### DCN 97.21321001.08



## Results of High Velocity Tests at Tampa Electric Company’s Big Bend 4 FGD System

Topical Report

DE-AC22-92PC91338

Prepared for:

U.S. Department of Energy Pittsburgh Energy Technology Center P.O. Box 10940 Pittsburgh, PA 15236

Prepared by:

David P. DeKraker Radian International LLC P.O. Box 201088 Austin, TX 78720-1088

October 15, 1997

### iii 

## Disclaimer

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United State Government or any agency thereof.

### v 

## Table of Contents

1.0 Introduction ................................................................................................................ ........1-1

2.0 Summary ..................................................................................................................... ........2-1

3.0 Test Conditions and Results..............................................................................................3-1 3.1 Test Approach ............................................................................................................... ...3-1 3.2 Test Measurements........................................................................................................... 3-5 3.2.1 Flue Gas Sampling ...................................................................................................3-5 3.2.2 Slurry Sampling and Chemical Analyses .................................................................3-6 3.3 Test Results ................................................................................................................ ......3-6 3.3.1 Mist Eliminator ........................................................................................................3-6 3.3.2 FGD System Performance Tests...............................................................................3-8 3.3.3 Analytical Results for Slurry Samples....................................................................3-10 3.3.4 Other Process Data................................................................................................3-17 3.3.5 Long-Term High Velocity Testing ..........................................................................3-18

APPENDIX A: ANALYTICAL DATA ................................................................................................ A-1

### vii 

## List of Figures

Figure 3-1. Recycle Slurry Pump Configuration..........................................................................3-2 Figure 3-2. Mist Eliminator Gas Velocity and Carryover Measurement Locations ....................3-4 Figure 3-3. Effect of Gas Velocity on SO 2 

### Removal .................................................................3-11 Figure 3-4. Effect of DBA Concentration on SO 2 

### Removal ......................................................3-12 Figure 3-5. Effect of pH on Quench Calcium Sulfite Relative Saturation.................................3-14 Figure 3-6. Effect of pH on Limestone Utilization ....................................................................3-16



## List of Tables

Table 3-1. High-Velocity Test Plan............................................................................................. ..3-3 Table 3-2. Slurry Sampling and Chemical Analyses ...................................................................3-6 Table 3-3. Mist Eliminator Velocity and Carryover Results........................................................3-7
Table 3-4. SO 2 

### Removal Efficiency Test Results ........................................................................3-8 Table 3-5. Comparison of Radian and TECo Calcium Carbonate Analyses .............................3-18 Table 3-6. Settling Test Results ............................................................................................... ..3-18

### 1-1 

## 1.0 Introduction

Based on the results of DOE-sponsored testing of DBA additive at Big Bend Station during November, 1992, Tampa Electric Company (TECo) has successfully completed modifications to treat flue gas from 445 MW Unit 3 as well as that from 485 MW Unit 4 in the original Unit 4 flue gas desulfurization (FGD) system. Currently, the integrated Unit 3 and 4 FGD system is treating twice the design amount of flue gas by operating all four modules (instead of three) at a maximum flue gas velocity of about 10 to 11 ft/s. This velocity is about 50% greater than the original design velocity.

Recent tests at EPRI’s Environmental Control Technology Center (ECTC) and by others have shown that operation at higher flue gas velocity improves mass transfer effectiveness. EPRI is currently evaluating an advanced limestone FGD system that is designed to operate at an absorber velocity of 18 ft/s. Tampa Electric is now considering scrubbing flue gas from 445 MW Unit 2 as well as Units 3 and 4 in the existing FGD system. Integrating Unit 2 into the FGD system would increase the absorber flue gas velocity to about 16 ft/s, or about double the original design value.

In order to evaluate the feasibility of integrating Unit 2 into the Big Bend FGD system, TECo has modified a single module of the FGD system to permit operation at flue gas velocities as high as 17 ft/s. This report describes results of additional tests to evaluate the SO 2 

### removal capability of the modified test module at high flue gas velocity.

Two sections follow this introduction: Section 2 provides a summary of the test results, and Section 3 provides details of the testing and results. Lab data are presented in Appendix A.

### 2-1 

## 2.0 Summary

Tests were conducted at the Big Bend Station on May 27 through June 6, 1997, to determine the feasibility of scrubbing gas from an additional boiler (Unit 2) in the existing FGD system. Testing was accomplished by increasing the gas flow through the D absorber tower and measuring the performance of this module. Key performance aspects evaluated during the testing include mist eliminator performance, SO 2 

### removal efficiency, oxidation of absorbed SO 2 

### , and limestone utilization (and its impact on gypsum purity). Oxidation and limestone utilization performance characteristics are especially important at Big Bend, since the station sells its gypsum byproduct commercially and must meet gypsum purity specifications.

Mist eliminator performance was assessed using a Phase Doppler Particle Analyzer (PDPA) probe to measure gas velocity and carryover through the mist eliminator. These tests showed that the existing mist eliminators could handle a gas velocity of up to 13.5 ft/s without excessive carryover. This falls short of the 16.5 ft/s which would occur if gas from Unit 2 was scrubbed in the existing absorbers. However, mist eliminator vendors reportedly have more advanced mist eliminator designs which are capable of handling the increased gas velocity. The advanced mist eliminator designs have not been tested at Big Bend, but assuming they perform as well as vendors claim, mist eliminator performance should not be an obstacle to scrubbing the flue gas from an additional unit in the existing FGD system absorbers.

SO 2 

### removal performance was measured during short-term tests at gas velocities up to 15 ft/s and in longer-term tests at gas velocities up to 13.5 ft/s. Dibasic acid (DBA) was added to the test module as a performance additive during all of these tests. The results of these tests indicate that it is possible to achieve high SO 2 

### removal efficiencies at the higher gas velocities. Removal efficiency tended to increase as gas velocity increased, a result that is consistent with other data from laboratory- and full-scale testing. In particular, a removal efficiency of 99% was measured at the highest gas velocity tested, 15 ft/s. Thus the ability to achieve adequate SO 2 

### removal while scrubbing flue gas from an additional unit should not be a problem.

The FGD system at Big Bend operates in a forced oxidation mode to produce a gypsum byproduct that is used as a feedstock for producing wallboard. Achieving compete oxidation of
the SO 2 

### removed is an important part of meeting the gypsum purity specifications. Oxidation efficiency is normally determined by measuring the composition of the solids produced in the FGD system. However, the tests performed were mostly short-term, and did not allow time for the solids

### 2-2 composition to come to steady state. Oxidation was instead assessed by looking at liquid phase chemistry, specifically, the calcium sulfite relative saturation. The calcium sulfite relative saturation was consistently less than 1.0 in the upper loop; this is an indicator of complete oxidation in this loop. On the other hand, in the lower loop the calcium sulfite relative saturation frequently increased to above 1.0. This indicates that a mixture of calcium sulfite hemihydrate and gypsum solids could be precipitated within this loop, and that oxidation was not complete. The high relative saturations occurred only at high lower loop pH. This suggests that complete oxidation could be achieved in the lower loop if the pH consistently remained low. Maintaining lower pH values would require minimizing the amount of calcium carbonate carried into the lower loop from the upper loop. Additional testing would be required to determine how to best do this on an ongoing basis. One possible solution would be absorber modifications to reduce slurry carry-up from the lower loop to the upper loop, thus minimizing the amount of upper-loop slurry that has to be feed to the lower loop to maintain slurry levels. Another would be to operate the upper loop with less excess calcium carbonate (higher limestone utilization) in the recirculating slurry.

