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The present invention is an apparatus for introducing a dry material into a fluid stream in a way that ensures a predictable, highly accurate and consistent application of the material. The invention applies variable amounts of dry material regardless of whether the fluid stream flow rate is fixed o

The present invention is an apparatus for introducing a dry material into a fluid stream in a way that ensures a predictable, highly accurate and consistent application of the material. The invention applies variable amounts of dry material regardless of whether the fluid stream flow rate is fixed or variable. The dry material is handled in dry bulk form and may be highly soluble or nearly insoluble. The dry bulk material is metered before being mixed into a slurry and injected to the fluid stream in a manner that continuously and automatically adjusts the application rate to compensate for varying fluid flow rates or chemical composition, in order to provide a precise fluid treatment level at all times. The present invention is capable of storing large quantities of the dry process amendment as an integrated and dust-free function of the apparatus. The invention is capable of monitoring and adjusting material levels and introduction rates in real time in response to variations in density, fluid flow rate and/or chemistry composition through the use of one or more sensors and a processor in communication with the metering device.

대표청구항 ▼

1. An apparatus for introducing dry powderous material into an external fluid stream to maintain a predetermined mixture level in said stream comprising:a. a vertically oriented silo for storing said dry material in bulk form, said silo having an inlet and an outlet for, respectively, receiving and

1. An apparatus for introducing dry powderous material into an external fluid stream to maintain a predetermined mixture level in said stream comprising:a. a vertically oriented silo for storing said dry material in bulk form, said silo having an inlet and an outlet for, respectively, receiving and discharging said material;b. a surge hopper located gravitationally downstream from the storage silo, said hopper being separated from the silo by a control valve;c. a volumetric feeder located gravitationally downstream from the hopper, said feeder including a horizontally oriented metering auger coupled with an intromitter for conditioning and feeding said dry material;d. a processor controlled variable speed motor for driving said metering auger and said intromitter for precise metering of said dry material;e. a mixing tank for receiving the dry material from said feeder and mixing it with a fluid to form a slurry, said tank including at least one mixer;f. a pump for removing slurry from said tank through an outlet and introducing it into said external fluid stream through an injection line connected between said pump and said external fluid stream;g. an inlet in said tank in communication with a source of fluid, and a float valve adjacent to said tank inlet for maintaining a desired level of slurry in said tank; andh. and a processor in communication with said motor and with at least one sensor in said external fluid stream,wherein said processor varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with readings from said at least one sensor so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said external fluid stream.2. The apparatus of claim 1 wherein said at least one sensor associated with said fluid stream comprises a flow rate sensor.3. The apparatus of claim 1 wherein said at least one sensor associated with said fluid stream comprises a first chemical sensor associated with said fluid stream upstream of said slurry introduction, and a second chemical sensor associated with said fluid stream downstream from said slurry introduction.4. The apparatus of claim 3 wherein said dry material is powdered gypsum and said chemical sensors are salinity sensors.5. The apparatus of claim 3 wherein said processor continuously varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with readings from said sensors so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.6. The apparatus of claim 3 wherein a branch line is provided off said fluid stream, and said slurry introduction and said sensors are provided in said branch line.7. The apparatus of claim 3 wherein a branch line is provided off said fluid flow upstream of said slurry introduction, and said first sensor is provided in said branch line.8. The apparatus of claim 1 wherein at least one weight sensor is provided with said silo in communication with said processor for detecting that dry material is being added to said silo.9. The apparatus of claim 1 wherein at least one weight sensor is provided with said silo in communication with said processor for detecting the level of dry material therein such that said processor closes said control valve if the level of dry material falls below a predetermined weight during filling of said silo.10. The apparatus of claim 1 wherein upper and lower fluid level sensors are provided in said mixing tank and in communication with said processor, and a shut-off valve is provided on said inlet conduit and in communication with said processor such that said shut-off valve is opened when the fluid level is between said upper and lower fluid level sensors and closed when the level rises above the uppermost of said upper and lower fluid level sensors.11. The