Innovate UK Real Time Detection of Respirable Crystalline Silica (RCS)

The concept behind this project is based on the use of spatial light scattering (SLS) analysis and related optical technologies to enable differentiation of Respirable Crystalline Silica from other ambient dust particles. It will consist of a miniature optical particle sampling chamber that will enable RCS particles to be individually identified, counted and sized separately from the background dust. When coupled with suitable data processing electronics and software to include particle loss mechanisms, density and other factors, the completed detector unit will provide a real-time output of RCS mass concentration in the environment. Being crystalline in nature, fracking sand splinters into particles that have facetted surfaces, i.e. flat mirror-like fractures, and it is this particular characteristic of RCS dust that forms the basis of the project. When passed through an illuminating light beam (such as that from a laser), faceted particles result in scattering patterns which are highly asymmetric about the beam axis, unlike virtually all other particle morphologies. This means that the Centroid of Intensity (COI), or the 'centre of gravity' of the light pattern of an RCS particle lies a significant distance from the axis, in contrast to those of other particles which are close to it. So, by setting a discrimination radius around the axis only facetted particles will be registered. RCS particles may represent a small percentage of the total particle population so a viable sensor would need a high throughput (typically ~ 10,000/second) so calculating the COI using conventional image processing techniques is impractical. Position Sensitive Devices (PSD), offer an ideal solution being low cost and producing accurate X-Y analogue outputs defining the COI of the light falling on the chip. Thus, a simple empirically-determined 'threshold' distance of the COI from the pattern centre allows differentiation of facetted particles patterns. An additional 'orthogonal' optical measurement, such as birefringence or fluorescence, will also be incorporated to provide a high discrimination level and minimize false-positive RCS detection. The project will involve close collaboration between Trolex and the Particle Instruments Research Group at the University of Hertfordshire. The University will be responsible for the sensor technology development, the design of the detection chamber and optics, and laboratory evaluation using prepared dusts. Trolex will be responsible for producing a fieldable technology demonstrator instrument that will enable the detector output to be presented as a real-time RCS density in a real-world environment.

The use of Silica in fracking represents a risk to both workers and the environment that has not yet received much publicity in the UK. There are considerable benefits in understanding and managing the risks associated with RCS exposure. Risks surround health and safety of workers and local inhabitants. Most national regulators have a detailed awareness of the medical basis of risks and have developed permissible exposure limits (PELs) and recommended exposure limits (RELs). Proposed OSHA PEL's for RCS are estimated to protect 2.2m workers (mostly in construction, 1.85m) with the remainder in general industry including foundries and fracking. New PEL is 50ug/cum air over 8 hour day. Net benefits are estimated at between US$2.8 - 4.7 bn/yr with up to 800 lives saved/yr in the US alone across all at-risk industries. Currently the UK limit for Respirable Dust is 4mg/m3 and for RCS 0.1 mg/m3. UK legislation is currently written around personal sampling for worker exposure however area sampling in real time will still help worker safety. Fixed perimeter monitoring would warn operators if dust or RCS levels approached concern levels for pollution of neighbouring areas. Permanent records will allow reliable, low cost, compliance monitoring. Monitoring RCS in real time ensures that workers are properly protected and that current operations are compliant with existing regulations. Formulation of new regulations is also assisted. The introduction of this new technology will advance the UK's position as a technical centre of innovation and excellence in the world industry. Adoption of this technology will accelerate the growth of the company and its distributors, developing the requirement for skilled labour both in manufacture and support which will be based in the UK, producing additional tax revenue. More than 98% of the shale gas activity and potential market will be outside the UK so considerable export revenues will accrue to UK plc. The availability of this technology could speed the development of the shale gas industry. In the UK a recent IoD report estimated 74,000 jobs could be supported by the industry and its supply chain. Spending by the employees would benefit local businesses. Environmental benefits are concerned primarily with minimising risks of RCS exposure. The replacement of costly time-lapse RCS monitoring will improve the health and safety of workers on site and reduce overall cost of operation as well as allowing earlier intervention in case of operational problems.