JP2015055375A - Power generation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To store coal while easily and reliably preventing spontaneous firing of coal and to achieve quite highly efficient power generation without reduction in heat quantity.SOLUTION: Provided is a power generating method by a power generation system including a coal combustion boiler using, as fuel, coal stored in an open-storage fashion in a coal yard provided adjacently, including: storing the coal in the coal yard in a state in which the coal is submerged in water by 50% or more of a total height thereof; unloading the stored coal in a wet state; drying the stored coal by bleeder steam generated from the power generation system by means of a steam tube rotary dryer or the like; and subsequently generating electric power using the dried coal as at least a part of the fuel of the coal combustion boiler.

Description

  The present invention provides a novel power generation method that can safely use coal piled up in a coal storage yard and can generate power in an industrially advantageous manner.

Stored coal is known to cause so-called "spontaneous ignition", in which hydrocarbons, carbon substances or sulfur in the coal oxidize with oxygen in the air to generate heat and eventually ignite. . Once ignited, it is very difficult to extinguish, which is not only a very big security issue, but also causes an economic problem of product loss. Furthermore, since the quality of coal itself is deteriorated even before ignition occurs, prevention of heat generation and ignition is a very important problem.
In recent years, the use of sub-bituminous coal, which is inferior in quality compared to anthracite and bituminous coal, has been demanded, and the sub-bituminous coal contains a large amount of volatile components. Sub-bituminous coal also has a quality problem that it has a high moisture content and a low calorific value per unit weight.

  Conventionally, as a method for preventing ignition of coal piled up, a method of spraying a coating agent such as a resin liquid or latex on the surface of a pile of coal (coal storage pile) to prevent intrusion of air or moisture into the coal layer (Patent Document 1) 2) A method of spraying a microalga culture solution (Patent Document 3), a method of spraying water as a simple method, and a method of blowing nitrogen gas, which is an inert gas, into a coal bed have been proposed ( Patent Document 4). Moreover, the method of storing water in storage tanks, such as a tank, and storing coal in it is proposed (patent document 5).

JP-A-53-38082 JP 51-137701 A JP 2011-162738 A Japanese Patent Publication No.54-31481 Japanese Unexamined Patent Publication No. 60-17905

The spraying method of the coating agent and the microalgae culture solution is inefficient in terms of cost because the coating cannot follow the deformation and sinking of the coal storage pile, causing breakage and cracks. The water spraying method is not effective for preventing heat generation inside because water penetrates only the surface of the coal storage pile. Excessive spraying deteriorates handling properties such as cutting and transportation after coal storage and combustion as fuel. It is difficult to control the application amount because it causes a decrease in efficiency.
The inert gas blowing method has complicated piping strength and condition setting. In addition, due to the recent increase in cargo handling facilities, the amount of coal piled up in the coal storage yard becomes large, and there is a problem that the effect is sustained and the amount of gas used is great. As a result, it has not been put to practical use in coal storage facilities that are open to the atmosphere.

  Therefore, at present, a method is adopted in which a plurality of temperature sensors are inserted into the coal storage pile, the temperature is monitored, and the coal at a high temperature is cut and reloaded at another location. However, this method requires a separate coal storage area for storing and storing the coal for the coal to be stored, so the scale of the coal storage area becomes unnecessarily large, and Therefore, a great deal of labor is required and it is not economical.

In contrast to the above method, the method of storing the coal in a storage tank filled with water can be said to be an extremely reliable storage method because the entire amount of coal is immersed in water. However, since this method uses a tank (coal pound), when the amount of coal stored increases, the tank needs to be enlarged, and there is a problem in industrial implementation. In addition, when the coal after storage is used in steam turbine power generation using a pulverized coal fired boiler or a stalker boiler, the coal immersed in the water has a large amount of adhering water, and therefore a treatment for drying and removing the water. Needed separately and had problems in economic implementation.
In addition, in the said well-known literature which shows the method of performing the storage of coal using the storage tank containing water, the example which applied this method to the piled-up coal, and the description which suggests this application do not exist at all.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained knowledge that coal can be sufficiently prevented from spontaneous combustion if submerged in a certain ratio or more, and can be used for storing coal that has been piled up in large quantities. By applying this idea, it is possible to store the coal easily and reliably while preventing spontaneous combustion of the coal, and the use of the extracted steam generated in the power generation facility for burning the above-mentioned piled coal Then, by evaporating the moisture and supplying it to the power generation facility for combustion, there is little decrease in the amount of heat due to the adhering water, and the amount of heat can be stabilized by adjusting the amount of moisture after evaporation, It has been found that extremely efficient and stable power generation can be performed, and the present invention has been completed.

