JPS60156531A - Method of desulfurizing flue gas from combustion apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for desulfurizing combustion apparatus flue gas by binding gaseous sulfur oxides to calcium.

According to the Federal Environmental Protection Act (B-Environmental Protection Act 5chG), and here in particular the Technical Standards for Maintaining Air Cleanliness (TA-Lu
ft), the operation of large industrial combustion units, such as power plants or cement kilns, requires that particulate or gaseous pollutants (e.g. dust, - (carbon oxide, sulfur dioxide, nitrogen oxide) must not be exceeded.

It is therefore necessary to use waste gas purification devices, especially for the dedusting and desulfurization of waste gases. Many industrial large-scale combustion plants generate extremely large amounts of flue gas containing relatively low concentrations of pollutants, requiring correspondingly reduced-volume waste gas purification equipment, which can be used to This results in significant research costs, followed by large investment costs, operating costs, maintenance costs and inspection costs. These costs must be borne by the resulting product. These therefore place a burden on the economy and production, competitiveness and security of the entrepreneur's position. It is therefore necessary to optimally choose the means used or suitable for the treatment and to take measures that maximize the improvement of waste gas purification technology and therefore of the environment involved.

The present invention provides a method for the flue gas desulphurization of industrial combustion equipment, such as boiler firing or cement kiln equipment, which provides an optimal and low-cost desulphurization of the flue gas. Based on basic issues.

This problem is successfully solved according to the invention if the flue gas is provided with at least partially deoxygenated cement meal as an absorbent.

In cement calciners, an at least partially deoxygenated hot cement powder is very advantageously produced as an intermediate product, which is cost-effective for processing in sufficient quantities and as an absorbent for gaseous sulfur oxides. It is extremely suitable as

It has the highest reaction activity for the conversion of sulfur oxides and calcium oxide to calcium sulfate. The external supply or preparation of further adsorbents (for example activated carbon, pure calcium oxide, milk of lime) for sulfur adsorption is therefore not considered. It is only necessary to convey cement meal containing a sufficiently high proportion of free calcium oxide into the waste gas line to be desulphurized.

In an embodiment of the invention, the deoxygenated cement meal is suspended in the flue gas stream in the form of an airborne dust cloud and separated from the flue gas stream after uptake or binding of sulfur oxides.

Thereby, the conversion of hot powder containing sulfur oxides and calcium oxide to calcium sulfate is advantageously achieved with extremely high conversion efficiency.

Furthermore, in one embodiment of the invention, the degree of deoxidation of the cement powder is at least 50%.

Already at this degree of deoxidation, a very high affinity of the coarse powder for the sulfur oxides of the flue gas is achieved, thereby achieving further desulfurization. In an embodiment of the invention, the cement hot powder is The cement hot powder is withdrawn from the conduit between the final stage of the heat exchanger and the rotary kiln inlet chamber. At this position of the heat exchanger tube, the deoxidation of the preheated feed material is maximized before the inlet of the kiln; Cement coarse powder or cement hot powder here has the highest proportion of free calcium oxide.

The removal of a partial stream of hot cement powder from the hot cement powder conduit is also easily carried out using known devices (see, for example, DE 28 15 161 A1).

In another embodiment of the invention, hot cement powder in a partially degassed suspension stream is withdrawn from the upper part of the main station gas line between the final stage of the heat exchanger and the rotary kiln. At this point, the proportion of thermally activated cement hot powder in the preheating gas stream is particularly high, so that a relatively small suspension partial gas stream is branched off, from which hot coarse powder is separated, and this is combined with sulfur oxides. added to the flue gas duct for.

In this case, obtaining a predetermined quantity of hot cement powder from the partial gas stream becomes particularly advantageous and simple.

In another embodiment of the invention, hot cement powder in a partially degassed suspension stream is withdrawn from the region of the rotary kiln inlet chamber.

