SU971829A2 - Process for recovering lime from lime slurry - Google Patents

Description

The invention relates to a technique for the regeneration of lime from limestone ishams, in particular the filter cake of sugar production.

According to the main auth. 941,328 is known a method for regenerating lime from limestone sludge, mainly a filter cake of sugar production, including spraying a portion of the sludge with heat from the flue gas exhaust gases and disposing of the waste gas after drying to clean the diffusion sugar production, spray drying the rest of the mill in a separate unit autonomous supply of fuel, mixing the dried material, roasting the mixture and cooling the resulting lime. At the same time, the content of carbon dioxide in exhaust gases is 30-50% 13.

The disadvantage of this method is that when spray drying a filter cake, a stream of high-temperature gases with a temperature above 200 ° C and heating of the material in the upper part of the calcining unit at a temperature of 200-500 ° C causes the decomposition of organic compounds in the filter cake in an amount of 5-13 % with the release of harmful volatile compounds. At the same time, the exhaust gases containing these harmful lags: volatile compounds, in the process of saturation, contaminate the purified diffusion juice and dissolve in it, which ultimately impairs the quality of sugar. Therefore, the presence of decomposition products in the form of harmful impurities is not allowed by the technological requirements for the saturation gas.

The fact of the presence of harmful volatile impurities in the saturation gas at the corresponding temperature of heat treatment was revealed during the experiments. During the experiments, the filter cake of the sugar refinery is subjected to heat treatment

20 at various temperatures.

The chemical composition of the sediment, wt.%: SiOii 1.08; AljOj 0.26; Re70ZO, 58; CaCOj 82.75; MgCOj 0.42; SOj 1,3, organic compounds 13.61

25

The composition of the exhaust gases is monitored by the chromatographic method (gas chromatograph Gazokhrom-3101).

The results of experiments carried out at different temperatures are listed in the table. Heat treatment temperature, ° C

WITH,

Other compounds not identified during the analysis: Decomposition products of the organic component of sugar production waste, noted in the gas phase, vol.%

3.42

330 0.76 0.08 0.067

1.52 4.28 900 30.4 When the filtration sludge is heated in the temperature range 200500, the organic compounding raw material decomposes with the release of harmful: volatile gases {CO, etc. As for this, decomposition occurs without burning organic matter. The aim of the invention is the elimination of harmful impurities in the gas saturation. The goal is achieved by the fact that the spray drying of the sludge is carried out at 100200 ° C. In the indicated temperature range, during the drying of the sludge, decomposition of the organic matter does not occur and the emission of harmful light volatile compounds does not occur. A - supply to the temperature zone of 550-1000 ° C leads to complete combustion 4, 2

5.6

4.38

0.85

0.4

0.4% of the organic part of the precipitate without the evolution of harmful gases. The drawing shows the technological scheme of lime regeneration from limestone waste from sugar production. An example. Lime waste from the sugar industry (filter cake) is fed to the mash 1 and diluted with water to a moisture content of 45%. The chemical composition of limestone waste, wt.%: SiOa 1.08; 0.26; 0/53; CaCOj 82.75; MgCOj 0.42; SOg, 1.3, organic compounds 13.61. The sludge prepared from the filter cake is divided into two streams, each with a volume of 5Q wt.%; and pumps through pipelines 2 and 3 under a pressure of 20-25 atm, fed to centrifugal nozzles 4 and 5. Using centrifugal mechanical nozzles, one stream of sludge is sawn in dryer 6 and the other in dryer 7, In spray dryer 7, sludge is dried by heat-removing gases from the cyclones of the vortex furnace 8, which are fed directly to the spray gun. The drying of the second stream of sludge in the dryer 6 is carried out by the autonomous supply of heat carrier from the burners 9 and 10. In this case, the heat carrier is also supplied to the spray. Due to this, in both dryers, the temperature in the drying zone is 120-140 ° C. This prevents the decomposition of the organic matter from the formation of harmful volatile compounds and the release of these harmful impurities in the gas saturation. Sludge drying in both dryers is carried out simultaneously.

The dried powdered material with the prevailing granule size (200-600) of YuM from the bottom of each of the dryers through chutes 11 and 12 is simultaneously fed into the zone with a temperature of 950-1000 ° C in a cyclone-vortex kiln. Fuel 13 is fed into the kiln by means of burners 14. When released into the temperature zone of 950-1000 ° C, the organic part of the filter cake is burned without the formation of easily volatile harmful compounds (CO, etc.). At the same time, the heat released from the combustion of organic matter allows a slight decrease in fuel consumption (by 4–5%) for decarbonating carbonate compounds.

In the cyclone kiln, the carbonation part of the raw material is de-carbonated to form calcium oxide and carbon dioxide.

The resulting lime from the bottom of the kiln enters the refrigerator 15, is cooled and supplied through chutes 16 to the finished product warehouse.

Exhaust gases 17 from drying 7 are cleaned from PE) Shea in the scrubber 18 and fed to the cleaning of the diffusion juice in the saturator 19. The concentration of CO2 in the saturation gas is 30-33%.

Using the proposed method of lime regeneration from limestone waste from sugar production, compared with the known method, eliminates harmful impurities in the saturation gas, reduces fuel consumption by 4-5% due to the use of heat from burning the organic part of the raw material.

Claims (1)

Invention Formula 25 The method of lime regeneration from lime sludge, mainly filtration sediment of sugar production, according to the author. No. 941328, which is characterized by the fact that, in order to eliminate harmful impurities in the saturation gas, the spray drying of the sludge is carried out at 100-200 ° C. Sources of information taken into account in the examination of 35 1, USSR Author's Certificate No. 941328, cl. C 04 B 1/02, 1977 (prototype).