PJF Microwave Separation of Oil-Water Slude-oiling to separate a wide variety of waste sludges. Cost-effective separation, especially in Cost-effective separation, especially in combination

The EPRl Center for Materials Produ 2-992. B

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Microwave Separation of Oil-Water Slu

David A. Purta Camegie Nlellon Research Institute Pittsburgh, Pa.

CMP Report No.

~ .rUI.C ~.P~SCICIUI I VI vtt~wuwst auagWS I: Application to Industrial Waste Sludges

CMP Report No. 94-3 CR-103872

R E P O R T S U M M A R Y SUBJECTS Microwave processDndustria1 wastes/Sludge treatment

TOPICS Microwave processes Sludges Metallic wastes

Oily wastes ~

- Industrial wastes Waste treatment

AUDIENCE Waste managers, environmental managers, industrial plant operators, utility marketing & customer service engineers, researchers

Microwave Separation of Oil-Water Sludges I: Application to Industrial Waste Sludges

This report summarizes the results of a project to evaluate a microwave process for separating a wide variety of industrial waste sludges. An economic analysis is also provided.

BACKGROUND There is a need in the metals industry for a technology to improve upon conventional methods used to separate and dispose of oil-water sludges. In 1992, the EPRI Center for Materials Production (CMP), funded a project at Carnegie Mellon Research Institute (CMRI) to evaluate the ability of microwaves to enhance the separation of oil-water sludges, particularly steel industry sludges. The results of this project were very promising, showing that oil-water separations could be accomplished in minutes, compared to hours for conventional processing. As a follow-up, CMP initiated this project to determine the effect of microwave processing on waste sludges obtained from a variety of other industrial processes.

OBJECTIVES The project's objectives were to determine the applicability and the cost of microwave processing for a wide variety of industrial sludges.

APPROACH With the assistance of EPRI utilities, industrial manufacturing firms were canvassed to complete surveys concerning the generation and treatment of waste sludges at their plants. The surveys were used to assist in the selection of 24 different types of waste samples obtained from materials production and fabricating firms. Since the project focused on deoiling wastes containing more than 5% solids, the samples were further screened in order to select 6 representative samples for in-depth microwave processing. These samples were treated with a combination of microwaves and chemical release agents. Separation time and quality were monitored. These results were then used to evaluate the applicability of microwave treatment and to estimate the costs for commercial scale-up of the process.

RESULTS/ PERSPECTIVE

Six representative waste sludge samples were treated with microwaves and release agents to separate the oil from the solids. Excellent treatment results were obtained on waste samples obtained from aircraft maintenance, machine tool, and steel production operations. After processing, the solids were free of residual oils. Likewise, recovered oils showed minimal water or solids. Both the cleaned solids and the recovered oil were in a form suitable for direct recycling. It was projected that operating and disposal costs for the commercial microwave processing would be in the range of $9 to $15/ton, compared to a sampled average of $153/ton for current waste disposal methods.

PROJECT W3243 EPRI Project Manager: R. J. Schmitt, CMP Contractor: David A. Purta, Camegie Mellon Research Institute

For technical information, call The EPRI Center for Materials Production,

4 12-268-3243

To order additional publications, call your local EPRI-member utility or contact The EPRIeAMP Program,

1 -800-4320-AMP

This report may be purchased from CMP for $200.00. The cost includes postage to domestic and overseas addresses.

For information on EPRI research programs, call EPRI Technical Information Specialists,

415-855-241 1

Microwave Separation of Oil-Water Sludges I: Application to Industrial Waste Sludges

Evaluation of a Microwave-Assisted Process for the Separation of Industrial Waste Sludges

CMP REPORT NUMBER 94-3 March 1994

Prepared by Carnegie Mellon Research institute

4400 Fifth Avenue Pittsburgh, PA 15213-2683

Principal Investigator David A. Purta

Prepared for The EPRI Center for Materials Production

Carnegie Mellon Research Institute 4400 Fifth Avenue

Pittsburgh, PA 15213-2683

Joseph E. Goodwill, Director The EPRI Center for Materials Production

Disclaimer of Warranties and Limitation of Liabilities NEITHER EPRI, ANY MEMBER OF EPRI, ANY COSPONSORy NOR ANY PERSON OR ORGANIZATION ACTING ON BEHALF OF ANY OF THEM:

(A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLED, (I) WITH RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS REPORT, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, OR (11) THAT SUCH USE DOES NOT INFRINGE ON OR INTERFERE WITH PRIVATELY OWNED RIGHTS, INCLUDING ANY PARTY'S INTELLECTUAL PROPERTY, OR (111) THAT THIS REPORT IS SUITABLE TO ANY PARTICULAR USER'S CIRCUMSTANCE; OR

(B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER (INCLUDING ANY CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY EPRI REPRESENTATIVE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOUR SELECTION OR USE OF THIS REPORT OR ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS REPORT.