apparatus of claim 1 wherein at least one weight sensor is provided with said silo and in communication with said processor, and said processor varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with the actual bulk density calculated from said at least one weight sensor as compared to the expected weight loss, based on the amount of material metered into said tank so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.12. The apparatus of claim 11 wherein said weight sensor is at least one digital load cell.13. The apparatus of claim 8 wherein said weight sensor is at least one radar level indicator inside said silo from which the processor can convert the level into a calculated weight.14. The apparatus of claim 11 wherein at least one vibration inducing device is attached to said silo and in communication with said processor and said at least one weight sensor such that said vibration inducing device is periodically activated by said processor to prevent bridging of the dry material contained in said silo.15. The apparatus of claim 14 wherein said processor activates said vibration inducing device when a predetermined difference is detected between the actual bulk density calculated from said at least one weight sensor as compared to the expected weight based on the amount of material metered into said tank.16. The apparatus of claim 1 wherein said at least one sensor associated with said fluid stream comprises an electrical conductivity sensor provided in said fluid stream downstream of the slurry introduction.17. The apparatus of claim 1 wherein a first electrical conductivity sensor is provided in said fluid flow downstream of the slurry introduction and a second electrical conductivity sensor is provided in said fluid flow upstream of the slurry introduction, with both sensors in communication with said processor, and wherein said processor continuously varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with readings from both of said electrical conductivity sensors so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.18. The apparatus of claim 1 wherein a dehumidifier is attached to said silo for removing excess moisture from the air inside said silo to prevent absorption by the dry material contained therein.19. The apparatus of claim 18 wherein said dehumidifier is in communication with said processor, and a moisture detecting sensor is provided in said silo and in communication with said processor such that said dehumidifier is activated by said processor according to the moisture level detected by said sensor.20. The apparatus of claim 1 wherein the storage silo is a mass-flow type.21. The apparatus of claim 1 wherein said dry material is gypsum and said fluid stream is irrigation water.22. An apparatus for injecting dry material into an external fluid stream to maintain a desired mixture level in the fluid stream comprising:a. a container for holding said dry material;b. a precision feed mechanism for metering said dry material at variable rates from said container;c. a tank in communication with a fluid source and in communication with said feed mechanism for receiving the metered dry material and mixing it with fluid from said source to form a slurry;d. a control in said tank for varying the amount of fluid from said source introduced into the tank to maintain a level of slurry in the tank;e. a pump connected to an injection line for removing slurry from the tank and introducing it into the external fluid stream, said line extending between said pump and said external fluid stream; andf. a controller connected to the precision feed mechanism and to at least one sensor located in the external fluid stream;wherein the controller adjusts the precision feed mechanism in accordance with readings from said at least one sensor to vary the concentration of dry material in the slurry so as to maintain a desired amount of said dry material per unit volume in the external fluid stream.23. The apparatus of claim 22 wherein said container is a vertical silo.24. The apparatus of claim 22 wherein said precision feed mechanism is a volumetric feeder including an auger.25. The apparatus of claim 24 wherein a processor controlled motor is provided for driving said auger.26. The apparatus of claim 25 wherein said controller continuously varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with readings from said at least one sensor so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.27. The apparatus of claim 25 wherein a first electrical conductivity sensor is provided in said fluid flow downstream of the slurry introduction and a second electrical conductivity sensor is provided in said fluid flow upstream of the slurry introduction, with both sensors in communication with said controller, and wherein said controller continuously varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with readings from both of said electrical conductivity sensors so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.28. The apparatus of claim 24 wherein an intromitter is provided as part of said feed mechanism.29. The apparatus of claim 22 wherein at least one mixer is provided in said tank.30. The apparatus of claim 22 wherein the control in the tank is a float valve.31. The apparatus of claim 22 wherein a control valve is provided between said container and said feed mechanism.32. The apparatus of claim 31 wherein a surge hopper is provided between said control valve and said feed mechanism.33. The apparatus of claim 