GB2306124A

GB2306124A - Humidity generator

Info

Publication number: GB2306124A
Application number: GB9620949A
Authority: GB
Inventors: Stuart Robert Seel
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-10-14
Filing date: 1996-10-08
Publication date: 1997-04-30
Also published as: GB9620949D0; GB9520963D0

Abstract

A gas burner 10 supplies heated gases to a tube 11. The heated gases leave the tube 11 and water is emitted in a spray from a head 15 into the tube 11 upstream from the outlet or in a spray (30, fig 3) alongside the exit from the air duct, to humidify the gases.

Description

HUMIDITY GENERATOR The present invention relates to a humidity generator and a method of generating humidity.

When pre-cooked meat is to be pre-packaged for boilin-a-bag meals or similar applications it is vital to the profitability of the operation that the portion size is controlled within narrow tolerances. One of the ways of doing this starts by pressing the pre-cooked meat into a plastic film sausage skin. The sausage is then heated to a core temperature in excess of 70"C to pasteurise it. The sausage can then be sliced on a precision slicing machine to provide portion sizes within very tight tolerances.

The sausage skins currently used have an upper temperature limit of approximately 120C. This limits the acceptable method of heating the filled sausage skin to atmospheric stem, which is normally provided by heating a pan of water within a steaming chamber with electric immersion elements, or by injecting live steam into the steaming chamber from a steam boiler.

Disadvant.acjes of the electrically heat steamer.

1. Running cost. The cost of electric power for a typical steamer rated at say 30 kw could be 4.50/batch of sausages.

2. Cycle time. The water in the pan has to be heated from cold each time the steamer is used. This incurs a time and cost penalty.

III. Disadvantages of the Steam Boiler Based System.

1. Initial capital cost. The process of raising steam involves relatively large and expensive capital plant.

2. Running costs. For every Kw of heat released in the boiler combustion chamber typically 500 W will be lost before the heat arrives at the point of use during the winter heating system. During the summer when space heating is not required of the same boiler the proportion of useful heat arriving at the process can fall to as low as 15% of the input heat.

3. Insurance costs. Steam boiler insurance is expensive. An inspection is required by the insurer every 13 months. The company pays for the cost of preparing the boiler for inspection and for the inspection itself. The preparation and inspection typically takes 2 days, but can be more if the inspector requires remedial work to be carried out before passing the boiler fit for insurance.

4. Loss of production. If the factory has only 1 boiler, then during the preparation and inspection, production is stopped.

Humidity Provision and Control System for Bakery Proofing Plant.

IV. History When bread products are being manufactured in a medium to large scale bakery, the formed dough ball is placed on a conveyor which passes thorough a large box, called a proover or proofer, within which the temperature and relative humidity are controlled. This enables the yeast to generate carbon dioxide, as a by-product of its multiplication. The carbon dioxide creates bubbles in the dough causing it to "rise" forming the desired open texture which is then baked in.

To ensure uniform conditions within the Proover the air is normally re-circulated from end to end or top to bottom depending on the manufactures design preferences, by an electrically powered fan. As the air is being recirculated it is re-heated as required and its relative humidity is adjusted to the desired level. Traditionally this is done using high pressure steam from the main plant steam boilers.

The air temperature is raised by passing high pressure steam through a steam heater battery installed in the re-circulation path-way. When heat is required to raise the air temperature to the desired level, an electrically operated solenoid valve opens, allowing steam into the heater matrix from where it is taken up by the re-circulating .lir stream. When the desired temperature is reached, the electrically operated solenoid valve closes, cutting off the heat source. The process is repeated as required to maintain temperature within defined limits.

When additional humidity is required to raise the relative humidity of the re-circulating air stream an electrically operated solenoid valve opens. The valve allows steam to pass to a sparge pipe installed in the recirculating air stream and hence into the proover. When the relative humidity reaches the desired level the electrically operated solenoid valve closes.

V. Disadvantages of the Traditional Steam Boiler Based System.

3. Insurance costs. Steam boiler insurance is expensive. An inspection is required by the insurer every 13 months. The bakery pays for the cost of preparing the boiler for inspection and for the inspection itself. The preparation and inspection typically takes 2 days, but can be more if the inspector requires remedial work to be carried out before passing the boiler fit for insurance.