Organization that prepared this report:

CARNEGIE MELLON RESEARCH INSTITUTE

0 Copyright 1994 Electric Power Research Institute, Inc. All rights reserved.

iv

ABSTRACT

In 1992, the EPRI Center for Materials Production (CMP), funded a project at Carnegie Mellon Research Institute (CMRI) to evaluate the ability of microwaves to enhance the separation of steel industry oil-water sludges. The results of the study showed that the CMRI developed microwave system can separate oil-water sludges in minutes compared to hours for conventional processing. Consequently, CMP funded CMRI to conduct a follow-up study to determine the ability of the novel microwave system to separate a wide variety of other types of industrial oil-water sludges.

With the assistance of EPRI utilities, samples of 24 different types of waste sludges were obtained for analysis. Six of the 24 samples were selected to be processed by microwave system and were successfully processed. Based on the results of the study it is concluded that the new microwave system should be commercially practical and a cost-effective method to treat a variety of industrial waste sludges for disposal. The next step in the development of the process is to demonstrate it in a variety of commercial applications. Industrial f m s or utilities working with CMP on a demonstration project should contact the CMP Office.

V

ACKNOWLEDGMENTS

The Carnegie Mellon Research Institute gratefully acknowledges the following individuals for providing assistance in this project.

EPRIKMP Mr. Joseph Goodwill

and Mr. Robert Schmitt

for their foresight and sponsorship.

EPRI Utility Members and Field Workers for their enthusiastic response and discussions

and for providing industrial waste samples.

Eriez Magnetics Inc. Mr. Richard Merwin

for the use of their magnetic hardware and for their discussions.

vi

CONTENTS

Section Page

Introduction .................................................................. Background .................................................................. Experimental ................................................................. Results of Testing ........................................................... D i s c u s s i o n .................................................................... Economic Analysis .......................................................... Conclusions and Recommendations ........................................ R e f e r e n c e s ....................................................................

1- 1

2- 1

3- 1

4- 1

5- 1

6- 1

7- 1

8- 1

.

.

Vii

FIGURES

Page

Figure 3-1 Estimate of sample composition by visual examination ......... 3-2

Figure 3-2 Microwave-chemistry evaluation system ......................... 3-5

Figure 3-3 Benchtop microwave de-oiling system ........................... 3-6

Figure 4-1 Distribution of oil. water. and solids in samples (before microwave processing) ......................... 4-2

Figure 4-2 Initial and final oil concentrations cleaned by microwave de-oiling (one stage) .............................. 4-2

Figure 4-3 Total oil cleaned by microwave de-oiling (one stage) .......... 4-3

Figure 4-4 4-3

Initial and predicted final oil concentrations cleaned by microwave de-oiling (two stage) ..............................

Figure 4-5 Predicted total oil cleaned by microwave de-oiling (two stage) .............................................. 4-4

Figure 5-1

Figure 5-2

CMRI microwave de-oiling model. showing % oil retention vs . % original oil on cleaned solids ............ Block diagram of CMRI/EPRI/CMP microwave de-oiling process ...................................... 5-4

5-2

Figure 6-1 Yearly disposal costs for the various waste types .............. 6-2

Figure 6-2 Disposal costs per gallon for various waste types .............. 6-3

Figure 6-3 6-3 Disposal gallons per year for various waste types .............. Figure 6-4 Disposal costs per ton for various waste types .................. 6-4

Figure 6-5 Tons per year disposed of for various waste types ............. 6-4

.

... vlll

TABLES

Page

Table 3-1 Descriptions of As-Received Samples 3-4 ------------- ------------ 3-4

Table 4-1 Oil Concentrations of Samples Cleaned by Microwave De-oiling .............................................. 4-4

Table 6-1 Comparison of Waste Disposal Costs ............................ 6-5

Table 6-2 Detail of Projected Operating Costs Using New Microwave Process for the Treatment of Sludge ................ 6-6

ix

Section I INTRODUCTION

In 1992, The EPRI Center for Materials Production (CMP) initiated a program with the Carnegie

Mellon Research Institute (CMRI) to evaluate the ability of microwaves to enhance the separation

of oil-water sludges. The project focused on separation of oil-water emulsions and hot strip rolling

mill sludge &2J. The results from this work projected cost-effective recycling of separated waste

components using a microwave de-oiling process. In order to more broadly demonstrate the

applicability of microwave de-oiling, this project work was undertaken to determine the suitability

of microwaves to separate and clean a wide variety of industrial wastes.

Needs exist in the metals production and fabricating industries for electrotechnologies to improve

upon the separation and disposal of oil-water sludges. For example, it is costly to dispose of the

sludge coming from steel plants and the landfilling of materials is a major problem from an

environmental perspective. The sludges generated from machine tool operations and from the

cleaning and degreasing of aircraft and airline equipment are other examples of costly disposal. It

is highly desirable to find more efficient ways to individually separate the oil, water, and solid

particles resulting from these sludge generating operations. The total disposal costs of the

separated oil and solid components, which then may be recycled, should be substantially less than

the waste disposal costs for the existing types of mixed sludges.