31 wherein at least one weight sensor is provided with said container in communication with said controller for detecting the level of dry material therein such that said controller closes said control valve if the level of dry material falls below a predetermined weight during filling of said container.34. The apparatus of claim 22 wherein said at least one sensor associated with said fluid stream comprises a flow rate sensor.35. The apparatus of claim 22 wherein said at least one sensor associated with said fluid stream comprises a first chemical sensor associated with said fluid stream upstream of said slurry introduction, and a second chemical sensor associated with said fluid stream downstream from said slurry introduction.36. The apparatus of claim 35 wherein said dry material is powdered gypsum and said chemical sensors are electrical conductivity sensors.37. The apparatus of claim 35 wherein a branch line is provided off said fluid stream, and said slurry introduction and said sensors are provided in said branch line.38. The apparatus of claim 35 wherein a branch line is provided off said fluid flow upstream of said slurry introduction, and said first sensor is provided in said branch line.39. The apparatus of claim 22 wherein at least one weight sensor is provided with said container in communication with said controller for detecting whether dry material is being added to said container.40. The apparatus of claim 22 wherein upper and lower fluid level sensors are provided in said mixing tank and in communication with said controller, and a shut-off valve is provided at said fluid source and in communication with said controller such that said shut-off valve is opened when the fluid level is between said upper and lower fluid level sensors and closed when the level rises above the uppermost of said upper and lower fluid level sensors.41. The apparatus of claim 22 wherein at least one weight sensor is provided with said container and in communication with said controller, and said controller varies the speed of said feed mechanism to vary the quantity of dry material metered into said tank in accordance with the actual bulk density calculated from said at least one weight sensor as compared to the expected weight loss, based on the amount of material metered into said tank so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.42. The apparatus of claim 41 wherein said weight sensor is at least one digital load cell.43. The apparatus of claim 41 wherein said weight sensor is at least one radar level indicator inside said container from which the controller can convert the level into a calculated weight.44. The apparatus of claim 41 wherein at least one vibration inducing device is attached to said container and in communication with said controller and said at least one weight sensor such that said vibration inducing device is periodically activated by said controller to prevent bridging of the dry material contained in said container.45. The apparatus of claim 44 wherein said controller activates said vibration inducing device when a predetermined difference is detected between the actual bulk density calculated from said at least one weight sensor as compared to the expected weight based on the amount of material metered into said tank.46. The apparatus of claim 22 wherein said controller continuously varies the speed of said feed mechanism to vary the quantity of dry material metered into said tank in accordance with readings from said at least one sensor so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.47. The apparatus of claim 22 wherein said at least one sensor associated with said fluid stream comprises an electrical conductivity sensor provided in said fluid stream downstream of the slurry introduction.48. The apparatus of claim 22 wherein a first electrical conductivity sensor is provided in said fluid flow downstream of the slurry introduction and a second electrical conductivity sensor is provided in said fluid flow upstream of the slurry introduction, with both sensors in communication with said controller, and wherein said controller continuously varies the speed of said feed mechanism to vary the quantity of dry material metered into said tank in accordance with readings from both of said electrical conductivity sensors so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.49. The apparatus of claim 22 wherein a dehumidifier is attached to said container for removing excess moisture from the air inside said container to prevent absorption by the dry material contained therein.50. The apparatus of claim 49 wherein said dehumidifier is in communication with said controller, and a moisture detecting sensor is provided in said container and in communication with said controller such that said dehumidifier is activated by said controller according to the moisture level detected by said sensor.51. The apparatus of claim 22 wherein the storage container is a mass-flow type.52. The apparatus of claim 22 wherein said dry material is gypsum and said fluid stream is irrigation water.53. An apparatus for introducing dry powderous material into a fluid stream to maintain a predetermined mixture level comprising:a. a vertically oriented silo for storing said dry material;b. a volumetric feeder located downstream from the silo, said feeder including an auger attached to a variable speed motor for feeding said dry material;c. a tank in communication with a fluid source and in communication with said