DD159010A3 - METHOD FOR INCREASING THE SPECIFIC BAY LOADS OF FIXED BEDGED GAS GENERATORS - Google Patents

Abstract

The method is used to increase the specific shaft load and to optimize the process execution of fixed-bed pressure gas generators for the gasification of brown or hard coal of various Inohlungsgrades. Based on the recognition that the grain structure in the pit of a fixed bed pressure carburetor in addition to some known Faktorren such. the fuel decay during drying and degassing is determined mainly by the behavior of the mineral constituents of the coal in the oxidation and reduction zone, the novel process shows new aspects to increase the performance of this shaft furnace process. According to the invention, it is proposed, with the change of the maximum reaction temperature in the oxidation zone, to bring about a modification of the grain structure in the generator shaft and thereby exploit the sintering and meltability of the mineral substance of the coal. Furthermore, proposals are made to change the mineral structure of the gasification material in such a way that, in the case of briquetting, additives of special minerals are used to modify the grain structure. For process control, the use of special reactor temperatures in the ash zone in conjunction with the discharge speed of the rotary grate is proposed.

Description

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a) Title of the invention

Method for increasing the specific shaft load of fixed bed pressure gas generators

b) Field of application of the invention

The invention relates to a method for increasing the specific shaft load and optimizing the Prοζeßdurchfuhrung Festbettdruckgasgeneratoren "for the gasification of lignite or hard coal of various levels of coalification.Here the usual specific shaft loads are exceeded.In the gasification agent, usually an oxygen-steam or a Air-vapor mixture, the non-oxidizing content is minimized.

Preferably, the method is to be applied where the nature of the coal contained in the mineral substance in the gas undergoes a very fine-grained and pulverulent structure during the gasification below the ash melting point and the gasification substance during the process run strongly for disintegration and pore grain formation inclines.

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c) Characteristic of the known technical solutions:

It is well known that the determining factor in the Pest bed gasification to define the power limit is essentially the dust discharge occurring.

> A number of constructive and procedural proposals have already been made for minimizing this process, which can occur depending on the specific properties of the fuel at very different performance limits. These can be divided into several groups.

You follow z. B. the goal, the fuel before and

^v - during the course of the process to be treated so that

Thermal and chemical processes are as little as possible. Such solutions are u. a. in the patents DD-PS 26 392, 38791, 119 814 and DD-PS Ϊ36505 find.

Constructive solutions, the optimal flow distribution in the upper part of the reactor, such. B. in the vicinity of the gas outlet, are u. a. in the patents DD-PS 132 980, 110 297, 133 817 and have been proposed. In the past, just as much attention has been given to optimizing the Pestbed Gasification of the design and operation of the rotary grate in conjunction with the feed of the gasification agent. Such suggestions were u. a. in the patents DD-PS 133 571, 134 243 and in DD-PS C 10 J / 209 772 submitted. '. The solution proposed by both groups is based on the common aim of directing the flow before entry and exit from the site,

that the most uniform possible distribution and thus an optimum in the Prozeßfiihrung is achieved. The disadvantage of these proposals is associated with the erroneous thesis, according to which the flow distribution as' crucial process variable for the performance

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fixed beds, much of the upstream and downstream facilities, such. As coal distribution and Gassammeiräume or grates, willjett influenced. However, this is not the pail. -More, the flow distribution is influenced in particular by the resulting in the course of the process grain structure. , , , Very fine-grained layers of bulk material in the reactor can, for. B. assume a flow resistance that can take higher values by several orders of magnitude compared to the resistance of internals in Gassammeiraum or on the rotary grate. Furthermore, Peinkorn has the very disadvantageous peculiarity that it is moved in the debris through the Pluid and deposited at any point of the reactor and thus potentiates the unevenness of the bulk structure. This even certain areas of the reactor can be brought to total blockage and the flow through the same can only be done in a channel shape with practically the principle and the advantages of the countercurrent reactor - lifted.

All of the above measures taken in the past, therefore, lead only to partial success, because their effect is limited to insignificant areas at the beginning and end of the debris.

