UA114198C2 - METHOD AND DEVICE FOR GASIFICATION OF SOLIDS - Google Patents

Abstract

In the gasification of carbonaceous solids with oxygen and/or steam, the solids are at least partly converted to CO and H2 in a first process step (10). In a second process step (20), a stream containing water then is separated from the product mixture obtained. This stream containing water finally is subjected to water purification in a third process step (30). This water purification is effected such that three streams (31, 36, 37) with different degrees of purity are obtained, at least one of which is recirculated in the process.

Description

The present invention relates to a method and device for gasification of solid substances containing carbon, and in the first stage of the method, solid substances are, at least partially, converted into CO and H in the gasification process, and in the second stage of the method, steam containing water is separated, and and at the third stage of the method, the water-containing steam obtained at the second stage is subjected to the water purification process.

Gasification is a chemical-physical process in which at least part of a solid substance turns into a gaseous end product. The gaseous end product is a mixture consisting mainly of carbon monoxide (CO) and hydrogen (Hg). Many reactions take place at the same time, which were not fully known until now. Actual gasification occurs due to exothermic combustion of solids. The products of this reaction can then react with the solids and the additionally introduced steam or with each other. Except for the combustion reaction, all basic reactions are equilibrium reactions, so the transformation can also go in the reverse direction. At relatively high temperatures during coal gasification (from 600 to 1600 C), the composition of the gaseous product is usually close to equilibrium.

In principle, three different types of solids gasification methods are known: gasification in a fluidized bed, gasification in a fixed bed formed by solids, and finally, gasification in a reactor with gasification in a flow.

Regardless of how the gasification reaction proceeds, the synthesis gas obtained in it with CO and Ne should not be purified afterwards. Since the reaction requires steam as a starting reactant and water is one of the possible reaction products, water, among other things, must be removed from the gas stream.

The separated water stream also contains impurities such as solids, ammonia, phenols, etc., so the water stream must be purified.

This method is known, for example, from OE 41 07 109 C1. Solid fuels are gasified at pressures ranging from 10 to 100 bar using a gasifying medium containing oxygen and steam to produce raw gas. The raw gas coming out of the gasification process is cooled to temperatures from 20 to 200 9C, with the help of which water-rich condensate is obtained.

The condensate is separated and, at least partially, evaporated, while the condensate steam and salt-containing brine are removed separately. The brine containing salt is burned, the condensate steam is partially added to the purified raw gas.

RE 35 15 484 describes that the condensate obtained during the step cooling of the gaseous product is cooled in a washing and cooling device, which is supplied with circulating water, by means of which the halogens are largely washed out. The used washing water, which has a temperature of 120 to 220 "C, is expanded to a lower pressure, with the help of which a vapor and a liquid phase are obtained. The vapor, practically free of halogens, is removed, the main part of the liquid phase is fed back into the device for washing and cooling , and the remaining liquid phase is sent for disposal.

ORE 32 07 779 A1 describes that the condensate obtained from the synthetic gas is expanded and fed to a separator from which the condensate phase, which is largely composed of water, is removed. The condensate phase is cooled by direct contact with the cooler gas before it is used to cool the raw gas stream. The heated cooling gas containing steam is fed to combustion and used, for example, to heat the reactor. ro 147679 describes the recirculation of a stream consisting mainly of water originating from a hydroclone in which a solids-rich stream is separated from a solids-poor stream. The flow from the upper drain, poor in solids, is mixed with the gasifier outlet flow and serves as a source of steam required for the reaction. The solids-rich underflow is distilled at atmospheric pressure for further purification.

OV 2 198 744 A, finally, describes the gasification of coal in a fixed bed, in which, after separation of gases, the flow of waste water is sent to a device for evaporation. From there, the gaseous component is recirculated into the reactor as a gasification medium.

Recirculation of water flow, which partly contains a significant amount of solids, is otherwise known from completely different processes. For example, 05 5 586 510 describes the production of cement in a rotary kiln, wherein the sludge from the cement production is recirculated into the rotary kiln, pulverized there and fired.

