Hot Briquetted Iron (HBI) – Guide For Assessing Product Quality

Prologue

i. Introduction

Every day around the world the iron and steel industry relies on the products of IIMA members to get the job done. The IIMA Certificate of Compliance Program was created to allow the Producer Members a tool to demonstrate the quality of their products to the steel industry.

The IIMA is committed to maintaining the highest level of confidence in its testing and certification program by providing impartial and objective assessment of the quality assurance systems of its Producer Members. This commitment includes involvement to manage conflicts of interest, ensure personnel competence, and maintain confidentiality of the information while promoting openness and improving communication among members.

ii. Standards

Achieving consensus on a comprehensive set of standards through active involvement with the International Organization for Standards (ISO) has been a goal of the IIMA. The IIMA, in cooperation with its Producer Members and technology and proprietary equipment manufacturer members (Associate Members), recognizes and suggests practices, specifications, technical publications, reports, and studies that address the HBI industry and the safe use of its products. These standards and practices are the basis of the IIMA Certificate of Compliance program.

iii. Environmental Principles

The members of the IIMA are fully committed to improving the environmental compatibility of their operations and the handling, shipping, storage, and use of their products. Our members recognize their responsibility to develop and use natural resources in an environmentally sound manner while protecting the health and safety of their employees, service suppliers, and customers.

To meet these responsibilities, IIMA members pledge to manage their businesses according to ISO Standards 9001-2000, 14001-2004, and to observe local laws and regulations according with the following principles:

    To recognize community concerns for the raw materials used, products manufactured, and the processes and systems operated.

    To operate plants and facilities and handle raw material and products in such a way that protects the environment and the safety and health of employees and the public.

    To make safety, health, and environment considerations a priority in planning improvements and developing new products, processes, and practices.

    To promptly advise employees, service suppliers, and customers of significant industryrelated safety, health and environmental hazards information and to recommend protective measures.

    To counsel customers, carriers, and related parties in the safe use, transportation, and disposal of raw materials, products, and related wastes.

    To commit to reduce overall emissions and waste generation.

    To promote these principles and practices by sharing experiences and offering assistance to others who produce, handle, use, transport, or dispose of similar products.

iv. Safe Stowage and Shipment

The IIMA and its members follow international and national regulations for safe stowage and shipment of HBI, with special attention given to properly conforming to the IMSBC Code for the shipment of solid bulk cargos such as DRI (A).

Definitions & Terms

This section aims to provide some clarification for the appropriate used of the technical terms of common use in industry regarding the DRI(A) products handling.

1.1 Apparent Density

Particle density considering pores

1.2 ASTM Standards

Technical standards for a wide range of materials, products, systems, and services developed and published by ASTM International.

1.3 Bulk Density

The weight of solids, air, and water per unit volume. Bulk density is expressed in kilograms per cubic meter (kg/m3), in general. The void spaces in the cargo may be filled with air and water.

1.4 Drop Test (a.k.a. Shatter Test)

Test used to determine the physical strength of bulk materials, such as coal, coke, sinter, iron ore pellets, and HBI. Material is dropped from a certain height a number of times and the fraction of +20mm is screened out. Consequently the percentage of the material larger than 20mm is reported as the drop strength.

1.5 HBI

Hot Briquetted Iron is known as Direct Reduced Iron (A) Briquettes, hot-moulded in the IMSBC Code. HBI is produced by reducing iron oxide lumps, pellets, or fines and compressing at a temperature of at least 650°C to achieve an apparent density of at least 5.0g/cm2.

1.6 IMO

International Maritime Organization (IMO) is a United Nations agency responsible for regulating the safety of shipping in an international framework.

1.7 IMSBC Code

The International Maritime Bulk Cargoes (IMSBC) Code is published by IMO to embody the best practices for the loading and unloading of ships and informs seafarers about the risks associated with bulk cargoes.

1.8 ISO

International Standards Organization

1.9 Metallization

Percentage of total iron in HBI present as metallic iron.

1.10 True Density

Particle density without any pores

1.11 Tumble Test

Test in which material is rotated in a drum and the fraction of 6.35 mm is screened out. Consequently the percentage of the material larger than 6.35 mm is reported as the tumble strength. Furthermore, a fines fraction (e.g. less than 0.5mm) can be reported as the abrasion index.

Handling And Sampling Of HBI

2.1 Introduction

IIMA Producer Members have manufactured HBI in four different direct reduction processes: FIOR and FINMET fluid bed processes and MIDREX and HYL pellet/lump based processes. All four processes use natural gas as reductant and as fuel.