feeder for receiving the dry material and mixing it with fluid from said source to form a slurry;d. a pump connected to an injection line for removing slurry from the tank and delivering it into said fluid stream, said line extending between said pump and said fluid stream; ande. a processor in communication with said motor and with a sensor in said fluid stream,wherein said processor varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with readings from said sensor so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.54. The apparatus of claim 53 wherein a control valve is provided between said silo and said feeder.55. The apparatus of claim 53 wherein a surge hopper is provided between said control valve and said feeder.56. An apparatus for introducing dry powderous material into a fluid stream to maintain a predetermined mixture level comprising:a. a means for storing said dry material in bulk form;b. a means for precisely feeding variable amounts of said dry material from said storing means to a chamber means;c. a chamber means in communication with said feeding means and with a source of fluid for mixing the dry material with fluid from said source to form a slurry;d. a means for maintaining a desired level of slurry in said chamber;e. a pumping means for removing slurry from said chamber means and transferring it into said fluid stream;f. conduit means extending between said pump and said fluid stream; andg. a processing means in communication with said feeding means and in communication with a sensing means located in said fluid stream,wherein said processing means varies the speed of said feeding means to vary the quantity of dry material metered into said chamber means in accordance with readings from said sensing means so as to introduce slurry from said chamber means through said conduit means in variable concentrations to maintain a desired volume of said material in said fluid stream.57. An apparatus for injecting dry material into a conduit through which a fluid stream flows to maintain a desired mixture level in the fluid stream comprising:a. a container for holding said dry material;b. a feed mechanism for metering said dry material at variable rates from said container;c. a tank in communication with a fluid source and in communication with said feed mechanism for receiving the metered dry material and mixing it with fluid from said source to form a slurry;d. a control in said tank for varying the amount of fluid from said source introduced into the tank to maintain a level of slurry in the tank;e. a pump connected to an injection line for removing slurry from the tank and introducing it into said conduit, said line extending between said pump and said conduit; andf. a controller connected to the feed mechanism and to at least one sensor located in said conduit;wherein the controller adjusts the feed mechanism in accordance with readings from said at least one sensor to vary the concentration of dry material in the slurry so as to maintain a desired amount of said dry material per unit volume in the external fluid stream.58. An apparatus for introducing dry powderous material into a fluid stream to maintain a predetermined mixture level comprising:a. a vertically oriented silo for storing said dry material in bulk form, said silo having an inlet and an outlet for, respectively, receiving and discharging said material;b. a surge hopper located gravitationally downstream from the storage silo, said hopper being separated from the silo by a control valve;c. a volumetric feeder located gravitationally downstream from the hopper, said feeder including a horizontally oriented metering auger coupled with an intromitter for conditioning and feeding said dry material;d. a processor controlled variable speed motor for driving said metering auger and said intromitter for precise metering of said dry material;e. a mixing tank for receiving the dry material from said feeder and mixing it with a fluid to form a slurry, said tank including at least one mixer;f. a pump for removing slurry from said tank through an outlet conduit and injecting it into said fluid stream;g. an inlet conduit in said tank in communication with a source of pressurized fluid, and a float valve adjacent to said inlet conduit for maintaining a desired level of fluid in said tank;h. and a processor in communication with said motor and with at least one sensor associated with said fluid stream,wherein said processor continuously varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with continuous readings from said at least one sensor so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream; wherein at least one weight sensor is provided with said silo in communication with said processor for detecting the level of dry material therein such that said processor closes said control valve if the level of dry material falls below a predetermined weight during filling of said silo.59. An apparatus for introducing dry powderous material into a fluid stream to maintain a predetermined mixture level comprising:a. a vertically oriented silo for storing said dry material in bulk form, said silo having an inlet and an outlet for, respectively, receiving and discharging said material;b. a surge hopper located gravitationally downstream from the storage silo, said hopper being separated from the silo by a control valve;c. a volumetric feeder located gravitationally downstream from the hopper, said feeder including a horizontally oriented metering auger