All methods have in common that a larger amount of wastewater cannot be further used in the method. Therefore, expensive subsequent treatment of the wastewater is necessary to treat the stream or streams so that disposal complies with environmental regulations.

For this reason, the goal of the invention is to reduce the production of wastewater during the gasification of solids.

According to the invention, this goal is solved by a method with the features of clause 1 of the claims. A solid containing carbon is gasified and, at least partially, converted to carbon monoxide and hydrogen in the presence of oxygen and steam. The produced gas mixture is then fed to a separator in which the liquid fractions are separated from the gas fractions, resulting in a stream of so-called raw gas and a stream containing water.

The liquid stream containing water is finally subjected to water treatment.

According to the invention, water purification is carried out in such a way that three streams with different degrees of purity are obtained. The first flow has the highest degree of purity, consists almost entirely of water and has the following composition:

Table 1:

Compounds contained in the first flow of internal

The total amount of iron (Re) μg/l "- 200, mostly " 20

The total amount of copper (Cy) μg/l is 30, mainly "Z

The total amount of silicon dioxide (5102 μg/l "- 200, mostly " 20

The total amount of sodium (Ma) μg/l "- 100, preferably " 10

Organic components of RH µg/l "2000, mostly "200 (chemical oxygen consumption, abbreviated SOJ)

Electrical conductivity μS/cmM « 0.2-2, preferably « 2

Oxygen (O2 μg/l 50-1000, preferably 50-250

Thus, such a flow is suitable for use in steam generation. If the flow does not reach these limit values, then the first flow can be used as cooling water inside the plant.

The second stream has an average degree of purity:

Table 2:

Compounds contained in the second stream

Organic components (chemical oxygen consumption, abbreviated SOJ) mg/l 100-10000

Organic components (biochemical oxygen consumption, abbreviated BOBV) mg/l 10-1000

Ammonium nitrogen (abbreviated MNa-M mg/l 5 - 500

Nitrate nitrogen (abbreviated MOz-M mg/l 5-1000

Phosphate phosphorus (abbreviated as POA-P) mg/l 2-100

The total content of suspended substances (abbreviated T55) mg/l 5-1000

The total content of dissolved substances (abbreviated TO5) mg/l 100-25000

The third stream has the lowest degree of purity and has a high solids content:

Table 3:

Compounds contained in the third stream

Organic compounds 95 by mass

Compounds containing nitrogen and/or phosphorus 95 by weight

Metal hydroxides 95 by mass

The procedure according to the invention involves recirculation of each of these three streams. The flow of water, which has the highest degree of purity, is supplied to the water inlet of the steam generator; the flow of water, which has an average degree of purity, is supplied for further processing of the ash obtained in the gasification reactor; and/or the water stream, which has the lowest degree of purity and is rich in solids, is sent back to the gasification reactor.

It is particularly advantageous when all three streams are recirculated in the gasification plant itself.

Thus, the amount of wastewater produced in the process can be significantly reduced, or can be completely reduced to zero.

At the same time, streams with an average and lowest degree of purity can also be recirculated together into the gasification zone, as a result of which a particularly complete use of the organic compounds contained in them can be made.

In part, the degree of purity of the first stream does not reach the purity necessary for steam production. At the same pH value, it then has a composition in which the individual components are present in a concentration three times, or partially even six times higher, compared to the concentration indicated in Table 1. A stream with this composition can be used as a cooling water stream at any point in the process without evaporating the cooling water, or can be added to the cooling tower of the gasification plant.

In one preferred aspect of the invention, the stream with the lowest degree of purity is separated in the first stage by means of decantation. It is also possible to reduce the water content, for example, by means of evaporation. Then, in the second stage, the remaining flow is fed to the reverse osmosis unit. Reverse osmosis is a physical process for concentrating substances dissolved in liquids in which the natural process of osmosis is reversed by applying pressure. The environment in which the concentration of a certain substance should be reduced is separated from the environment in which the concentration should be increased by means of a semipermeable membrane. In this case, the concentration of solids in the incoming stream of water should be reduced, and increased in the outgoing stream with the lowest degree of purity.

