Control system for particulate material drying apparatus and process

• US 20060112588A1
• Filed: 08/08/2005
• Published: 06/01/2006
• Est. Priority Date: 10/12/2004
• Status: Active Grant

• Current Assignee: Rainbow Energy Center LLC
• Original Assignee: Great River Energy
• Inventors: Coughlin, Matthew P., Wheeldon, John M., Ness, Mark A., Johnson, Adam M.
• Granted Patent: US 7,987,613 B2
• Time in Patent Office: Days
• US Class Current: 34/513
• CPC Class Codes: C10L 9/08 by heat treatments, e.g. calcining
• CPC Class Codes: Y02E 20/12 Heat utilisation in combustion or incineration of waste

Abstract

A control system for controlling the utilization of heated waste streams for fluidizing particulate matter such as coal in a fluidizing bed dryer. The control system includes a number of graphic user interfaces that allow an operator to more easily monitor and/or control the various regulator devices. The control system controls coal handling or transportation, fluid handling or flow, and the discharge of discarded or separated coal from the dryer.

Claims

1. A system for controlling the operation of a low-temperature, open-air process for reducing moisture contained within particulate material, wherein such process incorporates a wet particulate material storage bunker, a feed conveyor, a dryer apparatus, a first heat exchanger operatively connected to the dryer apparatus, a first waste heat source provided to the first heat exchanger for delivering heat content contained within the first waste heat source to the dryer apparatus, a second heat exchanger operatively connected to the dryer apparatus, a second waste heat source different in type from the first waste heat source provided to the second heat exchanger for delivering heat content contained within the second waste heat source to the dryer apparatus, a discharge conveyor, and a dried particulate material discharge destination, such controller system comprising:

(a) means for regulating the operation of a discharge gate on the wet particulate material storage bunker for controlling the discharge of particulate material from the wet particulate material storage bunker;

(b) means for regulating the operation of the feed conveyor for transporting the wet particulate material to the dryer apparatus;

(c) means for regulating the delivery of the first waste heat source to the first heat exchanger;

(d) means for regulating the delivery of the second waste heat source to the second heat exchanger;

(e) means for maintaining the particulate material within the dryer apparatus exposed to the combination of first and second heat sources for a sufficient temperature and time duration to achieve the desired degree of moisture reduction to produce dried particulate material;

(f) means for regulating the operation of a discharge gate on the dryer apparatus for controlling the discharge of the dried particulate material from the dryer apparatus;

(g) means for regulating the operation of the discharge conveyor for transporting the dried particulate material discharged from the dryer apparatus to the dried particulate material discharge destination.

2. The controller system of claim 1, wherein the dryer apparatus is a fluidized-bed dryer.

3. The controller system of claim 1, wherein the dryer apparatus is a fixed-bed dryer.

4. The controller system of claim 1, wherein the particulate material is coal.

5. The controller system of claim 1, wherein the waste heat sources are selected from the group consisting of hot condenser cooling water, hot stack gas, hot flue gas, spent process steam, and discarded heat from operating equipment.

6. The controller system of claim 1, wherein the temperature delivered to the dryer apparatus by the combined heat sources does not exceed 300°

F.

7. The controller system of claim 6, wherein the temperature delivered to the dryer apparatus by the combined heat sources is 200-300°

F.

8. The controller system of claim 1 further comprising means for regulating the delivery of at least one additional waste heat source to the dryer apparatus by means of an associated heat exchanger to which was provided an additional type of waste heat.

9. The controller system of claim 1 further comprising at least one additional waste heat source delivered to the dryer apparatus by means of an associated heat exchanger to which was provided a primary heat source.

10. The controller system of claim 1, wherein the low temperature, open-air moisture reduction process is used as part of a manufacturing operation.

11. The controller system of claim 10, wherein the manufacturing operation is an electric power plant.

12. The controller system of claim 1, wherein such low-temperature, open-air moisture reduction process further comprises:

(a) a fluidizing bed contained within the dryer apparatus for receiving a fluidizing stream to achieve repartition of fluidized particles and non-fluidized particles within the particulate material contained within the fluidized bed;

(b) a source of fluidizing stream operatively connected to the dryer apparatus;

(c) a conveyor means for transporting the non-fluidized particles inside the fluidized bed to the exterior of the dryer apparatus separate from the dried particulate material discharged therefore;

(d) means for regulating the operative connection of the fluidizing stream t the dryer apparatus; and

(e) means for regulating the operation of the conveyor means.

13. The controller system of claim 12, wherein the conveyor means is a screw auger.

14. The controller system of claim 12, wherein the fluidizing stream is air.

15. The controller system of claim 12, wherein the fluidizing stream is an inert gas.

16. The controller system of claim 12, wherein the fluidizing stream is heated by the first waste heat source prior to operative communication to the dryer apparatus.

17. The controller system of claim 12, wherein the non-fluidized particles removed by the conveying means from the dryer apparatus enhance the flow of the particulate material through the dryer apparatus to the discharge conveyor.

18. The controller system of claim 12, wherein the non-fluidized particles removed from the fluidized dryer separately form the dried particulate material discharge stream contains an increased weight percentage of at least one contaminant contained within the wet particulate material feed relative to the weight percentage of that contaminant within the wet particulate material feed.