coupled with an intromitter for conditioning and feeding said dry material;d. a processor controlled variable speed motor for driving said metering auger and said intromitter for precise metering of said dry material;e. a mixing tank for receiving the dry material from said feeder and mixing it with a fluid to form a slurry, said tank including at least one mixer;f. a pump for removing slurry from said tank through an outlet conduit and injecting it into said fluid stream;g. an inlet conduit in said tank in communication with a source of pressurized fluid, and a float valve adjacent to said inlet conduit for maintaining a desired level of fluid in said tank;h. and a processor in communication with said motor and with at least one sensor associated with said fluid stream,wherein said processor continuously varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with continuous readings from said at least one sensor so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream; wherein at least one weight sensor is provided with said silo and in communication with said processor, and said processor varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with the actual bulk density calculated from said at least one weight sensor as compared to the expected weight loss, based on the amount of material metered into said tank so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.60. The apparatus of claim 59 wherein said weight sensor is at least one digital load cell.61. The apparatus of claim 59 wherein said weight sensor is at least one radar level indicator inside said silo from which the processor can convert the level into a calculated weight.62. The apparatus of claim 59 wherein at least one vibration inducing device is attached to said silo and in communication with said processor and said at least one weight sensor such that said vibration inducing device is periodically activated by said processor to prevent bridging of the dry material contained in said silo.63. The apparatus of claim 62 wherein said processor activates said vibration inducing device when a predetermined difference is detected between the actual bulk density calculated from said at least one weight sensor as compared to the expected weight based on the amount of material metered into said tank.64. An apparatus for introducing dry powderous material into a fluid stream to maintain a predetermined mixture level comprising:a. a vertically oriented silo for storing said dry material in bulk form, said silo having an inlet and an outlet for, respectively, receiving and discharging said material;b. a surge hopper located gravitationally downstream from the storage silo, said hopper being separated from the silo by a control valve;c. a volumetric feeder located gravitationally downstream from the hopper, said feeder including a horizontally oriented metering auger coupled with an intromitter for conditioning and feeding said dry material;d. a processor controlled variable speed motor for driving said metering auger and said intromitter for precise metering of said dry material;e. a mixing tank for receiving the dry material from said feeder and mixing it with a fluid to form a slurry, said tank including at least one mixer;f. a pump for removing slurry from said tank through an outlet conduit and injecting it into said fluid stream;g. an inlet conduit in said tank in communication with a source of pressurized fluid, and a float valve adjacent to said inlet conduit for maintaining a desired level of fluid in said tank;h. and a processor in communication with said motor and with at least one sensor associated with said fluid stream,wherein said processor continuously varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with continuous readings from said at least one sensor so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream; wherein said at least one sensor associated with said fluid stream comprises a first chemical sensor associated with said fluid stream upstream of said slurry introduction, and a second chemical sensor associated with said fluid stream downstream from said slurry introduction; and wherein a branch line is provided off said fluid stream, and said slurry introduction and said sensors are provided in said branch line.65. An apparatus for introducing dry powderous material into a fluid stream to maintain a predetermined mixture level comprising:a. a vertically oriented silo for storing said dry material in bulk form, said silo having an inlet and an outlet for, respectively, receiving and discharging said material;b. a surge hopper located gravitationally downstream from the storage silo, said hopper being separated from the silo by a control valve;c. a volumetric feeder located gravitationally downstream from the hopper, said feeder including a horizontally oriented metering auger coupled with an intromitter for conditioning and feeding said dry material;d. a processor controlled variable speed motor for driving said metering auger and said intromitter for precise metering of said dry material;e. a mixing tank for receiving the dry material from said feeder and mixing it with a fluid to form a slurry, said tank including at least one mixer;f. a pump for removing slurry from said tank through an outlet conduit and injecting it into said fluid stream;g. an inlet conduit in said tank in communication with a source of pressurized fluid, and a float valve adjacent to said inlet conduit for maintaining a desired level of fluid in said