The environment in which the concentration must be increased is subjected to a pressure that must be higher than the pressure obtained by the osmotic demand for concentration equalization.

This leads to the migration of particles against the direction of propagation. In this process, the obtained purified first stream is preferably again subjected to a second reverse osmosis to obtain a stream with the highest degree of purity and a stream with an average degree of purity.

Intermediate purity fractions of the stream can also be obtained using an ion exchange unit located upstream of the reverse osmosis unit. Two medium-purity fractional streams from the ion exchange unit and the unit

From reverse osmosis, they are then mixed.

Before the separation of the three streams and/or between the separation of the stream with the lowest degree of purity, the water content of which is below 80 95 by mass, preferably below 50 95 by mass, and especially preferably below 3095 by mass, and reverse osmosis may provide further stages of purification , such as denitrification, nitrification and/or removal of organic compounds.

Denitrification refers to the conversion of nitrogen bound into nitrate (MOz-) into molecular nitrogen (Mg) with the help of heterotrophic and some autotrophic bacteria that are attached to the membrane. In this process, which is used to generate energy by bacteria, various oxidizable substances (electron donors), such as organic substances, hydrogen, hydrogen sulfide (He5), and molecular hydrogen, are oxidized by nitrate as an oxidant (oxidizing agent) in the absence of molecular oxygen (Og ) (oxygen-free conditions).

Nitrification means the bacterial oxidation of ammonia (AM) to nitrate (NO). It consists of two connected partial processes: in the first part ammonia is oxidized to nitrite, in the second partial process it is oxidized to nitrate.

Removal of organic compounds is mainly carried out by means of anaerobic treatment by bacteria in an oxygen-free environment.

Furthermore, it has been found to be advantageous to use the steam produced in the steam generation process within a steam supply system for a gasification process, for example to preheat feedstocks, for example in a distillation process, and/or to use the steam to generate electricity, e.g. to drive the turbine. In this way, the water requirement of the process can be reduced.

First of all, when gasification is carried out in a fixed bed reactor, the ash obtained there must be washed. For this purpose, according to the improvement of the invention, a stream of water with an average degree of purity is used.

During gasification in a fixed bed, this ash is produced as a result of the reaction of substances containing carbon, such as coal or biomass, and falls through the grate provided in the bottom region of the fixed bed. For further transport of ash, water is introduced and, thus, the ash is washed away.

In the method of gasification, which is carried out in a fluidized bed, it was found that it is particularly advantageous to recycle a flow with an average degree of purity into the reactor.

For in-stream gasification, it is recommended to mix the medium-purity stream either with the starting materials fed to the reactor as sludge and/or after rapid cooling with the sludge/wastewater stream.

In addition, it may be necessary for the water stream having the highest degree of purity and/or that water stream having the middle degree of purity to be subjected to further purification before recycling to the steam generator, or further ash treatment. Such post-treatment provides significant recirculation of wastewater streams even when large amounts of contaminants are introduced into the process by the solid feedstock used.

Possible further purification processes may be chemical processes such as reaction

Fenton (oxidation of organic substrates with hydrogen peroxide in an acidic environment, which is catalyzed by iron salts), ozonation (sterilization by the introduction of ozone), the use of activated carbon (as an adsorbent) and/or the addition of calcium hydroxide (to reduce water hardness by ion exchange). The use of precipitating or coagulation agents is also possible. In addition, separators and/or wastewater treatment plants may be used.

Additionally, one preferred aspect of the invention provides that solids are gasified in a fixed bed.

In fixed bed gasification, it has been found advantageous to inject a stream of water of the lowest degree of purity above the fixed bed, the stream being injected as finely divided as possible.

