APPENDIX N GAS PLANT DESIGN STRATEGY

Transcription

1 APPENDIX N GAS PLANT DESIGN STRATEGY

2 COTTON SEED DISTRIBUTORS Draft HCL Chemical Gas Plant April 30, 2016 Prepared for and on behalf of CSD by G.H. MacKinven 1

3 Contents INTRODUCTION... 3 HCL ACID SUPPLY... 4 CALCIUM CHLORIDE (CACL 2 ) FEED... 4 STEAM GENERATION... 4 DISTILLATION SYSTEM... 5 GLYCOL CHILLER... 5 MOLECULAR SIEVE DRYER... 5 HCL GAS ACCUMULATION... 5 HCL GAS REABSORPTION SYSTEM... 6 DELINTING BARRELS, GAS INJECTION & EXTRACTION... 6 WASTE WATER TREATMENT... 6 APPENDIX APPENDIX APPENDIX APPENDIX APPENDIX APPENDIX APPENDIX APPENDIX APPENDIX APPENDIX APPENDIX

4 INTRODUCTION Hydrogen Chloride (HCl) gas is used to remove the remaining "lint" from the cotton planting seed (fuzzy Seed) received from the various Gins. This process is called "delinting" and involves injecting HCL gas into a barrel containing a batch of fuzzy seed. The fuzzy seed and delinting barrel is heated and the fuzzy seed is tumbled for a period of 15 minutes. The HCL gas converts the remaining lint into a dust which is then extracted from the system. The delinted seed then passes through a number of downstream processes to clean and final treatment ready for sale. Delinting of cotton seed typically occurs late March to August. The current method of producing HCL gas on site is to burn Chlorine (Cl 2 ) and Hydrogen(H 2 ) in a gas synthesis unit to produce HCL gas. Given the ever changing nature of the cotton industry in Australia, CSD is looking to introduce a different method of producing HCL gas more safely and with greater certainty of feedstock supply in order to meet market demand. The new process replaces liquid chlorine with liquid hydrochloric acid feedstock. (The same hydrochloric acid is used in many households for adjusting the ph of their swimming pools.) This new process involves distilling HCl gas from 33% liquid Hydrochloric Acid. The HCL acid and other chemicals are fed into a distillation tower which produces hot moist HCL gas which is then cooled and dried before use in the delinting process. Any HCL gas not used is reabsorbed into water and recycled back into the process so no HCL is wasted. The process generates a small amount of water containing a very low concentration of HCL acid. This slightly acidic waste water is neutralised before release into the on-site detention dam. The following is a more detailed description of the system from HCL acid supply to disposal of the waste water with more details on volumes, equipment and processes Appendix 1 shows a schematic of the overall process from raw material supply to injecting HCL into the delinting process and management of the waste water. D. Betts Pty Ltd 3

5 HCL ACID SUPPLY The 33% HCL liquid acid is able to be sourced from various suppliers including Ixom and Coogee Chemicals The acid is typically delivered in tonne bulk tankers. The bulk tankers will be unloaded in a purpose built bunded area 30m x 4m to contain any spillage. Please see appendix 2 The acid will be pumped into a 65 tonne / 56m3 storage tank which will also be housed within a bunded area with a safety shower and other safety control systems Please see appendix 3 The acid will be fed into the distillation system at a rate of 210 kg/hour CALCIUM CHLORIDE (CaCl 2 ) FEED Calcium Chloride is used in the distillation process to improve the efficiency of generation of the HCL gas. The CaCl 2 is also circulated within the distillation system where it is separated from the HCl. Calcium Chloride is a non hazardous chemical, with properties very similar to common cooking salt. The distillation system consists of an azeotrope breaker tower and flash evaporative tower (see below) and requires periodic top up. Small amounts of CaCl2 solution is fed into the distillation via a small mixing tank and pump. STEAM GENERATION Steam is injected under pressure into the azeotrope and flash evaporator reboilers at the base of the 2 towers. A packaged LPG fueled boiler will be used to generate the steam at the pressure and temperature required. The boiler will be skid mounted and clad for weather protection and is 5 metres by 2.5 metres footprint. See appendix 4 There will be a LPG tank in the area to supply gas to both the boiler and to heat the delinting barrels. This LPG tank will be positioned to comply with the required separation distance from a "protected workplace". D. Betts Pty Ltd 4

6 DISTILLATION SYSTEM The process involves mixing CaCl 2 with the HCL acid in an "azeotropic breaking tower" which is heated using pressurised steam. The CaCl 2 is used to separate the water from the HCL gas. Effectively the boiling point of the water is raised. The water containing a low concentration of HCL drops to the bottom of the tower whilst the HCL gas is "stripped" from the water and vaporised to the top of the tower. The CaCl 2 solution is heated in a second tower using pressurised steam to produce strong concentrated CaCl 2 (55%) which is fed into the azeotropic tower to react with the liquid HCL acid. This is a continuous cycle producing 70kg of HCL gas from 210kg of liquid HCL acid. The hot and moist HCL gas is passed through a primary condenser using water as the coolant. See appendix 5 for an example of a Azeotropic breaker tower and process flow diagram GLYCOL CHILLER The HCL gas is then passed through a small skid mounted glycol chiller to remove some of the water in the HCl gas stream, and also to reduce it to the temperature required prior to drying. See appendix 6 MOLECULAR SIEVE DRYER The cooled gas then passes through a molecular sieve dryer to remove the remaining moisture. See appendix 7 HCL GAS ACCUMULATION Prior to use in the delinting process the gas is "temporary stored" in a steel buffer vessel, ready to be injected every 15 minutes into the delinting barrels. Any excess HCL gas produced and not able to be consumed in delinting is returned to the gas reabsorption system. See appendix 8 D. Betts Pty Ltd 5