That is, the present invention is a power generation method using a power generation facility equipped with a coal combustion device that uses coal stored as a fuel in a coal storage facility installed as a fuel,
In the coal storage, coal is stored in a state where 50% or more of its total height is submerged,
The stored coal is taken out in a wet state, and then the stored coal is heated and dried with extracted steam generated from the power generation facility, and then used as at least part of the fuel of the coal combustion device to generate power. The power generation method.
In the above power generation method,
1) The coal combustion device is a coal combustion boiler 2) The coal to be piled up is 20,000 tons or more,
3) The moisture content of the coal after drying is 7% by mass or less,
4) It is preferable that heating and drying of the wet coal with extracted steam is performed using a steam tube rotary dryer.

According to the present invention, it is possible to easily, reliably and continuously prevent a large amount of coal on the scale of several tens of thousands tons and hundreds of thousands of tons, and to prevent long-term storage. It becomes possible. Moreover, the coal which became wet by the said storage can be dried easily and economically using the extraction | collection vapor | steam of power generation equipment, and industrial implementation is enabled.
In addition, according to the above power generation method of the present invention, after taking out the submerged coal, the moisture is evaporated, and by performing predetermined management during the drying process, the amount of moisture adhering to the coal is made constant. It also has the advantages of being easy to manage and stabilizing combustion in the power generation equipment.

It is the schematic which shows the typical electric power generation method of this invention.

  Coal storage in the present invention is particularly effective in storing a large amount of coal storage of 20,000 to several million tons. The target coal is not limited to anthracite, bituminous coal, subbituminous coal, lignite, etc., but is particularly suitable for storing subbituminous coal that is easy to ignite. In addition, it is suitable for long-term storage of 2 weeks or more where the risk of ignition increases.

In the present invention, coal is stored outdoors in a pile, but it is characterized in that 50% or more of the total height of the stored coal is stored in a submerged state. The total height is the height from the coal storage floor to the top of the stored coal after field loading.
The field loading is performed by carrying it into the coal storage with a stacker or the like, and a method of compressing and storing with a bulldozer or the like is preferable every time the field height becomes 3 to 5 m. By expanding the pressure, not only the apparent specific gravity is increased and the amount of stored coal is increased, but also the gap between the coal grains is reduced, and the ignition prevention ability is effectively expressed with a smaller amount of submerged water than before the expansion.

The piled coal is stored with 50% or more of the total height submerged.
There is no particular limitation on the mode of submerging. A pool-like concrete structure is placed below the ground and coal is poured into it to submerge it, or as shown in Fig. 1, water around asphalt or concrete ground (coal floor) There is a method of constructing an impervious weir and putting water into and out of the coal storage to submerge it.
It is necessary to submerge so that 50% or more of the total height is immersed in water. If it is 50% or more, there is no particular limitation and it may be completely submerged. However, when handling a large amount of coal and taking into account the drying efficiency of wet coal, it is preferably 60 to 90% of the total height, particularly preferably A mode in which 70 to 85% is submerged is adopted. If the submergence is 50% or more of the total height, the water rises through the coal grain gap by capillary action, wets the coal located above the water surface, and can effectively prevent ignition. Although it is effective in preventing ignition if the stored coal is completely submerged, there is a concern that the equipment for submergence will be enlarged and the amount of water used for submersion and the energy and cost required for drying will increase. Is done.

  Coal storage facilities with the above-mentioned submergence facilities must be attached to the power generation facilities described later. Otherwise, not only will it take time and labor to transfer coal, but it will not be possible to effectively use the extracted steam generated from the power generation facilities, and it will be a comprehensive, efficient and economical combination of coal storage and power generation. Power generation effect cannot be achieved.

  Coal in the coal yard is taken out in a wet state and dried by the extracted steam from the adjacent power generation facility. Extraction steam is discharge steam after driving a steam turbine in a power generation facility, taking into consideration heating temperature and pressure at the time of subsequent use, low pressure steam of about 0.01 to 0.2 MPa, 0. There are medium pressure steam of about 2 to 1.5 MPa. The extracted steam and the amount of use thereof are appropriately selected in consideration of the amount of wet coal to be dried, the degree of drying, the moisture content of the coal, and the like. Among them, 0.1 to 1 MPa extraction steam is easy to handle and can secure the amount of heat necessary for drying, and thus is preferably used in the present invention.

  The above-mentioned coal storage ground is composed of a water supply facility that is appropriately selected from a water tank, a supply pump, a water supply pipe, etc., and a drain outlet, a drain pump, a waste water treatment device, etc. Drainage equipment that is appropriately selected and configured is provided.

  For taking out coal in a wet state, normal cargo handling equipment is employed without any particular limitation, but bulk cargo handling equipment such as a bucket crane is suitably employed. In addition, the extracted coal may be directly transferred to the drying process using a transfer facility such as a belt conveyor. Prior to the transfer, the coal is once drained with a draining facility constituted by a mesh, and then the drying facility is used. It is preferable to transfer to. At this time, as a transfer facility, for example, a belt conveyor, it is also a preferable aspect that the belt portion is made of mesh and the transfer and draining are performed simultaneously.

