Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
  • B22D11/051—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds into moulds having oscillating walls
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F1/00—Tubular elements; Assemblies of tubular elements
  • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
  • F28F1/40—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only inside the tubular element

Definitions

• the present invention relates to a method of manufacturing a cooling element for pyrometallurgical reactors, said element having at least one flow channel, and where the manufacture of the element is made by continuous casting, i.e. slip casting.
• the wall surface area of the cooling channel wall is increased with respect to its round or oval shape on cross-section without increasing the diameter or length of the flow channel.
• the invention also relates to the element manufactured by this method.
• the refractory of reactors in pyrometallurgical processes is protected by water-cooled cooling elements so that, as a result of cooling, the heat coming to the refractory surface is transferred via the cooling element to water, whereby the wear of the lining is significantly reduced compared with a reactor which is not cooled. Reduced wear is caused by the effect of cooling, which brings about forming of so called autogenic lining, which fixes to the surface of a heat resistant lining and which is formed from slag and other substances precipitated from the molten phases.
• cooling elements are manufactured in two ways: primarily, elements can be manufactured by sand casting, where cooling pipes made of a highly thermal conductive material such as copper are set in a sand-formed mould, and are cooled with air or water during the casting around the pipes.
• the element cast around the pipes is also of highly thermal conductive material, preferably copper.
• This kind of manufacturing method is described in e.g. GB patent no. 1386645.
• One problem with this method is the uneven attachment of the piping acting as cooling channel to the cast material surrounding it because some of the pipes may be completely free of the element cast around it and part of the pipe may be completely melted and thus damaged. If no metallic bond is formed between the cooling pipe and the rest of the cast element around it, heat transfer will not be efficient.
• the casting properties of the cast material can be improved, for example, by mixing phosphorus with the copper to improve the metallic bond formed between the piping and the cast material, but in that case, the heat transfer properties (thermal conductivity) of the copper are significantly weakened by even a small addition.
• One advantage of this method worth mentioning is the comparatively low manufacturing cost and independence from dimensions.
• Another method of manufacture is used, whereby glass tubing in the shape of a channel is set into the cooling element mould, which is broken after casting to form a channel inside the element.
• a well-known method in the prior art has been to manufacture a cooling element for a pyrometallurgical reactor by casting a hollow profile as continuous casting i.e. slip casting through a mandrel.
• the element is manufactured of a highly thermal conductive metal such as copper.
• the advantage of this method is a dense cast structure, good surface quality and the cast cooling channel gives good heat transfer from the element to the cooling medium, so that no effects impeding heat transfer occur, rather the heat coming from the reactor to the cooling element is transferred without any excess heat transfer resistance directly to the surface of the channel and onwards to the cooling water.
• the cross-section of the cooling channel is generally round or oval and the mandrel has a smooth surface. This type of cooling channel is mentioned in US patent 5,772,955.
• the heat transfer surface area of the element In order to improve the heat transfer capability of a cooling element it is however preferable to increase the heat transfer surface area of the element. As demonstrated by the explanation below, according to the present invention this occurs by increasing the wall surface area of the flow channel without enlarging the diameter or adding length.
• the wall surface area of the cooling element flow channel is increased by forming grooves in the channel wall during casting or by machining grooves or threads in the channel after casting so that the cross-section of the channel remains essentially round or oval.
• the invention also relates to cooling elements manufactured by this method. The essential features of the invention will become apparent in the attached patent claims.
• the difference in temperature between the wall and the tube is limited by the fact that water boils at 100 °C, when the heat transfer properties at normal pressure become significantly worse due to boiling. In practice, it is more advantageous to operate at the lowest possible flow channel wall temperature.
• the heat transfer coefficient can be influenced largely by changing the flow speed, i.e. by affecting the Reynolds number. This is limited however by the increased loss in pressure in the tubing as the flow rate increases, which raises the costs of pumping the cooling water and pump investment costs also grow considerably after a certain limit is exceeded.
• the heat transfer surface area can be influenced either by increasing the diameter of the cooling channel and/or its length.
• the cooling channel diameter cannot be increased unrestrictedly in such a way as to be still economically viable, since an increase in channel diameter increases the amount of water required to achieve a certain flow rate and furthermore, the energy requirement for pumping.
• the channel diameter is limited by the physical size of the cooling element, which for reasons of minimizing investment costs, is preferably made as small and light as possible.
• Another limitation on length is the physical size of the cooling element itself, i.e. the quantity of cooling channel that will fit in a given area.
• At least one flow channel is formed in the cast cooling element during slip casting, and rifle-like grooves are machined into the flow channel after casting.
• the grooves are advantageously made by using a so-called expanding mandrel, which is drawn through the flow channel. Grooving can be made to e.g. a hole closed at one end, in which case the mandrel is drawn outwards. A hole made in the channel, which is open at both ends, is made either by pushing or drawing a purpose-designed tool through the channel.
• Figure 1 shows a principle drawing of the cooling element used in the tests
• Figure 2 shows a cross-sectional profile of the test cooling element
• Figures 3a -3d indicate the temperature inside the element at different measuring points as a function of melt temperature
• Figure 4 presents the heat transfer coefficient calculated from the measurements taken as a function of the melt
• Figure 5 presents the differences in temperature of the cooling water and the channel wall at different cooling levels for normalized cooling elements.
• Cooling element A had a conventional smooth-surfaced channel, and this element was used for comparative measurements.
• the amount of cooling water and the temperatures both before feeding the water into the cooling element and afterwards were carefully measured in the tests.
• the temperature of the molten lead and the temperatures inside the cooling element itself were also carefully measured at seven different measuring points.
• Figure 1 shows the cooling element 1 used in the tests, and the flow channel 2 inside it.
• the dimensions of the cooling element were as follows: height 300 mm, width 400 mm and thickness 75 mm.
• the cooling tube or flow channel was situated inside the element as in Figure 1 , so that the centre of the horizontal part of the tube in the figure was 87 mm from the bottom of the element and each vertical piece was 50 mm from the edge of the plate.
• the horizontal part of the tube is made by drilling, and one end of the horizontal opening is plugged (not shown in detail).
• Figure 1 also shows the location of temperature measuring points T1 - T7.
• Figure 2 presents the surface shape of the cooling channels and Table 1 contains the dimensions of the test cooling element channels and the calculated heat transfer surfaces per metre as well as the relative heat transfer surfaces.
• Figures 3a - 3d demonstrate that the temperatures of cooling elements B, C and D were lower at all cooling water flow rates than the reference measurements taken from cooling element A. However, since the flow cross-sections of the said test pieces had to be made with different dimensions for technical manufacturing reasons, the efficiency of the heat transfer cannot be compared directly from the results in Figures 3a - 3d. Therefore the test results were normalized as follows:

