Device for changing nozzles

The invention relates to a device for changing nozzles. In numerous production processes spray nozzles are used for various purposes. This function can be condensation, cooling, cleaning, and vaporizing. According to function, various nozzle types are employed such as fan, hollow cone, or full cone.

As a rule the nozzles are set in the wall of a vessel or a process apparatus. Such mounting facilitates collecting and recirculating the process water and also ensures fixed positions for the sprays. Many processes must take place under pressures above or below atmospheric. Thus some medium must be sprayed into pressurized or vacuum vessels or conduits. In addition the vessel or conduit can be single- or double-walled and heated or cooled. For continuous operation as a rule several nozzles are provided. These nozzles need to be cleaned and changed periodically. When one nozzle is being changed at least one other must be left operational, to avoid changing the nonatmospheric pressure inside the vessel.

Such an applications of this invention is seen in a method of making polyethylene enterephthalate (PET). An apparatus using nozzles for condensing a process liquor and vacuum production by means of multistage steam injection with upstream spray condensers and downstream mixing condensers are described in EP 0,244,546. Here glycol is sprayed via nozzles into a subatmospheric-pressure stage.

Systems are known where the nozzles are fixed on a lance, inserted through a support tube, and secured in place. Other systems have lances that are inserted through a ball valve flanged to the support tube. In these systems it is however necessary to stop the process or put up with substantial leakage when servicing nozzles.

It is an object of the invention, starting from this state of the art, to provide a device for changing nozzles without having to change the pressure characteristics inside the process vessel or apparatus.

According to the invention this object is achieved in the above-described apparatus in that a support tube is mounted on the vessel and is connected via a valve with a seal housing for the lance and that seal rings are provided in the seal housing to ensure pressure-tight sealing between the vessel and its surroundings when the lance is inserted into the seal housing. This device can be used on a pressurized or vacuum conduit instead of on a pressurized or vacuum vessel. In addition this device works equally well for cooled or heated conduits or vessels as well as for single- or multiple-wall conduits or vessels.

Sealing is improved by feeding a blocking liquid into the seal housing. Instead of a liquid it also possible tp urge with gas and achieve additional sealing.

To ensure near perfect sealing, the blocking fluid is injected between two seals and between the seal assembly and the seal.

The conduits for feeding the blocking fluid in between the seal assembly can also serve for venting. When horizontal, the entire device ensures a complete venting of the system. When mounted vertically or at an angle a nearly complete venting of the system is possible.

A valve underneath the seal housing serves for draining the seal housing.

In order to ensure centering of the lance through the seal assembly and to prevent damage to the seals, the lance is centered by at least one guide in the seal housing. In this manner the nozzle is not damaged when the lance engages the flat or tapered seat surface.

FIG. 1 shows the arrangement of a nozzle lance in use;

FIG. 2 shows the intermediate position of the nozzle during installation and removal; and

FIG. 3 shows the outer position of the nozzle during installation and removal.

FIG. ( 1 ) shows a system with a vessel ( 1 ) that is above or below atmospheric pressure and that can be heated or cooled. This vessel ( 1 ) carries a support tube ( 2 ) that can be oriented horizontally, vertically, or at an angle. The tube has a flat or conically tapered seat surface ( 2 a ) against which a nozzle lance ( 7 ) can fit. A flange connects the support tube ( 2 ) with at least one pressure- or vacuum-tight ball valve ( 3 ) and a seal housing ( 5 ) so as to be pressure- and vacuum-tight. Other valves with straight-through passages such as for example slider valves can be used instead of the ball valve. A nozzle lance ( 7 ) is fitted to this arrangement, seated in the support tube ( 2 ). A tip of the lance ( 7 ) has a spray nozzle ( 8 ). The medium ( 20 ) to be sprayed in is supplied to the end of the lance ( 7 ) by a hose ( 10 ). The hose ( 10 ) is connected by a snap coupling ( 9 ) with the lance ( 7 ). The lance ( 7 ) is centered by a guide ( 6 ) in the tube ( 2 ). The seal housing ( 5 ) is directly sealed and flanged with the ball valve ( 3 ) and has at least two seal rings ( 13 a ) and ( 13 b ) that serve to maintain pressure in the vessel ( 1 ). A seal ring ( 13 c ) prevents leakage into or from the exterior. The seal housing ( 5 ) is pressurized with a blocking fluid between the seal rings ( 13 a , 13 b , and 13 c ). This blocking liquid is normally the same as that being sprayed in. The seals ( 13 a , 13 b , and 13 c ) can be corrugated or rod seal rings. The blocking liquid is supplied to the seal housing via valves ( 11 b ) from supplies ( 12 a and 12 b ). The seal housing is drained by a lower valve ( 11 c ). The seal housing is vented during insertion of the lance via the valves ( 11 a ) and ( 11 b ) and the supplies ( 12 a and ( 12 b ) while feeding in the blocking liquid. In use the lance ( 7 ) with ita nozzle ( 8 ) is fitted to the seat ( 2 a ) of the tube ( 2 ). In use the medium ( 20 ) to be sprayed in is supplied through the hose ( 10 ). The valves ( 11 a and 11 c ) are closed. The ball valve ( 3 ) and the valve ( 11 b ) are open. The supplies ( 12 a and 12 b ) are filled with blocking fluid.

To take out the lance ( 7 ), feed of the spraying medium ( 20 ) is first stopped. The lance ( 7 ) is moved into an intermediate position outward of the ball valve and adjusted (see FIG. 2 ). Then the valve ( 3 ) is closed. In order to equalize pressure the valve ( 11 a ) is opened. The valve ( 11 b ) is closed. The lance ( 7 ) is then moved into an outer position (see FIG. 3 ) so that the lance tip with the nozzle ( 8 ) is inward of the seal ( 13 c ). Then the seal housing ( 5 ) is emptied via the valve ( 11 c ). The lance ( 7 ) can then is be pulled completely out.

To insert the lance ( 7 ), it is moved into the outer position (see FIG. 3 ) so that the lance tip with the nozzle ( 8 ) is inward of the seal ( 13 c ). The ball valve ( 3 ) and the drain valve ( 11 c ) are closed. A small amount of the blocking fluid is fed through the lance ( 7 ) into the seal housing. Meanwhile the valves ( 11 a and 11 b ) are open. When the liquid levels in the supplies ( 12 a and 12 b ) reach predetermined levels, the supply of the blocking fluid is ended. The seal housing ( 5 ) is thus vented of air. The lance ( 7 ) is now pushed into the intermediate position just outward of the ball valve ( 3 ) (see FIG. 2 ). The valve ( 11 a ) is closed and the valves ( 11 b ) remain open. Then the ball valve ( 3 ) is opened. The lance ( 7 ) is pushed inward against the flat or conical seat ( 2 a ). If the support tube ( 2 ) gets dirty, it can be rinsed out during insertion of the lance ( 7 ) with the spraying liquid.