tank;h. and a processor in communication with said motor and with at least one sensor associated with said fluid stream,wherein said processor continuously varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with continuous readings from said at least one sensor so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream; wherein said at least one sensor associated with said fluid stream comprises a first chemical sensor associated with said fluid stream upstream of said slurry introduction, and a second chemical sensor associated with said fluid stream downstream from said slurry introduction; and wherein a branch line is provided off said fluid flow upstream of said slurry introduction, and said first sensor is provided in said branch line.66. An apparatus for injecting dry material into a fluid stream to maintain a uniform mixture level in the fluid stream comprising:a. a container for holding said dry material;b. a precision feed mechanism for metering said dry material at variable rates from said container;c. a tank in communication with a fluid source and in communication with said feeder for receiving the metered dry material and mixing it with said fluid to form a slurry;d. a control in said tank for varying the amount of fluid introduced into the tank to maintain a level of slurry in the tank;e. a pump for removing slurry from the tank and introducing it into the fluid stream; andf. a controller connected to the precision feed mechanism and to at least one sensor located in the fluid stream;wherein the controller adjusts the precision feed mechanism in accordance with readings from said sensor to vary the concentration of dry material in the slurry so as to maintain a desired amount of said dry material per unit volume in the fluid stream; wherein a control valve is provided between said container and said feed mechanism; and wherein at least one weight sensor is provided with said container in communication with said controller for detecting the level of dry material therein such that said controller closes said control valve if the level of dry material falls below a predetermined weight during filling of said container.67. An apparatus for injecting dry material into a fluid stream to maintain a uniform mixture level in the fluid stream comprising:a. a container for holding said dry material;b. a precision feed mechanism for metering said dry material at variable rates from said container;c. a tank in communication with a fluid source and in communication with said feeder for receiving the metered dry material and mixing it with said fluid to form a slurry;d. a control in said tank for varying the amount of fluid introduced into the tank to maintain a level of slurry in the tank;e. a pump for removing slurry from the tank and introducing it into the fluid stream; andf. a controller connected to the precision feed mechanism and to at least one sensor located in the fluid stream;wherein the controller adjusts the precision feed mechanism in accordance with readings from said sensor to vary the concentration of dry material in the slurry so as to maintain a desired amount of said dry material per unit volume in the fluid stream; wherein at least one weight sensor is provided with said container and in communication with said controller, and said controller varies the speed of said feed mechanism to vary the quantity of dry material metered into said tank in accordance with the actual bulk density calculated from said at least one weight sensor as compared to the expected weight loss, based on the amount of material metered into said tank so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.68. The apparatus of claim 67 wherein said weight sensor is at least one digital load cell.69. The apparatus of claim 67 wherein said weight sensor is at least one radar level indicator inside said container from which the controller can convert the level into a calculated weight.70. The apparatus of claim 67 wherein at least one vibration inducing device is attached to said container and in communication with said controller and said at least one weight sensor such that said vibration inducing device is periodically activated by said controller to prevent bridging of the dry material contained in said container.71. The apparatus of claim 70 wherein said controller activates said vibration inducing device when a predetermined difference is detected between the actual bulk density calculated from said at least one weight sensor as compared to the expected weight based on the amount of material metered into said tank.72. An apparatus for injecting dry material into a fluid stream to maintain a uniform mixture level in the fluid stream comprising:a. a container for holding said dry material;b. a precision feed mechanism for metering said dry material at variable rates from said container;c. a tank in communication with a fluid source and in communication with said feeder for receiving the metered dry material and mixing it with said fluid to form a slurry;d. a control in said tank for varying the amount of fluid introduced into the tank to maintain a level of slurry in the tank;e. a pump for removing slurry from the tank and introducing it into the fluid stream; andf. a controller connected to the precision feed mechanism and to at least one sensor located in the fluid stream;wherein the controller adjusts the precision feed mechanism in accordance with readings from said sensor to vary the concentration of dry material in