WO1998042786A9

WO1998042786A9 - Chemical mixing or reacting zone with controlled fluid through-flow

Info

Publication number: WO1998042786A9
Application number: PCT/US1998/005617
Authority: WO
Inventors: William M Porteous; John Mathew
Original assignee: Cabot Corp
Priority date: 1997-03-24
Filing date: 1998-03-23
Publication date: 1999-04-01
Also published as: WO1998042786A3; JP2001523159A; AU6867398A; US6399029B1; WO1998042786A2; EP0970150A2

Abstract

Components of a chemical processing system are disclosed. In particular, a chemical processing system is disclosed which includes a chemical mixing or reacting zone, an inlet to the zone, an outlet to the zone, and a vacuum or fluid flow source located downstream of the outlet. The chemical processing system further includes means to control the amount of vacuum or fluid flow through the zone. Also disclosed is a continuous feeder system having a first loss-in-weight and a second loss-in-weight feeder and means for measuring a lower limit of feed in each feeder. There is also a means to activate the second feeder when the lower limit is obtained in the first feeder and means to deactivate the first feeder when the lower limit is detected in the first feeder. A sample port assembly is also disclosed for obtaining a sample of material flowing through a processing system. The sample port assembly includes a port in the assembly and a sample cup holder adapted to be moved in the port to obtain a sample of material without substantially affecting the fluid pressure or flow within the system. The components of the chemical processing system can be used in processes to make carbon black having attached organic groups.

Description

CHEMICAL MIXING OR REACTING ZONE WITH CONTROLLED FLUID THROUGH-FLOW

FIELD OF THE INVENTION

The present invention relates to components of a chemical processing system. More particularly, the present invention relates to means for improving the chemical feed, means for improving sample removal from a chemical process in operation, and means for maintaining an acceptable fluid flow or vacuum through a chemical processing operation.

BACKGROUND OF THE INVENTION

In many types of chemical processing, there is a need for the

physical process parameters to be substantially maintained. Any

significant interruption of these parameters can degrade product quality,

decrease efficiency, and have other undesirable effects. For example, in

many types of chemical processing, there is a need for a substantially

uniform and uninterrupted fluid flow through a mixing or reacting zone,

such as a pelletizer. While a uniform and uninterrupted fluid flow needs to

be maintained, this presents a problem when it comes to trying to obtain a

sample of the product in order to check the quality of the product. Many

times, if one attempts to sample the product, this creates an interruption in

the fluid flow which can affect the product quality.

In addition, in certain types of chemical processing, there is a need

to maintain a continuous metering of chemicals into a mixing or reacting

zone. The metering of chemicals, many times, not only has to be

continuous, but must also maintain a consistent feed rate. Again, if there is an interruption in the continuous metering of chemical or an interruption

in the feed rate, this can lead to poor product quality. Accordingly, there is

a need to develop a system which permits the continuous metering of

chemicals and which can maintain a substantially consistent feed rate as

well.

SUMMARY OF THE INVENTION

It is an objective of the present invention to provide an overall

chemical processing system which achieves a substantially uniform and

uninterrupted fluid flow through a mixing or reacting zone.

Another feature of the present invention is to provide a means for

sampling products from a reacting or mixing zone without the interruption

of the fluid flow through the mixing or reacting zone.

A further feature of the present invention is to provide a means for

the continuous metering of chemicals while maintaining substantially the

same feed rate without interruption.

Additional features and advantages of the present invention will be

set forth in part in the description which follows, and in part will be

apparent from the description, or may be learned by practice of the

present invention. The objectives and other advantages of the present

invention will be realized and attained by means of the elements and combinations particularly pointed out in the written description and

appended claims.

To achieve these and other advantages and in accordance with the

purposes of the present invention, as embodied and broadly described

herein, the present invention relates to a chemical processing system

which includes a chemical mixing or reacting zone; an inlet to the zone;

and an outlet to the zone. The chemical processing system also includes

a vacuum or fluid flow source located downstream of the outlet and a

means to control the amount of vacuum or fluid flow through the chemical

mixing or reacting zone.