4. Loss of production. If the bakery has only 1 boiler, then during the preparation and inspection, they cannot produce products which have to rise.

According to one aspect of the present invention a humidity generator includes a duct arranged to have heated gas supplied to it with the duct having an outlet with water being arranged to be added to the heated gas.

With such an arrangement it is not necessary to provide a steam generator. Furthermore separate steam generators can be provided for each region that is required to have the humidity. Accordingly if a particular steam generator is closed down it is not necessary for all of the regions that require to have humidity control to be shut down. A further advantage is that the insurance requirements are significantly less for a humidity generator according to the present invention as compared to the insurance requirements for a steam generator.

The water may be arranged to be added at a location upstream from the outlet or, alternatively or additionally, downstream from the outset.

The water may be arranged to be added by spray means which may comprise a spray head.

The water may be arranged to be added at a location where the gas in the duct is arranged to undergo a change in direction and that change in direction may be substantially perpendicular. Alternatively the water may be arranged to be added in a direction alongside where the gas is emitted.

The water inlay be arranged to be added to the gas in the form of a cone which cone may be hollow.

The water may be arranged to form small droplets and, alternatively or additionally, to form steam.

The flow rate of the water may be arranged to be controlled, for instance between maximum and minimum flow rates and those maximum and minimum rates may be adjustable.

The supply of the water may include a pressure regulating vale.

The outlet of the duct may be arranged to be supplied to a heated chamber and may be arranged to be supplied indirectly via a conduit. The conduit may be arranged to recirculate gasses from a chamber. A fan may be provided to assist in ths recirculation of gasses from a chamber.

The outlet of the generator may be downstream of the fan.

The present invention includes a heating system incorporating a humidity generator substantially as herein described and the heating system may comprise a proofer or meat heater.

The present invention also includes a method of generating humidity comprising supplying heated gas to a duct and supplying water to the heated gas.

The method may comprise supplying water upstream of an outlet to the duct or supplying water to the heated gas after the gas has left the duct.

The method may comprise supplying water by spraying the water. The method may comprise adding the water to the duct in a region where the gas undergoes a change in direction. The method may comprise adding the water in the form of a cone. The method may comprise causing the water to form small droplets and, alternatively or additionally, causing the water to form steam.

The method may comprise adding water to the heated gas alongside the heated gas.

The method may comprise controlling the flow rate of the water, for instance between maximum and minimum rates.

The method may comprise adjusting the flow rate of the water. The method may comprise regulating the pressure of the water.

The method may comprise supplying the products of the generator to a chamber, for instance by indirectly supplying the products to the chamber via a conduit. The method may comprise adding the products of the generator to gasses that have been recirculated from a chamber. The method may comprise initially supplying heated gas and only subsequently supply water.

The present: invention may include a method of adding humidity to a system using a method of generating humidity as claimed in any preceding claim.

The present invention includes any combination of the herein referred to features or limitations.

The present invention can be carried into practice in various ways but two embodiments will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a first embodiment of a direct gas fired humidity generator; Figure 2 is a plan view of Figure 1; Figure 3 is a schematic side view of a second embodiment of a direct gas fired humidity generator; Figure 4 is a plan view of Figure 3; and Figure 5 is a schematic view of a proofer plant incorporating either of the humidity generators.

As shown in Figures 1 and 2, the equipment consists of a packaged force draught gas burner 10, a combustion tube 11, a regulated spray of water 12, evaporator tube 13 and a closed loop control system.

The gas burner 10 provides a stream of high temperature products of combustion which are forced down the combustion tube 11 by a combustion air fan 14 built into the burner. When the combustion process is complete water is sprayed into the air stream via a head 15. This is done in such a way as to form a hollow cone of water through which the combustion gasses pass. This breaks the water into small droplets and the water evaporates instantaneously into the combustion gases. The evaporated water may be steam and may be above 100"C at atmospheric pressure.

