MXPA97010423A - Method and apparatus for gasification of organi materials - Google Patents

Abstract

Process and apparatus for gasification of organic materials (typically incorporated in industrial household waste, including car recycling waste) to produce a useful synthesis gas (with a significant content of CO and H2) and which produces an effectively non-toxic waste, for means of at least one burner continuously operated and preferably stoichiometrically balanced (1: 2 for natural gas / oxygen) at least during startup and shutdown of the apparatus, optionally with some excess oxygen normally under stable conditions, for example with a 1: 4 or higher, especially if the load has a moisture content of more than 18%, directed into a first single-stage reaction zone, through a common opening also to discharge the product's effluent gas. reactor in such a way that its contact between both gases is ensured, said zone contains a moving load in a A horizontal rotary reactor in the form of a barrel heated to a temperature between 600 ° C and 800 ° C (inside, at the incipient melting temperature of the charge) resulting in a thermal decomposition and a gasification of the organic materials of the charge and in the reaction of the complex hydrocarbons with the gases generated by the load (1) normally with CO2 and H2 derived from combustion in the burner of a fuel and a gas containing oxygen in a high temperature flame typically 2500 to 3000øC, (2) with a excess of oxygen, and / or (3) partially with H2O and CO2 added to, or present in, the car

Description

METHOD AND APPARATUS FOR GASIFICATION OF ORGANIC MATERIALS RELATED REQUESTS This application is a division and continuation in part of the application serial No. 08/1 58, 195, filed on November 24, 1993 (scheduled to be published as patent No. 5,425,792 on June 20, 1995), which it was a continuation of the initial request and was in process serial No. 07 / 879,608, filed on May 7, 1992 (the content of which is incorporated herein by reference).

BACKGROUND OF THE INVENTION In these days, and primarily in the industrialized countries, there is a deep concern about the safe handling of domestic and industrial waste, which has acquired great ecological importance. These wastes often include a significant proportion of organic content.

Many wastes of this type frequently contain toxic and non-biodegradable substances. Therefore, they can not simply be discarded as sanitary landfills due to the problems of air and water pollution. Another alternative to get rid of this waste is incineration. However, normal and simple incineration is not allowed if the gases produced are not cleaned properly because they cause air pollution with toxic chemical substances, for example, chlorine compounds and nitrogen oxides. In some countries, environmental laws and regulations have been passed prohibiting the burial or incineration of these types of waste, therefore these alternatives to dispose of such waste are now subject to many restrictions.

An exhaustive description of the problems that the recycling industry is facing with regard to the elimination of "fluff and some suggestions for the use of the energy content of the fluff are found in the article by M.R. Wolman, W.S. Hubble, I.G. Most and S.L. Natof, presented at the "National Waste Processing Conference" in Denver, Colorado on June 14, 1986, and published by ASME in the summary of that conference. This article reports an investigation sponsored by the Department of Energy to develop a viable process to use the energy content of the fluff, however, the process suggested there is aimed at carrying out a total incineration of the waste, using the heat of said waste. incineration, to produce water vapor, while the present invention is directed to produce a high quality gas starting from organic materials as an energy source.

It has also been proposed in the past to carry out controlled combustion of organic waste and to use heat or other agents (such as process gases) formed by said combustion. These prior art processes typically gasify organic materials by one of two processes: pyrolysis, ie, thermal decomposition of the materials by indirect heating, or by partial combustion of the materials by means of air or oxygen.

Energy consumption is one of the most important costs in obtaining iron. Typical direct reduction processes consume 2.5 to 3.5 Gigacalories (109 calories) per metric ton of product, known as sponge iron or direct reduction iron (HRD). Therefore, many processes have been proposed using all types of available energy sources, such as coal, coke, liquid fuels, natural gas, reducing gases obtained from biomass, nuclear energy and solar energy. Most of these proposals have not been successful in practice, sometimes because the necessary materials and means have not been available or because the relative costs to use these alternative energy sources are greater than those of traditional fossil fuels.

The use of organic waste as an energy source for the iron industry offers great economic advantages and solves environmental problems in countries where large quantities of cars are recycled and where other wastes with a high content of organic material are generated. Scrap metal is recycled to make steel. The non-metallic waste from automobiles (fluff), however, had not been used to produce reducing gases useful in the production of iron or in other industrial processes.

DETAILED DESCRIPTION OF THE INVENTION A preferred embodiment of the invention applied to the "fluff" gasification is described with reference to the appended figures, where the common elements are designated with the same numerals in all the figures for ease of reference, with reference to figure 1, which shows partially a schematic diagram of the process and apparatus, the numeral 10 designates a loading hopper from which "fluff is introduced to the gasification reactor 18 by means of a feeder of the" auger "type or screw 20 having an" auger "14 ( shown in figure 2) moved by a motor 12.

The reactor 18 is of the rotary type and is provided with rings 22 and 24 which rest and roll on the support rollers 26 and 28. The motor 30 rotates the reactor 18 on its axis by means of a transmission equipment 32, by example of the chain type and Catarina 34, in a manner known in the art.

The discharge end 25 of the reactor 18 opens into a gas collecting hood 36, which has an emergency chimney 38, through which the produced gases can flow through a safety valve 40, and a lower discharge section To channel the solid waste or ash from the gasification of the fluff, a rotary valve (s) 42 is provided to regulate the flow of the solids discharge and contribute to prevent the Fuel gas leaks into the outside atmosphere A screw type conveyor 44 moved by motor 46 cools the ash and transfers it to hopper 48 for shipment outside the plant.

A burner 49 is positioned generally horizontally through the bell 36 so that its nozzle 40 reaches the interior of the reactor 18 as shown and described in the reference to Figure 2. The fuel gas and oxygen are fed to the burner 49 through ducts 52 and 54.

The gases produced in the reactor 18 are transferred from the bell 36 through the duct 58 to the hot cyclone 60. The small solid particles of fluff or carbon black 61 that are entrained by the gases of the reactor 18 are separated, collected, cooled and unload in hopper 48.

