Powder handling in Multi-product plants ‒ Nothing left to chance
Safety data do not make your plant safe – but without safety data it is very difficult to decide whether your chemistry can be operated in your Multi-product plant. SCHNYDER Safety in Chemistry Ltd. Scientific lab and consultancy for identification of hazard potentials in chemical and thermal processes. We provide the know-how to show the hazard potentials at all steps of chemical, thermal and physical processes. We investigate existing chemical processes with regard to inherent hazards, form «runaway scenarios» related to the appropriate operation and use risk analysis as a basis for decision making that is important for management to enable selection for the best procedure. We develop safety integrated more costeffective chemical processes –based on the knowledge of the hazard potentials as basic conditions. We perform this scientific work in our well equipped laboratories with the latest infrastructure, in which y all chemical processes can be run and investigated for safety, quality and efficiency. y all chemical and physical processing steps can be investigated for safety. Safety data for • chemical process analysis • process risk analysis • safe drying temperature • adequate explosion protection • classification of stored and transported goods • evaluation of electrostatic hazards
Hazards are inherent properties of the interaction of chemicals, their processing, plant and organisation.
Why are powders Risk Factors in In order to decide whether your Multiproduct facility can control the hazards Multi-product facilities?
of the given chemistry it is necessary to understand the nature of the reactive chemicals that are processed. Reactive hazards should be evaluated using reviews on all existing and on all new processes on a periodic basis. There is Multi-product chemistry possibly is the no substitute for experience, good branch of industry that has the broadest judgement, and good data in evaluating spectrum of dangers. Liquid, solid and potential hazards. gaseous chemicals are processed partly under high pressure and at high temWhat are the inherent risks by peratures. They might be toxic, compowder handling? bustible, decomposable and explosible. Multi-product chemistry manufactures, transports and stores chemicals with technical methods that might be faulty and susceptible to faults. And all that in plants that are not designed and built for a production in question, organised divisionally of labour and controlled by personnel that make mistakes occasionally. The core business of Multi-product chemistry is to manufacture products by processing reactive chemicals. The reactivity of chemicals that makes them useful also makes them hazardous.
The profile of requirement of a chemical production process as a rule does not suit the profile of performance of a Multi-product facility. Shortcomings will be removed by appropriate completion. Those shortcomings that can not be removed economically by technical Risk analysis with powder promeasures will be bridged by organisacessing in Multi-product facilities tional measures. Very different chemical and physical Hence, the safe operation of a Multiprocesses are carried out in the same product facility will be ensured by three Multi-product installation. The control different tools of the process is to a large extent detery process engineering and apparatus mined by the particular characteristics measures of the chemical process in question and of the Multi-product facility. Consey PCS measures quently, it is crucial to understand to y organisational measures what extent the chemical process is Process engineering and apparatus meas- controlled by the plant and to what ures are fixed in Multi-product facilities. extent by the operator. The processing of powders in Multi-product plants PCS measures are fixed as well.
requires a systematic methodology to assess their risks.
in the appropriate facility. The existing «Safety Modules» are visualised.
State of the art is
Fourth, the Risk Modules, the Process Modules and the Safety Modules are overlapped. So the potential risk is visualised.
y to be aware of the hazards, which are inherent in the physical processes with powders. y to have the adeptness for the decision whether the planned Multiproduct facility can process the hazard potentials of the appropriate powder. y to implement the proper technical and organisational measures and the proper personnel selections for a safe operation of the process steps which are deduced from the knowledge of the hazard potentials.
Process Module Risk Module
Risk
Safety Modules
Visualising the inherent hazard of the proccessed powder More often than not it is impossible to evaluate the inherent hazard of a powder by studying case histories. As well it is no easy task to judge whether the operation will be safe when it is processed in a Multi-product facility. Testing work is crucial to visualise the hazard that is coupled with the treatment of a powder in a process step. The most reliable method of assessing the hazard of a powder with regards to fire, explosion and thermal decomposition is to carry out a combination of standard tests. Knowledge of the hazard of a powder involves the understanding of the tendency to react dangerously and the violence of this reaction. The tendency with which a hazardous reaction occurs varies with the external stimuli. Different types of hazard are known.
The systematic approach consists in four tasks: Firstly, visualising the inherent hazards of the powder on the base of testing results. The powder is classified into «Risk Modules».
Risk Module
Safety Modules
Process Module
Second, visualising the capabilities of the plant. The planned facility that processes the powder, is classified into «Process Modules». Third, identifying the safety measures that are required to process the powder
The tendency with which a powder y ignites by external source of flame. y
decomposes or ignites upon heating.
y decomposes exothermically at elevated temperature. y spontaneously releases heat that triggers a homogenous thermal explosion. y decomposes, ignites or explodes due to ignition sources or by mechanical stimuli such as friction or impact. y decomposes due to deflagration or detonation. Or the tendency with which a y mechanically initiated decomposition triggers a deflagration or explosion.
Powder handling in Multi-product facilities
y hot spot triggers a decomposition reaction that leads to deflagration or detonation. y shock wave initiates decomposition reaction. y
detonation propagates in the powder.
The violence of decomposition, which is closely related to the extent of actual damage, must be estimated regarding the manner with which the powder is processed. Characteristics for determining the violence of decomposition reactions are the rate of decomposition or explosion, the temperature and the pressure that is reached, the amount of gas that is developed and the heat of reaction. These characteristics are affected not only by the type of powder, but also by the presence of additives, of its quantity, the method of storage, the size of packaging unit and the type of container.