the slurry so as to maintain a desired amount of said dry material per unit volume in the fluid stream; wherein said at least one sensor associated with said fluid stream comprises a first chemical sensor associated with said fluid stream upstream of said slurry introduction, and a second chemical sensor associated with said fluid stream downstream from said slurry introduction; wherein a branch line is provided off said fluid stream, and said slurry introduction and said sensors are provided in said branch line.73. An apparatus for injecting dry material into a fluid stream to maintain a uniform mixture level in the fluid stream comprising:a. a container for holding said dry material;b. a precision feed mechanism for metering said dry material at variable rates from said container;c. a tank in communication with a fluid source and in communication with said feeder for receiving the metered dry material and mixing it with said fluid to form a slurry;d. a control in said tank for varying the amount of fluid introduced into the tank to maintain a level of slurry in the tank;e. a pump for removing slurry from the tank and introducing it into the fluid stream; andf. a controller connected to the precision feed mechanism and to at least one sensor located in the fluid stream;wherein the controller adjusts the precision feed mechanism in accordance with readings from said sensor to vary the concentration of dry material in the slurry so as to maintain a desired amount of said dry material per unit volume in the fluid stream; wherein a first electrical conductivity sensor is provided in said fluid flow downstream of the slurry introduction and a second electrical conductivity sensor is provided in said fluid flow upstream of the slurry introduction, with both sensors in communication with said controller, and wherein said controller continuously varies the speed of said feed mechanism to vary the quantity of dry material metered into said tank in accordance with readings from both of said electrical conductivity sensors so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.74. An apparatus for injecting dry material into a fluid stream to maintain a uniform mixture level in the fluid stream comprising:a. a container for holding said dry material;b. a precision feed mechanism for metering said dry material at variable rates from said container;c. a tank in communication with a fluid source and in communication with said feeder for receiving the metered dry material and mixing it with said fluid to form a slurry;d. a control in said tank for varying the amount of fluid introduced into the tank to maintain a level of slurry in the tank;e. a pump for removing slurry from the tank and introducing it into the fluid stream; andf. a controller connected to the precision feed mechanism and to at least one sensor located in the fluid stream;wherein the controller adjusts the precision feed mechanism in accordance with readings from said sensor to vary the concentration of dry material in the slurry so as to maintain a desired amount of said dry material per unit volume in the fluid stream; wherein said precision feed mechanism is a volumetric feeder including an auger; wherein a processor controlled motor is provided for driving said auger; wherein a first electrical conductivity sensor is provided in said fluid flow downstream of the slurry introduction and a second electrical conductivity sensor is provided in said fluid flow upstream of the slurry introduction, with both sensors in communication with said controller, and wherein said controller continuously varies the speed of said motor to vary the quantity of dry material metered into said tank in accordance with readings from both of said electrical conductivity sensors so as to introduce slurry from said tank containing variable quantities of said material to maintain a desired volume of said material in said fluid stream.75. An apparatus for injecting dry material into a fluid stream to maintain a uniform mixture level in the fluid stream comprising:a. a container for holding said dry material;b. a precision feed mechanism for metering said dry material at variable rates from said container;c. a tank in communication with a fluid source and in communication with said feeder for receiving the metered dry material and mixing it with said fluid to form a slurry;d. a control in said tank for varying the amount of fluid introduced into the tank to maintain a level of slurry in the tank;e. a pump for removing slurry from the tank and introducing it into the fluid stream; andf. a controller connected to the precision feed mechanism and to at least one sensor located in the fluid stream;wherein the controller adjusts the precision feed mechanism in accordance with readings from said sensor to vary the concentration of dry material in the slurry so as to maintain a desired amount of said dry material per unit volume in the fluid stream; wherein said at least one sensor associated with said fluid stream comprises a first chemical sensor associated with said fluid stream upstream of said slurry introduction, and a second chemical sensor associated with said fluid stream downstream from said slurry introduction; wherein a branch line is provided off said fluid stream, and said slurry introduction and said sensors are provided in said branch line; wherein a branch line is provided off said fluid flow upstream of said slurry introduction, and said first sensor is provided in said branch line.