FIELD AND BACKGROUND OF THE INVENTION

This invention relates to the recycling of used oils and more particularly used lubricating oils. The treatment system and method of the present invention relies, in part, on microfiltration techniques. Microfiltration refers to a membrane permeation filtration process where a membrane acts as a particle trapping sieve acting on a fluid which passes through it. Microfiltration is generally performed with pore sizes ranging form 0.1 to 0.5 microns.

The expression "USED OIL" refers to a fluid which is discarded, after having been used for lubricating purposes and the like, when degradation of the fluid has gradually made it unfit for its intended purpose. The degradation takes place more or less rapidly as impurities enter the fluid or as chemical and physical degradation occurs. The following categories of fluids are generally covered by the expression "USED OIL": lubricating oils (motor, turbine, gear and the like); hydraulic systems oils (including transmission oils); metal working oils (including cutting, wetting, milling, rolling, coating oils and the like); insulating or heat transfer oils; residuals oils (including oily liquids, water/oil emulsions, greases and organic solvents and oil mixtures). Used oils primarily contain hydrocarbons. Used oils can also contain various additives and solvents along with physical and chemical impurities (for example solids such as dirt, metals and the like). For these and other reasons, used oils are classified in most industrialized countries as constituting hazardous wastes.

The elaboration of systems for the efficient recycling of used oils such as lubricating oils is increasingly necessary in view of the important volume of such fluids which are discarded after having performed their useful function as, for example, in the case of motor vehicle engine oil. Consequently the proper disposal or recycling of used oils is of primary importance.

Used oils can be recycled or otherwise treated by various known methods. For example, some of the industrial used oils regeneration processes currently used in North America are as follow: acid/clay treatment; vacuum distillation/clay; vacuum distillation/hydrotreatment; chemical treatment/distillation/hydrotreatment.

One method of reclaiming used fluids is described by Martin et al in U.S. Patent 5,141,628. The process taught therein proposes the purification of used oils by initially separating undissolved impurities by mechanical separation methods such as sedimentation, filtration or centrifugation. Afterwards the solution is mixed with an aqueous solution of polyalkylene glycol.

The mixture is then neutralized and filtered to separate therefrom contaminants and impurities. Finally, a vacuum distillation is performed to complete the purification. Similarly, Reid et al in U.S Patent 4,512,878, propose a first coarse filtration to eliminate solid impurities, such as dust and metals. Afterwards, a distillation process is described as eliminating water and light fraction contained in the used oil. The distillate is then heated up to 300 °C and treated on hydrogenated adsorbent beds to reduce the content of halogenated contaminants.

Other known processes also use a distillation step as the main part of the recycling process. One such process is found in U.S. Patent No. 4,941,967, wherein a lube oil feed is subjected to a vacuum distillation and

subsequently to thin-film evaporation under vacuum. Similarly, Fletcher et al in U.S. Patent 4,342,645 teach the regeneration of used oils by fractionated distillation.

Keim et al in U.S. Patent 5,049,258 propose a distillation followed by hydrocracking treatment to eliminate chlorinated contaminants found in some used oils.

Each of those processes carry important inconveniences mainly related to the generation of waste products and high energy consumption.

Nevertheless, other known methods which teach filtration techniques do exist for dealing with hydrocarbon fluids. One method is taught by McCants in U.S. Patent 4,904,385 and uses a centrifuge equipped with a filter of pore size of less than 50 microns (preferably 10 to 20 microns) to separate dust or solid impurities from petroleum emulsions. The oil is then heated to evaporate the water. Audibert et al, in U.S. Patent 3,990,963, reveal a process using ultrafiltration techniques. Ultrafiltration consists of the use of semi- permeable membranes acting as molecular sieves, generally retaining molecules from 5,000 or more in molecular weight, for fluids passing through them. In the process disclosed by Audibert et al, used oil is initially heated to a temperature between 200 and 500 °C under a pressure of 0.1 to 50 bars and then fractionated to remove light fractions and water vapor. Afterwards, using polymeric ultrafiltration membranes, the oil is filtered at a temperature between 10 °C to 80 °C. This latter operating temperature is quite low and corresponds to the typically low resistance limits of the ultrafiltration membrane. The obvious disadvantages of this process are its high energy consumption, the fragile nature of the ultrafiltration membrane, and the very low ultrafiltration temperatures