Another group of proposals to improve the process flow in coal gasification involves the control of the ash discharge. In particular, a more uniform flow and avoidance of channeling should be achieved, which is e.g.

also target of DD-PS 133 247.

Another proposal for a similar objective is the control of the ash discharge on the basis of an ash balance at the reactor

 Even with these proposed solutions is misconceived that for a uniform flow through the Pestbettes the

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Grain structure door in the fixed bed represents the decisive criterion for controlling the ash discharge ever. -

 The control of the ash discharge also does not make it possible to keep the fire zone constant because, if the grain structure of the fixed bed is ignored, it does not constitute a flat surface. On the other hand, this extends in the form of distinct channels, in which considerable mass flow of solids can move in the flow direction of the fluid, over large vertical areas of the fixed bed. . The inclusion of an ash balance in a scheme of ash discharge does not lead to the desired improvements, because, at a high solids discharge with the raw gas flow no flat ash bed and Feuerbeti position adjusts and also for a qualitative and quantitative coverage of the fluid entrained solids flow no practically applicable measuring methods are known.

d) Aim of the invention:

The aim of the invention is a method for increasing the specific shaft load and the improvement of the economy of fixed bed pressure gas generators for the gasification of brown or hard coal of various Inohlungsgrades, by, created by means of suitable methods for modifying the grain structure such conditions that optimum flow conditions as set crucial for a high load capacity of the bed and damit.für a high specific · fish power and improved process control and improved economy, creating a process automation is possible in conjunction mi ¹ the ash discharge.

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e) Presentation of the essence of the invention:

The invention is based on the object, the hitherto prevailing views regarding the influence of generator internals, such as coal manifolds, gas collection chambers or grates, on the flow distribution and thus · the mit.diesen connected stagnation in the further improvement of the Prpzessführung. overcome.

According to the invention, this object is achieved in that the formation of the grain structure in the fixed bed as a key variable for the process flow depending on the respective process conditions by way of process flow is controlled so that adjusts a stable Pestbett and a uniform flow of the debris .. Die . Necessary assessment of the grain structure, which is defined in terms of their fluidic quality in general with the characteristics of mean grain diameter d and the so-called void volume ε, is carried out according to the invention on the basis of the criterion vortex point velocity for each height element of the reactor.

The influence of the grain structure in the fixed bed of the reactor can be carried out in various ways.

Firstly, it is proposed to control the mandrel structure of the ashes obtained in the gasification and of the ash coke ash - coal mixture present in the middle part of a pressure gasifier by changing the reaction temperature in the oxidation zone. It was determined on large-scale pressure gasifiers that z. B. with the change in the reaction temperature in the oxidation zone not only the grain structure of the ash, in particular their Peinkornanteil, can be changed, but also the Peinkornanteil in the reduction zone, d. H. in the field of partially gassed coke.

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It is advantageous to increase the reaction temperature in the oxidation and reduction zone to such an extent that the sintering or melting point is exceeded for at least 30% of the mass fraction of the mineral balance of the coal. With the achievable, evenly flowed through bed is the risk of the formation of larger slag agglomerates low, because the fine grain content, consisting of ash and coke ash particles, due to the Hichtüberschreitens the vortex point velocity does not shift to a greater extent by the fluid in higher layers, '-:. and is therefore easily melted by selection processes.

zeiide eutectic forms. Furthermore, by avoiding the transport of fine grain into adjacent areas, the chemical-physical conditions for the process flow are always secured so that no different Re acti ons temperature can arise with the same nature of the gasification.- Thus, the risk of slagging on Minimum pushed back. If the vortex point velocity in the fixed bed is not exceeded at any point, especially in the oxidation and reduction zone, the reaction end temperature can be increased to such an extent that a higher proportion of the mineral substance is converted into a coarse (granular) bulk material which is thoroughly

is flowable.

Furthermore, it is added that at a sufficiently high reaction temperature in the reduction zone by the incipient sintering processes in teilvergasten coke the grain disintegration and thus the dust formation are already significantly limited.