A secondary burner 64, supplied with oxygen / air and / or fuel gas, is positioned before cyclone 60 for an optional addition of air or oxygen to gasify some hydrocarbons or coal that may reach this point.

The product gas flows through the duct 70 to a venturi type scrubber 72 where dust particles entrained by the gas are removed.

Preferably, the product gas can be cooled, for example to 150 ° C and passed through a bag house (with the subsequent vitrification of the collected materials). The bag filter removes, together with the collected dust, also the small traces of the gaseous hydrocarbons such as toluene, xylene, eumeno, etc. that could leave without decomposing in the product gas. The gas produced then passes through a packed bed column 74 where the acids (together with the benzene, C6H6, which passes through the bag filter) are removed by the wash water. An emergency pressure control valve 76 is provided in the purge line 78 to relieve excess pressure in the system if emergency conditions occur. The solids collected by the scrubber 72 are sent to the sludge tank 80 where they form the sludge 82.

The cold and clean product gas flows to the compressor 84 through the tube 86, connected to the chimney 98 provided with the valve 100 to release excess gas.

The product gas can be used for a variety of uses. For example, clean, high-quality gas can produce mechanical strength in an internal combustion engine 88, or it can be stored in a tank 90 for later use (for example, exploiting its calorific content by combustion), or used to produce electry in a gas turbine generator 92, or producing steam in a boiler 94 or used as a reducing gas in a direct reduction process 96.

Referring now to the more detailed figure of the gasification reactor 18 shown in Figure 2, the bed of material to be gasified 102 is formed in the reactor 18, and the solids move from the loading end 103 to the end of the reactor. discharge 35 by the rotation action of the reactor 18 and by the volumetric displacement of the solid ash in the bed 102 by the unreacted inert solids contained in the feedstock charged by means of the screw feeder 20. The stirring and mixing action of the ashes and hot inert solids in the feed material considerably increases the speed of heat transfer in the bed 102 and thus improves the speed and degree of gasification of the feedstock fed.

The depth of the bed 102 and the residence time of the material fed to the reactor 18 are determined by the diameter and length of the reaction zone and are also related to the length, diameter and inclination angle of the reactor 18 towards the end of the reactor. download 35.

A horizontal axis of rotation is preferred among other reasons because the seals 120 and 122, located on the periphery of the reactor 18 generally at its loading end 103 and at its discharge end 35, do not have to withstand excessive effort or thrust due to a non-uniform distribution of the center of gravity of the reactor 18. This also applies to the support rollers 26 and 28, which are of a simpler design and easier to maintain if the reactor 18 rotates horizontally.

In one of the preferred embodiments, the shape of the reactor 18 is an important feature of this invention because the hot volatile gases that are formed from the bed of material 102 have to be brought into immediate contact with the extremely hot combustion products (H2O and CO2). ) of the burner 49, in order to absorb more directly the high temperature energy of the flame via the exothermic reactions of fos complex gases to form gases of simpler compounds. The shape and length of the flame of the burner 49 is such that the volatile gases arising from the bed 102, along the length of the reactor 18, react with the combustion products at high temperature of the burner 49.

The reactor 18 is provided with a refractory liner 108 in a manner known in the art. The refractory lining 108 contributes to uniform and efficient heating of the bed 102 because the exposed portion of the refractory lining 108 receives heat from the flame by radiation and also by convection. The coating 108 includes an intermediate layer of insulating material 107 (shown in Figure 3) as a thermal protection for the metal wall 109 of the reactor 18. The rapid and efficient absorption of the heat from the burner 49 by the bed 102 also depends on the speed of rotation of the reactor 18 and it is necessary to avoid overheating of the areas of the bed 102 that are directly exposed to the heat of the flame, as well as to avoid overheating of the refractory lining 108. If uncontrolled overheating of the bed 102 and / or the refractory 108, there would be a melting and / or melting and agglomeration of ashes with ash and / or ash with the refractory 108 and the refractory lining 108 would be damaged.

It has been found that the process can be controlled in an adequate way by monitoring the heat in the reactor and making adjustments to keep the process operating within the preferred temperature range. This can be achieved by means of two thermocouples, one positioned in the widest part of the reactor and the other in the discharge throat of the reactor. The two or more thermocouples are positioned so that they project through the reactor wall and are exposed to the direct temperature of the waste and gases within the reactor.

A second burner 51 has been shown in dotted lines to illustrate an alternative embodiment having a plurality of burners. However, in the preferred embodiment only one burner 49 is used.

The adjustable position of the nozzle 50 of the burner 49, shown in solid and dotted lines, inside the reactor 18 is an important feature for the optimum operation of the process. The preferred position of the nozzle 50 will be that to which an effective reaction is carried out between the gases arising from the bed 102 and the oxidants produced by the flame of the burner 49. The flame causes a vortex near the discharge end 35 of the reactor 18 and the gases produced by the bed 102 must pass through the area of influence of the flame. This arrangement results in the production of a high quality gas in a single reaction zone.

The discharge end 35 of the reactor 18 is provided with a porous cylinder 110 for screening fine ash particles from coarse ones discharged from reactor 18. Fine particles 116 and coarse particles 118 are collected by ducts 112 and 114, respectively, for disposal or further processing.

The burner 49 in this preferred embodiment is stoichiometrically operated to minimize the direct oxidation of the bed material 102 within the reactor 18.

The seals 120 and 122 are provided to prevent a substantial introduction of atmospheric air into the reactor 18. The design of the seals 120 and 122 will be better appreciated with reference to FIG. 3. The design of the reactor 18, (shape, length and rotation on a horizontal axis), produces a minimum thermal expansion, both radial and axial. Seals 120 and 122 are specifically designed to absorb axial and radial expansions, as well as normal machining irregularities, without damaging them while maintaining a secure seal.

The seals comprise a static ring in the shape of a "u" 130 seen in cross section supported by an annular plate 132 which closes the end of the space 138 of the reactor and which in turn is joined by means of the flange 134 to the outer structure of the reactor. "auger" feeder 20. A fixed package 136 is provided to ensure that there is no gas leakage from the space 138 communicating with the interior of the reactor 18 through the annular space 140.

