JPS61151294A - Reducing water content of coal - Google Patents

Abstract

PURPOSE:To dehydrate coal with a small amount of heat energy, by mixing coal with a water absorbing and releasing polymer for absorption of water contained in the coal, separating the polymer from coal and dehydrating the recovered polymer for reuse. CONSTITUTION:Coal is mixed as homogeneously as possible with about 1% water absorbing and releasing polymer so that water in the coal may be absorbed by the polymer. The polymer includes starch/acrylonitrile graft polymer, polysodium acrylate type polymer, carboxymethylcellulose, etc. Then the polymer is separated from coal to obtain dehydrated coal and the recovered polymer is dehydrated by heating for reuse. The polymer may be filled in numerous small containers formed with a porous material which allows permeation of water but does not let dust coal through.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for reducing moisture content of coal without heating and drying it.

[Conventional technology]

Charging coal that is charged into a coke oven is carbonized in the oven, and water evaporates to become a gas liquid such as ammonium water, but the latent heat of vaporization is taken away in the oven, so from the perspective of heat energy consumption of the coke oven. Therefore, the less water the better.

Incidentally, the moisture content in raw coal used for coke generally fluctuates in the range of 7 to 11% by weight due to the influence of weather during coal storage in a coal yard, and is approximately 9% by weight on average. As for the water content in this charged coal, a change of 1% by weight increases the amount of heat consumed per 1 K of charged coal (approximately 15 c per +).
This appears as a change in al, and the increase or decrease in water content is a serious problem in terms of energy conservation.

Therefore, conventionally, in order to reduce the water content of the charged coal, the charged coal is heated using recovered heat recovered from some kind of waste heat source to evaporate the water content. The recovered heat includes, for example, the recovered heat recovered from the waste gas in the coke oven combustion chamber, the recovered heat recovered from the coke oven generated gas using a heat medium by installing a heat exchanger in the upper stomach tube of the coke oven, and the recovered heat recovered from the coke oven generated gas using a heat medium. Recovered heat recovered from heat sources such as circulating inert gas used in equipment is used.

In addition, methods that do not rely on recovered heat from waste heat sources include a method of preheating coal by irradiating it with microwaves (Japanese Patent Application Laid-Open No. 5/1-127901), and a method of preheating coal of high volatile content and inferior quality. A method of reducing volatile content by adding solid heat carriers such as coke powder, sand, and alumina balls to reduce volatile content without reducing density (Japanese Patent Application Laid-Open No. 571-148
No. 002) has been proposed, but all of them are the same in that the charged coal itself is heated.

Furthermore, as a method that does not use a heating method, 15 weight M%
For lignite containing more than 30Kg/cd-0
A method of dewatering by mechanically squeezing at higher pressures has been proposed (Japanese Unexamined Patent Publication No. 571-1/16801).
This is applied to lignite with a high moisture content of 15% by weight or more, especially 40% by weight or more.
It cannot be applied to coal with a pre-loaded weight percentage.

[Problem that the invention seeks to solve]

However, when heating the coal itself to reduce its moisture content, in addition to the thermal energy equivalent to the sensible heat required to warm the coal and the water contained in the coal to the evaporation temperature of water, Thermal energy equivalent to the latent heat of vaporization required to evaporate this water is required.

By the way, of the thermal energy required to reduce this water content, the portion equivalent to sensible heat will not be wasted if the coal is charged into the coke oven as it is in preheated milliliters. However, this poses the problem of a drop in temperature in the coal loading hopper and coal loading car, as well as the difficulty of having to install a preheating device near the coke oven. In addition, regarding the thermal energy equivalent to the latent heat of vaporization, it is the thermal energy originally consumed during carbonization in the coke oven, and although there is an advantage that it can be replaced with thermal energy recovered from the waste heat source. ,
In terms of the absolute amount of thermal energy consumed, there is little benefit to drying the coal before charging it into the coke oven.

[Means and effects for solving the problems] The present invention was devised in view of the above points, and is a method of drying coal by separating and removing moisture without heating the coal itself and without evaporating the water. This provides a method that can save overall thermal energy in the coke manufacturing process of drying coal culms or drying coal and carbonizing it.

