FIELD OF THE INVENTION:
The present invention relates to a process for generation of a briquetted sinter mix for metallurgical application. In particular, it relates to a process to provide adequate strength to iron ore agglomerates to withstand the pressure and temperature conditions f the blast furnace. More particularly the invention relates to a process to produce pre-shaped sinter through briquetting of sinter base mix.
BACKGROUND OF THE INVENTION:
A large percentage of iron ore fines generated during mining and steel making process are predominantly recycled through a process called sintering. Sintering is a generic term that is used to describe a high temperature process in which mixture of raw materials is converted into a fused mass known as sinter. Sinter produced from Iron ore fines and iron bearing solid waste materials generated during steel making are widely used in blast furnaces to produce pig iron.
Sinter is produced in the temperature range of 1000 ºC to 1100ºC without complete melting of the iron ore particles. Thus, the microstructure of sinter consists largely of unreacted ore particles, bonded by fairly large amount of complex ferrite phase, as well as, partially reduced hematite or magnetite phases. The type and amount of flux and fuel can thus affect the sinter quality.
Sinters are products of re-crystallisation and partial melting of iron ore fines and slag formation. Thus the quality of sinter is highly dependent on its micro structural characteristics.
In the Sintering process, around 10% of fines are generated during the crushing of sinter cake due to insufficient fusion of iron ore with the admixed raw materials and another 20% fines are generated during transportation of sinter from sinter plant to blast furnace. Sufficient cold handling strength of sinter is required to minimise fines generation and different processes are known to used for this purpose. These fines are re-circulated in the sinter base mix thereby increasing the circulation load and drop in net productivity. To circumvent this problem, a new class of agglomerates

based on the concept on ‘sizing before firing’ has been conceptualised by the present inventors.
In the sinter there is mainly slag bonding, and sizing is done after firing. The sized product is then transported to blast furnace. Generation of sinter fines occurs during transportation. In pelletisation process, the agglomerates are pre shaped before firing. In briquetting process the briquettes are made of coarse particle relative to pellet and are cold bonded.
OBJECTS OF THE INVENTION
An objective of the invention is to reduce the generation of fines during sintering process by avoiding need for the crushing of sinter cake.
Another objective of this invention is to reduce the generation of fines during the transportation of sinter.
Yet another object of the invention is to improve the Tumbler index (T1) and reduce overall fines generation in agglomeration process
SUMMARY OF THE INVENTION
In one aspect, the invention provides a process to produce agglomerates of iron ore, the process comprising steps of preparing a green mix, then charging the green mix into briquetting machine for assimilation then heating the sample to required temperature to achieve burn through point and dislodging the agglomerated cake into the cooler.
Cylindrical briquettes were generated from the existing sinter mix and were tested for its cold strength after firing.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 –defines the summary of the process defined above in various steps and how the said process is different from the conventional process. Figure 2 – Cold strength of PBS as compared to normal sinter. Figure 3 – PBS results for different time and temperature. Figure 4 – Microstructural analysis of above samples.
DETAILED DESCRIPTION OF THE INVENTION
The raw materials required for the experiments were collected from the plant. Chemical analysis was done using ICP-AES. To get a reasonable comparison the chemistry of the mix was fixed for all the experiments and is as given in Table 1.
Methodology for pre shaped briquette preparation
In accordance with various embodiment of the disclosure, following steps are
performed.
Step 1: Sinter green mix preparation is done. The composition of the sinter green
mix is provided in Table 1 with preferable composition. The top size of the green mix
is 8 mm.
Step 2: Pre-shaping of the sinter green mix to form briquette by means of a briquetting machine for assimilation of cake using compression load of at least 2 Tons is performed.
Step 3: The briquette is heated to sintering temperature between 1275-1325 deg. C to achieve burn through point.
Step 4: The hot sinter is cooled in cooling in cooler.


In accordance with the process above mentioned, size of the briquette has strength of Tumbler index of 70-75.
Experimental Analysis:
A 1000-gm of sample that consists of base mix from sinter plant was thoroughly mixed in a steel plate from (preferable composition used from Table 1). The blend was mixed further with 18% water solution, until a uniform moist mixture was obtained which takes around 10 minutes. The moist mixture was then statically compressed in a cylindrical mould with 25 mm in diameter and 30 mm in height. The compression was performed by manual hydraulic press and the compression load was 2 Tons. Specimens were then de-moulded, and kept in open atmosphere for 24 hours. Subsequently, the briquettes were fed in rapid heating furnace and were heated to a temperature of 1300 deg centigrade for 10 minutes. The heating rate of the furnace was 20 deg per minute
Results and Discussions
Figure 1 defines the summary of the process defined above in various steps and how
the said process is different from the conventional process.
The Cylindrical briquettes of 15-25mm, using sinter green mix were generated in the lab. To understand the effect of size of raw materials, raw feed was crushed, such that the chemistry was maintained. Briquettes of 15-125 mm were generated using raw materials with top size of -12mm, -10mm, -8mm, -6mm, -3.15mm, -1mm.

Experiments were done for different combination of time and temperature. Lab scale Nabertherm furnace was used for the heating. The cold strength variations between normal sinter and the briquettes obtained by the claimed process are shown in Figure 2. It clearly shows SP#4 samples generated by the claimed process are show higher strength.
It was observed that the samples at 1300oC with 10 mins holding time were giving best results. Thus this time and temperature combination was selected for further experiments. Approx. 500 gms of samples were tested for cold strength. Due to less quantity, samples were rotated in a RDI testing drum. The results of the same are as given in Figure 3.
Microstructures corresponding to Figure 3 are shown in Figure 4 which is self-explanatory. The shape of the grains as shown in Figure 4 is regular.
Advantages
Less amount of fines generation during sintering because there is no need of crushing the sinter after firing.
Sufficient strength is obtained to iron ore sinter to withstand the disintegration that can happen during handling, transportation and blast furnace process.
Decreased percentage of return fines of the agglomerates and thus improved Tumbler index (TI) is obtained.
This is also beneficial for agglomeration process to produce agglomerates for charging in blast furnace. It also helps in higher productivity, and lesser overall solid fuel consumption.

WE CLAIM:
1. A process for producing pre-shaped briquette through briquetting of sinter
green mix, the process comprising steps of:
preparing a sinter green mix of top size 8 mm with composition Fe(t): 53.00-55.00, Al2O3 : 2.50 - 3.50, SiO2: 4.80 - 5.80, CaO: 11.50 - 13.00, MgO: 0.74 -0.80;
pre-shaping the sinter green mix to form briquette by means of briquetting machine for assimilation of cake using compression load of at least 2 Tons;
heating the briquette to temperature between 1275-1325 deg. C to achieve burn through point; and
cooling the hot briquette in cooler.
2. The process as claimed in claim 1, wherein pre-shaped briquette has the
strength with Tumbler index of 70-75.