Document YDrZGEEMKyxYNVxxp0B9RDQQO

CS1MUSKCOI9P2 , E. I. d u Po n t d e Ne mo u r s 51 Co mp a n y INCORPORATED WILMINGTON, DELAWARE 19898 CHEMICALS AND PIGMENTS DEPARTMENT October 15, 1981 TI-PURE TITANIUM DIOXIDE SLURRY SYSTEMS BOOKLET (E-43017) The attached revised edition (E-43017) replaces A-90577 Rutile Pigment Slurries booklet. Please destroy your stock of A-90577. E-43017 updates the design, storage and handling tech nology gained through additional experience in handling bulk Ti02 slurries. Additional copies of E-43017 may be obtained through your normal Marketing Communications Department contacts. JDT/WWG:eg Attachment W. W. GREER N42099.01 FOREWORD As pioneers in the development oftitanium dioxide siurry technoiogy, Du Pont is in a unique position to advise you in the most effective use ofthis modern distribution and stun / u .'Jt'n etfti'vt'- et uiionvi \ m.d l ulu^'iul benefits'c i be derived from it If, after reading this booklet, you wish to explore the possibilities ofconversion to slurry, please contact your local Du Pant representative or our Wilmington office: E. I. du Pont de Nemours & Co. (Inc.) Chemicals and Pigments Department Wilmington, DE 19898 Attn: Manager, Ti02 Products INTRODUCTION Commercial titanium dioxide production in the United States began at the end of World War I, Forthe next fiftyyears, the standard shipping package was the 50* lb multi* wall paper bag. In the late 1960*s, an innovative departure from dry bagged pigment in the form of a high solids anatase TiOs slurry was offered to Ti02 users in the paper industry. Enthusiastic and rapid acceptance prompted development of rutile Ti02 slurries for the coatings industry. The first of these, designed for trade sales flat paints, was introduced in 1971. Since theft, high solids slurries for durable exterior coatings' and gloss y/all and trim, paints have been introduced. For paper, slurry offerings were broadened tolnClude especially developed rutile slurry (RP5) which offers improved optical performance both in wet end and paper and board coatings. TABLE OF CONTENTS FOREWORD INTRODUCTION SLURRY ECONOMICS ........................ SLURRY PROPERTIES ........................ STORAGE AND HANDLING SYSTEMS Design........ .................................... Unloading Station .................. ....... Storage Tanks .......... ................... . Agitation ................ ....................... Humidification............................... Distribution Systems...................... Pumps.......................... .............. Piping and Valves ..--................ Instrumentation .............. --......... Low Cost Slurry System...... .......... OPERATIONS .................................... . Unloading Practices ...................... Maintenance................................... Hygiene....................................... PERSONAL SAFETY ______ ____ ____ Page .. 1 ., 2 .. 2 .. 2 .. 3 .. 3 .. 4 ., 4 4 .. 5 ,. 6 .. 6 .. 6 .. 7 . .. 7 .. 7 .. 8 .. 8 DUP050070546 iiiiii :;;f|^|!i|spi|g|wl5iteitefc#ip:#lliilp^p!i;;iti!i iiiMiljiiBBi^WifciftBiiijipliiiiiiiMiiiii^teiwi aHHi SLURBY ECONOMICS Demand for TiOa slurry has grown rapidly, exceeding 90,000 tons/yr in 1980. By 1988, U S. consumption is projected lu be 170,000 tons annually. Economics support this ready acceptance and rapid expansion. In most cases, savings accrued from reduced process energy (predispersed product), increased production capability, and improved handling and storage are sufficient to cover the cost of a slurry system when the investment is amortized over a two to five year period. Factors such as actual savings generated, annual con sumption, cost of conversion, mode of delivery and freight costs contribute significantly to the economics: Paint producers report savings of two to six cents per pound of Ti02; paper mill savings can exceed ten percent of pigment consumption. Employing the checklist (Figure 1) is a convenient way to calculate savings. * No set amount of Ti02 consumption has been esta blished to justify slurry system installation. Under favorable conditions, as little as 300,000 tbs/yr of a Single grade may be sufficient although twice that amount is usually necessary. Slurry system costs are influenced by design com plexity , materials of construction, and degree of auto mation. Costs range from truckload scale for about $25,000, to a multigrade railcar system for over $200,000. Mode of delivery can influence both conversion and operating costs. Railcars contain approximately 10,000 to 12,500 gallons (60 to 75 tons Ti02, dry basis), depending on grade. The minimum recommended storage tank capacity is one and a half carloads. Smaller tanks than this make it difficult for the customer to schedule deliveries and can lead to detention charges. Slurry systems designed for rou tine