The present invention further relates to a sample port assembly for

obtaining a sample of material flowing through a processing system. The

sample port assembly includes a port in the assembly and a sample cup

holder adapted to be moved in the port to obtain a sample of the material

without substantially affecting the fluid pressure or flow within the system.

The present invention further relates to a continuous feeder having

first and second loss-in-weight feeders and means for measuring a lower

limit of feed in each feeder. The continuous feeder system further includes

means to activate the second feeder when the lower limit is obtained in the

first feeder and means to deactivate the first feeder when the lower limit is detected in the first feeder.

Each of these features can be used together in a chemical processing system or can be used individually in the chemical processing

industry.

It is to be understood that both the foregoing general description

and the following detailed description are exemplary and explanatory only

and are intended to provide further explanation of the present invention, as

claimed.

The accompanying figures, which are incorporated in and constitute

a part of this specification, illustrate several embodiments of the present

invention and together with the description, serve to explain the principles

of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic drawing of an embodiment of the present

invention representing a process system.

Figure 2 is also a schematic drawing of an embodiment of the

present invention showing a different process system.

Figure 3 is a side view of an embodiment of the sample port

assembly of the invention, with the cup holder in a closed position.

Figure 4 is a side view of an embodiment of the present invention

with the cup holder in an open position to permit insertion of the a cup and retrieval of a sample.

Figure 5 is a front view of an embodiment of the sample port assembly of the invention along the line A-A in Figure 3.

Figure 6 illustrates a top view of an embodiment of a sample cup

according to the present invention.

Figures 7 and 8 are end views of a sample cup according to one

embodiment of the invention taken along the lines B-B and D-D

respectively in Figure 6.

Figure 9 is a front view of a sample cup illustrated in Figure 6, taken

along the line C-C in Figure 6.

Figure 10 is a schematic of an embodiment of the present invention

showing a continuous dual feeder system.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The present invention relates to a chemical processing system

which involves the use of a vacuum or fluid flow through a chemical mixing

or reacting zone. The fluid flow is generally a gas, such as air. In

particular, the chemical processing system includes a chemical mixing or

reacting zone and an inlet to the mixing or reacting zone for the entry of

one or more chemical components. The processing system further

includes an outlet from the chemical mixing or reacting zone for the exiting

of one or more chemicals. For purposes of the present invention, the

chemical mixing or reacting zone can have more than one inlet and/or

more than one outlet. The chemical(s) and the fluid flow or vacuum pass through the inlet, the mixing or reacting zone, and the outlet of the mixing

or reacting zone. The fluid flow or vacuum is accomplished by a vacuum

or fluid flow source which may be located downstream of the outlet. The

processing system also includes means to control the amount of vacuum

or fluid flow through the chemical mixing or reacting zone.

The chemical mixing or reacting zone is an area in which one or

more chemicals are mixed or reacted with at least one other chemical

component. The chemicals that are processed in the chemical processing

system of the present invention can be in any state (i.e., a solid, liquid, or

gas). An example of a chemical mixing or reacting zone is a pelletizer or

pin mixer. A preferred example is a wet pelletizer. The present invention

for instance, can be used in the preparation of carbon black pellets having

attached organic groups.

In further detail, and only as an example of the preferred

embodiment, carbon black and a reactant such as solid sulfanilic acid can

be introduced into the inlet of a pelletizer through separate feeders. Once

these two components are in the pelletizer, a second reactant, such as a

sodium nitrite solution and water can be introduced into the pelletizer

through a separate or second inlet. While in the pelletizer, the solid

sulfanilic acid and the sodium nitrite solution form a diazonium salt which

in turn reacts with the carbon black to form carbon black having attached

organic groups. The details of the reaction and the type of organic groups that can be attached to the carbon black are described in detail in U.S.

