JPH03502464A - Treatment method for wastewater generated during coal pyrolysis - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] A method for treating wastewater generated during coal pyrolysis The present invention is a method for treating wastewater generated during coal pyrolysis. After filtering and distilling the wastewater, 1. Coke production process by reverse osmosis Separate the permeate with low salt content, which can be returned to the bath, and the salt-making solution, and remove all or part of the salt-making solution. The present invention relates to a method for decomposing salts in a reducing atmosphere at high temperatures and separating salts.

Typically, the excess wastewater produced during coal pyrolysis is contaminated with harmful inorganic and organic substances. Must be processed based on high loads.

Coal water (KohIewassar) is produced by coke oven gas processing manufacturing process assembly. The post-Kuri system may be designed in various ways. However, for all systems, organic matter It is in principle necessary to remove wastewater to ecologically acceptable limits in wastewater. Ru.

From West German Patent Application No. 35 32 390 a method of the above class is known. Yes, in this case wastewater purification can be done by filtration, vapor stripping, reverse osmosis, Under the use of process technologies such as concentration by flash evaporation and biological purification The permeate obtained can be returned to the process as service water. this process Concentrates produced in the technology contain chlorine, sulfate, nitrate, thiocyanate and thiocyanate. Salt solutions in which toxic hazardous substances such as osulfates are bound to cations, e.g. Na+ It is a liquid, and in the case of a dissipative system, fixed NH3 must be stripped in the same way. Must be.

For the use or detoxification of salt solutions, West German Patent Application No. 35323 According to No. 90, the salt-making solution is returned to the coking process or It is specified that the salts should be further processed in a separate salt decomposition unit with recovery. Coke The addition of salt-making solutions during the sulfurization process, especially when high water quantities are added at the same time, Problems may occur during sulfurization or damage to the coke oven walls may occur. natural salt content Disassembly during disassembly requires considerable additional costs in energy and equipment. The problem of the invention is to improve the method mentioned at the outset, especially with regard to this problem, and to improve it with code. Energy-saving and environmentally friendly as there is no need to discharge process wastewater from the processing system The purpose is to propose a method.

A solution to this problem is described in the characterizing part of the patent claims "Jl." Claims 2 to 14 contain useful embodiments of this method according to the invention.

In the method of the invention, an additional decomposition device for after-treatment of the salt-making solution can be omitted. Wear. Salt solutions can also be heated to high reaction temperatures using expensive additional energy. Not necessary. Instead, the heat sensitivity of the scorching coke is utilized after it leaves the coking chamber. At the same time, high-value hydrogen and carbon monoxide-containing cracked gases are generated. high temperature cord The thermal energy of the gas is also converted into useful chemical energy through steam conversion. .

Furthermore, harmful components of coal water are decomposed using high-temperature coke at 1000-1100℃. The present invention proposes a coke/wastewater mass ratio of t; which already eliminates the reverse osmosis process. can be used without further concentration; ~ In reaction kinetics, the first step is to react small coke particles or coke edges with water vapor. - Reverse osmosis method eliminates the need for dry coke post-treatment for dust removal steam and No additional energy in the form of gas is required; It has the advantage that poor gas utilization in a coke dry chiller is not necessary.

The principle of the method of the invention is illustrated illustratively in FIGS. 1 and 2, and numerical examples are given below. I will explain in detail.

Figure 1 shows the wastewater from tar/water separation before charging the salt solution directly to the hot coke. This shows the post-processing.

Figure 2 shows the specific principle diagram of the gasified coke cooling system, which has been changed compared to Figure 1. show.

All numerical values listed in the numerical examples below relate to hourly Asahi scientific quantities.

Coke 235 tons of coke per month with 10.4 tons of ash and 16.7 tons of free water. Coke 1 with a temperature of >1150 °C and up to 1100 °C when carbonizing 63.7 t and a temperature of up to 850° C. crude gas 71, . 3t is produced . The crude gas is cooled to 811°C by circulating water and subsequently cooled to 18°C in a precooler. Rejected. During this pre-purification, separation in tar/water separator 2 and decanting Approximately 6.3 tons of concentrated and absorbable components and 37.7 tons of crude tar were produced by cyanide. and aqueous phase 25.2 ( are generated.

The aqueous phase of the pyrolysis increases in volume to approximately 42 m35 due to the internal circulation wastewater stream and contains ammonia. 500 J+g of fixed salt and 146 kg of volatile salt and 75 kg of phenol, Loaded with 12 kg of lysine base and 3 kg of aromatic hydrocarbons and carboxylic acids there was.

