JPS6247472B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for increasing the unit hard furnace load and optimizing the process performance of a fixed bed pressure gas generator for lignite or coal gasification with various degrees of carbonization. In that case, the normal unit hard-hearth load is exceeded. The non-oxidizing content of the gasifying agent is usually minimized in the oxygen/steam mixture or the air/steam mixture.

Preferably, in this method, the mineral substances contained in the coal acquire a fine grain/powder structure due to the naturally endowed properties of the coal during gasification below the ash melting point, and the gasification material is Used where there is a strong tendency to disintegrate and form fine particles.

It is generally known that the factor that determines the capacity limit in fixed bed gasification is primarily the amount of dust discharged. Various design and process proposals have already been made in order to minimize this process-interfering phenomenon, which occurs even at various capacity limits depending on the specificity of the fuel. These proposals can be divided into several groups. For example, the aim is to treat the fuel before and during the process so that it generates as little flue dust as possible through thermal and chemical processes. This solution can be found, for example, in East German Patent Specifications No. 26392, No. 38791, No. 119814 and East German Patent Specification CIOJ/205413.

Design solutions aimed at inducing an optimal flow distribution in the upper part of the reactor, e.g. near the gas outlet, are described, for example, in East German Patent Specifications No. 132980, No. 110297,
Proposed in Nos. 133817 and 133819. In the past, when optimizing fixed bed pressure gasification, great attention was also given to the design and operation of the rotating grate, as well as the supply of gasifying agent. Proposals of this kind can be found, for example, in the East German Patent Specification No.
No. 133571, No. 134243 and East German patent specification
It was made in C10J/209772.

Underlying the solution proposals of both groups is a common interest in controlling the pre-filling and post-filling flow to achieve as uniform a distribution as possible and thus an optimization of the process guidance.

A disadvantage of these proposals is that the flow distribution, as a critical process variable for fixed bed performance, is influenced by upstream and downstream mechanisms, such as coal distributors, gas reservoirs or grate. It is connected to different theoretical propositions. This proposition is incorrect. Rather, the flow distribution is influenced inter alia by the grain structure produced during the process.

The particulate bulk material layer in the reactor can have a flow resistance that is, for example, several orders of magnitude higher than the resistance of the internal structure of the gas reservoir or the resistance of the rotating grate. Furthermore, fine particles are
It has the disadvantageous property of being moved by the fluid within the packing and deposited anywhere in the reactor, increasing the non-uniformity of the bulk structure. As a result, certain areas of the reactor are completely clogged, and the passage through the reactor only takes place in the form of passages, which in effect even cancels out the principle and advantages of a countercurrent reactor.

Therefore, all the above-mentioned measures carried out in the past were only partially successful, since their effectiveness was limited to a meaningless area at the beginning and end of filling.

Another group's proposals for process improvements in the pressure gasification of coal address the control of ash emissions. In particular, uniformity of the flow and the avoidance of channel formations are aimed at. This is also the purpose of East German patent specification no. 133247, for example.

Another proposal with a similar objective envisages controlling ash emissions based on ash balance in the reactor.

These proposed solutions also miss the point that for uniform flow through the fixed bed, the grain structure within the fixed bed is a decisive criterion for controlling the ash output.

Control of ash emissions still cannot keep the combustion zone constant. This is because if attention is not paid to the grain structure of the fixed bed, the combustion zone will not exhibit a flat surface. The combustion zone, on the other hand, extends over a considerable longitudinal extent of the fixed bed in such a way that a considerable amount of solids flow can be moved in the direction of the flow of the fluid through the pronounced channels.

Even if ash balance is linked to the control of ash emissions, the desired improvement will not be achieved. This is because flat ash and fire beds do not form when the amount of solids discharged by the crude gas flow is high, and there are no practical measurement methods known for the qualitative and quantitative detection of the solids flow co-expelled by other fluids. This is because it has not been done.

The object of the present invention is to provide a method for increasing the unit hard-furnace load of a fixed-bed pressure gas generating furnace for gasifying lignite or coal having various degrees of carbonization and improving its economic efficiency, by which the grain structure is modified. By means of suitable methods, the conditions leading to optimal flow conditions are created as a decisive prerequisite for increasing the loading capacity of the packing and increasing the unit performance in order to optimally guide the process and improve its economic efficiency. This allows automation of the process along with ash emissions.

The object of the present invention is to improve the process guidance by further improving the previously held views regarding the influence of the internal structure of the generator, such as the coal distributor, gas reservoir, and grate, on the flow distribution and associated stagnation. It is about overcoming.

This problem is solved according to the invention by the fact that the formation of the grain structure in the fixed bed is controlled as a decisive guiding variable of the process, depending on the respective process conditions, in order to achieve a stable fixed bed and a uniform flow of the packing. Therefore, it is resolved.

The flow engineering quality of the grain structure is generally defined by the measured value dsm of the average grain size and the so-called void volume, the determination of which is required here according to the invention for each height element of the reactor packing. This is done based on the criterion of vortex point velocity.

