JPS5843219A - Dry type waste gas desulfurization method and its apparatus - Google Patents

Abstract

PURPOSE:To dispense with cooling water for cooling medium or sea water, and to reduce desulfurization cost, by using the air for cooling an adsorbent regenerated by heating desorption, and this heated air having recovered the waste heat for the combustion of a boiler. CONSTITUTION:The waste combustion gas is introduced into an adsorbing tower 101 from a boiler 100, SOx is adsorbed from the waste gas, denitrated and freed of dust with a dust collector 102, and exhausted through a duct 11. An adsorbent having adsorbed SOx is led through a pipe 12 to a heat desorption regenerating tower 103, and the desorbed gas is sent through a pipe 13 to a sulfur recovering apparatus 104. The regenerated adsorbent is led through a pipe 16 to a cooling tower 106 to cool it by heat exchange with the air sent through a pipe 17. The heated air is joined with the gas fed through a duct 4 as combustion air to the boiler 100. The cooled adsorbent is classified with a classifier 107, returned to the adsorbing tower 101 for recirculation use. The classified pulverized adsorbent is sent through a pipe 20 to a pipe 3 as a fuel for the boiler 100 to mix it with coal fuel.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry flue gas desulfurization method and apparatus for removing sulfur oxides from combustion flue gas generated from coal-fired power plants and the like by adsorbing them onto an adsorbent.

Various methods have been proposed as desulfurization methods for removing sulfur oxides from combustion exhaust gas, and improvements have been made.

Recently, there have been many construction plans for coal-fired power plants, and the flue gas desulfurization method requires less water and wastewater than the wet method, and requires no reheating when releasing clean flue gas into the atmosphere. The dry method is attracting attention because of its unique characteristics. Furthermore, in this desulfurization method, the by-product is recovered as elemental sulfur, and the sulfur recovery type dry flue gas desulfurization method is attracting attention because it has a smaller capacity of about 115% compared to the gypsum recovery method in the wet method. It has been done.

In the sulfur recovery type dry flue gas desulfurization method, sulfur oxides in the combustion exhaust gas are adsorbed by an adsorbent.The adsorbent that has adsorbed sulfur oxides is then thermally desorbed and regenerated in a thermal desorption regeneration tower, and then regenerated and adsorbed. The agent is recycled.

The desorption gas generated in the thermal desorption regeneration tower is concentrated to a high concentration of sulfur oxides, so the desorption gas is then sent to a sulfur recovery process that reduces the sulfur oxides to elemental sulfur. This is a method of recovering sulfur.

As mentioned above, the adsorbent is used by circulating between the adsorption tower and the thermal desorption/regeneration tower. At this time, by heating the adsorbent to at least 350C to 450C in the thermal desorption regeneration tower, it is possible to desorb the sulfur oxides adsorbed on the adsorbent as dilute sulfuric acid. Therefore, the adsorbent regenerated by thermal desorption is heated to a temperature of t12oc~
Is it necessary to cool down to around 150C? gkt Cooling can be done indirectly with cooling water or seawater, but using cooling water requires equipment such as a cooling tower, so seawater is used. In some cases, there are problems with corrosion and hot drainage. When using seawater, the temperature of the seawater needs to be at least 4C below the intake temperature in order to prevent secondary environmental pollution from heated wastewater. There are problems such as increased capacity.

Even when cooling water is recycled, there are problems such as power consumption of the cooling tower and replenishment of cooling water.

The present invention attempts to improve the above-mentioned drawbacks, and its purpose is to use air to cool the regenerated adsorbent, and use the heat recovered air to improve the efficiency of combustion exhaust gas generators such as boilers. This is to reduce the cost of eliminating the law.

In the dry method, sulfur oxides in the combustion exhaust gas are adsorbed by an adsorbent, and the adsorbent is heated, desorbed, regenerated, and recycled. '
frAih') O'＊Kore, Kaiwa. . This results in oxidation of 0-1] and a decrease in the amount of adsorption. In the cooling method, indirect cooling using cooling water can be used to reduce the capacity of the desorption tower and achieve efficiency. However, in this case, the above-mentioned problems occur and the utility costs of the dry method become excessive. The running cost of the dry method is mainly the amount of desulfurization agent wasted and the electricity used for the equipment used in the process.If cooling water or seawater is used for this, these utility costs are included in the running cost. will be added to. Therefore, in order to reduce the desulfurization cost in the dry method, it is necessary to reduce the amount of wasted desulfurization agent and to efficiently recover heat in the process. In the present invention, as a heat recovery means in the process, air is used to cool the heated adsorbent in the thermal desorption regeneration tower to around the flue gas temperature, and the heated air is used as an air source of the flue gas generator such as a boiler. The heat recovery was measured by making the

Embodiments of the present invention will be described with reference to the drawings.

The drawing shows a combustion exhaust gas generating device (hereinafter referred to as a boiler) 100 such as a boiler and a dry desulfurization process incorporating a sulfur recovery system therein, with solid lines mainly showing the flow of solids and dotted lines mainly showing gas or gaseous substances. . Fuel coal is introduced into a boiler 100 through pipes 1 and 3, and in the boiler 100 it is combusted by air from an air pipe 4°5.6, and its combustion exhaust gas is introduced into an adsorption tower 101 through pipes 7 and 8. The adsorption tower 101 adsorbs sulfur oxides in the combustion exhaust gas, and the desulfurized combustion exhaust gas is passed through the pipe 1o to the denitrification and desulfurization device 10.
2 and is released to the atmosphere from the pipe 11.