The coal water and circulating flow contain tar and solids dispersed in the gravel filter system 6. The particles are removed and the colloid is subsequently removed in a filter system 10 according to the principle of cross-flow filtration. The index is adjusted to <l.

The permeate 11 of the filtration 10 is 35+m3 and the condensate 12 from the sulfur treatment process Addition of 1 m3 increases to 36 m3 as feed stream for NH3 separator 13. The stripper 13 is equipped with 6 tons of direct steam addition according to the principle of steam stripping. 15. From the top of the stripper 13, NH3, H2S, HCN Gases and volatile ammonia compounds such as L42kg, -y enol approx. 11k g, steam 1 loaded with about 11 bi+ of pyridine base and about 2 kg of aromatics. t flows out to the deoxidizing tower. Another 1 t to 2 t of water vapor is taken out from the center of the tower and deoxidized. Used as stripping steam for towers.

The wastewater 15a of the stripper 13 has a volume of about 40II3 and about 500 kg of salt. , phenol 64 was loaded with 9 and pyridine base and about 2 kg of aromatics. and has a pH value of 7-8. After cooling to 30°C, the wastewater is separated according to the principle of separation. The working reverse osmosis system (RO-system) 20-22 is divided into various parts.

Removal power of reverse osmosis membrane for inorganic and organic components (Rueckhaltver moegen) and selectivity depend on some rules. - Multivalent ions are rejected better than singly charged ions.

-The rejection power for weak inorganic and organic acids is strongly dependent on the pH value and the membrane.

A negative displacement force (increase in the concentration of the substance dissolved in the permeate) is possible, e.g. Aqueous solutions of phenols and pensol.

Using these rules, we developed a fractionated reverse osmosis system according to the invention as shown in Figure 1. Ta.

After cooling, the pH value of the stripped wastewater is adjusted to pH<5 by adding a small amount of acid. and passed through filter 18 for safety reasons.

The first stage 20 of the membrane system has a rejection rate of >93% for salts and a rejection rate for phenols. RO module with a membrane mainly composed of acetyl cellulose with a rejection rate of <7% It is le. For a pressure of 50 bar on the feed side, phenol 60129 and A permeate 23 29+a3 was produced which was loaded with 22 kg of salt. ll+m3 amount of reject, i.e. salt solution 32, is approximately 480 to 9 of salt and 4 kg of phenol. loaded, which exhibits an osmotic pressure of approximately 30 bar at 30°C.

The second stage 21 of the RO system operates at a pH value of 8-9, which is adjusted by the addition of a base 24. do. The membrane material in this stage is mainly made of polyamide, and the rejection rate for phenol is 9. It is 5%. At a feed-side working pressure of 30 bar, 57 kg of phenol (< 2% by weight) is obtained. From this exclusion 30 , directly obtain the phenol as product 31 or exclude the intended product in this example. In addition to the cooling and washing water4, as shown in do. In a condensed system, heptanols derivatives are distributed into a tar phase and an aqueous phase according to the law. Ru.

Permeate stream 25 is 26+i3 and still loaded with 3ky phenol and 7kg salt and the pH value increases to >11 as the feed stream to the third stage 22 of the RO system. be done.

In the third stage, we similarly worked with polyamide as the membrane material and under these conditions Its rejection power is good, containing less 7 enol and less than 0-151119/12. A permeate stream of 28.25 t with a salt content <29/Q is produced. ■lI3 exclusions Stream 29 is mixed with rejects 30 from the second stage.

The permeate stream 28 is purified; directly as industrial water to the gas treatment system, e.g. It can be used as wash water during H3 washing or as a complete desalination equipment feed. can.

The permeate stream 28 is directly treated as purified industrial water in the gas treatment system, e.g. 3. Can be used as wash water during washing or as feed for complete desalination equipment. can.

The 11 ml of salt solution from the first RO stage 20 contains about 480 to 90% salt and about 9% phenolics. It is loaded with 4 kg. Main constituents of salt 9H4CI, (NH4)2S 0 4, (NH4)2S203 and NH4CN5, which are highly hazardous substances. be ranked. Chlorine and sulfur enter the pyrolysis system through coal and are ecologically acceptable. Must be recovered in a manageable form. For sulfur, use the acid gas in the H2S absorber. There is a possibility of sulfuric acid or liquid sulfur production from the gas. Chlorine and S ions, e.g. For so4.52o3 and CNS, it is clearly difficult to dispose of them, so general binds to alkaline cations; is excreted by wastewater in the form of chlorides, sulfates and complexes. can be released.