Calcium carbonate concentration, especially in the lower loop, is also important because of its direct impact on gypsum byproduct purity. Calcium carbonate concentration is commonly reported in terms of limestone utilization: high limestone utilization indicates a low calcium carbonate concentration. The limestone utilization was generally high during the testing. However, during three tests (Tests 3, 7 and 8) the limestone utilizations were low enough that the lower loop calcium carbonate concentrations exceeded the value allowed by the gypsum purity specification (1.5% CaCO 3 

### maximum). During Tests 7 and 8, the low utilization was thought to be due to a blinding episode induced by the rapid addition of DBA to the absorber. Though the mechanism for this blinding is not well understood, blinding has been observed at other FGD systems when DBA is added to a scrubber rapidly. Since rapid addition of DBA was related to this short-term testing and would not typically occur during normal operation, the blinding which occurred during these two tests should not be a concern. The cause of the low utilization during Test 3 was not obvious, although plant personnel indicated that incidents of low limestone utilization recur occasionally during normal operation. Further testing is warranted to determine if it is possible to consistently avoid a repeat of the low utilization observed during this test.

Results from this program suggest that the analytical accuracy of the on-site calcium carbonate measurements should be verified: these measurements are important because they are used to determine if the gypsum byproduct meets its purity specification. A comparison of the test sample analyses conducted off site and the daily on-site analyses showed that the on-site analyses consistently measured higher calcium carbonate concentrations. Since these two types of samples

### 2-3 were collected at different times during the day, some differences are to be expected. However, the consistently higher results obtained in the daily on-site analyses suggest that there could be some bias in the measurement method. This could easily be checked by splitting samples for comparison
of results with one or more outside labs.

In summary, this test program did not conclusively determine whether or not gas from Unit 2 could be successfully scrubbed in the existing FGD system on a continuing basis. The ability to
achieve sufficient SO 2 

### removal, perhaps the most important aspect of scrubber performance, does not appear to be a concern. However, the sulfite oxidation and limestone utilization performance did not consistently meet the requirements of the gypsum byproduct purity specifications. Operational changes to improve the oxidation and limestone utilization performance were identified, but there was not sufficient time during the test program to make and test these changes.

### 3-1 

## 3.0 Test Conditions and Results

3.1 Test Approach The Big Bend FGD system uses dual-loop, countercurrent absorbers with packing in the upper loop. The system was originally configured with the upper-loop slurry recycle pumps feeding a common manifold to deliver slurry to three internal spray levels (see Figure 3-1). Two of the upper-loop pumps were in service during normal operation; they delivered a total slurry flow of approximately 30,000 gpm to give an upper-loop liquid to gas (L/G) ratio of 65 (gpm per thousand acfm treated) and an overall L/G of 87.

The FGD system was subsequently modified to scrub both Units 3 and 4. To scrub this additional flue gas, all four absorber modules are operated (no spare now), DBA is used as a performance additive (DBA is a mixture of adipic, glutaric, and succinic acids), and the absorber slurry piping was modified. The latter included revisions so that all three pumps would be in service, with pumps #1 and #3 providing slurry to the header above the packing and pump #2 providing slurry below the packing. This revision is also shown in Figure 3-1.

Prior to this most recent test program, additional modifications were made to one absorber module (Module D) to permit the scrubbing of additional gas. These included:

• Installing a larger booster fan motor and fan rotor;

• Replacing the upper-loop nozzles to increase liquid flow, to maintain liquid-to-gas ratio (L/G) at the high gas velocity conditions;

• Improving the upper-loop drain bowl capacity by installing a vortex breaker and extending the depth of the drain in the recycle tank;

• Upgrading the upper-loop hydrocyclones to control upper-loop density;

• Increasing the capacity of the upper-loop oxidation air headers; and

• Increasing the flow rate of the mist eliminator wash system.

Based on pump power calculations and pump performance curves, each of the three upperloop recycle pumps provides a flow of about 15,000 gpm. The lower-loop recycle pumps and piping were not modified. The total slurry flow to the lower loop was previously measured at about 10,000 gpm. With these changes, the overall L/G for the scrubber would be approximately 56 at the gas

### Upper-Loo p Pumps Lower-Loo p Pumps

Upper-Loo p Pumps Lower-Loo p Pumps



### Figur e 3-1

. Recycl e Slurr y Pum p Configuration Origina l Configuration

Curren t Configuration

3-2

### 3-3 flow expected if the FGD system were modified to scrub Unit 2 as well (16.5 ft/sec gas velocity). This L/G is about 35% lower than the original design value.

Some changes were also made to the Module D operating and control strategy. Previously, the upper-loop recycle tank level was fixed by overflow into the lower-loop tank and the upper-loop density was controlled by directing the hydroclone underflow either back to the upper loop or to the lower loop. With the higher oxidation air flow, the upper-loop recycle tank operating level had to be decreased from the normal overflow level of 26 ft to 21 ft. The tank level is no longer fixed by overflow, and is now controlled by directing all of the hydroclone underflow to the lower loop, and opening or closing the hydroclone feed valve to control level. The upper-loop density is not controlled and is allowed to vary with the amount of SO 2 

### removal.

Table 3-1 shows the test plan for the high-velocity tests. The tests began with two days of mist eliminator performance measurements. Mist eliminator performance was expected to be the limiting factor in high-velocity absorber operation. At high velocity, mist droplets that are collected on the chevron mist eliminator blades can be stripped from the blades and reentrained by the flue gas before they can drain back into the absorber.