This gives rise to the possibility of combining a sump for the partial withdrawal of rotary kiln waste gases with known or existing bypass lines to prevent alkali recycling. In this case, the existing partial degassing conduits, which serve for the constant withdrawal of the vaporized alkali-rich kiln gases, are also used for the purpose of withdrawal of the hot active cement powder from the flue gas desulphurization sump. Can be used.

In yet another embodiment of the invention, the extracted hot cement powder is at least partially dissolved in water. As a result, on the one hand, the branched furnace waste gas as carrier medium for the hot cement powder is very advantageously cooled to the desired temperature (corresponding to the temperature in the flue gas line by a fraction i), and on the other hand In this case, some of the free calcium oxide is converted into calcium hydroxide Oa (O
H) Move to 2.

In another embodiment of the invention, the extracted hot cement powder is added to the flue gas stream together with excess water. Due to the excess water in the flue gas stream, the conditioning of the waste gas leads to almost complete removal of pollutants as well as reacted adsorbents from the waste gas stream with little energy consumption in filter devices (e.g. electrostatic precipitators). is carried out very advantageously so that it is achieved.

In an embodiment of the invention, the skewered cement coarse powder or cement hot powder is added to the flue gas stream just before the grinding and drying device for the raw material which is preceded by the heat exchange device.

This ensures a strong mixing of the activated cement hot powder with the sulfur dioxide-containing flue gas stream in the grinding equipment, resulting in a higher efficiency of the conversion of sulfur oxides and calcium oxides to 0 calcium sulfate, and therefore less smoke. A high degree of desulfurization of the gas is achieved.

In another embodiment of the invention, the extracted hot cement powder is added to the flue gas stream before the flue gas cleaning device.

In this case, an excess of active adsorbent is used to deposit a thin active layer of reactive adsorbent on the inner surface of the filter.
This has shown that it is desirable to further combine residual SO2 components from the waste gas.

The reacted cement hot powder is removed from the filter and
Due to its high caso4 content it is suitable for addition to cement powders, for example as a bond retarder in cement mills or as an additive in plaster or binder production (stucco).

But it can be added, at least in part, to the raw materials in cement kilns.

According to the present invention, cement hot powder is preferably added as an adsorbent for flue gas desulphurization in large industrial combustion units, such as power plants or other combustion units, which are geographically close to or adjacent to cement calcining units. This opens up advantageous possibilities for carrying out waste gas desulphurization.

Agent Mitsuyoshi Ezaki Agent Mitsufumi Ezaki

Claims (1)

[Claims] 1. In a method for desulfurizing the flue gas of a combustion apparatus by binding gaseous sulfur oxide to calcium, deoxygenated coarse cement powder is added to the flue gas as an adsorbent. 2. A process according to claim 1, characterized in that the sulfur oxides are suspended in a gas and separated after absorption or binding of the sulfur oxides in the flue. (5) The method according to claim 1 or 2, wherein the degree of deoxidation of the coarse cement powder is at least 50%. 4. The method according to any one of claims 1 to 3, wherein the coarse cement powder is used for manufacturing cement. 5. The deoxygenated hot powder is drawn off in a suspended gas stream of partial degassing from a rotary kiln heat exchanger and separated from the gas stream in a separation stage. The method described in one or more of the following. 6. A method according to claim 1, wherein the deoxygenated hot powder is extracted in a partially degassed suspended gas stream from the region of the rotary kiln inlet chamber. 1. The method according to any one of claims 1 to 6, wherein at least a portion of the extracted high-temperature powder is dissolved in water. & A method according to any one of claims 1 to 6, in which the extracted hot powder is added to the flue gas stream together with excess water. 9. A process according to claim 1, in which the hot powder withdrawn is added to the flue gas stream immediately before the grinding and drying device for the raw material which precedes the heat exchange device. 10. A method according to any one of claims 1 to 9, in which the extracted hot powder is added to the flue gas stream before the flue gas purification device.