When an in-stream gasification reactor is used, it is possible to feed a water stream of the lowest degree of purity directly through the feed lines into the burner flame. In a fluidized bed reactor, spray over the fluidized bed must also be taken into account. When the gasification fuel in the stream is supplied as a slurry, it is recommended to mix the stream with this slurry before entering the reactor area.

On the one hand, coal can be used as a solid substance. Coal gasification processes have been used for decades. On the other hand, biomass can also serve as a source material, with the help of which renewable raw materials can be transformed into synthesis gas. First of all, during the gasification of biomass, the above-described method can

It is of interest, since the main amount of unburned material is discharged by the water flow.

In addition, the invention offers an installation for the gasification of a solid substance containing carbon, with features according to paragraph U of the claims. Accordingly, the installation comprises a gasification reactor in which the solids are at least partially converted into carbon monoxide and hydrogen, a separation device in which the raw gas is separated from the liquid water stream, and a water treatment device in which the aqueous liquid stream obtained in separator, is cleaned. During water purification, the water stream is divided into three streams with different degrees of purity. Through the first pipeline, the flow of water, which has the highest degree of purity, is supplied to the water inlet of the device for generating steam; through the second pipeline, this flow of water, which has an average degree of purity, is supplied to the device for further processing of ash from the gasification reactor; and/or through the third pipeline, the flow of water, which has the lowest degree of purity, is sent back to the gasification reactor.

Preferably, the device for separating the gas fraction from the liquid flow is made in the form of a condenser or in the form of a droplet separator. The design in the form of a condenser has the advantage that at the same time the gas flow is further cooled. When a droplet separator is used, the gas flow can already be pre-cooled and the thermal energy extracted during cooling can be used in some other place.

The installation according to the invention, preferably, between the gasification reactor and the separation device, also contains a device for cooling the gas, which is recommended, first of all, when the gas-liquid separator is made in the form of a droplet separator and, thus, the cooling must be carried out in a way in any another place

In addition, the installation according to the invention, preferably, between the separation device and the ash processing device contains a device for extracting ammonia.

In gas-liquid separation, the liquid stream from the gas cooler is further separated by decantation, with resins, oils, phenols and ammonia (MH3) being largely separated.

Further treatment of the water can be carried out downstream with the Phenosolvan process (Ripepozoimap). In the Phenosolvan process, water containing phenol is thoroughly mixed with Phenosolvan (trade name for diisopropyl ether) in a multi-stage BO extractor according to the mixer-separator principle After the next phase separation,

most of the phenols are present in the solvent. This process is repeated several times, and the water containing phenols and the solvent are sent in countercurrent. The solvent is separated from the phenols by distillation and flows back into the extractor to wash out the phenols.

After the "phenosolvan" process, the SI process can be carried out. (Spetiye I ip2-I shgdiU). In this process, acid gases and ammonia are removed from the condensate of the "phenosolvan" process by selective distillation.

Thanks to this plant design, especially in connection with the increasingly restrictive requirements for environmental protection, investment costs and operating costs can be significantly reduced, since the expensive treatment of the waste water to be disposed of can be completely or partially eliminated. By feeding a stream containing the bulk of the solids back into the gasification process, the separation of the solids from the water via the energy-intensive drying operation can be eliminated.

When a medium-purity water stream is used for ash washing, the cost of additional fresh water and the cost of further treatment of the medium-purity water can be saved.

Other characteristics, advantages and possible applications of the invention can also be taken from the following description, given as an example of an embodiment, and graphic materials. All features described or illustrated form the subject of the invention by themselves or in any combination, regardless of their inclusion in the claims or their back references.

On graphic materials:

Fig. 1 shows a scheme of the sequence of operations of a conventional method of gasification with subsequent treatment of waste water according to the known state of the art;

Fig. 2 shows a diagram of the sequence of operations of the method according to the invention.