Influencing the grain structure within the reactor fixed bed can be done in various ways.

First, it was proposed to control the grain structure of the ash generated during gasification and the grain structure of the ash/coke ash/coal mixture present in the center of the pressure vaporizer by changing the reaction temperature in the oxidation zone. Ru. For example, in large-scale operations, it is possible to change not only the grain structure of the ash, especially its particulate content, but also the particulate content in the reduction zone, i.e. in the range of semi-gasified coke, by changing the reaction temperature in the oxidation zone. It was tracked down with a pressure vaporizer.

Advantageously, the reaction temperature in the redox zone is increased to such an extent that at least 30% by weight of the mineral matter of the coal is above the sintering or melting point. Owing to the uniformly flowing fixed bed that can thereby be achieved, the risk of large slag agglomerates forming is reduced. This is because the fine fraction, consisting of ash and coke/ash particles, does not exceed the vortex velocity and is thus transferred to higher layers by the fluid over a wider area and is therefore more easily melted by the sorting process. This is because a molten mixture is formed. Furthermore, the chemical and physical process conditions are always ensured by preventing the transport of fine particles to adjacent areas, and no difference in reaction temperature can occur if the nature of the gasifying agent is the same. This minimizes the risk of slag formation.
If the vortex velocity in the fixed bed is not exceeded at any point in the redox zone, the final reaction temperature can be increased enough to transfer most of the mineral material into the form of coarse-grained bulk material that can be flowed through. . Moreover, if the reaction temperature in the reduction zone is high enough, the particle breakdown and dust formation are already significantly limited by the sintering process initiated in the semi-gasified coke.

It is the change in the oxygen content in the gasifying agent or the selection of its composition and the temperature of the gasifying agent that actually allows a change in the reaction temperature and grain structure of the redox zone.

The precise maintenance of a specified maximum temperature in the oxidation zone, which depends on various factors, is constantly monitored and controlled by a process control computer. This maintenance is necessary, on the one hand, to fully utilize the advantages of high reaction temperatures and, on the other hand, to prevent slag formation or the formation of large slag pieces.

For optimal reaction temperature adjustment, according to the invention, on the one hand, a temperature value is used which is preferably measured in the jacket of the generator at the height of the ash zone, which temperature value is subject to unstable temporal changes and abrupt changes. The change indicates that a vortex state has been achieved within the filling. This indicates that the flowability of the grain structure is poor, that is, the reaction temperature is too low. On the other hand, the target value for the amount of ash to be discharged from the generator is used as an auxiliary variable for adjusting the optimum reaction temperature, which target value results from the amount of coal gasified per time unit in the reactor. . If this target value is exceeded, the grain structure in the generator body is too fine and a significant amount of ash particles or coke-ash particles are discharged through the coarse gas outlet rather than through the grate. Furthermore, according to the present invention, the process is controlled through the operation of a rotating grate in conjunction with optimizing the reaction temperature of the oxidation zone on the basis of the ash or solids emissions, and the temperature of the ash produced from the oxidation zone and the A certain equilibrium temperature resulting from the backflow gasifying agent is always maintained.

Preferably the detection of this temperature is carried out directly within the reactor,
and at multiple locations on the outer circumferential surface of the reactor immediately below the oxidation zone. The average temperature calculated from the average value of at least two, preferably 4 to 6, measuring points is preferably used as a guideline for the amount of ash or solids discharged.

The control of the solids or ash evacuation mechanism is carried out according to the invention according to an algorithm that takes into account the temperature measurements, the time characteristics of the entire system and the equilibrium temperature limit. Furthermore, the oxidation zone reaction temperature and the amount of ash to be discharged from the reactor per unit of time are included in this algorithm together with the said auxiliary amounts to determine the stable firebed and the optimal final temperature of the amount of solids to be discharged from the reactor. Guaranteed. A value of at most 50 K is preferably determined as the target value for the temperature difference between the temperature of the ash to be discharged from the reactor and the inlet temperature of the gasifying agent flowing through the ash bed. This achieves optimal and effective process guidance and protects the structural parts of the solids discharge element, which usually have insufficient resistance to heat damage.

Furthermore, according to the present invention, in the case of briquetting the gasification material, suitable mineral substances are incorporated into the gasification material, so that the grain structure and the particulate content which impairs the process are eliminated above the reactor oxidation zone. The range is also affected to counteract particle disintegration due to particulate generation. The most suitable admixtures of this type are mineral components that solidify a coaly grain structure when subjected to thermal loading, or that form themselves a strong, compact structure as a result of the gasification process.
For example, clay minerals have such properties,
Lime contained in coal in the form of CaO also produces carbonate (CaCO ₃ ) when heated. This also causes tissue solidification up to a certain temperature level, thus counteracting particulate formation.