19. A system for controlling the operation of a low-temperature, open-air process for reducing moisture contained within particulate material, wherein such process incorporates a wet particulate material storage breaker, a feed conveyor, a dryer apparatus, a heat exchanger operatively connected to the dryer apparatus, a heat source provided to the heat exchanger for delivering heat content contained within the heat source to the dryer apparatus, a discharge conveyor, and a dried particulate material discharge destination, such controller system comprising:

(a) means for regulating the operation of a discharge gate on the wet particulate material storage bunker for controlling the discharge of particulate material from the wet particulate material storage breaker;

(b) means for regulating the operation of the feed conveyor for transporting the wet particulate material from the wet particulate material storage breaker to the dryer apparatus;

(c) means for regulating the delivery of the heat source to the heat exchanger, wherein the operative delivered to the dryer apparatus by the heat source does not exceed 300°

F.;

(d) means for maintaining the particulate material within the dryer apparatus exposed to the heat source of a sufficient temperature and time duration to achieve the desired degree of moisture reduction to produce dried particulate material;

(e) means for regulating operation of a discharge gate on the dryer apparatus for controlling the discharge of the dried particulate material from the dryer apparatus; and

(f) means for regulating the operation of the discharge conveyor for transporting the dried particulate material from the dryer apparatus to the dried particulate material discharge destination.

20. The controller system of claim 19, wherein the temperature delivered to the dryer apparatus by the heat source is 200-300°

F.

21. The controller system of claim 19, wherein the particulate material is lignite coal whose moisture level in the dried particulate material is reduced to a volume of 10-35% wt.

22. The controller system of claim 21, wherein the moisture level in the dried particulate material is reduced to 27-32% wt.

23. The controller system of claim 19, wherein the particulate material is subbituminous coal whose moisture level in the dried particulate material is reduced to a value of 10-30% wt.

24. The controller system of acclaim 23, wherein the moisture level in the dried particulate material is reduced to 20-25% wt.

25. A method of controlling the drying of a particulate material within a fluidized bed dryer in operative communication with at least one heated waste stream, and a source of particulate material, the method comprising operating computing apparatus to automatically perform the steps of:

substantially continuously feeding particulate material into the dryer for drying;

regulating the flow of heated waste streams into the dryer for fluidizing and drying the particulate material; and

substantially continuously feeding dried particulate material out of the dryer.

26. The method of claim 25, wherein substantially continuously feeding particulate material into the dryer for drying includes the steps of regulating a rate of conveying the particulate material, the regulating the rate of conveying comprising controlling:

a vibrating feeder that feeds the particulate material through a chute;

a crusher adapted to crush the particulate material into predetermined sizes for drying;

a sizing screen that receives the particulate material from the crusher that separates the particulate material by a dimension of the particulate; and

at least one conveyor that conveys the particulate material to the dryer for drying.

27. The method of claim 25, wherein regulating the flow energy or heated waste streams into the dryer includes the steps of:

determining an amount of energy available to evaporate moisture from the particulate material by receiving at least one signal from at least one of the group consisting essentially of a thermal sensor, a flow sensor, a pressure sensor, a level sensor, a switch sensor, a position sensor, and a valve sensor;

establishing a target set point for a percent loss of weight from a particulate feed rate to determine the energy required for a desired water removal rate; and

analyzing a ratio of energy available and energy needed and adjusting an inlet fluid temperature target set point of the fluid entering the dryer to achieve a desired water removal rate based on the analyzed ratio.

28. The method of claim 27, wherein the step of determining an amount of energy available to evaporate moisture comprises the steps of:

(a) adding a flow rate of the air at a first stage of the dryer with a flow rate of the air at a second stage of the dryer and a flow rate of the air in a duct entering the dryer, multiplying it by a difference between an air temperature entering the dryer and an air temperature leaving dryer, all of which is multiplied by 0.242 to obtain a result,

(b) multiplying the result by a sum of an air flow rate in a first scrubber box and an air flow rate in a second scrubber box and an air flow rate in a vent box, all of which is multiplied to a difference between a temperature of a fluid entering scrubber boxes and a temperature of the fluid leaving dryer, all of which is multiplied by 0.242 to obtain an amended result,

(c) adding the amended result to a product of a water flow rate between pumps and dryer and a difference between a water temperature leaving the dryer and a water temperature entering the dryer, all of which is multiplied by 1.0.

29. The method of claim 27, wherein the step of determining an amount of energy available to evaporate moisture comprises the steps of:

(a) determining a flow rate of air entering a mixing box, multiplying the flow rate of air entering the mixing box by a hot air temperature leaving the dryer and multiplying it by 0.242 to obtain a result,

(b) adding the result to a product of cold air flowing into the mixing box and a difference between a cold air temperature for the dryer and an air temperature leaving the dryer, all of which is multiplied by 0.242 to obtain an amended result,

(c) adding the amended result to a product of a water flow rate between pumps and the dryer, which is multiplied to a difference between water temperature entering the dryer and water temperature leaving the dryer.

30. The method of claim 27, wherein the step of determining an amount of energy available to evaporate moisture comprises the steps determining a flow rate of air entering a mixing box, multiplying a specific humidity of air leaving a dust collector by the sum of the flow rate of air entering a mixing box and a temperature of cold air entering the mixing box.