A preform cutting element for a drag-type rotary drill bit includes a facing table of polycrystalline diamond bonded to a less hard substrate, such as cemented tungsten carbide. The element is formed by first forming a solid substrate, and then applying an electron beam, laser, or other intense heating source to adjacent areas of the front surface of the substrate to melt the surface and form an array of holes or holes therein. A layer of polycrystalline diamond particles is applied to the substrate so that such particles fill the holes or holes, and the diamond layer and substrate are then subjected to pressure and temperature in a high pressure, high temperature press to bond the superhard layer to the substrate. The engagement of parts of the diamond table in the holes or holes in the substrate provides a mechanical interlock to improve the strength of the bond between the table and substrate.

Elements faced with superhard material

This patent describes technology for generating ammonia from urea. The method is based on the hydrolysis of an aqueous solution of urea and/or biuret by heating under pressure to form a mixture of ammonia, carbon dioxide and water. The gas mixtures produced are useful for supplying ammonia at controlled pressure and rate of flow for many industrial applications without the risks and hazards associated with the transportation and on-site storage of ammonia, thereby providing a significant safety advantage over present industrial practice.

Methods for the production of ammonia from urea and/or biuret, and uses for NOx and/or particulate matter removal

Improved apparatus and methods for the treatment of boiler flue gas with sulfur trioxide conditioning agent include the beneficial use of catalytic converters that can be located immediately adjacent the injection site for their sulfur trioxide output, that can be individually sized and manufactured for variable required conditioning agent outputs, that can be individually controlled and can provide substantially improved conversion efficiency and that can provide an efficient, flexible, effective and relatively inexpensive multi-boiler flue conditioning system.

Flue gas conditioning system

A preferred apparatus arrangement utilizes the enthalpy of the flue gas, which can be supplemented if need be, to convert urea ( 30 ) into ammonia for SCR. Urea ( 30 ), which decomposes at temperatures above 140 .degree. C., is injected ( 32 ) into a flue gas stream split off ( 28 ) after a heat exchanger ( 22 ), such as a primary superheater or an economizer. Ideally, the side stream would gasify the urea without need for further heating; but, when heat is required it is far less than would be needed to heat either the entire effluent ( 23 ) or the urea ( 30 ). This side stream, typically less than 3% of the flue gas, provides the required temperature and residence time for complete decomposition of urea ( 30 ). A cyclonic separator can be used to remove particulates and completely mix the reagent and flue gas. This stream can then be directed to an injection grid ( 37 ) ahead of SCR using a blower ( 36 ). The mixing with the flue gas is facilitated due to an order of magnitude higher mass of side stream compared to that injected through the AIG in a traditional ammonia-SCR process.

Selective catalytic reduction of NOx enabled by sidestream urea decomposition

Processes and apparatus for quantitatively converting urea to ammonia on demand are disclosed. One process includes the steps of: receiving a demand rate signal for ammonia; feeding reactants including urea and water into a reactor to provide a reaction mixture; and controlling temperature and pressure in the reactor to produce a gaseous product stream including ammonia and carbon dioxide at substantially constant concentrations. Another process includes the steps of: feeding molten urea or solid urea to a reactor; feeding water (liquid or steam) to the reactor; and reacting the urea and water at elevated temperature and pressure to form a gaseous product stream including ammonia and carbon dioxide.

Processes and apparatus for quantitatively converting urea to ammonia on demand

A method is provided for enhancing the efficiency of fly ash collection in an electrostatic precipitator by lowering the resistivity of the fly ash particles in the flue gas, comprising the steps of introducing an aqueous solution of ammonium sulfate or ammonium bisulfate into a slipstream of hot gas in a chamber external to the main flue gas duct wherein thermal decomposition is effected and distributing the decomposition products into the main flue gas stream exiting from the air preheater at a point upstream from the electrostatic precipitator.

Method for flue gas conditioning with the decomposition products of ammonium sulfate or ammonium bisulfate

A method is provided for improving the electrostatic precipitation of particulates, i.e., from combustion gases by withdrawing part of the flue gases, catalytically converting the SO2 to SO3 and reinjecting it into the main flue stream.

John P. Gooch

Papers

Method for flue gas conditioning with the decomposition products of ammonium sulfate or ammonium bisulfate

Catalytic oxidation of SO2 to SO3 in the presence of fly ash