Table 3-1. High-Velocity Test Plan

Test Objective Duration Velocity (ft/s) DBA (mg/L) ME-1 Traverse mist eliminator to locate high-velocity

areas 1 day 12 Normal (1000)

ME-2 Measure reentrainment to establish maximum sustainable operating velocity 1 day Variable Normal

ME-3 Measure reentrainment at maximum sustainable operating velocity 4 hrs. 13.5 Normal

1 Measure system performance at normal velocity 2 days Normal (10.5) Normal 2, 3, 4 Measure SO 2 removal versus velocity 2 hrs. 10.5, 13, 16 Normal 5 Measure FGD system performance at maximum sustainable velocity 2 days 13.5 Normal

6, 7, 8 Measure SO 2 removal versus DBA concentration 2 hrs. 13.5 1000, 1500, 2000



### Mist eliminator performance was monitored by a test crew from Koch Engineering using their Phase Doppler Particle Analyzer (PDPA), which measures mist droplet size and velocity using an optical laser technique. The PDPA probe was traversed along two cables suspended about two feet above the upper mist eliminator stage. Figure 3-2 shows the location of the test cables relative
to the absorber module cross section.2 ft 5 ft 8 ft 1 1 ft 1 4 ft 1 7 ft



### Figur e 3-2

. Mis t Eliminato r Ga s Velocit y an d Carryove r Measuremen t Locations

3-4

### 3-5 During the first test day (Test ME-1), the module was operated at a nominal flue gas velocity of 12 ft/s, and the module was traversed using the PDPA. The objective of this test was to examine the velocity profile through the mist eliminator to locate areas of locally high velocity. During the second test day (Test ME-2), the PDPA probe was fixed at the highest-velocity location and the flue gas velocity was increased incrementally until reentrained droplets were detected. During the third test day (Test ME-3), the absorber module was operated at the highest velocity that could be sustained without reentrainment during the previous test, and the module was traversed with the PDPA probe to verify the single-point results.

Following the mist eliminator testing, the remaining tests were designed primarily to examine the effects of absorber flue gas velocity on system performance. Two types of tests were done. Three two-day tests were done to enable complete evaluation of absorber performance and slurry chemistry at different steady-state conditions. The first two-day test (Test 1) was run at normal operating conditions (11 ft/s absorber velocity, 1000 mg/L DBA, 4.5 to 4.7 lb/mm Btu
inlet SO 2 

### ). For the second two-day test (Test 5), the absorber flue gas velocity was increased to about 13.5 ft/s, which was the maximum sustainable operating velocity with the existing mist eliminator configuration. For the third two-day test, the velocity was maintained at 13.5 ft/s, and
the inlet SO 2 

### was increased from the normal 4.5 lb/mm Btu to 6.1 lb/mm Btu by switching the coal fired in the boilers. These conditions were intended to evaluate absorber chemistry under the higher SO 2 

### loading that would be encountered with the normal fuel at velocities of 16 ft/sec or
greater.

Two groups of three two-hour tests were done to measure changes in absorber SO 2 

### removal efficiency with changes in either flue gas velocity or DBA concentration. For Tests 2, 3, and 4, the absorber flue gas velocity was set at 10, 13, and 16 ft/s, respectively, with other conditions remaining constant. For Tests 6, 7, and 8, the velocity was maintained at 13.5 ft/s and the DBA concentration was set at 1000, 1500, and 2000 mg/L, respectively.

3.2 Test Measurements Test measurements included flue gas sampling and analyses, slurry sampling and analyses, and process data obtained from on-line monitors.

3.2.1 Flue Gas Sampling
SO 2 

### removal efficiency for the absorber module was measured by continuous emissions monitors (CEMs). A certified monitor was already in place to measure inlet SO 2 

### concentration for the Unit 4 FGD system. Results from this CEM were available on line through the plant data

### 3-6 acquisition s y stem. The SO 2 

### concentration at the abs o rber outlet was measured b y a crew from
TECo ’ s Central Testing Laborato r y using a portable CEM. The absorber module outlet duct was traversed with the CEM probe and the results for the 24 points were averaged to calculate the
outlet SO 2 

### concentration.

3.2. 2 Slurr y Sampling and Chemical A nal y ses Table 3-2 summarizes the slur r y sampli n g and analyt i cal sc h edule for t h e tests. Each o f the samples desig n ated in the table i n cludes a sample from both the lower-loop and upper-loop
slurr y ta n ks. For each sample, slur r y pH was meas u red at the s ample points using a p o rtable pH
meter. F o r the two-d a y t ests, the two sets of samples were ta k en duri n g the afternoon o f the
second test d a y

. Table 3-2. Slurr y Sampling and Chemical A nal y ses

Test Perfo r m ance Indicators Nu m ber of S a m ples Liquid Analyses Solid Analyses
1 S O 2 r e m ov a l, utiliz a tion oxidati o n, g y psu m R

. S., chloride balance, solids properties 2 pH, Ca, Mg, Na, Cl, SO 3 , SO 4 , CO 3 , D B A Wt.% solids, acid insolubles, Ca, M g, SO 3 , SO 4 , CO 3 , SEM 2, 3

, 4 SO 2 r e m ov a l 1 pH, DBA Wt.% solids, CO 3 5 S O 2 r e m ov a l, utiliz a tion oxidati o n, g y psu m R

. S., chloride balance, solids properties 2 pH, Ca, Mg, Na, Cl, SO 3 , SO 4 , CO 3 , D B A Wt.% solids, acid insolubles, Ca, M g, SO 3 , SO 4 , CO 3 , SEM 6, 7
, 8 SO 2 r e m ov a l 1 pH, DBA Wt.% solids, CO 3



### Complete liquid and solid ana l y ses were done for samp l es from the two-d a y tests. Results
were used to calcu l ate important process performance parameters includin g limestone utilization, sulfite oxidation and g y psum relative saturation. Settling tests were also done with samples from
the two-d a y tests, and scanni n g electron microscopy was used to e x amine the size and shape o f
the g y psum b y prod u ct.

For the short- t erm tests, during which SO 2 

### removal efficie n c y was measured, s amples

were ana l y z ed on l y for liquid-phase DBA concentration and solid-pha s e carbonate (limestone) content, both of which affect removal efficie n c y

.

3. 3 Test Results

3.3. 1 Mist Elimi n ator The mist eliminator tests were performed to determine the maximum velocit y at which
the D absorber could be o p era t ed without e x perienci n g e x cessive car r y o v er. This was d etermined

### 3-7 through flue gas veloci t y and mist car r y over measurements made b y Koch Engineering using the Phase Doppler Particle Ana l y z er (PDPA); results from the testing are summarized in Table 3-3.

Table 3-3. Mist Eliminato r Velocit y and Carr y over Results

Test Date PDPA Lens ( m m ) Distance fr o m Wall (ft) Traverse Line Velocity (ft/s) Carryover (gr/acf)

ME1 5/28/97 100 2 Ce n ter 11.9 0.00 0 31 ME1 5/28/97 100 5 Ce n ter 11.6 0.01 6 28 ME1 5/28/97 100 8 Ce n ter 11.8 0.00 0 57 ME1 5/28/97 100 11 Ce n ter 12.0 0.00 0 34 ME1 5/28/97 100 14 Ce n ter 13.0 0.01 7 46 ME1 5/28/97 100 17 Ce n ter 14.0 0.00 0 38 ME1 5/28/97 100 2 L e f t 11.4 0.00 3 73 ME1 5/28/97 100 5 L e f t 11.6 0.00 3 51 ME1 5/28/97 100 8 L e f t 11.0 0.02 0 94 ME1 5/28/97 100 11 L e f t 11.2 0.00 0 74 ME1 5/28/97 100 14 L e f t 11.3 0.00 1 27 ME1 A verages 11.9 0.006 ME2 5/29/97 300 17 Ce n ter 13.6 2.02e