The present invention similarly removes residual sulfur when utilizing existing pyrolysis energy sources. Provides a method for recovery as acid or liquid sulfur and converting chlorine into e.g. Ca compounds do.

During coal pyrolysis of 235 tons of coal, approximately 165 tons of coke 33 at approximately 1050℃ are generated. Ru. The heat content of this high-temperature coke is about 41.69 cal, and the difference is up to 300℃. When cooling, it is about 31 gcal, and when cooling to 100°C, it is about 33 gcal. It is 9 cal. Although this energy has been negated in the past by direct water supply, , recently recovered indirectly as steam during coke dry cooling.

The present invention c. Carbon conversion (C+ H2O: CO+ H2) i: Heat energy of coke Under the recovery of chemical energy from energy and the utilization of concentrated liquid for wastewater post-treatment, the formula % formula % Provides a combination with salt decomposition by.

The principle of this system is as follows: high temperature coke 33 is heated by gasification cooling shaft) 4 1 from the top to the bottom, and to compensate for the batch work, the original gasification zone is It has a forehearth 42 in front. The guiding of the reactants takes place in countercurrent and partly in cocurrent. It will be done. Countercurrent flow is achieved by gas circuits 50.38 or 48, cocurrent flow is achieved by Inject the salt solution 32 directly onto the high temperature layer (1000-1100°C) above the coke. This is achieved by (Figure 1).

The energy of 289 cal of high temperature coke at 1050℃-400℃ is Using water vapor 9560729, coke C5300J29 becomes Co7900 Converted to N+*3 and H21190ONi+3, at which time ammonia salt is decomposed be used in a manner that

From the top of the gasified coke cooler, at 800-900°C and a slight overpressure, 50 4360 ONm3 of dry gas loaded with 4 tons of water vapor is taken out and the waste heat boiler It is indirectly cooled by the boiler feed water 35 in the boiler 35, and about half of the amount is used as circulating gas 38. It is circulated. The product gas 37 with CO+H21980ONl13 is water vapor 2t and HCI 11.89 or) (251,99/Nm” (W[) Loaded. The gas is further converted to hydrogen in the science system after the typical gas.

HCl is advantageously washed with milk of lime and obtained as CaCl2, H2S optionally It is processed in combination with a coke oven gas H2S absorption system.

According to the process diagram in FIG. 2, the circulating gas 50 at a high temperature of 800° C. approximately 1/245 is dispersed with salt solution lit countercurrently in the concentrator 44. 9. The gas is cooled to approximately 200°C and the water removed.9. Ot evaporates. child With the amount of steam, the amount of wet circulation 48 increases to about 3600 ONm3, It is fed into the lower part of the foot 41. Concentrated salt solution 462.0+I! 3 is the cooling system It is injected onto high-temperature coke at a temperature of 1000 to 1100℃ at the top of the shaft, and the salt is removed. Disassemble. For balance reasons, approximately O, St of water is still added to the system as gasified vapor 49. added. According to past experience, the reaction starts at 500℃, as per the law. It can be said that the gasification rate increases with increasing temperature. 300-50 0 coke temperature range for heating of the circulating gas and possibly for evaporation of added water. used for the purpose of release.

Residual cooling of coke from approximately 300℃ to 100℃ and heating up to 5% water are , addition of 16-24*3 water in the lower wet cooling zone 43 outside the actual reaction section This steam volume, in which 8 to 16 m3 is evaporated, may be completely or partially It can be added as reaction vapor 49 to the circulating gas. Excess amount of steam is coke It is condensed in a closed system 57-61 outside the cooling system and is used throughout the process as condensate water. used.

The entire process technology of the present invention is designed such that there is no need to drain process wastewater from the system. It is.

