DE4109231A1 - Use of carbonaceous waste contg. halogen - by partial oxidn. gasification in flame reaction to crude gas, and contacting gas with water contg. alkalising agent etc. - Google Patents

Abstract

In utilisation of carbonaceous waste loaded with halogen, by gasification with partial oxidn. in the chimney current, where the waste and a gasifying agent contg. free O2 are converted in a flame reaction at raised pressure to a crude gas contg. CO and H2, the crude gas at an end temp. of the flame reaction of at least 1100 deg.C is contacted with water contg. an additive with alkaline reaction, so that the crude gas is cooled and part of the water is satd. with water vapour by evapn. and the unevaporated remaining water takes up solid, liq. and water-sol. gaseous components of the crude gas; the pH in the unevaporated remaining water is measured, and addn. of the alkaline additive is controlled w.r.t. this pH. USE/ADVANTAGE - Contamination of the atmos., water and soil by toxic (in)organic Cl cpds. is avoided, and corrosion of the plant is reduced. The waste is esp. hydrocarbons loaded with organic Cl cpds., e.g. fractions from used oil processing contaminated with Cl-contg. solvents, and carbonaceous dusts loaded with (in)organic Cl cpds.

Description

The invention relates to a method for harmless Verwer halogenated carbonaceous materials and Waste materials producing a carbon monoxide and hydrogen-containing gas by gasification. Under halogen loaded carbonaceous materials or waste Substances are in particular with organic chlorine and / or Fluorine compounds contaminated hydrocarbon oils, Chlorinated plastics, containing chlorine compounds Sewage sludge or mixtures thereof with others carbonaceous materials and residues understand.

It is known, carbonaceous waste and re stoves using the heat produced. However, such materials are halogen compounds loaded, so exists during the actual combustion or during the subsequent cooling phase for Flue gas and any solid residues the risk of Formation of highly toxic substances. For example, lead already very low levels of polychlorinated biphenyls (PCB), as is often the case in waste oils from electrical engineering Directions and hydraulic systems found to the dangers of Formation of extremely toxic polychlorinated dibenzodioxins (PCDD) and dibenzofurans (PCDF). Known technical measure were to exclude the emission of PCDD and PCDF both on the leadership of the combustion process itself also on the downstream of suitable filters for  Retention of the toxins directed. They are high Effort and do not always lead to sufficient Success.

In the gas production technology is the gasification of fuel substances that are in a flowable state or can be transferred to this state by Partial oxidation in the airstream known. It is the Fuel with oxygen in the form of a flame reaction, often under increased pressure, in a carbon monoxide and converted hydrogen-rich gas. That under these Conditions generated raw gas is after appropriate Cooling, cleaning and optionally further conversion as synthesis gas, as reducing gas or for energetic Used purposes. In many cases, such gas generation is also in a gas turbine-steam turbine combined cycle power plant process for generating electricity.

Industrially proven gasification processes of this type verwen the often heavy fuel oils as fuel. It is, however Also known for solid fuel processes known the solid fuels after fine comminution ent neither by mixing with water or oil as pumpable Solid-liquid suspension (DE 25 36 249) or in a carrier gas stream suspended (DE 28 31 203) the process be supplied.

It has been suggested for gas generation Partial oxidation also carbonaceous or combustible solid and liquid residues or mixtures of such Using residues with an additional fuel,  as far as they are in a flowable state or in this can be brought. Give examples DE 28 31 208 and DE 38 20 013.

The invention is based on the object, the possibility Gasification on the principle of partial oxidation in Air flow for recovery halogenated carbon to use and contain materials and waste materials versatile carbon monoxide and hydrogen to produce rich gas. The technology of gasification, the also the cooling and cleaning of the raw gas generated closes, it is to be designed so that from the halogen load of the feedstock resulting Umweltbe Loads for atmosphere, water and soil due to toxic chloro-organic compounds and inorganic chlorvers avoided bonds and corrosion in the corresponding Plant remain largely restricted.