- 6 ME2 5/29/97 300 17 Ce n ter 13.6 1.10e

- 5 ME2 5/29/97 300 17 Ce n ter 14.0 0.00 1 89 ME2 5/29/97 300 17 Ce n ter 16.0 0.03 1 14

ME3 5/30/97 300 5 Ce n ter 12.0 4.71e

- 5 ME3 5/30/97 300 8 Ce n ter 13.4 0.00 0 39 ME3 5/30/97 300 11 Ce n ter 12.6 2.68e

- 6 ME3 5/30/97 300 14 Ce n ter 14.0 0.00 9 20 ME3 5/30/97 300 17 Ce n ter 15.2 9.82e

- 5 ME3 A verages 13.4 0.00195



### The first series o f tests (Test Series ME 1 ) was d esig n ed to obtain an a v erage veloci t y and

car r y over rate for the tower and also to identi f y the location of the hi g hest flue g as veloci t y

. Measurement d ata collected alo n g two tra v erse lines in the tower (F i gure 3 -2) showed an a v erage

car r y o v er rate of 0.006 gr / acf at an a v erage superficial vel o ci t y of 11.9 ft/s at the mist eliminator, resulting in a unit ra t e of about 9 x 10 -5 

### gpm/ft 2 

### . These tests also showed that the h i ghest vel o ci t y within the tower occ u rred at the cen t er, where the v eloci t y was ro u gh l y 20% h i g h er than the

average.

The second series of tests (Test Series ME2) was des i gned to de t ermine the a v erage flue

gas v eloci t y at which carry ov er b ecame e x cessive. F o r this test series, the PDPA probe was
located at the center o f the tower (the h i ghest veloci t y location), and meas u rements were then made at a several gas velocities. These tests showed that increased car r y over rates be g an to occur

### 3-8 at average vel o cities grea t er than 13.5 ft/s. The test d ata also indicated t h at large d roplets (indicative of mist eliminator reentrainment) began to be seen at velocities exceeding 13.5 ft/s. Allowing for a 15% area red u ction due to support structure and wash h eaders, and assumi n g that
the center v eloci t y was 20% h i g h er than the average v eloci t y , this limit corresponds to a mist
eliminator “breakt h ro u gh” vel o ci t y of about 19 ft/s, which agrees well with the e x pected performance of this mist eliminator t y pe (Munters T272/T271).

The third series of t ests (Test Series ME-3) was a partial traver s e of the mist eliminator with the flue gas veloci t y set at about 13.5 ft/s. This series of tests was intended to confirm the results of test ME2, that the mist eliminators do have satisfacto r y performance at a gas veloci t y of 13.5 ft/s. Results of this test series showed that an a v erage car r y o v er rate of 0.0019 gr / acf occurred at a gas veloci t y of 13.4 ft/s. This performa n ce was considered to be r i ght at the “edge”
at which car r y over beco m es signif i cant (ba s ed on car r y o v er rate and the p rese n ce of l arge diameter droplets which are suggestive of re-en t rainment from the mist eliminators) and was thus
selected as t h e hig h est veloci t y at which a n y subsequent lo n g-term test could be performed.

I t is important to note that the mist eliminator tests reflect the current mist eliminator performance; different mist eliminators ma y be able to handle h i g her g as velocities. I n particular, discussions with vendors suggest that newer mist eliminator des i gns could accommodate the gas velocities that would occur if all of the gas from Unit 2 was scrubbed in the existing FGD

s y st e m.

3.3. 2 FGD S y stem Performance T ests The objective of the FGD s y s t em performance tests was to determine the SO 2 

### removal
efficie n c y of the D tower as a fu n ction of gas veloci t y and DBA concentration. Tests were performed at gas velocities ranging from 10.3 to 15.1 ft/s and at DBA concentrations ranging from 1470 to 3850 ppm. A summar y of the removal efficien c y t est results is shown in Table 3-4.

Table 3-4. SO 2 

### Remo v al Efficienc y Test Results

Test Date T i m e Velocity (ft/s) pH Upper Loop DBA ( m g/L) SO 2 In (lb / m m Btu) SO 2 Out (lb / m m Btu) Eff. (%)
1 6/2 1447

- 1 6 13 10.3 5.56 1470 4.8 0.116 97.6 2 6/3 1147

- 1 3 49 10.5 5.39 1570 4.6 0.124 97.3 3 6/3 1505

- 1 6 47 12.9 5.26 1860 4.5 0.074 98.4 4 6/3 1746

- 1 9 27 15.1 5.24 1910 4.5 0.039 99.1 5 6/5 1019

- 1 2 01 1300

- 1 4 40 13.6 13.5 5.31 5.12 2060 2310 4.45 4.45 0.114 0.101 97.4 97.7 6 6/6 1002

- 1 1 45 13.5 5.35 1530 4.8 0.264 94.5 7 6/6 1233

- 1 4 17 13.5 5.45 2860 4.85 0.117 97.6 8 6/6 1455

- 1 6 38 13.5 5.27 3850 4.4 0.060 98.6

### 3-9 Operating conditions for performance Test 1 were established at 1800 on Saturday, 5/31/97, but steady-state operation was not achieved until Tuesday morning, 6/3/97, because the pH set point had been lowered during the night of 6/1/97. After operating at the correct pH setpoint (5.4) during the day on Monday, 6/2/97, the SO 2 

### removal efficiency measurement was completed that afternoon. The inlet SO 2 

### concentration was 4.75 lb/mm Btu (2040 ppmv), and the outlet concentration averaged 0.116 lb/mm Btu, for a removal efficiency of 97.6%. The absorber flue gas velocity for Test 1 was 10.3 ft/s. Steady-state samples for chemical analyses were taken early in the morning of 6/3/97.

Test 2 was conducted during the morning of 6/3/97. Because the absorber gas velocity for Test 1 was close to the desired velocity for Test 2, conditions were not changed for Test 2. The
measured SO 2 

### removal efficiency for Test 2 was 97.3% (4.6 lb/mm Btu inlet, 0.124 lb/mm Btu outlet). This result was close to that for Test 1, indicating good reproducibility for the tests.

After samples were collected at Test 2 conditions, the absorber flue gas velocity was increased to 12.9 ft/s for Test 3. All other operating conditions remained the same. However, it was observed on the control-room recorder that the lower-loop slurry pH increased somewhat because of reagent carryover from the upper loop into the lower-loop recycle tank. SO 2 

### removal efficiency for Test 3 increased to 98.4% (4.66 lb/mm Btu inlet, 0.074 lb/mm Btu outlet).

Test 4, the final test in the series at increasing flue gas velocity was conducted at 15.1 ft/s (also on 6/3/97). Again, all other operating conditions remained the same. For this test, SO 2 

### removal efficiency increased to 99.1% (4.5 lb/mm Btu inlet, 0.039 lb/mm Btu outlet).

Following Test 4, the absorber flue gas velocity was decreased to 13.5 ft/s, which was the maximum allowable for sustained operation, and Test 5 began (6/3/97). This was a two-day test to evaluate steady-state performance. Two successive measurements of SO 2 

### removal efficiency performed on 6/5/97 for this test yielded 97.4 % and 97.7 % removal. Two sets of slurry samples were collected concurrently with the SO 2 

### removal measurements.

Tests 6, 7, and 8 were conducted on the final day of testing, 6/6/97. These three two-hour tests were done to measure the effect of increasing DBA concentration on SO 2 

### removal efficiency. Test 6 was conducted at the DBA concentration that was present in the test module as a result of normal operations. For Tests 7 and 8, about 200 gallons of 50% DBA solution were added to the upper-loop recycle tank of the test module prior to each test. All other test conditions remained the same during these three tests.

