Ammonium Nitrate Granules Fluidized Bed Porosity
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Solution Overview
Problem
Current methods for producing explosive grade ammonium nitrate granules often result in granules with poor porosity and surface characteristics, leading to suboptimal performance in explosive compositions, such as ANFO, due to issues like moisture absorption and uneven size distribution.
Innovation Solution
The production of explosive grade ammonium nitrate granules is achieved through a fluidized bed process combining layering and agglomeration, with specific additives like alkyl naphthalene sulfonate and straight chain sulfonate salts, and controlled air conditioning to create spherical granules with microvoids and surface pores, allowing for efficient fuel oil absorption and tailored size and density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to produce ammonium nitrate granules, then production is simpler, but the granules have poor porosity and surface characteristics
Solution Approach 1:
The process is divided into two distinct fluidized bed stages: a first fluidized bed for granule formation and a second fluidized bed for cooling. This segmentation allows each stage to be optimized independently - the first bed focuses on creating proper porosity and surface characteristics through controlled granulation, while the second bed handles cooling without interfering with granule formation. This resolves the contradiction by breaking down the complex process into manageable segments that collectively achieve high manufacturing precision.
Solution Approach 2:
The invention employs parameter changes by controlling air temperature, humidity, and flow rates in the fluidized beds to optimize granule formation. Specific parameters such as air temperature (60-80°C in the second bed), relative humidity control, and fluidization air flow rates are adjusted to create the desired porosity (microvoids of 10-100 microns) and surface characteristics. This systematic parameter control enables precise manipulation of granule properties despite process complexity.
2Reliability
If granules are made with high porosity, then fuel oil absorption is improved, but granule strength may be reduced
Solution Approach 1:
The granules exhibit local quality through their specific pore structure - microvoids of 10-100 microns distributed throughout the granule interior while maintaining a smooth outer surface. This localized porosity arrangement allows fuel oil absorption to occur through controlled surface pores (4-8 microns) without compromising the overall structural integrity. The distinction between internal microvoids and external surface pores creates different functional zones within the same granule.
Solution Approach 2:
The invention utilizes porous materials by creating granules with a controlled pore structure consisting of microvoids (10-100 microns) and surface pores (4-8 microns). This porous structure is specifically designed to enhance fuel oil absorption capacity while maintaining granule strength through the layering and agglomeration process that creates a robust outer shell. The porous material approach resolves the contradiction by optimizing both absorption and strength through structural design.
3Manufacturing precision
If granules are produced with uniform size distribution, then explosive performance is improved, but production process becomes more complex
Solution Approach 1:
The invention applies preliminary action by using seeding particles in the first fluidized bed to initiate uniform granule growth. These seeds provide a consistent starting point for layering and agglomeration, ensuring that all granules develop from a uniform baseline size. This preliminary seeding step establishes size distribution control early in the process, preventing later variations and reducing the need for extensive sorting and reprocessing, thereby maintaining productivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting granules exhibit improved hardness, porosity, and flow characteristics, enabling higher or lower velocity of detonation depending on application, with enhanced performance in ANFO compositions, demonstrating increased detonation velocity and reliability compared to conventional porous prill ammonium nitrate.
Implementation Method 1
produced in a fluidized bed, the granules being formed through a combination of layering and agglomeration
Implementation Method 2
the granules being formed through a combination of layering and agglomeration
Implementation Method 3
spraying an ammonium nitrate melt containing from 92% to 96%, preferably from 93% to 95% by weight concentrate ammonium nitrate into the bed through at least one nozzle
Implementation Method 4
form ammonium nitrate granules
Implementation Method 5
cooling the ammonium nitrate granules to a temperature of 60°C to 80°C, preferably 70°C or less, in the second fluidised bed
Implementation Method 6
have surface pores ranging from 4 to 8 microns in diameter, through which fuel oil is absorbed
Implementation Method 7
surface pores ranging from 4 to 8 microns in diameter, through which fuel oil is absorbed
Data Source
AI summary
This invention relates to explosive grade ammonium nitrate porous granules. The granules are produced in a fluidized bed and are formed through a combination of layering and agglomeration to produce ammonium nitrate granules are spherical in shape, smooth, hard and dry and do not break down easily during handling. Ammonium nitrate granules of a specific size range and density can be prepared and the size range and density of the granules can be varied, depending on the application of the granules, and this has particular advantages in preparing granules for use in ANFO explosive compositions.