  The method for drying the wet coal with the extracted steam is not particularly limited, and a known method is adopted without limitation. Specifically, in an inclined and rotating cylinder, coal is supplied from one end, and on the other hand, extracted steam is supplied in parallel from the same side as the coal supply port, or is supplied and contacted from the coal discharge port side. And direct heating using a rotary dryer. However, in this direct heating method, at the time of drying, a part of the extracted steam condenses to become water and wets the coal, which may reduce the drying efficiency. Therefore, use of an indirectly heated steam tube rotary dryer is suitable for drying wet coal. In the dryer, the extraction steam is caused to flow through a plurality of tube-like heating tubes arranged concentrically in a rotating cylinder, and the heating tube and the coal come into contact with each other to dry the extraction steam and the coal directly. It has the advantage of not contacting.

It is preferable that the moisture content of the coal after drying is as small as possible in order to improve the combustibility in the boiler. Generally, 10% by mass or less is sufficient, and the lower limit of the water content is preferably 7% by mass from the viewpoint of economy. Moreover, in the said drying, it has the merit that coal which has the stable combustibility can be supplied to a power generation equipment by determining the moisture content after drying beforehand and adjusting a drying condition so that it may become this moisture content.
Here, the said moisture content says the ratio of the total moisture with respect to solid content (an absolutely dry state) of coal.

The dried coal is appropriately processed and used by a combustion apparatus and a power generation method. In the case of a pulverized coal fired boiler, the pulverized coal is pulverized to a size that passes 200 mesh (75 μm). Further, in the case of a fluidized bed boiler, it is generally adjusted to a size of 10 mm or less, and in the case of a stalker boiler, it is adjusted to a size of 30 mm or less.
The dried coal is usually used as a raw material for the following boilers and gasifiers for combustion, but is mixed with coal of different quality and moisture content obtained by other means. May be.

The power generation method of the present invention is applied to a power generation facility that generates extracted steam. Typically, it is suitably used for steam power generation, which includes a boiler that generates steam by burning coal and generates electricity by driving the steam turbine with the generated steam. Furthermore, the gas turbine power generation that gasifies coal and uses the combustion of the gas, and the high temperature exhaust gas after the gas turbine power generation generates high temperature steam, and the steam turbine is driven by this steam to perform the steam power generation together It is also adopted in gasification combined power generation (IGCC). In any case, the extracted steam generated as a result of power generation is used for drying wet coal stored under submergence.
The above power generation facilities shall be equipped with any conventionally known facilities necessary for power generation such as generators, condensers, flue gas denitration devices, flue gas desulfurization devices, dust collectors, and chimneys without any limitation. Can do.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not restrict | limited at all by these Examples. In addition, not all combinations of features described in the embodiments are essential to the solution means of the present invention.

Example 1
An embodiment of the present invention will be described using the equipment shown in FIG.
Coal (sub-bituminous coal) 1 was unloaded from the ship to a 20 × 30 m coal yard surrounded by concrete weirs 5 meters high so that the height to the top was 7 m. Water was supplied from the water supply facility 3 to the coal storage, and the water level was set to 5.5 m. When stored in this state for 4 months, no ignition of the coal was observed.
Next, from the coal storage, a bucket crane was used as the cargo handling equipment 4, and coal was supplied to the hopper 10 having a draining mechanism. In addition, a steam tube rotary dryer was used as the dryer 6, and 0.3 MPa extraction steam 7 from the power generation equipment 9 was supplied to the jacket (steam tube) of the steam tube rotary dryer and heated. Coal was supplied from the hopper 10 to the dryer 6, and the steam supply amount and the coal supply amount were adjusted so that the water content at the outlet of the dryer 6 was about 7 mass%.
The low moisture coal 8 dried and reduced in water content as described above could be stably combusted in the boiler of the power generation facility 9.

DESCRIPTION OF SYMBOLS 1 Coal 2 Water 3 Water supply equipment 4 Cargo handling equipment 5 Weir 6 Dryer 7 Steam 8 Low moisture coal 9 Power generation equipment 10 Hopper

Claims (5)

A power generation method using a power generation facility equipped with a coal combustion device that uses coal stored in an open coal storage as a fuel,
In the coal storage, coal is stored in a state where 50% or more of its total height is submerged,
The stored coal is taken out in a wet state, and then the stored coal is heated and dried with extracted steam generated from the power generation facility, and then used as at least part of the fuel of the coal combustion device to generate power. The power generation method.   The power generation method according to claim 1, wherein the coal combustion device is a coal combustion boiler.   The coal to be piled up is 20,000 tons or more, The power generation method according to claim 1 or 2.   The power generation method according to any one of claims 1 to 3, wherein the moisture content of the dried coal is 10% by mass or less.   The power generation method according to any one of claims 1 to 4, wherein the heating and drying of the wet coal by extraction steam is performed using a steam tube rotary dryer.