There are currently several process methods to de-oil waste sludges, slumes, and dispersions.

Examples of these methods are thermal extraction, solvent extraction, surfactant or soap-based

cleaning methods, and others. However these processes are generally expensive, energy

intensive, or they may generate secondary wastes that must also be disposed of or carefully

1 - 1

controlled to ensure worker safety and environmental compliance. Thermal extraction, for

example, typically raises bulk waste temperature above the vapor point of the oils and consumes

large amounts of energy. Solvent extraction methods have limits on VOC (volatile organic

compounds) emissions and concerns for worker safety and regulations. Soap and surfactant

cleaners generate soapy oils that must be disposed of (or filtered), and the oily filters also must be

disposed of in an environmentally safe manner.

The alternative method evaluated in this project was a microwave process developed by CMRI

under EPRI sponsorship. This process allows separation of oil-water sludges into water, oil, and

solids suitable for recycling.

1 - 2

Section 2 BACKGROUND

This project was undertaken with the main objective of evaluating and demonstrating microwave

de-oiling to separate a wide variety of waste sludges. Cost-effective separation, especially in

combination with recycling, has great potential to significantly reduce waste disposal costs.

The objectives were as follows:

Survey EPRI utility industries to select a wide variety of wastes for microwave testing. Obtain samples and perform microwave testing. Prepare a report for distribution to EPRI utilities.

The following tasks were chosen to achieve the project objectives:

In conjunction with CMP, a questionnaire was created about waste sludge generation and it was used to solicit EPRI utility companies and their clients assistance to obtain a wide variety of wastes for treatment. The questionnaire was structured to develop a data base comprised of type and amounts of oily wastes requiring disposal by industry (specific composition of wastes were obtained where possible), and information on present or conventional methods of treatment, disposal, and costs was developed.

Questionnaire responses were analyzed to identify and categorize waste types suitable for microwave processing methodologies.

Sample kits were sent to selected f m s to obtain waste samples for testing.

A microwave laboratory system was set up in order to process the waste samples.

A suitable microwave methodology was developed and tests performed on the samples received.

An economic analysis was conducted.

A CMP report giving the details of the project and results was prepared.

2- 1

Section 3 EXPE E TAL

Evaluation of Questionnaires and Sample Selection

Questionnaires were drafted and distributed to EPRI utility members. The EPRI utility then sent

the questionnaire to selected customers who have an oily sludge disposal problem. The

questionnaires were designed to gather information about various types of industrial waste sludges

and included the following questions:

Waste sample's general name? Approximate composition of oil, water, and solids, by analysis, if available? Brief treatment-process description concerning how the waste was generated? The current disposal method, if known?

* Volumes of wastes produced, for example tons/year or gallons/year? Present disposal costs, for example $/ton or $/gallon?

From these questionnaires, information was collected on a large variety of waste types. The

manufacturers' names and location were kept confidential. All questionnaires were evaluated and

ranked. The ranking criteria were first based upon the yearly disposal costs and the size of the

problem to industry which involved an estimation of the number of similar wastes. A second

ranking was based upon the amount of solids contained in the samples, and a final ranking was

determined by the amount of oil in the samples.

Sample kits were prepared and shipped to nearly all questionnaire respondents whose waste

samples were anticipated to have three components; oil, water, and solids, in their mixed

composition.

3- 1

The samples were first evaluated by visual inspection and an estimate made of the approximate oil,

water, and solids content. A graphical summary of the first pass evaluation can be seen in Figure

3-1.

yo Water r yo Oil

Figure 3-1 Estimate of sample composition by visual examination.

Each sample to be processed was given an identification number. The sample suppliers were

informed of their identification number so that they could quantitatively compare their sample's

data results against the anonymous information and data from others.

The next task used analytical testing to quantitatively determine the samples initial % oil, % water,

and % solids. This task further screened and enabled the final selection of the samples to be

processed using microwave de-oiling techniques.

3-2

All samples that did not have at least 5% solids and at least 2% oil were deemed not within the

scope of this current project and were not processed further. However, wastes comprised solely

of oil and water can be processed by existing microwave methodologies.

Laboratory T e s t s and Procedures

Two main types of laboratory tests were performed on the samples. The first test determined the

concentrations of oil, water, and solids in the as-received samples. The analytical methods used

were oven drying to determine water loss, followed by a Freon TF (MS- 180/C02, trichloro-

trifluoroethane) solvent extraction to determine the residual oil on the solids. Water loss and oil

residuals were determined from weight measurements by a gravimetric method using a Denver

Instruments Co. scale. The manufacturer's stated scale accuracy was +/- 0.001 gram. A summary

of the sample coding numbers and their respective descriptions appears in Table 3-1.

In the second test, performed selected samples were subjected to a microwave de-oiling process.