dictated by the membrane resistance which slows and generally hampers the filtration process as the oil is increasingly viscous and its flow becomes less turbulent as its temperature is reduced. It has also been suggested in the art to use microfiltration ceramic membranes with 0.2 micron pore size to reclaim used oils. However such processes have so far failed to exhibit the acceptable performance in part because of repeated clogging of microfiltration membranes. Danzinger et al in U.S. Pat. No. 4,179,019 discloses a multi-step portable filtration apparatus. A first filtration using coarse filters is followed by a distillation to remove water vapor and volatile fractions. The distillate is again filtered by this time through a bank of earth filters. Similarly, McGehee in U.S.

Pat. No. 4,784,751 advocate the use of a coarse filter to eliminate solid impurities. The used oil is then heated to 180 °C to remove water and volatile fractions fraction.

Finally, the use of polar membranes as also been discussed for the regeneration of used oils. For example, Chang et al in U.S. Pat. No. 4,595,507 use 10 to 500 Angstrom hydrophylic membranes to separate the light fraction from the heavy fraction at a temperature lower than 100 °C and a pressure between 50 and 1000 psi. Similarly, Taylor et al in U.S. Patent 4,886,603 also propose using hydrophillic membranes, such as cellulose fiber membranes, to remove water from hydrocarbons. In a subsequent step, other hydrophillic membranes are used to remove halogenated hydrocarbons.

In summary, although various attempts have been made to develop equipment and processes to reclaim used oil, there remains a long felt need for an improved process and method for reclaiming used oils.

SUMMARY OF THE INVENTION

According to the present invention, there is provided an improved microfiltration process and method for reclaiming and regenerating used oils so that the recycled oils can be use, for example, as a lube base stock for blending different types of lubricants. More particularly, the equipment layout and operating conditions disclosed herein allow yields of oil regeneration of at least 90 percent weight per volume of used oil feedstock while avoiding uncontrollable clogging of the microfiltration unit.

A further object is to obtain by the process and method of the present invention a regenerated oil with a composition, viscosity, and color similar to that of fresh oil.

Still further objects are to obtain process improvements resulting in an increased yield in purified oil on a weight percent basis of the used oil. Related objects are to reach improvements in the following areas: improved process control capabilities; obviating the need to evaporate light fractions; improved recuperation of metallic contaminants; increased quality and viscosity of the recycled oil; reduction of filtration membrane clogging; and increased viscosity of the by-product (retentate) of the recycling process. Incidentally, the by-product of the recycling process which is essentially a concentration of contaminants present in the used oil feed can also be usefully recycled by known processes for diverse uses such as bitumen preparation or synthetic rubber manufacturing.

Additional objects will be made apparent from the following description.

The system of the present invention is intended for use in a process for recycling used oils at yields reaching in excess of 90 percent of recycled oil per volume of used oils. Essentially the system of the present invention comprises: a feedstock of used oil entering the system through a feed line, circulation pump means for pumping a flow of used oil at a pressure of at least 105 psi, heat exchange means for heating said flow of used oil at a temperature of 200 °C to 500 °C, at least one microfiltration unit containing a plurality of microfiltration membranes with pore sizes ranging from 0.1 and 0.5 microns for microfiltering said flow of used oil and separating therefrom a permeate of recycled oil and retaining a retentate of used oil for recirculation in the system, whereby during operation of the system, the flow of used oil upstream of the microfiltration means is controlled by monitoring temperature or pressure in the system to remain at a Reynolds number of at least 2300.

The present invention also discloses a method of recycling used oil using the system of the present invention and comprising the steps of :

(a) feeding used oil feedstock into the system;

(b) heating the used oil feedstock to a temperature range of 200 °C to 500 °C;

(c) circulating the used oil at a flow rate corresponding to a Reynolds number superior to 2300; (d) microfiltering the used oil at a pressure of at least 105 psi, whereby a recycled oil permeate and a contaminated retentate are separated;

(e) recovering the permeate obtained in step (d);

(f) recirculating into the system the retentate obtained in step (d).

It has been found that to avoid clogging of the microfiltration unit membranes, it is necessary, that the Reynolds number of the used oil flow therethrough be higher than 2300.