Used methodology for assessing powder processes All the safety dates that are needed to visualise the inherent fire, explosion and thermal stability hazards of the processed powder are evaluated with standardised test methods of the «Powder Pack» and «Special Tests». Tests are run for dust layer and for dispersed dust. The Powder Pack is divided into two parts: y
the «Basic Tests».
y the extent of «Additional Tests» depends on the results of the Basic Tests. The systematic methodology to visualise the inherent hazards of powder processing is the result of long experience in this matter. The approach has been proven of working together with small to big-sized chemical companies. It enables the manager to decide whether the processing of a new product ‒regarding flammability, explosion and thermal decomposition‒ will be possible with the existing plant. The following table shows the approach for visualising the inherent hazards of a powder. The tests which are represented by the green fields are performed first, with the «Basic Tests». The extent of «Additional Tests» depends on the results of the Basic Tests. This Tests are symbolised by the yellow fields.
Powder sample preparation o fineness o particle size distribution o moisture content
Dust Layer
Dispersed Dust
Dust Fire Analysis Dust Explosion Analysis
Burning Number Decompostion in open cell
Burning Number in Vacuum Rate of fire propagation Exothermic decomposition
cabability for dust explosion
Decomposition in closed cell
Minimum ignition Energy
Decomposition with permanent flushing of the sample with air
Dynamic DSC Test Dynamic Decomposition Test Long-Time Decomposition Test Smouldering gases
Maximum explosion pressure Maximum rate of presssure rise
Decomposition with permanent flushing of the sample with argon
Explosible limits
Temperature for flammable smouldering gases
Limiting oxydation concentration
Volume of smouldering gases
Deflagration Test
Ignition temperature Self Ignition Temperature
Electrostatic behaviour
Smouldering temperature
Basic Tests
Impact sensitivity Additional tests depending on the results of the Basic Tests
Friction sensitivity Electrical Powder Resistivity
Special Tests
Result of Basic Test
Additional Test
Powder shows a spontaneous decomposition
Test for Volume of Decomposition Gas (VDI 2263)
Powder is suspected to deflagrate
y Deflagration Test (VDI 2263) y Friction sensitivity
Powder shows a positive Dust Explosion Test
Special Tests for the assessment of special risks comprise the tests to answer special questions to handle the very risky powders. y Ignition Test in 400 ml Wire Basket (SIT400), VDI 2263
y Minimum Ignition Energy for raised dust (EN 13821; VDI 2263) y Minimum Ignition Temperature for raised dust (BAM) y Powder resistivity (EC 93, EN 61241)
y Storage Test in Dewar Vessels (VDI 2263)
y Maximum Explosion Pressure and KSt-Value
y Smouldering Temperature according EN 50281, in case the maximum surface temperature derived from LTT is too conservative.
y
Explosible Limits
y
Limiting Oxygen Concentration
Powder handling in Multi-product facilities
Risk Module ER Risk Module E0
Explosion Risk Modules
Risk Module DR Risk Module E3
Risk Module E2
Risk Module E1
Risk Module BR
Risk Module B0 Burning Risk Modules Risk Module B1
Powder handling Hazards Risk Module D2
Thermal Decomposition Risk Module
Risk Module T0
y Charge Accumulation Risk Module Risk Module B2
Charge Risk Modules
Deflagration Risk Modules
Risk Module D1
Risk Module T1
Risk Module D3
y Deflagration Risk Module
Risk Module C0
Risk Module C1
Risk Module D0
Risk Module C2
Classification of Risk Modules for the processed powder On the base of the testing results the inherent hazards of a processed powder are visualised by risk modules. We define the following Risk Modules:
Read more about this subject in our TOPIC 4, Powder as a Risk Factor in Multi-product facilities, Topic 4, (20 Year Anniversary SCHNYDER Safety in Chemistry Ltd.).
Due to the specific hazards of the powder, the risk modules are subdivided into risk module-sections. Each risk modulesection allows to analyse the process module that processes the powder and whether the safety modules are proper suited. The classification to a risk module may change during the process.
If your chemical process includes powder processing, then you may be interested to know whether the protection concepts of the existing plant matches the decomposition, fire and explosion hazards of the processed powder. For example for the unit operations like drying, milling, mixing and sieving. The ÂŤPowder PackÂť provides data that are necessary to identify the inherent hazards of the processed powder. The decision can be made, as to whether the processing of a new product due to its flammability, explosibility and thermal decomposability is possible with the existing system. Additional data that are necessary for the design of appropriate protective measures such as pressure relief systems or inerting systems are also provided upon request. How we handle assignments
y A solid may contain flammable soly The customer describes the scope vents before drying but not after the dryof the project which may involve probing process. lem solving services, etc. y A flammable solvent that is well bound in a solid may be released after a y A confidentiality agreement is concluded between the customer and grinding process. SCHNYDER before sensible data are y Some granulation processes start exchanged. with dry powder that is treated during y SCHNYDER will submit an offer the process with flammable solvents. which outlines the assignments under consideration of the customer's speciOverlap of Risk Modules, Pro- fic requirements.
cess Module and Safety Modules
The task now is to overlap the Risk Modules, the Process Module and the Safety Modules. In this way the potential risks of the powder processing step y Explosion Risk Module can be visualised and the decision can y Burning Risk Module be made whether the process step in the y Thermal Decomposition Risk Module process module is safe.
The analysis of chemical and thermal processes – prevention is better than prosecution.
SCHNYDER Safety in Chemistry Ltd.
Gewerbehaus Oederlin, Landstrasse 2 b 5415 Rieden bei Baden Switzerland Tel. +41-56-282 29 39 Fax +41-56-282 28 52
Office@schnyderchemsafety.com /www.schnyderchemsafety.com
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