BE1004918A3 - Method for retrieving calories and acidifiers during gas and fumedecontamination - Google Patents

Abstract

The method consists in using a large quantity of fresh water as scrubbingwater, as opposed to recycled water, to treat contaminated water from fumeand gas decontamination and, after treatment, reusing said water in theproduction method. An installation comprises a scrubber (1) equipped withone or more spray manifolds (4, 5) supplied with scrubbing water composed ofa large quantity of fresh water, and connected to a flocculator (9) suppliedwith scrubbing water with its impurities from the scrubber (1) and itselfconnected to a settling tank (14), from which, firstly, clean water,separated from the impurities and conveyed to the production and, secondly,the impurities, are discharged.

Description

Process for recovering calories and acidifier During depollution of gas or smoke.

The present invention relates to the depollution of gas or smoke in various industries, and inter alia in the manufacture of beet sugar, and aims to improve the depollution process by eliminating the drawbacks of discharges and by using

The materials extracted by depollution in the manufacturing system.

The usual depollution process, being essentially focused on the elimination of dust, uses the minimum amount of water and often recycled water, resulting in a lesser elimination of C02, sulfur and calories, among other things, because all washing water will have to be processed, stored and discarded, which often poses big problems. Indeed, there is no point in cleaning up the atmosphere, if it is to pollute a river.

Currently, a first treatment of the depollution water in order to be able to recycle it is generally carried out with whitewash or caustic soda by stirring and mixing, then the water is separated from the residues by decantation. After this first treatment, these waters must be decontaminated in a depollution station, for example of the anaerobic type.

Because of all these constraints we try to put the minimum of new water in the usual depollution process.

Compared to the usual depollution process The invention is distinguished by the use of the maximum possible water, with a view to recovering the maximum of calories and of acidifier, such as CO 2 and sulfur and, at the same time, to collect the maximum of dust. This is new water as opposed to recycled water.

The process for recovering calories and acidifying during a depollution of gases or fumes according to the invention is characterized in that it consists in using as washing water a large quantity of new water, in contrast to a recycled water, to treat dirty water from the depollution of fumes or gases and, after treatment, to reuse this water in the manufacturing process.

According to the invention, the method consists in recovering, during the washing of the fumes or gases, calories with the washing water and in acidifying it with carbon dioxide and the sulfur gases, to be treated The washing water having wetted and captured the dust using a flocculant or a coagulant to allow the particles in suspension to agglomerate mutually and to be able to settle and, after separation of the impurities by settling, to use the clean water obtained hot and acid in manufacturing.

A treatment installation intended to carry out the process according to the invention is characterized in that it comprises a washer provided with one or more sprayer booms, supplied with washing water jstituted with large quantities of new water, and connected to a flocculator fed by the washing water with its impurities leaving the washer and connected itself to a decanter, from which come out on the one hand a clean water, separated from the impurities and directed to manufacturing, and on the other hand impurities.

To better understand the invention, it is now described in more detail on the basis of the appended drawing showing an embodiment of an installation for treating the drying gases of a sugar refinery, installation in which the following process is carried out. The invention.

The installation shown comprises a washer 1 provided with an inlet 2 for gases from the dryer and containing a large quantity of water vapor charged with pulp dust generally burnt.

These gases or fumes also contain the residues from the combustion of fuel oil, namely carbon dioxide (CO ^) and sulfur gases (SO ^, SO ^, SO ^).

In the distribution chamber 3 of the fumes or gases open a ramp 4, for example of eight sprayers, and a ramp 5, for example of fourteen sprayers. By these ramps is brought the washing water consisting of new water, as opposed to what is called recycled water, in very large quantities. By washing the fumes, on the one hand, the dust is wetted and captured by the washing water and, on the other hand, the washing water is heated by the calories recovered and acidified by carbon dioxide and sulfur gases .

The operation in the washer being carried out, we obtain smoke specific to +. 77 ° C, which escape to the atmosphere through the chimney 6, and black water like ink at a pH of +. 5 and a temperature of, +. 77 ° C.

This black water comes out of the washer 1 at 7 and is conveyed at 8 to a flocculation tank 9, where it is treated with a flocculant or a coagulant, introduced at 10, by an agitator 11 to allow the particles in suspension to agglomerate mutually and to be able to decant, The black water at the outlet 12 of the flocculator 9 being conveyed at 13 to a decanter 14, (here è three stages 14 ', 14 ", 14"' ', where the clean water is separated impurities, the operation can also be done by centrifugation or by a combination of the two, partially by decantation completed by centrifugation.

The clean water, obtained after this treatment in 15, is always hot and acidic and is conveyed as it is or as a mixture with other waters towards diffusion.

The impurities, obtained in 16,16 ', 16 "after the treatment in the proportion of 1% to 2% of the water in the case of a decanter and, here called sludge, are collected by slurry pumps 17 and transported in 18 to be mixed with the sugar scum, which serves as a by-product for soil improvement.

In the event that thicker sludge is to be obtained, the water can be separated from the impurities by centrifugation at the place of decantation.

