KR840002025B1 - Cold bonding mineral polletization - Google Patents

Abstract

In massing a mineral powder, a mixt. of mineral powder and starch pellets (wheat powder starch, tapioca starch, corn starch or potato starch) of 0.5-10 wt.% is pelletized and formed into green balls. As the starch is gelatinized, the pellet is dried. The mineral powder is pelletized at high temp. without going through a combustion process, so the consumption of energy is reduced. This pellet can be treated like combustion pellets.

Description

Cold bonding method of assembling optical powder

The present invention relates to a cold bonding method of assembling particles, in particular light granules.

Here, in particular, the use of the present invention in the assembling of iron ore is described, but the use of the present invention is, of course, not limited to this. This assembly is a method for agglomeration of iron particles in order to facilitate handling or transport, and has been widely practiced since the 1950s. When the first large iron ore assembly plant in the US started operation in 1955, it produced about 6 million tons of pellets per year, but by 1975, it produced more than 60 million tons of iron ore pellets per year. Today, assembly plants are in operation in several countries, including the Commonwealth of Australia, to facilitate the use of iron ore in domestic and international transportation of iron ore and in the steel industry.

F(1,300

C)의 고온에서 연소시키는 이단계 작업으로 되어 있다. 제1단계작업에서는, 습기가 있는 분광을 수평드럼이나 대부분의 경우에는 경사진 원판에 넣고 굴려서 "그린보올"(green ball)이라고 하는 구상체(球狀體), 즉, 펠릿들을 형성한다. 이 단계에서 펠릿들은 그 다음의 연소단계에서 다루는데 지장이 없을 정도의 적당한 강도를 가져야 하며, 이러한 강도를 가질 수 있도록 최소량의 무기 또는 유기결합체를 첨가하는 경우도 가끔 있다. 제2단계작업에서는, 펠릿들을 연소시킨다. 연소는 통상적으로 가스나 기름을 연료로 사용하는 용광도, 회전가마 또는 이등화상가마에서 실시한다. 이와같이 연소된 펠릿들은 직경이 약 14-15mm의 구상체이며, 그 냉압강도는 약 500p.s.i.이다.The most widely used methods include "combustion pellets", "hardening methods" or "silver bonding methods", which first form pellets at ambient temperature and then 2,350.

F (1,300

It is a two-stage operation to burn at high temperature of C). In the first step, wet spectroscopy is rolled into a horizontal drum or, in most cases, an inclined disk, to form spherical bodies, or pellets, called " green balls. &Quot; At this stage, the pellets should have a moderate strength that will not interfere with the subsequent combustion phase, and it is sometimes necessary to add a minimum amount of inorganic or organic binder to achieve this strength. In a second step, the pellets are burned. Combustion is usually carried out in furnaces, rotary kilns or second-burners that use gas or oil as fuel. The pellets thus burned were spherical bodies of about 14-15 mm in diameter and their cold pressure was about 500 psi.

Here, the term "cold strength" is a term commonly used by those working in this field, in which spherical pellets of a predetermined diameter are placed between two flat plates such as an Instron tester, and the pellets are added to each other. A measure of the load required to break. Pellets are often handled in large quantities when loaded onto or unloaded from a railroad car, for example in a port or steel mill, and often have to withstand mass transportation.

Depending on the size of processing required by the industrial sector, not only the capital investment required to equip the equipment necessary for the combustion stage of the coarsening, but also the energy consumption is large. The cost of running these facilities alone amounts to millions of dollars annually.

As a result, various attempts have been made to find other agglomeration methods, particularly methods of eliminating the combustion stage, but have not yet obtained satisfactory methods. The general requirements for obtaining high quality agglomerates can be handled in any way, can withstand long distance transportation, have no damage if stored externally, can be degraded prematurely in steel furnaces, or fully reduced without overexpansion. This includes.

Numerous cold bonding methods have been developed using inorganic binders such as cement, lime, magnesia, clay, bentonite, etc. or organic binders such as tar, petroleum grind, wax, flour, papermaking by-products, polymers, etc. It became. Pellets obtained by these methods are usually too expensive to produce and lack strength, impact resistance or abrasion resistance. Therefore, such cold bonding methods using organic or inorganic binders have not been used for commercial mass production, nor have they received widespread recognition.

It is an object of the present invention to provide a method of producing pellets of sufficient strength that can be assembled into pellets without the need to burn them at high temperatures and can be handled, transported and used in the same way as combustion pellets.

Still another object of the present invention is to produce pellets which are not combusted but which can be recognized as a substitute for pellets produced by the combustion pellet method commercially. For pellets to be commercially recognized, the cost must be competitive and satisfactory strength, eg 300 p.s.i. It should have the above compressive strength, preferably it can be manufactured with existing green ball forming equipment, and ideally, its working conditions should not be changed very much.

These objects are achieved in a preferred embodiment of the present invention by adding raw starch to the light granules, assembling the resulting mixture according to a conventional green ball forming procedure, and then gelatinizing the starch in situ.

C에서 연소시켜야만 상업적으로 이용할 수 있다. 어떤 경우에는 벤토나이트 및/또는 점토로 구성된 결합제에 소량(예를들면, 철광석의 1/4중량%)의 젤라틴 녹말을 하였다, 그러나, 이러한 경우에도, 젤라틴 녹말은 결합합성물을 윤활하기 위하여 사용하였을 뿐이고, 연소의 대용으로서가 아니라, 연소전에 사용하였다. 이전에는 젤라틴 녹말을 연소에 갈음하는 결합제로 사용하거나, 녹말을 그 자리에서 젤라틴화 한다는 제안이 없었다.Raw starch may be added to the mineral as a binder before granulation. As mentioned above, the binder may be added in the first stage of the combustion pellet process to allow the green pellets to have strength and wear resistance to withstand the processing performed in the combustion step. However, the resulting pellet has a compressive force of about 10 pounds, which is less than 1/20 of that of the combustion pellets.