servicing by truck permit smaller storage, and recommended capacity is one and one half (ruckloads. Systems with under 5,000 gallons storage capacity are in service. Because less investment is required, the cost of this size system is within reach of many smaller Ti02 consumers. FIGURE 1 Checklist Bag Ti02 vs. Slurry - Potential Savings Bag Handling Cost Unload & Transfer to Storage Deliver to Process Area Charge Process Remove Bags & Pallets Ti02 Losses Warehouse - Broken Bags Process Spillage & Dust Left in Bag - % to % Lb/Bag Waste Disposal Cost Bags Pallets Storage Cost-Area Occupied Bag TiOz Slurry TI02 Quality Control TiOj Errors Eliminated Uniform Batch to Batch Dispersion Uniform Quality Inventory Control Eliminate Counting Errors Running Total - Lbs In vs. Lbs Out Batch Totals - Cumulative Process Utilization Faster TI02 Charge Time Optimize Batch Size - Eliminate 50 Lb Increments Increase Throughput - No Dispersion Required Safety & Housekeeping Cleaner Work Area - No Dust & Spillage Eliminate Exposure to Forklift/Hand Truck Hazards The information set forth herein is furnished free of charge and is based on technical data that Du Pont believes to be reliable. It is intended for use by persons having technical skill and at their own discretion and risk. Since conditions of use are outside our control, we make no warranties, express or implied, and assume no liability in connection with any use of this information. Nothing herein is to be taken as a license to operate under or a recommendation to infringe any patents. DUP050070547 SLOPPY PROPERTIES -Slurry properties are carefully controlled in order to facilitate manufacture, shipment, storage and handling: Slurry rhpology is maintained newtonian at least in the shear range of common pumps. At the same time, slight thixotropy is imparted at low shear to retard settling. These properties are not expected to change with age. Proper rheology is Obtained without elabo rate dispersant combinations or high dispersant levels. Solids level is kept high to allow use in high solids paint and coatings formulas and to avoid shipping large quantities of water. Currently marketed grades range from 62% to 76% solids. Slurry density is Kept constant to insure accurate metering with commonly used flow meters, Slurry as shipped is sterile as are railcars and trucks. Since bacteria can live in slurry, biostats are included in the recipe. * Upon receipt, certain precautions must be taken by the customer to insure satisfactory storage and. use. Settling can be expected from any practical slurry. If the cake is soft, easily reincorporated and forms slowly, this can be tolerated Proper agitation, designed into the storage facilities is a necessity. Slurries are formulated at high solids; consequently, evaporation of even small amounts of water results in tormation of dried flakes on slurry wetted container ,,, . wails. It is therefore necessary to keep tank humidityat or near saturation by periodically injecting steam or atomized water. Slurry properties are strongly interrelated. The desire to achieve maximum percent solids and simple formulas with low dispersant levels is limited principally by dilatancy and increased tendency to form dry flakes. Formulation problems occur with higher levels of dis persant in slurry. Thixotropic slurries resist settling but do tend to thicken on aging and entrap air which causes density variations. An acceptable slurry is a careful balance of all properties. STORAGE AND HANDLING SYSTEMS Design Du Pont offers consulting and design assistance for installation and use of TiO? slurry facilities. Once the needs of a TjOg user in a given application are established, the design of facilities to use slurry is relatively straight- FIGURE 2 Typical Slurry System {For 2 Grades) DUP050070548 forward but recognition oi the slurries' unique character* istics is essential. Extensive experience in the manufacture, lit r In turn a ul u*e of TiOa enable us to recommend economical routes to using slurry effectively. Our design staff ic.ii puiMrt i it i|ilc l plciiis ui'il s i nates for a slur'v tin ii d. s m-i in [i"i i _ii ml in i iin-tal jt u 1 o' llu inipini it Sn t c nttds of t'ie user v ir\ v idtK we prefer to custom design installations Timing may take 7 to 10 months from project authorization to start-up. We have designed a package system for low volume cases (truck receipt) which can be installed in 3 to 5 months. In a well designed system, slurry can be pumped and stored as easily as otherbulk fluids. Conversely, inadequate design can lead to problems such as pigment settling resulting in tank heels and plugged lines and valves. A typical slurry installation consists of an unloading puinp station, storage tank, and distribution network (Figure 2) A facility for two grades of slurry will of