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PURATEK® solidification

ADVANCED PURATEK® STABI­LIZA­TION AND SOLI­DI­FI­CA­TION TECH­NO­LOGY FOR HAZAR­DOUS SOLID WASTE AND NORM* WASTE TREATMENT

(* NORM: NATURAL OCCU­RING RADIO­AC­TIVE MATERIAL)

The SOLI­DI­FI­CA­TION, also known under the terms STABI­LIZA­TION, IMMO­BI­LIZA­TION or CONDI­TIO­NING, is a chemical and physical process which encap­su­lates conta­mi­nants in a non-leachable and perma­nent way, thereby mini­mi­zing the risk of envi­ron­mental hazard.

Stabi­liza­tion and soli­di­fi­ca­tion processes aim at produ­cing a stable, landfill-disposable product with the lowest possible level of leaching. Here, the terms “stabi­liza­tion” and “soli­di­fi­ca­tion” are used. Depo­si­tion of stabi­lized hazar­dous waste at Class I and Class II Land­fills is permitted only if “total stabi­liza­tion” can be demonstrated.

One of the test criteria to prove the success of stabi­liza­tion and soli­di­fi­ca­tion of hazar­dous solid waste is the TCLP (Toxi­city Charac­te­ristic Leaching Proce­dure) test method 1311 described in USEPA publi­ca­tion SW-846. The target values of the Stabi­liza­tion and soli­di­fi­ca­tion treat­ment are shown and summa­rized in the table below:

Typical Target Values (product quality) of Stabi­liza­tion & Solidification

Typical Target Values (product quality) of stabi­liza­tion and solidification

By proces­sing of NORM waste mate­rial, beside over mentioned criteria, addi­tio­nally signi­fi­cant reduc­tion of radia­tion must be achieved, so that the final product is accep­table for safe disposal on the special controlled low radia­tion waste depot.

The limits for disposal of processed NORM waste mate­rial are stipu­lated in the National Regu­la­tions which slightly differs in each country. PURATEK® advanced tech­no­logy of NORM waste treat­ment provides final product quality which complies with the best current inter­na­tional practice.

Conven­tional stabi­liza­tion and soli­di­fi­ca­tion of heavy metal conta­mi­nated chemo toxic hazar­dous waste using Port­land cements or fly ash is based on the presence of free CaO in cement which is capable of forming inso­luble or slightly soluble metal hydr­o­xides with most metals.

The elements of the zinc group, cadmium and mercury: (Zn++, Ag++, Hg++, Cd++, Pb++, Cu++ and Ni++ in parti­cular), are known as excep­tions to this rule; ther­e­fore, the respec­tive sulfa­tion of this metals prior to fixing (encap­su­la­tion) in a cement-stone matrix is essential.

Inso­lu­bi­lity (or extre­mely low solu­bi­lity) of the compounds to be soli­di­fied is indis­pensable for successful comple­tion of the soli­di­fi­ca­tion process.

For this reason, a two-stage process is necessary.

The first stage provides for stabi­liza­tion and preci­pi­ta­tion of heavy metals. The second stage encap­su­lates the previously stabi­lized and preci­pi­tated conta­mi­nants into the crystal lattice or solid matrix of the final soli­di­fied product.

In the past 10 years, PURATEK® have deve­loped an advanced two-stage stabi­liza­tion and soli­di­fi­ca­tion tech­no­logy for successful treat­ment of hazar­dous solid waste and NORM waste, reali­zing the fact that stabi­liza­tion is a chemical process; ther­e­fore, the simple cemen­ta­tion in a concrete mixing plant cannot handle this task successfully. The common and simple cemen­ta­tion of waste using concrete mixing plants is not purpo­seful and unsui­table to achieve a proper soli­di­fi­ca­tion result.

Inso­lu­bi­lity (or extre­mely low solu­bi­lity) of the compounds to be soli­di­fied is indis­pensable for a successful comple­tion of the soli­di­fi­ca­tion process.

For this reason, a two-stage process is necessary.

The first stage provides for stabi­liza­tion and preci­pi­ta­tion of heavy metals. The second stage encap­su­lates the previously stabi­lized and preci­pi­tated conta­mi­nants into the crystal lattice or solid matrix of the final soli­di­fied product.

