JPH0774343B2 - Method and apparatus for coal gasification by PSA - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coal gasification method and apparatus, and more specifically, it conveys coal and other hydrocarbons with a carrier gas generated by an air separation device. The present invention also relates to a coal gasification method and a coal gasification device, which are supplied to a coal gasification furnace together with a coal gasifying agent produced by an air separation device, and are reacted under high temperature and high pressure to obtain a flammable gas.

[Conventional technology]

Coal is a useful energy source with abundant reserves, but its application field is limited as compared with petroleum and natural gas because it is a solid and contains a large amount of ash.
However, if this coal is converted into gas or liquid, the field of application can be greatly expanded and it can be a useful energy source, and thus coal liquefaction technology is being developed in each country. Under such circumstances, research and development of coal gasification is being promoted as an elemental device of an integrated coal gasification combined cycle power generation system, which is attracting attention as a next-generation power generation method.

Coal gasification refers to finely crushing coal and supplying it to a high-temperature gasification furnace together with an oxidizing agent to cause a reaction in the high-temperature furnace to cause a gasification reaction such as partial oxidation. As a result, a flammable gas containing carbon monoxide and hydrogen as main components is generated.

In the integrated coal gasification combined cycle power generation system, the sensible heat of the high temperature combustible gas obtained in this coal gasification furnace is recovered by heat to drive the steam turbine, and at the same time, the gasified combustible gas is used for gasification. It drives a turbine. With this system, the power generation efficiency can be improved by several percent as compared with the conventional steam turbine alone. In response to such large-scale demand as in the integrated coal gasification combined cycle power generation system, the coal gasification equipment has also been increased in capacity and efficiency.

When coal gasification is performed for the purpose of power generation, it can be roughly classified into two gasification methods, namely oxygen gasification using oxygen as an oxidant and air gasification using air as an oxidant. Table 1 shows the gasification efficiency, oxidizer production cost, and power generation cost depending on the difference in this gasification method.

In oxidative gasification, all the oxidizer reacts, so the efficiency of the gasification furnace is good. However, since the production cost of oxygen is required, the power generation cost becomes high. On the other hand, in air gasification, nitrogen that does not react as an oxidant is also supplied, so the efficiency of the gasification furnace is low. However, since the production cost of oxygen is unnecessary, the power generation cost will be low. Therefore, if PSA (Pressure Swing Adsorption) is used instead of the deep-cooling method (Japanese Patent Publication No. 55-25344) conventionally used for oxygen production, it is possible to obtain high gasification efficiency at low oxidant production cost. It is considered that the power generation cost can be further reduced as compared with a system in which quartz is gasified only by air. This PSA
As a prior art relating to this, there is Japanese Examined Patent Publication No. 57-50722.

However, there were the following problems in producing oxidizer with PSA and gasifying quartz. It is JP-A-58-23295
As described in the publication, a coal gasification furnace requires very high-purity nitrogen for the purpose of transporting coal. This is because if the gas supplied to the gasification furnace contains oxygen, the coal will be dust-explosed and dangerous. Generally, a rockhopper system is used to supply powder into a high-pressure furnace, but this method mixes pressurized gas and dust, so if the gas contains oxygen and coal is dusty. This is because it explodes and is dangerous.

In the conventional deep-cooling method, nitrogen is generated at the same time as oxygen, so it is sufficient to use the generated nitrogen as a gas for coal transportation. However, in PSA, the gas discarded when oxygen is generated has a higher nitrogen concentration than air, but it has a high oxygen concentration and cannot be used as a coal transportation gas.
As a result, nitrogen for coal transportation must be brought in from another plant, or a plant for producing nitrogen other than for producing an oxidant must be created (Japanese Patent Laid-Open No. 56-12289). as a result,
Eventually, it affected the cost of the entire plant and increased the power generation cost.

Here, the basic concept of PSA and coal gasifier is described. The ratio of the oxidizer for coal gasification to the supplied amount of coal is preferably the ratio that gives the highest cold gas efficiency. Here, the cold gas efficiency represents the ratio of the calorific value of the generated gas to the calorific value of the supplied coal. Coal gasification is generally based on a partial gasification reaction and is represented by the following formula.