Two independent rings 142 and 144, made of stainless steel, are forced to make contact with the static "u" shaped ring 130, by a plurality of springs 146. The rings 142 and 144 are fixed to the supporting ring plate 148 to form an effective seal between the ring 142 and the plate 148 with the conventional fixing means 150. The support plate 148 is fixed to the member 152 which forms part of or is fixed to the outer wall of the reactor 18.

The springs 146 maintain the sealing surfaces of the rings 142 and 144 pressed against the surface of the static ring 130 despite their wear or deformations by temperature. EXAMPLE No. 1 A pilot plant was operated incorporating the present invention during many test runs. The rotating reactor is of the order of 4.3 meters in length and 2.4 meters in width (14 x 8 feet) at its widest point and has the shape and accessory equipment as shown in figure 1. The following data were obtained: ASR material from a car recycling plant to the reactor as described in this specification.

The typical analysis of the material ASR in% weight, (also called "fluff") is the material that remains after the metal parts, such as bodies, appliances and sheet are milled and metals are removed, is as follows: Fiber 26.6% Metals 3.3% Fabric 1.9% Rubber foam 1.4% Paper 3.7% Plastics 12.5% Glass 2.4% Tar 3.6% Wood 1.4% Wiring 1.3% Elastomers 3.3% Earth / Others 38.6% TOTAL 100.0% It should be understood, however, that the actual analyzes vary in a wide range due to the nature and origin of the material. Depending on the recycling process, the "fluff contains a variable weight of non-combustible materials (ashes) .The bulk density of the fluff is approximately 448 Kg / m3 (28 Ib / ft3). In general, the non-combustible materials represent about 50% of the weight and the organic or combustible materials approximately the other 50%.

Approximately 907 kg / hr (2000 Ib / hr) of fluff was fed to the rotary reactor by means of the screw feeder after a period of reactor heating, so that its internal temperature was higher than 650 ° C (1202 ° F). During its stable operation, the temperature in the reactor was more or less homogeneous and close to 700 ° C (1292 ° F), although the temperature of the flame can reach 3000X (5432 ° F). n Endothermic reactions between the gases produced by the "hot fluff and the oxidants (CO2 and H2O) produced by the burner cause the temperature in the reactor's internal bed and the internal adjacent atmosphere to stabilize at approximately 700 ° C (1292 ° F). ).

The reactor was rotated at approximately 1. r.p.m. The burner was stoichiometrically operated using approximately 64.3 MCNH (normal cubic meters per hour) (2271 PCNH: normal cubic feet per hour) of natural gas and 129 MCNH (4555 PCNH) of oxygen. A high quality synthesis gas was obtained at 573 MCNH (20235 PCNH).

A typical analysis of the synthesis gas produced is:% Volume (dry basis) H2 33.50 CO 34.00 CH4 8.50 CO2 13.50 N2 5.50 C2H2 0.75 C2H4 3.50 C2H6 0.75 Total: 100.00 As can be seen, the product gas obtained contained 67.5% of reducing agents (H2 and CO) and 13.5% of hydrocarbons, which in some applications of this gas, for example, in the direct reduction of iron ores, can be reformed in the process of direct reduction and produce more reducing components (H2 + CO).

The calorific value (HHV) of the product gas was approximately 3.417 Kcal / m3 (384 BTU / ft3) which corresponds to a gas of medium calorific value and which can be used for example in an internal combustion engine, and can certainly be burned to produce steam or for any other heating purpose. As a comparison, effluent gases from blast furnaces have a calorific value of between 801 to 1068 Kcal / m3 (90 to 120 BTU / ft3) and are also used for heating in steel plants.

The amount of dry ash discharged from the reactor is about 397 Kg / hr (875 Ib / hr), and additionally about 57 Kg / hr (125 Ib / hr) was collected as sludge from the gas cleaning equipment.

The hot ashes collected directly from the discharge port of the reactor and the hot cyclone have a very low content of leachable heavy metals, and pass the TCLP (Toxicity Characteristics Leachate Procedure: consistency tests for leachable toxicity tests) consistently without any treatment. These ashes contain between eight and twelve percent of recyclable metals, including iron, copper and aluminum.

Hot ashes are composed of iron oxides, silica, alumina, calcium oxide, magnesium oxide, carbon, and minor amounts of other materials.

After separating the large metal pieces by means of screens, the remaining ashes are not harmful to the environment and can be used in sanitary landfills without any further treatment. The toxicity analysis of the concentration of the eight RCRA metals in an extract obtained by TCLP tests is illustrated in the following table.

The Concentrations Results of Regulatory TCLP * tests (mg / L) (mg / L) Silver 5.0 < 0.01 Arsenic 5.0 < 0.05 Barium 100.0 5.30 Cadmium 1.0 < 0.01 Chrome 5.0 < 0.05 Mercury 0.2 < 0.001 Lead 5.0 < 0.02 Selenium 1.0 < 0.05 * Toxicity Characteristics Leachate Procedure: Procedure for leachate toxicity characteristics of the Law on conservation and recovery of resources.

The solid powders collected from the gas washing system are recovered as sludge and have been analyzed on the eight RCRA metals as illustrated in the following table: The Concentrations Results of Regulatory TCLP tests (mg / L) (mg / L) Silver 5.0 < 0.01 Arsenic 5.0 0.06 Barium 100.0 3.2 Cadmium 1.0 0.78 Chrome 5.0 < 0.05 Mercury 0.2 < 0.001 Lead 5.0 4.87 Selenium 1.0 < 0.07 Several TCLP tests were made and in all cases the sludge materials have passed the tests without any additional treatment.

EXAMPLE No. 2 The effectiveness of the seals described and claimed in this application, constituting an important feature of the present invention, can be appreciated by comparing the results of two runs of the pilot plant (the first with a commercial stamp and the second with a stamp made of according to figure 3).