Patents Nos. 5,554,739; 5,559,169; and 5,571,311; and in U.S. Patent

Applications Nos. 08/572,336; 08/572,525; 08/572,542; and 08/572,545,

and PCT Publications Nos. WO/96 18688 and WO/96 18696, all

incorporated in their entirety by reference herein.

The carbon black having attached organic groups then exits through

an outlet and into a container and optionally on to further processing.

Throughout the pelletizer, there is a maintained vacuum or fluid flow (e.g.,

air flow). The vacuum or fluid flow is created by a blower or other suitable

device known to those skilled in the art. This vacuum or fluid flow is

created, for instance, by a blower which may be located downstream of

the outlet of the mixing or reacting zone. An example of a blower is a

regenerative blower, such as an EGG Rotron DR 606 regenerative blower.

In a preferred embodiment of the present invention, the source of

the vacuum or fluid flow is located between the outlet of the chemical

mixing or reacting zone and the container which receives the treated

carbon black. The vacuum or fluid flow source further has means to

control the amount of vacuum or fluid flow through the chemical mixing or

reacting zone. The vacuum or fluid flow source can have a manual

butterfly valve which can be used to manually adjust the vacuum or fluid

flow levels. For purposes of the preferred embodiment which makes

carbon black having attached organic groups, the vacuum levels should be from about -1.25 mbar gauge to about -0.75 mbar gauge. It is particularly

preferred that the amount of vacuum be about 1/10" of vacuum of water.

In making particular chemicals, such as a carbon black having

attached organic groups, it is important to maintain a certain vacuum or

fluid flow throughout the pelletizer without interruption. Using a vacuum or

fluid flow source that has means to control the amount of vacuum or fluid

flow permits this control. Generally, the vacuum or fluid flow is controlled

by a gauge indicating the amount of vacuum or fluid flow through the

chemical processing system and the use of a control system, which is

commercially available to maintain the desired fluid flow or vacuum. For

instance, the vacuum or fluid flow source can be controlled by a feedback

loop between a pressure sensor and a control valve located at the vacuum

^' or fluid flow source. In more detail, the feedback control is used to adjust

the manipulated variable of the fluid flow to a desired set point. The

manipulated variable could be the pressure/vacuum at the outlet of the

mixing or reacting zone. The manipulated variable could also be the

pressure/vacuum at the inlet of the mixing or reacting zone or the fluid flow

rate through the mixing or reacting zone. The controlling device could be

a variable speed fan or a control valve.

Previous operations in making carbon black generally involved

discharging the carbon black from a pelletizer into a dryer to remove

moisture. The drying of the carbon black would create steam and the emission of the steam, for instance, through a smoke stack, would create

a vacuum through the pelletizer. However, such a vacuum was not readily

controllable and the emission of such steam could also release

contaminants which would create certain environmental concerns. The

present invention avoids the emission of steam and the need for a dryer.

In a preferred embodiment, a condenser and/or a filter are located

prior to the vacuum or fluid flow source to ensure that moisture is removed

from the fluid, such as air, and to also ensure that any chemicals, such as

carbon black particles, are substantially removed from the fluid. A

schematic of the embodiments showing a processing system with and

without condensers and filters are set forth in Figures 1 and 2. Though

optional, the use of a condenser and/or filter further assists uniform and

uninterrupted fluid flow through the pelletizer which permits a consistent

and uniform feed and treatment of the chemicals entering the reacting or

mixing zone. Commercially available condensers and filters can be used

and are familiar to those skilled in the art. For instance, the filter can be

bags of standard Pulsaire 4.5 inch diameter bags.

In chemical processing where a vacuum or fluid flow is involved, it is

important to ensure that there is no fouling of the vacuum or fluid flow

system due to water and/or other chemical accumulations. Such fouling,

for instance, with the use of a pelletizer, decreases the fluid flow through

the peite izer. As the fluid flow decreases through the pelletizer, the residence time of the chemicals in the pelletizer correspondingly increases.