7 HCL GAS REABSORPTION SYSTEM The HCL distillation system is a continuous process and not designed to be turned on and off. This means during the delinting batch cycles any excess HCL gas produced will be reabsorbed into water and fed back into the distillation system, so there is no wastage of HCL gas produced. The re absorption process can occur from both before and after the drying stage. See appendix 9 DELINTING BARRELS, GAS INJECTION & EXTRACTION There will be 2 delinting barrels in the new delinting plant. These barrels will hold approximately 750 kg of fuzzy seed. Batches of fuzzy seed are dried and fed into the barrels. The barrels are heated using LPG as fuel, and HCL gas is injected from the gas accumulation tank. The barrels are rotated and the fuzzy seed is tumbled for approximately 15 minutes to remove the remaining lint. The HCL gas is extracted from the barrels and passed through a caustic scrubber. See appendix 10 WASTE WATER TREATMENT An output from the distillation process is a small amount of waste water which is separated out of the feed HCL. This contains <1% of HCL acid and some salt. Approximately 140kg per hour of the waste water will be generated at full capacity. The waste water will be pumped into 1 of 2 industrial grade poly tanks where the ph will be adjusted using Soda Ash, tested and the large majority of the treated water will be pumped into a 125,000 litre above ground tank that will be used for irrigating plants and gardens around the facility. The remainder will be recycled for use within the absorption process. One tank will be used for filling whilst the other one is being treated once full. See appendix 11 D. Betts Pty Ltd 6

8 APPENDIX 1 Schematic of the HCL gas plant from raw material supply to injection into the delinting barrels is separately provided (due to size). D. Betts Pty Ltd 7

9 APPENDIX 2 The following photo shows a typical bulk chemical tanker. A 30m x 4m concrete bund will be constructed and lined to contain any HCL acid spillage. D. Betts Pty Ltd 8

10 APPENDIX 3 Hydrochloric acid bulk storage tank... D. Betts Pty Ltd 9

11 APPENDIX 4 LPG fueled high pressure boiler internals & exterior cladding D. Betts Pty Ltd 10

12 APPENDIX 5 HCL Azeotrope & flash evaporator towers with reboilers D. Betts Pty Ltd 11

13 APPENDIX 6 Typical Glycol Chiller unit D. Betts Pty Ltd 12

14 APPENDIX 7 Please see attached diagram of the dryer... D. Betts Pty Ltd 13

15 APPENDIX 8 Gas accumulation tank... D. Betts Pty Ltd 14

16 APPENDIX 9 HCL gas absorption system... D. Betts Pty Ltd 15

17 APPENDIX 10 Please see attached diagram of the delinting barrels... D. Betts Pty Ltd 16

18 APPENDIX 11 Please see attached diagram of a typical industrial grade water tank... D. Betts Pty Ltd 17

19 CSD HCL gas production - Option 2 HCL Scrubber HCL azeotrope breaker system HCL gas absorption system Mersen Gas Accumulation system - current & new HCL gas injection - current & new Gas accumulation system - current 2540mm industrial poly tank HCL gas injection - current 30 minutes supply/capacity = 5 m3 HCL gas is injected at atmospheric pressure 5 m3 capacity = 2 x 2.5 m3 delinting cycles Approx. 2.5 m3 per batch Gas accumulation system - new Lined steel tank to withstand 2-3 bar of pressure 30 mins supply/capacity = 4 x 2.5m3 = 10 m3 New HCL injection system HCL gas to be injected at 2-3 bar pressure?m3 at 2-3 bar presssure to be determined Hot moist HCL gas 33% liquid HCL acid supply HCL storage tank Cooling Tower under pressure Nitrogen cylinder or generator 2 x delinting barrels - Ixom Inkorr to source BOC, Other - Coogee 38T road tanker recommended 52 cubic metre FRP tank 5040 kg / day (8 months 24/7) 65 tonne = 13 days inventory Tanker has pump to transfer into storage tank High & low level indicators Remote telemetry to supplier Safety shower 210 kg/hour Mersen Dryer 70 kg/hour Dry, non corrosive gas Molecular sieve Moist cooled HCL gas dryer Waste water treatment tanks under pressure Mersen Strongform 125,000 litre water tank for irrigation Bunded area ( tanker volume + 10%) Bunded area (65t tank + 10%) Concrete with impervious liner Concrete with impervious liner 30m x 4m x 0.3m 8m x 8m x 1m Steam 70kg / hour of HCL gas = 140kg of waste water 3360kg of water per 24 period LPG Hazchem 1789 < 1% HCL 130 litres per hour 2R Trace amounts of CaCl2 Class 8 corrosive Low PH 30,000 litres ( 10m x 2m) Condensate 2 x 10,000 litre Industrial grade poly tanks with agitator 960 days capacity Low PH Chemical dosage system (eg Soda Ash) AS 3780:2008 LPG Tank Treat in batches, test and release to drainage system HP Boiler Chiller "storage and handling of corrosive substances" Elgas or Origin 12 bar Frequency of release into drainage system TBC LPG required for Delinting as well East Coast Steam Glycol chiller Concrete with impervious liner 0.5m3/hour CaCl2 Mixing tank & pump 5m x 5m x 1m Thermal Engineering, Mayekawa, other Periodic replacement only Mersen to supply specs Others to supply D. Betts Pty Ltd 30/04/2016