DE3149413A1 - Process for the reburning of the defecation lime in the sugar industry - Google Patents

Abstract

When sugar is prepared from beets, lime (CaO) and carbon dioxide (CO2) are necessary for purifying the thin juice. This is why a lime shaft kiln is present in each sugar factory. The purification process leaves as a residue, the so-called defecation sludge, which consists essentially of CaCO3 sludge contaminated by organic components and is deposited in large sludge ponds. For reasons of economy and environmental protection, it is advantageous to regenerate this sludge, so that the demand for fresh lime can be significantly reduced. According to the invention this regeneration takes place by briquetting the sludge, fine coke formed during shaft kiln operation as waste being admixed with the briquettes. According to the invention, these briquettes are burned in a step-grate furnace.

Description

Subject: Procedure for burning back the vaginal

lime in the sugar industry.

Introduction: By leaching the sugar beet pulp with hot water the so-called thin juice is created. This is mixed with milk of lime (Ca (OH 2 + H2O) (Divorce).

This creates free acids like oxalic acid, citric acid and phosphates felled and the protein and colorants knocked down.

Excess milk of lime goes into solution as sacharat, which is released by introducing it split by carbon dioxide (CO2) and filtered from the solution as saturation sludge will. After enrichment, the so-called thick juice is created, which is filtered off is boiled off by calcium carbonates and crystallized. The filtered mud consists essentially of calcium carbonate with organic impurities. Of the Sludge is usually dumped. In view of the increasing difficulties There has been no shortage of attempts to find landfills, the calcium carbonate sludge to work up, i.e. to convert it into lime (CaO) by burning, which is around 1,100 " Can happen. The organic impurities also burn at these temperatures.

The CaO produced in this way can be dissolved in milk of lime by adding water transform. Rotary kilns, fluidized bed ovens and cyclone ovens can be used for firing to serve.

The problem with such processes, however, is that the CO concentration in the furnace exhaust gas is very low (approx. 2528) where, on the other hand, the CO concentration from one coke-heated shaft furnace is 40%.

The low CO concentration in the exhaust gas is probably the main reason9 backburning of the separating sludge on a large scale only in a few cases is practiced Another disadvantage is the high fuel costs for backburning the sheath sludge to CaO.

2) The solution according to the invention The invention avoids the above Disadvantages by using the following process steps: s) The separating sludge is dewatered mechanically (e.g. in filter presses) to such an extent that it can be granulated will.

b) The so dewatered sludge is with the coke abrasion (-10 mm) of the Shaft furnace mixed, which is ensured by suitable metering devices the coke content is constant, e.g. 5 'based on the weight of the sludge. If necessary, the coke must be crushed so that the grain size is -3 mm.

c) The Schlaem-Soks mixture turns into granules of size 15-20 mm diameter shaped; e.g. on granulating plates or in granulating drums. Under.

Under certain conditions it can be advantageous to make briquettes.

d) The granules, respectively. Briquettes are placed on a step grate oven (see picture 1) when there is a high excess of air the granules via a suitable metering device (1) and (2) to the preheating shaft (3) abandoned.

With the help of the push carriage (4.2), the granules are transported through the combustion chamber (4) promoted in such a way that small shafts between the individual push carts caused by the crossbeam (4.4). The back and forth movement the push carriage is carried out with the help of hydraulic pistons, those of one Hydraulic unit (4.6) can be operated.

Ul, gas or coal dust burners (8.1) protrude into the combustion chamber (4.7) which provide a support fire so that the temperature in the combustion chamber is kept constant e.g. at 1.100C.

The exhaust gases are transported through the individual dumps onto the push truck as indicated by (4.3), sucked in and get into the preheating shaft (3).

From there they are fed through a bag filter by a fan (9.4) (9.2), sucked a dust chamber (9.1) and pressed it into the chimney (9.3). The incurred Dust is removed with screw conveyors (9.5) from the bag filter, respectively. the dust chamber discharged and to Granulier- respectively. Briquetting facility promoted.

The granules burn essentially because of the added fuel itself, so that only a supporting fire is required. In this way, the exhaust gas have a high CO2 concentration, similar to the shaft furnace exhaust gases and can therefore be fed back to the cutting process.

The granules burned to CaO, respectively. Briquettes get into the cooler (6), which is also lined up (6.1). The cooling air is provided by a fan (8.4) via the pipeline. (8.5) blown into the shaft cooler (6). The warmed up Cooling air enters the combustion chamber (4) via the channels (8.5) and the burners (8.1). The fuel is supplied via (8.6).

The entire distillation system, including dosing, mixing and granulating is controlled from a control room (10).

The advantages of the burn-back process according to the invention are as follows: 1. The lime kiln in the sugar factory can be designed much smaller than before, since a large part of the lime is recycled.

2. The dumping of the lime sludge is largely eliminated.

3. The CO2 concentration in the exhaust gas from the burn-back system is comparable with the CO2 concentration of the shaft furnace.

4. The plant works very economically because it is essentially used as a fuel the coke abrasion from the lime shaft furnace is used.

5. Using the step grate ensures that the granules be treated very gently.

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Claims (2)

3) Claims: 1. Process for burning back calcium carbonate sludge (Scheide mud) in the production of beet sugar, characterized by the following Process steps: a) Dosed addition of fine coke to the calcium carbonate ° sludge, which was mechanically dehydrated to granulability; b) production of granules, respectively Briquettes made from this mixture; Burning of the granules, respectively. Briquettes on one Step grate oven. 2. The method according to claim 1, d.g. that the abrasion from the fine coke Xalkschatofen coke is used.