Explosion Science, Prevention and Protection (Explosion Safety) Coursework, University of Birmingham

Introduction

You have started work as a process safety engineer within a multidisciplinary project team for an international yeast extract manufacturer that has recently acquired a UK production business. Your team has been informed that a new spray dryer is to be installed at the leading UK facility to replace one of the older units on the site. Information on the existing facility, originally constructed in 1989, is described in the sections below. The parent company has never operated in the UK, so they are reliant on your team’s experience to ensure the project succeeds.

Production Facility

Process Description

Yeast extract is a highly versatile ingredient used as a flavour enhancer for many foods. These include snack foods, sauces, gravies, canned soups and ready-made meals. It is supplied to customers in a powder form. This powder is produced from a liquid product being processed by a spray dryer. The yeast extract liquid is produced by growing a mass of yeast in a series of vats in a water based solution before the yeast cream is autolysed, separated, and filtered. Prior to spray drying, the material is stored in a vessel next to the spray dryer. This acts as the feed vessel for the process.

Spray dryers have 3 primary steps in their operation:

1. Atomization of a liquid feed into fine droplets.
2. Mixing these spray droplets with a heated gas stream, allowing the liquid to evaporate and
leave dried solids.
3. Dried powder is separated from the gas stream and collected via a vibro-fluid bed.

The Task

Your team has been asked to perform an independent review of the process safety of the facility to determine if the existing facility meets the requirements of current legislation and standards and to determine the requirements for the new spray dryer to be installed. The new yeast extract dryer will be replacing one that mainly produced product 1 and you have been asked to assume that no fire or explosion mitigation is currently installed.

You have been asked to review the existing facility and potential future expansions with regard to process safety. A review of occupational health and safety will be completed by a different team and is not included in your scope. Also, if the project is successful, there is a possibility that a sister spray drying facility may be built in Southern Italy or Greece.

You have been asked to submit your review to your line manager in the form of a report containing the following:

1) What process safety considerations in relation to fire and explosion have you made for the existing facility and how have you approached this? This should include methods for identifying hazards and a high-level identification of hazards alongside relevant legislation. 

2) Complete a hazardous area classification and risk assessment for the following sections in the existing facility (including the minimum required ATEX equipment specification for each zone classified). Please use the risk matrix templates from Gexcon’s supporting lectures and the material data supplied. A fully worked example should be included in the main body of the report, showing how the hazardous area classification and risk assessment has been completed, highlighting the methodology for different material types. All other HAC and risk assessment results should be summarised/ tabulated appropriately. Full calculations are NOT required for each area. 
  a. Natural gas supply (including pressure reduction) – high pressure and low pressure side.
  b. Yeast Extract spray dryers including associated equipment, fluidised bed, offtake and storage.
  c. The use of Chemical X as a cleaning product in the spray dryer including the storage and distribution.

3) What hazard control measures and mitigations (with regard to fire and explosion safety) would you consider for the process and equipment that you have evaluated and why? 

4) For the design of the sister plant:
 a. Would you make any changes to the process/site with regard to fire and explosion safety? Please justify your answer. 
 b. If hydrogen was used instead of natural gas, what impact would that have on the design of the gas supply to the burner. Focus on any process safety aspects of this change, with respect to fire and explosion hazards 
 c. What impact would the location of the sister plant have on your safety considerations if any?