean solution is used as a cooling medium in the heat exchange and that the lean solution used in heat exchange and its temperature has been raised in the process, is used as a heat source during abortion.

In a further development of the invention, the procedure is such that a) the mentioned cleaning with a solvent by quenching with the gas liquid of the coke oven gas is carried out; b) the above-mentioned solution is made with ammonia water diluted; c) the mentioned liquid that comes from the solution is wastewater, obtained when the solution is treated with an activated sludge; d) the waste water is used as a cooling medium in the above-mentioned cooling of the coke oven gas used by heat exchange with a cooling medium; and e) the wastewater during The heat energy communicated by the heat exchange is used for evaporation or evaporation of the volatile components of the liquid, which in this case Water is to be removed, i.e. to concentrate or enrich the wastewater.

This development is a method of recovery of thermal energy from the coke oven gas, in which the coke oven gas is cleaned with a solvent is subjected to the volatile component of the gas remove so that a solution containing the volatile component dissolved is created and the cleaned and quenched coke oven gas is cooled by heat exchange is subjected to a cooling medium.

According to the invention, the coke oven gas is in this method Subjected to cleaning, the solvent for cleaning the gas liquid is, whereupon dilute ammonia water is produced from the gas-liquid, which the Waste water resulting from the treatment of the diluted ammonia water with activated Sludge, is used as a cooling medium in heat exchange and that the thermal energy, which is transferred to the wastewater during the heat exchange, is used to concentrate the wastewater, the wastewater to be concentrated either (a) is the wastewater to which the thermal energy has been transferred during heat exchange is and where the concentration is through ventilation of the wastewater whereupon evaporation of the water is accelerated by the transferred thermal energy or where (b) the wastewater is used as a cooling medium for heat exchange and concentration by evaporation of water under reduced pressure Heat takes place, which comes from the sewage to which the thermal energy is transferred has been.

Nn the. The following description are exemplary embodiments of the invention explained in more detail with reference to the drawings.

In the drawings, Fig. 1 is a flow chart showing a prior art Represents a method for cooling coke oven gas; Fig. 2 is a flow chart showing a Embodiment of the method for cooling the coke oven gas according to the invention represents; and FIG. 3 is a flow chart showing another embodiment of the Illustrates method according to the invention for cooling coke oven gas.

To facilitate understanding of the invention, a first known method for cooling coke oven gas described in connection with FIG. Coke oven gas 2 with a temperature of about 10000C, which is generated in a coke oven 1 is quenched to about 800C by a gas liquid 4 contained in a dry pipe 3 is sprayed. The coke oven gas cooled in this way is then further to about 35 0C with the help of at least one indirect gas cooler 6 and / or at least one direct gas cooler 7 cooled.

In the direct gas cooler 7, a dilute ammonia water 10 is used used as a cooling medium and by sea water or a circulating through a cooler 8 Chilled water. The heat originally contained in the coke oven gas 2 is increased the gas liquid 4 and the sea water 9 or that circulating in the cooling tower Transfer water 9 and then led out of the system and into the ambient air or released the outflowing seawater. The gas liquid circulates through a Tar separator 5 and is used again. Part of the gas-liquid, from the tar is deposited is withdrawn as dilute ammonia water at point 4a.

In this known cooling system, the main gas line 3 contains a Suitable design for gas / liquid cooling apparatus. The tar separator 5 is used to to separate the diluted ammonia water and tar due to the differences in density. The indirect gas cooler 6 is designed, for example, so that a cooling medium is a coil permeated and the gas to be cooled sweeps along the outer surface of the coil. The direct gas cooler is a gas / liquid contact device such as an F: Ullbody column, a spray tower or a column for working in stages. The dimensions that required heat exchange surfaces, the contact surfaces for the gas and others Details of the apparatus can be adapted to the respective conditions of the coke oven will.

The first embodiment of the invention, which is shown in FIG refers to the case that hydrogen sulfide is a volatile component in which coke oven gas is recovered.

The coke oven gas in line 2 coming from the coke oven 1 is Quenched to about 800C by gas liquid 4 sprayed into the main pipe 3 will and will continue to about 35 0C in an indirect gas cooler 6 and in one direct gas cooler 7 is cooled in a manner similar to that in the case of FIG. By doing indirect gas cooler 6 becomes part 15a of a lean solution 15 in this case from the bottom of a desorption column or volatile contaminant stripper 12 used as a cooling medium instead of sea water or a circulating cooling water. The temperature of this lean solution 15a is consequently increased by the heat exchange between the lean solution and the coke oven gas in the indirect gas cooler 6 is increased and flows through line 15b.

