JPS5889928A - Separation of dry fly ash from gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating a dry fly assembly from a gas. More specifically, the present invention is directed to / 00-. In separating the dry fly assembly from the gas having a temperature of 2000°C,
At least seven cyclones are used to remove the majority of the fly ash from the gas, and the gas is then subjected to at least two stages of scrubbing with water so that the fly ash obtained in the first stage is free of aqueous suspension. The present invention relates to an improvement in a separation method that involves injecting a portion of a suspension into a source gas.

In principle, any solid particle-containing gas can be purified by the method described above. However, this process is particularly suitable as a process for purifying synthesis gas obtained by partial combustion of coal. This gas contains, in addition to hydrogen, carbon oxides, carbon dioxide, light hydrocarbons and water vapor, fly-assy particles and by-products (mostly gaseous by-products) such as sulfur and nitrogen compounds. This method allows for the substantial removal of fly-assembly particles from the syngas.

After removing most of the solid particles by means of one or more cyclones, scrubbing with water is carried out in at least two stages. For this purpose, the gas is brought into close contact with water. This operation can be carried out using one or more venturis, distribution trays, packed columns or striped layers. 1 after each contact step,
The resulting aqueous suspension of solid particles and the gas are separated from each other.

This gas is sent to the next contacting stage. At least a portion of the suspension is returned to the previous stage.

The gas that has passed through the cyclones and/or more cyclones is first placed in a venturi as an aqueous suspension, part of which was obtained in the second contacting stage, and another part obtained in the second contacting stage. (obtained in one contact step). Preferably, therefore, the device for carrying out the first contacting step consists of a venturi. After the gas has been treated at this stage, the resulting mixture of gas and aqueous suspension is placed in a separator to separate the partially purified gas and the aqueous suspension of solid particles. A portion of this aqueous suspension is recycled to the venturi and another portion is introduced into the feed gas.

The latter contacting operation, i.e. contacting the hot feed gas with the recirculated aqueous suspension, is also preferably carried out in the penchili;
It is then advisable to evaporate the water in the suspension. This gas/steam/solid particle mixture is then passed through seven or more cyclones to remove most of the solid particles.

The effluent gas exiting the separator may be placed in a gas scrubber and brought into countercurrent contact with the aqueous suspension of solid particles. Preferably, the gas scrubber consists of a packed bed containing packing such as Raschig rings, Pall rings or Parr saddles. Advantageously, a portion of the aqueous suspension of solid particles exiting the gas scrubber is pumped into the pen chamber and partially cooled. In order to obtain sufficiently good results in this method, it was injected into the feed gas. The water in the aqueous suspension must be substantially evaporated after the injection operation is performed.

This condition can be satisfied as follows, i.e.
The temperature of the feed gas and the temperature of the injectate (and the amount ) The above conditions can be met by maintaining an appropriate balance between therefore,
In all cases the temperature of the feed gas should be above its dew point. In practice, therefore, the temperature of the feed gas will be at least 700°C.

The maximum temperature of the raw material gas in this gas purification method is the maximum outlet temperature of the previous treatment step. Partial oxidation of coal (
In the case of partial combustion), the temperature is at most 2000°C. Since the efficiency of a particle removal device such as the cyclone mentioned above increases further as the gas temperature decreases, the gas temperature
It is preferable to lower the temperature to below 000°C, preferably below 500°C. At least a portion of this temperature drop will occur due to evaporation of the injection suspension. 1. Another part of this temperature drop
can be achieved by direct or indirect heat exchange with the refrigerant,
The heat exchange can then take place, for example, in a steam boiler or by water injection.

By recycling the solid particles separated in the wet gas scrubbing stage in the form of an aqueous suspension towards the feed gas, the following effects are obtained: Quantity can be limited. because,
The solid particles separated there are transported to this integrated operation factory (in
This is because it is discharged from a tegrated plant in a dry state. In order to remove (recover) heat from the gas purification system after the dry separation stage, the exit temperature of the last gas scrubber depends on the amount of water condensed in the scrubber and the amount of water injected into the feed gas by recirculation. A recirculating suspension is also possible. In this case, the net water consumption is zero and no contaminated water is discharged from the gas refinery. From the coal partial oxidizer When using this method to treat the mixture of exiting gas and fly assembly,
Seven factors determine whether it is more advantageous to cool the reactor exhaust gas to the desired cyclone temperature by indirect heat exchange in a steam daisy or by direct heat exchange by water injection. This is the use of gas.

If a steam dailer is used, a temperature of the last stage (final zone) of the gas refinery plant of 25-200° C. will result in the lowest wastewater production and the lowest water consumption. The purified gas coming out of the gas scrubber is zo-
Preferably, the gas is cooled to a temperature of 20° C., in which case some of the water vapor remaining in the gas condenses and the resulting water separates from the gas.