C _n H _m (coal) + n / 2O ₂ → nCO + m / 2H _{2 Since} coal is simple, components such as ash are excluded and expressed as hydrocarbons. From the above equation, it can be said that the calorific value of the produced gas is highest when the carbon in the coal is all carbon monoxide. Since this reaction is an exothermic reaction, the reaction proceeds without applying heat from the outside. However, when trying to gasify coal with air, even if there is a certain amount of heat generation, it is diluted by nitrogen, an inert gas contained in the air, and the temperature inside the furnace cannot be raised, There is a drawback that the gasification reaction rate becomes slow and the gasification rate is reduced. In particular, when coal gasification is carried out in the airflow layer, a major feature of the airflow layer is that the ash content in the coal is melted and processed, but for this purpose, the temperature in the furnace is set above the melting temperature of the ash content. The amount of heat generated by the partial oxidation reaction in the above formula is insufficient. Therefore, generally, the amount of oxygen is increased so that the combustion reaction represented by the following equation is performed in parallel with the reaction of the above equation.

C _n H _m (coal) + (n + m / 4) O ₂ → nCO ₂ + m / 2H ₂ O However, when this combustion reaction is caused at the same time, the calorific value of the produced gas is reduced and the cold gas efficiency is reduced. Therefore, it is conceivable that the oxygen-rich air reduces the amount of nitrogen in the inert gas contained in the air to raise the temperature. The oxygen content of the oxygen-enriched air is not particularly required to be high-purity oxygen as long as the temperature inside the furnace is higher than the melting temperature of the ash, especially in the airflow layer.

From the viewpoint of spontaneous combustion, it is necessary that the gas for coal transportation has an oxygen concentration of at least 5% or less. Further, the required amount of gas for coal transportation is most preferably 0.1 / nitrogen supply amount / coal supply amount from the stable coal transportation conditions.

However, with PSA, the gas of a specific component is adsorbed at high pressure,
Desorb at low pressure. Therefore, the low-pressure purge gas has a high concentration of the above-described specific component gas, and the gas taken out at a high pressure has a low concentration of the specific component. Generally, in order to separate oxygen and nitrogen in the air, an adsorbent such as zeolite is used to adsorb nitrogen and generate a gas having a high oxygen concentration. Table 2 shows the gases obtained by this nitrogen adsorption type, oxygen-enriched air production method.

When the gas produced by PSA is used for coal gasification as described above, it is conceivable to use waste gas as a coal carrier gas.

[Problems to be solved by the invention]

However, it is not suitable to use the waste gas as it is as a gas for transporting coal, because it has a high oxygen concentration (low nitrogen concentration) and there is a risk of spontaneous combustion of the coal. Therefore, it is unavoidable to introduce this into another PSA again to further reduce the oxygen concentration before use. This method complicates the device, and
The cost of the entire plant is increased by introducing it to other PSAs, which is not preferable. Further, the amount of the coal transportation gas is not required to be four times as large as the oxygen-enriched gas which is the oxidizer for coal gasification, and may be a very small amount. The inventor has noticed that the waste gas of PSA does not always have a constant concentration but changes with time.
Figure 2 shows the changes over time in the waste gas of PSA. The waste gas of PSA shows a nitrogen concentration almost equal to that of air at the beginning of the desorption operation, but the nitrogen concentration increases as the desorption process progresses.
That is, the oxidation concentration decreases. This is because at the beginning of the desorption operation, the air filled in the voids in the tower is discharged, and as the desorption step progresses, the nitrogen adsorbed by the adsorbent in the adsorption step is desorbed and fills the tower. The oxygen concentration decreases.

An object of the present invention is to provide a coal gasification method and apparatus by PSA capable of gasifying coal without fear of dust explosion of coal by using oxygen-enriched gas and nitrogen-enriched gas produced by PSA. There is.

