Apparatus for continuously measuring flow rate of fine material flowing through transport pipe

In an apparatus for continuously measuring the flow rate of a fine material flowing through a transport pipe, which comprises:

• a hopper (2) having a closed structure;
• a fine material feeding means (7), arranged above said hopper (2), for feeding said hopper (2) with a fine material (11);
• a weighing means (3) for continuously measuring the weight of the fine material (11) contained in said hopper (2);
• a first communication pipe (4) for air-tightly communicating said fine material feeding means (7) and said hopper (2), said first communicating pipe (4) being adapted to introduce the fine material (11) in said fine material feeding means (7) into said hopper (2);
• a first valve (5), provided in said first communication pipe (4), for opening and closing said first communication pipe (4);
• a valve controller (15) for controlling opening and closing of said first valve (5), said valve controller (15) being adapted to control opening and closing of said first valve (5) in response to a measured value obtained continuously by said weighing means (3) so as to keep the weight of the fine material (11) contained in said hopper (2) within a prescribed range;
• a transport pipe (1) arranged below said hopper (2);
• a second communication pipe (8) for air-tightly communicating said hopper (2) and said transport pipe (1), said second communication pipe (8) being adapted to introduce the fine material (11) in said hopper (2) into said transport pipe (1);
• a second valve (9), provided in said second communication pipe (8), for opening and closing said second communication pipe (8);
• a carrier gas blowing means for blowing a carrier gas into said transport pipe for transporting the fine material (11) through said transport pipe (1);
• an equalizer (12) for air-tightly communicating the top portion of said hopper (2) and said second communication pipe (8), said equalizer (12) being adapted to equalize the pressure in said hopper (2) with the pressure in said second communication pipe (8);
• a flow rate calculating means (21) for calculating the flow rate of the fine material (11) flowing through said transport pipe (1), said flow rate calculating means (21) being adapted to continuously calculate the flow rate of the fine material (11) flowing through said transport pipe (1), on the basis of one of the following (A) and (B):
• (A) a measured value (G.sub.a) of the flow rate of the carrier gas flowing through said transport pipe (1) obtained by a flow rate measuring means (17), and a measured value (.DELTA.P.sub.T) of the pressure drop of a two-phase solid-gas flow which is flowing through said transport pipe (1) obtained by a pressure drop measuring means (62), said two-phase solid-gas flow comprising the fine material (11) and the carrier gas, said pressure drop being measured between two prescribed points of the transport pipe (1) in the axial direction thereof, and,
• (B) a measured value of the density of the fine material (11) flowing through said transport pipe (1) obtained by a density measuring means (63), a measured value of the flow velocity of the fine material (11) flowing through said transport pipe (1) obtained by a flow velocity measuring means (64), and, the cross-sectional area of said transport pipe (1);
• the improvement characterized by further comprising:
• an integrator (25) for integrating calculated values (G.sub.s) of the flow rate of the fine material (11) flowing through said transport pipe (1), which are obtained by said flow rate calculating means (21);
• a correction controller (22), said correction controller (22) being adapted to calculate the total weight of the fine material (11) which is fed, during a prescribed period of time in the period for which said first communication pipe (4) is closed by said first valve (5), from said hopper (2) into said transport pipe (1), on the basis of said measured value obtained by said weighing means (3) and an output value of said valve controller (15), and, being adapted to actuate said integrator (25) during said prescribed period of time;
• a correction commander (28) for informing said correction controller (22) of the starting point of said prescribed period of time;
• a divider (27) for calculating a correction coefficient (k) i.e., the ratio (W/S) of a calculated value (W), obtained by said correction controller (22), of the total weight of the fine material (11) which is fed, during said prescribed period of time, from said hopper (2) into said transport pipe (1), to an integral value (S), for said prescribed period of time, obtained by said integrator (25);
• and,
• a multiplier (23) for calculating a corrected value (G'.sub.s) of the flow rate of the fine material (11) flowing through said transport pipe (1), by multiplying said calculated value (G.sub.s) obtained by said flow rate calculating means (21) with said correction coefficient (k).