Waste Water Treatment Utilising Sprays and Atomisation Techniques in GTL Plant

Transcription

1 Waste Water Treatment Utilising Sprays and Atomisation Techniques in GTL Plant Professor Ghasem Nasr Chair in Mechanical Engineering and Innovation Head of Petroleum and Mechanical & Gas Engineering Director of Spray and Petroleum Research Groups University of Salford Manchester 9 th August

2 Outlines Conversion of Natural Gas To Liquids (GTL) GTL Process Waste-water production and Neutralisation Current Waste-water Treatment in GTL Plant Conventional Water Treatment Unit Proposed Waste water Treatment Unit utilising SA techniques Proof of Concept (PoC) Results Concluding Remarks 2

3 CONVERSION OF NATURAL GAS TO LIQUIDS WHAT IS GTL? Gas-to-Liquid process is a chemical process for conversion of natural gas into high-value hydrocarbon liquids such as methanol, diesel, and specialty chemicals/waxes 3

4 ) CONVERSION OF NATURAL GAS TO LIQUIDS (cont ) GTL PROCESS Four distinct steps are required to convert natural gas into liquid fuels: 1. Natural gas purification 2. Synthesis gas production (Reforming) 3. Fischer-Tropsch process 4. Hydro-cracking of synthetic crude 4

5 CONVERSION OF NATURAL GAS TO LIQUIDS (cont ) Reforming reaction CH 4 + H 2 O CO + 3H 2 CO + H 2 O CO 2 + H 2 (Carbon dioxide) Fischer-Tropsch reaction CO + 2H 2 -(CH 2 )- + H 2 O (waste water) Reforming reactions produce large volume of carbon dioxide, while Fischer-Tropsch reaction produces large volume of waste-water. 5

6 Current Waste-water Treatment in GTL Plant Skid Unit Basin Unit The conventional method involves the injection of imported sulphuric acid (corrosive) into the wastewater treatment basin for ph control of the alkaline waste-water before the water is discharged into the environment. 6

7 Conventional Wastewater Treatment Unit Distilled Water Inlet Acid Transfer Pump Acid Delivery from Truck From Reformer (CO 2 ) & Fischer Tropsch Reactor (H 2 O): Waste Gas & Water Inlet Waste Gas without CO 2 Out to Reformer Waste Water from other Sources Acid Dosing Pump Absorber Stripper Treated Water Discharge Amine + CO 2 + Waste Water Amine Return to Absorber CO 2 + Waste Water Waste Water

8 Proposed Waste water Treatment Unit utilising SA techniques From Reformer (CO 2 ) & Fischer Tropsch Reactor (H 2 O): Waste Gas & Water Inlet Waste Gas without CO 2 Out to Reformer Waste Water from other Sources Absorber Stripper Treated Water Discharge With By Product, Sodium Contents, for Further Applications Waste Water Amine Return to Absorber CO 2 + Waste Water Amine + CO 2 + Waste Water

9 Proof of Concept (PoC): (1)Waste Water treatment experimental setup Gas atomiser Waste-water treatment experimental setup (1) Full-cone atomiser Design of the 2mm holes, pipe sparger 9

10 Proof of Concept (PoC), cont : (2) Experimental setup for CO 2 Bubbles characterisation Synchroniser Camera Gas Atomiser PIV Laser Laser Beam Processor Perspex tank CO 2 bubble(s) CO2 Supply 10

11 Results (cont ): Using PIV for CO 2 bubbles characterisation setup (2) Velocity distributions for Gas atomiser and pipe spargers Drop Size distributions at various water level using Gas atomiser 11

12 Results (cont ): Using PIV for CO 2 bubbles characterisation setup (2) Increase in bubble velocity increases with CO 2 diffusion coefficient, while the coefficient decreases with increase in bubble drop size. 12

13 Results (cont ): Using PIV for CO 2 bubbles characterisation setup (2) Effects of bubble velocity on diffusivity Effects of bubble diameter on diffusivity 13

14 Proof of Concept (PoC): (1)Waste Water treatment experimental setup Gas atomiser Waste-water treatment experimental setup (1) Full-cone atomiser Design of the 2mm holes, pipe sparger 14

15 Results: Using waste water treatment setup (1) Effects of waste-water volume on CO 2 consumptions. Linear relationship is observed. Increase in effluent increases the consumption of carbon dioxide. 15

16 Results (cont ):Using waste water treatment setup (1) Neutralisation time for different spray nozzles: Gas atomiser achieved 12.8 min, pipe sparger 14.0 min and full cone atomiser 15.4 min. Neutralisation time increase with temperature (Exothermic reaction) 16

17 Cumulative Cashflow (M$) Results (cont ): Economic Analysis The payback period of the modified process is 3.4 years while that of the original process is 4.0 years Saving $MM Time (yrs) Existing Plant With CO2 Recovery New Plant WithOut CO2 Recovery 17

18 Results (cont ): Economic Analysis The higher the plant capacity the higher cash flow using SA technique 18

19 Concluding Remarks The gas atomiser produced superior neutralisation (12.8 min) than the pipe sparger (14.0 min) and full-cone atomiser (15.4 min) Gas atomiser produced smaller bubbles than pipe sparger and full-cone atomiser Smaller bubbles diffuse faster into the alkaline waste-water, thereby increasing the rate of neutralisation The volume of carbon dioxide consumed increases with increase in effluent volume Neutralisation time increases with increase in temperature (exothermic reaction) At least 80% of the daily carbon dioxide production, otherwise emitted to the atmosphere, used in the treatment process (reduction of carbon footprint) $MM saving can be achieved using the SA system The proposed system currently under development /commercialisation by multi-national companies 19