SU921664A1 - Method of regeneration of moulding and core mixture having calcium hydroaluminate or hydrogarnet binding - Google Patents

Description

The invention relates to foundry and can be used for the regeneration of waste mixtures containing as hydroaluminates or calcium hydrogranates. The known method of regeneration of spent molding and core mixtures consists in that the developed mixture is first crushed, then placed in an aqueous solution containing 5 wt.: While the mixture is treated with ultrasound at a frequency of 25 kHz for. 0 min, until the NaOH solution boils. The sand treated in this way is washed and dried. The main disadvantage of this method is that the regeneration technology is difficult and does not allow the molding sand to be regenerated, in which it uses garnet and hydroaluminate k-alci. Such technology allows only o /: restore, the mixture in the quartz sand component. The closest to the invention according to the technical essence and the achieved result is a method of regeneration of used core and molding mixtures, which means that the used mixture undergoes crushing, separation, calcination and additional selective grinding of mineral minerals 2. However, this method is characterized by incomplete recovery in the process of regeneration. This technology does not solve the main issue - the creation of a waste-free closed technology for the use of molding and core sands. The purpose of the invention is to restore the mechanical and technological properties of the spent mixture. To achieve this goal, a method for regenerating the form 392 is proposed.

Bleaching and core blends with BflwyuiUM as hydroaluminate or calcium hydrogenate, including crushing, separating and calcining the waste mixture, which means that after crushing and separating the worked mixture is treated with water or water vapor at C and the weight ratio in the resulting slurry is solid to liquid 1: (2-5) in the cilium of 1-5 hours with vigorous stirring, followed by separation of solid sediment from the pulp and calcination, until it is partially partially dehydrated into a slurry and cooled to 18-25 C.

While the waste mixture is treated with water for 3-5 hours

Moreover, the treated mixture is treated with water vapor at 110–180 ° C under a pressure of 0.5–9 atm for 1–2.5 h.

In addition, the waste mixture is treated with water vapor, at IiSiSO C under pressure atm. within 1-1.5 hours

The essence of the described method consists in the restoration of the original CaO-AV O xS iOfj (1, 5-X) source system from the 3 CaO ALOj-xS i Оp type compound contained in the spent mixture, Kizhe used in the description as abbreviated literature) the form of the designation of these compounds, as well as the intermediate.

During the processing of the compound C ASx contained in the waste mixture with water or water vapor at 25-180 ° C, the intermediate compound CzA5x {6-2x) Hg, 0 is formed.

Specified temperature interval; The treatments are concretized depending on whether the waste mixture is treated with water or water vapor, and at what pressure it is treated with water vapor. When treated with water, the temperature of the latter is selected in the range of 25,100 ° C.

In accordance with theoretical and practical data, the rate of hydration reaction of compounds of the species increases with increasing water temperature, however, when water temperature is higher, the reaction rate does not increase significantly, therefore this temperature is optimal4 4

In terms of the economics of the process. At a water temperature of 25 ° C, the hydration process takes place at 5 hours, and at a temperature below it takes much longer time and the process becomes uneconomical. At the water temperature, the hydration process takes 3 hours, but it requires a lot of energy to maintain this water temperature due to high vaporization. It is also clear that the temperature of water above UO-C at normal pressure is unattainable.

5 Hydrochemical treatment of SLD and C ,, ASx can be carried out in the solid phase by supplying saturated steam with a temperature of IIO-ISO C. For temperatures and 180 ° С

Q is the saturated water vapor pressure of 0.5 atm and 9 atm, respectively. The choice of precisely this temperature range is due to the possibility of obtaining saturated steam with such

5 parameters at the enterprises of the metallurgical industry. When CiASx is treated with water saturated steam at a pressure of 0.5 A and m, the hydration reaction time decreases.

up to 2.5 hours. As an optimal value, water vapor should be taken.

with parameters t,, 6 MPa, as most often obtained in industrial plants. With saturated t parameters: 80C and P9 MPa, the processing time is reduced to 1 hour. If you take for hydration pairs with temperatures below 110 ° C (pressure below 0.5 MPa), the process rate decreases to 3 hours, which roughly corresponds to the time of treatment with water at 95 C. Under these conditions, it is more convenient to use hot water than rlap. Steam with a temperature above (pressure above ат atm) is not advisable because it has a low coefficient of its use, since such a pair has a high dynamic speed and the time of its contact with the mass is small.