The microwave de-oiling was followed by a TFE solvent extraction to determine the residual oil on

the resultant cleaned solids. Identical microwave de-oiling chemistry and (nonop timized) single-

stage microwave process methodology were used to process each of the samples.

3-3

Table 3-1. Descriptions of As-received Samples

Identification Description

1 cutting fluid 2 rolling mill sludge 3 auto shop sludge 4 machine shop sludge * 5 machine grindings

6 steel mill sludge * 7 coolant tank sludge 8 wire drawing coolant 9 waste sludge 10 waste sludge

1 1 machine coolant 12 residual waste 13 filter cake 14 oily waste sludge 15 filter cake

16 filtered coolant 17 open system waste 18 machine grindings 19 machine coolant 20 coolant waste

21 steel mill sludge 22 steel mill sludge * 23b airline waste 24 steel mill sludge 27 industrial waste oil 28 rolling coolant

Sample's composition analyzed by CMRI

For commercial applications of microwave de-oiling, past work has shown that significant

refinements and optimizations are possible. CMRI has developed a model for the microwave de-

oiling process and plans to implement refinements on a case-by-case basis during the commercial

devdoprnenr. Refinements may invo!ve modifications to the precess chemistry to enhance a rapid-

phase release of the oil from the process chemistry. These refinements will enable specific

commercial applications of microwave de-oiling to be more efficient and cost effective than this

project's initial, nonoptimized runs.

3-4

Figure 3-2 shows the microwave laboratory hardware which was assembled and used for this

project. The equipment consisted of a modified MDS-2000 microwave process oven

manufactured by CEM Corporation. The hardware was equipped with rugged, pure-PTFE

(Teflon) sample vessels, a fiber-optic temperature probe, sample-pressure monitoring port, power

and energy monitoring capabilities, and an automated computer interface. This hardware was

specifically selected, designed, and assembled to evaluate microwave-process chemistries and

microw ave-process methodologies .

CMRI's specially constructed, commercially scaleable, benchtop microwave de-oiling system,

illustrated in Figure 3-3, was also available for project use. The commercially scaleable benchtop

system is used to verify refined process parameters, derived from the MDS-2000 system, when

using quart-to-gallon size waste samples.

Figure 3-2 Microwave chemistry evaluation system.

3-5

Figure 3-3 Benchtop Microwave De-oiling System

Selected Cases Using Microwave Processing

All samples that CMRI received were evaluated and ranked by selection criteria. These criteria

were used to select a subset of samples for further microwave processing. The selection was first

based upon cost and the size of the waste problem to industry. This fiist pass selection

specifically evaluated the yearly disposal costs and the number of similar waste types received ... in order to attempt to gauge the size of the problem for industries across the country. A secondary

ranking was mxie by a visual inspection and ai approximate deterininadon of the waste sample's

composition. When selected for further microwave processing, a sample was required to contain

an amount of solids greater than 5 % of the total waste's composition. This is because microwave

methods other than the CMRI de-oiling process already exist to process oiVwater emulsions or oily

3-6

wastes with low-solids content. Final selections were determined by the initial oil content in the

waste samples. The bulk of the waste samples contained higher than a few percent oil

contamination. Therefore, final selection criteria required that samples initially have more than 2%

oil.

Six sample types were selected for further evaluation and microwave processing. These samples

are described in the following text to specify their source, solids composition (if stated on the

questionnaire), and their approximate method of generation.

Coolant Tank Sludge (#7): During the machining process, fine particles of silicon and various

metals build up in the coolant system's cutting fluid and eventually settle out in the coolant storage

tanks. The solids composition of this sludge is 20% iron, 5% aluminum, and the balance - silicon. The oil and water content are (roughly) distributed equally.

Waste Sludge (W): This waste is generated from the processing of used industrial oils primarily

from the automotive and steel industries. The composition of this waste is a water/oil mixture with

various solids throughout the sample.

Filter Cake (#15): The waste is generated by recalculating semisynthetic coolant oil used on an

electric resistance tube welding mill. The coolant is filtered by a Hydromation filter. The waste is

primarily composed of oil/grease with the remainder being water and solids.

Machine Grindings (#18): The waste lubricants used during machining and grinding are collected

and removed from service due to contamination. The solids composition is 60% iron, 30%

aluminum, and the balance - lead.

3-7

Steel Mill Sludge (#22): This waste sample was magnetically concentrated sludge from a steel-

manufacturer's hot strip rolling mill. The sludge is comprised of mill scale (ferrous iron), rolling

oil, and water.

Airline Waste (#23b): The waste is generated from cleaning, decarbonizing, and degreasing of

aircraft ground support equipment and parts. The solids were comprised of ~ 1 % iron, the

balanc-ilicon and trace metals including aluminum. The waste treatment currently being used is

gravity separation in an API oil/water separator. The pH of the oily waste varies from 6.0 to 11.0.

The selected waste type was an oily-solids fraction from the API separator output.