A feature of the invention is that the lean solution 15b, whose temperature has been increased in the indirect gas cooler 6 as a heat source for the abortion or desorption column 12 is used. Because of this, you can use the Consider the indirect gas cooler 6 also as a preheater for the aborter 12. if and the amount of heat of the lean solution 15b due to the heating by the preheater a preheater 17 can be installed as a heat source for the stripper 12 is not sufficient which uses the hot gas liquid of the main line 3 as a heat source, to create a lean solution 15c that heats to an even higher temperature and which is fed to the aborter 12 together with the lean solution 15b.

The remainder 15d of the lean solution from the bottom of the aborter 12 becomes passed through a heat exchanger 14 and a cooler 13 and used as a cleaning fluid 15e fed to a cleaner 11 by using the lean solution 15e to remove the volatile impurities such as hydrogen sulfide in the coke oven gas. The resulting solution absorbing the volatiles Has and leaves the cleaner 11, i.e. an enriched solution 16 passes through the heat exchanger and is fed to the stripper 12 where the volatile constituents 18, such as e.g.

Hydrogen sulfide absorbed by the solution is desorbed and be deposited.

The heat originally contained in the coke oven gas is therefore in the indirect gas cooler 6 and the preheater 17 and serves as a heat source for the separation of the volatile constituents.

The aborter 12 has such a structure and such a mode of operation, that it can separate volatile constituents from a solution. Examples of suitable Apparatus are packed columns, columns for step-by-step work and constructions, which resemble the distillation columns. The hot lean solution 15b becomes in the aborter 12 spontaneously evaporated to produce steam, and the steam generated in this way is then brought into direct contact with the cold rich solution for heating.

Another embodiment of the method according to the invention is illustrated in FIG. 3. This process uses dilute ammonia water 4a obtained on the gas liquid 4 is purified by an active sludge (the device for this is not shown) and the resulting waste water is called Cooling medium used for the indirect gas cooler 6 for the coke oven gas, so that the waste heat of the coke oven gas, which is recovered in this way, for the Concentration of this wastewater is used.

As is apparent from FIG. 3, the coke oven gas 2 of the coke oven 1 becomes quenched to about 80 0C in the main pipe 3 by spraying the gas liquid and then when passing through the indirect gas cooler 6 similar to that shown in FIG cooled further. The wastewater 20a from an activated sponge process, which flows out of a cooling tower or a vacuum evaporator 21 is used as a cooling medium passed through the indirect gas cooler 6, instead of sea water or a circulating one Cooling water. The wastewater 20b from the activated sludge treatment, which leaves the indirect gas cooler 6, becomes a cooling tower or vacuum evaporator 21 fed and for the evaporation of the waste water 19 from the process with activated Used mud. In this case, the material of the heat transfer tubes in the indirect gas cooler 6 chosen so that it resists the corrosion of the sewage.

When the amount of heat to concentrate on the cooling tower or the vacuum evaporator 21 is not sufficient, a sewage heater 22 is installed, the hot gas liquid 4 from the main pipe 3 used as a heat source and a part 20c of the waste water from the sludge process is passed through.

The heated wastewater 20b of the activated sludge process is concentrated and by evaporation of part of the water content in the cooling tower or cooled in the vacuum evaporator 21 and again in the indirect gas cooler 6 and the sewage heater 22 returned. This concentrated wastewater becomes the Taken from the system and subjected to an end process, e.g. by incineration or Crystal separation (not shown).

An exemplary embodiment of a device for evaporating the water from the waste water 20b exiting the indirect gas cooler 6 is a cooling tower. In a cooling tower such as is generally used for cooling water the latent heat when evaporating the water to be cooled is used to achieve the cooling effect to reach and at the same time finds saturation as a result of the evaporation of the Water instead. In the invention, this becomes the satiety effect or concentration exploited. Because the wastewater to be concentrated is at an elevated temperature is because it is used as a cooling medium in the indirect gas cooler 6 is the amount of water evaporated in the cooling tower is greater than it would be if the Temperature nSht would have been raised. The heat energy of the coke oven gas is here effectively exploited. The construction of the cooling tower per se is known and it can E.g. a construction can be used, the inrry's "Chemical Engineers1-Handbuch" is described.

Another method of utilizing the thermal energy of the wastewater 20b, the temperature of which has been raised and which leave the indirect gas cooler 6 consists in using it as a heat source for heating a vacuum blower or Evaporator and for the concentration or accumulation of the wastewater 19 (from the sludge process) to be used, which is fed to the indirect gas cooler 6.

The construction of the vacuum evaporator can be selected accordingly and information about the required heat exchange surfaces and the degree of vacuum can be taken from the manual mentioned above or from other literature sources.