As residence time increases in the pelletizer, the amount of material within

the pelletizer increases and therefore motor load increases. A point is

ultimately reached where high levels of treatment and material hold-up

causes unwanted and rapid cake formation. The excessive cake

accumulations are in turn removed by the pins, resulting in erratic motor

loads, severe pelletizer vibration, and poor product quality. It has been

discovered that preferably when a condenser and a filter are used, fouling

can be even more significantly avoided.

A temperature indicator at the pelletizer's inlet and/or outlet can also

be used to monitor the temperature of the reactants and fluid flow through

the pelletizer. The temperature indicator can detect rises in temperature

which may be an indication of plugging in the pelletizer.

Tables 1 and 2 are representative with respect to a processing

system where carbon black having attached organic groups is made and

sets forth the various feed rates and pelletizer speeds and temperatures.

As can be seen in Table 2, acceptable and consistent flows were obtained

throughout the runs using the set up of the present invention.

In many chemical processing systems, there is a need to sample the

material being made to ensure quality control. In systems where a vacuum

or fluid flow is present such as the processing system described above,

there is a need to create a sample port assembly which does not

substantially interrupt the fluid flow or vacuum through the reacting or mixing

zone. An additional embodiment of the present invention addresses this need through a sample port assembly which permits the sampling of a

product without substantial interruption of the vacuum or fluid flow. A

preferred sample port assembly is shown in detail in Figures 3-9. The

sample port assembly can be located immediately after the outlet of the

mixing or reacting zone. A preferred embodiment of the sample port

assembly and the sample cup that the sample port assembly can hold is as

follows.

The sample port assembly illustrated in Figure 3 comprises a member

72 through which material is transported in the chemical processing system.

Member 72 may be a tube or pipe of circular cross section, but should be

understood to include any conduit of any suitable cross section through

which material is transported in the direction of the arrows from 50 to 52.

Member 72 is further configured with an intersecting channel or port adapted

to contain a sample cup holder generally designated as 59. The sample

port assembly may be constructed of any suitable material that resists

degradation by the materials used in the chemical processing system, such

as stainless steel.

Sample cup holder 59 comprises at least two elements which form a

generally fluid tight seal with the intersecting channel or sampling port to

substantially maintain the fluid pressure within the system during operation

of the system, and particularly during the sampling procedure. The two

elements illustrated in Figure 3 generally comprise plates 65 and 68 connected by rods 66 in any suitable manner. Although any number of

connecting rods may be used, it is preferable to use a minimum number to

connect the plates and provide support for the sample cup so that any

disruption of the flow of material through member 72 is minimized. Three

rods are preferred.

The plates are coated or otherwise contain gaskets 64 and 70 made

of any suitable material to create a substantially fluid tight seal with the

intersecting channel or sampling port. Any material may be used that will

form the required seal, and permit the sample cup holder to slide within the

channel or port. A rubber gasket is suitable. It will be noted that plate 65

need not fit within the intersecting channel or port, but may simply abut the

port to create the seal. •

The sample port assembly of Figure 3 is further provided with an

optional set of hinged cover sides 60 to further assist in maintaining a

constant fluid pressure or flow within the system during operation. Cover

sides 60 may be secured to the sample port assembly by hinges 62 and to

anchors 58 by threaded elements 56 and wing nuts 54. Although the use of

hinges permits ready access to the sample cup holder for the sampling

process, any suitable means may be utilized to secure the cover sides to the

assembly.

Figure 4 illustrates the cup holder 59 in an open position to permit

insertion of the sample cup in the cup holder and retrieval of a sample following the sampling procedure. In the open position, plate 68 and gasket

70 substantially maintain the fluid pressure within the system when the cup

is being placed in the cup holder and when the sample is being retrieved.

It should be understood that it is possible to configure the sample port

assembly and/or the cup holder 59 in ways to maintain the fluid pressure

within the system substantially constant during sampling, or to permit a brief

interruption to the uniformity of the fluid pressure within the system. For

example, as illustrated in Figure 4, as the cup holder moves from the closed

position to the open position, fluid pressure will not be held constant as plate

68 moves across the flow of material through member 72 unless the flow of

fluid, such as a gas like air, through the sampling port is reduced or

prevented. This break in fluid pressure could be readily eliminated by, for

example, providing another plate within the sampling port or configuring

plate 65 to fit securely within the sampling channel until plate 68 reaches the

position iiiustrated in Figure 4.

