DE3242699C1 - Method for the autothermal gasification of solid and liquid fuels in the flue stream - Google Patents

Abstract

In a method for the autothermal gasification of solid and liquid fuels, particularly residues of the hydrogenation of coal, in the flue stream under pressure, in which fuel and some of the gasification agents are introduced in parallel flow axially from the end into a reactor and product gases and slag are removed at the foot of the reactor, the fuel is atomised centrally in the burner head and the oxygen is introduced together with some of the steam coaxially within the annular slot with the formation of swirl, while the rest of the process steam is introduced laterally through the wall of the reactor into the outer edge zone of the reactor. If the process steam is introduced upwards and downwards along the reactor wall, a particularly good cooling of the reactor wall can be obtained. A further advantage is that the swirl in the stream of oxygen is varied as a function of the load. The gasification reactor is operated under a pressure of 25-50 bar, and preferably 40 bar.

Description

stromes, which is coaxial with the atomized hydrogenation residue in the reactor occurs, and the following Formation of an inner backflow zone This steam line is used for preheating and gasification of the hydrogenation residue enables.

In the gasification of hydrogenation residues with the process of the invention a higher water vapor: oxygen ratio can be maintained than with the known procedures. In particular, it should be between about 0.2 1 kg / kg and 1.5 1 kg / kg.

The swirl of the oxygen flow is for the inventive Process, especially for the formation of the desired reactions, such as. B. heating zone, Combustion zone and cooling zone, of great importance. The swirl number of the burner should therefore be between 0.6 and 3.0 according to the invention. The twist should be the oxygen flow can be changed depending on the load in such a way that despite the cooling a stable combustion zone is maintained by the steam.

High pressures, along with high temperatures, have proven to be another Proven advantage of entrained flow gasification according to the invention. The pressures should therefore between 25 and 50 bar, preferably close to 40 bar. The well-known swirl burners In contrast, they are all operated at atmospheric pressure.

When performing the process, there is sufficient atomization and handling of the viscous hydrogenation residue is of particular importance. On the one hand the hydrogenation residue is to be heated to about 270-330 "C, on the other hand the tendency to crack to be observed, which starts at temperatures above 300 "C.

To reduce the risk of cracking, it may be necessary to

Additives that lower the viscosity to the hydrogenation residue. The viscosities of hydrogenation residues are in particular of the type that are hydrogenated Coal and the concentration in the hydrogenation process. They amount to, for example for-T = 230 "C 400-600 mPa s and for T = 300" C 140-200 mPa s. As with viscosities above 300 mPa s Difficulties with the dosage may occur, should a preheating take place in the temperature range from 270-300 ° C. This is the viscosity of the hydrogenation residue however, it is still a power of ten higher than with burners with heating oil.

During gasification, the ratio of oxygen to the hydrogenation residue should be from 0.5: 1.5 kg / kg to 1.5: 1 kg / kg, preferably 0.9: 1 kg / kg. Using of a pressure atomizer should be the geometric relationships of oxygen and The hydrogenation residue feed must be designed so that the hydrogenation residue is central is injected while the oxygen enters concentrically around the atomizing nozzle.

The atomized hydrogenation residue should have a particle size of 300 so as not to exceed significantly.

In addition to the droplet size in connection with the twisted oxygen or air flow, the spray angle for the hydrogenation residue must also be taken into account. It should be so large that it heats up the drops of hydrogenation residue in the inner return flow zone and be so small that it has an impact on the Reactor wall prevented. Accordingly, the spray angle should be between about 40 and 90 " lie.

With the gasification of hydrogenation residues according to the invention a swirl burner, for example, the following advantages are associated. So will through the inner backflow zone ensured a stabilized ignition of the flame while at the same time the outer backflow zone cools the reactor wall works. Due to the spatial separation of the exothermic combustion achieved according to the invention from endothermic (heterogeneous) or weakly exothermic (homogeneous) gasification is also used for a hotter and smaller combustion zone than the known ones DC process ensured.

Further advantages of the method according to the invention are based on Drawing explained in more detail. It shows F i g. 1 the division of the flow and reaction zones of the swirl carburetor, FIG. 2 a flow diagram of a plant for the gasification of residues of carbohydrate hydrogenation.