COMMERCIAL SEAL SEAL ACCORDING TO FIG.3 MCSH (PCSH) MCSH (PCSH) Gases produced 574 (20,279) 64% 606 (21, 408) 94 Nitrogen 333 (11,753) 36% 36 (1, 263) 6 Total gas product 907 (32,032) 100% 642 (22,671) 100 Although it has been found that about 3% of the nitrogen contained in the final product gas originates from the fluff material, it can be seen that a significant decrease in the nitrogen content of the synthesis gas was achieved by the special construction of the seals of the invention, which contributes to the gas produced having a higher quality and value.

EXAMPLE No. 3 In order to evaluate the goodness of the synthesis gases produced in accordance with this invention for the chemical reduction of iron ores, the following material balance was made by running a simulation program designed specifically for this purpose. The calculation base was 1 metric ton of metallic iron produced.

Although the reducing gas produced in accordance with the present invention can be used by any of the known direct reduction processes, the material balance was calculated as applied to the HYL III process invented by employees of one of the companies holding this application. Examples of this process are described in United States Patents 3,765,872; 4,584,016; 4,556,417 and 4,834,792.

To understand this example, reference will be made to Figure 1, where one of the applications illustrated is the reduction of iron minerals, and Table I shows the balance of matter. 926 Kg (2042 Ib.) Of "fluff in reactor 18 was gassed. 95 MCN (3354 PCN) of natural gas and 190 MCN (6709 PCN) of oxygen were fed to burner 49. The gasification of this amount of "fluff produces 1, 000 MCN (35,310 PCN) of hot reducing gas (F < ) which after cleaning and cooling is reduced to 785 MCN (27,718 PCN) with the composition identified as F.

The clean reducing gas is combined with approximately 1,400 MCN (49,434 PCN) of recirculated gas effluent from the reduction reactor after cooling in the direct contact cooler 124 and dividing, having composition F7.

The mixture of fresh reducing gas F2 and recirculated gas F7 then passes through a CO2 separating unit 126, which can be of the type of packed bed absorption tower using alkanolamines which results in 1,876 MCN (66,242 PCN) with the composition of F3, which clearly is of a high potential reducing gas, of the type normally used in direct reduction processes. By means of unit 126, 297 MCN (10,487 PCN) are separated from the system as the current F-JO- The resulting gas stream F3 is then heated in heater 110 to about 950 ° C (1742 ° F) and fed to the reduction reactor 104 as the gas stream F4 to carry out the hydrogen and carbon monoxide reduction reactions with the iron oxides to produce metallic iron.

The effluent gas stream F5 of said reduction reactor 104 consequently has a higher content of CO2 and H2O as a result of the reactions of H2 and CO with the oxygen of the iron ore, therefore the effluent gas F5 is dehydrated by cooling it in a direct contact cooler 124 to give 1,687 MCN (59,568 PCN) of a CF gas. A purge is separated Fs of 287 MCN (10,134 PCN) of Fg gas and is extracted from the system to prevent inerts (e.g. N2) from accumulating in the system and also for pressure control. The rest of the gas is recirculated as described above as the stream F? (combined with F2, without CO2, and then fed to the reduction reactor as the F3 gas stream having the composition indicated in Table I).

Optionally, a cooling gas, preferably natural gas, can be circulated in the lower portion of the reactor in order to cool the direct reduction iron (HRD) before discharging it.

For this purpose, about 50 MCN (1,766 PCN) of natural gas F9 is fed to a cooling circuit and circulated through the lower portion of the reduction reactor 104. The effluent gas stream from the cooling zone of said reactor is cooled and cleaned in a direct contact cooler 106 and recirculated within said cooling circuit.

TABLE I Material Balance of the R.D. process HYL lll (from example 3) using synthesis gas from the gasification of ASR materials F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 H2 28 35 44 44 33 40 40 40 0.4 CO 26 33 26 26 14 16 16 16 0.1 CO2 1 111 14 11 13 13 13 0.4 100 CH4 7 10 16 16 13 16 16 16 93.7 N2 4 12 12 11 14 14 14 0.5 C3H8 0 4.6 C4H10 0 0.3 H2O 24 18 1 1 1 Flow 1000 785 1876 1876 2023 1687 1400 287 50 297 (MCN / Ton Fe) Temperature 500 30 40 950 639 30 30 30 25 30 (° C) FIELD OF THE INVENTION.

The present invention relates to a method and apparatus for producing reducing gases having a high content of hydrogen and carbon monoxide, commonly known as syngas (syngas), from solid organic waste. More particularly the invention relates to a method and apparatus for gasifying industrial and domestic wastes of various types, including non-metallic waste from automotive scrap, known as "Auto Shredder Residues (ASR) also known as" fluff, tire scraps, waste from the petrochemical, polymer and plastics industries, and in general waste organic compounds (including liquids and used motor oil), to produce a gas containing a high content of hydrogen and carbon monoxide (typically more than 50%, or up to more than 65% on dry basis) that can be used as raw material in other industrial processes, for example, to reduce iron ore to metallic iron in iron production processes known as Direct Reduction processes, or to be used as source of energy to operate an internal combustion engine or to produce steam and / or electricity. In its broader aspects, the method described here can be used for the devolatilization of coal or other similar sources of carbon and / or non-residual hydrogen and of complex molecular structure.

OBJECTIVES OF THE INVENTION Accordingly, it is an object of the present invention to provide a process and apparatus for producing reducing gases, also known as synthesis gas, preferably from low-cost carbon and hydrogen sources, such as garbage or other organic waste, and with a flexibility to accept a wide range of different kinds of loads (wet and dry), and that the synthesis gas is strongly reducing and therefore can be used as raw material in chemical processes and also as fuel.

It is another object of the invention to practice the process with a simplified, low cost device.

Other objects of the invention are described below or will be apparent to those skilled in the art.