3-8

Section 4 RESULTS OF TESTING

Comparison of Initial and Final Oil Concentrations

The key results for the microwave treatment and de-oiling of the waste samples are described in

this section. The results are graphically displayed; the initial waste sample compositions by CMRI

analysis are shown in Figure 4-1; the initial oil and the final microwave-processed oil

concentrations on a dry, water-free basis are shown in Figure 4-2. Further, the total oil removed

by the microwave de-oiling process is illustrated in Figure 4-3. Also the predicted total oil cleaning

ability by microwave de-oiling utilizing a two-stage microwave process is discussed below and

graphically shown in Figure 4-4 and Figure 4-5, respectively. The predicted data is based on the

CMRI Microwave De-oiling Model, CMRI-MD Model, is described in more detail in Section 5,

and shown in Figure 5-1. These results are summarized in Table 4-1.

The results demonstrate the remarkable ability of microwave de-oiling to successfully separate very

diverse range of waste sludges into water, oil, and solids.

4- 1

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#15 Filter #9 Oil #7 #22Steel #18 #23b Cake Waste Coolant Mill Machine Airline

Sludge Tank Sludge Grindings Waste

Figure 4-3 Total oil cleaned by microwave de-oiling (one stage).

m % Total Oil Removed

100%

2 .- a~ 80%

60%

40%

e 20%

P/o

s B -

YO Oil After Processing M c a,

2

#23b #18 #22Steel #7 #9Oil #15Filter Airline Machine Mill Coolant Waste Cake Waste Grindings Sludge Tank Sludge

Figure 4-4 Initial and predicted final oil concentrations cleaned by microwave de-oiling (two stage).

4-3

#15 Filter #9 Oil W #22Steel #18 #23b Cake Waste Coolant Mill Machine Airline

Sludge Tank Sludge Grindings Waste

Figure 4-5 Predicted total oil cleaned by microwave de-oiling (two stage).

0 % Total Oil Removed 7 I I

Table 4-1 Oil Concentrations of Samples Cleaned by Microwave De-oiling

Initial Oil Sample Type Content

(%)

Airline Waste (#23b) 54.87

Machine Grindings (#18) 29.53

Steel Mill Sludge (#22) 10.00

Coolant Tank Sludge (#7) 28.24

Oil Waste Sludge (#9) 95.00

Filter Cake (#15) 2.25

After Processing Oil Content

(%I

0.7 1

0.69

1.18

3.65

30.63

1.01

Oil Removed by One-S tage Microwave

Process (%I

98.7 1

97.66

88.20

87.08

67.76

55.11

Oil Removed, as Predicted by CMRI-MD Model with Two-Stage Microwave

Process (W 99.94

99.88

99.41

99.35

98.39

97.76

4-4

Coolant Tank SludPe (#7): This sludge had a composition of approximately 22% oil, 21% water,

and 57% solids. The initial oil concentration was 28% (dry, water-free basis) and the final

microwave processed oil concentration was 3.65% which translates to a first pass removal of 87%

of the total oil. Using the CMRI-MD Model, 99.35% of the oil can be readily removed when this

sample undergoes a two-stage microwave de-oiling process.

Waste Sludge (W): This refined industrial oil waste was comprised of approximately 77% oil,

19% water, and 4% solids. The waste prior to processing had an oil concentration of 95% (dry,

water-free basis). After an initial pass through the microwave system, the final oil concentration

was 30.63%. The total oil removed from this waste was 68%, but when a two-stage process is

incorporated, the CMRI-MD Model predicts a total oil removal of 98.39%, a substantial increase in

oil extraction.

Filter Cake (#15): The oil, water, and solids content for this sample was 2%, 15%, and 83%,

respectively. The initial oil concentration was 2% (dry, water-free basis) and the final microwave

processed oil concentration was 1.01% which translates to a first pass removal of 55% of the total

oil, but when a two-stage process is incorporated, the CMRI-MD Model predicts a total oil removal

of 97.76%.

Machine Grindings (#18): The composition of the machining lubricate waste was approximately

26% oil, 11 % water, and 63% solids. The initial oil and final microwave processed oil

concentrations were 30% and 0.69%, respectively. This corresponds to a total oil removal of

98%. The two-stage CMRI MD Model predicts that 99.88% of the total oil can be readily

separated from the solid particles.

4-5

Steel Mill S1udP.e (#22): This magnetically concentrated sludge contains 8% oil, 18% water, and

74% solids. Before processing the oil concentration was 10%. After a single pass through the

microwave system, 1.18% of the oil remained which means that 88% of the total oil was removed.

The CMRI-MD, two-stage, predicted total oil extracted from this sample is 99.41%.

Airline Waste (#23): The composition of the oily waste water was approximately 10% oil, 8 1 %

water, and 9% solids. The initial oil and final microwave processed oil concentrations were 55%

and 0.71%, respectively. This corresponds to a initial one-pass oil removal of 99%. The CMRI-

MD, two-stage, model predicts that 99.94% of the oil can be removed from this sample.