Optionally, the system may include an absorption unit to remove halogenated hydrocarbons, as well as heterogenous, naphthalic, and aromatic compounds from the permeate obtained from the microfiltration unit.

Also optionally, the system may include a distillation unit to remove volatile fractions and water vapor from the used oil.

Also optionally, the system may operate on a batch, continuous flow or cascading multi-stage modes.

The present invention using a microfiltration method yields oils essentially free of metallic impurities. The microfiltration membrane acts as a particle sieve to retain these and other impurities in a retentate. The retentate can also be further recycled by known processes to extract useful substances therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a flowsheet of the present invention in a batch mode embodiment;

Figure 2 shows a flowsheet of the present invention in a continuous flow mode embodiment;

Figure 3 shows a schematic perspective view of a ceramic microfiltration module; Figure 4 shows a schematic perspective view of a stainless steel microfiltration module;

Figure 5 shows a flowsheet of the present invention in a cascade mode embodiment wherein continuous flow unit A cascades into continuous flow unit B;

Figure 6 shows schematically an absorption column; Figure 7 shows a flowsheet of a preferred embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Batch mode operation

Referring now to FIG 1 there is shown one embodiment of the present invention wherein the reclaiming and regeneration of the used oil is accomplished in batch mode.

In batch mode, the startup procedure will first be described. The system includes a circuit open to feed tank 10 containing used oil. Through pump 12, the used oil goes through a conventional heat exchanger 14. The pump 12 can be a centrifuge type pump with a variable speed motor capable of delivering a pressure range of 80 to 150 psi. The pumping rate is adjusted according to the viscosity of the retentate in order to obtain a circulation rate sufficient to maintain a Reynolds number higher than 2300. The oil is temporarily recirculated to tank 10 to allow the used oil to be heated to a adequate temperature of above 200 °C. This is done when valve 16 is open and valve 18 is closed.

Once the used oil flow reaches a temperature superior to 200 °C, valves 18 and 20 are open and valve 16 is closed to pass the used oil through the microfiltration unit 22 containing microfiltration membranes having pores sizes inferior to 0.5 micron, and preferably between 0.1 to 0.5 micron. The filtrated oil (permeate) is routed toward holding tank 24. During the production run, the flow of permeate will gradually decrease as impurities will be concentrated in the circulation loop. To avoid clogging of the microfiltration unit 22, the circulation loop flow of concentrated used oil is maintained at a Reynolds number of at least 2500 and preferably 3000. This is done by supplying further heat and pump pressure to the circulation loop. When the Reynolds number of the circulation loop flow drops to approximately 2500, the production run is stopped and the retentate oil is flushed out of the loop to tank 26 by opening valve 28 and closing valves 16 and 18. In order to avoid heat loss, the system is properly insulated.

Continous mode of operation

Referring now to FIG 2 there is shown a continuous mode system of the present invention. The continuous mode system is essentially a closed loop system. Used oil is fed by variable speed gear pump 30 to the closed loop. Centrifugal pump 32 pushes the used oil through a conventional heat exchanger 34. On startup, valve 35 will be open while valves 36, 38, and 40 will be closed to allow the used oil to recirculate many times to be heated to a temperature of at least 200 °C. As in the batch process, centrifugal pump 32 has a variable speed motor generating a pressure range of 80 to 150 psi. The circulation flow

is again regulated according to the viscosity of the oil in the circulating loop in order to obtain a Reynolds number superior to 2500 and preferably superior to 3000. This ensures a turbulent flow which in turn prevents membranes clogging in the microfiltration unit 42. At steady-state valves 36, 38, and 40 are open while valve 35 is closed to pass the used oil through the microfiltration unit 42 containing microfiltration membranes having pores sizes inferior to 0.5 micron, and preferably between 0.1 to 0.5 micron. The filtrated oil (permeate) is routed toward holding tank 44. During the production run, the flow of permeate will gradually decrease as impurities will be concentrated in the circulation loop. To avoid clogging of the microfiltration unit 42, the circulation loop flow of concentrated used oil is maintained at a Reynolds number of at least 2500 and preferably 3000. This is done by supplying further heat and pump pressure to the circulation loop. When the Reynolds number of the circulation loop flow drops to approximately 2500, the retentate is directed to the tank 46. This operation is automatically accomplished by an automatic signal received from a viscometer 48 on valve 36. In order to avoid heat loss, the system is properly insulated.