The present invention comprises a process where the gasification of organic materials is carried out by thermal cracking of complex hydrocarbons and by the reaction of gases produced from said hot materials (preferably between 650 ° C and 800 ° C) with dioxide carbon and water (usually generated by combustion, preferably stoichiometrically at least initially, of a fuel and oxygen in at least one continuous burner at high flame temperatures typically between 2500 and 3000 ° C). For methane (CH4), the stoichiometric ratio of fuel to oxygen in the burner would be 1: 2 (natural gas, usually being methane for the most part, has approximately the same ratio). The heat produced by the combustion of fuel etc. it is transferred to the gasifiable materials not only by convection, but also by direct radiation of the flame and by agitated contact with the inner refractory lining of the reactor at high temperature.

The burner (s) inside the reactor is adjusted in its position and capacity in such a way that it is capable of releasing the heat necessary for the thermal decomposition of the materials and also to carry out the endothermic gaseous reactions of the complex hydrocarbons with water and carbon dioxide, as well as to provide the necessary quantities of the H2O and CO2 reagents for these reactions.

Another advantage of the present invention is that a high quality gas is obtained in a single stage or primary reaction zone. This results in a commercially acceptable, simple, low cost, low maintenance appliance that has relatively few exposed or mobile parts. Previous art processes are typically more complex, often requiring two stages (where most H2O and CO2 are produced in the second stage). Complex gases react by dissociation within the reduction zone according to their thermal and chemical equilibrium composition and are converted to simple gases derived from substantially stable hydrocarbons at lower temperatures resulting in a stable synthesis gas containing primarily hydrogen (H2 ) and carbon monoxide (CO), at least 50% or 60% on dry basis); and secondarily carbon dioxide (CO2), water (H2O), and nitrogen (N2); and minor amounts of residual hydrocarbons, including methane (CH4), ethane (C2Hg), ethylene (C2H4), and acetylene (C2H2) - One of the advantages of this invention is to provide a high quality process gas at a competitive cost with respect to traditional process gases (such as reformed natural gas), it may be necessary to activate the invention in one of its broader aspects and under certain market conditions and with certain kinds of "fluff or other waste materials to use in the burner or in the reactor an excess of oxygen with respect to the stoichiometric ratio to decrease the amount of fuel (eg natural gas) used in the burner in proportion to the amount of organic gasified waste, whether the cost of natural gas or other standard fuel is very high, the same synthesis gas produced can be used in the burner, however, essentially the same can be achieved preferably and in a more efficient way. This is achieved by reducing the fuel supplied to the burner so that it results in a relatively large excess of oxygen with respect to the stoichiometric amount. This is essentially the same result since the oxygen will react within the reaction zone with the dissociated molecules present in the components of the synthesis gas, which however are nevertheless advantageous in a state of high reactivity, and that it also avoids extra handling to extract, clean and essentially recycle the same "fuel". The net result of this alternative is that: (1) the same amount of waste is processed, (2) but at a lower cost since the effluent synthesis gas will normally be less expensive than natural gas, however (3) lower net production of synthesis gas. Less synthesis gas can be an advantage if it is to be used only as a medium-value fuel, since natural gas, which is a better fuel, has been saved to produce it. On the other hand, if the product is to be used as a reducing gas, the conversion of natural gas to H2 and CO has a value that to a certain degree must be balanced to decide how to adjust the burner feed ratio.

An excess of oxygen is also needed when the load has a water content greater than about 15%. By practicing the process according to the present invention in a demonstration plant, with a capacity of 4,000 pounds (1, 816 kg) of organic material per hour, the primary process burner was initially restricted, for safety reasons, to operating close to the theoretical stoichiometric ratio (1: 2) between the fuel and the oxygen to eliminate the possibility of very high temperatures and / or explosive conditions in the gasification apparatus. This condition works well when gassing (automobile shredder residue) ASR. At these moisture content levels the fuel to oxygen ratio of 1: 2 for the primary burner operates very efficiently. Nevertheless, it has been found that certain materials other than ASR, including municipal solid waste (MSW), recycled cardboard waste (RCR), and mixtures of each material with pieces of tires, contain between 25% and 50% free water (H2O) . This higher water content results in a lower gasification efficiency, when compared to the gasification of materials such as ASR that contain less water. To improve the efficiency of gasification of cargo materials with excessive levels of humidity (H2O) it is necessary to reduce the total water content in the gasification reactor, since the pre-drying of the loading material, such as the MSW, would not be economically feasible. The total water introduced into the gasification reactor is preferably lowered by reducing the amount of fuel fed to the primary burner with respect to the amount of oxygen. How this can be achieved is illustrated in the following examples: - For a 1: 2 ratio: Primary Process Burner CH + 2O2 - > CO2 + 2H2O With this ratio, 45% of the molecular weight of the combustion products is water.

For a ratio of 1: 4: Primary Process Burner CH4 + 402 - > CO2 + 2H2O + 2O2 With this ratio, 25% of the molecular weight of the combustion products is water.

The decrease in water introduced via the primary process burner operating at a fuel to oxygen ratio of 1: 4 results in a reduction in the total weight of water in the reaction zone of the gasification reactor of approximately 30%; assuming that the MSW material used in this example contained 35% water.

When the feed contains higher water levels, the lower gasification efficiency can be compensated by reducing the amount of fuel injected relative to the amount of oxygen in the primary process burner, as long as the temperature of the atmosphere inside the gasification reactor is keep in the preferred range, ie, 650 ° C to 800 ° C (or more preferably between 700 ° C and 750 ° C).

CO2 can be introduced into the reactor with the same effect as excess water in the cargo, serving as a low-cost substitute for natural gas, especially if CO2 is some unwanted by-product in the synthesis gas produced and in the reduction process. Direct described later. This last process is integrated with advantages to use synthesis gas. The CO2 can be introduced to the burner while the flame and the temperature range is adequately maintained, or can be introduced directly into the reactor, with compensation by means of the feed ratio to the burner to maintain the appropriate temperature range.