4-6

Section 5 DISCUSSION

The results of the testing program demonstrate the ability of microwave de-oiling to successfully

separate a very diverse range of waste sludges into water, oil, and solids. From progress to date,

it is expected that the microwave processing methodology, with CMRI's refinements for oily

solids, will be commercially practical and cost effective. The processing can be implemented using

commercially available waste handling equipment and microwave hardware components.

Basic Description of the Microwave De-oiling Process

In the CMRI process, reusable catalytic process fluid couples the microwave energy directly into

the sludge's oil interface. Utilizing principles of differing relative microwave dielectric absorption

and heating, the microwave energy generally does not directly heat either the water phase nor the

solids. In a controlled continuous-process flow condition only the oil interface is directly heated

by the microwaves, not the bulk of the material being processed. Therefore the energy

consumption is very low and is directed and isolated to where it does the most good - at the oil

interface. The heating of only the oil interface releases the oil from the solids, coalesces the oil

droplets, and separates the oil from the process fluid.

Based upon the microwave project work CMRI has developed a microwave de-oiling model. This

model predicts the final cleanliness of pmicles/materials as a function of the initial oil concentration

md process parameteis. A gmph of the most recent mociel results is iiiustrated in Figure 5- 1. The

model currently accounts for parameters such as dilution factors, process-chemistry extraction

efficiency, specific gravity, process-fluid retention on the solids and multiple process stages. The

graph displays curves for both nonoptimized and for theoretical-best de-oiling results and

5- 1

additionally for one and two stage microwave de-oiling methods. The second stage method

incorporates a rinse with clean process fluid to dramatically enhance oil separation efficiency.

a,

a, *-,

a c c

0 6co

O . O O l ! , , , , : I I , I : I , I I : , , , , : , , I #

0 5 10 15 20

% Orig ina l O i l on Cleaned S o l i d s (by w e i g h t )

Figure 5-1 CMRI microwave de-oiling model, showing

% oil retention vs. % original oil on cleaned solids.

Benefits of Microwave De-oiling

Microwaves cause a specific chemical de-oiling reaction without directly heating the water

or the solids.

Operational costs appear to be dramatically less than current alternatives.

De-oiling chemicals are nonflammable, nontoxic, and reusable in a closed-loop system.

5-2

Reclaimed materials are suitable for recycling.

Near-Zero waste process minimizes environmental problems.

Block Design

CMRI has developed process techniques and new chemistries that reduce general sludges into

separate components of clean particle/solids and recovered oil. The sludge recycling technology

utilizes conventional waste processing hardware in combination with commercial microwave

process hardware components. This process methodology provides full separation of both the oil

and the solids from general oil/water/solids sludges.

A simplified block diagram of the microwave de-oiling process can be seen in Figure 5-2. The

approach involves two key process steps. The first step uses conventional de-watering/sludge

concentration hardware to extract from the waste sludge as much water as practical. For sludges

containing ferrous materials, the preferred choice for de-watering is magnetic concentration

because of its good separation efficiencies with minimal operating costs. Other conventional

dewatering techniques such as filter presses, vacuum drum filters, API separators, dissolved air

flotation (DAF) systems and other filter/concentration techniques can be utilized to achieve the best

cost efficiency. Where applicable, the cleaned water extracted from the concentrationlde-watering

stage is returned to the main process flow or discharged according to public utility regulations.

This methodology minimizes the size of the process equipment and flow rates for the second step.

The second step uses microwave processing to achieve complete de-oiling of the solids that make

up the concentrated sludge. In this second step, reusable catalysts are added to the sludge to

achieve full separation when exposed to microwaves. This advanced technology eliminates the

need for much of the large-scale hardware and consumables that are employed in conventional de-

oiling technologies such as washing systems and solvent extraction.

5-3

Microwave Metallic Sludge Cleanup Process (Simplified Schematic)

Oil / Metal / Water Sludge

.~~

.-

I c Z Z ; z o r I Filter Water with Rinse Additive

Recovered Oil -

Recovered Metal I

Thickener

Figure 5-2 Block diagram of the CMRI/EPRI/CMP microwave de-oiling process.

For the CMRI microwave processing, the key process steps involve:

1) De-watering the oily sludge (containing solids) by magnetic or conventional filtrationhoncentration.

2) De-oiling the solids in a microwave process chamber using a special release agent which

3) Simple phase extraction of the cleaned oil from the process fluid for example by skimming

causes a phase separation of the oil from the solids.

or centrifugation of the oil.

settling and underflow draining or filtering of the solids. 4) Simple separation of the cleaned solids from the process fluid for example by gravity -

- The release agent is a proprietary formulation that is nontoxic, noncombustible and low cost. For additional details on the process please refer to the Ch" report #92-6, "Apdication of Microwaves to the SeDaration of Oil-Water Sludges",a.

