CS207867B1 - Method of decreasing the contents of sulphur in the combustion products and relief gases of the sorptions on the basic sorbents - Google Patents

Description

(54) A method for reducing the sulfur content of flue gases and off-gases by sorption on basic sorbents

BACKGROUND OF THE INVENTION The present invention relates to a process for reducing the sulfur content of flue gases and off-gases by sorption on basic sorbents suitable for use in a rotary drum adsorber or fluidized bed reactor.

Existing dry methods of desulphurization of flue gases containing sulfur oxides are based on their reaction with alkaline earth oxides, which are formed by thermal decomposition of the respective carbonates - mostly limestones or dolomites - at temperatures above 500 ° C directly in the combustion chamber. Experience to date has shown that during the metering of carbonates into the combustion chamber, there were clogging of the rear thrusts and exchange surfaces.

Using a fluid absorber placed behind the boiler in an area above the thermal decomposition level of carbonates would eliminate this difficulty, but taking off the flue gas at the desired, relatively high temperature would significantly reduce the efficiency of existing boilers and thus adversely affect the cost of power generation. Furthermore, an absorber of this type cannot be easily connected to existing boilers.

The fluidized bed method with desulphurization elegantly combines the process of burning and binding of sulfur oxides with basic solid media. However, it is not applicable to existing boilers, since the implementation of the fuel combustion process is fundamentally different. This method therefore assumes a deep rebuilding of the existing boilers and therefore a large investment cost.

Methods based on wet absorption processes still face difficulties in disposing of large volumes of liquid and pasty waste, which can be a source of contamination of surface and groundwater when disposed of and potentially economically acceptable exploitation is problematic.

The disadvantages of the described methods are eliminated by the method of reducing the sulfur content of flue gases and exhaust gases by sorption on basic sorbents according to the invention, which consists in restoring the active sorbent surface, such as carbonates or oxides of alkaline earth metals, or by abrasion by particles of a hard inert material such as quartz, basalt or glass by movements caused by mechanical stirring or flowing gas at temperatures in the range of 110 ° C to 500 ° C.

This method also solves the difficulties associated with ensuring a virtually quantitative reaction between the basic solid phase and sulfur oxides, even at temperatures downstream of the boiler, which are caused by low diffusion rates of gaseous sulfur oxides into the desulfurization grains and by inactivation of grain surfaces by the reaction , which prevents the penetration of sulfur oxides into deeper layers below the grain surface.

In the process according to the invention, by rubbing the sorbent particles between themselves or between harder inert particles, which act on the sorbent as a mechanical disconnecting agent, the inactivating layer of sulphite and sulphate is removed from the surface of the active substance. In this way, the sorbent component with a relatively small surface is constantly activated and at the same time the utilized part is discharged together with other solid drift, for example fly ash to the separators. Here it can be captured and further processed advantageously into lightweight building materials or suitably deposited together. Agitation of the reaction mixture, either mechanically or by flowing flue gas, or a combination of both, suppresses the undesirable effect of slow diffusion of sulfur oxides to the surface of the desulfurizing agent.

In this way, by providing abrasion, the selected sorbents can be utilized virtually whilst achieving more than 90% effective flue gas and flue gas desulfurization.

The method according to the invention will be explained in more detail by the following non-limiting examples, in which, however, the apparatus schematically shown in FIGS. 1 and 2 is used for illustration.

Example 1

The desulphurization of the flue gas in a mechanical rotary drum with calcium carbonate is carried out in the apparatus of FIG. 1, where the flue gas containing sulfur oxides enters through the inlet 1. Limestone with aggregates is added to the drum 2 via the hopper 3. Here, sulfur oxides are captured by sorption on the surface of the limestone. The surface of the limestone is restored by abrasion and the fine fractions of adsorbent, aggregate, or solid debris from the combustion process leave with air to the separator 4, such as a mechanical vortex separator, fabric filter or electric separator, where it is trapped with a given efficiency. The air is free of dust particles and more than 90% of the sulfur oxides is then blown by the fan 5 into the chimney 6 and discharged into the atmosphere. This type of desulfurization was tested in a drum dryer of a mercury plant where a oil burner was placed in inlet 1. In the drum 2, the aggregate with limestone was dried. In the flue gas leaving for chimney 6, the content of all sulfur oxides was determined by chemical analysis in an amount of 0.001 to 0.005%, which at 3% of the sulfur content of the black oil, normal combustion conditions and excess air M = 3 to 5 sulfur oxides.

Example 2

The flue gas desulfurization from a power boiler in which the sulfur-containing solid or liquid fuel is combusted by means of a fluid adsorber is carried out on the apparatus shown in Fig. 2.

The flue gas from the boiler 7 goes to the lower part of the fluidized bed reactor 8, to which adsorbent is supplied via the supply line 9, optionally with the addition of an inert hard separating material, for example calcium oxide with the addition of quartz sand. The desulphurized flue gas, together with the fly ash and adsorbent used, goes to the electric separator 10 where the solids are effectively collected.

Combustion gases free from more than 90% sulfur oxides and solids, such as fly ash, spent adsorbent, abrasion inert inert materials and the like, are blown by the fan 11 into the chimney 12 and into the free atmosphere.

The process according to the invention can be used to reduce the sulfur content of the flue gas and flue gas - for example, in the crushing plant of aggregates, in the treatment of flue gas from power boilers and the like.

Claims (1)

Object of the invention Method for reducing the sulfur content of flue gases and off-gases by sorption on basic sorbents, characterized in that the active surface of the sorbent, such as alkaline earth carbonates or oxides, basic slag and rocks, is restored by mutual movements of sorbent particles with each other; formed, for example, by quartz, basalt or glass, by movements caused by mechanical stirring or flowing gas, at temperatures in the range of 110 to 500 ° C.