The most rational processes of hydration of spent sand with obtaining Ca, ASx (6-2x) should be attributed autoclave treatment. In this case, steam with a temperature of 180 ° C serves as a heating agent supplied to the autoclave. At 145 ° C (pressure 3 ati) the time of complete hydration of the mixture is 59–1.5 hours, at 80 ° C (pressure 9 –ti) 1 hour. At the same time, the process of hydration of the mixture at a temperature below 145 ° C (pressure below 3 these) takes place over 2 hours and above 180 ° C (pressure above 9 these) the process becomes economically inexpedient due to the need to use expensive autoclave facilities. The optimum value of temperature and vapor pressure is determined from the given economics of the process and the actual production conditions. The above treatment is carried out at a weight ratio of solid to liquid 1: (2-5) The choice of T: W within 1: (2-5) for the hydration process is due to the need to fulfill hydrodynamic conditions. At T: L below 1: 2, the resulting pulp is practically not agitated and the hydration process lasts a considerable time (more than 10 hours). The upper limit of T: W is due to the minimum ratio that must be maintained for the subsequent operation of separating the solid from the liquid phase. For example, when you can use a filter apparatus (drum vacuum filter), and when, 5 you must already use a sump with a large separation surface, which greatly complicates the technology. The most appropriate T: L is the ratio of 1: 3, since in this case the separation of the pulp is carried out with high technical and economic indicators on drum vacuum filters. The next stage of the process is the partial dehydration of the compound CjASx (6-2x) in the composition of the spent mixture to obtain the compound Ci, ASX (l, 3-x). It should be noted that fully dehydrated CojASx compounds cannot be transferred by the action of water and water directly to partially C3A5x (1.5-x) partially dehydration compounds due to the difference in the CjASx (1,5-x) H (jO and C ,, ASx (6-2x) Noo.When treating CsAz with water or water vapor, CzA5x (6-2x) is obtained, but not CzA5x (1.5-X) only after special heat treatment from 4 (6-2x) Hg | 0 is obtained by CoA5x (G, 5th). Partially dehydration of compound C2 | ASx (6-2x) in the composition of the used mixture in accordance with the proposed method After the separation of the liquid aqueous component at, the choice of a specific calcination temperature within the specified temperature range depends on the value of the index X, i.e., the content of SiOfj B intermediate CftASj ((6-2x). Table .1 shows the optimal values of the calcination temperature depending on the value of the indicator X. At the optimum temperature, the yield of the desired form) 1,) HijO from intermediate C2ASx (6-2x) is maximum. Optimum values of the temperature of roiling depending on the magnitude of the indicator. Table 1 Taking into account that in the CzA5x intermediate connection (6-2x) the value of X leaves O to 1, it can be concluded that, at the calcination temperature lower than the lower (300 ° C) and higher than the upper () limits, the output of the required odds is CA $ x ( 1.5) decreases, and this affects the technological properties of the regenerate reagent that is obtained and impairs the economic indicators of the regeneration method. Thus, in the process of regeneration and re-use, the next cycle of transformation of mineralogical forms into a mortar takes place in the form of hydroaluminate or calcium hydrogranate, in the initial mixture for the manufacture of forms and rods, 5-X) - H, 20 - In the waste mixture, regeneration during regeneration (before heat treatment) CzA5x {6-x) in ready-to-use regenerate CzA5x (1, 5-x). In this case, a complete restoration of the remaining, mechanical and technological properties of the spent mixture is ensured and a closed waste-free process is created for the manufacture of castings using molds and rods from the mixtures with the specified one. Example. The used mixture in the amount of 10.5 kg, containing 10 kg of quartz sand and 0.5 kg of AlQ, Oi O, 2S iOj, is subjected to grinding and separation through a sieve with a size of cells of mm before passing through these cells. Then, it is mixed with 31.5 l of water (liquid: solid 4 phase 3: 1) at 95 ° C and the pulp is kept under vigorous stirring for 3 m. After that, the pulp is divided into a water containing clay component condensed product. Water from the clay component is separated on a laboratory bulk filter for subsequent regeneration. As a result of the water treatment, 10.8 kg of solid sediment is obtained, which includes 10 kg of quartz sand and 0.8 kg of calcium hydrogen garnet having the composition H ° 3 0, which is subjected to heat treatment at 350 ° C for 6 hours. 10.6 kg of a mixture of composition are obtained: 10 kg of quartz sand and 0.6 kg of dehydrated intermediate compounds of composition A1p | 0j O, 25 iO, 2 1, 3. The resulting regenerate is cooled to 25 ° C and mixed with concentrates of sulphite-yeast brew in the amount of 7.5 parts by weight, brews per 100 parts by weight of regenerate. Mixing is performed in a mixer for 2 minutes to obtain the finished mixture. Similar results were obtained when the mixture was regenerated with water vapor under a pressure of 0.5–9 atm. at 110-180 ° С, as well as water vapor under a pressure of 39 atm. at 145-180 ° C. The composition and technological properties of the regenerated mixtures are given in table 2.

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Claims (2)

tM 11, 9 From the data of Table 2 it can be seen that the mechanical and technological properties of the mixture obtained from the regenerate are almost identical to those of the mixture prepared on fresh raw materials and at the same time significantly exceed the properties of the mixture obtained on the regenerate according to the known method . The proposed method for the regeneration of mixtures with calcium in the form of hydroaluminates and calcium hydrogranates allows the creation of a closed wasteless technology, which is especially valuable in the conditions of depletion of natural reserves of molding sand. This method allows to reduce the consumption per person from 5 weight, h. up to 0.5 weight.h. (to compensate for natural losses) with repeated use, reduce the consumption of fresh quartz sand by 95 High strength and gas permeability make it possible to produce small, medium and large rods and shapes from the regenerated mixture. Claim 1. The method of regeneration of the molding and core mixture with calories calcified in the form of hydroaluminate or hydrogenate, including crushing, separation and calcination of the spent mixture. characterized in that, in order to restore the mechanical and technological properties of the spent mixture, the spent mixture after crushing and separation is treated with water or water vapor at 25-180 ° C and at a weight ratio in the resulting solid-to-liquid slurry 1: (2-5) in for 1-5 hours with vigorous stirring followed by separation of solid sediment from the pulp and calcining it at 300-410C to obtain partially dehydrated into a binder and cooling to 18-25 C. 2. The method according to claim 1, characterized in that the spent the mixture is treated water at 25-100C for 3-5h. 3. Method POP.1, which is also distinguished by the fact that the spent mixture is treated with water vapor at PO-180 ° C under a pressure of 0.5-9 MPa. within 1-2.5 hours. A method of claim 1 and 3, characterized in that the spent mixture is treated with water vapor at 145-180 ° C under a pressure of 3-9 MPa. within 1-1.5 hours. Sources of information taken into account during the examination 1. Japanese Patent No. 53-11822 4, cl. 11 A 211, published 1973. 2. USSR Author's Certificate No. 302165, cl. In 22 C 5 / OD. 1968.