5-4

Section 6 ECONOMIC ANALYSIS

The unavoidable problem exists that industrial processes generate oily sludges. The sludge

problem is exacerbated by the rising cost of waste disposal. Emerging microwave de-oiling

processes have exceptional commercial potential to solve these problems.

Typical costs for the disposal of general waste sludges, based upon the survey responses are in the

range of $0.10 to $1.30/gallon ($3 to $450/ton) and average $0.76/gallon ($153/ton). It is not

unusual for manufacturing plants to generate 20 tons of waste sludge per day, amounting to more

than 7000 tons/year. With conservative estimates of more than 800,000 tons (700,000 gallons) of

waste sludge generated per year, this projects to more than a $128 million dollar yearly expense

across industry."

* Total tons/year, gallons/year, or cosrs/year based upon he sum obtained from all survey respondents, multiplied by an estimate of 40 companies generating sludges for each sample type.

Graphical illustrations of dollars/year, dollars/ton, dollars/gallon, tons/year, and gallons/year from

all questionnaire respondents can be seen in Figures 6-1 through Figure 6-5. Table 6-1 details

disposal cost comparisons for the current disposal of waste sludges and the projected microwave

separation process' service treatment/disposal costs. The microwave process costs can be seen to

be significantly less than the majority of the current disposal costs.

6- 1

f i l t e r cake *I5 residual waste * I2

machine shop grindin s '5 industrial waste 019 *27

coolant tank sludge *7 wire drawing coolant *8

open system water waste * I7 oi ly waste Sludge * 14

auto Shop slud e *3 ro l l i n coolan?*28

cugting fluid * I mini -ml l l sludge *2

coolant waste *20 machine coolant * I 1

machine shop grindings * 18 waste sludge '9

steel m i l l sludge *6 airline waste *23

steel m i l l slud e *22 machine Shop s d g e 04

$1,000 $10,000 $100,000 $ I,000,000 $ I0,000,000

Dollars per Year (log sca le )

Figure 6-1 Yearly disposal costs for the various waste types.

6-2

ma(

rolling coolant *28

industrial w a s t e oil '27

machine coolant * I 1

oily was te sludge * I4

wire drawing coolant *8

coolant waste *20

auto shop sludge '3

coolant tank sludge *7 :hlne shop g r indhgs * 18

$0.00 $0.20 $0.40 $0.60 $0.80 $1.00 $ 1.20 $1.40

Dollars per Gallon

Figure 6-2 Disposal cost per gallon for various waste types.

coolant tank sludge *7 industrial was t e o i l *27 wire drawing coolant *8

auto Shop sludge 63 cutting f luid * I

oily was te sludge '14

machine Shop grindings * I 8

coolant waste *20

machine coolant * I I

rolling coolant *28 waste sludge *9

IO00 10000 I00000 100000

Gallons p e r Year Disljused ( i o g scaiej

' 0

Figure 6-3 Disposal gallons per year for various waste types.

6-3

open system water was te * I7

rilter cake *I5

residual was te p I 2

steel mlll sludge 622

steel mill sludge *6

mini-mill sludge *2

machine shop grindings '5

airl ine was te *23

machine shop sludge '4

$ 1 $10 $100 $ I ,oo

Dollars p e r Ton (log sca le )

Figure 6-4 Disposal costs per ton for various waste types.

machine shop grindings '5

f i l t e r cake *I5

residual was te * I2

mini-mill sludge

airl ine was te * steel mill sludge

machine shop sludge

open sys tem water was te * s t ee l mill sludge *

23

*6

*4

dollars/ton 0 ' 0

'17

'22 J IO 100 1000 10000

Tons per Year Dtsposed !!eg scale!

tonsly ear

Figure 6-5 Tons per year disposed of for various waste types.

6-4

Treatment service and disposal costs for the microwave de-oiling processes, based upon estimated

commercial systems' energy usage, closed-loop chemistry usage, and CMRI's microwave

separation refinements are estimated to be between $9 and $15 per ton or altematively about $0.10

per gallon which is significantly lower than most other disposal methods. Details of the estimated

microwave treatment service costs can be seen in Table 6-2. The resultant products from the

microwave process are transformed into separate oil, water, and clean material that can be recycled.

Table 6-1 Comparison of Waste Disposal Costs

WASTE TYPE machine shop sludge #4 steel mill sludge #22 airline waste #23 steel mill sludge #6 minimill sludge #2 open system water waste #1 machine shop grindings #5 residual waste #12 filter cake #15

Microwave Treatment Costs

WASTE TYPE waste sludge #9 machine shop grindings #18 machine coolant #11 coolant waste #20 cutting fluid #1 auto shop sludge #3 oily waste sludge #14 wire drawing coolant #8 coolant tank sludge #7