The physical and chemical properties of the HBI produced by the four processes are similar but not identical due to different feed-stocks and processing parameters. Typical HBI chemical analyses are listed in TABLE I.

Table 1 - Typical HBI Specifications

Table 1 – Typical HBI Specifications

2.2 HBI Sampling And Analysis Procedures Used

2.2.1 Objective and Field of Application

These procedures cover the HBI sampling methods used by IIMA members to perform physical and chemical analysis.

2.2.2 General

For sampling of HBI at the loading and unloading ports, the incremental sampling method is used and the following information should be taken into account:

    Tons of briquettes to be discharged – Normally the tonnage carried by vessels ranges from 15,000-50,000 tons, and vessels of this category normally have at least 5 to 7 holds.

    Size of the increment to be taken – Since the briquettes are uniform in size and a constant weight, the size increments should be calculated according to sampling method. Statistically the HBI quality has shown to be constant with respect to composition. As a result the variability is considered to be small when selecting the number of increments.

    Determination of number of increments – In order to determine how many increments, or samples, should be taken, TABLE II should be used and values should be selected from the small variation column of TABLE II.

TABLE II - Example of minimum number of increments required (n1) for desired sampling precision (ßS)  Source: Direct reduced iron and hot briquetted iron — Sampling and sample preparation ISO 10835:2007 (E)

TABLE II – Example of minimum number of increments required (n1) for desired sampling precision (ßS)
Source: Direct reduced iron and hot briquetted iron — Sampling and sample preparation ISO 10835:2007 (E)

2.2.3 Sampling Location and Method

The sampling normally should be done on the discharge belt conveyor only, not on the piles, using either an automatic sampling system or executed manually. The discharge system will have an influence on the method of sampling, and the procedure should take this into consideration.

The recommended sampling should be carried out according to the following procedure:

    The sample can be taken with the conveyor belt in service if the sampler is automatic. The conveyor must be shut down to sample manually. The location to take the sample and the procedure must to be well defined in advance, keeping in mind the safety of the personnel.

    To take the sample manually, a cut of the product will be made on the belt and a complete sample will be removed using shovel and broom to collect fines.

The samples taken will be placed in special containers designed for samples.

When sampling is finished, all containers will be transported to the laboratory to be prepared for physical and chemical analysis.

2.2.4 Calculating Increment Mass

    a. Increment Mass for Falling-Stream Sampling

    The mass of increment, m1, in kilograms, taken either mechanically or manually by a cutter-type primary sampler from the HBI stream at the discharge end of a conveyor belt is given by the equation:

    m1 = ql1/3,6vC

    where:

      q is the flow rate, in tons per hour of HBI on the conveyor belt
      l1 is the cutter aperture, in meters, of the primary sampler
      vC is the cutter speed, in meters per second, of the primary sampler

    The minimum increment mass that can be taken, while still avoiding bias, is determined by the minimum cutter aperture and the maximum cutter speed.

    b. Increment Mass for Stopped-Belt Sampling

    The mass of increment, m1, in kilograms, taken manually from a stopped belt is equal to the mass of a complete cross-section of HBI on the conveyor is given by the equation:

m1 = ql2/3,6vB

    where:

      q is the flow rate, in tons per hour of HBI on the conveyor belt
      l2 is the length of section of HBI removed from the conveyor, in meters
      vB is the speed of the conveyor belt, in meters per second

2.2.5 Calculation Example.

In order to demonstrate the use of the procedure, suppose that a total of 35,000 tons of briquettes are discharged.

    The increment mass is calculated according to 2.4.1 or 2.4.2

    For small quality variations, TABLE II shows that 35 increments should be taken

    The interval between increments will be Tonnage/(2 x n) = 35000/(2 x 35) = 500 tons

    Therefore, samples should be taken every 500 tons

The first sample can be taken at random at the beginning of the discharge, and subsequent samples should be taken at intervals equal to Tonnage at first sample + 500 tons.

The sample can be stored either in consecutively numbered containers or in a single large container with all samples.

2.2.6 Sampling Equipment

The following is the recommended equipment and tools for sample preparation and sampling of HBI:

    Containers to save prepared samples
    50 kg manual balance with large metal pan
    Sample screens of 1″, 1/2″, 3/8″, 1/4″ and 5, 80 and 100 mesh
    Primary jaw crusher that can crush to 1/2″ size
    Secondary jaw crusher that can crush to 1/4″ size
    Sample riffle type splitters of various reduction ratios
    Ring roller mill for grinding
    125 ml plastic sample containers
    Electronic balance accurate to 0.01 g
    Drying oven

2.2.7 Physical Analysis

In the physical analysis area of the laboratory, the entire sample of HBI has to be processed. This can be done either by hold or by entire cargo.