The inventive method assumes that a Halogenated, carbonaceous waste in one flowable state and a free oxygen-containing Gasification agent within a reaction space in the form a flame reaction at an elevated pressure to a converted carbon monoxide and hydrogen-containing raw gas become.

According to the invention, this is done at a temperature of at least 1100 ° C in the flame reaction generated with a gas with an addition of an alkaline reacting additive ver seen amount of water brought into contact, while cooled and  by evaporation of a portion of the water with water steam saturated, while the unvaporized remaining of the Amount of water solid, liquid and soluble in water gasför mige constituents of the raw gas absorbs. Next is the pH of the part of the amount of water remaining unevaporated measured and the addition of the alkaline-reacting additive adjusted as a function of this pH.

It has proved to be useful to measure the measurements pH still under the increased pressure, ie before the Ent to measure the voltage of the remaining water. Under these Conditions must be the addition of alkaline Addi tivs be regulated so that this pH is equal or greater than 4.

The alkaline-reacting additive is usually one Sodium compound from the group sodium hydroxide, sodium carbonate and sodium bicarbonate, preferably Sodium hydroxide selected.

In a preferred embodiment of the invention, the remained unevaporated remainder of the amount of water from the raw gas separated, relaxed to atmospheric pressure, by Verunreini freed by solid particles and into two streams subdivided, of which a first stream of the water quantity before their contact with the raw gas produced is added again and a second stream is subjected to an evaporation process, wherein the salt-like dissolved in said second stream Compounds as a concentrated solution or as a solid salt incurred.  

In the as a concentrated solution or as a solid salt anfal Lenden salt-like compounds are in particular those in the gasifying carbonaceous material contained halogens as alkali halides, for example bound as sodium chloride. After separation of the unvaporized Remaining residual amount of water becomes saturated crude Gas usually cooled further and the intended use appropriate cleaning and treatment subjected to processes. Incurred in these process stages Condensate can be returned to the amount of water that, provided with the addition of the alkaline-reacting additive, is brought into contact with raw gas. The same applies in the evaporation of said second stream ver steamed and condensed water again.

It has been found that organochlorine compounds completely decompose and thus highly toxic Ver compounds of the polychlorinated dibenzodioxine type or -furans are excluded in the gasification products, if by appropriate adjustment of the ratio of Oxygen to halogenated carbonaceous waste a final temperature of the flame reaction of at least 1100 ° C is maintained. A preferred range for this temperature is 1200 to 1400 ° C.

The generated gas can be directly with this exit temperature in contact with the with the addition of the alkaline reacted amount of added additive supplied which leads to simple apparatus constructions. With the goal of more intensive use of the (physical) Heat content of the generated gas can this also in the  indirect heat exchange with a cooling medium, for example wise in a radiant heat boiler to produce Steam, to be pre-cooled before it comes in contact with the ge called amount of water is brought. After the pre-cooling stage has the raw gas, for example, a temperature of 700 ° C.

Halogenated carbonaceous wastes containing recycled particularly favorable in the manner according to the invention are by organic chlorine compounds contaminated hydrocarbon oils, for example with chlorine Containing solvent contaminated fractions from the Used oil treatment as well as by organic or inorganic Chlorine compounds loaded dusty, carbonaceous Materials.

As a rule, the turnover of the waste material is sufficient with acid under conditions of partial oxidation, the means with an oxygen-fuel ratio essential below the minimum required for full combustion oxygen demand, the required final temperature of the flames to achieve a reaction of at least 1100 ° C. For waste substances with a relatively high mineral content or in strongly fluctuating compositions of the However, waste material may be advantageous, the partial Oxidation a flowable auxiliary fuel separately or in mixture with the waste material. As an addition fuel come, for example, flammable gases, too recycled gas of own production, liquid coals hydrogens or carbon dust suspended in the carrier gas in question. Due to the additional fuel, the yield increased gas generated.  