List of reference symbols D... Coal wastewater and tar, 2... Tar/water separator, 3... Crude tar, 4... Cooling and washing water, 5... Coal water, 6... Gravel filter, 7... ・Washing water, 8 pre-purified coal water, 9...purified circulating water, 10...cross flow filtration, 11... permeate, 12... condensate from the Claus apparatus, 13... Stripper, 14... H2S/NH3 vapor to deoxidizing tower, 15... Steam, 1 5a...phenol and salt-containing wastewater, 16...base, 17.26...mouth H value adjustment, 18...filter, 19...filtered water, 20-22...minutes Separate reverse osmosis system, 23.25...permeate, 24.27...base, 28...purification 29. 30... Circulating water, 31... Phenol water product, 32. ... Salt solution, 33 ... High temperature furnace coke, 34 ... Cooled coke, 3 5.52...Boiler feed water, 36.53...Steam, 37...Produced gas, 38 ...Circulating gas, 39...Cooling water, 40.47.54...Blower, 41... ・Gasification cooling shaft, 42... Forehearth, 43... Wet cooling zone, 44... ・Concentrator, 45...High temperature circulating gas, 46...Salt concentrate, 48...Steam Contained cooling gas, 49...Gasified steam, 50...High temperature gas, 51...Waste heat bottle 55... Production gas, 56... Added water, 57... Cooling steam, 58... ・Condenser, 59.60... Cooling circuit, 61... Circulating condensate international search report

Claims (14)

[Claims] 1. To treat wastewater generated during coal pyrolysis, the wastewater is filtered, distilled, and then subjected to reverse osmosis. The method separates the permeate into a low-salt content permeate and a concentrated salt solution that can be returned to the coke-making process. , a concentrated salt solution is completely or partially decomposed in a high temperature reducing atmosphere to separate the salts. In the process, a concentrated salt solution is completely or partially added during closed gasification coke cooling. , for the decomposition of harmful substances in this salt solution and for the production of hydrogen and carbon oxides. Coal heat is characterized by being combined with high-temperature furnace coke for utilization by A method for treating wastewater generated during decomposition. 2. During gasification coke cooling, the coke is continuously passed upward into the gasification cooling shaft. The salt solution is directly passed through the upper high temperature layer of about 1000-1100℃. Claim 1, wherein the steam-containing gas is injected upward and circulated in countercurrent to the coke. How to put it on. 3. 3. Steam is added to the circulating gas before it enters the gasification cooling shaft. How to put it on. 4. From claim 1, wherein water is injected directly into the lower part of the gasification cooling shaft for evaporation. 3. The method described in any one of 3. 5. About 300-600℃, especially 300-400℃ in the coke gasification circuit at a temperature below 100 °C and subsequently in a closed system by adding water. 5. According to any one of claims 1 to 4, resulting in a defined water content of 3 to 5%. How to put it on. 6. The salt solution is stored in a concentrator outside the gasification cooling shaft at approximately 800 mL for recirculation. It is concentrated by a part of the high temperature gas at ~1000℃, and the gas is evaporated at about 20℃ at the same time as water evaporation. 6. A method according to any one of claims 1 and 3 to 5, characterized in that it is cooled to 0<0>C. 7. The concentrated residue of the salt solution that did not evaporate in the concentrator is processed as described in claim 2, 7. The method of claim 6, comprising injecting into a gasification cooling shaft. 8. According to claim 5, all or part of the water vapor generated during cooling of coke is circulated. The method according to any one of claims 1 to 7, which is added to the ring gas as a reaction vapor. Law. 9. Excess steam generated during post-cooling is removed in a closed system outside the gasification cooling shaft. 9. The method as claimed in claim 8, wherein the method is condensed with water and used as condensate during the entire process. 10. Heat from the hot product gas from the gasification cooling shaft can be fully or partially evaporated. 10. The method according to claim 1, wherein the method is used for generating air. 11. The halogens in the product gas generated during cooling of gasified coke are 11. The method according to any one of claims 1 to 10, comprising washing with an alkaline solution or with an alkaline solution. . 12. Separating the pre-purified wastewater into a permeate with a low salt content and a concentrated salt solution is Acetic acid with pH value <5, rejection rate of salts >90%, rejection rate of phenol <10% 1st stage using membrane mainly composed of lucerose, pH value 8-9, phenol rejection rate A second stage using a membrane based on polyamide with >95% and a pH value >10 , purified wastewater with <0.15 mg/l of phenol and <2 mg/l of salt is produced. The third stage consists of a polyamide-based membrane with a very high rejection rate. 12. The method according to claim 1, wherein the method is carried out in a fractionated reverse osmosis system. 13. The acidic components of the coal water concentrate produced during the fractional reverse osmosis process are 13. The method according to claim 12, wherein the alkaline or alkaline earth ion is bound. 14. The phenol and water fractions generated during fractional reverse osmosis are fertilized through a perevaporation process. 14. The method according to claim 12 or 13, wherein the method is concentrated to a nol extract.