In determining the proper ratio for the burner for a given load, not much oxygen should be used in a manner that results in substantially insufficient gassing (producing H2O and CO2 at the expense of H2 and CO) or resulting in excessive temperatures over the preferred range, which would produce too much CO2 present in the synthesis gas, on a dry basis, and that also said high temperature could melt the residual ash in the reactor. Nor should the operation be modified in such a way as to result in a two-stage process as in the prior art with two significantly different temperatures and in which the second stage is carried out in the absence of a solid load. The limit for excess oxygen for some ASR materials, for example, would be up to 10% more oxygen with respect to the molar content in the fuel. Excess oxygen, especially during transient periods, can hinder the control of the process and make it safer if that excess is minimized. On the other hand, and according to the economy of the process, a portion of the synthesis gas previously generated can replace an equivalent amount of natural gas in the burner, up to 100% substitution.

In operation, the gasification process in the preferred apparatus is started in a period of 4 hours, heating the internal atmosphere and the refractory material of the gasification apparatus to approximately between 650 ° C and 800 ° C before introducing organic material into the zone. of reaction of the apparatus. The heating of the internal atmosphere and the refractory material is carried out by means of one or more process burners which are operated with a fuel to oxygen ratio of 1: 2; thus generating a sufficient volume of hot gases that essentially empty it of unburned fuel and free oxygen; that is, H2O and CO2. During the heating period the hot gases produced (CO2 and H2O) in the process burner pass to the reaction zone of the gasification device and through ducts through the gas cleaning system for a period of several hours, heating the device and purging it completely of oxygen (air) the gasification reactor as well as the product gas management system.

When the refractories and the atmosphere within the reaction zone of the gasification apparatus reach a temperature level sufficient to ensure the autoothermal combustion (above 650 ° C) of the organic gases with the residual free oxygen (air) that may exist in the reaction zone, a load of organic material is fed to the gasification apparatus. The organic solid materials are rapidly heated above their melting and boiling temperatures and organic vapors (gas) are made which at the autothermal ignition temperature are combusted with the last vestiges of free oxygen that may remain in the reaction zone of the apparatus of gasification. The reaction zone is rapidly emptied of free oxygen, and the heterogeneous mixture of organic vapors that are formed from the organic material of the charge enter the atmosphere of the reaction zone and make contact with the high temperature flame of the main process burner. and with the combustion products of said flame (CO2 and H2O). The process of gasification by exothermic and endothermic reactions results in the reformation and / or dissociation of complex molecular bonds and a stable production of synthesis gas is achieved.

As the produced synthesis gas passes from the gasification apparatus through the corresponding ducts and gas cleaning systems, the synthesis gas displaces the initial residual gases (CO2 and H2O) through the system until the entire management system of gases is free of said gases and of free oxygen (air); and the possibility of generating explosive mixtures of synthesis gas and oxygen is eliminated.

The total amount of energy provided to the process to maintain the adequate thermal balance and to counteract the energy consumption by the gasification reactions and the heat losses of the system, can be determined once the gasification process is in a stable state, and the preferred temperature has been reached in the gasification apparatus in the range between 650 ° C and 800 ° C, and when the organic vapors of the fed material come into direct contact with the flare of the primary process burner, operating at a ratio of fuel to oxygen of 1: 2. Once the optimum energy requirement has been determined, the base flow of oxygen feed to said burner can then be established. For example: assuming a feeding of 1 tonne per hour of organic material to the gasification apparatus (which generates 1/2 ton of ash), 3 million BTU / hr (756 million Cal / hr) are required, to counteract the heat losses; The primary burner operates with a ratio of natural gas as a fuel to oxygen of 2: 1 and also the high calorific value of natural gas is considered as 1000 BTU / standard cubic foot (252 Kcal / cubic meter standard) and twice that amount: 6000 scf / h (170 standard cubic meters per hour) of oxygen to have a stoichiometric combustion. Therefore, this example identifies the oxygen injection base flow.

Once the oxygen base flow is known, the fuel to the burner can be slowly lowered while the oxygen flow is maintained at the optimum level as determined above. At the same time, the organic vapors move towards the vortex of the high-speed flame replacing the fuel that is not fed (natural gas in this example). Organic vapors, instead of natural gas, react with the free oxygen present in the flame of the burner and the resulting exothermic reactions act to maintain the temperature of the atmosphere in the reaction zone of the gasification apparatus.

Direct combustion between the load of organic material and the oxygen injected through the primary burner will not occur due to the presence and availability of organic vapors that mix in the vortex of the flame of the primary process burner.

As the gasification process is modified from a fuel to oxygen ratio in the primary burner to a lighter ratio, the oxygen injection remains approximately at the same level that was set for the operation at a 1: 2 ratio. The material in the reaction zone and the temperature of the atmosphere within the gasification apparatus remain approximately at the same level as when operating at a fuel to oxygen ratio of 1: 2; however, the organic vapors contained in the synthesis gas are reformed to carbon oxides and hydrogen and the hydrocarbon content of organic gases tends to zero.

The greater amount of oxygen with respect to the fuel injected through the primary process burner does not produce a significant increase in the volume% of carbon dioxide in the resulting synthesis gas. The example given below was taken from actual operation data and reflects the relative effect of the ratio of fuel to oxygen in the burn over the composition of the resulting synthesis gas. Typical analysis of the synthesis gas produced by the primary process burner: Ratio 1: 2 Ratio 1: 4% Volume (dry basis) H2 35.96 36.60 CO 33.57 34.16 CO2 13.20 13.90 2 6.01 5.98 CH4 6.80 6.09 C2H4 2.60 2.06 C2H6 0.55 0.37 C2H2 0.67 0.40 C6H6 0.64 0.44 Total: 100.00 100.00 HHV 380 354 In the previous example, it is evident that the percentage of gaseous hydrocarbons is small and that the reduction in calorific value (HHV) is only 6.8%. By further reducing the ratio of fuel to oxygen, the gaseous hydrocarbons can be reduced to almost zero and the calorific value (HHV) will also be reduced to reflect the highest relative percentage of hydrogen: 325 BTU / ft3, (2,892 Kcal / m3) and of CO 323 BTU / ft3, (2,874 Kcal / m3) contained in the synthesis gas produced.

