Thermal reactor with self-regulating transfer mechanism

Details Thermal reactor with self-regulating transfer mechanism Thermal reactor with self-regulating transfer mechanism

1999-06-21

2001-06-05

Tran, Hien (Department: 1764)

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

Including heat exchanger for reaction chamber or reactants...

C422S111000, C422S112000, C422S242000, C137S014000, C137S572000

Reexamination Certificate

active

06241953

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to the formation of reaction products such as ceramic, magnetic, electrolyte, electrode and other powders, to the use of high temperatures to disintegrate unwanted compounds, and to a structure employed for these purposes which may operate at near critical, critical or supercritical temperatures and the corresponding saturated pressures of the working fluids.
2. Description of the Related Art
In my earlier U.S. Pat. Nos. 4,238,240, 4,366,121, 4,545,970, 4,753,787, 4,912,078, 4,983,374 and 5,026,527, I describe numerous structures and processes for forming reaction products. These patents are hereby incorporated by reference.
In my '240 patent I disclose a method for forming a reaction product in which the reaction constituents are mixed in an autoclave. The mixed reaction constituents are then reacted for a selected time to form reaction products, and the reaction products are transferred, at the end of the reaction, from the autoclave to another vessel (sometimes called a “receiving vessel” and sometimes called an “antipressure vessel”) connected to the autoclave by a flow passage. The pressure in the vessel is held in a controlled manner beneath the pressure in the autoclave during the transfer of the reaction products from the autoclave to the vessel. To maintain the pressure in the vessel in a controlled manner beneath the pressure in the autoclave during the transfer of the reaction products from the autoclave to the receiving vessel, I disclose an electronic control system which measures the pressures in the autoclave and the receiving vessel and which opens or closes a valve (shown as valve 101 in FIG. 1 of the '240 patent) attached to the receiving vessel (vessel 12 in the '240 patent) to maintain the pressure in the vessel a controlled amount beneath the pressure in the autoclave (shown as autoclave 10 in the '240 patent).
I also disclose an alternative embodiment in the '240 patent wherein the electronic control system is replaced by a throttle valve or by a valve and a vent pipe. Before the start of the transfer operation, a suitable pressure difference is established between the autoclave and the receiving vessel. Then, to start the transfer of the reaction product from the autoclave to the antipressure vessel, a valve between the autoclave and the vessel is opened and simultaneously or subsequently, as desired, a pressure release valve on the top of the receiving vessel is opened and left open during the transfer process. As a result, the reaction product from the autoclave flows into the receiving vessel at an instantaneous rate determined by the instantaneous pressure difference between the autoclave and the receiving vessel. As I disclose in the '240 patent, this pressure difference is controlled by the sizes of the valve and vent pipe or the setting of the throttle valve. This embodiment avoids the use of a control circuit but has the potential disadvantage that the transfer is not as precisely controlled as with a control circuit.
In my '787 patent, I provide a substantially simplified system for transferring the contents of the autoclave (shown as autoclave 10 in the '787 patent) to the antipressure vessel (shown as vessel 12 in the '787 patent). The system of that invention incorporates a pressure release valve on the antipressure vessel, the setting of which is precisely controlled by a control signal from a flow meter used to measure the volumetric flow of the reaction product. In the preferred embodiment, the pressure release valve is controlled to maintain a constant flow of reaction product from the autoclave to the antipressure vessel. A novel method of initializing the pressure in the antipressure vessel is disclosed in the '787 patent whereby gas (typically steam) is released from the autoclave through a vent pipe into the antipressure vessel prior to the transfer of reaction product from the autoclave to the antipressure vessel. When the pressure in the antipressure vessel is equal to the pressure in the autoclave, the vent pipe is closed and the pressure in the antipressure vessel falls slightly beneath the pressure in the autoclave as a result of the natural cooling of the gas in the antipressure vessel due to heat transfer to the relatively cooler walls of the antipressure vessel. As the antipressure vessel comes to a relatively steady state temperature after several batches of reaction product have been passed to the vessel, the pressure difference between the autoclave and the vessel due to this natural cooling effect becomes less. And, when the gas is steam, relatively little steam condenses to create this pressure difference. This method and structure avoids the use of costly compressors as in the prior art to initialize the pressure in the antipressure vessel. When the gas is steam, the method requires a surprisingly small amount of steam from the autoclave to pressurize the antipressure vessel due to the fact that the steam in the autoclave is at a high pressure and temperature and, therefore, contains a low volume of water per cubic meter. However, this embodiment has the disadvantage of requiring a flowmeter and expensive monitoring equipment in order to trigger a pressure relief valve if, for example, the flow enters the turbulent regime.
SUMMARY
In accordance with the present invention, I provide a substantially streamlined system for transferring the contents of an autoclave to a receiving vessel, even with respect to the earlier system embodied in my '787 patent. This invention employs a self-siphoning method for effecting the transfer. In the preferred embodiment, this is accomplished by introducing a certain amount of water into a preheated receiving vessel, prior to the transfer of the autoclave contents, where the temperature of the receiving vessel is below the temperature of the autoclave contents. The quantity of water added to the receiving vessel is calculated, taking into account the temperature of the receiving vessel, to be sufficient to yield a saturated vapor pressure in the receiving vessel. Heating the receiving vessel may then be stopped.
An initial pressure difference now exists between the receiving vessel and the autoclave. The reaction product slurry in the autoclave is then transferred via a pipe and heat exchanger(s) to the receiving vessel due to this initial pressure difference. An increased rate of transfer through the heat exchanger(s) causes the temperature of the reaction product slurry entering the receiving vessel to rise. The slurry entering the hot receiving vessel generates more steam and pressure at a higher slurry temperature than at a lower slurry temperature. Since an increased transfer rate causes the pressure within the receiving vessel to rise, which in turn lowers the transfer rate, the present system maintains a self-adjusted pressure difference between the two vessels to control the transfer rate of the slurry.
Additionally, a two-stage heat exchanger is preferably used, where a first heat exchanger acts as a steam generator by converting an externally supplied flow of water into steam as the water cools the hot slurry from the autoclave. This steam is supplied to the receiving vessel to additionally control the pressure differential between the two vessels. The flow rate of cooling water through the steam generator is used to vary the temperature of the steam generated (a higher flow rate of cooling water gives a lower steam temperature) and the temperature of the slurry, where a lower steam temperature reduces the pressure in the receiving vessel so as to increase the slurry flow rate. A higher steam temperature will raise the pressure in the receiving vessel and slow down the slurry flow rate.
The self-adjusting and self-siphoning reaction system described allows the autoclave to discharge the slurry at a desired flow rate without the prior art requirement of continuously monitoring and controlling the flow rate of reaction product and the relative pressures of th

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