Other mineral components or combinations thereof can also bring about the process stabilizing effects mentioned above, either in the form of admixtures or by themselves through specific coal selection or coal blends.

The setting of high reaction temperatures and the incorporation of mineral substances into the briquetting material are associated with subsequent phenomena in the form of significant solidification in the production furnace. The softened mineral material may optionally be bonded to the hardness wall if it is protected by a conventional refractory material, for example a brick. According to the proposal of the invention, the achievement of high reaction temperatures in the oxidation zone is preferably achieved in conjunction with a slag-resistant lining made of ceramic material with high thermal conductivity or based on metal.

The present invention will be described in detail below based on one embodiment.

Ash removal from the generator is generally carried out via a rotating grate, so-called vacuum cleaners being used as removal elements. The amount of ash discharged is calculated by the cross-sectional area of the vacuum cleaner, then by the speed of movement and the time of movement. The rotational speed and operating time of the rotating grate are used in practice as target quantities for the ash evacuation time.

According to the invention, the adjustment of the rotational speed of the rotary grate and the determination of the operating time or their variation are carried out in accordance with the invention at the permissible temperature, preferably as an expression of the permissible temperature difference between the temperature of the gasifying agent and the temperature of the ash, at the ash zone temperature measurement point. maximum
Ash discharge is increased step by step within a defined time period until below 50K is achieved.

If this temperature has been achieved in the form of an average value of several temperature measurement points in the ash zone, the starting value for the ash discharge can be adjusted, so that the ash bed in the generator can be adjusted in stable generator operation. This means that two-point height control is automatically provided. The control of this system is such that the end position of the ash bed height is controlled only at large time intervals, preferably two
It is done in such a way that it is achieved every hour. If a temperature rise not corresponding to the ash discharge occurs in the ash zone within this period, this implies the attainment of a vortex state in the fixed bed, so the reaction temperature in the oxidation zone is preferably adjusted to It must be increased by increasing the proportion. Similarly, if the amount of ash discharged from the reactor via the grate per time unit, independent of the trend of the temperature gradient in the ash zone, falls below the target value, the reaction temperature must be increased.
This can be controlled in a known manner via a corresponding fill level indicator in the ash control gate. The reaction temperature is again increased at a rate adapted to the type of coal.
The heating is terminated when the target value of ash discharge or a stable temperature gradient within the ash zone is achieved.

Due to the setting of high reaction temperatures and the incorporation of mineral substances into the briquetting material, the hard furnace of the generator furnace can be damaged, but this is preferably avoided by the invention with a slag-resistant lining made of ceramic material or based on metal. This can be prevented by

Claims (1)

[Scope of Claims] 1. The use of the grain structure in the fixed bed as a guide variable for process control and as a criterion for the stability of the fixed bed and the uniformity of flow through, which are decisive prerequisites for optimal process guidance. Fixed bed pressure gas generation for lignite or coal gasification with various degrees of carbonization, characterized by adjusting the allowable flow velocity of the fluid to always be below the vortex velocity by using the vortex velocity at each height element of A method to increase the unit hardness load of a furnace. 2. In the oxidation and reduction zones, in order to change the grain structure defined by the average grain size dsm and the void ratio,
Preferably, the oxidation content of the gasifying agent or its starting temperature is varied by selecting an easily melting eutectic mixture, and the slag-resistant ceramic or metal lining of the generator is used to reduce the sintering point and the mineral content of the coal. 2. Process according to claim 1, characterized in that a reaction temperature is used in the oxidation zone such that the melting point is exceeded. 3. In order to optimally control the grain structure of the oxidation and reduction zones through the final reaction temperature, the first
the ash bed temperature measured around the reactor and then the target value resulting from the solids balance of the process with respect to the minerals to be discharged via the ash gate, and if the ash bed temperature increases, the mineral discharge via the grate. It is characterized in that the speed is reduced and, conversely, if the ash bed temperature is high and the amount of ash discharged by the grate is too small, the final reaction temperature is increased through a change in the gasification mixture. The method according to claim 1. 4 Process control is performed using a process control computer according to an algorithm, using the average value of at least two or more measurement points as the starting amount for the ash bed temperature, and controlling the adjustment process of the lime control gate and the ash control gate. The ratio is regarded as a target value of the ash to be discharged, and if the ratio of the number of times of lime adjustment to the number of times of ash adjustment exceeds the target value, the reaction temperature is increased. The method described in section. 5. A patent claim characterized in that the average value of the ash bed temperature is limited to a maximum value of 50 absolute temperatures above the temperature of the gasifying agent by adjusting the ash discharge rate for effective and optimal process guidance. The method according to item 1 or 2 of the scope. 6 In the case of friketing, mineral substances such as clay or lime are preferably mixed in to influence the grain structure of the gasifying agent, which minerals produce a large average particle size during the gasification process in the reactor. 6. A method according to claim 1, 3, 4 or 5, characterized in that the enrichment of such components is influenced by the selection of coal for gasification.