In both modes of operation the microfiltration membranes could be either metallic, such as stainless steel membranes commercialized by DuPont Nemours, for example, model 2.5-626A-5P or, optionally, ceramic membranes such as those commercialized by U.S. Filter Corp, for example, model P 19-60. FIG 3 schematically illustrates a typical ceramic tube bundle microfiltration unit having a plurality of hollow thin walled and permeable tubes. For ceramic membranes, the operating conditions of the microfiltration unit are a circulation

temperature superior to 200 °C and an operating pressure superior to 105 psi up-stream of the microfiltration unit.

FIG 4 schematically illustrates a typical metallic tube bundle microfiltration unit 54. Tubes 56 are generally somewhat larger in diameter than in the case of ceramic membrane tubes. For metallic membranes, the operating conditions of the microfiltration unit are a circulation temperature superior to 200 C and a pressure superior to 105 psi up-stream of the microfiltration unit. As for the ceramic membranes, the operating conditions of the microfiltration unit are a circulation temperature superior to 200 °C and an operating pressure superior to 105 psi up-stream of the microfiltration unit.

It is to be understood that other microfiltration unit designs could be used such as stack, cross-flow or bi-flow stack, and spiral module designs.

Optional multi-stage cascading system

Turning now to FIG 5, it is important to note that the arrangement and number of microfiltration units and their operating conditions such as temperature and pressure does affects the production rate and yield of recycled oil (permeate) through the membranes. With this in mind, one versed in the art could conceivably optimize the number of membranes and microfiltration units to be used in a continuous system by devising a cascading multi-stage equipment layout. In a cascading system, the concentrated oil

(retentate) or the recycled oil (permeate) become the feedstock of a second microfiltration unit.

Consequently it becomes advantageous to operate with a cascading system to optimize the yield of the system. However, it must be kept in mind that such a system would entail higher capital investments in equipment.

FIG 5 shows a two-stage cascading system. The two-stage system is a cascade of two distinct systems (A and B) which are each essentially similar to the continuous mode system of FIG 2. The difference between units A and B lies in the pore size of the microfiltration membranes. Since Unit B receives the permeate of Unit A and is equipped with finer microfiltration membranes to further remove contaminants that may still be present. The used oil is injected into unit A by a gear pump 58, having a variable speed motor. A variable speed centrifugal pump 60 maintains a pressure of 150 psi up-stream of the microfiltration unit 62. The circulation rate is calculated depending on the viscosity of the oil in order to reach a Reynolds number preferably superior to 3000 corresponding to a sufficiently turbulent flow. The heat exchanger 64 heats the used oil to a temperature superior ranging from 200 to 500 °C. To maintain a Reynolds number superior to 3000 during the use of the system, the operating temperature will be constantly adjusted as a function of the viscosity of the used oil entering the system. The heated oil passes through microfiltration unit 62 having membranes with a 0.1 to 0.5 micron pore sizes. The permeate (permeate I) is stocked in a storage tank 66.

Meanwhile variable speed gear pump 68 uses the permeate I has the feedstock to unit B. The centrifugal pump 70 maintains a pressure superior to 125 psi up-stream of the microfiltration unit 72 having generally finer pore sizes than microfiltration unit 62. The temperature is controlled by heat exchanger 74. The recycled oil (Permeate II) is directed to holding tank 76. The

temperature and the circulation rate are again calculated in order to maintain a turbulent flow also corresponding to a Reynolds number superior to 2500 and preferably 3000. The permeate II generally has a viscosity of 23.5 cSt at 40 °C. In units A and B, the viscosity of the circulation loop is controlled by the viscometers 78 and 80. The advantage of the multi-stage system can be summarized in better viscosity control of the retentate and a product quality that is similar to commercial grade bitumen. Also, there is an increase of generally 5 to 10 % in the yield of the system based on weight recycled oil per volume of used oil when compared to a single stage system.

Optional distillation unit

Optionally, a distillation unit (atmospheric or vacuum) can be added up-stream or down-stream of the microfiltration unit, in either batch, continuous, or multi-stage systems, to separate the volatile fractions and the water vapor or to fractionate the permeate. Such an optional arrangement is shown in dotted lines in FIG 7.