[Means for solving problems]

The present invention has an oxygen concentration of 5% after the start of PSA nitrogen desorption operation.
The nitrogen-enriched gas reduced below is used as a coal-conveying gas that conveys coal and other hydrocarbons to a coal gasification furnace.

As another means, a pressure adsorption / separation device (PSA) for adsorbing nitrogen gas from air to generate oxygen-enriched gas and nitrogen-desorption operation for producing nitrogen-enriched gas, and this PSA
Carrier gas storage tank for storing the nitrogen-enriched gas, which is communicated with the nitrogen-enriched gas outlet and a communication line having a valve, and coal and other hydrocarbons carried by the coal-conveying gas in the carrier gas storage tank. And a coal gasification furnace for gasifying the transported coal and other hydrocarbons as the oxygen-enriched gas as an oxidant for coal gasification.

[Action]

The present invention separates the step of discharging the air filled in the voids in the tower at the beginning of the desorption operation of PSA from the original desorption step in the latter stage of the desorption operation, and the oxygen concentration discharged in the latter is 5%.
The following high-concentration nitrogen gas is used as the coal carrier gas.

〔Example〕

An embodiment of the present invention will be described with reference to FIG. The entire PSA is composed of a nitrogen adsorption / desorption tower 21 and a nitrogen adsorption / desorption tower 22, a carrier gas storage tank 23, a coal storage hopper 24, a coal gasification furnace 26, and a valve connecting the above equipments.

The downstream pipes of the air compressor 31 for compressing and supplying the air 1 are connected in parallel to the top of the adsorption / desorption tower 21 via the valve 11 and to the top of the adsorption / desorption tower 22 via the valve 13. Adsorption and desorption tower
21 and the adsorption / desorption tower 22 are filled with an adsorbent that selectively adsorbs nitrogen such as zeolite as compared with oxygen. In the wake of the bottom of the adsorption / desorption tower 21, the piping is connected via the valve 15,
The downstream pipes of the bottom of the adsorption / desorption tower 22 are connected in parallel to the gasifying agent compressor 33 via the valve 16. Gasifier compressor
The downstream piping of 33 is connected to a coal burner 25 attached to a coal gasifier 26. The pipe downstream of the top of the adsorption / desorption tower 21 is joined via a valve 12, and the pipe downstream of the top of the adsorption / desorption tower 22 is joined via a valve 14. The pipe after the merging is further connected to the low oxygen concentration gas utilization facility 3 via the valve 17 and the carrier gas compressor via the valve 18.
Connected to 32. The downstream pipe of the carrier gas compressor 32 is connected to the carrier gas storage tank 23, and the downstream pipe of the carrier gas storage tank 23 is connected to the coal burner 25 via the valve 19, and
It is connected to the coal hopper 21 via a valve 41. The downstream pipe of the coal hopper 21 is a rotary valve 40 and a valve.
It is connected to the coal burner 25 via 10.

Next, the operation of this embodiment having the above configuration will be described in detail. First, Table 3 shows how to open and close the valves 11 to 16.

As is clear from the table, when the adsorption / desorption tower 21 is in the adsorption state, the adsorption / desorption tower 22 is in the desorption state, and when the adsorption / desorption tower 22 is in the adsorption state, the adsorption / desorption tower 21 is in the desorption state. Below, the adsorption and desorption tower 21
The time when is in the adsorption state will be described.

The air 1 is pressurized by the air compressor 31 and sent to the top of the adsorption / desorption tower 21 via the valve 11. In the adsorption / desorption tower 21, nitrogen is selectively adsorbed as compared with oxygen. Therefore, the gas discharged from the bottom of the adsorption / desorption tower 21 is discharged as an oxygen-enriched gas having a higher oxygen concentration than air. This oxygen-enriched gas is pressurized by the gasifying agent compressor 33 and sent to the coal burner 25.
Incidentally, when the adsorption / desorption tower 21 is in the desorption state, the adsorption / desorption tower 22 similarly performs the above operation.

When the adsorption / desorption tower 21 is performing the above operation, the adsorption / desorption tower 22
Then, the detaching operation is performed. FIG. 2 shows the change over time in the nitrogen concentration of the exhaust gas during the desorption operation.