The invention is by two embodiments with associated schematic representations explained. there shows

Fig. 1 as a first embodiment of the schematic representation of a gasification of chlorine-contaminated dust-like material to synthesis gas,

Fig. 2 is a schematic representation of a variant of the United as a second exemplary embodiment of the proceedings for the use of a chlorine-loaded hydrocarbon oil with waste heat steam generation and energetic use of the gas generated.

1st embodiment

The embodiment relates to the utilization of a ge ground industrial waste with relatively high plastic content including plastics on polyvinylchloride Basis.

In the upper part of a reactor pressure vessel 1 a suitable for operation at high temperatures reaction space 2 is provided with a burner 3 . This burner is fed via the feed line 4 with the organic and inorganic chlorine compounds polluted dusty and combustible material (hereinafter referred to as feedstock) and fed via line 5 technical oxygen. Both components react to form a flame within the reaction space 2 with each other, producing a gas having the main components CO and H ₂ . In the reaction space there is a pressure of 26 bar. The neces sary for the process temperature conditions in the reaction chamber are controlled by controlling the ratio of oxygen to feedstock. It is set a temperature at the exit of the reaction space of 1350 to 1400 ° C. This is achieved in addition to virtually complete burnout of the carbon content that the mineral constituents of the fuel fes form a molten slag flowing down the wall of the reaction chamber and leaves the reaction chamber with the hot gas.

In the lower part of the reactor pressure vessel 1 immediately after the exit of the reaction space 2, a cooling chamber 6 is arranged. In this, the hot gas with water, which, as will be explained in more detail, is provided with an alkaline-reacting additive, brought into contact and at a pressure of about 26 bar - cooled to 200 ° C and simultaneously with water vapor to saturated saturated steam at this temperature saturated steam pressure with water. In order to achieve the contact water - gas, water is supplied via the line 7 , which is sprayed via a nozzle ring 8 in fine distribution in the gas stream. The remaining of the amount of water remained unvaporized forms at the bottom of the refrigerator a water bath 9 , in which also solidified slag particles and other, collected by the residual water impurities from the raw gas collect. The mirror of the water bath 9 is held by an overflow pipe 10 at its level and relaxed by means of expansion valve 11 into the flash tank 12 , which is equipped (not shown here) with a condenser for the water vapor released during the relaxation.

To discharge the accumulated in the water bath 9 slag a lock container 13 with corresponding shut-off valves and (also not shown in the figure) Einrich lines for relaxation and pressurization below the bottom flange of the reactor pressure vessel 1 is arranged. The slag falls into a discharge tray 14 with a scratch tape. The relatively small amount of water that accumulates in the discharge of slag is combined with the outflow from the expansion vessel 12 water.

In the flame standing in the reaction chamber 2 , the chlorine compounds contained in the starting material are converted predominantly into hydrogen chloride, the remainder in vapors of metal chlorides (primarily alkali chlorides), which enter the cold room with the raw gas and practically quantitatively of the remaining unvaporized rest of Amount of water to be absorbed.

With the help of the metering pump 16 of the cooling chamber 6 zu zu leading amount of water before its contact with the hot gas via the connecting line 17 sodium hydroxide in the form of sodium hydroxide solution is supplied as an alkaline-reacting additive. The dosage is carried out with the aid of a pH-value regulator 15 , the transducers continuously measures the pH of the running out of the water 9 residual water prior to its relaxation (ie at about 26 bar). The pH controller 15 controls the metering pump 10 so that the recorded measured value is constantly maintained in a range pH 4.5 to 5.0. This ensures that even the chlorine content primarily incurred as HCl is dissolved as sodium chloride in the residual quench water.

It turns out that under these conditions, the corrosion in the wetted part of the system can be controlled. It is noteworthy that the pH of the unevaporated residual water after its relaxation in the flash tank 12 increases to about 7.5. This is caused by the release of dissolved carbon dioxide during the relaxation.