Landscapes

• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Geometry (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Continuous Casting (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Metal Extraction Processes (AREA)
• Blast Furnaces (AREA)
• Furnace Housings, Linings, Walls, And Ceilings (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1998
  • 1998-12-22 ID IDP991166D patent/ID24579A/id unknown
  • 1998-12-22 FI FI982771A patent/FI108751B/fi active
• 1999
  • 1999-12-14 KR KR1020017007839A patent/KR100640706B1/ko not_active IP Right Cessation
  • 1999-12-14 PL PL99349155A patent/PL193460B1/pl not_active IP Right Cessation
  • 1999-12-14 EA EA200100690A patent/EA002584B1/ru not_active IP Right Cessation
  • 1999-12-14 RS YUP-448/01A patent/RS49726B/sr unknown
  • 1999-12-14 JP JP2000589886A patent/JP2002533649A/ja not_active Abandoned
  • 1999-12-14 CA CA002356138A patent/CA2356138C/en not_active Expired - Fee Related
  • 1999-12-14 DE DE69919745T patent/DE69919745T2/de not_active Expired - Fee Related
  • 1999-12-14 AU AU17818/00A patent/AU768282B2/en not_active Ceased
  • 1999-12-14 BR BR9916469-8A patent/BR9916469A/pt not_active IP Right Cessation
  • 1999-12-14 AT AT99961080T patent/ATE274683T1/de not_active IP Right Cessation
  • 1999-12-14 WO PCT/FI1999/001029 patent/WO2000037870A1/en active IP Right Grant
  • 1999-12-14 EP EP99961080A patent/EP1153254B1/de not_active Expired - Lifetime
  • 1999-12-14 PT PT99961080T patent/PT1153254E/pt unknown
  • 1999-12-14 CN CNB998149551A patent/CN100449242C/zh not_active Expired - Fee Related
  • 1999-12-21 AR ARP990106633A patent/AR021961A1/es active IP Right Grant
  • 1999-12-22 PE PE1999001308A patent/PE20001446A1/es not_active Application Discontinuation
• 2001
  • 2001-06-14 ZA ZA200104860A patent/ZA200104860B/en unknown

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