When the internal gas is discharged from the top of the adsorption / desorption tower 22, it will be discharged from the same direction as the air 1 to be supplied. At the initial stage of desorption of nitrogen gas, a gas having almost the same composition as air is obtained. To be When the gas in the column is further discharged, the pressure in the column is lowered, and the nitrogen adsorbed by the adsorbent is desorbed. As a result, the nitrogen concentration of the gas discharged from the top of the adsorption / desorption tower 22 increases. FIG. 2 shows the above tendency. In the present invention, by utilizing this fact, the nitrogen gas discharged from the top of the adsorption / desorption tower 22 is used as a gas for coal transportation of the coal gasification furnace 26.

It has been described above that the gas for coal transportation used for coal transportation needs to have an oxygen concentration of 5% or less, that is, a nitrogen concentration of 95% or more so as not to react with coal. Further, it has already been described that the amount of the coal-transporting gas used for transporting the coal can be extremely small compared with the amount of the gas used as the oxidizer for coal gasification. Therefore, in FIG. 2, the nitrogen gas discharged in the area A having a nitrogen concentration of 95% or less is used, for example, for the regeneration of a desulfurization device, and the gas discharged in the area B having a nitrogen concentration of 95% or more is directly fed to Used as a carrier gas.

That is, in the region A of FIG. 2, the valve 17 is opened and the valve 18 is closed to take out and utilize nitrogen gas having a nitrogen concentration of 95% or less. In the region B of FIG. 2, the valve 18 is opened and the valve is opened. By closing 17 and driving the carrier gas compressor 31, it is used as a coal carrier gas having a nitrogen concentration of 95% or more. The opening / closing control of the valves 17 and 18 may be manual, or may be automatic control by detecting a specific gas concentration.

This coal carrier gas is not produced continuously,
It is temporarily stored in the carrier gas storage tank 23, and the valve 19 is supplied to the coal storage hopper 24 while adjusting the supply amount via the valve 41.
It is supplied to the coal storage hopper 24 while adjusting the supply amount via the, and to the coal gasification furnace 26 while adjusting the supply amount via the valve 19. In the coal gasification furnace 26, the supplied coal 2 is efficiently gasified to produce a combustible gas 4.

According to this embodiment, since the compressor used to increase the pressure of the coal-transporting gas and the vacuum pump used in the desorption operation can be used as the carrier gas compressor 32, the entire apparatus can be simplified and the entire system can be simplified. The cost can be reduced.

FIG. 3 shows an embodiment in which the present invention is applied to a coal gasification power generation system. The integrated coal gasification combined cycle system includes a gas purification tower 27, a combustor 5 in addition to the equipment shown in the embodiment of FIG.
It is composed of a gas turbine 52, a steam turbine 54, a heat exchanger 53, an air compressor 55, and a generator 56.

The combustible gas 4 produced in the coal gasifier 26 is a gas purification tower.
It is sent to 27 to remove sulfur and ash. The purified combustible gas 4 is sent to the combustor 51, and is combusted in the combustor 51 by the air whose flow rate is adjusted by the air compressor 55 via the valve 62. This combustion drives the gas turbine 52. Further, heat energy is recovered as steam 7 from the combustion exhaust gas by the heat exchanger 53, and the steam turbine 54
Drive. The gas turbine 52, the steam turbine 54, the generator 56, and the air compressor 55 work together, and a part of the energy obtained by the gas turbine 52 and the steam turbine 54 is used as driving power for the air compressor 55. , And others are transmitted to the generator 56 and converted into electric energy.

The flow rate of the air pressurized by the air compressor 55 is adjusted by the valve 61, and then the air is sent to the adsorption / desorption towers 21 and 22 to be separated into high-concentration oxygen and nitrogen and used for coal gasification.

FIG. 4 shows a second embodiment. The basic configuration of this embodiment is the same as that of the first embodiment. The difference is that the vacuum pump 34 is provided downstream of the valve 17 in order to perform the desorption operation of the adsorption / desorption 21, 22 in a vacuum state.