The relative humidity of the stream of gases is controlled by automatically adjusting the water spray rate relative to the burner firing rate and its excess air level. This facility is provided by the high 16 and low 17 water flow rate solenoid valves operated by an indicator/controller and humidity transducer. The high and low flows are set to their desired rates by adjusting the high 18 and low 19 water flow rate trim valves and a pressure regulating valve 20 indicated in Figure 1. An isolation valve 21 and a filter 22 are included upstream of the regulating valve 20.

In the embodiment shown in Figures 3 and 4 like parts to those shown in Figures 1 and 2 have been given the same reference numerals. The modification in Figures 3 and 4 comprises the high temperature combustion products exiting the tube 11 from the end of that tube in the general direction of the longitudinal extend of the tube without the water having been added. Instead, the water leaves the head 15 in a spray 30 that is alongside the exiting combustion products and generally in the same direction of these products. This avoids any water condensing in the tube 11.

The mixed wet stream of gasses from the generator shown in Figures 1 and 2, or the separate streams of hot gasses and droplets of water from the embodiment disclosed in Figures 3 and 4 then pass into a working chamber 23 of a steamer or proover 24 shown in Figure 5 via a duct 29 where they are mixed with a re-circulated air stream from the working chamber. The temperature of the steamer or proover is controlled by automatically adjusting the gas firing rate. This facility is provided by the high and low water flow rate solenoid valves operated by an indicator/controller and temperature transducer. The high and low flows 16 and 17 are set to their desired rates by adjusting the high and low water flow rate trim valves 18 and 19 and the pressure regulating valve 20 indicated on the drawing.

If required, the ends of the tube 11 of Figure 3 and the head 15 can pass around a bend in order to cause their flow on exiting to be along the duct 29.

Product enters the proofer and conveyor 25 and travels in a serpentine manner before leaving as shown at 25. Gases from the chamber are drawn from a region near the outlet of the proover along a supply duct 27 by a recirculation fan 28. The hot moist gases from the steam generator are aclded to the gases leaving the fan 28 before being returned to the oven via the return duct 29.

Initially, hot combustion gasses only may be discharged into the duct 29 in order to heat up the systems prior tc water being sprayed into the duct 29 thus ensuring that when water is added it will not condense in the system.

VI. Advantages 1. Capital cost. The estimated retail capital cost of equipment would be approximately 1/3rd of a steam boiler of the same rating.

2. Floor space. The equipment could be installed in such a way that it was within the normal footprint of the steamer or proover to which it is fitted.

3. Energy consumption. The equipment would use approximately the same amount of energy as its electric equivalent and less than half the energy of a steam boiler to provide the same service level. The relative costs of fuels make it difficult to calculate the comparative running costs but 1/6th of the cost of electric and 90% of the cost of running a steam boiler on medium fuel oil is to be expected.

4. Stand by losses. The larger factory with several steamers or proovers runs a humidity generator for a piece of plant when it: is in operation. A steam boiler and its associated steam pipework would be running on standby just in case steam was required.

5. Insurance. No pressure vessel or steam boiler insurance is required 6. Loss of production. The production is not stopped every 13 months for an insurance inspection. In addition, if a steam boiler fails it affects all the plants which require humidity control. If a humidity generator fails, it can be replaced with a spare unit in about 20 minutes, and the failure only affects one plant.

The system can be used to heat meat or in a proofer, as previously described or for any other suitable application.

Claims

1. A humidity generator including a duct arranged to have heated gas supplied to it with the duct having an outlet, with water being arranged to be added to the heated gas.

2. A generator as claimed in claim 1 in which the water is arranged to be added at a location upstream from the outlet.

3. A generator as claimed in claim 1 or 2 in which water is arranged to be added at a location downstream from the outlet.

4. A generator as claimed in any preceding claim in which the water is arranged to be added by spray means.

5. A generator as claimed in claim 4 in which the spray means comprises a spray head.

6. A generator as claim in any preceding claim in which the water is arranged to be added at a location where the gas in the duct is arranged to undergo a change in direction.

7. A generator as claimed in claim 6 in which the change in direction is substantially perpendicular.

8. A generator as claimed in any preceding claim in which the water is arranged to be added in a direction alongside where the gas is emitted from the duct.