DOLLARWEAR $1,557,500

$525,000 $423,545 $28 1,138 $37,500 $15,120 $4,000 $3,200 $2,100

DOLLARSmAR $90,000 $65,000 $60,000 $50,700 $30,000 $26,000 $21,500 $9,000 $6,000

TONSrYEAR DOLLARSlI'ON 3500 7000 1300 281 1 250

5040 20 80 60

GALLQNS/YEAR 300000 50000

143000 78000 30000 26000 50000 20000 4800

$445.00 $75.00

$325.80 $1 00.0 1 $150.00

$3.00 $200.00 $40.00 $35.00

$15.00

DOLLARS/GALLON $0.30 $1.30 $0.42 $0.65 $1 .oo $ 1 .oo $0.43 $0.45 $1.25

$0. io

6-5

Table 6-2 Detail of Projected Operating Costs Using New

Microwave Process for the Treatment of Waste Sludge

MAX. M I C R O W A V E DE-OILING OUTPUT % Solids 5 0 % S lu r ry 15 GPM MAX. (Oil,water,solids)

Daily INPUT (*oi l/solids/water sludge) ave. density r a t i o water density 8.33 lbs/gallon MAX. TONS/DAY 125.9496 Tons/DAY MAX. OUTPUT 0 . 0 0 5 8 3 1 Tons/gallon

2 1600 gallons *

1.4 (rat io to water)

4597 1.604 MAX. Tons/YEAR

ELECTR I CAL COSTS COST/DAY COST/TON

Industrial Rate $0.05 per kwH

MICROWAVE PROCESS Source (kw) 2 5 0 kw Source/day 6 00 0 kw H/day $300.00 Pumps & motors HP 10HP Pumps & motors/day 182.4 kwH/day $ 9 . 1 2

MICROWAVE $ 3 0 9 . 1 2 /day SUBTOTAL

DE-WATERING SYSTEMS F i l t e r e d Dewate r ing E l e c t r i c a l Costs Pumps & motors HP 9 0 HP $82 .08 /day Pumps & motors/day 1 6 4 1.6 kwH/day

Magnet ic De-w a ter ing E l e c t r i c a l Operat ing Costs E 1 ec t rom agne t ic m in. Example: hot s t r ip 3 6 0 0 kwH m i l l

150 kw $ 1 8 0 . 0 0 /day

Electromagnetic Max. 5 0 0 kw Example: hot s t r ip 12000 kwH/day $600.00 /day m i l l

$ 2 . 4 5 /Ton

$ 0 . 6 5 /Ton

$ 1 . 4 3 /Ton

$ 4 . 7 6 /Ton

GENERAL CHEMICAL COSTS -

tank Y r . $ 0 . 0 3 /Ton

Chemical Makeup & Carry-off makeup $145 .80 /day $1 .16 /Ton

OPERATING COSTS General Maint. & Repair $ 1 . 0 0 /Ton LABOR TONS/yr.: 26000 Salary & $ 5 0 , 0 0 0 $ 1 . 9 2 /Ton

e n I 1 590 gallcr: prccess (me time) se:i;p 4-1. I I /day f l E t

-

Benefits:

6-6

BAS I S PROFIT GENERAL PROFIT FROM MARKUP

T y p i c a l P l a n t Operat ing Costs f o r One Year.

$ 5 . 0 0 /Ton

*** MWP = M l c r o W a v e P r o c e s s *** PER PLANT Tonslyear Cost/Ton Cost/Gallon Cos t / Y ear FIGURES Current Disposal 7 0 0 0 $75 .00 $0.44 $525 ,000 example: System New MWP, w / f i l t e r 7000 $12 .22 $ 0 . 0 7 $ 8 5 , 5 3 5 most nonferrous wastes New MWP, w/mag. 7000 $13 .65 $0 .08 $ 9 5 , 5 3 9 example: steel m i l l m in. sludge New MWP, w /mag. 7000 $ 1 6 . 9 8 $0 .10 $ I 18,882 example: steel m i l l max. sludge

LAST REVISION DATE: 12-22-93

6-7

Section 7 CONCLUSIONS AND RECOMMENDATIONS

Based on the results of the study it is concluded that the microwave processing methodology,

using CMFU's refinements for oily solids, should be commercially practical and cost effective.

The process can be implemented now using commercially available waste handling equipment and

microwave hardware components. The microwave process' commercial value resides in its cost-

effectiveness to individually separate waste components while simultaneously providing the option

to recycle these components. As the EPA imposes more control on industrial waste management,

landfills close, and the cost for disposal and treatment of waste escalates, it will make this recycling

process even more valuable.

The next step in the development of the microwave de-oiling process is to demonstrate it under

actual conditions in industrial applications. EPRI utilities interested in a project to demonstrate this

novel process to their industrial customers should contact CMP.

7 - 1

Section 8 REFERENCES

1 . Application of Microwaves to the SeDaration of Oil-Water Sludges, The EPRI Center for Materials Production, Pittsburgh, Pa., CMP Report ##92-6, July 1992.

2. Microwave Processing of Mill Waste Effluent, Carnegie Mellon Research Institute, Pittsburgh, Pa., Final project report to U.S. Steel, May 1993.

8 - 1