### 3-10 The most important result of these tests is demonstrating that it is possible to achieve 97% removal (or higher) over a range of gas velocities and DBA concentrations. Only one test (Test 6) recorded an SO 2 

### removal of less than 97 percent.

The effect of gas velocity on SO 2 

### removal for Tests 1-4 is shown in Figure 3-3. These
data indicate that the SO 2 

### removal increases as a function of velocity. Measured SO 2 

### removals ranged from slightly over 97% at approximately 10 ft/s gas velocities to roughly 99% at a gas velocity of 15 ft/s. The DBA concentration also trended slightly higher with the higher gas velocities; however it does appear that the primary factor leading to the increase in removal is the increase in gas velocity.

The effect of DBA concentration on SO 2 

### removal for Test 3 and Tests 5 through 8 (all tests at ~13 ft/s gas velocity) is shown in Figure 3-4. The most noticeable aspect of this figure is that the measured removal for Test 6 is surprisingly low compared to the other data obtained at ~13 ft/s. Some decrease in removal is expected at lower DBA concentrations, but the SO 2 

### removal measured during Test 6 is lower than expected, considering that removals measured during all other tests exceed 97 percent. The reason that the measured removal was low during Test 6 is not known; a review of the chemistry and operational data from the test did not provide any obvious explanations.

Excluding the Test 6 results, the data in Figure 3-4 suggest that SO 2 

### removal is fairly insensitive to DBA concentration over this range. Specifically, even at very high DBA concentrations (3850 ppm), the maximum removal that was achieved with DBA alone was 98.6%. Since a very high SO 2 

### removal (99.1%) was achieved at a comparatively low DBA concentration (1910 ppm) during Test 4, it seems clear that the primary factor leading to the high
SO 2 

### removal was the high velocity.

With almost all of the data falling within the 97% to 99% removal range, it is possible that a substantial portion of the variability among the measured removals is a result of measurement inaccuracy and normal process variability. However, with almost all of the data showing removal above 97%, it is clear that the scrubbers are capable of achieving a high level
of SO 2 

### removal when operating at increased gas velocities.

3.3.3 Analytical Results for Slurry Samples The slurry analyses provide insights into a number of important aspects of operating with increased gas velocities. These include the ability to oxidize the slurry, maintaining high

### Figure 3-3. Effect of Gas Velocity on SO 2 

### Removal Gas Velocity (ft/s) 8 10 12 14 16SO2Removal (%)

95 96 97 98 99 100



### 3-11

### Figure 3-4. Effect of DBA Concentration on SO 2 

### Removal DBA Concentration (ppm) 1000 1500 2000 2500 3000 3500 4000SO2Removal (%)

94 95 96 97 98 99 100



### 3-12

### 3-13 limestone utilizations in both the upper loop and lower loop, and the increased amount of slurry carry-up that occurs at higher gas velocities. The liquid- and solid-phase analyses are presented in Appendix A. Important results are discussed below.

One of the most important issues associated with increasing the amount of gas treated by the scrubbers is the ability to oxidize all of the SO 2 

### absorbed. In normal operation, this would be evaluated by looking at the solids oxidation results. However, since most of the tests were short term tests, there was usually not sufficient time to allow the solids to come to steady state at the operating conditions. So for these tests, oxidation is instead being evaluated based on liquid phase analyses, which respond much more quickly to changes in operating conditions.

The liquid-phase result that is most important for evaluating oxidation percentage is the calcium sulfite relative saturation. As long as the calcium sulfite relative saturation is below 1.0, calcium sulfite solids will not form, and under these conditions the oxidation will be close to or equal to 100 percent. If the calcium sulfite relative saturation exceeds 1.0, calcium sulfite solids will form and the oxidation percentage will be less than 100.

The calcium sulfite relative saturation in the upper loop was less than 1.0 for all tests. This indicates that the oxidation in the upper loop was adequate for the full range of the test conditions. On the other hand, the calcium sulfite relative saturation in the lower loop was often above 1.0. As shown in Figure 3-5, this generally occurred when the pH of the lower-loop slurry exceeded 4.0. However, because the high lower-loop pH levels corresponded with the high velocity tests, it may be that the increased sulfur loading and greater SO 2 

### removal also contributed to the difficulty in achieving complete oxidation. Because several variables changed at once, it is not possible to determine how each of these factors affects the oxidation. Additional testing would be required to confirm that complete oxidation in the lower loop can be achieved by maintaining the pH at 4.0 or lower. Since the pH in the lower loop is largely dependent on the amount of calcium carbonate carried over from the upper loop, this would entail minimizing the amount of calcium carbonate carried over from the upper loop.

The amount of carry-up from the lower loop to the upper loop is another aspect of performance that can be determined from the chemical analyses. In particular, the chloride concentration in the upper loop is an indication of the amount of carry-up that is occurring in the absorber. Chloride concentrations in the upper loop ranged from about 8300 ppm to over 14,000 ppm, roughly 70% to 80% of the lower loop concentrations. Since the primary way in which chloride enters the upper loop is through carry-up from the lower loop, the amount of carry-up

### Figure 3-5. Effect of pH on Quench Calcium Sulfite Relative Saturation pH 3.5 4.0 4.5 5.0 5.5CaSO3Relative Saturation



### 0 2 4 6 8



### 3-14

### 3-15 must be substantial. For comparison purposes, during the 1992 performance testing, conducted at ~7.5 ft/s gas velocities, upper-loop chloride concentrations were typically 20% to 30% of the lower-loop concentrations. During the month prior to the June performance tests, with the tower operated at ~10.5 ft/s, the upper-loop chloride concentrations were typically 55% to 70% of the lower-loop concentrations. The actual chloride concentrations are not a concern, since the absorber materials are capable of handling chloride concentrations as high as 20,000 ppm. However, the impact of carry-up on the absorber material balance is a concern.

Specifically, the concern caused by increased carry-up from the lower loop to the upper loop is that this carry-up must be balanced by feeding slurry from the upper loop to the lower loop to maintain slurry levels in the two recycle tanks. Feeding slurry from the upper loop to the lower loop is a problem in that the upper-loop slurry has a comparatively high calcium carbonate concentration. This increases the amount of carbonate in the lower loop, which increases the pH. This causes difficulty in maintaining complete oxidation and may also increase the carbonate concentration (potentially making the gypsum byproduct unsuited for reuse). Minimizing the amount of carbonate fed from the upper loop to the lower loop will thus be a key part of scrubbing gas from an additional unit. Possible ways this might be accomplished include operating the upper loop at lower excess carbonate concentration and/or making mechanical changes in the absorber to reduce the amount of slurry carry-up from the lower loop to the upper loop. Further evaluation would be required to determine how to best address the problems associated with this carry-up.