That is, the present invention involves mixing coal and a water-absorbing/extracting polymer as uniformly as possible, allowing the moisture in the coal to be adsorbed onto the water-absorbing/extracting polymer, and then separating the coal and the water-absorbing/extracting polymer. This is a method for reducing the moisture content of coal, in which the recovered water-absorbing and desorbing polymer is dehydrated and reused.
A large number of small containers made of a porous material that does not allow fine coal powder to pass through is filled with a water-absorbing and desorbing polymer, and as many small containers filled with this water-absorbing and desorbing polymer are placed inside the coal as much as possible. The coal is mixed uniformly and the moisture in the coal is adsorbed by the water-absorbing and desorbing polymer in the small container.Then, the above-mentioned coal and the small container are separated, and the recovered small container is dehydrated and the coal is reused. This is a moisture reduction method.

The water-absorbing and desorbing polymers used in the present invention include starch acrylonitrile graft polymers, sodium polyacrylate polymers, vinyl acrylate alcohol polymers, polyvinyl acrylate alcohol polymers, carboxymethylcellulose (CHC) and its like. Examples include crosslinked polymers and three-dimensional crosslinked polymers obtained by polymerizing an acrylamide derivative as a main component with the addition of a crosslinkable monomer.

For example, acrylamide derivatives are dry powders that do not dissolve in any common solvents and do not melt when heated. The biggest feature of this is that the polymer water-retaining gel absorbs and expels water depending on the temperature.
When a gel that has absorbed water is heated, the water does not evaporate and separate, but rather separates from the polymer before it evaporates.By utilizing this property, water can be separated without the need for latent heat of vaporization. This is something that can be done.

The present invention utilizes the above-mentioned properties of a water-absorbing and desorbing polymer to reduce the moisture content of coal. Since this water-absorbing and desorbing polymer is a dry powder, the question of how to use it is how to uniformly disperse it in a form that can be easily separated later, and how to separate the water when the water-absorbing gel is heated. .

In the present invention, preferably, if there is a difference in particle size between the particle size of the coal to be dried and the particle size of the water-absorbing/desorbing polymer used for drying, the particle size of the coal to be dried and the particle size of the water-absorbing/desorbing polymer used for drying are such that they can be easily separated. The former method is adopted, in which the two are brought into direct contact and then separated by sieving, or, if there is no difference in particle size to the extent that separation is easy, the water-absorbing and desorbing polymer is filled in a small container and the two are separated. The latter method of contact is adopted.

The latter method involves filling a small container with the above-mentioned water-absorbing and desorbing polymer and bringing the two into contact. It is also effective to use

In this case, by heating the sintered iron ball together, water separated from the water-absorbing and desorbing polymer flows out from the sintered iron ball.

The small container may be made of a filter body made of partially fused resin beads made of polypropylene, polyethylene, or the like. If the size of the container is larger than the largest grain of coal, it can be easily separated by sieving. Unless too large a portion of the coal is separated to the side of the vessel along with the vessel, even if only a small portion of the large grains of coal are sieved to the side of the vessel and heated, the process will not proceed as long as the hanging is not too large. It does not prevent its establishment.

That is, the sieving does not need to be exact. Therefore, there is no strict meaning to the largest grain, as long as most of the coal is separated from the container.

On the other hand, regarding the porosity of the container material, it is absolutely necessary to allow water and vapor to pass through, since it is permeable to water and vapor but not the finest coal powder. It is preferable that the material has micropores having . It is also undesirable for the finest particles of coal to enter the vessel as this prevents contact between water, steam and the polymer.

As mentioned above, even if the polymer is placed in many small containers and mixed with coal, in order for the moisture in the coal to move to the polymer, the diffusion of water in the coal, the water vapor pressure in the space in the coal, and the It takes time to reach equilibrium with the moisture on the surface of the coal, the equilibrium between this water vapor pressure and the surface of the polymer, and the diffusion of water in the polymer. In order to shorten this time, a mixture of coal and small containers is stored in a storage tank, and gas such as air or nitrogen gas is blown into the storage tank to uniformly reduce the water vapor pressure in the space inside the coal. By promoting vaporization from the surface of the coal to water vapor and promoting the flow of gas into the small porous container, the moisture content of the coal can be reduced in a short time. The polymer in the small container absorbs water, so regular air, nitrogen gas, etc. is sufficient, but
Of course, it is better to use dry air or dry nitrogen gas. Furthermore, the effect will be maximized if the flow m is injected to the extent that the coal becomes fluid.