For further processing of the gas, it is placed in a water-gas shift reactor together with concentrated water vapor.
At least one of the cooling operations of the exhaust gas from said partial combustion reactor is carried out if it is advantageous to carry out an operation in which the carbon monoxide content is increased and the hydrogen content is increased in a 5-hift reactor). Preferably, one part is carried out by direct injection of water into the gas. In this case, the temperature of the final scrubber should be set at 100
It is best to keep it at AO°C.

In this case, therefore, the cooling of the system can be limited or even omitted completely.

As mentioned above, most of the solid particles are initially removed from the gas by at least two cyclones. If this solid particle-containing gas is the exhaust gas of a coal combustion plant or a coal gasification plant, it will contain fly ash. The fly ash separated in the/or more cyclones is then preferably recycled to the combustion or gasification plant.

By recycling the cyclone-separated fly assembly to a gas combustion plant or gasification plant, the following benefits can be obtained: In other words, this recirculation allows as much unburned carbon contained in the fly ash to be combusted as possible, improving the coal conversion rate. If the combustion or gasification plant is of the slag-forming type, a significant portion of this recycled fly ash 6 will be discharged from the combustion device in the form of molten slag. The resulting vitreous slag particles or cinder can be absorbed into leachates of various types, such as rainwater or groundwater.
The harmful substances present in the slag never leach into its surroundings, ie no environmental pollution occurs.

The separation problem that occurs when fly ash, which can sometimes contain harmful components, is disposed of in the form of dust can be completely avoided by operating as described above.

The bulk of the fly ash is separated from the gas by/or higher cyclones at temperatures between 00 and 2000°C, preferably at most 500°C, and the remaining fly ash is removed from the gas by a scrubbing operation with water. The resulting aqueous suspension is injected into the feed gas. Therefore, in this gas purification method, only purified gas and vitreous slag are obtained as final products.

However, recirculation of the fly assembly to the combustor requires that the various volatile components be
) has the disadvantage of staying and accumulating within the body. Examples of components that can volatilize at high temperatures in combustion equipment include certain halides, cyanides, and formic acid, but these volatile components are not emitted with the slag and are absorbed by the surrounding gas. condenses or solidifies when the temperature of the fly ash decreases, and a part of it always goes into the recycled fly ash and the rest goes into the aqueous suspension of said fly ash. The concentration of volatile components in this stream will therefore always continue to increase. Since condensation of volatile components contributes to heat exchanger fouling, increased concentrations of this type of compound result in higher fouling rates. Furthermore, if the concentration of the compound is high, expensive high-alloy copper equipment must be used. Because normally, however, this problem can be completely solved by the present invention. This is because, as will be described later, in the present invention, all of the solid particle suspension obtained in the first contact step is not injected into the raw material gas, that is, in this contact step, only a part of the suspension is injected into the raw material gas. This is because it is simply removed from the separation system.

Therefore, the present invention provides for separating dry solid particles (dry fly ash) from a gas having a temperature of /00-2000 °C, using at least 7 cyclones to remove the majority of the solid particles from the gas, and then scrubbing the gas with water in at least two stages, thereby injecting a portion of the aqueous suspension of solid particles obtained in the first stage into the feed gas (i.e. the starting gas). , relates to a method for separating dry solid particles from a gas, characterized in that a part of the aqueous suspension of solid particles obtained in the first step is discharged. Preferably, said part of the liquid is recycled after treatment.

The aqueous suspension of solid particles obtained in the first contacting stage is 0.0
0! It is preferable to remove it from the purification system at a rate of -,2 KgA (gas). It has been found that this amount is sufficient to avoid accumulation of undesirable components in the recirculation piping of this gas purification process.

The discharged suspension is advantageously dewatered. This water can be reused after further purification.
Or it can be discharged outside. This dewatered suspension, which consists of wet fly ash particles, is preferably ground together with the coal and dried. The resulting coal-fly assy homogeneous mixture is advantageously used as feedstock in a combustion or gasification unit, i.e. in which it is used to carry out complete or incomplete combustion (partial combustion). The fly-assembly in the feedstock can then be discharged as slag from the combustion or gasification device. Dehydrated product/parts by weight of the suspension,
It is advantageous to mix it with at least 70 parts by weight of coal (both parts by weight values under anhydrous and ash-free conditions, respectively).

The dehydration described above can be carried out according to any known method. For this treatment, methods such as filtration, flotation, and sedimentation can be advantageously used. The bovine filtrate can optionally be reused after purifying it, or it can be purified externally (
In other words, it can be discharged into surrounding areas).

Another suitable method of disposing of the discharged suspension is
It is an advantageous processing method in that the low temperature heat of the raw material gas can be used for drying solid particles (
If desired, after recovering part of the heat of the feed gas,
the raw material gas can be used in this treatment method).

In this treatment method, the water contained in the discharged suspension is replaced with at least water having a lower concentration of volatile components. This replacement can be carried out, for example, by dewatering the effluent suspension, followed by scrubbing, and suspending the solid particles in relatively clean water. water replacement can be achieved.