Practical possibilities for changing the reaction temperature and thus the grain structure in the oxidation and reduction zone are the change in the oxygen content in the gasification agent or, whose composition is par excellence and the choice of the temperature of the gasification agent.

The exact compliance with a certain maximum tempera ture in the oxidation zone, which depends on various factors, is done by a constant monitoring and control by means of a process computer. This is also necessary, on the one hand, to be able to fully exploit the advantages of a high reaction temperature and, on the other hand, to reduce slagging or the formation of too large a slag.

to avoid pieces. ,

In order to set an optimal reaction toneratures, according to the invention, as auxiliary quantities, temperature readings which are preferably taken from the inner shell of the generator at the level of the ash zone are used which indicate the reaching of the vyrolysis condition in the slurry by a discontinuous time course and sharp changes. This leaves a poorly flowable grain structure, d. H. On the other hand, the setpoint value of the amount of ash to be discharged from the generator, which results from the amount of coal gasified per unit time in the reactor, is used as an auxiliary variable for setting an optimum reaction temperature. If this is fallen short of, the grain structure in the shaft of the generator is too fine-grained and significant amounts of ash or coke ash particles are discharged not via the grate, but via the raw gas outlet. It is further proposed according to the invention, the process flow in conjunction with the optimization of the reaction temperature of Oxydationsζone with respect to the ash or the Peststoffaustrages on the operation of the rotary grate to control so that always a certain equilibrium temperature resulting from the temperature of the originating from the oxidation zone Ashes and the opposite gasification agent results, is respected.

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Preferably, the detection of this temperature takes place directly in the reactor and at several points immediately below the Oxydationsζone on the outer periphery

of the reactor. As a reference variable for the ash or, solids discharge is preferably a mean temperature, calculated from the average of at least two, preferably 4-6, measuring points. According to the invention, the control of the discharge

Mechanism for the solid or the ash according to an algorithm that takes into account the Temperaturmeßwerte, the timing of the entire system and the limits for the equilibrium temperature. In. Furthermore, the reaction temperature in the "oxy-

dationsζone and per unit time from the reactor

Specifically discharged ash in conjunction with the aforementioned auxiliary variables such that always a stabj les fire bed and an optimum final temperature of the discharged de reactor solids amount is ensured is preferably used as a target size for the temperature.

difference between ash to be discharged from the reactor and the entry of the gasification agent flowing through the ash bed, a value of max. 50 K bestimmgelegi Thus, both an optimal energetic process control, as well as a protection of the most before thermal loading ( damage not completely resistant components of the

Discharge organs for the solid reached

 Furthermore, the invention proposes to add in the case d «briquetting of the gasification this suitable mineral substances, whereby the Kornstruktiu and thus detrimental to the process flow fine grain content can be influenced so that even in the range above the oxidation zone of the reactor a Kornzerfi with Feinkornbildung.weitgehend counteracted - becomes.

Most suitable for such additives are such miners? constituents which on thermal stress lead to solidification of the grain structure of the carbonaceous substance b2 as a result of the gasification process on its own

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form solid compact structure. Such properties have z. As clay minerals, and lime, in the form of CaO contained in the coal, when heated leads to carbonate formation (CaCOß), which leads to a certain temperature level to a structural strengthening and thus counteracts the fine grain formation ... , Other mineral constituents or combinations of them naturally also lead to such process-stabilizing effects in the form of additives or with a specific choice of coal or coal mixture.

f) embodiment:

The invention will be explained in more detail below using an exemplary embodiment.

The ash discharge from the generator is generally via a rotary grate, so-called scrapers are used as Austragsorgane. The amount of ash discharged is determined by the cross section of the scrapers, their number and running speed as well as by the running time. The rotational speed and the switch-on time for the rotary grate are used in practice as set values for the time ash discharge.