course need two storage tanks and two distribution systems, but one unloading station can Serve both grades. The major cost of the system is the agitated storage tank. Piping becomes a large cost consideration for long or complex runs. Instrumentation can be relatively simple or can become a large cost item when many use points or extensive automation is involved. Unloading Station The railcar unloading station (Figure 3) consists of a pump, piping, and water and compressed air service. The pump is used both to transfer slurry to the storage tank and to recirculate and wash out car heels with a charge of wafer Compressed air is used to dear the lines before and after unloading and j j i tin .. a tut u u efficient unloading Unloading can often be done with pressure alone (limited to 100 psig) but effective heel removal requires the pump for recirculation. (See Unload ing Practices.) The system is designed to unload at 150 gpm or more so that a 10,000+ gallon car can be emptied in about an hour. (See Pumps.) Truck unloading stations can be simpler since trucks do not require recirculation and are usually unloaded with air pressure. The lift and run however is limited by the pressure rating of the tank truck, usually 25 psig. Most trucks are equipped with their own power-take-off air pumps. Storage Tanks A typical TiOa slurry storage tank arrangement is shown in Figure 4. Tanks are typically flat bottom cylinders and hold a minimum of about lVi carloads (or truckloads) with usage and inventory needs dictating. Tanks may be made of fiberglass reinforced polyester FIGURE 3 Slurry Unloading Station 1" Air Line To Storage Tank DUP050070549 PMHMNMMIMiM jiv?? i:* .M' -S; ?=;-.'f: :;S 'if i'U^i#V'H` v'iHlI '^; Jll I fl:|if;^^|| (FRP), epoxy coated steel, concrete-tile, or stainless steel. Cost will be about $1 to $2 per gallon ol capacity. Under 10.000 gal, FRP will generally be most economical; in the 20.000 gal range, epoxy coated steel is generally lowest cost and in larger sues, concrete-tile is the economic choice. Stainless steel is an ideal material, but is usually more costly. For interior locations. FRP tank size will be limited by building access openings, but steel or concretetile tanks can be erected in place. Since slurry is loaded warm and has a high heat capacity, there is little risk of its freezing if tanks are insulated except during long periods of severe cold weather. Normal intermittent agitation keeps the slurry mured so that localized freezing will not occur; continued agitation can provide enough heat input to keep the slurry fluid. Our railcars are insulated and can deliver slurry in the coldest weather. Agitation TiO,,2 slurry storage tanks, must have agitation to prevent settling and maintain product uniformity. Slurry at full strength, or diluted to some constant solids level a percentage point or two lower, settles very slowly. Sedi ment formed in several days is reincorporated easily with agitation, but if left standing for several weeks can form heavy cakes that may resist reincorporation. Moderate agitation at about 1 hp per 1000 gallons is satisfactory, using turbine blades and wall baffles in the usual cylindrical fiat bottom tanks The.agitator will cost up to half as much as the tank itself. Recirculation of tank contents with a pump is not adequate to keep the slurry suspended for long periods but can be used to reduce settling during periods of agitator outage. We recommend a ti mer on the agitator forperiodic operation (15 minutes every two hours), to conserve power and avoid slurry Humidification It is essential to humidify storage tanks to prevent drying of slurry on the walls. High solids content of Ti02 slurry leaves little spare water and makes it quite vulnerable to drying and caking if tank humidity is not close to 100%. Dried Ti02 wall scale is extremely hard and is likely to show up as grit in coatings. With adequate humidification; the walls will remain wet and not show Ti02 buildup as level changes and splashing coat the walls with a film of slurry. Humidification is simply achieyed by providing water fog spray in the tank periodically. The fog can be produced by a pressure water spray, air atomized water spray, or steam jet. Fog nozzles are sized to deliver three to five gallons of water a day when operated a few minutes per hour; this will not be enough water to materially affect slurry solids content. PistHSsution Systems The simplest system delivers selected amounts of sluny FIGURE 4 wmmssmmrn illiiillllil ' - I1 . to a batch tank. This can be accomplished with a pump at the storage tank, a transfer pipe, and a batch meter at the - use point The pipeline from storage to-the meter may be ieft full of slurry between batches but it is desirable to provide a water flush through the meter after each batch delivery (.Figure 5). Normal intermittent use will avoid settling in the pipeline. If w idely separated use points are to be served, it is ofteh ' advisable to use a header line past the use points looped back to the storage tank and maintained under pressure by a control valve at the tank return. Individual take-offs can be metered at each location or with a main line meter as in Figure 2. When more than one grade of sluny Is used, it is advisable to duplicate the facilities up to the use point or a branching at adjoining use points (Figure 2). It is generally unsatisfactory to use one supply system flushed between changes of grade, In some applications, it is desired to deliver slurry to a mt nuous use point at a low Ti02 rate that would be difficult to meter and control accurately (TiOj feed to the wet end of a paper machine). In this case, slurry is diluted to some low concentration (1 lb/gal) and then metered to the use point at a manageable flow rate. A typical dilution/feed system is shown in (Figure 6). Here slurry dilution is controlled by density measurement in a water/ sluny mixing column which overflows to a holding tank from which it is Circulated through a loop line to the use points. Since diluted slurry settles rapidly, it is necessary to keep it agitated continuously and moving constantly in the pipelines. In a dilute system, no dead pipe areas can be tolerated. Pumps Either centrifugal pumps with open impellers, or air diaphragm pumps are preferred for Ti02 slurry service. Centrifugal pumps are generally chosen for higher pressure duty (above 80 psig) and/or continuous operation such as for a loop system; or where suitable air supply is not available for air diaphragm pump operation. Stainless steel is the preferred material of construction. Diaphragm pumps are chosen for lower pressure duty and for intermittent operation such as car unloading or direct batching. The air diaphragm is excellent for moving slurry and is simpler to install and monitor than a centrifugal and costs much less. Aluminum is acceptable for slurry service in an air pump. It will eventuallybecome eroded, but will give long service and is economical to replace (cost is about V\ that of a stainless unit or a centrifugal pump). For metered delivery, a pulsation damper at the pump discharge is advisable. For the free flow of car unloading, however, the air puinp pulsations are acceptable if piping is adequately supported. FIGURE 5 Batch Slurry Supply System Water Flush DUP050070551 Piping and Valves Either FRP or stainless steel is commonly used for slurry piping. Choice between the two is often a case of customer preference. FRP pipe gives good service and costs less botli to purchase and install than stainless, particularly where field welding may be hazardous. IJnreinforced plastic pipe can be used in some cases. It is necessary to keep line velocity at about 5 ft/second in order to overcome settling in pipes Minimum diameters recommended are W2 to 2 inches. Slurry piping should be run in' as direct a routing as practical and the system should drain to one end or the other but this is not essential if the line can be blown clear. Valve selection is limited to ball, butterfly, and diaphragm types. Other valves wiJl wear, plug, or bind, in slurry service. Ball valves are generally used for the best all around service, but particularly for frequent manual on/off operation and where complete shutoff is necessary. Butterfly valves are an economical alternative in less demanding locations such as in the unloading lines. For automatic control or regulation, diaphragm valves are preferred. Instrumentation Tank level indicators are a'matter of individual choice. In some cases visual indication through the translucent wall of an FRP tank is acceptable, bocal indication of level in opaque tanks may be obtained from a diaphragm pressure gauge installed near the tank bottom. If remote indication is desired, a differential pressure cell at the tank bottom may be used. Physical measurement with internal elements is undesirable because any structure in the tank is subject to high stress from the agitated TiOa slurry flow, and pigment will tend to block or plug confined floats, etc We have found the magnetic flow meter to give the best all around service in slurry metering applications. It can reliably measure continuous or batch deliveries of full strength or diluted slurries over a wide range. It does not require flushing after use, but rather is best left full of process fluid at all times. A lower cost alternative in the case of a batching duty where the meter may be flushed after use, is an oscillating piston meter. Although bushings require periodic replace* ment because of slurry abrasion, it is a simple job. An effective pumping-metering arrangement can be made using the positive