JP2000325730A - Char recovery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent failure of back washing operation of a filter for char recovery in a char recovery apparatus of a coal gasification power generation plant and the like, and carry out stable and efficient operation of the plant. SOLUTION: Char of coarse diameter is supplied to a filter 4 and the permeation of the char cake collected on the filter surface is improved to recover the back washing effect by installing a bypass line 20 for a cyclone separator 3 for coarse dust removal in the upstream side of the filter 4, detecting the inferior back-washing function for the filter 4, and leading a part or all of the produced gas to the bypass line 20 to bypass the cyclone separator 3. Further, for the decrease of the differential pressure in the cyclone, it is offset by addition to the operational differential pressure in the filter, hence the effective differential pressure of the filter can be set larger, and the quantity of the washing gas can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a char recovery system, and more particularly, to gasifying coal using a coal gasifier.
The present invention relates to a char recovery system suitable for a coal gasification power generation plant that generates electric power using gasified fuel gas.

[0002]

2. Description of the Related Art A large amount of unreacted char is contained in coal gasification gas, and if it is not recovered, it will lead to a significant decrease in plant efficiency. In addition, large troubles such as blockage and damage occur in the downstream desulfurization device or gas turbine.

[0003] In such a coal gasification power generation plant, for such a reason, a filter (filtration type dedusting device) that can obtain a dedusting efficiency close to 100% is provided downstream of the cyclone for coarse dedusting. Has been adopted.

Dust removal by a filter is performed by capturing dust such as char on the surface (outside or inside) of an element (hereinafter referred to as an element) in the filter. As the operation progresses due to the dust trapped on the element surface,
The differential pressure across the filter increases.

[0005] Since it is impossible to continue the operation as it is, the element is backwashed (hereinafter abbreviated as "backwash") before a certain differential pressure is reached, so that dust is removed. That is, the dust trapped on the element surface is removed by instantaneously flowing a high-pressure gas into the filter in the opposite direction.

[0006] As a char recovery device, a cyclone for coarse dust removal and a filter (filtration type dust removal device) for fine dust removal are usually used and installed in series. Naturally, for a cyclone and a filter, a particle having a large particle diameter is easier to collect.

[0007]

However, coarse particles are trapped in the cyclone on the upstream side, so that the load on the filter as a dust amount is small, but the fine particles increase, so that the filter differential pressure is increased. It is easy to rise.

That is, usually, by passing through a cyclone, the load as the amount of dust is reduced and the operation of the filter is facilitated. However, in some cases, if the particle size of the dust at the filter inlet becomes too small, the load of backwashing may be reduced. And the amount of backwash gas is required to be large.

Further, since the particle size of the char scattered from the gasification furnace changes depending on the type of coal and the operating conditions, even if the backwashing conditions (backwashing interval) of the filter are set in advance, depending on the changes in the operating conditions. In addition, backwashing must be performed more frequently than planned, and the amount of backwash gas greatly increases. In some cases, the amount of backwash gas cannot catch up, and the filter operation is stopped, that is, the plant is stopped.

[0010] An object of the present invention is to enable stable operation of a coal gasification power plant or the like without reducing the efficiency of the plant in response to the problem of shutting down the filter due to the failure of the backwashing operation of the char recovery filter. To provide a char collection system that performs

[0011]

The above object is achieved by installing a bypass line in a cyclone for coarse dust removal upstream of a filter,
During operation, if the backwash of the filter does not work or is about to stop functioning (the recovery differential pressure after backwash continues to increase even if the backwash interval is shortened), this is detected and the generated gas is detected. Is partially or entirely sent to the filter by bypassing the cyclone by the bypass line.

For example, a coal gasification power generation plant includes a coal gasifier that generates a combustible gas from coal using an oxidizing agent, a heat recovery boiler that recovers heat of the generated gas, and an unreacted char in the generated gas. It is composed of a char recovery system consisting of a cyclone and a filter (filtration type dedusting device) to be recovered, a desulfurization device for desulfurizing the produced gas, and a power generation facility for generating power using purified coal gasified gas.

In this char recovery system, a bypass line is provided in a coarse dust removal cyclone installed upstream of the filter, and when the backwash of the filter does not function or does not function at the time of steady operation (reverse operation). If the recovery differential pressure after backwashing continues to increase even if the washing interval is shortened), this is detected and a part or all of the generated gas is configured to bypass the cyclone by this bypass line.

As a result, coarse-grained char, that is, char having a coarse diameter is directly supplied to the filter, the permeability of char cake captured on the filter surface is improved, and the backwashing effect is restored. Further, by adding the difference in the pressure difference in the cyclone to the operation pressure difference in the filter, a large filter effective pressure difference can be obtained, and the amount of cleaning gas can be reduced.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing an embodiment of the present invention, a reference example of a dust recovery system such as a char will be described with reference to FIG. 5 using a coal gasification power plant as an example.

In FIG. 5, an oxidizing agent and coal 23 are supplied to a gasification furnace 1, and the generated gas and unreacted char are recovered by a heat recovery boiler 2, and the sensible heat is recovered. After the unreacted char in the produced gas is recovered and removed in 3, it is supplied to the filter 4.

In the filter 4, the remaining unreacted char in the produced gas is recovered and removed, and the recovered char together with the char recovered in the cyclone passes through the line 22 through the carrier gas 2.
5 recycles to the gasifier 1. The gas leaving the filter 4 is desulfurized by a desulfurizer 5 and then supplied to a power generation facility 6 as a fuel gas for power generation.