The physical analysis should consider the following:

    a. Grain Size Distribution

    The following screens should be used for the analysis: 25,4 mm; 12,7 mm; 9,525 mm; 6,35 mm and -6,35 mm (Pan) (1″, 1/2″, 3/8″, 1/4″, and -1/4” (Pan)). Some clients may request that different screens are used.

    The material that does not pass through the 25.4 mm or 1″ screen should be weighed. The rest should be screened on a lab screen sizer to determine the weight of each size.

    The briquettes used for the physical analysis should be saved for the chemical analysis.

    b. Apparent Density (minimum sample 10 briquettes)

    Dried briquettes are weighed in air, soaked in water, surface dried and weighed again: first in air and then in water. The apparent density and water absorption are determined, by calculation, from the masses obtained.

      Sampling and sample preparation shall be in accordance with ISO 10835.

      A test sample to provide at least 100 briquettes shall be obtained.

      Sieve the test sample by hand on a 40 mm test sieve to discard any – 40 mm material.

      Spread the test sample to form a single layer of briquettes, in the shape of a rectangle.

      At least 4 test portions, each of at least 6 briquettes, shall be prepared by taking at random single briquettes and placing them consecutively in 4 piles or containers.

      Take at random one of the test portions. The briquettes in the test portion may either all be tested at the same time or be tested individually in random order and the results averaged.

      Oven-dry the briquettes to constant mass at 105 C +/-5 C. Cool the test portion in air to room temperature and remove any adhering dust. Determine and record the mass (m1) of the test portion.

      Soak the dried briquettes of the test portion in a vessel containing water at a temperature of 22 C +/- 5 C. Allow the briquettes to remain submerged until all air bubbling stops.

      Remove the soak briquettes from the vessel. Let them drain momentarily and then gently surface-dry them with paper towels. Place them on a weighing device and immediately weigh. Determine and record the total mass (m2) of the test portion.

      Two methods are allowed for the determination the mass of soaked briquettes in water (ISO 15968): Testing of entire test portion – Wire suspension method (m3 , m4) and Testing individual briquettes – Wire suspension method (m4).

      The apparent density (ρa)is calculated from the following formula:

        Wire basket method – ρa = m1/(m4 – m3)
        Wire suspension method – ρa = m1/m4

Assuming density of water to be 1.0 g/cm3.

    m1 is the mass in air, in grams, of the dried briquettes;

    m3 is the apparent mass in water, in grams, of the wire suspension basket. This is equivalent to the “apparent volume” of the basket. In the case of the wire suspension method, m3is negligible;

    m4 is the apparent mass in water, in grams, of the soaked briquettes. This is equivalent to the “apparent volume” of the briquettes.

    c. Tumble and Abrasion Indices (per ISO 15967)

    The test portion is tumbled in a circular drum for a total of 200 revolutions, at 25 rpm. The product material is sieved with test sieves having square openings of 6.35 mm and 0.5 mm. The tumble index is expressed as the mass percentage of material greater than 6.35 mm, and the abrasion index as the mass percentage of material-less than 0.5mm.

      Sampling of a lot of HBI and sample preparation shall be in accordance with ISO 10835.

      A test sample of at least 70 kg, on dry basis, shall be obtained.

      Oven-dry the test sample to constant mass at 105 °C ± 5 °C and cool it to room temperature before preparation of the test portions.

      Sieve the test sample by hand on a 40 mm test sieve to discard any – 40 mm material.

      Spread the test sample on a smooth and flat plate to form a single layer of briquettes, in the shape of a rectangle.

      At least 4 test portions, each of approximately 15 kg shall be prepared by taking at random single briquettes and placing them consecutively in 4 piles or containers.

      Take at random one of the test portions, record its mass (m0) and place it in the tumble drum. Tightly fasten the door and rotate the drum at 25 rpm ± 1 rpm for a total of 200 revolutions. Stop the drum and keep the door fastened for at least 2 min before opening to allow the dust to settle.

      Remove all the material carefully from the drum and hand sieve it on the 6.35 mm and 0.5 mm sieves. Determine and record the mass of each fraction retained on 6.35 mm (m1) and 0.5 mm (m2) sieves to the nearest 0.1 g. Material lost during sieving shall be considered to be part of the minus 0.5 mm fraction.