In a conventional method, as shown in fig. 1, solids are introduced into the gasification reactor 10 through pipeline 1, and oxygen is introduced through pipeline 2. Through these pipelines, or through another pipeline not shown, steam is supplied to the reactor 10. Through the pipeline 14, the gas mixture formed as a result of the reaction is supplied from the reactor 10 to the gas cooling device 20. From this gas cooling device, raw synthesis gas is withdrawn through

From the pipeline 21. Through the pipeline 22, the obtained liquid flow is fed to the gas-liquid separator 23. From there, it is introduced into the device 25 for extracting ammonia through the pipeline 24.

Between the gas-liquid separator 23 and the device 25 for extracting ammonia, the "phenosolvan" process (not shown in Fig. 1) can be provided.

From the ammonia extraction device 25, a liquid stream containing water is transferred to the water treatment device 30 through the pipeline 26. From the water treatment device, on the one hand, the wastewater is discharged through the pipeline 31 and, if possible, is treated in such a way that the wastewater can be disposed of Through the pipeline 32, a stream containing most of the solid particles is taken and is therefore also called a sludge stream.

The stream containing the solids is fed to a drying device 33, in which the water contained in the stream is evaporated by the application of energy and released to the atmosphere. Then the dried sludge, for example, can be taken to a landfill.

From the gasification reactor 10, especially if gasification takes place in a fixed bed, the ash is discharged through the pipeline 11 and fed to the device 12 for further processing of the ash. The fly ash is then discharged through pipeline 13.

In this method, the water obtained from the wastewater treatment device is disposed of as wastewater, but is not recirculated into the process. Instead, fresh water is introduced at some point in the process.

In fig. 2 shows the configuration of the method according to the invention in the form of a scheme of the sequence of operations, and the solids to be gasified are also fed to the gasification reactor 10 through pipeline 1, and oxygen is fed through pipeline 2. From the gasification reactor 10, ash is removed through pipeline 11 and fed to the device 12 for further processing of ash. From this device for further processing of ash, ash is then discharged through pipeline 13.

In the illustrated embodiment, the gasifier 10 is designed as a fixed bed reactor and contains a substantially cylindrical vertical reactor with an outer water jacket. Coal or biomass is fed from above through a sluice into a solids distributor located inside the reactor, whereby a fixed bed is formed which rests on a rotating grate located in the lower region of the reactor 10. Oxygen and steam are also introduced from this lower region. Due to the hot gases rising in the upper part of the gasifier 10, the used coal or biomass is dried,

as well as desorption of physically adsorbed gases. Below the drying zone there is a reaction zone, in the upper part of which degassing of coal or biomass takes place. Inside the reaction zone, degassing is followed by the actual gasification of coal or biomass according to the Budois reaction. In the next, lowest zone, combustion of coal or biomass takes place, as well as the reaction of water gas formation and the reaction of water gas conversion. The resulting gas falls through the grate and is discharged from there. The hot gases, which are directed countercurrently to the coal or biomass falling from above, are discharged through an exhaust pipe located above the fixed bed.

Through the pipeline 14, the gas mixture obtained by the gasification reaction is removed from the reactor 10 and fed to the refrigerator 20. As a result of cooling, raw synthesis gas is obtained, which is discharged through the pipeline 21. Through the pipeline 22, a liquid stream containing water flows into the gas-liquid separator (separating device) 23. It is also possible that the separation of gas and liquid is caused exclusively by condensation in the gas cooler 20.

From the gas-liquid separator 23, which can be designed as a condenser or a droplet separator, the resulting liquid flow is recirculated to the ammonia extraction device 25 through the pipeline 24. Between the gas-liquid separator 23 and the ammonia extraction device 25, a "phenosolvan" process can be provided ( not shown in Fig. 2). From the ammonia extraction device 25, the pipeline 26 then leads to the water treatment device 30. The water stream obtained there is divided into three streams. That flow, which has the highest degree of purity, is supplied through the pipeline 31 to the steam generator, not shown. The steam produced there can then be used as a coolant in the current gasification process, for example, to heat the starting materials, or used to generate energy in a turbine. In principle, it is also possible to supply a flow of water as a cooling liquid to the cooling circuit. A cleanup of this thread, not shown, may be required.

