Document EqKdVNwVRwQVBgE6bXx05DBrn
CHLOR - ALKALI 2 1994
REACTIVE CHEMICALS REVIEW CELL AREA
DO A 046059 CONFIDENTIAL
CELL AREA CHEMICAL REACTIONS
TOTAL CEL1a
2 NaCl + 2 H2O +Current
------------------ >
MAIN REACTIONS IN ANODE; 2 NaCl
------------------ >
2 Cl-
------------------ >
MAIN REACTIONS IN CATHODE;
2 H2O + 2 e-
------------------ >
2 Na+ + 2 OH-
------------------ >
CI2 + H2 + 2 NaOH
2 Cl" + 2 Na+ CI2 + 2e'
H2 + 2 OH" 2 NaOH
Dow Confidential
DO A 046060
OONFTOFNTIAI
09/28/94
CELL AREA CHEMICAL REACTIONS
SIDE REACTIONS IN ANODE; HCI + OHCl2 + OH'
2 HOC1 + OC13 Cl2 + 6 NaOH
2 ohCI2 + H2O
HOC1 HOCI + OH-
> h2 + Cl-
> C1' + HOC1
> CI3" + C12 + h2
---------------- >
NaC103 + 5 NaCl + 3 H2O
---------------- >
------------------ > <----------------
1/2 + H2O + 2 e" HOC1 + H+ + C1"
> <------------------
H+ + OC1OC1' + H2
SIDE REACTIONS IN CATHODE; NaOCl
>
2 oci-
------------------ >
OC1' + H2O + 2 e-
>
Dow Confidential
1/2 2 + NaC1
O2 + CI2 + 2 e-
C1" + 20H_
DO A 046061 OONFTDFNTTAl
09/28/94
CELL AREA CHEMICAL REACTIONS
SODIUM BISULFITE ADDITION!
NaHS03 + NaOCl + NaOH
------------------ >
Na2S04 + NaCl + H20
SODIUM THIOSULFATE ADDITION:
Na2S203 + 4 NaOCl + 2 NaOH ------------------->
CELL WASH REACTIONS;
C02 + H20
>
<--------------------
h2co3
>
<--------------------
2 Na2S04 + 4NaCI + H20 H2CO3 pH -6.0
H+ + HCO3 pH -9.0
HC03-
> <----------------
H+ + C03= pH -11.5
Dow Confidential
DO A 04606? GONFIDFNT IA1
09/28/94
To E-201
CELL AREA
Steam from
CELL AREA RAW MATERIALS
RAW MATERIALS;
Brine
(Saturated)
Electric Current 68,000 AMPS/Circuit Maximum
HC1 16 %
Salt Slurry
PRODUCTS:
Chlorine Gas Hydrogen Gas Cell Effluent
95 %
99% 10 %
Dow Confidential
DO A 046064 CONFTDFNTI Al
07/17/92
CELL AREA
Chlorine Cells
Potential Problem: Loss of Anolyte Level
Result: Hydrogen in Chlorine Explosion; Arcing within cell
Preventative Measures:
- 2 level transmitters and 1 low level carbon probe
- 4" rectifier shutdown (2/3,2/2,171)
- backup side feed level controller
- low level alarms
low low-low
5.5" 5.0"
- 6" minimum operating head
- VRD conforming to CATC guidelines
- Level selection - high reading at >16" low reading at < 16"
- visual rounds
Potential Problem: High Series Hydrogen Pressure Result: Hydrogen in Chlorine Explosion Preventative Measures:
- 2 series relief on hydrogen stack at 4.5 - 6.0" - high H2 pressure alarm at 4" - foam drains
October 6,1994 Dow Confidential Information efp
DO A 04A065 CONFIDENTIAL
Potential Problem: High Hydrogen During Operation
Result: Hydrogen in Chlorine Explosion
Preventative Measures:
- 2" air dilution valves
- open air dilution valves between 0.5 and 1.0%
- "quickie H2" and "total gas H2" analyzers
- Troubleshooting plugged radial feeders take salt off (300 gpl max salt) look for restricted H2 outlets bad cells
- Follow CATC guideline concerning air dilution and shutdown
- series voltage alarm to detect possible clip drop voltage prob.
- clip drop profiles quarterly by cell crew
- anolyte and catholyte temperature alarms > 80 C
October 6,1994 Dow Confidential Information efp
DO A 0460A6 CONFIDENTIAL
Potential Problems Oxygen in hydrogen
Result: Explosion in hydrogen header ("pop" if minor in nature)
Incidents:
- 1993 Mod5 code problem resulted in no N2 purge on shutdown which lead to an explosion S-5/S-8 @ CA-2
- 1993 CA-2 Hydrogen log fire due to arcing at boot connection on S-8 hydrogen log caused by ground on series
- 1994 S-4 at Cl-1 plant; failure to bottle series before lowering head to stop under-cell leak.
- 1994 S-5 at Cl-1 between cell leak caused loss of catholyte level; H2 ignited above caustic trap.
Preventative Meaures:
- Nitrogen purge activated in startup/shutdown steps for the hydrogen stacks
- Low nitrogen flow alarm at 200 lb/hr; normal rate 500 lb/hr
- Nitrogen valve position alarms
- hydrogen compressor shutdown -1.5 INWA instantaneous or 1 /8 INWA for 2 seconds
- standard operating procedure to "bottle" series on all shutdowns (purges the cell with brine)
- off-line procedures for cell maintenance
- cell sprayers and housekeeping
October 6,1994 Dow Confidential Information efp
DO A 046067 CONFTDFNTTAl
LIST OF CRITICAL INSTRUMENTS IN THE CELL AREA
pFJCRIPTION
16 pH probes (2 on each series, one on east end and one on west end)
8 LSH carbon probes (1 on each series)
8 LSL carbon probes (1 on each series)
16 level transmitters (2 on each series, one on east end and one on west end)
Quickie hydrogen analyzer (Takes one stream off each series)
2 Sump l level transmitters (1 transmitter for CKT 1 side and 1 for CKT 2 side)
2 Sump 1 LSH level switches (1 switch for CKT 1 side and 1 for CKT 2 side)
2 Sump 1 LSL level switches (1 switch for CKT 1 side and 1 for CKT 2 side)
ALARM SETPOINT High - 4.3 pH Low - 1.5 pH
FREOUENCY CHECKED Weekly
High - 18 inches
Low - 4<Q inches
High - 19 inches Low Inches Low Low finches Low Shutdown -finches High - 0.5 % High High - 1 %
Monthly Monthly Monthly
Monthly
High - 87 % Low - 10 %
Semi-Annually
High - 90 %
Semi-Annually
Low - 15 %
Semi-Annually
DOW CONFIDENTIAL INFORMATION
Do A 046068 oonfidenttai
7/15/92