According to the invention, the setting of the rotational speed of the rotary grate and the determination of the duty cycle or the change of both variables is such that in fixed periods as long as an increase in the ash discharge is made until the temperature measuring parts of the ash zone permissible temperature as an expression of the permissible Temperature difference between gasification agent and ash preferably up to max. 50 K has been achieved

 If this temperature has been reached in the form of an average of several temperature measuring points in the ash zone, the initial values for the ash discharge are set,

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which automatically gives a two-step control of the ash bed height in the generator with stable generator operation. The regulation of this system is designed such that the end positions of the ash bed height intervals only in a long time, preferably in <2 h, are approached. If, within this cycle in the ash zone, there is a temperature rise not commensurate with the ash discharge, indicating the reaching of the fluidized state of the plague bed, the reaction temperature in the oxidation zone should be increased, preferably by increasing the proportion of oxidising constituents in the gasifying agent _r heightening the reaction temperature before increase as independent from the trend of the temperature profile in the ash zone from the reactor via the grate discharged temporally ash amount .unterschrei the setpoint This also known to be controlled by appropriate level indicator in the ash sluice. The increase in the reaction temperature is likewise to be carried out in step sequences which are adapted to the type of coal. The temperature increase is terminated when the desired value for the ash discharge or a stable temperature profile in the ash zone is reached.

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The temperature increase is terminated when the setpoint value for the ash discharge or a stable temperature profile in the ash zone prospect is. .......

By setting a high reaction temperature and the mixing of minerals to Brikettiergut damage can occur in the shaft of the generator, which can be avoided according to the invention by a slag resistant inner lining, preferably of ceramic material or on a metallic basis.

Claims (6)

221 53 0 Inventions addressed. 1. A method for increasing the specific manhole loading of Pestbettdruckgasgeneratoren for the gasification of lignite or hard coal of various degrees of incineration, characterized in that the grain size in a fixed bed is used as a reference variable for the process control and as a criterion for the stability of the fixed bed and thus the uniformity of the flow as a decisive prerequisite for optimal process control, the vortex point velocity at each height element of the reactor applies, wherein the permissible flow rate of the fluid is always to be regulated below the Y / irbelpunktgeschvandigkeit. 2. The method according to item 1, characterized in that is used to change the grain structure, which is defined by the mean grain diameter d and the void amount ε in the oxidation and reduction zone, the reaction temperature in the Oxydationsζone, preferably in the way that. the oxidizing components of the gasifying agent or its starting temperature are modified by a corresponding mixture preparation so that the sintering and melting point of the mineral constituents of the coal is exceeded using a slag resistant ceramic or metallic inner lining of the generator. 3. The method according to item 1, characterized in that for optimum control of the Koünstruktur in the oxidation and reduction zone on the reaction end temperature as auxiliary quantities for erste.-the measured at the periphery of the reactor ash bed temperature and second, the desired value resulting from the solid balance of the process for the mineral substance to be discharged via the ash sluice, used in this way 221 530 be that the discharge speed of Mineralbstanzanz over the grate is reduced when the slip bed temperature increases and vice versa and the reaction end temperature is increased via the change in Gasgasgemmsches when at high ash bed temperature with the grate discharged ash is too low. 4. The method according to item 1 and 2, characterized in that the process control takes place in such an algorithm with the aid of a process computer, that as an output for the ash bed temperature an average of at least two or more measuring points is used and as a basis for the desired value of the discharged ash the ratio of smuggling operations of the coal sluice and ash sluice shall apply, the reaction temperature being increased if the ratio of the number of coal sluices to the number of ash sluices exceeds the target value. 5. The method according to item 1 and 2, characterized in that for an energetically optimal process control of the mean value of the ash bed temperatures is limited by the regulation of the ash discharge to a maximum value which is 50 K above the temperature of the gasification agent. 6. The method of claim 1, 3, -4 and 5, characterized in that are mixed to influence the grain structure on Vergasungsgut in the case of briquetting mineral substances, preferably clays and lime, which cause the formation of a high average grain diameter during the gasification process in the reactor or with the selection of coals for the gasification on the enrichment of such components is worked.