The cooled in the cooling chamber 6 by the contact with water, saturated and largely free from impurities and wasserlös union gas components raw gas is discharged via a lateral port and the crude gas line 29 from the refrigerator 6 and after a not presented in the scheme Darge post-purification with droplet deposition of a convergent Tierungsanlage 30 supplied in the catalytic CO from the crude gas with water vapor to H ₂ and CO _{2 are} reacted. As a result of this conversion, the ratio of H ₂ to CO required for the intended use of the synthesis gas is set and, at the same time, the water vapor which has reached the raw gas due to the saturation in the cooling space is used.

The converted crude gas passes through the cooler 31 , is cooled under condensation of water vapor to ambient temperature and then, not shown in Fig. 1, the requirements of the synthesis gas cleaned accordingly, that is, in particular of hydrogen sulfide and CO ₂ freed. The resulting in the condenser condensate is returned via the condensate line 32 and the booster pump 33 into the conduit 7 . The remaining from the water bath 9 in the bottom of the cooling chamber 6 unreacted remaining water is fed via line 18 to a filter 19 for the separation of solid impurities. If necessary, the resulting sludge can be returned to the process after drying by addition to the feedstock. The effluent from the filter 19 residual water is divided into two streams. A first stream is fed via line 20 and pump 21 directly to the line 7 and thus again brought to contact with the hot raw gas. A second stream is supplied via line 22 to an evaporation plant 23 , which operates as a multi-stage vacuum evaporation plant. The evaporation is carried out to a concentrated salt solution (with sodium chloride as the main component), which can be worked up by means of a crystallizer 24 to the solid salt. The ver in the evaporation plant 23 vaporized water falls within this system as condensate at negative pressure. It is brought to atmospheric pressure with pump 25 and optionally fed via line 26 and booster pump 27 into the supply line 7 or fed via line 28 other uses.

The used dried waste has the following Analysis:

Water content | 4.0% Carbon content 34.5% ash content 41.0% chlorine content 1.9% calorific value 15.0 MJ / kg

Based on 1000 kg of feedstock, using 370 m ^{3 of} 1N technical oxygen, 1570 m ^{3 of} crude synthesis gas are generated (after conversion) with the following composition:

CO | 52.8% H₂ 4.2% CH₄ 0.0% N₂ 6.2% CO₂ 36.2% H₂S 0.6%

In addition fall (when returning the out in the filter 19 carried mud to the drying plant for the waste) 320 kg of slag in a granular, glassy form. The nozzle ring 8 2200 kg of water are supplied. Of this vapors evaporate in the cold room 6 1400 kg under saturation of the raw gas. The amount of water supplied via nozzle ring 8 40 kg of NaOH are added. Thus, a pH value of 4.5 is measured in the unevaporated remained, draining residual water prior to its relaxation, which increases to 7.5 after relaxation by the escape of dissolved CO ₂ .

In the evaporation plant 23 with crystallizer 24 60 kg of solid salts, of which 31 kg of NaCl, the rest vorwie ing as Na ₂ CO ₃ generated. For this purpose, the evaporation system 30% of the effluent from the filter 19 residual water supplied supplied, while the other part is fed directly into the line. With this in the cooling process zurückge led current 25% of the amount of water required for contact with the raw gas is introduced. 55% is condensate that accumulates in the cooler 31 and in the evaporation plant 23 , the rest is covered by fresh water.

2nd embodiment

By means of partial oxidation, a waste oil fraction containing chlorine and small amounts of PCB is utilized. As shown in FIG. 2, in the middle part of the reactor pressure vessel 1 between the reaction chamber 2 and the cooling chamber 6, a radiant heat boiler 34 instal profiled. The radiant heat boiler consists of a lot number of risers, which are welded by webs to a gas-tight membrane wall, and which are connected to a lower and an upper annular collector. The waste heat boiler further includes - not shown in Fig. 2 - outside the reactor pressure vessel 1, a steam drum and a series of downcomers, which are connected to the terminals 35 and 36 with the collectors.