      The tumble index (T) and abrasion index (A), expressed as percentages by mass, are calculated from the following formula:

      T = (m1 / m0) x 100
      A = [m0 – (m1 + m2)]/ m0 x 100
      m0 is the mass, in grams, of the test portion as weighed out and placed in the tumble drum;
      m1 is the mass, in grams, of the +6.35 mm fraction of the tumbled test portion;
      m2 is the mass, in grams, of the -6.35 + 0.5 mm fraction of the tumbled test portion

2.2.8 HBI Chemical Analysis

In order to do chemical analysis, the samples have to be prepared using the sequence indicated in Figure 1.

Figure 1 - Example Sampling and Sample Preparation Flowsheet Source: Direct reduced iron and hot briquetted iron — Sampling and sample preparation ISO 10835:2007 (E)

Figure 1 – Example Sampling and Sample Preparation Flowsheet
Source: Direct reduced iron and hot briquetted iron — Sampling and sample preparation ISO 10835:2007 (E)

The HBI sample is to be prepared for chemical analysis as specified below:

    1. The complete sample will be ground in the primary jaw crusher to 12.7mm (1/2″). The sample will be homogenized in all directions using a metal shovel.

    2. The sample will be split with the splitter into 4 equal parts. Three parts will be discarded and the fourth will be further ground with the secondary jaw crusher to 6.35 mm (1/4″).

    3. The sample will be homogenized with a splitter of 12.7 mm (1/2″) opening and one half will be discarded.

    4. The sample will once again be homogenized and split. The largest portion will be discarded.

    5. The smallest remaining portion will be repeatedly reduced in the splitter until a sample of 500g remains.

    6. This 500g sample will be ground in the ring-roller mill for 2 minutes to obtain a -100 mesh sample.

The prepared sample will be homogenized and split into 3 portions which will be stored in plastic containers and labeled as:

    Sample for chemical analysis- Buyer.
    Sample for chemical analysis- Seller.
    Referee Sample.

The sample then can be analyzed for chemical composition using the ISO methods shown in TABLE IV of section 3.2

2.3 Quality Loss in Storage

HBI will slowly re-oxidize or rust in storage, which results in a loss of metallic iron and metallization. The losses are higher on the outside layers of the pile, particularly on the surface layer, and diminish toward the center of the pile (see Figure 2).

Figure 2 – Effect of Weathering on HBI (Outdoor Storage)

Figure 2 – Effect of Weathering on HBI (Outdoor Storage)

ISO Standards And Recognized Testing Procedures

3.1 Introduction

This section presents the ISO Standards and internationally recognized testing procedures that, when properly applied, define the HBI and the characterization of all its properties as a manufactured product.

3.2 Product Specifications

3.2.1 ISO Product Quality Standards Followed For HBI

The ISO Chemical Standards shown in TABLE IV are the ones agreed and of common use on the HBI producing laboratories worldwide.

These standards are used not only for quality assurance by the producer but also for setting guaranties and verification by the customers.

Table IV - ISO Chemical Standards

Table IV – ISO Chemical Standards

The bromine methanol is not advised to be used on a regular basis by the producers due to human health risk, but it is useful for precision analysis on claims or clarification issues.

Due to the variety of standards and the new analytical techniques, the selection and use of a particular standard could be a matter of agreement between the producer and the customer.

3.2.2 ISO Physical Standards

TABLE V shows the industry accepted ISO standards for physical assurance of HBI quality. These tests require the agreement of producers and customers.

Table V - ISO Physical Standards

Table V – ISO Physical Standards

References

    1. ISO Standards Manuals.
    2. International Maritime Solid Bulk Cargoes Code and Supplemen.
    3. Dam, Oscar G. – Orinoco Iron Manual for the Transport, Handling and use of Orinoco Iron HBI.
    4. Dam, Oscar G., and Gibellini, Ido – Guide for The Safe Handling, Storing and Transport of DRI A (HBI). 1st Edition-HBIA 2009.
    5. Dam, Oscar G., & Ido Gibellini – Guide for The Safe Handling, Storing and Transport of DRI C (High Moisture). 1st Edition. HBIA 2009.
    6. Nuñez, Ernesto, Jaimes, Ender & Benguria, Joseba.- Orinoco Iron Quality Dpt. Modeling of the Hydrogen Emission and the Effect of the ventilation in a Hold of Boat with DRI Fines. September 2006.

(ISBN 978-0-615-57430-1)
Copyright© 2011 by HBI Association, Ltd.
This guide published by HBI Association, Ltd.

All rights reserved. No part of this guide may be used or reproduced in any manner whatsoever without the written permission of the Publisher.

2011 HBI Association Ltd.