The diluted ammonia water is made from the gas liquid and / or generated when quenching the coke oven gas, so that an aqueous part is obtained, from which non-aqueous components such as oils, tars and the like. Are removed. The processing of the dilute ammonia water that this way from the activated sludge process is won is known per se.

Exemplary embodiments are provided to further illustrate the invention indicated, which, however, are not intended to limit the invention in any way.

EXAMPLE 1 This example relates to the above Embodiment of the invention.

The method of the invention has been used in the treatment of 135,000 Nm3 / h of coke oven gas used, which contained 6.16g / Nm3 hydrogen sulfide, whereby the coke oven gas was quenched to 81 ° C in the main pipe by adding a gas liquid was sprayed with an amount of 2,000m3 / h. The gas liquid, the heat out had absorbed the coke oven gas, gave off the heat to the ambient air and took a temperature of about 75 0C.

Of five indirect gas coolers that were normally used two were used as preheaters, while the other three were used as normal indirect ones Gas coolers were used.

The lean solution flowing out at the bottom of the aborter with a Volume of 1,734 m3 / h was heated from 530C to 620C, while the coke oven gas from 81 0C was cooled to 610C. To compensate for the abortion's heat deficit and To regulate the heat, a boiler was installed, the gas liquid as a heat source used. Gas liquid at 750C was passed through this boiler, with a Flow rate of 1000m3 / h and the lean solution with a flow rate of 417m3 / h The temperature at the bottom of the aborter was from 53.degree. C. to 650.degree. That warmed up in this way lean solution was returned to the bottom of the aborter, which was with a vacuum of about 100 torr and the depressurization generated steam and the hydrogen sulfide was driven off from the rich solution, which was fed to the top of the aborter.

The gas that passed the indirect gas cooler was at 35 0C cooled in the direct gas cooler, in which diluted ammonia water circulated.

In this way, 80-9096 of the hydrogen sulfide were removed from the Removed coke oven gas and hydrogen sulfide gas with a concentration of 40 - 60 Volo was won. The steam consumption in the expeller for the volatiles was zero.

It was then a normal working method according to the above information, but carried out without applying the invention, from which it was found that the feed of steam at around 38 metric tons / h was necessary. It was also possible to reduce the amount of sea water for cooling the coke oven by 1000m3 / h.

AusfUhrungsbeispiel 2 This embodiment relates to the second embodiment according to the invention.

In a coking plant that produced 135,000 Nm3 / h of coke oven gas, 61.5 m3 / h of wastewater was generated from a sludge process for processing excess Ammonia water, processed according to the invention. The properties of the Wastewater from the sludge process are together with that of the concentrated Enter wastewater in table 1.

Of five indirect gas coolers that were normally used three were used as sewage liquid heaters, and sewage of 350C became passed through this indirect gas cooler with a flow rate of 1,660m3 / h and heated to 540. The coke oven gas was cooled from 81 0C to 520C. the other two indirect gas coolers were used as normal indirect gas coolers.

The waste water, which was heated to 540C, was in an R tower 21 cooled with a natural draft to 35 ° C by the evaporation of the water content in the air. This waste water was concentrated and was fed back to the indirect gas cooler 6.

In this way 54.2 metric tons / h of water were put into the cooling tower 21 evaporated with natural draft and concentrated wastewater with those in the table The data given in 1 was obtained with a flow rate of 1.3m3 / h.

It was possible to get this concentrated wastewater in a simple manner burn off by normal wet combustion or by sewage oxidation and it was possible to completely get rid of this wastewater.

In the example above, all of the heat was needed for concentration of the waste water was necessary from the heat of the coke oven gas at low temperature obtain.

Using steam would require about 58 metric tons / hour been. It was also possible to control the amount of sea water used to cool the coke oven gas was necessary to reduce 1,600m3 / h.

Table 1 Waste water from concentrated products the wastewater process with activated mud PH 9 3 - 9 COD (ppm) 165 500 CN "0.45 3 SCN n 5.8 10 cl "904 7000 S04-2 "626 4500 -2ft n 27.3 50 5203 Fe + 2 "1.3 10 Oa + 2 "6.5 50 Na + n 1160 9000 2 "1124 4000 SO3-2 n 6.5 50 The example mentioned and a known method will now be compared with one another. Examples of known methods of treating the waste water after it has been subjected to the activated sludge process are 1) a method in which the waste water is used to extinguish the coke; 2) a method in which the waste water is subjected to adsorption by treatment with activated carbon; and 3) a method in which the waste water is incinerated after concentration. All of these procedures have certain difficulties.