PURATEK® STABI­LIZA­TION REACTOR | FIRST STAGE

In most cases, the chemical stabi­liza­tion means chemical preci­pi­ta­tion of water-soluble inor­ganic conta­mi­nants which are present in hazar­dous solid waste.

PURATEK® stabi­liza­tion and soli­di­fi­ca­tion tech­no­logy starts in the first reactor where chemical stabi­liza­tion and preci­pi­ta­tion takes place. The stabi­liza­tion reactor is filled by using weig­hing and dosing units for solid chemo-toxic waste mate­rial or NORM waste material.

PURATEK® Weig­hing & Dosing units for filling up the stabi­liza­tion reactor

Weig­hing & Dosing unit for hot NORM ash, Dosing spiral conveyor with anti-wear mangan slide inserts

PURATEK® STABI­LIZA­TION REACTOR PSM 2400–2C | FIRST STAGE

Ashes after inci­ne­ra­tion, NORM ash, scale, slag, dross and other types of chemo-toxic solid wastes, contain reac­tive earth alkali heavy metal oxides (BaO and RaO for example) and/or elements of the zinc group plus cadmium and mercury. All these conta­mi­nants must be trans­formed into water-insoluble compounds by adding appro­priate liquid chemical reagents. NORM waste requires a treat­ment with special chemi­cals and tech­no­logy deve­loped by PURATEK®.

Chemical reac­tion between the above-mentioned conta­mi­nants and the added chemi­cals is almost always very inten­sive and strong exothermic. To put chemical reac­tion under control, PURATEK® have desi­gned an advanced and precise weig­hing and dosing system. Solid conta­mi­nates are dosed »not at once«, but in gradu­ally controlled way, followed by exact injec­tion of liquid chemi­cals. Chemical process is comple­tely under control of the intel­li­gent process controller.

The PURATEK® stabi­liza­tion reactor is espe­ci­ally desi­gned for this process. As this chemical reac­tion runs almost always exother­mi­cally, the gene­rated heat must be effec­tively dissi­pated. Ther­e­fore, the PURATEK® stabi­liza­tion reactor is equipped with a high-performance cooling system with extern­ally connected chiller and tempe­ra­ture control.

In order to guarantee the best possible realiza­tion of the stabi­liza­tion and preci­pi­ta­tion chemical reac­tion in bulk thick slurry, PURATEK® have deve­loped and built a special reactor which ensures:

  • inten­sive solid/liquid contact needed for chemical reaction
  • effec­tive dissi­pa­tion of chemical reac­tion heat

For best performing of stabi­liza­tion and preci­pi­ta­tion chemical reac­tion in bulk thick slurry, PURATEK® has deve­loped and build special reactor that assures:

  • inten­sive solid/liquid contact needed for chemical reaction
  • effec­tive dissi­pa­tion of chemical reac­tion heat

Mixing tool design

Finite Element Method (FEM) of PSM 2400 ‑2C cooling jacket — design

To meet both design requi­re­ments, PURATEK® have desi­gned the stabi­liza­tion reactor with unique mixing flow charac­te­ristics and high-performance heat transfer — cooling jacket.

A well-dimensioned central shaft turns the heavy-duty mixing tools thus performing the lateral left and right bulk mixing process. For micro mixing, two addi­tional high-speed mixers are installed. They cut solid particles into pieces, increase the solid/liquid inter­face and ensure the full comple­tion of the chemical reac­tion. PURATEK® recom­mend to use high chemical- and abrasive-resistant duplex steel as reactor cons­truc­tion material.

Ni-hardened heavy-duty mixing tools

Strong central shaft

PURATEK® STABI­LIZA­TION REACTOR PSM 2400–2C | SECOND STAGE

After the chemical stabi­liza­tion and preci­pi­ta­tion has been completed, the processed mate­rial is trans­ferred by gravity to the second reactor for further treatment.

Prepa­ra­tion of the final soli­di­fied mixture takes place in the second reactor — special heavy-duty pan mixer, made of stain­less steel, with inside lining and Ni-hardened anti-wear mixing tools, deve­loped by PURATEK®.