Another important performance indicator is limestone utilization measured in the upperloop and lower-loop solids. Maintaining high limestone utilization (low excess calcium carbonate concentration) is especially important in the lower loop, since high calcium carbonate concentrations can make the gypsum unsuitable for reuse. High limestone utilizations are also important in the upper loop, since upper-loop slurry added to the lower loop to maintain recycle tank levels can lead to excessive calcium carbonate concentrations in the lower loop.

The limestone utilizations for both the upper- and lower-loop sections are plotted as a function of pH in Figure 3-6. With the exception of Tests 3, 7, and 8, the lower-loop utilization values are over 98% (and CaCO 3 

### concentrations are less than 1.0%). During Test 3, a slightly lower utilization of ~97% (CaCO 3 

### concentration of 1.9%) was measured in the lower loop. The lower utilization of Test 3 appears to be caused by the addition of relatively high calcium carbonate content slurry from the upper loop to the lower loop to maintain level. However, the reason for the relatively high calcium carbonate content in the upper loop in Test 3 is not known.

### Figure 3-6. Effect of pH on Limestone Utilization pH 3.5 4.0 4.5 5.0 5.5 6.0Limestone Utilization (%)

60 70 80 90 100

Upper Loop

Lower Loop 8 7 8 7 3

3



### 3-16

### 3-17 During Tests 7 and 8, the upper-and lower-loop sections each experienced limestone blinding, apparently resulting from the very rapid addition of DBA to the test absorber. Though the mechanism for this blinding is not well understood, this is a relatively common occurrence when DBA is added to a scrubber rapidly. The blinding led to very low utilization and high
calcium carbonate concentrations for both of these tests. Because DBA was added to the test absorber at such a rapid rate only to facilitate these short-term tests, this blinding is not representative of what might be seen under normal conditions.

The solids analyses therefore indicate that it should be possible to meet the gypsum byproduct purity specifications while operating with the increased gas flows. Long-term operation at high gas velocities would be desirable to determine if it is possible to avoid the recurrence of the low utilization that was encountered during Test 3.

Comparison of the test data to the daily lab analyses also yield some interesting results. A summary of the calcium carbonate concentrations (wt. %) measured by Radian and by TECo is presented in Table 3-5. First, it is important to note that the samples being compared were not collected at the same time, so some variation between the analyses is to be expected. However, the analyses reported by TECo are consistently higher than those measured by Radian during the test runs. This tends to suggest that there may be some bias in the analytical methods. Because of the importance of accurate calcium carbonate analyses (which are used to assess whether or not the gypsum meets its purity specification), it may be worthwhile to perform comparative analyses on splits of the same sample to verify that accurate calcium carbonate measurements are being obtained.

3.3.4 Other Process Data Other data collected during the high velocity performance tests include settling test measurements and process data. Settling test data were collected daily, with the objective of detecting gross changes in the solids properties. Settling test results are summarized in the Table 3-6. Results are presented in terms of unit areas; the unit area represents the amount of thickener area (in square feet) that would be required to settle one ton per day of solids to a concentration of 30 wt. %. The corrected unit areas are adjusted to account for the difference in initial weight percent solids; in this case they are all adjusted to an initial concentration of 9 wt. % solids.

The differences between tests in the measured unit areas are relatively small; they are comparable to the “scatter” seen in previous settling test data from this site. The data thus indicate that the high velocity testing did not produce any substantial changes in solids properties.

### 3-18 Table 3-5. Comparison of Radia n and TECo Calcium Carbonate A na l y ses Radian Analyses TECo Analyses
S a m ple Date Ti m e CaCO 3 (wt. %) Date CaCO 3 (wt. %) Upper L oop 6/2/97 15:17 9.2 6/2/97 10.9
L o w er loop 15:25 0.1 1.9 Upper L oop 6/3/97 7:10 7.0 6/3/97 18.9
L o w er loop 7:20 0.0 1.0 Upper L oop 6/5/97 11:05 4.6 6/5/97 18.3
L o w er loop 11:15 0.1 3.0 Upper L oop 6/6/97 11:00 6.9 6/6/97 12.4
L o w er loop 11:10 1.1 1.5



### Table 3-6. Settling Test Results

Date Initial w t. % Solids Unit Area (sq. ft/tpd) Corrected Unit Area (sq. ft/tpd)

6/3/97 9 1.1 1.1
6/4/97 13 1.0 1.5 6/5/97 14 0.8 1.8



### Process data collected duri n g the s e performance tests included measurements of D tower booster fan vane position, upper and lower loop pH, inlet and outlet temperatures, upper loop oxidation air flow, pump motor watts, and lower loop densi t y . Also included were Unit 4 load,
inlet SO 2 

### concentration, and outlet SO 2 

### concentration. Because the pr o cess da t a collec t ed are quite voluminous, the y have not been included in this Topical Report.

3.3. 5 Long-Term High Velocit y Testing Following the mist eliminator and scrubber performance testing described above, TECo began a long-term test of h i gh veloci t y operation. This long-term test was stopped premature l y after appro x imate l y three weeks. The objective of the lo n g-term test was to monitor Module D performa n ce at sulfur loadi n gs similar to what would occ u r if an additional unit were scrubbed in
the e x isting FGD s y stem. The h i gh sulfur l o adings were obtained b y firi n g a h i gh sulf u r fuel (in
the 5.5 to 6.0 lb/MM Btu ra n ge) and operating Module D at a gas velocit y o f 13.5 ft/s. The s e conditions produce a sulfur l o ading t h at is similar to what would be seen if the s crubber operated at 16 to 17 ft/s with an inlet sulfur of 4.5 to 5.0 lb/MM Btu, the expected scrubber operating
conditions if an additional unit were scrubbed.

### 3-19 Results of these tests showed that at the high sulfur loadings in the test absorber, the oxidation air rate available was inadequate. This apparently led to high liquid-phase sulfite concentrations, and limestone blinding became a recurrent problem. As a result, calcium carbonate concentrations in the lower loop section were frequently above the 1.5% level in the gypsum byproduct specification. According to TECo personnel, the limestone blinding was severe enough that continuing the high sulfur loading tests became difficult, so the long term testing was suspended.

Limestone blinding is reportedly a recurring problem even under the current, normal operating conditions, but the high sulfur loading to Module D made the problem significantly worse. Although no other problems were reported during these three weeks of operation, a longer duration test would be desirable to assure that scaling does not occur at the high sulfur loadings.