The resulting new suspension is preferably recycled to the wet scrubbing system or returned to the recirculation line where the recirculated suspension is injected into the feed gas. The displaced water can be reused after its purification--or discharged to the outside (surrounding area).

Combustion of fly ash from a dry ash separation stage (e.g. separation stage with/or more cyclones) -
Alternatively, in the case of recirculation to the gasifier, it is advantageous to select the temperature of the dry ash separator so that the equipment upstream of the dry ash separator (e.g. the galler) is operated appropriately. In order to achieve this, it is advantageous to select said temperature in such a way that components which are desired to be present only in low concentrations are not to be selectively removed from the gas stream. Halides such as chlorides are well-known examples of the aforementioned components in this regard. It is therefore advantageous to choose a high temperature for this dry assembly separator. It is also advantageous to select a temperature within this range and/or above as the operating temperature of the dry ash separator if it is desired to produce fly ash containing a low concentration of the aforementioned components.

In order to more specifically illustrate the present invention, some embodiments of the method of the present invention and apparatus used therein will be described in detail with reference to the accompanying drawings.

In the accompanying drawings, the number / designates a reactor, which is of the type that completely combusts a feedstock 211 consisting of coal and a recirculating fly assembly in a stream of oxygen. A liquid slag stream is discharged from the reactor. The crude gas ≠ is put into an indirect heat exchanger j, where it is cooled to about 100°C by heat exchange with a water stream ♂, and the thus cooled gas ≠ is discharged from there. In addition, the steam 7 generated from the water stream is also discharged.

Gas O is placed in a cyclotron and separated into fly ash 10 and effluent gas //. . Fly assembly 10
is recirculated to the reactor / and the effluent gas / / is put into gas sucrano-72 and brought into close contact with the aqueous suspension of fly ash /3. Stream /j is the aqueous suspension of fly ash The liquid, a portion of which is cooled in a cooler, 2, is then combined with a water stream, either fresh water or recirculated water, and returned to the top of the gas scrubber 72 as stream/3.

A portion of the remainder of the flow /j is passed through the rotary filter /
Concentrate with B to form 1st 7, while the flow /j
The final remainder is injected into the feed gas (gas to be purified) (stream 2j). The water/g separated (liberated) at this stage is discharged to the outside from this thread. paste/
7 is a pressure-resistant ball mill operated by an extrusion feed pump 20;
Put it in.

This mill, 2/, is further fed with a stream of coal, 22, which heats the paste as it rotates, so that the paste is finely ground and dried. The pressure created by the generated steam can be up to 700 KgA-IIL2. The pressure value selected here should be approximately comparable to the pressure value in reactor I.

For example, the temperature inside Sol Mill 2/ is 23! 'C could be. The steam leaving the sol mill λ/ flows into the reactor/, keeping the coal and fly ash mixture 2II in a dispersed state. In this way, the 7 liter soybean can be completely recycled to the gasification process. At the same time, a predetermined or required amount of steam is supplied to the reactor/. The problem of contamination due to fly ash particles is successfully solved by this method, and furthermore, no undesirable high concentration accumulation of halodanides, formic acid, etc. occurs in this fly ash recirculation system.

[Brief explanation of the drawing]

The accompanying drawings are diagrams of the equipment used in embodiments of the present invention. /...Reactor, j...Heat exchanger, Ri...Cyclone, /2...Gas scrubber, /A...Rotor filter, 2/...Ball mill 1.2 B... Cooler. Agent's name: Kawahara 1) - Ho

Claims (9)

[Claims] (1) To separate the dry fly assembly from the gas having a temperature of 100-2000°C, at least 7
The majority of the fly ash is removed from the carcass gas using two cyclones, and the gas is then subjected to at least two stages of scrubbing with water such that an aqueous suspension of the fly ash obtained in the first stage is used. A method for separating dry fly ash from a gas, comprising injecting a portion of the liquid into the feed gas, characterized in that a portion of the aqueous suspension of fly ash obtained in the first stage is discharged. separation method. (2) 0.00% of the fly ash aqueous suspension obtained in the first stage! -2VKgC gas) is discharged. (3) The method according to claim 1 or 2, characterized in that the discharged suspension is dehydrated. (4) The method according to claim 3, characterized in that the discharged suspension is filtered. (5) The method according to claim 3, characterized in that the discharged suspension is dehydrated by a sedimentation operation. (6) The method according to claim 3, characterized in that the discharged suspension is dehydrated by flotation sorting. (7) Dehydrated fly ash is crushed together with coal, dried, and the homogeneous coal/fly ash mixture thus obtained is combusted or gasified. The method described in any of Section 6. (8) A method according to claim 7, characterized in that the dewatered fly assembly/parts by weight is mixed with at least 70 parts by weight of coal. (9) Scrubbing the dewatered fly ash and placing it in clear water and recycling the thus scrubbed fly ash suspension in water to at least/the gas scrubbing stage. or to the feed gas.