A special type of chemical resistant cement, inert fillers, fine sand and recy­cled process water are added to the mixture to achieve the desired consis­tency of the final soli­di­fied product. To reduce radia­tion, NORM waste mate­rial requires special addi­tives and tech­no­logy deve­loped by PURATEK®.

After the curing time of the soli­di­fied mixture, the soli­di­fi­ca­tion process is finished. The compacted soli­di­fied product reaches the desired result: full encap­su­la­tion of the chemo toxic compounds in a cement-stone matrix. Condi­tions for safe, perma­nent disposal at suitable land­fill are fulfilled.

Soli­di­fi­ca­tion Reactor PM 2250

PURATEK® SOLI­DI­FI­CA­TION REACTOR HD PM 2250, WITH WEIG­HING HOPPERS AND DISCHAR­GING FUNNEL

User-friendly opera­tion and adjus­t­ment of the recipe through touch-panel

The PURATEK® stabi­liza­tion and soli­di­fi­ca­tion process runs fully auto­ma­ti­cally accor­ding to recipes stored in the intel­li­gent process control unit. Specific recipes for the treat­ment of diffe­rent waste types are prepared and opti­mized during test operation.

PURATEK® ADVANCED HAND­LING CONCEPT AND LOGISTICS

The final product of the PURATEK® stabi­liza­tion and soli­difi­ca­tion process is a bulk-solidified mixture which can be loaded directly on a dumper truck and trans­ported to the landfill. Another option is to cast the soli­dified mixture into forms/molds. In this case, the soli­dified mixture can be compacted addi­tio­nally by means of a vibra­ting system. A higher quality, espe­ci­ally a higher compre­hen­sive strength of the final soli­dified product can be achieved.

Mold walls can be removed from the ingot after a very short curing period. However, the final strength of the ingot will be achieved after 30 days. The hardened final ingot shows a very low poro­sity which makes any water pene­tra­tion impos­sible. Any possi­bi­lity of leaching of hazar­dous compounds is excluded.

Hazar­dous solid waste should be handled and treated with a safe concept in order to avoid acci­dences: both human and envi­ron­mental. Safety at work is a prerequisite.

PURATEK® provide for a well-considered concept for mold hand­ling and logi­stics. This includes: prepa­ra­tion of empty molds, trans­port, posi­tio­ning, casting of molds, compac­ting, demol­ding, primary curing of ingots and final disposal of ingots.

Accor­ding to the PURATEK® hand­ling concept, an empty form/mold is trans­ported via a roller conveyor system under the soli­dified mixture discharge funnel where the vibra­tion unit is placed. After casting and vibra­ting, the mold is trans­ported via the heavy-duty roller conveyor system to the primary curing area. Alter­na­tively, a fork­lift can be employed for the same job.

The PURATEK® stabi­liza­tion and soli­di­fi­ca­tion process runs fully auto­ma­ti­cally accor­ding to the recipes stored in the intel­li­gent process control unit. Specific recipes for treat­ment of diffe­rent waste types are prepared and opti­mized during test operation.

Casting mold and finished ingots, approx. 1 m3

Casting mold and fi nished ingots, approx. 1 m³

Fully automatic operated roller conveyor for casting molds

Fully auto­matic operated roller conveyor for casting molds

Mold casting & vibration process

Mold casting & vibra­tion process

ngots after removing of side walls

Ingots after remo­ving of side walls

PURATEK® STABI­LIZA­TION AND SOLI­DI­FI­CA­TION PLANT CONCEPT & LOGISTICS

The golden rule is one batch — one mold which means that the complete capa­city of the second reactor is fully emptied into one mold. After the recipe has been opti­mized, one finished batch is filled and cast exactly into one 1.0 m³ mold.  For the reason of fluent hand­ling, there are two hydrau­li­cally driven, half-moon dischar­ging gates, arranged oppo­site to each other, on the bottom of the pan mixer. The dischar­ging gates are working alternately:

  • First soli­di­fied batch goes to right gate and to right dischar­ging funnel
  • Second soli­di­fied batch goes to left gate and to left dischar­ging funnel

In total — one single mold hand­ling period:

Filling one mold, vibra­ting one mold, remo­ving of one cast mold by fork­lift and brin­ging one empty mold on to the vibra­ting table is equi­va­lent to a double soli­difi­ca­tion batch time.