Optional absorption unit

The recycled oil (permeate) obtained from the microfiltration treatment of the present invention whether it be in batch, continous or multi¬ stage modes, has obvious qualities as specialty fuel oil. However, the recycled retains a dark tint given to it mainly by halogenated hydrocarbons, as well as

heterogenous, naphthalic, and aromatic compounds, and consequently is unsuitable to be re-used has a base oil for blended oils. A decoloration post- treatment by adsorbents, such as alumina, clay or the like is then required.

FIG 6 illustrates an absoφtion unit 82 which can receive the permeate obtained following microfiltration. The absoφtion unit 82 can, for example, be a packed column. Obviously other conventional designs are suitable. The adsorbent used, such as alumina has a particle size generally inferior to 48 Mesh, to allow good contact with the recycled oil. The absoφtion unit 82 generally operates at temperatures inferior to 200 °C and at pressures inferior to 150 psi. The pressure is generated by pump 84. Valve 86 is used to control the regenerated oil flow rate in function to the operating conditions. With such an arrangement, it is possible to obtain a regenerated oil with a yellow tint corresponding to a color indicae inferior to 3 according to ASTM D-1500 method. After this step, the regenerated oil can be recycled as part of a high quality lubricant.

Overall process diagram

FIG 7 shows an overall diagram of the used oil reclaiming system of the present invention, including its ancillary equipment. Firstly, used oil is transferred in a storage tank for quality control. The oil is then transferred to a second storage tank used to feed the system. In dotted lines there are shown optional distillation units used to separate the volatile fractions and water from the used oil stream. The permeate produced by the microfiltration system is routed to an adsoφtion system to obtain a lube base stock of light tint.

It is to be understood that various additives may be incoφorated at any point in the systems and methods of the present invention. The role of additives tends to enhance the used oil recycling process by lowering the viscosity of the used oil or to aid the microfiltration step.

Experimental

The present invention is further illustrated with the following examples, which should not be construed as limiting the scope of the invention.

Example 1:

In a continous system, as for example the system illustrated in FIG 2, a microfiltration loop was fed by a gear pump with used oil. The oil was further heated to a temperature of at least 225 °C by an electrical heat exchanger with a capacity of 30 kW. At steady state, a centrifugal pump downstream of the heat exchanger and upstream of the microfiltration unit generated a pressure of approximately 150 psi at the entry of a stainless steel microfiltration unit having 0.2 micron pore size and a total filtration surface of

3.2 square feet. The flow rate and the temperature of the circulation loop were periodically adjusted according to the viscosity of the retentate in order to maintain a flow rate corresponding to a Reynolds number of 3000. The temperature ranged from 225 to 300 °C. The system was shut down and the retentate was flushed out when the Reynolds number finally dropped below

2500. Flushing the system is necessary to avoid membrane clogging which frequently occurs when the flow becomes laminar at a Reynolds number lower than 2300. After discharge of the retentate, used oil was again fed to the system.

With such a system the resulting permeate was produced at a rate of 16 GFD, with a viscosity of 22 cSt at 40 °C, and a color indicae of 6 according to the ASTM-D1500. The yield of the operation, according to the viscosity of the used oil, is between 90 to 95 % volume of total recuperation of the recuperable lubricant content in the used oil. The permeate analysis indicate a constant density and viscosities at any concentration factor of the oil in the circulation loop. The metals recuperation at the applied temperature was satisfactory. Table 1 shows the comparative metal concentration found in the used oil and the permeate.

Table 1: Results of the demetallization of used oil

Example 2:

A used oil with an initial boiling point of 200 °C after distillation was processed using a continous mode of operation as shown in FIG 2 using a microfiltration unit equipped with ceramic membranes with a 0.2 micron pore size. The operating pressure generated by a variable speed centrifugal pump, located upstream of the microfiltration unit, was initially set at 125 psi. Heating of the system was effected by an electrical heat exchanger with a capacity of 30 kW in order to obtain an start-up temperature of 200 °C in the circulation loop of used oil. The pumping rate of the centrifugal pump and the temperature of the circulation loop were monitored and adjusted to maintain a state of turbulent flow of used oil (Reynolds number superior to 3000). Because the Reynolds number is related to the viscosity of the fluid and the rate of pumping, a temperature increase will decrease the viscosity which will in turn increase the Reynolds number for a given pump speed. As expected, during the operation of the system the viscosity of the retentate increased as impurities collected in the circulation loop. The temperature was adjusted to a maximum of 275 °C and the pump pressure to a maximum of 150 psi. When the Reynolds number finally dropped below 2500, the system was flushed of the retentate by an automatic signal coming from the viscometer 48 on the motorised valve 36 and further used oil was permitted to enter the circulation loop.