9. A generator as claimed in any preceding claim in which the water is arranged to be added to the gas in the form of a cone.

10. A generator as claimed in claim 9 in which the cone is hollow.

11. A generator as claimed in any preceding claim in which water is arranged to form small droplets.

12. A generator as claimed in any preceding claim in which water is arranged to form steam.

13. A generator as claimed in any preceding claim which the flow rate of the water is arranged to be controlled.

14. A generator as claimed in claim 13 in which the flow rate of the water is arranged to be controlled below a maximum flow rate.

15. A generator as claimed in claim 13 or 14 in which the water is arranged to be controlled above a minimum flow rate.

16. A generator as claimed in claim 14 or 15 in which either of the maximum or minimum flow rates are adjustable.

17. A generator as claimed in any preceding claim in which the supply of water includes a pressure regulating valve.

18. A generator as claimed in any preceding claim in which the outlet to the duct is arranged to be supplied to a heated chamber.

19. A generator as claimed in any preceding claim in which the outlet to the duct is arranged to be supplied to the heated chamber via a conduit.

20. A generator as claimed in claim 19 in which the conduit is arranged to re-circulate gases from a chamber.

21. A generator as claimed in claim 20 in which a fan is provided to assist in the re-circulation of gases from a chamber.

22. A generator as claimed in claim 21 in which the outlet of the generator is downstream of the fan.

23. A humidity generator substantially as herein described with reference to, and as shown in figures 1 and 2, or figures 3 and 4 or figure 5 of the accompanying drawings.

24. A heating system incorporating a humidity generator as claimed in any of claims 1 to 23.

25. A heating system as claimed in claim 24 comprising a proofer.

26. A heating system as claimed in claim 24 comprising a meat heater.

27. A heating system incorporating a humidity generator which system is substantially as herein described with reference to figure 5, or figures 1 and 2 and figure 5, or figures 3 and 4 and figure 5.

28. A method of generating humidity comprising supplying heated gas to a duct and supplying water to the heated gas.

29. A method as claimed in claim 28 comprising supplying water upstream of an outlet to the duct.

30. A method as claimed in claim 28 or 29 comprising supplying water to the heated gas after the gas has left the duct.

31. A method as claimed in any of claims 28 to 30 comprising supplying water by spraying the water.

32. A method as claimed in claim 29 or claims 30 or 31 when dependent upon claim 29 comprising adding water to the duct in a region where the gas undergoes a change of direction.

33. A method as claimed in any of claims 28 to 32 comprising adding water in the form of a cone.

34. A method as claimed in any of claims 28 to 33 comprising causing the water to warm small droplets.

35. A method as claimed in any of claims 28 to 34 comprising adding the water to form steam.

36. A method as claimed in any of claims 28 to 35 comprising adding water to the heating gas alongside the heated air.

37. A method as claimed in any of claims 28 to 36 comprising controlling the flow rate of the water.

38. A method as claimed in claim 37 comprising controlling the flow rate of the water to keep the flow rate below a maximum flow rate.

39. A method as claimed in claim 37 or 38 comprising controlling the flow rate to keep the rate above a minimum flow rate.

40. A method as claimed in any of claims 37 to 39 comprising adjusting the flow rate.

41. A method Rs claimed in any of claims 28 to 40 comprising regulating the pressure of the water.

42. A method as claimed in any of claims 28 to 41 comprising supplying the products of the generator to a chamber.

43. A method as claimed in claim 42 comprising supplying the products of the generator indirectly to the chamber via a conduit.

44. A method as claimed in either of claims 42 or 43 comprising adding the products of the generator to gases that have been re-circulated from the chamber.

45. A method as claimed in any of claims 28 to 44 comprising initially supplying heated gas only and subsequently supplying water.

46. A method of generating humidity substantially as herein describes with reference to figures 1 and 2, or figures 3 and 4, or figure 5 of the accompanying drawings.

47. A method of adding humidity to a system when using a method as claimed in any of claims 28 to 46.

48. A method of generating humidity when using a humidity generator as claimed in any of claims 1 to 27.