As for the rotary reactor described in the present invention, it comprises some unique characteristics, for example: it has a burner that operates continuously, has a common opening that serves both the burner gases entering the reactor and the gas outlet of the gas. produced synthesis (thus ensuring an intimate mixture of both gases), and the rotary reactor has a substantially horizontal position with respect to its axis of rotation, while other known rotary reactors are inclined so that materials that move laterally in the interior are move also from the loading end towards the discharge end. In the rotary reactor of the present invention the solids are moved from the point of charge to the point of discharge by effect of the rotary movement of the reactor, and by the volumetric displacement of the ashes of the solids that have already reacted in the bed of the unreacted material and inert solids contained in the feed material. The center of the reactor has a bulky shape to give the bed an adequate volume and a retention time of the charge and to conform the shape of the reactor to that of the flame of the burner.

The process may be carried out in another type of apparatus such as a stationary horizontal cylindrical reactor having inner inner vanes with a slight angle, which agitate and move the load. This type of apparatus has some disadvantages such as the possible obstruction of the single flame within the reaction zone and the engineering problems of the vanes and of the mobile support parts that are needed in the high temperature zones of the reactor.

Another important feature of the present invention is the unique structure of the high temperature seals that minimize the entry of outside air into the rotating reactor.

As the primary process burner is operated with oxygen and a fuel (natural gas, synthesis gas, fuel oil, coal, etc.) the nitrogen content in the synthesis gas produced is normally limited to the nitrogen content of the organic materials that they are gasified, therefore the nitrogen content of the product gas is normally less than ten percent by volume.

An important aspect of this invention is the mixing of the gaseous hydrocarbons produced and the powders having carbon black leaving the reactor through the vortex of CO2 and H2O at high temperature created in the interior of the reactor by the countercurrent gases of the reactor. burner.

Preferably, the flame of the primary process burner enters the reactor in a countercurrent direction relative to the movement of the charge material. The gases with dust generated by this process preferably pass through the burner, on its way to the outlet of the reactor, co-current with the load (ashes and materials in gasification).

In the preferred embodiment, the reactor rotates on its horizontal axis. At the load end of the reactor the feed tube fulfills the following functions: (1) as input for the raw material and (2) as atmospheric seal.

The raw material is introduced to the gasification reactor using suitable means, such as extrusion by means of a screw (auger) of standard commercial design; however, the diameter, length, and inclination of the feed tube to the reactor, as well as the exact position and tolerance between the tube and the rotating reactor, have been determined by practice and provide support for the design of the Rotary seal between the tube and the reactor. The solid material fed into the feed screw contributes to forming the atmospheric seal at the loading end of the reactor. The screw can also perform a breaking function of too large pieces of material.

Another method for feeding the raw material to the reactor includes using a hydraulic piston system in which two sets of hydraulic pistons act to compact and force the material through a specially designed feed tube.

The nature of the organic material consumed in this process is such that some materials have an extremely low melting temperature and volatilization; for example plastics, rubber and oils / fats. Therefore, it is important that the temperature of the fed material be controlled to avoid premature reactions before the material reaches the interior of the gasification reactor. The design of the extrusion feed tube and the receiver conduit or tube through which the fed material is introduced and through which the atmospheric seal must be maintained is a very important part of the design of this invention.

The process temperature must be controlled to prevent the materials in the bed from reaching their incipient melting temperatures, thus preventing the formation of agglomerates in the bed and on the walls of the reactor. The critical ash fusion temperature has been determined by practice for several types of raw material. In the ideal practice of the art of this process it is important to keep the temperature of the bed as high as possible, however the temperature of the bed should remain below the incipient melting point of the ash (hence the preferred range of 650 ° C to 850). ° C).

The non-reactive dust particles that are trapped by the gas leave the gasification reactor along with the product gas to the hot gas discharge hood and then, through hot ducts, to a cyclone, venturi, or other commercial equipment appropriately adapted. The gas then passes through a packed-bed column where the acids in the gas are washed and the pH of the wash water is adjusted to approximately seven (7). The clean gas is then moved by a compressor via a pipe to a warehouse or later use.

The design of the hot gas discharge hood is another important aspect of this invention. The hot gas discharge hood provides the support structure for the process burner.

The air / oxygen injector (s) may advantageously be located in the hot gas discharge hood and / or in the high temperature cyclone for purposes of introducing air and / or oxygen to control the temperature of the gas produced at as it leaves the hot gas bell and / or to help "finish" the gasification of any residual hydrocarbons or carbon black. In the practice of this process it is important to keep the product gas temperature high enough until the gas reaches the gas scrubber in order to avoid the condensation of any high molecular content gas that exits through the hood. The additional residence time of the product gas in the hot gas discharge hood, in the hot ducts and in the high temperature cyclone leading to the gas scrubber is such that the efficiency of the reactions between the gas and the portion is increased carbonaceous of dust.

By means of controlled additions of air and / or oxygen to the hot gas of the discharge hood, both the pressure and the temperature in the discharge hood can be better managed. It has been found that by raising the temperature of the product gas to about 700X by injecting about 5% oxygen by volume, the residual complex gaseous hydrocarbons are decomposed predominantly into carbon monoxide and hydrogen. Ideally, these additions are minimized in order to maintain the quality of the synthesis gas. However, the different types of load require adjustments to provide the flexibility required to the process. When the type of load is not standard, such flexibility can be made by adjusting the amount of air and / or additional oxygen. The amount of air and / or oxygen introduced into the hot gas duct must also be controlled in consideration of the energy requirements of the gas to be produced. For example: if the nitrogen content in the product gas is not critical with respect to its subsequent use, air can be used exclusively to control the temperature and pressure in the hot gas discharge hood. However, if the nitrogen content in the process gas has to be maintained at low levels to meet the BTU (calorie) specifications of the gas, oxygen may be used instead of air.

As the synthesis gas produced by this process naturally has a high content of particles and acid gases, the sensitive energy of the gas can not be easily used by means of heat exchangers. On the other hand, the gas can be controlled to contain between 1335 Kcal / m3 and 3557 Kcal / m3 (150 to 400 BTU / ft _) and can be easily cleaned of particles and acids.