Furthermore, if the culm does not need to be used for a short period of time, you can put the coal in a vertical storage tank and create a draft at the top.
When the pressure is reduced in the upper part and ventilation is made from the ventilation pipe at the bottom, if the coal does not contain water-absorbing and desorbing polymers, the entrance area of the ventilation will be dry, but as it moves towards the top, the ventilation air becomes saturated with water and becomes dry. Capacity decreases. However, if a water-absorbing polymer is mixed in, the moisture in the ventilated air will be adsorbed by the polymer, and the ventilated air will always be dry, reducing the moisture content of the charged coal to the top of the coal storage tank. Become.

The above-mentioned strong stirring by blowing gas has a large moisture reduction effect over a certain period of time, but on the other hand, it generates dust, so dust collection equipment such as a bag filter is required when discharging the gas. Slow ventilation requires time to dry, but there is no risk of dust generation.

In addition, in the case where there is no large difference between the particle size of coal and the particle size of the water-absorbing and dehydrating polymer, a method has been described in which the water-absorbing and dehydrating polymer is placed in a small porous container to dehydrate the coal. However, if the water-absorbing and desorbing polymer is significantly different in shape from coal, it may be possible to add it directly to coal. For example, if the water-absorbing and desorbing polymer is flocculent and has a shape significantly different from that of coal,
Even if it is mixed directly with coal, it can be easily separated, and the dehydration efficiency is also better when it is brought into direct contact with coal.

Now, when we compare the amount of heat required by the evaporation method and the method of the present invention in the case of drying coal with a water content of 10% by weight to 5% by weight, the amount of heat required is as follows.

(A) Required amount of heat in evaporation method Ql: Amount of heat to heat coal Q2: Amount of heat to heat and evaporate water WC: Amount of coal (dry) Kg Ww=0.1wc: Moisture mK9 Cc =0.25Kcal/Ky-'C :Specific heat C of coal
w = 1, 0Kca1/Ky ・'C: Specific heat of water t
2-80℃: drying temperature t1=25℃: initial temperature of raw coal 7w=551 cal/*g: latent heat of vaporization of water (at 80℃), then Q1+02=CC-WC・(12-1,) +CW-WW
・(12-to 1) 10γW-WW = wc (0,25x(80-25) + 1x O
, IX (80-25) + 551X O, IX O
,0510,13) =,4G,8x W C(nica1/ni9-coal)(
B) The heat required by the method of the present invention! (Q3) Wa =0.1W
C: Weight of water absorbing/desorbing agent tIK9WW=0.1WC: K for moisture
W Ca = 0.4 to cal/Kg ・°C: Specific heat of water absorbing and desorbing agent cw = 1. o to Ca1/Kg・℃: Specific heat of water t, -=
70°C: Dehydration temperature t of water absorbing/dehydrating agent = 25°C: Initial temperature of raw coal, o3=Ca -Wa -(t,--tl)+Cw-Ww
・(t1'-tl) -Wc (0,4x O,1x(70-25) +1.
OX O,1x O,05/ 0.1x (70-25)
)-4,05XWC (cal/Nff-coal), and water removal by the method of the present invention is about 1/10
It is an extremely energy-saving method for reducing coal moisture, and it has a great effect on reducing the overall heat unit in the cous oven.

Furthermore, reducing the moisture content of the charged coal increases the bulk density of the charged coal, which has the effect of greatly improving the strength of coke.

Example 1 10 Kg of coal with 9.5% and 10.4% moisture by weight
Fiber flocculent water absorbent/desorbent with water absorbent/desorbent retained in the fibers (manufactured by Nikko Tsukusran Kogyo, product name: Lancil F) 0.1N
g (1 weight % disease-resistant) and 0.3 kg (3 weight % disease-resistant) were mixed together and stirred for about 10 minutes with a mixer. Thereafter, it was transferred to a container and the elapsed time and change in moisture content were measured. Of course, the moisture absorbing and dehydrating agent was removed when measuring the moisture content. The results are shown in Table 1.

The results show that most of the moisture in the coal is absorbed during mixing and stirring. Furthermore, when stored in a container and allowed to stand still, moisture content hardly decreases. This is thought to be because there is no relative movement between the coal and the water absorbing/desorbing agent, so contact with moisture is insufficient. It is clearly effective when the amount of water absorbing and desorbing agent is increased (to 3% by weight against diseases). However, this should be determined based on the target moisture m and economy f1.

Since water absorption occurs in a very short time when mixing is sufficiently performed, it is considered that stirring time of less than 10 minutes is sufficient to produce a sufficient effect. Of course, this is a problem that should be determined in relation to the amount of water absorbing and dehydrating agent.