The used oil fraction has the following composition:

C | 83.7% H 12.9% O 0.7% S 0.7% Cl 2.0% ash 0.0%

Based on 1000 kg of feedstock, 3250 m ^{3 of} crude gas are produced using 950 m ^{3 of} industrial oxygen, leaving the reaction space 2 at about 1300 ° C. Under production of about 1500 kg of high-pressure steam in the radiant heat recovery boiler 34 , the temperature of the raw gas is reduced to about 700 ° C before it is brought into contact with water in the cooling chamber 6 . The cooled to about 175 ° C and saturated with water vapor raw gas should be used for energy purposes, so that a conversion of the CO content is omitted and the gas via the crude gas line 29 is fed directly to the radiator 31 . The cooled raw gas has the following composition:

CO | 43.0% H₂ 46.3% CH₄ 0.02 N₂ 4.6 CO₂ 5.8% H₂S 0.14%

To bind the resulting in the reaction chamber 2 by conversion of the chlorine compounds of the starting material hydrogen chloride material is added for contact with the crude gas to be supplied to the amount of water 35 kg NaOH. Thus, a pH of 4.4 is set in the unevaporated remained of the rest of the water before relaxation. Because of the low ash content in the feed oil is practically no slag, but 5 kg of soot, which is completely absorbed by unvaporized residual water. The loaded residual water is deviating from the previous execution, for example, discharged at the bottom of the reactor pressure vessel 1 via the Rußwasserleitung 10 A and then expanded via the expansion valve 11 into the flash tank 12 . The soot is separated with known devices, ver also simplifies as a filter 19 , separated from the remaining water, which is then divided as in the first Ausfüh tion example. In the evaporation plant 23 with crystallizer 24 about 50 kg of solid salts, of which about 33 kg of NaCl ge won with the use of 750 kg of wastewater. The nozzle ring 8 supplied amount of water is 4100 kg, again based on 1000 kg of fuel. Of these, 2250 kg, corresponding to 55% of soot freed recycled residual water, 34% condensate from cooler 31 and 11% fresh water. The discharged via the line 26 condensate of the evaporation plant 23 is used as feed water for the radiant heat boiler.

Claims (7)

1. A process for the recovery of halogenated carbonaceous waste by gasification on the principle of partial oxidation in the air flow, said waste and a free oxygen-containing Verga agent are reacted in the form of a flame reaction at elevated pressure to a carbon monoxide and hydrogen-containing raw gas, characterized in that the crude gas produced at a final temperature of the flame reaction of at least 1100 ° C is brought into contact with a provided with an additive of an alkaline additive additive amount of water, wherein the crude gas is cooled and saturated by evaporation of a portion of the water with water vapor and the remains undampened remaining amount of water solid, liquid and soluble in water gaseous components of the raw gas, the pH of the remaining unevaporated remainder of the amount of water and the addition of the alkaline-reacting additive in response to this p H-value is adjusted. 2. The method according to item 1, characterized in that the pH of the unevaporated remainder of the amount of water measured at the elevated pressure and the addition of the alkaline reacting additive is adjusted so that this pH is equal to or greater than 4. 3. The method according to claim 1 or 2 characterized that the alkaline-reacting additive from a group  of sodium compounds consisting of sodium hydroxide, Sodium carbonate and sodium bicarbonate - selected becomes. 4. The method according to claim 1 to 3, characterized that the unevaporated remainder of the amount of water Raw gas separated, relaxed to atmospheric pressure, from Impurities are freed by solid particles and in two Streams is divided, of which a first stream in the said amount of water before their contact with the generated Raw gas is recycled, and a second stream one Is subjected to evaporation process, wherein said in the second stream dissolved salt-like compounds as concentrated solution or as a solid salt. 5. The method according to claim 1 to 4, characterized that the raw gas generated in the flame reaction immediately bar with the with an alkaline reacting additive provided amount of water is brought into contact. 6. The method according to claim 1 to 4, characterized that the raw gas generated in the flame reaction in a indirect heat exchange with a cooling medium pre-cooled and then in contact with the alkaline reacted amount of added water provided becomes.   7. The method according to any one of claims 1 to 6, characterized characterized in that together with the halogenbelasteten carbonaceous waste a flowable fuel as additional fuel with the free oxygen containing gasification agent in the form of the flame reaction is implemented.