Of course, the apparatus shown in the drawing is for illustrative purposes only and other devices of the same kind can be used in carrying out the process, which already makes the process advantageous on the economic plan.

The process according to the invention has great advantages. On the one hand, it allows better depollution of gases or fumes with a total absence of polluting discharge into the environment and, on the other hand, the components coming from the simple and inexpensive depollution treatment - Water clean hot and acidic and impurities - are recovered and valued in manufacturing.

Maximum recovery and better depollution are obtained with the method according to the invention while using known material.

The process is particularly advantageous economically. Or the example of a sugar refinery, which treats 10,000 t of beets per day and dries all of its pulp. This candy therefore grates +. 417 t / h of beets and _ + 375 m3 / h of water is needed to extract the sugar from these beets in the diffuser.

This water must be acidified to a constant pH between 5 and 6 and heated between 72 ° C to 78 ° C.

In general, the pulp pressing water, which still contains a little sugar and which is at + 60 ° C and acid, represents a good half of the water necessary for diffusion, ie + 200 m3 / h.

So add + _ 175 m3 / h of water. This can come from: - either condensed water from the evaporation of beet juice (water containing a little NH ^ in the proportion of _ + 800 mg / l with a pH of. + 9.5 and a temperature of + _ 45 ° C); - either water from boreholes, wells, rivers with a pH of 7 to 8 and a temperature of +. 10 ° C; - Or water having already been used for another use, for example for cooling a machine, with a pH of +. 7 to 8 and a temperature of _ + 30 ° C.

It is therefore necessary to harvest + _ 175 m3 / h of water to acidify, in general, with SO ^ but also with CO ^, H ^ SO ^, ... and to reheat with Steam from the third or fourth evaporation body. These two operations are expensive.

To acidify these diffusion waters we use for example SO ^ - This product costs +. 15 F / kg and between 200 g and 400 g of SO2 per tonne of beets are needed depending on the starting water. We get for the above-mentioned candy for 200 g / SO ^, or 3 F per tonne of beets: 0.200 X 10,000 = 2,000 kg of SO2 / day, and for an 80-day sugar companion:

2,000 X 80 = 160,000 kg of S02 i.e. 160,000 X 15 F = 2,400,000 F

To heat these diffusion waters you need j calories bringing 175 m3 / h of water from 50 ° C to 75 ° C, that is to say: 175,000 X <4t) 25 X (Cp) 1 = 4.375 .000 kcal / h, and for a campaign of 80 days of 24 hours: 4.375.000 X 24 X 80 = 8.400.000.000 kcal.

However, 1 kg of extra heavy fuel contains _ + 9.400 kcal, from which it is necessary: 8.400.000.000 = 893.617 kg of fuel.

9.400

The price of fuel being 5 F / kg, the costs of calorie intake for the campaign amount to:

893.617 X 5 = 4.468.085 F

We can therefore say that The process according to the invention applied in a sugar refinery processing 10,000 t / day of beets allows: - a gain in SO2, from two million francs to four million francs, depending on whether it is supposed to use 200 gr / SO ^ ou 400 gr / S02 per tonne of beets, a gain in calories from one million francs to four million francs, depending on the recoveries already made in the sugar refinery.

We can also add a gain due to the elimination of all the costs of a normal purification process, that is to say the neutralization of lime and soda water, water purification, taxes rejection, etc.

The process according to the invention can find various applications other than that described above, that is to say everything relating to extraction in a hot and acid medium.

Claims (5)

1. Process for recovering calories and acidifier During depollution of gases or fumes, characterized in that it consists in using as washing water a large quantity of new water, in contrast to recycled water, to treat the SaLe water from the depollution of fumes or gases and, after treatment, to reuse this water in the manufacturing process. 2. Method according to claim 1, characterized in that it consists in recovering during the washing of the fumes or gases from the calories with the washing water and in acidifying it with carbon dioxide and sulfur gases, to be treated. washing water having wetted and captured the dust using a flocculant or coagulant to allow the particles in suspension to agglomerate mutually and to be able to settle and, after separation of the impurities by settling, to use l clean water obtained hot and acid in Manufacturing. 3. Method according to claims 1 and 2, applied to the manufacture of beet sugar, characterized in that it consists in using the gas washing water to dry it ie to supply hot and acidic water to the diffuser producing l extraction of sugar beet juice. 4. Treatment installation intended to carry out the method described in one or more of claims 1 to 3, characterized in that it comprises a washer (1) provided with one or more sprayer booms (4, 5), supplied with washing water consisting of large quantities of new water, and connected to a flocculator (9) fed by the washing water with its impurities leaving the washer (1) and itself connected to a decanter (14), whence emerge, on the one hand, clean water, separated from impurities and directed to manufacturing and, on the other hand, impurities. 5. Processing installation according to claim 4, intended more particularly for the manufacture of beet sugar, characterized in that the impurities or sludge are introduced at the outlet of the decanter (14) into a by-product of the manufacture used for the 'soil amendment.