Example 2 0.3 kg of water absorption/desorption agent was added to coal 30 to 9 in the lower water distribution section.
(1% by weight against disease) was added. The water absorbing/dehydrating agent is a starch-acrylic polymer (trade name: Saniwet SW-1000, manufactured by Sanyo Chemical Industries, Ltd.), which is in the form of a powder of 20 to 150 mesh. This powder was filled into 30 cloth bags each weighing 10 g and mixed with coal. In this case, since the cloth pouch will be torn, mixing by stirring is not performed, but instead a cylindrical container with a diameter of 250φ and a height of 1,300 mm with many holes in the bottom is filled with compressed air that is drained from below. Infused. This was done by a method of aerating air through the mixture packed with coal and water absorbing/desorbing agent bags.The aeration time was 8 hours, and the aeration amount (superficial velocity Vmm/s) was avoided to change the original sample water suspension and after aeration. The moisture content was measured.

When no aeration is performed (V=O), the result is the same as in Example 1 where the mixture is allowed to stand without stirring, and there is no moisture reduction effect. When a water absorbing/desorbing agent is mixed and aeration is performed at V=10 mm/s, the moisture reduction effect is almost the same as when aeration is performed at V=40 mm/s without a water absorbing/desorbing agent. However, in the case of no absorbent 112 water agent, although the lower part of the cylinder is dry, the water vapor associated with the air tends to condense in the upper part, and the higher the cylinder, the lower the effectiveness. On the other hand, when a water absorption/desorption agent is mixed, dry air passes to the upper part of the cylinder and the coal above is evenly dried.

(Example 3) Powder of acrylamide derivative three-dimensionally crosslinked polymer in coal 1 K9 with moisture content of 9.4% by weight was placed in 10 porous hollow spheres made of polypropylene at 1 g each. The mixture was mixed and filled into a cylindrical container having a porous rostrum below, and compressed air, excluding the drain, was passed through from below at a superficial velocity of 40 mm/S. After 6 hours of ventilation, the moisture content in the coal was reduced to 3.5% by weight. In this case, when the hollow sphere was separated from the sieve and heated to 60°C, 82% by weight of the absorbed moisture was expelled without evaporation, so it could be immediately reused for drying coal. Ta.

〔Effect of the invention〕

According to the present invention, moisture in coal is adsorbed by a water-absorbing and desorbing polymer, and is removed by dehydration from this water-absorbing and desorbing polymer. The weight of this water-absorbing and desorbing polymer is several tens to hundreds of times its own weight, and the culminess may be about 1% by weight of the charged coal in order to adsorb moisture in the coal. Therefore, unlike conventional coal drying methods, it is not necessary to heat all of the coal, but only the water-absorbing and desorbing polymer (approximately 1% by weight of the charged coal) needs to be heated.

Moreover, the water-absorbing and desorbing polymers differ depending on the type, but
Since those with good water absorption and dehydration properties separate water by heating to 50 to 70°C, the latent heat of vaporization of water is not required, and the amount of heat for heating and dehydration can be greatly reduced.

Claims (4)

[Claims] (1) Mix coal and water-absorbing/desorbing polymer as uniformly as possible,
Coal characterized by adsorbing moisture in the coal onto a water-absorbing/extracting polymer, then separating the above-mentioned coal from the water-absorbing/extracting polymer, and dehydrating the recovered water-absorbing/extracting polymer for reuse. How to reduce moisture. (2) Putting a mixture of coal and a water-absorbing and desorbing polymer into a storage tank,
2. The method for reducing moisture in coal according to claim 1, wherein moisture in the coal is transferred to and adsorbed by the water-absorbing and desorbing polymer by blowing gas or ventilation into the storage tank. (3) A large number of small containers made of a porous material that allows water and steam to pass through but does not allow fine coal powder to pass through, and filled with a water-absorbing and desorbing polymer. The small container is mixed in coal as uniformly as possible, the moisture in the coal is adsorbed to the water-absorbing and desorbing polymer in the small container, and then the coal and the small container are separated, and the collected small container is is a method for reducing the moisture content of coal, which is characterized by dehydrating it and reusing it. (4) A mixture of coal and a large number of small containers filled with a water-absorbing and dehydrating polymer is placed in a storage tank, and by blowing gas or ventilation into the storage tank, the water in the coal is absorbed and desorbed into the small containers. The method for reducing the moisture content of coal according to claim 1, wherein the moisture content of coal is transferred and adsorbed onto a carbonaceous polymer.