Because of the limestone blinding problem which caused the testing to be discontinued after three weeks, it was not conclusively determined whether the Big Bend Unit 4 FGD system can operate successfully at the high gas velocities required to also scrub flue gas from Unit 2. Further testing is warranted to determine if it is possible to consistently avoid limestone blinding episodes. Potential solutions to this problem include increasing the oxidation air rate available in each loop, reducing the amount of slurry carry-up from the lower loop to the upper loop, and operating at higher limestone utilization in the upper loop.

### A-1 

## Appendix A

Analytical DataTable A-1. Liquid-Phase Analyses**Description Test 1** **SO 2** **Upper Loop Test 1** **SO 2** **Lower Loop Test 1** **Run 1 Upper Loop** **Test 1 Run 1** **Lower Loop Test 1** **Run 2 Upper Loop** **Test 1 Run 2** **Lower Loop Test 2** **Upper Loop** **Test 2 Lower** **Loop Test 3** **Upper Loop** **Test 3 Lower** **Loop Test 4** **Upper Loop** **Test 4 Lower** **Loop**Date 6-2-97 6-2-97 6-3-97 6-3-97 6-3-97 6-3-97 6-3-97 6-3-97 6-3-97 6-3-97 6-3-97 6-3-97Time 15:17 15:25 07:10 07:20 07:40 07:55 12:45 13:00 16:05 16:15 18:30 18:40Ca, mm/L 37.1 34.9 36.8 36.2 33.9 39.0 36.8 35.4 37.9 44.6Mg, mm/L 138.3 169.1 141.1 168.2 138.2 177.8 148.0 190.2 165.3 196.8Na, mm/L 81.7 101.7 82.9 99.6 82.0 104.5 86.7 112.2 96.3 115.8Cl, mm/L 236.7 307.5 251.3 310.2 235.1 325.4 253.7 348.6 280.8 355.7CO3, mm/L 2.6 2.5 3.0 2.4 3.2 2.7 3.2 3.3 4.3 3.6SO3, mm/L 0.1 5.7 0.2 9.1 0.2 9.6 0.4 19.5 1.0 24.4SO4, mm/L 63.8 61.7 58.8 60.6 55.7 62.6 55.7 61.0 60.8 61.1Succinic, mm/L 2.3 3.3 2.1 3.2 2.8 3.2 2.6 3.6 3.7 4.0 3.7 4.2Glutaric, mm/L 7.2 7.5 7.1 7.3 6.6 7.4 7.8 8.4 8.6 9.5 8.9 9.9Adipic, mm/L 1.7 1.7 1.6 1.6 1.4 1.6 1.7 1.8 2.0 2.2 2.0 2.2pH 5.56 4.00 5.35 3.81 4.94 3.85 5.39 3.95 5.26 5.18 5.24 4.29Temp, C 55.4 55.2 54.0 54.3 54.1 54.1 54.8 54.6 54.8 54.6 54.8 54.9Ca, mg/L 1487 1399 1476 1451 1358 1565 1475 1418 1519 1787Mg, mg/L 3362 4111 3429 4088 3359 4321 3598 4623 4019 4784Na, mg/L 1879 2338 1905 2289 1885 2403 1994 2580 2215 2663Cl, mg/L 8390 10901 8910 10998 8336 11534 8994 12356 9955 12611CO3, mg/L 158 147 181 146 193 160 193 195 256 218SO3, mg/L 12 455 13 731 13 770 35 1562 81 1956SO4, mg/L 6128 5928 5645 5818 5352 6010 5352 5857 5839 5866Succinic, mg/L 277 390 244 376 331 376 310 429 434 476 442 493Glutaric, mg/L 947 986 932 970 871 972 1024 1116 1139 1258 1173 1309Adipic, mg/L 245 249 229 235 205 238 242 262 290 317 299 321Relative SaturationGypsum 1.23 1.05 1.14 1.06 1.01 1.13 1.04 0.89 1.08 1.14CaSO3*0.5H2O 0.05 0.07 0.03 0.12 0.06 0.17 0.13 4.17 0.27 1.01CaCO30.01 0.00 0.00 0.00 0.02 0.00 0.01 0.01 0.01 0.00



### A-3Table A-1 (continued)**Description Test 5** **Run 1 Upper Loop** **Test 5 Run 1** **Lower Loop Test 5** **Run 2 Upper Loop** **Test 5 Run 2** **Lower Loop Test 6** **Upper Loop** **Test 6 Lower** **Loop Test 7** **Upper Loop** **Test 7 Lower** **Loop Test 8** **Upper Loop** **Test 8 Lower** **Loop**Date 6-5-97 6-5-97 6-5-97 6-5-97 6-6-97 6-6-97 6-6-97 6-6-97 6-6-97 6-6-97Time 11:05 11:15 13:45 13:55 11:00 11:10 13:25 13:35 15:45 15:55Ca, mm/L 37.4 43.0 39.2 42.0 34.3 38.9 41.2 45.9 44.9 61.3Mg, mm/L 224.7 265.1 229.8 270.3 185.9 238.4 204.8 274.4 224.3 293.2Na, mm/L 129.1 155.4 133.2 159.2 109.7 137.7 118.9 160.4 131.0 169.6Cl, mm/L 403.8 497.6 407.0 494.4 315.3 421.4 359.8 510.9 393.9 546.3CO3, mm/L 3.8 3.6 4.0 3.3 3.7 2.9 4.4 3.0 4.4 4.7SO3, mm/L 1.3 24.6 1.2 20.4 0.5 19.8 1.0 31.5 0.4 65.2SO4, mm/L 72.9 75.9 72.8 79.0 68.5 74.1 68.6 75.4 67.6 64.7Succinic, mm/L 3.9 4.5 4.3 4.9 2.8 3.7 5.4 6.0 7.3 8.0Glutaric, mm/L 9.4 11.2 10.7 12.1 6.9 9.0 13.1 14.7 17.7 19.3Adipic, mm/L 2.5 2.5 2.6 2.6 2.0 2.0 3.4 3.3 4.4 4.4pH 5.31 5.22 5.12 4.07 5.35 4.25 5.45 4.21 5.27 4.66Temp, C 55.3 55.1 55.4 55.4 55.5 55.5 55.5 56.1 55.4 56.4Ca, mg/L 1501 1723 1571 1683 1373 1560 1652 1838 1798 2456Mg, mg/L 5463 6445 5586 6571 4520 5796 4979 6670 5452 7129Na, mg/L 2968 3573 3062 3661 2521 3165 2735 3688 3011 3899Cl, mg/L 14315 17641 14429 17528 11178 14939 12756 18112 13965 19366CO3, mg/L 227 215 240 196 223 175 267 183 263 280SO3, mg/L 104 1972 99 1635 43 1589 79 2521 36 5221SO4, mg/L 7001 7288 6991 7593 6582 7115 6587 7244 6491 6215Succinic, mg/L 456 536 510 574 330 435 632 712 865 949Glutaric, mg/L 1240 1484 1414 1594 913 1185 1735 1947 2340 2552Adipic, mg/L 365 363 384 384 291 294 492 479 641 636Relative SaturationGypsum 1.03 1.06 1.07 1.15 1.03 1.09 1.10 1.16 1.09 1.17CaSO3*0.5H2O 0.36 6.10 0.25 0.45 0.16 0.63 0.38 1.02 0.13 7.00CaCO30.02 0.01 0.01 0.00 0.02 0.00 0.04 0.00 0.02 0.00