Table 2: Comparative analysis of used oil and of permeate obtained by microfiltration.

Proprieties Used oil Permeate

Viscosity @ 40 ^* C (cSt) 32 22

Flash point ( ^* C) 90 120

Water (%) Trace —

Lead (ppm) 32 < 0.5

Copper (ppm) 13 < 0.5

Arsenic (ppm) <0.2 < 0.2

Zinc (ppm) 656 <0.2

Chrome (ppm) <0.2 <0.2

Vanadium (pP ^m ) 2.2 <0.2

Calcium (ppm) 432 < 1.0

Iron (ppm) 146 < 1.0

Magnesium (ppm) 546 < 1.0

Sodium (ppm) 58 1.0

Nickel (ppm) 1.4 < 0.2

Example 3

This example used a two-stage cascading unit as illustrated in FIG 5. Used oil with a viscosity of 36 cSt at 40 °C, was injected by a variable speed gear pump at a maximum rate of 10 GPM into the microfiltration unit A. The centrifugal pump maintained a pressure of 150 psi upstream of the microfiltration unit equipped with stainless steel membranes. An electrical heat exchanger with a capacity of 30 kW kept the temperature of the circulation flow superior to 200 °C. The circulation loop flow rate and temperature were calculated according to the viscosity of the oil so that turbulent flow (Reynolds number superior to 2500 and preferably 3000) was maintained. Temperature was gradually increased to a maximum of 275 °C to reduce the viscosity in the circulation loop. The heated oil was passed through the stainless steel microfiltration membranes having 0.5 micron pore size. The permeate (permeate I) was produced at a rate of 17.1 GFD and was stocked in a tank for subsequent analysis. The yield of the operation was 92 to 97 % volume of total recuperable lubricant fraction. A second variable speed gear pump introduced the permeate I as feedstock of the second stage Unit B. The centrifugal pump maintained a pressure of 150 psi upstream of the microfiltration unit, the latter equipped with stainless steel membranes having 0.2 micron pore size. The temperature was controlled by an electrical heat exchanger with a capacity of 30 kW. The temperature and pumping rate in the circulation loop were calculated in order to maintain a turbulent flow rate. The permeate II produced at a rate of 18 GFD has a viscosity of 23.5 cSt at 40 °C. In a subsequent step the permeate II was passed through a upright catalytic adsorbent column containing particles of aluminum oxide, said column having a height of 30 cm and a diameter of 5 cm. The particle size of aluminum oxide used was mesh 24. The column was operated under a pressure of 40 psi and a temperature of 70 °C. The resulting recycled oil obtained had a color indicae less than 3 as calculated from the ASTM-D1500 method. Table 3 presents the data obtained.

Table 3: Results of microfiltration and absoφtion

Proprieties Used oil Permeate Absorbed oil

Viscosity @ 40 ^* C (cSt) 36 23.5 21.4

Flash point ( ^* C) 90 120 122

Water (%) Trace — -

Color 10 6 2

Lead (ppm) 32 < 0.5 <0.1

Copper (ppm) 13 < 0.5 <0.1

Arsenic (ppm) <0.2 < 0.2 <0.1

Zinc (ppm) 656 <0.2 <0.1

Chrome (ppm) <0.2 <0.2 <0.1

Vanadium (ppm) 2.2 0.2 <0.1

Calcium (ppm) 432 < 1.0 <0.1

Iron (ppm) 146 < 1.0 <0.1

Magnesium (ppm) 546 < 1.0 <0.1

Sodium (ppm) 58 1.0 <0.1

Nickel (ppm) 1.4 < 0.2 <0.1

Although the invention has been described above with respect with one specific form, it will be evident to a person skilled in the art that it may be modified and refined in various ways. It is therefore wished to have it understood that the present invention should not be limited in scope, except by the terms of the following claims.