displacement feature of the airdiaphragm pump. Control systems are available to count the pulses of the pump and Convert them into volume readings which are then displayed and used to operate valves, pumps, etc. Cost is relatively low and reliability good since the pump itself is the metering element. Low Cost Slurry System One exception to the general practice of custom designing each slurry system is our low cost slurry system (LCSS). FIGURE 6 Dilute Slurry Supply System {Continuous Use Points) DUP050070552 i a 5,000'^kilon system for small volume users et to M cei\e tui V s iipm uts 11 d deliver metered Pressurize the car. Pump the car empty. < or .luiij .o <1 SIIU, t M- ( nt , Add 100 gal or more of water and recirculate for Vz * in,i-ituie7 nb ' (1j i u c i >ottom gn witliOu' m <*q atn Slu,p si s j i iimiu i md Pump the Car empty and blow lines clear. h i'ueved bv 1i on <<. ulu n through a iteuul nead r |i f i Ar m did[ In. gn i uup Cars can be unloaded with air pressure alone but pt.aidt l c i iutua * *' .\erv l.r liiu{i` iulu i-pbucmpmg/recirculation is advisable to completely empty B- ,,t with an oscillating pis'on meler, and includes automatic:? water flush. The tank and piping are FRP ^ OPERATIONS Unloading Practices the Ti02. Using air pressure on the car during pump unloading speeds up the unloading and promotes more complete draining of slurry from the walls. Trucks are usually unloaded with air pressure alone and most do not have recirculation headers, Settled pigment is not generally a problem with trucks since they are t.Re id Personal S. * tv V ction before handling unloaded within a, tew days of filling, Most trucks are Ti02 Slurry) equipped with their own power-take-off air pump. Air is R, art unoudiu as cescribed in detail in our iiistri t*m mi mi t R il< ii Mull uIingProcedures forTi used to blow the lines clear after unloading. The truck may be hosed down manually if desired. re IiOj M'it , Maintenance le basic unloading procedure is to pump the car empty, i th on J.& recircuiation step to clear the heel, then blow the lines clear with air as follows: Slurry tank$ normally requires minimum of maintenance. Concrete-tile, FRP, and S5 tanks are essentially mainte nance free. The lining of a steel tank should be inspected Clear the car outletvalve withbrief air blpw-back, then periodically as it may require repair or replacement in 5 to sparge air through the recirculation header for a few ? 10 years; small defects in the lining can be patched with minutes. 4F^ an air-dry epoxy. FIGURE 7 Low Cost Slurry System DUP050070553 IlSlIill! `*w^0&W$< iliiil BmMmP (iitiitiiti Ipfilililft iipt iiiiii iPlliiSiiiiiiiiiii iiiiiiiiiliiiiS Slurry tanks should be inspected frequently to assure that the humidification system is performing satisfactorily. Wall scale formation in inadequately humidified tanks is a major source of qualify problems. Normal maintenance practices are satisfactory for slurry equipment, but the caking and settling properties of slurry must be considered during system shutdown. A full strength slurry line mav be left full for about three days if it is not open to atmosphere However, a dilute slurry line should be flushed with water for any shutdown over 30 minutes. Hygiene A clean system is essential to prevent bacterial contamina tion of the slurry. Slurry is delivered in sterilized cars Although TiOjj pigment is inert, the dispersants are susceptible. Contaminated slurry may lose its dispersion stability and can pass bacteria along to the rest of the process. We recommend sterilization of new systems by filling them with water containing 400 ppm of hypochlorite (such as HTH swimming pool formula) After the wash solution is drained, it is important to flush the system with water because small amounts of the chemical will severely flocculate pigment PERSONAL SAFETY If titanium dioxide slurries are allowed to dry down, dusts may form Under some circumstances, exposure to these dusts are subject to regulation or control recommendation. Before using Du Pont Ti-Pure titanium dioxide slurries, review the Data Sheets and Matenal Safety Data Sheet for the appropriate Ti-Pure grades. DUP050070554 illllilpIM *V- E. I. du Pont de Nemours & Co. (Inc.) Wilmington, Delaware 19898 u. s. s CHARLOTTE NC 28230 i2,,UFlijn a/ Pd PO Bux3C517 704-364-1550 CHICAGO. IL 60631 O Fij i a Plaz i Sj iI '60 =-25 E Ri.c'RJ 312-635-1220 CLEVELAND OH (Suburban) EliO Fic'Kside Wcwils 3uj e.ard Suitt 2o6 InJjyti iden o OH 44131 PIC 447 U8s8 HOUSTON. TX 77056 Suit. 1620 Po-tOli Tj*.r / 1o C/7 5600 NEW YORK, NV 10118 Rm 1129, Empire State Bldg. 350 Fifth Ave 212-971*4000 PHILADELPHIA, PA (Suburban) ,,06 E LarcastcrAi/e Wynnov ocd P 1903b 216 896 200C SAN FRANCISCO CA94111 Suite 31 IQ. 50 California Stic*-* 416-391*7300 E-43017 7/81 <3M) Printed in O.S.A. DUP050070555