According to FIG. 1 are those with the swirl burner and the steam feed generated reaction zones illustrated. The inner backflow vortex forms in zone 1 of the swirl burner, in which the injected hydrogenation residue is heated, degassed and already partially burns. In contrast, the actual combustion takes place in zone 2, followed by gasification in zone 3, in which the water vapor is both homogeneous as well as heterogeneous gasification reactions is implemented. In zone 4, where the outer reverse flow vortex forms, the water vapor is heated while it is simultaneously the reactor wall cools.

According to FIG. 2, the hydrogenation residue ground to <3 mm is removed a storage bunker 5 with a discharge device placed on a weighfeeder 6, from which it is conveyed into the melting container 7. To avoid oxidation of the hydrogenation residue is the melting container 7 under an inert gas atmosphere held. The hydrogenation residue is heated here to such an extent that it can be removed by the pump 8 can be pumped to the atomizing burner 9. The one for sufficient atomization necessary temperature is only in a heater 10 just before the atomizing burner 9 set in order to largely avoid cracking reactions in the melting tank 7. The oxygen is also preheated in the heater 11 and in the atomizing burner entered where it receives the required twist. The water vapor is against it through slots 12 made in the walls of the refractory-lined reactor 13 blown in.

The raw gas formed as well as the liquid at the gasification temperatures Slag are withdrawn from the reactor 13 and passed through a suitable gas guide separated, the raw gas to the processing and heat recovery part of the plant is supplied while the slag is cooled in a water bath 14 and via a Lock is withdrawn in solid form from the system.

EXEMPLARY EMBODIMENT A hydrogenation residue with a typical Elemental analysis (anhydrous) of C 74% by weight H 6% by weight N 1% by weight S 1% by weight O / o 0 2 wt .-% ash 16 wt .-% are gasified. With a throughput of 3000kg / h hydrogenation residue and 3700kg / h gasification agent (2700 kg / h O2 and 1000 kg / h H2O) is used in one pressure from 40 bar a product gas of the following composition is obtained: kg / h mn3 / h vol .-% CO 4685 3748 50.6 H2 236 2643 35.6 CO2 764 389 5.2 N2 30 24 0.3 CH4 5 7 0.1 H20 468 582 7.9 H2S 32 ~ 21 0.3 6220 7414 100 At a medium temperature in the reaction space of approx. 1200 ° C. and an average residence time required for the reaction of the gases of 10 s, the volume of the reaction space follows from the gas volume flow of 1000 m3 / h to V = 2.78 m3.

A construction with a concentric central tube is used as the burner used, the hydrogenation residue being fed through the central tube, and through the surrounding annular gap the oxygen flow to be swirled. Since the twist is changeable should be, a burner is advantageous, which by means of controllable axial air and tangential air proportion a variation of the twist is allowed in the annular space (e.g. VDI reports 95 (1966), p 28).

If the atomizer lance is based on a diameter of dd = 60 mm, follows with a torch neck cross-section of do = 69 mm and the inlet conditions of p = 40 bar, T = 300 "C, a velocity in the open for the oxygen flow Torch neck cross-section of w = 30 m / s. The resulting Reynolds number Re> 5 106 is well above the stability limit of the recirculation zone of Re = 18,000, so that even with larger variations of w and dz there is a stable swirl flame Pressure can be generated. You can see four slot-shaped openings for entry of the tangential gas in the annulus, which has a slot cross-section of 40 5 mm have, so can with a diameter of the circle on which the inlet ports are tangent, from dk = 180mm an ideal twist number Sid = 3.45 can be achieved, which can be achieved by corresponding Lowering the tangential gas proportion can be reduced as required.