Figure 5 is a front view of a sample port assembly according to this

invention along the line A-A of Figure 3 illustrating a suitable configuration of

the connecting rods 66 which connect the plates that create a substantially

fluid tight assembly within the sampling port. The illustrated configuration of

the rods provides for a stable connection of the plates and minimum

disruption to the flow of material through the assembly. Guides 73 may be

provided on member 72 to contact one or more rods of the cup holder. Figures 6-9 illustrate one embodiment of a sample cup within the

scope of the present invention. Figure 6 is a top view of a sample cup 74

having a rectangular shape and comprising several rods to reinforce the

sample cup. Figures 7 and 8 are end views of a sample cup 74 taken along

lines B-B and D-D respectively in Figure 6. The semicircular shape is

merely illustrative because any shape that is sufficient to collect and retain a

sample of material would be suitable. Rods 76 are illustrated and can be

secured to the cup in any suitable manner and may be used to cooperate

with a rod in the cup holder to provide a desired orientation of the cup 74 in

the cup holder 59. Figure 8 is a front view of sample cup 74 taken along

line C-C in Figure 6.

During operation of the processing system, the sample port assembly

is maintained in a closed position as illustrated in Figure 3. When a sample

is desired, one of the hinged covers 60 is opened, the sample cup holder 59

is moved to an open position as illustrated in Figure 4. A sample cup, such

as 74 illustrated in Figure 6, is placed in cup holder 59 in such a way that it

will collect a sample of material moving through the sample port assembly

72 when in a closed position. The cup holder is moved to a closed position

for a sufficient period of time for an adequate sample to collect in the cup.

The cup holder is then moved to an open position to permit removal of the

cup and the sample of material. The cup holder is then returned to a closed

position without the cup, and the hinged cover returned and secured in a closed position. With the sample port assembly of this invention, the

sampling procedure can be accomplished with little or no disruption to the

fluid pressure or flow in the system.

The present invention further relates to a system to meter and feed

solid chemicals in a continuous manner using dual feeders. In particular,

continuous metering of solid chemicals can be essential in the processing

industry. Loss-in-weight (LIW) feeders are largely used to accomplish this

metering. Currently, the industry generally uses a single loss-in-weight

feeder on load cells. The feed rate is estimated based on the weight loss

over a period of time. Once the feeder is nearly empty, it is refilled quickly.

However, a problem with this set-up is that a true feed rate cannot be

measured during the refill operation. During the refill operation, manual or

fixed output operation is used in an attempt to maintain an accurate and

consistent feed rate. Maintaining an accurate and consistent feed rate

during this refilling period is even further complicated when the feed does

not have a consistent density, such as with certain types of carbon black.

To avoid this problem, another embodiment of the present invention

uses two LIW feeders in sequence. In other words, when the first feeder

obtains a preassigned lower weight limit in the hopper, a control gradually

switches the feed to the second LIW feeder. Once the control completely

switches to the second feeder, the first feeder is then refilled. This switching

and refilling is continued for as long as needed. There are a number of 8/42786

ways the switching from the first feeder to the second feeder and vice versa

can be performed. One manner is to ramp the set point of each feeder

simultaneously. A second way is to ramp the output of one LIW feeder

while controlling the other feeder on the total rate. Due to the nonlinear

relationship between the screw output and the feed rate, this could involve

more sophisticated controls like a feed forward or a fuzzy logic controller. A

third way to obtain switching is to switch instantaneously using a diverter

valve. A fourth way is to switch instantaneously by turning off one feeder

and starting the other at the memorized implied valve position. A

loss-in-weight feeder suitable for use in the present invention may be

obtained from AccuRate. Figure 10 sets forth one example of a continuous

dual feeder system wherein a solid chemical enters the feeders through an

agitator tank.