In the drawing, the denitration process is shown as a post-desulfurization process, but it is also possible as a pre-desulfurization process. The adsorbent that has adsorbed sulfur oxides is then guided through the pipe 12 to the thermal desorption regeneration tower 103 and heated to a temperature of 350 to 450 r, thereby desorbing the sulfur oxides adsorbed to the adsorbent as dilute sulfuric acid. . SO2,
The desorption gas whose main composition is CO2 and H2O is led to the sulfur recovery device 104 through a pipe 13, and S02 is reduced to sulfur or a part of SO2 is converted to H2S, 802 (!: H2s).
A Zuklaus reaction is also used to reduce SO2 to elemental sulfur and recover by-product sulfur 14. Gas such as unreacted H2S or cos in the sulfur recovery device 104 is led to the oxidation tower 105 through a pipe 15, where the sulfur compound is oxidized to SO2, and the oxidation reaction gas is passed through the pipe 9 to the above-mentioned combustion exhaust gas pipe 6. 7 and led to the adsorption tower 101.

The adsorbent regenerated in the thermal desorption regeneration tower 103 is led to the next cooling tower 106 through a pipe 16 (actually, the adsorbent is guided through the thermal desorption tower 103
and cooling tower 106 can be implemented as an integrated tower).

In the cooling tower 106, air is introduced through a pipe 17, and the high-temperature adsorbent and air exchange indirect heat, and the cooled adsorbent is led to the next classifier 107 through a pipe 18. On the other hand, the heated air flows through the tube 6 as an air source for the boiler 100, joins with the air in the tube 4, and is guided through the tube 5 to the boiler 100. On the other hand, the cooled adsorbent is led to the classifier 107 from the duct 18, and the adsorbent classified into fine powder is sent to the pipe 3 from the pipe 20 as fuel for the boiler 100, where it is mixed with fuel coal from the pipe 1. Most of the cooled adsorbent is returned to the adsorption tower 101 through pipe 19,
Use in circulation. Here, in the process of circulating the adsorbent through the adsorption tower 101 and the thermal desorption regeneration tower 103, the adsorbent undergoes mechanical loss corresponding to the flow in the pipe 20 and chemical loss that evaporates from the adsorption during thermal desorption regeneration. Adsorbent corresponding to the total amount of physical and chemical loss is replenished from pipe 21 or pipe 22. When replenishing the adsorbent from the pipe 22, the adsorbent is brought into the process from outside the system, and when replenishing the adsorbent from the pipe 21, the adsorbent is produced at the process site.

That is, when making an adsorbent at a process site, if part of the fuel coal is used as the raw material coal for the adsorbent, the raw coal is led from the pipe 2 to the adsorbent manufacturing device 108, and coal other than fuel coal is used. In this case, the raw coal is introduced from the pipe 24 and led from the pipe 23 to the adsorbent manufacturing device 108. Replenishment of these depleted desulfurization agents can be carried out by the methods described in several cases. Since it is used as a source, cooling water, seawater, etc. are not required, and utility costs can be reduced, heat can be recovered, and desulfurization costs can be reduced. .

According to the present invention, air is used to cool the adsorbent that has been thermally desorbed and regenerated, and the heated air heat-exchanged here is used as air for a combustion exhaust gas generating device such as a boiler. Water, seawater, etc., and additional equipment are not required.

Furthermore, by using the heated air as an air source for a combustion exhaust gas generating device such as a boiler, the combustion efficiency of the boiler can be improved and desulfurization costs can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing is a system diagram showing a sulfur recovery dry flue gas desulfurization process according to an embodiment of the present invention.

Claims (1)

[Claims] 1. Sulfur oxides in exhaust gas discharged from a combustion exhaust gas generator are adsorbed onto an adsorbent, the adsorbent that has adsorbed the sulfur oxides is thermally desorbed and regenerated, and the regenerated adsorbent is In the dry flue gas desulfurization method for recycling, the regenerated adsorbent is cooled by air cooling and then reused as an adsorbent,
In addition, the dry desulfurization method is characterized in that air whose temperature has been increased by heat exchange for cooling the adsorbent is sent to the combustion exhaust gas generator. 2. An adsorption tower that adsorbs sulfur oxides in the exhaust gas discharged from the flue gas generator onto an adsorbent; a thermal desorption regeneration tower that thermally desorbs and regenerates the adsorbent that has adsorbed sulfur oxides in the adsorption tower; In a dry flue gas desulfurization device that recycles and uses the adsorbent regenerated in a thermal desorption regeneration tower, there is provided a cooling tower that indirectly cools the regenerated adsorbent with air, and a cooling tower that cools the adsorbent whose temperature has been lowered by cooling in the cooling tower. A dry flue gas desulfurization device characterized by being provided with a pipe line for returning to the adsorption tower and a pipe line for sending the air whose temperature has been increased by heat exchange with the adsorbent in the cooling tower to the combustion exhaust gas generator. .