Startup sequence for roller crusher
System and method for controlling the startup sequence of a roller crusher is disclosed. The roller crusher includes two generally parallel rollers that are separated by a gap where the rollers rotate in an opposite direction. During startup, the gap between the rollers is greater than the gap during normal production and a feeding arrangement is run at a speed that is lower than a normal production feed rate. The rollers are rotated at a predetermined speed that is less than the speed during normal production. Other parameters of the system are set such that material is fed over the entire length of the rollers and the no crushing force is exerted during the startup. The method and system of the present disclosure reduces the amount of stress on the rolls, frame and hydraulic system of the roller crusher.
1. A method for starting a roller crusher having two generally parallel rolls arranged to rotate in opposite directions and separated by an adjustable gap, wherein the roller crusher further comprises a feeding arrangement for feeding material to be crushed to the rolls, the method comprising the following steps:
a) setting a gap width between the rolls to a predefined value (x), where the predefined value (x) is greater than a production operating gap (X);
b) running the feeding arrangement at a feed rate (r) which differs from a normal production feed rate (R), where the feed rate (r) is less than the normal production feed rate (R);
c) rotating the rolls in opposite directions at a predetermined speed (s), where the predetermined speed (s) is greater than 0 rpm;
d) setting parameters in steps a)-c) such that
i. material to be crushed passes between the rolls along substantially an entire crushing length (L) of the rolls; and
ii. no or substantially no specific crushing force (f) is exerted on the material by the rolls,
e) when i) and ii) are achieved, increasing the feed rate (r) gradually until desired production para meters of the production feed rate (R) and the crushing force (f) are achieved.
2. The method according to claim 1 , further comprising the step of setting a force control set point (F) in step b) and increasing the feed rate (r) and/or the force control set point (F) in step e).
3. The method according to claim 1 , wherein in step c) the rolls are rotated at a reduced speed in comparison with a normal production speed (S) such that the predetermined speed (s) is less than the normal production speed (S).
4. The method according to claim 3 , wherein the predetermined speed (s) is 20-40% of the normal production speed (S).
5. The method according to claim 3 , wherein the predetermined speed (s) is 30-35% of the normal production speed (S).
6. The method according to claim 2 , increasing the force control set point (F) and the feed rate (r) in a coordinated manner in step e).
7. The method according to claim 2 , increasing the force control set point (F) and the feed rate (r) independent from each other in step e).
8. The method according to claim 6 , increasing the feed rate (r) and/or the force control set point (F) only after the crushing force (f) has reached a predefined value.
9. The method according to claim 7 , increasing the feed rate (r) and/or the force control set point (F) only after the crushing force (f) has reached a predefined value.
10. The method according to claim 6 , increasing the feed rate (r) and/or the force control set point (F) only after the feed rate (r) as defined in an antecedent iteration has lasted a predefined time.
11. The method according to claim 7 , increasing the feed rate (r) and/or the force control set point (F) only after the feed rate (r) as defined in an antecedent iteration has lasted a predefined time.
12. The method according to claim 3 , increasing the predetermined speed (s) of the rolls to the normal production speed (S) when production crushing force (f) and the crushing force (R) are achieved.
13. The method according to claim 1 , changing the production crushing force (f) by changing the predefined value (x) of the gap width between the rolls.
14. The method according to claim 1 , further comprising the following steps:
f) screening of material passing the rolls in a screening arrangement located downstream of the rolls; and
g) recirculate any oversize material.
15. The method according to claim 8 , increasing the feed rate (r) and/or the force control set point (F) only after the feed rate (r) as defined in an antecedent iteration has lasted a predefined time.
16. The method according to claim 9 , increasing the feed rate (r) and/or the force control set point (F) only after the feed rate (r) as defined in an antecedent iteration has lasted a predefined time.