The present invention will be further clarified by the following

examples, which are intended to be purely exemplary of the present

invention.

EXAMPLES

A dual LIW feeder system was designed to feed the carbon black to a

pelletizer in a continuous mode. The schematic is shown in Figure 10.

Briefly, two high capacity screw feeders were employed to fill two AccuRate

feeders (LIW-E and LIW-W) with carbon black from an agitator tank. To achieve optimal overall system performance, a reasonably large hopper

capacity and a high rate of refill are preferred, but due to agitator tank to

floor plate clearance, hopper volume was 0.524 m³ (18.5 ft³), and the screw

feeder to a 0.3 m (12 inch) diameter unit. This combination of equipment

resulted in a maximum refill rate of 0.765 m³/min (27 ftVmin), with a

corresponding theoretical refill time of 41 seconds. Actual refill time can be

less, depending on the angle of repose of the carbon black being processed.

Screw feeder specifications were as follows:

Housing: 13 in I.D. tubular housing, with 34.5 inch inlet to outlet,

10 gauge, type 316, SS all wetted parts.

Screw: 12 in O.D. sectional screw, 8 inch pitch length, 3/16 inch thick

flights, 3" schedule 40S pipe, type 316 SS all wetted parts.

Reducer: Dodge shaft mounted reducer, 25:1 reduction, size

no. SCT225, with waste packing seal.

Motor: 3 HP, 1750 RPM, frame 182T, TEFC, 460 Volt, 3 phase,

explosion proof, variable speed.

Capacity: 0.765 m³/min (27 ftVmin) at maximum recommended speed of

60 rpm.

The carbon black feed rate was controlled at a fixed rate using a

single feeder. When the carbon black in the feeder reached a lower weight

limit, the control was gradually switched to the other AccuRate feeder. Once

the control was completely switched to the second feeder, the first feeder was refilled. This switching and refilling can be continued until the agitator

tank runs out of black.

There are a number of ways the switching can be performed. In this

trial, a simultaneous ramp of the set points of the two feeders was employed. The sequence was as follows:

1. When the black in the feeder on control hits a lower weight

limit, the black rate set point begins a ramp to zero.

2. Simultaneously the other feeder begins ramping from zero to

the desired black rate, with the cumulative black rate of both

feeders equaling the desired black rate. (The upper and lower

weight limits as well as black rate and ramp rate are operator

parameters.)

3. Once the switch from one feeder to the other is complete, the

"charge" phase begins on the empty feeder which consists of:

3.1 Starting the high capacity screw

3.2 Opening the agitator tank slide valve

3.3 Starting the agitator

3.4 At this point the weight of the feeder is scanned every

two seconds until the high weight limit is reached.

3.5 Subsequently, the charge equipment is shut down.

The logic was accomplished using two Fisher Provox FSTs (Function

Sequence Table). Experiments at different carbon black rates were performed with

various variables such as carbon black type, ramp rate, PID tuning

constants, screw, and nozzle. The individual LIW feeders were tuned for

each combination of screw, nozzle, and carbon black. The paddle agitator

on the LIW-W feeder has a separate drive from that of the screw and this

was set at 30% of maximum. This speed was chosen for two reasons: 1)

at high agitation speeds, the carbon black may pack in the hopper, and 2) at

low speeds, the uneven force on the load cells may not be averaged out.

The appropriate screw and nozzle of the AccuRate feeder can be an

important factor in providing a consistent feed of the carbon black. In the

case of feeding fluffy carbon black, it was found that for the range of carbon

black rates (25-100 kg/hr) investigated, a 3 inch screw with a center rod and

a 4 inch nozzle with end discharge gave satisfactory performance. In the

case of ground Vulcan 7H carbon black (ground pellets), a modified 3 inch

screw with a 3 inch nozzle with end discharge gave uniform feed.

Other embodiments of the present invention will be apparent to those

skilled in the art from consideration of the specification and practice of the

invention disclosed herein. It is intended that the specification and examples

be considered as exemplary only, with a true scope and spirit of the

invention being indicated by the following claims.