### A-4Table A-2. Solid-Phase Analyses**Description Test 1** **SO 2** **Upper Loop Test 1** **SO 2** **Lower Loop Test 1** **Run 2 Upper Loop** **Test 1 Run 1** **Lower Loop Test 1** **Run 2 Upper Loop** **Test 1 Run 2** **Lower Loop Test 2** **Upper Loop** **Test 2 Lower** **Loop Test 3** **Upper Loop** **Test 3 Lower** **Loop Test 4** **Upper Loop** **Test 4 Lower** **Loop**Date 6-2-97 6-2-97 6-3-97 6-3-97 6-3-97 6-3-97 6-3-97 6-3-97 6-3-97 6-3-97 6-3-97 6-3-97Time 15:17 15:25 07:10 07:20 07:40 07:55 12:45 13:00 16:05 16:15 18:30 18:40Ca, mm/g 6.25 6.05 6.35 5.93 6.24 5.98 6.18 6.01 6.34 5.98 6.04 6.07Mg, mm/g 0.02 0.00 0.02 0.00 0.01 0.00 0.01 0.00 0.02 0.01 0.01 0.00SO3, mm/g 0.01 0.01 0.01 0.01 0.00 ND 0.01 0.01 0.01 0.02 ND 0.01SO4total, mm/g 4.95 5.65 5.05 5.67 5.27 5.66 5.26 5.66 5.03 5.57 5.32 5.60SO4, mm/g 4.95 5.65 5.05 5.66 5.27 5.66 5.25 5.65 5.02 5.56 5.32 5.58CO3, mm/g 0.92 0.01 0.97 0.00 0.70 0.02 0.68 0.06 1.09 0.19 0.59 0.09Inerts, Wt. % 1.24 1.08 1.36 1.12 1.20 1.16 1.24 1.32 1.32 1.28 0.88 1.04Solids, Wt. % 10.65 10.72 8.81 7.87 12.30 9.02 9.50 10.68 11.01 11.50 12.00 13.00pH 5.56 4 5.35 3.81 4.94 3.85 5.39 3.95 5.26 5.18 5.24 4.29Temp, C 55.4 55.2 54 54.3 54.1 54.1 54.8 54.6 54.8 54.6 54.8 54.9Reagent util, % 84.3 99.9 83.9 99.9 88.3 99.7 88.5 99.0 82.2 96.7 90.0 98.4Reagent ratio 1.19 1.00 1.19 1.00 1.13 1.00 1.13 1.01 1.22 1.03 1.11 1.02Oxidation, % 99.9 99.9 99.9 99.9 100.0 100.0 99.8 99.8 99.8 99.7 100.0 99.8Solid solution, Wt.% 0.1 0.1 0.1 0.1 0.0 0.0 0.2 0.2 0.2 0.2 0.0 0.2Gypsum, Wt. % 85.1 97.1 86.8 97.4 90.6 97.4 90.2 97.2 86.3 95.5 91.5 96.0CaCO3, Wt. % 9.2 0.1 9.7 0.0 7.0 0.2 6.8 0.6 10.9 1.9 5.9 0.9Inerts, Wt. % 1.2 1.1 1.4 1.1 1.2 1.2 1.2 1.3 1.3 1.3 0.9 1.0ClosuresWeight, % -2.8 -0.1 -0.7 -0.3 -0.1 -0.1 -0.6 0.4 -0.4 -0.2 -1.2 -0.3Molar, % 3.2 3.4 2.8 2.3 2.3 2.6 2.1 2.5 2.0 1.9 1.2 3.3Acceptable, % 6.6 7.1 6.6 7.1 6.7 7.1 6.7 7.0 6.5 6.9 6.7 7.0



### A-5Table A-2 (continued)**Description Test 5** **Run 1 Upper Loop** **Test 5 Run 1** **Lower Loop Test 5** **Run 2 Upper Loop** **Test 5 Run 2** **Lower Loop Test 6** **Upper Loop** **Test 6 Lower** **Loop Test 7** **Upper Loop** **Test 7 Lower** **Loop Test 8** **Upper Loop** **Test 8 Lower** **Loop**Date 6-5-97 6-5-97 6-5-97 6-5-97 6-6-97 6-6-97 6-6-97 6-6-97 6-6-97 6-6-97Time 11:05 11:15 13:45 13:55 11:00 11:10 13:25 13:35 15:45 15:55Ca, mm/g 6.28 5.96 6.19 6.02 6.27 5.92 6.83 6.36 6.90 6.52Mg, mm/g 0.01 0.00 0.02 0.00 0.01 0.00 0.04 0.02 0.04 0.03SO3, mm/g 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.08SO4total, mm/g 5.39 5.65 5.27 5.62 5.16 5.62 4.30 5.04 4.34 4.79SO4, mm/g 5.39 5.63 5.26 5.60 5.15 5.60 4.28 5.02 4.32 4.71CO3, mm/g 0.46 0.01 0.67 0.07 0.69 0.11 2.26 1.03 2.27 1.52Inerts, Wt. % 0.68 0.80 0.48 0.68 0.68 0.36 0.80 0.76 0.52 0.76Solids, Wt. % 13.13 14.46 14.01 15.16 12.33 14.54 17.75 20.51 20.48 25.13pH 5.31 5.22 5.12 4.07 5.35 4.25 5.45 4.21 5.27 4.66Temp, C 55.3 55.1 55.4 55.4 55.5 55.5 55.5 56.1 55.4 56.4Reagent util, % 92.1 99.8 88.7 98.8 88.2 98.1 65.5 83.0 65.7 75.9Reagent ratio 1.09 1.00 1.13 1.01 1.13 1.02 1.53 1.20 1.52 1.32Oxidation, % 99.9 99.8 99.8 99.8 99.8 99.7 99.5 99.6 99.5 98.3Solid solution, Wt.% 0.1 0.2 0.1 0.2 0.2 0.2 0.3 0.3 0.3 1.3Gypsum, Wt. % 92.6 96.8 90.5 96.3 88.5 96.3 73.5 86.3 74.3 80.7CaCO3, Wt. % 4.6 0.1 6.7 0.7 6.9 1.1 22.6 10.3 22.7 15.2Inerts, Wt. % 0.7 0.8 0.5 0.7 0.7 0.4 0.8 0.8 0.5 0.8ClosuresWeight, % -0.2 -0.9 -1.1 -0.7 -2.0 -1.2 -1.6 -1.1 -0.9 -1.1Molar, % 3.7 2.6 2.1 2.9 3.6 1.7 2.3 2.5 2.4 1.8Acceptable, % 6.8 7.1 6.7 7.0 6.7 7.0 6.2 6.6 6.2 6.4



### A-6