On the other hand, in the filter 4, as dust such as char accumulates on the surface of the element 10, the differential pressure (differential pressure gauge 11) before and after the filter increases. Before the pressure reaches the maximum allowable differential pressure, the backwash valve 13 is instantaneously opened and closed by the control of the control box 12, and the high-pressure backwash gas 24 flows in the filter in the reverse direction, so that the backwash gas is captured on the element surface. Peel off dust.

FIG. 2 shows the differential pressure across the filter 4.
Part a is the initial differential pressure, that is, the pressure loss of the filter media itself. Recovery pressure difference after stabilization after repeating backwashing several times in part b.
Part c is the differential pressure at the start of backwashing (the maximum allowable differential pressure at the filter).

The operation of the filter is performed in the section c (the maximum allowable differential pressure).
And between part b (recovery differential pressure after backwashing). here,
The recovery differential pressure of the filter and the rising speed of the differential pressure vary depending on operating conditions (filtration speed, char load, etc.) and the type of char.

As the operating conditions of the filter, the backwashing interval is set in advance based on the filtration speed, dust load, etc. so as not to exceed the maximum allowable differential pressure in the filter. The particle diameter of the scattered char varies due to the variation of

As the particle diameter of the scattered char becomes smaller, the recovery differential pressure increases and the rate of increase of the differential pressure increases. Therefore, if backwashing becomes frequent and still cannot keep up with
The operation of the filter must be stopped.

FIG. 3 shows a backwash interval when the recovery differential pressure becomes high. FIG. 4 shows a backwash interval when the rate of rise of the differential pressure increases. As shown in these figures, in each case, the backwashing interval becomes zero as much as possible, and the backwashing becomes impossible.

In this case, in the prior art, it is impossible to lower the recovery differential pressure or reduce the rate of increase of the differential pressure by operating operation or the like. Was.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, in the char recovery apparatus according to the present invention, a bypass line 20 is installed in a cyclone 3 for coarse dust removal upstream of a filter (filter-type dust removal apparatus) 4.

Thus, during normal operation, when the backwashing of the filter 4 is not functioning or is no longer functioning (the recovery differential pressure after backwashing continues to increase even if the backwashing interval is shortened). By detecting this, a part or all of the generated gas is bypassed through the cyclone 3 by the bypass line 20.

In this way, a char collection system for improving the permeability of char cake captured on the filter surface and recovering the backwashing effect by supplying coarse-grained char, that is, char having a coarse diameter, to the filter 4 is constructed.

By adding the pressure drop in the cyclone 3 to the operation pressure difference in the filter 4, the effective pressure difference in the filter can be increased, the backwash effect can be recovered, and the backwash gas amount can be reduced. And

At the time of low load operation such as start-up, or at the time of steady operation, a change in the operation state of the gasifier 1 causes
The case where backwashing of the filter 4 becomes impossible due to supply of a finer particle diameter than the plan, that is, fine-grained char to the filter 4 will be described more specifically.

As shown in FIG. 3 or FIG.
When the backwashing becomes impossible, that is, the backwashing becomes frequent due to an increase in the recovery differential pressure detected by the differential pressure gauge 11 or an increase in the rate of increase in the differential pressure, and the backwashing still cannot catch up.

In such a case, the control box 1
The flow control valve 1 is controlled by the control previously incorporated in
By adjusting 4 and 15, a part or all of the product gas is bypassed to the cyclone 3 by the bypass line 20.

As a result, char having a coarse diameter can be supplied to the filter, so that the permeability of the char cake captured on the element surface is improved, the backwashing effect can be recovered, and the filter can be operated continuously. .

Further, by allowing a part or all of the generated gas to bypass the cyclone 3 by the bypass line 20, the difference in the pressure difference in the cyclone is added to the operation differential pressure in the filter 4, so that the filter effective differential pressure is increased. Since the pressure can be increased, the backwash interval can be lengthened, and the backwash gas amount can be reduced.

[0034]

According to the present invention, in a coal gasification power plant, the char recovery filter can be operated stably without lowering the efficiency of the plant, and the plant can be stably operated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a differential pressure before and after a filter.

FIG. 3 is an explanatory diagram showing a differential pressure before and after a filter.

FIG. 4 is an explanatory diagram showing a differential pressure before and after a filter.

FIG. 5 is a configuration diagram showing a reference example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gasifier 2 Heat recovery boiler 3 Cyclone 4 Filter 5 Desulfurizer 6 Power generation equipment 10 Element 11 Differential pressure gauge 12 Control box 13 Backwash valve 14, 15 Flow control valve 20 Bypass line 21, 22 Line 23 Coal and oxidizer 24 High pressure Backwash gas 25 Carrier gas

Claims (4)

[Claims] 1. A cyclone for collecting coarse-grained char from product gas generated in a coal gasifier, and a filter installed downstream of the cyclone for filtering fine-grained char from the product gas. And a bypass line in which the generated gas bypasses the cyclone and reaches the filter. 2. The char recovery system according to claim 1, wherein the coarse-grained char scattered from the gasification furnace is:
A char recovery system, wherein the cyclone is bypassed by the bypass line and supplied to the filter. 3. The char recovery system according to claim 1, wherein the differential pressure detecting means for detecting a differential pressure before and after the filter and a rise in the differential pressure detected by the differential pressure detecting means. Control means for supplying generated gas to the filter through the bypass line. 4. A coal gasifier for supplying coal to generate combustible gas, a heat recovery boiler for recovering heat from the gas generated in the coal gasifier, and a downstream side of the heat recovery boiler. And a char recovery system comprising a cyclone and a filter for recovering the char in the product gas, a desulfurization device installed on the downstream side of the char recovery system to perform desulfurization of the product gas, 4. A coal gasification power generation plant comprising a power generation facility for generating power using purified gas, wherein the char recovery system is the char recovery system according to any one of claims 1 to 3. Chemical power plant.