After curing time, soli­di­fied ingots can be safely put to land­fill without risk of leaching conta­mi­nants from the encap­su­lated and soli­di­fied waste.

PURATEK® ADVANCED HAND­LING CONCEPT AND LOGISTICS

NORM WASTE MATE­RIAL requires special hand­ling. To prevent radia­tion leaking, the final NORM soli­dified product should be sealed with a clean concrete shield.

PURATEK® recom­mend a tech­nical solu­tion for casting, hand­ling and storing the final NORM soli­dified product. Radia­tion shiel­ding can be achieved by using 1.0 m³ concrete pots with inte­grated bottom and walls and sealed cover. Cast and water­proof sealed concrete pots with 100 – 120 mm walls can be trans­ported and handled safely by a PURATEK® heavy-duty carousel or roller conveyor and handled and loaded on to a truck by a speci­ally shielded forklift.

A recom­mended tech­nical solu­tion ensures effec­tive radia­tion shiel­ding and allows perma­nent safe storage of soli­di­fied NORM waste mate­rial on the espe­ci­ally controlled low radia­tion waste depot.

APPLI­CA­TIONS FOR STABI­LIZA­TION AND SOLI­DI­FI­CA­TION FOR WASTE TREATMENT

PURATEK® STABI­LIZA­TION AND SOLI­DI­FI­CA­TION TECH­NO­LOGY WAS SUCCESSFULLY USED FOR DIFFE­RENT TYPES OF HAZAR­DOUS SOLID AND CHEMO TOXIC WASTE:

  • Indus­trial inor­ganic hazar­dous solid waste
  • Bottom ash and fly ash from inci­ne­ra­tion plants
  • Spent cata­lyst from petro­che­mical industry
  • EAF dust from steel production
  • Slag and dross from steel production
  • Spent blas­ting mate­rials – conta­mi­nated with heavy metals and paint
  • Spent mole­cular sieve – conta­mi­nated with toxic chemicals
  • Ash from muni­cipal inci­ne­ra­tion plants
  • Spent acti­vated alumina — conta­mi­nated with toxic chemicals
  • Sludge and filter cake from Aluminum Extrusion
  • Plant high aluminum content
  • Sludge from galva­ni­zing Plant – with high heavy metals content
  • Sludge from leather industry
  • Chemo toxic liquid waste
  • Conta­mi­nated soil
  • Hazar­dous muni­cipal waste

NORM WASTE APPLICATIONS

  • NORM ash from incineration
  • NORM scale from oilfield pipes conta­mi­nated with RaSO4 and RaCO3
  • NORM sludge and scrapings
  • NORM dril­ling mud
  • NORM waste mate­rial in gas proces­sing facilities
  • NORM conta­mi­nated equipment
  • Low radio­ac­tive material

TYPICAL CUSTO­MERS FOR THE STABI­LIZA­TION AND SOLI­DI­FI­CA­TION PLANT ARE:

  • Waste treat­ment facilities
  • Land­fill faci­li­ties, in parti­cular hazar­dous waste land­fill facilities
  • Hazar­dous waste inci­ne­ra­tion facilities
  • Inci­ne­ra­tion facilities
  • Muni­cipal waste and hazar­dous waste inci­ne­ra­tion plants, power plants
  • Waste treat­ment opera­tion compa­nies, also soil treat­ment companies 
  • Envi­ron­mental service companies
  • Oil dril­ling companies
  • Refi­ne­ries
  • Chemical industry
  • Petro­che­mical industry
  • Metal proces­sing industry
  • Steel produc­tion industry
  • Galva­ni­zing industry
  • Leather industry
  • Nuclear power industry
  • Disposal faci­li­ties for NORM waste

PURATEK® SCOPE OF SERVICES:

  • Concept studies
  • Labo­ra­tory testing
  • Basic engi­nee­ring, inclu­ding layout of the plant
  • Detail engi­nee­ring

  • Manu­fac­tu­ring of equip­ment in in-house factory

  • Deli­very to site and construction/assembly

  • Commis­sio­ning
  • Opti­miza­tion of the process
  • After sales service
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