According to this embodiment, since desorption is performed in a vacuum state, the adsorbent can be used with excellent characteristics and the separation efficiency can be improved. Usually, most adsorbents desorb at low pressure levels.

FIG. 5 shows an example in which an adsorbent excellent in adsorption / desorption performance at high pressure was used.

At present, since the gas generated by PSA is used under normal pressure, an adsorbent that exhibits excellent performance under normal pressure is common. However, since coal gasification requires a gas such as an oxidizer under high pressure, it is conceivable that an adsorbent excellent in adsorption / desorption performance under high pressure may be used. In that case, adsorption and desorption towers 21,2
The operating pressure of 2 can be the pressure of the coal carrier gas. Then, it is not necessary to install the carrier gas compressor 32 and the gasifying agent compressor 33 as shown in FIG. 3 of the first embodiment. However, the required pressure of the coal gasification oxidizer and the required pressure of the coal transportation gas are different, and the pressure control valve 70
Set up.

According to this embodiment, the carrier gas compressor 32, the gasifying agent compressor 3
Since it is not necessary to install 3, the device can be simplified,
Also, since the operating pressure of the adsorption / desorption towers 21 and 22 can be increased,
The size of the adsorption / desorption towers 21 and 22 can be reduced.

〔The invention's effect〕

According to the method of the present invention, the suffocation-enriched gas generated by PSA is used at an oxygen concentration of 5% or less, so that it can be used as a coal-transporting gas without fear of dust explosion of coal, and another coal-transporting gas is generated. There is no need to provide a device for doing so.

Further, according to the device of the present invention, since PSA can be used as it is, the structure of the entire coal gasification device can be simplified, and the size is not increased.

[Brief description of drawings]

FIG. 1 is a configuration diagram of the first embodiment of the present invention, FIG. 2 is an explanatory diagram showing an operation range of the present embodiment in the characteristics of the adsorbent, and FIG.
The figure is a block diagram combining the power plant with the first embodiment,
FIG. 4 is a block diagram of the second embodiment, and FIG. 5 is a block diagram of the third embodiment. 21 …… Adsorption / desorption tower, 22 …… Adsorption / desorption tower, 23 …… Carrier gas storage tank, 24 …… Coal storage hopper, 25 …… Coal burner, 26
...... Coal gasifier, 27 …… Gas refining tower, 31 …… Air compressor, 32 …… Carrier gas compressor, 33 …… Gasification agent compressor, 34
…… Vacuum pump, 51 …… Combustor, 52 …… Gas turbine,
53 …… Heat exchanger, 54 …… Steam turbine, 55 …… Air compressor, 70 …… Pressure control valve.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C10J 3/72 Z

Claims (3)

[Claims] 1. A pressure adsorption / separation device (PSA) adsorbs nitrogen gas from air to produce an oxygen-enriched gas, and the oxygen-enriched gas is used as an oxidizing agent for coal gasification to gasify coal and other hydrocarbons. In the coal gasification method using PSA,
PSA-based coal characterized by using a nitrogen-rich gas whose oxygen concentration has dropped below 5% after the start of the nitrogen desorption operation of SA as a coal-conveying gas for conveying coal and other hydrocarbons to a coal gasifier Gasification method. 2. A pressure adsorption / separation device (PSA) for adsorbing nitrogen gas from air to generate oxygen-enriched gas and nitrogen-desorbing operation for producing nitrogen-enriched gas, and an outlet for the PSA nitrogen-enriched gas. And a carrier gas storage tank that is connected by a communication line having a valve and stores the nitrogen-enriched gas, and a coal storage hopper that stores coal and other hydrocarbons that are carried by the coal carrier gas in the carrier gas storage tank. ,
A PSA coal gasification apparatus comprising a coal gasification furnace for gasifying the transported coal and other hydrocarbons by using the oxygen-enriched gas as an oxidizing agent for coal gasification. 3. A vacuum pump is provided in an exhaust line provided by branching a communication line according to claim 2.
Coal gasifier by PSA.