The stream with an average degree of purity through the pipeline 37 is directed to the further processing 12 of the ash and serves there as a liquefaction agent. In this way, the introduction of make-up water can be completely excluded. It may also be possible to provide further treatment 38 of the water for flow in the pipeline 37.

Through pipeline 36, the flow that contains most of the solids, finally

Zo is transported back to gasification. When the reactor 10 is designed as a fixed bed reactor, it is recommended to spray the stream containing the solids onto the fixed bed from above. In this way, the energy-consuming and therefore expensive drying of solids can be avoided. In addition, the valuable products still contained in it can thus be submitted to gasification. 35 With the help of this method, it is possible to ensure gasification of solids, in which no waste water is obtained.

List of references 1,2 pipeline 10 gasification reactor 40 11 pipeline 12 further processing of ash 13, 14 pipeline 20 cooler 21, 22 pipeline 45 23 separation device 24 pipeline 25 ammonia extraction 26 pipeline further water treatment 50 31, 32 pipeline 33 drying of solids 34-37 pipeline 38 subsequent treatment of water pipeline

Claims (9)

FORMULA OF THE INVENTION 1. A method of gasification of carbon-containing solids, and at the first stage of the method, solids are at least partially converted into CO and H" in a gasification reactor, and at the second stage of the method, a liquid stream containing water is separated from the gas stream, and at the third stage of the method, the stream containing water is subjected to water purification, which differs in that during water purification, the stream containing water is divided into three streams with different degrees of purity, and the first stream of water, which has the highest degree of purity, is directed to steam generation, with the second water stream, which has an average degree of purity, directed to the solids-to-slurry conversion, which includes ash washing from the solids gasification reactor, and with the third water stream, which has the lowest degree of purity, recycled to the solids gasification process . 2. The method according to claim 1, which differs in that the second and third streams of water are mixed and recirculated together in the process of gasification of solids. 3. The method according to claim 1 or claim 2, which differs in that the third stream of water is separated using decantation and then the first and second streams of water are obtained using the reverse osmosis method. 4. The method according to one of the preceding points, which is characterized by the fact that the steam produced in the steam generator is used to ensure the steam gasification process and/or to generate electrical energy. 5. The method according to one of the preceding points, characterized in that the first stream of water, which has the highest degree of purity, and/or the second stream of water, which has an average degree of purity, are subjected to further purification before recirculation. 6. The method according to one of the previous clauses, which differs in that the gasification of solids is carried out in a stationary layer. 7. The method according to claim 6, which differs in that the third flow of water, which has the lowest degree of purity, is sprayed into the solids gasification reactor above the fixed bed. 8. Installation for the gasification of solids containing carbon, primarily for carrying out the method according to any of the previous clauses, with a gasification reactor (10) in which the solids are at least partially converted into CO and He, with a separation device ( 20), in which a liquid stream containing water, Zo, is separated from the raw synthesis gas obtained by gasification and with a device (30) for water purification, in which the stream containing water is purified, which is distinguished by the fact that the device (30) for water purification is made in such a way that the stream containing water is divided into three streams with different degrees of purity, and that the device (30) for water purification is connected through a pipeline (31) to a device for purifying steam and/or through a pipeline (37 ) with a device for converting solids into slurry, and/or through a pipeline (36) with a gasification reactor (10). 9. Installation according to claim 8, which is characterized in that the separating device (20) is a condenser or droplet separator. I. stump 2 i- m 21 35 sn shsh te 34 ! | It's 33! nninonosy I I Because zo she to nyu 28 I | 26 Kai Ya Z ang 20 te 14 1 - 22 , | 25 24 and 28 --1.pi.-A- zo FIG. 00 Computer keyboardG. Payalnikovo (00000000 State Intellectual Property Service of Ukraine, 45 Vasyl Lypkivskyi St., Kyiv, MSP, 03680, Ukraine SE "Ukrainian Institute of Industrial Property", 1 Glazunova St., Kyiv - 42, 01601