The ash that is discharged from the reactor and the cyclone has a very low content of leachable metals. This ash does not require additional treatments to be disposed of in a way that is not harmful to the environment. The powder that remains in the product gas leaving the hot cyclone can be extracted in a venturi-type scrubber and recovered from the water as mud. This sludge may contain a relatively high level of leachable metals and therefore requires treatment to be disposed of in a manner not detrimental to the environment.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a partially schematic diagram of a preferred embodiment of the present invention useful for gasifying organic waste to produce a synthesis gas, illustrating a variety of end uses of said gas; Figure 2 schematically shows a vertical section in greater detail of the rotary reactor of the type illustrated in Figure 1; Y Figure 3 shows a schematic cross section of a high temperature seal for the loading end of the reactor of Figure 2.

Claims (19)

R E I V I N D I C A C I O N S

1. Method for gasifying organic materials in a first reactor having a single reaction zone to produce a synthesis gas, said method comprises: Feeding a load of organic waste materials to a loading end of said reactor and continuously stirring said waste materials in said reactor to form a bed in said reactor and moving said bed towards the discharge end of said reactor; Heat the organic waste materials sufficiently to volatilize them, decompose them thermally and gasify the hydrocarbons contained in the organic materials, producing gases generated by the organic materials and residual ash, by means of at least one stream of high temperature gases on said bed formed by combustion with a gas containing oxygen (1) of a fuel independent of said charge and suitable to produce CO2 and / or H2O and (2) of said gases generated when there is an excess of said oxygen-containing gas, said fuel and said gas containing oxygen in a ratio and in a volume such that the amount of said fuel is sufficient to maintain the temperature of the bed and of the adjacent atmosphere within said first reactor above 650 ° C and below the melting temperature of said ashes; Continuously operate said, at least one, high temperature burner to produce a stream of burner gas at the discharge end to provide sufficient energy and oxidizing combustion products within said first reactor to react with the gases generated in said first reactor to produce a synthesis gas; Y Download said residual ashes and synthesis gas at the discharge end and counter-current with respect to the flow of the burner gas stream in such a way that said burner gas stream makes good contact with the gases generated.

2. Method according to claim 1, wherein said combustion is substantially stoichiometric.

3. Method according to claim 1, wherein said oxidizing combustion products include H2O and CO2.

4. Method according to claim 3, wherein said charge has a moisture content between about 15% to 50% and the burner is operated with a ratio of fuel to oxygen in excess with respect to the stoichiometric ratio sufficient to maintain the temperature within said reactor above 650 ° C and below the melting temperature of said residual ash.

5. Method according to claim 4, wherein the burner has a fuel to oxygen ratio of about 1: 4.

6. Method according to claim 3, wherein said high temperature gas stream is generated as a flame at a temperature in the range between 2500X and 3000 ° C.

7. Method according to claim 3, wherein said produced synthesis gas is dehydrated and the CO2 is separated and where at least a portion of the latter gas is recirculated through said burner or directly to said reactor.

8. Method according to claim 3, wherein said synthesis gas exits said first reactor at a temperature above about 650 ° C and contains less than two percent by volume of gases with a molecular structure of more than two carbon atoms.

9. Method according to claim 8, further comprising maintaining the temperature of said synthesis gas leaving said first reactor above 650 ° C; transferring said synthesis gas to a second reactor; increasing the temperature of said synthesis gas in the second reactor by contacting said synthesis gas with a stream of a secondary adjustment gas injected there; said secondary gas stream of adjustment being chosen from the group consisting of products of combustion of a fuel with an oxygen-containing gas, which is injected into the effluent synthesis gas of the first reactor at a rate of up to about 5 percent by volume with with respect to said effluent synthesis gas; and wherein the temperature of the synthesis gas is raised in the order of up to 50 ° C, and where at least a portion of the carbon particles and complex hydrocarbon gases in said effluent synthesis gas of said first reactor react and / or are dissociated preferentially to CO and H2.

10. Method according to claim 9, further comprising separating the particles entrained by said synthesis gas from the second reactor by cyclonic separation and wet washing of said synthesis gas.

11. Method according to claim 9, wherein said adjusting secondary gas stream is produced by combustion of a fuel with a gas containing oxygen and is injected at a rate such that the temperature of said effluent synthesis gas of the first reactor is increased by above 700 ° C, and at least a portion of the free carbon or gaseous complex hydrocarbons remaining in said synthesis gas react and / or dissociate preferentially to CO and H2.

12. Method according to claim 1, wherein the charge containing organic materials is selected from the group consisting of automobile recycling waste (ASR); trash; municipal waste; plastic waste; pieces of tires; engine oil; and waste derived from the petrochemical, polymer and plastics industries different from those already listed above.

13. Method according to claim 1, wherein said heating is carried out by means of a plurality of burners positioned and directed towards the interior of said first reactor in such a way that the oxidizing combustion products contact the gases generated and the gas The resulting synthesis contains less than two percent by volume of gases with a molecular structure that has more than two carbon atoms.

14. Method according to claim 1, wherein said agitation is carried out by rotating said reactor on its horizontal axis; where the charge containing organic materials is fed to said first reactor at said loading end and the waste is discharged from said first reactor by volumetric displacement through an opening at said discharge end and by said agitation.

15. Method according to claim 1, wherein said fuel for said first reactor is composed partially or totally of said synthesis gas.

16. Method according to claim 1, wherein said fuel is selected from the group consisting of natural gas, synthesis gas, fuel oil, and coal.

17. Method according to claim 1, further comprising using the synthesis gas in a direct reduction process of iron ores.

18. Method according to claim 12, wherein the iron ore is reduced by a reducing gas containing hydrogen and carbon monoxide in a reduction zone and the resulting spent reducing gas is recirculated, having been dehydrated and separated the CO2 prior to its reintroduction to the reduction zone, said synthesis gas having been dehydrated and introduced to the recirculation circuit at least before the separation of the CO2.

19. Method according to claim 1, wherein at least a portion of the CO2 separated from the spent reducing gas is recirculated through the burner or directly to said reactor.