Method of processing filter perlite powder

FIELD: process engineering.

SUBSTANCE: invention relates to processing of heterogeneous liquid radioactive wastes, particularly, to processing of used fine abrasive filter materials and can be used for processing of waste filter perlite powder of special water treatment systems. Proposed method consists in extraction of filter perlite powder pump from storage tank, removal of excess moisture, transfer by hydrotransport, cementation, and adding ion exchange resins in amount of 10÷75% of filter perlite powder volume at density of 1÷1.5 g/cm3 to said pulp before transfer from storage tank.

EFFECT: 80-100 times decreased wear of equipment and pipelines.

2 dwg

 

The invention relates to the field of heterogeneous processing of liquid radioactive waste (LRW), in particular the reprocessing of spent fine abrasive filtering materials, and can be used in the reprocessing of spent filtrability (AF) systems specutacular.

In specutacular NPP are used upstream of the filters for the purification of aqueous media from oils and mists in which as alluvial filtering material use filtrability nuclear class. In the process of filtering surface layer filtrability polluted with sediment, hydroxides corrosion products of metals, oils and other, the resistance of the filter layer increases. When the excess pressure drop is higher than the permissible values are regeneration upstream of the filter, i.e. the removal of reclaimed filtrability. Spent filtering material hydrotransport is sent to storage tanks, where it is argued that transport water is decanted and sent for recycling. At many sites use separate storage of filtering materials of different nature, keep filtrability separately from the filtering materials of a different type. In recent years, the NPP begin to create the installation processing of the accumulated filtering materials, in particular, by cementing. However, when transporting filterprotocol certain difficulties, due to its abrasive action on the material equipment. Filtrability has a high porosity (up to 85÷90% of the volume) and low bulk density component of 0.1÷0.15 kg/DM3. In the technical specifications of the powder perlite filter (GOST 30566-98) indicated that the grain structure is determined by filtration on a sieve with a mesh size of 0.14 mm At nuclear power plants supply filtrability technical conditions with smaller grain structure. To obtain the AF nuclear class with a higher filtration capacity to colloidal impurities and high chemical stability, perform additional processing of the AF powder, consisting of ultrasonic grinding particles, and chemical processing, to create on the surface of particles of polycondensation and copolymer films. Filtrability is a natural aluminosilicate with a high silicon content. The resulting particles filtrability have needle configuration, together with the hardness of volcanic glass determines its abrasive action, leading to rapid wear of rubbing parts and decommissioning of equipment. The operating experience of the equipment cementing spent the filtering materials of the Ignalina NPP (Lithuania) showed that the failure of (the lack of pressure on the outlet) screw pump "Muan" eventough mixer cement compound occurs during the day. A known method of processing filtrability is bitumirovannaya. In practice, however, the inclusion of filtrability in bitumen practically do not produce, because it greatly reduces the fluidity of bitumen and its incorporation into the bitumen compound does not exceed 10% of the mass. on the dry filtering material.

The closest analogue of the claimed invention is a method of processing radioactive filteroperator described in the patent of Russian Federation №2435240. According to this method the pulp of filtrability is extracted from the storage tank, remove excess moisture and transported by the transport container, which is done by cementing. Filtrability chemical composition perfectly combined with cement, however, the degree of inclusion in the cement matrix is limited by its high porosity. In the Portland cement - 400 can include up to 12.5% of the mass. while maintaining sufficient mechanical strength of the cement blocks. When the mass ratio of the components is dry AF, PC-400 and water is 1:3:4, the volume of the Central Committee exceeds original OP only 15%, i.e. Kv=1,15.

The disadvantage of the nearest analogue of the method of processing radioactive waste filtrability is the complexity of the operation of the transportation hydrotransport of filtrability because of its high hardness and holchester configuration of particles filtrability that riodic to great wear and tear of transportation pipeline and pumps.

The problem solved by the invention is to reduce wear of the transport pipeline, pumps during transportation filtrability and simplifying the operation of the transport slurry.

The essence of this technical solution is that in the method of processing radioactive waste filtrability, which includes operations: extracting the pulp of filtrability of storage capacity, the removal of excess moisture, transportation hydrotransport and cementing proposed in the pulp prior to transportation from the storage tank to enter the waste ion-exchange resin in an amount of 10÷75% of the volume of filtrability at a density of 1÷1.5 g/cm3.

Conventional transportation suspension exhaust AF hydrotransport and further processing leads to abrasive wear of the equipment and pipelines. It is known that the negative impact of AF can be reduced by increasing the ratio of liquid: AF, which will increase the volume of LRW (water transport) and, therefore, increase the cost of treatment, and will also reduce the performance of the plant radioactive effluents and make it ineffective. To reduce wear of the equipment and pipelines proposed transportation and reprocessing of spent filtrability to produce together with spent IO is obmennymi resins (IOS) specutacular NPP, particles which have the correct a spherical shape with a density of 1÷1.5 g/cm3are elastic and do not have a negative impact on the equipment and pipelines. Grain of ion-exchange resins have a larger diameter and with a certain number of them, blocking the contact of grains filtrability with the surface of the equipment or pipeline, significantly reducing wear and tear.

Examples of the implementation of the proposed method with graphical demonstration of the values of the declared parameters are summarized in the table shown in figure 1, 2. The grain size of the ion is 0.35÷2.00 mm with a density of 1÷1.5 g/cm3, filtrability - 0,006÷0,030 mm Fine particles FP will occupy the free space between the grains of ion exchangers. The volumetric ratio of ion exchangers: AF is presented in figure 1, 2. Consider option 2 limit moisture stored pulp spent filtering materials in the storage containers. The moisture content of the pulp is 60÷65%, i.e. the volume ratio of T:W=1:1 (all the moisture from the pores and between the grains of the slurry). The first option (item 1, figure 1) ion - exchange resin is missing, depreciation of equipment and pipelines maximum. The second option (item 4, figure 2) is the most complete filling of the mixture of spent ion exchangers. The most dense packing of grains of ion-exchange resins (balls with the average size) is a face-centered or volume is but centered cubic packing. The volume occupied by the ion exchange resins in such packages will be 75%. When filling the entire space between the grains of resin wet filteroperator humidity 60÷65% volumetric ratio of T:W in the pulp will be 4:1. In this case, the minimum number of grains of AF will touch the surfaces of equipment and piping, any of them. It is possible to increase the content of ion exchange resins to correlation with filteroperator 90:10%, but in this case, a portion of the space between grains of ion exchangers will be used inefficiently and will remain filled with filteroperator. Usually the transportation of slurries OP and ion exchangers is carried out by hydrotransport, when the ratio of T:W compiled from 1:10 to 1:20 (item 3, figure 2). With the increase in the ratio T:W reduce abrasive action of FP on the equipment and pipelines, so the amount of insertion of spent ion-exchange resins in relation to the volume of filtrability can be reduced to 10% (item 2, figure 1). Joint transportation of spent filtrability and spent IOS is preferable also in view of their subsequent co-curing in the installation cementing heterogeneous waste.

This invention reduces the wear and tear of equipment and pipelines in the implementation of the method of processing radioactive waste filtrability in 80-100 times.

Spacepirate radioactive waste filtrability, includes extract of the pulp of filtrability from storage tank, remove excess moisture, transportation hydrotransport and cementing, characterized in that the pulp before transportation from storage tank to enter the waste ion-exchange resin in an amount of 10÷75% of the volume of filtrability at a density of 1÷1.5 g/cm3.



 

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