Claims

WHAT IS CLAIMED IS:

1. A chemical processing system comprising:

a chemical mixing or reacting zone;

an inlet to said zone;

an outlet to said zone;

a vacuum or fluid flow source located downstream of said

outlet; and

means to control the amount of vacuum or fluid flow through

said zone.

2. The chemical processing system of claim 1 , wherein said fluid

flow source is a gas flow source.

3. The chemical processing station of claim 2, wherein said gas

flow source is an air flow source.

4. The chemical processing station of claim 3, wherein carbon

black and sulfonic acid enter through a first inlet zone and sodium nitrite

solution and water enters through a second inlet zone and a carbon black

having an attached organic group exits said outlet.

5. The chemical processing system of claim 1, further comprising

a condenser located between said outlet and said vacuum or fluid flow

source.

6. The chemical processing system of claim 1 , further comprising

a filter located between said outlet and said vacuum or fluid flow source.

7. The chemical processing system of claim 1 , further comprising

a condenser and a filter located between said outlet and said vacuum or

fluid flow source.

8. The chemical processing system of claim 1 , wherein said

chemical mixing or reacting zone is a pelletizer.

9. The chemical processing system of claim 8, wherein said

pelletizer is a wet pelletizer.

10. The chemical processing system of claim 1 , wherein at least

one feeder is located before said inlet.

11. The chemical processing system of claim 1 , further comprising

a sample port Rssembly located between said outlet and said vacuum or fluid flow source.

12. The chemical processing system of claim 1 , wherein said

means to control the amount of vacuum or fluid flow through said zone is a

variable speed fan or a control valve.

13. The chemical processing system of claim 1 , further comprising

a feedback control located before said inlet or after said outlet and which

measures the amount of vacuum or fluid flow.

14. The chemical processing system of claim 1, wherein said

vacuum or fluid flow source is a blower.

15. The chemical processing system of claim 14, wherein said

blower is a regenerative blower.

16. The chemical processing system of claim 1, wherein said

vacuum or fluid flow source is controlled by a feedback loop between a

pressure sensor located at said outlet and a control valve located between

said outlet and said vacuum or fluid flow source.

17. A continuous feeder system comprising: a first loss-in-weight feeder and a second loss-in-weight feeder; means for measuring a lower limit of feed in each feeder;

means to activate said second feeder when said lower limit is obtained in said first feeder; and

means to deactivate said first feeder when said lower limit is

detected in said first feeder.

18. The continuous feed system of claim 17, wherein said first and

second loss-in-weight feeders contain carbon black.

19. A process for maintaining a consistent feed rate comprising:

dispensing a feed from a first loss-in-weight feeder at a feed rate;

detecting a lower limit of feed in said first feeder and switching

to a second loss-in-weight feeder containing the same type of feed and

maintaining substantially the same feed rate in said second feeder.

20. The process of claim 19, wherein said feed is carbon black.

21. The process of claim 19, further comprising refilling said first

feeder after said lower limit is obtained and said first feeder is deactivated.

22. A sample port assembly for obtaining a sample of material flowing through a processing system comprising

a port in the assembly,

a sample cup holder adapted to be moved in the port to obtain

a sample of material without substantially affecting the fluid pressure or flow

within the system.

23. A sample port assembly comprising

a port in the assembly having a substantially uniform internal

dimension,

a sample cup holder having end plates providing a substantially

fluid tight seal in the port,

said holder being movable within the port.

24. The sample port assembly of claim 23, further comprising a

plurality of rods connecting the end plates.

25. The sample port assembly of claim 23, wherein the end plates

are provided with a rubber gasket.

26. A sample port assembly kit for obtaining a sample of material

flowing through a processing system comprising

a sample port assembly with a port and a sample cup holder adapted to be moved in the port without substantially affecting the fluid pressure or flow within the system, and

a sample cup adapted to be held by the sample cup holder.