Claims (2)

Claims: 1. Process for autothermal gasification in entrained flow under pressure from solid and liquid fuels, especially residues of carbohydrate hydrogenation using oxygen and water vapor, in which under Maintaining a direct current of fuel and oxygen axially from the end face introduced into a reactor and withdrawn product gases and slag at the bottom of the reactor , with the preheated, liquid fuel in the burner head centrally below Pressure is atomized and the oxygen coaxially in the annular gap as a twisted flow is introduced, characterized in that the process steam flows through the side the reactor wall is introduced into the outer edge zone of the reactor. 2. The method according to claim 1, characterized in that the process steam is entered up and down along the reactor wall. The invention relates to a method according to the preamble of the claim 1. The gasification of liquid fuels, especially heavy oils, partial oxidation in the entrained flow process under pressure is already known. Here, the gasifying agents are oxygen and steam before entering the reactor mixed, while the heavy oil means after being preheated by an atomizer Pressure atomization is injected into the reactor. The management of the material flows in the burner head takes place in this process in such a way that oxygen and steam coaxially through a Annular gap are introduced into the reactor, on the other hand preheated heavy oil centrally is injected. In this way, oxygen and steam occur concentrically around the Atomizing lance of the heavy oil into the reactor (Ullmann, Enzyklopädie der Technische Chemie, 14, 395 (1977)). It is also known to inject the fuel in liquid form and the To add oxygen as a swirled stream, but with an upper limit of the tangential to be adhered to the axial entry speed to with low rotational movement to get the longest possible flame (DE-OS 25 39 888). In another known method, the preheated heavy oil atomized with steam and coaxially in the annular gap of the burner as an oil-steam mixture in introduced into the reactor while the oxygen was introduced centrally in the burner head (Ullmann, Encyclopedia of Industrial Chemistry, Vol. 14 (1977), page 396). Known are also various options for the burner of this process Guiding the reactant streams in the inner part and the surrounding annular gaps of the Brenners (DE-AS 22 04 061). The main feature of both processes is therefore an intensive mixing the hydrocarbons-water vapor-oxygen mixture at the outlet of a burner, so that the oxidation and steam gasification of the hydrocarbons as competing Reactions take place in the generated flame (direct current flow). Thus entrained flow gasification processes are with water vapor and oxygen known as reactants for liquid and dispersed solids, where even partially a limited twist of the gasification agent is provided. The known processes have in common that both gasifying agents (oxygen and water vapor) be introduced into the reactor via the front of the burner. Swirl burners, in which the oxygen swirls the burner head leaves, are known from the operation of combustion chambers with gas, oil or pulverized coal are operated, with the concentrically guided secondary air has been twisted in the annular space of the burner. This creates a increased internal and external recirculation of the combustion gases achieved (VDI report 95, pp. 13-38 (1966); Gaswärme int. 19 (1970l pages 474-481, 20 (1971), pages 18-24). Based on the above prior art, the present Invention set the task with a twisted oxygen atom a high To achieve the degree of swirl that can be achieved from combustion chambers operated with gas, oil or coal dust is known. In the inner backflow zones created by the twisted oxygen flow the sprayed hydrogenation residue is to be heated, degassed and partially burned. The outer backflow zones, on the other hand, should be provided with a new type of water vapor input lead to the cooling of the reactor wall. This object is achieved according to the invention by a method according to Characteristics of claim 1 solved. In the entrained flow gasification according to the invention it is achieved that the inner backflow zone due to the transport of hot gases igniting the flame stabilized. The outer backflow zone, which performs this task in the case of swirl-free flames comes, can thus in cooperation with the steam introduction according to the invention can be used laterally through the reactor wall as a cooling zone. In addition, the flow control of the reactants Intensive mixing and partial combustion of the hydrogenation residue in the swirl flame achieved. Due to the spatial separation of the exothermic combustion reaction from the endothermic (heterogeneous) or weakly exothermic (homogeneous) steam gasification reaction can also have a hotter but at the same time smaller combustion zone than the known entrained flow gasification can be achieved. Since the water vapor in the outer return flow zone, according to the invention up and down along the reactor wall, is therefore no clear direct current principle of all reactants given. By the invention Rather, guiding the reactants should be a two-stage reaction, namely initially a partial oxidation and then the gasification step take place, and continue through the swirl of the oxygen achieved that the for favorable reaction rates necessary temperature only arises inside the flame, while the reactor wall also is protected from excessively high temperatures without intensive cooling measures. The main difference to the known methods is thus in the Steam flow, the reaction and thermal technology as a kind of cross flow principle can be referred to, and in the cooling of the reactor. walls by blowing water vapor along the reactor wall. By the twisting of oxygen.