It must be combusted at C to be commercially available. In some cases, a small amount of gelatin starch (eg, 1/4 weight percent of iron ore) was added to the binder composed of bentonite and / or clay, but even in this case, gelatin starch was used only to lubricate the binding composition. It was used before combustion, not as a substitute for combustion. Previously, there was no proposal to use gelatin starch as a binder for burning or to gelatinize the starch in place.

According to a first aspect of the invention, the method of collecting the mineral particles consists of the following three steps.

(1) Assemble the mixture consisting of mineral powder and raw starch.

(2) Treat the pellets so that the starch is gelatinized.

(3) Allow the pellets to dry or to dry.

According to a second aspect of the present invention, the treatment step of the method according to the present invention includes heating the pellets according to a predetermined temperature and time in the presence of sufficient moisture for the starch to gelatinize.

According to a third aspect of the invention, the pellets according to the invention consist of mineral granules and gelatin starch.

The present invention will be described with reference to Examples.

The iron ore is ground to a size suitable for granulation, followed by the addition of some fresh starch. Starch may be used, for example, tapioca starch, corn starch or potato starch, but it has been found that flour starch generally provides stronger pellets. It has also been found that the short chain length of the starch molecules lowers the cold pressure strength obtained thereby. Starch requirements are calculated by a trade-off between the strength of the starch final pellet and the reduced value of minerals. In practice a concentration of 0.5-10%, preferably 3-7%, is a satisfactory compromise. Starch may be added to the ore before it is fed to the bowling drum or bowling disc, or may be added via bowling spraying water during assembly.

Assembly is carried out in a conventional manner with the addition of an appropriate amount of water to the ore during the process. Since the amount of water is not particularly important in the present invention, water to the extent necessary to perform satisfactory assembly is used. In practice, about 10% by weight of the ore is suitable for iron ore, but for other minerals such as diatomite, more than 100% by weight of the ore will be needed.

C의 온도로 처리하는 시판용 규격의 펠릿들은 약 10분 이내에 최대냉압 강도의 90%에 이르게 되고, 약 1시간 이내에 최대강도에도달하게 된다.After assembly, the green bowls are transferred to a suitable container and heated to gelatinize the starch. The required time and temperature depend on the source of the starch, the size of the pellets, the final required strength, the amount of water in the pellets and the nature of the ore. In the case of iron ore, when using flour starch, about 100 in high humidity atmosphere

Commercially available pellets treated at a temperature of C reach 90% of maximum cold strength within about 10 minutes and reach maximum strength within about 1 hour.

The pellets are then dried at ambient temperature, for example in air. When about 4 1/2% by weight of flour starch of the bowling ore is used in the manner described above, dry iron pellets of about 14 mm in diameter and about 400 pounds in average cold strength are produced. By leaving the dry pellets in equilibrium with the atmospheric level, in the case of severe cold strength, the dry pellets are reduced to about three quarters of the cold strength of the dry pellets. Drying the pellets again restores the original cold strength.

In another embodiment of the present invention, the gelatin starch is rounded with ore and then dried. In this case, gelatin starch may be added via bowling spray during assembly. However, the gelatin spray supply becomes viscous and difficult to handle, and moreover, surface imaging tends to cause a change while the bowling device is in operation. After the starch is introduced into the raw starch, the gelatinization on the spot is for other reasons, but the bowling parameters remain unchanged, the assembly machines can be operated conventionally, and the gelatin starch is handled. Is very advantageous because it is relatively difficult.

The strength of the product obtained through this process is sufficient as a substitute for pellets obtained by the combustion pellet method for most purposes. The gelatinization step is simple, low capital, and can be carried out in a device with lower fuel consumption than the furnace used in the combustion pellet method. Since it is unnecessary to burn in a kiln or furnace, the capital investment and operating costs are low. Significant savings compared to law. Moreover, the pellets made by the process according to the invention have a lower moisture content in the atmospheric equilibrium, for example in the case of international shipments, compared to iron ores which have been added with water to prevent dust contamination.

Gelatinization with heat is preferred, but starches may be modified to add chemicals or enzymes or to promote gelatinization, in which case a method of minimizing molecular chain shortening is preferentially adopted. This method can be applied to agglomeration of various ores and to make artificial mixtures such as organic and bean curd powders.

Cold pressure of the various optical powder pellets made by the method similar to those described for the iron ore by the present invention is shown in Table 1.

For practical purposes, the pellets only need to have sufficient strength to handle the intended application. Absolute strength is a function of pellet size and composition.

Therefore, in the case of diatomite granulation, the compressive force of the pellets is limited by the strength of the diatomite ore. In addition to binders, fiber reinforcements may be added if higher strength is required.

Assembled innoculants, hot topping steel additives, etc., have limited handling, and the compressive strength requirements are not as stringent as for iron ore granulation.

TABLE I

Claims (1)

In the method of agglomeration of mineral granules, the step of granulating a mixture composed of 0.5-10% by weight of starch granules and pellets and treating the pellets to gelatinize the starch to dry or dry the pellets Cold bonding method for assembling the included optical powder.