In method 1), in which the waste water is used to extinguish the coke is used, a large amount of corrosive fumes with the attached coke odor will be produced generated. The second method is to use the activated carbon very expensive, so that there are high costs for the apparatus and the operation. at the third method is a large amount of thermal energy, e.g. B. in vapor form er $ rderEth to concentrate the wastewater and the cost of the apparatus are also high.

In contrast, the method according to the invention is involved a very advantageous method that eliminates the difficulties of the known methods do not occur.

The large amount of thermal energy required for the concentration of the wastewater is required by recovering waste heat from the coke oven gas covered, whereby not only the use of an additional heat source, e.g. in form of steam is unnecessary, but the concentration of the wastewater by utilizing it takes place by equipment that is required for the normal cleaning of the coke oven gas are.

For this reason there is almost no need to expand the facility and expand, so that there are great economic benefits. When combined the specified method according to the invention and a conventional wet combustion or wastewater oxidation, the wastewater can be completely eliminated.

According to the invention explained in more detail in the exemplary embodiments can be achieved by using indirect gas coolers, which have already been used for cooling have been used by coke oven gases or with minor modifications of the used material and the temperature maintaining devices and the heat exchanger in the gas-liquid system, the low-temperature coke oven gas acts as a heat source for further processes, e.g. the purification of the coke oven gas and the concentration the wastewater liquid used will. That way will the consumption of thermal energy, e.g. steam, when operating a system is reduced and at the same time the consumption of sea water as a coolant is reduced, so that the flow rate of the discharged warm seawater can be reduced.

Furthermore, since the concentration of the wastewater by the method according to the invention up to such a con- centration can be carried out so that this waste water is possible in an economical way with known processes of combustion or oxidation, the waste water can be completely removed from the coking plant by combining this known process.

Furthermore, there are those commonly used in a coke making plant Apparatus can be used and almost no additional apparatus or Equipment for waste water concentration is required and only individual Parts of the apparatus need to be supplemented is the method of the invention extraordinarily economic.

Another advantage of the invention is that for the treatment of the Sewage practically no additional space is required.

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Claims (7)

Patent claim 1. Process for the recovery of thermal energy from Coke oven gas, in which the coke oven gas is cooled by heat exchange with a Cooling medium and cleaning with a solvent is subjected so that a solution is created that contains a volatile contaminant component of the gas, characterized in that a liquid which originates from the solution, and the has a temperature lower than the temperature of the blast furnace gas at the Heat exchange is used as a cooling medium in heat exchange, and that the Thermal energy that is transferred to the liquid during heat exchange, in addition is used to remove the volatile component of the liquid by evaporation. 2. The method according to claim 1, d a d u r c h g e k e n n z e i c h not that the solution is subjected to heat abortion of the volatile component is, with a lean solution that the lean solution as a cooling medium when Heat exchange is used and that the lean solution used in heat exchange has been used and the temperature of which has been raised, as a heat source in the. Abortion is used. 3. The method according to claim 2, characterized in that the volatile the component to be driven off is hydrogen sulfide. 4. The method according to claims 2 or 3, characterized in that the lean solution used as a heat source with which to perform the abortion is preheated by indirect heat exchange with hot gas liquid wwd, which is obtained by extinguishing the coke oven gas. 5. Process for the recovery of thermal energy from coke oven gas, in which the coke oven gas is subjected to cleaning with a solvent, to remove a volatile contaminant component of the gas, a Solution is created which contains the volatile component and which is cleaned Coke oven gas is subjected to cooling by exchanging heat with a cooling medium is characterized in that the coke oven gas is subjected to cleaning, in which the solvent for cleaning is the gas liquid from which the diluted Ammonia water is obtained that wastewater resulting from the treatment of the diluted ammonia water with an activated slim results as a cooling medium is used in heat exchange, and that on the waste water in heat exchange transferred thermal energy is used to concentrate the wastewater, whereby the wastewater to be concentrated is either (a) the wastewater on which the thermal energy is applied when heat is transferred, and where the concentration is through ventilation of the wastewater is carried out in which an evaporation of the water by the transferred thermal energy is accelerated, or wherein (b) the water as Cooling medium is used in the heat exchange and the concentration by evaporation the water takes place under reduced pressure under heat that comes from the wastewater, to which the thermal energy has been transferred. 6. The method according to claim 5, characterized in that the waste water, to which the heat energy is transferred during heat exchange, which is used for this is used to concentrate the wastewater, through indirect heat exchange with the hot gas liquid is preheated, which is obtained during the cleaning of the coke oven gas will. 7. The method according to claims 5 or 6, characterized in that the ammonia water from the gas liquid by removing an aqueous portion is won.